Flow field evolution mechanism and fine separation performance of coal slime in a novel cyclone cluster with a tapered column section

Abstract

Single-stage hydrocyclones struggle to meet the requirements for the fine separation of coal slime. Existing combined hydrocyclones are constrained by the discharge capacity of the transverse underflow port, where the recirculation vortex at the bottom induces flow field instability and degrades separation efficiency. To overcome the cognitive limitations of structural optimization that solely focuses on the connection methods between the two stages, this study proposes a novel combined hydrocyclone featuring a primary hydrocyclone modified with a tapered column section. A coupled numerical simulation and experimental approach was employed to elucidate the regulatory mechanism of the tapered column section on the flow field evolution and multi-component separation of coal slime. The results demonstrate that the tapered column section drives the axial migration of the primary separation zone, mitigates turbulence interference between the recirculation vortex at the bottom and the primary separation zone, and optimizes the synergy between the two-stage flow fields. Compared to conventional combined hydrocyclones, the novel structure enhances the screen yield of the secondary overflow by 18.1% and increases the ash content of the secondary underflow by 12.5%. This configuration provides a quantifiable technical pathway for the short process fine separation of coal slime.