Filter Cake Dewatering by Changing Filtrate Flow Pattern

Abstract

Filter cake dewatering in a horizontal plate filter is achieved by using hydraulic expression in a specially designed chamber with an impermeable membrane. The expression mechanism due to a change in the filtrate flow pattern is studied under constant-pressure conditions. A method is presented for analyzing the dehydration rate on the basis of Terzaghi's model for two-dimensional consolidation.
The change in the filtrate flow pattern, which occurs after cake formation is completed, necessarily causes a change in the hydraulic pressure and compressive pressure distribution through the cake, thus leading to consolidation of the cake. The average moisture content of the compressed cake at the end of the operation is quite close to the final average moisture content obtained by the mechanical expression, since the impermeable membrane assists in compressing the cake. The expression rate heavily depends on the applied pressure and the thickness and radius of the filter chamber.
The experimental results of the expression rate for slurry material of Korean kaolin agree well with predictions based on the compression-permeability cell data.