Bayer process

The Bayer process refines bauxite into alumina by dissolving aluminum-bearing minerals in concentrated sodium hydroxide, then precipitating aluminum hydroxide and heating it to form alumina.

Bauxite: Bauxite is a mixture of aluminum-bearing minerals and impurities that serves as the principal ore of aluminum. It is the variable natural feed that the process digests.
Gibbsite: Gibbsite is an aluminum hydroxide mineral and one of the main aluminum-bearing minerals in bauxite. It dissolves readily in caustic liquor under Bayer digestion conditions.
Alumina: Alumina is aluminum oxide, a ceramic compound and the principal feedstock for primary aluminum smelting. It is the refined product made by the process.
Sinter process: The sinter process treats bauxite with soda and lime at high temperature to produce sodium aluminate-bearing material. It offers an alternative route for bauxites difficult to process by conventional digestion.
Sodium hydroxide: Sodium hydroxide is a strong alkaline compound used in aqueous solution as a caustic reagent. Its concentrated solution dissolves aluminum-bearing minerals as soluble aluminate.
Boehmite: Boehmite is an aluminum oxyhydroxide mineral found in some bauxites. Its lower solubility generally requires harsher digestion conditions than gibbsite.
Hall–Héroult process: The Hall–Héroult process produces aluminum metal by electrolyzing alumina dissolved in molten cryolite. It consumes the alumina that Bayer refining supplies.
Combination process: A combination process integrates Bayer refining with sintering to recover aluminum from difficult ores or residues. It adds a sinter circuit where the Bayer route alone leaves valuable aluminum behind.
Digestion (Bayer process): Digestion is the high-temperature, pressurized treatment of bauxite with concentrated sodium hydroxide. This stage transfers much of the ore's aluminum into solution.
Diaspore: Diaspore is a crystalline aluminum oxyhydroxide mineral that occurs in some bauxites. Its refractory character can demand especially high digestion temperatures.

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