Strategies for Decreasing the Unit Energy and Environmental Impact of Hall Heroult Cells

Abstract

The electrolytic production of aluminum in a molten cryolite bath depends upon, as major raw materials, alumina, electrical energy, coke, pitch, and aluminum fluoride. From both economic and environmental aspects, conservation of these inputs, decreasing the energy in or operating voltage across cells, raising production, controlling and minimizing emissions from reduction plants are extremely important to every primary aluminum producer. Due to the complex and interactive nature of the parameters, fixed and variable, fundamental to the electrolytic process, there is a hierarchy of choices possible for addressing and improving, for instance, components of cell voltage, heat balance and conservation, variability amongst and stability within pots, consistency of high current efficiency, life of the cells, management of anode effects, etc. The impacts that operational procedures and work practices have on key parameters, their relationship to the inventory of basic knowledge about the Hall Heroult process and the expectations for relative improvements are identified and quantified to the extent possible. Additionally, with recent increased concern for global warming and environmental effects of CO₂ and CF₄ enlarging the industry’s continuing concern and responsibility for the immediate surroundings of a plant, aspects for characterizing and decreasing fluorocarbons are discussed.