Application of a simplifying model to the breakage of different materials in an air jet mill

This paper describes the application of a unifying ‘master curve’ model for single impact size reduction in an air jet mill. Based on a dimensional analysis and a modified fracture mechanical theory, it enables to relate the weight percentage of broken particles under sieve cut size to the mean sieve cut size of the studied material, the net kinetic energy provided to the material, the number of impacts and a global parameter fMat.. Altogether 11 sieve cuts of different materials are impacted in an experimental air jet mill. Minimum breakage energies are derived and are shown to vary with a power function of the sieve cut size. The simplifying model is then successfully applied and enables to derive the fMat. parameters. In our situation, the experimental data do not show a direct relationship between fMat. and the minimum breakage energy and sieve cut size for all the materials.

► The experimental impact data of 11 samples fits the ‘master curve’ model.
► The breakage threshold follows Wmin=axb with b always between 1 and 2.
► The material function fMat. ∝ (x ⋅ Wmin)− 0.9.
► The larger the energy utilization p, the larger the material function fMat..