METHOD FOR PRODUCING ALUMINA, MAINLY FROM HIGH-SILICA BAUXITE Russian patent published in 2023 - IPC C01F7/20 C01F7/26 C22B21/00 C22B3/06 

FIELD: metallurgy.

SUBSTANCE: invention relates to the production of metallurgical alumina during the processing of high-silicon bauxite with a silicon module μ_Si≤ 3 to obtain alumina of metallurgical grades. Obtaining alumina from high-silica bauxite includes preparing a reagent solution from a mixture of ammonium bisulphate and sulphuric acid, followed by leaching bauxite with it, filtering the resulting pulp, cooling to precipitate ammonium aluminium sulphate alum from the sulphate-ammonium solution, followed by their separation from the mother liquor. The alum is washed, dissolved in water, aluminium hydroxide is precipitated by raising the pH of the solution with gaseous ammonia, filtered and the resulting pulp is washed, after which the aluminium hydroxide is calcined in air. Leaching is carried out with a solution of a mixture of ammonium bisulphate and sulphuric acid with a volume ratio of solutions of 12.5:87.5-87.5:12.5 vol.% and a concentration of 30-40% and 25-40%, respectively. The precipitation of aluminium hydroxide is carried out for 60-120 minutes and the temperature of the solution is 80-95°C with the addition of a seed of gibbsite (Al(OH)₃) with an average particle size of 40-60 microns in the amount of 100-300 g/l.

EFFECT: method allows to intensify the leaching process and increase the size of alumina particles.

4 cl, 3 dwg, 2 tbl, 4 ex