METHOD FOR PRODUCING ALUMINA

The invention relates to metallurgy in particular to acidic methods for producing alumina and can be used in the processing of low grade aluminium containing stock. The method for producing alumina comprises burning the aluminium containing stock treating the product with hydrochloric acid salting out aluminium chloride by saturating the clarified chloride solution with gaseous hydrogen chloride calcining the aluminium chloride in order to produce aluminium oxide and pyrohydrolyzing the mother liquor with the hydrogen chloride being returned to the acid treatment stage and being salted out. In order to increase the quality of the alumina and reduce energy consumption the aluminium chloride precipitated during the salting out process is treated with ammonium hydroxide the residue produced is sent for calcination and the solution of ammonium chloride is mixed with the aluminium containing stock before the latter is burned or during the burning process ammonia separated out during the burning is dissolved in water and the ammonium hydroxide produced is sent for treating the aluminium chloride. The solution of ammonium chloride can be subjected to phased concentration by evaporation with repeated use of heating steam before being mixed with the aluminium containing stock. The ammonium chloride separated out when concentrating the ammonium chloride by evaporation can be mixed with the aluminium containing stock.