| Primary Aluminium | |||
Aluminium can be produced via two different routes: primary aluminium production from ore and recycling aluminium from process scrap and used aluminium products. The production of primary aluminium consists of three steps : bauxite mining, alumina production and electrolysis. The last two mentioned will be described hereafter, bauxite mining is covered in the section Environment, Ecology & Recycling. Alumina production Bauxite has to be processed into pure aluminium oxide (alumina) before it can be converted to aluminium by electrolysis. This is achieved through the use of the Bayer chemical process in alumina refineries. The aluminium oxide is released from the other substances in bauxite in a caustic soda solution, which is filtered to remove all insoluble particles. The aluminium hydroxide is then precipitated from the soda solution, washed and dried while the soda solution is recycled. After calcination, the end-product, aluminium oxide (Al2O3), is a fine grained white powder. Four tonnes of bauxite are required to produce two tonnes of alumina which in turn produces one tonne of aluminium at the primary smelter. In 1998, 45 million tonnes of alumina were produced world-wide. The main production areas are :
Electrolysis
At regular intervals, molten aluminium tapped from the pots is transported to the cast house where it is alloyed in holding furnaces by the addition of other metals (according to the user's needs), cleaned of oxides and gases, and then cast into ingots. These can take the form of extrusion billets, for extruded products, or rolling ingots, for rolled products, depending on the way it is to be further processed. Aluminium mould castings are produced by foundries which use this technique to manufacture shaped components. World-wide trends in production are shown in the following graph. Aluminium output has increased by a factor of 13 since 1950, making aluminium the most widely used non-ferrous metal. In 1998, world-wide production of primary aluminium was about 22.7 million tonnes per year for and installed capacity of 24.8 million tonnes.
The main production areas are North America (6 million tonnes), Europe (3.6 million tonnes) Africa, Australia, CIS, Central and South America, and the Middle East. In Europe the main producing countries are France, Germany and Norway. World-wide, production plants are mainly located where suitable electrical energy resources are available. Source:European Aluminium Association |
