Bauxite is an aluminium ore and the main source of aluminium. Australia is the top producer of bauxite worldwide. QAL’s bauxite is mined in Weipa, far north Queensland and shipped over 2000 kilometres south to Gladstone.
QAL produces alumina. Alumina is the common name for the compound, aluminium oxide, which is extracted from bauxite using a four stage chemical process known as the Bayer process.
The alumina we produce is shipped to our customers locally and around the world. Aluminium has a unique combination of properties that can be utilised through alloying. It is a particularly durable material as well as being light weight and corrosion resistant.
Alumina is produced through the Bayer process.
- Digestion - dissolving bauxite's alumina content Bauxite is finely ground in mills, and then mixed with a hot, caustic soda solution. This dissolves the alumina contained in the bauxite. The solution is then cooled in a series of flash tanks.
- Clarification - settling out undissolved impurities The solid impurities settle as a fine mud in thickening tanks. This red mud is a by-product of the process. After several washing stages to recover caustic soda, this residue is neutralised with sea water and pumped to storage dams. The clear solution is send to Precipitation to have the alumina recovered from it.
- Precipitation - forming alumina crystals Precipitation involves the recovery of alumina crystals from the caustic solution. In open-top tanks, the solution is stirred by mechanical agitation and seeded with previously precipitated alumina to assist crystal growth.
- Calcination - high-temperature drying of alumina The precipitated material (called hydrate) is washed, filtered and then heated at temperatures exceeding 1,000°C. This removes water molecules, creating a fine white powder known as alumina.