One-Dimensional Solid-Liquid Separation: Commentary

Summary

A brief review of the current industrial methods for quantifying filtration, expression and gravity thickening is given. The new treatment of Smiles and Kirby (1988) is an attempt to develop a unified mathematical approach to the three processes based on experimental measurement of water content - compressive stress and permeability - compressive stress relationships. Whilst the limited experimental data provide confirmation that the theory holds in the subatmospheric region, its extrapolation to pressure filtration and expression situations remains unproven. Moreover, the theory suffers from the constraint of being one-dimensional and does not account for the nonplug-flow phenomena (channelling and funnelling) occurring in full scale plant. It is relatively easy to relate the parameters of the Smiles and Kirby treatment to those used in industrial practice. Use of the Smiles and Kirby approach ensures that effects such as varying moisture content throughout the cake and the effect of solids movement are accounted for.