Theory of sedimentation of aggregated particulate systems

Abstract

Sedimentation of mono- and polydispersed aggregated particulates is considered with due regard to effects of volume changes which follow aggregation. It is shown that velocities and flux densities depend on volume fractions occupied by particles in slurry and within aggregates, if they are monodispersed, and also on size and volume fraction distributions if they are polydispersed. Velocities of smaller and lighter aggregates may be reversed due to motion of larger and heavier ones. Increase of total volume fraction occupied by particles in slurry, decrease of their volume fraction in aggregates, and increase of standard deviation of related distributions enhance reversal of velocities of larger and heavier aggregates. In continuous steady-state sedimentation velocity of slurry must be adjusted so as to offset negative velocities which may occur in the slurry. Illustration of numerical examples is provided and significance of results discussed.