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2008 — Environment
Extending pot life to reduce waste
A series of initiatives at the Deschambault Smelter resulted in the development of a new technology to extend the life cycle of pots. This innovation, which has also been adopted in Australia, Iceland and the United States, received a 2008 Alcoa Impact Award for North America.
In 1997-98, the typical life cycle for a pot was approximately 1,500 days – a little more than four years. A minimum of five years can be expected using modern technology.
After analyzing the types of erosion that were affecting the cathodes and life cycle of pots, we concluded that the priority was to identify alternatives to how the electrical current was passing through the cathodes. In doing so, we could avoid the peaks that were causing perforations in the cathodes.
An initial prototype was installed in the summer of 1999, and we noticed that a reduction in voltage enabled an increase in amperage and that the energy saved could be used to produce more aluminium. The number of prototypes was increased to six in 2000 and, in 2001 the decision was made to gradually modify all of the pots at the end of their life cycle. This process is now completed.
The environment also comes out a winner. When a pot is replaced, all of the materials that remain inside – the used pot liners – must be disposed of. By extending the life cycle of the pots, which we aim to extend to seven years by 2010, we will be able to reduce the number of pots being replaced and the accompanying waste by over a third.
The technology developed by the Deschambault Smelter was patented in 2001, and has since been implemented in over a hundred pots at the Portland Smelter in Australia, in about 50 pots at the Baie-Comeau Smelter, in two prototype pots at Mount Holly in South Carolina, and in all 336 pots at the Fjardaál Smelter in Iceland.