(177b) A New Design Method for Solvent Extraction Columns Based On Single Drop Experiments

Solvent extraction is becoming increasingly attractive as a thermal unit operation. This is especially true in light of the future change in chemical feedstock, where bulk chemicals will be increasingly produced from biomass, whose comparably high oxygen content results in low vapour pressure, rendering distillation less feasible. Until recently, extraction columns were designed based on pilot-plant experiments. Bart et al. (2006), however, showed that expensive and time-consuming pilot-plant experiments can be replaced by lab-scale measurements with single drops and appropriate simulation of the column behaviour with drop-population balances. ReDrop is a drop-population balance tool which was developed at AVT - Thermal Process Engineering and which can predict the behaviour of extraction columns based on these single-drop experiments. ReDrop tracks a certain number of drops during their entire lifetime in an extraction column; it can thus be seen as a Monte-Carlo solution of drop-population balances. Real world phenomena like drop sedimentation, break-up, coalescence and mass-transfer are taken into account. These phenomena are modelled employing single-drop models which have system-specific parameters determined from lab-scale experiments with single drops. Simulations with ReDrop for pulsed extraction columns with sieve trays and structured as well as random packings have been validated for a variety of liquid-liquid systems, even for industrial ones. Recent research has focused on extending ReDrop for extraction columns with rotating internals like the RDC- or Kühni-geometry (Kalem et al. 2011).

During the presentation, the ReDrop concept and the basic algorithm will be introduced. Simulation results of the hydrodynamics and the separation performance for different extraction columns with rotating internals and liquid-liquid systems will be compared to experimental data. Simulation results of a system with an ionic liquid as a solvent will also be presented and compared to experimental data.

Bart, H.-J., Garthe, D., Pfennig, A., Schmidt, S., Stichlmair, J., 2006: Vom Einzeltropfen zur Extraktionskolonne. Chem. Ing. Tech., 78 (5), 543-547.

Kalem, M., Buchbender, F., Pfennig, A., 2011: Simulation of Hydrodynamics in RDC Extraction Columns Using the Simulation Tool "ReDrop". Chem. Eng. Res., 89, 1-9.