Energy-size relationship for breakage of single particles in a rigidly mounted roll mill

Abstract

The breakage of single particles in rigidly mounted rolls has been analyzed from a fairly general expression for the thrust profile on the roll surface. The model permits one to estimate an equivalent particle-nip diameter for irregularly shaped particles which is about 90% of the nominal sieve diameter. In agreement with the model, the energy expended in breakage of single particles of quartz, dolomite, limestone and hematite is strongly dependent on the difference between the equivalent diameter and the roll gap. For various combinations of feed size and roll gap tested, a reduction ratio index increases linearly with energy consumed. This seemingly is a consequence of the highly efficient utilization of energy in this mode of size reduction. The slopes of the reduction ratio-energy plots provide a uniform measure of grindability that is least distorted by energy losses terms, such as those which occur in media mills.