A numerical study on efficient recovery of fine-grained minerals with vortex generators in pipe flow unit of a cyclonic-static micro bubble flotation column

Abstract

In the past decade, intensive research has proved that the cyclonic-static micro bubble flotation column (FCSMC) is an efficient flotation device which can be used to separate fine-grained minerals. The main way to strengthen the recovery of fine-grained minerals is further improvement of the highly-turbulent flow field of the pipe flow unit in the flotation column. With a decrease of fine-grained mineral diameter, the turbulence intensity in the pipe flow should be increased so as to strengthen the recovery of the fine-grained mineral. In this paper, the effect of vortex generators (VGs) on the turbulence kinetic energy and the turbulence dissipation rate in a pipe flow unit are primarily investigated by numerical simulations. The results showed that a staggered arrangement (S=20mm) exhibited the maximum volume-averaged turbulence kinetic energy and volume-averaged turbulence dissipation rate among different arrangements of VG arrays in the pipe flow unit. Streamwise vorticity was formed behind the VGs along the flow direction. With an increase of VG arrays from 0 to 5, the volume-averaged turbulence kinetic energy increased from 0.015m2/s2 to 0.05m2/s2. Similarly, with an increase of VG arrays from 0 to 5, the volume-averaged turbulence dissipation rate in the pipe flow unit increased from 1.99m2/s3 to 11.8m2/s3. A flotation experiment using coal slime was conducted by using different structures of pipe flow unit (including empty pipe and pipe with different VG arrays). The results showed that cumulative yield and combustible recovery were greatly improved due to the influence of VG arrays. The results of the study are equally beneficial in helping understand the recovery of fine-grained minerals in other separation equipment.