Intensification of fine particle flotation with less energy input using vortex generators

Abstract

The separation of fine mineral particles has always been challenging in flotation. Previous studies generally believed that intensifying fine particle flotation necessarily involves higher energy expenditure. To explore the more effective intensification, this study measured the flotation performance of diaspore particles smaller than 20 µm in a mineralization pipe. The energy input was regulated by varying the slurry flow rate in the mineralization pipe and incorporating wedge-shaped vortex generator (VG) with different pinch angles. The results of flotation tests indicated that introduction of VG can achieve superior flotation performance with reduced energy input. A flotation rate of 0.86/min was obtained in the mineralization pipe with VG and a pinch angle of 60° (VGP-60) at an energy input of 27.29 W, much higher than that of 0.53 /min in empty pipe at 37.59 W. The more effective intensification is attributed to the high turbulent dissipation rate (ε) induced by VG. The volume-averaged ε in VGP-60 is 31.8 m²/s³ at an energy input of 27.29 W, exceeding that in empty pipe at 37.59 W. The increased ε enhances the collision rate between particles and bubbles, thus causing the flotation rate to grow as a power function with exponent of 0.5.