A Study on Grinding Mechanism of Fine Particles in a Sand-Mill by Using an Image-Processing Techinque and a Development of an Original Sand-Mill.

针对内叶片和外圆筒反向独立旋转的卧式砂磨机，首次提出了一种显示介质颗粒运动的测量技术。利用这一实验技术，测量了磨机内磨矿介质的速度分布、速度脉动强度和出现频率。结合这两种旋转方式下介质颗粒的流动特性，考察了氧化铝微珠对碳酸钙的研磨性能。结果表明，两种旋转方法得到的磨矿产品中值直径不仅与速度脉动的强度相关，而且与以出现频率加权的速度脉动的强度有很好的相关性；此外，在内、外圆筒反向独立旋转的卧式砂磨机中，对3种叶片(法向盘型、孔盘型和十字型)的研磨介质运动进行了可视化。研究了叶片几何形状对磨矿介质的速度分布、速度脉动强度和出现频率的影响。通过对碳酸钙的粉磨试验，探讨了这些流动特性与粉磨速度的关系。结果表明，两种旋转方式下叶片的磨削特性与以出现频率加权的速度波动强度具有很好的相关性。在此基础上，提出了一种新型叶片(十字涡轮式)，并结合磨削介质的运动对其磨削速率进行了研究。结果表明，与常用的三种叶片相比，一种新型叶片的性能最好。

A measuring technique to visualize the motion of media particle is originally developed for a horizontal type sand mill of which internal blade and external cylinder rotate inversely and independently. Using this experimental technique, velocity distribution, intensity of velocity fluctuations and appearance frequency of grinding media in the mill were measured. Relating to these flow characteristics of media particles for both rotation metods, grinding performance of calcium carbonate with alumina beads was investigated. The results show that the median diameter of ground products obtained in both rotation methods can not be correlated only with the intensity of velocity fluctuations, but can well be correlated with the intensity of velocity fluctuations weighted by appearance frequency.In addition, motions of grinding media were visualized for three types of blade (normal disk type, hole disk type and cross type) in a horizontal type sand mill of which internal blade and external cylinder rotate inversely and independently. The effects of blade geometry on velocity distribution, intensity of velocity fluctuations and appearance frequency of grinding media were investigated. The relationship between these flow characteristics and grinding rate was discussed by carrying out grinding tests of calcium carbonate. The results show that grinding characteristics obtained for each blade in both rotation methods can well be correlated with the intensity of velocity fluctuations weighted by appearance frequency.A new type of blade (cross turbine type) was proposed on the basis of the above mentioned information, and its grinding rate was investigated in connection with the motion of grinding media. The results show that a new type of blade is the best compared to usual three types of blade.