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Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly
2015 Vol.16 No.10 P.820-829
Effect of dilution of fuel in CO2 on the conversion of NH3 to NOx during oxy-fuel combustion
Abstract: The indirect chemical effects of fuel dilution by CO2 on NO formation were investigated numerically in this paper. CH4 doped with NH3 was used as fuel, while CO2 and O2 were mixed as oxidant. The dilution effect of CO2 was then investigated through adding extra CO2 to the reaction system. An isothermal plug flow reactor was used. An unbranched chain reaction mechanism is proposed to illustrate the chemical effects of CO2 on the H/O/OH radical pool and NOx. Due to the reaction between CO2 and H, extra NO will be formed in fuel-rich conditions, while NO will be inhibited in fuel-lean conditions and high CO2 dilution conditions. The reaction affected the radical pools of OH, H, and O of the branched chain reaction, and then the formation and reduction of NO. The pool of H had the greatest effect on NO reduction. The results suggest that the indirect chemical effects on NO formation differ between diluted fuel oxy-fuel combustion conditions and normal oxy-fuel conditions.
Key words: CO2, Oxy-fuel combustion, NO, Fuel dilution
创新点：提出一种无分支链式反应解释说明CO2在还原性粒子环境中对反应的影响。
方法：通过Chemkin Pro中塞流式反应器模块对混入NH3的CH4燃料在O2/CO2气氛中反应进行数值模拟，同时改变CO2的稀释程度来探索CO2浓度对NOx生成的影响，并比较不同反应机理下的模拟结果，探索此环境中NOx的生成机理（表1）。
结论：1. 无支链反应机理可用于解释CO2在还原性粒子环境中对NOx生成与还原的影响；2. 随着CO2浓度的升高，无支链反应和支链反应相互竞争H，进而抑制NO的生成；3. 在对NH3转化效率的影响方面，CO2浓度增加引发的无支链反应和支链反应对H的竞争，在富燃料条件下从促进转化变为抑制转化，在化学当量和贫燃料条件下从无影响变为抑制转化。
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DOI:
10.1631/jzus.A1300231
CLC number:
TQ534
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On-line Access:
2015-10-01
Received:
2013-07-04
Revision Accepted:
2015-07-27
Crosschecked:
2015-09-15