Research On The Media Ball Motion And Key Parameters Of Vertical Mill Based On Discrete Element Method

Vertical screw stirred mill possesses advantages of high energy efficiency,product size fine,superior grinding mechanism,simple equipment structure,etc.Vertical screw stirred mill is currently the most promising one of the ultra-fine grinding equipment.The movement of grinding media in vertical screw stirred mill and its key parameters affecting on the grinding performance is one of grinding theory,but movement of grinding media is complex,scholars at domestic and foreign studying the grinding media kinetics analysis is still relatively few,the mechanism for key parameters affecting on the grinding performance is not yet clear,which makes the parameters optimization and large-scale design of vertical mill lacking the necessary theoretical basis.Therefore,based on the development and research status of vertical screw stirred mill,this paper analyzes the grinding mechanism and key parameters of vertical screw stirred mill,and establishes the simulation model of vertical screw stirred mill by using discrete element method(DEM).Movement laws of grinding media and key parameters affecting on the grinding performance was studied in this research work,the following are the main contents of this paper:(1)In this paper,the development history and application status of vertical screw stirred mill are introduced.The research status of discrete element method in grinding equipment is described in detail.At the same time,the grinding mechanism,grinding kinetics and determination principles of key parameters were analyzed.(2)The discrete element method is used to study the movement law of the grinding media in detail.The simulation model required for numerical simulation is established.The single media ball and integral media ball are mainly studied from mechanics,kinematics and the energy perspective for analysis.The results show that the speed and the kinetic energy of the grinding media reach the maximum at the edge of the screw,the collision force of the grinding media,the rotational angular velocity,the rotational kinetic energy,the collision energy can reach the maximum at the outer edge of the agitator;The collision force and velocity gradient are larger at the annular area,so the annular area is an important grinding area.(3)The mechanism for key parameters affecting on the grinding performance was studied by the discrete element method and the key parameters were optimized.Agitator speed,the spiral outer diameter and the helix angle of the stirrer were chosen as the key parameters.Thecollision force,collision frequency,wear,energy consumption,energy utilization rate and other factors are adopted to represent the grinding performance of the vertical screw stirred mill.The results of the study indicate that,under the premise that the material meets the crushing requirements,the vertical screw stirred mill should select low speed;when the ratio of the spiral outer diameter to cylinder diameter is 0.75 0.81,the spiral outer diameter of the stirrer obtains the suitable value;when the spiral angle of the stirrer near 16°,grinding performance of the vertical screw stirred mill is relatively good.(4)Laboratory grinding experiments were carried out using different agitator speeds and different helix angles.The experimental results show that,as the agitator speed increases,the product size gradually becomes finer and the energy consumption increases;when the stirrer helix angle is 16°,the vertical screw stirred mill has the best grinding performance.By laboratory tests,the accuracy and reliability of the numerical simulation are verified.In this paper,the discrete element method was used to simulate and analyze the vertical screw stirred mill and laboratory grinding experiments were carried out.The movement law of the grinding media and the mechanism for key parameters affecting on the grinding performance was studied.It provides a reference for the structural design and parameter optimization of the vertical screw stirred mill.