Viscometry and rheology of coal water slurry

Abstract

This paper presents the results of a detailed experimental study on rheological behaviour of coal water slurry (CWS). In contrast to earlier rheological studies at shear rates of rather narrow ranges, this study covered a much wider range of shear rates: 0–800 s −1 in a rotational viscometer and 400–10000 s −1 in a capillary viscometer. While the gap width of a rotational viscometer had no effect on the apparent viscosity of CWS, it was found that selection of proper tube dimensions in a capillary viscometer was important, Thus, the viscosities of CWS measured in both viscometers at the overlapping shear rates of 400–800 s −1 were in good agreement. Consequently, it was possible to study the effect of shear rate higher than 800 s −1 on slurry rheology. In addition, the effects of coal content, coal particle size and size distribution, and temperature on the slurry rheology were investigated. The slurry, a dispersion of coal particles in a pseudoplastic fluid, became more viscous and less pseudoplastic as the coal content was increased. The pseudoplasticity of a highly concentrated utility grind CWS approached that of a concentrated suspension of 40–50 μm solids in a Newtonian fluid. Also, the slurry pseudoplasticity was enhanced at a slightly elevated temperature, but significantly reduced as the shear rate exceeded a threshold dependent on coal content and particle size and size distribution.