Comparison of the characteristics and mechanism of CO formation in O2/N2, O2/CO2 and O2/H2O atmospheres. (15th December 2017)

• Record Type: Journal Article
• Authors: He, Yizhuo; Zou, Chun; Song, Yu; Luo, Jianghui; Jia, Huiqiao; Chen, Wuzhong; Zheng, Junmei; Zheng, Chuguang
• Is Part Of: Energy. Volume 141(2017)
• Page Start: 1429
• Page End: 1438
• Publication Date: 2017-12-15
• Subjects: Oxy-fuel combustion -- Oxy-steam combustion -- Reaction mechanism -- Plug-flow reactor -- CO; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2017.11.043
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: The characteristics and mechanisms of CO formation in O2 /CO2 and O2 /H2 O atmospheres were investigated both experimentally and numerically. Comparison experiments in O2 /N2, O2 /CO2 and O2 /H2 O atmospheres were performed in a flow reactor at atmospheric pressure covering fuel-rich to fuel-lean equivalence ratios and temperatures from 973 K to 1773 K. Experimental results demonstrated that CO formation in an O2 /CO2 atmosphere is the highest and that CO formation is the lowest under all fuel-rich, stoichiometric and fuel-lean conditions. The updated chemical kinetic mechanism satisfactorily reproduced the experimental results. For O2 /CO2 atmospheres, the presence of a high CO2 concentration enhances CO2 + H = CO + OH and CH2 (S) + CO2 = CH2 O + CO dramatically, strengthens HCO + M = H + CO + M by the chaperone effect of CO2, and contributes exclusively to CH3 OCO = CH3 O + CO. The contribution of the pathway CO2 → CO is significant, and CH3 → CH3 OCO → CH2 O and CH3 → CH3 OCO → CO are exclusive channels in O2 /CO2 atmospheres. For O2 /H2 O atmospheres, although the high chaperone effect of H2 O facilitates HCO + M = H + CO + M, CO + OH = CO2 + H is enhanced due to the abundant OH radicals and HCCO + H = CH2 (S) + CO is suppressed due to the lack of H radicals. The pathway CO→CO2 is enhanced due to sufficient OH radicals, and CH3 → (CH2 (S)) → CH3 OH → CH3 O → CH2 O and CH3 → (CH2 (S)) → CH3 OH → CH2 OH are exclusive channels. Moreover, the pathway CH2 O → HCO → CO is amplified in both O2 /CO2 and O2 /H2 O atmospheres. Highlights: The oxidation of CH4 in O2 /CO2 and O2 /H2 O atmospheres is evaluated experimentally. The chemical kinetic model predicts the experimental data satisfactorily. In O2 /CO2, CO2 → CO through H + CO2 = CO + OH is dramatically strengthened. In O2 /H2 O, CO → CO2 through CO + OH = H + CO2 is enhanced. The pathway CH2 O → HCO → CO is amplified in both O2 /CO2 and O2 /H2 O.