Optimizing the Agitation Position in a Continuous Stirring Settler: A CFD-PBM Strategy for Enhanced Liquid–Liquid Separation

Mixer-settlers are pivotal in the solvent extraction industry, yet spatial control of agitation to intensity separation remains underexplored. This study proposes a novel strategy by localizing agitation strictly within the dispersion band. Through the developed computational fluid dynamics coupled population balance model (CFD-PBM) resolving droplet breakup/coalescence dynamics and laboratory experiments, it demonstrates that the agitator position critically governs dispersion band thickness and separation efficiency. It should be emphasized there was no significant difference between the experimental and the simulated. Optimal separation is achieved only when the agitation zone overlaps the dispersion band, balancing droplet fragmentation and coalescence while minimizing turbulence in settling regions. Conventional uniform agitation designs are suboptimal due to spatial sensitivity. The CFD-PBM framework establishes a physics-based tool for scalable mixer-settler design, enabling energy-efficient separation by decoupling mixing and settling energetics. This work provides an advanced solution for using the solvent extraction via targeted agitation optimization, emphasizing both scientific rigor and industrial applicability.