The Portland Aluminium smelter consists of four 750 metre potrooms each housing 102 smelting pots. The potrooms are the heart of the smelting process as it is here that the molten aluminium is produced.
In the potrooms, the alumina is fed into a large graphite lined steel furnace known as a pot.  The alumina is dissolved in molten cryolite, also known as aluminium fluoride or ‘bath’. 
A high electric current is passed through the pot at low voltage via the anodes which enables the alumina solution to split into its components of aluminium and oxygen. The oxygen reacts directly with the carbon anode, which gets consumed to form carbon dioxide that bubbles away and the aluminium collects at the bottom of the pot. The electricity also maintains the temperature of the pot at 960 degrees Celsius.
The aluminium is siphoned from the bottom of the pot using a crucible and is then transferred to the ingot mill for casting.
Each pot at Portland Aluminium produces two tonnes aluminium a day.  Over time, the graphite pot lining will wear and need to be replaced.  The steel shells of the pots are also refurbished and relined in the pot lining facility.