Aluminium World Journal 2014

Global Media Communication Ltd.

2014 Edition

Charles Martin Hall

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Aluminium World Journal 2014 Global Media Communication Ltd. Managing Director Christopher Fitcher-Harris, Production Manager Sofia Henriksson Sales Manager Peter Jones Production Design: row1graphics Published by: Global Media Communication Limited Telephone: +44 208 579 0594 E-mail: gmcproduction@gmx.com Website: globalmediacommunication.com The opinions and views expressed in the editorial of content in this book are those of the authors alone and do not necessarily represent the views of any organisation with which they may be associated. Material in advertisements and promotional features may be considered to represent the views of the advertisers and promoters. The views and opinions expressed in this book do not necessarily express the views of the publisher. While every care has been taken in the preparation of the book, the publishers are not responsible for such opinions and views or for any inaccuracies in the articles or advertisements. ©2014 The entire contents of this publication are protected by copyright.

Full details are available from the publishers. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior knowledge of the copyright owner.

Cover illustration: Alcoa

Foreword By Christopher Fitcher-Harris Aluminium World Journal 2014 features editorials, case studies, company profiles, and product reviews.

The publication is divided by industry sector sections to ensure ease of navigation.

This edition contains special feature articles produced by TMEIC entitled “TMEIC Serving the Aluminium Industry”, and Rio Tinto Alcan on the “Start-up of the Arvida Smelter, AP60 Technology Center”. We are pleased to present new independent authors for this edition: Dr. Ing. Joachim Heil from MetCons with the paper “Aluminium Reduction Cell Technology Providers – a 2014 Review” and Louis Dekker, Process Engineering Specialist from LeProCon, with the concept article on “An Intermediate Step in Cost Reduction for Inert Anodes” and would like to thank them for their contributions.

I take this opportunity to thank all the participating companies for providing Aluminium World Journal 2014 with editorial, company profiles, advertisements and corporate sponsorship.

Aluminium World Journal 2014 is available for you to read online, download, and in print format. Visit us online at: www.globalmediacommunication.com If you should wish to discuss with me anything concerning the content of this edition, do not hesitate to contact me.

Hope you enjoy the read!

Christopher Fitcher-Harris

Managing Director

Charles Martin Hall had a purpose to his life.

And it wasn’t a small one, either.

“Mr. Hall revealed that probably his chief ambition in life was to make some discovery which would be revolutionary with regard to the present conception of the constitution of matter and which would be of immense benefit to mankind,” wrote Arthur Vining Davis, former president and chairman of the Aluminum Company of America (Alcoa), which Hall helped found in 1888.

For Hall (1863-1914), the ticket to making his dream into a reality was his love for science and interest in aluminum.

From the time he was a teenager, Hall noted that although aluminum was the Earth’s most abundant metal, the process for extracting it from its ore in a laboratory was so difficult it was only made in small quantities. Supply and demand made aluminum as expensive as silver. Hall vowed to find a better way. During his years at Oberlin College in Ohio, he tried and failed repeatedly. Still, he stayed positive and worked to discover an easier method of extraction.

Day and night, “consciously and subconsciously, he was still working on the problem of producing cheap aluminum,” wrote Julius Edwards in “The Immortal Woodshed: The Story of the Inventor Who Brought Aluminum to America.” “Hall was at heart . . . a tireless experimenter.”

He approached science deliberately and logically. He formed theories based

The first small, shining globules of aluminum reduced through the Hall Process. They are referred to as Alcoa’s “”crown jewels””. Shown here on a page of handwritten minutes from a company meeting, circa 1890.

on his experiments, then asked others to confirm his findings.

After graduating in 1885, Hall returned to his family’s home to continue his experiments. He went over his records to re-evaluate the problem, and then embarked on a new strategy. He realized he’d need more work space and new equipment, so he moved his lab out of the house and into the woodshed.

While his fellow graduates jumped into the business world, Hall focused on making his discovery so he could make his mark in that world. He locked

himself in the woodshed, combining countless substances in his quest. He carefully logged each attempt and its outcome. When he found a promising combination, he tried numerous variations until he was sure it wouldn’t work.

Then, in February 1886, Hall made his breakthrough: electrolyzing alumina dissolved in molten cryolite. He’d discovered an inexpensive method for isolating pure aluminum from its compounds.

He wasn’t alone, however: The potential rewards for a cheaper aluminum isola-

Alcoa’s lightweight aluminum helped revolutionize the automotive and aviation industries; aluminum foil eased the lives of housewives everywhere.

Demand for Hall’s aluminum led to production soaring from 10,000 pounds in the company’s first year to 15 million by 1907. One plant grew to three.

In 1911, Hall was internationally recognized with the Perkin Medal for his contributions to chemistry.

1886-1920. The Hall family home in Oberlin, Ohio. Hall discovered the aluminum process in a summer kitchen attached to the back of the home.

tion process had scientists the world over racing to find a workable method.

French chemist Paul L.T. Héroult was one of them, and he developed the same method at about the same time as Hall. The process became known as the Hall-Héroult process.

Quick Action Aware of the other efforts, Hall moved immediately to protect his method. He wrote immediately to the U.S. Patent Office, submitting his process.

Patent number 400,655, granted to Hall in 1889, changed the aluminum industry forever.

To make his efforts profitable, Hall knew he had to make the process available for widespread use. So he worked as relentlessly in finding backers and raising capital as he did in the lab.

He made a list of industries that might use aluminum. He prepared drawings and charts to show how the process could be applied. Then he made appointments with various wealthy individuals to show how they’d benefit if they invested in his idea.

His presentation persuaded some investors to join him, and the Pittsburgh Reduction Company was born. The firm was re-named the Aluminum Company of America (Alcoa) in 1907.

“Hall’s process is a new discovery. It is a decided step forward in the art of making aluminum. Since it has been put into practical use, the price of aluminum has been reduced from six or eight dollars a pound to 65 cents.

This is a revolution in the art and has had the effect of extending the uses of aluminum in many directions not possible when its price was high . . .

Hall was a pioneer and is entitled to the advantages which that fact gives him in the patent law,” said Judge William Howard Taft, later U.S. president, in a 1893 ruling in Hall’s favor regarding a patent case.

By 1914, the cost of aluminum was down to 18 cents a pound.

Hall’s parents gave him a solid educational foundation. His mother taught him to read before he was 5. Books were plentiful in the Hall household, and young Charles pored through every one he could get his hands on. He even delved into his father’s college chemistry books: the heavy tomes introduced him to, and sparked his love of, science.

“I have often seen him, after he had read for a while, lying asleep with his face on the book. . . . Someone would pick him up, still sleeping, and put him and his beloved book in a safe place,” Hall’s sister Julia recalled years later.

Hall’s love of reading and education stayed with him his entire life.

Drawing of the interior of the Smallman Street works of the Pittsburgh Reduction Company depicting the reducing pots used in the company’s process. (1888)

“He used to read the Encyclopedia Britannica night after night, year after year, literally . . . He used to . . . open it wherever it happened to open; then he would spend the evening reading, and he accumulated a big fund of information in that manner,” Davis said.

Learning From The Best Figuring he could learn from those who’d gone before him, Hall studied the lives of successful people, especially inventors such as George Westinghouse. From the “Scientific American,” he learned about patent law and practices, and keeping ideas secret until they’re ready.

The New Kensington office building of Pittsburgh Reduction Company. (1891)

Even as his success and net worth increased, Hall’s work ethic remained solid. “He was not just satisfied with having someone else promote his process, Edwards wrote.” Although a director and vice president of his company, he worked long hours at the plant, determined that the success of his process and (of the) company should far exceed any of his original prophecies.”

Science wasn’t Hall’s only interest, however. He had a lifelong love and appreciation of nature, and music had been a passion for him since childhood. Playing the piano was a source of relaxation his entire life, and helped him clarify scientific problems, Edwards wrote.

He also fed his soul. He attended church regularly, and drew strength from the stories of great men who sacrificed for their convictions. “The creed which found most significant expression in his works and deeds emphasized the importance and value of good character,” said his brother, George Hall.

While Hall helped to change industry and make many goods available to the masses that would otherwise have been unaffordable, he never forgot what helped make him a success. Upon his death, Hall bequeathed Oberlin College more than $5 million.

First ingot being charged into remelting furnace at Alcoa Tennessee Plant. (1920)

Authors: Investor’s Business Daily Photo Credit: Alcoa

INDEX Special Feature

p. 9-12

Global Issues

p. 13-17

Primary Smelting and Processes

p. 19-59

Anode Plant Technology

p. 61-87

Materials Handling And Transportation

p. 89-95

Company Profiles

p. 97-103

Advertiser and Web Index

p. 104

TMEIC Serving the Aluminum Industry

15 ALUMINUM MILLS AUTOMATED IN THE PAST 10 YEARS. TMEIC delivers. In fact, we’ve been a leading force in the metals industry for more than 50 years, and have been the preferred partner for most of the recent aluminum mills in the world.

TMEIC’s Advanced Process Automation Control System features fast and effective level 1 controls and integrated level 2 models for aluminum mills.

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SPECIAL FEATURE

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SPECIAL FEATURE TMEIC Serving the Aluminium Industry

p. 10-12

AWJ 2014

9

TMEIC Serving the Aluminum Industry Introduction The Aluminum industry has been facing continuing market challenges for the last 50 years and the future looks to be just as demanding and challenging as the past. Currently the aluminum market depends on the transportation industry, the construction industry, industrial applications and the UBC market for utilization of aluminum flat rolled products. With the UBC market declining in traditional uses as well as the construction industry rebounding very slowly after the 2008 market collapse in the developed portion of the world, there is hope for continued growth in the transportation sector and in the emerging markets.

Traditionally, the commercial aircraft segment of the transportation market has grown with the ever increasing number of wide-bodied aircraft being bought worldwide. While the use of composite material has replaced many kilograms of aluminum utilized in the two newest planes from Boeing and Airbus, the rise in the total number of single-aisle planes expected to be ordered through to 2020, will keep the total amount of aluminum being delivered into this market segment growing at a single digit rate.

The real opportunity for aluminum growth is in the automotive segment of the transportation market. As automotive manufacturers are being pressed to deliver higher fuel mileage many strategies are being evaluated, with weight reduction being primary.

Replacing low carbon sheet steel with an alternative material that is lighter and competitively priced, but still retains the high strength required for structural integrity, is in high demand.

Aluminum mills serving these markets are challenging the traditional material suppliers for market share. Buyers are seeking tighter gauge tolerances, tighter temperature control, more product classifications, better shape and flatness performance, better surface

10 SPECIAL FEATURE

quality and most of all, complete coil documentation to be delivered to the customer along with the coil. While raw material costs or scrap prices are controlled by upstream operations or outside forces, the mill must understand and control operational costs such as energy usage, labor, maintenance and upgrade costs, and scrap losses. In these areas, mills in Europe and North America may be at a disadvantage against those more recently built in the Pacific Rim. Most flat mills in Europe and North America have been in operation for at least 30 years while those in the Pacific Rim, outside of Japan, have been built within the last 10 years, with several in the planning or construction phases.

This gives the operational advantage to the newer mills with the latest in technological improvements in mill design, level 1 control and higher levels of automation, while older mills have the advantage of better operational practices and an established customer base. The latter is open for invasion by new suppliers providing better pricing, better customer service or better quality, if available.

An existing mill must develop and depend on its suppliers as a partner to enable new ideas to be incorporated, to help develop a strategy to upgrade performance and to keep the mill from becoming obsolete. These suppliers can be a source of ideas on how to reduce downtime, reduce scrap, reduce energy consumption, or at least recover lost energy, and possibly to increase throughput beyond design capacity.

TMEIC the Company TMEIC was formed in 2003 through a powerful alignment of global leaders, Toshiba, Mitsubishi-Electric and GE. TMEIC has earned a reputation by supporting the legacy control systems of its parents and providing reliable, state-of-the-art industrial products and system solutions for new mills.

Advanced technology, excellence in engineering and years of accumulated experience are brought to each system to provide the customer with a solution to match the project needs. TMEIC serves a variety of industrial markets including Metals, Material Handling, Oil and Gas, Mining, and Cement, as well as utility scale Solar Power.

In Metals, TMEIC applies its capabilities built on 60 years of rolling mill experience supplying comprehensive, high-performance control solutions.

TMEIC is recognized as the leading global supplier of level 2 and process model automation. Our range of control and automation includes the ability to supply complete systems using Motors, Drives, level 1 control consisting of Programmable controllers, I/O, and HMI’s, Level 2 and networks, process models and instrumentation. Projects range from small upgrades to resolve obsolescence issues, to complete major upgrades of mill capabilities to meet the current market needs. One recent development, TMEIC’s uTool®, provides the ability to upload mill performance data, such as production, coil data, energy usage, or mill delays, through the user company’s intranet to any mobile device or computer. This allows maintenance, support personnel or mill management to react and analyze issues from anywhere accessible by internet. Improved response that shortens delays or minimizes scrap losses translates directly to increased productivity and to the customer’s bottom line.

Recent Aluminum Projects Of the 10 hot aluminum mills built in China in the last 10 years, six chose TMEIC as the system control and automation supplier. These mills include 1+1, 1+3, 1+4 and 1+5 mill configurations. Including all of the Pacific Rim, there are 2 additional new mills that chose TMEIC. The pictures below show the first coil put

through the mill. Success is measured in meeting and exceeding customer expectations.

TMEIC has also focused on revamp projects. Control system revamps

require very close cooperation between the customer, TMEIC, and the mechanical supplier, if mechanical modifications are necessary. TMEIC has worked with more than 15 aluminum mills worldwide in delivering upgrade

solutions. Detailed discussions are required to clearly define the work scope, the customer’s goals during multiple shutdown periods, the list of pre-shutdown tasks, and a detailed schedule for the entire shutdown period. This schedule must be reviewed and agreed to by all stakeholders involved, including management, production, maintenance, major vendors and engineering personnel.

Active participation from all parties is required to allow for joint success after the start-up.

Mill Control System

Aluminum Strip

First Coil from Mill

TMEIC’s AC main drive motors are designed and built to meet or exceed industry standards, and are known for exceptional quality. Driven by our customers’ continuous need for sustained reliability and reduced lifecycle costs, TMEIC employs cuttingedge technology in design supported by state-of-the-art manufacturing capability to offer the world’s most advanced motors. With more than 100 years of motor experience, TMEIC consistently tackles tough applications around the globe with designs delivering quality, performance, and efficient operation. TMEIC is among the few large motor suppliers with the capability to provide both Induction and Synchronous motors for rolling mills, in the range of 1,500 kW through 30,000 kW depending on the application.

With over 30 years of variable speed drives experience, TMEIC has the broadest offering of high performance coordinated system drives, ranging from low voltage drives to powerful 3,300 volt drives for large mill stands.

The TMdrive-70 medium voltage drive has become the industry leading drive with a reliability MTBF of over 30 years, utilizing the IEGT (Injection Enhanced insulated Gate bipolar Transistor). This drive can provide up to 36,000 kVA power in its four-bank configuration. Over 1,200 of these

AWJ 2014

11

TMEIC Serving the Aluminum Industry

TMEIC Main Rolling Mill Motor

TMdrive-70e2 Variable Frequency Drive

Customer Service water cooled 3,300 volt drives have been supplied worldwide to rolling mill applications.

Process models are critical in the aluminum industry to provide the demanding product specifications.

TMEIC has worked with aluminum companies to provide complete control automation including level 2 and models or systems that allow for the customer’s proprietary models.

TMEIC has a global network of offices and engineers to support customers around the world. This support includes spare parts for drives and control systems with immediate delivery in Europe, India, the Americas and Asia. Training classes are available for projects as well as on-going training for mill personnel. In addition to normal maintenance support, the focus of our training is to allow the customer to analyze and determine any production issue or adjust control systems for

Our modern control systems include: • Pass schedule calculation

• Inner-stand tension control

• Roughing mill setup

• Inner-stand cooling

• Finishing mill setup

• Work roll coolant control

• Finish temperature control

• 1 Gbps Ethernet communications

• Coiler temperature control

• Hot backup level 2 strategy

• Roll thermal wear

• On-line and Off-line model operation modes

• Strip crown and flatness control

• Remote diagnostics

• Automatic gauge control

• Graphical interface that allows operators to visualize operation and performance

12 SPECIAL FEATURE

new products. TMEIC’s technical advisory service provides a backup for the customer’s personnel through our 24-hour phone support, or onsite support as requested by the mill.

Long term partnering with TMEIC allows aluminum companies to access our engineering expertise to plan for future capital modernizations as well as make comparisons of existing operations against design capabilities. This service has been used by some customers to plan upgrades that extend market reach with new products.

Authors: Paul Weary, Metals Sales Manager, TMEIC Phone: (+1) 540-283-2110 Jim Trexel, US Metals Sales Manager, TMEIC Phone: (+1) 540-283-2193

GLOBAL ISSUES UC Rusal New Horizons

p. 14-17

AWJ 2014 13

364"- New Horizons

Boguchansk HPP, 50% owned by RUSAL

China, the world’s largest aluminium market, is showing a serious commitment to improve efficiency in the country’s aluminium industry.

These changes could play a pivotal role in the global aluminium market development, and unlock potential for a tighter cooperation between China and Russia in the ‘winged metal’ production.

The big and the growing China is the world’s fastest growing economy. According to analysts’ estimates, China is on track to surpass the US and become the largest world economy by late 2020s. Over 46% of China’s soaring GDP comes from the country’s rapid industrial growth driven by the massive urbanization which is increasing demand for aluminium and the raw materials used in its production.

The ‘winged’ metal’s consumption in the country is supported by increasing car production and infrastructure investments. During 2013, the Chinese automotive industry was the top gainer,

14 GLOBAL ISSUES

surging 14.9% after record sales of 21.98 million vehicles according to the China Association of Automobile Manufacturing. The National Bureau of Statistics data also showed that new construction projects rose by 13.5% in 2013. China is forecast to post robust growth in its auto market in the coming years, whereas the construction sector is strongly expected to expand further following the government’s latest urbanization initiatives.

According to the recently published blueprint, authorities intend to raise the proportion of urban residents to 60-65% of the total population by 2020, from the current 53.7%. By 2030, China’s cities will have added 350 million more people and five million buildings will be built. The new growth agenda will need the expansion of railways, roads, highways, and airlines to facilitate labour flows.

Urbanization along with the urban income growth will drive China’s transport and construction sectors which jointly account for over 50% of the country’s

total aluminium consumption, thus propelling demand for aluminium. As of today, the country accounts for 45% of global aluminium consumption, but is forecast to boost this share to 56% by 2025, extending its lead as the world’s biggest aluminium consumer.

Focus on efficiency In 2013, China produced over 25 million tonnes of primary aluminium, almost half of the global output. However, further development of the Chinese aluminium industry is subject to certain limitations in terms of power consumption and emissions by operating smelters.

Efficient resources utilization is one of the urgent issues now in China where over 90% of primary aluminium smelters source energy from coal-fired power plants that account for 75% of all CO2 emissions in aluminium production.

The government is also encouraging reduction in consumption of power, which accounts for about 40% of a smelter’s operating costs.

364"-

VAP production at RUSAL’s Bratsk smelter

In particular, the National Development and Reform Commission (NDRC) announced at the end of 2013 that efficient aluminium producers will continue to pay the same rates, but less-efficient producers will have to pay more. According to NDRC, producers that require 13,700-13,800 kilowatts to produce a tonne of aluminium will be charged an additional 0.02 yuan per kilowatt, while those who exceed 13,800 kilowatt per tonne must pay an additional 0.08 yuan per kilowatt. The surcharges would be effective increases of 1.8% - 7.4% to produce the metal in Henan province. The government is hoping that the move will push producers who have kept older facilities running in the hope of higher prices to finally cut their losses.

The situation in the industry is nevertheless still characterized by a net capacity increase. In 2013, despite depressed prices for aluminium, record high capacities were commissioned in China in 2013 (4.3 million tonnes) resulting in a 2.2 million tonnes net capacity increase.

In the first two months of 2014, the trend continued as Chinese aluminium industry experienced a net capacity rise of 1.6 million tonnes. Shutdowns in the central and southern parts of China amounted to 700 thousand tonnes in Jan-Feb 2014. Some aluminium smelters in the Central parts of China continue cutting output to reduce loss due to the falling domestic aluminium price.

Over 60% of Chinese aluminum production is underwater at the current domestic SHFE aluminium price. As expected, around 3 million tonnes of Chinese aluminium production will be cut in 2014 as a result of a low aluminium price. However, some amount of new low-cost aluminium capacity will still go into production in Xinjiang and other North Western regions in 2014.

It should be noted here, that although China still appears to be a self-sufficient aluminium market, the country’s 12th five-year national development plan presumes transfer of some aluminium

production to the western parts of China with abundant coal resources and lower power costs as well as abroad.

Siberia next door With that said, closer cooperation with Russia which shares a border with China could open up new opportunities for the Chinese aluminium industry that is taking important steps to improve its environmental footprint by spearheading innovation and developing renewable energy and reducing its addiction to coal – the source of 70% of China’s electricity and a major contributor of CO2 emissions.

Indeed, with a shared boundary of more than 4,000 km in length, it is logical that Russia and China are bound to develop mutually beneficial cooperation. Russia is home to the world’s second-largest hydro-energy resources with 75% of hydro-energy capacities located in Siberia. The greatest unrealized resources are in Eastern Siberia and the Russian Far East, perfectly located to meet growing demand from China.

AWJ 2014 15

364"-

Pot Room at Rusal’s Khakas smelter

Cost-effective, renewable and environmentally friendly hydro-energy constitutes as a major competitive advantage of the region, home to six HPPs and eight power plants with possible capacity expansions, Siberia’s hydro potential utilization rate is only 20%.

China’s proximity to Siberia, where most of the country’s production capacities are based, is yet another factor that would enable China to reap considerable benefits from expanding cooperation with Russia. The country’s clear logistical advantage allows delivering physical metal to Chinese consumers at lower shipping costs within 2 weeks, versus 3-4 weeks offered by other global suppliers. This is particularly important, as Chinese aluminium smelters are increasingly being shifted to the Western provinces which will result in additional transport implications for downstream enterprises in the East of the country.

Another promising avenue of cooperation with Chinese companies could

16 GLOBAL ISSUES

be the development of downstream clusters in Russia which have considerable growth potential on the home market in the coming years. In the light of expectations for the strong increase in Russia’s per capita aluminium consumption and the downstream segment’s profitability, it is clear that any capital injections into this area will generate a healthy return. In terms of returns potential, aluminium can production, automotive components and extrusion production are seen as particularly promising.

RUSAL is currently working on conversion of its production facilities in the Western part of the country to produce aluminium- and aluminium alloysbased automotive components, rolled and cable products. The potential is huge. For instance in the automotive industry, despite a slight drop in car sales in 2013 due to the negative macroeconomic environment, the Russian automobile market remains the second-largest in Europe and is poised to overtake Germany to become Europe’s largest by 2016, and the world’s

fifth biggest, by 2020, according to the latest forecasts. Presently there are only 290 cars per 1,000 Russians, versus the already saturated market in Europe, where 560 of every 1,000 is a car-owner. The first step in this direction has been made recently, with RUSAL teaming up with an Israeli company Omen High Pressure Die Casting to create a joint venture to produce automotive components at the site of the Volkhov aluminium smelter.

The world’s biggest aluminium companies RUSAL, Chalco and Shandong Xinfa Group are already discussing the prospects for partnership including a joint smelting project in Siberia, bauxite exploration and technology exchange in red mud processing. Moreover, RUSAL has prepared several road maps that set up plans for investment projects aimed at transforming its loss-making aluminium smelters and the development of new hi-tech production, which are open to foreign capital.

In view of the above, it is clear that the potential for deepening Russia-China

364"-

UC RUSAL is a leading global aluminium producer

aluminium cooperation is as enormous as the benefits that both countries could reap through strengthening their ties. Therefore, the aluminium sector could become yet another area of intense bilateral cooperation, on top of successful projects in oil and gas, energy industries as well as various high-tech sectors.

Company profile UC RUSAL is the world’s largest aluminium producer, accounting in 2013 for approximately 8% and 7% of global aluminium and alumina production respectively. The Company’s current capacity allows it to produce 4.5 million tonnes of aluminium and 11.9 million tonnes of alumina per annum.

UC RUSAL is vertically integrated to a high degree, having secured substantial supplies of bauxite and alumina production capacity. RUSAL’s assets include over 40 smelters and production facilities in 13 countries, across 5 continents. RUSAL employs 67,000 people.

The Company’s core smelters, located in Siberia, benefit from access to stranded hydro generated electricity, with its principal Siberian facilities in close proximity to important European and Asian markets.

The Company’s key sales markets are Europe, Russia and the CIS countries, North America, South-East Asia, Japan and Korea. The major end users consist of over 700 companies representing transport, construction and packaging industries.

Value added products account for over 40% of total metal produced.

RUSAL’s ordinary shares are listed on The Stock Exchange of Hong Kong Limited (Stock code: 486). Global depositary shares representing UC RUSAL’s ordinary shares are listed on the professional board of NYSE Euronext Paris (RUSAL/RUAL). Russian depositary receipts representing RUSAL’s ordinary shares are listed on the Moscow Exchange (RUALR/ RUALRS).

RUSAL owns a 27.8% stake in MMC Norilsk Nickel, the world’s largest producer of nickel and palladium and one of the world’s largest producers of platinum and copper.

Together with the Kazakhstan’s National Welfare fund “Samruk-Kazyna” RUSAL is developing the Ekibastuz coalfield in Central Asia. The 50/50 LLP Bogatyr Komir coal joint venture in Kazakhstan provides RUSAL with a natural energy hedge.

RUSAL is currently focusing on strengthening its competitive advantages, including its considerable raw material base, access to renewable energy sources, proprietary R&D capabilities and proximity to key markets.

UC RUSAL Phone: +7 (495) 720-51-70 Email: Press-center@rusal.ru Web: www.rusal.ru/en/

AWJ 2014

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AP Technology

TM

Rio Tinto Alcan’s AP Technology solutions: The world’s most productive smelter technology

2013: Start-up of AP60 pots at the historical center of aluminium development in Canada A new milestone for reduction technology has been recently reached with the successful startup of the Arvida AP60 Technological Center in Jonquière, Quebec, Canada.

With the demonstration of AP60 at Arvida Technology Center and APXe at Laboratoire de Recherche des Fabrications (LRF) in France, Rio Tinto Alcan makes available high productivity and low energy consumption technologies to its partners and customers, and thereby offering the most productive, cost effective and cleanest smelting technology in the world.

AP60/APXe: the reduction technology of choice for your project!

18

PRIMARY SMELTING AND PROCESSES

Technology sales department 725, rue Aristide Bergès - BP 7 38341 Voreppe Cedex France T +33 (0)4 76 57 85 00 For more information about Rio Tinto Alcan and its AP Technology solutions, visit www.riotintoalcan.com ap-technology.com

PRIMARY SMELTING AND PROCESSES ECL ECL™ makes your operations easier.

p. 20-23

Aluminium Reduction Cell Technology Providers A 2014 Review: Dr.-Ing. Joachim Heil

p. 24-45

Rio Tinto Alcan Start-Up Of Arvida Smelter, AP60 Technological Center

p. 46-48

FLSmidth MÖLLER Alumina Handling Systems

p. 49-51

Streamline.

Sensotech

ECL™ makes your Inline concentration monitoring operations easier.

p. 52-55

Power Jacks Precise Anode Beam Positioning from Power Jacks

p. 56-59

ecl.fr

AWJ 2014 19

Streamline.

ECL™ makes your operations easier.

20 PRIMARY SMELTING AND PROCESSES

ecl.fr

ECL™ makes your operations easier.

Regulation system to improve quality of the metal sucked during tapping operation

One of the objectives you can target from the whole process of primary aluminium production is to deliver a metal free from impurities. The tapping operation consisting of sucking liquid aluminium from the pot in a crucible through a tapping tube remains an operation requiring precautionary measures. On one hand, the operator has to correctly insert the tapping tube into the electrolytic cell at the lower part of the metal pad. And on the other hand, the volumetric flow during tapping is difficult to regulate.

If the flow is excessive, it can result in the bath being sucked in with the metal. Bath adjunctions have many negative effects, both on electrolytic cell operation and equipment soiling but above all on metal casting.

To avoid such concerns, ECL works in close collaboration with Rio Tinto Alcan in order to develop and adapt a system based on components of the shelves.

This system allows controlling and regulating the flow rate of aluminium sucked from the pot by means of loops control and signal processing in the PLC, which controls a valve on the

compressed air supply. 200 tapping operations have been performed in the Alma plant resulting in proving the efficiency and reliability of the solution and providing significant benefits, such as less equipment cleaning cycles and better metal casting.

Here is the reality whatever is the production: produce more by combining quality, rapidity, cost-savings and safety. The Engineering Department of equipment suppliers such as ECL works hard to meet these expectations.

The aim is to provide the smelters with solutions allowing them to both save money, in particular by supplying energy-saving equipment or solutions, reducing equipment maintenance costs; and produce high quality aluminium in a safe environment.

The solution of the ECL regulation system meets all these criteria. It took as its starting point that a significant amount of electrolytic bath (typically 15 kg of electrolytic bath per ton of molten aluminium in most cases) was sucked during tapping operation due to a lack of flow rate control. This

undesirable bath intake has negative effects notably for metal casting and especially when it comes to producing certain aluminium alloys requiring a low sodium concentration. Consequently, the bath removal from the electrolytic cell impacts its operation negatively.

Tapping equipment is soiled faster and metal treatments before casting are more demanding with regard to efforts and costs. It should also be noted that the more the electrolytic bath is sucked in with the metal, the more the tapping tube and the crucible will be soiled, eroded and even blocked. The required frequency of the cleaning of the crucible therefore becomes substantially elevated.

The regulation system is also in correlation with the technical developments of the electrolytic process, particularly with the new standard of low Anode-CathodeDistance (ACD) pots. Decreasing the amount of ACDs lowers the voltage and energy requirements of the cell (costsavings) but weakens the stability of the process, especially during tapping operation. That is why the ability to

AWJ 2014 21

• A risk of ‘sludge’ aspiration In the second case, the bath will be sucked by a vortex effect.

Once well positioned, a vacuum is induced into the crucible, usually using an air injector whereby the metal is aspired through the tube. The air flow through the air ejector can be controlled manually using a valve on the compressed air supply. To resume, a good tapping operation depends on the right immersion depth of the tube (operations conducted carefully and diligently) and the flow rate control (good and stable target flow rate).

regulate and control the metal flow rate to avoid bath fluctuations will impact positively the stability of the process.

The objective of the regulation system is clear: limiting the siphoning of electrolytic bath during the tapping operation to minimize those negative effects and help smelters in their daily efforts to produce more, cheaper and faster.

As a brief reminder of the aluminium production process: many different operations on the electrolysis cells are essential in producing metal in the pots. These operations can be grouped into two categories: operations related with anode changing and operations related with tapping operation. A tapping operation consists of drawing liquid metal from an electrolytic cell and filling a crucible with a predefined mass of metal. The mass of metal to be siphoned is predefined, in accordance with standard operating procedures, and will depend on the production

levels of the electrolytic cell and the minimum metal levels required to maintain a cell in operation. When it comes to proceeding to tapping operation, several aspects have to be taken into account in order to limit bath siphoning and reaching a good quality level of molten aluminium. The tapping operation from an operating electrolytic cell is usually done with a crucible embarked on the Pot Tending Machine.

The first important step is to insert the tapping tube into the electrolytic cell at the right depth in the metal.

The insertion should be neither too deep nor too high above the metal where the bath is. In the first case, we can observe: • An excessive speed due to the reduced liquid flow cross section and consequently an erosion of the cathode. This excessive speed could also lead to a powerful vortex resulting in more bath entrainment

22 PRIMARY SMELTING AND PROCESSES

In practice, very light touch is required so as not to overshoot the target metal flow rate. Consequently a stable metal flow is rarely, if ever, obtained and very large fluctuations can be observed during tapping of a bunch of cells.

Some of the numerous factors, which can explain some of the variations in flow rate are for example: the position of the crucible relative to the metal/ bath interface, any obstructions limiting free flow of metal into the tube; such as surface variations on the cathode surface of the electrolytic cell or lumps of solidified bath, variations in air temperature during tapping, variations in how well the crucible is sealed during tapping, variations in air pressure supply, crusting of tube from bath entrainment, movements of the metal in the pot etc.

General principle of the tapping regulation system Given the difficulty to provide manually the fine adjustment in vacuum to maintain an ideal metal flow rate which maximizes productivity without compromising quality (bath entrainment), ECL designed, set up and tested in the Alma plant a system based on the automatic control of the flow rate to reach the target metal flow rate. Basically the system comprises among others a control unit and by means of loops control and signal processing in the PLC adjusts the supply of compressed air in the air

ejector through a valve and therefore the vacuum pressure depending on the headspace in the crucible and the weight of the crucible during tapping.

This system, allowing for siphoning the metal and for it to be transferred at a pre-determined target flow rate into the crucible, consists of: • An air ejector coupled to a source of compressed air and in close communication with the headspace in the crucible.

• A vacuum transducer between the source of compressed air and the air ejector, connected to the control unit delivering actual vacuum pressure changes in the headspace.

• A valve assembly operated by a valve actuator responsive to an electric current-to-pressure converter which is coupled to the control unit. The valve actuator receives information from the control unit to determine the flow through the outlet of the valve assembly. It will open or close the compressed air supply as needed.

• A dedicated algorithm which filters the weight signal and the vacuum level to reach a stable target.

• Control units connected with weighing means in order to receive weight measurements and calculate on due time the liquid flow rate of liquid being drawn in the crucible. The control unit then simultaneously adjusts the flow rate of the compressed air flowing through the regulating valve in order to reach the target flow rate. The control unit includes a programmable logic controller (PLC). The PLC is directly connected with a main compressed air directional valve to open the valve when a tapping operation begins and to close it when the target mass of metal has been siphoned into the crucible.

Advantages of the solution More than 200 tapping operations have

Schema of the principle of the aluminium tapping operation Load cell PLC

I/P

Master loop

PTA compressed air line

ejector Short loop P/I

vacuum pipe

been performed with the regulation system at the Alma plant. The results are clear. The maintenance of an ideal metal flow rate maximizes productivity without compromising quality. The less the bath is siphoned, the less the tapping tube is soiled or blocked or requires changing. The less the bath is siphoned; the easier the metal is processed in the cast house. The less the bath is siphoned, the less the crucible is soiled and needs to be cleaned. Consequently we can expect a decreased frequency of the crucible bricklaying. All those quantifiable advantages will help smelters to save money on maintenance costs and spare parts costs while decreasing the cost of the aluminium alloy treatment. Casting operation will be made easier and the quality of metal sucked will generate less waste.

Crucible

integrated directly in the automatic system of the Pot Tending Machine or installed in the tapping beam of the crucible.

Conclusion The regulation system is a selfadaptive system. It requires no action or adjustment from the operator. The system provides transparency and combines good process quality with fast potline operation.

Author: Anne-Gaëlle Hequet ECL™ Communication and Public Relations Manager

The solution, whether we are talking about a Greenfield project or a Brownfield one, is adaptable to any smelter configurations using the AP Technology™. The system can be

AWJ 2014 23

Aluminium Reduction Cell Technology Providers – a 2014 Review Introduction This article is the second, updated edition of a paper published in the context of the European Metallurgical Conference 2011 (EMC2011), organized

by GDMB of Germany. Special thanks go to my former colleagues, Dr. R. Minto and T. Heitling, who helped establishing the first edition which has been published in the EMC2011 conference proceedings [1].

Consultation of an article on the topic published in 2000 gave rise to the question who would be providing aluminium reduction cell technology today.

The referenced article elaborates on cell technologies developed by wellknown companies which mostly have been in business for a long time, some since inception of the Hall-Héroult process. Potline current values cited in the article are in a range of 250 – 320 kA for the then latest technologies; further tiers of reduction current are the 150 – 200 kA range and anything below

that down to 50 kA, the latter mostly for an illustration of the historical evolution of the electric current as a qualifier for the advancement of reduction cell technology.

Since 2000, the global primary aluminium industry has grown at a remarkable rate of 5,5 % year-onyear: production capacity rose from 23,7 million tpy (Mtpy) in 2000 to 39,8 Mtpy in 2008, with a recess to some 37,5 Mtpy in 2009 in the aftermath of the financial crisis, just to rebound to 47,3 Mtpy in 2013. China has grown its share in the primary aluminium market from about 10 % in 2000 to some 21,5 Mtpy or 45 % of global supply in 2013, which is equivalent to almost all of the above increase in global production tonnage.

The same period has seen an equally unprecedented change amongst the players in the primary business: mergers and acquisition have led to a concentration of the industry into

fewer but bigger players. This trend along with management buy-outs, bankruptcies and changes of business strategy has led to the disappearance of quite a few of the traditional primary producers´ names including some of the long-established cell technology providers.

128 years after Hall and Héroult independently applied for their patents for the still unrivalled aluminium electrowinning process, this paper gives an updated review of who today would be developing and providing aluminium reduction cell technology to primary smelters, be it new greenfield or brownfield expansion projects.

1 Summary of Reduction Cell Technology as at Year 2000 In early 2000, Tabereaux published a global review on prebake cell technology [2] in which he elaborated the then prevailing situation with regard to cell technology developers and operators.

The article also included an overview

Table 1: Most Advanced Reduction Cell Technologies as at the Year 2000, excerpts from [2] UPBN: Universal Prebake Cell Nomenclature, proposed by Tabereaux Company

Cell Type

UPBN

I / kA

Alcan

A-275

AC-28

A-310

AC-31

P-225 A-817

Alusuisse

EPT-18

Comalco-Dubal

CD-200

Hydro

HAL-230 HAL-250

Kaiser

P-80

KA-18

190

Pechiney

AP-30

AP-30

300 - 325

Reynolds

P-20S

RY-17

170

P-23S

RY-18

180

CA-180

VAW-18

180

CA-240

VAW-24

240

CA-300

VAW-30

V-350

VN-35

C-255 C-300

Alcoa

VAW

Venalum Russia/VAMI China

Pots installed

Year

Remarks

280

5

1981/92

310

n. inv.

n. inv.

AA-23

225

n. inv.

n. inv.

Massena, Tennessee

AA-30

300

n. inv.

n. inv.

Portland

AS-18

180

n. inv.

n. inv.

Rheinfelden, closed 1991

CD-20

200

5

1990

Test cells at Dubal

HAL-23

230

n. inv.

n. inv.

Hoyanger, Venalum PL5 (1988), Slovalco (1995)

HAL-25

250

4

n. inv.

Test cells in Ardal

6

1981

Test cells in Tacoma, shut down

2040 + 720*

n. inv.

Various smelters, global spread

n. inv.

n. inv.

Alcasa, Alscon

n. inv.

n. inv.

Test cells at Alcasa

115

1980

Upgraded Töging version now in Nordural, 120 pots

5

1980/93

Test cells in Töging, shut down for CA-300 prototype

300

3

1992/93

Test cells in Sayanogorsk, shut down**

320

5

n. inv.

Test cells

RU-26

255

n. inv.

n. inv.

Tajik, Sayansk, Volgograd

RU-30

300

3

1992/93

P-280

CH-28

280

n. inv.

n. inv.

Qingyang

P-320

CH-32

320

30

n. inv.

Test cells, Pingguo

Test cells in Jonquière, shut down

Test cells in Sayanogorsk, shut down**

*: 720 cells under construction at that time **: VAW and Sayanogorsk jointly built and operated a test facility in Russia, each partner contributing 3 pots n. inv.: not investigated

24 PRIMARY SMELTING AND PROCESSES

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy of the developmental steps taken by individual companies. This historic part of Tabereaux´s review will not be repeated here and interested readers are referred to the original source. For this update, only the 2000 spearhead cell technologies, in terms of highest amperage will be quoted as reference points. A condensed summary of those reduction cell technologies is presented in Table 1.

Table 1 shows more than one entry for some companies and countries. The intention is to highlight the development potential that can be seen in operational test cells.

The original table further included companies Montecatini, Elkem, Sumitomo and Egyptalum as cell technology holders. These have been omitted here as their cell technologies are considered outdated at publication in 2000, no progress is recognized since, or due to their solely local significance, all in the context of this article.

The 10 companies in possession of aluminium cell technology mentioned in Table 1 comprise the big traditional industrial names, four of which can even be traced back to the inventors of the Hall- Héroult (HH) process: Alcoa and Alcan are the direct result of Charles Hall´s entrepreneurial activities in North America while Alusuisse and Pechiney are the European offspring of Paul Héroult. VAW can be considered a late arrival, founded 1917 to support German armament during WW I but without direct ties to the founding fathers of the industry.

Kaiser and Reynolds can be regarded as the generation of heirs as they came into the primary aluminium business in close timely connection to WW II, e. g. by snapping up from Alcoa, in an US government initiated auction, what was considered overcapacity after the war. Norsk Hydro, founded 1905 as a hydro-power company with associated power-consuming assets (fertilizers, explosives), entered the aluminium business even later, after

VAW-led initiatives to build a German production basis in Norway during WW II had not been finished before the end of the war. Although Hydro itself had contemplated aluminium production repeatedly since 1907 (including failed own process inventions outside Hall-Héroult) only in 1963 did Hydro diversify into the aluminium business by building its first smelter in Karmøy; later in the last century Hydro started buying history through acquisition of older Norwegian smelters [3]. That leaves Comalco-Dubal and Venalum as representatives of an upcoming new generation of more recent birth and, due to the still prevailing lack of detail insight (in 2000), the Russian and Chinese aluminium industries pooled by Tabereaux just under the country names.

Concluding from the above summary, it can be seen that by the year 2000, aluminium reduction cell technology know-how that had been deployed internationally appears to be almost exclusively held by big western enterprises with a long history in the industry to the extent that the original inventors can still be traced. The Russian and Chinese industries had been contained within their respective borders and, due to their lack of involvement outside of their territories, had remained opaque until way into the 1990s. However, internal cell development had reached a similar amperage level as the western technologies.

The reduction cell development had obviously reached peak line amperages of 300 – 325 kA while a lot of cell technologies still hovered at between 180 and 280 kA. Tabereaux in his outlook mentions, without being specific, that further testing into the 400 kA region was underway and that this amperage was expected to establish the next reduction cell generation.

While in principle aluminium can be produced in cells with either Söderberg (S) or prebaked (PB) anodes, all of the modern high-amperage cells are

based on prebaked anodes. Another distinguishing element of reduction cell construction and operation is the concept of supplying the alumina feed to the electrolyte. Historically, PB cell feeding has been developed from side work (SW) to center work (CW), and finally to point feeding (PF) systems.

While SW pots were fed (several) hundred kilograms of alumina at a time in intervals of 1 – several hours, CW pot feeding occurred in doses of tens of kilograms several times per hour and PF feeding involves quantities of 1 – 1.5 kg/shot some 2 – 3 times per minute. All modern high-amperage cells exclusively utilize point feeders and can thus be characterized as pointfed pre-bake or PFPB cell types.

Finally, at the bottom line of Tabereaux´s article, his minibio significantly refers to Dr. Tabereaux as working for Reynolds Metals. However, the article was printed just a few weeks before Alcoa finally finished its takeover of Reynolds Metals in May 2000. This leads to the indicated sub-topic of dramatic changes in the primary aluminium industry since publication of Tabereaux´s article which will also be highlighted below.

2 State of the Primary Aluminium Industry at the Turn of the Millennium The 1990s had started off with one of the worst economic periods in the primary aluminium industry: as a consequence of the fall of the iron curtain, aluminium that would have otherwise been used by the former Soviet Union and its allies was sent into the western markets and particularly into LME warehouses. At that time, the traditional correlation between metal inventory/ consumption and price was still intact, so the influx of excess metal sent the LME prices, coming from above 2.000 USD/t (incl. a peak of above 3.500 USD/t) into steep decline down to the 1.100 USD/t range at which level almost all smelters would face losses. It took the industry huge joint efforts in terms of mutually agreed curtailments for the price to escape the 1.100 – 1.300

AWJ 2014 25

Aluminium Reduction Cell Technology Providers – a 2014 Review 4.000

Monthly Average Primary Aluminium Price (LME spot) in USD/t

3.500 Al Price LME spot Mean

3.000

Median Mode

2.500

2.000 1.666 1.552

1.500

1.164

1.000

500

0

Figure 1: Monthly Average Primary Aluminium Price, 01/1981 – 04/2014 [4]

USD/t range which only succeeded in about mid 1994. Players and individual smelters with less solid balance sheets were forced into shutdowns or became prey for takeovers.

In addition to considerable pressure from marginal product proceeds at low LME prices, cost pressures were also on the rise, particularly from the energy cost end. Smelters faced expiry of their long-term power contracts and more often than not the new contracts included hefty increases of electric power prices. In this context, the Bonneville Power Administration (BPA), a US governmental (not-for-profit) power agency, achieved some doubtful fame as a result of pressurizing their US aluminium clients for many years, in some instances to the brink of bankruptcy.

Only during the second half of the 1990s did the primary aluminium industry regain enough stability to be able to entertain new developments.

In reflection of the tough times, the aluminium industry started forging stronger entities through mergers and by acquiring weaker players.

3 Aluminium Industry Consolidation at Corporate Level from 2000 – 2014 3.1 Western Primary Aluminium Industry The new millennium started off with two major reorganizations among the big western players. In May 2000, Alcoa finalized the acquisition of Reynolds Metals in a 4,5 blnUSD deal, almost one year after the offer had been submitted [5]. The merger combined the two biggest aluminium producers of the US, or numbers one and three on a worldwide scale, making Alcoa by far the biggest aluminium producer globally.

Soon after, in October 2000, Alcan (of Canada) finalized its merger with Alusuisse (of Switzerland) [6]. This merger was what remained of an initially contemplated three-way merger that would have included Pechiney (of France) as well. However, the idea of including Pechiney was mutually abandoned as the project faced stiff opposition from regulatory authorities over market dominance in the flat-

26 PRIMARY SMELTING AND PROCESSES

rolled products business resulting from Alcan´s 50 % ownership in the giant Alunorf rolling mill in Germany. Alcan now was number two on the global list of primary aluminium producers.

In February 2002, Kaiser Aluminium, then the third largest aluminium producer in the US, filed for bankruptcy protection under Chapter 11 following a failed debt repayment of some 25 MUSD and facing another upcoming debt repayment of 174 MUSD. The Kaiser bankruptcy was mainly attributed to a failed diversification into the chemical business [7]. However, the weak aluminium business during the 1990s will have contributed its share. Additionally, Kaiser had been hampered by an explosion, in July 1999, at its Gramercy alumina refinery, which took its 1 Mtpy production off the market for 1,5 years [8]. Kaiser was also one of the victims of BPA´s new increased power tariffs which, among others, forced them in late 2000 to contemplate shutting down its Mead smelter and selling the freed power back to BPA at the higher price. Ironically, this idea was opposed by BPA

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy (and thus the US government) as they did not entertain a private company making a windfall profit to the tune of 300 MUSD out of a public utility [8]. It actually took Kaiser until 2006 to reemerge from Chapter 11 protection.

Still an aluminium company today, Kaiser has, however, divested all alumina and primary aluminium assets. Under the new business model, Kaiser is now a producer of engineered aluminium components with an emphasis on the aerospace market [9].

In March 2002, Hydro Aluminium (of Norway) took over VAW aluminium AG (of Germany) from E.ON AG, a German holding company formed in 2000 through the amalgamation of VIAG AG and VEBA AG, in a 3,1 bln € deal [10].

VIAG had been the holding owner of VAW since its inception. VIAG´s portfolio included basically power producing and power consuming industries whereas VEBA held a portfolio of power producers and chemical plants. The new E.ON strategy was to concentrate on power generation so all industrial holdings, including VAW, were divested as a consequence.

The takeover of VAW promoted Hydro Aluminium to position four, behind Alcoa, Alcan and RusAl, in the global primary aluminium producer ranking.

Meanwhile, the new Alcan had obviously not entirely given up the idea of integrating Pechiney since in September 2003 they gained clearance from the European Commission, though there was an obligation to divest major parts of the downstream business including the flat-rolled production [11].

The latter was finally spun-off in 2005 as Novelis which now, since 2007, is wholly owned by Hindalco. The incorporation of Pechiney boosted Alcan´s primary aluminium output close to that of Alcoa, however Alcan remained in second place.

After almost 2 years of a long unsuccessful courting period, Alcoa then made an unsolicited takeover bid to Alcan early May 2007 [12] which was

immediately rejected as it supposedly did not properly reflect the true value of the new Alcan [13]. Alcoa bid 33 blnUSD for Alcan, however, after Alcan management´s rejection of Alcoa, Rio Tinto offered 38 blnUSD. When Vale (CVRD at the time) also entered the takeover-war, Rio Tinto and Alcan settled the deal at 38,7 blnUSD, one of the biggest takeovers ever. In October 2007, the aluminium activities of Rio Tinto, i.e. the Comalco business, were combined with Alcan and are known today as Rio Tinto Alcan or RTA. The combined primary production has put RTA in second place, closely behind the new RusAl. In May 2010, Hydro Aluminium signed an agreement with Vale to take over Vale´s aluminium business (primary smelters, alumina and bauxite activities) for 4,9 blnUSD [14]. After approval from regulatory authorities, the deal was finalized early 2011 [15], giving Hydro upstream access to bauxite and making Hydro a long alumina producer.

To summarize, the last decade has shrunk the number of potential western reduction cell technology providers from 10 (or rather 8 + 2, the 2 being Comalco-Dubal and Venalum) to 3 + 2: Alcoa, Hydro Aluminium and Rio TintoAlcan + Dubal and Venalum, see graphic representation in Figure 2.

Dubal appears to have discontinued the joint technology development agreement it had with Comalco before 2005 and now has developed its own DX series of high amperage cells. While Dubal is continuing with reduction cell development no similar information is available from Comalco since 2006 - when Comalco reported about five modified CD26 test cells operating at the Boyne smelter, which were being considered for the intended potline 1 and 2 modernization. The so-called B32 (RTC-28) cell was operating at 270 and 280 kA between 2002 and 2005 [16]. Interestingly enough, for Boyne´s potline 3 construction between

1995 and 1997, Rio Tinto Comalco had already opted for AP-30 technology over the in-house CD technology. Developments of Comalco cell technology have probably been discouraged after the Rio Tinto – Alcan merger in 2007 since this has given Rio Tinto/ Comalco direct access to the more advanced Pechiney technology.

3.2 Eastern Primary Aluminium Industry Russia started primary aluminium production on an industrial scale in 1929.

All Soviet smelter technology R&D was concentrated in the All-Union Aluminium Magnesium Institute (“VAMI”) founded in 1931 (and re-named AllRussian Aluminium Magnesium Institute VAMI in 1993) [17]. Historically, Söderberg technology had long been dominant, and still continues to be largely present, in Russian smelters.

The dissolution of the communist bloc after the fall of the iron curtain brought about unprecedented upheavals in the formerly planned and centralized economies, specifically in the Former Soviet Union (FSU). Both, aviation and armament industries, the biggest consumers of aluminium in the FSU, had broken away almost entirely, and domestic consumption dropped from 17 kg/capita in 1990 to a mere 2 kg/ capita in 1994. Before production outputs could be adjusted, an overhang of aluminium had been produced which was subsequently shipped westward deluging the global markets. FSU smelters found themselves disconnected from their alumina supplies which were now situated in foreign countries (i.e. in the now independent previous Soviet republics) and started operating on a tolling basis. In an almost lawless, mafia-like environment, proverbial aluminium and alumina wars took place with huge profits to be made but also leaving casualties at the wayside. Since the state-owned smelters were effectively ownerless, a major privatisation took place from 1993 onwards.

AWJ 2014 27

Aluminium Reduction Cell Technology Providers – a 2014 Review In this environment, a few individuals started building ownership in individual smelters, then progressing into grouping individual plants together to form strong groups almost mimicking the earlier communist structures, but now under private ownership. So-called “oligarchs” concentrated aluminium assets under the names Sibirsky Alumini (1997, Oleg Deripaska), Sibneft (1999, Roman Abramovich) and SibirskoUralskaya Aluminievaya Kompania (SUAL, 1996, Viktor Vekselberg).

Also in the eastern hemisphere, the new Millennium started with yet another major concentration of market share. In 2000, Sibirsky Alumini and Sibneft merged to form Russian Aluminium (RusAl) with a production capacity of more than 2 million tpy of aluminium representing almost 10 % of global output [18].

During the following years RusAl and SUAL grew independently through further acquisitions of international scope and in 2003, RusAl acquired the All-Russian Aluminium Magnesium Institute VAMI [19].

In 2007, with the merger of RusAl, SUAL and the alumina business of Swiss trading house Glencore, a new industrial giant was born. The new United Company (UC) RusAl was then worth some 30 blnUSD and controlled 4,4 million tpy of primary aluminium output - placing the new RusAl on top of the producer´s ranking and overtaking Alcoa [20].

In summary, the Russian primary aluminium industry is now controlled by UC RusAl. RusAl, after a total disintegration, in the 1990s, of the stateowned assets, has almost rebuilt the Soviet-era industry including control of the VAMI R&D facilities, though now under private shareholding ownership and with a global reach, through acquisitions.

The early days of the Chinese primary aluminium industry remain obscure

due to a combination of long-lasting shielding of the country and the existence of a multitude of small smelters (down to the 5 ktpy level) which went unrecognized globally or remained unknown due to non-reporting. According to Zhongxiu, in 2002 there were still 128 operating Chinese smelters with only 17 smelters having more than 50 ktpy capacity [21]. Taking the IAIpublished Chinese production figure of 4,321 Mtpy for 2002 into consideration [22], the average output from a Chinese smelter was a mere 33,7 ktpy.

By 2013, China had increased primary output to 21,936 Mtpy [23] equivalent to an average of 175 ktpy from each of its 125 operating smelters.

The ownership of Chinese smelters appears to be scattered between the government, semi-public entities and partially or wholly private ownership.

The largest single Chinese entity in this context is the Aluminium Corporation of China Ltd. (Chalco), which was formed in September 2001 to oversee the aluminium and alumina business of state-owned Aluminium Corporation of China (Chinalco). Chalco was partly floated on the New York and Hong Kong stock exchanges in December 2001 which reduced Chinalco´s majority ownership to some 44 % while Alcoa picked up an 8 % share of Chalco [21]. Chalco has continued to expand by acquisitions (of other Chinese smelters) and by building new smelting capacity at rapid pace. Despite a production increase from 690 ktpy in 2000 to >4,2 Mtpy in 2012, Chalco´s share of the total Chinese primary aluminium output has, however, fallen from 25 % to some 21 % [23], [24].

Concluding from company information collated by Pawlek [26], Chinese aluminium production appears to have started in the 1930s, based on VAMI Söderberg pots, but later Elkem and Japanese technology providers have also been sporadically mentioned. In the 1980s, obsolete Japanese smelter equipment was imported into China (as a consequence of Japan exiting the

28 PRIMARY SMELTING AND PROCESSES

primary business after the oil crisis) and the VAW CA 115 from Töging (as a consequence of the smelter shutdown in 1994 after Russian metal flooded the market) had been bought secondhand.

However, the overwhelming majority of Chinese smelters apply home-grown aluminium reduction cell technology which has historically been developed by two institutes: Shenyang Aluminium & Magnesium Engineering & Research Institute (SAMI, founded in 1951) and Guiyang Aluminium Magnesium Design & Research Institute (GAMI). Both are now managed by the China Aluminium International Engineering Corporation (Chalieco), which is a wholly owned subsidiary of Chinalco. These two institutes, SAMI and GAMI, have recently been developing high-amperage cell technologies separately and they are competitors, even though both have the same parent company. SAMI and GAMI designed potlines constitute the bulk of China´s current primary aluminium industry.

Established in 1981 and restructured in 2003, the Northeastern University Engineering & Research Institute (NEUI) has followed a similar technology development path as SAMI, and within a few recent years, NEUI has developed and put into operation a series of high-amperage reduction cell technologies in China.

The historic development of western and eastern reduction cell technology providing companies is graphically summarized in Figure 2.

4 Aluminium Reduction Cell Technology Providers at the Turn of 2013/2014 4.1 Alcoa Alcoa has not reported any progress on their 300 kA cell technology since more than a decade as far as the TMS´s annual Light Metals proceedings are concerned. Actually, it appears that the only industrial application of Alcoa´s

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy

Primary Aluminium – Ancestry

   







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



                            

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 

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

   

                          

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       

Figure 2: Historic Timeline of Reduction Cell Technology Providers

own most advanced reduction cell is at Portland Aluminium in Australia.

The acquisition of Reynolds by Alcoa in 2000, including their cell technology R&D department, did not bring about any obvious revival of cell technology development activities at Alcoa.

Alcoa´s North American operations, which utilize Alcoa’s own cell technology, are applying line currents of between 120 kA and 245 kA, according to information available from Pawlek´s PASaPoW [26]. Among these there are 3 smelters that exceed 210 kA, namely Mt. Holly (215 kA), Tennessee (245 kA) and Massena (230 kA) while the latter also houses an unspecified number of A-716 type test pots operating at 280 kA and 450 kA (?).

Much of Alcoa´s global assets today have been acquired, i.e. these have an inherent lower probability of using Alcoa cell technology, and actually Alcoa inherited a wide variety of different technologies from the original owners.

However, there are again 3 smelters outside of the USA using Alcoa cell technology beyond 210 kA: Point Henry

(215 kA, P-155 cells), Alumar (228 kA, A-697 cells) and Portland (320 kA, A-817 cells). Concluding from PASaPoW [26], Portland appears to be the only smelter in the Alcoa organization that has been built using Alcoa´s most advanced technology. Portland was commissioned in 1986 with an initial line current of 275 kA, which has obviously been crept to 320 kA. Since Portland was started up in 1986, Alcoa appears to have reduced activities in terms of building its own new smelter capacity. Only in the second half of the first decade of the new millennium, did Alcoa resort to expand through building new smelters: Alumar underwent 2-step brownfield expansions which were commissioned by September 2005 and from November 2005, respectively. Alcoa A-697 cell technology (developed as AA-18, after boosting now operating as AA-23) has been used for the new potline 3 at Alumar. In April 2007, Alcoa started commissioning its new Fjarðaál smelter in Iceland - which presently operates at 380 kA. Interestingly, Alcoa did not implement its own cell technology but

built a one-potline smelter based on Alcan (i.e. Pechiney) AP38 cell technology. Also in Alcoa´s most recent participation in the Ma´aden smelter project in Saudi Arabia Rio Tinto Alcan AP37/39 technology has been implemented [27].

The European Economic Commission (EEC) in 2003, on the occasion of the Alcan/Pechiney merger, issued a merger procedure that assessed the concentration of market shares for the new entity. Amongst other items, the market shares of a combined Alcan/ Pechiney in the aluminium reduction cell development and licensing business were investigated in relation to their competitors. One of the competitors mentioned by Alcan/Pechiney was Alcoa. However, the EEC assessment found that Alcoa in fact had ceased licensing cell technology to third parties in the 1980s. Consequentially, Alcoa was regarded by the EEC as a hypothetical competitor only [11].

As a conclusion of the above, it seems that Alcoa not only has largely discontinued implementation of its own

AWJ 2014 29

Aluminium Reduction Cell Technology Providers – a 2014 Review Table 2: Hydro Aluminium Cell Performance Data at Slovalco as per [26]

reduction cell technology in smelters they own but has also discontinued licensing to third parties. The latest Alcoa greenfield projects are based upon reduction cell technology licensed from RioTintoAlcan. This together with the total absence of publication of cell technology advances could be interpreted that Alcoa has abandoned primary aluminium reduction cell development altogether in favour of external licensing.

4.2 Hydro Aluminium (incl. VAW) When Hydro Aluminium acquired VAW in 2002, the VAW cell technology R&D department was also included in the deal. VAW had operated five CA 240 (VAW-24, in Töging) and three 300 kA test cells in Sayanogorsk, the latter project having been hampered by the Russian conditions in the years just after 1990. This experience lead to a VAW decision to replace the VAW-24 cells in Töging with CA 300 (VAW30) test cells. However, this project was stopped in 1994, shortly after orders had been placed and construction work had begun. The so-called Töging potline 2, which was to receive the test cells, was decommissioned (as a result of Russian metal flooding the market depressing the LME ingot price), dismantled and finally rebuilt in Iceland (Century´s Norðurál smelter).

The former VAW´s cell technology R&D group (aka VAW-ATG) continued to work on cells, mostly on smelter upgrades, retrofits and the like but the VAW-30 remained shelved. However, Hydro acquired the residual know-how and also the manpower and modeling and engineering tools developed by VAW. Today, the ex-VAW R&D know-how is a vital part of the Hydro Aluminium cell technology development as can be concluded from ongoing Hydro publications including former VAW staff.

Hydro Aluminium had licensed its HAL-23 cell technology to Venalum (potline 5, commissioned 1988) and also to the Slovalco smelter where the HAL technology replaced three

Cell Technology (UPBN) Parameter

HAL230 (HAL-23)

HAL250 (HAL-25)

Unit

Amperage (design)

230

250

kA

Amperage (operation)

230,3

258

kA

Number of Pots / Potlines

172 / 1

54 / extension

-

Current Efficiency (CE)

96

94

%

Anode Effect Frequency (AEF)

0,044

n.a.

AE/(day · pot)

Specific Energy Consumption

13,5

13,2

kWh/kg aluminium

1950s Söderberg potlines. Slovalco commissioned the HAL pots from June 1995 and achieved operational results as presented in Table 2.

Slovalco was expanded by adding 54 pots of HAL250 technology which was commissioned from July 2003. At the same time the line amperage for the existing potline had been increased to match the HAL250 technology of the new pots. Today, Slovalco operates at 258 kA. In December 2002, Hydro started commissioning 11/2 potlines comprising 340 pots in its Sunndalsøra smelter (the so-called Sunndal 4 or SU4 project), also replacing older Söderberg potlines, implementing their HAL250 cell technology. Even during commissioning the amperage was raised to 275 kA - the reported value when the last pot was energized in August 2004. This cell technology is dubbed the HAL275 (HAL-28) and the Sunndal smelter is the biggest European single site smelter [28], [29]. It has been reported that the HAL275 pots at SU4 have been crept to 290 kA (HAL-29) as of April 2007 [26].

It appears that both the Slovalco and the Sunndal SU4 potlines might go down in history as the last newly-built smelters in (Central) Europe, or at least the last for quite some time to come, unless the European energy prices allow for new smelter projects to proceed again in the future.

The HAL275 cell technology was also licensed to the new greenfield smelter Qatalum, in Qatar, which was started up in December 2009. According to

30 PRIMARY SMELTING AND PROCESSES

information available on the Qatalum website, the operation was supposed to start at 300 kA which would allow a production of 585 ktpy of potroom metal from their 704 pots [30]. This would require a current efficiency of 94,5 %. Output in 2012 reached 628 ktpy [31] which would have required an amperage creep to some 320 kA at 95 % CE, so the Qatalum pots should now be categorized HAL-32. The rectifier-transformers (RTs) installed at Qatalum (5 x 85 kA) would even have enough rated capacity for future line amperage creep to 340 kA without compromising on the N+1 RT configuration [32].

In its latest development, in June 2008, Hydro Aluminium has commissioned six HAL420 or HAL4e (HAL-42) cells in its Årdal research facility, operating at 420 kA and designed to operate at up to 450 kA. The first commercial implementation of the HAL4e technology was foreseen to begin after 2014 [33].

In 2013, a 70 ktpy pilot smelter applying HAL “next generation technology” to be sited at Karmoy was under study [34]. The pilot HAL-42 cells achieved specific energy consumption of 12,5 kWh/kg in 2012, with a 2014 target of 12,3 kWh/kg and a mid-term target of <11,8 kWh/kg for an extra energysaving variant called HAL4e ultra [35].

A full set of performance data from the first months of operation of the HAL-42 test cells had been published in 2009, and the results achieved are shown in Table 3.

One distinguishing unique HAL technology feature common to all of the above mentioned variants (except perhaps at Venalum) is that a HAL potline is housed under one common roof.

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy 2 rows of pots.

This HAL specific potline configuration is very advantageous in terms of land usage, i.e. the annual output per m2 of built-up area is comparatively high.

The HAL potline concept also achieves lower potroom construction investment and operating costs.

A satellite image comparison of a traditional vs. a HAL potline arrangement is shown in Figure 4, whereas the yellow lines are 1000 m and 250 m long, respectively.

Figure 3: Typical HAL-32 Potline, Photo: copyright Qatalum

This is called by Hydro Aluminium the double potroom concept, or alternatively the half-potroom concept.

Usually, modern PFPB side-by-side potlines consist of two rows of pots.

These are traditionally housed in two distinct buildings (potrooms) which are spaced apart by an open courtyard of typically some 60 m open width to keep the reciprocal magnetic disturbance of the two rows at a minimum.

Due to the courtyard, the center-tocenter spacing of pots between the

two rows would be of the order-ofmagnitude of 80 – 90 m and maybe more for the very high amperage cell technologies. Hydro Aluminium places the two rows of a potline in two halfpotrooms which share a common yet unclad central building wall instead of an open courtyard. The center-tocenter spacing of HAL pots between the two rows is then only about 30 m [37]. This configuration somewhat resembles the traditional end-to-end potline arrangement where there are 2 potrooms but each of them housing

Table 3: Hydro HAL420/HAL4e (HAL-42) Cell Performance Data as per [36] Parameter

Value

Unit

Amperage

420

kA

Number of Pots

6

Test cells

Current Efficiency (CE)

95

% (assumed)

Pot Voltage

4,1

V

Anode Effect Frequency (AEF)

< 0,03

AE/(day · pot)

Specific Energy Consumption

12,83 – 12,93

kWh/kg aluminium

1 potline, 360 pots (AP36). 360 ktpy - Aluminium

2 potlines, 2 x 352 pots (HAL275), 585 ktpy - Qatalum

Hydro Aluminium also reports that its development will consider potshells with forced cooling (with an undisclosed cooling medium) on the sidewalls and usage of the resulting off-heat for power generation. Heat extraction from the pot off-gas in the GTC area for district heating purposes is already a feature of some Norwegian smelters. Another topic of Hydro technology development is dealing with concentrating the CO2 content in the pot off-gas (from <1 % to > 4 %) which would reduce the size of gas handling and treatment equipment and eventually facilitate future uses, e.g. in CCS (carbon capture and sequestration) [37].

© 2010 Google © 2011 LeaDog Consulting © 2011 GeoEye

The HAL-32 technology based Qatalum smelter cost was 9.000 USD/ktpy installed capacity [38].

4.3 RioTintoAlcan (including Comalco, Alusuisse & Pechiney) As already discussed, RTA is now pooling the previous R&D activities of Comalco, Alcan, Alusuisse and Pechiney. The current RTA reduction cell technology is equivalent to the former Pechiney technology (RTA technology is still marketed under the APXX denomination). In the context of this review, it is assumed that RTA reduction cell technology today is equivalent to Pechiney AP technology and the other technology developments have been discontinued or, if not, at least their contribution remains

Figure 4: Land Usage of 1 AP Potline vs. 2 HAL Potlines (yellow lines: 1000 / 250 m long)

AWJ 2014 31

Aluminium Reduction Cell Technology Providers – a 2014 Review Table 4: Overview of Smelters based on RTA AP Cell Technology as per [44], [45]

invisible to the public (this contrasts with RTA alumina handling and storage technology which is still marketed

by RTA under the previous Alusuisse brand “Alesa”). Pechiney has a longstanding and well documented track record of reduction cell technology development. Their AP18 (180 kA) technology was commercialized in 1979 and almost 10 years later, the AP30 was first commissioned on an industrial scale in 1986. The first higher amperage applications were both built inside the Pechiney smelter facilities at Saint-Jean-de-Maurienne, France.

Extrapolating from this historical path, it was justifiable for Tabereaux to expect the launch of the next generation AP reduction cell about the time he wrote his review in 1999. The next generation was expected to be of 400 kA while he also expected that this required the solution of some technical problems, e.g. wear of cathode lining, heat balance, emissions, cell instabilities, higher magnetic fields and metal loss due to increased cell turn-around time for relining [2].

Tabereaux was not mistaken, since in July 2000, Pechiney indeed presented its new cell generation. Pechiney, however, had skipped the 400 kA and immediately went to the AP50 technology - to be operated at 500 kA [39].

Within about a year, a first project site was identified at Coega/RSA to host a 460 ktpy greenfield smelter, which was to be the first commercial implementation of the AP50 technology on a large industrial scale. Agreements for power supply with Eskom were made and environmental clearance was achieved by early 2003, however Pechiney looked for investment partners as they only wanted to retain about 40 % ownership in the project. After Alcan had gained control over Pechiney in late 2003, including the Coega project, the project was delayed triggering investigation of several alternative scenarios. The whole process was further protracted due to Rio Tinto then taking over Alcan which, in mid 2007, resulted in a downscaling of the project

Cell Technology (UPBN) Parameter

AP3X (AP-30/39)

Unit

Total Potlines (PLs)

19 + 3 *

PLs

Total Pots

5274 + 810 *

Pots

Average Pots

280 (excl. u/c pots)

Pots/PL

Total Installed Capacity

5,25 (excl. u/c pots)

Mtpy

Average Output

290 (excl. u/c pots)

ktpy/PL

Avg. Potline Voltage **

1170 (excl. u/c pots)

V/PL

*: 3 PLs with 810 pots under construction in Iceland and India; pots not included in below calculations **: assuming 4,2 V/pot

to 360 ktpy combined with a decision to implement the project with AP36 cell technology. In the winter of 2007/08, Eskom´s severe shortfall of maintaining power generation and distribution systems came to the surface - leading to country-wide blackouts in RSA. This was probably only the last in a string of events that caused RioTintoAlcan to abort the Coega AP50 project finally in October 2009 [40].

was achieved in December 2013 [42].

Jonquière could later be expanded to 460 ktpy using the second generation AP60 cells which would be operated at 600 kA [43].

RTA still markets its AP30 technology successfully which has been further developed stepwise. Due to the creeping amperage this technology is now called AP3X and can be operated

Table 5: RTA AP3X and AP50 Cell Performance Data as per [45], [46], [47] Parameter

Value

Unit

Amperage

300 – 500

kA

Current Efficiency (CE)

94,1 – 96 ,0

%

Pot Voltage

4,2

V

Anode Effect Frequency (AEF)

0,23 – < 0,03

AE/(day · pot)

Specific Energy Consumption

13,01 – 13,41

kWh/kg aluminium

Obviously frustrated by the inability to launch the AP50 at Coega, Alcan had started building a semi-industrial short potline of 44 AP50 pots within its own organization, at the Jonquière smelter in Canada. Commissioning of this 60 ktpy potline was envisioned for mid 2008. However, the financial stress caused by Rio Tinto´s 38 blnUSD outlay for Alcan still persisted when the global financial crisis started to hit in 2008.

This did not favour the Canadian AP50 project which was then slowed down.

During the slowdown, the project was re-engineered and RTA announced that the Jonquière short potline will now receive the latest development, AP60, instead of the AP50 previously announced [41]. In keeping with the 60 ktpy production capacity target, the pilot potline now consists of 38 pots of first generation AP60 cells operating at 570 kA after full capacity

32 PRIMARY SMELTING AND PROCESSES

at up to 390 kA. RTA´s AP3X range of reduction cells has so far dominated the reduction cell technology licensing business outside of Russia and China.

The AP technology market share of the world’s modern smelters outside of Russia and China is estimated to be at least 80 %. The global application basis of AP3X is summarized in Table 4. Besides that, there is one 405 kA potline under construction at Kitimat.

The latest AP performance data can be characterized as follows (see Table 5), summarizing from various publications in TMS Light Metals and RTA company brochures. This appears to be supported by the RTA confirmations that the AP3X and the AP50 test pots have maintained their performance data level throughout the entire amperage range.

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy The higher amperage range of the AP3X reduction cells is understood to be applied to pots with unchanged outer dimensions with moderate adjustments to anode size and potlining.

This means that at the high amperage end, current density and energy input to the AP3X cells is higher compared to the basic AP30 cell. It is also understood that this will require forced sidewall cooling, which consists of low pressure air blown through channels attached to the sidewalls of the potshells. The resulting heated air is released to atmosphere.

The AP-36 technology based Sohar smelter was built at 6.670 USD/ktpy installed capacity [48], while the AP60 pilot potline has cost a staggering 18.330 USD/ktpy [42], and it remains to be seen how much this cost can be lowered for a full commercial smelter project.

4.4 United Company RusAl (including VAMI) Most of UC RusAl’s aluminium smelters were built between 40 and 60 years ago, and the majority of these smelters are still based on Söderberg technology [49]. According to RusAl, more than 80 % of Russian primary aluminium originates from Söderberg cells [50] while the international share of Söderberg smelters was only 18 % in 2005 [51]. Modernizing their Söderberg aluminium production sites has an ongoing high priority for RusAl (dry anode technology, hooding, gas treatment, anode gas incineration, alumina

Figure 5: Typical RA-30 Potline, Photo: copyright Rusal

feeding etc.). Prebake smelters have been built in the FSU from around 1975 [26]. An overview of RusAl high amperage reduction cell performance is presented in Table 6.

A year into its existence RusAl started development of a high amperage PFPB reduction cell (in 2001) and five pilot cells were commissioned at their Sayanogorsk smelter (SAZ) at the end of 2003. The so-called RA-300 (RA30) reduction cells have been used for the construction of the Khakas smelter (KhAZ) which was started-up in 2006 and operates 341 (336 + 5?) pots at 320 kA. In 2005, a newly developed RA-400 (RA-40) prototype was commissioned at SAZ, and by 2010, sixteen RA-400 cells were in operation at 435 kA.

As example for a typical Rusal PFPB potroom see a photo from the Khakas smelter in Figure 5.

The RA-400 is to be installed at RusAl´s new Taishet smelter; construction commenced in 2007 but was suspended by the end of 2008. The Taishet smelter will comprise 672 pots with production capacity of 750 ktpy [57].

BEMO (Boguchanskoye Energy and Metals Complex) is a combined hydropower plant (HPP) and aluminium smelter project under construction.

The 3 GW HPP project originally started 1979 but was stopped from 1994–2005.

Meanwhile 6 out of 9 generators are

Table 6: RusAl Cell Performance Data as per [52], [53], [54] Cell Technology (UPBN) Parameter

OA-300M1 (SU/RA-30)

RA-300 (RA-30)

RA-400 (RA-40)

RA-500 (RA-50)

Unit

Smelter Site

IrkAZ

KhAZ/ *

SAZ/ **

SAZ

Amperage (design)

300

300

400

500

kA

Amperage (operation)

330

320

415 – 435

520

kA

Number of Pots

200

336 + 672*

16 + 672**

?

Current Efficiency (CE)

94

95

> 93,5***

> 93,5***

%

Pot Voltage

4,33

n.a.

4,3 - 4,4***

4,3 - 4,4***

V

Anode Effect Freq. (AEF)

0,13

0,15

< 0,05***

< 0,05***

AE/(d · pot)

Specific Energy Cons.

13,73

n.a.

< 13,8***

< 13,8***

kWh/kg Al

*: under construction (BEMO project, 588 ktpy) **: under construction (Taishet project, 750 ktpy) ***: target values

AWJ 2014 33

Aluminium Reduction Cell Technology Providers – a 2014 Review operating, and smelter construction would see first hot metal later in 2014.

The smelter comprises 672 pots of RA-300 technology for a total output of 588 ktpy [58].

is expected to be < 12 kWh/kg. In the absence of information to the contrary, it is assumed that a cryolite-based electrolyte would be used as opposed to the chloride-based trials that Alcoa conducted in the late 1970s using a similar cell but with multiple horizontal bipolar electrodes [50], [53].

Before their merger with RusAl, SUAL reported that they were operating six OA300M1 type 300 kA test cells (SU30) at its Ural smelter (UAZ), designed

by SibVAMI. Commissioned in 2005, the amperage of the test cells was later increased to 330 kA. In early 2010, a full 170 ktpy potline (potline 5) at Irkutsk (IrkAZ) was commissioned with plans to increase the amperage to 330 kA. The IrkAZ potline 5 comprises 200 OA300M1-based pots which are now (after the merger with RusAl) also dubbed RA-300 [55].

RusAl claims that they can build a smelter in Russia at a cost of 2.300 – 2.800 USD/tpy installed capacity [56].

The Khakas smelter is said to have been built in less than 24 months.

4.5 Dubal Dubal started operations in 1979 with 3 potlines implementing National Southwire technology (an improved

version of Kaiser P69 (KA-15)) [59].

The reduction cells were modified and retrofitted over the first decade of operation by Kaiser and Norsk Hydro [26].

When potline 4 was commissioned in 1990, the first five CD-type test pots, jointly developed with Comalco, were also started at 190 – 200 kA. Potlines 5 (commissioned from 1996) and 6 (1999) both implemented the so-called CD20 cells on an industrial scale. In the Comalco-Dubal nomenclature the number actually represents the number of anodes and only roughly coincides with the amperage level.

So, in UPBN terminology, this was a CD-21 (210 kA) cell. In 1997, again five test cells of further advanced amperage were commissioned, called

During 2007/2008, RusAl further advanced development of a 500 kA reduction cell. However, it remains unclear if a prototype has already been built or if this is yet to happen. There are plans to build an experimental RA-500 potline between 2011 and 2014 [54].

RusAl further reports that it is experimenting with inert anode technologies in two ways: firstly, as a replacement for prebake carbon anodes in standard Hall-Héroult cells and secondly, in trial cells that implement multiple vertical inert anodes and cathodes. The latter trial cells would have a much higher time-volume-related output as compared to standard Hall-Héroult cells. Specific energy consumption

Figure 6: Dubal DX Pilot Potline, Photo: copyright Dubal

Table 7: Dubal Cell Performance Data as per [67], [69], [70] Cell Technology (UPBN) Parameter

DX (DU-35)

DX (DU-38)

DX+ (DU-44)

Smelter Site

Emal 1 *

Dubal

Dubal, Emal 2

Amperage (design)

340

340

440

kA

Amperage (operation)

380

380

440

kA

Number of Pots

756

40

5 + 444

444 DX+ under commissioning at Emal 2

Current Efficiency (CE)

95,8

95,5

95

%

Pot Voltage

4,2 – 4,22

n.a.

4,24

V

Anode Effect Frequency (AEF)

0,1

< 0,02

< 0,05

AE/(day · pot)

Specific Energy Consumption

13,12

13,04

< 13,4

kWh/kg aluminium

*: Emal 1 values during commissioning phase

34 PRIMARY SMELTING AND PROCESSES

Unit

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy CD26 (CD-28). Further expansions into potlines 7 (2003) and 9 (2005), however, deployed the cell type D20 (DU-23) which may be taken as an early indicator that the Comalco co-operation had been put on the “backburner”. In 2006, five independently developed test cells of DX (DU-34) type have been commissioned and, in 2008, the technology was semicommercialized in an in-house 40 pot short potline (potline 8) at Dubal [60], [61]. A photo of this pilot potline is shown in Figure 6.

Between 1997 and 2004, Dubal’s interest to expand outside of its UAE Jebel Ali smelter site was also based on commercialization of the Comalco-Dubal CD reduction cell technology. Projects for a proposed 530 ktpy smelter in the Gulf, using CD20 technology [62], a 500 ktpy smelter in the Bintulu region of Malaysia [26], and a 520 ktpy smelter in Qatar based on CD26 technology [63] did not progress, however, and Dubal withdrew from the latter project in January 2004 for undisclosed reasons [64].

The impending split between Comalco and Dubal became evident in mid 2006.

On 26th June 2006, Comalco and General Holding Corporation (GHC) of Abu Dhabi signed a heads-of agreement for a feasibility study of a 550 – 700 ktpy greenfield smelter at Ruwais/Abu Dhabi whereas a joint venture between Dubal and Mubadala Development Company of Abu Dhabi had, on 28th June 2006, awarded the feasibility study for a 700 ktpy greenfield smelter to be located at Taweelah/Abu Dhabi [65]. While the Comalco–GHC project did not materialize, the Dubal–Mubadala project, called Emirates Aluminium (Emal), has since been constructed and is fully commissioned since 31st December 2010 [66].

For the Emal project, Dubal has licensed its own DX (DU-35) technology.

The 2 potline smelter comprises 756 pots and has been started up at 350 kA with key performance indicators keeping up with those of the experi-

mental pots at Dubal (see Table 7). At this amperage, Emal will achieve an output of 740 ktpy.

Meanwhile, Dubal has further challenged its DX cells in potline 8 at the Jebel Ali smelter, Dubai. Originally designed for 320 kA, the DX pots have, since October 2010, been boosted to 380 kA while sustaining the target key performance indicators (see Table 7).

Dubal anticipate that, with a modified potshell, the DX cell technology´s operating envelope can be pushed even further to 400 kA before reaching physical limitations [67]. This improvement has already been transferred to the Emal smelter which operates, after a rectifier upgrade, at 380 kA since 2012 boosting the Phase 1 output to 800 ktpy [71].

In an attempt to avoid such physical constraints, Dubal has begun developing a new generation of reduction cell technology called DX+ (DU-44). Five DX+ test cells, built at Jebel Ali, are already being tested at 420 kA since August 2010 and reached 440 kA in February 2012 [68]; the performance data achieved so far are included in Table 7. Dubal is predicting that this new generation DX+ technology can even operate at above 440 kA with good key performance indicators [69].

Emal has meanwhile built an additional potline implementing DX+ technology.

FHM was achieved on 15.09.2013, and it is said that the potline current is already set at 440 kA. This single potline expansion comprises 444 pots, and as such is the longest globally, with capacity of 545 ktpy. DX+ technology may be further deployed if and when the Alba Line 6 expansion gets the goahead; for now, DX+ technology has been the basis of a recent feasibility study evaluating this expansion.

The DX (DU-35) technology based Emal Phase 1 smelter was built at 8.240 USD/ktpy installed capacity [71], while the DX+ (DU-44) technology for Emal Phase 2 has cost 7.500 USD/ktpy [72].

4.6 Venalum In 2000, Corporación Aluminios de Venezuela S.A. (CAVSA) presented a technology website describing its so-called V-350 aluminium reduction cell developed by the CVG Venalum R&D department. The V-350 (VN-35) cell was designed for operation at 320 – 350 kA and test pots were said to be operating at 322 – 325 kA [73].

Further performance data mentioned are presented in Table 8.

In 2004, Berrueta presented a paper at TMS on the planned expansion of the Venalum smelter by two potlines with 240 reduction cells each of V-350 (VN-35) type. Groundbreaking was scheduled for March 2004 and the first of the two potlines (potline 6) was planned to be commissioned from the end of 2006. The additional electric power was to be provided by CVG Edelca, a state-owned power provider within the same CVG group, which was said to have included some generating units in the Caruachi dam project on the Caroni River to provide for the Venalum demand. This hydroelectric power project was supposed to generate energy by 2005.

Berrueta also presented an estimate of the capital expenditure (CAPEX) necessary for one potline, including casthouse, carbon and dock facilities.

The estimated CAPEX of 652 mUSD, for a production capacity of 220 – 230 ktpy, would translate into a specific investment of around 2900 USD per tonne installed capacity [74].

However, according to Pawlek´s PASaPoW [26], no further potline construction activities have been recorded at Venalum, and the V-350 test pots are supposed to have been taken out of service and dismantled.

The author therefore believes that Venalum cell technology development was ceased altogether.

4.7 Chalieco-SAMI SAMI had initially developed Söderberg cells (until the mid 1970s) and by the

AWJ 2014 35

Aluminium Reduction Cell Technology Providers – a 2014 Review Table 8: Venalum V-350 (VN-35) Cell Performance Data as per [73] Parameter

Value

Unit

Amperage (design)

320 – 350

kA

Amperage (operation)

322 – 325

kA

Current Efficiency (CE)

95 – 96

%

Pot Voltage

4,1 – 4,2

V

Anode Effect Frequency (AEF)

0,1 – 0,2

AE/(day · pot)

Specific Energy Consumption

13,0 – 13,3

kWh/kg aluminium

late 1970s designed a first prebake anode cell for 135 kA (SY-14). Development was now focused on prebake cells and continued stepwise (SY-16, SY-19/20, SY-23/24, SY-28) until the turn of the millennium. All these cell types have been applied commercially in the Chinese primary aluminium industry. In June 2002, the first full 300 kA potline in China using SY300 (SY30) cell technology was commissioned after 12 months of potline construction; the 200 ktpy potline is quoted to have been built at 1.707 USD per t installed capacity [75]. By 2007, 13 potlines using SY-300 technology had already been commissioned in China, including 2nd generation pots operating at 317 kA and 3rd generation pots applying 335 kA - with plans to further increase potline current to 350 kA. The investment cost was quoted as being 1.200 – 1.500 USD per t installed capacity for a standard SY300 potline of 200 ktpy capacity [76]. The 350 kA target was obviously achieved by 2010 and SAMI even reported implementation of 350 – 400 kA cells and a first 500 kA potline being under construction.

Summarizing from a presentation given

by SAMI in November 2010 [77], SAMI high amperage ( 300kA) reduction cell technology had reached more than 5,5 Mtpy capacity in operation

and over 3 Mtpy under construction, exclusively located in China. Furthermore, 23 additional operating potlines utilizing SY190 – SY240 reduction cells were mentioned [78]. A fresh comparison with Pawlek´s PASaPoW [26] reveals a lot of uncertainty regarding the aforesaid as the smelters directly attributed to using SAMI technology do not match. The author, therefore, lumped together explicit SAMI technology smelters with those mentioned in Pawlek´s PASaPoW as using “Chinese Technology”, clustering the result into 3 amperage categories. The result is presented in Table 9.

So far, only one SAMI cell technology application is known outside China which is the Iralco expansion in Arak/ Iran, consisting of 1 potline with 120 ktpy capacity implementing SY200 cell technology which was commissioned from mid 2007 - 2009. There is some confusion because Pawlek stipulates GAMI as technology provider [26] whereas SAMI itself mentions it in one of their publications [78]. The following Table 10 summarizes the performance data of SAMI reduction cells as published.

A typical SAMI potline is shown in Figure 7.

4.8 Chalieco-GAMI: GAMI seems to have followed a similar development to SAMI, although there is very little publication. The GAMI development was initially based on a 160 kA cell - first commercialized in the Guangxi smelter in 1994. It appears, from an evaluation of information provided by Pawlek in his PASaPoW directory [26], that GAMI has further developed this technology into the 200 – 280 kA range. A number of potlines are reported to have been commissioned using GAMI reduction cell technology in this amperage range, though there is no primary source that confirms this [26]. In 1998, the GP320 reduction technology was jointly developed by GAMI and the Pingguo Aluminium Company (PGAC). The first GP320 pots came on stream in October 1999, in a 30 cell trial potline. This trial potline achieved a current efficiency of 94,4 % with specific energy consumption of 13,323 kWh/kg Al, operating at up to 325 kA. The cell voltage was reported as 4,18 V with anode effect frequency of 0,3 – 0,4 AE/(d · pot) [79]. Further performance data for GAMI technology appear to be publicly unavailable.

As there is little GAMI publication, Pawlek´s PASaPoW seems to be the only accessible source of information about GAMI. However, due to limited information about Chinese aluminium smelters in general, this directory also remains vague on China and some of the information is contradictory (e.g. there sometimes appears to be a mismatch between amperage, number of pots and output) which cannot be finally resolved by the author. That said, evaluation of PASaPoW for explicit

Table 9: Overview of Chinese Smelters based on SAMI Cell Technology 300 kA as per [26], SAMI and “Chinese Technology” lumped together for better match with [77] Cell Technology (UPBN) Parameter

SY300 (SY-30)

SY400 (SY-40)

SY500 (SY-50)

SY300 (SY-30)

SY400 (SY-40)

SY500 (SY-50)

Unit

Smelter Status

operatg.

operatg.

operatg.

u/c

u/c

u/c

-

Total Potlines (PLs)

27

20

4

0

8

8

PLs

Total Pots

6310

5902

1236

0

2256

2584

Pots

Average Pots

240*

290

310

-

275

325

Pots/PL

Total Installed Capacity

4,17

4,84

1,71

-

2,45

3,51

Mtpy

Avg. Potline Voltage **

1010

1220

1300

-

1160

1365

V/PL

*: excluding 1 short potline of 86 pots/70 ktpy considered an outlier **: assuming 4,2 V/pot

36 PRIMARY SMELTING AND PROCESSES

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy related industrial applications remains largely unknown. The first potline using NEUI400 (NE-40) cell technology has been energized in 2008 at the Zhongfu smelter. The potline comprises 216 pots with capacity of 240 ktpy, now operating at 406 kA with pot voltage of < 3,9 V. Further operating results have been reported as follows: current efficiency of 94 %, specific energy consumption of 12,5 kWh/kg Al and anode effect frequency of < 0,01 AE/ (d · pot) [80], [81].

Figure 7: Typical SAMI SY400 Potline, Photo: copyright SAMI

GAMI high amperage ( 300 kA) reduction cell technology (with one attempt to mend an obvious mismatch and back-calculating some missing data in the directory) has resulted in the following tentative overview of GAMI technology proliferation (to be read with due caution), see Table 11. In addition, > 2,8 Mtpy capacity appear to be based on GAMI 200+ kA cells which seem to have been fairly frequently implemented during the past 12 years besides the high amperage technologies.

Outside of China, GAMI has licensed its technology to some smelter projects.

The GP320 technology has been the basis of an expansion of the BALCO smelter, located in the Korba district, India. The project comprises one potline of 288 GP320 pots with a capacity of

250 ktpy; the potline commissioning was started in February 2005. GAMI has also licensed its GP215 technology for the Press Metal smelter project in the Sarawak region, Indonesia. The project consists of one potline with 204 pots and has a capacity of 120 ktpy; commissioning began in mid 2009. The Det. Al smelter in Ganja, Azerbaidjan, uses GP240 cells for its 164 pots potline with capacity of 100 ktpy.

4.9 NEUI As a fairly young entity, NEUI also has little published track record. However in 2010 they reported their latest achievements with the development of highamperage reduction cells. The NEUI technology portfolio is reported to cover the ranges 200/240 kA, 300/330 kA and 400 kA, while the extent of its

The NEUI 400 kA technology is currently applied in four potlines, built between 2008 and 2010 running at 415 – 460 kA. Six new potlines of 400 kA are said to be under construction without giving any details. The four operating smelters are reported to run with current efficiency around 94 % and specific energy consumption of less than 12,5 kWh/kg Al [82]. Not entirely surprising, also in case of NEUI technology, information provided by Pawlek in his PASaPoW directory [26] does not fully match the aforesaid, see Table 12.

Meanwhile, NEUI has taken their reduction cell development to the 500 kA level. However it is understood that to date this only covers simulation and modeling, based on the modeling tools used for the development of the NEUI-400 reduction cells [83].

NEUI further reported that they are continuously testing (since March 2008) pots with so-called novel structural cathodes (NSC) which consist of cathode blocks with a baffled surface.

Table 10: Summary of SAMI Cell Technology Performance Data ( 300 kA) as per [77], [78] Cell Technology (UPBN) Parameter

SY300 (SY-30)

SY350 (SY-35)

SY400 (SY-40)

SY500 (u/c) (SY-50)

Unit

Amperage (operation)

300 – 335

348 – 378

400

500

kA

Number of Pots

3074

444

n.a.

288

Current Efficiency (CE)

93,8 – 95,7

94,15 - 94,5

94,16

94

%

Pot Voltage

n.a.

n.a.

4,19

< 3,94

V

Anode Effect Freq. (AEF)

0,1

< 0,3

0,08

0,05

AE/(d · pot)

Specific Energy Consumpt.

12,9 ± 0,06

12,8 – 13,5

13,26

< 12,5

kWh/kg Al

AWJ 2014 37

Aluminium Reduction Cell Technology Providers – a 2014 Review Table 11: Tentative Overview of Chinese Smelters based on GAMI Cell Technology 300 kA as per [26] Cell Technology (UPBN) Parameter

GP300 (e.g. GP-30)

GP400 (e.g. GP-40)

GP500 (e.g. GP-50)

GP300 (e.g. GP-30)

GP400 (e.g. GP-40)

GP500 (e.g. GP-50)

Unit

Smelter Status

operatg.

operatg.

operatg.

u/c

u/c

u/c

-

Total Potlines (PLs)

26

2

1

4

0

0

PLs

Total Pots

6322

510

288

840

0

0

Pots

Average Pots

280*

260

290

210

-

-

Pots/PL

Total Installed Capacity

5,75

0,55

0,39

0,76

-

-

Mtpy

Avg. Potline Voltage **

1175

1100

1220

880

-

-

V/PL

*: excluding some obvious test sections and 2 short potlines of 84 pots/138 ktpy **: assuming 4,2 V/pot

There are different shapes and patterns of protrusions under test, all with the aim of reducing the metal rotating velocity and ultimately, although not explicitly mentioned, lessening the

While for decades Alcoa and the US had been the unchallenged leaders in primary aluminium production, their share of global primary aluminium production today is 7,9 % and 4 %,

Table 12: Tentative Overview of Chinese Smelters based on NEUI Cell Technology 300 kA as per [26] Cell Technology (UPBN) Parameter

NEUI300 (NE-30)

NEUI400 (NE-40)

NEUI500 (NE-50)

Unit

Smelter Status

operatg.

operatg.

operatg.

-

Total Potlines (PLs)

1

4

0

PLs

Total Pots

180

1006

0

Pots

Average Pots

180

250

-

Pots/PL

Total Installed Capacity

0,15

1,19

-

Mtpy

Avg. Potline Voltage *

760

1050

-

V/PL

*: assuming 4,2 V/pot

5 Summary and Conclusion The author has highlighted the developments since the turn of the new millennium that have led to a considerable concentration of primary aluminium production capacity by way of mergers and acquisitions while some traditional producers have exited the primary aluminium business.

This trend is equally observed in the western world as well as in Russia and China. Along with this development, the number of companies developing and licensing reduction cell technology has shrunk in number, specifically in the western world.

This trend replicates the equally tremendous shift of the primary aluminium production base from west to east.

respectively, whereas Chalco (8,9 %) and RusAl (8,8 %) are now the biggest players with almost equal market share and China is the biggest producing region, representing a massive 45 % of global supply. As an update to the reduction cell technology providers presented in Table 1, the following Table 13 gives an overview of the remaining and new players at the turn of 2013/2014, together with their

It can be concluded that two of the remaining technology providers, namely Alcoa and Venalum, appear to be inactive in the field of reduction cell technology development and their technologies would probably not be available for licensing today. This leaves reduction cell technology know-how with only two western companies (RTA and Hydro Aluminium), one each from the Middle East and Russia, and three Chinese research and development institutions.

From the western companies, RTA has

7.000 6.000 Reduction Cells in Operation

ACD. The test pots are reported to operate at around 3,7 V resulting in 12,0 kWh/kg specific energy consumption and achieving 93 % CE [84].

achievements in terms of cell amperage and the underlying application basis, expressed as the number of operating pots and installed capacity.

The reference to new reduction technology players actually only applies to Dubal because the other Russian and Chinese “new” players in fact have quite a history though this went largely unrecognized due to their long-lasting geopolitical isolation. A graphical representation of pots in operation by technology provider is given in Figure 8.

5.000

300 - 399 kA 400 - 499 kA > 500 kA

4.000 3.000 2.000 1.000

0

Alcoa

Hydro

RTA

Dubal

Venalum

Rusal/VAMI

SAMI*

Figure 8: Reduction Cell Technology Proliferation (operating pots)

38 PRIMARY SMELTING AND PROCESSES

GAMI*

NEUI*

*: estimated

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy Table 13: Reduction Cell Technology Providers as at the Year 2013 Company Alcoa Hydro

RTA

Dubal Venalum

Chalco / Chalieco

Rusal/VAMI

NEUI

SAMI

Cell Type

I / kA

Pots

Capacity / Mtpy

installed

u/c

installed

u/c none

Remarks

A-817

AA-32

320

448

none

0,388

HAL-230

HAL-26

240 - 258

ca. 410

none

0,285 e

none

Hoyanger, Venalum PL 5, Slovalco

HAL-275

HAL-30

290 - 320

1044

none

0,90

none

SU4, Qatalum

Portland

420

6

none

negl.

none

test cells in Ardal

300 - 400

5274

1194

5,25

1.22

various smelters, global spread

HAL4e

HAL-42

AP30/40

AP-30/40

AP50

AP-57

570

41

none

0,065

none

St. Jean-de-Maurienne, Jonquière

AP60

AP-60

600

none

none

none

none

460 kpty planned for Jonquière

DX

DU-38

380

796

none

0,85

none

Dubal PL 8, Emal 1

DX+

DU-42

440

449

none

0,55

none

Emal 2, Dubal test cells

V-350

VN-35

325

5

none

none

none

test cells shut down and dismantled (?)

RA-300

RA-33

330

536

672

0,47

0,59

Tajik, Sayansk, Volgograd

RA-400

RA-44

435

16

672

0,02

0,75

test cells in Sayanogorsk

RA-500

RA-52

520

?

none

?

none

test cells (to be) in Sayanogorsk (?)

SY300

SY-30-38

300 - 375

4.752

0

4,17

0

SY400

SY-40-45

400 - 450

4.402

2.256

4,84

2,45

SY500

SY-50-52

500 - 520

1.236

2.584

1,71

3,51

CT300/350

CT-30-35

300 - 350

1.558

-

1,32

-

400

1.500

-

1,63

-

300 - 365

6322

840

5,75

0,76

China unspec CT400 GAMI

UPBN

CT-40

PASaPoW 05-2013, plus private communications R. Pawlek unspecified Chinese Technology per PASaPoW 05-2013 & private communications R. Pawlek

GP300/370

GP-30/37

GP400

GP-40

400

510

0

0,55

0

GP500

GP-50

500

288

0

0,39

0

NEUI300

NEU-30

306

180

?

0,15

?

NEUI400

NEU-46

415 - 460

1006

?

1,19

?

6 PLs u/c: ??

NEUI500

NEU-50

500

?

?

?

?

modeling completed ?

the most widespread global proliferation of their Pechiney-based reduction cells. RTA also licenses its technology independently of project ownership.

Their application base of AP3X pots is impressive and is still growing, however this is almost dwarfed by the spread of China-developed reduction cells which, at comparable amperage, all occurred during little more than the last 12 years.

While in the past Hydro Aluminium and RTA have licensed their technologies on a global scale, the application of Dubal, RusAl and the Chinese cell technologies remains, by and large, confined to their respective homelands, with only a few exceptions.

This is, among other reasons, probably due to some persisting questions over the long-term performance of the eastern technology cells. Looking at the performance presented in the tables of the previous chapters, this appears not to be justifiable since the

gap between published eastern and western performance data seems to have narrowed. Other issues are the reported low investment costs and short construction durations in their home countries, which raise the question of transferability into an international framework where the specific Russian or Chinese local conditions do not apply. Also, the project scope of facilities and materials/equipment supply sources behind such figures often remain unknown - which makes benchmarking extremely difficult and potentially misleading. Finally, international aluminium smelter projects are often based on project finance with money to be raised on the international financial markets. International financing institutions would normally apply a rigid scrutinization of the project, technically and financially, including compliance checks with international standards such as the World Bank Standards or the Equator Principles. These issues will be much less prominent if

PASaPoW 05-2013, plus private communications R. Pawlek, see Chapter 4.8

a project is financed out of equity or by a government, as may be the case in the eastern hemisphere.

Coming back to Tabereaux´s expectations that future high-amperage reduction cells would require the solution of technical problems related to, e.g., wear of cathode lining, heat balance, emissions, cell instabilities, stronger magnetic fields and greater metal losses due to increased cell turn-around time for relining [2], the following general trends can be noticed.

The reduction cell technologies have, over the years, undergone a few creeping changes that are worth mentioning.

Reduction cells are usually developed for a certain amperage. Cells developed up to the 1980s were still very delicate when operating parameters, specifically the cell amperage, were changed and small amperage increases frequently met with major disturbances. It appears

AWJ 2014 39

Aluminium Reduction Cell Technology Providers – a 2014 Review that cells developed in the 1990s and later have a much higher tolerance. For example, this can be concluded from the AP30 creep to AP39/40. This creep has happened within a given potshell with only minor modifications such as the addition of cooling fins or forced (air) cooling systems, adjustments to the anode size and changes in the potlining. While increasing the amperage (and thus the aluminium output) by about 30 %, the performance figures could be maintained despite the stronger magnetic fields with their potentially detrimental effect on cell performance. This can be taken as evidence that the modeling tools applied during reduction cell development have reached a level of sophistication that the behaviour of reduction cells under modified operating parameters can be simulated quite precisely. The same conclusion is applicable for the development of new reduction cells which seems to happen in ever shorter periods of time with less time required for pilot cell trials.

The creep previously mentioned comes along with an increased energy input to the cell, which up to now is just dissipated as heat into the environment. The crucial issue of the presence (or absence) of a frozen layer of bath (ledge) to protect the sidewall lining is largely left to the success of ventilation enforced by natural draft.

Thus, the aluminium reduction cell can be regarded as rare sample of a metallurgical furnace (in German: Elektrolyse-Ofen) operating at just short of 1.000 °C that is left to natural forces for the successful furnace cooling as opposed to forced cooling (using media other than air) which would even allow the partial recovery of the dissipated energy.

An achievement of modern PFPB cells that usually goes unnoticed outside the industry is the lowering of the anode effect frequency (AEF) and duration which is due to ever smarter, more reliable alumina feeding and pot control systems. Obviously, this lowers the amount of energy wasted during anode

effects and disruption of the electrolytic aluminium deposition as well as the thermal cell disturbance related to the additional heat input. Generation of the powerful greenhouse gases CF4 and C2F6 (PFCs) is directly related to the occurrence and duration of anode effects and the industry as a whole has achieved remarkable reductions in the co-production of PFCs. Modern PFPB cells can almost entirely suppress anode effects which “in the old days” (which started ending maybe only 20 years ago) were considered an indispensable means for good cell operation. Older technologies (SWPB, CWPB, Söderberg) have inherent difficulties in supporting such achievements because the feeding systems do not allow the elimination of anode effects, which means that smelters operating such reduction cells will be under increasing environmental pressure in the future.

Modern high-amperage reduction cells would normally use highly or fully graphitized cathode blocks which are softer than blocks made from anthracite with low graphite content. As a consequence, one would expect shorter cathode life for cells with graphitized cathodes. Nevertheless it appears that the cathode life is not becoming shorter but indeed longer with a tendency to achieve 2000 days or more on average. Connected to this there should also be no negative effect on productivity (or rather cell availability) from a relining point of view. If cells are not lined in-situ but in a dedicated pot delining/relining facility, turnaround time - and hence loss of metal production - can be kept low and, as a positive side effect, the working environment for the delining/relining activities can be better controlled.

As a summary to the above, today´s computer-based modeling tools (for modeling electro-thermal, electromechanical, magnetic, and magnetohydrodynamic effects) used during reduction cell design are very capable of predicting the behaviour of such

40 PRIMARY SMELTING AND PROCESSES

cells. Modern cells designed with such tools have high probability of achieving low energy consumption and, at the same time, high current efficiency because detrimental effects of strong currents and the associated magnetic field can be compensated during design. This results in the required robust cell design necessary for stable cell operation. Sophisticated cell control algorithms (including fuzzy logic) and development of more robust sensors support operation to achieve favourable operating parameters including low AEF. These core reduction cell issues seem to be fairly well controllable even when current intensities well in excess of 300 kA are applied.

From a potline construction point of view, high-amperage cells then require more focus on some rather profane peripheral issues which have been much less important on lower amperage levels. Aluminium reduction cells have, despite some higher anodic/cathodic current densities, almost exclusively grown in one direction with increasing amperage which is the length of the potshell; potshell width and depth have almost remained unchanged over the past 2 – 3 decades. Construction elements affected by a longer potshell are the potroom building width; wider crane span combined with heavier lifting loads; consequentially heavier foundations and structural steel elements; wider superstructures that need to support more own weight plus more weight from additional anodes without too much sagging, just to name a few.

As has been indicated in the previous chapters on individual reduction cell designs, potlines have grown in number of pots installed per line. Specifically western technologies are now implementing potlines with 350 – 400 pots per line whereas eastern technologies seem to only follow this trend more hesitantly (usual pots per potline are still around 200 – 300). While the trend towards longer potlines saves on investment cost for common equipment like the rectifier-transformers (RTs) for

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy each potline it is also more demanding in terms of voltage level for such units.

Recently built long potlines based on Dubal, Hydro and RTA technology now require RTs of 1.700 ± 50 V while this level for eastern technologies is still in the 1200 V range (and below). The RT manufacturers are offering 2.000 V RTs by now, and the Emal 2 potline with 444 pots is the first where this RT technology is practically applied. The 2 kV RT, however, has two major implications.

Firstly, potlines would be able to grow into the 450 pots per potline size which would support 500 ktpy capacity out of just one potline (assumed @ 400 kA).

In case of a power failure (generation, transmission, rectification), the entirety of this production capacity would be at risk and it remains to be seen how venturesome the aluminium industry and its financiers will be. Secondly, the 2 kV RT creates higher demands for the electrical insulation of potline buildings and the insulation strength of all affected electrical equipment inside those buildings (motors, cables, PLCs etc.).

Higher metal output per cell also requires more metal handling and more anode carbon to be replaced. An increase of pot interventions (for tapping or anode changing) or an increase of potroom and plant traffic would not be welcome by operators so new concepts might have to be devised, e.g. for tapping, there are limitations to increasing the height of the crucible because of the metallostatic pressure that needs to be overcome.

6 Alternatives and Outlook The Hall-Héroult (HH) cell is a comparatively inefficient metallurgical reactor, even at the 600 kA level: one 600 kA cell produces only 4,5 t per day or 1.670 tpy, but occupies an area of some 4 m x 18 m = 72 m2. For a commercially viable plant, between 200 and 450 of these cells have to be installed which causes quite a big land usage. In comparison: one single modern iron blast furnace (BF) unit of 10 m hearth diameter, or a footprint of 78 m2, produces 7.260 t per day

or 2.650.000 tpy (2,65 Mtpy!), and there are bigger ones also. HH cells operate at 950 °C or ca. 300 °C above the melting point of pure aluminium and usually yield aluminium of 99,7 % purity or better, whereas the iron BF operates at a tapping temperature of ca. 1.450 °C which is actually some 90 °C below the melting point of pure iron (this is possible because the iron BF does not produce pure iron but an iron-carbon alloy with about 4 % C plus some other metallic impurities which together lower the melting point of the impure, so-called pig iron, which needs to be purified in another step).

So who is to blame for this disparity? In brief, aluminium production is hampered by its very own natural properties, first and foremost its very strong chemical bond to oxygen, but also its trivalence, its low atomic weight and density, plus the fact that common reducing agents like carbon do not work quite well in aluminium metallurgy. These facts required that the harshest of all possible reducing agents had to be deployed to break the aluminium-oxygen bond: pure electrons in the form of electric current in an electrolytic process, and its industrial manifestation is the HH cell.

Up until now, all investigated or discussed alternatives struggle with some form of fundamental problem related to the strong oxygen-affinity of aluminium and its position in the electrochemical series. Let’s look at some of the potential alternatives:

Electrolysis • Near ambient temperature and/or water based electrolytic process (maybe similar to copper): aluminium hardly dissolves in aqueous solutions, and if, its position in the electrochemical series favours reduction (= production) of other components of such systems instead of aluminium.

•Electrolytic process closer to aluminium´s melting point of 660 °C, say at around 700 °C (instead of 950

°C): no suitable electrolyte has been found that would combine alumina solubility, electric conductivity etc. like fluoride based cryolite. There are chloride based alternatives which have their own disadvantages, see below.

• Inert anodes: Materials investigated so far are not exactly inert yet, causing co-deposition of more noble metals affecting impurity levels. Widespread industrial application of inert anode materials always seems - at any given time - to be 15 – 20 years away. In principle, such anodes would just release oxygen, no carbon would be consumed and no CO/CO2 generated, no pot intervention for anode change, and no anode plant would be required. However, the change of the sum reaction would require some 0,5 – 1 V higher pot voltage compared to HH cells.

• Wettable, drained cathode: would reduce magneto-hydrodynamic (MHD) effects and would help avoid the deep pool of liquid aluminium in each cell (15 – 25 cm of dead inventory) required to control the MHD effects; industrial implementation, similar to inert anodes, always seems far away. A new development from China comprises the mentioned NSC baffled cathode blocks which might help in this context though these NSC cathodes are made of conventional carbon material and therefore are not to be confused with wettable, drained cathodes.

Novel Processes • Carbothermal Reduction (preferably similar to the iron blast furnace process): the quick answer is that thermodynamically, carbon can only reduce alumina above 2000 °C, and that the product is an unwanted and unstable Al4C3 instead of aluminium.

However, the issue is much more complicated and can be summarized as follows: up to 2.160 °C, only an aluminacarbide slag (AlO, AlO2, AlC) but no liquid aluminium metal is produced; above 2.160 °C there is also a second phase: something like liquid metal but in fact it is an aluminium-carbon alloy with some 10 % C; at the required

AWJ 2014 41

Aluminium Reduction Cell Technology Providers – a 2014 Review process temperature of > 2.200 °C, additionally there will be considerable evaporation of aluminium in the form of aluminium and aluminium sub-oxide (Al2O) vapors which can amount to up to 25 % of the produced metal and may require a vacuum process stage [85].

Carbothermal reduction is said to be further investigated by an Alcoa-Elkem JV which designed process reactors called Advanced Reactor Process (ARP) and Vapor Recovery Reactor (VRR). While Alcoa-Elkem estimate that Capex and Opex of a commercial ARP + VRR plant would be 30 % less than an equal-sized HH smelter, the authors of [85] also point out that major issues of the carbothermal process still remain unsolved.

In the personal opinion of the author of this review, it appears to be very unlikely that the 50 Mtpy primary smelter community can be convinced to switch from the established HH process (operating at a manageable 950 °C, directly yielding a single, high-quality product without fritting) to a novel carbothermal process that requires extremely high temperatures (> 2.200 °C), and scatters the desired aluminium across 3 product streams, whereby those products are far from being pure aluminium hence requiring some sort of post-treatment for metal purification.

• Alcoa Smelting Process (ASP): it may be argued that this is not a novel process as it has been developed around 1970 already, that the pilot facility was shut down in 1985, and that it should have been mentioned under Electrolysis above. Nevertheless, the author of this review wants to point out some of the ASP´s conceptual advantages which may justify its categorization as novel process. Published data on the ASP are scarce, so the below rests on summary information published in [86] and [87], from which also the ASP cell (or rather electrolyser) sketch is taken, see Figure 9.

Cl3, dissolved in a chloride electrolyte (e.g. NaCl + LiCl), operating at 700 ± 30 °C. No PFCs would be generated/ emitted.

HH cells consist of one single, horizontal anode-cathode pair (also PB cells where the anode may consist of some 40 individual anode blocks). In contrast, the ASP electrolyser comprises 12 horizontal bipolar anodecathode pairs stacked above each other, i.e. the underside of each electrode acts as anode whereas the upper side acts as cathode (see Fig.9). In this way, one ASP electrolyser replaces 12 HH cells.

The 1980s ASP electrolyser is quoted to have produced in excess of 13 tpd; crunching the few available numbers, back-calculation reveals that the amperage would have been 140 kA (which fits very well with the rectifier capabilities of the early 1970s) resulting in 13,2 tpd or 4.820 tpy per single ASP electrolyser (at an assumed CE of 98 %), which is 3 times the output of one AP60 cell.

No dimensions for an ASP electrolyser are available but, based on a number for current density, the author of this review dares an educated guess: the size of one ASP electrolyser was

probably about 3 m x 3 m (W x L) with height between 2 and 3 m. This means, one single ASP electrolyser produces 1,47 t/(m2 day) which is 2350 % of one AP60 cell, despite the ASP only requiring 140 kA or 23,3 % of the AP60 current intensity.

The bipolar electrodes are inert, i.e. no electrode changes would occur (probably, after some time the ASP electrodes would also deteriorate to some extent and would have to be replaced about once every 3 years, which is more similar to cathode relining in HH cells). An ASP smelter would therefore not require any anode plant and no CO/CO2 would be generated/ emitted.

The interpolar distance (ACD) is quoted as 1 – 2 cm (HH: ca. 5 cm), and the cathode surface only carries a thin film of aluminium which is swept off by the anodic chlorine gas-induced electrolyte circulation. As a consequence, MHD disturbances in ASP electrolysers would be minimal which would most certainly allow placing electrolysers much closer to each other in an industrial ASP smelter (recap: HH pot rows are spaced some 30 – 90 m apart). A higher CE of (assumed) 98 % seems also justifiable for ASP electrolysers due to lower MHD impact.

Feed port

Upcomer Terminal anode

Downcomer

Bipolar Terminal cathode

Anode - cathode space Aluminium sump

The ASP consists of electrolysing AlFigure 9: Sketch of Alcoa Smelting Process Electrolyser [87]

42 PRIMARY SMELTING AND PROCESSES

Dr.-Ing. Joachim Heil MetCons – Metallurgical Project Consultancy Due to use of a chloride electrolyte, single-cell voltage (i.e. one anodecathode pair) is 2,7 V, so one electrolyser would require some 32 V, plus external busbar losses. ASP´s specific power consumption is quoted as < 9,5 kWh/kg.

Despite the clear advantages that such an ASP based smelter would present, the author does not want to hide that there are obviously major challenges that lead Alcoa to stop this development 30 years ago. One area of concern is the preparation of the intermediate AlCl3 which is a nasty chemical compound as it is highly corrosive, volatile, hygroscopic (attracts water) and hydrolyses (e.g. with humid air) forming aluminium oxi-chlorides. Both water and oxygen impair the electrolytic process and must be kept at minimum levels. There would also be formation of chlorinated biphenyl which needs to be removed in order to avoid pollution issues.

However, the author of this review believes that it may be worthwhile revisiting the underlying ASP concept again, given some 30 years of scientific progress in material science, process engineering, and computational simulation tools.

In order to demonstrate the potential behind the ASP concept let’s make the following thought experiment: Assume it is possible to stack 20 bipolar anodecathode pairs (instead of 12) in one ASP electrolyser. Additionally you put 2 of these stacks into one electrolyser so one electrolyser would now have dimensions of 3 x 6 x 3,5 m3 (W x L x H), and the increased electrode area would permit 300 kA at only incrementally higher current density. Imagine a smelter with 100 ASP electrolyser units, and the capacity would be a whopping 1.720.000 tpy!

Looking forward, it looks as though the Hall-Héroult process at its 128th anniversary is here to stay for quite

some time. Alternative processes are not close to any kind of industrial implementation.

Concluding from this it means that the primary aluminium industry would continue to improve the Hall-Héroult process gradually. How far the increase in potline amperage, one-dimensional growth of cell length and ever longer potlines can be sustained before some kind of optimum configuration is reached remains to be seen.

Aluminium demand growth seems to continue in line with global urbanization and population growth, and recycling efforts should be reinforced as much as possible. However, recycled material will only continue to complement primary aluminium production which will likewise (have to) continue to be the major source of any future aluminium supplies.

7 Acknowledgements Special thanks go to my former colleagues, Dr. Robert Minto and Thiago Heitling, who helped establishing the first edition. For this second edition, I would like to thank Anne Tappen for her friendly support and Rudolf Pawlek for his private communications regarding latest intelligence on Chinese smelters.

[5] MATTHEWS, R., Alcoa Completes Acquisition of Reynolds Metals, The Wall Street Journal, New York 04.05.2000 [6] New Alcan hungry for more acquisitions: Earnings surge, National Post, Montreal 17.10.2000 [7] Metals Giant files for bankruptcy, BBC News, 12.02.2002, http://news.bbc.co.uk/2/ hi/business/1816870.stmv [8] Kaiser restarts Gramercy alumina refinery, Metal Bulletin, 18.12.2000, 5 [9] Can Jack Hockema make Kaiser fly?, American Metal Market, 13.03.2006 [10] Norsk Hydro acquires VAW, Metal Bulletin 07.01.2002 [11] Regulation (EEC) No. 4064/89, Merger Procedure, ALCAN/PECHINEY (II) EEComm. 53, 29.09.2003, http://www. worldlii.org/eu/cases/ECComm/2003/53. html#Heading5#Heading5 [12] Alcoa to offer to acquire Alcan for US$73.25 per share in cash and stock, Business Wire 07.05.2007 [13] Recommendation to Reject the Alcoa Offer, Excerpts from May 22, 2007 Directors´ Circular, Alcan Presentation, downloaded from Alcan website (website no longer exists) [14] Hydro will pay $4.9 billion for Vale´s aluminium assets, Metal Bulletin 10.05.2010,5

[1] HEIL, J., Minto, R., Heitling, T., Aluminium Reduction Cell Technology Providers – an Updated Review, Proceedings of the European Metallurgical Conference Emc 2011, Volume 3, pp 793 – 824, Düsseldorf, Germany, 2011

[15] Vale concludes sale of Al, alumina and bauxite assets to Hydro, Metal Bulletin 28.02.2011 [16] BILLINGHURST, D. et al.,Development of B32 Cell Technology, in: Light Metals 2006, Proceedings of the Annual TMS Aluminium Committee Meeting, GALLOWAY, T. J. (Editor), A Publication of TMS, Warrendale 2006, 255 – 257

[2] TABEREAUX, A. (2000): Prebake Cell Technology: A Global Review, Journal of Metals, February 2000, 23 – 29

[17] DROZDOV, A., Aluminium: The Thirteenth Element – Encyclopedia, The RUSAL Library, Moscow 2007, 81

[3]SAGAFO,O,Eine norwegische Erfolgsgeschichte – Hydro 1905 – 2005, Pax Forlag, Oslo 2005

[18] History of the Russian Aluminium Industry, http://rusal.ru/en/aluminium/ history.aspx

[4] Data for LME price chart extracted from: http://www.indexmundi.com/commodities/ ?commodity=aluminum&months=360

[19] RusAl Company History, http://rusal. ru/en/about/history.aspx

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AWJ 2014 43

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44 PRIMARY SMELTING AND PROCESSES

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[80] XIQUAN, Q. et al., Successful commercial operations of NEUI400 Potline, in: Light Metals 2010, Proceedings of the Annual TMS Aluminium Committee Meeting, JOHNSON, J. (Editor), A Publication of TMS, Warrendale 2010, 359 – 363 [81] BAN, Y. et al., Baking Start-up and Operation Practices of 400 kA Prebaked Anode Pots, in: Light Metals 2010, Proceedings of the Annual TMS Aluminium Committee Meeting, JOHNSON, J. (Editor), A Publication of TMS, Warrendale 2010, 369 – 373 [82] DINGXIONG, L. et al., New Progress on Application of NEUI400kA Family High Energy Efficiency Aluminum Reduction Pot (“HEEP”) Technology, in: Light Metals 2011, Proceedings of the Annual TMS Aluminium Committee Meeting, LINDSAY, S. (Editor), A Publication of TMS, Warrendale 2011, 443 – 448 [83] DINGXIONG, L. et al., Development of NEUI500kA Family High Energy Efficiency Aluminum Reduction Pot (“HEEP ”) Technology, in: Light Metals 2011, Proceedings of the Annual TMS Aluminium Committee Meeting, LINDSAY, S. (Editor), A Publication of TMS, Warrendale 2011, 455 – 460 [84] JIANPING, P. et al., Development and Application of an Energy Saving Technology for Aluminium Reduction Cells, in: Light Metals 2011, Proceedings of the Annual TMS Aluminium Committee Meeting, LINDSAY, S. (Editor), A Publication of TMS, Warrendale 2011, 1023 – 1027 [85] BALOMENOS, E. et al., Theoretical Investigation of the Volatilization Phenomena Occurring in the Carbothermic Reduction of Alumina, Erzmetall 64 (2011), 6, 312 – 320 [86] Grjotheim, K. et al., Aluminium Electrolysis, 2nd Edition, Aluminium-Verlag, Düsseldorf 1982, 17 – 21 [87] Thonstad, J. et al., Aluminium Electrolysis, 3rd Edition, Aluminium-Verlag, Düsseldorf 2001, 340 – 341 Author: Dr.-Ing. Joachim Heil Contact Information: jogaheil@t-online.de

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AWJ 2014 45

START-UP OF ARVIDA SMELTER, AP60 TECHNOLOGICAL CENTER. well as other physical constraints, the target intensity of the prototype was set at 550 kA. Table 1 shows performance results achieved with the cell over a 6 month period.

Key indicator

Results

Intensity (kA)

550

Current efficiency (%)

94.2

SEC (kWh/t)

13260

Table 1. Performances of AP60 prototype cell at LRF over 6 months

The Arvida Smelter AP60 Technological Center

Fig 1: Arvida Smelter, AP60 Technological Center.

Introduction A new milestone for reduction technology has been recently reached with the successful start-up of the Arvida Smelter, AP60 Technological Center in Jonquière, Quebec, Canada. Since December 2013, the 38 first generation AP60 cells deliver an annual production capacity of 60,000 tons of aluminium.

Starting from the development of the first prototype AP60 cells, this article presents the start-up of the new smelter in 2013 and gives an overview of the future Rio Tinto Alcan reduction technology developments to come.

Development of AP60 at the LRF The development of AP60 technology started 4 years ago at the Rio Tinto Alcan â&#x20AC;&#x201C; Laboratoire de Recherche des Fabrications (LRF) installation in Saint-Jean de Maurienne, France.

Reducing Full Economic Cost (FEC) using new knowledge developed in Rio Tinto Alcan R&D centers was the key driver that pulled up the development of AP60 over formally proposed AP50 technology.

Key Development steps of AP60 technology at prototype level AP60 was designed using in-house Rio Tinto Alcan specialized thermoelectrical, MHD and thermo mechanical models. After the design phase, it was decided to build one cell at the St-Jean de Maurienne LRF facility in France in order to test the performance of the technology at a prototype level while at the same time starting the construction of the new Arvida Smelter, AP60 Technological Center in Saguenay.

The AP60 prototype cell was started in December 2011. Taking advantage of the numerous AP30 reduction potlines and cells, a large number of the technology bricks used in the cell design had already been optimized and tested on AP30 technology. For example, the design of the low resistance cathode has been tested on hundreds of AP30 cells. This capability to test technology bricks on several cell technologies (AP18, AP30, and P155) has sped up and strengthened the AP60 cell development.

Due to substation limitations at LRF as

46 PRIMARY SMELTING AND PROCESSES

While the prototype cell at the LRF did operate at 550 kA, the objective of the Arvida smelter AP60 Technological Center is to operate the AP60 technology up to 600 kA. Some of the differences between the prototype cell and the cells at the Arvida Smelter AP60 Technological Center include; anode height, cover material composition, magnetic fields and exhaust gas flow rate. All these differences were analyzed and taken into account in the industrial design of the cell, and in the projected plant performance.

The notice to proceed for construction of the 38 cell demonstration plant was awarded in December 2010. The substation was built in order to sustain a future expansion to a full line smelter.

Technology Transfer Process The rigorous Rio Tinto Alcan process of technology package transfer was a key element of the strategy to build the Arvida Smelter AP60, Technological Center (Figure 1). This methodology ensures that all engineering phases are done with carefully controlled information. Emphasis was put on quality control by technology experts for the most important aspects of the new technology. The plant was designed, engineered and built without having to go back to the drawing board and without any constructional issues being encountered.

specialized thermocouples on the cathode surface and other measurement techniques.

Out of the 38 cells, 11 were started using a dry start-up methodology. This way of starting a cell is important as it provides a method for starting a greenfield smelter without having liquid bath at hand.

For all 38 cells, an extensive measurement campaign was performed to provide data on mechanical behavior of the shell, superstructure and busbar at start-up and during the stabilization phase. Among the measurements done were the dynamic deformation of the shell and superstructure.

Fig 2: AP60

Given that the new plant will be the platform for future developments of the AP60 technology, strategic R&D equipment was integrated into the package at the construction phase. A booster section, complete with exhaustive instrumentation for cell monitoring, will be used by R&D teams with expertise in modeling, measurements, cell design, and operation to develop the full potential of the technology.

The commissioning of the technology At the end of the construction phase, the plant was turned over to the operations team who began a series of tests to commission the new equipment.

Among these tests were those more specifically related to the ability of busbars to handle 600 kA of current intensity. Measurements of temperature, displacement of the busbars and short circuit equipment testing were done at different current intensities allowing development of an in-depth knowledge of this critical subject.

The short circuit tests were followed by magnetic field testing of potroom equipment. The level of amperage of AP60 technology leads to the development of very high magnetic fields (greater than 600 gauss). It was identified early on as a technology risk that the magnetic field may cause

malfunctions of potroom equipment.

Well before the start-up phase, many components were tested in high magnetic fields and mitigation plans were put in place. Even with all this early testing, it was still found that some equipment had to be modified. However, no significant outstanding issues were found at this late stage confirming the efficiency of the rigorous gate process used along the implementation of the project.

During this time, more general potroom equipment testing was also being performed. This phase allowed operators to be trained and get used to the new equipment and operating procedures. This also allowed operating people to interact with internal technology experts dispatched on the site to increase local knowledge of the new AP60 technology.

Cells start-up The 38 cells of the smelter were started in Q4 2013. The first two cells were started at 550 kA while the remaining 36 were started at 560 kA. Each AP60 cell required the addition of up to 14 t of liquid bath.

Before adding the liquid bath to the cell, the preheating phase was critical to limit the risks of infiltration. This phase was carefully controlled using

The measured values were compared with the modeled ones and the deviations were analyzed. The results will be used for further development of the technology.

The start-up of the line was accomplished according to the schedule and without significant start-up and early life issues, a tribute to the expertise of all the teams involved.

Early results at Jonquière.

The MHD modeling software developed by the RTA R&D teams has evaluated the bath metal interface of the LRF cell and the Arvida smelter cells. It shows that the Arvida smelter cells will have a flatter interface than the LRF cell, opening the way for very promising results.

This prediction has been confirmed by the early operation of the cells at the Arvida smelter. After a few months of operation at 565 kA, the cell stability was very good. The cellâ&#x20AC;&#x2122;s instability (WRMI) was less than 40 Nano-Ohms.

This unique cell stability will be used for further development of the AP60 technology.

After the initial start-up phase, current intensity has been ramped-up from 560 kA to 565 kA in Q1 2014.

AWJ 2014 47

A specific and comprehensive performance test will be done to assess the industrial performance of the technology. At the time this article was written, the performance test is planned to be organized in Q2 2014.

The next steps of the AP60 technology development.

As table 3 shows, the two technologies have been developed and tested in parallel, using the same optimizedframework (busbars, shell and superstructure) and equipment to operate the cells. Specific elements such as cathodes, anodes, and shell ventilation differentiate the two cell designs in order to operate at a high amperage (AP60) or low energy (APXe).

The Arvida Smelter, AP60 Technological Center will be the platform for future development of the AP60 technology. Table 2 shows the targets for the development of this technology.

13,5 kWh/t

Intensity (kA)

570

600

12,0

SEC (kWh/kg)

13.3

13.0

11,5

Production (t/day)

4.31

4.51

AP60 and APXe In response to market demands, Rio Tinto Alcan has developed a strategy based on a common platform able to deliver high performance cells: a high amperage cell with AP60; and a low energy cell with APXe.

AP50

13,0

AP60 Second Generation

The center will also be used to develop new environmental technology as well as operational automation development such as a fully automated anode change.

Conclusion The 38 AP60 cells have been successfully started in the new Arvida smelter AP60 Technological Center. In delivering the project, Rio Tinto Alcan teams

14,0

AP60 First Generation

Table 2. Futures targets of AP60 Technology

ment), APXe will benefit from the industrial validation of AP60 at Arvida Smelter.

12,5

450

Hi Productivity

AP60

LE

APXe 500

550 Amperage (kA)

600

650

Figure 3: Operating regions of new AP cell technologies

AP60 will operate at 600 kA with energy consumption in the 13-13.3 kWh/kg range. APXe will operate around 500 kA with an energy consumption target of 12 kWh/kg (see Figure 3).

In addition to energy efficiency and cost-effectiveness, AP60 and APXe comply with Rio Tinto Alcan’s demanding HSE standards.

Since APXe (low energy) and AP60 (high productivity) share the same optimized framework (busbars, shell, superstructure and operating equipAP60

APXe

Busbar

Common

Shell

Common

Superstructure

Common

Alumina Feeding device

Common

Anode assembly

Common

Cathode and Lining

High productivity

Low energy

Shell ventilation

High productivity

Low energy

Gas flow

High productivity

Low energy

Pot Control System (Alpsys™)

Common

Equipments (Pot Tending Assemblies, Vehicles, ladles,…)

Common

Buildings

Common

Table 3. AP60 and APXe configuration

48 PRIMARY SMELTING AND PROCESSES

have shown complete mastery of all aspects of this very challenging high amperage pot technology, from design to construction, to start-up and finally operation. This represents an important milestone for the aluminum industry as AP60 dramatically increases cell productivity over previous technologies.

The new industrial platform is already equipped with a booster and will be the basis for future development of the technology.

With the validation of AP60 at the Arvida Smelter, AP60 Technology Center and the APXe cell at the LRF, these two technologies enable Rio Tinto Alcan to stay in the vanguard of reduction technology for the benefit of its own pipeline of internal growth projects, and of the projects of its partners and customers.

The authors would like to thank all of the pioneers involved in the development, construction and demonstration of the AP60 technology from both France and Canada.

© Norsk Hydro © Dubal

Expertise in Alumina handling FLSmidth® is your expert in handling of fresh alumina, reacted alumina, crushed bath and aluminiumfluoride s

Large capacity storage silo including anti-segregation filling and discharge

s

MÖLLER® airlift conveying

s

Pressure vessel dense phase conveying either with MÖLLER Turbuflow® or standard conveying pipe

s

Truck/wagon loading and unloading stations

s

Dosage systems

s

MÖLLER Fluidflow® pipe air slide conveying systems

s

MÖLLER direct pot feeding systems

s

PTM filling stations

s

Modular designed systems - plug and play -

FLSmidth Hamburg GmbH Tel: +49 4101 788-0 s hamburg@flsmidth.com www.flsmidth.com

AWJ 2014 49

MÖLLER Alumina Handling Systems – High performance, high efficiency

About FLSmidth FLSmidth® is a market-leading supplier of equipment and services to the global minerals and cement industries.

FLSmidth supplies everything from single machine units to complete minerals and cement flow sheets including associated services.

With more than 15,000 employees, FLSmidth is a global company with headquarters in Denmark and local presence in more than 50 countries including project and technology centres in Denmark, India, USA and Germany.

FLSmidth has over the past 131 years developed a business culture based on three fundamental values: competence, responsibility and cooperation.

It is FLSmidth’s vision to be the customers’ preferred full-service provider of sustainable minerals and cement technologies. This is reflected in focused research and development efforts aimed at fulfilling customers’ future needs in terms of innovative technical solutions, high reliability and availability, minimum environmental impact and the lowest possible product lifecycle costs.

FLSmidth’s in-house resources are primarily engineers who develop, plan, design, install and service equipment, with most manufacturing being outsourced to a global network of subcontractors. This has proven to be both a robust and sustainable business model.

FLSmidth therefore has a flexible cost structure, which makes it possible to plan and adjust resources to prevailing market conditions.

FLSmidth is a learning organization, and our people are our most valuable resource. FLSmidth’s strategy entails strong emphasis on selecting, attracting and retaining the right people who can support value creation in FLSmidth.

FLSmidth in the alumina business FLSmidth first entered the alumina industry more than 100 years ago. Today FLSmidth has an experienced team of engineers and support staff with extensive alumina experience located in offices around the world – and offers the latest equipment for most areas of an alumina plant.

50 PRIMARY SMELTING AND PROCESSES

Red side, white side and alumina handling Based on the Bayer process, invented by the Austrian chemist Josef Bayer, the alumina production process can be split into a ‘red side’ and a ‘white side’.

Red side solutions FLSmidth offers equipment for the complete bauxite handling, storage, crushing and grinding flowsheet, complementing the digestion or dissolution of bauxite in hot caustic liquor. This is followed by the complete SettlerWasher train flowsheet for Red Mud using the leading technology acquired from Dorr-Oliver Eimco.

White side solutions FLSmidth offers white side equipment, covering the complete flowsheet after the hydrate precipitation process, including MÖLLER equipment technology for alumina handling and load-out.

Overall, FLSmidth equipment covers more than 50 percent of the equipment needs of a complete alumina plant, from the bauxite mine to the above refinery equipment. In addition,

FLSmidth also offers all equipment for alumina handling in the smelters.

MÖLLER Technology Through its MÖLLER® technology, FLSmidth specializes in design, engineering, procurement, erection and commissioning of pneumatic material handling systems for turnkey projects and components for the alumina industry. Our capabilities of handling fresh alumina, reacted alumina, crushed bath and aluminium fluoride comprise: • Large capacity storage silos (up to 85.000 t realized) including antisegregation filling and discharge • MÖLLER airlift conveying systems (up to 6oo t/h realized) • Pressure vessel dense phase conveying either with MÖLLER Turbuflow® or our standard conveying pipe • MÖLLER screw pump conveying systems • Truck/wagon loading and unloading stations

• Dosage systems • MÖLLER Fluidflow® pipe air slide and rectangular air slide conveying systems • MÖLLER direct pot feeding systems either with 100% MÖLLER Fluidflow pipe air slide conveyiing technology or as a hybrid of MÖLLER Turbuflow conveying pipe and MÖLLER Fluidflow pipe air slide • PTM filling stations • Modular designed systems – plug and play For more than 75 years the MÖLLER® brand has stood for high quality standard systems with more than 5.000 references worldwide.

Presently FLSmidth‘s Hamburg office is executing three main orders in the aluminum smelter industry.

plying two MÖLLER direct pot feeding systems, reacted alumina silos, PTM filling stations, fresh alumina truck unloading stations and pressure vessel dense phase conveying systems for a mix of crushed bath/alumina oxide.

2. UC RUSAL/RusHydro’s Boguchansky Aluminium Smelter - A MÖLLER direct pot feeding system is under installation.

3. CVG ALCASA, Venezuela - Supply of a MÖLLER pot feed system for two production lines consisting of a total of 400 electrolytic cells. The installation and commissioning has to be executed during operation of the smelter and shows the high adaptability of this proven technology to serve brownfield aluminium smelters.

FLSmidth Hamburg GmbH Haderslebener Strasse 7 25421 Pinneberg, Germany hamburg@flsmidth.com

1. Emirates Aluminium Smelter Phase 2 – with a length of 1.640 m the longest pot rooms ever build - FLSmidth is sup-

AWJ 2014 51

Inline concentration monitoring in cleaning, pickling and etching baths

Figure 1: Directly in the bath the LiquiSonic® analyzer of SensoTech measures quickly and accurately the cleaner concentration and degree of contamination.

Efficient cleaning of industrial parts and treatment of surfaces by inline analytical technology Concentration fluctuations in cleaning and treatment baths affect the bath quality and resource efficiency if meeting desired nominal values ​​is not monitored continuously or only imprecisely. Since the initial cleaner concentration decreases during the process, without proper bath monitoring the replenishment will be either too much or too little. Underdosing of the cleaner results in not meeting the cleanliness requirements; overdosing results in wasting valuable resources.

Further, the degree of bath contamination is subject to fluctuations that influence the cleaning performance and resource efficiency. During the cleaning process, the degree of contamination increases steadily. Having the information about reaching the contamination limit, bath changes can be done efficiently. Consequently, costs caused by frequent bath changes, which are reflected in the energy and raw material consumption, can be reduced.

Cleaners are aqueous, anhydrous, basic or acidic agents, for example. To measure the concentration of the cleaner and the degree of contamination in the bath continuously, accurately and quickly, the LiquiSonic® analyzer of SensoTech will be directly integrated into the process. Figure 1 shows an immersion sensor and the controller of the analyzer. The technology measures inline and properly in various bath liquids, because the measuring method is independent of the turbidity, colour and conductivity of the liquid and has a high tolerance of soiling as well. The automatic real-time measurements every second show immediately how much cleaner must be replenished to keep the cleaning result constant. This eliminates time-consuming manual measurements, which provide delayed laboratory results.

For example, the analyzer is used in cleaning and degreasing baths, in rinsing baths, pickling and etching baths and coating and plating baths as well.

Numerous industries like metal, automotive, semiconductor or plastics industries, include such surface and

52 PRIMARY SMELTING AND PROCESSES

cleaning processes. In metal production, the LiquiSonic® technology is applied particularly in pickling baths. In this application, the analyzer monitors the concentration of acid or alkali, so that the replenishment can be done immediately and automatically. Moreover, in pickling baths LiquiSonic® also analyzes the content of the iron salt, which arises as a by-product in the bath due to the consumption of acid or alkali. In addition to monitoring pickling baths, the inline analytical technology optimises further process stages in metal production. For example, these include acid regeneration processes, rolling emulsion controls or electrolyte analyses in continuous galvanizing and roller chrome plating.

The pickling process Pickling baths are used downstream of the hot rolling process to clean, modify or passivate metal surfaces and to remove tinder or rust for the further treatment in the following production steps. Finally, the metal can be reformed in the cold rolling process, for example, or electrolytically galvanized within the surface refinement.

Figure 2: The pickling process can include several LiquiSonic速 measuring points for optimal process monitoring.

Pickling baths primarily contain solutions or mixtures of different mordants.

There are either diluted acids or bases used. For example, typical chemicals are sulfuric, hydrochloric, phosphoric or nitric acid as well as caustic soda.

During the process, the concentration of the mordant decreases, whereas the portion of interfering components such as metal salts increases at the same time. In order to keep the pickling bath quality in an optimal range, it is necessary to redose with fresh acid or lye in a targeted manner. Moreover, the metal salts do not only arise by etching of contaminations, but also the mordant dissolves the metal surface.

In order to produce with an awareness of quality, economic factors and the environment, checking the concentration of the bath ingredients precisely and continuously is required.

The permanent bath analysis reduces the frequency of bath changes and avoids overdosages. Thus, it leads to resource-efficient process control. In addition using online monitoring, an optimum pickling result is ensured.

For this purpose the LiquiSonic速 analyzer of SensoTech is integrated directly into the pickling plant. Figure 2 represents a pickling process including different LiquiSonic速 measuring points for optimum monitoring of each process step. The analyzer consists of one or more sensors and one controller. Installing the sensors into the bath pipeline is easy and suitable for every cleaning or surface processing plant.

For an effective measurement neither a bypass nor smooth flow pipe sections are necessary. Due to the robust construction and corrosion-resistant material, the sensors are maintenancefree with a long lifetime. SensoTech offers immersion sensors with variable lengths or flange sensors.

Due to the option of a separated electronic housing, the sensors can be even installed in mini-plants with limited space. In case of low liquid flows, flow meter adapters having a minimum dead volume are used.

The measuring results are updated every second and are available immediately and at any time. The controller

visualizes and manages the data that can be transmitted to control systems via fieldbus, analog outputs, serial port or Ethernet. Thus an automatic, targeted cleaner dosage is guaranteed. For process transparency and traceability, the measuring data are permanently recorded and stored in the controller.

Clear trend charts and custom data protocols provide a comprehensive overview of the process flow. In consequence of the reproducible process management, it is possible to always operate the pickling plant in optimum condition.

Sonic velocity combined with conductivity The bath liquid consists of the following components: water, acid or lye and metal salts. The metal salts accumulate through the reaction of the mordant with the metal in the bath.

The concentration monitoring of the pickling solution and of the salts is essential for optimal bath results. In such a 3-component mixture two physical values are necessary to determine the single concentrations of these both substances. The measuring principle is

AWJ 2014 53

Inline concentration monitoring in cleaning, pickling and etching baths

Figure 3: For concentration measurement in a 3-component mixture, a LiquiSonic® measuring point consists of a sonic velocity flange or immersion sensor and a conductivity probe.

based on the different effects exerted by concentration changes of a liquid‘s single components on physical values such as sonic velocity, conductivity or density. This characteristic is stored as a calculation model in the LiquiSonic® controller, so that the measuring results of the physical values can be converted into concentrations. So measuring two physical values concurrently, the simultaneous determination of two concentrations can be realized.

According to studies, sonic velocity combined with conductivity has turned out as the best measuring method.

Therefore, the LiquiSonic® analyzer consists of a sonic velocity sensor and a conductivity probe. The sonic velocity sensor measures the concentration of the mordant and is made of stainless steel or Hastelloy. In aggressive chemicals the stainless steel sensor is coated with a special material such as Halar or PFA. The conductivity probe is made of PEEK or coated with PFA. Thus, both type of sensors are corrosion-resistant in almost all chemicals and can be used at temperatures of up to 180 °C. Furthermore, the LiquiSonic® sensors

feature a highly efficient ultrasonic ceramic that ensures a proper measurement even in the event of a high proportion of gas bubbles in the liquid.

The conductivity probe measures the salt concentration and is connected, together with the sonic velocity sensor, to the controller. Figure 3 shows a LiquiSonic® measuring point, where a flange sensor and a conductivity probe is installed into a pipeline.

Use at AMAG The company AMAG Austria Metall AG is the nation´s leading manufacturer of aluminium semis and casthouse products for the processing industry.

The group purchased the LiquiSonic® analytical technology of SensoTech that is used successfully to optimize the processes in the aluminium pickling plant. The bath operates with caustic soda at a temperature between 50 °C and 70 °C. Therefore, it consists of water, sodium hydroxide and sodium aluminate. Sodium aluminate results from the reaction of sodium hydroxide with aluminum. In the past AMAG worked in a batch process and used a titration analysis to control the pickling bath. However, this measuring method presents problems because of manual

54 PRIMARY SMELTING AND PROCESSES

sampling and time delays of the measuring results. Consequently, the goal was to control inline and in real time the quality of the pickling bath.

By the installation of the LiquiSonic® analyzer, this challenge has been satisfactorily resolved. The combination of sonic velocity and conductivity measurement makes it possible to analyze the pickling process continuously. The concentration of caustic soda is determined by an immersion sensor made of stainless steel and the concentration of sodium aluminate by a conductivity probe made of PEEK. Both sensors are mounted with flange fittings in a DN 50 pipeline close to each other. The rugged sensor design, non-corrosive materials and the resistant sensor and controller housing prepare the analyzer for best usage under tough production conditions. Figure 4 shows the installed LiquiSonic® immersion sensor in the pickling plant of AMAG. Via Profibus the measuring data are passed to the process control system. The results are reproducible and logged in the LiquiSonic® controller.

In case of exceeding or falling below a predefined threshold, or if process

Figure 4: In the pipe of the aluminium pickling plant of AMAG Austria Metall AG the LiquiSonic® immersion sensor is installed to monitor inline the concentration of caustic soda.

problems occur, the analyzer immediately signals an alarm. Therefore, it is possible to react quickly on deviations and take countermeasures. “In our case, changing to the continuous process was very important, because in the past we had to stop the pickling process once a week to exchange the bath. Using the inline analyzer of SensoTech, we are now able to control our pickling process continuously and in a targeted way. So we have gained in yield significantly and can save production costs”, explains Christian Pointner, Process Engineer at AMAG.

Conclusion The inline analytical technology LiquiSonic® measures precisely, continuously and directly in the process the cleaner concentration as well as the degree of contamination in various bath liquids. This enables an accurate and automatic replenishment of cleaner and an efficient control of bath changes. An application focus is pickling baths in the metal industry, for example. In these kinds of baths, the analyzer monitors the concentration of the pickling solution and of the metal salt. Via common interfaces, the analyzer can be integrated into existing control systems.

The online monitoring leads to an efficient, safe and eco-friendly run of the pickling process. On the one hand significant results are quality assurance and increasing the yield.

On the other hand costs are reduced by saving energy and material.

Author: Ms. Rebecca Dettloff Marketing Manager SensoTech GmbH Steinfeldstr. 1 D-39179 Magdeburg-Barleben GERMANY Contact: Headquarters SensoTech GmbH Steinfeldstr. 1 D-39179 Magdeburg–Barleben Germany U.S. Office SensoTech, Inc. 1341 Hamburg Tpk., Suite 2-3 Wayne, NJ 07470 USA

SensoTech: For over 20 years SensoTech has been focused on the development, manufacturing and sales of inline analysis systems for process liquids. With worldwide installed, highly precise and innovative measuring systems for monitoring of concentrations, compositions and changes of chemicals as well as properties directly in the process, SensoTech has significantly contributed to the enhancement of the state-of-the-art. In addition to the measurement of concentration and density, the phase interface detection as well as the monitoring of chemical reactions like polymerization and crystallization are typical applications. SensoTech inline analyzers set standards in the technological and qualitative valence, user friendliness and reproducibility of process values. Special calculation methods and sophisticated sensor technologies enable reliable and precise measuring results even under the most difficult process conditions.

The knowledge and the experiences of the highly motivated and committed SensoTech staff are the result of many different applications supported by well-known customers from the chemical and pharmaceutical industry, food technology, semiconductor technology, automobile and metal industry as well as many other industries. In addition, these experiences also open up unimagined solution possibilities for new measuring challenges.

T + 49 39203 514100 F + 49 39203 514109 info@sensotech.com www.sensotech.com T +1 973 832 4575 F +1 973 832 4576 sales-usa@sensotech.com www.sensotech.com

AWJ 2014 55

Precise Anode Beam Positioning from Power Jacks

UK Manufacturer Power Jacks has been a supplier to the Primary Aluminium Industry for Anode Beam Positioning Systems ever since the very first commercial smelters were established.

Based near Aberdeen in Scotland, at the heart of the North Sea Oil & Gas industry, the company manufactures for a diverse range of industries where lifting and position solutions are required and exports its products to more than 70 countries worldwide.

The products are supplied to end users and OEM’s in various sectors including Energy, Industrial Automation, Defence, Medical, Transport and Civil Engineering.

The Company was presented with a Queens award for Enterprise in International Trade in 2011.

The company’s product portfolio includes screw jacks, actuators and lead screws that offer an electromechanical alternative to hydraulic actuation for positioning applications with loads from a few kilograms to hundreds of tonnes.

Electromechanical solutions can provide significant advantages over hydraulics, not least removing the need for expensive hydraulic pumps and pipework, but also where there is a demand for increased safety (in the event of power loss, screw jacks can be self-locking), the need for machinery to operate with better energy efficiency, machinery that operates with greater levels of precision, less maintenance or manual intervention,

Hydro

56 PRIMARY SMELTING AND PROCESSES

and also providing cleaner and quieter solutions.

While users normally associate the term ‘jack’ with lifting, the company is keen to emphasise that its products are used for many different applications in industry. As well as lifting and lowering, the products are equally used for tilting and pivoting, rolling, locking/unlocking and tensioning of loads in any direction.

The energy sector is a key market for the company with many applications in the Oil and Gas industry, both topside and subsea with bespoke pressure compensated products operating successfully 3000m below the surface on the seabed. Applications in renewable energy include wind, wave and increasingly solar energy where they are used to position mirrors (or heliostats) in large solar arrays.

For the Primary Aluminium industry, in particular aluminium smelter pot rooms, screw jack systems are the tried and proven method for the lowering

and precise positioning of the anodes and anode beams and also for “highjacking” of frozen pots. The same method is used in both Soderburg and Prebake although jack styles and configurations vary depending on the technology employed.

The screw jacks can be individually motorised or mechanically linked through a combination of transmission elements and the anodes are positioned via an electronic control system.

The company says it has more than 15,000 units deployed in smelters around the world. Lifetime spares generally represent less than 1% of the total capital investment over the lifetime of the products being least 35 years.

This demonstrates the quality and reliability of the products in what is an integral function of the potroom operation.

For positioning the anode beam on a reduction cell, the company designs

products to cope with the harsh operating environment encountered in an aluminium smelter.

The use of special alloys and heavy duty sealing arrangements protect the product from abrasive alumina dust to ensure durability.

Products are designed that allow specifically for side-loading stresses caused by thermal expansions on the superstructures with either tilting or swivel mechanisms, used extensively in pre-bakes where the beam is not self-supported, allowing for pivoting movement in the lifting screw from the vertical in any direction.

Power Jacks has developed products to suit reduction cells derived from all the major PB technologies including Alcoa, Alusuisse, Dubal, Hydro, Kaiser, Pechiney, Reynolds, VAW and others.

In tailoring a product to fit within the OEM’s superstructure, Power Jacks aim is to minimise potline cost and support the client to maximise yields.

The company says that while reduction cell amperages have increased significantly as has the carbon area with the use of larger anodes, there is scope to optimise the anode-cathode interface.

Power Jacks believes that as many smelters constructed 40 – 50 years ago will ultimately need to replace their anode beam positioning systems, new technology could offer the industry greater positional accuracy that could lead to significantly reduced running costs.

In pre-bakes, the anodecathode interface should ideally remain constant at a level where the voltage maintained is as close as possible to the theoretical tension imposed by the electrochemical reaction and the Faraday efficiency is highest.

If the interface is too high, parasite Joule effect causes heat losses in the bath. If too short, the same occurs in the anode and stem.

Dubal

AWJ 2014 57

Dubal

Alusuisse

Pechiney

58 PRIMARY SMELTING AND PROCESSES

Traditional jacking systems adjust periodically the interface by lowering the anode system. This frequency in a pre-bake is generally much lower than the alumina feed frequency which itself provokes a change in bath resistance and justifies an adjustment.

Without going into print on details, the company claims that a new design of anode jacking system could offer both greater positional accuracy, continuous duty cycles and load feedback information enabling the anode to be adjusted in conjunction with the alumina feed.

Power Jacks is interested in talking to aluminium smelters willing to act as partners for the new technology.

In addition to new installations, the company offers of all existing anode beam positioning systems in the field whatever the origin. It recognises the need to eliminate downtime and will work with smelters to offer fast repairs and to establish annual spares requirements.

Author: Bruce Bultitude, Managing Director, Power Jacks Ltd. Contact: bruce.bultitude@powerjacks.com www.powerjacks.com

www.powerjacks.com AWJ 2014 59

60 PRIMARY SMELTING AND PROCESSES

ANODE PLANT TECHNOLOGY Fives Performance of the Eolios Pitch Fume Treatment System

p. 62-65

Hydro historical evolution of closed type anode baking furnace technology

p. 66-71

An Immediate Step In Cost Reduction For Inert Anodes Louis Dekker

p. 72-73

Innovatherm Operational and environmental benefits of the new baking furnace at Boyne Smelters by use of an advanced firing technology

p. 74-81

Upgrade of an existing Fume Treatment Plant at ALUAR to cope with higher production in the new open type anode baking furnaces

p. 82-87

AWJ 2014 61

Performance of the Eolios Pitch Fume Treatment System Coal Tar Pitch: The Source of PAH Emissions Nature of PAHs PAHs are the main components of coal tar pitch, used as a binder for the fabrication of anodes. To be used in the process fabrication of anodes, it is heated to become liquid and is mixed with pre-heated aggregates (Calcined Petroleum Coke) to obtain a homogeneous hot paste (160200°C).

Eolios at Qatalum paste plant

By Belbachir Salima, Solios Carbone and Alix Courau, Solios Environnement Green anode plant activities for aluminum smelters generate noxious vapors containing CTPV (Coal Tar Pitch Volatiles) – especially PAHs (Polycyclic Aromatic Hydrocarbons). Fumes collection and treatment prevent the release of these pollutants into the working environment and atmosphere.

Traditional pitch volatile capture has been performed with coke injection followed by filtration (conventional dry scrubbers).

In recent years, RTOs (regenerative thermal oxidizers) have been used at some plants to improve PAHs destruction particularly on the lighter fractions characterized by their low boiling point. In order to increase destruction efficiency at lower operating costs, Fives Solios provides a dual approach based on the combination of a conventional dry scrubber and an RTO. In such an approach, the RTO is dedicated to hot pitch fumes, while the dry scrubber is dedicated to lower light PAH fraction emissions This combined solution is named Eolios and has been successfully installed in Mosjøen, Norway and in Qatalum, Qatar.

Upon reaching this temperature range, the coal tar pitch releases a high amount of CTPVs which are mainly composed of PAHs. PAHs can be divided into two groups: light and heavy fractions.

The EPA regulation has identified 16 PAH molecules as priority pollutants to monitor, based on their carcinogenicity and occurrence, including naphthalene whose carcinogenicity for human health is today contested by some studies. The OSPAR regulation only monitors 11 PAH molecules, which are mainly the heaviest PAHs, i.e. the most carcinogenic ones.

PAH Emissions in the Fabrication Process of Anodes In paste plants, PAH emissions occur in all areas where coal tar pitch is used or stored at a high temperature. The main areas affected by these emissions are the paste mixer, the paste cooler and the anode forming area.

The proportion of light PAHs appears to be 70% of total emissions, compared to around 30% for heavy PAHs. The anode paste cooler equipment has been introduced in the anode fabrication process to improve anodes density. Using water to cool down anode paste lowers the partial pressure of PAH vapors generated by the paste, thus realigning the equilibrium towards the production of light PAH fractions.

Consequently, adding water into the paste cooler drastically increases the

62 ANODE PLANT TECHNOLOGY

amount of light PAHs. This phenomenon was first confirmed at the Alcoa Deschambault paste plant, (Canada) where light PAH emissions were multiplied by six after paste cooler installation.

Conventional Coke Dry Scrubbing System The dry scrubbing system is derived from the potline alumina dry injection scrubbing technology. This treatment system was developed by Fives Solios in 1977, and has been installed since then in more than 70 plants in the world.

It consists of injecting coke fines in a gas stream loaded by pitch fumes: causing an adsorption phenomenon to occur between the coke and pitch fumes. Then, the fines fraction of coke, readily available for the preparation of the anode paste, is injected countercurrently to the fume-laden stream.

Turbulence and highly efficient contact between the pitch fumes and aerosols are thus promoted inside a Venturi reactor. Pitch loaded fines are then collected through the dust collector and reintroduced into the anode paste recipe with their condensed hydrocarbons. Finally, the clean gases are released to the atmosphere through a discharge stack.

The global PAH capture efficiency of dry scrubbing varies between 90% and 98%, depending on the treatment temperature and the list of PAHs involved.

This efficiency ratio is higher for heavy PAHs. For these components, the common efficiency is about 99.5%.

The dry scrubbing system philosophy is based on the ability of PAHs to condensate when establishing contact with coke fines inside the reactor: this allows their adsorption on the surface of coke fines. That explains the higher efficiency of the process on heavy PAH fractions, which condensate even more easily in comparison to the lighter PAHs. The most toxic PAHs being the heaviest fractions (B(a)P or equivalent), they are extremely well handled by conventional coke dry scrubbers.

Coke + Pitch

Paste Mixer

+Water Paste Cooler Coke Fines Injector

Anode Former Area

Typical Dry-Scrubbing - scheme

RTO: New Technology for a Better Destruction of light PAHs The RTO Principle PAHs, mainly composed of C-H bonds, are easily broken by oxidation as follows: CaH2b + (a+b/2) O2 --› aCO2 + bH2O + Heat

valves to isolate inlet & outlet duct fumes and one purge valve per chamber.

Eolios at Qatalum Paste Plant: An Innovative Solution for Optimum Emission Performances

The oxidation temperature is about 850-900°C, depending on the nature of PAHs. Good combustion practices include management of the “3Ts”: Temperature, Turbulence and Time.

Once the system was fine-tuned, performance tests were undertaken at the main stack by a third party. PAH emissions were measured as per ISO 11338-1-1 standard.

RTO Description

RTO at Qatalum paste plant

The RTO is a compact equipment composed of 3 main elements:

Stringent emission requirements have led Fives Solios to install the Eolios system to treat coal tar pitch fumes.

• The combustion chamber, where the oxidation reaction takes place

measurements were performed in order to estimate the relationship between RTO temperature and destruction efficiency. The FID measures the concentration of Total Volatiles Organic compounds and they show clearly that a higher combustion temperature enhances RTO efficiency due to an increase in organic compounds destruction: 91.2% efficiency measured at 840°C against 96.2% at 870°C.

• Ceramics beds, used as heat exchangers: which store and recover heat to preheat the inlet gas flow, allowing for energy savings,

The high concentrated fumes collected from the paste cooler, which contain mainly light PAH fractions and water vapor, are specifically treated by an RTO unit. Fumes emitted by the remaining pieces of equipment (mixer, vibrocompactor, etc.) are treated by a dedicated dry scrubber.

• The valve box, which includes two

A set of FID (Flame Ionization Detector)

Results display a 0.96 mg/Nm 3 concentration for 16 PAH (Norwegian Standard 9815) corresponding to a global destruction efficiency for the Eolios system of 99%. This value sets a new benchmark for Eolios designed without pre-filter.

Eolios at Mosjøen: Good Results after 6 years Fives Solios supplied its first Eolios at Alcoa Mosjøen Aluminium Smelter in 2007.

AWJ 2014 63

Stack Dry Scrubbing System

Calcined Petroleum Coke + Liquid Pitch

Paste Mixer

Electrical Hot Air Generator

Coke Fines Injection

Offers Suction Points (Anode Forming Area Mixer)

RTO

+Water

Paste Cooler

Eolios at Qatalum paste plant

On this reference, the ventilation of the green anode plant is split into two separate lines: the wet fumes line, treated with a dry-scrubber followed by the RTO and the dry fumes line, treated with a dry-scrubber only. These two lines are implemented in parallel and join each other at the stack.

On both lines in-line coke injections are installed which allow for the catching of pitch vapors on the coke fines close to the location of emissions. The dry line generates a low concentration of pollutants mainly taken in charge by a Venturi reactor with coke injection followed by filter bags. The wet line collects much more gaseous tars and PAHs treated by RTO associated to a pre-filter with coke injection.

Eolios performance has met the PAH plant requirements of 0.05 kg/h (NS 9815) or 0.8 mg/Nm3 for the whole plant.

The first important maintenance intervention on the RTO appeared after 6 years operation. Regarding the dryscrubber, regular preventive maintenance has ensured the correct running of the plant over this whole time.

Eolios vs. Full RTO The introduction of the RTO in the Eolios technology can raise a question about the possibility to use it for all paste plant streams.

The advantage of such a configuration is to have a diluted stream that is optimal for RTO operation. However, as the RTO is more efficient on light PAHs, the global destruction efficiency for PAHs in whole (light and heavy) is limited at 95%. This limited efficiency is due to the adsorption/desorption phenomenon of heavy and intermediate PAHs that occur in heat exchangers during a cycle. This configuration seems totally unable to achieve the 99% efficiency observed with Eolios at Qatalum and Mosjøen Paste plant.

An alternative to the full RTO is the Hybrid RTO which conveys highly concentrated streams directly to the combustion chamber via a specific burner.

The energy consumption for such configurations (full RTO and full Hybrid RTO) is another parameter to take into account: A more diluted stream

64 ANODE PLANT TECHNOLOGY

Mosjøen Paste Plant RTO

decreases pitch fumes concentration, taking the RTO away from auto thermal mode. A full RTO of 50,000 Nm3/h, requires around 100 m3/h of gas, whereas a RTO integrated in the Eolios technology will only consume about 20 m3/h of gas. The hybrid RTO requires even higher gas consumption, up to 120 m3/h (hybrid flow rate: 3,000 Nm3/h & main RTO inlet: 27,000 Nm3/h).

EOLIOS

RTO: 5 000 Dry Scrubber: 45,000 m3/h m3/h

97/98% (Proven) 1mg / Nm3 (Measured)

RTO: 50,000

m3/h

Full RTO

PAH16 Destruction / Capture Efficiency (NS9815) 95% max guaranteed >5mg/Nm3 (Published)

By pass: treatment by the DS during RTO maintenance <20 m3/h (44,000 €/year) 170 T/Year

By pass not possible: = redundancy required or prod. Stoppage Natural Gas Consumption 100 m3/h (220,000 €/year) CO2 Emissions 850 T/Year

Full RTO vs Eolios

Moreover, the flow rate passing through the heat exchanger is used to size the RTO. RTO dimensions will increase with flow rate, therefore considerably increasing CAPEX.

by the coke dry-scrubber and keep the RTO ready to run on dirty fumes without delay when the problem is solved and inlet conditions are back to normal operational ones.

In both configurations, the system (full RTO and hybrid RTO) cannot benefit from the biggest asset of Eolios: flexibility. RTO direct by-pass to the atmosphere does not exist in the Eolios solution, as the RTO by-pass is directed to the dry-scrubber. It means that pitch fumes are at least treated by the coke dry-scrubber in case of an unexpected problem that would require stopping the RTO. This offers an attractive possibility to switch on the dry-scrubber by-pass which remains quite “clean” in terms of emissions. This is very comfortable for operation.

Last but not least, Eolios offers a higher treatment capacity. To limit full RTO CAPEX, RTO suppliers tend to reduce the treated flow rate as much as possible, where temperature is high enough for condensation problems.

Eolios does not need to heat fumes on its dry-line, as coke injection of the dry-scrubber adsorbs tars at an ambient temperature. It is quite interesting to be able to increase ventilation of the paste plant, as the possibility to treat more air with same inlet data is directly linked to safety issues (ambient air quality in paste plant). The possibility to increase the treated air flow is also useful for revamping considerations and much easier to perform on Eolios than on a full RTO solution.

Whereas a direct by-pass must be used at the strict minimum in case of emergency, Fives Solios by-pass including fumes treatment can also be used during maintenance or operation.

An RTO has important inertia due to its ceramics and can be protected, using the by-pass, from abrupt and impetuous variations at the inlet. Therefore, any of these variations can be absorbed

from pitch vapor. Dry scrubbers remain the most efficient technology to treat heavy PAHs, however the introduction of an RTO to treat lighter PAHs is a radical improvement for the whole pitch fumes treatment system.

The Eolios solution, which combines dry scrubbing and an RTO, allows operation of the green anode plant while maintaining PAH emissions at a level below such stringent requirements.

Eolios exhibits a lower operating cost and a smaller carbon footprint than alternative technologies, such as full RTO for instance, while providing very comfortable flexibility of operation thanks to its convenient by-pass to dry-scrubber.

The implementations of Eolios at Mosjøen Paste plant and recently at Qatalum Paste plant confirm the benchmarking performance and benefits associated with this technology.

Conclusion Environmental emissions treatment requirements are becoming more and more stringent, especially for suspected carcinogenic substances such as PAH’s

AWJ 2014 65

Hydro Aluminium’s historical evolution of closed type anode baking furnace technology carbon plants in Sunndal and Årdal to supply the company smelters with sufficient quantities of anodes in the desired dimensions.

The plan was to design and construct two proprietary prototype sections.

These were tested in the baking furnace at Sunndal in 1983.

The main design criterion for the test sections was to adapt the pit geometry to new anode dimensions and to maintain or increase production capacity.

The key aims during the reconstruction of the furnace was that it should be done within the existing building, without major dimension changes to the existing concrete tub and that the distance between the headwalls was maintained.

Figure 1. Construction site of the Riedhammer furnaces #1 and #2 in Årdal (1958).

Authors: Michal Tkac1, Anders Ruud1, Inge Holden2, Hogne Linga1 1. Hydro PMT, Primary Metal Technology, Årdal, Norway 2. Hydro Aluminium Årdal Carbon, Årdal, Norway

Abstract This paper summarizes the historical evolution of the closed anode baking furnace technology from the Riedhammer design to the Hydro Aluminium concept in the Norwegian carbon plants; Årdal and Sunndal over the last 50 years.

The increasing demand for higher production and larger anodes during the last 30 years has required Hydro Aluminium (HAL) to design a proprietary high capacity HAL baking furnace concept. Some major aspects and challenges connected to the rebuilding of the furnaces are described, including maximum utilisation of the existing factory space, allowing a low CAPEX per annual production capacity.

Development of new repair and maintenance methods for critical

refractory parts were essential in order to maintain a high anode quality and to extend the furnace service life.

Main improvements related to the process control, process safety and performance data of the current technological status are presented.

Introduction Historical Development at Sunndal Furnace The production of prebaked anodes in Sunndal was initiated in connection of the paste plant start-up in 1968.

The first anodes were produced in a closed type Riedhammer furnace designed for an annual capacity of 54,000 tonnes.

Until 1984, Norsk Hydro (ÅSV) had five anode baking furnaces of the closed Riedhammer design in operation in Norway. The total annual production of these furnaces was 160,000 tonnes.

The need for higher metal production volumes and consequentially bigger anodes initiated a strategic plan for the

66 ANODE PLANT TECHNOLOGY

After a one year successful test period, the entire Riedhammer furnace was rebuilt according to the design of the prototype sections. The Sunndal furnace was rebuilt divided in to 28 sections, each with 7 pits and was operated with two fires.

The annual production prior to reconstruction in 1984 (54,000 tonnes of baked anodes) increased to 63,000 tonnes (about 17%) after the rebuilding.

With the next furnace retrofit in 1997, the Sunndal furnace achieved a further increase in capacity to 80,000 tonnes.

Historical Development at Årdal Furnaces The very first production of prebaked anodes in ÅSV Årdal is dated back to 1958. Two closed Riedhammer type furnaces #1 and #2 were built with an annual capacity of 18,000 and 15,000 tonnes. Due to the demand for larger anodes, the height extension of furnace #1 was done in two steps; in 1971 and then in 1980. Furnace #2 was modified in a similar way in 1977.

Sunndal furnace SNC Start Operation Technology Annual capacity (t/y)

Ardal furnace #1 AAKI

Ardal furnace #2 AAK2

Ardal furnace #3 AAK3

Ardal furnace #4 AAK4

1968

1958

1958

1970

1971

Riedhammer

Riedhammer

Riedhammer

Riedhammer

Riedhammer

54,000

18,000

15,000

34,000

34,000

Number of fires

2

2

2

2

2

Number of sections

28

24

24

30

30

Number of pits/section

6

4

4

5

5

Number of anodes/section

108

60

60

90

90

Production rate (kg/pit/per hour)

514

257

214

388

388

1984 HAL 1st. gen

1971 and 1980

1977

1989

high extensions

high extensions

HAL 1st. 80,000 gen

63,000

22,000

22,000

53,000

Start Operation Technology modification Annual capacity (t/y) Number of fires

2

2

2

2

Number of sections

28

24

24

30

Number of pits/section

7

4

4

5

Number of anodes/section

126

60

60

105

Production rate (kg/pit/per hour)

514

314

314

605

prod. stop 1997

prod. stop 2010

Start Operation Technology modification Annual capacity (t/y)

1997 HAL 1st. gen

2004 HAL 1st. gen

1998 HAL 2nd. gen

80,000

112,000

102,000

Number of fires

2

2

2

Number of sections

28

30

30

Number of pits/section

7

7

7

Number of anodes/section

126

168

168

Production rate (kg/pit/per hour)

652

913

832

Table I. Overview of historical evolution of baking furnace technology in ÅSV furnaces in Sunndal and Årdal

During the operational period both furnaces were also used for calcining of cathode blocks. Årdal Furnaces #1 and #2 were eventually closed down in 1997 and 2010 respectively, mainly due to operational economy issues and low pit capacity utilisation.

Due to the metal production expansion in Årdal, two new Riedhammer furnaces #3 and #4 were built in the beginning of the 70’s. Each of the new furnaces had double the capacity of furnaces #1 and #2, mainly because of the increased number of sections, one extra pit and a shorter fire advance cycle.

In 1988, based on the operating results from the redesigned furnace at Sunndal, it was decided to rebuild furnace #3 in Årdal to the same concept, which was denominated as the “HAL” concept.

Baking furnace #3 had 30 sections and was operated by two fires. After the reconstruction a production increase, from 34,000 tonnes to 53,000 tonnes (about 56 %), was achieved.

New designs of the refractory brickwork structures were also developed in order to achieve the ability to produce even larger anodes within the increased section load.

The reconstruction projects mentioned above are described as 1st Generation HAL Baking Furnace Technology, which

were implemented within the existing concrete tub and without alteration of the factory buildings.

The gas cleaning and transportation facilities were upgraded to coincide with increased production and modification of the anode dimensions. The total reconstruction times (i.e. furnace shutdown) varied from 80-130 days, except with Årdal Furnace #3 where rebuilding was carried out in stages during a period of 10 months and adjusted to a nearly normal production level.

The last projects carried out were the rebuilding of Årdal Furnace #4 in 1998 and modernization of Årdal Furnace #3 in 2004, to what we

AWJ 2014 67

denote as 2nd generation HAL Baking Furnace Technology. Unlike with the 1st generation, the existing concrete tub was fully or partly renewed. The concrete tub was still located within the existing buildings, but it now allowed for adjustments of the length and width so that the pit geometry could be tailored to the necessary production capacity and the anode dimensions required.

Section B-B Årdal Furnace #4 had 30 sections and was operated by 2 fires and the initial production capacity in 1971 was 34,000 tonnes/y. Since the rebuild in December 1998, designed capacity was for 102,000 tonnes/y. Reduced output due to limitations in pit utilization and periods when the furnace was operated by one fire (50 % production), resulted in an average production of 86,000 tonnes/y. Årdal Furnace #3 was restarted after the reconstruction of HAL 2nd generation concept in April 2004. Design capacity was increased to 112,000 tonnes/y, but the average annual production has been 96,000 tonnes. Furnace #3 in Årdal achieved a production increase of 110 % since the previous rebuild (HAL 1st) and an increase of 230 % compared to the original furnace design.

Currently the total production of the 3 furnaces with HAL technology in operation (furnaces #3 and #4 in Årdal and the Sunndal furnace) is approximately 290,000 tonnes/y.

Main Features of Riedhammer and Hydro HAL Baking Furnace Technology Both Riedhammer and HAL concepts are so-called closed type furnaces with a vertical flue gas pattern.

The principle of the flue gas pattern for the Riedhammer furnace is shown in Figure 2. The exhaust gas enters from the previous section underneath the headwall and turns upwards through the firing shafts with counter flow firing.

Under the section cover, the gas is

Figure 2. Schematic drawing of the flue gas pattern for closed type Riedhammer baking furnace

dividing wall. After an energy input from downstream firing, the flue gas is channelled first upwards through the A part of the flue wall. Approximately 60% of the fuel energy required per section is supplied in such a way.

Under a section cover, the rest of the fuel energy input is injected from the vertically oriented cover burners and the flue gas is sent downstream through the B part beneath the pit floor.

The exhaust manifold is connected directly from the section cover to the ring main at the first section of the fire zone.

Distribution of gas and energy input between the A and B parts is the key feature of the HAL concept which enables operation of the furnace with a high production rate per pit as shown in Table I [1].

Section B-B Figure 3. Schematic drawing of the flue gas pattern for closed type HAL baking furnace.

distributed downwards into the flue wall channels and transferred via the bottom channel system into the next section. At the front of the fire zone, the exhaust manifold leads off gas from the exhaust take-off duct to the ring main (Figure 6). In this way flue gas passes the whole fire zone and heats up the furnace sections.

The Hydro closed type furnace design was developed with a different flue gas pattern, as shown in Figure 3. The exhaust gas enters the section through the bottom part of the headwall directly to the flue wall. Flue walls and the bottom part of the pit are physically divided into A and B parts by the

Rebuild to HAL 1st Generation Baking Furnace Technology The main requirements and major aspects connected with the rebuild of the Riedhammer furnace to HAL technology are further discussed.

The most challenging part during the rebuild was to adopt the new furnace design into the existing building and the same concrete tub.

This solution included step changes on previous essential furnace construction parts with a simultaneous focus on low investment cost. All these changes were adjusted in order to avoid major changes in the existing infrastructure to achieve the shortest construction time without a large production loss.

The major cost saving was partly achieved by reducing the amount of installed refractory compared to the previous furnace design (Table II). This was achieved through a new headwall design which included

Riedhammer

HAL 1st. generation

Sunndal furnace

11,500

10,000

Årdal furnace #3

12,500

11,000

Årdal furnace #4

12,500

Installed Refractory (t)

HAL2nd. generation

Table II. Overview for tonnage of installed refractory material for furnaces.

68 ANODE PLANT TECHNOLOGY

10,800 10,500

Figure 4. The new cover design for HAL furnace. The exhaust take off hatch is on the short side of the cover. Auxiliary equipment is integrated in the cover.

removal of the firing shafts and the exhaust take off ducts [2]. In this way, the section width increased for two additional pits (Figure 5 and Figure 7). New headwall brickwork was more simple and required less brick types and tonnage installed. The increased section volume allowed loading of several larger anodes which resulted in a higher section load and improved furnace productivity.

The extension of section dimensions and the new concept of exhaust gas take off required construction of new section covers and exhaust manifold.

The new HAL section cover design enabled even distribution of the flue gas flow due to the rectangular geometry of the cross sectional area.

Consequently, the flue gas velocity gradients in the corners over the outer and inner pits, were minimised [3, 4].

The main operational advantage of the HAL section cover design is that all peripheral equipment (gas burners, thermocouples, additional air fans) are integrated in the cover.

An increase of the cover width and length required modification of the construction design. The original rigid cast iron frame was replaced with a flexible steel frame construction supported by a torsion stable steel structure. The new cover was designed with the intention to withstand mechanical and thermal stresses during the whole fire cycle. Thermal expansion measurements and thermomechanical analysis were done prior to modifications of the cover bottom frame [5, 6]. As a result, expansion

Figure 5. Top view of the Riedhammer design furnace #3 section from 1970. Exhaust take off duct is integrated in the headwall.

Section A-A Figure 6. Cross sectional view of the Riedhammer design furnace #3 section from 1970. Section with 5 pits, exhaust manifold is connected to the exhaust outlet.

Figure 7. Top view of the HAL 2nd generation design furnace #3 section with 7 pits after retrofit in 2004.

Section A-A Figure 8. Cross sectional view of the HAL 2nd generation design furnace #3 section after retrofit in 2004. Direct exhaust take off is from the section cover.

joints at the long side of the steel frame were introduced. This measure also helped to reduce the mechanical stresses on the cover arch insulating brickwork.

Rebuild from HAL 1st Generation to HAL 2nd Generation Baking Furnace Technology Increasing amperage in pot rooms set persisting demand for larger anodes during the 90â&#x20AC;&#x2122;s, which resulted in further evolution of HAL 1st generation baking furnace technology. Further retrofit of the furnaces involved a gradual rebuild of Sunndal and both Ă&#x2026;rdal furnaces #4 and #3.

Major modifications of the furnaces comprised dimensional changes in the concrete tub, both in length and width. The most remarkable change was the retrofit of furnace #3 where the amount of pits increased from 5 to 7 per section. Increased loading tonnage per section required calculations of strength and an evaluation of concrete tub thickness with respect to the wall stability and thermal stress [7].

The 3D finite element (FE) modelling of the furnace bottom structures was done in order to ensure sufficient bearing capacity and optimised flue gas flow distribution [8]. The same study evaluated several cases with various widths (cross sectional opening) of the flue wall bricks to show the effects on the flue gas pressure loss and the flow distribution in the flue wall. Heat profile calculations, confirmed by temperature measurements, enabled reduction in the sidewall thickness and furnace substructures height which in turn increased the pit depth [9, 10].

Modelling and subsequent optimisation of the important furnace constructions allowed for a reduction in the amount of installed refractory without losing its functional value. Lighter construction allowed operation with a faster fire advance cycle and increased the furnace productivity. After 4 years of operation of furnace #3, extensive modelling was conducted. 3D finite element (FE) model of a baking furnace and thermal and structural analyses helped to understand the mechanisms for stress build-up in the baking furnace. The FE-model was also used to compare the pros

AWJ 2014 69

and cons of different furnace design solutions [11].

Refractory Maintenance The Hydro furnace concept has adopted the continuous refractory maintenance strategy. This approach assumes that the maintenance of refractory parts is carried out without loss of the furnace production. The furnace is in continuous operation during the regular maintenance; such as a change of the flue wall or pit floor.

Production is stopped only during the major rebuild periods when the main furnace structures like sidewalls, bottom insulation and headwalls are replaced.

The evaluation of maintenance and the lifetime of a baking furnace very often depend on the amount of fire cycles.

For example furnace #4 in Årdal was originally built as a Riedhammer type furnace in 1971 and was in continuous operation until the rebuild in 1998. This means that the original headwalls, sidewalls, bottom insulation and covers were 27 years old. Assuming an average 17 cycles per year, the furnace had passed a minimum 460 cycles during its service lifetime.

Another important fact was that the complexity (amount of special brick shapes) of the HAL design for the critical refractory structures was simplified. Thus less refractory tonnage was installed which reduced the heat capacity of the whole furnace structure and enabled operation with faster fire advance cycles. Improved heat exchange between the anode and the flue wall was reflected in lower energy consumption. Lifetime of furnace refractory brickwork depends mainly on: • Refractory quality • Heat stress under normal operation condition • Mechanical load combined with operational routines • Routines deployed for continuous maintenance under furnace operation

When the furnace structures of the new HAL furnaces were designed selection of high refractory quality, according to the installation position, enabled customized solutions for the high heat and mechanically loaded structures such as the headwalls and bottom pillars.

Selection of the refractory quality resulted from an extensive test program which included the characterization and the evaluation of previous operational experience. The most important testing methods and the refractory properties were selected [12]. Testing included both the characterization of the new materials and the analysis of used refractory which reflected the ageing effect of thermal cycling.

Results gained from testing helped to identify and increase understanding of the thermo-mechanical and chemical stresses influencing the critical brickwork structures of the furnace.

In connection with the introduction of the HAL 2nd generation furnace design, new maintenance and repair methods were adopted. Evaluation of the baking furnace brickwork condition is based on the inspection of sections with varying extent of damage.

General condition monitoring is done at least every 2 years. Sections with potential for large deformations and displacements, especially the headwall, are checked at shorter intervals (4-6 months). Damage mechanisms and causalities for observed critical deformations were explained and the maintenance method solutions were proposed [13].

Routine follow-up and evaluation of the brickwork condition is an important tool to predict and determine a timeframe for a new renovation or modernization of a furnace. Therefore, it is crucial to focus on the construction portions that are time-consuming and costly to maintain. Hence, the condition of the headwalls is crucial in determining when to rebuild a furnace.

70 ANODE PLANT TECHNOLOGY

Figure 9. Schematic drawing of a surgical reparation of the flue wall cracking in the bottom corner of pit. The damaged part of the brickwork is demolished and rebuilt while the rest of the wall is stabilised by a chain jack and maintenance platform.

Flue Wall Reparation Methods During operation, packing coke tends to stick to a flue wall and forms slag around anchor slots in the headwall.

Blockage of expansion joints in a headwall will prevent the flue wall from free movement and cause deformation and cracking. A deformed flue wall causes narrowing of the pit and makes loading of anodes difficult. In addition, large cracks in the bottom of the flue wall will cause problems with excessive airburn of the anodes and packing coke. Packing coke runs under the pit floor and causes restrictions in flue gas flow and prevents optimal heat distribution.

With an introduction of so-called “surgical reparation” of the flue wall and pit bottom, it is possible to replace only the damaged part of the brickwork without changing the whole wall. This reduces maintenance time and cost significantly.

Refractory Lifetime and Consumption The combination of improved understanding of stress build-up mechanisms (FE-modelling) and operational experience has resulted in a major leap in the flue wall lifetime.

This is exemplified by the lifetime distribution figures for the latest rebuild of furnace #3 in 2004. The foreseen

Amount of flue walls

120

Lifetime distribution 1st generation flue walls Lifetime distribution 2nd generation flue walls Operational time distribution 2nd generation flue walls

100 80 60

Benefits from the continuous refractory maintenance strategy are reflected in a positive way by the extended refractory lifetime of flue walls and low specific consumption of refractory material.

40 20 0

This includes routine follow-up of the brickwork condition, and precise planning of maintenance work with minor production disturbance. Developed surgical maintenance reparation methods assure maximum extension of the refractory brickwork lifetime and minimal maintenance cost.

500

Figure 10. Lifetime distribution of

1000 1st

1500

2000

[days] andLifetime 2nd generation of the flue walls at furnace #3.

refractory maintenance consumption over the furnace lifetime of 20 years is close to 5 kg/tonnes baked anodes.

The surgical maintenance of flue walls gives a potential for further reduction of maintenance cost and an increased lifetime of furnace brickwork.

Furnace Design vs. Process Safety The inherent design of the closed top baking furnaces enables fire zones to be set to a safe state in case of loss of draft situations. The routines include flaring of the pitch volatiles until an oxygen excess situation is reestablished in the fire zones.

When the surplus air is established in all fires, normal operation can be reestablished without any risk of forming flammable gas mixtures by restarting the draft. The inherent design feature of the furnace, which allows the fire zones to be set to a safe state, forms the basis for the SIL21-classified safety system of the HAL-furnace [14].

Conclusion Increased potline amperage and expanded metal production at ÅSV during the 80’s resulted in a demand for larger anodes. As a consequence, a new HAL anode baking furnace concept was developed and introduced through 1st and 2nd generation evolutionary phases. All rebuild changes were done

with a strong focus on the investment cost. The main dimensions of the new baking furnaces were adapted to the existing building with minor changes to the existing infrastructure. The reduced amount of installed refractory and the short reconstruction time without production loss had a positive effect on the overall project cost.

Design modifications for the HAL 1st ‘generation furnace were done without major dimensional changes on the existing concrete tub or the distance between headwalls.

Main features of the HAL 2nd generation furnace comprised of a partial renewal of the concrete tub. Adjustments to the length and width of the pit geometry were tailored to the anode dimensions required, without alteration of the factory building. After retrofit, the new HAL furnace section dimensions allowed operation with a higher section load and production of larger anodes. New design of brickwork structures and less refractory tonnage installed enabled operating with faster fire advance cycles. As a result, a considerable increase in furnace capacity was achieved. New section covers with integrated auxiliary equipment were developed in order to fit the new furnace section dimensions. The Hydro furnace concept has adopted a continuous refractory maintenance strategy.

References [1.] Holden et al., “New process control system applied on a closed baking furnace”, TMS Light Metals 2006, 603-608 [2.] Anders Ruud, “Baking furnace concept – new headwall design”, TEK95/015, Internal report, 1995 [3.] Nigel Anderson, “Differences in flue gas distribution between take off from headwall and cover”, TEK93/110, Internal report, 1993 [4.] Nigel Anderson, Anders Ruud, “Direct take off from section cover for HAL furnace. Test summary from Dec. 93 - Feb 94”, TEK 94/023, Internal report, 1994 [5.] E. Sandvik, J. H. Skaar, “Development of cover for baking furnace with larger section”, TEK96/156, Internal report, 1996 [6.] Anders Ruud, “Cover design HAL7P – Dimensional stability and temperature profile in steel frame”, TEK97/149, Internal report, 1998 [7.] Fredleiv Fosse, “AAK baking furnace 3, Concrete tub for baking furnace, Building evaluation of construction”, Urheim AS Consultant engineering, External report, 2002 [8.] Aage Jøsang, “Pressure loss calculation HAL7P and HAL7Ps furnace 3 AAK”, Research centre Porsgrunn, Internal report, 2001 [9.] Aage Jøsang, “Heat balance sidewall HAL7P furnace 3 AAK”, Research centre Porsgrunn, Internal report, 2001 [10.] Aage Jøsang, “Heat balance bottom pit and sidewall HAL7P furnace 3 AAK”, Research centre Porsgrunn, Internal report, 2002 [11.] Henrik Bruzell, “FE analyses of AAK Furnace 3”, Validus Engineering AB, document ref: R0501-02_revA, External report, 2008 [12.] Anders Ruud, “Refractory materials for baking furnace, testing criteria with respect to selection of material quality”, TEK90/100, Internal report, 1996 [13.] Anders Ruud, “Maintenance of brickwork for furnace AAK3. Recommended activities and reparation methods”, Internal note, 2004 [14.] Holden et al., “Safe Operation of Anode baking Furnaces”, TMS Light Metals 2008, 905-911

AWJ 2014 71

An Intermediate Step in Cost Reduction for Inert Anodes

Process steps from idea to deployment IDEA GENERATION

PROOF OF CONCEPT Gate 2

Gate 1 Generate idea and assess potential

PROTOTYPE

Develop the idea into a feasible technology

Gate 3 Evaluate and validate at pilot scale

DEPLOYMENT

DEMONSTRATION Gate 4 Demonstate and optimize in lead plant

Gate 5 Encapsulate the technology in a commercial package

Process steps from idea to deployment

The Aluminium Industry has seen many innovations in recent years developed for smelters, especially in the areas of pot design concepts and dealing with ever higher amperages, and more recently in the inert anodes of Rusal (still to be commercially proven). The inert anodes are not yet operational at a large scale and will likely require many years of further development before they can be applied in smelters worldwide.

A transitional phase will take place to reduce the current costs occurring in smelters. One area of cost reduction relates to the mechanical and electrical connection of the anodes to the rod stub in the rodding shop. The current connection method has a number of drawbacks that contribute to the high cost of aluminium production.

The mechanical connection of anodes to the rod stub by means of grouting the rod stub to the anode stub hole with liquid cast iron has the disadvantage that the seal created by this method shrinks during the cooling process. Due to this shrinkage an optimal electrical contact between the anode and the rod stub can not be achieved. Further disadvantages caused by forming stub holes with splines in the paste plant are the risk of crack formation and broken out pieces which lead to an increase of rejected anodes.

A new design concept of plug and play stub holes would reduce the amount of rejected anodes caused by faulty stub holes as well as reducing the

cost incurred in anode production, especially taking into consideration that the application of liquid cast iron is expensive and involves a certain degree of risk for the operator. A possible solution is at hand.

the principle drawing fig 1). A major advantage of the M-connection method is making the formation of a stub hole a lot easier as it eliminates the need for splines. Consequently, the risk of crack formations is largely reduced.

spiral spring

which establishes the mechanical connection 2

electrical conductive ďŹ&#x201A;uid X expands by heat

Anode Fig 1. Mechanical and Electrical connection

A New Connection Method Concept Mechanical Connection Creating a plug and play connection for the mechanical connection of anodes to the rod stub by using liquid iron is no longer necessary. I propose a new method for the mechanical connection of the rod stub to the anode stub hole, here referred to as the M-connection method.

This method can be achieved by mounting a spring on the existing rod stub and machining a groove in the lower part of the stub hole.

These modifications will allow the M-connection method to work as a plug and play system (as shown in

72 ANODE PLANT TECHNOLOGY

The groove in the stub hole required for the spring needs to be milled (forming is not recommended).

Adapting the M- connection method would increase the cost of manufacturing anodes only marginally as the initial cost would be outweighed by the resulting cost savings that could be achieved in the rodding shop (20 to 30%).

Since tapped holes occupy an elevated position above the anodes, the required amount of butts is significantly reduced, - in effect allowing for cheaper anode production cost and expanding anode pot life.

An Intermediate Step in Cost Reduction for Inert Anodes

Electrical Connection

Anode connected to a rod stub

The electrical connection can be accomplished by an application of electrically conductive fluid (X) which will expand after the use of an activator that will react upon reaching a specific temperature (Y), becoming one hundred percent conductive. Once the connection is established voltage loss becomes minimized, resulting in a fixation of the rod stub to the anode.

The Principle of New Style Rodding

Stubhole Spline

The modified rod stub will slide into the stub hole and the spring will click on the anode connecting with the groove in the stub hole, thus establishing the M-connection. Simultaneously the conductive fluid (X) will flow around the rod stub and start to expand and harden upon reaching the correct temperature (Y). One important property of the conductive fluid (X) is the ability to penetrate the porous surface of the stub hole, thus establishing an optimal electric conductive connection.

The advantages that can be gained are: â&#x20AC;˘ A new, fast, safe and effective way of connecting a rod stub to an anode

Stubhole Defects A.

â&#x20AC;˘ A connection method offering excellent electrical conductivity and significant cost savings for rodding shop anode production.

Looking forward to the future, it will be extremely interesting to discover whether the new plug and play type M-connection method concept has sufficient commercial value for further development according to the principles and model introduced here.

Author: Louis Dekker Contact Information: louis.dekker@zeelandnet.nl

Stubhole Defects B.

AWJ 2014 73

Operational and environmental benefits of the new baking furnace at Boyne Smelters by use of an advanced firing technology This paper will outline the special technologies used and demonstrate the results that can be achieved to allow for smarter and cleaner baking cycles in combination with relevant safety standards and system availability.

Figure 1. BSL on Boyne Island

Abstract In February 2012, a new baking furnace was commissioned at Boyne Smelters Limited (BSL) on Boyne Island, Australia. This new furnace replaced the production of two existing closed type furnaces and set new benchmarks in production performance.

The advanced firing technology was based on latest safety requirements

of the Australian Gas Authority (AGA) gas standards. In parallel, new selfrecovery network structures behind the wireless network have been developed to maximize the redundancy and availability of the system. Finally, intelligent control modules have been implemented for on-line optimization of the baking process.

Introduction Now part of Pacific Aluminium, Boyne Smelters Ltd. (BSL) is a primary smelter put into operation in 1982

by Comalco Aluminium and its joint venture partners. BSL has undergone extensive expansion over time. The smelter underwent a A$1 billion expansion in 1997 introducing a third reduction line which increased aluminium production from 260,000 to more than 550,000 tons per annum.

The company has further undergone a significant modernization with the re-building of Carbon Baking Furnace 3 (CBF3) and the construction of a new Carbon Baking Furnace 4 (CBF4) to upgrade the baking technology.

The new baking furnace replaced the two existing closed type furnaces that were obsolete and fully outdated in terms of energy efficiency, emissions of greenhouse gases and high refractory maintenance and operational cost. An aerial view of the smelter is provided in Figure 1.

Details of the Carbon Bake Furnace 4 The new baking furnace is an open-type Rio Tinto Alcan AP design. It consists of 66 sections, each with 9 flues and 8 pits. BSL operates 4 fire groups on this furnace. The configuration includes 3 sections in the preheat area, 3 sections in the firing area and 6 sections in the cooling area. Figure 2 shows the actual fire configuration.

The fire cycle time can vary between 24 and 32 hours, depending on the production requirements.

Advanced Firing Technology The Advanced Firing Technology is a tailored system to suit the requirements of BSL. The control philosophy is based on the implementation of intelligent Figure 2. New Firing System for CBF4 at BSL

74 ANODE PLANT TECHNOLOGY

Figure 3: Fire configuration for CBF4

optimization modules on top of the basic automation for an optimum system using today’s state-of-the-art and future oriented technology.

The firing system provides the following features: 1* Fully automatic system operation 2* Preheat Control with complete internal pitch burn 3* Automatic Cross Over strategy 4* Safety interlocks according to Australian Gas Association (AGA) standards 5* High pressure pulse burner technology 6* Preparation of the equipment for fire direction reversal 7* Simple and easy operation 8* Advanced Control Modules for Firing Optimization.

In addition to the firing control system the following Auxiliary systems were implemented: 9* Main Gas Supply Skid for furnace gas supply, including emergency stop (E-stop) circuit 10* Fume treatment centre (FTC) data interface including main draught interlock

11* OPC (standard data communication protocol) interface to plant wide Manufacturing Execution System (MES) 12* Ring main duct explosion vent monitoring 13* Start-up Burners for firing control below 750 °C An overview of the operator control screen is shown in Figure 3.

Safety Requirements for AGA The firing and control system for the Boyne Smelter upgrade project requires extensive safety interlocks as per AGA and Queensland Government requirements.

Each of the local programmable logic controllers (PLC) executes process control functions. All (classified) safety interlocks are handled independently from the process PLCs and are realized by separate safety integrity level (SIL) 2 safety hardware. Safety signals are forwarded independently from the network infrastructure via a hardwired daisy chain to the respective system unit, as a result of a risk assessment and the HAZOP study with the AGA Queensland inspector.

The significant safety interlocks required to comply with AGA standards are: • Hard-wired flue draught release for the burner ramps of the same fire • High and Low Temperature interlocks at each burner ramp • E-Stops for the Main Gas Supply Skid along the furnace bay • Main draught release (from FTC) for the Main Gas Supply Skid.

Beside these primary interlocks listed above, the following safety functionalities have been implemented for maximum operational safety: 14* Tightness test of primary safety shut-off valves at the Burner Ramp before fire start and after each fire move 15* Pipe tightness test at Burner Ramp before fire start and after each fire move 16* Low Gas pressure supervision and cut-off at the Burner Ramp 17* Emergency–Stop at each Burner Ramp 18* PLC watchdog on each Ramp 19* Automatic calibration of all draught / pressure sensors every hour 20* Life Zero check for the draught

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control system and the MES located in the central control facilities. The communication system becomes an important key component of the firing control system.

Wireless communication became the logical state-of-the-art concept as the equipment in the field needs to be moved every day and a wired communication concept immediately creates reliability, operability and maintenance issues. However, the demand of a control system for anode baking furnaces results in very specific design criteria for the wireless communication system and equipment.

The design as developed for CBF4 ensures a maximum availability of the system by implementing redundancy in combination with industrial Ethernet and wireless equipment.

The wireless network in the field is executed by four (4) stand-alone industrial access points (AP) which work independently to each other to provide maximum redundancy. In the worst case, one AP is sufficient to provide the necessary communication between the ramps. Additionally the APâ&#x20AC;&#x2122;s are connected to each other via selfrecovering fibre optic ring architecture through industrial Ethernet switches.

The control architecture is illustrated in Figure 4.

Figure 4: Self recovery network structures

/ pressure sensors every hour.

The combination of these additional safety features and interlocks leads to a significant increase of operational safety and a more reliable and sustainable production of anodes with respect to the baking furnace environment.

Self-recovery Control Architecture on Wi-Fi Bases Due to the nature of the anode baking process the firing system consists of movable ramps performing the required firing discipline while the product remains at a constant position during the baking process.

Each ramp operating on the furnace is controlled by a local industrial PLC

located inside the control cabinet of this particular ramp. All sensors and actuators are connected to this PLC. For local visualisation and backup operation an Operator Panel (HMI) is installed which interacts with the PLC and the connected instrumentation executing the required control functions for that particular ramp. With the help of the local HMI the operator is able to interact with the ramp locally in different operation modes on the furnace floor and monitor process and equipment status information (Level 1 control).

The automated control of the anode baking process requires data communication between each of the ramps forming a fire group as well as to the Level 2 Advanced firing

76 ANODE PLANT TECHNOLOGY

Compared to public Wi-Fi zones where the wireless infrastructure mainly provides access to the internet via a common gateway, in an industrial network mainly control components (PLCs and PCâ&#x20AC;&#x2122;s) need to communicate to each other to exchange process and safety data within an industrial environment.

Since control components such as PLCâ&#x20AC;&#x2122;s usually do not have a built-in wireless interface, special wireless client modules (WCM) are required to provide wireless connectivity of the firing ramps. Such WCM clients have been developed for the particular demands of industrial control components and industrial environments, so these

Figure 6: Firing Index Module

industrial WCMâ&#x20AC;&#x2122;s have become the benchmark technology around the world.

Each local control cabinet on the firing ramps contains a WCM. The WCM creates the connection from the PLC to the radio network. The WCM transmits all data sent from the PLC to the stationary network (backbone) via a corresponding wireless access point.

These wireless components require an industrial design for mounting inside the climate controlled electrical control panels as well as performing required functionality within an industrial automation system. Due to the daily fire move / crane handling, the equipment (especially for the ramps of the firing system) needs to be installed in accordance to industrial standards as an integral component of the firing control system, for example: 21* Mountable on standard DIN rail 22* Heavy duty / industrial power and signal connectors 23* Suitable for industrial control voltage (24V DC) incl. standard allowable tolerances 24* Vibration / shock resistant

Figure 5: Flooding Index Module

25* Suitable for industrial control panels 26* Easy to troubleshoot, analyze and maintain.

Intelligent Control Modules The design objective at BSL is to maximize the production performance and achieve this in parallel with cleaner baking cycles. For this purpose the anodes must be produced with: 27* Low energy consumption 28* Low emissions, and 29* High consistency of heat treatment.

The following intelligent control modules have been implemented which ensure an on-line optimization of the process even under changing production conditions.

Oxygen Control by Flooding Index With the on-line calculation of a Flooding Index [1] the actual oxygen levels in the firing area of the furnace can be evaluated, especially at the front burner ramp. Any lack of oxygen is automatically prevented via the Flooding Index Module as shown in Figure 5 by dynamic limitation of the

burner capacity. Due to this module the system ensures a complete combustion of the gas fuel fed into the burners.

Firing Index Changes to the fuel input as a result of the flooding index module make it necessary to leave the target baking curve temporarily. In order to ensure the same heat supply to all pits and thus a maximum consistency, the heat supply to the pits is recalculated by the Firing Index Module [1] and compensated by the control system as shown in Figure 6.

The Firing Index Module allows even greater deviations from the baking curve during the pitch burn phase. Here the burner capacity must be reduced in order to guarantee sufficient oxygen for the volatile combustion.

Pitch Burn Module The Pitch Burn Module requires a specific recognition of the oxygen levels during the pitch burn phase.

The Pitch Burn Module incorporates the opacity reading in the collection pipe of the exhaust ramp and the temperature gradients in the preheat sections, as illustrated in Figure 7.

AWJ 2014 77

Figure 7: Pitch Burn Module

As a result of these observations the pitch burn module dynamically increases the draught (volume) in the individual flues and reduces the fuel gas consumption at the burner ramps in a two-step strategy.

Zero Point Control The zero point control is also one of the essential technologies to minimize energy consumption and maximise the anode quality consistency. Therefore it utilizes one controlled blower ramp, a second “measurement” ramp for sensing the pressure behind the heating area and one uncontrolled cooling ramp. The furnace and equipment arrangement for zero point control is shown in Figure 8.

Between the last burner ramp and the controlled blower manifold all peepholes remain closed. So the cooling air can only leave the cooling area via the flue gas channels into the firing area. The preheated air enters the firing area and can be utilised for the firing/combustion process. For CBF4, the air volume of the blower manifold is produced from one central fan and controlled for each of the nine flues by individual motorized dampers to an accuracy of +/- 1Pa. Since the flue gas volume that is necessary for the heat exchange process is normally larger than the necessary combustion air for the burners in the firing area, exclusively

7

6

5

4 Section

Figure 8: Cooling principle with “Zero Point” and controlled blower ramp

78 ANODE PLANT TECHNOLOGY

Precise control of the combustion air into the flues also minimises the potential for excess combustion of the packing coke in the pits. Too much pressurised air introduced into the flues can result in cooling air passing through the openings in the refractory walls and in coming in contact with the packing coke at temperatures above 650ºC.

Blower manifold (controlled)

Zero Point Ramp

Firing Area

preheated air from the cooling area will be used for the combustion. This heat recuperation from the baked anodes is one of the largest contributors for the energy efficient operation of an open type anode baking furnace.

Cooling manifold

3

2

1 Last filled section

CBF4 natural gas consumption [GI/mt baked anode] 2.2 2.1 2 1.9 1.8 1.7 1.6 1.5

Week 1

Week 2

Week 3

Week 4

Figure 9: CBF4 natural gas consumption

Results Operational Safety and System Reliability All existing baking furnaces at BSL have a hard-wired connection between each of the ramps of the fire group to connect the draught safety release signal. This system has been in use for many years and provides a high level of inherent safety to the fire control system due to the physical connection of equipment with a lead.

The disadvantage is the need for leads to be placed across the floor of the furnace, and mechanical faults with the plugs and leads as the equipment ages.

For CBF4, a full wireless fire control system would not satisfy the AGA regulations. The design was adapted to incorporate a hardwired connection

between the Measurement ramp and the Burner ramps. For BSL, the new design allowed the elimination of some plug and lead operational issues, while being compliant with the gas regulation.

The introduction of a wireless network communication between other ramps in the fire group was a new development for BSL. A second wireless network is in use for the CBF4 building, for communications from the furnace cranes. Testing of the strength and reliability of the fire control system network was performed with the cranes in operation and travelling to all areas of the furnace building to simulate all expected operating scenarios.

Gas Consumption and Off-Gas Emissions Commissioning of the first fire group commenced in February and the fourth and final fire group was completed in mid April. By May, the furnace was fully operational and supplying all anodes previously supplied by the existing closed baking furnaces. Early gas consumption for the new furnace was in the range of 1.9 to 2.1 GJ/mt of baked anodes (Figure 9). Further opportunities have been identified to reduce consumption by tuning of the zero point and adjustment of the target temperature curves.

Sampling of the off-gases from the furnace duct revealed low levels of volatile organic and polycyclic aromatic hydrocarbon (PAH) species, as well as

Stack CO Concentration [mg/Nm3] 40 35 30 25 20 15 10 5 0 27/05/12

29/05/12

31/05/12

02/06/12

04/06/12

Figure 10: Carbon monoxide in the off-gases from CBF4

06/06/12

08/06/12

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Parameter Baking level

Units

Typical Value

ºE

1,225 (40)

Electrical resistivity

µO.m

57 (4.5)

Baked apparent density

kg/m3

1560 (7)

CO2 Reactivity Residue

%

94 (2)

CO in furnace off-gases

mg/Nm3

25 – 40

ºC

200 – 250

GJ/mt baked anode

1.9 – 2.1

Anode temperature at time of unload Natural gas consumption

Table I – Early CBF4 furnace and anode property data. Standard deviation shown in brackets

carbon monoxide (CO), an effective indicator of pitch volatile combustion.

Carbon monoxide readings (Figure 10) in the range 25-40 mg/Nm3 were measured in the off gases during performance testing of the furnace and fume treatment centre.

Selection of the target temperature curves for the new furnace was a key contributor to early achievement of the low natural gas consumption. In particular, the complete combustion of the pitch volatiles and the use of this heat energy in pre-heating the anodes is a key contributor to low overall natural gas consumption. The pre-heat target temperature curves were selected based on the collective experiences of the commissioning team, made up of Innovatherm, Rio Tinto Alcan, and BSL process engineers. Once the curves were selected, the advanced Intelligent Control modules of the firing control system allowed precise and repeatable control of the operating window around these target temperatures.

Anode Quality For BSL, the goal with the CBF4 startup was to commission all four of the fire groups and achieve an acceptable initial baked anode quality in the shortest possible time frame. BSL were not able to sustain the operation of three furnaces due to pressure on green anode supply and manning, so it was important to have enough confidence in the early baked anode quality to shut down the existing closed furnaces.

A summary of the early anode quality

data for CBF4 is given in Table I. At BSL, final anode temperatures and pit temperature profiles are assessed at using the equivalent temperature technique. A small crucible of green petroleum coke is placed in the stub hole of the anodes in the pits, and the crystal structure analysed after the baking process and converted into an equivalent temperature [2].

challenges that will no doubt arise in the highly competitive aluminium smelting industry.

The early results from CBF4, along with a small-scale trial of the anodes on the Reduction Line gave BSL the confidence to commence a rapid de-commissioning of the existing closed baking furnaces. Further, the initial results have given the plant process engineers a basis for further optimisation of the target temperature curves and burner set-up to reduce variation in temperatures within the pit and reduce the natural gas consumption.

Glenn Gordon; Sathya Moodley, Boyne Smelters Limited, Handley Drive, Boyne Island, QLD 4680, Australia

Summary This paper describes the results that can be achieved when a commissioning team comprised of experienced start-up and operations personnel is combined with a bake furnace fire control system with advanced process control functionality. It also demonstrates that the adoption of modern Wi-Fi communications technology and more stringent furnace safety requirements is no barrier to high system availability.

BSL has entered into a new era of anode baking capability, and is well prepared for the present and future

80 ANODE PLANT TECHNOLOGY

Authors Andreas Himmelreich, Detlef Maiwald; Domenico Di Lisa, innovatherm GmbH&Co.Kg Am Hetgesborn 20, Butzbach 35510, Germany

Integrated Technology Firing and Fume Treatment for Anode Baking Furnaces

ProBake Advanced Firing Systems Lowest energy consumption Total pitch burn Higher quality consistency

ProClean Fume Treatment Technology Higher adsorbtion ratios Lower emissions Higher reliability

Your Sustainable Partner

ddilisa@innovatherm.de

www.innovatherm.de

One Design 路 One Technology 路 One Company AWJ 2014 81

Upgrade of an existing Fume Treatment Plant at ALUAR to cope with higher production in the new open type anode baking furnaces gas volume of 90.000 am3/h and a maximum exhaust gas temperature of 130 째C. It was a three chambers Bag house Filter Concept with Alumina as adsorbent without cooling tower due to the low exhaust gas temperatures at the exit of the closed type furnaces.

For the higher production of anodes in the new open type furnaces, more exhaust gas volume is generated at temperatures up to 220째C which implies the installation of a new FTC to maintain the higher volumes and the higher exhaust gas temperatures. The specific volume per ton of produced anodes is now in the range of 5.000 Nm3/t of baked anodes compared to 2.900 Nm3/t before.

Fig.1 Former Fume Treatment Centre at Aluar

Abstract Aluar Aluminio Argentino has been operating with two closed type furnaces for the production of anodes for more than 35 years. Due to the continuous expansion by amperage increase in the potlines, these furnaces were replaced by two new open type baking furnaces, due to present anode requirements only one was started. As a result, the existing Fume Treatment Plant had to be upgraded to cope with higher volume and temperature requirements.

This paper explains the most economical solution for an FTC concept upgrade, which integrates major existing components but in parallel enhances the plant by new equipment and process technologies to attain the targets. Finally it outlines the actual results achieved by presenting key performance figures, including emission levels.

Introduction The Aluar Aluminium Smelter at Puerto Madryn (Argentina) had a production capacity of 250.000 tons/year before the last expansion project was initiated.

But once the ramp-up of all new pots and the amperage increase process in the existing ones was finished, the production output was raised to 430.000 tons/year.

Other facilities of the Smelter like the anode plant had to adsorb these changes in production. Higher aluminium production output also enforced production of more anodes.

The green anode plant was expanded and designed with some spare or extra capacity for maintenance purposes.

Regarding the baking furnaces, two of the existing three furnaces were of closed type technology. The anode quality requirements for the new process conditions in the pots as well as the difficulties to perform the refractory maintenance routines were causes, which drove the decision to replace the 2 closed type furnaces by open type technology. In addition, this modification has lead to an increase of the baked anode production.

The existing FTC as shown in Fig.1 had been designed for a nominal exhaust

82 ANODE PLANT TECHNOLOGY

Targets for a solid state upgrade The driving idea for the new FTC design: try to keep and use as much as possible from the existing installation in order to get the best economical concept for minimum CAPEX and still reach the performance and the environmental limits.

Further targets for a solid-state upgrade of the FTC were: 1. Enlarge the surface of the filter chambers to serve for the higher capacity of 155.000 am3/h without adding new chambers or compartments inside the shape of the existing baghouse.

2. Insurance of a maximum reliability and operational safety to run 24-7-365 without any major interruptions.

3. High filtration efficiency of harmful components with low adsorbent consumption and filtration ratios of < 1,05 m3/m2 and minute.

4. Spare capacity and redundancy for compensation of plant aging effects and for maintenance works to be performed without production stop, operation with n-1 chambers and n-1 fans to ensure 2.

5. A continuous high performance to ensure anode production at high quality with minimum OPEX and minimum emissions.

6. High-level FTC process automation concept in order to guarantee an optimized and smooth FTC operation without any interruptions incl. automatic switch-over to multiple modes of operation without any interaction of the operator.

The new FTC process technology The new concepted FTC as shown in Fig.2 was completely embedded around the former FTC (baghouse). A new cooling tower was added. Around this, the plant was designed to provide “ideal” movement of the gases from the furnace to the stack. This is achieved by means of calculation of optimum main component dimensions, including those of the cooling tower and fabric filter, as well as the minimisation of diversions. Pressure losses were minimized using computer modelling to ensure maximum flexibility even at high baking furnace pressure losses.

The plant is operated under constant and controlled draught conditions.

This negative pressure ensures that no crude gas or contaminated adsorption media are emitted to the environment.

The baking furnace off-gases are taken from the end of the furnace building into a new crude gas channel and then routed to the conditioning cooling tower.

Three advanced features are implemented in the crude gas channel for operational safety and reliability (24-7-365) before the gases reach the cooling tower inlet: 1. The crude gas channel is designed as a special “emergency stack”, including an “emergency damper” at the highest point of the gas channel.

2. A diesel generator supplied fan (SDS=Safety Draft System) is installed for aspiration of the furnace flue gases in case of

Fig.2 The new FTC in operation

breakdown of the electrical power supply.

3. A spark detection system is installed in the crude gas channel followed by automatically operated “extinguishing” ring nozzles.

In case of breakdown of electrical and air supply, the FTC will automatically switch over to the status “Natural Draft” and together with the SDS-System to the Mode “Forced Natural Draft”. This mode will keep the furnace building free of pollutants; further movement of the furnace equipment will be possible.

The spark detection and extinguishing system operates independently from all other systems and ensures that sparks emitted from the bake furnace will be automatically extinguished without any interruption of FTC operation as a preventive fire protection system.

Cooling tower The conditioning cooling tower is designed as a direct current cooler.

The off-gases are guided to the top of the cooling tower (gas inlet) and leave the cooling tower at its base. A special design ensures that the off-gases are treated with atomised water produced by a two-phase nozzle technology in an area where “plug-flow” is reached.

The cooling tower design is optimized with regards to the following tasks: 1. Adequate evaporation distance 2. Even “plug-flow” within the evaporation distance 3. No deposit build-up at the inner surface of the cooling tower 4. Dry condition at cooling tower hopper - outlet 5. Dry discharging of heavy particles at tower hopper These tasks are verified and optimized by a CFD study of the cooling tower design, as shown in Fig. 3.

The off-gas temperature at the conditioning tower outlet is maintained constant at ±0.5°C by automatic control of the water flow injection. The tower’s conditioning system is provided with

AWJ 2014 83

full redundancy and automatic handling of breakdowns. This allows lances and nozzles to be inspected and/or maintained without interruption or setting the FTP to bypass mode.

Fig.3 CFD Study Cooling Tower

A final, special surface coating protects the tower against corrosion, acid attack and deposits. Deposits and particles such as packing material from the baking furnace have already been extracted in the lower part of the tower by means of a cyclone and a double pendulum damper. Fig. 4 shows the new cooling tower in operation.

The performance of the cooling tower is also dependent on the quality of evaporation. The lance system provides a dual-phase nozzle technology, which generates finest droplets of less then 25 μm. Figure 5 shows such a spray nozzle system, consisting of 5 nozzles per lance.

Fig.4 The new Cooling Tower in operation

the alumina silo, is directly injected after the cooling tower and entry of the main reactor duct by a special alumina injector. The injection of fresh alumina early after the cooling tower is a key parameter for the performance of the FTC, especially for the bonding of preliminary phases of acids.

Fig. 5 Dual phase spray nozzle system

The pre-cleaned and conditioned offgases are channelled through the lower side conical outlet into the main reactor chamber. Fresh alumina, sourced from

The enriched off-gases are then guided into individual secondary reactor chambers and finally to the fabric filters. The secondary reactor chambers are also charged using the

84 ANODE PLANT TECHNOLOGY

alumina injector. This injector is fed with recirculated secondary alumina from the individual fabric filter chambers. As a result, the recirculation takes place at high concentrations of alumina, resulting in high adsorption rates for all kinds of pollutants. Finally due to the long sections of the reactor chambers and intensive mixing of the adsorbent media, the aerosols not only adsorb off-gases but fines in the media also absorb them and both are extracted at the fabric filter cloth as “filtration cake”.

As a secondary benefit, the consumption of primary alumina is very low (< 800 kg/h) and still achieves a maximum offgas efficiency in terms of HF, organics and other acids.

Duct systems and Dampers The duct system guides the gases through the FTC. The existing Duct Systems and Dampers had to be checked carefully. Non-optimized layouts with multiple bends and elbows lead to high pressure losses (hpl). The same applies for special types of dampers. A proper design of the duct system is the basic task to minimize these pressures losses. Also the change of a damper design can improve the performance of the FTC tremendously. For the overall system, consisting of ducts, dampers and filter chambers, a compromise between low-pressure loss and longest dwell period of alumina enriched with flue gas had to be found. Figure 6 shows the “optimized lpl” design to optimize flows and minimize pressure losses.

Filter chambers The adaptation of the existing filter chambers is strongly depending on the existing infrastructure and the existing design. The process requirements for a redesign of an existing filter chamber was easy to formulate, but not easy to realize. The design target was the enlargement of the fabric surface in the space of the existing filter chambers.

An additional chamber was no option due to economical aspects. The future value of the filter surface load should be favourable in a range of < 1,0 m3/ m2 and minute. High gas flow rates in a range of 18 m/s in the ducts and reactors have to be reduced in steps to less than 1 m/s in the area of the filter bags. The separation of heavy particles (agglomerates) needs to be executed prior to the filtration cake.

In this area gas speeds of < 2m/s are obligatory.

new pre-separation chamber was designed and installed in front of each filter chamber to ensure the staggered deceleration of the gas speed.

It would have also been possible to raise the filter chambers and to prolong the filter bags. But the maximum length is limited by the efficiency of the pulse jet cleaning system and the maximum physical load on the filter bags during the cleaning cycle. Filter bags up to 6m are feasible, longer bags need to be examined with care.

Figure 7 shows the inner part of the modified filter chamber.

For daily operation and fast maintenance of the filter bags two main topics have to be considered:

The gas flow onto the filter bags has to be oriented in a wide area from bottom to top.

Fig. 7 Inner part of the filter chamber

Fig. 6 “Optimized lpl” design of the duct system

In order to ensure a good alumina transport without sedimentation within the ducts, a minimum flue gas speed of > 12 m/s is necessary. Especially during different phases of FTC operation with only one or two furnaces in operation, the minimum flue gas speed has to be maintained. For these dynamic conditions an automatic controlled flue gas recirculation system was designed and implemented.

Technical solutions, which contain a horizontal flow, generate an early wear and tear of the fabrics by partial overloads and in parallel inactive areas inside the filter chambers.

In a first approach all disturbing installations had been eliminated.

After that the filter chamber was fully furnished with a maximum possible amount of filter bags. In addition a

1. The Production must be possible even with n-1 chambers in operation, meaning with 1 chamber isolated.

2. The change of one complete set of filter bags for one chamber should be possible during one production shift.

Consequences for the fans The existing fans had a power of 160 kW each. To ensure the desired flow, 3 new fans with a power of 200 kW each for nominal and 1 spare fan for extra capacity had to be installed to reach the necessary volume flow and draft with enough spare power for compensation of future plant

AWJ 2014 85

Fig. 8 Fan system in operation

aging effects. An operation mode of n-1 is implemented, because every malfunction of a fan would disturb the furnace production immediately.

Systematic maintenance incl. turndown of fans is mandatory to reach the desired performance and reliability.

Figure 8 shows the new fan system in operation.

Conclusion After all these aspects have been technically realized, the desired performance for higher production was available. As a positive effect the dosing of fresh alumina after finetuning was minimized to 800kg/h; this corresponds with a fresh alumina load of 7,8g/Nm3 flue gas.

If the right balance is found between fresh and recirculated alumina, the wear and tear in all aspects of the FTC

will be minimized in the long term and the adsorption ratio, respectively the cleaning effect is maximized.

This leads to minimum emissions in the clean gases, which are vented to atmosphere.

Operational results The fluorides and total dust values were obtained following the US EPA13a method. Each monthly value was obtained as an average of two or three individual values.

The condensed soluble tars values were obtained following EPA429 method and correspond with international standard test measurements.

The total dust concentration obtained by this method during these measurements was 0.54 mg/Nm3, which is equivalent with the monthly average obtained by the other method.

86 ANODE PLANT TECHNOLOGY

The very low condensed soluble tar values (< 0,008 mg/Nm3) correspond with the design criterias but also with an optimum pre-process condition for the FTC, i.e. the excellent adjusted interactions between furnace, firing system and a professional baking process conduction through the carbon team.

Summary The results presented above show impressively that the upgraded FTC technology even in the given boundary conditions can achieve or surpass emission values stipulated by international regulations by far.

The project was executed in time and in budget which finally assured the technological and economical benefits for the carbon plant of ALUAR Aluminium.

For gaseous fluorides the following emission values were measured:

Fig. 9 Measurement of gaseous fluorides.

For the particulate fluorides the following emission values were measured:

Fig. 10 Measurement of particulate fluorides.

Total dust at stack measured and is showing values far below the environmental limits:

The emissions of condensed soluble tars is shown in the following figure:

Fig. 11 Measurement of total dust .

Fig. 12 Measurement of tars:

Authors E. Cobo; L. Beltramino; J. Artola, Aluar Aluminio Argentino Dr.-Ing. F. Heinke; Dipl.-Ing. D. Maiwald; D. Di Lisa; Innovatherm Prof.-Dr. Leisenberg GmbH & Co KG, Butzbach, Germany

AWJ 2014 87

Trusted by more smelters than any other.

For over forty years Alesa has been supplying aluminium smelters with systems to handle and convey bulk materials such as fresh and reacted alumina, crushed bath, coke and fluoride.

Our knowledge goes beyond materials handling.

Being an aluminium producer we understand how our systems impact your process. Alesa is a full service technologies supplier that also offers automation, pot controls systems and reduction technologies.

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TECHNOLOGY 8 88 ANODE GLOBALPLANT ISSUES

MATERIALS, HANDLING & TRANSPORTATION Vigan Engineering Pneumatic unloaders, a most convenient way for handling alumina

p. 90-91

Siwertell Siwertell unloaders offer industry changing advantages for

p. 92-95

alumina handling

AWJ 2014 89

VIGAN pneumatic unloaders, a most convenient way for handling alumina

Pneumatic suction of alumina by VIGAN continuous ship unloader

The trade of alumina remains strong and very competitive: therefore port operators continue to focus on achieving low unloading costs as well as minimizing the environmental impact which is becoming an evermore important topic.

The very free flowing and abrasive characteristics of this white powder make its handling a rather challenging goal in order to achieve these two main targets.

Most frequently, alumina is unloaded from sea vessels into a specially designed conveying system for transport to storage facilities, or into a hopper from which it is loaded into trucks, but it can also be directly packed on the quays, into 1 or 2 ton big bags for instance, to be transported to smelting plants later on.

Although the traditional unloading method is done by grabs and simple hoppers on the quay, this is not the most effective one, namely due to dust pollution and spillage:

• Dust pollution is a serious problem, mainly in urban areas. Any moderate breeze will blow away alumina, thus contaminating the air and surrounding areas which must then be continuously cleaned.

• Spillage represents a material loss of 0.2 to 0.5 %. Considering that generally large quantities of this valuable product are conveyed, spillage adds to the costs incurred in unloading operations. The use of hoppers with dust suppression devices such as suction fans and air filters is feasible, but the investment cost involved can be relatively high. Furthermore the time spent for completing each complete cycle of the grabs can significantly reduce the average unloaded yield.

Pneumatic unloading: a proven method with up-to-date technology Pneumatic unloading is the most suitable way for handling alumina: its free flowing characteristics make its suctioning very easy, and because

90 MATERIALS HANDLING AND TRANSPORTATION

the product is conveyed in a totally enclosed system, the issues of pollution by escaping dust and spillage are avoided.

VIGAN expertise in alumina pneumatic unloading include: • Optimized design of the suction line with unique high wear-resistant alloys; • Specific know-how for separating the alumina from the conveying air without any airlock, which provide maintenancefree operation; • State of the art filter design and filtering materials to guarantee dust-free air exhaust.

Self-propelled on rails or on rubber wheels for instance, VIGAN pneumatic unloaders are able to move with ease along the ship and no additional equipment (such as hoppers) is required for ensuring quick and reliable unloading operations.

The direct drive is another major improvement because it reduces not only the number of bearings compared with a traditional drive of belts, but also the mechanical wear on the turbine shaft.

Launched in the same time period as the turbine control with inverters, it has become a standard device for all large size VIGAN pneumatic CSUs. Continuous monitoring of the performance and operating parameters of the machines has revealed the power consumption of this type of equipment is quite comparable with the method using grabs for instance, especially when the average unloading performance and the directly related operating costs or consecutive savings are taken into consideration.

Optimum alumina unloading equipment choice Old and new designed TURBO blower assembly with direct drive.

A most frequently commented aspect of pneumatic CSUs in comparison with the traditional method performed with grabs is the power consumption required.

However, most recent technological developments such as the installation of frequency inverters and the direct drive of the turbo blowers, both duly correlated with an optimized design of the suction nozzle, are consequently enabling much lower power consumption than in the past.

In comparison with 12 to 15 years ago, power consumption of pneumatic equipment in use for unloading agribulks has decreased from 0.9 to 1.0 kWh/t down to 0.6 to 0.8 kWh/t.; and similar power consumption decreases have been measured for alumina.

Frequency inverters (also called speed variators) allow continuous and precise control of the suction pattern.

The air flow is now controlled by the inverter.

Air over flow is regulated in order to limit the power absorbed by the main electrical motor.

The power delivered to the blower by the electrical motor is automatically controlled with the inverter by limiting the torque at a maximal value. When only air is sucked, the torque limitation will automatically reduce the electrical motor velocity.

Also when the suction is stopped by the operator or by the interlock system of the storage system, the inverter will stop the blower, delivering additional power saving during downtime.

Inverter systems installed on VIGAN equipment have been proven to add 25% to 30% power saving.

For more than 12 years VIGAN has installed frequency inverters on pneumatic ship unloaders with an in-house expertise for optimized calibration.

Indeed, it is a real challenge for many executives in the alumina sector.

A cost effective pneumatic technology for unloading remains the best performing alternative for many ports and the alumina processing industry.

VIGAN team commitment with about 25 years expertise in various countries such as Finland, France, Poland, China and Iran, is to supply its customers with the best expertise by providing the most suitable solutions for their requirements.

Contact Details: Vigan Engineering s.a.

Rue de lâ&#x20AC;&#x2122;Industrie 16 1400 Nivelles, Belgium Phone: + 32 67 89 50 41 E-mail: info@vigan.com Web: www.vigan.com

AWJ 2014 91

Siwertell unloaders offer industry changing advantages for alumina handling

Alumina unloading is one of the few industrial areas which have not been touched by modern advances, and Cargotec believes that it would benefit from the substantial advantages inherent in its Siwertell screwtype unloaders “There is always one market where you know that you could make a real difference, and for us that market is alumina unloading,” says Per Karlsson, Managing Director of Siwertell bulk handling solutions at Cargotec. “While we are well known in alumina loading with numerous successful references, we have not yet established ourselves as the first choice for unloading equipment; pneumatic and grab systems are currently favoured by the industry, but both of these technologies have major drawbacks, such as high power consumption and spillage.

“We know that our screw-type unloader is ideal for discharging alumina and will deliver huge cost savings. However, the industry is resistant to change.

Therefore, to prove without doubt that we can offer the best system, we are very keen to perform a full scale test with one of our mobile unloaders to demonstrate how incredibly effective and environmentally-friendly our system is.

“We are so confident of our claims that we will undertake one of these tests for a potential client later this year and demonstrate how our mobile unloader discharges a vessel. We will do this, free of any charge. Perhaps there are others that would also like to see a demonstration? I hope that someone reading this article will take the lead. I know they will not be disappointed.”

Approximately two tonnes of alumina is needed to produce one tonne of aluminium. It poses specific and complex handling problems due to its highlyabrasive and extremely free-flowing

92 MATERIALS HANDLING AND TRANSPORTATION

properties. This means that unless the port’s unloading equipment is totally enclosed, it will face problems with spillage and dust.

“Alumina is a very expensive material, currently about US$400/tonne and therefore any loss of material should be avoided as it has a huge impact on the actual running cost,” explains Mr Karlsson. “For example, a port that imports 1 million tonnes of alumina per year and uses a grab crane will lose about 1.5 percent of material due to spillage; the value of the lost material will be approximately US$6 million each year that this operational set-up exists. Based on a typical ship unloading equipment lifetime, about 20 years, the total loss of the operation will be around US$120 million.

A figure of this magnitude should be impossible to ignore.”

A totally enclosed Siwertell screw type unloader completely eliminates spillage. “Lifetime cost savings of this magnitude easily justify the initial in-

vestment in a Siwertell unit,” notes Mr Karlsson. “In addition to these substantial cost savings, dust creation is reduced to a minimum, providing a healthier working environment and avoiding conflict with the increasing levels of environmental regulation.”

While pneumatic unloading systems do not suffer from spillage, they have other characteristics which make them far from ideal for handling alumina.

The high velocity inside the conveying tubes leads to high rates of wear on the conveying line. More importantly, high speed conveying results in a high degree of crushing for the material being transported. While this may not seem to be a particularly significant problem, it is in the case of alumina because of its effect on the smelting process.

The high conveying speed and consequent crushing cause approximately 5-6 percent degradation of the alumina. This increased percentage of fines in the alumina has a negative impact on the already energy-intensive

aluminium smelting process, as fine alumina requires significantly more energy to process. Therefore, use of a pneumatic unloader, which itself has a high power consumption, also incurs significant additional costs further down the line in the production of aluminium. Mr Karlsson says this can be as much as a factor of three or four compared to processing undamaged raw material. “To put a figure on this, if the port is still unloading about 1 million tonnes of material a year and the price per kWh is about US$0.15, the cost for the additional energy will be in the range of US$1.2-1.5 million per annum.”

Given that using a Siwertell screw-type ship unloader for handling alumina will address the problems of spillage and crushing, along with the substantial associated costs, it is hard to understand why the industry has not eagerly taken up the technology. Mr Karlsson believes that this reluctance may have a lot to do with peoples’ difficulties in accepting that a screw-type unloader

can have such a gentle touch on the material passing through it.

“Everyone can see that there is no spillage and hardly any dust; that is not an issue. And the quiet, economical operation is very easy to verify. I believe the sticking point for many operators is the issue of cargo degradation.”

“Intuitively they feel that a screw-type unloader must be harsh on the cargo.

While intuition certainly has its place in business, it should be rejected when the facts and figures clearly show that it is wrong. And we have overwhelming evidence to prove our claims in the context of alumina unloading.”

The cargo-friendly nature of Siwertell screw-type unloaders and conveyors has been repeatedly proven both by both full-scale tests and testimonials from satisfied customers throughout the brand’s 40 years experience of bulk handling.

Tests include those carried out over a ten-year period in Bosnia-Herzegovina at Aluminij Mostar d.o.o’s alumina in-

AWJ 2014 93

take at Port of Ploçe in Croatia, using a Siwertell 5000 S-GT unloader. The results provide clear evidence of cargo degradation at less than 0.2 percent. A full-scale test using a Siwertell 640-D at Fremantle, Australia in December 2006 controlled by SGS confirms negligible degradation of less than 0.1 percent. In contrast, the degradation typically experienced by operators using pneumatic unloaders is in the region of 5-6 percent.

Siwertell is continuously developing its technology to further improve efficiency and reduce operational costs; however current performance is already extremely impressive. Siwertell has undertaken performance tests where the unloader has exceeded 75 percent through-ship efficiency. Siwertell offers guaranteed lifetimes for unloaders handling abrasive materials of up to 10,000 hours for Siwertell screws and tubes.

In conclusion, Mr Karlsson says he believes that by offering alumina handling operators guarantees relating to material breakage, power consumption and spillage, along with lifetime warranties, Siwertell will take alumina handling to a new level that will generate huge cost savings for those with the vision to put the past behind them and adopt the optimum technology.

Cost-efficiency comparison: Siwertell unloader and pneumatic unloader

Per Karlsson “We know how to load and unload alumina, and our units meet all the known regulations related to safety and the environment,” says Mr Karlsson. “Over the years Siwertell screwtype ship unloaders have become the industry-standard for handling many kinds of dry bulk materials; 400 installations in operation worldwide speak volumes about the quality, reliability, cost effectiveness and minimal environmental impact of our technology, along with our maintenance and service offerings.”

Yearly intake

One million tonnes

Operating hours/day

20 hours

Ship size

65,000 dwt

Ship cost/day

US$25,000

Rated capacity, pneumatic

600t/h

Efficiency, pneumatic

55 percent

Rated capacity, Siwertell

1,000t/h

Efficiency, Siwertell

70 percent

Unloading days, pneumatic

152 days

Ship cost, pneumatic

US$3.8 million/year

Unloading days, Siwertell

72 days

Ship cost, Siwertell

US$1.8 million/year

A saving of US$2 million per year is possible in shipping costs alone using a highly efficient Siwertell unloader.

94 MATERIALS HANDLING AND TRANSPORTATION

Contact Details: Email: blksales@cargotec.com Tel: +46 4285800 Website: www.siwertell.com

Say goodbye

to crushing, dust, spills, and additional fines in

alumina unloading Take advantage of a free demonstration at your facility and let us show you what advanced alumina handling really looks like.

There is nothing to lose and so much to gain. We are waiting to hear from you. blksales@cargotec.com

www.siwertell.com

1974

40 2014 AWJ 2014 YEARS

95

Stressometer® Systems. From hot to cold.

The long standing problem of flatness measurement and control in aluminum hot rolling mills is now solved by ABB. Achievements in the field show yield improvements of 2 % and rolling speed improvements of 10%. Altogether this corresponds to millions of dollars on the bottom line. One reason for this is, as one of our customers put it, ”Good tail-out from the hot rolling mill results in high quality head-in to the cold rolling mill”.

The range of applications where the Stressometer system sustainably improves your business includes all kinds of cold rolling mills; and now also aluminium hot rolling mills. www.abb.com/pressductor

ABB AB Force Measurement Phone: +46 21 32 50 00

96 COMPANY MATERIALSPROFILES HANDLING AND TRANSPORTATION

COMPANY PROFILES ABB Making your processes measure up

p. 98-99

Hycast Game changer casthouse solutions

p. 100-102

AWJ 2014 97

Making your processes measure up

We are helping thousands of clients all over the world to boost their productivity and yield

Stressometer Flatness Control System installed in an aluminium rolling mill.

ABB Measurement Products Force Measurement Vasteras, Sweden At the heart of ABB technology is the understanding that flatness, tension, pressure, position and dimension can be sensed accurately, reliably and repeatedly on a continuous basis. The data generated by such sensing devices can then be used to control external equipment in such a way that process parameters are kept constant.

And as a result, operators can increase productivity and achieve higher levels of consistency in product quality. Our products not only measure the forces within a process, they help make sure that production measures up to expectations. Using state-of-the-art technology, ABB provides purpose built solutions for your force and dimension measurement needs. Making it possible for your production output to accurately match the most varying and demanding requirements.

Challenge the hidden potential within your application with the leading measurement technologies:

Pressductor® Technology ABB’s well-known Pressductor® Technology is a measurement principle based on the magneto-elastic effect – the magnetic properties of a metal are influenced by the mechanical force applied to it. Because the signals produced are not reliant upon physical movement or deformation, the load cells combine sensitivity with extraordinary tolerance to overloads and virtually no built-in limit to the number of load cycles.

ABB’s Pressductor® transducer stands for unbeatable load cell performance, thanks to its unique combination of accuracy, overload capacity and ability to withstand harsh environments. By using this technology you will achieve higher quality and reliability, especially under demanding conditions.

Pulsed Eddy Current Technology ABB has developed a completely new way of performing measurements with eddy current technology. It is a method that makes it possible to measure, in real time and in line, dimensions and other attributes with exceptional accuracy.

98 MATERIALS COMPANY PROFILES HANDLING AND TRANSPORTATION

The new ABB technology is based on measurements of the voltage pulse induced in the coil when the current is suddenly interrupted. By measuring this value at three different times three parameters can be derived; the distance, the electrical resistivity and the thickness.

Since this is a non-contact technology it eliminates the drawbacks of common systems based on X-ray or isotope contact measurement.

Flatness Measurement & Control Based upon our experience from more than 1200 installations of flatness measurements and flatness control systems worldwide we continuously develop new generations of the market leading flatness system – the Stressometer® System FSA. This system will not only make your mill more competitive today, it will also provide you with tools and methods to ensure that you keep in front of your competition in the future. Internet technology gives you a non-proprietary platform - independent way of

ABB’ Millmate Thickness Gauging System installed in an aluminium rolling mill.

expanding the system functionality and the CPU power when your needs are growing.

Advanced control methods, such as the Extended Singular Value Decomposition (ESVD), bring rewards to our customers exceeding 100,000 USD per year.

Some of the benefits with the Stressometer® System are: • • • •

Improved yield out of each coil Improved strip quality Shorter production cycles Reduction of number of strip breaks • Reduction of cost for process development • Reduction of cost for maintenance Lab accuracy in the mill The Millmate Thickness Gauging Systems (MTG), utilizing the Pulsed Eddy Current Technology, open up a new dimension in metal strip gauging with superior features:

Millmate Strip Scanner System installed in a rolling mill,

• Contact-free and yet material independent Gauging for non-ferrous metals • Robust and completely insensitive for conditions in the measuring gap, such as oil, water, coolants, steam, etc.

• Accuracy to a level of 0.1% • Poses none of the risks associated with X-ray or isotope gauges • Measures as accurately in production as in the laboratory

Modern rolling mills often use a variety of measurement and control facilities. One of the most important parameters is the position of the strip.

If this is not correctly measured, there is a great risk of rolling the strip under incorrect presumptions. This leads to poor flatness, especially at the edges, and to a final product of inferior quality or even strip breakage. In addition to this, the strip width must be kept within the specified tolerances – essential for good economy of production.

A non-contact, non-optical measurement system The Millmate Strip Scanner System determines the edge position of a metal strip in a rolling mill down to millimeter resolution. High, consistent quality is always the aim when producing steel, aluminum or copper strip.

This is equally true in rolling mills and process lines.

AWJ 2014 99

100 COMPANY PROFILES

Hycast

®

Game Changer Casthouse Solutions

In 1990 Hycast AS was established by Hydro to be a commercial manufacturer and market organisation for casthouse technology developed in-house at Hydro’s R&D centre at Sunndalsøra.

The first product was an inline degasser but shortly after casting technology for extrusion ingots, and stations for pot line metal fluxing followed. Most of the Hycast products have been captive during these two decades.

Today the Hycast product portfolio covers the whole casting centre and includes;

RAM Removal of Alkali Metal.

Crucible treatment for alkali metal removal, the removal of alkaline metal is carried out by the introduction of aluminium fluoride (AlF 3) to the liquid aluminium through a rotor using argon as a transport medium.

The RAM system is a customized system that is tailor-made for the tapping system on the smelter.

Hycast® RAM - characteristics and results • High removal efficiency for alkaline metal and carbides • Environmentally friendly - no need for chlorine in the cast house process line

Hycast® SIR - characteristics and results • Excellent removal of Hydrogen and inclusions (especially Oxides and Carbides) - especially important in locations with a high humidity

• Mould carriage can be customized for extrusion ingot as well as rolling slab casting • State of the art internally guided stroke cylinder • Breakaway-torque limiter for cylinder guide protection

• For extrusion ingot lines, no mechanical filtration system is required downstream the I-60 SIR

• Easy access to critical components, e.g. torque limiter

• Exceptionally low dross generation due to inert atmosphere in the reactor

• Platen with open steel frame, industry-proven safety system in an automated system

• Low operational cost - few rotors and very low Argon consumption

• Fully automated casting sequence obtainable in combination with Hycast® CCS

• Fully automated - environmental and operator friendly • Small footprint in terms of floor space requirements • Unique and patented melt refining concept • Drain free reactor unit • Available with Chlorine for improved Alkali removal efficiency

CMV Casting Machine Vertical.

GC – Gas Cushion / LPC – Low Pressure Casting, extrusion ingot casting technologies.

GC/LPC

The Hycast® GC (Gas Cushion) Billet Casting Technology is ideal for production of high quality extrusion billets with excellent surface quality and extrudability. The system is proven worldwide over more than two decades in casthouses owned by Hydro Aluminium and its partners.

Hycast® LPC (Low Pressure Casting) Billet Casting Technology is ideal for the production of larger diameters and hard alloys.

• Optimized furnace cycle time due to minimized or eliminated infurnace melt treatment

Hycast® CMV internally guided casting cylinder and mould carriage system.

The Hycast® CMV comprises of a vertical casting machine with a single acting internally guided hydraulic casting cylinder for extrusion ingot and sheet ingot casting. The mould carriage system is supplied as a tilt frame on a fixed foundation, or a rollaway mould carriage system with or without an integrated tilt-frame.

• Patented rotor design and injection system

Hycast® CMV - characteristics and results.

• Other diameter available upon request

• Founded on solutions proven to be successful in full-scale operation

• Patented dual graphite rings for optimal oil and gas distribution

• Mould carriage tailor-made to customer-specific requirements

• High pit utilization due to optimized mould arrangement

• Reduced inclusion level in the potline metal transferred to the casting furnace • Dross formation in casting furnace is reduced due to low Na content

SIR Inline Melt Refining.

The Hycast® SIR sets the benchmark for the in-line refining of molten aluminium at casting centers.

Hycast® GC / LPC - characteristics and results • GC diameter range 127mm 405mm (5” - 16”) • LPC diameter range 127mm 735mm (5” - 29”)

AWJ 2014 101

Hycast

®

Game Changer Casthouse Solutions

• High productivity, pit recovery, excellent and consistent surface quality

stantly achieve better quality at lower operation cost and thereby increases the competiveness of its customers.

• A fully automated casting sequence can be obtained by combining the Hycast® Billet Casting Technologies with the Hycast® CCS

• Technology and process development

AFM – Adjustable Flexible Moulds / FM – Flexible Moulds, sheet ingot casting technologies.

• Complete casthouse support for customers

AFM/FM

The Hycast® AFM (Adjustable Flexible Mould) Rolling Slab Casting Technology is developed to reduce the number of moulds needed to produce ingots with optimized geometry and surface quality. Hycast FM® (Flexible moulds) have been used within Hydro Aluminium for more than a decade.

Flexible moulds with fixed width and moulds with fixed geometry may also be provided – an option for smaller dimensions.

Hycast® AFM - characteristics and results • Geometry range: Thickness 330mm -700mm, Width 1100mm2500mm • Adjustable range: 300mm -400mm • Unique and patented flexible mould technology to ensure optimal ingot geometry from start to end, and for varying casting speeds • High productivity, pit recovery and excellent and consistent surface quality • A fully automated casting sequence can be obtained by combining the Hycast® AFM with the Hycast® CCS and the Metal Level Control System

Hycast Service Knowledge and Competence.

Hycast supports customers to con-

102 COMPANY PROFILES

• Project management, engineering (mechanical and electrical/automation) • Close link to Hydro Aluminium’s R&D facilities, including Reference Centre • Cooperation with NTNU and SINTEF in Trondheim, Norway The business model of Hycast is to be an engineering company for aluminium casthouse projects. Manufacturing is done by a limited number of qualified suppliers. Innovation is a highly prioritized task and new product development is done in close collaboration with Hydro’s R&D and production systems, technology partners, customers and suppliers. The core competence of Hycast is actually multi-disciplinary.

Aluminium metallurgy knowledge is the basis for all our products and services but process understanding, mechanical and electrical engineering, automation and project execution are equally important competences at Hycast. Over the years a substantial number of small and large projects have been completed in most corners of the world. HES have been the backbone of Hycast from day one. Since the start in 1990, no Hycast employee has been injured at work! No fatality related to the operation of Hycast equipment has ever been reported.

Hycast was the first to deliver a technology portfolio that eliminated the need for Chlorine in the cast house.

This was made possible by combining the AIF3 pot line fluxing (RAM) with the SIR inline melt refining unit. The casting processes delivered by Hycast are highly automated and minimize

the need for operators to be in close proximity to the casting pit during all phases of the cast. The Hycast Safety Philosophy is embedded in the automation system, including hardwiring of all emergency functions.

In the past Hycast has introduced new technologies to the market. In 2012, Hycast introduced the Adjustable Flexible Moulds (AFM) for sheet ingot casting. The new AFM technology is based on the proven Hycast flexible mould technology a unique and patented technology that ensures optimal sheet ingot geometry from start to end, and for varying casting speeds. Additionally the AFM reduces the number of mould sets needed in the casthouse as the technology has an adjustable range of up to 400mm depending on the mould width. During TMS 2014, Hycast presented the Low Pressure Casting (LPC) technology for extrusion ingot casting; the foundation of this new technology is based on proven Hycast GC technology. LPC is a new direct chill casting technology for applications where surface quality matters. It’s also ideal for production of larger diameters and hard alloys.

The LPC provides a new standard in surface quality as well as thinner inverse segregation zone compared to other technologies.

Service and support is a challenge when working globally. To meet this challenge Hycast is staffed with highly skilled, experienced and mobile service engineers. In addition, in many cases customer assistance may be done from the Hycast office by accessing the cast house systems online for investigations and trouble-shooting. Hycast supports customers to constantly achieve better quality at lower operation cost and thereby increases the competiveness of its customers.

For more information see; www.hycast.no Contact: hycast@hydro.com

Some things live forever. Like the famous photo of Marilyn Monroe. Like aluminium, which can be recycled and live on in new products. And like Hydro, which has been renewing itself for more than a century.

www.hydro.com

AWJ 2014 103

Advertisers and Web Index

PAGE No.

COMPANY

WEB ADDRESS

ABB AB Force Measurement

www.abb.com/measurement

96

ABB Switzerland Ltd.

www.abb.com/aluminium

2

Alcoa Inc.

www.alcoa.com

1/4

Cargotec/Siwertell

www.siwertell.com

95

ECL

www.ecl.fr

20

Fives

www.fivesgroup.com

FLSmidth

www.flsmidth.com

49

Hycast A/S

www.hycast.no

100 66/103

60/106

Hydro

www.hydro.com

Innovatherm

www.innovatherm.de

81

Power Jacks

www.powerjacks.com

56

Rio Tinto Alcan

www.riotintoalcan.com

18

RTA AP-Technology

www.ap-technology.com

46

RTA Alesa Ltd.

www.rta-alesa.com

88

Sensotech

www.sensotech.com

52

TMEIC

www.tmeic.com

UC Rusal

www.rusal.ru/en/

Vigan

www.vigan.com

104 ADVERTISERS COMPANY PROFILES AND WEB INDEX

8 14 90/105

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AWJ 2014 105 71

ANODE PLANT TECHNOLOGY