Thermal reduction of red mud - from Bayer aluminium process using cpd contng calcium oxide

摘要

The red mud is melted, the sludge formed and the ferrous prodt. are sepd. and the Na2O and Al oxide content of the reduced sludge are recuperated by scrubbing. Specif. chalk or calcite or cpds. contng. CaO are added to the red mud in molar proportions, based on the dry wt. of the latter. of CaO:SiO2 = 1.8-2.2, CaO:TiO2 = 0.9-1.1; CaO:Fe2O3 = 1.8-2.2; CaO: (Al2O3-Na2O) = 0-12/7, the mixt. is fused, and after sepn of iron sludge, the reduced sludge, contng. sodium and calcium aluminate, is scrubbed into 2 phases using a scrubbing agent and Na2CO3 or into a single phase using a soln of Na2CO3 contng. a scrubbing agent.