Study On Mechanism And Performance Of Material-beds Comminution Based On The Discrete Element Method

With the increase of the demand for the powder,the energy consumed by crushing is getting more and more.Material-beds comminution has been widely used in the production because it can reduce energy consumption and improve working efficiency.In order to combine the theory of material-beds comminution with grinding equipment better and play a greater role,this paper makes study on the process of material-beds comminution by using the discrete element software EDEM(Engineering Discrete Element Method)based on the vertical roller mill.The main work and the conclusion are as follows:(1)According to the process of material-beds comminution in the vertical roller mill,it has three stages:the squeeze process,the crush process and the cluster process of material-beds.Through the change of the height of material-beds during material-beds comminution process,it is concluded that the shrinkage of material-beds is related to the material introduction angle.(2)This article analyses the movement and the force of the material during the material-beds comminution process in the vertical roller mill.Conclusioncan be drawn that the disc radius and the friction coefficient between the material and the disc affect the particle movement state,and the force of the process of the material-beds comminution is mainly related to some factors,including the properties and strength of the material,material-beds height,material-beds density at each stage of the crushing,and final pressure on the unit area in the vertical roller mill based on the mathematical model.(3)The three-dimensional model of the vertical roller mill can be created based on the FPP800 disk roller mill,and the model of limestone material can be created based on the model of BPM(Bonded Particle Model).In order to reduce the disturbance of variables when simulate the process of the material-bedscomminution,a uniform material-beds model was established.It provides two judgment criteria for judging whether the material-beds is formed or not in the EDEM,they are stable material-beds thickness and suitable hydraulic cylinder pressure.(4)The factors that affect the process of material-beds comminution are analyzed in the simulation.Through simulating the effect of material properties on material-beds comminution,the efficiency of the material-beds comminution is best when the particle size is 50mm.The simulation of the material-beds comminution with different shapes shows that block-shape particle is more easily broken than flat particle.Through simulating the effect of working parameter and structural parameter of vertical roller mill on the material-beds comminution,it is found that there is an optimal value for the speed of the grinding disc and the number of the roller.The higher speed of the grinding disc and the more rollers are not the reason of the higher efficiency of the material-beds comminution.From the comparison of several sets of numerical values in this article,the efficiency of the material-beds comminution in the vertical roller mill is the best when the rotation speed of the grinding disc is 55r/min and the number of the roller is two.