METHOD OF PRODUCING METALLURGICAL ALUMINA (VARIANTS) Russian patent published in 2018 - IPC C01F7/20 C01F7/30 

FIELD: metallurgy.

SUBSTANCE: group of inventions refers to metallurgy and can be used in recycling low-grade high-silicon aluminum-containing raw materials. Crushing of the aluminum-containing raw material is carried out, followed by opening with hydrochloric acid, which is an acid recycled mother liquor. Formed chloride pulp is separated into a waste silica precipitate and a clarified chloride solution. Crystallization is carried out from a clarified chloride solution of aluminum chloride hexahydrate. Thermal decomposition of aluminum chloride hexahydrate into aluminium oxide followed by its calcination, with the production of crude alumina as an intermediate is produced. Crude alumina is leached with recycled alkaline solution with decomposition of the resulting aluminate solution. 15 % acid mother liquor is subjected to pyrohydrolysis. Concentration of chloride ion in crude alumina is maintained at the level of 0.2–5.0 %, the chloride ion concentration in the recycled alkaline solution is at the level of 40–90 g/l. Alkaline recycled solution after decomposition in an amount of 10–40 wt % of the total is evaporated until the crystals of chlorine-containing compounds are precipitated; they are removed from the process.

EFFECT: increase in the quality of alumina and reduction in energy costs during its obtaining.

16 cl, 1 dwg, 1 ex, 2 tbl