A model for slurry rheology

A semi-empirical model has been developed to predict slurry rheology from easily-measured slurry properties. The model demonstrates the complex influence of these properties on rheology, and also permits rheological information to be predicted in cases where it cannot be measured. It is intended for use with slurries commonly encountered in mineral processing. The model first predicts machine output readings of the on-line Debex slurry viscometer at various bobbin rotational speeds, from solids concentration, solids size distribution and temperature. The machine readings and the bobbin rpm are then converted to shear stress and shear rate using the turbulence correction method described in an associated paper. (The simulation of the Debex is a convenience; the method is essentially independent of any particular instrument if the full data reduction procedure is followed.) The model has been applied to 127 sets of Debex viscometer measurements of a variety of slurries totalling more than 1200 data points, with good agreement between the predicted and the measured data. Different slurry types require different model parameter values, but it was found that the rheology of many common slurries could be described by a single set of parameter values over a wide range of conditions. In other cases, adjustments in only one or two parameters were required. The separate effects of solids volume fraction and particle size on slurry rheological nature, simulated using the model and turbulence-corrected by the TC curve procedure, are demonstrated graphically. The influence of various factors on slurry rheology is discussed, and it is shown that a single slurry can exhibit many different rheological natures, depending only on the concentration and size distribution of the solids. This has important implications in mineral processes such as grinding and dense medium separation.