CFD Study on the Effect of Hydrocyclone Structure on the Separation Efficiency of Fine Particles

Effects of geometric structure parameters of 10 mm-diameter hydrocyclones on the particle separation efficiency are studied using computational fluid dynamics (CFD). The fluid velocity profiles and particle trajectories are simulated using RFLOW software with a standard isotropic k-epsilon turbulent model. The JIS standard CaCO3-17 particles are adopted as a particulate sample in simulations and experiments. Comparing the simulated results with experimental data, a maximum deviation about 20% in partition curves occurs for 5-10 mu m particles. However, fairly good agreements for the cut-size predictions and the fish-hook phenomenon are obtained. The simulated cut-size d(50) is only 2 mu m larger than that measured in experiments, while the value of d(100) can be accurately predicted. An increase in overflow diameter or a decrease in underflow diameter leads to a lower separation efficiency but a clearer separation sharpness due to lower fluid underflow rate. A short-and-wide rectangular inlet is more efficient for particle separation than a tall-and-narrow one. An inclined inlet conduit plays an inessential role on the efficiency improvement but gains a 2 mu m reduction in d(100). Comparing the simulated results, the hydrocyclone used in the experiments of this study exhibits a higher separation sharpness than the Rietema type and a higher efficiency than the Bradley type based on the same operation capacity and hydrocyclone size.