METHOD OF ALUMINA PRODUCING Russian patent published in 2015 - IPC C01F7/22 C01F7/30 

FIELD: metallurgy.

SUBSTANCE: invention can be used in metallurgy. Method of alumina producing includes treatment of aluminium containing raw stock by hydrochloric acid, crystallisation of aluminium chloride hexahydrate from clarified chloride solution, two-stage thermal decomposition of aluminium chloride hexahydrate with alumina producing, and thermohydrolysis of master solution with hematite recovery. The first stage of the thermal decomposition of the aluminium chloride hexahydrate is performed till creation of oxychlorides and amorphous aluminium hydrate, their part is by portions injected to the clarified solution prior to crystallisation of the aluminium chloride hexahydrate until achievement of pH = 1.6-2.2, at that the created deposit of the iron hydroxide is separated and mixed with the master solution, and part of the produced hematite is returned to the clarified solution after achievement of pH = 1.6-2.2.

EFFECT: invention increases quality of the alumina, reduces Fe₂O₃ content in product by 0,003-0,007% (abs) without other chemical injection to the process.

1 dwg, 1 tbl, 1 ex