The Development And Study On The Trommel Screen Used For Dewatering And Desliming Of Coal Slime

Coarse coal slime is an associated coal slurry in the process of coalprocessing. This kind of slime has small particle size(about1mm), widegrade, complex shape and large moisture content. It is abundant in coalplant. If can be effective to dewater and deslime the coal slime and torecycle has significant economic benefits. In recent years for coarse coalslime independent separation has become an established process. But dueto the influence of particle size in hydraulic separating equipment makesthe fine material of ash content is always greater than the coarse material.While the effect of existing desliming equipment is unsatisfactory, resultin the ash content of fine coarse coal slime is high. So it is need to study anew type of high efficient coarse coal slime dewatering and deslimingequipment to improve the effect of coarse coal slime recovery.The paper attempts to apply the trommel screen in the process ofdewatering and desliming coarse coal slime. We manufacture a kind oftrommel screen which is applicable to process coal slime, and on the inner wall of the screen added spiral vane, rather than by installing angleto discharge. The drum screen is mainly adopts the filtration principle, thematerial through the feeding device to into the rotating screen, coarseparticles to the wall of cylindrical screen, rapid subsidence due to thecylindrical screen rotation driven wall layers in tilted up settling downand back, so that the upper suspension by the bed resistance decrease andfast through sieve, not through the sieve of solid particles under the roleof gravity and spiral discharge along the axis of cylindrical screendirection. So as to realize the filtrate by sieve seam down, and the bed bythe spiral vane axial wizard.The operation parameters (the rotational speed and the volume flowrate) and the material properties (the mass concentration and the sizedistribution) have been studied for improving the efficiency ofclassification. the result show that using trommel screen for desliming ofcoal slime is a effective method and the classification efficiency reached80%; the material properties have a significant impact on dewatering anddesliming of the trommel screen, so we can adjust structure parameters ofthe trommel screen to improve the classification efficiency.Using the discrete element method software EDEM simulate theprocess of trommel screen. The simulation experiment studies the motionstate and screening probability of each fraction particles under differentrotational speed. The simulation test results of classification efficiency compared with actual test grade efficiency, the same classification ruleshow: as the speed increased, classification efficiency increased. Byanalyzing the motion of particles within the trommel screen, it isconcluded that the movement of different graded within the trommelscreen state is different: the smaller particle size, the greater positionangle when sliding motion state, the greater fall angle when fallingmotion state. Otherwise, the position angle and fall angle is smaller; Withthe increase of rotational speed, the sieve area develop with the rotationdirection, when the speed of0.91Nc, particles will through screen almosteverywhere in the circumferential direction. Through the analysis of thechange rule of the screen each grade, it is concluded that different graded,the promoting function of spiral vane, the smaller the particle size, thesmaller the promoting function of spiral; Through the analysis of differentgraded particles through the sieve, we can find that the higher the speed,the faster through sieve; the smaller of the graded, the easier through thescreen.This article studied the trommel screen respectively from twodifferent aspects of using the actual material test and EDEM simulationtest, some useful conclusions have been drawn, providing a certain basisto guide the design and optimization of the trommel screen.