Experimental and Numerical Study in the Inlet Region of a Circulating Fluidized Bed

The behavior of the gas-solid flow in a riser was evaluated by means of an experimental and numerical study. Axial velocity measurements for the both phases were conducted at the inlet region in a cylindrical riser of a cold-flow circulating fluidized bed (CFB) bench unit. The riser has an internal diameter of 0.104 m, a height of 2.4 m and the region where measurements were taken is made by Plexiglas. The side inlet used for catalyst feeding is positioned 0.5 m above the gas inlet and makes a 45° angle with the riser axis. The investigations were performed at different heights for five operational conditions, namely: the clean flow, two superficial gas velocities and two constant mass flow rates. Particle- and gas-phase velocities were acquired by means a Laser Doppler Anemometry (LDA) probe at profiles aligned with solids inlet and at 90° from it. Numerical simulations were performed by Computational Fluid Dynamics (CFD) techniques and compared with the experimental data obtained. For the gas-solid flow the Eulerian approach was applied. The gas-phase turbulence was modeled by the dispersed k-ε model and the solid phase model applies the Kinetic Theory of Granular Flow (KTGF), employing the energy minimization multi-scale (EMMS) drag model. Numerical results showed a good agreement with the experimental data and a partial validation of the mathematical model was achieved.