Performance of ventilation air methane combustion over transition metal oxide oxygen carriers

The performance of combustion of ventilation air methane (VAM) over transition metal oxide oxygen carriers was studied through experiments with using tube reactors. The results show that the activity of activated oxygen carriers in converting CH₄ to CO₂ is as follows:CuO60/γ-Al₂O₃ > NiO60/γ-Al₂O₃ > Fe₂O₃60/γ-Al₂O₃. CH₄ conversion based on CuO60/γ-Al₂O₃ decreases with increasing gas hourly space velocity, but increases with increasing bed temperature and CuO loading. The lower the initial CH₄ concentration of ventilation air methane, the lower is the temperature for the CH₄ conversion of 90%. There are catalytic combustion mechanisms and chemical-looping combustion mechanisms for CH₄ combustion over both CuO60/γ-Al₂O₃, for which dispersion of the active component is low but loading is high, and CuO5.5/γ-Al₂O₃, for which dispersion of the active component is high but loading is low. There exists a maximum for CH 4 conversion based on the catalytic combustion mechanism at some temperatures, and when the bed temperature is higher than this temperature, the contribution of chemical-looping combustion is greater than that of catalytic combustion. The initial activity of CuO5.5/γ-Al₂O₃ is higher than that of CuO60/γ-Al₂O₃, while the stability of CuO60/γ-Al₂O₃ activity is better than that of CuO5.5/γ-Al₂O₃ activity under the same conditions.