Study On Falling De-Attachment And Air Flow Classification Process Of Wet Coal

Precisely screening of wet coal is a big difficulty in steam coal classification.Due to high moisture content,coal particles have a wide range of sticking phenomena,and it is easy to plug or paste hole and other phenomena in the screening,and the screening effect is poor.The common methods to avoid these problems are mostly to raise lower limit of separation upto 6mm.This limits the removel of-6mm refuse particle and decreases product quality.The new designed air classifier combines probabilistic impact loose desorption with air classification process to strengthen wet coal classification efficiency.It presents good classification results,low operating costs,and has broad application prospects.However,the collision desorption process and wind classification process have not been further tested and theoretically studied.Based on the results of previous studies,this study conducted with experimental research on collision dispersion process of moist coal particles,and theoretical analyze of air classification process.Aiming at collision and desorption process,relationship between amount of adhesion,the amount of desorption and the mass of coal particles was first studied from the rules of adhesion and desorption of coal particles.Subsequently,a suitable reference evaluation index for evaluating collision and desorption effect of particles was found.By comparing data of entire sample group,the data of different mass range,and applicability of this reference index for different desorption ratio in same mass range.Finally,it is found that the(average)relative mass-impulse in the four alternative index can more accurately evaluate and predict the impact desorption effect.Using this index and the degree of collision desorption,the collision desorption of 8%and 11%external moisture coal particles was compared,and it was found that due to increase of external moisture,stronger adhesion and the increase in mass of adhered particles result in nonideal collision desorption.For the air classification process,based on the analysis of force in flow field of spherical particle,combining input height H,inlet slit opening s,average wind speed v_s,angle?between elastic rod and vertical direction,and particle size d_c,particle kinematics equations and particle trajectories used in the high-speed jet zone of air classifier are derived.The principle and process of particle classification were analyzed,and the influence of these parameters on classification process was analyzed.This thesis was based on 46 figures,15 tables and 83 references.