Aluminum

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27 SESSION

ALUMINIUM 2006

SESSION 27: INTERNATIONAL SYMPOSIUM ON ALUMINIUM: FROM RAW MATERIALS TO APPLICATIONS — COMBINING LIGHT METALS 2006 AND THE 17TH INTERNATIONAL ICSOBA SYMPOSIUM Aluminium Reduction Technology Sponsor(s): Light Metals Section, The Metallurgical Society of CIM and ICSOBA Chair(s): A. TABEREAUX, Alcoa Primary Metals, Canada and M. BARBER, Alcan Ltd., Canada Room: Salon Drummond ouest–Level 3 PAPER 27.1 — 8:30 180 KA BOOSTER CELLS OPERATION AT ALBRAS G.E. DA MOTA, J.E.M. BLASQUES, H.P. DIAS and G. DE GREGORIIS, ALBRAS, Brazil In recent years, like many other smelters around the world, Albras has been increasing line current. The necessary adjustments to the work practices and process variables need to be made on all potlines, which in this case means on 960 cells at the same time. It was a challenging task to adjust the process parameters to the new amperage. In July 2003 potlines II, III and IV were running at 173 kA and the goal at that time was to reach 180 kA. Preliminary trials with 180 kA were performed on a group of 10 boosted cells on potline III in order to investigate possible operational problems. It was decided to increase the amperage in three steps accompanied by continual evaluation of the state of the process. In July 2004 the target of 180 kA was achieved with good operational results. This paper presents the overall results, the parameter adjustments made during the amperage increase in the booster group and how the increase was implemented on the other potlines. PAPER 27.2 — 8:55 AUTOMATIC ANODE SETTING AT ALBRAS A. CARNAVALE FILHO, B.S. ROCHA FILHO, C. TOMAZ GUIMARÃES, G. ARCANJO BICALHO, H. PENNA DIAS, L. SANTOS ALMEIDA, M.N.M. SOUZA, P. NAZARENO RODRIGUES, U.A. COURBASSIER and V. LUCIO SILVA, Albras, Brazil During primary aluminum production the anode changing is a very important task. So improvements on it will be essential to avoid disturbance and have a better operational control. After anode changing a good current distribution will be guaranteed using a cavity cleaner and precise anode setting. At Albras switching a manually anode setting to an automatic one solved the setting problems. In this paper it will be shown some pot line results and the improvements on workers ergonomic and safety conditions. The device was developed in a partnership between Albras and Festo. PAPER 27.3 — 9:20 RECOVERING POT PROCESS CONTROL AFTER LONG POWER INTERRUPTIONS AND SEVERAL LOAD REDUCTIONS J. YAMAMOTO, C. EDUARDO ZANGIACOMI, Alcoa, Brazil and L. PAULINO, Alcoa, Canada This paper presents the learning from Alcoa Poços de Caldas Smelter in Brazil, after several energy restrictions resulting from the failures of three rectifier units at its power switchyard. Starting on December 27th, fuses and diodes failed in

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PAPER 27.4 — 9:45 STEP CHANGES IN POTROOM OPERATION SCHEDULE AT ALCOA DESCHAMBAULT SMELTER G. PROULX, P. DOIRON, P. CHAMPOUX and J. PAQUIN, Alcoa, Canada After nine years on a 36 hour schedule and two programs of creeping, the Alcoa Deschambault Potroom of faced the necessity of changing its organization for many reasons: the anodes butts were too small, the anode schedule was unbalanced, the iron content in the metal trends had increased, the metal tapping volume did not convene with crucible capacity and the liquid measurement task was delayed by tapping activities. A kaizen activity inspired the Potroom department to improve the organization. A team of 15 people including the process engineer, the process technician, team supervisors and Potroom operators developed a scenario, which would permit flexibility to creep pots if energy is available and an increase of added value production. This paper will describe the systematic approach, the communication method, the trials, the changes, and our success, along with the problems experienced by the team during the adaptation of Alcoa Deschambault Potroom organization over a 20 month period. Coffee Break — 10:10–10:40 PAPER 27.5 — 10:40 JOURNEY THROUGH A RE-START: AN ABI ADVENTURE! J. PETIT, Aluminerie de Bécancour Inc., Canada In July 2004 workers at the ABI Smelter in Bécancour (Québec, Canada) went on strike. Contingency plan were ready to face the situation and plan was done to operate one potline out of three. Two lines were stopped; keeping in mind the restart on cold metal after the strike was over. The subject to be presented and shared includes a summary of work organization including training, schedule of restart, pot cleaning, pot preparation, crash start method, follow up after crash start, safety and environment. This major project has been a very big challenge. It shows that people involvement is a must and the key success. It is then true to say: “People who believe in success will work and act in order to get there” and “People who don’t believe in success will act in such a way to fail” Then both will prove they were right to think their own way ! Sharing such experience can be interesting because it’s a true story and people like true stories.

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three rectifier units of Potline #1, causing a long and dangerous power interruption. Even after current was reestablished, amperage was only 70% of the line target leading to a bath freezing process that lasted for around 48 hours. The process engineering team played with several potroom parameters as pot resistance, bath and metal levels, alumina feeding and bath chemistry in an attempt to minimize impact on the potline metal output and energy consumption. As it will be illustrated, the first battle was to keep the pots running on a “survival” approach. After that, several changes took place on the procedures used to run at reduced current which were considered rather successful. Finally, some recommendations will be given to foresee and prevent transformers and rectifiers from undesirable failures.

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27 SESSION

ALUMINIUM 2006

PAPER 27.6 — 11:05 BATH RATIO CONTROL IMPROVEMENTS AT ALCOA POÇOS DE CALDAS — BRAZIL – AN UPDATE L. PAULINO, Alcoa Canada, Canada, J. YAMAMOTO, R.A. CAMILLI and J.C. ARAUJO, Alcoa, Brazil The first paper presented on this work [1], showed how bath ratio was increased from 78% to over 95% using a structured approach to reduce bath chemistry variability. This update will illustrate the steps taken and update the results presented earlier, showing the effects of long power interruptions and several load reductions as well as load increase during the period from 1999 to 2005. Current efficiency was affected by such processes upset; however, bath ratio in range (±0.05) is still higher than 90%, even after an increment of more than 6 kA. This review will explain each of the steps taken to reach stability in this critical smelting parameter. PAPER 27.7 — 11:30 RECYCLING ‘SCRAP’ ALUMINA AT ALCAN ARVIDA WORKS – CANADA P. BERGERON, J. DEMERS, P. HUDON, R. LECLERC, A. LESSARD and H. VERMETTE, Alcan Ltd., Canada The Arvida Smelter marked its 80th anniversary in 2006. Arvida currently operates 6 potrooms equipped with prebaked side-feeding pots producing 160 000t of aluminum per year, requiring the supply of 300 000t of alumina per year. In the past, to ensure reliable alumina supplies to the pots, especially in winter, a safety stock of alumina was kept inside the plant. The improved reliability of shipping on the Saguenay River has cut the need for such a stock. However, the stoppage of 8 Söderberg-technology potrooms, starting in the 1980s up to 2003, generated alumina from the cleaning of pot pits, totaling 18000t and leading to the buildingup of a significant alumina stock again. Concerns over working conditions, effect on potroom operations, and dust emissions prevented Arvida from tackling effectively this impressive alumina stock. Yet the increasing cost of alumina has created a strong motivation to use the stored alumina. In 2004 Arvida launched a project to recycle the stored alumina. This 4-year project aimed at clearing the alumina stock without affecting the operation of the smelter. It involved changing work organization, improving equipment and controlling the effect of the recycled alumina on the smelting process and working conditions.

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