Computational simulation of fluid and dilute particulate flows on spiral concentrators

Spiral separators are used globally in the fine coal and heavy mineral processing industries as gravity-concentration devices. Consisting of an open trough that spirals vertically downwards in helix configuration about a central axis, a slurry mix of particles and water is fed to the top of the concentrator. Particles are then separated radially on the basis of density and size as they gravitate downwards. To enhance performance, the geometric design has evolved historically by experimental trial-and-error investigations to develop a prototype suited to the given industrial application. This approach has proved somewhat prohibitive for design purposes however, and researchers have accordingly turned to numerical techniques in an attempt to develop a fully predictive and reliable model for use in the design process. Towards this end, the present paper uses Computational Fluid Dynamics (CFD) analysis to simulate fluid and dilute particulate flows on one operational spiral unit. The free-surface Volume-of-Fluid (VOF) algorithm, isotropic RNG k–ε turbulence model and Lagrangian method have been used for this purpose. Satisfactory predictions have been obtained with respect to a collaborative experimental program, and the model forms the basis for future examination of the two-way fluid-particle coupling processes and inter-particle effects.