Validation and comparison of discrete element model and two-fluid model for dense gas-solid flow simulation in a fluidized bed

Two-fluid model (TFM) and discrete element model (DEM) are the two most widely used methods for numerical simulation of dense gas-solid flow in a fluidized bed. It is of great interest to investigate the differences in the physics of these two models and their applicability regime in modeling the dense gas-solid flow accurately. In this study, a quasi-2D spouted fluidized bed was simulated by DEM and TFM separately. In DEM, the hydrodynamic flow field is computed by solving the incompressible continuity and Navier-Stokes equations, while the motion of the solid particles is modeled by the Newtonian equations of motion. The results show that the TFM cannot predict the evolution of the bubbles in the fluidized bed accurately, but it could predict the height of the bed better in the initial period of fluidization. Compared to the TFM, it is foUnd that the DEM is closer to the experiment in determining the changes in the bubble shape, bed pressure fluctuations, and particle velocity; however, the bed height predicted by DEM is slightly lower than the experimental value. The TFM simulations based on the Eulerian approach although computationally more efficient are not very accurate in capturing the flow features of the fluidized bed. It is concluded that for accurate simulation of transient dense gas-solid flow simulation of a fluidized bed, DEM should be used and not the TFM based on the kinetic theory of granular flow.