Study On Optimizing Parameters Of Hydrocyclones Based On Flow Patterns

Hydrocyclones have a widespread use in mineral processing engineering,chemical engineering and environmental engineering owing to their design simplicity,flexibility of operation and high capacity.The inner flow field in hydrocyclones is a key factor to determine the separation performances and determined by geometrical parameters and operational parameters.Therefore,the investigation into effects of different parameters on the inner flow field is an effective method to explore the separation mechanism for solid particles in a hydrocyclone.The expected separation target can be achieved by adjusting the inner flow field.Thereby,it can provide theoretical instructions for the design and application of a high performance hydrocyclone.Aiming at characteristics of the inner flow field in a hydrocyclone,the numerical experiment in this paper was based on CFD(Computational Fluid Dynamics),where RSM(Reynolds Stress Model)was used to calculate turbulence and VOF(Volume of Fluid)model was used to capture the interface of water and air.Primary flow field features could be obtained.On this basis,solid particles were added into the hydrocyclone.The Mixture model was used to model the particle motion and water-air interface transient characteristic.Then characteristics of liquid-solid flow field and separation performances could be quantitatively described.Selected mathematical models were proved to be accurate and reliable by comparing the numerical results with the experimental data.The numerical results showed that the tangential velocity distribution can be considered as a Rankine vortex.At the bottom of the vortex finder the tangential velocity in the free vortex region decreased with decreasing the radius because of the high turbulence intensity.There was an axial circulation flow region in the cylindrical section and the upper part of the conical section.Short circuit flow can be found at the bottom of vortex finder diameter.Distribution characteristics of different sized particles showed that 0.5 μm fine-grained particles were mainly dominated by turbulence dissipation and were more likely to move alongside the water flow.The distribution rates of underflow for 0.5 μm particle were mainly associated with split ratio.With the increase of the particle size,the influence of turbulence dissipation on solid particles decreased gradually,and the influence of the inertial centrifugal force was gradually increased,and the particles equilibrium radius increased.Effects of geometrical parameters and operational parameters on the flow field stability and separation performances were studied.Results showed that a steady inner flow field was the guarantee of the normal separation of a hydrocyclone.When feed flow rate,inlet diameter,vortex finder diameter,vortex finder depth,underflow orifice diameter and cone angle were not in the normal range,the stability of the flow field was damaged.The unstability of the inner flow field was characterised by the rapid increase in turbulence intensity and short circuit flow,the change in LZVV shape and the decrease in air core stability.Therefore,regular distribution along the radial direction for different sized particles was destroyed.The distribution rates of underflow for coarse particles were dramatically decreased,and that were sharply increased for fine particles.Thus,the classification precision was decreased.Interactions between the feed particle size and the feed flow rate,overflow diameter and underflow diameter were investigated.It is found that there is a significant interaction between the feed particle size and the feed flow rate and underflow diameter.In a certain range,the increase in feed flow rate or underflow diameter could mitigate adverse effects of feed particle size fluctuation on separation performances,to ensure the normal operation of the hydrocyclone.Feed particle size has little correlation with the vortex finder diameter.Effects of inlet curvature radius on separation performances were studied.Results showed that decreasing curvature radius within a certain range could improve flow field symmetry and decrease the turbulence intensity and the amount of short circuit flow.When using a smaller curvature radius inlet,the pre-classification effects on solid particles could be improved,and the classification precision could be improved to some extent.Based on numerical test results,implementations on improving classification efficiency of Φ660mm hydrocyclone in Anqian Mining were proposed.According to the solution,industrial trials were conducted.Results demonstrated that the content of-74 μm sized particles was obviously increased for overflow products and the separation efficiency was increased by 5.53 percent.