PIV measurement and CFD simulation of liquid-liquid flow of a settler in rare earths solvent extraction mixer-settler

Mixer settler is widely applied in solvent extraction, especially in hydrometallurgy and rare earth element separation. The study and development of the settlers are to achieve clean separation, reduce the loss of the reagents and the occupied areas. Hydrodynamic characteristics of settlers have been investigated in present work, both by experimental and numerical approaches. Experiments that explored the influences of different parameters on the settling characteristics, such as impeller speed in mixer, volume flow of aqueous and organic phase, have been conducted by particle image velocimetry (PIV). Meanwhile, a three dimensional computational fluid dynamic (CFD) simulation has been developed to predict the flow characteristics of the settler, which was proved to be well consistent with experimental data. Preliminary explorations of new design with baffles were proposed. Compared with the non-baffle settler, the residence time distribution was increased and entrainment in the aqueous outlet was reduced in the settler with baffles, which indicated a better phase separation. The hydrodynamic simulation offers an easier, cheaper and time-saving idea to realize better designs for a settler.