Research On Classification Performance Of W-type Reflective Plate Hydraulic Classifier

The classification of fine particles has important engineering application value for effectively enhancing the high added value of mineral resources.The hydraulic classifier has been widely used in the field of separation science with excellent performance.However,the powders separated and extracted by the existing classifiers have a large particle size,and the powders are mixed with each other,resulting in impure powder texture,which cannot meet the industrial requirements for fine powders.This paper presents a new type of hydraulic classifier with W-shaped reflector and tangential inlet.The methods including theoretical analysis,numerical simulation,laboratory testing and industrial operation verification methods are used to study the flow field and separation performance of the classifier.The results show that the new classifier can effectively improve the classification accuracy and classification efficiency.The research results have certain reference value for revealing the classification mechanism of the classifier.The Fluent software is used to numerically simulate the flow field of the Φ200mm W-type reflector classifier,and the simulation results show that compared with traditional classifier,the new W-type classifier can lower the hedging effect of falling materials and rising water,and improve the stability of the flow field,attributing to the tangential feeding structure.Different from the traditional classifier,the new classifier adds a W-shaped reflecting plate at the bottom of the feeding tube.The reflection of the slurry make it reenter and mix with the rising water again,and the interference sedimentation is conducive to the formation of suspension bed of slurry in the grading cavity,thereby improving classification accuracy and efficiency.Studies have shown that appropriately increasing the feed rate is conducive to the spiral decline of the slurry and the stability of the flow field in the classification’ area,which can effectively improve the classification accuracy.But if the feed rate is too high,the rapidly downward slurry will disturb the flow field.Properly increasing the inlet water speed can reduce the disorder of the flow field inside the classifier,which is conducive to form the effective stratification of the slurry and improve the classification performance.However,when the inlet water speed is too high,the classification and separation effect will be reduced.Appropriate insertion depth of the feed pipe can increase the classification area of the classification area and the settlement area of the classification cavity and improve the classification accuracy.With appropriate structure size of the W-shaped reflector,the slurry can be effectively ejected and layered,which is conducive to form a stable slurry suspension bed and improve the classification accuracy and efficiency.Experimental research shows that:within a certain range,when the feed speed is increased,the classification performance is significantly improved.When the feed speed is 1.2m/s,the classification efficiency of particles below 45 μm in the overflow can reach 56.62%,and the yield can reach 33.18%,but when the feed speed exceeds 1.2m/s,the slurry falling at high speed will disturb the flow field stability of the classifying cavity.Properly increasing the inlet water speed can improve the classification performance.When the inlet water velocity is 0.9m/s,the classification efficiency of particles below 45 μm in the overflow can reach 66.71%,and the yield can reach 36.32%.Appropriate feed concentration can reduce the occurrence of agglomeration caused by viscous forces between materials.When the feed concentration is 25%,the classification efficiency of particles below 45μm in the overflow can reach 67.46%,and the yield can reach 35.15%.The depth of the insertion tube affects the initial position of the slurry when it enters the classification cavity.If the insertion depth is too shallow,the material will enter the overflow without effective classification,leading to increament of the classification mismatch rate.If the insertion depth is too deep,the space between the reflector and the water inlet cavity will be narrowed,resulting in increased turbulent kinetic energy in this area and causing classification disorder.The structural size of the W-shaped reflector affects the repulsive throw distance of the material,directly affects the residence time of particles in the flow field,and then affects the classification accuracy.After comprehensive comparison,the optimal combination of optimal structural parameters and operating parameters is obtained:the feed speed is 1.2m/s,the inlet water speed is 0.9m/s,the feed concentration is 25%,and the feed pipe insertion depth is 350mm.The gap between the W-shaped reflector and the classification cavity is 25mm.Based on the research results and according to the specific requirements for the classification of a certain magnetite powder,a three-product hydraulic classifier with W-type reflector and double-inlet was designed and developed,and the industrial operation test was conducted.After verification,the overflow yield can reach 47.49%,and the classification efficiency reaches 64.9%,which is 8.62%and 11.34%higher than those of the traditional classifier respectively.