Microchannel Device for Droplet Generation, Mixing, and Phase Separation for Continuous Counter-Current Flow Extraction

Process intensification is a major goal in chemical engineering, which is often obtained by miniaturized devices with enhanced heat and mass transfer characteristics. This work shows a microchannel device for liquid-liquid extraction and reactions with integrated droplet generation, enhanced mixing and phase separation. Monodisperse droplets with diameters in the range from 0.3 to 0.7 mm are generated by co-current jet flow with different operating modes of aqueous and organic phase. Flow regime maps indicate operation conditions for small and monodisperse droplets of the organic phase. A glass plate with a single microstructured channel serves for sufficient residence time and intensive mixing between the two phases. At the outlet, a wider channel leads to droplet coalescence and agglomeration at a hydrophobic wall and outlet tube for the organic phase. A complete phase separation was possible over a wide range of flow rates. The closed channel setup of droplet generation, mixing and phase equilibrium, and finally phase separation allows for countercurrent switching of the plates. This arrangement needs additional pumps to overcome the pressure drop over the plates, at least one pump more than the number of plates.