The Separation Performance Of Hydrocyclone To Inorganic Superfine Particle In Sewage

The influent of sewage treatment plant usually contains a certain amount of inorganic particles,among which the larger parts can be removed with high efficiency by traditional sedimentation,while inorganic superfine particles(no more than 30 ?m)are difficult to be seperated from influent with removal efficiency less than 10%.These inorganic superfine particles will enter into the biochemical pool along with the sewage and accumulate in the biochemical pool,affecting the sewage treatment process,such as reducing the proportion of active components in the sludge;reducing the oxygen transfer efficiency and increasing the aeration power consumption of the blower.In order to achieve effective removal of inorganic superfine fine particles from wastewater treatment plants,This paper studies the separation performance of the hydrocyclone using the method of numerical simulation and experiment,including measuring the flow field by the particle image velocimeter(PIV),and calculating hydrodynamic flow field and separation performance by fluid dynamics(CFD).Finally,the numerical simulation of the hydrocyclone with different parameters was carried out.The main findings are as follows:(1)The hydrocyclone has excellent separation performance for inorganic superfine fine particles in wastewater.The separation efficiency of 25 ?m particles is more than 80%,and the separation efficiency of 15 ?m particles is about 43%,the separation efficiency of 5 ?m particles is also up to 20%.The separation performance of hydrocyclone is superior to the traditional gravity separation equipment.(2)Comparing the results of experiment with the numerical simulation,we found that the tangential and axial velocities only differ on the maximum value and wall surface,and the difference is small;the experimental value of pressure drop at the overflow is 12.5%higher than the simulation value,and the pressure drop at the underflow is 11.4%higher than the simulation value,because the flow field is simplified during simulation and some energy losses are ignored.Due to the fracture of particles under turbulence,the experimental separation efficiency of particle below 15 ?m is higher than the simulation,and the experimental separation efficiency of particle above 15 ?m is lower than the simulation.(3)Among the structural parameters and operating conditions,only the diameters of the overflow pipe and the underflow pipe have a significant effect on the split ratio of the hydrocyclone.When the diameter of the overflow pipe increased from 15 mm to 22 mm,the split ratio decreased from 23.5%to 3.89%.When the diameter of the underflow pipe increased from 10 mm to 16 mm,the split ratio increased from 10.3%to 31.37%.Hydrocyclone separation efficiency is sensitive to the change of cone angle and inlet flow velocity.For particles of 20 ?m,when the cone angle changes from 28° to 16°,the separation efficiency increases from 39.26%to 66.80%;when the inlet flow rate increased from 2.0 m/s to 3.5 m/s,the separation efficiency increased from 44.52%to 63.16%.(4)The tangential velocity of hydrocyclones has the most significant effect on the separation efficiency among three vectorial speeds.When Do/Du>2,if the other parameters are unchanged,increase the diameter of the overflow pipe or decrease the diameter of the underflow pipe,the tangential velocity would increase.The inlet velocity has a significant effect on the tangential velocity.When the inlet velocity increases from 2.0 m/s to 3.5 m/s,the maximum tangential velocity increases from 3.6 m/s to 6.9 m/s;the split ratio and the material concentration has small influence to tangential velocity.The results obtained in this study can provide an effective treatment method and theoretical support for the removal of inorganic superfine fine particles from wastewater treatment plants.