Numerical Simulation Of Separation Characteristics Of Central Cone Hydro-cyclone

Carbide slag is an industrial waste,which has huge emissions in China.Its main component is Ca（OH）₂,and also contains a small amount of impurities such as Al₂O₃,SiO₂ and Fe₂O₃.The Ca（OH）₂content in carbide slag can be increased by particle fractionation,which can replace limestone as material for producing calcium carbide,and the recycling of resources can be realized.Based on the physical and chemical characteristics of carbide slag and the separation characteristics of hydro-cyclone,a central cone hydro-cyclone suitable for purifying the carbide slag is designed in this paper.The specific research work is as follows:（1）testing of physical and chemical properties of calcium carbide slag.The composition,diameter range and the content of Ca（OH）₂ in different particle size of the carbide slag was measured,according to the physical and chemical characteristics of carbide slag,the content of Ca（OH）₂ in carbide slag with particle size less than 75μm can be determined to meet the requirement of producing carbide slag instead of limestone.（2）the design of the central cone hydro-cyclone.In order to overcome the problem of overflow run out caused by air column and ensure the separation accuracy of carbide slag,a central cone hydro-cyclone for purifying carbide slag was designed.The central cone hydro-cyclone is installed in a static hydro-cyclone with coaxial conical structure inside.The central cone occupies the position of the air column to make the flow field more stable;The lower cone section of the center cone has an effect of forced separation on the upward movement of the internal swirl,which makes the coarse particles involved in the internal swirl are forced to move back to the outer swirling flow and discharge from the underflow orifice,which can improve the separation precision.The upper cone section of the central cone has the function of diversion to reduce the turbulence caused by the collision between the inner slurry and the cone below the center cone.（3）Determination of the structural parameters of the central cone hydro-cyclone.Because The separation of carbide slag by hydro-cyclone has an dispersive effect on it,if the hydro-cyclone is designed as the target separation particle size less than 75μm,it is difficult to ensure that the internal impurities can be effectively separated.In order to ensure the separation accuracy,the separation target particle size less than 50μm is used as the design basis of the hydro-cyclone.A mathematical model is established according to the maximum tangential velocity trajectory method,and the diameter of the hydro-cyclone segment is determined to be 50 mm.On the basis of determining the diameter of the column section,the shell structure parameters of the central cone type hydro-cyclone are determined by the empirical formula as follows:D=50 mm,a=25 mm,b=15 mm,Do=15 mm,Du=8 mm,H=85 mm,L=20 mm、θ=6°;Fluent is used to simulate the flow field of the core cone hydro-cyclone and the static hydro-cyclone.the center cone structure is optimized by the central composite test design combined with the simulation results,the central cone structure parameters optimized by the surface response results are center cone position A=10 mm,the upper cone angle of central coneθ₂=45°,and the lower cone angle of the central coneθ₁=140°.（4）numerical simulation and experimental verification of the separation characteristics of the central cone hydro-cyclone.The same simulation conditions are set by Fluent to simulate the flow field between the central cone hydro-cyclone and the static hydro-cyclone with the same structure parameters,by comparing the pressure distribution,the tangent velocity,the turbulent kinetic energy,the zero axis speed envelope,the velocity vector and the DPM discrete phase simulation of the internal flow field,the advantage of the central cone hydro-cyclone is verified;Make use of 3D printing technology to produce center cone-type hydro-cyclone,build the test platform,according to the center of the composite test design and design test,to verify the effect of cone-type hydro-cyclone separation of carbide slag.The best operating parameters of the central cone hydro-cyclone were obtained by the surface response method:the treatment volume Q=1.9 m³/h,the feed concentration is 10%,and the test result is:the overflow separation precision limit D₉₅=54μm,the separation efficiency is 87.2%,and the separation accuracy factor is 41.3%.