Investigation of a 75mm axial flow hydrocyclone for industrial use: an alternative to the reverse flow hydrocyclone

The axial flow hydrocyclone is a competitive alternative to the reverse flow hydrocyclone for industrial use. A comprehensive study of axial flow hydrocyclone will enormously improve the understanding on the possibility of its use for industrial applications. In this work, the influence of particle concentration on the axial hydrocyclone’s pressure drop (∆P), separation efficiency, cut size (d50) and sharpness of separation (I) was investigated numerically using computational fluid dynamics (CFD). The length and diameter of the 75mm reverse flow hydrocyclone from Hsieh’s (1988) experimental work were used as the reference geometrical dimensions for modelling the 75mm axial flow hydrocyclone with a tangential inlet. Three hexahedral grids of 6.5, 7.5, and 8.5 million cells have been used for the simulation, and the quality of the grids was checked using the grid convergence index (GCI). To compare their particle separation efficiencies, the performance of the axial and reverse flow hydrocyclone were compared for different particle concentrations. The LES turbulence model was used to model the continuous phase flow field, and the Lagrangian discrete phase model (DPM) was used to model the particle trajectories. As there is no entrainment of air through the outlets, the air core formation was not modelled. The investigation showed that the cut size of axial flow hydrocyclone (d50=20.46 and 20.3 micrometres) was larger than the reverse flow hydrocyclone (d50=17.73 and 17.81 micrometres) at particle concentrations of 4.88% and 10.47%, respectively. The pressure drop over the axial hydrocyclone is significantly lower than that of the reverse flow hydrocyclone. The pressure loss was found to be 1.24 and 8.3 kPa for axial hydrocyclone, whereas the reverse flow hydrocyclone has a pressure loss of 60 and 69.3 kPa for particle concentrations of 4.88% and 10.47%, respectively. The CFD-based investigation showed that the axial flow hydrocyclone could be successfully used to classify particles in the industry with a substantially lower pressure loss and pumping energy requirements.