Theoretical and experimental studies in cake filtration

Filtration of liquid suspensions is a widely practiced process in many industries. While a substantial number of investigators have made valuable contributions to the literature, experimentation still plays the essential role in the prediction of filtration characteristics, particularly when compressible cakes are involved. In an actual filtration, both the flow rate of liquid and migration rate of solids vary throughout the cake. The internal flow variations in filter cakes have a significant effect on the observed filtration behavior when the feed slurries are highly concentrated. Taking variable flow rates of liquid and solid into accont, the so-called modern filtration theory is developed. Validity of the theory is examined by considering experimental variation of porosity and hydraulic pressure within the filter cake. Characteristics of constant pressure, constant rate and variable pressure-variable rate filtrations can be accurately predicted on the basis of compression-permeability cell data corrected for cell-wall friction. In view of the effective filtration area factor, non uni-dimensional filtration problems can be solved in an analogous manner to conventional uni-dimensional problems. The generalized filtration theory which can be applied to both Newtonian and non-Newtonian fluids is developed on the basis of the power-law model for non-Newtonian fluids.