Entrainment quantification in static mixer settler setup

Entrainment is a crucial problem in industrial solvent extraction processes, which results in a loss of solvent, impurity accumulation in a final product, and a decrease in process capacity. Basically, in such processes, entrainment comes from physical solubility and/or from very fine droplets that are not able to coalesce or separate. Thus, the first step towards reduction and removal of entrainment involves the experimental quantification of entrainment to determine the relative contribution of the physical solubility and the droplet entrainment, which ultimately determines the strategy to be used. In this regard, physical properties especially interfacial tension can play an important role in determining which of the above contributions will be dominant. This paper presents the results of entrainment characterisation for caprolactam-water-toluene system under different flow conditions and for two different concentrations of caprolactam in the aqueous phase. It was found that at low concentration of caprolactam (high interfacial tension), the entrainment mainly resulted from the physical solubility; however, at high concentration (low interfacial tension), the droplet entrainment turned out to be more significant. The water entrainment in the organic toluene stream after phase separation in the settler was