| In the deep screening equipment of moist fine coal,the flip-flow screen with elastic screen plate can provide 30-50 g ejection acceleration for screening particles,which is good for the screening penetration of the fine coal.Therefore it is widely used in the deep classification of coal.However,in the practical screening process,the fine coal easily adheres to form the agglomerate due to the external moisture of the raw coal.If the wet coal agglomeration is not depolymerized in time,it is easy to form mismatches and deteriorate the screening process.In order to improve the screening effect of the flip-flow screen on wet fine coal,this dissertation uses discrete element numerical simulation and experimental research to analyze the influence of the flip-flow screen surface morphology on the screening effect of wet fine coal.It is concluded that the use of a reasonable screen surface morphology can increase the degree of crushing and dispersing of wet coal agglomerates,and can also increase the complexity and diversity of material movements,thereby improving the screening efficiency.The main research contents are as follows:(1)Based on the discrete element theory,the particle body force and the particle factory plug-ins in the EDEM application programming interface were compiled,and a wet coal agglomeration model composed of particles with various particle sizes was established to provide a more reasonable aggregation model for the screening simulation of the flip-flow screen.(2)The morphological parametric modeling idea was put forward,and the morphology of the flip-flow screen surface was parameterized into shape parameters and spacing parameter.And the stress of the impact collision of a single coal particle on the screen surfaces with different shape parameters is analyzed based on the finite element display dynamics.Then the dynamic screening processes of wet coal agglomerates on the screens with different spacing parameters under the optimal shape parameters are simulated by the EDEM-Recur Dyn co-simulation.Based on the gray decision theory,the simulation results were analyzed and the optimal spacing parameter under single factor conditions was obtained.Finally,the optimal parameters of the morphological sieve surface were obtained.(3)Based on the above studies,the screening process of wet fine coal material group on the optimal morphological screen surface and the nonmorphological screen surface was simulated.And by analyzing screening state,screening efficiency,crushing degree,the average velocity of the particles and the trajectory of the particle.The results show that the optimal morphological screen surface can improve screening efficiency of the flip-flow screen,increase the degree of deagglomeration of wet coal agglomerates and the complexity of the material movement.(4)Finally,a test bench for the principle of the flip-flow screen was designed and constructed,and the screening of wet fine coal material group and wet coal agglomerates on the optimal morphology and non-morphology screen surface was tested.Through the statistics and analysis of the screening results,it is obtained that compared with the non-morphological screen surface,the optimal morphological screen has a better screening effect on wet fine coal,and increases the degree of crushing of wet coal agglomerates,and reduces the content of mismatches in the products on the screen.Therefore,the experimental results further verify the feasibility and reliability of the screen surface morphology model.The research work and conclusions in this dissertation can provide some theoretical and reference basis for the optimal design of the flip-flow screen. |
