CFD investigation of hydrodynamic behavior of a circulating fluidized bed

CFD investigation of hydrodynamic behavior of a circulating fluidized bed

Hydrodynamics plays a crucial role in defining the performance of circulating fluidized beds (CFB). The numerical simulation of CFBs is very important in the prediction of its flow behavior. From this point of view, in the present study CFD method is employed considering the hydrodynamic behavior of CFB. The MFIX results are compared with and validated against atmospheric cold bed CFB unitsʹ experimental data given in the literature for axial and radial distribution of void fraction, solids volume fraction and particle velocity, total pressure drop along the bed height and radial solids flux. Ranges of experimental data used in comparisons are as follows: bed diameter from 0.05–0.418 m, bed height from 5–18 m, mean particle diameter from 67–520 μm, particle density from 1398 to 2620 kg/m3, mass fluxes from 21.3 to 300 kg/m2s and gas superficial velocities from 2.52–9.1 m/s. As a result of sensitivity analysis, the variation in mean particle diameter and superficial velocity, does affect the pressure especially in the core region and it does not affect considerably the pressure in the annulus region. Radial pressure profile is getting flatter in the core region as the mean particle diameter increases. Similar results can be obtained for lower superficial velocities. It has also been found that the contribution to the total pressure drop by gas and solids friction components is negligibly small when compared to the acceleration and solids hydrodynamic head components.