Beneficiation of High Silica Bauxite Ores of India an Innovative Approach

Abstract

Many bauxite reserves in India have Al₂O₃/SiO₂ ratio of 4 to 6 and hence pose difficulties in production of alumina through the Bayer process. The extraction of alumina from bauxite in low temperature digestion circuit frequently involves a desilication step in which kaolinite dissolves and reprecipitates as sodalite, a caustic insoluble sodium alumino silicate. Thus formed insoluble sodium alumino silicate gets separated from the process into the red mud, thereby entailing the loss of valuable caustic soda and alumina. The more is the silica, higher is the soda consumption which increases the cost of alumina production.

Physical beneficiation techniques are employed to reduce the reactive silica content of bauxite. Based on several investigations it has been made possible to remove ~30% of silica with 92% recovery depending on the characteristics of the ore. The results of detail studies are presented in this paper and it is expected that these findings will lead to improved Alumina Refining practice in the future.