Micro-Scale Liquid-Liquid Separation in a Plate-Type Coalescer

The plate-type coalescer was constructed and tested for the continuous separation of immiscible liquids in micro-scale. Two plates formed the main structure of the coalescer. A flat and rectangular channel was situated between the plates. The material options for the plates were PTFE, stainless steel and glass which formed the contact surfaces for the fluids in the device. The liquid-liquid dispersion generated by the standard slit interdigital micromixer was fed in the coalescer where the coalescing of the droplets occurred. The coalescer had two outlets, one for the aqueous phase and the other for the organic phase enabling the continuous separation and withdrawal of separated phases. The performance of the coalescer was evaluated with respect to the channel height, flow rate, residence time and plate configuration. It was observed that in suitable conditions, the plate-type coalescer offered the efficient phase separation continuously under stable operation. The separation method utilizes the interaction between the fluids and channel surface. The flat channel, 100 μm or 200 μm, enabled the fluid-surface interaction. By using PTFE and stainless steel materials as channel surfaces and the total flow rate less than 180 ml/h, the stable operation and complete separation of aqueous and organic phases were possible. 180 ml/h corresponds superficial velocity of 3.3 cm/s in 100 μm height channel and 1.7 cm/s in 200 μm height channel. The phase separation in the coalescer took place considerably faster than conventionally in a decantation container.