Counter current liquid-liquid extraction is frequently used in chemical, biochemical, mineral and nuclear industries. In spite of these facts, the prediction of the performance of such equipment performing these operations is still unsatisfactory. The discrepancy between theoretical and actual performance is due to the complex nature of the dispersed phase, where it loses its identity due to droplet coalescence and breakage through its interaction with the turbulent continuous phase. Thus, the hydrodynamics and mass transfer in liquid-liquid extraction columns are determined by the behavior of droplet swarms, comprising the dispersed phase. The behavior of droplets and its size distribution could be described, using PPB, by carrying out a differential droplet population balance for droplets of different sizes.

The requirement for the online control over sensor technology lies in the development of efficient control structures. A modern approach towards droplet size distribution controlled appliance has to be developed such as the OPOSPM and then exemplarily tested in RDC columns (which are available at the chair). Therefore, a reduced mathematic model of the column performance (based on the secondary and primary particle concept) must be developed in order to describe the dynamic performance of a counter-current extraction column.

The model conceptualizes a hierarchy in column dynamics starting from the simplest one primary-one-secondary (OPOS) particle model to a multiprimary-one-secondary (MPOS) detailed one. The reduced model is equivalent to the “base case” in process design, while the detailed one is a superstructure model taking into account secondary particle interactions (breakage and coalescence).