Kinetics of comminution in micro- and sub-micrometer ranges

Abstract

Fine grinding in the area of particle size of a few micrometers is becoming an increasingly conventional process. For this range of grinding, the most suitable are the various types of agitated-ball mills. Despite the fact that this is a well known area of grinding, in terms of the required conditions, there are still many unknowns regarding the kinetics of grinding, particularly in the submicron range when we are approaching the lower grinding limit. We are often satisfied if the upper limit of granulation of the product (100% undersize) is obtained. We know that the significant parameters for very fine grinding are primarily the following: the size of grinding balls, the concentration of solid phase, the medium, the dispersion agent, the design of the pearl mill and, of course, the time of grinding (which relates, of course, to the energy consumption). All of these parameters can not be generalized for each grinding process separately, but the knowledge of the speed of grinding for individual particle size is very useful. In this paper we refer precisely to this range of granulation, investigating the laws of kinetics of wet grinding. The paper deals with the grinding of various substances, primarily fillers and pigments for commercial use. For the sake of comparison we also present the data regarding the kinetics of grinding in the planetary and vibration ball mills. The experimental data are presented in the form of a median particle size ( d 50) as a function of grinding time.