ABSTRACT

The design of equipment for solvent extraction is a challenging task. Two major types of equipment shall be regarded, namely extraction columns and mixer-settlers. The challenge in designing a mixer-settler with respect to its major dimensions lies in the difficulty of predicting coalescence and thus settling behavior, which strongly depends on the material system due to the significant influence of trace impurities like salts and surfactants on the drop coalescence. Since the models for the drop-based simulation of extraction-column behavior also need to take the interaction between the drop swarms and the column internals properly into account, the lab-scale measuring cells for drop behavior have been augmented correspondingly. In the extraction column, coalescence and breakage of the drops determine the drop-size distribution and, therefore, the volume-specific interfacial area for mass transfer. The results of the drop-based simulations show that they allow the prediction of the behavior of extraction equipment on a pilot-plant and technical scale with good accuracy.