World at work: hazards and controls in aluminium potrooms.

T he primary aluminium industry is one of the largest industries in the world today. World production exceeded 20 million metric tons in 2001 (IAI, 2002) and production is widespread throughout the world. Aluminium as the pure metal or in alloys is used to make a range of products including aircraft, utensils, scientific and domestic apparatus, electrical conductors, and automotive parts. Aluminium powders are used in paints, explosives, and fireworks. Aluminium is produced by the HallHeroult process, which involves the electrolytic reduction of alumina (Al2O3) in large carbon lined steel vessels called pots. Hundreds of these pots are housed in a ‘‘potroom’’. Pots may be of two types of technology, either Søderberg or prebake, with prebake potrooms the preferred design in modern smelters because of lower levels of emissions. In a pot, alumina is partially dissolved in an electrolyte of molten cryolite (Na3AlF6) at approximately 960 C̊. It is a continuous process that requires large amounts of direct current electrical power to operate the pots (Giga-watt-hours per annum). The older Søderberg process bakes the anode paste in situ in the pot, whereas the prebake process uses baked anodes manufactured in a separate part of the smelter, usually called the anode factory or electrode plant.