Three-dimensional CFD simulation of hydrodynamics in an interconnected fluidized bed for chemical looping combustion

A hydrodynamic model of an interconnected fluidized bed for chemical looping combustion was established based on the Eulerian–Eulerian two-fluid model with the kinetic theory of granular flow. The effect of the drag model on the computational results was investigated and detailed hydrodynamics were predicted in the three-dimensional circulating fluidized bed (composed of a riser, bubbling bed, pot-seal and cyclone). Both qualitative and quantitative results indicated that the drag model had a significant effect on the flow behavior. The Gidaspow and the Syamlal & OʹBrien drag models both produced accurate predictions in this study. The pressure balance of an interconnected fluidized bed revealed that the pressure in the bubbling bed was lower than that in the pot-seal and the riser, whilst still being higher than the pressure in the cyclone. The riser and bubbling bed were individually operated in fast and bubbling fluidization regions. The three distinct regions identified from the bottom to the top of the riser were: entrance region, bulk region and exit region. The solids volume fraction was higher in the near-wall region but lower in the center region for both the riser and bubbling bed. The coupled characteristics of the fluidized bed were predominantly identified by the strong effect of operational gas velocity in the riser on the hydrodynamics in the bubbling bed.