CFD simulation of a solvent extraction pump mixer unit: Evaluating Large Eddy Simulation and RANS based models

Abstract

Mixer-settler equipment is widely used for solvent extraction (SX) operations. The pump mixer is the heart of an SX process. Any improvement in understanding of hydrodynamics and flow instabilities within a SX pump mixer unit would enable effective design of the mixer-settler equipment. In this direction, the present work investigates the predictive performance of the Large Eddy Simulation (LES) model vis-à-vis the PIV experimental results and RANS based model. Comparisons have been made initially for single phase operation of a Mixer unit, and then for the multiphase operation. The ANSYS/CFX modelling package has been used to set-up a transient three-dimensional CFD model using the sliding mesh approach for impeller motion and Eulerian-Eulerian approach for multi-phase flows. The present paper compares the flow patterns predicted by the LES model and compares them to RANS model prediction and PIV data. The prediction of flow structures and turbulence intensities will eventually pave the way for determination of droplet size and mass transfer rates, which are required in designing these systems.