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Alumina refinery process flow diagram |
Bauxite is used as raw material for the production of alumina; the composition of bauxite contains about 50% of aluminium oxide and about 5% silica. The process involves crushing of bauxite to 100- mesh and dissolved in Bayer digesters with the help of caustic soda and lime in the presence of hot water and steam under sufficient pressure by which sodium aluminate is formed, silica forms as the precipitate by forming sodium aluminium silicate.
Drum filters separate the red mud from the solution and by cooling the filtered solution sodium aluminate form a precipitate of aluminum hydroxide. This residue is washed and filtered in rotary drum filter. By using rotary calciner which operates at 9800C the aluminum hydroxide is calcined and cooled in rotary cooler and shipped. The filtrate of caustic soda is concentrated and reused in the process. Most of the red mud is used in the batch process to collect the alumina content at once.
There are other famous processes which are Mexican process also known as the U.G process. A French Pechiney-Ugine Kuhlmann process, by using aluminum chloride subjecting to continuous electrolysis.
Drum filters separate the red mud from the solution and by cooling the filtered solution sodium aluminate form a precipitate of aluminum hydroxide. This residue is washed and filtered in rotary drum filter. By using rotary calciner which operates at 9800C the aluminum hydroxide is calcined and cooled in rotary cooler and shipped. The filtrate of caustic soda is concentrated and reused in the process. Most of the red mud is used in the batch process to collect the alumina content at once.
There are other famous processes which are Mexican process also known as the U.G process. A French Pechiney-Ugine Kuhlmann process, by using aluminum chloride subjecting to continuous electrolysis.