Research On The Screening Mechanism And Simulation Optimization Design Based On Dem Of Cross Screen

Coal is the main primary energy in China.Screening is the basic process for efficient processing and clean utilization of coal resources,and it is also the key link of the coal preparation process.The content of fine coal in raw coal mined by modern coal mining technology is high,and the content of external water is high.The use of ordinary vibrating screen equipment is prone to problems such as screen surface plugging and hole paste,which seriously affects the normal operation of screening operation.The cross screen is a new type of screening equipment suitable for deep dry screening of moist fine coal,which has gradually been widely used in coal preparation operations.However,the current research on cross screen is mainly focused on applied research,and there has been no research on the screening process mechanism of cross screen.The lack of optimization design of process parameters and screen surface structure of cross screen restricts the development of cross screen technology.Therefore,this thesis conducted experimental research on the screening process of cross sceeen,and used DEM(Discrete Element Method)to numerically simulate the screening process of cross screen.The results obtained can provide reference for the optimization design of cross screen.The main work is summarized as follows:The experimental study on the screening process of cross screen was carried out.The particle size analysis of materials under different screen surface structures(segmented screen surface structure,integral screen surface structure,banana type screen surface structure)was carried out.The passing and screening effect of materials under different screen surface structures and external water contents(w =0%,w =6%,w=9% and w =13%)were explored.The numerical correspondence between external water content and cohesion energy density was established by the coal stacking angle experiment and simulation.On this basis,the DEM model of the screening process of the cross screen was established and the numerical simulation study was carried out.The reliability of the DEM model of the screening process of the cross screen was validated by comparing the material yield and screening efficiency of each section of the screening experiment and DEM simulation.DEM simulation work was conducted on the screening process of cross screen,analyzing the influence mechanism of feed rate,rotational speed of rollers,screen surface inclination angle,and cohesion energy density on screening efficiency,fine particle mismatch rate,passing,and particle average velocity.The working parameters for the best screening effect were obtained,and the influence of different screen surface lengths and eccentricity methods(shaft eccentricity and disc eccentricity)on screening efficiency and particle average velocity was explored.Structural design was carried out on the segmented screen surface inclination angles(6°-9°-12°,9°-12°-15°,12°-15°-18°,15°-18°-21°and 18°-21°-24°)of the cross screen.The mechanism of the influence of segmented screen surface inclination angles(screen surface inclination angle I,screen surface inclination angle II,and screen surface inclination angle III)on the screening process of the cross screen was studied.To investigate the significant impact of the inclination angle of each segmented screen surface on the screening effect of the cross screen and the interaction between the inclination angles of each segmented screen surface,the screening efficiency was used as an evaluation index.The response surface method was used to optimize the screening effect of the cross screen segmented screen surface inclination angle.A regression equation was established between the screening efficiency and the inclination angle of each segmented screen surface,and the significance ranking of the impact of the inclination angle of each segmented screen surface on the screening efficiency was obtained.The optimal combination of segmented screen surface inclination angles has been determined.In this thesis,there are 47 figures,26 tables and 97 references.