Experimental and computational analysis of immiscible liquid-liquid dispersions in stirred vessels

This work is aimed at investigating the fluid dynamic characteristics of a stirred tank of standard geometry for the dispersion of organics in water. Two different aspects have been considered. Firstly, the dispersion conditions at different impeller speeds and the flow features of both the continuous and the dispersed phases have been examined. The two-phase turbulent flow fields of a dilute liquid-liquid system as measured by means of Particle Image Velocimetry (PIV) technique are presented. The mean velocity and the turbulent characteristics of water and oil droplets flow are compared with those of the corresponding single-phase flow and discussed; the influence of the dispersed phase on the continuous one is assessed. For the second aspect, starting from moderately agitated conditions, corresponding to completely separated phases, the different dispersion regimes taking place in the tank at increasing impeller speeds have been identified. The capability of a CFD approach based on the solution of Reynolds averaged Navier-Stokes equations and on an Eulerian-Eulerian description of the two phases in catching the dispersion features has been critically assessed.