RHEOLOGICAL PROPERTIES OF COAL OIL MIXTURE FUELS

The rheological properties of coal-oil mixtures (COM) of a bituminous coal in four types of oil have been studied. Variables investigated were the coal concentration, coal particle size, temperature and time effects. Rheograms were obtained using the Ferranti-Shirley cone and plate viscometer. The COM was classified as a Newtonian fluid at coal concentrations up to 30 wt% and as a Bingham plastic at higher values. The relative viscosity was found to increase rapidly with coal concentration, reaching 100 for a 60 wt% COM. Both COM viscosity and yield stress decrease with increasing median particle size and decreasing slope of the particle size distribution. This effect is stronger at high solids concentrations. The COM viscosity is much less sensitive to temperature than the base oil. The COM yield stress increases up to 350 Pa with increasing coal concentration, decreasing temperature and aging.