Anode plant – aluminum smelter

A major improvement in the durability and electrical conductivity properties of anodes was made recently by preparing the paste at high temperature, followed immediately by a rapid cooling with cold water in a mixer. However, adding water to the paste is accompanied by a marked increase in VOC and HAP concentrations, such as naphthalene, benzo-a-pyrene, fluoranthene and other toxic and heavy aliphatic compounds. A BIOTOX® regenerative thermal oxidation unit was adapted and installed for the first time in the world on this type of application in a modern aluminum plant in Canada. The BIOTOX® process has the following characteristics:

• High destruction efficiency, greater than 99.8% on all compounds (light and heavy), PAHs, in comparison to 70% efficiency for the conventional process on light compounds such as PAHs and naphthalene;
• Adaptation to processes and especially to the production cycle of VOCs-PAHs in a paste mixer;
• Treatment in the regenerative incinerator of VOCs-PAHs whose concentrations vary greatly;
• Development of a gas recirculation system that is both flexible and keeps VOC-PAH fumes above the dew point at all times;
• System and equipment security;
• Special features of Biothermica technology.

Improvements made to the process allowed an anode plant to meet very strict environmental norms while still producing high-quality anodes. Other improvements have been made, such as:

• Emergency system for rapid heat evacuation from the interior of the BIOTOX® unit combustion chamber;
• Patented recirculation loop accompanied by a burner;
• Special construction of bed bottoms.

This unit earned the highest international award, the Sausenbaugh Award from the Air and Waste Management Association in 1999, for Biothermica’s technological achievement in air pollution control.