Effect of particle characteristics on the solids density of Bayer mud slurries

The solids density that is achieved in residue areas, washer underflows or on filters varies considerably with bauxite type. In particular Jamaican mud settles to a much lower g/1 solids than those derived from most other bauxites. A fundamental study of the physical properties that affect solids density was undertaken to determine if the differences could be explained. This included particulate modelling based on particle interactions. Various characteristics of muds were measured including particle size, porosity, surface area, mineralogy and absorptivity. Sizing of muds was complicated by the effect of pH on sizing. Those data, together with the particulate modelling, enabled predictions of differences in solids densities that compared well with those obtained in practice. Comparisons between muds must be on a volume/volume basis.