A.N. Mainza

The Development of a Simplified System for Measuring the Passage of Particles on and Through Moving Screen Surfaces Using DEM

Screening is the practice of separating granular materials into multiple size fractions, and is employed in most mineral processing plants. Currently, the design and scale-up of screens relies on rules of thumb and empirical methods. To go beyond the current state-of-the-art in screen modelling, DEM was employed to study particle motion along a dynamic (vibrating) inclined screen. Granular flow on vibrating screens exhibits complex phenomena such as segregation, percolation and flow of oversize material over the separating medium. In this work, a unique granular rheology is established for particles moving on a vibrating screen. DEM was used to provide key data (velocity, volume concentration, shear rate, bed depth) for the development, testing and calibrating the granular flow models. A binary mixture of glass beads flowing on an inclined vibrating screen was simulated. The subsequent continuum analysis of the flowing layer revealed a co-existence of three flow regimes—a dense quasi-static regime, an intermediate liquid regime, and a gaseous regime—which are based on the measured volume concentration. The appropriate constitutive shear stresses were then used to derive a new rheology that captures all phases of the flow transition points observed in the simulation.