Aluminum is almost never present in his pure form in the nature. In order to obtain it, it must be extracted from a more complex molecule, such as alumina ( Al2O3 ).The extraction process consist to inject solid alumina in an electrolysis cell containing a highly corrosive solution and liquid aluminum. A strong electric current go through the cell and the liquids are keep at a temperature close to 960o Celsius, according to Joule effect. The two fluids are immiscible and moving due to electromagnetic forces.
The main chemical reactions that allow to extract aluminum from alumina can be summarized by the following equation :
2 Al2O3 + 3 C = 4 Al + 3 CO2.
In a very simplified way, due to the presence of the solvent liquid, the alumina molecules are ionized and transported by the electrical current. The oxygen part react with the carbonic anodes and produce carbon dioxide and thus allow the formation of pure aluminum.
As part of a strong scientific collaboration between the EPFL and RioTinto-Alcan (Laboratoire de Recherche et Fabrication based in Saint-Jean de Maurienne – France), the chair ASN developped for many years an aluminum production simulation software (Alucell).
As an example, here is the geometry of a realistic cell, used for industrial simulations.