METHOD OF PROCESSING LOW-GRADE BAUXITE INTO ALUMINA Russian patent published in 2002 - IPC

FIELD: nonferrous metallurgy. SUBSTANCE: method involves grinding bauxite with return solution, leaching it, diluting boiled pulp, subjecting the latter to desiliconization in common with sintering branch aluminate solution, thickening and washing red sludge, filtering it, decomposing aluminate solution to give aluminum hydroxide and return solution, caking red sludge with soda and limestone, leaching sludge cake to give aluminate solution and cake sludge, thickening aluminate solution after leaching of cake to give clarified aluminate solution and grey sludge. The latter is filtered to give filtrate and cake, which is washed for 0.5-1.0 h and withdrawn from process. Clarified portion of aluminate solution is treated with limestone dust, in particular marble dust, to achieve silica module at least 180 units, after which pulp is subjected to common leaching with Bayer branch solution, whereas grey sludge filtrate is treated in common with clarified portion of aluminate solution. EFFECT: reduced consumption of sods ash, reduced equipment usage in caking branch, and reduced iron and silicon impurities in aluminum hydroxide product. 3 cl, 2 dwg, 2 ex