CFD Modeling of Cold-Flow Fluidized Beds and Validation with X-ray Computed Tomography

The hydrodynamics in a 152 mm ID bubbling fluidized bed filled with 500-600 μm glass beads have been simulated using the computational fluid dynamics (CFD) code Fluent 6.3, and the results are compared to experimental data obtained using pressure measurements and 3D X-ray computed tomography. The grids in a Cartesian coordinate system used in simulations are made by 2D (8×8 mm, 4×4 mm, 2×2 mm, and 1×1 mm) and 3D (4×4×4~6 mm). 4 mm grid resolution is sufficient and excellent to use on this scale reactor study to analyze of the time averaged, time and spatial averaged local gas holdup throughout the glass bead bed in 2D and 3D simulations. Throughout the whole fluidized bed, there are two larger symmetric circles of glass beads, in which the gas holdup about 0.460.52 is larger than in the middle of the fluidized bed about 0.44-0.46. The 3D simulations with SyamlalO’Brien and Gidaspow drag models better predict the local gas holdup variation throughout the whole fluidized bed, comparing with the experimental data. The results of simulations with Wen-Yu drag model are generally over predicted. The injector air path extends further into the bed along the axial height from quarter to half of radial long, where the maximum gas holdup is decreasing from 0.9 to 0.6 in the Y-Z slice throughout the fluidized bed with side air injection. But the simulations could not exactly predict the gas path. Because the side air has little effect on the X-Z slice, there remain somewhat symmetric.