1997 TMS Annual Meeting: Tuesday Session

ALUMINIUM REDUCTION TECHNOLOGY: Session III: Smelter Technology

Session Chairperson: Jerry Johnson, Alumax Inc., Intalco Plant, P.O. Box 937, Ferndale, WA 98248

8:30 am

COMMISSIONING OF ALUSAF HILLSIDE SMELTER REDUCTION POTS: Jean-Paul Aussel, Jean-Claude Frison, Aluminium Pechiney, Licensing Department, BP 7, FR-38340 Voreppe, France; Shaun Kroutz, Gideon Stander, Alusaf Hillside Smelter, P.O. Box 897, RSA 3900 Richards Bay, Republic of South Africa

From the 18th of June 1995 to the 21st of June 1996, Alusaf Hillside Smelter started the 576 AP30 reduction pots of its two potlines. The promising results achieved by the first stabilized pots allowed the Process management team to finely tune the potlines around 310 kA and to achieve current efficiency in excess of 95.5% and energy consumption very close to 13000 kWh/t during the first half of 1996. The results of these first 6 months of operation of the first full potline are discussed. It includes data on the raw materials, the organisation and the training programs of the Reduction Department which were all instrumental in engineering this success. The evolution of the Reduction Process parameters and results described in the paper will be updated for the final presentation with the available data of both potlines.

8:55 am

FROM 110 TO 175 kA: RETROFIT OF VAW RHEINWERK. PART I: MODERNIZATION CONCEPT: D. Vogelsang, I. Eick, M. Segatz, Ch. Droste, VAW Aluminium-Technologie, G.-v.-Boeselager-Str. 25, D-53117 Bonn, Germany

Modernization of the 210,000 tpy VAW Rheinwerk smelter includes installation of point feeder, alumina conveying system, state-of-the-art pot control system and forsees an increase in amperage of up to 175 kA. For the modernized pots, concepts for the potlining as well as for improvements of the busbar system were developed, based solely on computer simulations. For the layout of the potlining a new three-dimensional thermoelectric cell model was applied that allows prediction of side ledge countours as well as heat and voltage balances. Based on this model the choice of semi-graphitic vs. fully graphitized cathode blocks was evaluate with respect to the anticipated increase in system amperage. Temperature fields and side ledge contours predicted are in good agreement with measurements. The busbar system, designed originally for a current load of 110 kA, was improved in a very efficient manner to cope with the higher amperage. Magneto-hydrodynamic simulations predicted and plant measurements demonstrated significant improvements in cell stability and performance.

9:20 am

FROM 110 TO 175 kA: RETROFIT OF VAW RHEINWERK. PART II: CONSTRUCTION & OPERATION: J. Ghosh, A. Steube, B. Levenig, VAW Aluminium AG, Koblenzer Str. 122, D-41468 Neuss, Germany

Construction, start-up and operation of ten retrofitted 165 kA prebaked pilot cells in the Rheinwerk smelter are described. The excellent performance of these pots led to the DM 40 Mill. investment decision to retrofit all three potlines. The hot-change of cells during full potline operation minimizes production losses. The pilot cells are equipped with improved steel shells and lining, modified busbar system and modern pot controller and point-feeding system. To evaluate the most cost-effective solution with best performance, four cells are provided with two point feeders and six cells with three point feeders. The new-developed VAW-ELAS process controlling system with improved algorithms and a user-friendly graphical interface allows system atic surveillance and interpretation of all pot parameters and has a major contribution to the highly improved pot performance.

9:45 am

DEVELOPMENT OF A 200 kA REDUCTION CELL TECHNOLOGY - CD200: Geoff Bearne, Mark Dunn, Comalco Research Centre, P.O. Box 316, Thomastown 3074 Australia; Mike Roberts, Yousef Ali Mohamed, Dubai Aluminium Co. Ltd., P.O. Box 3627, Dubai, United Arab Emirates

In 1990, Comalco and Dubai Aluminium Co. Ltd. (Dubai) joined forces to develop a modern high amperage reduction cell design known as the CD200. This technology was aimed at the 190 to 200 kA operating range. It was designed to be compatible with future expansion plans at Dubai as well as at the Comalco managed New Zealand Aluminium Smelters Ltd. (NZAS) plant, while remaining within the scope of the present anode design. The cell incorporated a cathode lining design and alumina feeding technology which had been successfully demonstrated at NZAS. The bus bar system was developed using computer modelling at the Comalco Research Centre (CRC). Dubai provided the financial investment and operational experience as well as improvements in process control strategies. Five cells were installed in Dubai's potline 4 and these have operated since 1991. During the last five years, there have been changes to the bus bar design and cathode lining, introduction of larger anodes and further enhancements of the process control systems and operating practices. As a result, the operational performance and the power efficiency of the prototype cells have met or exceeded all targets. Subsequently, the technology has been selected for expansions at both NZAS and Dubai. NZAS has installed 48 cells to be operated at 190 kA, with commissioning from mid 1996. 2 is installing 240 cells to be operated at 195 kA, with start up scheduled in September 1996.

10:10 am BREAK

10:30 am

AN ANALYSIS OF THE ELECTRICAL PREHEAT TECHNIQUE BASED ON THE START-UP OF THE CD200 PROTOTYPES AT DUBAI ALUMINUM CO. LTD: Mark R. Dunn, Comalco Research Centre, P.O. Box 316, Thomastown 3074 Australia; Q.M.I. Galadari, Dubai Aluminum Co. Ltd., P.O. Box 3627, Dubai, United Arab Emirates

In 1991 the Dubai Aluminum Co. Ltd. And Comalco Research & Technology set up a joint project to develop a 200 kA cell in a facility attached to the end of Dubai's potline 4 (then under construction). One aspect of this project was the development and assessment of a suitable electrical preheat practice, based on Dubai's current methods. This paper reports on the process used and the extensive monitoring that took place during the preheats. The effect of current distribution control was also quantified in terms of cathode temperature variation.

10:55 am

ELECTRIC POWER CONTRACTS AND OTHER FACTORS AFFECTING SMELTER ECONOMICS: Nolan E. Richards, 117 Kingswood Dri., Florence, AL 35630; Helge O. Forberg, 8A Quail Ridge Court, Owensboro, KY 42303

The cost of electric power for smelters varies from less than 15% to more than 35% of operating costs. For a smelter with a high power rate, it becomes important to obtain a premium in the market for finished products, produce a higher proportion of premium grade metal, increase volume supplemented with purchased scrap, reduce other cost factors or negotiate a power contract that would allow power modulation. The large difference in cost of power demand between a peak period, normally between 6 p.m. and 10 p.m., and the no-peak period can give some smelters the opportunity to negotiate advantageous contracts for reductions in demand of 20-30% during the peak period. Provided the smelter can implement the changes necessary in the operating procedures to maintain control of potroom operations during the modulations, the decreased power rate can have a substantial beneficial affect on the plant's economics. Some of the strategies and major changes which could be considered for a reduction plant to improve economics are discussed in this paper.

11:20 am

CAPACITY CREEP - THE HIDDEN POTENTIAL GROWTH OF ALUMINIUM SMELTING CAPACITY: K. J. Driscoll, CRU International, Ltd., London WC1X 0AD, England

Given the lack of firm expansion plans for aluminium smelting capacity over the next few years, many people are expecting a smelter bottleneck to develop towards the end of the century. However, CRU believes that a potential source of capacity growth, which we call "capacity creep", is being ignored. As well as new greenfield and brownfield expansions which might fill the new capacity requirements, incremental production gains at existing smelters can be achieved through lower cost upgrades or improvements in operational efficiencies. Indeed, we believe that such capacity creep has historically added around 0.50-0.75% per year to industry capacity, although many of these capacity increases remain undocumented. This paper will present the results of an extensive study of the potential for growth in aluminium smelting capacity, in which we will review how and where capacity creep has occurred, and show that the potential for further capacity creep remains substantial.

11:45 am

ORGANISATION AND INFORMATION SYSTEMS: WHERE INTEGRATION COMES: S.A. Ferre, Aluminium Péchiney, 235 Avenue Alsace Lorraine, 73007 Chambery Cedex, France; P.W. Cowie, Alusaf Limited, 9 West Central Arterial, P.O. Box 897, Richards Bay 3900, Republic of South Africa

Managing an aluminium plant within a concurrential environment demands a greater use of leading edge technology. This technology is of course related to the smelting process but also deals with the organisation scheme and the information provided. During the engineering phase and the construction phase of the Alusaf smelter, Aluminium Pechiney has provided Alusaf with the AP30 technology and has elaborated an organisation with its SA partner. The design and the construction of the information systems have been done in partnership between AP and Alusaf. The information system is based on the use of the state-of-the-art technology and more important is really designed to fit the organisation and to evolve with it. It is built using the 4 classic levels of the CIM model. It takes advantage of packages as SAP R/3 and Microsoft Office Suite tools for routine processes and uses specific developments defined by AP and is used by Alusaf to implement value-adding processes.