| 摘要 |
Alumina is produced from Al-contg. ores, e.g. bauxite, by digestion with caustic soda soln., sepn. of red slurry and calcining the alumina hydrate. After digesting at >200 degrees C and pressure >40 atomos. the mixt. of Na aluminate soln. and red slurry is cooled to 95-110 degrees C by indirect heat exchange with the residue of leaching, and the concn. of the mixt. is held constant.The residue of leaching is expanded in several steps, and the resulting steam is used to heat the starting mixt. Sufficient water is added to dilute the mixt. and maintain the water balance.The modified process offers an increased rate of leaching and improved efficiency. The requirement for evaporation of the liquors is avoided, saving energy and equipment.
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