Study On Dynamic Simulation And Optimization Of The Vertical Screw Stirred Mill

As an important technical equipment for fine grinding and ultrafine grinding,the vertical screw stirred mill is widely used in industries such as metallurgy,chemical engineering,and building materials due to its high productivity and low energy consumption.With the improvement of the productivity of the vertical screw stirred mill,it is crucial to study its dynamic characteristics for the development of efficient,energy-saving,and reliable mills.In this paper,in combination with the key scientific and technological research projects of Shanxi Province and the needs of enterprise product development,the dynamic performance simulation and optimization of the vertical screw stirred mill are studied.By establishing a coupled dynamic model of the vertical screw stirred mill,the electromechanical coupling dynamic performance of the mill is analyzed.Based on the discrete element method and multibody dynamics,the performance of the vertical screw stirred mill is predicted,and the multi-objective optimization design of the mill structure is carried out accordingly.The vertical screw stirred mill mainly uses the parallel mode of friction crushing,supplemented by extrusion crushing and impact crushing to comminute the ore.The influence of mill speed,screw diameter,spiral angle,aspect ratio,grinding media filling rate,and grinding media properties on mill performance is analyzed.The mechanical analysis of the screw stirrer of the vertical screw stirred mill is conducted,and the torque calculation model for the steady-state operation stage of the mill is established.Based on the working principle of the vertical screw stirred mill and the mathematical model of the asynchronous motor,coupled dynamic analysis of the mill is conducted by combining the multibody dynamics model of the vertical screw stirred mill and the discrete element model of the grinding media,and its validity is verified through experiments.Simulation analysis of the mill steady state conditions is carried out,and the results show that the velocity and force of the grinding media at the edge of the spiral blade are maximum,and the maximum stress of the weld of the screw stirrer occurs at the root of the screw.Finally,simulation analysis is conducted on the coupled dynamic model and the DEM-CFD coupled model,and the results show that the coupled dynamic model can better reflect the dynamic characteristics of the vertical screw stirred mill.Based on the established coupled dynamic model of the vertical screw stirred mill,the electromechanical dynamic performance during the start-up and steady-state operation of the mill is analyzed.The results indicate that the fluctuation of the mill load torque is significant during both start-up and steady-state operation,and the current fluctuation is more significant during the start-up phase.The mean and variation coefficient of the current are not only affected by the mill load but also by the mill speed.Additionally,the analysis of the grinding media velocity in the "annular region" shows that the velocity difference of the grinding media is significantly influenced by the screw diameter,the grinding media diameter,and the mill speed.The object of this study is a large vertical screw stirred mill provided by a certain enterprise,and the initial operating conditions of the vertical screw stirred mill are analyzed.The results indicate that the grinding media at the edge of the agitator has the highest velocity,and the wear amount is the highest at the bottom and edge positions of the agitator.Taking the cylinder side clearance,cylinder bottom clearance,and pitch as the influencing factors,and the average normal contact force of the grinding media,mill power,and agitator wear as the evaluation indicators,a mathematical model is established to evaluate the indicators in relation to the influencing factors,and the mill structure is subjected to multi-objective optimization.The results show that the optimized mill power and wear are both reduced compared to the original mill,and there is a significant increase in the average normal contact force between the grinding media.In summary,this paper first establishes the torque mathematical model of the vertical screw stirred mill during steady-state operation.In order to explore the electromechanical coupled dynamic performance of the vertical screw stirred mill,the coupled dynamic model of the vertical screw stirred mill is established,and its rationality is verified through experiments.Finally,by establishing the performance prediction model of a large vertical screw stirred mill,the structure of the vertical screw stirred mill is optimized.The research work in this paper provides a reference for the development of large vertical screw stirred mills.