A model describing the hydrodynamics and mass transfer of countercurrent liquid-liquid extraction columns s developed and solved. The hydrodynamic model assumes that the dispersed-phase drops behave as spheres of uniform diameter. The model has been found to be qualitatively in agreement with experimental results published in the literature. It is shown that conventional dispersion interface level control using the continuous-phase effluent flow rate as the manipulated variable causes unavoidable overshoots and oscillations in the mean holdup and outlet concentrations, while an alternative scheme using the continuous-phase feed flow rate leads to a significant improvement in the dynamic response. A model-based decentralized MIMO control scheme is designed and tested by simulation, and is shown to provide excellent servo and regulatory performance.
- Dynamic simulation and control
- Liquid-liquid extraction column
- Mathematical models