Influence of suspension concentration on cast formation time in pressure filtration

Expressions for the formation rate of an incompressible cast in batchwise p ressure filtration are formally derived from Darcy's law and Kynch-theory f or pure filtration and filtration with sedimentation and compared with expe rimental results from the filtration of submicron cr-alumina dispersed in w ater. The influence of suspension concentration on the cast formation time is investigated numerically. A maximum cast formation time is found at a ce rtain suspension concentration phi(s) for pure filtration and a constant fi lling height. The value of the maximum cast formation time depends solely o n the cast concentration if the filter resistance is negligible. For a cons tant final cast thickness, the cast formation time always decreases with in creasing phi(s). The cast formation time in a filtration set-up decreases w hen particle sedimentation is important, especially when sedimentation and filtration have the same direction. (C) 2000 Elsevier Science Ltd. All righ ts reserved.