1992 Volume 18 Issue 5 Pages 708-713
The dynamic microfiltration behavior of high-viscosity slurry containing finesize solids is examined under constant pressure, using a rotating membrane filter with a ceramic cylinder. On the basis of an empirical correlation of flux-controlling parameters, a method of evaluating the effects of liquid viscosity on transient and steady filtration rates is studied.
The rotating microfiltration of the viscous slurry proceeds on the principle of thin -cake filtration after operation begins, and has a common feature : gradual reduction initially, followed by a roughly uniform value of final flux. Based on the filtration rate equation with the dynamic coefficient defined as the ratio of cake resistance in unstirred and stirred filtration, it is shown that the liquid viscosity effects a remarkable variation in both the passage of filtrate through the membrane and the sweeping off of filter cake from the membrane. The time dependence of thin-cake resistance is related simply to a number of operational parameters, in view of the fact that the final equilibrium velocity can be estimated as a power-function of the shear stress acting on the cake surface and Ruth's coefficient of constantpressure filtration. It is also suggested that the relative motion between slurry and membrane, created by the high-speed rotation of the latter, can be efficiently utilized to achieve a high -flux filtration of the viscous liquid -solids system.
