Furnaces International Issue 4 by Quartz

BLAST FURNACES

REFRACTORIES

BUBBLER TECHNOLOGY

FOREHEARTHS

CARBON GRINDING SOLUTIONS FOR BLAST FURNACES

INSULATING CASTABLE REFRACTORIES FOR ALUMINIUM

COLOUR CHANGE EFFICIENCY IN CONTAINER GLASS

ENERGY SAVINGS WITH FUEL EFFICIENT FOREHEARTHS

www.aluminiumtoday.com/furnaces/ Issue 4

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Contents

Regulars Comment News

4 5

Forehearths Energy savings with fuel efficient forehearths

Blast furnaces Carbon grinding solution for blast furnaces

Casthouse technology Preheating technology for recycled metal in furnaces

Bubbler technology Colour change efficiency in container glassmaking

18 Furnce guide cover_FINAL.indd 1

Heat treatment Movable HSH - High Speed Homogenising furnace

US Steel report The mighty minis

BIFCA column Top ten tips for improving efficiency in heat treatment

Stolzle Glass Furnace unveiled at container glass producer

Company profile: Techglass Glass furnace supplier with an emphasis on quality

Refractories Insulating castable refractories for aluminium furnaces

Aluminium melting Less dross and higher efficiency

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9/20/16 7:52 AM

Front cover: www.grancoclark.com

Issue 4 Furnaces International r 3

Comment

Editor: Sally Love Tel: +44 (0) 1737 855154 Email: sallylove@quartzltd. com Designer: Nikki Weller Sales/Advertisement production: Esme Horn Tel: +44 (0) 1737 855136 Email: esmehorn@quartzltd.com Sales Director: Ken Clark Email: kenclark@quartzltd. com Subscriptions: Elizabeth Barford Email: subscriptions@quartzltd.com Managing Director: Steve Diprose Chief Executive Officer: Paul Michael Published by Quartz Business Media Ltd, Quartz House, 20 Clarendon Road, Redhill, Surrey RH1 1QX, UK. Tel: +44 (0)1737 855000. Fax: +44 (0)1737 855034. Email: furnaces@quartzltd.com Website: www.aluminiumtoday.com/furnaces/ Furnaces International is published quarterly and distributed worldwide digitally

4 r Furnaces International Issue 4

Comment Welcome to 2017 – and I say that tentatively, given the curveballs and surprises that 2016 managed to throw our way. Among business owners, however, the fear initially generated by the results of both Brexit and the US Presidential election appears to have subsided somewhat into a less fervent mood of ‘let’s wait and see’, as the dust settles and even (albeit short term) positive effects emerge. For example, Adrian Curry, Managing Director of Encirc, one of the UK’s largest container glass producers, recently told me that following Brexit the company had enjoyed short-term benefits as customers saw the benefits of paying in sterling. For the longer term, he said, uncertainty is the biggest threat to business. On the theme of uncertainty, following Brexit the UK’s steel industry also looks to have settled down. Tata bosses dropped plans to sell its UK operations and announced a plan that will keep its largest site, Port Talbot, open until 2021 at least, with no job cuts during this time and a £1 billion investment over 10 years across its UK operations. Amongst other reasons, the result of Brexit has improved the economic outlook for Tata in the UK: the resulting drop in the value of the pound increased the competitiveness of its UK operations, of which 40% of its production is exported. This has been credited with putting the company, which at one point was losing £1 million a day, back in the

black. This does, however, put an end to Liberty owner Sanjeev Gupta’s plans to replace the current twin blast furnaces at the Port Talbot plant with electric-powered arc furnaces, with the idea to melt scrap rather than raw materials. Proposed last year when he emerged as a potential buyer for the plant, Mr Gupta’s plans would not only have generated big business for the furnace industry (the cost of installing an electric arc furnace of that size is estimated to be around £100 million), it would also be a ‘greener’ and more sustainable option for the industry. Over in the US, meanwhile, Trump’s victory – although initially sending shock waves around the world – has received strong backing from the US steel industry amongst others. His promise to protect the steel industry in particular from cheap imports and to use American steel to “send our skyscrapers into the sky” not only makes him popular amongst the industrialists there, it sent the stock prices of the largest US steel companies soaring after his win. For the US steel industry at least, Trump’s victory has been an overwhelming positive result. Perhaps then, 2017 will bring an end to the uncertainty of 2016 as politicians clarify their policies and businesses are able to plan accordingly. Sally Love Editor, Furnaces International sallylove@quartzltd.com

www.aluminiumtoday.com/furnaces

News

Linde and Praxair set to merge Linde and Praxair, Inc. plan to merge. The two companies said they

in technology with Praxair’s efficient operating model. The combined company

intend to combine in a merger

would enjoy strong positions

of equals under a new holding

in key geographies and end

company through an all-stock

markets and create a diverse

transaction. The companies

and balanced global portfolio.

have signed a non-binding

A conference focused entirely

It would also enable the

R&D, have both agreed

term sheet and expect to

on digital manufacturing has

development and delivery of

been launched by Steel Times

to present papers, while

execute a definitive Business

more products and services to

leading manufacturers of

Combination Agreement as soon

International magazine.

customers.

as practicable.

The combined company

steel production technology, The event, which will

including Danieli Automation,

would be governed by a single

concentrate solely on the

Fives Group, Primetals

combination would create

Board of Directors with equal

subject of Industry 4.0 – or

Technologies and SMS group

a company with pro forma

representation from Linde and

‘smart manufacturing’ as

will also be represented.

revenues of approximately $30

Praxair. Linde’s Supervisory

it is known in the USA – is

What is Industry 4.0 and

billion (€28 billion), prior to

Board Chairman, Professor Dr.

aimed at senior level steel

how can it assist the global

any divestitures, and a current

Wolfgang Reitzle, would become

executives, particularly chief

steel industry in its quest for

market value in excess of $65

Chairman of the new company’s

technology officers, who

greater efficiencies? These

billion (€61 billion).

Board. Praxair’s Chairman and

want to know more about the

are two key questions, among

Based on 2015 results, the

The proposed merger would

CEO, Steve Angel, would become

philosophy behind the topic

many others, that will be

bring together two companies

CEO and a member of the Board

and get involved in the live

answered by the experts in

in the global industrial gas

of Directors.

discussion.

Warsaw next summer.

industry. The transaction would unite Linde’s strength

Vetropack Austria celebrates flint glass furnace

Future Steel Forum will

Other key speakers

take place at the Sheraton

scheduled to appear include

Hotel in Warsaw, Poland,

Jane Zavalishina, CEO of

between 14 -15 June 2017

Yandex Data Factory, who

and promises to be an

will explain how Industry

informative event.

4.0 can save steelmakers

Major steelmakers have

money, and Dr. Dirk Shaefer,

already expressed an interest

associate professor of

in taking part as speakers and

design engineering at the

Vetropack Austria celebrated two events together with numerous

there are a number of leading

University of Bath in the UK.

guests and an anniversary.

technology companies eager

He will will take an holistic

The glass works in Pöchlarn has been part of the Vetropack Group

to explain the theoretical

approach to the subject and

for 30 years. In addition, the new flint glass furnace was completed

and practical elements of

examine cloud-based design

and the Vetropack Group’s training centre was opened.

digital manufacturing and

and manufacturing and the

its relationship to steel

growing role of ‘servitisation’

production in the 21st century.

in Industry 4.0.

The hosts of the celebration, Claude R. Cornaz, CEO Vetropack Holding, and Johann Reiter, Managing Director Vetropack Austria, welcomed not only a large number of customers and partners but also personalities from politics and business.

From the world of

For further information

primary steel production, Dr.

on Future Steel Forum and

Michael Eder, global chief

details on how to be involved

newly constructed white-glass furnace from the inside, before it is

digital officer for the world-

as a speaker, delegate or

gradually heated up to 1580°C for melting glass again.

leading Austrian steelmaker

exhibitor, log on to www.

Voestalpine AG, and Pinakin

futuresteelforum.com.

The guests enjoyed the unique opportunity to take a look at the

“Investment in the modernisation of our production facilities is essential in today’s economic climate. It secures our success and

Chaubal, general manager

competitiveness in the long term,” explains Claude Cornaz.

of ArcelorMittalGlobal

www.aluminiumtoday.com/furnaces/

Issue 4 Furnaces International r 5

News

Seventh blast furnace at EVRAZ

EVRAZ Group is to build a seventh blast furnace at its NTMK facility in Nizhnij Tagil, Russia. The new furnace will be of similar design to the existing BF5 and BF6 furnaces with a

the new BF 7 in 2018. The new

this modern furnace,” said Paul

will repeat their successful

ironmaking plant configuration

Wurth. “This includes a parallel

application in an evaporative

will allow full steel production

hopper Bell Less Top charging

cooling system. The BF top

even during periodical repairs

system, a hearth refractory

gas cleaning plant with axial

of the site’s blast furnaces, says

lining with a ceramic cup and

cyclone and annular gap

the company.

two sets of fully hydraulic

scrubber as well as the de-

tapping machinery.”

dusting systems for stockhouse

“Contracts have now been

hearth diameter of 9.8 metres,

signed by EVRAZ-NTMK and

an inner volume of 2,200 cubic

Paul Wurth for the design and

vertical copper stave coolers

minimal environmental impact

metres, 22 tuyeres and 2 tap

supply of technology and key

in the high-heat loaded bosh,

and a maximum material

holes, each unit can produce

equipment, which will ensure

belly and stack area – the same

return to the main process of

2.5Mt of hot metal per year.

reproducible operations and

configuration as the plant’s

steelmaking.

support a long campaign for

BF5 and BF6 since 2004 –

EVRAZ plans to commission

Verallia in €22 million Oiry furnace investment

According to Paul Wurth,

and casthouse will ensure

Glaston secures Austrian order Glaston has closed a deal with Austria’s Glas Gasperlmair.

production. ProBend can process glass in a wide range

Verallia has invested €22

work on site with production

million in a new furnace at its

of the first bottle from the

ProBend bending and

toughened, heat-strengthened

Oiry site in France.

kiln expected to begin in early

toughening furnace with turnkey

and laminated products.

October.

installation.

Work is currently being undertaken to dismantle the

The current 100m2 furnace

The deal includes Glaston’s

of sizes for high-quality bent

Glas Gasperlmair has relied

The machine will be delivered

on Glaston glass processing

current 515 tonnes per day

has been in place for 12 years

to the customer in summer

equipment for more than 20

furnace which will be replaced

operating at 1200 degrees

2017.

years and already operates

later this month.

celsius for 24 hours a day.

More than 350 workers will

With its zero-tooling process

four Glaston FC furnaces. The

and short changeover time,

deal completes the company’s

Glaston ProBend offers a

product range of glass.

cost-effective and flexible

6 r Furnaces International Issue 4

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News

Reprieve for Tata Steel’s Port Talbot steelworkers Tata Steel has guaranteed that its flagship UK steelworks in Port Talbot, South Wales, will remain in operation for at least five years and that £1 billion will be invested there over the next decade. The future of the Port Talbot works has been in doubt ever since Tata Steel announced in March that it was putting its UK businesses up for sale. Now steelworkers in South Wales can breathe a sigh of relief and the British Government can rest a little easier, safe in the knowledge that, for now, more than 4,500 jobs have been saved.

Meanwhile...

ThyssenKrupp labour chief angered by Port Talbot concessions That ThyssenKrupp should ‘pick up the tab’ for concessions being offered to British trade unions by Tata Steel, has angered the German steelmaker’s labour chief, Wilhelm Segerath, according to a report by Reuters. It is claimed that Segerath

that ThyssenKrupp plants ‘will now be endangered in a consolidation’. According to Reuters, ‘Tata has offered to guarantee production at Port Talbot, Wales, for five years and to invest across its British business in return for

VOA celebrates the restart of furnace no.2

‘sees no reason why

being able to close the final-

ThyssenKrupp’s plants should

salary pension scheme to future

suffer because of job and

accrual’.

The team working for

the end of 2015 and came into

investment guarantees offered

glassmaker VOA (Verrerie

service at the beginning of 2016.

to workers at Port Talbot’.

Segerath spoke of ‘massive resistance’ if ThyssenKrupp

d’Albi) has marked the restart

Fully refurbished in turn,

of furnace no.2 with a match-

furnace no.2, which produces

been in discussion over the past

consolidation and claimed

lighting ceremony at the plant.

green, dead-leaf and cannelle-

year with a view to merging

that Port Talbot has major

colored bottles, has just

operations in order to cut

structural problems, having lost

restarted.

costs and reduce overcapacity;

an estimated $1.22 million per

Verallia has invested more than €46m in one year to modernise VOA’s two furnaces.

VOA, which celebrated its

The two steelmakers have

plants are endangered by

but, says Reuters, Tata’s huge

day in its last financial year.

120th anniversary in 2016,

pension deficit in the UK is

The business has since turned a

to the production of very high

employs more than 300 people

the elephant in the room and

profit due to higher steel prices

quality flint and extra-flint glass,

and manufactures 800,000

Segerath says he won’t accept

and a weaker pound, Reuters

underwent a complete rebuild at

bottles every day.

VOA’s furnace no.1, dedicated

Phoenix releases its updated data logger Two way RF communications: which allows reset and download while the system is in the furnace, and auto data retrieval (‘catchup’) if there is a loss of RF signal - for example if the logging system is in a water quench, or if the PC is not available for entire trial. Faster sampling rate: down to 0.2 seconds over the full 20 channel selection without any loss of accuracy. Increased memory: to 3.8 million data points, allowing high sampling rates even in long processes. Bluetooth connection: in addition to the standard USB, allowing remote system set up check even if the logger is sealed in a ‘In process’ temperature monitoring refers to the technology of

thermal barrier.

sending a thermally protected data logger through a furnace,

‘On – board’ calibration data: the data logger memory contains

together with the products being heat treated to obtain true

the latest calibration correction data as well as a signed copy of the

temperature data.

original calibration certificate, which can be printed if required. The data can be transferred with a ‘click’ into Thermal View software,

In this field increased industry requirements, specifically in furnace surveying and temperature profiling, have led to the development of a new range of data loggers from Phoenix. Based on the dependable PTM1000 series data loggers, the

saving manual input of the correction factors. The new PTM1200 series data logger retains the proven qualities of the PTM1000 family; superior robustness, a waterproof case (up to IP 67) and fast and reliable service.

new PTM1200 generation with 6, 10, & 20 thermocouple channel

Caption: The new PhoenixTM PTM1220 data logger in various

variations, has many new features including:

thermocouple types.

www.aluminiumtoday.com/furnaces/

Issue 4 Furnaces International r 7

Forehearths

Energy savings with fuel efficient forehearths Side combustion exhaust flues for exhaust of combustion gases Central cooling exhaust flue for exhaust of cooling air Vented mantle block with exit for cooling air

Simon Parkinson* explains the science behind the technology that can provide container glass manufacturers with up to 50% energy savings.

Butterfly valve located in cooling air ducting for control of cooling air flow Cooling air fan for supply of cooling air

Movement of cooling actuator sets position of dampers and cooling air butterfly valve via horizontal control shaft

As the primary consumer of fuel in the glass container factory, the furnace is the main focus for energy efficiency improvements. However, through the application of modern forehearth and distributor designs and technology, and through correct forehearth and distributor specification, substantial energy savings can be achieved. Energy efficiency can be viewed from two distinct perspectives: â&#x20AC;˘ rThe savings achievable through reduced fuel consumption. â&#x20AC;˘ rThe savings achievable through increased glass quality and increased production leading to a reduction in the fuel consumption per tonne of glassware sold. The purpose of this article is to highlight the energy savings which can be made, using real life examples illustrating savings of up to 50%, and explain how the PSR System 500 forehearth achieves optimum results with regards to fuel consumption 8 r Furnaces International Issue 4

Fig 1. Model of a System 500 Forehearth.

and glass quality. The function of the forehearth is to provide gobs of glass to the forming machine at a constant, uniform temperature suitable for the particular forming process, at a constant weight and shape, and at the required speed of the machine. Although a lot of heat needs to be removed, additional heat input is also required, particularly at the sides of the forehearth channel where the heat loss is naturally greater, to ensure that a high degree of temperature uniformity is achieved throughout the body of the glass at the feeder spout. The main features of PSRâ&#x20AC;&#x2122;s System 500 (Fig. 1) are explained below.

Single piece profile roof block design The modular roof block shape is designed to effectively separate the cooling zone transversely into two side longitudinal combustion zones and a central longitudinal cooling zone. The roof block is also designed to radiate www.aluminiumtoday.com/furnaces/

Forehearths heat from the side wall burners back towards the channel side walls. This allows the forehearth to target the heating requirements at the sides of the forehearth to overcome the additional heat loss through the channel sidewalls, while cooling the central hotter stream of glass. This results in effective control of the glass thermal homogeneity at the spout entrance position. Separate exhaust of the combustion gases and cooling air In conventional, longitudinally cooled forehearths, the cooling air and combustion products are all exhausted through one common exhaust flue and so must mix together inside the forehearth, reducing the combustion efficiency and the effectiveness of the cooling air. By employing individual cooling and combustion exhaust flues, separated within the forehearth by the profiled roof block design, we ensure that the cooling air is exhausted through the central cooling flue and the combustion products are exhausted through the side combustion flues. This can be seen in Fig. 2, which shows a System 500 forehearth cooling sub-zone operating at a typical medium cooling level. The three damper blocks are partially open and the butterfly valve on the cooling air inlet is partially open. It can be seen in the image that the two side combustion flues are much brighter in appearance than the central cooling exhaust flue which has a dull appearance. This indicates that the cooling effect is contained in the central chamber of the forehearth, with the cooling air exhausting through the central cooling flue. The combustion effect is contained in the side chambers of the forehearth, with the combustion products exhausting through the side combustion flues.

Synchronised control of the exhaust dampers and cooling air inlet The cooling and combustion exhaust dampers operate simultaneously with a butterfly valve controlling the cooling air inlet volume to provide control of the internal forehearth pressure. The swinging motion of the exhaust

Combustion exhaust flies

z Fig 2. Layout of the

System 500 dampers, showing the duller (cooler) appearance of the central cooling flue, compared with the brighter (hotter) appearance of the side combustion flues.

Cooling exhaust flues

dampers, rather than a vertically lifting motion, simulates the operation of a port valve, providing better control of the exhaust volumes and internal forehearth pressure. The value of this can be seen when compared to direct radiation cooled forehearths, which often cannot maintain a positive internal forehearth pressure when the large radiation flues are open. The resultant negative pressure causes parasitic cold air to infiltrate through openings and cracks in the forehearth superstructure as well as around the burner nozzles on each side of the forehearth. This cools the sides of the glass flow, increases the need to heat the sides, and greatly reduces the combustion efficiency. Radiation cooled forehearths are also difficult to control due to the inherent temperature cycling caused as the glass is rapidly cooled as it flows under large radiation openings before it is then reheated.

Automated control of the cooling system Many conventional cooling systems, whether they use radiation or longitudinal cooling, employ manually controlled cooling systems or at least manually controlled cooling dampers. This necessitates the use of excessive cooling so that the glass temperature can be controlled by the combustion system. Therefore, additional fuel input is required to overcome this set Continued>>

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Issue 4 Furnaces International r 9

Forehearths cooling level. The system 500 forehearth operates with automatically controlled cooling, which works in unison with the combustion system. This prevents adverse interactions between the two functions, and eliminates the extra fuel required to overcome a set cooling level.

Ability to heat as well as cool the glass When no cooling air is required the combustion exhaust dampers are completely closed, however the central cooling damper block contains a small notch which allows exhausting of the combustion products through the central cooling flue. This allows the forehearth to input heat into the glass across the entire forehearth width while in heating mode, allowing it to react to any changes in production, reducing down time between jobs. However, the profile design of the roof block still reradiates heat from the combustion system back towards the channel side walls, and the closure of the combustion dampers prevents any heat loss to atmosphere, allowing preferential heating of the side streams of glass. Sub-zoning concept Cooling zones are sub-zoned wherever possible to maximise the effect of the cooling system. By introducing two cooling air inlets and two cooling air exhausts in each cooling zone, we halve the path length of the cooling air within the forehearth, optimising the use of the cooling air volumes and minimising the possibility of overcooling the glass surface at the cooling air inlet point. Cooling air is introduced centrally via a vented mantle block that is also the zone separation block, maximising the total length of roof available for cooling. Distributor an extension of the forehearth (Fig. 3) Traditional working ends or refiners are designed as part of the furnace using construction techniques, combustion, cooling and temperature control systems 10 r Furnaces International Issue 4

z Fig 3. Model of a

complete PSR Forehearth & Distributor System.

based on furnace technology. They have a high superstructure with arched crown, utilising nozzle mix type burners in the working-end breast walls and being controlled from thermocouples installed in the crown. Cooling is normally provided by shutting off the gas supply to the burner and blowing combustion air through the burner. The technologies employed cannot target the heating and cooling where they are required, and therefore no significant glass conditioning can take place before the glass enters the forehearth. PSR views the distributor as an extension of the forehearth, not the furnace, and therefore the forehearth technologies can be installed all the way back to the throat riser, starting the glass conditioning process as soon as the glass leaves the furnace and maximising the energy savings achievable.

Results The System 500 Forehearth is specifically designed to separate and optimise the heating and cooling functions of the forehearth, and customers have reported that conversions of conventional longitudinal forced air cooled forehearths to System 500 forehearths have produced fuel savings of up to 20%. Similarly, conversions of direct radiation cooled forehearths have produced fuel savings of up to 40%. Savings are not only achieved through reduced fuel consumption, but also through increased glass quality and therefore production output of the forehearth. www.aluminiumtoday.com/furnaces/

Forehearths For example, one customer converted a radiation cooled forehearth to the System 500 by replacing the superstructure refractories, steelwork and cooling mechanisms. They recorded the glass thermal homogeneity figures, the tonnage of glass which could be pulled by the forehearth and the pack rates of the forehearth, before and after the conversion. The maximum tonnage of the forehearth increased from 137 to 142 tonnes/day, the typical thermal homogeneity value increased from 92% to 97% and the pack rate increased from 92.5% to 93.5%. This 1% increase in pack rate, along with the increased forehearth load, resulted in a 5% increase in the absolute pack rate of the forehearth, providing a payback time for their investment of just a few weeks. One case study carried out recently relates to a client in the Middle East that operates two adjacent furnaces, each manufacturing white flint or emerald green glasses. Furnace ‘A’ has three productions lines with PSR System 500 forehearth and distributor technology, whilst Furnace ‘B’ has two production lines with forehearth and distributors supplied by the furnace supplier. The forehearths installed on Furnace ‘B’ employ conventional direct longitudinal cooling with the cooling air introduced at the front of the cooling zones and exhausted, along with the combustion gases, at the rear of the zones through one common, manually controlled exhaust flue. Over a period of several years the client noticed discrepancies in energy efficiency between the two systems. They decided to carry out a study over a 25 day period during which all five forehearths were producing white flint glass under roughly equivalent operating conditions. The fuel consumption was recorded over this 25 day period and it was found that the three System 500 forehearths and distributor on Furnace ‘A’ were consuming 380.8 normal m³/day and the two forehearths and working end on Furnace ‘B’ were consuming 446.5 normal m³/day, which equates to 17% additional fuel. In order to obtain a direct comparison www.aluminiumtoday.com/furnaces/

of the fuel consumption between the two systems, the fuel consumptions relative to the size of the systems, in terms of glass surface area within the forehearths and distributors, were considered. It was found that the System 500 forehearths and distributor on Furnace ‘A’ used 12.63 normal m³ of LPG per m² of glass surface area per day compared to the 19.11 normal m³ of LPG consumed by the forehearths and working end on Furnace ‘B’. This represents a 50% increase in specific fuel consumption over the System 500. This discrepancy in fuel consumption was then put into monetary terms by the provision of an average fuel cost of £0.80 per m³ of LPG. When the energy costs were considered over a typical 10 year furnace campaign it was found that an expected saving of £449,860.00 could be achieved by converting the existing conventional longitudinally cooled forehearths to the System 500 forehearth, and a saving of £588,090.00 achieved by the System 500 forehearths on Furnace ‘A’.

Contact *Director, Parkinson-Spencer Refractories, West Yorkshire, UK www.parkinson-spencer.co.uk/

Conclusion The System 500 forehearth and distributor was introduced almost 25 years ago and with more than 600 installations worldwide, continuous development has ensured that it remains at the forefront of glass conditioning technology. What is often overlooked is the superior fuel efficiency that it can achieve as a direct result of the automatic cooling system and close control of the internal forehearth pressure. Sadly, not enough glassmakers are able to make reliable comparisons between our equipment and our competitor’s equipment in the way that our Middle Eastern client did, and as a result investment decisions are often based more upon initial capital cost than longer term energy savings or production efficiencies. The savings demonstrated are not only achieved over the lifetime of the furnace but, through re-using the equipment at subsequent rebuilds, the benefits can be reaped for decades to come.

Issue 4 Furnaces International r 11

Blast furnaces

Carbon grinding solution for blast furnaces Rui Alves* describes a new grinding machine for blast furnaces from Lizmontagens, which aims to increase efficiency and reduce costs in the iron and steel industry.

Fig. 1: A schematic of the Cobra Carbon Grinder operating in a blast furnace.

The demand for fast and safe maintenance solutions is becoming more and more important for blast furnace operators, to reduce downtime and loss of production. Itâ&#x20AC;&#x2122;s also important that the total repair cost iskept to the bare minimum. The Cobra Carbon Grinder (Fig. 1) is a new technical product for the grinding process of blast furnace carbon layers. The Cobra Carbon Grinder is a robotic grinding machine that closely correlates with todayâ&#x20AC;&#x2122;s contemporary market trends of increased efficiency and safety, a minimum loss of production, and reduction of project costs.

How it came into existence The initiative to develop an improved system for the grinding of blast furnace

carbon bottom-layers came into existence when, after realising that the use of conventional systems was unsatisfactory, we looked at the overall duration and the limits to the furnace diameter. The use of conventional grinding systems resulted in significant operational complications; extensive exposure to carbon dust; and relatively slow progress, thus increasing repair duration. Complex and manual handling puts pressure on the grinding accuracy. This is influenced by the large size, height and weight of the grinding machine. This results in a longer downtime period of the furnace than needed, resulting in high project costs and production loss. After evaluating and realising the operational discrepancies, it became clear that there are opportunities to improve on the existing conventional grinding system. Extensive studies were made as to how to improve the conventional systems and eliminate existing operational problems. At a time where integration of sophisticated IT-software and robotic handling in the iron and steel industry is growing, we looked at the possibility to combine these, working towards the solution to the cause. The idea was simple: a robot operated by a software programme that grinds the floor automatically without the need Continued>>

12 r Furnaces International Issue 4

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Blast furnaces of manual labour, thereby diminishing the complications with the existing conventional systems. Another criteria used in its development was to have a grinding tool that is able to Fig. 2: The Cobra Carbon grind local areas in the fastest way with Grinder robot. the highest accuracy, such as adjustment courses or taphole areas. Blast furnace repairs can be made leaving the bottom in place and adjusting the ring walls to the required new dimensions.

The technology behind the Cobra To understand the techniques behind the Cobra, one should look at the combination Fig. 3: The grinding head. of the interconnected parts, each being crucial for delivering high-performance results. The robot It was of high importance that the robotic part of the Cobra suited the requirements of flexibility in movement and grinding capabilities. The machine must be able to grind the floor over the whole circumference of the blast furnace, as close to the shell as possible. Moreover, the robot also had to be small in size and low in weight to ensure easy handling for transportation. A robotic arm designed by ABB suited our requirements perfectly. The flexibility in movement and transportation of the robotic arm makes the Cobra Carbon Grinder unique in its grinding movement and localisation (Fig. 2).

Fig. 4: The de-dusting system.

Fig. 5: The IT software.

The grinding head The grinding head (Fig. 3) is a very costly part of the machine that requires replacement multiple times during operation due to rapid wear and tear. Many spare parts are needed, significantly affecting costs and project duration. With Fig. 6: Laser scanning survey instrument. the Cobra Carbon Grinder, an upgraded and improved diamond grinding head is attached to the robot that grinds for a longer period of time with less wear and tear. This significantly reduces the amount of spare parts needed and increases net working time.

14 r Furnaces International Issue 4

Fig. 7: The Cobra movement system.

De-dusting system Extensive exposure to dust during operations is a very common problem with grinding carbon and graphite materials, especially in confined spaces like a blast furnace. It affects workersâ&#x20AC;&#x2122; health and affects the visibilty and electrical problems during the works. In order to diminish this problem, an improved de-dusting system is applied to the grinder of the robot (Fig. 4), preventing the carbon dust from spreading over the working area. Suction of dust occurs continunously during grinding. Moreover, the hose is attached to a vacuum unit, positioned close to the blast furnace, collecting all carbonaceous dust generated during grinding. Operating computer Traditional grinding systems are mostly semi-automatic, meaning that the only automatised part is the grinding itself. Manual labour is needed to adjust the position and elevation of the grinding head, which increases the risk of insufficient flatness of a bottom layer. Since the robot has to be replaced a number of times in the furnace in order to cover the whole surface, 100% accuracy is mandatory in obtaining the correct elevation and flatness. This is achieved by the self-positioning of the robot, directed by the specially developed software and the laser survey equipment. The Cobra Carbon Grinder IT software monitors and controls the whole grinding process with a maximum deviation of less then 0.5 mm over the surface (Fig. 5). Survey instrument In order to assure the grinding accuracy, a laser scanning survey instrument (Fig. 6) will be in contact with the operating computer to send out the coordinates of the surface. The combination of the survey instrument and sophisticated IT software plays a crucial role in the grinding accuracy. Movement system The Cobra is held in place by a vacuum system, which is mounted to the bottom. www.aluminiumtoday.com/furnaces/

Blast furnaces When the Cobra must be repositioned, the vacuum system will be disconnected. The Cobra can then be repositioned using the swinging wheels (Fig. 7).

How it works Our three-man team of experts will operate the Cobra. Prior to the grinding, the surface will be inspected on integrity and then measured by means of a laser scanning survey instrument to determine the right grinding elevations. The measured coordinates will be entered in the operating computer with a bluetooth communication with the Cobra. A push-button activates the grinding, which will then be 100% automatic. Depending on the base materials and required accuracy, grinding depth can vary from 0.5 to 10mm.

to a bare minimum; • Grinding accuracy is improved due to the combination of IT and robotics; • Project delays are minimised due to a low rate of wear and tear; • Simple handling and transportation due to the compact size of the unit. The Cobra is readily available worldwide with a delivery time of three weeks.

Contact *Marketing & Communication, Lizmontagens Thermal Technologies info@thecobra.eu +31 (0)72 700 0056. www.thecobra.eu

The advantages of using the Cobra Carbon Grinder: • Extensive exposure to dust is reduced

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19/04/2016 13:25 Issue 4 Furnaces International r 15

Casthouse technology

Preheating technology for recycled metal in furnaces

Fig. 1: The VHE Metal Preheating Oven.

Barry Woodrow* discusses a joint project between Iceland’s VHE and Rio Tinto Alcan’s Straumsvik smelter which looked to solve the issue of steam explosions in furnaces. Aluminium smelters, in common with many primary metal producers, charge recycled metal to casthouse furnaces. In the aluminium industry this is likely to be sourced from internal recycling, such as crops, potroom leakout, and out-of-specification metal, together with P1020 ingots, sows, and T-bars imported to maximise useful furnace capacity. Imported metal can often be wet, at least superficially; sows are prone to cracking, allowing water to permeate to the interior. Internally recycled material may also pick up moisture, both from floor spillage and from condensation in humid conditions. Potroom leakout tends to be quite porous and readily absorbs water. When damp metal is charged to a hot furnace, moisture flashes to steam, and a steam explosion may occur. There is then a very real risk that molten metal will be blown out of the furnace, presenting a life-threatening situation to personnel, particularly the fork lift driver charging the furnace. Smelters have adopted various procedures to minimise these risks, including storing recycled metal indoors in dry conditions for some time before use; charging only to cold furnaces; heating the metal with gas burners; and holding the charge adjacent to the hot furnace for some minutes before use. All have drawbacks, from the requirement to carry larger inventories, to time and energy constraints.

The project In 2007 VHE, an Icelandic engineering company focusing on the primary aluminium industry, was approached by Rio Tinto Alcan’s (RTA) Straumsvik smelter to seek a permanent solution to this problem. RTA internationally had mandated that all recycled material must be dried before use. Traditional methods were seen as too cumbersome and wasteful of resources and energy. Initial discussions led to a detailed analysis of RTA’s requirements and a provisional outline design of a metal 16 r Furnaces International Issue 4

Casthouse technology preheating oven. Certain aspects were All showing the quickly adopted – the energy source would VHE Metal Preheatbe Iceland’s geothermal / hydro renewable ing Oven installed electricity; gas and oil do not feature at the Rio Tinto Alcan smelter at strongly as economical energy sources in Straumsvík, Iceland : Iceland. A key requirement was for energy efficient elements operating in a recirculating air Fig. 2: Top view, showing heating design, reducing heat ramp up time, and cassettes. improving energy efficiency. The elements chosen were Kanthal’s air heating cassettes, a proven modular plug-in system, light weight and with a high power output and long service life. The heating cassettes and recirculating fan motors were installed on top of the furnace ensuring easy access for maintenance purposes. An important consideration in the design was for short empty / charge durations, both to minimise cooling of the oven structure and to maximise operational Fig. 4: The VHE throughput. This requirement precluded a Metal Preheating drive-in design for pallet / basket loading Oven – closed. by forklift, where some considerable cooling would have been necessary between heating cycles. The solution adopted was for a chassis travelling in and out of the oven on floor rails. The oven front is an integral part of the moving chassis, maximising the oven opening for rapid removal of dried metal and loading of a new charge. As installed the chassis is accessible from both sides, further reducing the unload / load times. The resulting drying oven now in operation for eight years at RTA Straumsvik is an economic solution, both in capital investment and operating cost. It is able to heat 15 tonnes of aluminium to 200°C within 2 hours. At this temperature all water and many low-boiling point organics are fully removed, minimising the risk of vapour explosions when the metal is Fig. 6: The VHE Metal Preheating charged to the melting furnace. Oven – open, empty. The oven is controlled by a PLC with programmed heating sequences for the most common material loading Contact configurations - for instance sows, crop from rolling ingots, potroom leakout. The *Commercial ManVHE metal preheating oven is economical ager in use and offers an excellent return on VHE, Iceland investment, with a short pay-back period. www.vhe.is www.aluminiumtoday.com/furnaces/

Fig. 3: Control panel.

Fig. 5: The VHE Metal Preheating Oven – open, empty.

Issue 4 Furnaces International r 17

Bubbler technology

Colour change efficiency in container glassmaking

Grahame Stuart* reports on how a precision-controlled colour change bubbler system has helped decrease colour change time and losses in container glassmaking sites.

Typical Throat Bubbler Installation for Colour Change Purposes.

Many container glass manufacturers will agree that carrying out a colour change can present problems with prolonged glass defects as the old colour is gradually flushed out of the furnace, working end and forehearths. This is an issue particularly when going from a dark composition to a lighter one and can lead to defects such as the colder, darker glass becoming entrained from areas such as the corners of the throat and any areas where there is a transition in depth or glass flow direction. The effects can last a number of days, coming and going as temperatures and pulls are changed. A number of years ago Electroglass was asked to look at the possibility of installing its Precision Controlled Bubbler System

18 r Furnaces International Issue 4

(PCBS) in areas of the furnace, throat and working end where dark glasses may stagnate, causing the problems already mentioned.

Homogeneity At that time the Electroglass PCBS had been employed by glassmakers throughout the industry to help improve thermal and chemical homogeneity in many glass types by using single or multiple rows across the hot spot of the furnace. The systemâ&#x20AC;&#x2122;s simplicity of operation and proven reliability at slow bubbling rates had found favour with companies looking for ways to employ bubbling without the pitfalls found with conventional continuous and semi continuous systems, namely, increased refractory wear, parasitic bubble entrainment and premature bubbler failure

www.aluminiumtoday.com/furnaces/

Bubbler technology

due to blockage. The ability to effectively stop the bubblers for prolonged periods meant that the system could conceivably be employed for applications such as colour change bubbling, where bubbler operation may only be needed for 12-24 hours during the ‘off’ colour period.

Colour change Through a combination of physical model testing and experience, Electroglass engineers set about identifying areas where cold glass could accumulate and cause problems during and immediately after a colour change. The first colour change bubbler system was installed by Electroglass’ own in-house hot drilling team in the days leading up to a colour change on a furnace producing 250 tonnes per day of soda-lime glass in various colours for beer and wine bottle production. Bubblers were placed in the throat entry and exit, forehearth entries from the working end and all four corners of the furnace. After installation the bubblers were left switched off in readiness for the ‘off’ colour period during which glass could not be used for production and was simply drained to waste. When ‘off’ colour was reached the furnace operators could switch on individual bubblers and adjust them independently thanks to a PLC control system which allows individual setting of bubble pressure, bubble duration and bubble frequency. Bubblers were then operated until the desired colour could be seen at the spouts, at which time the bubblers were shut down and effectively stopped until the next colour change, when, by following an established bubbler start up procedure, bubbling could recommence with ease. The furnace in question runs around six colour changes each year and the customer reports that the colour change bubbler system has helped decrease colour change time and losses significantly.

A 7 point precision control bubbler undergoing final testing in Electroglass workshops.

In addition to the systems supplied for furnace colour change there is also scope to install a similar system in colouring feeders where the sweeping out of old colour could save many hours improving overall production yield, particularly where frequent colour changes are required. The special, blockage resistant bubbler injectors designed and manufactured by Electroglass are the key to the system’s continued success. Having the ability to stop bubbling and a PLC control system that allows a start-up procedure to be implemented easily and quickly will no doubt continue to allow the use of bubblers to evolve and meet changing needs of glassmakers for many years to come.

Contact *Project Sales Engineer, Electroglass Ltd, UK. www.electroglass.co.uk info@electroglass.co.uk

Heat treatment

Movable HSH – High Speed Homogenising Furnace

Fig 1. Movable HSH homogenising furnace

Homogenising of billets and slabs is necessary for achieving the required properties of semi-finished products for downstream sec processing after casting. The increasing demand on aluminium products results in increased heat treatmentactivities, especially because the demand on properties is rising with new applications of aluminium products. By Hermann J. Meyer* This leads to more heat treatment in existing narrow facilities and requires special, unique solutions. The development of a movable homogenising furnace, which fulfils today’s heat processing requirements and allows the installation and production in existing workshops and infrastructures, is therefore required. Besides the numerous solutions for recycling, melting and casting, Tenova LOI Thermprocess developed the system for batch homogenising and that special movable furnace for restricted spaces. The system fulfils the increasing heat treatment requirements with less demand on space. This furnace allows heat-treating billets and slabs on the restricted space inside existing casthouses. Handling of the goods is easily done by existing lifting equipment. The movable homogenising furnace will not be loaded by moving the load into the furnace, but by moving the furnace to a prepared batch. This batch is arranged on one of two positions, which serve as preparation stand, heat treatment place, cooling place and disassembling stand.

Process requirements 20 r Furnaces International Issue 4

The homogenising process is applied for removing inhomogeneity of alloying elements in cast items. During homogenising, alloying elements are dissolved for homogenous dispersion. Agglomerations inside the castings, resulting from the casting process, are repaired. The time for homogenising has to be adapted to the specific alloys. While some are dissolved within a shorter soaking time, others require a longer soaking time. The time has to be precisely controlled in order to achieve high quality. Furthermore, the temperature control should be accurate in order to be flexible regarding the possible set temperature range. The homogenising furnace should achieve a range of properties of the treated goods so that the following is required for the homogenising of billets and slabs: � Adaption of heating and soaking time to geometry of parts � Adaption of soaking time to specific alloys � Implementing a homogenous temperature distribution in the furnace � Avoiding hot spots and overheating � Maintaining accurate temperature during www.aluminiumtoday.com/furnaces/

Heat treatment soaking � Reduction of heating time � Reduction of energy consumption Preparation and post-processing of goods Typically, the goods are arranged to batches at a preparation stand. From here the batch would be taken and placed into the furnace by a charging machine. The charging machine is running in front of the furnace or the furnace line. Upon completion of the heat treatment, the charging machine will take the batch out of the furnace and place it either on a preparation stand for disassembling or on a cooling stand from where the batch will be transported to the preparation stand for disassembling. The individual layers of goods in the batch are separated by spacers. That allows sufficient flow of recirculating air in between the layers and a most homogenous flow around the goods – a main requirement for even heating of the batch. For fitting to this arrangement a uniform horizontal airflow is installed in the heat treatment area from one side to the other.

The homogenising furnace The homogenising furnace can typically heattreat a set of about 30 to 50 tons of aluminium strands. The specific weight of the batch depends on the good’s size and shape. The heat treatment temperature typically is between 450 and 585°C. The HSH furnace concept is designed for a quick and homogenous heating of batches, which can be achieved by increased recirculation flow and higher heating temperature. Increased recirculation flow requires high-performance fans, while a higher temperature is applied only during the heating-up. Hot spots on the goods themselves are avoided, because the air temperature is increased only during the heatingup. The recirculation inside the furnace is implemented as a horizontal crossflow around the goods. Spacers between the layers allow the recirculating air getting access to each surface inside the batch, which results in a uniform heating of the whole batch. A uniform airflow across the heat treatment area is ensured by air guiding systems on both sides of the heating area. The furnace comprises several recirculation sections; each is equipped with a recirculation fan, heating and a temperature control of its own. The fans are frequency-controlled and will be set www.aluminiumtoday.com/furnaces/

according to recipe and calculation results. Adaption of the furnace length to the heat treatment goods is possible by adjusting the number and length of the recirculation sections. The also possible longitudinal flow would result in a temperature drop from one end of the goods to the other. Due to the resulting properties, which vary within the billets from one end to the other, a longitudinal flow pattern is mostly not acceptable under consideration of the intended quality requirements. In addition to a uniform recirculating airflow, the heating of the flow should also be uniform to achieve minor temperature fluctuations during soaking. Layers of hot air in the recirculating flow can result in overheating of the goods in some areas, which is not allowed. Therefore the temperature of the recirculating flow is controlled on both, the inlet and the outlet channel. Electrical heaters with low power density or gas burners on the inlet side of the recirculation fan ensure a uniform heating of the airflow. Reversing the flow direction is intended for a more uniform heating of the goods. The temperature drop from one side to the other is mirrored; consequently the whole batch is heated more homogenously. The arrangement of the fans allows an easy change of the flow direction. The fans are axial fans and can be reversed by only changing the rotation direction. The fans are located on the furnace roof. Thus the flow is installed with the same homogenous flow distribution in both directions. The installed burners are equipped with a wide control range for maintaining the narrow temperature accuracy during holding. Electrical heaters are designed for low power density, which results in a uniform heating of the circulating air. Continuous control allows a more homogenous and sensitive heating. For higher productivity a higher temperature during the heating-up phase is chosen for the HSH furnace. This allows installing lowperformance recirculation fans, which reduces the consumption of electrical energy. Moreover, recuperative burners are installed for reducing the energy consumption. They use the flue gas temperature for preheating the combustion air. Recovering the heat from the flue gas reduces CO2 emission. The characteristics of the HSH furnace ensure high productivity and optimum economic conditions: Continued>> Issue 4 Furnaces International r 21

Heat treatment �

Significant reduction of heating-up

time � Reversing flow direction, depending on actual temperature � Reduced fan power requirements, resulting in a saving of electrical energy � Uniform heat application by the heating system for a homogenous temperature distribution with temperature fluctuations of less than +/-3K

Furnace control An excess temperature of the recirculating flow is possible up to reaching the soaking temperature at the goods, which requires a predicting control strategy. Measuring the actual temperature of the recirculating flow by sensors and calculating the resulting part’s temperature by mathematical modelling (Heat Mod) allows a good forecast of the actual temperature and enables exact control. Based on the batch characteristics and the trend of temperature changes on the recirculating flow, the actual temperature of the goods is calculated by mathematical modelling. Also the time sequence for reversing the flow direction is calculated by the control system. The required process safety can be ensured by redundant temperature sensors. Recipes, stored in the control system, can be chosen by the operator according to the intended heat treatment; they provide the pre-settings for processing the goods in accordance with alloy, size and expected properties. The automatic control minimises changes of the flow direction and optimises related time sequences. It is aimed at achieving the set temperature on both sides of the batch at the same time. The process data are recorded for every batch. As a batch number is given to every batch for identification purposes, the recorded data can be allocated to the individual batch. Movable homogenising furnace The typical homogenising furnace arrangement requires space for preparation stand, charging machine and furnace. Most of the existing narrow casthouses cannot fulfil the respective space requirements. The movable HSH homogenising furnace implements the same furnace arrangement regarding recirculation, heating, control and 22 r Furnaces International Issue 4

Contact *Tenova LOI Thermprocess GmbH www.tenova.com

characteristics, but it is movable between two heat treatment positions. For moving the furnace between these positions, it is equipped with a wheel set and one door at each end of the furnace (Fig.1). This concept allows for a reduction in the space occupation because only two positions for batches are required. The batch will be stacked on one of the heat treatment positions. After the previous heat treatment process has been finished, the furnace is moved onto the newly arranged stack and can start heating immediately. In parallel, a cooling device can be put onto the hot batch for cooling. This device consists of a frame structure with cooling air fans, which blow fresh air onto the batch. After the set temperature has been reached, the device is lifted by an overhead crane and placed onto the furnace roof. Now the batch can be disassembled and a new batch can be arranged on that place. Due to the easy access to the heat treatment area, any kind of lifting equipment can be used for arranging and rearranging the batches. The movable homogenising furnace requires only two places for heat treatment, stacking, destacking and cooling. The control system is installed on the furnace sidewall and moving with the furnace. For sealing the furnace to the outside, a sealing system, which is installed under the furnace, is lifted, while the doors are closing. As there is no need to handle the whole batch as one unit, the tray structure for arranging the stack can be very light-weight compared to typical homogenising furnaces with a charging machine. Due to its flexibility and easy handling, the furnace concept can be used for small lots of one kind of material. Due to the compact design and less foundation requirements the furnace can be installed in almost any workshop within a short time.

Summary As the movable version of the HSH furnace requires less space, it improves the productivity of homogenising strand castings. The HSH technology provides energy saving and economic processing besides optimum process control. Its smart control optimises heating up, soaking and treatment time and additionally cares for homogeneous processing. www.aluminiumtoday.com/furnaces/

VAS are the UK’s number 1 provider of products & services for the heat treatment industry. Boasting the most comprehensive engineers, VAS are the single biggest provider of services for both Vacuum Furnaces, & Atmosphere Furnaces. Now agents for the world’s largest furnace manufacturer, Ipsen, VAS are also able to provide the most technological advanced, & highest quality heat treatment furnaces. VAS not only boasts the most experienced furnace engineers within the industry, but are global experts in the following – 

Vacuum Furnace Repairs, Relines & Overhauls



Atmosphere Furnace Repairs Relines & Overhauls



Heat Treatment Relocations



New & Used Vacuum & Atmosphere Furnaces



Spare Parts for all Heat Treatment Equipment



On & Off-Site Technical Services

VAS have had the privilege of undertaking work on all manufactures of Heat Treatment Furnaces, such as Ipsen, Schmetz, Seco/Warwick, TAV, BMI, Wellman Etc... Using this to our advantage VAS has built a vast knowledge, & gained priceless experience which is why we are the number one heat treatment service company within the industry. For all enquiries please contact us on +44 121 544 4385, or Email - enquiries@vacat.co.uk

US steel report

The mighty minis: US steel

Despite overall tepid US steel demand, domestic electric arc furnace (EAF) steelmakers have been making some gains this year. This is partly due to moves by integrated producers to idle or close some of their steelmaking capacity. By Myra Pinkham. But there are other factors as well, including investments enabling them to have increased participation in such stronger, traditionally integrated end-use markets as automotive and appliances at the same time that – at least for the time being – they are experiencing more favourable raw material costs. “We are proud of being part of an industry which we think is transforming how steel is made and how ultimately America is going to compete on the global scene,” says Philip K. Bell, president of the Washington-based Steel Manufacturers Association (SMA), the trade association that represents the US EAF steelmakers. While total US crude steel output is expected to decline 1% this year to about 86 million short tons, Christopher Plummer, managing director of Metal Strategies Inc., West Chester, Pa., estimates that domestic EAF crude steel production will actually see a 6.6% year-onyear increase to 58.1Mt, while the portion of raw steel produced by the basic oxygen furnaces (BOFs) used by integrated steelmakers is expected to decline by 13.9% to 27.9% for the full year of 2016. Also, according to Keval Dhokia, a metals analyst for Metal Bulletin Research (MBR), 2016 capacity utilisation for US EAF steelmakers is expected to be as high as 75% of rated capacity compared with 62% for 24 r Furnaces International Issue 4

steel produced in BOFs and overall capacity utilisation of about 70%. This, Plummer says, is despite the fact that US production of reinforcing bar (rebar), merchant bars, special bar quality (SBQ) bar, structurals and wire rod has been relatively weak this year, and virtually all steel long products and only about a third of flat rolled products, are produced using EAFs.

Imports decline Plummer notes that both EAF and integrated steel producers have been helped by a sharp decline in US imports, which was partially the result of several successful trade cases, particularly those for sheet and plate products. Total US finished steel imports were down 23.3% year-to-date through August versus the first eight months of 2015, according to preliminary US Census Bureau data. Gains in US EAF steel market share isn’t a new phenomenon. “The proportion of US raw steel output produced using EAFs has increased consistently over the past few years,” observes MBR’s Dhokia. As recently as 10-15 years ago about 60% of the steel produced in the United States was done so by integrated steelmakers, George Koenig, director of business and technology development for Hatch Management Consulting, points out. “But now that has reversed.” www.aluminiumtoday.com/furnaces/

US steel report

Plummer agrees noting that EAF steelmakers only accounted for 47% of the 112.3Mt of crude steel produced in the United States in 2000 compared with 67.6% in 2016. The breakdown by steelmaking capacity is even more striking. While EAFs already account for between 75% and 80% of US steelmaking capacity, that percentage is going to continue to grow, SMA’s Bell says, noting that analysts from Bank of America Merrill Lynch are predicting that by 2025 almost 80% to 85% of all domestic steelmaking capacity will be EAF. There are several factors contributing to this gain, some of which are shorter term in nature while others could be indicative of a longer-term trend. “But over the long haul it appears that EAF steelmakers could have an advantage over integrated producers,” Koenig says. One reason for recent EAF gain is a shifting of capacity, some of which has been a reaction to weaker domestic steel market dynamics, while others are connected with the desire to take advantage of expectations of future strength.

Voluntary idling “Over 92% of BOF production decline this year came from a voluntary idling of production capacity as opposed to integrated producers losing market share to the mini-mills,” Plummer maintains, observing that with US Steel Corp. permanently closing its Fairfield, Ala., operation in May 2015 and idling its Granite City, Ill., facility in the fourth quarter of last year; AK Steel Corp. indefinitely idling its Ashland, Ky., plant, also in the fourth quarter; and ArcelorMittal idling its No. 3 blast furnace at its Indiana Harbor www.aluminiumtoday.com/furnaces/

West complex (which it reportedly is going to restart soon) early last year, US BOF output was down 5.5Mt in 2015 and is expected to be down another 6Mt in 2016, even as certain traditionally integrated end markets, such as automotive and appliances, remain strong. Meanwhile EAF steelmakers, while in some cases temporarily reducing some of their shifts, have not idled any of their facilities, Plummer says, although ArcelorMittal did sell some of its EAF operations as part of its recent restructuring efforts. He estimates that they were able to pick up a quarter to a third of the volume ceded by the integrated mills despite the fact that overall domestic steel demand was down about 7%. At the same time more EAF steelmaking capacity is coming online. Bell observes that this includes two greenfield facilities. The highest profile addition is Big River Steel in Osceola, Ark., which is expected to begin producing hot rolled steel in December and other more downstream steel products, including cold-rolled and galvanised steel, late in Q1 2017. Commercial Metals Co (CMC) is also looking to build upon the success of its existing micro-mill in Mesa, Ariz., by constructing a similar facility in Durant, Okla, which is expected to be commissioned in the fall of 2017. There have also been murmurs that the idled former RG Steel LLC mill at Mingo Junction, Ohio, could be restarted, possibly with foreign ownership, as early as in the first half of next year, although most industry observers are not very optimistic about its success, especially given current Continued>> Issue 4 Furnaces International r 25

US steel report market conditions. “I don’t see Mingo Junction being restarted. If it does it could possibly fail again, especially if it produces commodity grade steel. There is already plenty commodity grade steel in the marketplace,” says John Anton, director of steel analytics for the pricing and purchasing service of IHS Markit. He says it depends on what the new owners would change to make the facility successful now when it wasn’t successful previously.

Market demand As for as Big River, Koenig says its success will largely depend upon market demand and pricing. “While they plan to ramp up slowly and not be disruptive to the market, adding any new capacity when steelmakers are operating at 70% capacity utilisation is difficult. Big River, however, sees itself as more of a niche player, ultimately making more specialised steels, says Mark Bula, its chief commercial officer, focusing on certain high growth markets, such as automotive. “We are working on conducting more research and development work to help automakers to have access to the kinds of steels they need in the future, including third generation advanced high strength steels.” In general EAF steelmakers are looking to increase their presence in the automotive market. “Nucor Corp., for example, has been investing in more specialised equipment to do so,” observes John Tumazos, the principal and a metals analyst for Very Independent Research LLC. Plummer observes that already about 10% of Nucor’s sheet steel goes into the automotive market for non-exposed body panels. This includes some advanced high strength steel. Likewise, Steel Dynamics Inc. is converting 10% to 15% of the sheet capacity of its Columbus, Miss., facility, which was originally part of Severstal North America, from making more commodity grade steel to steel capable of being used in automotive applications. Plummer says that other than Nucor’s Berkeley, S.C., mill, Steel Dynamics Columbus and Big River, EAF producers lack the width capabilities on their rolling mills to make auto sheet. Big River will also have a leg up over its other EAF brethren because of its RH degasser. The other EAF mills use tank degassers. Currently EAF steelmakers are enjoying 26 r Furnaces International Issue 4

some improved pricing competitiveness versus their integrated counterparts, observes MBR’s Dhokia, especially given the recent jump in coking coal costs, which has increased the cost of hot metal relative to scrap prices. Anton agrees that could be the case, at least for companies that have not yet locked in their 2017 coal prices, with Australian metallurgical coal jumping from $100 per ton cfr China in August to $230 per ton in mid-October. This comes at the same time as, according to Plummer, Midwest No. 1 busheling scrap prices fell from $267 per long ton in August to $205 per ton. Tumazos, however, says he doesn’t believe that the cost of metallics will be that much of a factor, as trends related to both prices of iron ore (which is currently on par with scrap) and metallurgical coal tend to influence the price of scrap. Anyhow, Dhokia says he expects metallurgical coal prices to ease into next year. While EAFs benefit, to a certain degree, from lower scrap costs, SMA’s Bell points out that low scrap prices also result in low prices for finished steel products. Plummer notes that US steel prices have already been weakening since June, with rebar prices falling from $555 per ton to $490 per ton in mid-October and hot-rolled sheet prices falling from $637 per ton to $480 per ton. But given that their fall hasn’t been as steep as that for scrap, Anton says that there is room for them to come down further before damaging profitability.

Contact

Myra Pinkham, US correspondant for Steel Times International.

Healthier balance sheets Bell says that the EAFs also have certain other advantages versus integrated producers. “The EAFs seem to have healthier balance sheets overall and are the companies that are tending to lead the way in both merger and acquisition activity,” including the purchase of certain downstream operations, such as Nucor’s recent acquisition of Independence Tube Corp. and Steel Dynamics’ purchase of Vulcan Threaded Products Inc. Overall Anton says the EAF steelmakers could see slightly stronger demand next year, especially if construction activity continues to improve and the energy sector picks up. “It will not, however, be a boom as it is unlikely that any end market is likely to improve by a gamechanging amount.” www.aluminiumtoday.com/furnaces/

BIFCA

British Industrial Furnace Constructors Association

Top 10 tips to improve efficiency in heat treatment processes In the second installment of Eurothermâ&#x20AC;&#x2122;s Material Processing Knowledge Series, Amber Watkin asks: What do we mean by Precision Control?

PID Control Basic controllers are fine for many applications but when it comes to regulated industries, they are just not good enough. The difference between basic and precision controllers is in the embedded intelligent control strategies. Basic controllers may use a PID control algorithm, which works well in normal applications that are predictable and do not need high levels of accuracy. The problems arise in applications where there is always some kind of variation in the load or process causing temperature lag in the system, or where sudden temperature changes can occur, such as when a furnace door is opened or a gas is introduced. Add to this the issue of having to comply with industry standards, and you will find what you really need is a precision controller. Precision controllers use PID control but with additional algorithms unique to the company of manufacture that are specially designed to maintain control in certain situations and applications. For example, the overshoot, lag and instability commonly seen in heat treatment applications can be better controlled using PID with Cutback and Cascade features. These work in harmony with each other to keep the PV as close to the setpoint as possible during the process. It is worth searching out controller manufacturers who are knowledge experts in the heat treatment industry as they will offer products designed particularly for heat treatment applications, such as Zirconia Probe inputs, Vacuum Furnace Controllers, Carbon Potential Controllers and Thermocouple/ Pyrometer Switchover Control. This type of manufacturer will also typically offer I/O, toolkits and function blocks specifically designed for better control of heat treatment processes that provide simple setup of control parameters for applications like Vacuum, www.aluminiumtoday.com/furnaces/

Contact BIFCA enquiry @bifca.org.uk www.bifca.org.uk

Carbon Diffusion, 3-Gas IR, Zirconia Probe and AMS2750 standards.

Autotune Setting PID terms and feature parameters on a basic controller is normally a time consuming manual task that requires a skilled operator or engineer. The benefit of modern precision controllers is the Autotune feature, which sets a lot of the parameters automatically. This can be run by a less skilled operator, with very quick feedback that greatly speeds up the process. Setpoint profiling Heat treatment cycles often require multi-stage control profiles to heat up, dwell and cool down the workpiece for specified amounts of time. These profiles are defined by the work piece material type, component specifications and regulatory standards, and are usually maintained against controlled recipes. Temperature profiling is a time consuming manual task when built in a standard control environment where typically, the entire programme is built by creating function blocks by hand or in a list format, requiring many lines of instructions. The probability of making mistakes is high and it is difficult to make quick changes to the programme. The easiest way to programme is by using a Continued>> Issue 4 Furnaces International r 27

BIFCA Setpoint Programmer (SPP) with easy segment parameter entry in spread sheet format that will closely integrate with the PID control to maintain the setpoint within a tight tolerance. Typically, SPP segments can be configured to Dwell, Ramp Rate, Ramp Time, Wait and Repeat in conjunction with other events, and the different programs can be easily selected using a recipe function.

Gain Scheduling Today’s furnaces tend to be used at multiple temperatures and their control performance can vary depending on the effects of convection, conduction and radiation at elevated temperatures. To ensure the tightest levels of control, precision PID controllers offer multiple ranges of PID sets (commonly called Gain Scheduling) that can be matched to the furnace characteristics at particular points in the program to help achieve those hard to reach temperatures. Guaranteed Soak Specified soak times also vary and the best set point programmers can be configured to wait until every part of the workpiece has reached the specified soak time (known as Guaranteed Soak). Accurate I/O Accurate PID control cannot be achieved without accurate analogue Inputs and Outputs (I/O). The main issues that affect accuracy are electrical noise in the cables, interference from other channels and circuits, and temperature drift over time. In precision controllers, this is solved by the use of high quality components and good analogue circuit design. Look for I/O that is isolated from other channels and circuits, with specifications that quote the noise rejection and long term drift. A high noise rejection ratio and low ppm (parts per million) drift/year will help aid compliance with heat treatment standards by easily maintaining stability and accuracy within the specified calibration periods. Precise Power Control The energy used in heat treatment furnaces is one of the biggest contributors to costs in the materials processing industry. Energy suppliers provide energy on a tariff and if not managed carefully it is possible to draw more energy at certain times than your tariff allows. This can result in hefty fines. Many older style electric furnaces still use on/off control connected to electromechanical contactors in order to switch heaters on and off. The problem with this method is that it is nearly impossible to get good heater control as the heater is either 100% 28 r Furnaces International Issue 4

on or 100% off, no matter how much heat demand is actually required to get to the SP. The result is wasted energy, with the PV oscillating around the SP, and the uncontrolled way that heaters are switching on and off across a whole plant can cause you to exceed your agreed energy tariff. The switching of contactors also creates a lot of electrical noise on the mains supply that can affect other electronic devices and reduces the life of the heaters due to thermal stress. The next step up is to use basic thyristors which have no moving parts and therefore are much more reliable. Models are available with different firing modes that gradually supply power to the heater based on % of demand. These methods provide smoother power control than on/off but can still create harmonic noise and flicker that reduce the power factor. Power factor is one of the main aspects that drives up energy costs. Most utility companies apply a surcharge when the power factor goes below 0.9 (or 90%). Over a year this can translate in thousands or even tens of thousands of dollars, depending on the size of the installation. The best solution is to move to modern SCR (thyristor) power controllers. These smart devices are available with a large variety of industrial communications that allows them to communicate with each other across the plant. They provide multiple firing modes for specific types of electric heaters and can automatically switch modes, for example from phase angle to bust firing based on resistance or temperature of the element. The key differentiators are specially designed algorithms for managing the power by evenly spreading loads across different furnace zones, multiple furnaces and the rest of the plant. This kind of Predictive Load Management uses clever load balancing, sharing and shedding strategies to equally distribute power and maintain a balanced overall consumption. Eliminating peaks in power demand helps make the best use of your energy and keeps finance managers happy by operating within your specified tariffs For more information on Predictive Load Management download Eurotherm white paper ‘Energy Cost Reduction through Load Balancing & Load Shedding’: http://www.eurotherm.co.uk/en-gb/products/powercontrol/epower/

You can read the next installment from Eurotherm’s top ten tips on improving effeciency in heat treatment in the next issue of Furnaces International, out in March. www.aluminiumtoday.com/furnaces/

Stolzle Glass

Furnace unveiled at container glass producer Stรถlzle

Stรถlzle Glass Group invited its customers and partners to celebrate the recent rebuild of its white flint furnace and extensive revamp of the plant in Knottingley, UK. Guests were given a tour of the plant after a welcome speech from Plant Manager, Thomas Riss. Greg Morris was among those to attend the celebratory event. Stรถlzle Flaconnage has officially inaugurated its new furnace and modernised site at its plant in Knottingley, UK. The ยฃ17 million investment included a 180t a day white flint furnace, which will allow the company to increase its feeder colour capacity and capability in the high-end luxury drinks sector. The investment will also allow the company to increase its flexibility, meeting the trend for small volume production runs and quick turnarounds. The new furnace will pull glass on an area of 65m2 and feed five flint production lines. The focus will be on tallware, gift products and feeder colouration, all made of flint glass with a fire polishing option on all

Thomas Riss, Plant Manager of Stolzle Flaconnage, addresses the attendees of the inauguration.

production lines. The new IS machines allow several different bottle shapes to be manufactured simultaneously and allow bottles of up to 4.5 litres to be produced. Further investments were made in cold end inspection facilities and decoration technology, implementing a high speed spraying line and a new automated printing machine and accessory application. As plant manager Thomas Riss said, the company also did not forget the environment. As well as providing better quality glass, the furnace will also save energy and reduce emissions. Thanks to the optimised engineering of its combustion chamber, gas feed, burner and regenerator set up, the new furnace will Continued>>

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Issue 4 Furnaces International r 29

Stolzle Glass

Above: the old furnace at Flaconnage, and below: the new one, from Poland’s Techglass.

reduce the plant’s carbon footprint by 13% per tonne of glass produced. Substantial improvements in the plant’s water consumption and compressed air were also realised. The company has decreased its water consumption by 50%, saving the equivalent of 450,000 bathtubs of water a year, with almost all process water being recycled.

Investment The inauguration took place almost a year to the day when Stölzle’s owner, Dr. Cornelius Grupp, decided to invest in the factory after completing an evaluation of the business. The original furnace was built 21 years ago in 1995. In 2006 it had a repair, and was then partially rebuilt in 2009. It was pulling 150 tonnes at the end of its life. The new furnace was installed over the course of this summer, with work starting to disassemble the furnace on July 4, with glass to glass taking 56 days. 30 r Furnaces International Issue 4

The work required a batch house modification from Forglass and a new furnace from Techglass – both companies are based in Krakow, Poland. Stölzle also introduced two new IS machines from Bottero, one being a tallware machine for bottles up to a size of 500mm capability, which it did not have before. On top of that, two of the machines are equipped with colouring equipment. The installation of the tallware machine required Stölzle to install a new lehr, supplied by Antonini. At the cold end it introduced new inspection equipment and, for the first time, installed a completely automatised palletising line, from Emmeti. Parallel to the investments on the production line, it invested in a KBA Kamman K15 printing device, which will allow Stölzle to print four colours in one pass. Group CEO Johannes Schick also attended the inauguration event and said Stölzle Flaconnage will be a centre of excellence with regards to the development, production and decoration of premium prestige bottles. “Our task is to ensure our customers can be proud and to help create a best selling bottle. We want to say we have helped build a brand which is fast growing.” He added: “We wanted to create a place where our workers can feel proud of what they do and where wonderful bottles are the outcome. It’s important they don’t feel hidden in the darkness, we want to give them the space where they can set the standards for tomorrow.”

Contact Stölzle Flaconnage, Knottingley, UK www.stoelzle.com

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Company profile: Techglass

Glass furnace supplier with an emphasis on quality

Polish company Techglass recently installed a new furnace at Stölzle Flaconnage’s site in Knottingley, UK. Here, its president and founder, Andrzej Skowiniak, provides a company overview.

Congratulations on your recent furnace installation at the Stölzle Knottingley site. Can you tell us a little bit more about the furnace and why, in your opinion, Stölzle chose you to do the job? Thank you. It is a medium size U-flame regenerative furnace producing high quality container glass for alcoholic beverages. It is fuelled by natural gas and electric boosting is installed for bigger pull. High quality of glass and reduced environmental impact were the main requirements of this project. It was then our great advantage from the beginning that other furnaces that we supplied to Stölzle in the past are known for excellent glass quality and reduced environmental impact. The new furnace is built where the old one was, with no changes to the spouts’ positions. It was a challenge to design a furnace with pull higher than the old furnace had and which would fit in the same space. For a green field project you can get a standard design from your archive and modify it slightly to fulfil all requirements. That’s relatively easy. You can’t use the same easy strategy for a project like the one executed in Knottingley www.aluminiumtoday.com/furnaces/

Above: The main requirements from Stölzle for the furnace, such as the one shown, were high quality glass and low energy consumption.

and it is exactly where a skilled and experienced design team, like our team, makes a difference. Our offer for Stölzle covered every system, every piece of equipment from batch charger to the spouts. We did it all by ourselves, without any subcontractors. That is why we were able to guarantee a short glass-to-glass period, which of course was also significant for the customer.

What other projects have you worked on with Stölzle? Although it was our first project for Stölzle UK, we’ve cooperated with Stölzle for many years in numerous projects of various scale: from small repairs to new turn-key projects. We have good experiences in cooperation with Stölzle in the Polish market. Stölzle has two glass plants there – in Czestochowa (STC) and in Wymiarki (STW). Techglass has constructed two fully equipped furnaces with forehearths of its own design for STC. The last of these big turnkey projects was completed successfully in 2012. Since then we have been providing different kinds of services connected with the maintenance Continued>> Issue 4 Furnaces International r 31

Company profile: Techglass of the furnaces and forehearths in STC. When Stölzle bought the Wymiarki plant it quickly decided to rebuild it and they chose us to do it. Techglass performed the rebuild from glass to glass there in 2015. So, based on our positive experiences in cooperation the next project was just a matter of time. The same year we were queried about the furnace cold rebuild in Knottingley, UK.

Did the Knottingley installation require any particular challenges or was it a straightforward job? A project like this is never straightforward. The sheer amount of old materials to be dismantled and transported out of the production shop and then the new ones to be transported in and installed in a very specific order, would give every project manager a headache. Sometimes only refractory materials with some steel structure are replaced. In Knottingley every system was replaced as well, from combustion system, cooling systems to control system. It was a challenge to execute a project this big in the small space of the production hall in a short time. Quite often the ideas that look good on paper during the preparation phase, turn out to be nonworkable on site and you need to come up with new solutions. In Knottingley, we had assumed for example that we’d be able to use a crane for heavy lifting, but it was not possible due to insufficient space. We proposed a solution that was accepted by Stölzle and the works were not delayed. Every plant is different, so every project brings its own problems to be solved. We are very good at that, it is one of our main strengths that we never give up on finding the best solutions, and since we have a lot of experience, we do it fast. The Stölzle team was very helpful in making their decisions concerning our proposed solutions, so we were able to finish the project before the deadline. Why should glass manufacturers consider Techglass when they source new equipment for their factories? First of all, our team is the company’s greatest advantage. We employ 140 people – from designers, technology engineers, control systems engineers to steel workers. We are 32 r Furnaces International Issue 4

therefore capable of executing turn-key large scale projects based on our own human resources covering the whole production process, from modelling through designing to construction and heat-up. I think that the second key factor is the high quality of the products we provide. Due to the fact that most of the systems and equipment Techglass supplies comes from our in-house production, we are able to control its quality thoroughly. We can cover the entire scope from the batch silo to the spouts, so choosing us the customer limits the number of contractors on site and it is much easier to plan all activities. Needless to say, that greatly lowers the risk of collision problems, which take a lot of time to solve if more than one contractor is involved. What is more we always treat every customer individually, providing them tailored solutions. Techglass does not sell the furnaces off-the-shelf. Also, we do care about the after sales services, trainings and consulting to make our customers familiarised with our installed furnaces. Furthermore, we provide hot works and audits between the cold rebuilds to help our customers keep their furnaces in a good state of repair. Combining these factors all together leads to the successful outcome of the projects and customers’ satisfaction.

Can you tell me a little about the company’s history? Techglass was formed in 1990 by a group of people formerly employed by the stateowned ‘Institute of Glass and Ceramics’. In Poland it was a time of great opportunities after the breakthrough of 1989 when it was finally possible to start your own company. At the beginning our operations were limited to minor repairs, but step by step we gained momentum and extended the range of our services and products to the current level. Now, after 25 years, we are a trusted supplier of companies such as Owens-Illinois (O-I), Saint-Gobain, Zoujaj and Stölzle for turnkey multimillion projects, which shows the distance we covered from the humble beginnings in the 1990s. Have you noticed any recent trends from glassmakers? One trend that clearly stands out concerning glass melting is the reduction of the www.aluminiumtoday.com/furnaces/

Company profile: Techglass environmental footprint of the furnace. It follows the rise of awareness of the environmental protection in the population, but also the penalties for exceeding limits of emissions reinforce this trend.

all companies is about 3500 thousand tons per year. Glass containers – mostly bottles – constitute about 1400 thousand tons out of the total output. This volume is achieved by a couple of international companies which are present in the market such as O-I, Ardagh, Can-Pack, BA Glass, Stölzle and Zignago Vetro. Most of the Polish glass plants have been overhauled recently. Concerning the float glass sector, there are also several worldwide players active in Poland: SaintGobain, Euroglas and Pilkington. They produce approximately 1200 tons per year and their facilities are among the most modern in Europe. There are also glass wool producers, like Isover and Ursa, present in Poland. In our opinion the glass container branch has the greatest potential of growth in the Polish glass market.

Where is Techglass’s strongest geographical region? Europe is our strongest region, but we are present in many others. For example, now we are in the last phase of a turn-key project in Saudi Arabia, our second turnkey project there in two years, and in the furnace construction phase of a turn-key project in Poland for Zignago Vetro. This year we completed two complex furnace rebuilds in Ukraine for Verallia and for Vetropack. Last year we executed rebuild projects in Germany for O-I and SaintGobain. Of course, the Polish market is important for us and we are very active there. In the last two years we have completed two complex furnace rebuilds for O-I and for Zignago Vetro. In the mentioned period, we also executed a turn-key project for Can-Pack. In addition to these big projects, we have been also involved in many smaller ones in different countries such as India, The Netherlands, France and Egypt. Is there an emphasis on innovation and Research and Development? We focus on two main research areas: energy consumption and process automatisation. There are a couple of ways to optimise energy consumption, like heating the batch or waste gas energy recuperation. The aim of automatisation of the glass melting process is to have a system with only a couple of parameters to be set, like the type of the bottle or the pull. Everything else, the temperature curve, the electric boosting power and others, should be controlled automatically. Currently we are quite far away from that vision, but we’re getting there. How strong is the Polish glass industry and does it have a rich glass heritage? The Polish glass industry is not among the strongest in the European Union, but its growth is the fastest. The total output of www.aluminiumtoday.com/furnaces/

How would you like to see your company evolve over the next 5 to 10 years? We are now in a long transition process in the company. The employees that joined us in the first years and became key to our operations are gradually retiring. A new generation is replacing them and this process takes time. This is the biggest challenge we are now facing, but I’m positive that everything will be fine. We are lucky that we specialise in glass furnaces as in the years to come there will be most probably no material that could replace glass and no new glass manufacturing technology. The demand for our products and services will be therefore at least maintained at the current level.

Contact

*President, Techglass, Krakow, Poland www.techglass.pl

How many staff do you have and how many offices/plants? We employ 140 employees. They belong to one of our departments: Furnace Design, Combustion Systems, Control Systems, Masonry, Steelworks, Production, Logistics, Project Management and Office Administration. The headquarters and production hall are located in Krakow. The Furnace Design Department is based in Warsaw.

Issue 4 Furnaces International r 33

Refractories

Insulating castable refractories for aluminium furnaces Best practice for furnace and kiln applications, by Lance Caspersen* Aluminium furnaces rely on high temperature insulation materials to optimise production yield and minimise energy costs, which can rise rapidly if excessive heat escapes from the point of operation. Insulating castable refractory materials are key to this energysaving process due to their inherent low heat conductivity as well as advantages derived from ease of placement and structural strength. However, with so many local, national and global manufacturers delivering to market a myriad of material technologies and products, accurate specification is a highly challenging task. This article examines the key considerations for specifying castable refractory insulation systems, offering advice on achieving the best value solutions which minimise energy consumption, optimise outputs and meet the needs of both the installer and end user. This is particularly important for aluminium furnaces, which use large amounts of energy during the process heating required to melt, purify, alloy, and treat the metal during smelting. Refractories are used to contain thermal processes and provide protection for personnel and furnace structures. Whereas refractories provide wear resistance and thermal conductivity, secondary layers of less dense, more thermally insulating materials are often used to reduce heat flux and better contain the energy source used in the application. By insulating 34 r Furnaces International Issue 4

these refractories, industry can also benefit from a reduction in greenhouse emissions that results from burning less fuel. Customer requirements for higher performance products, and installer needs for easy to apply materials, drive the leading refractory manufacturers worldwide to continue to invest heavily in the research and development of next-generation industrial insulation materials. The aim is to bring to market castable products that combine optimum insulation performance with other important attributes, such as strength, operator safety and ease of installation. Specifying insulating castable refractory systems has become a real challenge, with those containing alternative, highperformance core monolithic ingredients, such as crushed Insulating Firebricks (IFBs), now an increasingly popular specification staple for complex high-temperature applications. That said, the use of conventional raw materials such as perlite, an amorphous volcanic glass, and vermiculite, a hydrous phyllosilicate mineral, remains prevalent in many sectors. Despite crushed IFB containing insulating castable mixes outperforming conventional material choices in both application precision and product performance, habitual specification behaviour is preventing customers in certain industries from moving in favour of better alternatives. As with any change in specification, education is key to enable decision-makers

to select a product which is best suited to each individual application in accordance with environmental factors, application considerations, desired outcome and, of course, cost. With advances in materials technology set to continue, and product variety expected to increase even further, specification best practice will become continually more challenging to apply. With that in mind, it is vital for specifiers to obtain and uphold a detailed understanding of the key products, their technical capabilities, application processes and how each one can facilitate or hinder key drivers including installation, lifetime cost and energy efficiency.

Understanding the ingredients of each castable mix On the face of it all insulating castable refractories look the same, comprising a mixture of aggregates, cement and additives, such as clay and fillers. When mixed with water, they will form a slurry suitable for application via casting, gunning, ramming, pouring or plastering, and in some compositions, pumping and shot-creting. It is important to realise that all castable refractories can be different, and therefore should not be commoditised. By learning the difference between each castable type, specifiers, contractors and installers can select and install a product which is better matched to their application, delivering improved energy and output performance, increased lifespan and associated cost efficiencies as a result. The best way to facilitate an www.aluminiumtoday.com/furnaces/

Refractories ongoing learning curve is by partnering with an established and knowledgeable manufacturer that can not only encourage best practice throughout the specification process, but will also assist specifiers and procurement teams in making the right purchasing decision on a site-by-site basis, in accordance with customer requirements. The difference between working closely with a manufacturer and seeking a commodity castable refractory solution is simple. A highly experienced and wellestablished manufacturer has refractory products to suit even the most complex insulation challenge, balancing properties such as density, strength and thermal conductivity; something that is particularly useful when specifying for an environment, which is particularly harsh or requires a specific method of application. It is also important to understand that while raw materials in insulating castables vary, there are three main ‘core’ aggregate raw materials on the market, used to form a variety of insulating castable refractory products. Before we go any further, it is important to assess these key ingredients:

2) Vermiculite Vermiculite is a hydrous phyllosilicate mineral which occurs naturally as an alteration product when certain types of rocks form next to each other. When heated to around 572°F, exfoliation occurs and vermiculite expands to approximately 30 times its original size. There are large commercial vermiculite mines in Russia, South Africa, China and Brazil, producing material for a variety of industries. For insulation purposes in certain mixes, vermiculite and perlite can withstand temperatures of up to 2,000°F and 2,100°F (1,093°C and 1,149°C), respectively before excessive shrinkage occurs.

1) Perlite Perlite is a completely natural siliceous volcanic mineral, formed by the sudden cooling and solidification of volcanic ash, which traps crystalline water into its masses. Used widely in construction, as well as agriculture for the aeration of soil, perlite is mined throughout the US, Greece, China and Italy. World reserves of perlite are estimated at 700 million tonnes, with around 1.5 million tonnes being mined and processed each year. Characterised by its ability to expand to up to 20 times its original size when rapidly heated to 1,472°F and 1,742°F (800°C and 950°C), Perlite is essentially a mass of minuscule glass bubbles which give it the insulating properties for which it is known.

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3) Crushed insulating firebricks Used as an alternative core raw material for making insulating castable refractories, typical cast process crushed IFB offers superior heat-resistance capabilities of up to 2,800°F (1,538°C). Having already been fired to a high temperature during the brick manufacturing process, crushed IFB is a pre-shrunk aggregate which, when mixed to make a castable refractory, contracts very little during high temperature use. With the inherent structural strength capacity of an insulating fire brick and a density of 34PCF (545kg/m³) compared to perlite’s 8PCF (128kg/m³), monolithic castable mixes which use crushed IFB as the core material will not only perform extremely well in high temperatures, but can also be formulated specifically to offer increased strength and thermal insulation performance in harsh furnace and kiln environments. While there are a number of manufacturers worldwide that promote IFBs, there are very few which crush special cast produced IFBs for use in monolithic castable refractories, making Morgan Advanced Materials the leading innovator in this area of materials technology.

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Refractories Key specification criteria With a clearer understanding of the three main core raw materials in aluminium castables, the next question is: Which base aggregate to choose? There are a number of key criteria which would be considered best practice in specifying insulating castable refractories. These include the method and complexity of application, the quality and cost of the product and the environment in which the product is expected to perform. Get these three elements right and the product specified, assuming it has been correctly installed, should deliver optimum furnace or kiln performance and improved energy efficiency over a longer lifespan. Here we look at the three variables in more detail. Application consistency Taking an industrial or commercial furnace or kiln out of operation is inconvenient and incredibly expensive, so specifying an insulating castable refractory which is quick and efficient to apply, while providing long reliable service, is of great benefit to the end user. There are two main concerns when selecting a product that will facilitate a predictable and efficient application; ease of use generally by casting or gunning and product loss usually via rebound or material compaction. Insulating castable products which are deemed easy to install are consistent in production and can be applied under a wide variety of conditions. Cast process crushed IFB based castables have a consistent density and particle size enabling tight control on water addition resulting in a smooth castable with good flow characteristics. They also lend themselves to installation by gunning and by pumping since a more porous aggregate will tend to clog the hoses. It is this application downfall, which has seen many specifiers and contractors to move in favour of castable materials using raw material technologies such as crushed IFB, so that material costs can be more accurately controlled prior to application. The other key consideration here is ‘rebound’, which is the name used during installation to describe the situation when gunned material falls off the walls or ceiling onto the floor. Waste caused by rebound is usually the 36 r Furnaces International Issue 4

aggregate, which is why leading manufactures like Morgan have engineered specific formulations to minimise rebound to as low as 10% while providing greater consistency of the installed product. Finally, material compaction is when the gunned castable mixture compacts when being installed on the wall due to the force of application, requiring additional material in order to deliver the desired thickness. Despite its beneficial lightweight characteristics, perlite-based castable products are known to compact up to 20% when gunned, which can make what is, at first glance a costeffective material, a more expensive overall installation. Meanwhile, IFB-based insulating castables suffer very little, if any, on the wall gunned compaction since the hard fired raw material does not easily break down during the application process. Thanks to the uniform and reliable manufacturing methods used in creating crushed IFB insulating castable refractories, installers can also benefit from simplified and consistent application processes. Monolithic refractories with a core of crushed IFB mix into a smooth, homogenous ‘ball in hand’ consistency, compared with other insulating castables which are typically grainy and less cohesive. The consistency of IFB mixes allow for more precise control during application, requiring less air or water adjustments and potential surging during the gunning process.

The quality vs cost argument The quality vs cost argument is an age-old specification problem, especially when working with large companies with an in-house procurement team tasked with identifying cost savings. Tackling this issue in accordance with best practice means engaging with both the technical and purchasing teams to aid a process of understanding. Put simply, by encouraging an appreciation of the benefits which a better quality product can offer in the long run, when compared with a lesser quality material with a more attractive perceived initial cost, specifiers can guide other decisionmakers within the purchasing chain to opt for a refractory which not only delivers enhanced performance and product reliability, but a more www.aluminiumtoday.com/furnaces/

Refractories sustainable whole life cost too. It can even be said that an application which only requires a low to moderate level of thermal insulation could reap the benefits of ‘over-specifying’ on quality in order to enjoy better whole life costs and minimize the risk of costly kiln failure. A good example of this would be the purchase of a $1,100/metric ton castable material rather than a $1,000/metric ton alternative, which might potentially deliver more reliable product service life, as well as added performance, insulation and speed of installation benefits which come with a better quality product. One has to look at the total cost: The price of the material, the installation production rate, the density on the wall, the installed material performance and service life. Specifying on a project-by-project basis It is not uncommon for specifiers to have preferred manufacturers or suppliers for materials or building products whom they use on a regular basis. For some materials though, including insulating castable refractories, this approach is not always conducive to best practice. Commercial and industrial furnaces and kilns can be subject to a variety of different application-specific factors and there may be a number of operational variables at play too, which will shape the specification requirement. The key here is to really get to know the environment you are specifying for, so that you can recommend a product that will provide adequate insulation, performance and lifespan. The simplest example of having to specify on a project-by-project basis is that of operating temperature. While all furnaces rely on intense heat, there can still be a significant difference in temperature between one environment and the next. As not all monolithic refractories offer thermal resistance to the same level, a furnace or kiln which operates at 2,000°F, for example, could be insulated with a perlite, vermiculite or crushed IFB based refractory, but an alternative environment reaching much higher temperatures would rule out perlite and vermiculite mixes completely. The formulation of the mix will change depending on the temperature requirements of each project, with more www.aluminiumtoday.com/furnaces/

cement and a denser aggregate providing increased strength, and less cement but a better insulating aggregate being most suitable for higher temperature operations. This is true for a number of environments within the ceramics sector, such as the manufacture of small ceramic spheres for LNG fracking, which requires a highstrength castable capable of performing in extremely high temperatures. An established manufacturing partner will be able to assist in specifying the right mix for the job, providing guidance on best practice and how to accommodate the change in formation with appropriate application methods. Other important considerations here are the presence of contaminants in the operator’s process, which will require a purer castable refractory, as well as the issue of ‘thermal cycling’, which describes the scenario where a furnace or kiln is heated then cooled frequently during operation. This constant change in temperature may cause cracking in a lower strength castable while an insulating castable mix formulated with a pre-shrunk core material, like IFB aggregate, would be more suitable.

Contact www.morganthermalceramics. com/F&KRefractories

Changing the specification habits of a lifetime Many areas of the supply chain can be resistant to change, especially in environments where planned downtime or furnace failure is extremely costly. It is this resistance as well as a focus on simple material price that is slowing the shift towards better materials technologies in some sectors, despite the obvious benefits. When considering best practice, the unfortunate truth is that the very nature of specification can bring about habitual behaviours, which can eventually lead to sub-optimal product choices if decisionmakers do not keep up to speed with technological advances and market changes. However, it is crucial to remember that improved castable refractory materials offer enhanced performance, better insulation and ultimately, energy and costs savings over the life of the product – so they should be embraced as early as possible. Issue 4 Furnaces International r 37

Aluminium melting

Less dross and higher efficiency

Fig. 1: Two Quadraflo Sweep burner flame pattern.

Benjamin KĂśster, Rui Fontes, James Nabors & Bill Andrews* of Hotwork International outline the Quadraflo Sweep Aluminium Melting System. The oxygen based combustion system helps manufacturers of aluminium to reduce their CO2 footprint and improve production. Of course oxygen burners are generally more energy efficient than cold air or preheated air burners, but how is it possible to reduce the dross so drastically, when applying oxygen combustion technology? Aluminium is the third most abundant material in the earthÂ´s crust. It has a strong affinity for oxygen and because of this affinity, aluminium does not occur as a metal naturally. Therefore you may ask how and why is it possible to use pure oxygen with natural gas to melt aluminium without increased oxidation? It is achieved through proper application of oxygen burner technology within an aluminium melting or holding furnace. Xothermic Inc. has developed the Quadraflo Sweep Aluminium Melting System. Instead of applying a burner used in other high temperature applications such as glass, steel, copper or other related fields, Xothermic researched aluminium melt applications and developed an optimal design through field trials. According to the company, the melting technology offers the highest energy efficiency and lowest dross

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formation for the best economics. As a direct partner for the industry, Hotwork International has the license for the Quadraflo Sweep Technology, in cooperation with Xothermic Inc.

Design philosophy Our initial penetration into the aluminium market was secondary aluminium reverbratory furnaces. This is the traditional furnace utilised worldwide for both primary and secondary aluminium melting. It is primarily a refractory lined steel box with energy input from a combustion system, an exhaust port, cold metal charge port, and in some cases a separate dross port and molten metal discharge port. There are many configurations of this design, however the basic principle of operation is the same for all designs. A heat source from the combustion system transfers heat into the cold metal with sufficient force to cause the metal to retain the heat until the melting point is reached (657Â°C on average). During this process, it is most desirable to do this heat transfer with minimum amounts of oxidation. Further heating is required to provide sufficient www.aluminiumtoday.com/furnaces/

Aluminium melting energy to maintain the aluminium in a molten state during the final end process of the production cycle (750°C on average).

Fig. 2: Burner block and typical set-up.

What causes excess oxidation? All aluminium forms an oxide layer from interaction with the oxygen in the atmosphere. This degree of oxidation depends on the age of the metal and its condition, such as paint, enamel or other types of passivation. In most cases, this is minor. The oxidation that is referred to is oxidation created during melting as a byproduct of the combustion process. Excess oxidation is generated from exposure of the cold charge to excessive heat and oxygen concentrations. How to prevent excessive oxidation? This is the main premise behind the design philosophy of the Quadraflo Sweep Aluminium System. We designed a burner system to minimise generation of a hot spot on the charge material. This was achieved with the use of a flat fishtail shaped flame that moved or swept across the charge. Another requirement is that burner velocities are low in momentum to minimise disturbing the molten metal bath. The flame movement is up to a 45°angle. Moving the flame over a period of several seconds allows the heat to be transferred over a significantly greater area than a fixed flame. Fixed flame burners heat an area of the charge to excessive temperatures in an effort to transfer heat to other parts of the pile. This creates significant hot spots and greater dross formation. Flow control systems are also provided to maintain a very close tolerance on the oxygen to fuel ratio. This is vital as you are paying for the oxygen and therefore do not want to waste it. Excess oxygen, even with air, creates more dross. It must be understood that regardless of the oxygen source, air or pure oxygen, the excess oxygen is still the same, on the order of several percent. Because pure oxygen is used, it does not mean the dross will go up. It is the excess temperature that has a greater effect. In fact, putting a blanket of pure oxygen over a bath of molten aluminium at 657°C and www.aluminiumtoday.com/furnaces/

Fig. 3a & b: Reverb furnace with Quadraflo Sweep burner.

Fig. 4: Tower Melter with Quadraflo Sweep burner.

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Aluminium melting no flame will show little or no increase in dross over a blanket of air at 21% oxygen.

Application and experience As mentioned before, there are numerous reverb and other furnace designs, therefore there is a demand for individual design modifications unique to the particular furnace design and application. Tilting reverb Regenerative to Oxygen Conversion Oxygen burners produce about 60-80% less exhaust gasses than an air burner, as the nitrogen has been removed. This results in better energy efficiency, less NOX production and less gas to clean prior to exhausting to the atmosphere. The energy efficiency compared to regenerative burners can be as high as 50%. On top, the furnace pressure can be reduced significantly, avoiding flames during high fire that can damage refractory and furnace doors. The furnace generally operates cooler with an air fuel burner. Various conversations have proven: • Energy saving: 35-40% • Dross reduction: 20-40% • Melt rate increase: 20-40% Oxygen to oxygen conversion Existing oxygen combustion systems produce localised overheating and as a result, increased dross. Low momentum Quadraflo Sweep Burners with full automatic controls can be installed. The roof mounted Quadraflo Sweep burners utilise a greater area of the furnace for melting with a very even heat and no localised overheating, as the flame is not fixed in one spot. The charge pile melts down evenly with less oxidation. Post combustion, to compensate for hydrocarbon gases from burned off coating etc., can be achieved with the automatic control system. In addition to the production increase, a corresponding increase in energy efficiency and metal recovery can be seen: • Energy saving: 15-25% • Dross reduction: 20-40% • Melt rate increase: 20-40%

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Fig. 5: Quadraflo Sweep burner hot face.

Fig. 6: Quadraflo Sweep typical flame.

Fig. 7: Quadraflo Sweep burner typical skid on roof installation.

Tower melters The Quadraflo System also includes burners for the Tower Melter. This melter operates primarily with clean scrap and ingot and is used by continuous casters. This is not a batch operation nor is alloying done; most ingot is at specification. Because of this, it is possible to have a continuous pour operation. This suits the Tower Melter design very well. A major supplier of cast aluminium auto parts required an increase in capacity, as there was insufficient room for additional furnaces. Emissions were also a concern, and therefore there was a need to minimise the pollutants from the process while increasing production. A Tower Melter has a tall refractory lined shaft with a melt box at the bottom that serves as the main melt zone, as well as a preheat for the incoming charge and an exhaust conduit. The molten aluminium flows from the melt box into the holding chamber over a raised ledge. The holding furnace attached to the tower served only for holding, with no melting. The initial design used an oxygen burner in one of the air fired burner positions. The production was increased from 1.4mton/hr to 2.1mton/hr or 50% with a reduction in dross by 1%. It was observed that greater yields could be achieved through the use of hot gas recirculation using an oxygen burner to heat the hot recycled gas as it entered the melt box at the bottom of the tower. An outside supplier in conjunction to the burner technology provided the hot gas fan. The increased volume from the recycled gas, which provided energy savings by coming in at 900 to 110°C, increased melt rate and reduced both energy consumption as well as dross. The melt rate was increased to 3.5 mton/hr or 150% over the air burners. Dross was reduced significantly by over 60%. The emissions were also within the legal limits set by the State. Holding/melting Many processors utilise two furnaces that complement one another. One such application was for a Rotary/Holding furnace. The customer wished to increase www.aluminiumtoday.com/furnaces/

Aluminium melting control monitor when the charge is melted, minimises metal loss by firing longer than needed and burning metal. Typically, one can expect the following benefits from converting to oxygen from air firing. These numbers are ranges as the type of material dictates the ultimate benefits from oxygen conversions: • Energy saving: 40-60% • Dross reduction: 20-40% • Melt rate increase: 15-30% The control system for any of these installations is fully automatic and can be expanded to cover such items as furnace pressure, temperature and associated items such as bag houses for emissions control.

holding capacity and add some melting capability to the holding furnace. The problem was that the holding furnace had absolutely no room for air burners and the bulk of the material to be melted was silicon for alloying and sows. The rotary was providing in excess of 80mtons per cycle to a holding furnace that was in excess of 120mtons. Approximately 10% of the holding furnace capacity was charged as silicon as one charge. The solution was two 1800 kW nominal (900 to 3600) Quadraflo Automatic Sweep burners mounted in the roof. After conversion from cold air fired burners and furnace enlargement, there was a significant reduction in energy consumption and a 20% reduction in dross. The customer was impressed to the point of ordering a second system within a month and two new furnaces with the Quadraflo Automatic Sweep burners within the year.

Rotary furnaces One traditional furnace that has undergone numerous improvements is the rotary furnace. With the advent of new and better refractories and the inclusion of oxygen burner technology, the Rotary Furnace has come of age. Depending on the application, rotaries come in either fixed bed or tilting designs. It can be used to demag aluminium, used for irony scrap, dross processing and general scrap aluminium melting. We have found that by providing a low momentum, high luminosity burner with an adjustable flame pattern as well as an adjustable bracket, it is possible to tailor the burner operation to the specific use for maximum energy efficiency, maximum metal yield with minimum down time. The bracket can be moved, thus moving the burner and placing the heat where it is needed to do the most good. Burner life is dependent on plant maintenance. Periodic cleaning of the area around the burner ensures maximum life for the burner. A monitoring system can be installed for dirty scrap, which allows an increase in oxygen to help burner up volatiles as they evolve off the charge. Additional features in our automatic www.aluminiumtoday.com/furnaces/

Process controls and instrumentation Hotwork and Xothermic utilises combustion control equipment with various types of PLC controllers and HMI touch screens. Electrical and mechanical systems are CE rated for European compliance. Flow sensing is from 0 to maximum flow with a high degree of accuracy. Ratios and temperature control is by PID control. NEMA 12 rated electrical enclosures are used to protect the electrical components. Upon request by the customer we can incorporate into the control system other mechanical and electrical components of the furnace. Some common additions are: Chlorine injection monitoring and control, molten metal pump control, furnace pressure, door opening and closing, bag house monitoring. The customer’s furnace design and control is often incorporated into the touch screen displays for convenience.

Contact

*Benjamin Köster, Rui Fontes, James Nabors & Bill Andrews, Hotwork International www.hotwork.ag/ home

Conclusion Today, focusing on environmental friendly production and products, such as lighter products in vehicles and air crafts, Hotwork International is facing these challenges with its oxy-fuel aluminium melting technology. With lower emissions and higher efficiency, the Quadraflo Sweep burner assists customers in reducing their CO2 footprint, getting credits and improving production all at the same time.

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