ENERGY SPLIT AND KINETICS OF BALL MILL GRINDING OF MIXTURE FEEDS IN HETEROGENEOUS ENVIRONMENT

Complex interactions between the constituents of a multicomponent mill charge can be conveniently characterized by an energy split factor, which is defined as the ratio of energies consumed per unit mass of a component when it is ground in an admixture and ground alone for equal time intervals. It is shown that the grinding paths of the components are independent of the homogeneous or heterogeneous nature of the particulate environment, and as a consequence the energy split factors can be computed from a mill power-grinding rate correlation. Using these split factors, it is possible to track the flow of energy to the constituents of the feed charge and integrate the energetic and kinetic aspects of multicomponent grinding. Extensive data on dry and wet ball mill grinding of binary feeds comprising calcite-quartz, hematite-quartz and dolomite-hematite mixtures in different proportions have been analyzed using the energy split factors. Interaction effects between hard and soft minerals are quantified, energies expended in grinding individual constituents are estimated, and kinetics of mixture grinding are simulated successfully. Some industrial implications of grinding in heterogeneous environments are discussed.