Estimation of Cleaning Efficiency of Clay Removal from Bauxite

Bauxite ore is used as the raw material for the production of alumina in the Bayer hydrometallurgical process. Clay agglomerates on the bauxite surface create lot of complications in the Bayer process. Its concentration in the ore is decreased by washing the ore inside trommels or drums followed by classification and screening in which the agglomerates are detached and are removed with the action of water. The aim of bauxite washing is to increase the concentration of alumina i.e. alumina grade and reduce that of silica (clay) grade in the Bayer process plant feed. Therefore, the ratio of alumina grade to that of silica grade (A/S) is one of the deciding parameters for the bauxite ore processing. The cleaning efficiency of the washing process can be characterized by determination of the amount of silica (clay) agglomerates removed from bauxite surfaces. A semi-empirical model has been developed in which the mass and composition of the washed products and tailings streams can be easily estimated. The model developed is a function of material retention (washing) time in the washing trommels or drums and the amount of silica (clay) in the run-of-mine bauxite ore