Comalco Aluminum Limited

Comalco Limited

David J Milne

William H Andrews

Ronald W Moyle

James P Peters

Pearson J Cresswell

Robin David Holliday

A leaching process employing acidic chloride solutions, whereby the iron content of aluminous materials such as lower grade iron-containing bauxite ores is reduced, enabling the obtention of valuable products such as metallurgical grade alumina and refractory grade bauxite, previously obtainable only from higher grade low-iron aluminous materials.

Treatment of aluminous materials

A process for recovery of alumina and soda from materials containing sodium aluminosilicates, such as red mud and desilication products, comprises treating said materials with lime at elevated temperature and pressure. In a preferred embodiment of the invention, hydrothermal treatment of red mud with lime is integrated into a Bayer process to improve the overall efficiency of that process.

Production of alumina

Removal of iron from aluminous material such as bauxite is effected by treatment with a gas mixture comprising sulphur dioxide and carbon monoxide in a first step, followed by chlorination in a second step whereby ferric chloride is produced and removed by volatilization. Aluminium chloride of low iron content may be obtained from the purified aluminous material by chlorination.

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North Balwyn, Australia

David J Milne