RHEOLOGICAL BEHAVIOR OF COAL-WATER MIXTURES .2. EFFECT OF SURFACTANTS AND TEMPERATURE

Abstract

The theological characteristics of coal-water mixture (CWM) were investigated, including the effects of surfactant type and concentration, presence of added electrolytes and slurry temperature. The slurryability of coal could be enhanced considerably by the addition of surfactants and some electrolytes and the slurries almost exhibited shear-thinning behaviour, i.e. were pseudoplastic with n < 1, which is a desirable theological characteristic for CWM. The slurry viscosity increased as the temperature, the amount of anionic surfactant and electrolyte, and the HLB value of non-ionic surfactant decreased. The addition of nonylphenol non-ionic surfactants also enhanced the resistance of CWM to sedimentation, and this effect was more pronounced, the greater the number of ethylene oxide groups in the surfactant molecule. The CWMs displayed a higher degree of pseudoplasticity with decreasing amount of surfactant and temperature. The effect of temperature on the slurry viscosity could be described by the simple Andrade equation, but the rate of reduction of apparent viscosity associated with the temperature rise began to decrease above a certain temperature which seems to mark the onset of an adverse effect of temperature.