CROSS-FLOW CAKE FILTRATION MECHANISMS AND KINETICS

An experimental investigation of the cake filtration behaviour of 125-180-mu-m polyethylene particles, suspended in a neutrally buoyant Newtonian fluid, has been carried out. Static cake filtration measurements of both filtrate volume out-flow and cake thickness kinetics show the familiar t1/2 time dependence. In addition. the hydraulic resistance of the cake was found to be pressure independent, indicating that incompressible cakes were formed under the pressure conditions examined. When cross-flow is applied, the filter cake tends towards a reduced limiting thickness but surprisingly the corresponding filtration rate or flux is observed to decrease. Direct in situ observations of the cake deposition process clearly reveal the mechanisms controlling particle capture at the surface and this effect, together with a particle deposition model where the packing within the filter cake is cross-flow dependent, is used to successfully describe the observed experimental behaviour.