Determination of the critical pressure drop for filtration of super-compactible cakes

In accord with Darcy's law, the flow rate through a porous bed depends upon the pressure drop Deltap(c). In general, increasing Deltap(c) leads to increased values of flow rate and average percentage solids in filtration operations. When cakes become super-compactible, their behavior undergoes an unexpected change in which both the flow rate and the percentage solids reach maximum values and thereafter are unaffected by increasing Deltap(c). The critical pressure drop Deltap(cR) is defined as that value at which the flow rate reaches 90% of its ultimate value. When Deltap(c) is greater than Deltap(cR) and is doubled or tripled, the cake resistance approximately doubles or triples leaving the rate virtually unchanged. The super-compactibility problem is analyzed theoretically, and is verified by stepped pressure filtration experiments on different materials from Houston and Korea.