Liquid–Liquid Flow in a Continuous Stirring Settler: CFD-PBM Simulation and Experimental Verification

Mixer-settlers have been widely employed in the rare earth element separation industry. Presently, reducing the loss of reagents and occupied areas and achieving a highly efficient separation in the settler are challenging issues. In this work, we report numerical simulations of the liquid–liquid flow in a stirring settler and thereafter describe the experimental validation. A computational fluid dynamics coupled population balance model (CFD-PBM) was developed to investigate the liquid–liquid flow characteristics and settling performance. The dispersion band thickness predicted by the turbulent aggregation model was in good agreement with the experimental measurements. The effects of the total liquid flow rate and initial average droplet diameter on the settling characteristics were further investigated. It was found that the dispersion band thickness increased significantly as the droplet diameter decreased. Moreover, this research shows that the CFD-PBM coupled model is promising for designing large-scale stirring settlers.