PRODUCTION OF ALUMINA Russian patent published in 2015 - IPC C01F7/38 

FIELD: process engineering.

SUBSTANCE: invention relates to production of alumina from man-made wastes, particularly, from mineral part of brown coal combustion ash. Charge is prepared by mixing of ash-slag wastes of thermal power plants and limestone taken in exceeds of 28.0-75.0% of stoichiometric amount and, thereafter, sintered. Obtained cake is leached at mixing to get cake pulp and desilicated by calcareous milk and filtered to obtain slime and filtrate. Slime is flushed and carbonized by CO₂-bearing gas-air mix to filter produced hydrate pulp to get aluminium hydroxide and mother soda solution recycled for cake leaching. Cake leaching is conducted by carbonate solution containing at least 52.0 g/dm³ of Na₂CO₃ at 75-80°C. At aluminium oxide leaching from cake, additional primary vibro-cavitation processing is performed. At desilicating of cake pulp by calcareous milk vibro-cavitation processing is reiterated.

EFFECT: higher yield and quality of aluminium oxide.

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