Sun Haifeng, Zhang Zhongnong, Sun Hanxiao, Yao Bin, Lou Chun
Huadian Electric Power Research Institute Co., Ltd., Hangzhou 310030, China.
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Entropy (Basel). 2022 Jul 1;24(7):922. doi: 10.3390/e24070922.
In this paper, a theoretical numerical analysis of the thermodynamics second law in ammonia/ethylene counter-flow diffusion flames is carried out. The combustion process, which includes heat and mass transfer, as well as a chemical reaction, is simulated based on a detailed chemical reaction model. Entropy generation and exergy loss due to various reasons in ammonia/ethylene and argon/ethylene flames are calculated. The effects of ammonia addition on the thermodynamics efficiency of combustion are investigated. Based on thermodynamics analysis, a parameter, the lowest emission of pollutant (LEP), is proposed to establish a relationship between the available work and pollutant emissions produced during the combustion process. Chemical reaction paths are also analyzed by combining the chemical entropy generation, and some important chemical reactions and substances are identified. The numerical results reveal that ammonia addition has a significant enhancement on heat transfer and chemical reaction in the flames, and the total exergy loss rate increases slightly at first and then decreases with an increase in ammonia concentration. Considering the factors of thermodynamic efficiency, the emissions of CO and NOx reach a maximum when ammonia concentration is near 10% and 30%, respectively. In terms of the chemical reaction path analysis, ammonia pyrolysis and nitrogen production increase significantly, while ethylene pyrolysis and carbon monoxide production decrease when ammonia is added to hydrocarbon diffusion flames.
本文对氨/乙烯逆流扩散火焰中的热力学第二定律进行了理论数值分析。基于详细的化学反应模型，模拟了包括传热传质以及化学反应在内的燃烧过程。计算了氨/乙烯火焰和氩/乙烯火焰中各种原因导致的熵产生和火用损失。研究了添加氨对燃烧热力学效率的影响。基于热力学分析，提出了一个参数——污染物最低排放（LEP），以建立燃烧过程中可用功与污染物排放之间的关系。通过结合化学熵产生分析了化学反应路径，并识别了一些重要的化学反应和物质。数值结果表明，添加氨对火焰中的传热和化学反应有显著增强作用，总火用损失率起初略有增加，然后随着氨浓度的增加而降低。考虑到热力学效率因素，当氨浓度分别接近10%和30%时，CO和NOx的排放达到最大值。从化学反应路径分析来看，向烃类扩散火焰中添加氨时，氨的热解和氮的生成显著增加，而乙烯的热解和一氧化碳的生成减少。
