Study Of Effects Of Structural Parameters On Grinding Performance In A Horizontal Stirred Mill

Ultrafine powders are mainly made by mechanical grinding and chemical method, and mechanical grinding is the primary processing means of ultrafine powders. Over the years, the traditional roller ball mill has been the main equipment of fine grinding, and with the development of the grinding equipment, the stirred mill was used in many fields. Compared with traditional ball mill, the energy efficiency of the stirred mill is higher in the fine grinding and the ultrafine grinding.How to improve the performance of the stirred mill, namely how to improve the grinding efficiency of the mill and reduce the power consumption of the mill, which is a research direction many scholars have been committed to. Compared with the vertical stirred mill, the horizontal stirred mill basically overcomes the influence of the gravity and converts most of the energy into kinetic energy of the grinding media. Because its shaft is placed horizontally, the horizontal stirred mill can be operated more high-speed operation. Thus, the grinding intensity and the grinding efficiency can be increased. Compared with the stirred mill with bar stirrer geometry, the stirred mill with disc stirrer geometry has a higher speed of the stirrer-the circumferential velocity of discs can reach to20m/s or so). Thus, the media can be uniformly distributed in the annular area between the inner wall of the grinding chamber and the stirred shaft, and then the uniform velocity gradient and the higher energy efficiency can be obtained.Before, many scholars have studied the operating conditions of the stirred mill, and obtained the optimum operating conditions in which the grinding efficiency of the mill will be the highest. However, studies on effects of structural parameters on grinding performance in a stirred mill are very few. According to this situation, after a lot of investigation and survey, the horizontal stirred mill with disc stirrer, namely high-speed ultrafine stirred mill which is worth researching and promoting has been selected to study. And effects of some structural parameters on grinding performance in a stirred mill have been studied. The detailed contents of the work are as follows:(1) After a lot of investigation and survey, the overview of the development and the status of the research of the stirred mill at home and abroad have been expounded, and then, the contents and methods of the study have been proposed.(2) The basis theory of discrete element method has been described, and three-dimensional software EDEM based on discrete element method have been briefly introduced.(3) The research results about the grinding mechanism in the stirred mill of scholars in recent years at home and abroad have been summarized. Then, the grinding mechanism of the horizontal stirred mill with disc stirrer has been analysed combining with simulation results of EDEM, and correlative grinding theories have been also introduced.(4) Previous research about grinding efficiency and power consumption of the stirred mill have been synthesized, evaluation method of grinding performance of the horizontal stirred mill with disc stirrer has been put forward-make ensure that the grinding intensity is high enough while the grinding energy efficiency is higher, i.e. a comprehensive consideration on the grinding intensity and the grinding energy efficiency should be given.(5) The theory of discrete element method and discrete element method simulation software EDEM have been used to separately study the three main structural parameters which affect the performance of the mill:the spacing between the edge of stirrer and the inner wall of the cylinder, the thickness of the disc and the spacing between discs. Control variable method has been used, and the research control variables, and finally a set of the optimal structural parameters have been obtained.(6) Based on the results of the preceding research, the several forms of the stirred discs have been studied, and the form of the stirred discs with which the grinding performance was optimal has been obtained. Finally, several mills with different shape of the inner wall of the cylinder have been studied, and an optimal shape of the inner wall of the cylinder has been obtained.The same operating conditions of the mill speed, the media filling rate, media size, and physical properties of materials, etc. have been used during the entire study. And the types of ground materials have not been considered. The physical quantities such as the force on the particles, the collision frequency and collision energy, as well as the power consumption of the mill which are associated with the grinding performance have been studied respectively.