CFD prediction of solid particle distribution in baffled stirred vessels under partial to complete suspension conditions

Solid-liquid mixing within tanks agitated by stirrers can be easily encountered in many industrial processes. It is common to find an industrial tank operating at an impeller speed N lower than the minimum agitation speed for the suspension of solid particles: under such conditions the distribution of solid-particles is very far from being homogeneous and very significant concentration gradients exist. The present work evaluates the capability of a Computational Fluid Dynamics (CFD) model to reliably predict the particle distribution throughout the tank under either partial or complete suspension conditions. A flat bottomed baffled tank stirred by a Rushton turbine was investigated. Both transient and steady state RANS simulations of the stirred tank were performed with the commercial code CFX4.4. The Eulerian-Eulerian Multi Fluid Model along with the k-ε turbulence model was adopted. Either the Sliding Grid or the Multiple Reference Frame technique was employed to simulate the impelle...