CFD–DEM study of the effect of particle density distribution on the multiphase flow and performance of dense medium cyclone

A mathematical model is developed to study the coal-medium flow in a dense medium cyclone (DMC) of 1000 mm body diameter. In the model, the motion of coal particles is obtained using the Discrete Element Method (DEM) facilitated with the concept of “parcel–particle” while the flow of medium as a liquid-magnetite mixture Computational Fluid Dynamics (CFD) based on the local averaged Navier–Stokes equations. In addition the Reynolds Stress Model (RSM) is adopted to describe the anisotropic turbulence, the Volume of Fluid (VOF) model is used to describe the air-core position and multiphase mixture model used to estimate the flow of fine magnetite particles. The simulated medium and coal flows allow estimates to be made of pressure drop, efflux stream medium densities and partition curves for coal particles of different sizes and densities. These estimates are compared favourably with industrial scale measurements of a 1000 mm DMC operating under similar conditions. On this base, the effect of particle density distribution that represents the major difference between two major coal type, i.e., coking coal and thermal coal, is studied. The results are analysed in terms of medium flow pattern, particle flow pattern, partition performance and particle–fluid, particle–wall and particle–particle interaction forces.