Measurement of phase holdups in liquid–liquid–solid three-phase stirred tanks and CFD simulation

Phase holdup is an important hydrodynamic characteristic of multiphase systems relevant to optimization and scale-up of related process equipment. In the present article, measurements of phase distribution of solid particles and oil droplets are conducted in a lab-scale stirred tank by sample withdrawal under various operating conditions. A Eulerian–Eulerian three-fluid model is established for the prediction of phase distribution of two dispersed phases in the agitated liquid–liquid–solid dispersion system. The turbulence structure in the system is described by an extension of the standard k–εk–ε turbulence model to three-phase flow including the influence of presence of two dispersed phases as an additional source of turbulent kinetic energy. Momentum exchange between continuous and dispersed phase as well as between the two dispersed phases are incorporated into the model formulation. Comparison of model predictions with experimental data suggests reasonable agreement for the dispersed oil phase. The predicted distribution of solid particles shows some discrepancies in comparison with the measurements, but the agreement is significantly improved for higher impeller speeds.