Dynamic Modeling of Oxygen Carrier-Aided Combustion in a Packed Bed Reactor

Oxygen carrier-aided combustion (OCAC) is a promising technology with a high combustion efficiency and low NO x emissions. Up to now, investigations on OCAC have been mainly conducted in the fluidized bed reactor. Differently, this study delves into the operational characteristics of OCAC applied in the packed bed reactor (PBR) by dynamic simulation. The OCAC-PBR mode utilizes the advantages of both chemical looping combustion (CLC) and porous media combustion (PMC). A one-dimensional heterogeneous model is established, validated, and then used to predict the evolution of temperature fronts in the bed and their effects on the combustion performance. First, OCAC exhibits a comparable fuel conversion capacity to PMC under oxygen-rich conditions; however, under fuel-rich conditions, OCAC demonstrates a higher fuel conversion. Second, the combustion wave in OCAC-PBR is more likely to remain stationary with increasing air-to-fuel ratio (Phi) compared to PMC, indicating its potential for stable operation. Third, the principles of improved fuel conversion under fuel-rich conditions are explored. The movement of the heat front makes more oxygen carriers (OCs) at high temperatures, providing more lattice oxygen for the reaction. The faster the heat front moves, the higher fuel conversion is observed. Finally, for the efficient operation of OCAC-PBR, ensuring a stationary combustion wave is crucial. Stable operation can be achieved by adjusting the composition and flow rate of inlet gas. Benefiting from the capacity of OC donating lattice oxygen under fuel-rich conditions, OCAC-PBR exhibits stronger resistance to unstable inlet gas flow rates and Phi.