Numerical study on liquid-solid flow characteristics in inverse circulating fluidized beds

The flow behavior of particles in inverse liquid-solid circulating fluidized beds was simulated using the Eulerian-Eulerian approach incorporating the kinetic theory of granular flow. The Syamlal-O'Brien drag model was used to account for the interphase interaction between the liquid and solids phases. A detailed description of the model equations used in this work has been presented. Predicted results were compared with the experimental data obtained by other group members. A good agreement between the numerical simulations and experimental results has been achieved. The inverse flow characteristics of particles were studied using a single type of particles and multiple types of particles with different densities under different liquid velocities and solids flow rates. The results indicated that for the particles with different densities, 950 kg/m³, 850 kg/m³ and 640 kg/m³, the cross-sectional average solids holdup along the axis was uniform and the radial flow structures at different bed heights were identical. Particles moved from the walls to the center at the top region of the bed. Such tendency diminished as the particles move downwards. The axial velocities of solid particles were higher in the center and lower near the walls. For the particles with a density of 28 kg/m³, due to the randomly generated vortexes of particles, the solids holdup radial distributions and the velocities of particles were more irregular. For the mixed particles with two different densities of 850 kg/m³ and 950 kg/m³, the trend of solids holdup radial distribution, and the trend of the lateral and axial velocities of each particle group were similar to those in the simulation using the single-density particles.