An empirical model for the prediction of the viscosity of slurries of coal fly ash with varying concentration and shear rate at room temperature

Coal fly ash is attracting increasing attention as a raw material for processing into multiple products. Well designed processing equipment requires an understanding of how a suspension’s rheology changes with increasing solid concentration and shear rate. Current rheological models applied to coal fly ash are insufficient to describe rheology behaviour over a wide range of concentrations. The current paper analyses the flow curves of two types of coal fly ash differing in particle size, shape, and distribution over a range 10–70 wt.%. It has been shown that both samples exhibit complex non-Newtonian behaviour including shear thinning and shear thickening. A new generalised modelling procedure has been proposed to predict the viscosity behaviour of solid suspensions. The resulting model was able to predict the relative viscosity as a function of both concentration and shear rate with a high degree of accuracy. It is envisaged that this will be extremely useful for the purpose of processing equipment design involving mixing operations.