Aluminium encyclopaedia

The term "smelter" describes an industrial plant in which metals (for example in an iron smelter) or non-metals (such as in a glass smelter) are extracted from their natural ores, industrial residues or scrap material. If aluminium oxide is processed in an aluminium smelter, one usually describes the product as "primary aluminium", occasionally as "raw aluminium". If scrap is used as the starting material, the metallurgical plant is called a "secondary aluminium smelter" because it uses secondary raw materials and the product is "recycled aluminium" (often called "secondary aluminium"). After alloying, primary and recycled aluminium are processed in rolling mills and extrusion plants to semi-finished products or in foundries to castings.

A primary aluminium smelter comprises three major production areas:

• The focal point is potroom, where aluminium extraction takes place using fused-salt electrolysis.

• The anodes for the fused-salt electrolysis process are manufactured in the anode plant (up to 0.5 kilograms of anode material is consumed for every kilogram of aluminium extracted).

• The extracted aluminium is cast into ingots or shapes (such as rolling ingots) in the casthouse.

When choosing the location of a primary aluminium smelter, the availability of aluminium oxide and cheap electricity are usually decisive (a smelter with an annual capacity of 100,000 tonnes of aluminium requires about 200 megawatts of electric power); with secondary smelters, the availability of scrap is of vital importance. In the past few decades, new primary smelters have mainly been constructed near to hydroelectric power plants or supplies of coal or natural gas that enable low-price power generation.