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The 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 Hall-Heroult 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.1 In a pot, alumina is partially dissolved in an electrolyte of molten cryolite (Na3AlF6) at approximately 960°C. 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 pre-bake process uses baked anodes manufactured in a separate part of the smelter, usually called the anode factory or electrode plant.
JOBS AND TASKS IN THE POTROOM
In prebake and Søderberg potrooms there are many jobs and tasks, but the main ones common to most prebake potrooms are:
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Tapping and anode changing, which involves crust breaking, carbon anode changing, molten metal removal (tapping), transferring molten electrolyte, and covering of anodes with ore. In most modern pre-bake smelters the anode changing and tapping tasks are now usually undertaken from purpose built overhead cranes which house the operator in an air-conditioned and filtered cabin. The crane has all attachments necessary to carry out the routine …
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