COMMINUTION OF SINGLE PARTICLES IN A RIGIDLY-MOUNTED ROLL MILL .3. PARTICLE INTERACTION AND ENERGY-DISSIPATION

With increasing feed rate to the rigidly-mounted roll mill, the stipulation of single-particle comminution begins to break down as crushed piles of solids in the grinding zone of the rolls interact with each other and with incoming feed particles. The total energy required to comminute particles under these conditions is analyzed as a function of the feed rate. The resulting model equation is employed to isolate that component of the energy input which is dissipated by interaction and ensuing friction. The experimental results indicate that the interaction energy depends on the feed size, compression ratio and the deformation rate. The sum of the interaction energy and the single-particle comminution energy provides a rough estimate of the energy consumption in confined particle-bed grinding, such as in the high-pressure roll mill or under uniaxial compression in a piston-die press. The predicted values agree reasonably well with the experimental results, especially in regard to the fact that the energy consumption in particle-bed grinding tends to be twice as much as that in the single-particle crushing mode.