Theory of Flocculation for Continuous Flow System

Abstract

The Smoluchowski equation for orthokinetic equation is applied to the case of a couette-type flocculator with continuous flow. With the inner cylinder tapered to provide a decreasing principal velocity gradient in the direction of flow, a three-dimensional velocity gradient field is established. Based on a mathematical model, flocculation is compared with such a tapered flocculator, and one in which the velocity gradient is uniform. The importance of the limitation of the floc size by fluid shear is established, but the mode of floc particle breakup is not so significant. With both initially monodispersed and polydispersed suspensions, the tapered flocculation is better, judged by the number of fine particles remaining as the suspension leaves the flocculator. The relative efficiency of the tapered flocculator increases with increased values of velocity gradient and with initial concentration of particles.