Experimental investigation of filter cake deposition under cross-flow and static filtration conditions

Effects of cross-flow velocity, filtration pressure, and solid concentration on filter cake properties are studied by using a new filtration setup that allows performing filtration tests under a wide range of operating conditions. The main feature of this setup is that pressure and cross-flow velocity are decoupled, so it was possible to independently investigate the effect of these variables on filter cake properties. Filtration tests have demonstrated that particle invasion into filter media pores occurs initially, leading to the formation of an external filter cake. The increased cross-flow velocity creates an erosive shear stress at the surface of the external cake, which limits cake growth, indirectly maintaining a high filtrate flow rate. This high filtrate rate imparts a considerable drag force onto suspended particles, driving a high count into the porous substrate where these particles could deposit. Increasing pressure amplifies this internal particle deposition, particularly where there is no or limited external filter cake to limit filtrate drag and screen particles at the cake surface. The effect of cross-flow velocity on pore blocking and filter cake structure is observed and demonstrated by CT scanning and scanning electronic microscopy.