MECHANICAL ACTIVATION OF BAUXITE - POTENTIAL AND PROSPECTS IN THE BAYER PROCESS

Abstract

Abstract Mechanical activation of bauxite is known to have a beneficialeffect on the alkali leaching of gibbsite. Mechanical activation isfound to be more effective, in terms of improvement in aluminarecovery and minimisation of soda losses at lower temperature andsoda concentration. Coupling of mechanical activation with theleaching process is an important issue in the exploitation of thebeneficial effect of the activation. Two separate schemes, namely,‘simultaneous milling and leaching’ and ‘separate milling andleaching’ have been explored. Both approaches result incomparable alumina recovery. However, greater soda loss wasobserved in the latter case. This is explained in terms of greaterduration of leaching and its effect on the dissolution of differentphases. The results show that the concept of simultaneous millingand leaching is superior in terms of leaching time, energyutilisation and simplicity of operation. Introduction The Bayer process accounts for the majority of the world’s productionof alumina. The process involves digestion of bauxite in a caustic sodasolution. The temperature of digestion may range from 100-250