The Effect of Inlet Velocity on the Separation Performance of a Two-Stage Hydrocyclone

Abstract

The “entrainment of coarse particles in overflow” and the “entrainment of fine particlesin underflow” are two inevitable phenomena in the hydrocyclone separation process, which canresult in a wide product size distribution that does not meet the requirement of a preciseclassification. Hence, this study proposed a two-stage (TS) hydrocyclone, and the effects of the inletvelocity on the TS hydrocyclone were investigated using computational fluid dynamics (CFD).More specifically, the influences of the first-stage inlet velocity on the second-stage swirling flowfield and the separation performance were studied. In addition, the particle size distribution of theproduct was analyzed. It was found that the first-stage overflow contained few coarse particlesabove 40 μm and that the second-stage underflow contained few fine particles. The second-stageunderflow was free of particles smaller than 10 μm and almost free of particles smaller than 20 μm.The underflow product contained few fine particles. Moreover, the median particle size of thesecond-stage overflow product was similar to that of the feed. Inspired by this observation, wepropose to recycle the second-stage overflow to the feed for re-classification and to use only thefirst-stage overflow and the second-stage underflow as products. In this way, fine particle productsfree of coarse particle entrainment, and coarse particle products free of fine particle entrainmentcan be obtained, achieving the goal of precise classification.