Yield stress of phosphate rock slurries for gravity thickening

Ground phosphate rock slurries are first concentrated in a gravity thickener before being store in large tanks for subsequent conversion to phosphoric acid via reaction with sulphuric acid. Phosphate rock from various parts of the mine in Phosphate Hill formed thickened slurries that displayed quite different yield stress property. With some of these slurries pumping and processing problems were encountered because the yield stress was too high. In this study the yield stress behaviour of phosphate rock slurries from various part of the mine was characterised as a function of solids concentration. Surface chemistry and Particle size distribution effects were also evaluated