The improved separation of liquid-liquid dispersions by coalescence has stimulated significant interest since the development of more efficient, microprocessing methods. This is due to the requirement to create fine droplet dispersions for increased mass transfer rates. However, efforts to increase mass transfer rates via an efficient mixing method are futile, if the dispersions created cannot be effectively separated.
By combining the separation properties of different advanced settling devices, the basic plate-type separator (P-TS) is highly efficient at separating immiscible fluid dispersions. This is shown through the achievement of 83% separation with a non-optimised P-TS, separating an immiscible water-kerosene dispersion of initial droplet size 100 μm. The P-TS is manufactured from two plates, one hydrophobic and the other hydrophilic. The difference in interaction of the aqueous phase with the two plates is proven to enhance the separation efficiency of the P-TS. The simple, compact design with few crevices and no moving seals, reduces the likelihood of corrosion and increases the potential lifespan of the unit. The simplicity of the design makes the P-TS perfect for industrial application, in particular the nuclear industry; where is it easy to predict how the unit would operate within a nuclear reprocessing facility and how decommissioning with traditional methods would be achieved.
This work was completed in three stages. Firstly, an understanding of the coalescing interface was developed with static droplets. Next, the commissioning and testing of a simple P-TS was completed, with completed tests challenging the overall separation mechanism of the device with increasing plate spacings. Finally, design alterations were made to enhance coalescence and separation based on results from the previous stages.
Overall, it was found that maximising the difference between plate interaction with each phase through the use of a super-hydrophobic and hydrophilic plate configuration, the utilisation of confinement theory thought the reduction of the plate spacing, and the introduction of localised turbulence with the presence of plate textures, provided a final optimised design achieving a separation efficiency of 96.9%
