EXPERIMENTAL INVESTIGATION AND THEORETICAL MODELLING OF MASS-TRANSFER INDUCED EFFECTS AT INTERFACES OF SEDIMENTING DROPLETS

摘要

Liquid-liquid extraction columns can be designed based on single-drop experiments. For this purpose, adequate models are necessary. Experiments in this work with the standard reactive extraction test system Zn + D2EHPA show that the models used traditionally for describing the movement of single drops in physical extraction systems are not valid if a reaction involving interracially active species is taking place. The influence of reaction and mass transfer on the sedimentation velocity was measured and compared to systems undergoing physical mass transfer showing significant and systematic differences. As a first step in modeling the motion of droplets, CFD-Simulations of single n-butanol droplets freely sedimenting in an aqueous continuous phase were performed and compared to experimental results as well as semi-empirical models showing good agreement. For modeling the influence of surfactants, the test case of a toluene droplet levitating in an aqueous counter-current in the presence of surfactants was considered in CFD-simulations. A direct quantitative comparison of the fluid velocities inside the droplet showed good results compared to NMR-experiments. A combination of the two test-cases lays the foundation for a robust