Influence of Rotary Speed and Fill Rate on Grinding Efficiency of Mill

The working parameters of the inside media of ball mill has an essential linkage with the movement conditions of the media. The grinding process of ball mill is a dynamic process which is influenced by many factors such as fill rate, rotary speed, diameter of the grinding media and the proportioning of the media. The fill rate and the rotary speed determine the movement state and energy state of the grinding media; the diameter of the media obviously influence the quality of the media, which means the energy the media can carry, thus influencing the material grinding and impacting forces and the potential energy and impacting energy of the grinding media. Researching the influences of the working parameters on the movement of the grinding media theoretically will provide theoretical reference for discrete element model simulation analysis and experiment of ball mill.

The rotary speed of ball mill has great influences on the grinding effect of materials because the rotary speed of ball mill plays a decisive role in the improving force and movement state of the grinding media of the grinding mill and the rotary speed is the most important factor of realizing the movement state. When the rotary speed is low, the grinding mill cannot raise the grinding media to a certain height or even cannot bring the media up, so that the grinding media can only slide inside the mill and grind and crush the materials relying on the weak sliding force. If the rotary speed is too high, the inertial centrifugal force of the grinding media will make it attach on the internal wall of the mill and move around with the mill, so that it will not be able to effectively crush the materials. In order to make full use of the grinding and impacting force of the grinding media in the movement process to crush the materials, the customers must carefully select the rotary speed for ball mill according to the actual powder grinding conditions.

Fill rate is another important factor that influences the powder grinding efficiency of grinding mill. On the condition of the same cylinder column, if the fill rate is increased, the number of effective media of grinding and crushing will increase, which can improve the productivity to some degree. However, if the fill rate is too high, on one hand, the number of the internal media is increased, but the crushing ability of the internal media is not very strong; on the other hand, the media will pile very high which relatively decreases the effective impacting height of the media and reduces the impacting effect. For this reason, high fill rate is not conducive to ore grinding.

Thinking from the point view of actual production, if the granularity and hardness of the materials are all big which need high crushing power, the fill rate should be high. In addition, if the rotary speed of the grinding mill is high and the efficiency of the lining board is high, the fill rate can be relatively low.