Computed NOx emission characteristics of opposed-jet syngas diffusion flames
Computed NOx emission characteristics of opposed-jet syngas diffusion flames
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DOI：
10.1016/j.combustflame.2011.12.025
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发表时间：
2012-05
影响因子：
4.4
通讯作者：
Hsin-Yi Shih;Jou-Rong Hsu
中科院分区：
文献类型：
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作者：
Hsin-Yi Shih;Jou-Rong Hsu
本文对反射流合成气扩散火焰的nox排放特性进行了数值研究。窄带辐射模型与OPPDIF程序耦合，该程序使用详细的化学动力学和热输运性质来研究具有火焰辐射的一维逆流合成气扩散火焰。考察了合成气组成、压力和稀释气体对H2/CO合成混合火焰nox排放的影响。详细的火焰结构、化学动力学和氮反应途径分析表明，在常压下，在贫氢和富氢合成气火焰中，NOxare通过Zeldovich（或热）、NNH和N2O途径形成。Zeldovich路线是主要的NO形成路线。因此，与贫氢合成气火焰相比，富氢合成气火焰由于火焰温度更高而产生更多的NO。虽然NNH和N2O途径也是主要的NO形成途径，但大量的n2将从NNH和N2O物种中转化出来。对于富氢合成气火焰，NNH和N2O途径生成NO较少，其中NO可以更积极地通过NH+NO→N2+OH和NH+NO→N2O+H的反应消散。在较低压力下（0.01atm）， nnh -中间途径是NO的唯一生成途径。增加压力会增强NO生成反应，尤其是通过Zeldovich机制。然而，在更高的压力下（5-10atm），对于贫氢合成气火焰，NO通过反向的N2O途径转化回n2，对于富氢合成气火焰，NO也通过NNH途径转化回n2。此外，还研究了CO2、H2O和n2o对H2/CO合成气火焰NO排放的稀释效应。H2O稀释后的贫氢合成气火焰，由于NNH+O→NH+NO反应速率降低，NO产率最低。而对于co2稀释后的富氢合成气火焰，火焰温度明显降低，导致Zeldovich路径NO生成减少。
This paper reported a numerical study on the NOxemission characteristics of opposed-jet syngas diffusion flames. A narrowband radiation model was coupled to the OPPDIF program, which used detailed chemical kinetics and thermal and transport properties to enable the study of 1-D counterflow syngas diffusion flames with flame radiation. The effects of syngas composition, pressure and dilution gases on the NOxemission of H2/CO synthetic mixture flames were examined. The analyses of detailed flame structures, chemical kinetics, and nitrogen reaction pathways indicate NOxare formed through Zeldovich (or thermal), NNH and N2O routes both in the hydrogen-lean and hydrogen-rich syngas flames at normal pressure. Zeldovich route is the main NO formation route. Therefore, the hydrogen-rich syngas flames produce more NO due to higher flame temperatures compared to that for hydrogen-lean syngas flames. Although NNH and N2O routes also are the primary NO formation paths, a large amount of N2will be reformed from NNH and N2O species. For hydrogen-rich syngas flames, the NO formation from NNH and N2O routes are lesser, where NO can be dissipated through the reactions of NH+NO→N2+OH and NH+NO→N2O+H more actively. At a rather low pressure (0.01atm), NNH-intermediate route is the only formation path of NO. Increasing pressure then enhances NO formation reactions, especially through Zeldovich mechanisms. However, at higher pressures (5–10atm), NO is then converted back to N2through reversed N2O route for hydrogen-lean syngas flames, and through NNH as well for hydrogen-rich syngas flames. In addition, the dilution effects from CO2, H2O, and N2on NO emissions for H2/CO syngas flames were studied. The hydrogen-lean syngas flames with H2O dilution have the lowest NO production rate among them, due to a reduced reaction rate of NNH+O→NH+NO. But for hydrogen-rich syngas flames with CO2dilution, the flame temperatures decrease significantly, which leads to a reduction of NO formation from Zeldovich route.