Study on the flow field and improved separation performance of a three-stage cone water-only cyclone

Abstract

In this study, computational fluid dynamics (CFD) numerical simulations were applied to comparatively evaluate the flow field of a three-stage cone water-only cyclone (TWOC) with that of a single-stage cone water-only cyclone (SWOC). The reliability of numerical simulations was validated using particle image velocimetry (PIV) technology. According to the analyses of the influences of the flow field characteristics on the separation process, the reasons for the improved separation performance of the TWOC were reasonably explained. The differences in the flow fields inside of the two cyclones only exist in their cone components. In the TWOC cone, the tangential velocity and the axial velocity are both smaller than those of the SWOC, the near-wall fluid is disturbed and two secondary eddies are formed. The secondary eddies increase the looseness of the coal particles and prompt the radial separation of the coal particles. In the TWOC, low-ash coal particles below the theoretical separation density (δ50) are sufficiently separated into the overflow products throughout the downward motion. Most of the coal particles reaching the cone bottom are high-ash coal particles above δ50 that are basically discharged through the underflow pipe. Even if some coal particles are forced into the internal spiral flow, these particles will be re-separated by the secondary eddy.