F&S International Edition 2017

D 11665 F

International Edition

2017

International Edition

CUT Membrane Technology the application specialists – worldwide!

CU is an innovative CUT e manufacctu t re er of micro- an nd ultrafiltrattion n pr prod oduc ucts uc ts.. We ts W bui uilld ld a var a iety of tubularr and d ho ollow ow fiber filltr trat atio ion n mo modules in our facilities ne near ear a Düs üsse selld se ldor ldor orff,f, Germany.

Filter media test rig MFP 3000 HF WĂƌƟĐůĞ ƐŝnjĞ ƌĂŶŐĞ͗ ϭϬ Ŷŵ ƚŽ ϰϬ ʅŵ͕ ƌĞůĂƟǀĞ ŵ͕ ƌĞůĂƟǀĞ ŚƵŵŝĚŝƚLJ͗ ϭϬ ƚŽ ϴϬ й͕ ƚĞŵƉĞƌĂƚƵƌĞ͗ ͲϭϬ ƚŽ ϱϬ Σ Ğ͗ ͲϭϬ ƚŽ ϱϬ Σ

Havi Havi ving ng more e than a decad a e off experience we are able to supp port you with high level process know whow. We offfer our services in different wastewater err and hygienicc related applications and for various sectors such h as chemical, food & beverage, environmenttal and more.

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As part of th he Bürkert group we provide a comprehenssive range of filtration solutions with a global produ uct availability.

sĞŚŝĐůĞ ŝŶƚĞƌŝŽƌ Ăŝƌ ĮůƚĞƌƐ Θ ĞŶŐŝŶĞ Ăŝƌ ĮůƚĞƌƐ

'ĞŶĞƌĂů ǀĞŶƟůĂƟŽŶ Ăŝƌ ĮůƚĞƌƐ

dƵƌďŝŶĞ Ăŝƌ ĮůƚĞƌƐ

Are you look king for customized membrane solutions? Our application specialistss will be glaad to support you. Please get in touch wi with th us!

More Information CUT Membrane Technology GmbH Part of the Bürkert Group Feldheider Str. 42 D-40699 Erkrath, Germany Phone: +49 2104 17632-0 E-Mail: filtration@burkert.com www.burkert.com/cut

Further information on waste water treatment www.ww-treatment.com

for Filtration and Separation Technologies

Call for Papers Present your latest findings at FILTECH 2018 to an international audience.

Submit your abstract until

8 August 2017

FILTECH March 13 – 15, 2018 Cologne – Germany The Filtration Event

www.Filtech.de

Platform for your success More Space · More Exhibitors · More Solutions for your F+S Tasks Conference: Suzanne Abetz E-mail: abetz@filtech.de Phone: +49 (0)2132 93 57 60

Exhibition: Jens-C. Chittka E-mail: jens@filtech.de Phone: +49 (0)2132 93 57 60

Highlights 2016

Dear Readers,

In Germany and the neighbouring countries, the magazine F&S has been quite an institution for the past 30 years – after all, it is the only German-speaking trade journal exclusively dedicated to filtration and separation technology but also to the treatment of disperse substance systems.

Our readers and advertisers especially value F&S because of the high quality of the published articles and essays that were often trendsetting and also describe today’s valid standards.

For the seventeenth time, we have now had a small part of our broad editorial spectrum translated into English. These are contributions that were published in the year 2016.

By doing so, we want to provide the contents of our magazine to process engineers in non-German-speaking countries as well.

As we said, this is only a small selection of our articles. With a complete translation of all the articles that were published in the year 2016, you would now hold a thick book of nearly 450 pages in your hands.

We would like to wish you a lot of reading pleasure and would be pleased to receive your feedback.

If you would like to find out more about the German F&S, please do not hesitate to contact us at the address listed below (also see imprint: page 26).

With best regards

Eckhard von der Lühe Publisher

VDL-Verlag GmbH Heinrich-Heine-Straße 5 D - 63322 Rödermark Phone: + 49 (0) 60 74 / 92 08 80 Fax:

+ 49 (0) 60 74 / 9 33 34

E-mail: vdl-verlag@t-online.de Internet: www.fs-journal.de

F & S International Edition

No. 17/2017

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EĞǁ ĮůƚĞƌ ŵĞĚŝĂ ƚĞƐƚ ƌŝŐ D&W ϯϬϬϬ ,& dŚĞ D&W ƐLJƐƚĞŵ ĮůƚĞƌ ŵĞĚŝĂ ƚĞƐƚ ƌŝŐƐ ĨƌŽŵ WĂůĂƐΠ͕ ƚƌŝĞĚ ĂŶĚ ƚĞƐƚĞĚ ĨŽƌ ŵĂŶLJ LJĞĂƌƐ͕ ŚĂǀĞ ŐƌŽǁŶ͘ tŝƚŚ ƚŚĞ ŶĞǁ D&W ϯϬϬϬ ,&͕ ŝƚ ŝƐ ŶŽǁ ĂůƐŽ ƉŽƐƐŝďůĞ ƚŽ ƐĞƚ ƚŚĞ ƌĞůĂƟǀĞ ŚƵŵŝĚŝƚLJ ĨƌŽŵ ϭϬ ƚŽ ϴϬ й Žƌ ƚŚĞ ƚĞŵƉĞƌĂƚƵƌĞ ĨƌŽŵ ͲϭϬ ƚŽ ϱϬ Σ ͘ dŚĞ ŝŶŇŽǁ ǀĞůŽĐŝƚLJ ŚĂƐ ďĞĞŶ ĞdžƚĞŶĚĞĚ ƚŽ Ă ƌĂŶŐĞ ŽĨ ϰ ĐŵͬƐ ƚŽ Ϯ ŵͬƐ͘ ƉƉůŝĐĂƟŽŶƐ ĨŽƌ ƚŚŝƐ ƚĞƐƚ ƌŝŐ ŝŶĐůƵĚĞ Ğ͘Ő͘ ƐŝŵƵůĂƟŽŶ ĨŽƌ ƚĞƐƟŶŐ ŽĨ ǀĞŚŝĐůĞ ŝŶƚĞƌŝŽƌ Ăŝƌ ĮůƚĞƌƐ Žƌ ĞŶŐŝŶĞ Ăŝƌ ĮůƚĞƌƐ Ăƚ ŚŝŐŚ ƚĞŵƉĞƌĂƚƵƌĞƐ͕ ƵŶĚĞƌ ĚƵƐƚLJ ĂŶĚ ĚƌLJ ĐŽŶĚŝƟŽŶƐ Žƌ ŽĨ ƚƵƌďŝŶĞ Ăŝƌ ĮůƚĞƌƐ ĨƌŽŵ ƉŽǁĞƌ ƉůĂŶƚƐ ůŝŬĞ ƚŚŽƐĞ ĞdžƉŽƐĞĚ ƚŽ ƐĂůƚ ƉĂƌƟĐůĞƐ Ăƚ ŚŝŐŚ ŚƵŵŝĚŝƚLJ ŽŶ ƚŚĞ ĐŽĂƐƚ ƵŶĚĞƌ ďĂĚ ǁĞĂƚŚĞƌ ĐŽŶĚŝƟŽŶ͘ dŚĞ D&W ϯϬϬϬ ,& ĮůƚĞƌ ŵĞĚŝĂ ƚĞƐƚ ƌŝŐ ŝƐ Ă ŵŽĚƵůĂƌ ĮůƚĞƌ ƚĞƐƚ ƐLJƐƚĞŵ ĨŽƌ ŇĂƚ ĮůƚĞƌ ŵĞĚŝĂ͕ ǁŚŝĐŚ ŝƐ ďĂƐĞĚ ŽŶ ƚŚĞ D&W ϯϬϬϬ ŵŽĚƵůĂƌ ĮůƚĞƌ ƚĞƐƚ ƌŝŐ͘ dŚĞ D&W ϯϬϬϬ ,& ƐĞƌǀĞƐ ƚŽ ĚĞƚĞƌŵŝŶĞ ĮůƚĞƌ ƉĂƌĂŵĞƚĞƌƐ͕ ƐƵĐŚ ĂƐ ͻ ƚŚĞ ĚŝīĞƌĞŶƟĂů ƉƌĞƐƐƵƌĞ ŽĨ ƚŚĞ ĮůƚĞƌ ŵĞĚŝƵŵ Ăƚ ĚŝīĞƌĞŶƚ ŝŶŇŽǁ ǀĞůŽĐŝƟĞƐ ͻ ƚŚĞ ĨƌĂĐƟŽŶĂů ĞĸĐŝĞŶĐLJ ĂŶĚ ƚŚĞ ĚŝīĞƌĞŶƟĂů ƉƌĞƐƐƵƌĞ Ăƚ Ă ĚĞĮŶĞĚ Ăŝƌ ǀŽůƵŵĞ ŇŽǁ ͻ ƚŚĞ ĚŝīĞƌĞŶƟĂů ƉƌĞƐƐƵƌĞ ĂŶĚ ƚŚĞ ĨƌĂĐƟŽŶĂů ĞĸĐŝĞŶĐLJ Ăƚ Ă ĚĞĮŶĞĚ Ăŝƌ ǀŽůƵŵĞ ŇŽǁ ͻ ƚŚĞ ĚƵƐƚ ŚŽůĚŝŶŐ ĐĂƉĂĐŝƚLJ ĂŶĚ ƚŚĞ ĂƐƐŽĐŝĂƚĞĚ ŐƌĂǀŝŵĞƚƌŝĐ ĞĸĐŝĞŶĐLJ Ăƚ Ă ƉƌĞƐĐƌŝďĞĚ Ăŝƌ ǀŽůƵŵĞ ŇŽǁ ĂŶĚ ŝŶĐƌĞĂƐĞ ŝŶ ĚŝīĞƌĞŶƟĂů ƉƌĞƐƐƵƌĞ͘ ^ƉĞĐŝĂů ŶĞǁ ĨĞĂƚƵƌĞƐ ŝŶ ƚŚĞ D&W ϯϬϬϬ ,& ǀĞƌƐŝŽŶ͗ ͻ ĚũƵƐƚĂďůĞ ƌĞůĂƟǀĞ ŚƵŵŝĚŝƚLJ͗ ϭϬ ƚŽ ϴϬ й ͻ dĞŵƉĞƌĂƚƵƌĞ ƌĞŐƵůĂƟŽŶ ŽĨ ƚŚĞ Ăŝƌ ǀŽůƵŵĞ ŇŽǁ͗ ϮϬ ƚŽ ϯϱ Σ ;ͲϭϬ ƚŽ ϱϬ Σ ŽŶ ƌĞƋƵĞƐƚͿ ͻ džƉĂŶƐŝŽŶ ŽĨ ƚŚĞ ŝŶŇŽǁ ǀĞůŽĐŝƚLJ ƚŽ ϰ ĐŵͬƐ ƚŽ Ϯ ŵͬƐ ͻ /ŶƚĞŐƌĂƟŽŶ ŽĨ ĂŶ hͲ^DW^ ŝŶƚŽ ƚŚĞ D&W ϯϬϬϬ ,& ĞdžƉĂŶĚƐ ƚŚĞ ƐŝnjĞ ƌĂŶŐĞ ĨŽƌ ƚŚĞ ŵĞĂƐƵƌĞŵĞŶƚ ŽĨ ĮůƚĞƌ ĞĸĐŝĞŶĐLJ Ăƚ ƚŚĞ D&W ϯϬϬϬ ƚŽ ϭϬ Ŷŵ ƚŽ ϰϬ ђŵ ͻ /ĐĞ ƚĞƐƟŶŐ ŶĞǁ ƚĞƐƚ ƌŝŐ ĐŽŶĐĞƉƚ ŚĂƐ ďĞĞŶ ŝŵƉůĞŵĞŶƚĞĚ Ăƚ WĂůĂƐΠ ĨŽƌ ƚŚŝƐ ƉƵƌƉŽƐĞ͕ ǁŚŝĐŚ ƉƌŽǀŝĚĞƐ ĨŽƌ ƉĂƌƟĐƵůĂƌůLJ ƐƚĂďůĞ ĚĂƚĂ ŽŶ Ăŝƌ ĐŽŶĚŝƟŽŶŝŶŐ ĂŶĚ ŝŶĐůƵĚĞƐ ĂŶ ŝƐŽƚŚĞƌŵĂů ŵĞĂƐƵƌŝŶŐ ĐŚĂŝŶ ƚŽ ƉƌĞǀĞŶƚ ĞǀĂƉŽƌĂƟŽŶ ĂŶĚ ĐŽŶĚĞŶƐĂƟŽŶ ĞīĞĐƚƐ ŽĨ ƉĂƌƟĐůĞƐ ŝŶ ƚŚĞ ƚĞƐƚ ĐŚĂŶŶĞů͕ ĂƐ ǁĞůů ĂƐ ĚƵƌŝŶŐ ƐĂŵƉůŝŶŐ ĂŶĚ ƉĂƌƟĐůĞ ŵĞĂƐƵƌĞŵĞŶƚ͘ dŚĞ ŵŽĚƵůĂƌ ƐLJƐƚĞŵ ĞŶĂďůĞƐ ƚŚĞ ƵƐĞ ŽĨ ĚŝīĞƌĞŶƚ ƚĞƐƚ ĂĞƌŽƐŽůƐ ůŝŬĞ ƐĂůƚ ƉĂƌƟĐůĞƐ͕ ,^ ƉĂƌƟĐůĞƐ ĂŶĚ ƚĞƐƚ ĚƵƐƚƐ ůŝŬĞ /^K Ϯ &ŝŶĞ͘ dŚĞ D&W ϯϬϬϬ ,& ĞŶĂďůĞƐ ŝŶǀĞƐƟŐĂƟŽŶƐ ŽŶ ƚŚĞ ƐĞƉĂƌĂƟŽŶ ĞĸĐŝĞŶĐLJ ĂŶĚ ĚƵƐƚ ŚŽůĚŝŶŐ ĐĂƉĂĐŝƚLJ ŽĨ ĮůƚĞƌ ŵĂƚĞƌŝĂůƐ ƵŶĚĞƌ ƌĞĂů Ăŝƌ ĐŽŶĚŝƟŽŶƐ͘ ,ĞƌĞ LJŽƵ ǁŝůů ĮŶĚ ĨƵƌƚŚĞƌ ŝŶĨŽƌŵĂƟŽŶ ŽŶ ƚŚĞ D&W ϯϬϬϬ ,&͗ ǁǁǁ͘ƉĂůĂƐ͘ĚĞͬĞŶͬƉƌŽĚƵĐƚͬŵĨƉϯϬϬϬŚĨ ƉƌŽĚƵĐƚͬŵĨƉϯϬϬϬŚĨ

Contents W Highlights 2016

6

Industry 4.0 and the possible effects that it might have on production and processing technologies S. Ripperger

6

Processing machines communicating with extraction systems

12

Measures for eliminating micro-pollutants during water and waste water processing Report from the 11th Aachen’s Conference on Water technology H. Lyko

13

Water ferns used to separate oil from water K. Schinarakis

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Membrane technology for water and waste water processing: Findings from the module and process developments H. Lyko

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Optimized operation at Löhnen / Dinslaken water treatment plant, the largest drinking water nanofiltration plant in Germany J.-J. Lagref, N. Bischoffberger, R. Reisewitz , M. Binder, M. Hörsken

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The biggest reverse osmosis plant for the recovery of drinking water

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Evaluation of integrity test methods for membrane modules for the ultrafiltration of ultrapure water in the semiconductor industry R. Berndt, J. Ruth, G. Heser

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Enhancing Bubblepoint testing capabilities on wire meshes by numerical analysis D. Herper, M.Sc.

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The effects of electrical fields on the filtering of suspensions with flocculated quartz powder L. Petersen, H. Hamm, F. Feser, S. Ripperger, S. Antonyuk

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W Membrane technology for water and waste water processing: Findings from the module and process developments

WĂůĂƐ 'ŵď, ϳϲϮϮϵ <ĂƌůƐƌƵŚĞ͕ 'ĞƌŵĂŶLJ WŚŽŶĞ͗ нϰϵ ϳϮϭ ϵϲϮϭϯͲϬ &Ădž͗ нϰϵ ϳϮϭ ϵϲϮϭϯͲϯϯ ŵĂŝůΛƉĂůĂƐ͘ĚĞ ǁǁǁ͘ƉĂůĂƐ͘ĚĞ

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F & S International Edition

No. 17/2017

Contents Highlights 2016

Filtrenergy-powered mesholutions

by PACO & Group

Magnetic separation of very fine particles from liquids A. Vetter, S. Ripperger, S. Antonyuk

47

Field-flow fractionation – A separation process for very fine particles and macromolecules S. Ripperger

54

New developments and results in the fields of air quality monitoring, filter testing and nanoparticle measuring technology Report from the 30th Palas aerosol technology seminar H. Lyko

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Efficiency of cabin air filters during life cycle with regard to particle filtration and adsorption F. Schmidt, A. Breidenbach, U. Sager, E. Däuber and T. Engelke

66

A test bench for compressed air filter testing – even beyond the standard H. Lyko

72

Efficient air purification filtering technologies – as seen at the POWTECH and IFAT exhibitions H. Lyko

76

Our “Wire & Mesh“ solutions – Mesholutions – are not just products made of mesh woven from metal wire. Our Mesholutions provide complete solutions. The cloth, the filter or the screen is not an end in itself, but a means of providing our customers the benefits that really matter to them: efficiency, safety and success.

The PACO difference gives the extra energy that we put into the development and implementation of our solutions.

Selective use of plants for cleaning the air

Download the new "PACO Filtrenergy" brochure online!

80 3dLaserScanning for performance analysis of process components Ch. Ferling Imprint

81 26

PAUL GmbH & Co. KG Metallgewebe- und Filterfabriken Auf der Hohle - Industriegebiet West Postfach 12 20 D - 36396 Steinau an der Straße Phone +49 (0) 6663 978 - 0 Fax +49 (0) 6663 978 - 919116

W Efficiency of cabin air filters during life cycle with regard to particle filtration and adsorption

www.paco-online.com info@paco-online.com

HETA Verfahrenstechnik GmbH Gottlieb-Daimler-Straße 7 D - 35423 Lich Phone +49 (0) 6404 6677 - 0 Fax +49 (0) 6404 6677 - 20 www.heta.de info@heta.de

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Highlights 2016

Industry 4.0 and the possible effects that it might have on production and processing technologies S. Ripperger* “Integrated industry”, “Digitalisation” and “Industry 4.0” are key words used to denote an expected development that according to the classic industries, will cause a revolutionary change in the associated production and processing technology. The communications and information technologies already being used will have to provide the necessary infrastructure, process know-how and “embedded systems” needed for this. Possible developments in the production and processing technology sectors will be outlined in conjunction with this in the following contribution.

1. Introduction At the Hanover exhibition held in 2013, the main focus, under the “integrated industry” slogan, was on the increasing networking being used throughout the industrial sectors as a result of Communications and Information Technology (CIT). The event was a driver for the future research project that was previously called the “fourth industrial revolution” but is now known as “Industry 4.0”. It is expected that this will supersede the “third industrial revolution”, which has enabled widespread automation of production lines through the use of electronics and Information Technology (IT) since the 60s in the last century. One can expect that today’s classic industries will be revolutionised by the associated production and plant technologies resulting from the fourth industrial revolution or Industry 4.0 and through the use of “cyber physical systems” and the “internet of things”.

In 2013 the descriptions of the expected developments were still vague and a wide public discussion about the new possibilities was initiated. The BITKOM, VDMA and ZVEI industry associations opened the “Industry 4.0 platform” for further development during the same year and also created a joint information portal on the internet. This was broadened at the Hanover 2015 exhibition. It is now supported by politics, science and the trade unions as well. The Federal Government is now promoting digitalisation opportunities in business.

Today, many conferences, congresses and comments about this topic present a somewhat specific image so there is still much speculation about the effects that Industry 4.0 might have on processing and process engineering technologies. * Prof. Dr.-Ing. Siegfried Ripperger Information and Engineering Services (IES) GmbH Luxstr. 1, 67655 Kaiserslautern, Germany Tel: +49 (0) 177 -605 -1291 Email: www.ie-services.eu

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However, the present state of the art technology must be outlined first.

2. State of the art technology Processing and process engineering technologies, which are used for the production of numerous goods as well as environmental protection, already show a high degree of automation. Technology based on Programmable Logic Controllers (PLCs) and conventional measuring, controlling and management equipment contributes here so that the processes can be run as securely and reliably as possible and within the optimum range of the processing parameters and in accordance with the objective. The following aspects, amongst others, come into focus here: Operating safety Today, technical systems must all have high availability and guaranteed efficiency. Prompt detection of irregularities is the key to preventing faults and interruptions here. The recording, displaying and/ or logging of the relevant rating values for operational safety, signalling when the limit values have been exceeded and implementing an emergency stop when-

ever necessary are all state of the art technology.

Process stability The measuring and control technologies in use today are responsible for maintaining the planned processes as well as minimising the effects of breakdowns.

Process optimisation Processing parameters are measured (analog or digital) in real-time and sent to a processing computer in order to optimally maintain the planned processes and they are evaluated in connection with the parameters from a processing model.

Numerous processing parameters, such as volumetric flow, temperature, pressure, conductivity, pH value, clouding and filling levels are recorded, displayed and processed online or inline within the necessary measuring ranges. However, inline or online measuring technology capability is still unavailable for a range of other parameters. They also include nanoparticle content, microorganisms, complex dissolved substances (e.g. hormones and medicine residues during water treatment).

Such parameters are important with regard to the controlling of the separation pro-

Cloud

People Computer

Machine I

Process 1

Fig. 1: Networked system under Industry 4.0

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Highlights 2016

cesses, etc. They are often determined using expensive laboratory methods. Today’s automation is mainly restricted to a technical process realised in the form of a technical system. Data is transferred over fixed cable systems that are mainly analog systems (4 - 20 mA technology) here. These systems are robust, safe to operate and easy to maintain.

3. Possible developments in processing and associated production technologies Future developments will be in broader production networks across the overall value-added chain. One can expect to see greater networking over several production processes (horizontal) as well as processing levels (vertical). This type of networking will enable real-time integrated data recording, analysing and graphical displays to be realised. Additional consideration of data from the business processes will make the production processes and the associated operation transparent, which means that the current data can be accessed from any location and at any time. It will then be possible to map the entire processing chain, ranging from procurement right up to the end customer, in real-time. This will enable supply-chain optimisation through projecting the requirement situation and the globally coordinated production, packaging and distribution of the products. This means that plant utilisation can be increased and the stock can be reduced, which will produce cost advantages.

The networking is based on communications and information technology. This has enabled the creation of an “Internet of things”, services and data that can then be used to control highly complex processes. This will also include automation technology and measuring technology as other core technologies on the way to “Industry 4.0”.

3.1 Process controlling and management Controlling and management of process plants will be based on the parameters that have to be measured and monitored in the process. Many technical processes will be operated as combined processes. For example, data from other operations will be taken into consideration in conjunction with the production planning data. Today, data evaluation is already based on models, in order to define optimum operating states or production processes. Sensor data generated from within the process can be included so that any deviations from the optimum process can be detected.

Such mathematical models can be expanded in conjunction with “Industry 4.0” so that more states and disturbance values can be taken into consideration. As a result of the incorporation of data from the business processes (e.g. orders, sales, procurement and logistics data) the processes can be optimised better than ever before to meet the relevant requirements. This enables better planning of plant utilisation, the production of possible product variants and the associated quantities and delivery schedules in the case of production plants. The embedded systems allow real-time order monitoring and forecasting as to whether the planned objective will be realised or not.

Many production processes have diminished the importance of standard products due to increased customer requirements. This increasingly involves individual products that have been developed for very specific customers or applications. The flexibility of the production and associated processes must also be increased due to the greater range of available products. This development will present great challenges to an industry that produces using production processes with high throughout rates in operating plants that might possibly have to run continuously.

Rapid technical changes will also shorten the economical service lives of the products. Therefore new or improved products should be developed over shorter periods and the production processes optimised accordingly. The proportional per unit costs

F & S International Edition

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11 – 15 June 2018 Frankfurt am Main

BE INFORMED. BE INSPIRED. BE THERE. › World Forum and Leading Show for the Process Industries › 3,800 Exhibitors from 50 Countries › 170,000 Attendees from 100 Countries

www.achema.de 7

Highlights 2016

for development and conversion will also increase due to the increasing number of small series or small batch sizes. One must also expect that a product’s profit contribution during its economic life will diminish faster than ever before. The costs topic will become increasingly more important.

These developments will also mean that the tasks within the company will become more complex, specific and varied.

The view of many experts is that developments implemented as part of “Industry 4.0” will contribute to business processes becoming more complex in the conflicting fields of customer requirements, product development and the optimum realisation of safe and economical production.

3.2 Improved or expanded sensor and measuring technologies A prerequisite for optimum control and management of technical processes is a fast and precise evaluation of the relevant data used in a process. This can be data for chemical processes and reactions or about the state variables of complex, substance disperser systems. Many of the actual target variables (e.g. concentrations of material compounds, particle sizes or particle size distributions as well as substance properties) cannot be recorded in-line or online today as the necessary measuring instruments are still not available. A backlog of demands are emerging in this field that could be partially solved by further developing known laboratory methods to meet the inline or online process measuring technology requirements.

Fast recording of data during the processing is just the first step. The exchanging of data across process borders far away and a corresponding evaluation with regard to process optimisation is the second step. Not only sensor data but also product properties, data from plant components such as pumps and drives as well as data from business processes must also be taken into consideration for this.

Possible plant breakdowns can be detected early on, suitable maintenance measures can be introduced and the process can be optimised quasi automatically based on this data. The sensors are networked within digital production and their data is recorded and evaluated in conjunction with other information.

3.3 Modularisation Modularisation is gaining more and more importance within plant technology.

It includes validated plant modules for recurring process levels, such as heating up or cooling down, pumping, mixing, filtering, centrifugation or complete functional units such as water treatment systems or CIP cleaners. The individual modules consist of pre-assembled functional units (units or skids) and they have 8

been designed and constructed so that they can be combined in compliance with the modular principle. Sensor data is compiled in the functional units and the complete process is controlled by actuators. Industry 4.0 requires uninterrupted networking of all of these components. Standardised interfaces in between the specific modules are therefore a prerequisite for Industry 4.0 concepts. However, the advantage of modularisation can only be fully developed if optimised modular software is also provided and it has been adapted to work with the units in the individual modules and the interfaces in between the modules. Modularisation is usually simultaneously linked with standardisation, whereby in-house economic and technical advantages will emerge during the order processing, engineering, documentation, assembly and automation as well as purchasing and stocking of components.

3.4 Paperless documentation A range of plans, documents and manuals have to be created and recorded in conjunction with the setting up of a technical system and nowadays they are predominantly digital. Many documents must be created in compliance with the legal requirements, such as CE Declaration of Conformity, ATEX certificate or material certificate. They also include written documents covering operation, maintenance and repairs. Some of these documents will be supplemented over time and changes or alterations will be made accordingly. It can be seen that any documents that have to be digitally created and recorded over the service life of the system as part of Industry 4.0 will have to be intelligently interlinked to one another, so that they can be quickly accessed whenever necessary.

Providers of components and services must bear in mind that they will have to meet the paperless documentation requirements more than ever before.

3.5 Remote monitoring and after sales services Optimal maintenance and servicing of technical systems ensures high operating safety and prevents certain losses from damage and downtimes. Many suppliers leave the maintenance of a system to the customer after delivery and acceptance.

However, suppliers know the system service requirements far better than their customers. Therefore, a service quote customised by the system provider to the meet the plant’s needs can be useful to both parties. This guarantees high system availability for the operator and the ability to plan the maintenance costs. The system provider can avoid image losses associated with a fault and use the experience gained at the user to further develop or launch new developments whilst achieving high customer loyalty.

The suppliers provide 24 hour service in some sectors. There are many indications that such services will grow under the umbrella of “Industry 4.0”. Remote system monitoring and the resulting buildup of analysed diagnostics data will have a greater significance in conjunction with this in the future. The information technology and the machines and plant engineering grow together here. The embedded systems and cable-connected or wireless communications networks established under “Industry 4.0” can also be used for remote system monitoring. Data from measuring, control and management technologies and special sensors that are used can be sent to a central server via wireless mobile communications. Internet-capable devices (e.g. Tablets) can be used to access the server’s data. The data can be evaluated there as part of a diagnostics system. The system supplier can propose action instructions to the customer in the event of deviations from the target values or even implement measures to ensure correct further system operation.

3.6 Cloud services System providers can also provide cloud services in conjunction with remote monitoring and data analysis services.

This can reduce the data storage costs for users and the continually growing amounts of system data can be evaluated as needed.

General Electric (GE) has developed such a service under the “Predix cloud” name especially for industrial data analysis purposes. The platform records and analyses industrial data and also complements local data recording and processing. A pre-configured industrial PC records the processing data and sends it as prepared code to the cloud. Other defined parameters can be calculated and stored in the cloud. The visualised data can then be accessed from a mobile device or the web-browser in the PC. Such solutions enable one or more production processes to be monitored and evaluated. Furthermore, sales and service data as well as data from the supplier can also be taken into consideration. This will create an “intelligent” system that will enable what initially appears to be a vast amount of data to be viewed and analysed in a specific context.

Despite the known advantages, the market for cloud services is developing slowly. Many potential users have concerns with regard to data security.

Deutsche Telekom holds an European seal of approval, which guarantees that the data will be stored in the EU and the strict European data protection and data privacy laws will always be adhered to.

The Euro-cloud seal of approval, which was first introduced five years ago, lists the location of the computer centre, but does not give any details about which law F & S International Edition

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it is used under, e.g. for US companies.

Subsidiaries of US companies, who also hold this seal of approval, can use it under American law.

3.7 Mobile assistance systems Mobile devices, such as smart-phones and Tablets, are intensively used in the private sector, whereas the integration of this technology in process engineering sector is still in the early stages. Mobile devices can be used to call up high quality information and data at high speeds. This opens up new options with regard to monitoring, controlling and training measures in the processing technology sector. The

increasing use of these systems is conceivable in conjunction with Industry 4.0.

For example, the Comos WebView, Version 2.0 software from Siemens enables comprehensive system management to be implemented from touch-screen devices. A user can obtain web-based access to a system’s performance figures and reports as well as the documentation.

Mobile assistance systems can be used to support and control work processes that are not automated, e.g. through user guidance in system operation. Orders can also be placed and a better work process balance can be also be realised. Additional remote support can also be provided and

Explanation of the terms used here Big Data The term “Big data” stands for the immense data flow that arises in conjunction with automated technical processes. It can be expected that the quantity of data generated per time unit as a result of the development of “Industry 4.0” will become substantially greater. One can detect a resource that is also growing in this data flow, which in conjunction with computer-supported evaluation processes can guarantee different views of really complex processes. Based on this, processes can be better optimised and upgraded to meet changing requirements as necessary.

Furthermore, future developments can be determined using tendencies, scenarios and risks. Inter-disciplinary evaluations of data and the use of so-called data-mining algorithms will also play a role here.

Cyber-Physische Systeme (CPS, engl. Cyber-Physical Systems) Cyber Physical Systems (CPS) Cyber physical systems are physical objects that are linked to one another and exchange data over the internet as well as running predetermined programed control processes. For example, this includes systems that can collect, evaluate and compile planning data from procurements or sales with data from many branches of associated real production processes and also trigger reactions. CPS often work in conjunction with embedded systems.

Embedded Systems The term “embedded systems” describes computer systems that we do not notice yet they normally support or protect us whilst they are working.

Terms often used here are “embedded microprocessors”, “embedded controllers” and “embedded devices”. These are normally systems that are not assigned to classic data processing and computer technology via a PC (see www.embedded.com).

Industrie 4.0 Industry 4. 0 is a synonym for the term “fourth industrial revolution”.

One uses it to describe the expected basic or revolutionary upheavals in the industrial sectors from the use of “cyber physical systems” and the internet. The information and communications technology should provide the necessary infrastructure, the process know-how and the embedded systems for this. In the USA they also talk about “connected industry” or “industrial renaissance” with regard to Industry 4.0. The term “industry of the future” has been introduced in France.

Industrielle Revolution A process covering basic upheaval or restructuring in industrial sectors as a result of technical developments. The first industrial revolution began around the middle of the 18th century in England with the mechanisation of work processes using water and steam power and the start of manufacturing in Great Britain. The second industrial revolution occurred at the end of the 19th century with the introduction of mass production of products using electrical power. This was followed by the third industrial revolution

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used to improve the human / machine interactions. It is conceivable that 3D data glasses and Tablet -PCs will be used for maintenance and repair work in order to provide the personnel with important documents such as spare part lists, construction plans or construction manuals.

KSB AG has taken this a step further.

The KSB Sonolyser App turns a smartphone or Tablet PC into a measuring device, in which the sound frequency of the asynchronous motors can be recorded and checked to see if any potential energy savings exist. The pump’s flow rate can be estimated using an algorithm developed by KSB that is based on the determined shaft

at the start of the 60s in the 20th century, which enabled electronics and information technology (IT) to be used for extensive production automation.

One expects that through the use of “Cyber Physical Systems” and the internet, the classic industries will once again undergo basic upheaval and restructuring, which will be called the fourth industrial revolution or Industry 4.0.

Internet der Dinge The Internet of Things (IoT) refers to products that are interlinked to the internet and can communicate across it. Products that communicate with each other form Cyber Physical Systems (CPS). The data can be saved, called up or evaluated using software in conjunction with computers.

Integrated Industry The term describes the automated exchange of information in industry, realised through electronic networking. The basis for this is modern Information Technology (IT). It enables machines and plants to communicate with each other as well as automatic monitoring and controlling or management to be carried out. This means that production processes can be optimised and warnings can be generated. Integrated industry is a term that describes, in addition to the increasing technical and electronic networking, the inevitable interlinking of company and cross-sector cooperation between all of the subdivisions within the industry.

One is of the opinion that increasing networking within industry will be a decisive success factor in competition between the companies and the national economy. The anticipated global networking and its consequences are known as the fourth industrial revolution and “Industry 4.0”.

Smart Factory The term stands for an “intelligent” factory. In a smart factory networked “embedded systems” and “Cyber Physical Systems (CPS)” are linked to physical objects with predetermined and programmed control processes.

The control process can be regarded as an embedded service. Machines and equipment are networked together in a smart factory and the data is saved and creates its own logic. Some of the machines and equipment are tagged, which means that information about the manufacturer, product names and performance are saved in the machines and equipment. They often have their own programmed interface, which can also be addressed and controlled via the internet.

The term “smart” can also be applied to other units in this sense. Good examples of this are smart product, smart building and smart home. The share of electronics and software used with these types of units with embedded services will continually increase.

PLC Programmable Logic Controllers, which assume local control and management tasks in many plants. The international IEC 61131 standard includes PLC basic principles.

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Details of the organisations referred to above: BITKOM Bitkom e. V. is an association that represents German companies operating in the digital economy. The companies in the association offer a range of software, IT services, telecommunications and internet services, manufacture hardware and consumer electronics, operate in the digital media or networking industry sectors or play a role in the digital economy in other ways. Office location: Berlin; Internet: www. bitcom.org eco eco is an association of internet companies in Germany and represents their interests with regard to policies and in international committees. Eco, which has more than 600 companies as its members, is shaping the internet. Internet: www.eco.de EuroCloud EuroCloud is an independent, non-profit organisation that is organised in two levels (national & international). Countries in Europe can participate in this network by recognising the EuroCloud statutes. Internet: www.eurocloud.org IPA Fraunhofer Institute for Production Technology and Automation (IPA), Stuttgart, Internet: www.ipa.fraunhofer.de VDMA The Verband Deutscher Maschinen- und Anlagenbau e. V (Mechanical Engineering Industry Association) is an association of companies operating in the capital goods industry (machines and plants), Office: Frankfurt a. M., Internet: www.vdma.org ZVEI Zentralverband Elektrotechnik- und Elektronikindustrie e.V.; is an association of companies operating in the electrical industry in Germany; Office: Frankfurt a. M., Internet: www.zvei.org

IT Security law The German „Gesetz zur Erhöhung der Sicherheit informationstechnischer Systeme” (“Law for increasing the security of information technology systems”),(short: IT-Sicherheitsgesetz or IT-SiG), which came into force with the publication of the Bundesgesetzblatt (on 25th July 2015, is the foundation of the Federal government’s “Digital Agenda” to improve security for citizens as well as companies with regard to the internet. The law describes the IT security requirements regarding so-called “critical infrastructures”. These are devices that are of central importance to communities. This also includes power supply, traffic, healthcare and telecommunications sectors as well as banks and insurance companies, etc. The operators of such “critical infrastructures” then had to make organisational and technical arrangements to ensure a minimum level of IT security proof of the implemented precautionary measures must be provided by means of security audits, tests or certification at least once every two years. Significant IT security incidents must be reported to the “Bundesamt für Sicherheit in der Informationstechnik (BSI) (Federal Office for Information Security) after occurrence. The BSI evaluates this information and makes the results available to “critical infrastructure” operators as soon as possible afterwards so that they can improve their own IT security. The IT security law extends BSI’s advisory function and warning capabilities.

The BKA’s responsibility for investigating IT crimes is also strengthened under this law. Furthermore, the requirements for providers of IT services under telecommunications and telemedia laws are increased The law will be supplemented by planned legislative ordinances, some of which are still being discussed.

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rpms and the pump performance data entered by the user. The App can only be used with KSB pumps and is provided free-of-charge.

3.8 Social media Mobile devices such as smartphones and Tablets have also contributed to the huge spread and use of social media. They enable the users to exchange information and media content between themselves or between groups. Anyone can communicate with anyone else using these devices and systems. Whereas private use is still well to the forefront today, applications as part of Industry 4.0 are also conceivable.

A current example is the “Shift doodle” shift planning app, which is a well-known internet planning tool that makes it easier to make a common schedule for several participants. “Shift doodle” is not only for private schedules, it is also a system for planning flexible working hours as well. The employees can then use their smartphones to decide whether they will report for a requested shift or not. The system was developed as part of the “CapaflexCy” project (self-organised capacity flexibility in Cyber Physical Systems), which was funded by the German Federal Ministry of Education and Research and which involves many organisations and companies. With “Shift doodle”, companies can manage employee utilisation in conjunction with the employees flexibly, at short notice and throughout the company. The required processing technology flexibility can be realised in conjunction with revisions, maintenance, modifications or problems. Not all of the work can be planned in advance with regard to these contexts.

3.9 General development In the future it can be expected that distributed sensors and other information providing components in conjunction with technical software components as well as mechanical and electronic parts will communicate via a data infrastructure such as the internet.

This will result in so-called embedded systems, which make it possible to control and manage even complex decentralized production processes without the need for human intervention. A good example of this is the driverless car, whereby GPS controls and finds a predetermined target whilst taking into consideration unpredictable road traffic situations. Systems that work in this way come into being as the result of the networking of embedded systems through wired or wireless communication networks.

One can also envisage that large, widely distributed and complex systems will exist and that they will be highly dynamic and be able to automatically adapt themselves to meet the respective requirements as well. For example, they can be used with automatically working power and water supply systems, for controlling traffic or needs-oriented controlling of a technical production plant. Even military early warning and defence systems are based on cyber physical systems.

The terms “intelligent factory” or “smart factory” are used in conjunction with a production facility. For example, the employees in an “intelligent factory” can be supported through information and communications technologies. Machines and plants are networked and they communicate amongst themselves and organise largely on their own in order to process and complete production orders.

4. Cyber security Cyber security has become more important than ever before as a result of the increasing integration of communications and information technologies into processing technology, mainly in conjunction with big data analytics or cloud-based platforms. This is a condition for the development of Industry 4.0. The “Increasing the security of information technology systems” law (i.e. the IT security law), which came into force on 25th July 2015, was the first step taken by the legislators to guarantee the security of IT systems with “high importance with regard to polity” in Germany.

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It applies to operators of “critical infrastructures”, such as power and water providers and these are already being controlled and managed today over the internet. The operator now has to fulfil a range of legal obligations in order to guarantee the security of his IT system (see separate note).

It is also expected that a significant expansion of technology-oriented IT services will be interlinked with the development of Industry 4.0. This includes cyber security services and their interlinked maintenance options. The development of systems and programs for detecting and defending against threats to the network will significantly define developments for Industry 4.0.

providers should also be included as huge optimisations are also possible throughout the company.

The company’s management must be aware that with the introduction of “Industry 4.0”, much of the data that is now considered to be “internal data” will have to be exchanged far beyond the company’s walls. This development must also be implemented and supported. In this context the question will arise as to what will actually benefit the company or the operation. This question must be answered for every measure. Against this background it can be expected that the transition to Industry 4.0 will be carried out over many small steps in the drive towards full processing technology.

5. Conditions for fast developments

Supplementary reading:

An important condition for Industry 4.0 is an extensive and secure broadband network with high connection stability and low latencies. A policy is required here that will create this condition.

A legal framework must also be created that guarantees adequate handling of the growing amount of company data both internally as well as externally. Harmonisation of the different national data protection guidelines is imperative with regard to the planned cross-border development. Furthermore, standards and uniform interfaces must be defined for exchanging information digitally.

The slogan “never change a running system” is often used in conjunction with technical processes. This slogan is understandable if one thinks that high security and reliability standards are guaranteed with the existing systems. The new system must first prove that it can meet the highest process technology level. This is why rapid change cannot be expected in processing technology.

However, suppliers and service providers who show possible developments in their offers or even new developments must also be considered. If this produces advantages, then they should also be used.

For example, for a supplier of filters with exchangeable cartridges this could mean that the cartridge change could be planned and implemented based on sensor data and software for estimating the remaining service life. Necessary spare part ordering can be realised automatically based on the inline recorded data. The optimum changing time and the necessary employee utilisation planning can be determined by taking into consideration the production planning data. The example shows that in this case the offer goes far beyond the provision and supplying of functional and exchangeable cartridges.

Affected employees must be included and trained accordingly with regard to developments for Industry 4.0. Suppliers and service

Leitfaden Industrie 4.0 – Orientierungshilfe zur Einführung in den Mittelstand Published by: VDMA in cooperation with the Department of Data Processing in Construction at the TU in Darmstadt and the wbk Institute for Production Technology and the Institute of Technology (KIT) in Karlsruhe Can be obtained from: http://leitfaden-i40.vdma-verlag.de/; free-of-charge for VDMA members, non-members must pay a token fee of 40 euros plus VAT as well as the shipping costs.

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Industrie 4.0: Auf dem Weg zur smarten Fabrik – die Elektroindustrie geht voran Published by: ZVEI Can be obtained from: www.zvei.org/verband/publikationen (free-of-charge) Whitepaper 4.0: Industrie 4.0 – Von der Vision in die Praxis Published by: Bosch Can be obtained from: www.bosch-si.com (free-of-charge) Industrie 4.0 –Whitepaper FuE-Themen Published by: Fraunhofer Institut for Production Technology and Automation (IPA) Can be obtained from: http://www.ipa.fraunhofer.de/fileadmin/ user_upload/Leitthemen/Industrie_4.0/ (free-of-charge) Industrie 4.0 – Chancen und Perspektiven für Unternehmen der Metropolregion Rhein-Neckar Fraunhofer IPA study under contract to the Industry and Chamber of Commerce, Rhine-Neckar, Palatinate and Darmstadt Rhine-Main Neckar; 64 pages (free-of-charge)

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Processing machines communicating with extraction systems Keller Lufttechnik GmbH + Co. KG reports on an example of what Industry 4.0 makes possible and what this involves. A system was installed, in collaboration with Festo, in their new technology facility in Scharnhausen near Stuttgart, whereby the processing machines and extraction systems are networked together in the production halls. Permanent monitoring of many different plant parameters enables optimum operation as well as planned maintenance and care to be realised. Festo has also launched a new extraction concept that decisively improves the quality of the air in the hall.

Turning, drilling, milling and grinding all take place within the 66,000 m2 technology facility. Valves, valve terminals and electronic products are manufactured here as well as other products. The claim is that the machines communicate with each other and the employees via the internet and this improves the processes and also increases the availability of the equipment.

The initial approaches were implemented in Scharnhausen.

Example: Extraction systems One example that is already in use is simultaneous extraction from over 100 processing machines. Coolant mist and any dust must be removed from the relevant machining cabin and a specific air change must also be maintained so that the machines can continue the high-quality workpiece machining. The associated air volume must be extracted and be reliably cleaned by the separators. The extraction systems need to communicate with the processing machines to be able to realise this. It would automatically readjust itself if the extraction power wandered out of the defined tolerance range.

However, this should never happen. Festo, in collaboration with the experts from Keller Lufttechnik, has developed a system that allows permanent monitoring of the plants. The system will generate alerts in good time if parameters such as the differential pressure or filling level start to exceed or drop below specific limit values.

The data is only recorded by Festo at the present moment. The system will become

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Fig: The new extraction concept decisively improves the air in the production hall in Festo’s new technology facility

internet-based in the future so that it can also be accessed by the experts at Keller Lufttechnik. Care and maintenance can be planned and optimised through such monitoring. It is envisaged that Festo will no longer have to stock spare parts in the future. The monitoring system should report the need for spare parts well in advance so that the required parts can then be purchased. This will reduce the warehousing costs.

The excellent air quality in the production hall is a huge plus-point for the new factory from the employees’ point of view.

Festo kept to all the limit values in the old facility, but the air in the production hall always smelled strongly of coolants. Every processing machine had its own small separator working in recirculation mode, i.e. the filtered air flowed back into the hall.

This resulted in residual emissions that were not removed being transitioned into the gas phase as part of the lubricants and passed through the filter. Festo decided on a continuously operating central extraction systems for the new facility.

Keller Lufttechnik was authorised to design and implement this system. Festo is very satisfied with the result of this collaboration. Together with Keller Lufttechnik,

Festo implemented a total of twenty process extraction systems, each of which centrally filters ten to twelve machines and then feeds the filtered air into the open air.

The idea of feeding the warm extracted air through a heat exchanger and recovering the heat was also discarded. The building, which was awarded the highest platinum certification from the German Sustainable Building Association (DGNB), already produces a heat surplus and this meant that more heat recovery from the extracted air was not required.

The decision to convert the extraction systems in the production hall to continuous operation presented new challenges.

Those planning the new factory had to install meter-long pipelines that connect the processing machines with the separators and then feed them from there into the open air, so that they visually disrupted the hall as little as possible. A new fire protection concept was also needed as fires could spread through the pipes. All of the difficulties were mastered through excellent team spirit according to the participants.

Further information is available from: www.keller-lufttechnik.de Facility technology: www.festo.com/group/de/cms/10967.htm

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Measures for eliminating micro-pollutants during water and waste water processing Report from the 11th Aachen’s Conference on Water technology H. Lyko* Besides new developments in the field of membrane technology /1/, the elimination of micro-pollutants from waste water flows as well as during the production of drinking water was one of the two main topics at the 11th Aachen’s Conference on Water Technology held in November 2015, which was jointly hosted by the Institute for Chemical Process Engineering and the Institute for Environmental Engineering at RWTH /1/. Adsorption on activated carbon and chemical oxidation have both proved suitable for many substances as the technologies of choice for eliminating trace elements in the past. If one considers the diversity of the substances, their different (bio) chemical properties and the diversity of possible substance combinations and concentration proportions in different drainage areas on the one hand and the local conditions for specific clarification plants or waterworks on the other hand, it becomes clear that a universal “plug-and-play” plant for the removal of micro-pollutants does not exist. Besides, if the overall relatively low substance concentrations are taken into consideration, not every process is equally or economically relevant to water protection at every location. Different types of adsorption and oxidation processes as well as various combination processes were also presented and discussed at the Conference.

The significance of micro-pollutants with regard to water pollution control The loading of surface waters with micro-pollutants, which predominantly emerge from waste water treatment plants, is directly related to the effort needed for treating drinking water, especially if the raw water needed for the production of drinking water is extracted directly from rivers. This is generally the case in in North-Rhine Westphalia. Dr Viktor Mertsch, from the Ministry for Climate Protection, Environment, Agriculture, Nature Conservation and Consumer Protection in the State of NRW, described the situation in this state where the extraction of water for drinking water purposes is only 2 km from the nearest inlet to a clarification plant in some places. From a total of 637 clarification plants in NRW, about half are responsible for the fact that about one third of the water bodies, in which they discharge their own effluent, consists of waste water. As things currently stand, it will be difficult to achieve compliance with the EU requirement of nationwide ecologically intact waters by 2027. The target value for the micro-pollutants is a concentration of 100 ng/L for each substance that is being considered.

The PNEC values (Predicted No Effect Concentration) are clearly exceeded espe* Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

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cially in the effluents of smaller treatment plants and the different depositions accumulate in the flowing water. For example, the contamination caused by the medicament Dichlophenac is sometimes around 20 times higher than the PNEC value. A reduction in these loads can be attained either through manufacturing and application prohibitions or by improving the efficiency of industrial and municipal clarification plants as well. With the start of the 2nd water management plans in NRW, the wastewater treatment plants have had to measure the microbial concentrations in their processes since the beginning of

2016. The initial planning manual for plants that eliminate micro-pollutants is already available and their construction will be subsidised /2/ .

Adsorption on activated carbon Activated carbon adsorption processes have been and are being examined using Powdered Activated Carbon (PAC) or Granulated Activated Carbon (GAC) as well as special types of abrasion-resistant, spherical adsorbent agents or coarsegrained powder activated carbon. The general difference between the processes that use PAC and those that use GAC is

Fig. 1: Flowchart of micro-pollutants elimination process with continuous counterflow adsorber (Picture: IUTA)

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Fig. 2: Experimental setup for continuous counter-flow adsorption using highly activated, abrasion-resistant adsorbents (Photo: IUTA e.V.)

that the powdered adsorbent passes through the plant once and is separated at a specific point and is not reused as an adsorbent again, whilst the GAC remains in the system for a longer time and is periodically regenerated.

In Aachen, the following issues were discussed with regard to different activated carbon processes: - At what stage does adsorption occur during a clarification process?

- What elimination rates were implemented using which quantity / volume concentrations of absorbent?

- How is the dispersed PAC most effectively separated from the water phase and how, if necessary, is the transition of the carbon particles into the effluent of the treatment plant monitored?

- How is the penetration of the GAC monitored and which regeneration process is economical and how it is controlled?

From the comparison of the different research projects involving activated carbon adsorption, no absolute elimination rates can be determined for specific micro-pollutants, since the boundary conditions are too different (types and absorption capacities of the carbons, concentration or contact time, etc.), but general trends indicate which substances are easily adsorbed and those that cannot be adsorbed or only if high amounts of activated carbon and delay times are used. The former include polar substances such as carbamazepine, metropol or benzotriazole and acesulfame and gabapentin /1/ as well as X-ray contrast agents are included amongst the latter /2/. The dosing of the PAC into a downstream cleaning stage becomes advantageous if a unit for the subsequent separation of the carbon is already available. This is the case in clarification plants where a flocculation filtration system is installed to eliminate the phosphor. Johannes Altmann, et al., from the Berlin Technical University and the Berlin Water Authority,

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have examined this PAC dosing and flocculation filtration combination using a pilot filter equipped with anthracite and quartz sand and varying the PAC concentration. In order to obtain high elimination rates of about 90% or more for more easily adsorbable micro-pollutants, it was necessary to use PAC concentrations of 35mg/L or even higher. With some substances, a biological transformation acting as a degradation mechanism in the filter was also detected. Other PAC separation methods have to be found if a flocculation filter is not connected up to the secondary clarifier.

Nikolai Otto et al., have been experimenting with a combination of hydro cyclones and cloth filters at the Institute for Sanitary Engineering at Stuttgart university /3/. PAC with coarser particles was also used (x50 = 96 μm) as compared to a finer carbon (x50 = 26.9 μm) in order to increase the separation efficiency in the multi-hydro cyclone separator. On average, the coarser PAC improved the separation efficiency in the multi-hydro cyclone by 16%. The disadvantage of the coarser carbon, which is based on raw materials other than the finer ones, is its low elimination efficiency with regard to the micro-pollutants. This could be improved by recirculating the carbon through additional dosing, but it was found that the coarser carbon was pulverised in the pump, which further worsened the separation rate. A separation efficiency of more than 90% of dispersed carbon particles could only be achieved by using downstream cloth filters. Due to the fact that one can expect partial discharge of PAC into the effluent of the clarification plant when using PAC in secondary clarifiers or similar, the necessity exists to determine them quantitatively and thereby clearly isolate them from the other suspended solids.

A new method was developed in Stuttgart for this and it is based on measuring the pure density differences between the PAC and the other solids. Andreas Vogel, et al., presented the results from comparative measurements made using this method and semi-quantitative detection using optical comparison of filter blackening as well as by thermal analysis. In the pure density process, samples of clarification plant effluents were analysed with and without a known PAC concentration (PAC with a known pure density), so that a type of calibration curve (correlation between pure density and PAC concentration) was created. Thereby unknown samples from the same clarification plant process can also be analysed using density measurements. This process is more accurate than comparing blackening from filters and easier to handle and more cost-effective than using thermal analysis. But it is still in the experimental stage.

Fixed-bed adsorption filters using GAC can also be considered for use as an alternative to PAC. The effectiveness of the GAC is determined here as the throughput in the form of the number of bed volumes up to the penetration of the substances to be adsorbed. The carbon must be regenerated when the maximum absorption capacity is reached. F. Zhao is experimenting with the microwave carbon regeneration technology at the RWTH Institute for Environmental Engineering. He has determined the optimum reactivation operating conditions using orthogonal experimental planning. Initially this technology promises to use less energy than conventional regeneration methods and, unlike conventional processes, it can be installed directly in the clarification plant.

A continuous process that uses regenerable adsorbents requires the carbon particles to be controlled and circulated between the adsorption and regeneration reactors. The mechanical stability of conventional granulated activated carbon is insufficient for this purpose. However, the polymer-based adsorbents made by Blücher GmbH, Erkrath, exhibit this abrasion resistance. In a cooperation project with the Institute for Energy and Environmental Technology (IUTA) in Duisburg, a process for counter-flow adsorption with in-situ regeneration is currently being developed and tested in an experimental plant at IUTA (see Figs. 1 and 2).

Franziska Blauth described the process concept and the individual stages in which dry adsorbents are introduced into the reactor,

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wetted and transported through the adsorption reactor and then discharged again.

The particles must be dewatered and fed in for regeneration afterwards. This shows the importance of the abrasion resistance in the polymer-based adsorbents as compared to conventional activated carbon.

This material is also characterised by its high adsorption capacity, which is hardly affected by frequent regeneration.

Example of the oxidation process The work carried out with regard to the possible oxidation processes dealt with the following questions: - Which possibilities and limits are produced by the different oxidizing agents (ozone, H2O2 and photocatalytic degradation by TiO2 and UV radiation) - What elimination rates can be realised by using different substances?

- How was the oxidation integrated into the entire plant?

- How was the elimination efficiency monitored?

- How does one deal with possible by-products?

Extensive experience has been gained with the degradation of micro-pollutants through the use of ozone at the Swiss Federal Institute for Water Supply,

Wastewater Treatment and Water Protection (EAWAG). The results of a practical test for controlling the ozone dosing using absorbance measuring at the Neugut waste water treatment plant are shown here. This clarification plant is the first Swiss clarification plant to have full ozone technical treatment for the entire waste water treatment process. In order to be able to optimise the dosed quantity of ozone to the raw water load, i.e. in order to be able to achieve adequate elimination of the micro-pollutants and to prevent over-dosing and the danger of generating unwanted by-products, the UV light (254 nm) absorbency of the water has to be measured at the inlet to the ozonisation process. Online measuring of the absorbency differences between the inlet and outlet of the ozonisation reactor was also considered as a further strategy. Although this method is not optimum with regard to the signal quality at the reactor outlet, it is considered to be even more promising as the actual effect of the ozone on the water constituents can be included in the dosing control process.

Biocides are assumed to be potentially hazardous to water ecosystems due to their usage quantities and impact. V. Linnemann has been examining the effects of different oxidation processes on the

BenzyldiMethyl-Dodecyl Ammonium chloride (BDMA), Benziso-thiazo Linon (BIT) and Irgarol (IRG) model substances in pure water at the RWTH in Aachen.

The combination of UV254 irradiation and H2O2 dosing was identified as a process with a high degradation rate with regard to the substances that were monitored. In this presentation it was also made very clear that 90 % degradation of a model substance does not mean complete mineralisation, but that organic reaction products are formed that might be possible to degrade biologically.

Using the photocatalytic effect of TiO2 for the degradation of organic water constituents in the presence of UV light is known in principle. An arrangement must be created in any possible technical implementation in which the catalyst is brought into direct contact with the water and good light irradiation is ensured. Ira Brückner, from the Eifel-Ruhr Water Association, used an inorganic binder, a type of coating, to fix TiO2 in a carbon-doped anatase modification on a glass plate. During the experiments that were carried out to degrade diclofenac, it was found that this novel TiO2 catalyst is suitable for removing the substance up to just below the detection limit. However, the film of coating used to fix the catalyst in place

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substances adsorbed on the CNT tube and to the subsequent regeneration of the adsorber. The fact that the Fenton reaction does not occur in the wastewater itself but in the special electrolyte solution means that the electrolyte solution can be used several times and the waste water does not have to be acidified and neutralized again afterwards. The adsorbing gas diffusion electrode made from CNT is produced using a hollow fibre membrane for the microfiltration process. The procedure as well as the initial results using an azo dye as the model impurity are described in detail in /4/.

Combined processes that use membrane technology

Fig. 3: TiO2 activated foam ceramics with different pore widths fitted in a flow cell and used for photocatalytic disinfection and elimination of micro-pollutants (Picture: Fraunhofer IKTS)

during in the photocatalytic reactions was also attacked and visually damaged.

At the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) foam ceramics modified with TiO2 were made and tested for their suitability for use in micropollutant elimination and disinfection processes. As Erik Schulze et al. has shown, one has to find a compromise between the inner surface and the ability to illuminate the whole structure, which is an indispensable prerequisite for activating the catalyst when selecting the pore size of the shaped ceramic bodies. The foam ceramic is fitted in a flow-through cell (see Fig. 3). The optimum experimental conditions (volumetric flow and foam configuration) were determined by analysing the production of OH radicals. Carbamazepine (CBZ) and diclofenac (DCF) were then used as model substances for measuring the degradation efficiency. This showed that the substance concentrations did not decrease linearly with the irradiation time, but approached a minimum asymptotically. 26 mg CBZ could be degraded to 87% from 10 L of solution and to 95% from around 30 mg of DCF after 240 minutes of treatment time. The disinfecting effect of this process was determined using samples from a clarification plant in which the measured E-coli reduction was dependent on the number of passes through the cell.

The emitter expended 64 KWh of energy in order to achieve the reduction of the model substances in the 10 L solution mentioned above. 1.6 KWh/m3 were needed to disinfect the clarification plant in order to fulfil the Bathing Water Directive.

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A completely new method of micro-pollutants oxidation using electro-Fenton processes has been described by Youri Gendel, Hannah Roth et al., from RWTH Aachen. The oxidation of organic substances takes place in such a process with the help of OH radicals, which were formed beforehand through the reaction of bivalent iron ions with hydrogen peroxide: Fe2+ + H2O2 è Fe3+ + OH- +OH+ The disadvantages of the classical electro-Fenton processes are the reaction conditions (pH 2.8 - 3.0), the necessary separation of the Fe3+ ions together with subsequent disposal of the iron-containing sludge as well as the elaborate structuring of the gas diffusion electrodes that were used to help oxidise the oxygen into H2O2.

In the process described here, a microtube made up of carbon nanotubes (CNT) acts both as a high-porosity adsorber as well as the gas diffusion electrode /4/. This micro-tube is fitted inside a PVC cylinder and is surrounded by a cylindrical electrode made of a titanium fleece in which a platinum-iridium catalyst is embedded.

The waste water that has to be treated passes through the space between the CNT tube and the titanium fleece during the initial processing stage. The organic water constituents are first adsorbed without electric current onto / into the CNT. In the second stage, an adapted electrolyte solution containing Fe2+ ions is passed into the ring gap, as well as oxygen into the interior of the CNT micro-tube with voltage applied. The formation of H2O2 at the gas diffusion electrode and the subsequent Fenton reaction results in the oxidative degradation of the organic

Various possibilities were considered for the integration of one or several processes for eliminating the micro-pollutants as well as the membrane technology in waste water treatment plants and these are shown in a very simplified form in Fig. 4. The flocculant dosing position is not shown in the graph nor is the resulting re-circulation of the partial flows.

The combination of a membrane bioreactor and PAC adsorption appears interesting because the PAC retention problem is completely resolved here and the membrane’s barrier effect also contributes to the hygienisation of the water.

Jonas Löwenberg, from WABAG Water Technology, examined such a process combination using deep bed filtration in comparison to PAC dosing, whereby the membrane and deep bed filtration systems were installed in different clarification plants. Iron chloride was added as a flocculant in addition to the PAC. Pressuredriven ultrafiltration and an immersed microfiltration system were compared against one another as the membrane processes. The immersed modules were fitted with ceramic membranes and the external UF modules contained polymer multibore membranes (BASF-Inge). The presence of PAC in the immersed module caused a reduction in the TMP increase in the membrane and this was attributed to the adsorption of fouling agents and the abrasive effect that the carbon particles had on the layers on top of the membrane surface. The pressure-driven ultrafiltration system was not affected by the presence of carbon and the flocculation also showed a positive effect on the filtration efficiency.

If the PAC concentration, which is based on the water’s CSB value, is similarly adjusted, a similar elimination rate for micro-pollutants can be realised using immersed microfiltration and deep bed filtration. The combination of PAC dosing into an aerating tank with ultrafiltration provided by immersed hollow fibre mod-

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Fig. 4: Simplified representation of the possible classification of adsorption and oxidation processes as well as membrane processes in waste water purification with specific trace element elimination. The term “post-treatment” can mean process-related PAC separation, residual ozone elimination or, if necessary, biological post-treatment after oxidation

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with and without the addition of H2O2, ozonisation and activated carbon filtration downstream from a semi-technical membrane bioreactor. The waste water came from two clinics with different

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ules was developed by GE Water & Process. Sven Baumgarten et al. described the comparisons between a conventional activated sludge process with a downstream contact reactor and filter, an activated sludge process with simultaneous PAC dosing and a downstream filter and a MBR reactor equipped with ZeeWeed hollow fibre modules into which the PAC is added simultaneously.

The latter combination has proven itself during a 7-month test in a Swiss clarification plant. The adsorption capacity also benefited from the increased age of the sludge and better PAC availability as compared to the PAC dosing / flocculation combination. High micro-pollutants elimination efficiency (> 90%) was detected overall. A negative effect on the service lives of the membranes is not expected due to the low PAC levels.

In addition to the PAC dosing in front of the membrane modules, several projects were also presented in which MBR technology was used in subsequent downstream processes. The advantage of this is that the membrane filtration alone contributes to a certain retention of specific substances and that, in the case of adsorption processes, no competition from the adsorption of biodegradable ingredients and persistent substances is to be expected.

MBR processes that used downstream adsorption and/or oxidation were tested in two projects for treating waste water from hospitals and nursing homes. Josean Gil, from Grundfos, presented the results obtained using bio-booster technology, a pressure-driven, dynamic membrane filtration (see /4/) and two parallel strands with GAC adsorption and ozonisation used in different sequences.

UV disinfection was the last polishing stage in both cases. The experiments were conducted using waste water from the Herlev (Copenhagen) university hospital. The results show that some of the substances from the extensive list of analysed medicaments are already retained to a large extent in the MBR system. With regard to the effect of the two downstream GAC and ozonisation elimination methods, the variant with the adsorption proved to be the most effective, whereas not all of the micro-pollutants concentrations could be pressed below the PNEC level in the other variant. The total treatment costs for the best process combination are less than one third of the costs incurred by the clinic for the discharge of its own waste water into the sewer. Danièle Mousel, from ISA at RWTH, reported on comparative studies conducted on the degradation efficiency of the three UV irradiation processes

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priorities and a nursing home. A material-dependent retention of up to 95% could be measured just in the MBR here.

In general, all of the other elimination processes have also been found suitable for removing the medicament residues and the metabolites.

Marcel Koti, from the IWW Water Centre in Mülheim, examined processes which ran according to the diagram shown at the bottom in Fig. 4. Membrane filtration used as integral part of the further purification of the effluent from a conventional clarification plant, was placed behind the ozonisation. Only ceramic membranes exhibited the necessary chemical stability.

AL2O3 microfiltration membranes made by Metawater were used for this. PAC and, in almost all cases, flocculants were dosed into the membrane filtration inlet in some experiments. The presence of ozone on the membrane surface had a positive effect on the hydraulic operating performance part of the membrane filtration process.

ASKURIS and IST4R The joint ASKURIS and IST4R projects sponsored by the German Federal

Ministry of Education and Research and several Institutes from the TU Berlin, the Berlin Waterworks, the Berlin Water Competence Center, the Federal Environmental Agency, the Helmholtz Center for Environmental Research in Leipzig and the state water supply in Stuttgart, represent an integrated approach to the subject of micro-pollutants. It considers the partially closed water circulation system, in which the Tegel lake is integrated as an inlet water and drinking water reservoir. The lake collects the clarified waste water from the Schönerlinde clarification plant after it has passed through a further phosphorus removal treatment stage before entering the confluence.

Prof. Martin Jekel, from the Department of Water Conservation at the Technical University of Berlin, described the important results from these projects, which have now been completed, whereby in addition to assessing the effectiveness of various elimination procedures he also included the further development of analytics for the detection of trace elements and an energetic assessment of the elimination processes. The results presented on the project’s website show how the

costs increase and the CO2 footprint of micro-pollutants elimination also increases with increasing expenditure (carbon consumption or ozone concentration) (more detailed information available at: askuris.tu-berlin.de). Unfortunately there are still substances that cannot be eliminated without great expenditure, especially the X-ray contrast agents.

Literature: /1/ J. Pinnekamp, M. Wessling: Wassertechnologie in der Wasseraufbereitung und Abwasserbehandlung; 11. Aachener Tagung Wassertechnologie, 27.-28. Oktober 2015, ISBN 978-3-95886-056-8 /2/ ARGE Kompetenzzentrum Mikroschadstoffe. NRW (Hrsg.): Anleitung zur Planung und Dimensionierung von Anlagen zur Mikroschadstoffelimination; Stand 20.03.2015 /3/ M. Jekel: Zusammenfassung der Verbundprojekte ASKURIS (Anthropogene Spurenstoffe und Krankheitserreger im urbanen Wasserkreislauf: Bewertung, Barrieren und Risikokommunikation) und IST4R (Integration der Spurenstoffentfernung in Technologieansätze der 4. Reinigungsstufe bei Klärwerken), Abschlussveranstaltung 14.

September 2015, TU Berlin, s. askuris.tu-berlin.de /4/ H. Roth, Y. Gendel, P. Buzatu, M. Wessling: Tubular carbon nanotube-based gas diffusion electrode removes persistent organic pollutants by a cyclic adsorption – Elektro-Fenton process, Journal of Hazardous Materials 307 (2016), S. 1-6 /5/ H. Lyko: Membrantechnik zur Wasser- und Abwasseraufbereitung: Ergebnisse der Modul- und Verfahrensentwicklung – Bericht von der 11. Aachener Tagung Wassertechnologie, F&F Filtrieren und Separieren 30 (2016) Nr.1, S. 25 – 29

Fig. 5: Site plan with indicated measuring stations and measured trace concentrations from the Tegeler See water circuit (Image: TU Berlin, Faculty III Process Sciences Institute of Technical Environmental Protection, Department of Water Conservation

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Water ferns used to separate oil from water K. Schinarakis *

Literature: /1/ C. Zeiger, I. C. Rodrigues da Silva, M. Mail, M. N. Kavalenka, W. Barthlott, H. Hölscher: Microstructures of superhydrophobic plant leaves - inspiration for efficient oil spill cleanup materials. Bioinspiration & Biomimetics. DOI: 10.1088/1748-3190/11/5/056003 Online publication: http://iopscience.iop.org/article/10.1088/1748-3190/11/5/056003

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Some water ferns can absorb large amounts of oil in a very short time. Their leaves are extremely water-repellent and they can also bind a large amount of oil. A research team from KIT has discovered, together with colleagues from the University of Bonn, that the water plants owe their oil-binding properties to the hair-like microstructure on the surface of their leaves /1/. This discovery now serves as a model for the further development of a synthetic material called Nanofur. This material should make it possible to eliminate oil pollution in an environmentally-friendly way.

Conventional methods for removing oil spillages have specific disadvantages. Burning the spilt oil as well as the use of chemical agents to accelerate its decomposition, both pollute the environment. Many natural materials used for absorbing spilt oil, such as sawdust or plant fibres, are less efficient because they also absorb large amounts of water. The researchers compared different species of water ferns in their search for an environmentally-friendly way to remove oil spills. It was already known that the leaves of these plants are water repellent. The oil absorption property was studied very closely at KIT’s Institute for Microstructure Technology.

The water ferns, which originate from tropical and subtropical regions, are now found in parts of Europe as well. They are regarded as a bothersome weed in some places as they propagate prolifically. However, they have the potential to be used as low cost and environmentally-friendly oil absorbent. The leaves reach their maximum absorption level after less than 30 seconds and they can then be scooped up together with the absorbed oil. An aquatic plant with the biological name of Salvinia has trichomes on the surface of its leaves, which are hair-like runners, between 0.3 and 2.5 mm in length. It was seen that the leaves with the longest hairs were not necessarily the ones that absorbed the majority of the oil when different species of Salvinia were compared to one another.

It is also the shape of the hair ends that is decisive with regard to the oil absorption capability. The leaves of the Salvinia molesta species absorb the most oil, as their hair ends are interconnected in the shape of a whisk. The work was developed in collaboration with scientists from the Nees Institute for Biodiversity of Plants at the University of Bonn, which was founded by the bionics pioneer, Wilhelm Barthlott.

The researchers at KIT want to use their new knowledge about the interrelationship between the surface structure of the leaves and their oil absorption capacity in order to improve the developed material called Nanofur. This synthetic nano-skin imitates Salvinia’s water-repellent and oil-absorbing properties for separating oil and water.

The research was funded by a doctoral studies grant from the Carl Zeiss Foundation, Ciências sem Fronteiras, which is a Brazilian research and exchange programme and the Karlsruhe Nano Micro Facility (KNMF) high-tech platform at KIT.

* Kosta Schinarakis PKM – Themenscout Tel: +49 721 608 41956, Fax: +49 721 608 43658 Email: schinarakis@kit.edu

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Membrane technology for water and waste water processing: Findings from the module and process developments H. Lyko* As compared to previous conferences, the word “membranes” has disappeared from the title of the 11th Aachen’s Conference, but not from the programme (see /1/). However, it was so clearly split into two sections that one could not cover all of the topics even if one kept to membrane technology used for treating water only. Recording and elimination of micro-pollutants was another main focal point of the event in addition to the module and process developments.

Conventional clarification technologies were also highlighted under the aspect of the recent soar in requirements applying to waste water treatment. In order to be able to devote enough space to the event’s main topics, the coverage of the 11th Aachen’s Conference has been divided into two sections this time. This article focusses on selected presentations from the membrane technology sector.

The biggest MBR plant in the world Construction started in Stockholm on the Henriksdal communal clarification plant during the first half of the year 2016. This will be the final communal clarification plant for the Swedish capital and it will be upgraded membrane modules. The premium for the delivery of the with submerged membrane modules, which at today’s planning stage is a 700 million euro project and in the final expan* Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

sion phase these membrane reservoirs will cover an area equal to 230 football pitches, was given to GE Water & Process for supplying the immersed ZeeWeed 500 d LEAPmbr type hollow fibre modules. Jonas Grundestam, from Stockholm Vatten, described the procedures used during the planning and contracting for the plant and the technical details, whose implementation started in 2016. A feature of the plant’s location lies in the fact that all of the activation and filtration tanks are buried underground beneath rocks. This means that today’s design must include the necessary cleaning capacities that will last for a very long time, as short-term

expansion is hard to imagine. A detailed description of this project was published in /2/.

Module developments for MBR plants The market for immersed modules continues to develop dynamically and several of the presentations were dedicated to new and further developments in this sector.

The third generation of the IPC concept (IPC stands for Integrated Permeate Channel) developed by the VITO research institute in Belgium, has now come into existence. Behind the IPC concept lies the motivation to combine the benefit of

Fig. 1 Overview sketch of the Henriksdal communal clarification plant in Stockholm, which will clean Stockholm’s entire volume of waste water after completion (design size of 1.6 million PE) (Image: Stockholm Vatten)

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Fig. 2: 2nd generation IPC membrane pocket: both sides of the membranes were mounted on a three-dimensional fabric (Image: VITO NV, Belgium)

Fig. 3: Laser welding process for securing the membrane onto the carrier plate in MicroClear filter cartridges (Image: Newterra GmbH)

the immersed flat membrane modules, namely the low-pitched braiding, with the backflushing capabilities of the hollow fibre module /3/. With the first and second generation of IPC membranes the self-supporting flat membrane was generated through applying the polymer solution directly onto a three-dimensional textile medium. The textile medium used for the first generation was knitted, whereas the membranes used during the second generation were made from fabric (see Fig. 2). This enabled the textile medium to fulfil the function of a stabilising sub-structure as well as being a drainage medium for the permeate. The permanent bonding between the textile fibres and the polymer in the membrane produces adequate stability during backflushing.

Producing the membrane on a three-dimensional knitted fabric has now finished but the 2nd generation membranes are still in the market introduction phase. With A3 GmbH one has found a partner who can integrate these membranes in a 35 m2 module.

The membranes are available as microfiltration membranes (0.2 0.3 μm) made from PES and ultrafiltration membranes (0.08 μm) made from PVDF. The third generation of these special membrane elements deviates from the textile support and drainage-structure concept, as these supports can be expanded too easily. The third generation has a 3.6 mm thick, double-walled layer of polycarbonate inbetween the membranes. The polycarbonate layers are perforated at the ends of the membrane and structured internally with horizontal lands so that horizontal channels are created for draining off the permeate. The membranes are directly polymerised, as they were with the textile medias, and permanent bonding is formed between the polycarbonate by letting the solvent for the membrane polymer solve also parts of the polymer plate. A separate processing step to seal the edges is not necessary and this concept also allows individual aeration of each specific membrane pocket. The 2nd and 3rd membrane pocket generations were tested in laboratories using industrial and communal waste water and were compared to a commercial, non-backflushable plate module.

The two types of IPC membranes render the critical flow and therefore the flow rate at which the module permanently operates can be increased considerably.

The basic design of the MicroClear membrane module from Newterra GmbH has been in existence for a few years. In his presentation, Dr. Peter Ohles showed the specifics of the module’s design, in which robust plastic injection moulded support plates are welded onto the lands at both ends of the flat membranes.

The patented laser welding process (refer to /4/ as well) fuses the membrane’s support layer onto the filter plate material, without the membrane being damaged (see Fig. 3) and this enables backflush-

ing to take place without the membrane being detached from the support plate. The channels, through which the permeate can flow out, form inbetween the welding lines. Special features of the module now being provided are the permanent hydrophilic PES membrane, which can dry up and be wetted again as well as optimised module aeration (medium-sized bubble aeration). A module with an 80 m2 membrane surface was installed in a container unit at the clarification plant in Gießen and was tested using waste water from the primary treatment plant. A larger one with a 400 m2 membrane surface has been installed in the training centre simas at the clarification plant in Seelscheid. Average permeabilities (temperature corrected) of 289 l/(m2 h bar) were realised during a trial period of several months. The purging air requirement amounted to around 5 Nm3 air/m3 of filtrate (as measured in Gießen) and, according to details released by Newterra, this is approx.50% less than when using conventional (not specified) plate systems. The MicroClear cartridge product family grew in 2015: 640 and 800 m2 membrane surface sizes are now available (see Fig. 4).

A new company called Membion is a pure development company that has set itself the goal of developing a new, improved membrane module with innovative operating concepts especially for MBR applications. The new module should be compatible with the established systems from the main competitors available on the market. Dr. Klaus Voßenkaul, who in former times had developed the Puron hollow fibre modules produced at Koch, presented

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Fig. 4: MicroClear filter cartridge BG-MX800 (Image: Newterra GmbH)

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the new hollow fibre module concept.

The existing disadvantages of commercial hollow fibre modules will be considered and eliminated during the concept’s early stages. The Membion membrane filter is similar to the Puron module, but only exhibits changed in-feed and distribution of the purging air. The disadvantage is recognised in particular here, whereby the air in the Puron modules has the opportunity to exit on the way from the bottom to the top of the membrane bundle so that

it will no longer affect the surface of the membrane. This phenomenon should have an opposite effect in Membion modules as the upward pointing open tube acts as an sheath around the hollow fibre bundle.

A very important part of the development work lies is in the completely newly designed foot element (Fig. 5). This element combines a membrane carrier, a sheath piece that holds the hollow tube for the membranes, the activated sludge infeed and the air as well as the permeate

Fig. 5: Details of the immersed hollow fibre module concept made by Membion GmbH (Image: Membion GmbH)

Fig. 6: Functional example of a Membion membrane filter (Image: Membion GmbH)

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drainage line. The sludge infeed and the patented air distribution system have also been designed so that both of the media are already mixed together before they enter the intermediate area inbetween the membranes. The existence of parallel flow channels, in which the smallest difference in the flow resistance will result in severe inequality with regard to the distribution of the entering volumetric flows, should be prevented in all cases, as well as the accumulation or establishment of extraneous materials. The tube surrounding the membranes not only represents a side barrier for the ascending air flow, but also creates a chimney effect that increases the crossflow speed. One is of the opinion that this could possibly result in an energy requirement reduction of up to 30%. To what extent the energy savings, which have only been determined theoretically at the time of the address, can be realised in practice will be determined in tests using sludge at the clarification plant of Konzen. The production and the testing of a functional sample (see Fig. 6) of the new module occurred as part of a project sponsored by the German Federal Environment Foundation. Whereas the prototype of the foot element was created in a 3D printing process, it will be produced for series production using an injection moulding process. In a large-scale module there will be 7 x 200 mm diameter tubes in a single stack and there will be 4 of these stacks in each module, giving an overall total of 1,500 m2 of membrane surface area.

The MBR system from Grundfos, which is marketed under the BioBooster name, is a dynamic filtration system with rotating membrane disks and integrated backflushing, in which both ceramic as well as polymer membranes are used. Ceramic membranes are preferable if frequent chemical cleaning is necessary. A single 6.3 m long and 500 mm in diameter pressure pipe has been designed for 10 m3/h (using ceramic membranes) or 13 m3/h (polymer membranes) of waste water. If ceramic membranes are used, average flow rates of 40 or 80 l/(m2h) can be achieved and regarded as a peak flow over a maximum of 5 days. Solid concentrations of up to 40 kg/m3 can be processed in this way.

8 pressure pipes will be provided on a single frame in each case as a system ready for connecting up with integrated pre-dewatering of the sludge at 4 – 8%. In Aachen, Josean Gil showed a clarification plant fitted with one of these systems for the complete treating of the waste water from the hospital in Herlev (Copenhagen).

The MBR plant integrated in this plant is one of several processing stages used for treating waste water and other processing

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stages for the elimination of pharmaceutical residues are also being tested. The tubular module from Pentair X-Flow is being used as an external module in MBR plants. As in all cross-flow systems that use static membranes, the filtrate flow through the membrane is limited by the concentration polarisation and fouling. Dr. Jens Potreck reported on the experiments using a coil, made from thin wire or thread, fitted to the inner wall of the tube, which increases the turbulence and also reduces the tendency for materials to accumulate on the surface of the membrane. One has determined that the flow through the membrane will be increased with this type of internal fitting, but unfortunately, it also increases the flow resistance in the free cross-sections. Furthermore, the subsequent fitting of turbulence generating elements is seen to be too expensive for mass production. This is why a form of spacer consisting of membrane polymer was integrated into the inner wall of the tube during production. The protrusions caused by this on the surface of the membrane will not have sharp edges like an externally applied wire, i.e. the pressure loss caused by this will be vastly lower.

The coil-shaped roughness of the wall will impose a rotational movement on the flow. These membranes, which are called helix membranes, were installed in Airlift MBR systems, in which the membrane module is installed vertically and is supplied with air from below and in parallel to the conventional tubular membrane modules of the same design. The results from the communal sewage treatment plant in Antwerp have shown that an increase in the membrane flow of approximately 50 to 70 l/(m2h) can be achieved.

Even more pronounced is the difference when used in anaerobic MBR plants (no air supply), where the helix membrane shows a doubling of the flow through the membrane.

were recovered using nanofiltration afterwards. The phosphor was precipitated from the permeate afterwards by using a sodium hydroxide solution to increase the pH. The main focus of the study presented by Therese Krahnstöver was on nanofiltration.

The phosphor yield should be maximised by the highest possible metal retention through the selection of suitable membranes and processing conditions. The phosphor will exist as phosphoric acid under acidic conditions and can pass through the membrane.

Four nanofiltration membranes were tested and their respective resistances to acid were taking into consideration. It shows the dependence of the phosphor yield on the transmembrane pressure difference and the pH value. The higher the TMP, the smaller the required membrane area, but the phosphor yield will also be reduced. In addition to this, the passage of metal ions increases with the increasing pH value and the increased amount of high concentration in the raw solution. A maximum phosphor yield of 84% can be realised through the use of diafiltration. Whether and under which conditions and with which membranes the process becomes economical, was not conclusively clarified according to the described tests. Carrying out pilot trials on a large scale is recommended here.

Dairy operation without an external water connection Industrial waste water treatment reduces the quantity of waste water that has to be transported away as well as the associated costs resulting from it and the procurement cost of the fresh water will also be reduced by reusing the treated waste water. Dairy operations are one of the biggest consumers of industrial water.

Energetic optimisation through biogas generation The recovery and generation of biogas from sludge is an option for covering the energy requirements of conventional clarification plants. Anaerobic sludge stabilisation is not normal in membrane bioreactors as the high oxygen content in the excess sludge means that it is not suitable for biogas recovery due to the effects of the crossflow aeration. One is always looking for options to reduce the external energy demand as MBR plants already consume more energy than conventional plants. Daniel Bastian, from the Institute of environmental Engineering at RWTH Aachen, described the experiment, in which a membrane bioreactor plant was integrated in the primary treatment plant. This experiment was carried out a two-line, semi-technical MBR plant belonging to LANUV NRW. A second membrane line without primary treatment was operated in parallel as the reference plant. The primary treatment process reduces the mass flow going into the MBR by approx. 20 to 30%.

This shows that the overall quantity of sludge and the biogas yield per m3 of waste water can be increased through primary treatment and that the cleaning efficiency of the clarification plant will not be effected. If the sludge is older than 25 days, then the membrane’s filtration efficiency will also not be effected. A reduction in the age of the sludge will have a positive effect on the production of gas and this will result in increased membrane fouling. A meaningful compromise needs to be found here.

Phosphor recovery from sludge The phosphates were removed from the waste water by precipitating them with metal salts either separately or simultaneously in the bioreactor plant. In order to be able to recover the phosphor contained in the sludge as a material, a trial was carried out at the University of Applied Sciences and Arts in North-West Switzerland, in which sulphuric acid was used to extract the chemically and biologically bound phosphor from the sludge whereby all of the suspended solids were separated using centrifugation and ultrafiltration and the metals still remaining in the solution

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Highlights 2016

If powdered milk has to be produced, then a total of approx. 85% of the raw materials used, i.e. the milk, goes through various concentration stages until it is evaporated as water or water vapour, which can be treated for reuse. Heribert Möslang, from Aquantis GmbH, presented the implementation of a process and waste water treatment concept, whereby a dairy in the Nestlé Group in Mexico was able to operate without the need for fresh water.

1,600 m3/d of groundwater was used in this operation before the implementation of the “zero fresh water” project. The project includes the treatment of 1,000 m3/d vapour condensate from the powdered milk production process and the continuous treatment of the dairy’s waste water. The condensate is treated using hygienic reverse osmosis followed by activated carbon adsorption and a disinfection stage and afterwards it still contains less than 5 mg/l in the TOC. For example, this makes it suitable for use as process water, i.e. the diafiltration water, provided that specific hygienic requirements are complied with. The waste water from the dairy is fed into an existing conventional clarification plant. Afterwards it is treated in a NEOSEP MBR plant developed by Veolia and is disinfected in a subsequent reverse osmosis process using UV irradiation and is then available for use as industrial water. Another plant example from a Belgian dairy was also presented, in which the vapour condensate was treated in a biological floating and fixed bed reactor (BiopROtector) and two membrane filtration stages (UF and RO). The biological stage is used to eliminate any organic trace elements in the vapour condensate, which are partially retained in the reverse osmosis process (as compared to Mexico: the RO permeate still contains a residual concentration in the TOC). A water quality can be produced using the combined processes that can be approved for use as replacement drinking water in dairies (e.g. as CIP water). This was confirmed by an analysis of the condensate treated in Belgium that was carried out by the IWW Water Centre in Mülheim.

An example of drinking water preparation The preparation of drinking water using membranes for separating suspended solids and hardness is technically well established. Furthermore, new application options for membrane technology are

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opened up. Among others, combinations of membranes with conventional processes are included. Andreas Wied, from the WAT membratec plant construction company, described different examples of various drinking water-works in Germany.

More specifically a low-pressure reverse osmosis for partial desalination in parallel to a fast decarbonisation and an ultrafiltration for decolourising the drinking water were shown. The management of the chemicals is of vital importance with regard to optimising a low-pressure reverse osmosis operation and focus is placed on the selection and dosing of antiscalants in particular. Ultrafiltration was combined with coagulation for the decolourisation process. The selection of the coagulant is decisive with regard to the final filtering capability and pinpoint dosing can be provided in a large technical plant by using a controller, which works in conjunction with SAK254 online measuring. Another important aspect for ensuring safe plant operation is cleaning management and the implementation of flexible, self-detecting management was shown as an example. Different pre-programmed cleaning levels based on the membrane permeabilities and the degree of membrane contamination were chosen for the membrane here.

The colouring of raw water used for the production of drinking water is generated by multiple humins, that is natural organic materials (NOM). Dr. Volker Preuß, from the Institute of Water Technology at the BTU in Cottbus-Senftenberg, reported on the experiment that was carried out to remove this matter through the use of direct ultrafiltration without any coagulation. In laboratory tests with UF membranes made from PES that exhibit separation limits of 1, 3, 5 and 10 kDa, complete decolourisation was successfully achieved using the three finest membranes. When compared to different water samples taken from various groundwater plants it could be seen that membrane retention clearly depends on the aromaticity and molecularity of the dissolved organic matter and the salt content as expressed by the conductivity. The higher the aromaticity and the lower the conductivity, the better the membrane’s decolourisation capacity.

The tendency to membrane fouling and the effectiveness of the chemically supported flushing was tested in long-term tests that used constant membrane flows. A drop in permeability occurs after the filtration process starts due to irreversible fouling.

However, permeability losses occurring during further operation could be offset by flushing to the largest extent.

Drinking water treatment would be necessary at a consumption site where a hygienic and harmless public drinking water supply cannot be guaranteed.

For example, this is the case in certain regions of India, as the demand for household drinking water preparation sytems is increasing. They are available at clearly different prices and use different techniques. Benedikt Aumeier, from the Institute for Mechanical Process Engineering at RWTH Aachen, reported on stress tests carried out at an electrically driven system that was equipped with expensive ultrafiltration and reverse osmosis units as well as a simple gravity-driven system. The latter consists of microstrainer filtration and two activated carbon stages with intermediate passive chlorine dosing. The plant equipped with membrane filters was approx. 15 times more expensive but it can treat virtually 5 times as much water and also uses a screen and activated carbon filter at the inlet, an activated carbon filter after the RO module and UV disinfection at the outlet. UF and RO modules are operated in parallel and the two flows are mixed together afterwards. The proportion of the overall water volume flowing through the RO module was 93% during the stress tests. The stress test, which was carried out in accordance with the recommendations of the US Department of the Environment and the WHO, provides for chemical (organic materials and salts), physical (clouding, suspended solids) and microbial loads through E-coli and MS2 phage. The most important result of the test was: microbialy-clear water could be produced using both systems. The membrane system also fulfils the reducing clouding, colouring and salt content functions. Neither of the two units could maintain a nominal flow rate over more than three days under the stress test conditions.

Literature: /1/ J. Pinnekamp, M. Wessling: Wassertechnologie in der Wasseraufbereitung und Abwasserbehandlung: 11.

Aachener Tagung Wassertechnologie, Aachen, 27.-28.

Oktober 2015, ISBN 978-3-95886-056-8 /2/ J. Grundestam: Stockholm’s Future Wastwater treatment – Building the worlds’s largest MBR; F&S Global Guide of the Filtration and Separation 2016-2018 , p. 229234, ISBN 978-3-00-052832-3 /3/ H. Lyko: neue Flachmembran auf Spacerstruktur für getauchte Systeme; F&S Filtrieren und Separieren 23(2009) Nr. 2, S. 87 -88 /4/ Weise Water Systems GmbH: Filtertasche, WO 2008/055486 A1, 15. Mai 2008

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Optimized operation at Löhnen / Dinslaken water treatment plant, the largest drinking water nanofiltration plant in Germany J.-J. Lagref, N. Bischoffberger, R. Reisewitz *, M. Binder, M. Hörsken ** Introduction To ensure the water supply for the city of Dinslaken (Germany), the water treatment company – Wasserwerk Dinslaken GmbH – has since 1961 operated the Löhnen plant which is located approximately 2.5 km from the river Rhine (Fig.1).

The water treatment plant (unit 1), fed by 6 vertical wells and driven by large pumps (150 m3/h each), was in 1989 expanded by the addition of a second more flexible treatment unit (based on 3 speed-controlled pumps - 50 to 150 m3/h each).

Since the expansion of the process treatment plant in 2003 by the addition of a highly flexible duty Nanofiltration plant with two rapid cold softening reactors and 6 downstream turbidity filters, the plant reached a minimum processing capacity of 400 m3/h and a maximum treatment capacity of 1,100 m3/h. According to the existing water agreements, the two production * Dr. Jean-Jacques Lagref Norman Bischoffberger Robert Reisewitz Toray Membrane Europe Grabenackerstrasse 8b, 4142 Münchenstein, Schweiz Tel.: +41 61 415 87 64, Fax: +41 61 415 87 20 ** Marco Binder Michael Hörsken Stadtwerke Dinslaken GmbH

units (I and II) can allow the production of a total of 5.6 million m3/a. In the city, the daily highest water consumption is 19,000 m3/d.

The new filtration technique became necessary in anticipation of future coal mining projects in the area of Mommbach causing deterioration in feed water quality due to risk of over extraction of water from the local water table resulting in ingress of Rhine river bank filtrate (with it all unwanted impurities). After prefiltration of the well water by passing through gravel and sand filters, it feeds to the Nanofiltration Plant to remove any residual particulates and dissolved but undesired minerals and organics substances.

Energy supply of the Löhnen Plant The water treatment plant is connected to two 10-kV electrical power lines however a full-load operation can be achieved with just one electrical line which will deliver the needed 2.000 kVA power.

The second electrical line gives the ability to add an additional 700 kVA power.

In regards of the background previously detailed, and due to the fact that the membrane system is operated over a wide range of frequency, 2 air-cooled emergency electrical generators were installed with

Fig. 1: Aerial photo of the Löhnen drinking water treatment plant. The membrane filtration is located in the rear building.

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a capacity of 1.250 kVA each. This extra set-up ensures that during a power supply failure, the Nanofiltration Unit, both water production plants as well as the water pumping station can still function fully.

High retention The retention / rejection efficiency for the water constituents is determined by the type of membrane used. In the Löhnen plant, Toray TMH20-430 composite polyamide membrane elements were chosen following a pilot study at the RheinischWestfalische Institute for Water (IWW), which showed this membrane’s superior retention / rejection capability. The resultant water quality was close to that which could be achieved by conventional reverse osmosis membranes but with an inlet operating pressure of under 8 bar major energy savings could be made; hence the commonly used term - low-pressure / low energy reverse osmosis membranes.

The salt rejection of the selected membrane is 99.3%. The plant design enables a treated water capacity of 1.100 m3/h by having a parallel arrangement of 11 processing lines, each with a capacity of 110 m3/h (one line is kept as a reserve).

Each line is operated with a speed-controlled feed-pump (Capacity = 110 m3/h; Pel = 46.8 kW) and protected by two

Fig. 2: Visualization of the plant configuration (by courtesy of Wetzel & Partner)

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Tab. 1: Summary of the water treatment costs due to the membrane system in the Löhnen treatment plant

pre-filters connected in series (5 μm, then 1 μm). In each line there is a two-stage Nanofiltration array having 15 vessels, 10 in the 1st stage and 5 in the second. The concentrate of the first-stage feeds the second-stage.

Standby lines are kept preserved in sodium meta bisulfite solution.

RPI Hardness Stabilizer (or Antiscalant) The operating performances are correlated to the site specificity. In the Löhnen case, the RO membranes are smoothly operated with a flux of 25 l/m2/hr, a transmembrane differential pressure of about 5.5 bars and a maximal yield of 87%. Reaching such high recovery would not be feasible at all, without the use of a – crystal growth inhibitor – also named anti-scalant. As a safe and environmental friendly substance, sodium poly-Phosphonate is used. This will prevent for example the immediate damage of the membranes due to the formation of abrasive crystals like CaCO3 or CaSO4. In Löhnen, the ROPUR sodium poly-Phosphonate only needs to be dosed at 2 mg/l (or 2ppm).

The family of sodium poly-Phosphonates are included in the list of “treatment substances and disinfection methods according to paragraph §11 TrinkwV 2006”.

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More specifically why must an antiscalant be used here?

The raw water used is pumped up from a depth of 17 meters. It is then pre-treated before it flows into the Nanofiltration banks. As the natural product that comes from the Löhnen sources, is “very hard”, it contains many minerals such as Calcium, Magnesium or Carbonate cations and anions.

During the desalination process, using nanofiltration / low pressure reverse osmosis membranes, the water molecules pass rapidly through the membrane while the ions (anions and cations), metal oxides, and silicate particles will be filtered and thus concentrated and later be discharged with the concentrate.

In this situation of high recovery, the natural solubility of one or more salts is immediately exceeded resulting in rapid formation of a crystals that precipitate onto the membrane surface.

The consequence of the deposition, apart from the required higher inlet pressure for the same filtrate flow, the progressive increase in filtration resistance (higher pressure is needed) and the corresponding increase in power consumption, there is the immediate risk of irreversible membrane damage from crystal surface abrasion leading to poor permeate quality and loss of membrane performance. In this

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eventuality, the only technical solution is the replacement of the membrane elements, resulting in an increase in replacement frequency and operating costs.

To avoid such damage, Toray Membrane Europe AG developed and produced a range of nine different antiscalants. Each of these products has been developed to prevent a specific scaling risk whilst complying with strict national and international safety and quality standards (NSF60, KIWA, ISO9001 and ISO14001).

Historically, the first RPI antiscalant was sold in 1987 by the company ROPUR located in Münchenstein (Switzerland).

The ROPUR AG company was taken over later on by the Japanese Toray Group to become Toray Membrane Europe AG. Since 1987, the ROPUR RPI products are exclusively manufactured and sourced in Germany to ensure the highest quality standards.

The RPI ingredients currently used are from the latest generation of poly-phosphonate salts. They have a 100 times higher efficiency than comparable products such as ATMP and only need to be used in surprisingly low concentrations making it highly cost effective. They prevent or delay the formation of CaCO3, CaSO4, barium and strontium sulfate in crystalline form. Thereby, the membrane surface is kept free of inorganic and organic components and thus the filtration flow through the membrane layer is stabilized at optimum rates. This allows for a constant high flow rate at a moderate and stable pressures resulting in a low energy consumption and extended membrane life.

Conclusion The operation, the energy efficiency as well as the reliability of the Water Treatment Plant Dinslaken are the result of the association of trained engineers, designers, managers and high performance elements and Antiscalant. The daily plant operation relies on the fine tuning of dozen of parameters like, flow rates, hydraulic pressures, pH, recovery rates...etc. The Toray Membrane Europe team, with over 30 yrs experience, is proud of its contribution to this success story.

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The biggest reverse osmosis plant for the recovery of drinking water In our issue No. 4 (2015) /1/ we reported on the reverse osmosis plant for the recovery of drinking water from seawater with a capacity of 204,000 m³/day to supply 300,000 people in Carlsbad, California, and we are now able to report on the construction of a plant with a capacity of 624,000 m³/day to supply more than 1.5 million people in Israel. The plant in Sorek (Israel) will also be developed and built by a consortium that is managed by IDE Technologies Ltd. It sets new industry benchmarks in terms of desalination technology, capacity and water costs.

The plant will be built in the form of an operator model (BOT - Build Operate Transfer). This term identifies the three phases that the operating model consists of: the construction phase, the concession phase in which the operating company operates the plant, in this case SDL (Sorek Desalination Ltd.) and the transfer phase, in which the plant will be transferred to the customer at a later date. In practice, a new concession phase is usually negotiated after a specific operating phase, as the

end customer normally has little interest in operating the plant itself. In the case of the Sorek plant, the drinking water supply was offered at a price of 0.585 USD/m³ in accordance with the quote submitted in 2009. According to the details released by IDE Technologies, this is the lowest price ever agreed upon for a BOT project for seawater desalination /2/.

The following factors enabled IDE Technologies to offer the best price: - a contractual structure with optimised risk allocation - the pressure centre concept - the introduction of large membrane modules (16”) - the innovative design that uses vertical membrane module arrangements - the advanced energy recovery system with the lowest energy consumption - its own power supply as well as the favourable electrical power costs, - creative financing based on both NIS (New Israeli Shekel) and the EURO. The plant is being built on an 100,000 m² surface area.

Disturbances to the marine environment, the coast and the adjoining mainland will be minimised through using long pipelines with large diameters for the pipe jacking, intelligent construction and sludge treatment for reducing the energy and chemical consumptions.

IDE Technologies is the global market leader for water treatment plants and they specialise in the development, engineering, construction and operation of such plants. IDE has installed more than 400 plants in more than 40 countries for longer than the last five decades. IDE currently operates some of the world’s largest desalination plants in China, India, the US, Australia and Israel as well as other countries.

Literature: /1/ Großanlage zur Trinkwassergewinnung in den USA. Filtrieren und Separieren 29 (2015) Nr. 4, S. 269-270 /2/ F. Lokiec: Sorek 150 Millonen m³/year seawater desalination facility build, operate and transfer (BOT) projekt. Preprint: IDA World Congress, Perth, Western Australia 4th - 9th. September 2011 (can be called up at: www.ide-tech.com)

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Highlights 2016

Evaluation of integrity test methods for membrane modules for the ultrafiltration of ultrapure water in the semiconductor industry R. Berndt, J. Ruth, G. Heser* High-quality ultrapure water in great quantities is used throughout the manufacture of semiconductor integrated circuits. Thereby ultrafiltration (UF) is applied to remove particles, colloids and large macromolecules. Early detection of defects (leaks, pinholes, hollow fiber breaks) in membrane modules is an essential prerequisite for quality-insuring filtration and defect free manufacturing. Just counting particles upstream and downstream ultrafiltration is not sufficient.

Periodic pressure-hold tests enable much higher sensitivity of integrity testing and are an indispensable measure for preventive service and maintenance. This applies – beyond semiconductor industry – for all critical UF applications where low, varying particle numbers in feed are combined with low removal ratings and high demands on reliable retention.

1. Ultrapure water in the production of semiconductor devices Referring to the quantity supplied and the number of applications, ultrapure water (UPW) is by far the most important operating material for the production of semiconductor devices. UPW is used as rinsing and cleaning agent, solvent, carrier and for many other purposes, by itself or as main component in mixtures of chemicals. High UPW quality is a pivotal precondition for the production of defectfree devices.

Most quality criteria for UPW in critical applications of semiconductor industry are superior to those for common deionized water (DIW) and even for water for injection (WFI). Among others, this concerns – besides an extremely low specific conductivity of ≤ 0.055 μS/cm (18 MΩ·cm) – the total organic carbon (TOC), bacteria and particles. Each new technology node in design and manufacturing of integrated circuits is associated with smaller feature sizes controllable only by complete removal of particles above a critical size. Table 1 shows in extracts the particular requirements according to ITRS Roadmap /1/ with a critical particle size of currently 17 nm which will drop to * Prof. Dr.-Ing. Rolf Berndt ¹, Dipl.-Ing. Jochen Ruth ², Dipl.-Ing. Gerd Heser ² ¹ RBFM Consulting Eichstraße 16 D-01309 Dresden Phone +49 (0) 351-31778056 rbfm_consulting@t-online.de ² Pall GmbH, Dreieich Philipp-Reis-Straße 6 D-63303 Dreieich Phone +49 (0) 6103-307292 pugde@europe.pall.com

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10.7 nm in the next few years. Not more than four particles above this size are accepted per milliliter UPW. Ultrafiltration (UF) by means of porous polymeric high-quality membranes is the state-of-the-art method to meet these extreme demands. Typically these membranes are asymmetric and double-skinned hollow fiber membranes (Fig. 1). The hollow fiber bundles are placed in housings of ultrafiltration (UF) modules. Up-to-date high-performance modules include 7,000 to 20,000 hollow fibers that provide A = 20 to 40 m2 membrane area. The molecular cut-off of 4,000 to 6,000 Dalton correlates with 90 % retention at less than 10 nm particle size.

The feed water enters the shell void of the module housing at maximum 9 bar.

The major part, typically 95 %, penetrates the membranes in an outside-in mode and is filtered thereby. The permeate (filtrate) is collected inside the hollow fibers and escapes from them upwards as well as downwards, the both streams being unified outside the UF module. The permeate streams of individual UF modules are unified in pipes. A minor part of the feed stream, typically 5 %, flows upwards through the shell void outside the hollow fibers. This reject stream carries those contaminants (such as particles, colloids, macromolecules) that did not pass the membranes. They are being diffused from the boundary layer near the membrane surface back to the reject core flow due to gradients of concentrations. Limitation of the permeate flow QP keeps convective transport towards the membrane and diffusive return balanced. A steady mean permeate flux at QP/A ≅ 350 l/(m2·h) as a typical figure at 25 °C is created by 0.75 bar mean trans-membrane pressure

difference (TMP). High-speed crossflow is – unlike to most UF operations – not applied. Corresponding to the volumetric concentration factor, the concentration of retained contaminants in the reject flow rises on its way tangentially to the hollow fibers from an initial concentration to an exit level about 20 times higher.

A fully functional UF unit complies with several requirements, among them - Sufficiently fine pores in the membrane (e.g. 4,000 or 6,000 Dalton molecular cut-off in Pall Microza1 OAT or OLT modules, respectively).

- No generation of particles due to abrasion, or due to external contamination of components in the UF unit - No by-passing of the membrane barrier, whether because of local damages in the membrane or in the potting material, or through completely broken hollow fibers.

Meeting the first two of these preconditions requires careful design of the UF system, proper selection of components, and manufacturing under cleanroom conditions. Moreover, advanced UF units for UPW (Fig. 2) are encased in closed cabinets with slight overpressure during installation and maintenance. Thus airborne contaminants are prevented from polluting temporarily accessible wetted parts of the unit.

Unfiltered bypass flow (defect flow) would contaminate the permeate. To avoid this, non-destructive integrity tests are needed for early detection of such defects and for scheduled preventive service and maintenance. Access to and correct application of such test methods are mandatory ¹ Microza is a trademark of Asahi Kasei Chemical Corporation

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Tab. 1: UPW requirements ref. to particle numbers and sizes (according to /1/)

Fig. 1: UF module (Type Microza O*T) with flow paths and cross section of a hollow fiber

prerequisites for a successful quality management.

Real life has confirmed this position consistently. Fig. 3 shows a typical example /2/ for the implication of hidden module damages on UPW quality. A leading manufacturer of semiconductor devices for automotive applications runs two UPW loops, each of them equipped with one UF rack. Particle monitoring in both loops supplied completely different results. Particle counts and particle retention by UF in loop “200 mm” was satisfying whereas water in loop “150 mm” contained too many particles due to insufficient particle retention by ultrafiltration. Two defect UF modules were identified by integrity tests.

Fig. 2: Advanced UF system for ultrapure water

counts or turbidity. In UPW applications, only the former is applicable; turbidity levels are by far too low to be used.

Indirect methods must be applied if direct testing cannot be carried out continuously or sufficiently often. There is no proven method of continuous membrane integrity testing available that is both sufficiently sensitive and continuously applicable.

Direct methods are more sensitive but not continuous. Indirect methods can be used continuously but they lack sufficient sensitivity. Direct and indirect integrity testing methods are complementary.

Monitoring particle counts is an established part of UPW quality control in semiconductor industries. Its resolution, however, is limited. A possible by-pass flow QD through membrane defects is extremely diluted by the properly filtered permeate flow QP, the latter orders of magnitude larger than the former. Thus the concentration of particles in the total permeate (particles originating from the unfiltered defect flow) is too low to generate a significant signal, especially when the initial particle concentration is on its normal low level and when small critical

2. Methods for integrity testing of UF membrane modules Direct as well as indirect methods of non-destructive integrity testing are available /3/. Both of them set control limits whose exceedance triggers diagnostic testing and/or repair. Direct methods are physical tests applied to a module or membrane in order to identify integrity breaches. Examples are pressure-based tests and marker-based tests (the latter not feasible for UPW installations due to contamination risks). Indirect methods are generally based on monitoring water quality upstream and downstream ultrafiltration, e.g. by measuring particle

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Fig. 3: Particle counts and particle retention by ultrafiltration in two UPW loops (R. Bosch GmbH; 150 mm loop contains two defect UF modules)

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Fig. 4: Exalted cumulative particle concentration due to replacement of ion exchange resins (cited in /2/; first publication in SEMI Task Force, Ballot 5621A)

Fig. 5: Basics of pressure-based integrity tests; DBP – pore diameter at balanced forces; σ – surface tension of fluid; θ – contact angel water membrane

particle sizes in a single-digit or low double-digit range complicate particle counting. During service of an UPW plant, however, exalted short-period particle challenges may occur, e.g. after exchange of ion exchange resins (Fig. 4). Temporarily particle concentration in the feed rises high, increasing also the particle concentration in the permeate beyond alarm limits due to previously undetected membrane defects. Quick countermeasures are hardly possible.

Intolerable, often irreversible risks for quality of products and cleanliness of equipment and piping systems are taken. To minimize such risks, additional pressure-based integrity tests are necessary in addition to routine monitoring of retention. Additionally, those tests are extremely helpful for testing and releasing new modules prior to service.

3. Pressure-based integrity testing – procedure and performance criteria Basics As generally known, in pressure-based direct integrity tests a testing pressure below a critical value is applied which relates to the so-called bubble point being dependent on the size of a defect in a wetted membrane. This bubble point refers to the critical gas pressure difference ?pc that is balanced with the surface tension of a liquid in a capillary (membrane pore). Further increase of test pressure would blow the capillary open. Then the gas flows through the capillary in a convective way (Fig. 5). At subcritical pressure differences Δp < Δpc, the gas escapes merely by diffusion through the liquid filling the pore. At test pressures exceeding the critical value Δpc, the gas flow becomes significantly higher than the diffusive one.

A recommended test pressure difference for water applications of UF membranes is Δp = 2 bar /3/. This refers to a critical diameter DBP = 1.44 μm of a cylindrical pore in an ideally hydrophilic membrane at 25°C. A test pressure difference at 2 bar makes sure that no pore of an intact UF membrane (typical diameter < 10 nm) is emptied.

Fig. 6: Types and models of defects; SEM micrograph of an incipient fiber crack (defect 2)

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Test procedure A pressure-hold test applying clean dry air (CDA) or filtered nitrogen gas is the most feasible method for membrane modules.

Initially, with reject valve closed and permeate valve open, the pressure in the module is increased and eventually stabilized at 2 barg. Serious membrane damages (e.g. several fibers broken) immediately become obvious as they inhibit pressure stabilization.

After stabilization, gas feed is stopped, and pressure decay in the module housing is measured. The baseline of pressure decay refers to mere gas diffusion (no pore has been emptied). For 6” modules,

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it is typically about 50 mbar within 120 seconds. 100 mbar within 120 seconds is a tried and tested threshold. All modules showing faster pressure loss fail the test.

Test performance criteria Reproducibility, sensitivity and resolution are essential performance criteria for a test method. Reproducibility of pressure hold tests has been demonstrated in ďŹ eld tests /4/. To evaluate resolution and sensitivity, information is needed about - water ďŹ&#x201A;ow through typical leaks - convective airďŹ&#x201A;ow through these leaks - loss of particle retention due to these leaks.

For these purposes, three typical defects were deďŹ ned, and approximated by geometric duct models (Fig. 6) in which 200 Îźm is considered as membrane thickness, and 600 Îźm as inner hollow ďŹ ber diameter.

Case 1) Narrow pinhole: A constant-radius cylindric duct, 200 Îźm long, diameter 10 Îźm, linearly crosses the membrane in outside-in direction.

Case 2) Incipient ďŹ ber crack: A cylindric duct with elliptic cross section, 200 Îźm long, diameters 600/50 Îźm, linearly crosses the membrane in outside-in direction.

Case 3) Complete ďŹ ber crack: Widely isolated crack planes provide unresisted inďŹ&#x201A;ow into the two hollow ďŹ ber ends.

The respective defects are assumed to be situated 30 mm above the lower end of the hollow ďŹ bers which is a position typical for case 3.

4. Flow calculations Presuppositions The calculations are meant to provide information on the range of defect ďŹ&#x201A;ows (water as well as air) through membrane defects, and to permit a comparison with trans-membrane streams in an intact UF membrane module. Based on this comparison, the negative impact of defects on particle retentation can be calculated.

The trans-membrane water ďŹ&#x201A;ow (convective permeate ďŹ&#x201A;ow) in an intact UF module from type Microza OLT-6036H is typically QP = 12 m3/h at 25 °C and 0.75 bar TMP (trans-membrane pressure difference). The trans-membrane diffusive air ďŹ&#x201A;ow at 25 °C and 2 bar TMP is m¡ dif = 6.67¡10-06 kg/s.

The calculations aim at approximate results. A comparison of ranges of the defect ďŹ&#x201A;ow ďŹ gures with the ďŹ&#x201A;ow ranges in an intact module is sufďŹ cient for a proper evaluation of integrity tests.

Hence conventional calculation methods of ďŹ&#x201A;uid dynamics and gas dynamics are applied. They are in this connection less time-consuming than Computational Fluid Mechanics (CFM).

Water Flow The water ďŹ&#x201A;ow through a defect duct towards the permeate exit is driven by the pressure difference Î&#x201D;p between the pressure p0 in the moduleâ&#x20AC;&#x2122;s shell outside hollow ďŹ bers, and the pressure p2 in the permeate exit ports (Fig. 7). Water needs ďŹ rst to overcome the friction loss in the local defect ducts 1 or 2 (negligible in case 3). Then â&#x20AC;&#x201C; as a jet - it penetrates the void of the hollow ďŹ ber and makes an impact on the inner counter wall, dissipating its kinetic energy (cases 1 and 2). At a pressure p1, it branches into two streams, ďŹ&#x201A;owing through the two legs of the hollow ďŹ ber downwards and upwards, respectively, under further friction loss. At the very ends,

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Tab. 2: Darcy friction factors /5/

FB= f(Re = f(Q)), equations (2a) and (2b) must be solved by iteration. The coefficients for λ = f(Re) are listed in Table 2. In case of a completely broken fiber (Case 3), the first term in equations (2a) and (2b) is negligible due to A1 >> AHF and (l/d)1 >> (l/d)HF. Air Flow

the two exit jets dissipate their kinetic energy in the permeate port filled with practically stagnant water.

Bernoulli’s equation for incompressible fluids, with elevation terms neglected and total friction losses included, can be combined with the Darcy–Weisbach equation for the given situation, resulting in (1) After re-arrangement and common simplifications, the water flow rates Q through a defect hollow fiber – upwards and downwards, respectively – are

In contrast to water, the compressibility of air needs to be taken into consideration. Due to its short hold-up time in the flow channels, the gas flow is considered as adiabatic. The local defect ducts according to case 1 and case 2 are rather short compared to their diameters whereas the slenderness ratio of the two legs of a broken hollow fiber (defect case 3) is orders of magnitudes larger. These are good reasons to assume frictionless adiabatic nozzle flow for the local defect ducts case 1 and case 2. In contrast, friction losses in the hollow fiber legs are notable and to be included necessarily (Fanno flow in a constant area duct).

The totally available pressure difference is Δp = p0 – p2. The state changes from p0 to p2 in the flow through defects 1 and 2 may be characterized in four steps (Fig. 8).

1) Adiabatic, expanding, accelerated, friction-less gas flow at mass flow rate m· 1 from shell space through local defect duct to its end: 2) Jet flow from defect duct exit into hollow fiber:

(2a) (2b)

3) Adiabatic, expanding, accelerated, friction-involving gas flow at mass flow rate m· up/down through either of the two legs of the hollow fiber:

Index “1” (alternatively “2”) stands for the flow through the local defect duct 1 (or 2) as defined above. “HF” refers to “hollow fiber”. Flow distribution between upwards and downwards flow paths is described by FBV = Qup/Q. Due to λ = f(Re = f(Q)) and

4) Dissipation of kinetic energy of the jet flow going from hollow fiber into piping:

Fig. 7: Water flow paths through defect duct and module (schematic)

Fig. 8: Airflow paths through defect duct and module (schematic)

Fig. 9: Calculated airflow vs. measured airflow through nozzles at two pressure differences

Fig. 10: Particle retention of a defect UF module compared to an intact one (95% initial retention, 95% permeate recovery, 34 m² membrane area, 11,600 hollow fibers)

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In defect case 3, incoming gas streams initially without remarkable friction into the two free ends of a completely broken hollow fiber, again splits into two similar streams flowing downwards and upwards (step 3). They leave the hollow fiber legs as exit jets dissipating their kinetic energy in the stagnant air (step 4).

Steps 1) and 2) are described by the nozzle equation for an ideal gas /6/

Tab. 3: Calculated defect flowrates – results and comparisons

(3) · The mass flow m 1 results from eq. (3) by multiplication with the cross sectional area A1 and the density ρ1 (4) The enthalpy decline at the access of the jet (w1,1; p1; ρ1 = ρ0*(p1/p0)1/κ) into the stagnant space (w1’; p1’; ρ1’= f(p1’)) appears as pressure drop to (5) The flow through the hollow fiber legs in step 3 is also known as Fanno flow. It resembles the gas flow in a pipeline. Equation (6) for the exit gas pressure pHF2,up /7/ applies to negligible kinetic energy losses: (6) An analogous equation is valid for the downwards Fanno flow; flow distribution between upwards and downwards flow branches is described by FBm = m· up /m· 1. Table 2 lists the friction factors λHF1/2.

The density varies because of the adiabatic change of condition according to (7) The viscosity of the gas does not seriously depend on pressure since the mean free path of gas molecules (~60 nm) is negligible compared to the channel width /8/. The pressure further drops from pHF2 to p2 (step 4) due to energy dissipation in the jets that leave the hollow fiber ends: (8) The equations above enable – under variation of p1 and FBm – an approximate, iterative calculation of the gas mass flow through the defect ducts caused by a pressure difference p0 - p2.

Figure 9 demonstrates the excellent coincidence of calculated data with measured ones without any empiric matching. Calculated influences of defect width, defect length and pressure difference are fully confirmed. Hence the calculation methods explained above are applicable for an approximate calculation of gas flow through local defect ducts in the wall of a hollow fiber.

6. Results and interpretations Calculated water flow and airflow through defect ducts Applying the equations above, water flow and airflow rates were calculated that are caused by defects in a single hollow fiber (see Fig. 6). These additional flow figures were compared with the convective permeate flow (permeate) and with the diffusive air flow, respectively, of an intact membrane module 6 inch sized. Table 3 summarizes these results.

One issue becomes obvious at first glance. Any examined defect – even a complete fiber break – adds only little water flow to the permeate flow of an intact UF module. Neither permeate flow

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5. Experimental Verification of Methods The Bernoulli equation and the Darcy-Weissbach equation for water as well as the Fanno flow equation (6) for gas are proven and tested methods that do not need further evaluation. Yet the nozzle flow equation (3) in combination with eq. (5) is not self-evident from the outset. It implies two essential assumptions: ideal gas and adiabatic flow. An experimental verification is advisable.

For this purpose calculated values were compared with experimental results /9/. A plate (about 150 μm thick) with well-defined cylindrical laser-made holes was used to provide data on the influence of pressure difference and channel width on mass flow of gas.

In Figure 9 the results are presented as gas flow Q in standard liters per minute (sl/min), i.e. normalized for 25°C feed temperature and 1 bar differential pressure. Channel widths ranging from 2.9 μm to 100.4 μm as well as applied pressure differences Δp = p0 - p1’ perfectly cover the range of note. For the purpose of comparison, gas mass flow figures were calculated by means of eqs. (3), (4) and (5), and normalized for similar standard conditions.

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observation nor monitoring of particle counts upstream/ downstream a module indicate module damages with acceptable sensitivity. Substantial increase of particle counts (as in Fig. 3) needs severe membrane damages combined with high particle challenge.

Airflow is different. Convective defect airflow enlarges the total airflow significantly versus mere diffusive flow through an intact membrane. Defects are indicated with a resolution that is improved by a factor 104…105 compared to water flow.

Defect flow effects on retention of particles; indication of defects Overall particle transmission TN = 1- RN = cP/cFi is defined as number-based concentration of membrane-passing particles cP referring to the number-based particle concentration cFi in the feed.

Then the overall retention RN,0 of an intact membrane is (9) Assuming complete passage of particles of a certain size through defects, the number of particles NP,D penetrating with the by-pass flow QD is (10) as particle concentration on the feed side of the membrane increases from an initial value cFi to an exit value cFe according to permeate recovery RV. To put it simply, the arithmetic average of the particle concentration on the unfiltered side is applied. Eqs. (9) and (10) combined give the overall particle retention rate RND of the defect membrane module (11) Fig. 10 illustrates the outcome of this equation. Assuming - a particle retention RN,0 = 95% (baseline) of the intact membrane for a certain particle fraction - 30 % loss of retention as threshold, eq. (11) supplies: At least 52 completely broken fibers, or 347 incipient cracks, or 0.9 million pinholes (10 μm wide) are needed to recognize defects by sheer particle monitoring.

In contrast, pressure hold tests are by far more sensitive. Again 30 % increase compared to baseline is assumed as a threshold, i.e. about 30 % more pressure loss in a given time. Table 3 indicates that this threshold value is exceeded by just one broken hollow fiber, or by just one incipient crack of a hollow fiber, or achieved by 12,500 pinholes.

Acknowledgment The authors of this paper thank Robert Bosch GmbH for permission to record and to present field data on particle numbers in ultrapure water loops.

Symbols A AHF cP, cFi

-

DBP di dHF FBM li ldown, lup

-

· m 1 · m dif p0

-

p2 Δp; Δpc

-

QD; QP

-

Rair RV T0 wi w1,1 wHF1down/up

-

ζi

-

η κ λi

-

λm

-

membrane area cross-sectional area of a hollow fiber channel relating to dHF number-based particle concentration in permeate and initial feed critical capillary diameter channel diameter of defects i inner diameter of a hollow fiber · /m · flow distribution factor FBm = m up 1 channel length of defects i length of a hollow fiber sector below and above of a local defect convective gas mass flow rate caused by defects diffusive gas mass flow rate pressure outside of hollow fibers; approximately feed pressure permeate exit pressure pressure difference; critical pressure difference (“bubble point pressure”) volume flow rate through defect ducts; permeate volume flow rate specific gas constant of air permeate recovery by volume, RV = QP/QF feed temperature (absolute) mean velocity of the fluid in defect duct i exit velocity of the gas at defect 1 initial gas velocity in a sector of the hollow fiber; wHF1up= · /(A ·ρ ) m up HF HF1 pressure loss coefficient at exit of a defect duct; ζ1 ≅ ζ2 ≅ 1 , i.e. complete dissipation dynamic viscosity isentropic exponent, ratio of specific heats Darcy friction factor for a defect duct i; λi= C/Rei; Re = (w · d · ρ) / η mean friction factor in a hollow fiber sector between positions 1 and 2; λm = (λHF1+λHF2) / 2 density gas density at the entrance and exit of a hollow fiber sector, respectively

7. Summary and conclusions

ρ ρHF1, ρHF2 -

As successfully demonstrated above, pressure-based direct testing of integrity of UF membrane modules is by far more sensitive and more reliable than indirect testing by particle monitoring in feed and permeate. The latter, however, enables continuous on-line testing whereas the former is applied just periodically. Hence the two test methods are complementary.

Single serious defects in a module, e.g. completely broken fibers or even beginning fiber breaks, are safely recognized in a routine pressure-hold test. The test is an inherent part of commissioning by Pall GmbH and can be applied to each new membrane module. On the other hand, it is helpful for preventive maintenance, too. Early detection of defects enables module replacement early enough, i.e. prior to disastrous impacts of retention losses on products and equipment. Therefore scheduled pressure-hold tests at least twice a year are recommendable.

A combination of direct and indirect integrity tests ensures highest quality of supplied ultrapure water in terms of particulate and colloidal purity. Hence this approach allows best for defectfree manufacturing. This applies to ultrapure water applications in the semiconductor industry especially, but also for all critical UF applications which need reliably high permeate quality.

Literature: /1/ International Technology Roadmap for Semiconductors (ITRS); http://www.itrs2.net/2012itrs.html /2/ B. Eliosov, J. Ruth, G. Heser: New generation POU particles control for UPW; UPW Micro Confererence, Phoenix/ AR, 2.-3. Dezember 2014 /3/ C. Liu and J. K. Schaefer: Regulatory implications of LT2ESWTR and USEPA membrane filtration guidance manual for membrane applications in drinking water; Texas Water 2004, Arlington/ TX, April 5.-7. April 2004 /4/ J. Ruth, R. Berndt: Quality Control for Ultrafiltration of Ultrapure Water Production for High End Semiconductor Manufacturing; SEMI Advanced Semiconductor Manufacturing Conference, Saratoga Springs/ NY, 16.-19. Mai 2016 /5/ A. Schweizer: Formelsammlung und Berechnungsprogramme für Anlagenbau; http:// www.schweizer-fn.de/stroemung/druckverlust/ (2016) /6/ Dubbel, Taschenbuch f. d. Maschinenbau, S. D15. 18. Auflage, Springer-Verlag New York, Berlin, Heidelberg (1995) /7/ B. Glück: Hydrodynamische und gasdynamische Rohrströmung; Druckverluste; S. 145, VEB Verlag für Bauwesen, Berlin (1988) /8/ www.chemie.de/lexikon/Viskosit%C3%A4t.html#Viskosit.C3.A4t_von_Gasen, CHEMIE.DE Information Service GmbH (2016) /9/ R. Jaehnchen: Test report; Pall GmbH, Dreieich (2015), previously unreleased

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Enhancing Bubblepoint testing capabilities on wire meshes by numerical analysis D. Herper, M.Sc.* The Bubblepiont test is a wide spread test in filter media quality control. It uses the phenomenon that liquid filled pores will only become permeable for a gas, if a certain pressure is applied. Measuring this specific pressure makes it possible to calculate an equivalent size of the pore. Unfortunately the physical correlation between pressure and pore diameter is only valid for cylindrically shaped pores.

In order to determine openings of pores of different shape one uses a correction factor. This correction factor is currently determined empirically or simply estimated. As this correction factor determination is very vague the pore sizes for arbitrary pore shapes determined with the help of the Bubblepoint-Test are not very reliable.

This paper describes a procedure which makes it possible to find a correction factor by CFD-Simulations, making the determination of the pore size much more precise and reliable.

1. Introduction The Bubblpoint-Test is a standard test for filters and filter media.

There are a lot of standards defining the measurement procedure for different applications. One finds the ISO 2942 dealing with the Bubblepoint determination for filter elements or the ASTM F316 which is restricted to membrane filters. The BS 3321 describes the procedure for woven filter media and textiles.

The main idea behind the measurement lies in the detection of the largest opening found in a filter medium and assessing the filters quality with this quantity. But the determination of the pore size with the Bubblepoint test being described in the norms mentioned above is only valid for cylindrically shaped pores.

Making a clear statement for the pore size of woven wire meshes, which show everything but cylindrical pores, a correction factor is needed. The current method to determine this factor is conducting various laboratory measurements or simply estimating a value.

This way of finding a correction factor is very unprecise due to the vast number of assumptions that have to be made. To be able to make precise and reliable statements on the real pore’s size GKD - Gebr. Kufferath AG uses numerical models. These multiphase simulation models make it possible to find a sturdy value for the correction factor needed. * Dominik Herper, M.Sc. GKD – Gebr. Kufferath AG, Metallweberstraße 46, 52353 Düren, Germany Phone: +49 (0) 2421 803 180 Fax: +49 (0) 2421 803 342 E-Mail: dominik.herper@gkd.de

Fig. 1: Sketch of the Bubblepoint test

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2. Theoretical description and measurement principle For conducting a Bubblepoint measurement a sample of the filter media, which is to be tested, is needed. It is cleaned and then clamped into the measurement device (s. Fig. 1). The specimen is wetted with a testing liquid, afterwards a constant volume flow of air is applied which increases the pressure below. As the specimen is a porous filter medium a bubble will form at its largest pore the further the pressure increases. Increasing the amount of air even further will make the bubble pop; this marks the end of the test.

The pressure under the specimen is monitored throughout the test.

The largest value of this pressure is recorded and is defined as the Bubblepoint of the filter medium.

Converting the pressure into a diameter needs a physical correlation between the two quantities. For cylindrically shaped pores this is known as capillarity. A liquid rises in a cylinder pore due to its surface tension. (s. Fig. 2) Using the equilibrium of forces on this configuration yields: (1) Solving for r gives: (2) One now substitutes the radius by the diameter and estimates a fully wetting liquid. In addition to this one notices that the denominator in Eq. 2 is in fact a pressure. This yields: (3)

Fig.2: Capillarity

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Fig. 3: Comparison of pressure over time for the simulation (left) and the analytic result (right)

Fig. 4: Sequence of Bubblepoint simulation on an Optimized Dutch Weave (ODW 38)

The derivation of Eq. 3 clearly shows that it is only valid for a cylindrical pore. Fitting the correlation to an arbitrary geometry needs a correction. In practical laboratory measurement one introduces a correction factor C. This factor includes all deviations from a perfect cylinder shape. The pressure in the denominator is equal to the pressure difference determined in the Bubblepoint test.

This transforms Eq. 3 into: (4) The correction factor C does not have a dimension and is found in literature as the capillary correction factor. In ASTM F316 its value is given for membranes with 2860, with Δρ in Pa and σS in mN/m. An equation for the derivation of the pore size from a measured pressure has now been found. Due to its definition the capillary correction factor is only valid for one specific pore geometry. In fact it has to be newly determined as soon as something in the pore’s geometry changes. The empirical approach used so far is way too time consuming to be performed for every new geometry and thus every new filter medium. This is why averaged or estimated values are used in current analysis. One also realizes that these estimated values can lead to huge deviations from the real pore size.

Modelling As averaged and estimated capillary correction factors are not very precise and the deviations are not acceptable for certain weave types, the idea of modelling the Bubblepoint test virtually and through the numerical experiment finding a sturdy correction factor was born. The fact that the system poses a multiphase problem (air + testing liquid) made it necessary to also develop the simulation as a multiphase simulation.

The simulation tool of choice for this problem is the computational library OpenFOAM as it already contains a number of ready

36

to use multiphase solvers. To find out whether the solvers are suitable for the Bubblepoint test simulation, a test case was set up. The Bubblepoint for a cylindrically shaped pore is simulated in this test case. The test problem can be solved analytically by using Eq. 3 and therefore the deviation between simulation and the analytic value can be determined very easily. A simple geometry of a plate with a 1mm hole was chosen in the test. The testing liquid used is 2-propanol. This configuration was now simulated.

The results of the test case were very promising. The calculated pressure value for the configuration described above was 85,54 Pa. Using this value in Eq. 3 yields a diameter for the opening of 0.996 mm. The relative error between simulation and analytic solution in this case is 0.4% so the consistency of the solver was seen to be proven.

In the next step the simulation model was fitted to the much more complicated geometry of a woven wire mesh. The model was developed on GKD’s Optimized Dutch Weave (ODW) mesh family. The reason for this decision was that on the one hand a vast number of laboratory measurements are available for ODWs in the company’s data base; on the other the geometries of ODWs are rather simple and therefore much easier to cope with. The geometric model of the mesh was generated using Math2Markets tool WeaveGeo of the software GeoDict. The geometry was transformed into a computational grid by the use of OpenFOAM’s snappyHexMesh.

Simulation The parameters of the simulation were chosen to represent the Bubblepoint test as realistic as possible. The weave geometry in the simulation was wetted with 2-Propanol and the pressure underneath was increased by a constant volume flow of air. It became apparent that the computational grid has an enormous effect on the simulation run time as well as its stability. This is why most

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of the development time was put into the issue of mesh generation. This effort made the computation time decrease from six weeks down to ½ up to two days. The computations were performed on GKD’s in-house cluster. The simulation used 12 to 24 cores depending on the individual model’s complexity. A principle course of a simulation is shown in Fig.4.

The numerical model gives, just like the real experiment, a pressure value. What makes the difference between the two is the fact that in the simulation model the pore size of the mesh is known as the geometry of the mesh is available in the computer. The pore size of the virtual model was determined using the GeoDict Module Porodict. The data generated by the numerical experiment is therefore: the (simulated) Bubblepoint pressure, the opening determined by GeoDict and the surface tension of 2-propanol. With the help of these magnitudes one can solve Eq. 4 for the capillary correction factor C. This calculated correction factor is then used in the real experiment.

Tab. 1: Comparing different measurement techniques for the larges pore

Comparing measurement and simulation

Fig. 5: Simulation results vs experiment for different weaving types

A number of laboratory test were carried out to validate the results of the simulation. The wire meshes tested in the laboratory were then simulated and the results were compared. For measurement GKD uses a porometer PSM 165 manufactured by the company TOPAS GmbH. Fig. 5 shows three types of weaves which are compared as an example. One notices that the deviations between calculated and computed pressure values are very small.

The deviation observed lies between 1% and 2%. In a few cases it can rise to about

Largest pore [μm]

Measurement technique Bubble Point Particle counter Glass bead test

4%. Furthermore the pressures computed are always higher than those being measured. A possible explanation for this observation is the fact that the geometric computer model is not capable of reflecting the tolerances in wire diameter and those brought in by manufacturing the weave. The largest pore in the real mesh will therefore always be a little bit bigger than the one found in the computer model and, like it is described in Eq. 4, always give a slightly lower pressure value.

With the help of the simulated pressure values and the known openings of

the 3D mesh models capillary correction constants were computed for every weave model. These were than used in the real experiment to determine the largest pore in the mesh sample measured. The results matched those determined by other measurement techniques to detect the largest opening in the mesh (s. table 1).

The advantage of the Bubblepoint test for quality control is the time being consumed for the measurement. The particle counter method takes about three to four hours of working time, a glass bead test takes approximately 30 minutes.

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This distribution now fits the expectations made. The majority of pores is distributed around the nominal value of 20 μm. The small pores which were incorrectly detected with standard device configurations do not occur in the measurement anymore. The adjustments made were also transferred to other meshes and showed that this new method is applicable and shows good results for all kinds of meshes.

Prospect and further development

Fig. 6: Pore size distribution measured with standard configuration

Fig. 7: Pore size distribution measured with optimized configuration and enhanced correction factor

Measuring the Bubblepoint and converting the pressure recorded into a diameter takes less than one minute.

Results and model usage The numerical determination of the capillary correction factor gives GKD a mighty new tool for an efficient and precise pore size determination which beats conventional methods clearly by the time consumed for measurement. On top of that the precision of the Bubblepoint testing method is put to a new, so far unknown level. To find a reliable correction factor it only takes one single computation for every mesh. The comparison of the new model with the conventional method of determining correction factors is especially interesting. The vast number of measurements needed for a sound value for the capillary correction constant using the conventional method could only be efficient if the constant was averaged for one family of weaving types. The evaluation of different weaving types with the new simulation model now showed that the capillary correction constant can vary about ± 100% in one weaving type family.

Due to the linear characteristic of Eq. 4 the pore size determined with the old method can therefore also give a mistake in pore 38

size by ± 100%. This once again makes clear that it is extremely important to calculate the correction factor for each and every weave separately if reliable results for the pore size are favored.

Based on these new discoveries the determination of the pore size distribution which can be determined by a porometer (s. ASTM E1294) was to be optimized as well. Woven wire meshes are highly regular structures with defined pores. Alhough there are still minor fluctuations in pore sizes due to tolerances in wire fabrication and the weaving process. The analysis of the pore size distrubution can help to detect these fluctuations. Fig. 6 shows the pore size distribution of a mesh with 20 μm pores measured with standard device configurations One notices that the measurement doesn’t make sense as a weave of 20 μm will never have pores in the range of 16 μm or even below. One would expect a tight pore size distribution around the value of 20 μm. With the help of the porometer manufacturer and by the physical insights gained with the Bubblepoint simulation the measurement method was optimized. In addition to that a cappilary correction constant being computed by the simulation described above was used. The result can be obtained in fig. 7

The knowledge generated on the Bubblepoint measurement technique is already active in GKD’s mesh development. The development process of the new ODW 6 was significantly supported by the simulation and the optimized measurement method. This made it possible to quickly and efficiently detect difficulties in the development process and to eradicate them immediately. GKD’s quality control also takes an enormous advantage of the model. The improved measurement methods are already included in the quality department ensuring a faster and more reliable quality control. Meshes being developed on customer needs can now be checked for their Bubblepoint even before a single meter of mesh has been produced.

GKD was able to find capillary correction constants for all standard weaveing types as the model is independent of the geometry being checked for Bubblepoint. This makes pore size determination a fast and precise process.

Nomenclature Symbols Symbol Unit C d g h p r θ ρ σ

m m/s2 m Pa m rad kg/m3 N/m

Indices, Index A K S

Definition capillary correction constant diameter gravity of earth height pressure radius wetting angle density surface tension

subscript Definition atmospherecapillary surface

Abbreviations Abbreviation Meaning DTW Dutch Twilled Weave ODW Optimized Dutch Weave S Square Mesh

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No. 17/2017

Highlights 2016

The effects of electrical fields on the filtering of suspensions with flocculated quartz powder L. Petersen*, H. Hamm, F. Feser, S. Ripperger, S. Antonyuk* The filtration of very fine particles from aqueous suspensions is normally expensive, as the majority of the concordant charged particles show a poor tendency towards aggregation. This results in filter cakes with highly specific flow resistances. One possible way of making the separation easier is to filter the particles using polymer flocculants to coagulate them and to filter them afterwards. However, if microporous membranes are used then an overdose of polymer flocculants will have a negative effect on the filtering. This is why a filtration process using flocculated suspensions under the effect of an electrical field was examined. A cationic polymer was used as flocculating agent (FA).

An optimum flocculating agent dosing concentration was determined for when the electrical field was switched on or off.

1. Introduction In many technical sectors, such as the metal and paper industries, the treatment of waste water and in the bio technology * Dipl.-Wirtsch.-Ing. Lars Petersen Helga Hamm Dipl.-Ing. Frank Feser Prof. Dr.-Ing. Siegfried Ripperger Prof. Dr.-Ing. Sergiy Antonyuk TU Kaiserslautern Phone: +49 (0) 631-205-21, www.uni-kl.de/mvt

finest particles must be separated from liquids. Microporous membranes are increasingly being used for this. Very fine particles always exhibit very slow sedimentation speeds and they form filter cakes with very high flow resistances.

A method for improving the solids / liquid separation exists in which the particles form larger solid states through flocculation. The flakes that are formed exhibit a faster sedimentation velocity. The

flakes usually form a very porous and very permeable filter cake. The flakes can be built using a flocculant or a flocculating agent (FA). Substances that affect the charging of the particles in such a way that the electrostatic repulsion is reduced and the particles aggregate into flakes as a result of collisions arising from the van der Waals force, are known as flocculants. Metal salts are mainly used as flocculants [1].

Spaltsiebe & Präzisionsfilterrohre Slotted Screens & High Precision Filter Tubes

STEINHAUS GmbH Platanenallee 46 45478 Mülheim an der Ruhr Germany

F & S International Edition

No. 17/2017

Phone +49 (0)208 / 58 01- 01 e-mail filter@steinhaus-gmbh.de e-mail spaltsieb@steinhaus-gmbh.de website www.optima-spaltsieb.de

optima-17-12.1-4c

Sieben, Filtrieren und Entwässern in höchster Qualität!

Screening, filtration and dewatering in highest quality!

39

Highlights 2016

Voltage supply connection

Compressed air

Suspension

Compressed air supply

Filling nozzle Perforated plate Inner casing

Voltage supply

Sintered metal plate

Outer casing

Filtrat

Perforated plate Filter material Scales Sintered metal plate Fig. 1: Filter funnel construction

Flocculating agents are macro-molecules that simultaneously form bondings with several particles and this process ensures that a bridge is formed between the particles. Flocculating agents are usually water-soluble polymers. The chemical nature of their functional groups as well as the charge density, the molecular weight or the length of the molecule chains can be sub-divided according to their charging properties [2]. Synthetic flocculating agents are normally used as the molecular parameters such as the charging density and molecular weight can be optimised for specific applications by varying the synthesis conditions. Polyacrylamide is frequently used as the homopolymer and for the polyacrylamide-copolymer. The substance systems can be affected by an electrical field as a result of the uneven distribution of the electrical charge on particles in aqueous solutions and the ionic character of the polymer flocculant.

The solid / liquid separation kinetics can be changed accordingly by the creation of an electrical field. For example, the setting velocity of the negatively-charged particles will be increased in most cases during a sedimentation. During filtration a created electrical field can completely or partially impede the formation of the cake on the filter material [3], [4]. The filtration velocity can be considerably increased using this method.

The use of polymer flocculating agents in conjunction with filtration enabled an optimum flocculating agent dosing quantity to be determined in many of the studies [5] - [9]. If the concentration was too low, the result was that not all of the particles were bonded into flakes.

If the concentration was too high, the

40

Fig. 2: Experimental set-up

result was that the particles could become stabilised. An excessive dosage could result in the polymer on the surface of the particles being adsorbed and the formation of a coating on the particles, especially with cationic polymers. This means that it is possible that particles that were originally negatively-charged could have positively-charged coatings. This would result in further particle repulsion [2], [10]. If the flocculating agent concentration is too high this could also result in the unattached polymer in the filter cakes being enriched. Furthermore the use of microporous membranes can also separate the unattached polymer and form a low permeable coating of gel on the membranes, which would greatly increase the flow resistance [9].

A study was undertaken to determine in which way the negative effect of excessive dosing on the filtration kinetics could be reduced by the application of an electric field. Cationic polymer was used as the flocculating agent. A sintered metal plate was used as the anode below the filter medium and a perforated plate that was well away from the filter medium was used as the cathode in order to keep the micro-molecules away from the filter medium. This configuration meant that no positive effect was expected from the electrical field on the actual filtration process as the particles drifted well away from the filter material due to their negative charges.

2. Measuring principle and experimental set-up The filtration experiments were carried out using a funnel filter designed by the Institute for Mechanical Process

Engineering at the TU in Kaiserslautern.

The funnel is shown in Fig. 1.

A 50 mm in diameter perforated plate was fitted on a threaded rod made from PVC and inserted inside the funnel. This enables the height of the perforated plate and the strength of the electrical field to be adjusted linearly. The perforated plate functioned as the cathode. A sintered metal plate that functions as the anode was fitted in the foot of the funnel. The filter medium was fixed across the sintered metal plate. Fitted in the upper lid there is a power supply connection, a filling nozzle for the suspension and a compressed air supply connection. The filtrate flows into a collecting tank through the funnel attached to the bottom. The weight of the tank is recorded by electronic scales and then displayed by a computer during the filtration process. The internal diameter of the funnel is 50 mm and the height is 300 mm. The filter funnel has a double casing for temperature control purposes. The experimental procedure is shown schematically in Fig. 2.

Fennopol K 4250 T made by Kemira AG was used as the flocculating agent. It is an acrylamide-based cationic polymer flocculant. The suspensions were created from distilled water and Microsil M 500 made by Euroquarz GmbH. Microsil M 500 consists of silicon dioxide (> 99%) and has an average particle size of x 50.3 = 3.2 μm. The particle size distribution was determined using a LA-950 laser diffraction spectrometer made by Horiba.

Nadir MV020 made by Microdyn-Nadir GmbH was used as the filter material.

This is a membrane made from polyvinylidene fluoride with a nominal pore size

F & S International Edition

No. 17/2017

Present your company in the Global Guide of the Filtration and Separation Industry: D 11665 F Special Edition Sonderausgabe

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Global Guide of the Filtration and Separation Industry

Global Guide 2018- 2020 Welt-Handbuch der Filtrations- und Separationsindustrie Illustration Ill t ti in i original i i l size. i 5th completely l t l revised i d and d updated d t d edition. diti

Global Guide of the Filtration and S The international company presentation of the Filtration and S a clearly structured layout and a great reading comfort. C

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The target group:

Total circulation: 8,500 copies

Users and providers of filtration and separation technologies in all relevant industries worldwide.

Dispatch circulation: 6,000 copies Distribution: Q Q

The content:

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*Of those (approx. values): EU countries: 57%, Eastern Europe: 4% North America: 18 %, South America: 4 % Asia/Pacific: 17 %

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Another 2.000 copies: Distribution at all relevant industry fairs, conventions and other industry events in Germany and abroad in 2018, 2019 and 2020.

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Companies in the industry from A-Z Extensive search term register with reference to the suppliers and providers in the industry Presentation of establishments, universities and industry associations Expert contributions: Status and perspectives of solid/liquid separation, centrifugal technology, membrane technology, gas purification, filter testing, (particle) measuring technology Market analyses and trend reports Dictionary of important terminology (English-German, German-English) (A selection of more than 1800 industry terms)

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In addition, all company portraits will be published on the F&S Homepage and linked with the enterprises being presented (www.fs-journal.de).

A

Company presentations

A

Company presentations

ANDRITZ SEPARATION GmbH

Ahlstrom Aunankaari 4 33840 Tampere, Finland Phone +358 10 888 14

Dillenburger Strasse 100 D-51105 Cologne Phone +49 (221) 9856 0

Fax +358 10 888 4610 filtration@ahlstrom.com www.ahlstrom.com

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Company presentations

BASF SE Water Solutions D-67056 Ludwigshafen Phone +49 (0)621 60 0

Fax +49 (221) 9856 202 separation.de@andritz.com www.andritz.com/separation

Decanters, centrifuges, and filter presses

Dekanter, Zentrifugen und Filterpressen

ANDRITZ SEPARATION GmbH is part of ANDRITZ SEPARATION – the world’s leading separation specialist.

Our objective is to develop and provide new technologies and innovative solutions for process-optimized use in filtration technology. We research the market needs, sound out the possible technological synergies, and promote cross-industry ideas. We consciously depart from the usual paths in order to fulfil your requirements in the best way possible.

ANDRITZ SEPARATION GmbH ist Teil von ANDRITZ SEPARATION - dem weltweit führenden Spezialisten für Trenntechnik. Unser Ziel ist es, neue Technologien zu entwickeln und innovative Lösungen für den prozessoptimierten Einsatz in der Filtrationstechnologie zu bieten.

Wir erforschen die Bedürfnisse des Marktes, sondieren die Möglichkeiten technologischer Synergien und fördern branchenübergreifende Ideen. So verlassen wir bewusst die Pfade, um Ihre Ansprüche bestmöglich zu erfüllen.

Our decanters, centrifuges, and filter presses are all used in different markets and applications:

Unsere Dekanter, Zentrifugen und Filterpressen werden für verschiedene Märkte und Anwendungen eingesetzt:

Centrifuges: Food industry, chemical industry, industrial wastewater

Zentrifugen: Lebensmittelindustrie, chemische Industrie, Industrieabwasser

Filter presses: Chemical products and pigments, metallurgical products and ores, minerals and inorganic products, mining, industrial and municipal waste water sludge, food, and pharmaceutics

Filterpressen: Chemische Produkte und Pigmente, metallurgische Produkte und Erze, Minerale und anorganische Produkte, Bergbau, Industrie- und Kommunalabwasserschlämme, Nahrungsmittel und Pharmazie

Ahlstrom Filtration – setzt Maßstäbe in der Entwicklung von Filtrationsmedien

Ahlstrom Filtration is a global technology leader in design, development and manufacture of innovative filter media.

Our long experience in chemistries and fibers has been setting benchmarks in the filter media market and our large technology portfolio is a proof of our commitment to ensure that your specific filter media performance requirements are met.

Our manufacturing plants in North and South America, Europe and Asia work continuously to improve product performance in order to be our customer’s first choice.

Our global manufacturing platforms and global Sales Network allow us to offer customer focused solutions with tailor-made products We serve our customers in many industries. Some examples are in Engine and Industrial applications including filter media for: Air intake, Oil, Fuel and Cabin Air. Industrial applications cover High Efficiency Air, HEPA / ULPA, Dust Collector, Power Generation and Hydraulic. We have long experience and wide product portfolio for Laboratory and Life Science filtration applications. Ahlstrom Disruptor® has been successfully used in many residential and industrial water filtration applications.

Our range of filter media technologies assures that you will find the right technology to suit your needs. In line with our strategy, we are committed to growing and creating value by providing the best performing sustainable fiber-based materials.

Ahlstrom Filtration ist weltweiter Technologieführer in der Konstruktion, Entwicklung und Herstellung innovativer Filtermedien. Aufgrund unserer langjährigen Erfahrung in den Bereichen Chemie und Fasern setzen wir Maßstäbe für den Filtermedienmarkt. Unser umfassendes Technologie-Portfolio ist der Beweis für unser Engagement, sicherzustellen, dass Ihre speziellen Anforderungen an die Leistung von Filtermedien erfüllt werden.

Unsere Produktionsstätten in Nord- und Südamerika, Europa und Asien arbeiten beständig daran, die Produktleistung zu verbessern, damit wir für unsere Kunden die erste Wahl sind. Durch unsere weltweiten Produktionsplattformen und unser weltweites Vertriebsnetz sind wir in der Lage, kundenorientierte Lösungen mit maßgeschneiderten Produkten anzubieten.

Unsere Kunden sind in vielen Branchen tätig. Zu den Anwendungen im Bereich Motoren gehören Filtermedien für: Luftansaugfilter, Öl-, Kraftstoff- und Kabinenluftfilter. Die industriellen Anwendungen umfassen HEPA-/ ULPA-Filter, Staubfilter, Stromerzeugung und Hydraulik.

Wir verfügen über eine lange Erfahrung und ein breites Produktportfolio für Filtrationsanwendungen für Labore und die Biowissenschaften. Ahlstrom Disruptor® hat sich in vielen Filtrationsanwendungen für Haushalte und die Industrie bewährt. Unsere Palette an Filtermedien-Technologien gewährleistet, dass Sie die Technologie finden, die Ihre Anforderungen erfüllt.

Core competencies

Kernkompetenzen

Core competencies

Kernkompetenzen

Core competencies

Kernkompetenzen

• Global Filter Media Producer • Advanced products for Advanced Applications • Leader in Transportation applications • Wide technology portfolio • Expert in filter media chemistry

• Weltweiter Hersteller von Filtermedien • Führende Produkte für spezielle Anforderungen • Marktführer für Filtrationslösungen im Transportwesen • Breites Spektrum an Technologie Lösungen • Experten für zukunftsweisende Filtermedien

• Centrifuges • Filter presses • Treatment of municipal and industrial sludges • System solutions

• Zentrifugen • Filterpressen • Aufbereitung von Kommunalund Industrieschlämmen • Systemlösungen

• Sustainable water treatment • Specialist for ultrafiltration membranes • Extensive pre and after sales support

• Nachhaltige Wasseraufbereitung • Spezialist für Ultrafiltrationsmembranen • Umfangreicher Pre- und After-Sales-Support

Chemical centrifuge, type A6 Chemiezentrifuge, Typ A6

www.ahlstrom.com

Global Guide 2016-2018

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Side-bar filter press, type SE1000 – food Filterpresse Seitenholm, Typ SE1000M – Lebensmittel

www.andritz.com/separation

Chemical centrifuge, type AS14 Chemiezentrifuge, Typ AS14

Global Guide 2016-2018

Ennigerloher Str. 64 D-59302 Oelde Phone +49 (0)2522 300

Max-Fischer-Str. 11 D-86399 Bobingen Phone +49 (0)8234 9670 561

Q Q

Fax +49 (0)8234 9670 558 contact@jm.com www.jm.com

Sauberes Wasser für die ganze Welt

Professional in dynamic separation

Führend in dynamischen Trennprozessen

Woven Wire Cloth, Filter Elements and Particle Analysis Products

Drahtgewebe, Filterelemente und Partikelanalyse

Where Clean Begins: JM Filtration Media

JM Filtermedien – Damit die Dinge ins Reine kommen

Die Produktpalette der BASF umfasst die Schlüsselprozesse der industriellen und kommunalen Wasseraufbereitung. Wir zählen zu den führenden Anbietern von Chemikalien zur Wasserklärung bei der Trinkwasserherstellung, zur Behandlung von Abwässern und industriellem Prozesswasser, zum Schutz von Entsalzungs-anlagen, Kühltürmen und Boilern.

We are one of the leading manufacturers and suppliers of high-quality, custom designed pusher and scraper centrifuges. We achieve this through a unique combination of experience, precision quality, a high degree of innovation and close customer contact.

Wir sind einer der führenden Hersteller + Lieferanten hochqualitativer, maßgeschneiderter Schub- und Schälzentrifugen durch eine einzigartige Kombination aus Erfahrung, Präzision, einem hohen Grad an Innovation + engem Kundenkontakt.

• Custom built, intelligent solutions • Added value through in-house production + quality control • Environmentally sustainable • Lean manufacturing + assembly • Excellent service support

• Maßgeschneiderte, intelligente Lösungen • Mehrwert durch eigene Produktion + Qualitätskontrolle • Ökologisch nachhaltig • Herstellung + Montage nach Lean-Aspekten • Hervorragende Kundenunterstützung

Als ein führender Hersteller von Filtermedien bietet Johns Manville (JM) nicht nur Produkte von höchster Qualität, sondern auch eines der umfassendsten Produktprogramme der Glasfaser- und Polyesterspinnvliesindustrie.

JMs hochwertige Filtermedien kommen in unterschiedlichen Gebieten zum Einsatz wie z.B. Automobil, Flüssigfiltration, industrielle Entstaubung, Luftreinhaltung, Klima- und Heizungslüftungstechnik, Öl- und Nebelabscheider und Batterien.

Unsere Zentrifugen genügen höchsten Ansprüchen in der Pharma-, Feinchemie- + Lebensmittel-Industrie sowie der Umwelttechnologie. Qualität, Flexibilität, Zuverlässigkeit + Langlebigkeit zeichnen unsere effizienten Zentrifugen aus.

Production Technologies: Spunlaid, Airlaid, Wetlaid, Drylaid, Meltblown, Composite, Sliver & Yarn, Microfiber.

Produktionstechnologien: Spunlaid, Airlaid, Wetlaid, Drylaid, Meltblown, Verbundvliesstoffe, Faserband & Garne, Mikrofasern.

With our innovative products, we are always one step ahead: • Integrated thickener for pusher centrifuges • Pulsed washing for pusher centrifuges • Metallic filter cloths for scraper centrifuges

Mit unseren innovativen Produkten sind wir immer einen Schritt voraus: • Integrierter Eindicker für Schubzentrifugen • Pulsierende Waschung für Schubzentrifugen • Metallfiltertücher für Schälzentrifugen

Used centrifuges from the original supplier offer an interesting alternative. If needed we will modify the machine using optional equipment to fulfil the latest regulations + guidelines and offer consultation + support to implement your specific requirements.

Gebrauchtzentrifugen vom Originallieferanten bieten eine interessante Alternative. Wenn nötig passen wir die Maschine mit optionalen Ausrüstungen an, um die neuesten Normen + Richtlinien zu erfüllen und bieten optimale Beratung + Unterstützung zur Umsetzung Ihrer spezifischen Anforderungen.

Seit mehr als 125 Jahren prägt Haver & Boecker die Technologie des Drahtwebens maßgebend, entwickelt und verfügt über Fertigungsverfahren, mit denen Drahtgewebe und Drahtgewebelaminate zu Filtern und Formteilen weiterverarbeitet werden, die höchste Anforderungen erfüllen. Ob in der Luft- und Raumfahrt, der Automobilindustrie, Elektrotechnik, Medizinaltechnik, Chemie, Wasserfiltration, beim Maschinenbau oder bei der Kunststoffverarbeitung – überall dort schaffen maßgefertigte Lösungen von Haver & Boecker die Basis für effiziente Produktionsabläufe, sichere Funktion, optimale Produktqualität oder unverwechselbares Design.

Haver & Boecker konzipiert, konstruiert und produziert Metallgewebe aus Stahl und Edelstahllegierungen bis hin zu Sonderwerkstoffen. Bestimmte Einsatzbedingungen stellen besondere Herausforderungen (z.B. Hochtemperatur-/ Seewasserbeständigkeit), denen unter anderem mit der Verwendung unterschiedlicher Werkstoffe begegnet wird.

In Verbindung mit einer differenzierten Qualitätssicherung vom Draht bis zum fertigen Produkt sorgt unser nach DIN EN ISO 9001:2008 zertifiziertes Qualitätsmanagementsystem für zusätzliche Sicherheit.

Für die besonderen Anforderungen der Automobilindustrie ist der Geschäftsbereich HAVER AUTOMOTIVE auch nach ISO TS 16949 zertifiziert.

As a leading manufacturer of filtration media, Johns Manville (JM) offers the industry’s broadest range of products. With years of experience and a deep understanding of the market, our state-of-the-art technology guarantees high-quality products. JM’s top of the line filtration media are used in different applications, including automotive, liquid filtration, industrial air filtration, air pollution control, HVAC, mist elimination, and battery.

Our centrifuges comply with toughest requirements in the pharmaceutical, fine chemical, food and environmental industries. Ferrum centrifuges stand for efficiency, quality, flexibility, reliability + durability.

Haver & Boecker has been a pioneer in the technology of wire weaving for more than 125 years. The company develops and processes woven wire cloth and woven wire cloth laminates into filters and fabricated parts fulfilling the highest standards. Whether it is the aerospace, aviation, automotive, electrical engineering, medical technology, chemicals, water filtration, machine building or for the processing of polymers – everywhere Haver & Boecker creates customized solutions that form the basis for efficient production processes, reliable function, optimum quality and distinctive design.

Haver & Boecker conceptualises, designs and produces metal woven wire cloth made of steel, stainless steel alloys and special materials. Certain application conditions involve special challenges (e.g. high temperature - / sea water resistance) which can be fulfilled by using certain materials.

In combination with a differentiated quality assurance ranging from wire to finished product, our DIN EN ISO 9001:2008 certified quality management system assures additional reliability.

For the special requirements of the automotive industry, the business unit of HAVER AUTOMOTIVE is also certified as to ISO TS 16949.

Innovation: One of JM’s latest product developments is a polyester bico spunbond for air pollution control.

The cleanable filter media offers excellent mechanical strength combined with low pressure drop. It can be used with all pleating technologies. This new polyester bico spunbond media ensures exceptional stiffness within the filter pleats. It is also available with antistatic or oleo-hydrophobic treatment.

Innovation: Eine der neuesten Produktentwicklungen aus dem Hause Johns Manville ist ein Polyester BiCo Spinnvlies für Anwendungen im Bereich der industriellen Luftreinhaltung. Das abreinigbare Filtermedium der Staubklasse M kombiniert exzellente mechanische Festigkeit mit niedrigem Druckverlust. Es ist für alle Plissiertechnologien geeignet. JM’s neues Polyester BiCo Spinnvlies sorgt für eine hohe Steifigkeit der Filterfalten. Das Produkt ist auch als antistatische Variante oder mit öl- und wasserabweisender Ausrüstung erhältlich.

Core competencies

Kernkompetenzen

Core competencies

Kernkompetenzen

Core competencies

Kernkompetenzen

• Pusher centrifuges • Scraper centrifuges • Inertisation systems • Used centrifuges • Automation

• Schubzentrifugen • Schälzentrifugen • Inertisierungssysteme • Gebrauchtzentrifugen • Automation

• Woven wire cloth and wire cloth products • Filter elements and fabricated parts • Filtration and fluidization • Particle analysis – traditional und photo-optical • Screen sections and screen frames

• Drahtgewebe u. Drahtgewebeprodukte • Filterelemente und Formteile • Filtration und Fluidisierung • Partikelanalyse – traditionell und photooptisch • Industriesiebe und Siebrahmen

• Highly efficient filtration media • Tailor-made products • Broad product range • Extensive technology portfolio • Years of experience

• hocheffiziente Filtermedien • maßgeschneiderte Produktlösungen • umfassendes Produktprogramm • großes Technologieportfolio • langjährige Erfahrung

BASF is the leading provider of inge® ultrafiltration membrane technology, a membrane process used to treat drinking water, process water, waste water and sea water. The extremely small-pore and highly resilient filters of the Multibore® membrane reliably intercept not only particles, but also microorganisms such as bacteria or even viruses.

With a global reach enhanced by its network of partners, the company has completed numerous reference projects around the globe featuring its cutting-edge technology.

www.watersolutions.basf.com

BASF ist der weltweit führende Technologieanbieter für inge® Ultrafiltrationstechnologie, einem Membranverfahren zur Aufbereitung von Trink-, Prozess-, Ab- und Meerwasser. Die extrem kleinporigen und belastbaren Filter der Multibore® Membranen halten neben Partikeln selbst Mikroorganismen wie Bakterien und Viren zuverlässig zurück und sorgen so für sauberes Wasser.

Die leistungsfähigen Ultrafiltrationsmodule sind schnell und leicht einzubauen. Die Wasseraufbereitungsanlage kann durch platzsparende Rack-Konstruktionen einfach geplant, kostengünstig installiert und betrieben werden.

Das Unternehmen ist weltweit direkt oder über Partner aktiv und hat zahlreiche Referenzprojekte rund um den Globus mit seiner Technologie ausgerüstet.

inge® Multibore® Membranes

inge® T-Rack® 3.0

Global Guide 2016-2018

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www.ferrum.net

Global Guide 2016-2018

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Global Guide 2016-2018

www.diedrahtweber.com

www.jm.com

Content of the company profiles: Q

J

Company presentations

Johns Manville Sales GmbH

Fax +49 (0)2522 30404 dw@haverboecker.com www.diedrahtweber.com

BASF offers products used in the key processes of industrial and municipal water treatment. We are one of the leading suppliers of chemicals to clarify the raw water used for the production of drinking water, to treat the waste water stream and industrial process water, to protect desalination plants, cooling towers and boilers.

Zetag® Flocculant

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Company presentations

HAVER & BOECKER Fax +41 (0)62 889 15 13 centrifuges@ferrum.net www.ferrum.net/en/gbz

Clean Water for the world

The highly-efficient ultrafiltration modules allow rapid and easy installation. This makes planning a water treatment facility much simpler, enabling customers to achieve low-cost installation and operation.

ANDRITZ SEPARATION verfügt über die Erfahrung und das Know-how, seine Kunden bei den täglichen Herausforderungen in der Trenntechnik zu unterstützen.

H Die Drahtweber

Centrifuge Technology CH-5503 Schafisheim Phone +41 (0)62 889 14 11

Ahlstrom Filtration – setting benchmarks in filter media developments

ANDRITZ SEPARATION uses its expertise and knowhow to help its customers with their daily separation technology challenges.

F

Company presentations

Ferrum Ltd. Fax +49 (0)621 60 42525 water.solutions@basf.com www.watersolutions.basf.com www.inge.basf.com

Complete company name (headquarter), contact person, street, post code, city, country, telephone and fax number, email and Internet address Colour print of the company logo Printing of up to three colour photos/images/graphics/tables

Global Guide 2016-2018

99

Separation Industry 2018 – 2020 d Separation Industry with a clearly definde target group, t. Completely bilingual (English/German)

How to showcase your company:

The design: Robust thread-stitching for intensive and frequent use, reinforced cover, high-quality paper: cover 300 g/m2, interior 115 g/m2

Send us your short company profile (up to 1,000 characters) together with the headline (up to 50 characters) Provide up to three colour photographs of your choice (poss. with a short caption, max. 35 characters per image) State your core competence with at most 5 keywords (170 characters) Send us your company logo together with the complete company name including email address and internet address (and contact person, if available).

On the enclosed search term register, list the search terms in which your company is to appear.

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Book format: 24 cm height x 17 cm width

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Volume: Approx. 420 pages Publication date:

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Spring 2018 Q

Publication period: Every two years Utilization period: 2018 – 2020 (at least 2 years)

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The price/performance ratio for your portrait: Q

1/1 page, 4-colour: including all layout and translation services: Introduction price: EUR 1,950 (with self-provided translation EUR 1,850)

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2/1 page (double page) 4-colour: Introduction price: EUR 2,950 (with self-provided translation EUR 2,800)

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Company presentations

JVK Filtration Systems GmbH

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Company presentations

LANXESS

We will take care of everything else for you.

Prior to publication you will receive a proof.

Deadline for bookings: 9 February 2018 Deadline for printing material: 14 February 2018

Copyright: VDL-Verlag GmbH, Eckhard von der Lühe Heinrich-Heine-Straße 5, 63322 Rödermark / Germany Phone: +49 (0) 60 74 92 08 80 Fax: +49 (0) 60 74 9 33 34 Email: evdl@vdl-verlag.de or fs-journal@mgo-communications.de www.fs-journal.de S

Company presentations

Sandler AG

S

Company presentations

T

Company presentations

T

Company presentations

STEINHAUS GMBH

TAMI Deutschland GmbH

TROX GmbH

Platanenallee 46 D-45478 Mülheim an der Ruhr Phone +49 (0)208 5801 01

Heinrich-Hertz-Str. 2-4 D-07629 Hermsdorf/Thuringia Phone +49 (0)36601 81012

Heinrich-Trox-Platz D-47504 Neukirchen-Vluyn Phone +49 (0) 2845 2 02 0

Deutschland GmbH Obere Lerch 2 D-91166 Georgensgmünd Phone +49 (0)9172 707 0

Fax +49 (0)9172 707 77 jvk@jvk.de www.jvk.de

Kennedyplatz 1 D-50569 Cologne, Germany Phone +49 (0)221 8885-2013

lewabrane@lanxess.com www.lpt.lanxess.com

Lamitzmühle 1 D-95126 Schwarzenbach/Saale Phone +49 (0)9284 60 0

Fax +49 (0)9284 60 269 filtration@sandler.de www.sandler.de

Contact person / Kontaktperson Peter Reich

More than 50 years JVK -JVK: Rely on the Experts in Filtration

Über 50 Jahre JVK -JVK -- Die Experten in der Filtration

One-stop supplier for water treatment

Komplettanbieter für die Wasseraufbereitung

Innovative Producer of Filter Nonwovens

Innovativer Hersteller von Filtervliesstoffen

Founded in 1962, JVK Filtration Systems is the leading global supplier of state-of-the-art filter elements made from thermoplastic polymers PP PE PVDF and aluminium.

JVK membrane filter plates with exchangeable or fixed membranes NR EPDM NBR FKM TPV PP PVDF temperature membrane and chamber plates for cake drying in filterpresses in sizes up to 3 x 4 m are designed for the most demanding solid-liquid separation applications for filter presses. Our installation-list covers industries on all continents: Waste- and potable water treatment, sludge dewatering, chemical, pharmaceutical, ceramic, food, mining, metallurgy, paper, biofuels etc.

The superior and most reliable performance of JVK filter elements for decades has been the key to outstanding customer satisfaction and an ever increasing customer base. Constant innovation is a hallmark of JVK filter plates as well as our unique manufacturing ICM process.

JVK’s excellent and experienced expert team supports customers in all questions of calculations & technical layouts, filtration trials, commissioning, custom-tailored technical solutions for specific filtration processes.

A medium-sized and independent family business with approximately 200 employees is based near Nuremberg.

Our products are 100% “Made in Germany” and distributed through an experienced network of global representatives.

Bereits 1962 hat JVK Filtration Systems die weltweit erste Filterplatte aus PE entwickelt und sich seither als Marktführer und technologischer Trendsetter für thermoplastische Filterelemente (PP PE PVDF) und Alu etabliert. JVK Filterplatten mit austauschbaren oder festen Membranen (NR EPDM NBR FKM TPV PP PVDF), temperierbare Membranund Kammerplatten für die Kuchentrocknung in der Filterpresse in Größen bis 3 x 4 m eignen sich optimal für anspruchvollste Fest-Flüssig-Trennung mit Filterpressen und sind weltweit im Einsatz für: Abwasser, Schlammentwässerung, Trinkwasseraufbereitung, Chemie, Pharmazie, Keramik, Lebensmittel, Bergbau, Metallurgie, Papier, Biotreibstoffe usw. Überdurchschnittliche Kundenzufriedenheit und die beständig wachsende, weltweite Referenzliste sind Ausdruck des herausragenden und stets zuverlässigen Leistungsvermögens unserer Produkte. Hochqualifizierte und erfahrene Experten beraten Sie in allen Fragen zu technischer Auslegung, Filtrationsversuchen, Inbetriebnahme und Spezialentwicklungen für Ihre spezifische Anwendung und sorgen gleichzeitig für die ständige Weiterentwicklung unserer Produkte und unseres speziellen Fertigungsprozesses ICM. Als mittelständisches Familienunternehmen setzen wir konsequent auf „Made in Germany“ und vertreiben unsere Produkte über ein globales Netzwerk von erfahrenen lokalen Vertretungen.

LANXESS offers its customers a wide range of products and extensive experience in two key areas of water treatment – membrane technology and ion exchange.

Lewatit® ion exchange resins have been synonymous with high performance and quality for over 75 years.

LANXESS bietet seinen Kunden ein breites Produktspektrum und umfassende Erfahrung für zwei wesentliche Bereiche der Wasseraufbereitung: Membrantechnologie und Ionenaustausch. Lewatit®-Ionenaustauscherharze stehen seit mehr als 75 Jahren als Synonym für Leistungsfähigkeit und Qualität.

Sandler AG ranks among the 15 largest nonwoven producers worldwide and continues to strengthen its international market position as a supplier of highquality filter media.

Die Sandler AG gehört zu den 15 größten Vliesstoffherstellern weltweit und baut ihre internationale Marktposition als Lieferant qualitativ hochwertiger Filtervliese weiter aus.

The product range comprises carded and meltblown nonwovens as well as multi-layer composites. Fibre based, needle-punched nonwovens cover the grades G2 to M5. Fine dust filter media for filter classes up to E11 are produced using submicron fibres.

Zum Produktionsprogramm zählen kardierte Vliese, Meltblown-Vliesstoffe und Mehrlagenverbunde. Faserbasierende, genadelte Vliese decken die Klassen G2 bis M5 ab. Feinfiltermedien für Filterklassen bis E11 werden auf Basis von Submicron-Fasern hergestellt.

Sandler develops and produces media for HVAC applications, air and fuel filtration in vehicles, synthetic vacuum cleaner bags, customised special filters for liquid filtration as well as medical and hygiene applications.

Sandler entwickelt und produziert Medien für HVACAnwendungen, Luft- und Kraftstofffiltration in Fahrzeugen, synthetische Staubsaugerbeutel, Spezialfilter für die Flüssigkeitsfiltration sowie den Klinik- und Hygienebereich.

Self-supporting filter media are suitable for all common pleating technologies. Synthetic pocket filter media feature a low pressure drop, are shedding-free and bacteriostatic.

Eigensteife Filtermedien eignen sich für alle gängigen Plissiertechnologien. Synthetische Taschenfiltermedien haben niedrige Druckverluste, sind shedding-frei und wirken bakteriostatisch.

Latest developments for Indoor Air Quality applications combine high efficiency and long operating lives with energy efficiency, thus meeting the requirements of new testing standards.

Neuste Entwicklungen unter dem Schlagwort Indoor Air Quality vereinen sehr gute Filterleistung mit langen Standzeiten bei bester Energieeffizienz und erfüllen neuste Prüfnormen.

Core competencies

Kernkompetenzen

• Coarse and fine dust filter media • Pleatable filter media • Liquid filtration • Synthetic vacuum cleaner bags

• Grob- & Feinstaubmedien • Plissierfähige Filtermedien • Flüssigkeitsfiltration • Synthetische Staubsaugerbeutel

Mechanical and Thermal Cake Drying with JVK Filter Elements in different Systems in all industries.

Special designed membrane- and combination plate up to 3,2 m x 2,8 m with large filter area for big capacities.

JVK feed and compression plates for high squeezing pressure up to 6,0 MPa

LANXESS is the only European manufacturer of RO membranes. Several tens of thousands of Lewabrane® membrane elements have already been installed in over 25 countries worldwide since these were launched on the market in 2012.

The products have been developed in line with the latest technology for desalinating seawater, brackish water and low-salinity water and are used to treat process and drinking water.

The portfolio also includes ASD models that contain a new type of feed spacer. This ensures optimized flow in the element and thus lower energy consumption.

Lewabrane® RO membrane elements

LANXESS ist der einzige europäische Hersteller von Membranen für die Umkehrosmose (UO). Seit der Markteinführung 2012 wurden bereits mehrere zehntausend Lewabrane®-Membranelemente in über 25 Ländern weltweit installiert.

Die Produkte sind nach dem neuesten Stand der Technik zur Entsalzung von Meerwasser, Brackwasser und schwach salzigen Wässern entwickelt worden und werden für die Aufbereitung von Prozess- und Trinkwasser eingesetzt.

Das Portfolio umfasst auch so genannte ASD-Typen, die einen neuartigen Feedspacer enthalten. Dieser sorgt für optimierte Fließeigenschaften im Element und damit für einen geringeren Energieverbrauch.

For quality assurance purposes each individual Lewabrane® element is checked in an element tester.

Kernkompetenzen

Core competencies

Kernkompetenzen

• Membran- & Kammerfilterplatten • Innovative Filtrationstechnologie • Anwendungstechnik & Optimierung • Kundenspezifische Entwicklungen • Zuverlässiger Kundendienst

• Extensive product portfolio • State-of-the-art production sites in Bitterfeld and Leverkusen, Germany, and in Jhagadia, India • Worldwide technical and product-related customer support • Innovative LewaPlus® software for combined IE/RO system configuration • Outstanding expertise in polymer science for membranes and ion exchange resins

• Umfangreiches Produktportfolio • Hochmoderne Produktionsstandorte in Bitterfeld und Leverkusen, Deutschland sowie Jhagadia, Indien • Weltweiter technischer und produktbezogener Kundensupport • Innovative Software LewaPlus® für kombinierte IE/UO-Systemauslegung • Herausragende Kompetenz in der Polymerwissenschaft für Membranen und Ionenaustauscherharze

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Fax +49 (0)36601 81170 td-info@tami-deutschland.de www.tami-deutschland.de

The company

Das Unternehmen

Innovative ceramic pipe membranes

Innovative keramische Rohrmembranen

A corporate policy of controlled, self-financed growth realised consistently for more than 90 years of company´s history (1922-2012) secures us today not only a healthy economic base but also quite an impressive presence throughout the world. STEINHAUS is part of a corporate group with over 50 companies and more than 3,000 employees. Modern workshop facilities, state-of-theart production methods and own product research & development, backed by a strong team of salesmen and engineers, combined with numerous national and international partners are the guarantee for reliable quality products and expertly advise for our clients in more than 50 countries all over the world.

Eine in mehr als 90 Jahren Firmengeschichte (1922-2012) konsequent umgesetzte Unternehmenspolitik des kontrollierten, eigenfinanzierten Wachstums sichert uns heute nicht nur eine gesunde wirtschaftliche Basis, sondern auch eine beeindruckende weltweite Präsenz.

STEINHAUS gehört zu einer Unternehmensgruppe mit über 50 Unternehmen und mehr als 3.000 Mitarbeitern.

Rationelle Fertigungsmethoden, moderne Betriebsanlagen, eigene Produktentwicklungen sowie eine leistungsstarke Vertriebsmannschaft im Innen- und Außendienst mit einer Vielzahl von in- und ausländischen Partnern sind Garanten für zuverlässige Qualitätserzeugnisse und kompetente fachliche Betreuung für unsere Kunden in über 50 Ländern der Welt.

TAMI Group specializes in the development and production of ceramic pipe membranes for crossflow, micro, ultra and nanofiltration of liquid media. As largest subsidiary of TAMI Industries, TAMI Deutschland is in charge of producing macroporous membrane carriers and the distribution of membranes in German-speaking countries, the Benelux states, northern, central and eastern Europe as well as on the territory of the former Soviet Union.

Die TAMI Gruppe ist spezialisiert auf Entwicklung und Fertigung keramischer Rohrmembranen für die Crossflow- Mikro-, Ultra- und Nanofiltration flüssiger Medien.

TAMI Deutschland ist als deutsche Tochterfirma von TAMI Industries zuständig für die Fertigung der grobporösen Membranträger und verantwortlich für den Vertrieb der Membranen im deutschsprachigen Raum, den BENELUXStaaten, Nord-, Mittel- und Osteuropa sowie dem Gebiet der ehemaligen Sowjetunion.

OPTIMA High Precision Filter Tubes Used as direct filters but also as support elements for very fine metal or textile filter cloths as dewatering pipes, well pipes, filter candles, intake or outtake filters, drainage elements etc.

Filter/Formfilter made of Metals or Synthetics filter, clean, regenerate liquids and gases Filter Media made of Textile Fibres produced as filter hoses, filter bags, filter pockets or cloth

OPTIMA Präzisionsfilterrohre Als direktes Filterelement aber auch als Stützelement bei feinen Filtermaterialien als Entwässerungsrohr, Brunnenfilter, Filterkerzen, Aus-/Einlauffilter, Drainageelemente usw.

Filter/Formfilter aus Metallen und Kunststoffen filtern, reinigen, regenerieren Flüssigkeiten und Gase.

Filtermittel aus textilen Faserstoffen hergestellt als Filterschläuche, -beutel, -taschen oder -tücher

Main application fields for the membranes are filtration and separation processes in the food and beverage industry, chemical process engineering, biotechnology as well as water and wastewater treatment. TAMI’s standard products are multi-channel membranes with non-circular channel geometries. These achieve maximum use of the active filter surface per membrane element. The membranes distributed by the brand name „InsideCeRAM“ are available in altogether 13 different cut-off sizes together with stainless steel housings in six different size classes.

Haupteinsatzgebiete für die Membranen sind Filtrationsund Separationsprozesse in der Lebensmittel- und Getränkeindustrie, der chemischen Prozesstechnik, der Biotechnologie sowie der Wasser- und Abwasserbehandlung. Als Standard vertreibt TAMI Mehrkanalmembranen mit nichtkreisförmigen Kanalgeometrien. Damit wird die Maximierung der aktiven Filterfläche pro Membranelement erreicht. Die Membranen unter der Marke „InsideCeRAM“ werden in insgesamt 13 verschiedenen Trenngrenzen zusammen mit Edelstahlgehäusen in 6 unterschiedlichen Größenklassen angeboten.

Fax +49 (0) 2845 2 02 2 65 trox@trox.de www.trox.de

Filter Technology from A to Z Filter units and filter elements from TROX

Das ganze Spektrum der Filtertechnik – TROX Geräte und Elemente

TROX is leading in the development, manufacture and sale of components, units and systems for the ventilation and air conditioning of rooms. Whether you require an air handling unit, air terminal devices, controllers, intelligent control systems or filters, TROX offers components that are perfectly complementary to each other, all from a single source.

TROX ist führend in der Entwicklung, der Herstellung und dem Vertrieb von Komponenten, Geräten und Systemen zur Belüftung und Klimatisierung von Räumen.

Ob Klimazentralgerät, Luftauslässe, Regler, intelligente Steuersysteme oder Filter, TROX liefert optimal aufeinander abgestimmte Komponenten aus einer Hand.

With an extensive and diverse filter portfolio, TROX has suitable filter units and filter elements for the most varied installation situations and fields of application. Installed in walls, ducts, ceilings or air handling units, whether in shopping centres, schools, production facilities or pharmaceutical labs, TROX filters are used all over the world.

TROX verfügt mit seinem umfassenden Filterprogramm über Geräte und Elemente für unterschiedlichste Einbausituationen und Anwendungsbereiche. Ob in Wänden, Luftleitungen, Decken oder Zentralgeräten, ob in Einkaufszentren, Schulen, Fertigungsbetrieben oder Pharmalaboren, TROX Filter kommen weltweit zum Einsatz.

They satisfy the most stringent quality requirements, comply with international standards and impress with minimal pressure losses, hence ensuring long service lives.

Sie erfüllen höchste Qualitätsstandards, entsprechen internationalen Normen und überzeugen durch geringe Druckverluste zur Erzielung langer Standzeiten.

Tested to international standards • depending on type of filter tested to either EN 779 or EN 1822 • fine dust filters of filter classes M5 to F9 tested to EN 779 and certified by EUROVENT • TROX test rig verified by accredited testing institutes SP in Sweden and VTT in Finland

Prüfung nach internationalen Standards • je nach Filterart Prüfung gemäß EN 779 oder EN 1822 • Feinstaubfilter der Filterklassen M5–F9 zertifiziert nach EN 779 EUROVENT • TROX Prüfstand mit akkreditierten Prüfinstituten SP in Schweden und VTT in Finnland abgeglichen

New feedspacer with „Alternating Strand Design“ (ASD)

Core competencies • Membrane & Recessed Filter Plates • Innovative Filtration Technology • Process Application & Optimization • Customer Specific Solutions • Reliable After Sales Service

www.jvk.de

Fax +49 (0)208 5801 500 filter@steinhaus-gmbh.de www.steinhaus-gmbh.de

www.lpt.lanxess.com

www.sandler.de

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Core competencies

Kernkompetenzen

• Screen Panels (made of steel and polyurethane) • OPTIMA Slotted Screen Panels • Wire Conveyor Belts • Filter Media (made of textile fibres, metals and synthetics) • OPTIMA High Precision Filter Tubes

• Siebböden aus Stahl und Polyurethan • OPTIMA Spaltsiebböden • Drahtfördergurte • Filter aus textilen Faserstoffen, Metallen und Kunststoffen • OPTIMA Präzisionsfilterrohre

www.steinhaus-gmbh.de

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Core competencies

Kernkompetenzen

Core competencies

Kernkompetenzen

• Maximum filter surface per element • Cut-off selection • Module and sealing concept • Robust material properties • Application diversity of the membranes

• Maximale Filterfläche pro Element • Trenngrenzenauswahl • Modul- und Dichtungskonzept • Robuste Materialeigenschaften • Einsatzvielfalt der Membranen

• Testing to international standards • A suitable filter solution for every requirement • Most advanced production facilities • High standards in quality assurance

• Prüfung nach internationalen Standards • Für jeden Anspruch die passende Filterlösung • Modernste Fertigungseinrichtungen • Hohe Standards in Qualitätssicherung

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Specialised F&S translators will take care of the complete and proper translation of your company portrait unless you want to provide the translations yourself.

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Highlights 2016

3. Findings The effect of the electrical field on a pure solution with a flocculating agent was examined initially. It could be seen here that some of the polymer was retained by the membrane. The filtrate clearly became more viscous as the flocculating agent (FA) concentration increased. A clear coating of gel could be seen on the membrane by the end of the experiment and this thickened as expected as the concentration was increased. The filtrate flow timing with the electrical field switched both on and off is shown as graphs in Fig. 3.

It should be noted that the duration of the filtration process for a filtrate mass of 63 g had to be prolonged as the concentration was increased. The duration of the filtration process was clearly reduced when the power supply was switched on.

As a cationic flocculating agent was used, the electrode arrangement used during the experiment ensured that the electrical force on the molecules acted against the filtration direction. Consequently, the formation of the gel coating had a counteracting effect and the filtrate flow was increased. The filtration periods for different flocculating agent concentrations with

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Tab. 1: FiItration times for attaining a filtrate mass of 63 g using pure FA solutions

FA concentration [w-%] Voltage [V]

Filtrate mass [g]

Filtration duration [s]

Filtrate mass [g]

of 0.2 μm. It can retain virtually all of the solid particles.

An aqueous solution with 0.1 w-% flocculating agent can be used initially. This is needed to detach and swell the flocculating agent [7]. The swelling time is 20 minutes.

The particles and water were initially dispersed and afterwards the flocculation agent was added to 100 g of suspension and agitated slowly. The resulting mixture was then poured into the funnel through the filling nozzle, the power supply was switched on and the pressure was applied by opening the pressurised gas connection.

All of the experiments were carried out using a 2-bar pressure difference. The silicon dioxide concentration was 5 w-% and the temperature of the suspension was 25.8° ± 0.2°C and the standard gap between the electrodes was 20 mm. The applied voltage was either 0V or 60V, which corresponds to an electrical field strength of 0 or 3V·mm-1. The reproducibility of the experiments was high. The cathode in the form of the perforated plate realised a filtrate volume of approx. 63 ml below the level of the liquid when an electrode gap of 20 mm was used. The mobility of the particles in the electrical field was restricted when the level of the liquid dropped below the perforated plate. For this reason the main focus of the experiment evaluation was on the filtrate flow until 63 ml or 63 g of filtrate was attained.

Time [s]

Time [s]

Fig. 3: Filtrate mass depending on the filtration time for a pure FA solutions with and without the electrical field being switched on

the voltage sources switched on or off are compiled in Table 1.

The filtration duration for 63 g of filtrate is considerably longer for all configurations that used flocculating agents than the filtration durations for when pure water was used. Accordingly, the filtration resistance’s dominance did not come from the membrane, but from the gel coating that was being formed. The filtration time reduction caused by the electrical field occurred over the same range of 51% 56% in all cases. As the reduced filtration time was always significantly greater than when using pure water, it can be assumed that only a part of the polymer was kept away from the membrane.

Pure suspensions without a flocculating agent were filtered in other experiments. A lesser negative effect was realised by the electrical field here. This can be explained by the fact that the electrical field boosted the negatively-charged particles in the direction of the anode and they then drifted over the membrane. The formation of the filter cake was accelerated by this, which in turn slowed down the filtration process. In a further series of experiments the suspensions being used were filtered with flocculating agents. The graphs for the filtrate flows with flocculating agent concentrations of 0, 0.002 and 0.004 w-% are shown in Fig. 4.

The filtration duration was the shortest when using a flocculating agent concentration of 0.002 w-% without an electrical field. An apparent excess dosing occurred with 0.004 w-%, as the filtration duration was significantly greater than when a flocculating agent was not used. In fact the particles were bound into flakes, even

though there was an excess of polymer present. This was adsorbed into single particles or else it formed a coating of gel on the membrane and this clearly increased the filtration resistance. When the electrical field with switched in, the time curve for the filtrate mass was 0.002 and 0.004 w-% lie above that of the 0 w-% flocculating agent. Some of the non-bonded polymer and the polymer coated particles were kept away from the membrane and the filter cake and this clearly reduced the filtration duration. The filtration times realised using the different flocculating agent concentrations are shown in Table 2 and in Fig. 5.

As the flocculating agent concentration increased, the filtration time initially waned and flowed at a minimum of 0.002 w-%. The filtration time increases if the concentration is further increased.

The increase in the filtration time is very high if a concentration is added without an electrical field. With a concentration of 0.01 w-% the filtration duration increased by 13 times as compared to the filtration duration without the addition of a flocculating agent. The increase in the filtration time was clearly flatter when the field was switched in. The filtration duration was approx. 20% longer than without a flocculating agent at 0.01 w-%. In the case of concentrations that were less than the optimum concentration, the electrical filed had a lesser negative effect on the filtration duration. As the anode is positioned below the filter medium and not all of the particles were bonded into flakes, this results in the filter cake forming more rapidly. In the case of a concentration of polymer flocculating agents that lies above the optimum

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Highlights 2016

Tab. 1: Filtration times for attaining a filtrate mass of 63 g for suspensions with 5 w-% solids and different FA concentrations with and without an electrical field

FA concentration [w-%] Voltage [V] Filtration duration [s]

series of experiments with a concentration of 0.002 w-%. This indicates that an excessive dosing of flocculating agent is already present at 0.004 w-%. The flakes that were formed could be boosted to keep away from the membrane by increasing the strength of the field and this reduces the filtration time.

Filtrate mass [g]

Filtrate mass [g]

4. Conclusions

Time [s]

Time [s]

Fig. 4: Filtrate mass depending on the suspension (5 w-% solids) filtration time with and without FA, with and without the electrical field being switched on

FA concentration [%] Fig. 5: Filtration time for attaining a filtrate mass of 63 g, for suspensions with 5 w-% solids with different FA concentrations with and without the electrical field being switched on

46

age was kept at 60V in this case and the gap between the perforated plate and the membrane, which was 20 mm in the previous trials, was altered. The filtrate flows for a suspension with a 0.004 w-% flocculating agent and electrical field heights of 10, 15 and 20 mm are shown as graphs in Fig. 6. This corresponds to electrical field strengths of 6, 4 and 3 Vmm-1.

The filtration duration for attaining a filtrate mass of 63 g drops as the field strength increases. It can be seen that the shortest filtration time with a gap of 10 mm between the electrodes is less than the minimum realised during the previous

Filtrate mass [g]

Filtration time [s]

concentration, the electrical field will have a strongly positive effect on the filtration duration. The electrostatic force action will affect the polymer-bonded particles as well as the non-bonded polymer in the cathode direction, i.e. away from the filter medium. This method keeps them away from the membrane. However, the electrical field might not be strong enough to keep all of the positively charged particles away from the membrane as the filtration duration also increases as the concentration increases.

The strength of the electrical field was varied in another series of trials. The volt-

Time [s] Fig. 6: Filtrate mass depending on the suspension filtration time with 5 w-% solids and 0.004 w-% FA and using different field strengths

A filtration process using flocculated suspensions under the effect of an electrical field was examined. A cationic polymer was used as the flocculant in the flocculating process. An optimum flocculating agent dosing concentration was determined for when the electrical field was switched on or off. The optimum concentration was the same regardless of whether the electrical field was switched on or off. The electrical field had a weak negative effect on the filtration in the case where the polymer concentration was less than the optimum concentration. The electrical field had a strongly positive effect on the filtration if an excessive dosing of flocculating agent was present. It can be accepted that in this case some of the excessive polymer was kept away from the membrane as a result of the electrical field. The examination process using an electrical field could be used sensibly if the particle concentration varies widely and optimum flocculating agent dosing is impeded. The electrical field can be used to realise comparatively high filtrate flows even with highly excessive dosing.

Literature: [1] S. Schwarz et al., Chem. Ing. Tech 2006, 78 (8), 1093.

DOI: 10.1002/cite.200500173 [2] I. Anger in Handbuch der mechanischen Fest-FlüssigTrennung (Ed. K. Luckert), Vulkan-Verlag, Essen 2004.

[3] S.P. Moulik, Colloid & Polym. Sci. 1976, 254 (1), 39.

[4] S.P. Moulik, Environ. Sci. Technol. 1971, 5 (9), 771.

[5] D. Dollimore, T.A. Horridge, Water Research 1972, 6, 703.

[6] W.-M. Kulicke, R. Budirahardjo, M. Prescher Chem.

Ing. Tech 1989, 61 (10), 828.

[7] H. Burkert, H. Horacek, Chem. Ing. Tech 1986, 58 (4), 279.

[8] V.K. La Mer, R.H. Smellie, in Proc. of the Ninth National Conference on Clays and Clay Material (Ed: A. Swineford), Pergamon Press, London, 1962.

[9] M.T. Nguyen, Deckschichtbildung in Kapillarmembranen bei der Querstrom-Mikrofiltration und ihre Beeinflussung durch polymere Flockungsmittel, Dissertation, TU Dresden 2004.

[10] J. Gregory in The Scientific Basis of Filtration (Ed. K.J. Ives), Sijthoff&Noordhoff, Alphen aan den Rijn, 1978.

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Highlights 2016

Magnetic separation of very fine particles from liquids A. Vetter, S. Ripperger, S. Antonyuk* When magnetic separation is used for separating fine particles from liquids it is often discussed in conjunction with maintaining lubricating and hydraulic oils. Depth filters are primarily used for this today. Other applications using magnetic separators in conjunction with surface-modified magnetic particles (so-called “magnetic micro-beads”) are possible in biotechnology. The specific attachment of substances or cells to the surfaces is used here for the recovery of valuable substances from fermentation broths or for magnetically-activated cell sorting. The following contribution reports on a new magnetic separation concept that was tested with regard to maintaining oils.

1. Introduction The magnetic separation of ferromagnetic materials, such as iron, cobalt, nickel as well as ferrimagnetic materials such as magnetite (Fe3O4), have now been used in treatment and environmental technologies for several years /1, 2/. The recovery of valuable substances from fermentation broths using magnetic particles, the so-called “magnetic micro-beads” and magnetically-activated cell sorting are right at the forefront in biotechnology. In the first instance, the valuable substances are selectively adsorbed into the modified surfaces of the “magnetic micro-beads” and the “micro-beads” are then separated using magnetic separators (see /3/). In the second instance, the magnetic particles are bound to the relevant cells together with the antibodies and they are then removed by the effects of the magnetic force /4/. The combination of the magnetically-activated cell separation and the Direct Epifluorescence Filter Technology (DEFT) for rapid biomonitoring of harmful microbes in complex biological substances systems is reported on in /5-7/.

The “micro-beads” normally exhibit paramagnetic properties so that the magnetic effect on the cells disappears with the removal of the magnetic field.

Magnetic forces are also being increasingly used to separate the finest particles from viscous liquids /8-10/. They are also being used in conjunction with separating particles from lubricating and hydraulic oils. This has a decisive significance with regard to operating safety and the availability of machinery and plants. Therefore the particle content in the oils must be continuously reduced in this way in order to increase the service lives of the machinery and the plants /11/. Depth filters are generally used for this. They also act as * Dr.-Ing. Alexandra Vetter Prof. Dr.-Ing. Siegfried Ripperger Prof. Dr.-Ing. Sergiy Antonyuk TU Kaiserslautern Institute for Mechanical Process Engineering

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storage filters, i.e. the separated particles are collected in the filter matrix. The drop in pressure will increase as a result of this and this means that it will be necessary to change the filter after a specific operating period.

Magnetic separation is also becoming increasingly more interesting with regard to oil maintenance as it has been determined that adhesive non-magnetic pollutants in the oil can also be separated in addition to the generation of the magnetic drive. Large flow cross sections can also be realised using magnetic separators, which are associated with a low pressure drop. In an earlier contribution /12/ it was shown that a magnetic separator often cannot replace depth filtration, but the service lives of the filter elements used for this purpose can be considerably extended.

2. A magnetic separator’s working principle and the basic theory In the magnetic separation process examined here, the magnetisable particles are channelled through an inhomogeneous magnetic field that is generated by permanent magnets. The particle separation process is based on the cross-flow separation principle (Fig. 1), i.e. the particles are diverted transversely across the suspension’s main flow direction due to the effects of the magnetic force. The magnetic field works as an open flow channel so that it is an “Open Gradient Magnetic Separator (OGMS)” as opposed to a “High Gradient Magnetic Separator (HGMS)”, in which the flow channel is filled by a magnetisable separation matrix, which is usually in the form of thin wires. The magnets are positioned at a specific level outside the flow channel in the developed OGMS. The magnets are arranged alternately between the poles in order to generate large magnetic field strength gradients.

The magnetic field applied to a magnetisable particle creates a magnetic dipole, which aligns the particle within the magnetic field. Forces of different magnitudes

occur at the poles of the dipole in an inhomogeneous magnetic field so that a magnetic force FM will have an effect in the direction of a larger or smaller field strengths. The inhomogeneity of the magnetic field is decisive with regard to particle separation within the magnetic field. If the particles are in a liquid then the particle’s volume-related susceptibility κP must be taken into consideration along with the liquid’s volume-related susceptibility κf . The following applies to the magnetic force: (1) μ0 is the magnetic field constant in a vacuum.

The susceptibility of many liquids (e.g. water) is so low that it can be ignored, so in this case one can say that: (2) The magnetic fields that form as a result of the magnetisation of the surrounding particles also affect the particles in a suspension. It affects the interactions between the particles as well as the magnetic field that is active inside a particle /2/. Nevertheless, Equation (2) only applies when particles in the suspension can be considered as isolated.

The susceptibility of particle κP will be influenced by the susceptibility of the particle material κM as well as by the magnetisation and the internal magnetic field produced by the particle’s shape. This weakening of the external magnetic field inside a particle is taken into account by the use of the demagnetisation factor E. The following applies: (3) Due to the susceptibility of the particle material κM and the relative permeability μM resulting from it applies: (4) If a subdivision into paramagnetic, ferromagnetic and diamagnetic materials is

47

Highlights 2016

of the higher magnetic field strength for a spherical paramagnetic or ferromagnetic particle: Suspension flow

(7)

Fig.1 Operating principle for transverse separation in a magnetic field

carried out, then the following applies: κM > 0 bzw. μM > 1 Paramagnetic particles: This state occurs when they are magnetised by an external magnetic field; whereby the internal magnetic field is strengthened in proportion to the external magnetic field; the paramagnetic particles in the air and the water wander in the direction of the larger magnetic field strengths. κM < 0 bzw. μM <1 Diamagnetic particles: This state occurs when they are magnetised by an external magnetic field, however the internal magnetic field weakens in proportion to the external magnetic field; the diamagnetic particles in the air and the water wander against the direction of the larger magnetic field strengths. κM > 0 bzw. μM > 1 Ferromagnetic particles: According to their background they have a magnetisation that can be greatly intensified by an external magnetic field; the magnetisation and the polarisation do not increase in proportion to the field strength over the entire area, but strives for a maximum value in the case of large field strengths so that the following applies: κP = f (H))

If one takes the case shown in Fig. 1 in which the particles are separated perpendicular to the liquid flow, it can be seen from Equations 1 and 2 that the effect of the magnetic force applied to a particle with field strength H, depends on the inhomogeneity of the field strength and the particle volume. If paramagnetic or ferromagnetic particles are assumed, then the magnetic force and the weight force will be downward and the alignment will be perpendicular to the flow as shown in Fig. 1. These forces work against the resistance and lifting forces on the same pitch line of a freely moving particle. For small spherical particles, a laminar circulation can be assumed so that the following applies to the resistance force that counteracts the deflection: (5) In the case of small particles, the weight and buoyancy force when compared to the magnetic force FM and the resistance force Fw are so small that they can be neglected, so that this approximation applies: (6) Equations 2 and 5 give the result for the velocity of the deflection in the direction

As already explained, the gradient of the magnetic field strength in the flow channel of the developed magnetic separator is not constant so that the deflection speed and the effect of the magnetic force on a particle in the flow channel can both change whilst it is moving. In the case of permanent magnets, the local changes in the flow channel depend on the type and arrangement of the magnets, etc. A particle is considered to have been separated after it has been removed from the flow and is attached to the wall of the flow channel or to a plate. The separation efficiency η is the ratio between the quantity of separated particles to the overall quantity of particles that flow into the separator. If one describes the total quantity of particles in the separator’s inlet with the concentration cin and the quantity exiting with cab then the following applies: (8) D is the transition, i.e. the number of particles that cannot be separated.

The deflection Δz, or the distance travelled in the z-direction (Fig. 1), in a particle travels as a result of the flow through the flow channel, depends on the particle’s delay time tv in the magnetic field. The following applies: (9) In accordance with Fig. 1, a particle (analogous to a transverse flow in a sedimentation tank) is considered to have been separated when it reaches the wall with the magnets within the delay time. Therefore particle separation is also substantially affected by the delay time of the particles

Magnet Fluid Upper plate

Heatable storage tank

Perforated plate Spacer Perforated plate Lower plate

Fig. 2: Schematic layout of an open-gradient magnetic separatorw

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Separator Pump

Fig. 3: Flow chart for an experimental plant for determining particle separation efficiency

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0,0 0,5 1,0 1,5

cm cm cm cm

Gap, Gap, Gap, Gap,

without without without without

perforated perforated perforated perforated

plate plate plate plate

Separation efficiency /-

Separation efficiency /-

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Particle size /μm

(10) is the volumetric flow through the free Volume of the flow channel.

cm cm cm cm

Gap, Gap, Gap, Gap,

Rv Rv Rv Rv

1,5-3 1,5-3 1,5-3 1,5-3

Particle size /μm

Fig. 4: Fractional separation efficiency of Magnetite M40 LST with different gaps inbetween the magnets; version without a perforated plate

in the magnetic field. If one accepts that the particles move in the main flow direction (x-direction) together with the liquid and the Cross-sectional area Aq is constant over the Length L of the flow channel, then with regard to the delay time one can also say that:

0,0 0,5 1,0 1,5

Fig. 5: Fractional separation efficiency of Magnetite M40 LST with different gaps inbetween the magnets; version with perforated plate Rv 1.5-3

3. The developed magnetic separator In principle, the developed magnetic separator corresponds to the design shown in Fig. 1. It consists of an upper and a lower stainless steel plate as well as an intermediate layer that acts as a spacer, where the square flow channel can be formed (Fig. 2).

Two perforated plates made from magnetised steel are also positioned at the top and bottom of the flow channel. The

flow takes the separated particles through the holes and they are removed from the actual flow channel. The perforated plate simultaneously distorts the magnetic field and this creates additional gradients that have a positive effect on the particle separation process. If the holes in the perforated plates are continually filled with particles, they can easily be removed from the separator just by changing the plates.

A free height of 3 mm was set for the flow channel in the separator used in the following tests. The width of the flow

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Highlights 2016

Tab. 1: Pressure drop in an open-gradient magnetic separator when using different flow manipulators and a flow rate of 80 L/h

Flow manipulator

Pressure drop / bar

Without Polynet 0238 Enka-Spacer 7209 Enka-Spacer 5006, Straight EnkaSpacer 5006, Oblique

Separation efficiency /-

Fig. 6: Flow manipulator "Enka spacer 5006 H"

by Colbond

Without manipulator Polynet 0238 Enka-Spacer 7209 Enka-Spacer 5006, Straight Enka-Spacer 5006, Oblique

Prototype 1

Particle size /μm Fig. 7: Fractional separation efficiency of Magnetite M40 LST with the effects of different flow manipulators

channel was 40 mm and the length of the channel was 600 mm. Strontium-ferrite magnets (SrFe magnet, 100 mm x 100 mm x 25 mm) were used. The magnets can be placed on the top plate, the lower plate or even on both. The magnetic separator is distinguished by its large solids absorption capacity that results from the perforated plates. The tests were carried out to establish a specific solid absorption rate of approx. 300 mg/cm2 of the perforated plate. In this case the pressure drop of 0.2-bar at a flow speed of 0.18 m/s was not exceeded. With these values this type of magnetic separator can effectively relieve the load on a downstream depth filter and significantly increase its service life. The initial results from using the separator have already been described in /13/.

- Experiment implementation The experimental plant’s flow chart for testing particle separation using the new magnetic separator is shown in Fig. 3.

In the experiments, the separator was operated using the FVA 3 reference oil, to which magnetite particles were added.

The reference oil is a mineral oil that can be used as the transmission oil without the need for any additives. This is described in greater detail in the reference oil catalogue /14/. The experiment was conducted at a standard 40°C. The oil’s kinematic viscosity was approx. 90 mm2/s at this temperature. The oil density at 40°C was 860 kg/m3.

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Fig. 8: Cross-section of the oil sump with gearwheels

M40 LST magnetite made by Alroko was used as the particle system. It has a density of 5,500 kg/m3 and monomodal particle size distribution with a modal value of approx. 4 μm and a width of approx. 1 to 60 μm. The particles have an irregular shape. The specific magnetisation was 92 Am2/kg.

An Abacus mobile fluid oil single particle counter made by ‘Klotz’ was used for the particle analysis. The unit has 16 measuring channels and it can record particle sizes ranging from 0.9 μm up to 200 μm. The unit was calibrated by the manufacturer in accordance with ISO 11171 /16/ using ISO MTD (Medium Test Dust) over a measuring range of 4 μm - 100 μm.

The maximum possible particle concentration is 90,000 P/ml.

The following experiments were carried out in single-pass mode using a volumetric

flow of 80 L/h. The particle concentration in the suspension was 12.5 mg/L. A suspension volume of 8 litres was used.

- Experiment results Experiments without perforated plates were carried out in order to establish the effect of the gaps inbetween the magnets.

Plastic blocks made of PVC with different widths (0.5 cm, 1.0 cm & 1.5 cm) were placed inbetween the six SrFe magnets, which were all positioned on one side.

The measured separation efficiencies are shown in Fig. 4. Particles of approx. 1 μm were only separated up to approx. 3% in all cases. Particles with diameters of 5 μm were not separated. However, the previously determined fraction separation efficiencies are influenced: a) due to the separation of the particles in the flow channel and

Sample removal nozzle ¼" Prototype 1

Fig. 9: Cross-sectional of the oil sump with gearwheels

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Highlights 2016

b) due to the agglomeration effect as well. They can mutually attract and agglomerate as a result of the magnetisation and orientation of the particles.

Agglomerates were detected as single particles, e.g. the smaller particles in the agglomerates are “moved” into a larger particle class.

As described in the literature, the separation deteriorated as the gaps inbetween the magnets increased /15/.

In a further experiment the magnetisable perforated plates (Rv 1.5-3) were placed on the separation surfaces and the experiments were repeated under the same experimental conditions. The separation efficiency curves determined here are shown in Fig. 5. In this case the separation efficiency clearly improved when there was a gap of 1 cm inbetween the magnets.

All-in-all a magnetisable perforated plate had a more beneficial effect on the particle separation process.

As a result of the magnetisation of the perforated plates, the magnetic field strength gradients occur at the edges of the holes and this affects the particle separation process. The lines of force change at the hole edges with the different gaps inbetween the magnets, so that in this case the best results were attained when there was a gap of 1 cm inbetween the magnets.

Non-magnetisable flow manipulators were fitted in the flow channel in further experiments in addition to the perforated plates (Rv 1.5-3). Several types of such manipulators were tested in combination with the perforated plate (Rv 1.5-3). All had an open structure in order to keep the pressure drop in the flow channel as low as possible. A non-magnetisable flow manipulator is shown in Fig. 6.

Two different versions of the EnkaSpacer 5006 flow manipulator shown in Fig. 6 were tested. In the first version the

Magnets

Magnet housing

Magnetic separator Flow manipulator (Enka Spacer 5006H) Perforated plate Rv1,5-3 (underneath the flow manipulator) Rotating gearwheels Oil Fig. 11: Oil-filled oil sump with rotating gearwheels

peaks and valleys of the wave-shaped structure extend in the flow direction (hereinafter referred to as straight) and in the second version they extend transversely (hereinafter referred to as oblique).

The fractional separation efficiency determined here is shown in Fig. 7. As can be seen in Fig. 7, when flow manipulators were used, particle separation could only be improved when compared to an operation with perforated plates (gap inbetween the magnets = 0 cm). The best separation efficiencies were attained using the “Enka-Spacer 5006” flow manipulators in an oblique arrangement as shown in

Fig. 6. The pressure drop increases with the flow through the flow channel as the flow channel is partially constricted by the manipulator. The pressure losses measured with the different manipulators in the single-pass experiment are listed in Table 1. One can see that the Enka-Spacer 5006 manipulator slightly increases the pressure drop with regard to practical use.

The results show that particle separation in a separator can be improved by both the incorporation of a magnetisable perforated plate as well as by the use of non-magnetisable flow manipulators.

Separation efficiency /-

without magnet

Fig. 12: Fractional separation efficiency at different points in time with a perforated plate (Rv 1.5-3) and an Enka Spacer 5006H used as the flow manipulator

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Test stand housing

Temperature-controlled oil sump

Particle size /μm

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Magnetisable perforated plate

Fig. 10: Arrangement of the magnets, perforated plate and the flow manipulators at the bottom

Separation efficiency /-

without magnet

Non-magnetisable flow manipulator

without magnet 20NdFeB-magnet 2 SrFe-magnet

Particle size /μm Fig. 13: Fractional separation efficiency after 120 min, perforated plate (Rv 1,5-3), Enka Spacer 5006H

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Separation efficiency /-

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Rv Rv Rv Rv

1,5-3 without manipulator 1,5-3 with manipulator 4-6 without manipulator 4-6 with manipulator

seen afterwards, e.g. particles with a size of 3.5 μm were already separated up to 50% after 120 minutes. The two strontium-ferrite magnets were replaced by 20 x NdFeB magnets (50 mm x 20 mm x 8 mm) afterwards. This increased particle separation once again.

In further experiments where a perforated plate with large, rounded and offset holes (Rv 4-6) was used, small particles (1.45 μm) could be better separated after 120 minutes testing time if a flow manipulator was used as opposed to not using one. One is of the opinion that the manipulator assists particle agglomeration and separation as well. In experiments where a perforated plate with smaller holes (Rv 1.5-3 perforated plate) was used, no clear difference could be seen with and without a flow manipulator after 120 minutes (Fig. 14).

5. Summary

Particle size /μm Fig. 14: Separation efficiency comparisons with perforated plate (Rv 1,5-3), with and without Enka Spacer 5006H after operating for 30 and 120 min w

4. Particle separation within a gearbox On the basis of the results described above, an experiment was carried out to see if the magnetisable particle separation concept could also be used inside a gearbox. The housing was reproduced in the form of a stainless steel oil sump, in which two rotating plastic gear wheels produced the movement in the liquid. The side walls are double-walled so that temperature control is possible.

The sump’s basic dimensions can be found in Figs. 8 and 9. 20 neodymium-iron-boron magnets (NdFeB magnets, 20 mm × 50 mm × 8 mm) were placed under the bottom of the sump as shown in Fig. 10. 2 large SrFe magnets (100 mm x 100 mm x 25 mm) could also be used as an alternative. A 1 cm thick steel plate that deflected the lines of force was placed around the magnets.

A magnetisable perforated plate (Rv 1.5-3) with becalmed flow zones was used in the sump to collect the separated particles and to distort the magnetic field. A non-magnetisable flow manipulator was also placed on the perforated plate in some tests to divert the flow and to support the agglomeration.

5 litres of pre-heated FVA 3 reference oil (with a fixed space inbetween FVA and 3) were poured into the oil sump and the temperature was maintained at 40°C. 0.12 g magnetite was weighed out afterwards and suspended in 50 ml oil. The suspension was then dosed in through an opening in the lid. Samples could then be taken out through connections in the oil sump.

- Experiment results The results of the experiments using 20 NdFeB magnets, the Enka Spacer 5006H and the perforated plate (Rv 1.5-3) are shown in Fig. 12. The gearwheels turned at a frequency of 15 Hz. The determined fraction separation efficiency over the duration of the experiment is shown in Fig. 12. One can see that more than 80% of the particles with sizes > 20 μm were separated after 10 minutes. The separation efficiency, especially with small particles, improved as the experiment’s time was increased.

The magnets were removed after 120 minutes. It can be seen that hardly any particles were separated after longer than two hours.

In a further experiment, the oil sump was first operated after the addition of the suspension without magnets but with the perforated plate (Rv 1.5-3) and the Enka Spacer 5006H. The oil was moved by turning the gearwheels. As can be seen in Fig.13, larger particles were already separated in the becalmed areas in the sump.

Smaller particles (< 10 μm) could not be separated without using magnets. 2 x SrFe magnets were then placed underneath the oil sump. Particle separation of smaller particles could also be clearly

52

It has been shown that the magnetic separation of smaller magnetisable particles is also possible in highly viscous gear oil using the magnetic separator provided. Particle separation can be considerably improved by fitting a perforated plate. A further increase in the separation efficiency is possible by altering the gap between the magnets. It can also be seen that the flow manipulators that were used had a positive influence on the particle separation process, but this also depends on the perforated plate. The separator principle could be transferred to an oil sump, in which the oil is moved by the rotating the gearwheels. The particles already separated by the flow manipulators did not return to the oil circuit despite the removal of the magnets. Particle separation of small particles (< 3 μm) can be improved by using a flow manipulator.

Acknowledgement: We would like to thank the Federal Ministry of Economics and Technology for their support. Support measure: SIGNO; Support code: 03SHWB042 Literature: /1/ H. Schubert (Hrsg.): Handbuch der Mechanischen Verfahrenstechnik, Wiley-VCH, Weinheim (2003) /2/ H. Schubert: Aufbereitung fester mineralischer Rohstoffe, Bd. II, 3. Aufl., Deutscher Verlag für Grundstoffindustrie, Leipzig (1986) /3/ P. Dunnill, M. D. Lilly: Purification of Enzymes using Magnetic Bio-Affinity Materials.

Biotechnology and Bioengineering, 16 (1974), Nr. 7, S. 987-990 /4/ D. Rechtenwald, A. Radbruch (Hrsg.): Cell Separation - Methods and Applications.

Marcel Dekker, New York (1997) /5/ E. Boschke, S. Ripperger, Th. Bley: Biomonitoring by Combination of Immunomagnetic Separation and Direct Epifluorescence Filter Technique. Biotechnology 4 (2000), S. 318-319 /6/ E. Boschke, J. Steingroewer, S. Ripperger, E. Klingner, Th. Bley: Biomonitoring by combination of immunomagnetic separation and direct epifluorescence filter technique.

Online journal „European Cells & Materials“, 3 (2002) Supplement 2: S. 146-147 /7/ J. Steingroewer: Biomagnetische Separation in einem Verfahren zum schnellen Biomonitoring von Kontaminanten in Lebensmitteln. Dissertation, TU Dresden, 2005 /8/ B. A. Bolto: Magnetic particle, technology – Desalination and water reuse application.

Desalination 106 (1996), S. 137-143 /9/ D. A. Norrgran: Advances in the magnetic collection of fine particles, in: Vol. 6: New Filtration and Separation Equipment (R. W. Perters, Hrsg.), Cahners Publishing Company (1992) /10/ Magnetfilter zur Abscheidung feinster Partikel. Produktinformation Filtrieren und Separieren 18 (2004) Nr. 5, S. 295 /11/ A. Möhrle L. Steinke, S. Ripperger: Verschleißschutz durch eine effektive Partikelabscheidung. Teil 1: Verschleißschutzfiltration Filtrieren und Separieren 25 (2011), Nr. 5, S. 278-284 Teil 2: Testverfahren zur Bewertung von Partikelabscheidern Filtrieren und Separieren 26 (2012), Nr. 1, S. 15-20 /12/ A. Vetter, L. Petersen, S. Ripperger: Magnetische Separation feinster Partikeln aus Flüssigkeiten in Kombination mit einer Tiefenfiltration. Filtrieren und Separieren 27 (2013), Nr. 2, S. 66-71 /13/ A. Möhrle, S. Ripperger: Abtrennung von Partikeln aus Schmier- und Hydraulikölen durch magnetische Separation. Filtrieren und Separieren 24 (2010), Nr. 6, S. 290-297 /14/ Forschungsstelle für Antriebstechnik (FVA) e.V.: Datensammlung „Referenzöle“, Heft 660, Frankfurt, 2003 /15/ W. Baran: Fangmagnetsysteme aus periodisch angeordneten BariumferritDauermagneten ohne Eisenpolschuhe - Magnetfelder, Anziehungskräfte und Konstruktionsvorschriften. Dissertatation, TU Braunschweig (1965) /16/ ISO 11171; Hydraulic fluid power - Calibration of automatic particle counters for liquids, 2. Edition, 2010-10-25

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Highlights 2016

Field-flow fractionation – A separation process for very fine particles and macromolecules S. Ripperger* Processes for the classification of very small particles, especially nanoparticles and macromolecules, are increasingly in demand. They are interesting for use with products whose characteristic properties result from specific object dimensions, structural dimensions or surface effects. The classification effects occurring in laminar flow channels were examined in detail. Previously they were mainly used for analytical purposes. Field flow fractionation and the related methods are presented in the following article.

1. Introduction A laminar flow within a flow channel is an important prerequisite for the methods described in this article for classifying particles and macromolecules. A constant pressure drop is established over the flow length in the case of a stationary laminar flow between two stationary plates or in a tube. The parabolic velocity profile is obtained using the highest velocity in the centre of the gap or the tube (Fig. 1, y = 0).

This profile is created after a certain inlet length. When particles are introduced into the flow, they migrate through the channel in the x-direction at the flow velocity present there and in accordance with the adjusted arrangement on the y-coordinate.

Vary small particles are also affected by the diffusion force. This affects the particles as a result of collisions between the particles and the surrounding molecules. The Scottish botanist Robert Brown described the random zigzag motions of small particles and his description was based on his observations of pollen in water. The reason for this is the movement of the surrounding molecules that collide with the particles. Since the number of impacting molecules and their velocity fluctuate by average values, the force effect per unit of area acting on the particles must also fluctuate. Opposing forces do not always compensate simultaneously for this force effect on the particles. These impacts result in a force effect that causes zig-zag movements in the case of very small particles. Like the movement of the molecules, this is called a Brownian motion. Albert Einstein has shown that * Prof. Dr.-Ing. Siegfried Ripperger Information and Engineering Services (IES) GmbH Former holder of the chairs for “Mechanical process engineering” at the TU Kaiserslautern and TU Dresden Luxstr. 1 67655 Kaiserslautern, Germany Tel: +49 (0) 177 -605 -1291 Email: www.ie-services.eu

54

Fig. 1: Laminar flow in a gap

the particle concentration gradient lies in a direction perpendicular to a cross-sectional area for a long period of time and that several zig-zag movements cause a directed particle flow into a lower concentration area /1/. This compensation process is essentially influenced by the particle size, whereby it can be reinforced with smaller particle sizes.

Another force effect on particles is the one transverse to the main flow direction that is caused by the shear flow and the associated non-uniform incoming flow.

In such a case a force component acts on a particle, perpendicular to the inflow direction, the dynamic lift. It is the result of unsymmetrical distribution of pressure on the surface caused by the asymmetrical flow. The latter occurs especially in the vicinity of the flow along the walls. A lower static pressure is produced on the high speed side as opposed to the low speed side and this causes the particles to move in the lower pressure direction.

Particles in the vicinity of a wall therefore move away from the wall and, in the case of a capillary flow, arrange themselves in a size-dependent equilibrium radius /2 - 4/.

This force effect is also dependent on the particle size. In this case it increases with the particle size. It is the dominant force effect against diffusion for particles that are larger than approx. 1 μm. There is also a strong dependency on the velocity gradient to which the particles are

exposed, so that the force effect decreases in relation to the gap from the wall. An unsymmetrical incoming flow also produces a rotation, which also effects the particle’s movement in the case of freely moving particles.

The effect of the forces described above can be used in a flow channel for the classification or fractionation of particles.

2. Field flow fractionation (FFF) Previously Field Flow Fractionation was mainly used for analytical purposes.

The arrangement used here resembles that of chromatography, whereby the separation is usually carried out in a flat laminar flow separation channel, through which the eluent flows. A sample is dosed into the eluent at the inlet of an approximately 150 to 300 mm long and approximately 50 to 500 μm high separating channel and it is separated into several fractions during its flow through the channel. Therefore the process is discontinuous. A parabolic flow velocity profile forms in the channel so that the highest flow velocity is realised in the centre of the channel. The field force simultaneously acts on the particles or molecules to be separated perpendicularly to the laminar channel flow in the case of an asymmetrical FFF. J. Calvin Giddings (1930-1996) is considered to be the inventor of FFF. He taught at Utah university (USA) and patented and described it in

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Fig. 2: REM image of CMP Slurry A /11/

1966 /5/. He developed various forms in his working group as they depend on which field force is used for the separation.

2.1 Asymmetric FFF In asymmetrical FFF the laminar flow in the channel and the forces acting on it have another force superimposed on them, which is applied to the particles transversely to the main flow direction. The following forms can be discerned, but they depend on which type of force is superimposed on the laminar channel flow: - Electrostatic FFF: An additional deflection in the y-direction can be realised by means of an electric field that is perpendicular to the main current and the resulting electrophoretic force in the case of molecules and particles with excessive electric charges.

For example, such a field is generated when the upper and lower channel walls act as electrodes with different polarities.

- Thermal FFF: It is possible to heat the upper wall and cool the lower one analogously, so that a temperature gradient forms transversely to the main flow direction. This additional effect on the diffusion forces is also referred to as a thermophoretic force effect /6/.

- Asymmetric flow FFF (shortened to: AF4): A one-sided semi-permeable wall allows the channel flow (main flow) to superimpose a flow through the channel wall so that a second flow direction

is superimposed across the main flow (crossflow mode). A corresponding Stokesian resistance will also occur as a result of the flow component in the y-direction and this will produce a transverse movement that is dependent on the particle size. M. Myers also describes an operating mode in which both sides of the flow channel are permeable and a part of the eluent is applied to one side and discharged from the other side /9/. This results in a transverse flow being completely superimposed on the main flow.

- Gravitational FFF: The Earth’s gravitational field and its gravitational force can also be used in a specific way to produce a transverse movement dependent on the particle size if the orientation of the flow channel is horizontal.

- Sedimentation FFF: In order to enhance the separation effect and enable the separation of finer particle fractions as well, a circular and curved separating channel was laid in the interior of a centrifuge so that the centrifugal force acts on the particles perpendicular to the flow in the channel and this produces a transverse movement that is perpendicular to the main flow direction /8/.

The specific methods used by M. Myers are discussed in an overview contribution /9/. He differentiates between three effects or operating modes: a “normal” mode, a “steric” mode and a “hyperlayer” mode. In the “normal” mode with particles smaller than 1 μm, a concentration equilibrium is established in the flow over time as a result of the effect of the force being transverse to the main flow and the diffusion movement acting away from the wall. In this dynamic equilibrium the particles are arranged according to their size at different distances from the channel wall and they are discharged as a result of the parabolic velocity profile and after different retention times. In this case the retention times for small particles or molecules are less than those for larger ones.

The particles and molecules collect up in the immediate vicinity of the wall and move with the flow in “steric” mode. They are more or less caught by the flow according to their size. A larger flow resistance force acts more in the direction of the flow on larger particles than on smaller particles due to the flow profile on the wall. The larger particles will be the first to emerge from the flow channel as opposed to “normal” mode.

Particles that are larger than about 1 μm can also be transported into the centre due to their dynamic buoyancy so that they leave the separation channel within an even shorter retention time, but this depends on both the flow rate and the resulting conditions.

This effect or operating mode is referred to a “hyperlayer” mode.

In general the asymmetrical force effect and the superimposed

Sample inlet

Temperature gradient Channel inlet

Heating Separating channel Foil (spacer)

Channel outlet Cooling medium

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Sample outlet

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Fig. 3: a) Design and b) TFFF measuring principle /11/

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Ultracentrifuge TFFF PCS HPPS PCS Nicomp Ultrasonic spectroscopy

Particle size distribution Q3 (x), %

Particle size distribution Q3 (x), %

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Particle size x, nm Fig. 4: Particle size distribution in Slurry A

diffusion cause particles or molecules of different sizes to be arranged in different wall spacing in the flow channel and to migrate through the flow channel at different speeds. The result of the described force effect on the particles and macromolecules in conjunction with the laminar flow profile is that, depending on their size or other different properties, they move at different speeds through the separating channel and reach the flow channel outlet at different intervals. The substance system which is fed in at the separation channel inlet is therefore segregated or separated during its passage through the channel.

The separation methods are mainly used for separating the finest particles in the range from a few nanometres up to 100 μm and for separating molecules with relative molar masses in the range from 103 kg/ kmol to 106 kg/kmol. Proteins, biopolymers (e.g. polysaccharides) and artificial polymers all fall within this range.

It was mainly analytical tasks that were at the forefront with regard to previous applications. The devices developed for this purpose incorporate a 150 to 300 mm long separating channel with a rectangular cross-section (width approx. 10 mm, height ranging from 50 to 500 μm).

Samples up to a few milligrams could be fractionated. FFF is arranged as a separation stage in front of a measuring device that detects the separated molecular or particle fractions. These often act as detectors and they are also used in chromatography.

These include, for example, mass spectrometers, light-scatter photometers and absorption photometers. The separation channel is combined with a multi-angle light scattering detector (light scattering photometer) when used for analysing macromolecules. It is possible to determine the average molar mass, the gyration radius and the hydrodynamic radius of the individual fractions based on the measured values.

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TFFF PCS HPPS PCS Nicomp Ultrasonic spectroscopy

Particle size x, nm Fig. 5: Particle size distribution in Slurry B

2.2 Example: Using Thermal FFF (TFFF) Kuntzsch also studied the particle spectrum of CMP slurries, etc., including the use of TFFF /10 &11/. CMP slurries are polishing suspensions used in the electronics industry during the processing of wafers. These are mostly suspensions with amorphous silicon dioxide particles, as shown in Fig. 2.

The polishing suspensions have a pH of around 10.5 and in this state they also have high stability due to electrostatic repulsion. In the device used for thermal FFF, the separation channel was formed by a sealing film with a thickness of 127 μm being fitted in between two plates (see Fig. 3). The particles are driven in the direction of the cooled channel bottom (accumulation wall) as a result of the temperature gradient. This movement counteracts Brown’s diffusion.

The diffusion movement in the separation channel is influenced by the particle size as well as the temperature gradients.

In the dynamic equilibrium the particles arrange themselves according to their size and at different distances from the channel wall as they flow through the channel.

The TFFF was combined with a detector for static multi-angle scattered light measurement. This enabled the scattered light to be detected over 18 angles simultaneously.

A particle dimension can be determined for each fraction based on this. Fig. 4 shows the volume-related particle size distributions determined for Slurry-A (Fig. 2) using dynamic light scattering (PCS, HPPS and Nicomp), ultrasound spectroscopy and TFFF. The result of an analytical ultracentrifugation was also specified by the slurry manufacturer. The particle size distributions, which were determined using the above-mentioned measurement methods, are relatively well suited for the slurry being tested and correspond to the values that can be estimated from the microscopic images. The TFFF result

shows higher values for the particle sizes and a narrower distribution, possibly due to incomplete fractionation. In the case of incompletely fractionated particles, larger particles dominate because of the dependence on scattered light intensity I~x6.

It must also be taken into account that the gyration radius can be determined in which the distances of the individual primary particles from the centre of gravity enter into an agglomerate with the second power. This results in a particle size distribution that has the largest particle dimensions.

The particle size distributions determined by the different methods used for Slurry B are shown in Fib. 5. The average particle size of the volume-related distributions x50,3 show very good concurrence with the results from the four listed measuring instruments.

3. Symmetrical Flow FFF Symmetrical Flow FFF (shortened to: SF4), consists of upper and lower surfaces of the flat channel made from a material (e.g. a membrane) which is permeable to the eluent, which makes a transverse flow possible. The separation effect is also affected by this due to the diffusion. The same effect is also used in hollow fibre flow FFF (shortened to: HF5). In this case a hollow fibre membrane replaces the flat separating channel with a rectangular flow cross section.

Schauer also distinguishes between “normal” mode and the “steric / hyperlayer” modes as they depend on the effect of the liquid flow discharged over the porous wall /12/. In “normal” mode with particles smaller than 1 μm, a dynamic equilibrium is established with the flow over time as a result of the transverse flow, which moves the particles up to wall of the membrane and the diffusion movement is away from the wall. In this case the small particles or molecules are discharged from the flow channel as larger ones after a shorter retention time.

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This behaviour is reversed with particles larger than 1 μm in the “steric / hyperlayer” modes. Smaller particles are arranged closer to the wall as a result of the transverse flow, and the larger particles, in which diffusion is a secondary effect, leave the separating channel because of their size and possibly because of the dynamic buoyancy having shorter retention times as well.

The resulting conditions are substantially affected by the channel height as well as the longitudinal flow velocity and the flow velocity that is transverse to the channel length.

4. Hydrodynamic chromatography In HDC (HydroDynamic Chromatography) the classification occurs in a very narrow laminar flow channel and the eluent also passes through this channel. Channel heights of just a few micrometres are normal. As with FFF, the sample is dosed into the eluent at the inlet to the separation channel. The difference when compared to FFF is that no field forces or cross-flow are superimposed. The arrangement and method used here are similar to those used in chromatography.

The particles or molecules are arranged in the vicinity of the wall due to the narrow channel. Larger particles or molecules are detected by their higher velocities resulting from the parabolic flow profile so that an effect corresponding to the “steric / hyperlayer” modes described above can occur. Accordingly, larger particles or molecules migrate faster through the channel than the smaller ones. The classification is based on the size and geometry of the particles or molecules or their hydrodynamic radius and the laminar flow in the channel. Hydrodynamic chromatography is also used to determine the particle sizes of the polymer latices.

The determined particle sizes range between approx. 2 μm to 0.01 μm /13/.

7. Summary Various methods for the classification of fine particles and macromolecules were dealt with here in which fractionation occurred in a laminar flow channel. Both discontinuous as well as continuous processes were presented. The discontinuously operated methods were mainly used for analytical purposes previously. A more detailed description is given in /17/.

Literature: /1/ A. Einstein: Annalen der Physik 322 (1905), Nr. 8, S. 549–560 /2/ G. Segre, A. Silberberg: J. Fluid Mech. 14 (1962), S. 115 /3/ G. Segre, A. Silberberg: J. Fluid Mech. 14 (1962), S. 136 /4/ A. Brand, G. Bugliarello: Trans.Soc. Rheol. 10 (1966), S. 229-251 /5/J. C. Giddings: Separation Science Technology 1 (1966), S. 123–125. /6/ G. H. Thompson, M. N. Myers, J. C. Giddings: Analytical Chemistry 41 (1969), Nr. 10, S. 1219–1222 /7/ J. C. Giddings, F. J. Yang, M. N. Myers: Science 193 (1976), S. 1244-2145 /8/ J. C. Giddings, F. J. F. Yang, M. N. Myers: Analytical Chemistry 46 (1974), S. 1917-1924. /9/M. N. Myers: J. Micro Sep. 9 (1997), S. 151-162 /10/ T. Kuntzsch, U. Witnik, H. Hollatz, M. Stintz, S. Ripperger: Chem. Eng. Technol.

26 (2003), Nr. 12, S. 1235-1239 /11/ T. Kuntzsch: Dissertation, Institut für Verfahrens- und Umwelttechnik, TU Dresden (2004) /12/ Th. Schauer: Part. Part. Syst. Charact. 12 (1995), S. 284-288 /13/ M. Blom: Ph.D. thesis, University of Twente (2002) /14/ J. C. Giddings: Separation Science Technology 20 (1985), S. 749-768 /15/ S. R. Springston, M. N. Myers, J. C. Giddings: Anal. Chem. 59 (1987), S. 344 /16/ P. Matulka, P. Walzel: Chem.-Ing.-Techn. 82 (2010), Nr. 10, S. 1671- 1678 /17/ M. Schmipf, K. Caldwell, J. C. Giddings (Eds): Field-flow-fractionation handbook. WileyInterscience, New York (2000)

5. Split flow thin cell fractionation Split flow thin cell fractionation is a continuously running separation process and it is a further development of gravitational FFF /14, 15/. It is also referred to as SPLITT FFF and corresponds to the usual laminar cross-flow hydro-classifiers used in classification technology. The Earth’s gravitational field and its gravitational force are used in this method in order to realise fractionation in the case of horizontal flow channel orientation. Fractionation is realised with a very short delay time due to the separation channel’s low height of approx. 500 μm. The substance system that has to be separated is continuously fed in at the top of the separation channel’s inlet and is continuously removed at the other end as upper and lower flows. The discharge corresponds to the “suspension subdivision” model, which is known from classification technology. This method can be used for preparative fractionation of different dispersed substance systems.

6. Particle separation in a laminar tube flow with downstream flow expansion Matuka and Walzel studied the movement of particles in a laminar tube flow with downstream flow expansion /16/. The transverse forces described above also affect the particles in the radial direction. As particle systems with particles larger than 1 μm were used, the diffusion is of subordinate importance so that the transverse movement of the particles is mainly affected by the hydrodynamic buoyancy. The size-dependent equilibrium radii and the required tube length, from which the particles are arranged in their respective equilibrium radius, are decisive with regard to the separation process. The experiments show that the effect of the particle interaction in the flow tube on the radial positioning of the particles up to a value of about 5% volume is low. The effect of the radial equilibrium position in the laminar tube flows could be enhanced by downstream flow expansion. Small particles, which are closer to the tube wall in this case, move into the flow expansion. Large particles that have positioned themselves near the tube axis are drawn off via the centrally arranged coarse substance separator.

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Highlights 2016

New developments and results in the fields of air quality monitoring, filter testing and nanoparticle measuring technology Report from the 30th Palas aerosol technology seminar H. Lyko * For the 30th time, Palas CEO Leander Mölter and the event’s moderator, Prof. Christoph Helsper, were able to welcome the speakers and the audience to the Palas Aerosol Technology seminar in Karlsruhe. A total of 205 speakers from external industrial companies, research institutes and associations as well as universities have come to the seminar over the last 30 years. Among the participants in the jubilee event were a large number of regular guests, who have accompanied and also formed the development of aerosol technology as both developers and users, especially in the air quality monitoring, filter development and testing as well as nanoparticle technology sectors.

1. Air filter testing for the automobile industry Of the approximately 30 different filters installed in cars, engine intake air filters, oil separators (crankcase separators), tank ventilation filters, diesel soot filters and cabin air filters, all of them are used for air / gas filtration. Martin Schmidt, from Palas, compared the test conditions for these types of filters against the currently applicable standards as well as those still being prepared. He showed how these requirements were met and exceeded for certain test procedures using the components and test systems available from Palas. The latter relates to the new test stand for cabin interior filters, whose adjustable temperature and relative humidity both go far beyond that stipulated in ISO TS 11155-1 and 2. The PM1, PM2.5, PM4 and PM10 fine dust values can also be determined here. The raw gas concentration setting (test aerosol is motor oil) was so high that the integrated coincidence correction had to be applied to the aerosol spectrometers when the crankcase separators were tested. When the motor pre-air filter and cabin interior filter tests were compared it was found that the corresponding test standards stipulated extremely different raw gas concentrations (1,000 mg/m3 for motor pre-air filters and 75 mg/m3 for interior filters), even though the same raw gas (outside air) is drawn in through these filters during normal operations.

2. Particle measuring technology used in air quality monitoring Dr Norbert Höfert from the Commission for Air Pollution Control at DIN and VDI * Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

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continued his presentation about the development of the new VDI Directive 3491 given at the seminar in 2015. /1/. Pages 1 - 4 of the 6 pages that comprise the new Directive ( Measurement of particles Methods for generating test aerosols) have now been completed. This time the progress on Parts 5 (combustion / condensation) and 6 (transport and conditioning) was presented. Part 5 also deals with other processes in which particles are generated and dispersed from precursors via a chemical reaction in addition to aerosol generation through combustion (soot generator).

Three aerosol generators from Germany (Palas and MoTec) and Switzerland (Jing) were shown as marketable devices. Part 6 is comparatively extensive because many aspects have to be considered when transporting and conditioning aerosols. These aspects cover partial flow removal and sub-division as well as dilution in addition to the actual transportation. The conditioning includes measures for changing the state of the charge, drying and considering specific size fractions as well as other measures for adapting to the test conditions, increasing particle concentrations and removing troublesome components.

VDI Directive 3871 covering electrical aerosol monitors based on diffusion charging is also a work in progress in which the lung-deposited surface area (LSDA) concentration of particles in sizes ranging between about 10 nm and 1 μm in the concentration range of about 1 to 20,000 μm2/cm3 can be measured. This measuring process is used in portable industrial safety aerosol monitors. In the EU’s NanoIndex project, which is co-ordinated by IUTA (Dr. Christof Asbach), such devices were tested and the results were published in a guideline /2/. Furthermore Höfert cited the CEN/TS (Technical

Specification) 16976 “Outdoor air - determining the particle number concentration of atmospheric aerosols”) as being the most important standard publication of the year and in which the performance criteria of a condensation core counter and the sampling device are defined (see Tables 1 and 2).

Particle measuring systems measure different particle diameters (e.g. aerodynamic diameter, mobility diameter, scattered light diameter), but this depends on the applied measuring principle. The different methods used can cause significant differences in the results, especially with regard to non-spherical particles. Dr Maximilian Weiß, from Palas, showed that the direct conversion of scattered light diameters (as recorded by aerosol spectrometers) into aerodynamic particle diameters measured by an impactor being used as a reference device is hardly possible. This is because information on particle densities, refractive indices, shape factors and possible volatile particle constituents must be available, which is not the case in real air quality measuring. Instead, the aerosol properties measured by the optical aerosol spectrometers (used in the Fidas system) were correlated with those from the reference process, using data from a total of 20 worldwide measurement campaigns. The Monte Carlo process was used for optimising the fine dust algorithm. The correlation showed gradients between 0.9 and 1.1 at all sites and the R2 factors were all better than 0.92, with the majority of them being higher than 0.95. This high conformity between all of the measuring sites suggests that optical properties, densities, and shape factors were similar in all of the test campaigns. In a further study, the dae and dDiffr diameters determined by the two measuring processes, in which

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Tab 1: CPC performance criteria as per CEN/TS 16976

Fig. 1: Fidas Frog, fine dust measuring system for interior areas (Image: Palas GmbH)

Fidas devices with Sigma 2 sampling heads and PM10 separators were used in both, were compared directly. This meant that the penetration in the PM10 separator, based on the optical diameter, could be determined. The correlations between the two types of diameters were equally good at all sites with just one exception. The exception was the fine dust measurement from a tunnel in Melbourne, where Fidas only detected about 25% of the fine dust concentration that was measured by the impactor process. The cause of this was given as the extremely high dust concentration and the site was seen more as an emission site instead of an immissions site. This illustrated the application limits of Fidas as an immission measuring device under the certification conditions.

Whereas Fidas has been designed as an outdoor air measurement device, Fidas Frog now offers the option of using the same technology to measure fine dust concentrations in interior areas, for example, in the workplace. Karsten Pletscher presented the compact, portable device (Fig. 1), which enables time-resolved measuring of PM1, PM2.5, PM4 and PM10 particle fractions as well as total dust concentrations, particle counts and particle size distributions. The particle size measuring range lies between 180 nm and 40 μm. The technology and the evaluation algorithm from the certified Fidas 200 are implemented in the device. The housing and various components are produced by 3D printing. Operation is via a detachable Tablet PC, which means that it is also possible to place the measuring device in an inaccessible site.

3. Assigning fine dust immissions to their emitters In the discussions about measures to reduce air pollution from fine dust and nitrogen oxides, it is always of interest to note which emitters contribute which proportions of air pollution at specific measuring stations. At the end of his lecture, Dr Höfert referred to the project

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Tab. 2: Performance criteria for the sampling device

to determine the spatial and temporal distribution of UFP concentrations (particles <100 nm) in the vicinity of major airports, which was announced in the BMUB’s departmental research plan for 2016, and he also presented the results of the first tests made in the vicinity of the major Frankfurt/Main airport. At the measuring station in Raunheim, which is to the west of the runways, it was determined during the September 2015 to March 2016 period that the particle load clearly depended on the wind strength and wind direction.

The UFP concentration rose sharply as the wind blew from the direction of the airport, and the higher the wind speed, the more pronounced it was.

The low emission zones should improve air quality in metropolitan areas. On the 1st March, 2011, about 62% of the urban area in Leipzig was declared to be a low emissions zone and, with just a few exceptions, only vehicles with a green sticker are now allowed to enter it. This measure was accompanied by a comprehensive measuring campaign so that the effects of the low emission zone could be analysed not only by the PM10 value (this type of monitoring is a legal requirement), but also by such fine dust particles that are specifically classified as being engine emissions. Dr Gunter Löschau from the State Department for the Environment, Agriculture and Geology in the Free State

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of cellulose and hemicellulose, and potassium as constituents in each wood as well as benzo(a)pyrene (BaP). Whilst the contribution of the proportion of wood combustion in an earlier study was derived from concentration measurements of these tracers taken at different public measuring stations, a test stand was used afterwards in which combustion emissions were determined under defined conditions (different operating conditions and combustion methods) in both hot and cold exhaust gases as well as being measured in thinned, cooled exhaust gas /3/. This enabled the emission factors for the different tracer substances to be measured (as g dust/mg tracer substance) and compared against the literature data. It showed that the levoglucosan concentration is strongly dependent on the type of wood and the combustion process and therefore a site-independent emission factor could not be derived from these experiments. However, this could be realised using potassium whose emission factor, despite fluctuations, was more consistent with values previously published in literature. When the BaP concentrations that were taken at the Stuttgart Neckartor measuring station during a fine-dust alarm were compared against the values from the somewhat rural measuring station in TübingenUnterjesingen (which did not exceed the PM10 limit value during the same period), it could be seen that the proportion of wood combustion in the PM10 value was highly site-dependent. Even though the PM10 value in Tübingen was significantly lower than that in Stuttgart, the BaP concentration was 12 times higher.

4. Special methods used in atmospheric aerosol research

Fig. 2: Effects of the low emission zone on particles, soot and NOx loads in Leipzig, shown as the average measured parameter weekly loads (Source: State Department for the Environment, Agriculture and Geology in the Free State of Saxony)

of Saxony remarked on the concentrations of black carbon (BC) and fine dust particles in the 30 to 200 nm size range in the air that were also being measured by the air network measuring stations in addition to the PM10, PM2.5 and NOX values (see Fig. 2).

These particles are attributed to the engine exhaust gases. Löschau showed that in the period under review from 2010 to 2015, the PM10 load was significantly reduced overall as were the particle concentrations in the 30 - 200 nm size range and the values for black carbon. The latter’s contribution to the PM10 reduction was only 2.9 - 5.4% and this reduction also contributed to a reduction in the health risk by up to 27%. The introduction of the low emissions zone was a success in terms of particle pollution, but no improvement was seen with regard to the NOx load despite the accelerated modernization of existing diesel engine fleets in Saxony as compared to other regions. More detailed information and data can be called up online from the publication database /2/.

Wood-burning furnaces also contribute to the fine dust load. This was studied at the State Agency for Environment, Measurements and Nature Conservation in Baden-Württemberg, which was represented by Dr Harald Creuznacher. This was also studied against the background of the measuring station with the most frequent fine dust alarms (PM10 concentration > 50μg/m3), which is at Stuttgart Neckartor, where operation of so-called comfort chimneys (fireplaces, which are not required for heating) is also prohibited on such days. Specific tracer substances were measured as fine dust indicators from wood furnaces. For example, these could be either levoglucosan, an anhydrous sugar formed by the pyrolysis

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The analysis of atmospheric aerosols requires flying objects to be used to carry measuring devices so that the required data can be recorded at specific altitudes. Dr Ottmar Möhler, from the Karlsruhe Institute of Technology, showed that unmanned lightweight aircraft that could be used to close the measuring gap between the ground measuring stations and the aircraft measurements in the altitude range from approx. 100 to approx. 4,000 m.

When fitted with aerosol collectors or suitable measuring sensors, they should be able to supply data on air conditions and aerosols and they can also be used in dangerous environments (e.g. in storms, thunderstorms, forest fires or volcanoes). Low-cost, small and lightweight optical particle counters were presented for use in the case of direct on-site aerosol measurement. The Printed Optical Particle Spectrometer (POPS, see /4/) weighs 800 g and contains a measuring cell made using a 3D printer. It works by scattering laser light sideways and detects up to 10,000 particles per second and they can range in size from 140 to 3,000 nm. The OPC-N2 sensor that was developed by the University of Herfortshire weighs a good 100 g and can measure in 16 different size channels ranging from 0.38 up to 17 μm. It has now been marketed by Alphasense Ltd /5/. The Ultra-PASS system is also a new development. This is a single-particle optical counter with two detectors working with the forward and side spreads. Therefore the so-called aspect ratio and the information about the particle shape are also determined in addition to the particle size.

Not the lightest, but the most versatile flight object due to its range and recording capacity is the Global Hawk, which is used, amongst others, by NASA for the reconnaissance of tropopause flows. This drone was equipped with a large range of measuring instruments when used in the NASA Airborne Tropical TRopopause EXperiment (ATTREX) /6/.

Natural phenomena with far-reaching and long-lasting effects on aerosol concentrations and compositions in the atmosphere also include volcanic eruptions. The eruption of “Eyjafjallajökull” in Iceland in spring 2010 had far-reaching consequences for air traffic. A flight ban was announced for zones with a total aerosol concentration> 2mg/m3. This did not distinguish between volcanic ash particles, ice particles or water droplets. The sizes of

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Fig. 3: Diagram showing the experimental setup for the dual-wavelength measuring instrument for differentiating between water droplets and mineral particles (image: Institute for Aerosol and Sensor Technology at the University of Applied Sciences and Arts in North-West Switzerland)

Fig. 4: Laboratory setup for the dual-wavelength measuring instrument for differentiating between water droplets and mineral particles (Image: Institute for Aerosol and Sensor Technology at the University of Applied Sciences and Arts in North-West Switzerland)

all of the particle types lie in the 1 - 20 μm range, but only the volcanic ash particles endanger air traffic. Prof. Heinz Burtscher and his team from the University of Applied Sciences in NorthWest Switzerland developed an optical system that enables ice and water droplets to be distinguished from mineral particles. It is based on the various refractive indices dependencies of these substances on the light wavelengths. The particle types involved can be distinguished by comparing the scattered light intensity at two wavelengths, of which one is at 2,750 nm in the vicinity of the ice and water adsorption line. The R ratio of the scattered cross-section differential to be determined for specific substances at two wavelengths depends not only on the kind of substance but also on the particle size. In a laboratory experimental setup (see Figs.

3 and 4) that used two lasers with different wavelengths and two detectors, the system was tested using water droplets, cement dust, test dust as well as volcanic ash from Mt. Etna and the measured R values were compared against the values calculated from the refractive index curves /7/. The optical design has been modified for use in the atmosphere so that all of the measurement technology components are fitted inside a housing whilst the particles to be detected remain on the outside. The emitted and reflected measuring beams each pass through a heatable sapphire window.

This system has now been successfully tested in field measurements (including on the Jungfraujoch at temperatures below -20°C and with strong winds) as well as aircraft measurements, in which the system was installed in a gondola fitted under the wing. One is presently looking for a way to market the system, which could also serve as an early warning system on airplanes with regard to problematic aerosols.

an acceleration voltage of less than 5 keV and can therefore be used flexibly and without any bureaucratic overheads. It could be seen that the X-ray charge produces a somewhat more symmetrical charge distribution with less multiple charges than the radioactive source when the 85Kr-β emitter and the X-ray charges were compared. With the new unit it is also possible to measure using two different polarities by switching between positive and

5. Developments in nanoparticle measuring technology During nanoparticle measuring the particles are classified according to their size, which is based on their electromobility, so that single size fractions can be enlarged in a condensation core counter afterwards using condensation from the liquid and counted in an aerosol spectrometer. The classification based on electromobility requires a defined aerosol charge setting. As Frederik Weis from Palas explained, the discharge can be made using a radioactive source (often 85Kr) or by using soft X-rays. He presented the DEMC XB as an innovative device that is equipped with an X-ray neutralizer, which is not subject to approval with

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Fig. 5: Measuring arrangement in the mobile demonstrator for nanoparticle characterisation using WALS and LII (Image: Institute of Technical Thermodynamics at the Friedrich-Alexander University in Erlangen-Nuremberg; reproduced from: /9/ Rev. Sci. Instrum. 87, 053102 (2016), with kind approval from AIP Publishing)

the particles are. The size and fractal shape of the particle aggregates can be determined with the help of elastic light scattering. The gyration radius and the fractal dimension of a particle can be determined from different curve sections of the scattered light intensity, which is dependent on the scatter-angle. However, the technical implementation of a process that uses a scattered light detector installed on a goniometer is not really suitable for use in industrial processes. Wide angle light scattering (WALS) represents another variant of elastic light scattering in which an ellipsoidal mirror is used. This mirror is used to reproduce the scattered light onto a CCD camera, i.e. the angle-dependent scattered light intensity will then be seen as a single camera image. This makes it a “real-time” process and it is also suitable as an online measuring method. This was confirmed by real-time measuring using a soot generator. A statistical evaluation that reduces the number of possibilities is needed in order to estimate the aggregate size distributions using WALS. Huber et al. used the Bayesian statistics /10/. A mobile measuring system consisting of WALS and LII units was built at the Institute as a demonstration system, which makes the characterisation of nanoparticle aerosols possible in industrial processes over a wide range of concentration and size ranges. The production and subsequent sintering of SiO2 nanoparticles was cited as an application example.

6. Aerosol and gas emissions from 3D printers

Fig. 6 Combination of WALS and LII plus an evaluation computer on a trolley (Image: Institute of Technical Thermodynamics at the Friedrich-Alexander University in Erlangen-Nuremberg; reproduced from: /9/ Rev. Sci. Instrum. 87, 053102 (2016), with kind approval from AIP Publishing)

negative electrode voltages and also to measure simultaneously using two different particle classifier or counting units. It is possible to draw conclusions about the charge distribution of an unknown aerosol when using such an arrangement.

Franz Huber and colleagues at the Institute of Technical Thermodynamics at the University of Erlangen-Nuremberg used a series of laser-optical measuring techniques for comprehensively characterising nanoparticles. For example, the formation of agglomerates is not only detected as altered size information as they are also indicated by their fractal dimen-

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sion, gyration radius and the number of primary particles they contain. A method developed at the Institute for determining the sizes and concentrations of nanoparticles is called laser-induced incandescence (LII). The particles are heated by a laser pulse here, and the increased thermal radiation and the cooling performance of the particles are measured afterwards. The temporally triggered LII signal is obtained through a numerical solution to the mass and energy balances and each particle size produces its own decaying curve. The longer the signal’s decay time, i.e. the slower the cooling down takes, the larger

Additive manufacturing processes are gaining in importance in the industrial production of prototypes as well as in the serial production of components made of plastics or metals. 3D printers are becoming increasingly popular amongst DIY enthusiasts and hobbyists. Studies into the various additive production processes in which gases or aerosols are emitted are still in the early stages. Dr Stefan Seeger is busy with printer emissions at the German Federal Institute for Materials Research and Testing (BAM). He presented the different device types and pointed out that currently no emission protection standard exists and that only the very expensive systems are fully enclosed. A platform with a test chamber for measuring the emissions from different printers has been constructed at BAM. A system for powder bed fusion and material extrusion was tested initially. The first uses a laser beam to combine any metals or ceramics that are present as a powder and the extrusion printer melts any polymers present as filaments and the object to be printed is then built up layer by layer. The platform’s

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Fig. 7: MMTC H filter test stand system design for realising catalytic low-temperature denitrification with particulate catalysts on a cleanable filter medium (Image: IUTA)

measuring equipment enables both gas analysis using various spectrometric or chromatographic methods as well as particle analysis of sizes ranging from 2.5 nm to 30 μm with particle concentrations of 0.1 to 108 particles/cm3 to be used. When the laser beam strikes the powder coating the corresponding energy input results in the release of particles with dimensions of about 100 nm and the particles also lie in the range up to 300 nm during extrusion.

During polymer extrusion it was also noted that the gas and particle emissions very much depending on both the raw materials being used and the processing conditions.

7. Biological validation of the airborne germ collecting equipment Back in 2013, Anja Konlechner from the University of Natural Resources and Applied Life Sciences in Vienna reported on the development of a calibration chamber for airborne germ collecting devices, which was undertaken in cooperation with Palas /11/. Whereas the physical evaluation was made using Arizona test dust, Clara Pogner now presented results obtained from using living test organisms in this chamber. An important step here was that various germs suspended in a liquid could be successfully atomised in the chamber with high survival and low loss rates. Up to three germ collectors can be tested next to each other in the chamber and the devices are operated one after the other in order to ensure that they do not interact with each other. A total of 7 different collectors and 4 different collecting principles were compared. It was found that the efficiency of different types of collectors varied with different microorganisms (spores, yeasts), which is why the review of the collecting methods and the organisms is considered useful for determining the limit values. Hydrophobic organisms are still problematic with regard to this chamber because the detergents used for stabilising the suspensions are of

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nearly the same particle sizes and this falsifies the counting result from the aerosol spectrometer.

8. Combining noxious gas removal and particle filtration The particle separation and noxious gas elimination functions have to be fulfilled in parallel or in succession during exhaust gas cleaning. This also applies to small and medium-sized biomass incineration plants. Dr Ingo Hartmann et al. at the German Biomass research Centre in Leipzig, Germany, have developed a controllable filter for such small plants, which is significantly below the currently applicable limit values regarding dust, HCl, SO2 and PCDD / PCDF (polychlorinated dibenzodioxins / dibenzofurans) emissions in accordance with 4th Federal Emissions Protection Act, as part of a ZIM project. The flue gas cleaning is carried out with the aid of a hose filter system with a filter area of up to 8.64 m2 (25 hoses), to which a sorbent (Ca (OH)2) is added either continuously or periodically. The described measuring campaign was used to optimise the operating parameters and the precoat dosing, which will subsequently be used to operate a practical plant. The optimum precoat dosage was determined using HCI breakthrough curves. The dust formed during biomass burning is somewhat complex and one must expect to find inorganic salt particles smaller than 100 nm, soot particles of around 100 nm and inorganic oxide particles up to 10 μm as well as the coarse dust. The broad particle size range requires the use of two measuring processes measuring the fraction separation efficiencies, an SMPS system for particles up to and around 900 nm and an optical particle counter for the larger particles. Different physical quantities, the electromobility diameter and the scattered light diameter also have to be covered here through suitable conversions in the overlapping area in the measuring ranges.

In the end, it was possible to attain a separation efficiency better than 94% for all

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pollutants and to reduce the total dust content in the clean gas to less than 5 mg/m3 (current limit value: 20 mg/m3).

A process for the catalytic low-temperature denitrification of exhaust gases, in which the catalyst particles are retained by a surface filter, was developed at the Institute for Environmental and Energy Technology (IUTA) in Duisburg in collaboration with the Institute for Technical Chemistry at the University of Leipzig. Dr Stefan Haep reported on the status of the project in which new catalyst materials (manganese, copper or iron oxides on activated carbon and modified as necessary, and ceramics or mixed oxides used as carrier materials) were being tested. The processing temperature should remain under 200°C here (earlier catalysts worked at 280° – 380°C). The two catalyst materials (Cu and Mn) that have already been tested have shown that the system’s degradation efficiency clearly depends on the powder’s tendency to form a complete filter cake.

The catalyst activity, which depends on the temperature and the relative humidity of the raw gas, must also be monitored.

The core of the experimental work is the new MMTC 2000H filter test stand, which enables cleanable filter media to be tested at increased temperatures and increased relative humidities (see Fig. 7).

9. Testing filter media and systems Aerosols are generated using different methods during the filter testing and this can result in aerosol charging as this depends on the type of particle dispersion and the material being used. Dr Thomas Laminger studied the effects of test dust particle charging on the separation efficiency and filtration-specific parameters of needle felts at the TU in Vienna. Particle neutralisation is not stipulated in the applicable test standards for cleanable filter media and it is optional in VDI standard 3926. A VDI test bench was equipped with a bipolar discharge path in which a

Tab. 3: Dust classes for industrial dust extractors as per DIN EN 60335-2-69, Appendix AA (Source: Institute for Occupational Safety and Health of the German Social Accident Insurance (DGUV at: www.dguv.de)

positive and a negative voltage could be set up independently of each other and an electrometer for this project. The filtration efficiency factors were determined for neutral, positively and negatively charged aerosols for two different needle felts, whereby the Pural NF test dust that was used could not be completely neutralised because of the broad particle size distribution. The effects of the aerosol generation on the charge can also be determined in addition to recognising that the initial separation rates for negative as well as positively charged aerosols are similarly increased as compared to the separation efficiencies for neutral aerosols.

Even slight variations in the brush speed or the pre-pressure will change the test dust’s charge state. Choosing another filter medium that exhibited a lower tendency to generate charges to the dust resulted in a shorter cycle time and a rapidly increasing residual pressure loss at the start of the filtration process. All of the charge effects are hardly measurable from about the 10th filtration cycle onwards, i.e. the aerosol charge does not affect the long-term performance of the needle felt.

Ute Kreißig from the Saxonian Textile Research Institute in Chemnitz, Germany, reported on the possible causes of measurement inaccuracies in repeated filter tests from her many years of experience gained during filter testing. Every filter medium initially undergoes quality fluctuations, which are caused by possible changes in the raw material quality or aging of the fibre material.

Textile parameters can vary by about 5 - 15%. Furthermore, using different batches of test dust in the brush dosing device can also alter the test results.

The differences in quality, especially with regard to the coarse part, were shown in two batches when Pural SB test dust was used. As the piston in the brush dosing device is manually filled, dust weight or filling density differences caused by the personnel can result in fluctuating dust dosing widths. A tolerance of ± 10% for the dust application concentration is permitted when determining the dust storage capacity of a filter in compliance with VDI 3926-1. If a belt feeder is used for feeding the dust into the scales, then external influences (e.g. vibrations from

Fig. 8: Interior view of an industrial vacuum cleaner of class H after the assembled system being tested with limestone dust (Image: DMT GmbH & Co. KG)

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other machines present in the room) might also have an effect.

The aging of a filter medium during its storage might also affect the test result.

The systems and product safety department at DMT Group is involved, amongst other things, with the testing of commercial vacuum cleaners and dust extractors in accordance with DIN EN 60335-2-69 (Appendix AA). Dr Dirk Renschen introduced the conditions under which air return is permitted during activities involving carcinogenic, mutagenic and fertility-impairing dusts in compliance with the Technical Regulations covering Hazardous Substances (TRGS) 560. Accordingly, approved processes or equipment must be used that have a minimum separation efficiency of 99.995% (Dust class H), provided that no additional requirements are specified in the substance-specific TRGS (classification of the devices into Dust classes, see Table 3). The scope of testing for industrial vacuum cleaners is very high. The transmittance efficiency is determined for Dust class L and M equipment using a total of 6 samples from the main filter materials, whereas the transmission efficiency of the main filter element is measured for Dust class H equipment. The main filter media test stand, in which the dust-laden air is drawn through the filter material for an hour and the clean air quality is then measured using a photometer, is installed at the Institute for Occupational Safety and Health of the German Social Accident Insurance. The DMT operates a test stand for determining the transmittance efficiency of main filter elements, which is carried out using a test aerosol of paraffin oil, dispersion oil particles or NaCl that is supplied in concentrations that range between 10 and 200 mg/m3, whereby 90% of the particles are smaller than 1 μm. A large number of other test tasks are undertaken on the machine installed in a test chamber. These relate to safety aspects (bursting strength, protective equipment), manageability and cleanability as well as aspects of dust collection and removal in addition to determining the suction power and filter efficiency. A polydisperse limestone dust with a specific particle size distribution (10% < 1 μm, 22% < 2 μm, 75% < 5 μm) was dusted on at a concentration of 5 g/m3 for these tests. Fig. 8 shows an impression of the interior of an industrial vacuum cleaner after being impacted by limestone dust.

The separation of liquid droplets on a coalescing filter is very complex and theoretically difficult to predict due to the many forces involved. Dr Wolfgang Mölter-Siemens and his co-workers, from IUTA, have been working on coalescence filter, in particular a compressed air filter, for several years in a test bench built especially for this purpose. This time he reported on how the reintrainment of previously separated liquids depends on the filtration conditions. If such a filter is being operated in a stationary condition, then the surface of the liquid contained in the medium is in contact with the reagent side so that the liquid droplets are carried away by the air flowing through the filter. This reduces the filter’s separation efficiency. The size-dependent clean gas concentration was measured during the tests using two compressed air filters with different filter grades together with various raw gas concentrations, volumetric flows, pressures and temperatures, both during the saturation phase of the new filter and in the saturated state. It was found that the concentration of the so-called primary penetrates (particles / droplets that are not retained by the filter from the outset) depends on the saturation and the loading capacity, whilst the extent of the reintrainment depends on the saturation, the volumetric flow and the temperature. A real filter breakthrough occurs when the volumetric flow reaches 1.4 times the nominal volumetric flow. Whether the primary particle penetrate or the reintroduction in the clean gas prevails depends on the quality of the filter, as the finer it is, the lower the proportion of the primary particle penetrate. The temperature dependency that was found led to the recommendation to restrict the permissible temperature range used in the compressed air filter test standard (ISO 12500-1) in order to obtain comparable results.

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Literature: /1/ Lyko, H.: Fortschritte in der Aerosoltechnologie unterstützen Aerosolforschung, Filterentwicklung und Filterprüfung; F&S Filtrieren und Separieren 29 (2015) Nr.6, S. 390 – 396 /2/ C. Asbach et al.: Assessment of Personal Exposure to Airborne Nanomaterials – A Guidance Document, Mai 2016, zum Download unter nanoindex.eu (stand Oktober 2016). /3/ Publikationsdatenbank des Landesamts für Umwelt, Landwirtschaft und Geologie des Freistaats Sachsen zur Umweltzone Leipzig: https://publikationen.sachsen.de/bdb/artikel/14411 https://publikationen.sachsen.de/bdb/ artikel/18590 https://publikationen.sachsen.de/bdb/artikel/23885 https://publikationen. sachsen.de/bdb/artikel/25641 /4/ LUBW Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg (Hrsg.): Bestimmung des Beitrags der Holzfeuerung zum PM10-Feinstaub an zwei Messstationen im Baden-Württemberg von Oktober 2008 bis Dezember 2009, Dokument Nr. 64-01/2010, Dezember 2010 /5/ R.S. Gao, H. Telg et al.: A light-weight, high-sensitive particle spectrometer for PM2.5 aerosol measurements; Aerosol Science and Technology Vol. 50 (2016) Issue1, http:// dx.doi.org/10.1080/02786826.2015.1131809 /6/ http://www.herts.ac.uk/research/centres-and-groups/cair/particle-instruments-anddiagnostics/low-cost-particle-detectors (Stand Oktober 2016) /7/ E.J. Jensen, L. Pfister et al.: The NASA Airborne Tropical Tropopause Experiment (ATTREX): High-Altitude Aircraft Measurements in the Tropical Western Pacific; Bulletin of the American Meteorological Society; 2015; DOI: http://dx.doi.org/10.1175/ BAMS-D-14-00263.1 /8/ Z. Jurányi, H. Burtscher, M. Loepfe, M. Nenkov, E. Weingartner: Dual-wavelength lichtscattering technique for selective detection of volcanic ash articles in the presence of water droplets, Atmos. Meas. Tech., 8 (2015), S. 5213-5222, doi:10.5194/amt-8-5213-2015 /9/ F.J.T. Huber, M. Altenhoff, S. Will: A mobile system for a comprehensive onlinecharacterization of nanoparticle aggregates based on wide-angle light scattering and laserinduced incandenscence, Rev. Sci. Instrum. 87(2016), http://dx.doi.org/10.1063/1.4948288 /10/ F.J.T. Huber, S.Will, K.J. Daun: Sizing aerosolized fractal nanoparticle aggregates through Bayesian Analysis of wide-angle light scattering (WALS) data, Journal of Quantitative Spectroscopy and Radiative Transfer Vol 184 (2016) 27-39 http://dx.doi.org/10.1016/j. jqsrt.2016.06.030 /11/ H.Lyko: Höhenflug der Aerosoltechnologie – Bericht vom 27. Palas-AerosoltechnologieSeminar, F&S Filtrieren und Separieren 27(2013) Nr. 6, S. 379 – 385.

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Efficiency of cabin air filters during life cycle with regard to particle filtration and adsorption F. Schmidt *, A. Breidenbach *, U. Sager **, E. Däuber ** and T. Engelke ** Introduction Air filters are tested with standardised tests for quality assurance and in order to make their efficiency comparable for customers.

Cabin air filters are tested in compliance with DIN 71460 [1] or ISO 11155 [2]. Both standards consist of two parts, Part 1 describing the tests for particle filtration, part 2 the tests for gas cleaning by adsorption.

Part 1 sets out the test methods for determining the pressure loss depending on the volumetric flow rate and the fractional efficiency of the filter in the initial stadium. The required minimum separation efficiency range for filters installed in passenger cars or trucks (tested at a volumetric flow rate of 300 m³/h using ISO A2 test dust) is given in VDI 6032-1 [3]: Combi-filters (particle filters with a thin additional activated carbon layer) are used in passenger cars to prevent noxious gases, in addition to particles, from entering the vehicle’s interior. The filter’s adsorptive performance is tested in compliance with ISO 11155-2 (Note: DIN 71460-2 corresponds to ISO 11155-2 and has therefore been withdrawn) at a temperature of 23°C and 50% relative humidity. Test results are breakthrough curves for the respective test gas which are used to calculate the adsorbed mass and the filter capacity.

The aim of filter tests in compliance with standards is to make their performance comparable [4]. The test results are not appropriate for estimating the filter performance in real operation over the entire service life. For this purpose additional tests are required, simulating filter aging during the life cycle.

At the IUTA e. V. an ‘aging’ test stand was therefore set up as part of a research project and was used for the continuous, * Prof. Dr.- Ing. Frank Schmidt A. Breidenbach University Duisburg-Essen¸ Nanoparticle Process Technology (NPPT) Duisburg, Germany ** Dr. U. Sager, E. Däuber and T. Engelke Institut für Energie- und Umwelttechnik e. V. (IUTA) Duisburg, Germany

Fig. 1: Filter test stand with four separate test ducts

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Tab. 1: Required minimum initial separation efficiency of filters that are installed in passenger cars and trucks, tested at a volumetric flow rate of 300 m3/h using ISO A2 testdust

parallel loading of four cabin air filters with ambient air. The filter tests were subsequently performed on the filter test stand at the University of Duisburg-Essen. The filter’s separation efficiency in its initial stadium and after aging using ambient air was determined using a DEHS test aerosol (standard for testing air filters for general ventilation, see DIN EN 779 [5]). The efficiency of cabin air filters (used or aged with ambient air) with regard to their adsorptive separation capabilities was tested using n-butane, toluene or nitrogen dioxide (NO2) as test gases.

All cabin air filters tested within the study as presented - new, used and artificially aged - were of the same type. Used filters which had been utilized in vehicles under real operating conditions for 1-2 years were provided by authorised garages, where the filters had been replaced during inspections. Thus, all used filters had unknown loading histories, and compared with new filters the pressure loss at a flow rate of 200 m3/h was about 15 Pa higher.

2. Description of the test stand for artificial filter aging The test stand consists of four separate test ducts, allowing a continuous loading of up to four filters over a period of several weeks (Fig.1). The cabin air filters can be loaded with ambient

Fig. 2: Pressure loss comparisons for cabin air filters of one type: Load ‘aging’ test stand / test stand according to DIN 71460-1w

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Fig. 3: Number distribution (average minutes / average over 6 h) in the ambient air used for aging

air or alternatively with soot / diesel soot [6]. The test ducts are housed in an air-conditioned container, which is located in the immediate vicinity of a logistics location situated at a street with high traffic (Duisburg). The radial fans enable volumetric flows of between 150 m³/h and 740 m³/h in each duct. The pressure losses over the cabin air filters are recorded in each of the four ducts as a function of the volumetric flow and compared against those measured at the test stand according to DIN 71460. The conformity concerning the dependence of the pressure loss on the volumetric flow rate between the four ducts and the test stand according to DIN 71460 is very good (Fig. 2).

Temperature, relative humidity, wind speed and wind directions were continuously recorded during aging in order to better analyse the results of the subsequent filter tests, i.e. to be able to detect seasonal fluctuations as well. It should be noted that filters treated at the same time on the stationary test stand undergo the same seasonal climatic fluctuations during accelerated aging, whereas filters used in cars are exposed to locally different immissions.

Fig. 4: DEHS efficiencies for untreated and IPA-treated new filters

Measurement of the particle number concentrations and size distributions in the ambient air was carried out using a Fast Mobility Particle Sizer (FMPS, TSI GmbH, Germany). Unlike the Scanning Mobility Particle Sizer, the FMPS enables the measurement of temporary high-resolution particle size distributions and is therefore suitable for evaluating transient processes. Both the temporary progression of the measured data from the number concentrations as well as the size distributions taken at discrete points of time show, as expected, the transient character of the ambient air. Fig. 3 shows a two-minute average from the number concentration distributions taken over several hours.

3. Particle filtration efficiency of new, used and artificially aged cabin air filters In the first part of the study new, used and artificially aged cabin air filters were tested with a DEHS test aerosol according to DIN 71460-1 and the efficiency curves were compared. The fraction separation efficiencies were determined using a light-scattering aerosol spectrometer

(WELAS, Palas GmbH, Germany) or an aerodynamic particle sizer (APS, TSI GmbH, Germany). The optical scattered light particle diameter detected with the WELAS corresponds to the geometric one using a DEHS calibration curve. For the conversion of the aerodynamic equivalent diameter measured with the APS into the geometric equivalent diameter the DEHS density was used.

Artificial aging was performed using the described test stand with a continuous ambient air flow rate of 200 m³/h. Time periods of artificial aging were three days and one, two and four weeks. Three days of continuous aging with ambient air correspond to about four months of real driving, assuming a driving time of 1 hour per day for 20 days per month. A time period of four weeks of filter aging corresponds to virtually three years’ usage, which is a period during which a filter exchange would already have taken place in the vehicle.

As described, all tested cabin air filters, new, used and artificially aged, were of the same type.

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Fig. 5: DEHS efficiencies of new and artificially aged filters

3.1 Experimental results of particle filtration tests Performance was first tested of the new filters, once untreated and once treated with isopropanol (IPA). Fig. 4 shows the mean DEHS efficiencies determined from 4 filter tests. As expected, the fractional separation efficiency of the filters treated with IPA is clearly lower than the one of the untreated new filters.

In Fig. 5 the fraction separation efficiencies of the new filters already shown in Fig. 4 are compared with those of artificially aged filters exposed to ambient air for different time periods during the summer months. The measured fraction separation efficiencies of the artificially aged filters are comparable to the efficiencies of the IPA-treated filters. Apparently the aging with a continuous flow over a period of three days had electrically neutralised the filters. The aging over the four week period did not lead to any improvement in efficiency as a result of the deposited particles.

The influence of the particle load in the ambient air used for aging on the filter performance was investigated by cleaning

Fig. 7: DEHS efficiencies of new and used filters

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Fig. 6: DEHS efficiencies of new filters and artificially aged filters loaded with particle reduced ambient air

the ambient air from particles with an upstream high-efficiency particulate air filter (HEPA filter). The air is loaded with particles to a very small extent and it is therefore possible to determine whether the change in the separation characteristics is based exclusively on the loading of ambient air particles on the filter fibres or whether the loss of the filter’s electret action was caused by the temperature and humidity of the air flowing through the combi-filter. In Fig. 6 the fraction separation efficiencies of the new filters – untreated and treated with IPA – are compared with those of artificially aged filters with ambient air, which had been purified of particles by the additional HEPA-filter.

The results for one, two and four week aging are in the same range that was determined for the IPA-treated filters. Only the efficiency curve of the filter aged for the shortest time period of three days (blue curve) is slightly above that of the IPAtreated filter. Apparently the filter still had not been completely electrostatically neutralised. The temperature range during the four weeks’ period of artificial aging was between 12°C and 39°C and the humidity

range was between 25% and 96%. These boundary conditions have led to the elimination of the filter’s electret effects.

Fig. 7 shows the comparison of the DEHS efficiencies of new (blue curve) and used cabin air filters (black curves).

The efficiency curve of the new filters is based on the average of five filters, with the error bars indicating the standard deviation. The efficiencies of used filters are all clearly lower than those of new filters.

Presumably used filters lose much of their electret characteristics during service life.

The fact must be taken into account that the used filters tested are not all derived from the same production batch and can have structural inhomogeneities and different electrostatic charging. For the new filters, the individual storage conditions after production and before the tests can influence the efficiency of the individual filters. It is not possible to quantify the individual influencing factors – loss of electret characteristics or increasing efficiency due to the formation of a filter cake – from the efficiency curves.

Fig. 8: DEHS efficiencies of an electret medium at 23°C and various relative humidities

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Fig. 9: Filter test stand for conducting adsorption tests acc. to ISO 11155-2

In order to study the effects of moisture and temperature on the electret effect of the cabin air filters, further experiments were carried out with a new filter medium with a pronounced electrophoretic effect, still using DEHS test particles. After the first test determining the initial efficiency at 23°C and 30% relative humidity, further tests were conducted at successively increasing relative humidity up to 90%, and subsequently at decreasing relative humidity back to 30%. Conditioned air was passed through the filter medium for about one hour. The fraction separation efficiencies measured are shown in Fig. 8 The efficiency curve of the same filter medium type treated with IPA (red data points) is depicted additionally for comparison. It can be seen that the humidity variations at this temperature level within just a few hours led to a reduction in the separation efficiency approaching that of the IPA-treated medium.

3.2 Conclusions of particle filtration tests Electret filter medium is usually used for cabin air filters. The change in the filter’s efficiency due to increased loading

Fig. 10: Comparison of n-butane breakthrough curves of new, used and artificially aged filters (23°C, 50% RH, c1 n-butane = 80 ppm)

or service life results from the interaction between the decreasing electrophoretic contribution to the separation process and the improving mechanical separation, with a corresponding increase in the amount of dust that is stored.

If the cabin air filters are loaded using A2 test dust (ISO 12103-1 [7]) as set in DIN 71460-1, and if the efficiency is also determined using A2 particles, then a break in the retention will occur and there will be a further increase to a comparatively higher level. The interaction between the weakening electret effect and the gradual separation improvement through progressive loading is affected by the particle size distribution and the high electrical charge state of the A2 aerosol being used. In contrast, the retention using DEHS particles to measure the efficiency is significantly lower. If cabin air filters are classified according to DIN EN 779 [5] for filters for general air-conditioning, their filter class is in the M5 or M6 range.

The efficiencies of IPA-treated and therefore electrically neutral filters could be considered as minimum efficiencies that can occur during service life.

Fig. 11: Comparison of toluol breakthrough curves of new, used and artificially aged filters (23°C, 50% RH, c1toluene = 80 ppm)

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Used filters with unknown loading history exhibited only moderate increases in pressure drop compared to new filters. The results demonstrate that cabin air filters lose much of their electret effect during service life and are clearly less efficient when it comes to particle separation.

An accelerated artificial filter aging of cabin air filters with a stationary, continuous flow can simulate the decrease of filter efficiency due to normal service life.

Artificial filter aging can also be realized in time periods of a few hours when the filters are exposed to changes of temperature and especially to humidity, which also causes a significant reduction in the separation efficiency.

The efficiency determination according to DIN 71460-1 [1] (without considering the decrease in electret properties when a highly charged test aerosol is used) leads to unrealistically high fraction separation efficiencies (see above table as per VDI 6032-1 [3]), which are not at all representative for filters during service life. Filter tests using a neutral test aerosol and an IPA-treatment of the filters result in more practical performance data.

Fig. 12: Comparison of n-butane breakthrough curves of artificially aged filters with normal and particle reduced ambient air (23°C, 50% RH, c1 n-butane = 8 ppm, aging: 1 week at 200 m³/h)

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Fig. 13: Comparison of toluol breakthrough curves of artificially aged filters with normal and particle reduced ambient air (23°C, 50% RH, c1 toluene = 80 ppm, aging: 4 weeks at 200 m³/h)

4. Adsorption efficiency of new, used and artificially aged cabin air filters The second part of this study investigated the performance of new, used and artificially aged cabin air filters with regard to the adsorptive separation of n-butane (8 ppm), toluene (80 ppm) and NO2 (4 ppm).

One objective was to get information about the decrease of adsorption capacity of cabin air filters as a result of their use in cars during their life cycle. Another topic was to investigate if it is possible to simulate the normal aging process during service life by exposing the filters to a continuous and high flow rate of ambient air for a considerably shorter time period.

For purposes of the investigation the breakthrough of the three test gases through new, used and artificially aged filters of the same type was tested according to ISO 11155-2 [2].

The artificial aging of the filters with ambient air took place on the test stand at IUTA e. V., which has already been described in Chapter 2. For artificial aging, filters were subjected to different flow rates and time periods: - 200 m3/h for three days (3D),

Fig. 14: Comparison of NO2 breakthrough of new, used and artificially aged filters (23°C, 50% RH, c1 NO2 = 4 ppm)

- 200 m3/h for one to four weeks (W) and - 600 m3/h for two or four weeks (W).

The breakthrough tests were conducted on the filter test stand for cabin air filters at the University of Duisburg-Essen; a sketch of the test device is shown in Fig. 9. Filter samples were taken and analysed upstream and downstream of the filter. The hydrocarbon concentrations were measured using flame ionisation detectors (3002 RC, Bernath Atomic, Germany), the nitrogen oxide concentrations were measured with two chemiluminescent analysers (AC31M, Environnement S.A, France).

4.1 Experimental results of adsorption tests The results from the breakthrough tests are presented as breakthrough curves. The concentration of the test substance measured downstream of the filter (c2) with respect to the upstream concentration (c1) is plotted as a time function. The tests were carried out either up to a 100% breakthrough or for a test period of 90 minutes.

Fig. 10 shows the breakthrough curves of the test substance n-butane (8 ppm) through filters of different status. As expected, the 100% breakthrough of the

Fig. 15: Comparison of the NO production of new, used and artificially aged filters (23°C, 50% RH, c1 NO2 = 4 ppm)

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used filters is significantly faster than of new filters. In used filters, the butane capacity is almost completely exhausted at the beginning of the experiment; the full breakthrough occurs already after two minutes of test time. The breakthrough curves of the artificially aged filters have a quite similar curve progression irrespective of the loading time and are situated between those which had been measured on new and used filters.

The results of the tests with toluene as test gas are presented in Fig. 11. The specifications M2 or M3 in the caption mean that the corresponding breakthrough curves were averaged from 2 or 3 experiments. The breakthrough curve of new filters is averaged from five experiments with error bars indicating the standard deviation, which is relatively large for new filters of the same type. This is attributed to different product batches and storage conditions. The breakthrough curves of toluene of new cabin air filters are favourably s-shaped, whereas the used and artificially aged filters show significantly higher breakthroughs at the start of the tests. Nevertheless, after a test period of 90 minutes with 80 ppmV of toluene as test gas, the capacities of all filters were virtually exhausted. The breakthrough of toluene takes about four times longer, however, compared to butane. The capacity of activated carbon for toluene is higher than for the highly volatile n-butane.

Another topic was the influence of the particle load of the ambient air used for artificial aging of new filters, on the adsorption of the test substances n-butane and toluene. For purposes of the investigation a further test series was conducted using n-butane and toluene as test substances with filters which were artificially aged, partly with normal ambient air and partly with ambient air, to a large extent purified of particles by an additional HEPA-filter. However, there was no difference between the breakthrough

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curves of n-butane and toluene of filters artificially aged using normal ambient air and particle-reduced ambient air (Figs. 12 and 13). Thus, the particle load in ambient air used for artificial aging did not affect the adsorption capacity observable. In contrast, a previous study on this topic with NO2 as test gas showed an influence of the particle load in the air used for aging on the deposition behaviour [8].

Fig. 14 shows the breakthrough of NO2 as adsorptive through new, used and artificially aged (with normal ambient air, no reduced particle loading). The NO2 breakthrough of used filters is clearly faster than that of new filters, whereas that of artificially aged filters depends on the time period of aging respective to the flow rate used. The performance drop due to normal filter usage is again greater than due to artificial aging.

A further result of the test series with NO2 as test substance concerns the reduction of NO2 to nitric oxide (NO). Even though only NO2 was supplied as test substance in the tests previously described, significant amounts of NO could be measured downstream of the filters. The reason for this is that when NO2 is adsorbed onto activated carbon, NO is produced by catalytic reduction with the activated carbon as

catalyst, which is clearly not intended [9].

Fig. 15 shows the volumetric content of NO measured downstream of the different filters during the breakthrough experiments. It can be seen that in new filters more NO is catalytically formed than in artificially aged or used filters.

4.2 Conclusions of adsorption tests Cabin air filters which had been used in cars have a clearly reduced adsorption capacity for n-butane, toluene and NO2 compared to new filters. However, in tests with NO2 as test gas it was found that less NO2 was reduced to NO on used or artificially aged filters.

The decrease of adsorption capacity of n-butane, toluene and NO2 effected by the normal aging process during service life can only be approximately simulated with artificial aging of cabin air filters with a continuous and high flow rate of ambient air over a time period of some weeks.

Adsorption tests with toluene or n-butane as test substances and artificially aged filters with ambient air are not affected by the particle load of the ambient air.

Acknowledgement: The authors would like to thank the German Federal Ministry of Economic Affairs and Energy (BMWi) for financial support as part

of the agenda for the promotion of industrial cooperative research and development (IGF), following a decision of the German Bundestag.

The access was opened by the IUTA e. V., Duisburg, and organized by the AiF (IGF-Project No. 16793 N).

Literature: [1] DIN 71460, Straßenfahrzeuge – Luftfilter für Kraftfahrzeuginnenraum, Part 1: Prüfverfahren für Partikelfiltration, April 2006, Part 2: Test for gaseous filtration, 2006-03, withdrawn [2] ISO/TS 11155, Road Vehicles – Air filters for passenger compartments,Part 1: Test for particle filtration, Part 2: Test for gaseous filtration, 2009-01 [3] VDI 6032 Sheet 1: Ventilation and indoor-air quality in vehicles. Hygiene requirements for ventilation and airconditioning systems. 2015-05 [4] Schmidt, F.; Breidenbach, A.; comparative testing of cabin air filters for cars;, F&S Global Guide of the Filtration and Separation Industry (2012-2014); 198-204; ISBN: 978-3-00-037568-2 [5] DIN EN 779, Partikel-Luftfilter für die allgemeine Raumlufttechnik - Bestimmung der Filterleistung; Deutsche Fassung EN 779:2012, Oktober 2012 [6] Schmidt, F.; Stahlmecke, B, Kaminski, H. Finger, H.; Characterisation of soot as a test dust for air filters; F & S International Edition No. 9, 2009, 189-193 [7] ISO 12103-1, Road vehicles - Test contaminants for filter evaluation - Part 1: Arizona test dust, Titel (deutsch): Straßenfahrzeuge - Prüfstaub zur Bewertung von Filtern Teil 1: Arizona-Prüfstaub, Dezember 1997 [8] Sager, U., Schmidt, F., Breidenbach, A., Suhartiningsih: Adsorption performance of cabin air filter during a life cycle; Filtration+Separation, 38-41, July/August 2012 [9] Sager, U.; Schmidt, F.: Adsorption of Nitrogen Oxides, Water Vapour and Ozone onto Activated Carbon, Adsorpt. Sci. Technol. 27(2), 2009, 135-145. DOI: 10.1260/026361709789625243

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A test bench for compressed air filter testing – even beyond the standard H. Lyko* Virtually every industrial facility or workshop has its own compressed air system. Depending on the industry branch, the quality of the products manufactured by them, as well as on the specific application of compressed air this must satisfy certain requirements. The user can determine the requirements using the compressed air purity classes, which are determined and specified separately in compliance with the ISO 8573-1 standard for the three types of contaminants particles, water and water vapour as well as oil.

Oil is the main focus of the filter test described here, for which a total concentration in mg/m3 is specified for determining the compressed air purity classes. This value includes the content of dispersed oil droplets and of vaporous oil components in the air. A compressor is the main source with regard to contaminating compressed air with oil. The separation of oil droplets is the initial and most significant stage in the conditioning of compressed air after compression. Choosing to use an oil-free compressor as an alternative is not suitable for the upper performance range, i.e. when high volumetric flows are needed.

Which compressed air quality the filter can provide depends on its separation efficiency under operating conditions. A compressed air filter cannot hold back the vaporous oil constituents present in the air.

This is evident from the operation principle of these filters that is described below.

It is generally known that the equilibrium between the liquid and the vapour phase is temperature dependent. The currently valid test standard, ISO 12500, stipulates that filter testing should be carried out at * Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

Tab. 1: Required compressed air quality for supplying a test stand as per ISO 12500-1

room temperature. This test condition was not sufficiently adequate for a Dutch filter manufacturer to be able to carry out conclusive testing of its filter products, especially as compressing the air resulted in a temperature increase that could exceed the test temperature stipulated in ISO 12500.

The filter test stand described in the following is made by Ehrler Prüftechnik Engineering GmbH from Niederstetten, Germany, and has been designed for testing at temperatures of up to 80°C. Other design features are particularly aimed at high flexibility with regard to the test devices that will be used and safe, automated and low-energy operation.

Design and operation of a filter for separating the oil in compressed air Compressed air filters are cylindrical filters in which several layers of different media are arranged on top of each other.

The filter medium, a nonwoven that is mostly made of synthetic fibres and also retains solid particles, is absolutely essential for separating the oil droplets. Modern compressed air filters are fitted with pleated media that also contain nanofibres in order to implement the separation of especially fine particles and droplets. Oil droplets retained in the filter medium are coalesced and are discharged through the drainage medium that lies directly behind the filter medium in the flow direction and and collected in a reservoir. A support medium for attaining the mechanical

Fig. 1: Design and operation of a coalescence filter for separating the oil aerosols (compressed air or compressor filter)

stability is also fitted in the filter element in addition to the filter and the drainage medium. As Mölter-Siemens et al. have explained, the droplet separation and liquid drainage process inside a multilayer filter element is a very complex process that involves several stages /2/. Therefore the possibility of the oil components seeping into the clean gas side of the filter not only comes from the vaporous constituents that seep through the filter medium, but also from the penetration of individual fine droplets as well as from the reservoir that is located on the clean gas side of the

Fig. 2: Compressed air filter test arrangement as per ISO 12500-1

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Tab. 2: Compressed air filter test stand performance data

Fig. 3: External view of the compressed air filter test stand with control stand

filter. The latter process involves both the re-entrainment of droplets as well as the evaporation of the oil components from the reservoir. The fact that the temperature plays an important role in these processes is due solely to the saturation vapour pressure of the oil constituents and the oil’s viscosity, both of which are dependent on the temperature.

Determining the oil and particle separation efficiency in accordance with ISO 12500-1 and 12500-3 The oil separation efficiency and the pressure loss caused by the filter that has previously been saturated with oil at 7 bar and 20°C ± 5°C are measured using the

test arrangement according to ISO 125001. A polydisperse oil aerosol having average droplet diameters of between 0.15 and 0.4 μm is used for this purpose. The oil concentration on the inflow side is set to either 10 or 40 mg/m3, as this depends on the compressor type being used and the conditions under which the test filter would be used in practice. The Reynolds number for the flow in the feed line should be at least 4,000 (turbulent flow) in order to prevent the oil settling in the feed line.

The test arrangement as per the standard is shown in Fig. 2.

The test stand, arranged to comply with the test arrangement shown in Fig. 3, has to be supplied with compressed air that meets quality classes 2, 6 & 1 in order

to be able to determine the oil separation efficiency. The meaning of this number combination can be found in Table 1.

The equilibrium state of the coalescing filter is considered to be realised when liquid oil can be seen in the reservoir and the indicated filter pressure loss only changes by less than 1% per hour. Sampling is provided on the clean gas side for determining the oil concentration and the oil retention efficiency in the saturated state. The actual measurement of the oil concentration can be carried out gravimetrically via a collecting filter and this can be taken from the full volumetric flow or a branched partial volumetric flow (see /3/) or alternatively by using a white light aerosol spectrometer.

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Fig. 4: Measuring path inside the test stand set-up

Fig. 5: View of the processing section of the filter test stand with filters (left), heat exchanger, compressed air supply and compressor

A guide for the determining the size-dependent particle retention efficiency of the filter medium is given in ISO 12500 Part 3 together with a subdivision into fine and coarse filters. The limit for these two types of filters, which also affects the test method to be used, is a particle size of 5 μm. The separation efficiency of the course filters can be determined gravimetrically (as a sum parameter) or by using an optical particle counter. Laser particle counters, optical aerosol spectrometers, electrometers or condensation nuclei counters are available for determining the particle concentrations on the clean or raw gas sides (if necessary,) but which one to use depends on the particle size that is

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awaited. The aerosol flow rates using KCl or NaCl particles or DEHS droplets are given for testing the fine filter media.

Design and operation of the filter test stand The filter test stand described here satisfies all of the standard’s needs and it also has a few special features that allow a low-energy mode of operation as well as easy handling and it also enables the required measurements to be taken using increased test air temperatures. A complete view of the test stand together with the control stand is shown in Fig. 3 and its performance data is listed in Table 2.

The air is circulated in this set-up, as opposed to the method shown in Fig. 1.

This has the decisive advantage in that the compressor installed in the system is only needed in order to overcome the pressure loss in the circuit caused by the test device and the pipelines during continuous operation. The air supply and the pressure level needed during commissioning are produced using the compressed air from the user’s own company system. A pre-pressure in the compressed air line of approx. 8 - 10-bar is needed for adjusting the operation of the test stand to a stable 8-bar absolute (this corresponds to the maximum operating pressure).

The circuit principle applied here was realised for the first time in the large compressed air filter test stand, which was constructed for the Institute of Energy and Environmental Technology (IUTA) in Duisburg. This test stand can apply a standard volumetric flow of up to 3,000 Nm3/h /5/. In contrast to open operation of such a test set-up, on can save about 80% of the compression energy at a test pressure of 7 bar, because the circuit compressor only needs to be applied to overcome the pressure losses caused by the test device and the pipelines.

Two aerosol generators are incorporated in the test stand described here. The larger one, which is an AGF 3000 model from Palas GmbH, was especially developed for loading the compressed air filters under excess pressure and it produces a maximum oil mass flow of 10 g/h. The second aerosol generator is a PLG 3000 (Palas), which produces an aerosol with a droplet size distribution that complies with ISO 12500-1 and a concentration of between approximately 0.1 and 2.4 g/h, both of which are needed for measuring the fraction separation efficiency.

The measuring section with test filter, pressure measuring and the elements for sampling and aerosol measuring can be seen in Fig. 4. Two white light aerosol sensors from Palas (welas) are connected to the Promo 3000 H common evaluation unit by fibre optics and the sensors are used to measure the filtration efficiency factor. More specifically, the pressure-resistant welas 2070 sensor with integrated heating is fitted on the raw gas side and it is designed for concentrations of up to 10 6 particles/cm3, whereas the aerosol concentration on the clean gas side is recorded using a welas 2300. This sensor can detect concentrations of up to approx. 40,000 particles/cm3. It is possible to measure the particle concentration distribution in the raw and clean gases alternately through the fibre optics by using a time interval of

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approximately 10 s. The test filter’s filtration efficiency factor can then be calculated for both distributions during stationary operation. The second sample removal position on the clean gas side leads to an absolute filter for the gravimetric determination of the residual oil content.

Fig. 5 shows the rear of the system together with the processing filters for the compressed air in the circuit, the heat exchanger, the external compressed air supply and the circulation compressor. The heat exchanger is fitted with a separate temperature control circuit. The system is heated by an integrated electrical heating system or cooled by on-site cooling water, depending on the requirements.

The filter used to process the clean gas will ensure that a compressed air quality that corresponds to the standard is achieved at the position where the aerosol is fed in, regardless of the efficiency of the filter that has to be tested.

The housing with the safety door and the spring units for the vertical adjustment of the raw and clean gas pipelines are mentioned as special design features.

The operating pressure needed for the test cannot be applied as long as the sliding door is open and the closed door cannot be opened whilst the system is pressurised.

The vertical height of the raw and clean gas pipelines is adjusted linearly using the four spring balancers (see Fig. 4) and they allow flexible adaptation to a large number of filter sizes with different vertical arrangements for the raw and clean gas supports.

A mineral oil, as used in compressors, and DEHS (DiEthylHexylSebacate) is used as the test aerosol, as can be seen in Table 2. This mineral oil is used to measure the oil separation efficiency according to ISO 12500-1, whilst DEHS is provided as the test aerosol for determining the particle separation efficiency in accordance with ISO 12500-3. This makes it possible to carry out both test procedures using the same aerosol generators. It is necessary to clean the system using hexane when changing the test aerosol. The measuring section has to be removed from the test setup and disassembled for this. The triclamp flanges make this easy to do.

Configuration and control Comprehensive control software is installed in the test stand and it contains menus for configuring, diagnosing and calibrating the sensors and measuring elements and secondly, it can also control project-specific measurement sequences. The user can manually operate the plant using specific measuring masks, i.e. valves, blowers and door locks can

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Fig. 6: Controlling the compressed air filter test stand: Display with all relevant measuring and switching positions

be switched manually. All of the values recorded by the various sensors (temperature, pressure) and the system status (doors closed, compressed air present) are displayed in the measurement mask (see Fig. 6). The two particle sensors are controlled via an interface on the Promo evaluation unit and the measured values are also read out via this path.

In addition to manual operation, the automated processes implemented in the software also provide the possibility to guide the operator via menus through all of the stages needed to carry out the filter test according to the ISO 12500-1 and ISO 12500-3 standards. In particular, this means that: - The values set by the user are applied to the pressure, temperature and flow rate.

- Filter element saturation is detected automatically as it is based on either the differential pressure or an oil level meter fitted on the filter housing.

- The values for controlling the particle generators are taken from a previously defined characteristic curve and converted to the actual flow rate.

- Switching between the particle sensors in the raw and clean gas is carried out automatically.

- The raw data from all of the particle measurements and all of the sensor values will be saved. A protocol containing the results of the test will be generated upon completion.

The progress of the measuring program is displayed for the user and he will be notified when the absolute filter has to be changed during the oil separation test or if the filter element has to be weighed and refitted afterwards.

Other application options This type of test set-up also provides the opportunity to study other issues in addition to testing compressed air filters according to the standards as well as using increased temperatures. An important issue in gas technology is the effect of elements such as filters on the accuracy of a gas flow measurement that is dependent on the temperature. In this case it was not the filter that was the test device, but the gas meter.

Literature: /1/ ISO 12500-1:2007: Filters for compressed air – Test methods – Part 1: Oil aerosols /2/ ISO 8573-2:2007: Compressed air – Part 2: Test methods for oil aerosol content /3/ ISO 12500-3:2009: Filters for compressed air – Test methods – Part 3: Particulates /4/ W. Mölter-Siemens, G. Lauber, A. Kerßenboom, J. Lindermann, H. Finger, S. Haep: Separation of ultrafine droplets with multi-layer fibroid filter media using the example of ceompressed air filtration; F&S International Edition (2011), pp. 56 – 61 /5/ Lyko, H.: Aerosol technology faces new challenges – Report from the 25th Palas Aerosol Technology Seminar; F&S International Edition (2011), pp. 67 - 72

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Efficient air purification filtering technologies – as seen at the POWTECH and IFAT exhibitions H. Lyko* Manufacturing, processing and the transporting of powders and bulk solids as well as many mechanical and thermal processing and conversion processes are all related to the creation of dusts of varying compositions and some are also related to the emission of gaseous air pollution. Air purification technologies are an essential element with regard to the treating and cleaning of product streams as well as protecting the environment against the effects of various industrial processes. Besides the aspects particle retention and cleaning efficiency, the topics energy efficiency and resource consumption were also at the forefront here. The industry demonstrated these aspects in an impressive way at last year’s Powtech and IFAT exhibitions.

Activities in and with the VDMA Many manufacturers of air purification components and systems are members of the similarly-named specialist department of the German Engineering Association (VDMA). This industrial association was represented by special exhibitions at both trade-fairs. Energy-efficient solutions for ventilation, dust extraction, filtering and drying technologies were presented as part of the special show covering the Blue Competence sustainability initiative at POWTECH. For the first time ever at IFAT, the specialist department was represented together with member companies on a separate 150 m2 exhibition stand.

Whilst each of the participating companies was able to present their products and services on their main stands, other important air purification aspects were shown directly to the trade fair visitors in the so-called ‘Live garden’ theme park.

Under the motto “Air cleanliness is of far better value! Preventative. Integrated.

Recovering.” the following subjects were demonstrated: - Capturing hazardous substances directly at their points of origin or exit as an essential element of air monitoring and work safety procedures used in production halls - Measures for preventive and constructive explosion protection used in industrial dust extraction technology. In particular, these included the inertisation of dusts with additives, potential equalization with earthing, the pressure relief through the use of burst discs and flameless pressure relief from using Q-tubes, explosion suppression through the use of an extinguishing agent and isolating an explosion * Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

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site and the plant’s environment by using explosion protection valves - Low dust disposal of swarf and dusts: Briquetting for volume reductions, improved working conditions and process reliability - Extraction of contaminated air in laboratories using multi-stage filtration systems and recirculating the purified air (workplace safety) - Filter media cleaning demonstration using intensive compressed air impulses (jet pulse) - Modern, energy-efficient bag filter systems for use in waste management and recycling technology - Bridge building between legislation and air pollution control technologies.

The “Bridge building” exhibit emphasised the close interactions between the developments in labour and environmental protection laws and industry’s innovative ability and willingness. Specific solutions customised for the relevant industry are needed in order to comply with the legal requirements. It is always necessary to find the right balance between cleaning performance and efficiency for these solutions.

Extraction technology and dust separation in the workplace One of the success stories of the VDMA’s Blue Competence initiative is the eco + range of dust extractors and hall ventilation systems from Esta because they are especially energy-efficient (a good example is the Dustatomat 4 dust extractor shown in Fig. 2). The energy saving is achieved by a newly developed, sensor-based control, in which a frequency converter for the start-up and speed control of the fan motor is coupled with dust sensors fitted on the raw and clean air

sides so that the extracted volumetric flow is adapted to the current demand. Energy savings of up to 50% should be realised in comparison to differential pressure controlling. The dust extractor’s cleaning effect is implemented through the combination of an impact separator for removing any coarse or heavy particles and a cleanable cartridge filter for separating the fine dust. The dust extractor range is designed for use with dry and free-flowing dusts and is available with two different power ratings up to a maximum airflow of 3,300 m/h.

Since April 2014, new workplace exposure limits were applied to alveolar dusts, which should not exceed a concentration of 1.25 mg/m3 instead of the previously applicable 3 mg/m3.

Ringler, one of the companies in the Kärcher Group, places its emphasis on occupational health and safety in its dedusting devices, which are used to absorb suspended matter or welding fumes in the metal, plastics, pharmaceutical and food industries. The dust extractor works with horizontal filter cartridges, which can easily be replaced through a flap from the outside. Therefore the removal of the filter, which is cleaned using compressed air until the end of its service life is reached, is a low-dust procedure. The sound insulation ensures that these dust extractors work very quietly.

The company Dustcontrol produces industrial extractors that use technology based on three filtration stages. The initial stage removes the coarse particles through cyclone separation and the air flows through a fine Class M filter afterwards, which separates up to 99.9% of the fine dust. A HEPA filter function as last filtration stage for particulate matter separation, so that an overall separation efficiency of 99.995% can be achieved.

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Tab. 1. Classification of containment levels applicable when handling dusty materials

High-efficiency particulate matter filter systems High-efficiency particle filters as well as the filter classes that are used are distinguished by the effort needed to entrap the separated dust in a closed (containment) system. The containment system protects people in the vicinity of the filtration plant from coming into contact with the dust both during the regular emptying of the dust collecting container and during the replacement of the filter cartridges. The choice of containment system (the OEB value) depends on the concentration range of a substance that an employee can be exposed to during a working period of 8 hours (see Tab. 1). The manufacturer of the HET dust filter systems knows from many

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Fig. 1: The “Live Garden” exhibition area on the VDMA air purification specialist department’s stand at IFAT (Photo: VDMA)

Fig. 2: Dustomat 4 dust extractor from the eco+ range (Image: Esta Apparatebau GmbH & Co. KG)

years of experience which filter design and specification is most frequently required in industry. A standard system has been designed, i.e. the HET Basic D system, which is low-cost and is available with a delivery time of 6 weeks, which is much faster than a system that is individually planned according to a customer’s requirements. The basic version fulfils the OEB 2

requirements and is therefore suitable for a variety of industrial applications. It is a welded, dissipative and pressure-resistant system made of powder-coated steel with two cleanable HEPA filter stages. The modular design allows flexible use with up to 5 filter chambers so that a discontinuous volumetric air flow of up to 3,600 m3/h or a continuously incidental volumetric flow

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of 900 - 7,200 m3/h can be treated. The corresponding OEB 2 containment system includes a safe-change system for the contamination-free filter changing (see Fig. 3) as well as a dust discharger with fitted cover bag and a manual flap between the dust funnel and the transition piece going to the dust container. The filter system can also be upgraded by using an HET clamp up to OEB 4 to replace the liner system for closing and replacing the dust bag in order to realise higher containment levels.

Amongst the items presented by Infastaub, a company based in Bad Homburg in Germany, at Powtech was their updated Infa-micron cartridge filter, which is a two-stage system that is also used for separating toxic dusts or powders, e.g. those from pharmaceutical production. The added value of these innovations, particularly for the pharmaceutical industry, consists of improvements in user-friendliness, increased gas-tightness, easier cleaning both inside and outside and a lower overall height. Users from industries with potentially explosive atmospheres will benefit from a higher permissible KST value (this describes the increase in dust pressure during an explosion) than that of the previous version so that the filter can now be used with hybrid mixtures as well. In addition to applications used in the pharmaceutical industry, other application examples of the

use of these cartridge filters are utilisation as a second filter stage for the mixing and filling aspirations during the production of spice mixes or extracting the dust from slightly radioactive residues.

Exhaust air dust extraction using surface filters The PowerAir Tube system from Venti Oelde represents a compact and maintenance-friendly filtering system for exhaust air purification, which also comes with the possibility of returning the purified air into the production hall. It acts as a circular filter for separating dry dust. The compactness is achieved by integrating the fan into the head of the unit. This produces a shorter path for the clean gas with a correspondingly reduced pressure loss. When working together with the integrated volume flow control it produces high energy efficiency, which can be further increased during the cold months by recirculating the purified extracted air. Air purification takes place over two stages in the form of cyclone separation of the coarse particles caused by the tangential air entry into the filter cylinder and fine dust retention through the filter bags. Processed air is used to clean the filter bags, which means that an additional compressed air supply is unnecessary. By using a sophisticated filter bag arrangement, the filter’s footprint can be optimised in such a way that a

Fig. 3: Safe-chance system for contamination-free filter changing (shown here fitted to a HET Dynamic system)

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system with a footprint of about 13 m2 can treat an air flow of 90,000 m3/h. A filter with this capacity has an installation height of 9.45 m.

Jet pulse cleaning is the standard process used for cleaning surface filters. It should be both effective and energy efficient and the filtration cycles should not be too short because any removal of the filter cake will lead to a reduction in the filter’s separating efficiency. It is also important to ensure that the entire filter surface is cleaned in the case of long filter hoses. Infastaub implemented a jet pulse process inside an acrylic glass case at Powtech in order to demonstrate the jet pulse cleaning process. As compared to the other options for regenerating a surface filter such as backflushing and mechanical cleaning (shaking or tapping), the application of intensive compressed air impulses is standard for large plants > 200,000 m3/h and high dust loads. It is not so kind to fabrics as backflushing cleaning, which is why Infastaub rate a shorter service life for filter mediums that undergo jet-pulse cleaning (1 - 5 years) as compared to the service life that can be realised with backflushing (maximum of 10 years).

Filtration plants that use rigid-body filter media are a more compact alternative to bag filters as are cartridge filters. The Herding sintered lamella filters are compact rigid filter elements that work as pure

Fig. 4: PowerAir Tube purging air filter made by Venti Oelde

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surface filters. The proven filter elements have been extended by 50% from 1.5 to 2.25 m for especially high volumetric air flows.

The total filter area of a system with the same footprint can also be increased by 50% with the installation of long Delta 2250/9 elements.

This is a clear advantage in the MAXX system for volumetric air flows of up to 1 million m3/h. The rigid body filter element is also mentioned as part of the Blue Competence initiative because it is extremely durable (it has a service life of more than 10 years if compressed air cleaning is used).

Self-supporting flat filter elements are also available with filter media made from textiles. A good example of this are the Purepact elements from ProjectGreen, in which different versions are fitted with self-stabilising needle felts and polyester media with or without a PTFE membrane. Special features of these flat filters, which are available in the filter classes G - H13, are the venturi-type head shapes and the large-volume, rhombic-shaped flow channels that allow effective jet pulse cleaning.

Membrane coating or nanofibre layer?

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Fig. 5: Viledon SinTexx Plus filter cartridges (Image: Freudenberg)

be renewed at such a laser cutting plant in an Austrian shipyard because the filter’s pressure loss was too high during the extraction of aluminium dust and its service life was too short. Through installing 12 Viledon SinTexx Plus cartridges the extraction volumetric flow could be increased from 11,000 to 14,000 m3/h and the pressure difference could be reduced by 75%.

Nordic Air Filtration offers its lamellar filter cartridges as a more compact alternative to bag filters together with approx. 20 different filter media. Some of these media are fitted with e-PTFE membranes. These media, as well as others, are recommended for all applications related to powders and bulk solids used in the food industry, including many applications that require a conductive version in accordance with ATEX. The high degree of dust release in food applications is important with regard to cleaning, as the dust is not in fact waste but a product (perishable). The medium listed in the company’s standard programme, which is integrated with electrospun nanofibres, is recommended for use here (amongst others), for extracting the dust in sandblasting plants and the removal of unspecified dusts without any smoke content.

Literature: /1/ T. Haynam: Was Sie über Filtermedien und deren Bauarten wissen sollten; Powder and Bulk Engineering; 2014

IPA Conditioning Cabinet for testing Air Filters according to ISO 16890-4

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Selecting a filter medium depends on the degree of separation and the energy consumption as well as the stability of the filter material under operational conditions. Two measures are mentioned as alternatives for achieving an improved surface filtration by suppressing the irreversible dust penetration into the lower regions of the filter medium: laminating a PTFE membrane onto a carrier material (e.g. glass fibre fleece) or applying a nanofibre top layer on the medium. A typical application example of filter media with PTFE membranes is dust extraction in the cement industry, whereby the chemical and thermal resistance of the PTFE also plays a role in addition to the filtering principle being shifted to surface filtration. Donaldson Membrane reported on the re-equipping of a cement plant in Beijing, where conventional filter bags made of glass-fibre media could only attain a service life of 12 months. The exhaust gas that had to be purified accumulated at a temperature of 260°C, and it also contained relatively high SOx. A production-related increase in the capacity of the filtration plant and a reduction in the emissions also had to be realised in addition to improving the low service lives of the glass-fibre media. The new acid-resistant glass-fibre fabric bags with ePTFE membranes have faster flow rates so that an initial reduction from the original 12 to 10 m was possible despite the required capacity increase. The pressure loss now stabilises in the 100 to 300 mm Pa range and the required limit value of 20 mg / Nm3 for the clean gas concentration can be maintained.

Kayser also presented their e-PTFE laminate, which is marketed under the Kay-Tex name, which has the advantages of increased air throughput with reduced differential pressure, improved separation efficiency, good regenerability and higher service lives overall. The disadvantage of the membrane media, which was the topic of some discussions, is its lower mechanical stability, (which is also manufacturer dependent) when stressed by sharp-edged particles or solids. A key decisive criterion for a nanofibre medium could also be the price, which is clearly below that for a membrane filter medium according to information from United Air Specialists /1/. If surface filtration with corresponding easier cleanability is required and the requirements regarding the chemical and thermal stability are not too high, then nanofiber media can be provided.

Freudenberg presented their Viledon SinTexx Plus filter cartridges that are fitted with a nanofibre medium (see Fig. 5) and these were specifically developed for the extraction of smoke and fine dusts.

Microscope images of the nanofibre layer were compared with that of an ePTFE membrane, whereby the membrane being examined in connection with these filter products had a more inhomogeneous pore structure than that of the nanofiber medium. As practical example for the use of these filter cartridges the separation of dusts from laser cutting of steels was given. The filtration plant had to

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Selective use of plants for cleaning the air The effect of plants as dust separators and air cleaners is becoming progressively recognized. The now deceased botanist from the University of Bonn, Prof. Dr. Jan-Peter Frahm, proposed using moss as a natural air filter as long ago as 2007. His workgroup realised that moss acts like a biological microfibre dust-collecting cloth that attracts the finest air particles and also degrades certain exhaust gas components.

Some of the bacteria that currently live on moss leaves are also involved. The padding-like mosses that are formed obtain a large part of their nutrients directly from the rainfall and the deposited dust. Dust not only accumulates on it but it is also converted /1/.

Moss has been used as bio-indicators since the late 1960s. In the air purification commission at the VDI and DIN, P. Frahm also initiated the preparation of a VDI guideline covering bioindications resulting from the use of moss. The stress situation can be used for many metal elements and nitrogen in conjunction with the large-scale mapping of bio-accumulations.

Moss is already being used for the greening of walls. Examples of this are listed in /2/. A guide to the application of moss cultures was also prepared by J.-P. Frahm /3/. They are cultivated on fleeces, so that they can be used in the form of mats for greening walls and roofs. Moss is evergreen, saves water and some species can also endure dehydration. Fertilisation and care is hardly needed.

In a previous issue of this magazine we reported on the “City Tree”, a four meter high and three meter wide freestanding body with a moss substrate and flowering plants on both sides. When deployed in urban areas it acts as a natural filter and this contributes to air purification as well as urban design /4, 5/.

A model experiment was started in Stuttgart in the street with the highest particulate matter pollution in Germany, in which the reduction of the particulate matter pollution using moss will be studied by means of structural implementation within the inner city as well as long-term plant care /6/.

The Institute for Textile and Process Engineering Denkendorf (ITV) is now working on this approach together with its project partners Ed. Züblin AG and the State Natural History museum in Stuttgart.

They are working together on the development of moss-based particulate matter panels (Fig. 1), which are designed

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Fig. 1: Moss particulate matter panel belonging to the project partners, i.e. the Institute for Textile and Process Engineering, Denkendorf (ITV), Ed. Züblin AG and the State Natural History museum in Stuttgart

Water

Aqua element Textile Moss

Textile fastenings for affixing the moss in place Homogeneous watering in the complete vertical plane Textile structures used for water management to adapt the moss Water element for sizeadjusted matching to the ambient conditions Textile sensors for controlling the moisture (optional)

System design Fig. 2: Construction of the moss particulate matter panel produced by project partners from the Institute for Textile and Process Engineering, Denkendorf (ITV), Ed. Züblin AG and the State Natural History Museum in Stuttgart

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Highlights 2016

to improve the quality of life in badly affected urban areas without restricting mobility. The moss can also be used to bind and metabolise the particulate matter.

For example, it was found that grey jagged moss, which grows in nature on dry and sunny rocks and does not need any soil and is also very resistant, is particularly suitable for use in vertical greening projects. As the moss absorbs the majority of the particulate matter when it is in a slightly moist state, the research group has developed an intelligent textile-based module system (Fig. 2). It ensures that the plants are optimally supplied and are able to adapt to the changing ambient conditions such as temperature, exposure to light and moisture. It is also possible to use a textile sensor system that can monitor the moss and control the individual modules. Another benefit of the modular principle is that the individual elements can be exchanged easily. Textile fastenings ensure that the moss remains attached

in the vertical plane. The panels can also be integrated into existing tunnel portals or crash barriers.

The living walls also have other benefits: Not only do they provide pure air, but they also enhance the urban image and even have a good noise prevention effect.

A prototype of the moss-based particulate matter wall could be viewed at the State Horticultural Show in Öhringen from the 6th to the 17th July 2016.

Scientists from the Helmholtz Centre in Munich have discovered that plants can also lock onto nitrogen monoxide (NO) in the air with the help of the plant’s haemoglobins. According to the information provided by the scientists, the plants contribute far more than was previously known with regard to improving the air quality.

The detailed results were published in /7/.

Up to now it was always assumed that NO was not available to plants from the air. The researchers have also found that plants absorb NO directly from the air

and incorporate it into their metabolism afterwards. In fact it has also been noticed that high amounts of nitrogen monoxide are not toxic in plants but actually improve plant growth. One must assume that this mechanism has been created to ensure that the plants can survive even with a lack of nitrogen. This plant characteristic could also contribute to improved air quality in cities with high concentrations of nitrogen.

Literature: /1/ J.-P. Frahm: Der Einfluss von Ammoniak auf Stickstoff liebende Flechten in verkehrsbelasteten Gebieten.

Immissionsschutz 12 (2007), Nr. 4, S. 164 /2/ siehe: http://vertiko-gmbh.de /3/ J.-P. Frahm: Mit Moosen begrünen - Gärten, Dächer, Mauern, Terrarien, Aquarien, Straßenränder eine Anleitung zur Kultur. 3. Auflage, Weißdorn-Verlag, Jena (2014), 106 Seiten /4/ Filtrieren und Separieren 29 (2015), Nr. 6, S. 397 /5/ siehe: http://greencitysolutions.de /6/ Filtrieren und Separieren 30 (2016), Nr. 2, S. 93 /7/ G. T. Kuruthukulangarakoola et al.: Nitric oxide-fixation by non-symbiotic hemoglobin proteins in Arabidopsis thaliana under N-limited conditions. Plant, Cell & Environment 39 (2016) doi: 10.1111/pce.12773

3dLaserScanning for performance analysis of process components Ch. Ferling * Process components are mainly manufactured in a make-to-order mode thus bearing the risk of individual deviations of dimensions amongst the pieces, even being manufactured the same time. These deviations may during operation result in performance variations. Being mostly complex geometrical nature a detailed comparison of these components was not manageable, so that only main dimension were monitored, that were not sufficient to explain different performance characteristics.

Having the 3dLaserScanning adapted to the process industry requirements Second First Maschinenhandel (SFM) now has a mobile, digital and robust system for precise and detailed measurement at site available for customers’ service to analyze performance issues in particular for components in use for the chemical, pharmaceutical and food processing industry (Fig.1). * Dr. Christof Ferling Second First Maschinenhandel GmbH Seeholzenstr.6 81266 Gräfelfing Tel.: 089-852777 Christof.ferling@second-first.de www.second-first.de

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Accuracy of the 3dLaserScanning process itself basically shows 28 μm which in combination with merging measured data across ranges around some 2/10 mm.

In an ongoing project SFM has agreed with a customer of the chemical branch to measure up 4 of their individually manufactured peeler screws and to analyze the deviations in all geometrical details. For this reason regular shut-down / operation

changes are used to measure the peeler screws and determine the wearing process status of the individual component.

Background of this project is the professional involvement of SFM for the periodical reworking of the peeler screws since some years, where SFM has traditionally inspected and reinforced the helical vanes using welding, grinding and machining processes for wear protection.

Fig.1: 3dLaserScanning for high precision, mobile measurement of process components at site

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Fig. 2 Peeler screw with green shadow-cone to show required congruence

Fig. 3 Detail – Cross-section of helical vanes having a relief grind of 4 x 45°

Fig. 4 Comparison of measurement between Real-Scan and CAD-Modell

Fig. 2 shows the peeler screw having the new vanes welded onto the corpus measured by the 3dLaserScanning process. This measurement ensures the precise monitoring and control of the required dimensions inside the green cone. At the bottom of the component a counterbalance weight can be seen – resulting from the balancing test.

Fig. 3 shows the cross section af a vane segment precisely stipulating the dimension an the relief grind of 4 X 45°. Using the 3dLaserScanning the inclination and the bending of the helical vanes can be verified and monitored all from top to bottom with an accuracy level of 1/10 mm.

Fig. 4 shows the Real Scan and the CAD-modell being the benchmark for all the 4 individually manufactured peeler screws.

Fig. 5 shows one of the worn out peeler screws measured against the CAD-model using a coloured comparison mode, in which the green colour represents full congruence while strong red and dark blue significant deviations. In this figure 5 the strong red zones represent the worn out vane sections missing, the dark blue section shows the bending of the vanes, while the green zones of the core flanges, corpus and inner sections of the vanes show the high degree of congruence.

This sample of measuring shows, that precise mobile digital measurement using the 3dLaserScanning under real conditions on site is manageable and ideally supports maintenance activities with very reasonable efforts. The complete geometrical dimensions of the peeler screw had been measured up in detail and stored as a digital data file for further processing. Cross sections of all vanes, undercuts, relief grinds and partially visible surfaces can be taken into CAD-programs for reverse engineering purposes with accuracy of 2/10 mm. A developed Best-PractiseProcedure has qualified SFM as a competent partner to the processing industry.

By means of the 3dLaserScanning SFM offers to their customers a broad field of applications covering high precision onsite measurement, performance analysis topics and wear prognosis issues on geometrical details as well as monitoring and quality control of manufacturing steps for welding, grinding and machining that prior were ruled out for cost and time reasons.

For peeler and decanter screws, centrifuges, sludge dryers and compounders SFM can offer measuring as well as reverse engineering and manufacturing services out of the in-depth process know-how and the long standing branch experience.

Fig. 5 Deviations shown in Off-Colour mode for the CAD-Modell and the Real-Scan

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Call for Papers Present your latest findings at FILTECH 2018 to an international audience.

Submit your abstract until

8 August 2017

FILTECH March 13 – 15, 2018 Cologne – Germany The Filtration Event

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Platform for your success More Space · More Exhibitors · More Solutions for your F+S Tasks Conference: Suzanne Abetz E-mail: abetz@filtech.de Phone: +49 (0)2132 93 57 60

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