Alumina, synthetically produced aluminum oxide (Al2O3), is a white crystalline substance that is used as a starting material for the production of aluminum metal. The world-wide production is close to 90 million tons of alumina per year.
The Bayer process is the principal industrial means of refining bauxite to produce alumina. In the Bayer process, bauxite ore (containing 30 – 55% Al2O3), is digested by washing with a hot solution of sodium hydroxide at 175°C. The slurry is then filtered and sent to a rotary kiln calciner to dry and, under very high temperature (1000°C), is transformed into the fine, white powder known as alumina. A large amount of the aluminum oxide so produced is then subsequently smelted in the electrolytic process in order to produce aluminum.
Alumina – Uses of Alumina
– The main raw material for the production of aluminum
– Manufacture of refractory and ceramic