Effect of cone angles on single-phase flow of a laboratory cyclonic-static micro-bubble flotation column: PIV measurement and CFD simulations

Combination of cyclonic flotation and conventional column flotation is a novel column flotation technology. A cyclonic-static micro bubble flotation column (FCSMC) using this technology significantly improves recovery rate during flotation. However, the mechanism of cyclonic separation still remains black box. This paper presents CFD simulations on single-phase to find how different the reversal cone, a key part in cyclonic flotation unit in FCSMC, can affect the fluid flow, then corresponding mineral processing efficiency. PIV measurement is established for simulations validation. RSM-S turbulent model is used to obtain hydrodynamic characteristics in FCSMC. 38-, 48-, 58-, 68-degree cone angle cases are explored. Results show that three kinds of vortexes exist in a laboratory FCSMC: spiraling-up quasi-free vortex near wall, spiraling-up quasi-forced vortex near column axis and spiraling-down quasi-forced vortex between wall and axis of column. The vortexes are greatly affected by the angle of the reversal cone. In the column flotation unit, diameter and flux of quasi-forced vortex spiraling down increase while quasi-forced vortex spiraling up decreases with the angle increasing from 38° to 68°. Smaller angle generates larger overflow in cyclonic flotation unit. Both tangential velocity and centrifugal intensity in cyclonic flotation unit decrease. Disordered fluid flow in cyclonic flotation unit is generated under too small cone angle, like 38°. Besides, under too large cone angle, like 68°, centrifugal intensity in column flotation unit increases and quasi-forced vortex spiraling up flux in cyclonic flotation unit decreases or disappears. So the separation environment is deteriorated. Among the four degrees, optimal fluid flow of the laboratory cyclonic-static micro bubble flotation column can be maintained under an angle of 48°.