| Grinding is the last operation before ore separation,and its main task is to realize the dissociation of ore and provide qualified size of grinding products,therefore,the grinding efficiency is directly related to the subsequent separation index and the economic efficiency of the plant.The grinding media(steel balls)is an important factor affecting the grinding efficiency.Since the ore crushing process is essentially a mechanical process,the impact force,impact momentum and impact energy of the steel balls play a decisive role in the crushing process.In recent years,many scholars have conducted a lot of research on the steel ball system and verified it in laboratory and industrial tests.The research results show that accurate steel ball size and ratio can optimize the quality of grinding products,improve the processing capacity of ball mill,reduce the consumption of steel balls and energy consumption,so the research on grinding media has great practical significance.In this paper,based on the research on the influence of grinding media and ore collision on the grinding process by domestic and foreign scholars,a section of Ekou iron ore grinding is studied to optimize the steel ball size of a section of Ekou iron ore grinding based on the calculation of steel ball and ore impact momentum,so as to achieve the purpose of improving the efficiency of a section of Ekou iron ore grinding and to provide reference for the same type of processing plant.Firstly,the impact velocity of the steel ball is derived based on Davis' ball motion theory and the impact momentum equation of the steel ball on the ore is derived.Based on this,the impact impulse of the ore is derived by combining the particle size distribution and the mechanical properties of the ore.By applying the momentum theorem to establish the equation of impact momentum of steel ball and impact impulse of ore,the equation of steel ball size based on the impact momentum of grinding media and ore is derived,and the sizes of steel balls for 10 mm,8mm,5mm and 3mm ore to be ground in Ekou iron ore are calculated as 95.25 mm,82.08 mm,60mm and 42.69 mm,and the sizes of steel balls are selected according to the specifications of steel ball production The sizes of steel balls are 100 mm,80mm,60 mm and 40 mm respectively.Secondly,to verify the reliability of the theoretically calculated steel ball size scheme,a simulation test model was established based on the laboratory?450mm×450mm mill using the calculated steel ball regime scheme,setting a single size steel ball with a single ore scheme,and setting a multi-stage proportioning scheme according to the proportion of ore to be ground: the theoretically calculated scheme(recommended scheme)is: m(?100):m(?80): m(?60):m(?40)= 30:35:15:20,and the field solution is m(?120):m(?100):m(?80):m(?60)= 25:25:25:25.The simulation test was conducted by setting the theoretical calculation solution as the recommended solution and the field steel ball solution,and the experimental results show that:(1)The trajectory and the velocity change of the steel ball in the single-size steel ball scheme for the drop motion are in accordance with the Davis theory of steel ball motion;(2)By analyzing the velocity of the grinding media as a throwing motion in the single size steel ball solution,it is deduced that the impact momentum of the grinding media of95.25 mm,82.08 mm,60mm and 42.69 mm in the ?5.03m×6.4m ball mill of Ekou iron ore is 6.86 kg·m/s,4.79 kg·m/s,1.77 kg·m/s,0.59 kg·m /s and 10 mm,8 mm,5 mm,3mm ore to be ground impact impulse difference is only 0.19 kg·m/s,0.24 kg·m/s,0.1kg·m/s,0.01 kg·m/s,the error is 2.8%,5.6%,6.0%,1.7%,the overall error is less than6%,the simulation results and the theoretical calculation results are in good agreement with the theoretical calculation results,which verifies the reliability of the theoretical calculation results.(3)The simulation of the multi-stage proportioning scheme show that the recommended scheme has a smaller grinding kidney area and more steel balls in the grinding process,which is conducive to improving the grinding efficiency.(4)The normal and tangential collision energy of the recommended scheme is closer to that of the field scheme but the collision frequency is significantly higher,and the useful energy ratio of the recommended scheme is higher than that of the field scheme,and its effective energy utilization rate is 10.04% higher than that of the field scheme.The grinding efficiency of the recommended scheme is significantly higher than that of the field scheme.In order to further verify the influence of the steel ball scheme calculated based on the matching of steel ball and ore impact momentum on the grinding efficiency of Ekou iron ore,a comparative grinding test was conducted in a laboratory ?450mm×450mm ball mill.(2)the technical efficiency of grinding is 2.63% higher than the on-site solution,which effectively improves the grinding quality index;(3)The utilization efficiency of-0.074 mm mill is 3.99% higher than the on-site solution,which effectively improves the grinding quantity index.The recommended steel ball proportioning scheme can effectively improve the grinding efficiency,which verifies the reliability of the steel ball scheme calculated by the impact momentum of steel balls and ore. |
PDF Full Text Request