Inclusion of incremental damage breakage of particles and slurry rheology into a particle scale multiphase model of a SAG mill

Abstract

Coupled DEM+SPH models are able to predict the motion of the coarse particulates and the slurry phase in a SAG mill. An extension of this model is proposed in which breakage of coarser particles (which are resolved in the DEM sub-model) in accordance with the incremental damage theory is included. This allows direct prediction of the resident size distribution of the rock component of the charge. It also allows the finer unresolved progeny from the breakage to be added to the slurry whose rheological properties then become a dynamic prediction of the model via the evolving local solids density of the slurry. It also allows transport of the fine material within and from the mill to be predicted. This model is demonstrated for an industry standard 1.8 m diameter by 0.6 m long pilot SAG mill. It allows the nature of the damage accumulation by the rock particles and its linkage to the flow structure of the charge to be explored. A flux of particles rebounding from the liner in the impact zone of the mill colliding with cataracting material produces the strongest incremental damage. Damage is also generated by cascading material arriving in the toe region. The presence of a slurry pool restricts the opportunity for incremental damage from the rebounding particles in the impact zone by damping rebound in places where particles fall directly into slurry. Finally, the coupled DEM+breakage+SPH model enables a mechanistic linkage between the slurry properties and the rock breakage.