Shear-Induced Agglomeration of Particulate Suspensions

Abstract

The “demixing” of an initially well-dispersed suspension of particulates arising from shear-induced, interparticle collisions in laminar flow was examined with the help of a transparent, cone-and-plate device. Experiments were conducted on a model system consisting of narrow-size distribution, noncolloidal, glass spheres suspended in aqueous corn syrup with added surfactant. The rate of agglomerate growth was measured as a function of time for different constant shear rates and suspension compositions. Data revealed a rapid buildup of particulate size at short times but a leveling off at extended times of shear due to the influence of hydrodynamic shear forces that determine the equilibrium agglomerate size. All the observations could be qualitatively explained by a simple agglomeration analysis that is developed here, and agglomerate growth could be quantitatively represented using an equation resulting from this theoretical analysis.