| 摘要 |
Bauxite is reacted with spent caustic soda solution at 113 DEG C. to 205 DEG C. to produce a first pregnant liquor stream, a granular residue stream and a muddy substance stream wherein the granular residue stream is discarded, the muddy substance stream is reacted with or without a small portion of bauxite, but with a spent caustic soda stream at 206 DEG C. to 350 DEG C. to produce a second pregnant liquor stream and a red mud stream which is discarded; the first and second pregnant liquor streams are filtered, cooled to 50 DEG C. to 87 DEG C. and then seeded to precipitate alumina hydrate containing less than 0.017% Fe2O3 by weight.
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