Research On Screening Performance Of Double-deck Linear Vibrating Screen Based On Discrete Element Method

Vibrating screen is a key equipment for screening bulk granular materials.It is widely used in chemical industry,agriculture and metallurgy.Due to its large screen surface,double-deck linear vibrating screen is easier to grade and screen the particles and suitable for application in large capacity industrial environment.Plastic particles are widely used in the field of chemical industry,but the investigations on the screening process and characteristics of plastic particles are not common.Based on the horizontal topic of " Domestic replacement project of vibrating screens for large extrusion pelletizing units," the motion characteristics and screening rules of industrial plastic particles in the screening process are analyzed in this thesis.This thesis provides reference for theoretical analysis,structural design and domestic manufacture of double-deck linear vibrating screen.In this thesis,double-deck linear vibrating screen is taken as the research object.The discrete element method is used to study plastic particles screening process and effect of some influence factors on the screening performance of double-deck linear vibrating screen.The BP neural network is established through simulation data and the screening parameters are optimized by optimization function.The thesis mainly completes the following four aspects:(1)On the basis of probability theory,the penetration theory of double-deck linear vibrating screen is analyzed.The factors affecting particle penetration are obtained through comparing and analyzing the difference of single particle and particle group penetration probability on single-deck vibrating screen and double-deck vibrating screen.(2)Based on the discrete element method,the simulation model of the doubledeck linear vibrating screen and plastic particles is established.The simulation is carried out by using EDEM to compare and analyze the motion state,motion speed,the law of plastic particles movement on the double-deck linear vibrating screen and the penetration behavior of particles in different areas of the screen surface.The motion characteristics of plastic particles in the process of complete screening,the movement rules of particle groups on the screen surface and the collision and distribution rules between particles are obtained.At the same time,the speed and penetration of different shapes of particles on the screen surface are analyzed,and the differences of different shapes of particles in the screen are compared and analyzed.(3)On the basis of single factor control variable method,the screening efficiency is taken as the index of screening performance.The relationship between vibration parameters,screen surface structure parameters,screen surface installation spacing,particle composition,feed rate and screening efficiency are studied.At the same time,the orthogonal test method is used to figure out the effects of vibration frequency,amplitude,vibration direction angle and screen angle on screening efficiency.(4)In order to better reflect the relationship between the vibration frequency,amplitude,vibration direction angle and screen surface inclination and the screening efficiency of the two layers of screen surface,the nonlinear relationship between the screening parameters and the screening efficiency is created through BP neural network.And the screening parameters are optimized through target achievement method in Matlab.The optimal screening parameter combination and the corresponding screening efficiency are obtained,and the results before and after optimization are compared.