Influence of compartment geometry on the residence time of single drops in Kühni extraction columns

Based on the experimental findings a stochastic model comprising three sub-models, one for each individual zone (lower toroidal vortex, impeller region, upper toroidal vortex) is developed. In this model, drop movement is described by superimposing drop sedimentation velocity onto the axial velocity of the toroidal vortex, which is a function of the drop's radial position. The model uses stochastic methods to account for stator impact or drops being back-mixed between the individual compartment zones. With this model, it is possible to quantitatively describe not only the mean residence times of drops but also the residence-time distribution for different drop diameters, impeller speeds and open-area fractions of the stator.