| 摘要 |
Treatment of alumina trihydrate bauxite by subjecting it to the action of caustic soda by the Bayer process. After crushing and desilication, a first fraction (3a) of at least 40 % by weight of said trihydrate bauxite is subjected at atmospheric pressure to the action of a decomposed liquor aliquot (12) recycled as a leaching liquor (13). The remaining bauxite fraction (3b) is subjected to the action of the remaining leaching liquor (13b) at 130-180 DEG C. The process then includes mixing the two suspensions (4a and 4b) so formed and diluting (D) them preferably using a washing water (20) countercurrent to the red mud (F) to form a third suspension (5), the Al2O3/Na2O g/1 concentration ratio Rp being 1.13-1.28 and the caustic soda concentration being 140-160 g Na2O/litre at a temperature of 100-107 DEG C. Finally, the supersaturated sodium aluminate solution (7) which is filtered (G) after separation by decantation (E) of the insoluble residues or red mud (19) of the suspension (5), is decomposed (H) in the presence of seeds.
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