Australian mined Bauxite to
SOLIDAL® architectural metals
Aluminium smelting is the process of extracting aluminium from its oxide, alumina, generally by the Hall-Héroult process. Alumina is extracted from the ore bauxite by means of the Bayer process at an alumina refinery.
Australia is the world’s fifth largest producer of aluminium, and has 5 operating smelters. As electricity is a key input in aluminium smelting, smelters are usually located in areas with reliable, lost cost energy.
The Australian industry is at world’s best practice on electricity efficiency, while also leading the global industry in controlling greenhouse emissions.
The Hall- Héroult process is the main method of smelting aluminium used today, and consists of five steps: adding bath and alumina; anode; electrolysis; tapping; and primary casting.
1 Add Bath and Alumina
Inside a pot, alumina is dissolved in a “bath” of molten cryolite (sodium aluminium fluoride) and other materials.
A pot is a large rectangular cell, lined with carbon blocks and insulating bricks. This lining forms the “cathode”.
A potline is a long building, or collection of buildings, which contain a series of “pots”, or large electrolytic cells, in which aluminium is made.
Anodes are used to conduct electricity into the smelting cells/pots in the pot room. Anodes are consumed in the smelting process and the remaining portions (known as butts) are recycled.
Anodes are attached to rods and suspended into the electrolytic cells in the pot room where they are slowly consumed in the aluminium smelting process.
Carbon anodes, made from petroleum coke and pitch, are often manufactured on site.
A high electric current is passed through pots via the anode. The current flows continuously from the anode (positive) through alumina/cryolite mix to the lining of the pot (negative) and then onto the next pot.
Electricity maintains the temperature of the process at about 950°C and enables the alumina to split into aluminium and oxygen.
At regular intervals the molten aluminium is tapped from the pots and transported to the casthouse.
5 Primary Casting
The molten aluminium is cast at a temperature of just over 700°C to form ingots, slabs, billots and t-bars.