CFD studies of dual circulating fluidized bed reactors for chemical looping combustion processes

• Hydrodynamics and reactive characteristic of CLC in the DCFB is investigated.
• The reactive multiphase model with considerations of cluster effects is applied.
• Simulations are in agreement with experiments.
• The effect of temperature and air/fuel ratio on gas compositions is predicted.

Chemical looping combustion (CLC) processes in a dual circulating fluidized bed (DCFB) reactor are investigated by means of computational fluid dynamic (CFD) method. A two-fluid model with consideration of heterogeneous chemical reactions is adopted. The kinetic theory of granular flow is employed for closure. A cluster structure-dependent (CSD) drag coefficient model is applied to account for the effect of meso-scale heterogeneous structure involving clusters or strands. The simulations are performed to predict gas–solid flow behaviors and reactive characteristics in dual circulating fluidized bed reactors during the CLC process. By a comparison of the outlet gas concentrations with the measured data, the CSD drag model can obtain a more reasonable prediction than the Ergun/Wen–Yu drag model. The influence of reaction temperature and air/fuel ratio on the performance of the DCFB reactor is also evaluated.