Multiphase flow and tromp curve simulation of dense medium cyclones using Computational Fluid Dynamics

Dense Medium Cyclone (DMC) is a high capacity device widely used in coal preparation. Although this device is simple in design, the swirling turbulent flow, the presence of medium and coal with different density and size fraction and the presence of the air core make the flow pattern in DMCs complex. In this article the flow pattern simulation of DMC was performed with computational fluid dynamics (CFD) and Fluent software. Simulations were performed to give the axial velocity profile and the air core. Multiphase simulations (air/water/medium) were carried out with Reynolds Stress Model to predict turbulence dispersion, Volume of Fluid model to achieve interface between air and water phases, Mixture model to give multiphase simulation and Discrete Phase Model to predict coal particle tracking and tromp (partition) curve. The numerical results were compared with previously reported experimental data by Subramanian and close agreement was observed. In addition, separation efficiency of DMC was predicted using CFD simulations and shown by the Tromp curve. The comparison of simulated and measured Tromp curves showed that CFD simulation can predict Tromp curve reasonably within acceptable tolerance, however, for more accurate multiphase simulation including solid phase, Discrete Element Modeling (DEM) approach coupled with CFD was suggested. Through this research, it was found that characterization of mineral separation efficiency in DMCs based on Tromp curve concept can be done by CFD numerical simulation, which is very helpful in process optimization studies.

Keywords:

Dense medium cyclone , gravity coal preparation , multiphase modeling , Tromp curve