Influence of parameters of new stacked vibrating screen on coal slime screening based on DEM

The high viscosity of coal slime particles is one of important reasons why the sieve is easy to stick to screen during its screening process. By changing the structure of traditional linear vibrating screen, the sticking sieve can be better avoided. Aiming at the characteristics of high viscosity of coal slime and easy to stick to screen, a new type of stacked vibrating screen that can prevent the sticking screen was proposed,and the structure of the stacked vibrating screen with the staggered arrangement of dynamic and static screen bars and relative motion was designed. The force analysis and comparison of the sieving process of the particles stuck in the screen slits and the coal slime that had been bound into lumps on the stacked vibrating screen and the ordinary linear vibrating screen were carried out,and the principle of the anti-paste screening of the stacked vibrating screen was studied. The 3D simulation model was established. And the screening process of coal slime particles on the stack vibrating screen was simulated by using discrete element software. In order to improve the screening effect of stacked vibrating screen,based on the DEM and using the Hertz-Mindlin with JKR bonding model,the effects of vibration parameters(negative inclination angle of screen surface,vibration direction angle,amplitude,and vibration frequency)on the screening efficiency of wet slime and distribution proportion under the screen were analyzed. The research results show that the screening efficiency increases first and then decreases with the increase of the negative inclination of screen surface in the range of-1°——5°. When the negative inclination angle of screen surface is-4°, the screening efficiency is the highest. When the vibration direction angle is in the range of 35°-55°,the screening efficiency gradually increases with the increase of vibration direction angle,but the screening efficiency of 55° is not significantly improved compared with 50°. When the amplitude is in the range of 1.5-3.5 mm,the screening efficiency increases gradually with the increase of amplitude. The screening efficiency of 3.5 mm is not significantly improved compared with that of 3 mm, but the vibration intensity will be greatly improved. When the vibration frequency is in the range of 14-24 Hz,the screening efficiency first increases and then decreases with the increase of vibration frequency. When the vibration frequency is 22 Hz,the screening efficiency reaches the maximum. The screening efficiency at 22 Hz is not significantly improved compared with 20 Hz,but the vibration intensity will be greatly improved. The increase of the negative inclination angle of screen surface,the vibration direction angle,the amplitude and the vibration frequency will make the slime layer on the screen surface thicker. In most cases, the distribution ratio of fine slime particles under the screen gradually decreases with the direction of screen surface. The changes of the negative inclination angle of screen surface and the vibration direction angle have little effect on the screening efficiency,while the changes of the amplitude and vibration frequency have a greater effect on the screening efficiency.