How to Optimize Phosphate Slurries Rheology?

The OCP Group shifted, since 2014, the transport mode from train to pipeline. This pipeline is designed to transport phosphate slurry at high concentration typically around 60% solids content. To transport the slurry in the best conditions and to avoid any difficulty, the critical parameter is the control of its rheology. At such high solid content, phosphate dispersions behave like yield stress fluids with specific intrinsic characters: they flows above a yield stress and behave like solids below. The objective of this paper is to highlight the best practices in term of rheology characterization like equipment and protocol, to understand the relationship between the rheological parameters and the slurry composition and to then find ways to increase solids content of phosphate slurry to enhance transportation capacity. In a first part, this paper reviews the key physical parameters of mineral slurries. The characterization of the yield stress behavior is done via two different rheological approaches: experiments done in static and dynamic mode are detailed. The objectives are respectively to understand how to make the slurry flow and when it is going to stop flowing. A special attention is given to the measurement of yield stress and how to avoid any artefact during measurements. In a second part, our method used to increase slurries solid contents is presented and shows that it is possible to optimize slurry transportation capacity while keeping good flowing conditions.