METHOD FOR PREPARING ALUMINA FROM BAUXITE Russian patent published in 2004 - IPC

FIELD: non-ferrous metallurgy. SUBSTANCE: invention relates to processing bauxites consisting of mainly aluminum trihydrate oxide with low content of silicon oxide. Method involves mixing bauxite with alkaline-aluminate solution, leaching bauxite in autoclaves, separation of slime from aluminate solution, decomposition of aluminate solution to obtain aluminum hydroxide and mother liquor, evaporation of mother liquor, mixing slime obtained after leaching bauxite in autoclaves with evaporated mother liquor in the concentration of alkali 160-260 g/l of Na₂O_k and caustic modulus 2.6-3.2, exposition at temperature 98-100 C, separation of slime from aluminate solution and feeding aluminate solution to leaching bauxite in autoclaves that is carried out for 1-2 h to obtain aluminate solution in the concentration of alkali 150-200 g/l of Na₂O_k and caustic modulus in the final aluminate solution by 0.03-0.10 unit above its equilibrium level under conventional conditions of leaching. Invention provides enhancing the effectiveness of Bayer process. EFFECT: improved preparing method. 2 cl, 1 dwg, 1 ex