Factors affecting on the extraction of alumina from kaolin ore using lime-sinter process

Abstract

The extraction of alumina from the kaolin ore excavated from the Irkutsk region, Russia by a combination of Pyro- and Hydro-metallurgical Processes was investigated. The kaolin ore was processed using lime-sinter process by sintering kaolin-limestone charge in the temperature range 800 -1400⁰C for 1hr. Factors affecting the percent recovery of alumina from kaolin ore such as the briquetting pressure and the sintering temperature were investigated. The sintering process leads to the dehydroxylation of the kaolinite and activates its transformation to 12CaO∙7Al2O3 - CaO∙Al2O3 phases from which alumina can by extracted easily using aqueous solutions of sodium carbonate. The highest recovery of alumina of about 80% was obtained at 1360°C sintering temperature and 5 MPa briquetting pressure. The obtained sludge composed mainly from 2CaO∙SiO2 phase with a suitable chemical and mineralogical composition that makes it suitable to be used as cementation material in the production of the Portland cement.