| Based on the National 863 Plan of China(No.2012AA062002): The mining technology and equipment in large-scale open pit mines, the grinding mechanism and process of the vertical spiral stirred mill were studied. The working principle was analyzed, grinding performance index and process parameters were studied, and the power was derived. Respectively the method of discrete and fluid mechanics were used to study the grinding process. Finally coupling method of the discrete and finite element was used to study the stress and strain of the agitator at work, analysis and optimize its structure.By reviewing the domestic and foreign literature, the research background and significance of the mill were introduced, and the application and research status were reviewed. The crushing theory, research methods and research results were summarized, pointing out three main crushing theory analysis. Grinding performance indicators such as stress intensity, particle collision frequency of media were studied. The effects of structure and characteristic parameters on the performance were discussed and the power was derived.Using the discrete element method, the simulation model of mill was established, start torque and power were analyzed, and the medium ball movement trajectory, velocity distribution and the collision energy spectrum inside the mill were studied, force and energy loss and wear contours were extracted, and the effective grinding area was obtained. The influence on grinding effect for mill speed, helical pitch, and particle size distribution was studied respectively, finally comprehensive grinding index was put forward, the orthogonal experiment analysis was used to study the effects of various factors on the grinding performance, and the optimal combination of grinding was obtained under specific weight coefficient.The simulation model was established using fluid mechanics assuming that single-phase Newtonian fluid, and the performance in the turbulent flow field was analyzed. The fluid flow and velocity isoline were analyzed, the turbulent intensity and turbulent kinetic energy were studied, and the effective grinding area was consistent with the results of the discrete element. The effect of various factors such as helical pitch, mill speed and fluid viscosity in three variables was studied on the grinding effect, finding that speed and the viscosity had a greater influence on grinding performance.The stress and strain of the agitator at work was analyzed based on EDEM- Workbench coupling method, finding that the top stress was larger and the bottom deformation was larger due to one end support, easy to produce the deflection phenomenon, affecting the stable operation and efficiency. A method to increase the diameter of the upper end was put forward resulting in improved partial pendulum phenomenon, which was of great significance to improve the comprehensive performance of the mill.This paper studied the vertical spiral agitating mill grinding process through discrete and fluid mechanics simulation analysis respectively, the mechanism of mill and the effects of process parameters on the grinding were discussed. Key structural improvement was carried out based on the discrete element and finite element coupling, improving the comprehensive performance of the mill, which provided reference for structure design and performance study on vertical spiral stirred mill. |
