Viscosity Prediction of Highly Concentrated Polymodal Coal-Water Slurries

摘要

In the present paper a preliminary semi-empirical method is developed to predict the rheological properties of high concentration, plymodal coal-water slurries at low shear rates. The results presented represent work still in progress. The basis of the analysis is to consider a polydisperse pulverized coal slurry as made up of two relatively distinct particle fractions - a coarse fraction and a smaller fine fraction. The particles in the fine fraction are of micron size and are assumed to behave as a colloidal suspension in the carrier liquid. The coarse fraction takes up much of the space and its hydrodynamics with respect to the suspension are assumed to be the same as if it were in a pure liquid with the same viscous behavior as the suspension. The theory is first applied to truly bimodal high concentration suspensions of two different size spherical particles. It is shown that at low shear rates the viscosity of these slurries can be accurately matched to viscosities calculated on purely geometric arguments, which had previously been found to agree well with experiment. A semi-empirical analytical model based on this bimodal concept, which employs results from the simpler truly bimodal case, is applied to six high concentration polymodal coal-water slurries with continuous particle size distributions ranging from about 1 to 300 microns. The results are found to support the idea that these slurries can be treated as bimodal. 6 refs., 1 fig., 4 tabs. (ERA citation 10:023406)