Simulation And Parameter Optimization On Grinding Performance Of Large-type SAG Mill

As one of the main equipment in mineral processing, the trend of large-type semi-autogenous(SAG) mills has come into a mainstream. For the problem of high consumption of power and steel of large-type SAG mill in the process of practical production, grinding performance is studied using DEM and operating parameters are also optimized in this thesis which is based on the National Natural Science Foundation Program(NO.51265020): Design method and theory of heavy hydrostatic bearing with hollow shaft under multi-physics field coupling. The main contents are as follows.(1) DEM model of the large-type SAG mill is created and the release angle and lifting height of single ball in the outermost layer of mill are obtained. With charge motion theory, their theoretical results are calculated and compared with simulation results. The comparisons show that relative error of theoretical results and simulation results is receivable which verifies the accuracy of DEM model.(2) The motion traces of steel balls under different filling levels are obtained through the test of a pilot scale mill. Equivalent model of pilot scale mill is built and simulations of ball motion are conducted. Test results and simulation results of equivalent model are compared. The comparisons show that test results of ball motion agree well with simulation results. So, the simulation accuracy of equivalent model and the accuracy of analyzing grinding performance of large-type SAG mill using EDEM are verified.(3) With incremental breakage model of oral and wear model of liner, the effects of different parameters including speed ratio, filling level, height and face angle and quantity of liner on charge motion, power, effective collision number between ball and ore and maximum wear height of liner are researched, respectively. The optimal value range of operating parameters is obtained.(4) The operating parameters are optimized based on uniform design method. Twenty-five simulation groups are conducted. Mathematical model between parameters and indexes is obtained through the quadratic polynomial stepwise regression analysis and analysis of variance. Optimum parameters combination is also obtained under every evaluation indexes further. The results show that the best optimum parameters are not in accordance with each other, when evaluation indexes of grinding performance are optimum.(5) Comprehensive evaluation mathematical model of grinding performance is established on the basis of the hierarchy analysis method. Judgment matrix with consistency check is constructed and the weight value is calculated by analyzing the relative importance between parameters and indexes. Then, the optimum parameters combination is determined which is compared with the original condition. The results show that when speed ratio is 84%, filling level 35%, quantity of liner 52, height 200 mm and face angle 35°, power per unit mass and effective collision number between ball and ore increase 10.78%, 15.47%, respectively, maximum wear height of liner decreases 10.81% and comprehensive grinding performance increases 17.25%.With uniform design method and hierarchy analysis method, grinding performance of large-type SAG mill is improved effectively in this paper, by optimizing operating parameters. A guideline for the research of grinding performance of large-type SAG mill is provided.