Study On The Impact Behavior Of Sieve Plate Of Flip-flow Screen And Particles

In coal mining,coal generally has a certain amount of moisture and high content of finegrained coal,which leads to the phenomenon of coal agglomeration and blocking the screen hole in the screening process,and then causes the deterioration of screening environment and low screening efficiency.The unique polyurethane sieve plate and the staggered relaxation movement of the relaxation screen make the material moving on the screen surface get greater throwing strength,which can effectively realize the screening of wet fine coal.At present,the research on the collision and depolymerization of wet coal agglomerate and sieve plate of flipflow screen is relatively slow.In order to give consideration to the depolymerization of wet coal agglomerate and the service life of sieve plate,this thesis establishes the discrete element model of wet coal agglomerate based on the screening test of agglomerate,and carries out the modeling and dynamic analysis of sieve plate,and then analyzes the collision and depolymerization of agglomerate and sieve plate of flip-flow screen through the discrete element-multi-body dynamics joint simulation and the influencing factors were analyzed by changing the parameters.The specific research contents are as follows:(1)Wet raw coal with 10.5% water content was prepared by adding water to a certain quality of dry raw coal.The aggregate structure was determined,and some wet coal aggregates with similar overall size were selected.After drying,they were screened by multi-layer screen,and the mass composition of central particles and small particles with different particle sizes was counted,and then the density of coal was determined by drainage method.By using EDEM and its secondary development function,a more realistic discrete element model of wet coal agglomerate is established,which is composed of non-spherical particles in the center and small particles with non-equal diameter.It provides a reasonable wet coal agglomerate model for the collision analysis of wet coal agglomerate and the flip-flow screen.(2)Through the analysis of the mechanical model of the screen surface of the flip-flow screen,the maximum distance between two adjacent screen frames is calculated.Combined with the motion characteristics of the flip-flow screen,the parameters of the screen plate model and the reference range of the structure and motion parameters are determined.The model of flexible sieve plate is established,and the variation and distribution law of screen surface deflection,stress and strain,and the distribution law of maximum velocity and acceleration are analyzed by using ANSYS Workbench,which provides reference for the parameter setting of subsequent co-simulation.(3)Co-simulation of EDEM and Recur Dyn was established to simulate the collision and depolymerization process of wet coal agglomerate and flexible sieve plate of the flip-flow screen.The collision and depolymerization mechanisms of agglomerate,static sieve plate and relaxation sieve plate were compared and analyzed.The results show that the process of coalescence can be divided into initial depolymerization stage,rapid depolymerization stage and stable state.The flexible relaxation sieve plate can enhance the collisional depolymerization of the agglomerates obviously.A test bench for the principle of the flip-flow screen was designed and built,and the prepared wet coal aggregates were collided with static sieve plate and relaxation sieve plate,which were observed by high-speed camera.The experiment and simulation have good consistency,which verifies the effectiveness of simulation to some extent,and the depolymerization behavior of wet coal agglomerate is further analyzed combined with the experiment and simulation.(4)The effects of different eccentricity,rotating speed and small particle gravity on the collision and depolymerization of wet coal agglomerate were studied by co-simulation of EDEM and Recur Dyn,and the depolymerization of different particle sizes in the agglomerate was analyzed.The results show that increasing the rotation speed and eccentricity of the relaxation sieve within a reasonable range can effectively improve the degree of depolymerization and depolymerization of the wet coal agglomerates and the adhesion of fine particles is the main factor hindering the depolymerization of wet coal agglomerates.