Refining Process
The aluminium industry relies on the Bayer process to produce Alumina from Bauxite. Bauxite is crushed, ground and digested in caustic soda at high pressure and temperature. The resulting liquor contains a solution of sodium aluminate and un-dissolved Bauxite residues containing iron, silicon, and titanium. These residues, known as “red mud”, settle gradually to the bottom of the settling tank and are filtered and removed. The clear sodium aluminate solution, which is called aluminate liquor, is pumped into a huge tank called a precipitator. Fine particles of alumina are added to seed the precipitation of pure Alumina particles as the liquor cools. The precipitation process is in batches. The solid particles concentration increases, which are removed, filtered and washed, and are then passed through a rotary calciner at 1100°C to drive off the chemically combined water. The result is a white powder, pure Alumina.

Refinery
Madras Aluminium Company Ltd. (MALCO) has a 80,000 TPA refinery at Mettur Dam Complex.