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Technologies and Equipment
Generic Technologies
Primary aluminum is produced by the Hall-Heroult process which involves the electrolysis of alumina dissolved in a molten cryolite-based electrolyte. Electric current is used to separate the alumina into aluminum and oxygen. Alumina itself is produced from bauxite ore feedstock in a thermal digestion process. Scrap pretreating and melting to produce secondary aluminum takes place in fuel-fired (or occasionally electric) furnaces. Forming processes use mainly electricity to drive casting machines, rolling mills, and other forming and finishing equipment.
Unit Operation |
Purpose |
Major Technologies |
Electrolysis |
Remove the oxygen from aluminum oxide to produce aluminum metal |
Hall-Heroult reduction cell |
Process Heating |
Extract alumina from bauxite ore, pretreat scrap, melt scrap, reheat ingots prior to rolling or other forming operations, recover metal from dross |
Digesters, scrap dryers, delacquering furnaces, reverberatory melting furnaces, induction furnaces, flotation melters, dross furnaces, walking beam furnaces, soaking pits |
Forming |
Shape aluminum into forms and semi-finished products |
Casting, hot and cold rolling, extrusion, drawing, finishing, cutting |
Source: DOE 1997
About 36% of aluminum facilities report using adjustable speed motors to increase efficiency
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