An Empirical Study of Comminution in an' Open-Circuit Ball Mill

CIM Bulletin, 1970

F. J. KELLY, Senior Scientific Officer, Hydrometall urgy Section, Extraction Metallurgy Division, Mines Branch, Dept. of Energy, Mines and Resources, Ottawa, Ontario

A central composite experimental design was used to determine empirical relationships between the operating rnriables of a ball mill and the characteristics of the ground products. The independent variables selected for the study were the work index and size distribution of the feed material, the feed rate and the pulp density. The measured responses included product size distribution, product surface area, viscosity of pulp discharge, weight of dry solids in mill, mill time constant and emitted sonic vibrations. The ball mill was operated continuously in open circuit during each experimental run. Multivariable regression techniques were used to derive linear empirical models from the experimental results. Of the four factors studied, the grindability of the feed material significantly affected every measured response. The size distribution of the ground product was affected significantly by the feed rate and the size distribution of the feed, but not by the pulp• density. Feed throughput capacity and pulp density were significant to the viscosity of the pulp discharge, the weight of solids in the mill and the mill time constant. Significant first- and second-order models are given for the above relationships. The relationships between the characteristics of the sonic vibrations of the operating mill and the various dependent variables have not as yet been established.
Keywords: ball mill, feldspar, micron, Mill Time Constant, Standard Deviation and Work Index, Feed rates, Materials, Mill, Mills, Size distribution, test, Tests, Work index