Analysis of the change in particle shape during comminution using vibration mill

Abstract

The present work studied effects of two major factors, grinding time and weight ratio between grinding media and particles, on shape and flowability of ground feldspar using a vibration ball mill. A Powder Characteristics Tester was employed to evaluate flowability whereas particle shape analysis was carried out using a novel concept of fractal geometry. The raw material used in this work was feldspar in the size range 1190-2000 micron. After comminution, die ground product were sieved into three size ranges (149-210 micron. 210-297 micron and 297-420 micron) for discriminate effects of size and shape of particle. From the experimental results, it was found that as grinding time increased, the flowability of ground feldspar in each size ranges became smaller. On the other hand, it was also found that the shape irregularity increased as the die grinding time increased. For the effect of weight ratio between grinding media and particle on die flowability of ground feldspar, it was found that the ground feldspar at weight ratio between grinding media and feldspar of 4:1 has the best flowability in ad of three size ranges. On the other hand, at weight ratio 3:1. 5:1 and 6:1 flowability of ground feldspar become worse. It can be explained by considering die motion of grinding media in die mill. If the mill contains more grinding media (which represents by higher weight ratio), the collisions between media and feldspar occur more frequently. This led to cracking of particles which may cause die higher degree of irregularity of particle's shape. However, if the mill contains less medias such as weight ratio between media and feldspar 3:1, the grinding media and feldspar will collide more violently due to the less energy loss. This led to the high shape irregularity of ground feldspar. Therefore, the flowability of ground feldspar in this case become lower than the case of weight ratio 4:1