Simulation of the fluid dynamics of solvent extraction columns from singledroplet parameters

A droplet population balance model is used to simulate the hydrodynamic beh aviour of solvent extraction columns. This model describes the axial change of local column hold-up and local droplet size distributions caused by bas ic phenomena such as droplet rise, axial dispersion, and droplet break-up a nd coalescence. In order to reduce the effort invested in experimental scal e-up, single droplet experiments were performed in small-scale laboratory d evices. A Rotating Disc Contactor (RDC) with 5 compartments was used for th is purpose. The single droplet movement is investigated by using a light so urce to reproduce the three dimensional particle trajectories on a two-dime nsional screen. The resulting pictures are analysed by digital image proces sing. The experiments were performed for different droplet sizes under diff erent agitation and throughput conditions. Droplet rise is found to slow do wn with increasing agitation whereas higher continuous phase throughput sho ws only a weak influence on the relative rising velocity. Simultaneously th e axial dispersion coefficient decreases at higher agitation and continuous phase flow rates. Based on these single droplet parameters, the population balance equation is solved numerically for a RDC column using a Galerkin m ethod.