Bauxite digestion in ball mill - for simultaneous fine grinding, leaching and silica removal

摘要

In bauxite digestion by simultaneously leaching and grinding bauxite with caustic soda in a ball mill, the novelty is that (i) the mill is a stirred ball mill; (ii) the charge also contains lime in an amt. corresp. to the stoichiometric amt. of 1-3 (1.8-2.2) mol. CaO per mol. SiO2 which otherwise goes into soln.; and (iii) the mill (or its contents) is heated to 80-98 (88-92) deg.C. ADVANTAGE - Process effects simultaneous fine grinding, leaching and silica removal, without Al2O3 and Na2O losses during silica removal and without red mud formation. After cooling obtd. aluminate liquor, aluminium hydroxide pptn. is induced by stirring so pptn. duration is shortened and hydrated alumina yields are increased.