Accurate Discrete Element Modeling And Verification Of Ore Crushing Simulation

Ore crushing is an important part of the grinding process,and the grinding process determines the production efficiency and processing quality of the ore.The crushing characteristics of the ore directly affect the crushing and grinding,which is the key factor in the formulation of grinding process parameters.There is a great difference between the ore crushing test and the grinding process,so that it is difficult to achieve good results by the grinding process based on the ore crushing characteristics obtained from the test,which is an urgent problem to be solved in grinding process optimization and mill selection.The ore crushing process can be simulated by discrete element method,but its accuracy depends on the agreement between the ore model parameters and the actual ore crushing characteristics.Improving the accuracy of discrete element modeling is always the key and difficult point of ore crushing simulation.Bonded particle model is the basis of ore crushing discrete element simulation,but at present,there is still a lack of systematic and effective methods to determine the parameters of bonded particle model,so it is difficult to simulate ore crushing behavior accurately.Therefore,the relationship between ore crushing characteristics,grinding process and discrete element simulation model is deeply analyzed,and the accurate modeling and simulation method of discrete element bonded particle model are studied.It is of great significance and practical value of engineering to improve the grinding process,grinding efficiency and control of grinding particle size.In this paper,in order to solve the difficult problem of determining the parameters of ore crushing model in grinding simulation,the discrete element method was used to construct a bonded particle model with basic particles and bonds as key parameters.The ore crushing behavior was studied deeply and systematically from the three dimensions of ore strength,ore size and impact energy,and the drop weight test was used to verify the applicability and accuracy of the bonded particle model.The modeling method of bonded particle model was discussed which can accurately reflect the crushing characteristics of ore.The main research contents and innovative achievements of this paper are as follows:（1）The modeling technology of ore bonded particle model for discrete element crushing simulation was studied.The bonded particle model was modeled by using EDEM software,and the drop weight crushing simulation under different impact energy was carried out.By comparing the mass percentage of broken ore of different size obtained by drop weight test and simulation,the applicability of the model was verified.（2）The drop weight tests of three sizes of copper ore,gold ore and iron ore had been completed.The mass percentage and distribution characteristics of broken ore obtained from drop weight test were analyzed,and the characteristics of strength changes of different ores were discussed.In this paper,the ore crushing strength index t_n10,which normalizes the impact energy of t₁₀,was used to characterize the ore crushing strength.The expression method of the relationship between the ore crushing strength and the bond of the bonded particle model was found.（3）The method of determining the basic particle type and particle size of the bonded particle model was studied.The crushing mass percentage distribution from ore drop weight test was analyzed.The types of basic particles and the principle of determining particle size were discussed.The selection of three kinds of basic particles can meet the needs of modeling,and the selection of basic particle size is related to the size of ore samples.The model based on three kinds of basic particles has flexibility and high efficiency of modeling.The contradiction between modeling accuracy and modeling efficiency can be well solved by using spherical basic particles of three diameters,uniform distribution of particle diameter,and the maximum particle diameter is less than the minimum particle size in the drop weight test.（4）The method of determining the number of basic particles in the bonded particle model was studied.Five groups of basic particles were designed for modeling and crushing simulation.Taking the variance of mass percentage from drop weight test and simulation crushing as the optimization objective,the optimal basic particle volume ratio was obtained.The optimal volume ratio of basic particles is closely related to the size of ore samples.The number of basic particles is determined by the basic particle volume ratio,and the optimal basic particle volume ratio of the bonded particle model with different sizes is obtained by optimization,which can reduce the error of the mass percentage of crushing simulation and improve the accuracy of the bonded particle model.（5）The characteristics and characterization methods of bonds in bonded particle model were discussed.Taking three kinds of copper ores as examples,the drop weight crushing simulation was carried out,and the bond parameters were obtained,which are consistent with the mass percentage of the drop weight test Based on the analysis of the crushing simulation results of different bond parameters,the equivalent critical deformation was proposed to characterize the critical stiffness and critical stress of the bond in the bonded particle model.The bond strength determines the accuracy of the bonded particle model,and the bond strength can be accurately characterized by the equivalent critical deformation of the bond.The equivalent critical deformation decreases with the increase of the model size,which is the same as the change trend of the actual ore strength.The equivalent critical deformation can effectively characterize the crushing characteristics of the bond of the bonded particle model,and setting the bond parameters according to the equivalent critical deformation can improve the modeling accuracy.（6）The method of determining the bond of particle bonding model was studied.Based on the crushing simulation of copper ore,the relationship between ore crushing strength and bond equivalent critical deformation was studied.The linear equations of bond equivalent critical deformation and ore crushing strength index t_n10 of bonded particle model were given.A bond determination method based on ore crushing strength and basic particle size was proposed.Taking gold ore and iron ore as an example,three sizes of bonded particle models of gold ore and iron ore were constructed.The simulation results show that the particle size mass percentage of the crushing simulation is completely consistent with the drop weight test,which verifies the correctness of the method for determining the key parameters of the bonded particle model.It can be seen that determining the equivalent critical deformation of the bond according to the ore strength index t_n10 can ensure the accuracy of the bond parameters and significantly improve the modeling efficiency and model accuracy.In this paper,the effects of basic particle parameters and bond parameters of bonded particle model on the accuracy of ore crushing discrete element simulation were studied systematically by means of combining discrete element simulation and drop weight test.The types of basic particles and the principle of determining particle size were given.The relationship between ore crushing strength and equivalent critical deformation of bond was discussed,and a bond determination method based on ore crushing strength index t_n10 was put forward,which lays a foundation for establishing a general modeling method of ore bonded particle model and provides method support for accurate simulation of ore crushing process.