PROCESS FOR EXTRACTING ALUMINA FROM ALUMINA-CONTAINING ORES

摘要

PROCESS FOR EXTRACTING ALUMINA FROM ALUMINA-CONTAINING ORES In a process for extracting alumina from alumina-containing ores on a two-stream system by individually preheating a slurry of alumina-containing ores and an aqueous alkali solution each in preheaters of indirectly heating, mixing the preheated slurry with the preheated aqueous alkali solution, and extracting alumina from the ores in a digester of heating type of direct injection of live steam or heat-insulated type, the alumina is extracted from the ores by preparing the slurry of alumina-containing ores with water or a diluted aqueous alkali solution, particularly drain obtained by recovering steam from an evaporator for cooling slurry resulting from extraction, and utilizing the recovered steam in preheating the slurry of alumina-containing ores or decomposition solution or both, preheating the slurry of alumina-containing ores, and mixing the preheated slurry with an aqueous alkali solution preheated as another stream as the decomposition solution. Scale formation can be prevented completely or substantially on an inside surface of the preheater for the slurry of alumina-containing ores.