An analysis of multiphase flow and solids separation inside Knelson Concentrator based on four-way coupling of CFD and DEM simulation methods

Abstract

Knelson Concentrator (KC) has been widely used in industrial gravity separation processes. In the present study, the separation process for a multiphase flow in a laboratory Knelson Concentrator (LKC) is numerically simulated using a 4-way coupled CFD-DEM approach. The simulation of the complex multiphase flow is carried out by using a hybrid Eulerian–Lagrangian model, dense discrete phase model (DDPM), as well as DEM collision model to include the solid inter-particle collisions and to compute individual particles trajectories. The particle–fluid interaction is considered by exchanging momentum through the interaction forces such as drag force, virtual mass force and pressure gradient force between the DEM and the CFD computations. The Realizable Mixture k-ε turbulence model is selected to model the turbulence of fluid phase due to its swirling nature. Since coupled simulations are computationally expensive and challenging, the separation process inside the laboratory KC bowl was simulated for a real process time of 20 s under the specific conditions. Coupled CFD-DEM simulation yields valuable information about both particle and fluid flow patterns such as residence time distribution and velocity magnitude of particles inside the rings which are difficult or even impossible to measure experimentally with sufficient accuracy; meanwhile, the simulation results are expressed in terms of performance indices, i.e., concentrate grade and total recovery. To validate the simulation predictions, the authors carried out an experimental test under the same operating conditions used in the simulation. A complete agreement between simulation predictions and laboratory measurements for concentrate grade and total recovery was observed both qualitatively and quantitatively which validates coupled CFD-DEM simulation.