Rheological Investigation of Coal Water Slurries With and Without Additive

Abstract

Coal Water Slurries (CWS) are concentrated suspensions of coal particles in water and are used as fluid fuels. The rheological properties of Coal Water Slurries depend on a number of factors such as the type of coal, the solid content and its size distribution, the temperature, the pH and the presence of electrolytes and chemical additives. In the present study rheological behavior of Indian coal water slurry (CWS) was investigated using an Anton Parr RheolabQC rheometer.The objective of the current work was to determine the effect of concentration,particle size and additive on the rheological behaviour of coal water slurries. It is observed that the coal water slurry exhibits shear thinning/thickening effects at low concentrations while at 50% Cw and above the slurry prepared from both coal samples consistently shows shear thinning behaviour. The slurry prepared from finer coal particles(53-75μm) is more viscous as compared to coarser particles(75-106μm) for a given coal slurry sample at all concentrations. The increase of viscosity is found to be exponential with concentration. The viscosity is significantly affected by surfactant Triton X-100 which is observed to lower the viscosity at all selected dosages (i.e:0.5%-2.4% by weight of slurry).The optimal dosage is 1.5% of additive by weight of slurry. The maximum reduction in viscosity is about half at 1.5% additive dosage at 50% Cw of slurry. From work on surfactant loading it can be concluded that it might be possible to produce pumpable coal slurries at concentrations of 50% and above by adding suitable dispersant/additive at optimal dosage.