Self-sustained catalytic combustion of CO enhanced by micro fluidized bed: stability operation, fluidization state and CFD simulation

● Catalytic combustion in fluidized bed realizes efficient heat and mass transfer. ● Catalytic combustion in fluidized bed reduces the lean combustion limits. ● Catalytic combustion and flame combustion can be coupled. ● The diffusion/kinetics limited reaction model is suitable for catalytic combustion. A micro fluidized bed reactor was used to study the self-sustaining catalytic combustion of carbon monoxide (CO). The Cu1−xCexOy catalyst, as well as the pure CuO and CeO2, are used to investigate the contributing mechanism of different active sites including dispersed CuO and Cu–Ce solid solutions. The ignition temperature (Ti) of CO over these catalysts at a flow rate of 2000 mL/min followed the order: 74 °C (Cu0.5Ce0.5Oy) < 75 °C (Cu0.25Ce0.75Oy) < 84 °C (Cu0.75Ce0.25Oy) < 105 °C (CuO) < 500 °C (CeO2). Furthermore, the lean combustion limits (equivalence ratio ϕ) over these catalysts under the flow rates of 750–3000 mL/min (through fixed, bubbling, and fluidized bed) were also measured, which are Cu0.5Ce0.5Oy < Cu0.25Ce0.75Oy < Cu0.75Ce0.25Oy < CuO < CeO2. The fluidized bed was simulated using the Eulerian two-fluid model (TFM) coupled with a diffusion/kinetic-limited reaction model to evaluate the influence of operation conditions on the self-sustained combustion of CO. The predicted maximum temperature agreed with the experimental measurements, demonstrating the validity of the kinetic model and simulation parameters. The results of catalytic combustion with increasing CO concentrations suggest that the catalytic combustion reaction could co-exist with the flamed combustion. When a high concentration of CO is used, a blue-purple flame caused by CO combustion appears in the upper part of the fluidized bed, indicating that the range of CO-containing exhaust gas purification could be expanded to a larger range using the fluidized-bed catalytic combustion technique.