Optimization of bauxite grinding by means of empirical model

The grain size distribution of ground bauxite plays an important role in the extraction yield of alumina and digestion kinetics. The ground bauxite product of ball mills can be characterised by a function of relative size distribution, F (xi =X/X(50)), even at different grinding capacities. The median of the ground product at a given mill depends on the grinding capacity which can be determined by direct measurements (that is X(50) = f (Q) function) or can be estimated by equations Bond-Rowland-Kjos. The expected grain size distribution under modified conditions can also be calculated by means of the above equations, so the grinding process can be optimised. The results of the calculations have been confirmed by plant-scale bauxite grinding tests. A new universal Hardgrove mill was used for fast laboratory determination of grindability of different kinds of bauxite.