Numerical Study of Hydrodynamics of Tapered Fluidized Beds Using CFD-DEM

In the present study, the hydrodynamics of tapered fluidized beds (TFBs) for two types of particles, namely, Geldart D and Geldart B with mean diameters of 2 mm and 0.287 mm, respectively, were studied by CFD-DEM in 3D frameworks. The particles phase was simulated by dense discrete phase model (DDPM) in which the particle-particle collision was modeled by the discrete phase method (DEM). While the continuous phase (gas phase) was simulated by the Eulerian approach by considering k-ε turbulent model for this phase. The well-known drag model of Gidaspow was applied for computing the momentum exchange between the phases.  It was found that the bed pressure drop and the bed expansion ratio predicted by the proposed model were in close agreement with the corresponding measured data. By evaluating power spectral density in TFBs, it was found that the dominant frequency is about 2.3 Hz for a TFB which is quite different than that calculated in bubbling fluidized beds (BFBs).  Due to the fact that this study is one of the few Eulerian-Lagrangian works on TFBs, it can be a suitable basis for future studies in numerical simulation of TFBs.