| 摘要 |
Process for treating alumina monohydrate-based bauxite by high-temperature caustic digestion characterized in the following series of operations: a) digestion of the bauxite at a temperature in excess of 200° C. with a liquor concentrated to more than 160 g Na2O/liter and having a A/C weight ratio between 0.45 and 0.75, for a contact time which is sufficient to extract the aluminate monohydrate and to attain a A/C ratio between 1.10 and 1.20; b) cooling of the slurry and introducing alumina trihydrate in said slurry, at a temperature of less than 200° C., in order to obtain a A/C ratio of the aluminate liquor between 1.20 and 1.30; c) first diluting to a concentration between 160 and 175 g Na2O/liter; d) settling to separate the insoluble residue from a sodium aluminate liquor with an A/C ratio between 1.20 and 1.30; e) filtering the aluminate liquor; f) lowering the aluminate liquor with a complementary dilution before or during crystallization; g) after separation of the alumina trihydrate by filtration, recycling the spent liquor which, after concentration, is reused as digestion liquor with a caustic concentration above or equal to 160 g Na2O/liter.
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