Modelling of incremental rock breakage by impact – For use in DEM models

Abstract

DEM simulations of AG and SAG mills indicate that breakage in a single impact is almost certainly a rare event. However, there are many events which might cause some damage. Hence it becomes important to be able to model how damage might accumulate and with what severity a particle is likely to break after accumulating sufficient damage. An investigation of incremental impact breakage of a well characterized ore sample has been carried out by Whyte (2005) [Whyte, R., 2005. Measuring incremental damage in rock breakage by impact. BE (honours) Thesis, The University of Queensland (unpublished)]. The outcomes of this work are encouraging. A modified version of a JKMRC developed equation – which relates severity of breakage to specific energy input – also provides a good description of the degree of incremental breakage for each size range of particles which was tested when breakage does occur. The other factor of interest for a DEM model is the probability of survival after a number of impact events. The work of Vogel and Peukert (2004) [Vogel, L., Peukert, W., 2004. Determination of material properties relevant to grinding by practicable labscale milling tests, International Journal of Minerals Processing, 74S, S329–S338] provides a useful model for multiple impacts with identical energies. This model has been modified and extended to different input energy levels. This model proposes a minimum specific impact energy E 0 below which no damage is accumulated by the body of the particle. Perhaps the most important insight from this work is a way to quantify energy inefficiency of breakage in comminution devices. Each successive impact after the first one fails to utilize E 0 because the particle must be loaded again to E 0 before any further damage can be achieved. For the ore tested, achieving a similar degree of severity of incremental breakage using multiple impacts typically required substantially more total energy than was required for a single impact. However, even very small interactions will still cause some surface damage and generate fine progeny.