Session: 10.4.1 - Vortex Dynamics I

Paper Number: 158124

158124 - Grinding Mechanism From Flow Characteristics of a Ball Mill 

Abstract: 

A ball mill is a grinding machine that produces fine raw material particles. In a ball mill, the grinding material and hard balls are mixed in a cylindrical container, and the material is grinded by the collisions and friction between the balls caused by the rotation of the container. There are two types of ball mills, wet type, in which a liquid is mixed in, and dry type. Wet type ball mills have a high grinding speed and are superior in terms of fine grinding. However, the effect of the flow characteristics of liquid on the hard balls during the grinding process, as well as the grinding speed and superiority of fine grinding have not been understood sufficiently. The purpose of this study is to clarify the effect of the flow characteristics of the liquid in a wet ball mill on the behavior of the hard balls and the grinding ability. In particular, we clarify the influence of the flow characteristics of the liquid in the ball mill on the grinding ability based on the diameter ratio of the ball mill to the hard balls, the rotational speed of the ball mill, the volume fraction of the liquid, and the dynamic behavior of the hard balls. The flow characteristics of the liquid inside the ball mill are quantitatively visualized by PIV measurement, and the grinding mechanism of the wet ball mill is clarified by PTV analysis of the hard balls. In this study, the grinding material is not considered, the flow characteristics of the liquid in the ball mill and the dynamic behavior of the hard balls are used to clarify the characteristics that contribute to the grinding ability. The PIV measurement system to clarify the flow characteristics of the liquid (water) in the ball mill consisted of an acrylic ball mill (diameter : 100 mm, length : 150 mm), a high-speed camera, and a laser sheet. The rotational speed of the ball mill and the volume fraction of the liquid (water) were set to ω = 40, 80, 120, and 150 rpm and V = 34, 51, and 68%, respectively. In addition, PTV analysis was also performed using the same system to capture the behavior of a hard ball. The hard ball (specific gravity : 3.73, diameter: 10 mm) was set to 34% of the ball mill volume, and this experiment was performed under both dry and wet conditions (52.6 wt%). These measurements will clarify how the flow characteristics of the liquid in a wet ball mill affect the dynamic behavior of the hard balls and contribute to their grinding ability.

Presenting Author: Masaki Fuchiwaki Kyushu Institute of Technology

Presenting Author Biography: Masaki Fuchiwaki: He received his B. Eng., M., Eng. and Dr. Eng. degree in mechanical engineering from Kyushu Institute of Technology in 1994, 1996 and 2000, respectively. After completion of his Ph.D program, he worked in Osaka Science & Technology center as a researcher, the Kyushu Institute of Technology. He is currently a professor in the department of Intelligent and Control Systems at Kyushu Institute of Technology. His research interests are in Sweeping jet in cross flow, detailed vortex structure around the moving elastic airfoils, characteristics of dynamic forces acting on them and the flow field around a butterfly wing.