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Aluminium Smelting Process
Alumina is made up of aluminium and oxygen. To produce aluminium metal, these two elements need to be separated. Two tonnes of alumina are needed to make one tonne of aluminium.
Alumina is dissolved in an electrolytic bath of molten cryolite (sodium aluminium fluoride) within a large carbon or graphite lined steel furnace known as a ‘pot’. There are hundreds of pots at a typical smelter.
A high electric current is passed through the pot at low voltage, via carbon blocks called anodes. The strong electric current flows continuously from the anode (positive), through the alumina/cryolite mixture to the carbon or graphite lining of the pot (negative), and then to the next pot, and so on.
The electricity enables the alumina to split into its components of aluminium and oxygen. The oxygen bubbles away and the aluminium settles to the bottom of the pot. The electricity also maintains the temperature of the process at about 950 degrees Celsius.
The molten aluminium is cast at a temperature of just over 700 degrees Celsius to form ingots.
Student aluminium smelting process notes
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