A MODEL FOR SLURRY RHEOLOGY

A semi-empirical model has been developed to predict slurry rheology f rom easily-measured slurry properties. The model demonstrates the comp lex influence of these properties on rheology, and also permits rheolo gical 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 o n-line Debex slurry viscometer at various bobbin rotational speeds, fr om solids concentration, solids size distribution and temperature. The machine readings and the bobbin rpm are then converted to shear stres s and shear rate using the turbulence correction method described in a n 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 applie d to 127 sets of Debex viscometer measurements of a variety of slurrie s totalling more than 1200 data points, with good agreement between th e predicted and the measured data. Different slurry types require diff erent model parameter values, but it was found that the rheology of ma ny common slurries could be described by a single set of parameter val ues over a wide range of conditions. In other cases, adjustments in on ly one or two parameters were required. The separate effects of solids volume fraction and particle size on slurry rheological nature, simul ated using the model and turbulence-corrected by the TC curve procedur e, are demonstrated graphically. The influence of various factors on s lurry rheology is discussed, and it is shown that a single slurry can exhibit many different rheological natures, depending only on the conc entration and size distribution of the solids. This has important impl ications in mineral processes such as grinding and dense medium separa tion.