A method for producing alumina with middle and low grade bauxite

摘要

A method for producing alumina with middle and low grade bauxite is characterizedin that the Bayer process digestion is performed by adding the dealuminizingresidue as an additive instead of lime into middle and low grade bauxite duringthe Bayer process; the red mud after the Bayer process digestion is subjectedto reversal washing, then mixed with recycling alkali liquor, digested afterthe lime being added, and the resulting red mud is discharged after it is separated,a portion of the resulting solution is used to reversal wash the red mud obtainedfrom Bayer process digestion, then supplemented with alkali after it is sentto Bayer process system, the dealuminizing residue and the recycling alkaliliquor for wet-treating the red mud obtained from Bayer process are obtainedafter lime is added into another portion of the resulting solution, and the dealuminizingresidue , i.e. calcium aluminate hydrate, as a additive, is added to the Bayerprocess digestion instead of lime. The method is a wet-treating process, is suitablefor middle and low grade bauxite, and has advantages of simpleness, low energyconsumption, low alkali consumption, high yield of alumina, high level of resourcesutilization, low red mud discharging, and comprehensive utilization of redmud.