The above graph shows the combined results of average fluoride emissions for the stacks at the fume treatment centers and the roof vents at the potrooms. A new standard of 0.95 kg F/t Al for annual fluoride emissions was established in 2011 for the three plants using the prebake technology. The Deschambault Smelter has been subject to this standard since 2007.
Despite a strong performance at the Baie-Comeau Smelter at the beginning of the year, emissions increased in June, notably due to intensity variations associated with problems at the rectifiers. In Bécancour, average emissions at the roof vents remained as high as in 2010 for all three potlines. However, emissions at No. 1 potline exceeded the new monthly limit in July and, by extension, the new annual limit. These emissions are attributable to operational, equipment and maintenance issues. Emissions at the Deschambault Smelter also increased in 2012 due to problems with coal dust in the electrolysis process.
Fluoride emissions – Söderberg Plant
Fluoride emissions at the Söderberg potrooms exceeded the limits set in the environmental agreement with the Ministère du Développement durable, de l’Environnement, de la Faune et des Parcs, which became regulation in 2011. Annual fluoride emissions were particularly impacted by the poor quality of the raw materials received at the beginning of the year.