CFD study on separation enhancement of mini-hydrocyclone by particulate arrangement

Abstract

Several mini-hydrocyclones are designed to improve fine particle separation using computational fluid dynamics. This article based on the idea of particle arrangements at the entrance of a hydrocyclone, designed a common mini-hydrocyclone (CM-hydrocyclone), positive rotation mini-hydrocyclone (PRM-hydrocyclone), with particle size increasing from the inside to the wall at the entrance, and a reverse rotation mini-hydrocyclone (RRM-hydrocyclone), which with an opposite-particle arrangement. The particles’ arrangement and separation-strengthening mechanism are studied with FLUENT software. The governing equations are coupled using the SIMPLE algorithm, while the Reynolds Stress Model is employed for the hydrocyclone turbulent model due to its anisotropic nature. Particle trajectories are simulated based on a Lagrangian frame considering continuous phase interactions. The results show that the particles closer to the outer wall or to the lower part of the entrance tend to be separated with the underflow. The particles injected from upside of the inlet tend to be trapped in the under-cover flow with a long path and get discharged with the shortcut flow. The main separation zone for the mini-hydrocyclone located in the region between the vortex finder tip and the upper quarter of the cone. Particle arrangements at the entrance of hydrocyclone have a significant impact on separation efficiency of fine particles. RRM-hydrocyclone with particle size that increases from the wall to the inside of the entrance can improve separation efficiency. RRM-hydrocyclone demonstrated 83% separation efficiency when the average particle size is 0.53μm. This is much higher than the values demonstrated by CM-hydrocyclone and PRM-hydrocyclone. However, PRM-hydrocyclone, with particle size that decreases from the wall to the inside of the entrance, can eliminate short circuit flow.