Oil-water separation is a critical aspect of produced water treatment, oil spill cleanup, and refining of petroleum products. Hydrocyclones are commonly used in these operations. A hydrocyclone is a device that separates two phases based on centrifugal forces acting on the two phases. Conventional hydrocyclones possess a finite turndown ratio and are effective for removing droplets greater than approximately ten microns. The understanding of hydrodynamic phenomena that limit the turndown ratio is crucial for improving hydrocyclone performance and finding a device that is reliable, efficient, and that has the potential to decrease the environmental footprint of oil and gas production. In this work, a quantitative understanding of the turndown ratio of an individual class hydrocyclone has been developed. A computational search is applied for redesigning the geometry of different modules of hydrocyclone. In addition, the desirable attributes of a crossflow filter and a vortex separator are combined into one unit to develop a crossflow filtration hydrocyclone (CFFH) for enhancing separation.The hydrodynamic characteristics of single and multiphase flows encountered in hydrocyclones, the trajectories of dispersed droplets, interaction of phases that involve breakup and coalescence of dispersed droplets, and the geometry and operating principles that characterize the performances of a hydrocyclone are investigated based on computational fluid dynamic (CFD) simulations using the Eulerian-Lagrangian, the Eulerian-Eulerian, and a coupled CFD-PBM (Population balance method) approaches. Results show that the finite turndown ratio in conventional hydrocyclones is a hydrodynamic effect that depends on the length of reverse flow core. Tailoring of hydrocyclone geometry with hyperbolic swirl chamber and new underflow outlet geometry significantly increases the separation efficiency and improves the turndown. Based on a parametric study, a novel hydrocyclone design is proposed that is able to achieve desired separation efficiency by a unit operation and possesses a large turndown. CFD studies were also performed on CFFH devices and showed that the swirl can aid in removing droplets from the membrane/filter surface.The novel hydrocyclone identified provides a stable reverse flow core for an increased range of feed Reynolds numbers and yields less energy loss. With increasing the feed Reynolds number, the novel hydrocyclone gradually decreases the cut size (a size of droplet having 50% separation efficiency); this does not appear in a conventional hydrocyclone. For the feed Reynolds number of 60,000, the cut size in the novel hydrocyclone is less than 10 microns whereas the conventional hydrocyclone has a cut size of 65 microns and is ineffective for droplet less than 10 microns.
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