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2008 — Environment
A noteworthy performance in GHG emission reduction
In 2002, Alcoa Canada Primary Metals was the first corporation to sign a voluntary greenhouse gas (GHG) emissions reduction agreement with the Government of Quebec. This five-year agreement fixed specific reduction targets and required compensation to be paid if the targets were not reached.
At the end of 2007, Alcoa had not only reached but surpassed all of the government’s targets, reducing by approximately 17% its total GHG emissions compared to 2001, despite a 4.4% increase in production. These results were obtained thanks to the dynamic exchange of best practices among our facilities, to process improvements and, especially, to the sustained efforts of our technical and production teams.
Improvements at Electrolysis The efforts focused on the electrolysis process, the largest source of GHGs in a smelter. In fact, this process emits CO2and perfluorocarbons, or PFC, which are also greenhouse gases. CO2 production is difficult to reduce because of the nature of the process. However, the production of PFC (CF4 and C2F2) can be decreased since it is linked to anodic effects, which take place in the electrolytic pots when there is a shortage of alumina.
By improving its processes, Alcoa reduced PFC emissions linked to anodic effects by 49% between 2001 and 2007. While all of our plants have taken action to address this important issue, the efforts of the Bécancour (ABI) and Baie-Comeau smelters are particularly noteworthy.
Bécancour Smelter In 2001, ABI decided to optimize the automatic treatment of anodic effects, enabling it to reduce the duration of anodic effects by 39%. Then in 2003, it developed a computer application to predict anodic effects. Workers now receive a signal about 30 minutes before an anodic effect. Upon receiving the signal, the operator can check the pot’s alumina feeding system. The more time there is to react, the better the results.
At the end of 2005, a further improvement was made to the process that allows an adjustment in the quantity of alumina being supplied to the pot based on its historic performance. Creating a new algorithm for the pot microprocessors is one of the major challenges undertaken by our automation technicians. This latest improvement results in a significant reduction in PFC emissions, from 153 kg CO2 equ./mt of aluminium in 2005 to 48 kg CO2 equ./mt of aluminium in 2006. This performance was maintained in 2007.
Baie-Comeau Smelter The Baie-Comeau Smelter has enhanced its performance both at its prebake and Söderberg plants. In the prebake plant, the treatment of anodic effects was improved by implementing a prediction program based on the one developed at ABI. The plant also applied and improved the management by position of its pots, a method developed by the Deschambault Smelter to optimize the operation of individual pots. The gradual implementation of a new computerized pot control system, QLC (Quiet, Lean and Cool), which began in 2007, should result in even better results down the road.
The Söderberg pots are a significant source of PFC because there is no modern way to control the supply of alumina going to the pots, like there is in the prebake. Everything is done manually. After some reductions achieved between 2002 and 2004, there was an increase in emissions in 2005 due to changes made to reduce other types of emissions. We had to react. By applying ABS (Alcoa Business System) methods, as well as daily management and problem-resolution approaches, we succeeded in reversing the trend thanks, in part, to:
Exchange and standardization with other plants that use the Söderberg technology;
The installation of 12 progress charts with visual indicators (one in each work zone) to visualize the reduction in the duration of anodic effects compared to the established standard;
The purchase of three vehicles to enable quicker reaction time; and,
Individual feedback given to employees on their performance regarding the treatment of anodic effects.
This work translated into a 33% reduction in PFC emissions at the Söderberg plant in 2007, and a reduction in absolute emissions for the entire smelter (prebake and Söderberg) of 18% compared to 2006 and 27% compared to 2001.
Kudos Alcoa recognized ABI for having the best PFC emissions performance in the world for prebake technology. The Baie-Comeau Smelter was granted the highest honour at the Alcoa North America Impact Awards for its reduction in GHG emissions at the Söderberg potrooms.