Autoclave Desilication of Digested Bauxite Slurry in the Flashing Circuit

Abstract

Bauxite digestion conditions should provide not only the maximum alumina recovery from raw material into liquor, but also the required desilication to produce further alumina of high quality. Several desilication circuits are common for alumina industry, namely low temperature predesilication of crude and digested slurry, Sumitimo process. These processes usually involve extensive process equipment. The proposed option of autoclave desilication in the flashing circuit of the bauxite slurry allows implementation of the process at higher temperature enhancing chemical reactions of green liquor desilication. This improvement gives an opportunity to sharply reduce the retention time, facilitates reduction in the balanced silica content in the liquor. The mud produced after digestion and high temperature desilication has better sedimentation properties as compared to that obtained as a result of low temperature desilication.