Numerical study of the effect of vortex finder configuration in dense medium cyclones

A mathematical model is proposed to describe the multiphase flow in a 1000 mm industrial dense medium cyclone (DMC). In this model, a Mixture Multiphase model is employed to describe the flow of the dense medium (comprising finely ground magnetite contaminated with non-magnetic material in water) and the air core, where the turbulence is described by the well established Reynolds Stress Model. The stochastic Lagrangian Particle Tracking model is used to simulate the flow of coal particles. The proposed approach is qualitatively validated using literature and industrial data and then used to study the effect of the vortex finder configuration including the vortex finder length and diameter. The results show that the operational head, density differential and the medium split reporting to overflow increase to a maximum and then decrease as the vortex finder length increases. Because of the effect of the short circuit flow, the vortex finder in DMC cannot be too short or too long. As the vortex finder diameter increases, the operating head decreases and the density differential and the medium split increases dramatically. A high medium tangential velocity distribution is found in the DMC with a thin vortex finder, which results in a high pressure gradient force on coal particles and reduced separating efficiencies.