| Due to the simple structure and easy maintenance of ball mills, they are widely used in various industrial areas. As the improvement of grinding process in the industrial cement mill, cement grinding mill process system has developed into semi- final roller press and ball mill grinding joint process. The crush job has been transferred to the more efficient roller press, while the fine grinding job is mainly done by the ball mill. However, most of the existing theory focused on the impact crushing. And the theory of grinding is rarely discussed. With a conversion function of the ball mill in the joint cement grinding system, whether the rotation speed of ball mill is still appropriate for the current working conditions should be considered. Therefore, it’s significance to research the influence of rotation speed on crushing and grinding effect of the cement grinding system. This paper studied the movement of the media inside the ball mill and test evaluation at different grinding stage. Moreover, we also study the influence of rotation speed on crushing and grinding effect, analyzing the mechanism of ball mill coarse grinding and fine grinding.The paper use inverter technology to control laboratory mill speed. Each experiment is divided into coarse grinding and fine grinding, which is used for the simulate of the crushing and grinding warehouse in cement mill, We study the influence of rotation speed rate of 58%-88% on crushing and grinding effect in different filling rate. We choose reduce speed of a certain particles sieve to evaluate its crush rate. While use increasing speed of the specific surface area to evaluate the grinding rate. When the filling rate is 18%, the crushing effect and grinding effect increase as the increase of rotation speed. When the filling rate is 30%, the crushing effect is best when the rotation speed rate is 76%-79% in coarse grinding stage. In the fine grinding stage, the grinding effect increase as the increase of rotation speed. On the other hand, at the same speed, low filling rate(18%) exhibits a better crushing effect and grinding effect that of high filling rate(30%).Several conclusions could be summarized by analyzing the movement energy of media in the ball mill. In the coarse grinding stage, the particle size of the materia l is mainly influenced by the impact, the main factor for the crushing effect is the normal impact energy. In the fine grinding stage, the decrease of particle size is not merely influenced by the impact or grinding. The major factor is different in different rotation speed. When the rotation speed is in the low speed range rate of 79%-82%, the main factor is the normal impact energy. When the rotation speed is in the high speed range rate of 79%-82%, the main factor for the grinding effect is the tangential grinding energy. The media motion was studied in a transparent mill. The increase of filling rate improves the ball mill production However, the falling distance of the media becoming short, and its energy is reduced. On the other hand, the kidney-shaped wriggle area is bigger than that at the low fill rates, leading to the increase of media invalid movement.Our research provides several suggestions: with the change of cement grinding process, ball mill is playing more important functions on grinding. So, in the actual grinding proc ess, in order to improve the overall grinding energy utilization and achieve better energy-saving effect, we can reduce the load of ball mill and increase the speed of the ball mill by frequency conversion technology, with the premise of the total power not exceeding the safe operation power... |
PDF Full Text Request