Experimental Study And Discrete Element Simulation Of Coal Slime Dewatering Sieving Drum Screen’s Performance

In recent years, the contradiction of economic development and environmental protection is increasingly prominent. Coal washing and dressing as well as the efficient utilization of coal resources has become the need of development. Sieve dehydration of coarse coal slime in the process of coal washing and dressing is very important, of which the effective classification dehydration can improve the separation efficiency of coal preparation plant and improve the quality of products.Common fine particle classification dewatering equipments in coal preparation plants arc mainly arc sieve, high frequency sieve and coal slime dewatering centrifuge. Drum screen as a kind of sieve dehydration equipment is seldom applied in coarse coal slime desliming wet screening, of which the design and manufacture are proceeding on the basis of practical experience. Meanwhile, the sieving principle and process of drum screen are rarely studied, and the material analysis of drum screen is mainly about single-particulate movement.In this paper, through the theory analysis of material movement in drum screen, three stages of material sieving in the drum screening can be summarized: shock sieve, hybrid sieving and dehydration cluster. According to the material movement type and simulation results, we can conclude that theoretical movement time of the material is consistent with the blade forward time, and the approximate theoretical calculation formula of material movement length in the drum screen is elicited. The influence of rotate speed on screening and dewatering effect are studied by the experiments when coarse slimes are sieving by the drum with small diameter and big screen seam, as well as large diameter and small screen seam. Several conclusions can be drawn that sieving efficiency of the drum with small diameter and big screen seam is decreasing as the rotate speed increases gradually, of which the drum with large diameter and small screen seam is firstly rising and then reducing. Therefore, the influence of rotate speed on sieving efficiency is related to the sieve seam size and the cylindrical screen size. In addition, associated structure are added to the drum screen, and the influencing factors of sieving and dewatering efficiency are studied. We conclude that the function of striking and rinse watering can increase the efficiency of drum screening, which is verified in the double screening test. Lastly, the test of different distribution numbers of material entrance in the drum screen are proceeding, and the conclusion can be drawn that speed of screen impacted by material decreases and effect of sieving deviates as the number of distributors increases.A series of experimental studies on the double drum screen are proceeded, and the results show that screening effect of double screening is consistent with the single layer, but the secondary screening effects advance with the increase of drum rotation speed. At the same time, the best drum rotation speed, as well as the interference effect of one passage screen underflow should be taken into account when we choose the diameter of double drum screen. The results show that the function of striking and rinse watering can increase the efficiency of double drum screening.Under the precondition of simplification on the granulometric composition and screening conditions, the simulation experimental research on screening process is proceeded by EDEM software. After the analysis of grain amount in different minus sieving areas and motion parameters of sieve materials, it can be found that granular materials of 0.5mm is suitable for drum sieving with small diameter. Afterwards, simulation of sieving process in screen drums with different diameters is accomplished by changing the guide vane pitch. It can be concluded that sieving process of large cylindrical screen is greatly affected by the variation of pitch. Meanwhile, the influences of different material entrance’s speed on sieving efficiency are simulated, and the results have facilitated effect on drum screen’s application in the field of coal slime classification dehydration.