Using SPH one-way coupled to DEM to model wet industrial banana screens

Abstract

Large banana screens with multiple decks are used extensively in the process separation of many valuable export commodities. They are high capacity vibrating screens with a curved profile. Discrete Element Method (DEM) modelling using non-spherical particles has previously provided significant insight into the operation of these dry industrial screens. Here we introduce the use of Smoothed Particle Hydrodynamics (SPH) to model the flow of slurry (water and fine material) through a double deck banana screen. This paper firstly reports on the underlying DEM model of the coarse particulate flow on a full-scale banana screen. We then use Smoothed Particle Hydrodynamics (SPH) to model the transport of fine particle slurry over and through the double deck banana screen. Finally, we combine the DEM with SPH models using a one-way coupling to simulate the effects of adding a slurry flow to coarse particulates on the banana screen. The key outcomes from this study are that; SPH is ideally suited for the high speeds and the high fragmented and filamentary nature of the fluid flow through the screen deck openings; the fluid only (SPH) model of slurry behaves similarly to the DEM approach in that more fluid is screened as the velocity slows, except near the earlier panels on the top deck; and, use of a porous media derived from DEM in one-way coupled approach with SPH produces clear and reasonable changes in fluid structure, separation and wetting of the screens consistent with slurry behaviour. Specifically, the fluid layer was much thicker in the coupled case, with slurry being trapped inside a coarse particle bed and which is sensitive to the fluid viscosity.