Analytical and numerical modelling of the effect of filter medium resistance on the mechanical dewatering of wastes and industrial filter cakes

Abstract

A nonlinear model is proposed to predict the effect of filter medium resistance on the filter cake compression and dewatering at constant pressure. This model is based on the Darcy-Terzaghi-Shirato filtration-compression equations presented in material coordinates and modified to consider the power-law pressure dependence of the specific cake resistance α. Above mentioned model is extended to consider the filter medium resistance Rmintroducing the number of Biot, Bi=αavWRm.Local profiles of compressive pressure and filter cake characteristics, as well as consolidation ratio and cake dryness, are simulated and compared for different moderately and highly compressible filter cakes (silica, activated sludge, Baker’s yeast, and CaCO3) based on the analytical and numerical solutions of the model. It is shown that the behavior of cake compression and dewatering significantly depends on the filter medium resistance Rm, especially at the small numbers of Bi≤1.