Effect of lime addition on the predesilication and digestion properties of a gibbsitic bauxite

Abstract

The effect of lime addition on the predesilication and digestion properties of a gibbsitic bauxite in industrial Bayer liquor at different temperatures was investigated in the present paper. Lime increases the desilication efficiency of gibbsitic bauxite during the predesilication process, which promotes the conversion of sodalite and cancrinite to hydrogarnet in the presence of CO32-. Lime slightly decreases the alumina digestion rate of gibbsitic bauxite at both 145 °C and 245 °C when the lime dosage is 2 wt%. However, the soda consumption during the digestion process is decreased due to lime addition, especially at the higher temperature. Lime can also promote the conversion of aluminogoethite to hematite during the digestion process, which improves the digestion property of aluminogoethitic alumina in the gibbsitic bauxite.