DYNAMIC MICROFILTRATION OF DILUTE SLURRIES WITH A ROTATING CERAMIC MEMBRANE

The transient behavior of dynamic microfiltration, where a dilute slurry containing submicrometer sized solids is filtered through a ceramic membrane under constant pressure, is studied using a rotating ceramic membrane. With a ceramic membrane of a much smaller pore size than the particle size of the suspended solids, the dynamic microfiltration follows the principle of thin-cake filtration. A filtrate velocity equation is derived for the thin-cake filtration process by introducing a dynamic filtration coefficient, defined as the ratio of deadend to dynamic cake resistance, into the conventional Ruth filtration equation. On the basis of the fact that the dynamic factor depends on a controlling variable composed of the shear stress acting on the cake surface and the coefficient of constant pressure filtration, a method is presented for calculating the variation of filtrate volume with time. A basis for the design and evaluation of rotational microfiltration is proposed.