Evolution of NOx Precursors during Rapid Pyrolysis of Coals in CO2 Atmosphere

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• 作者：Xiangpeng Li ; Shihong Zhang ; Wei Yang ; Yi Liu ; Haiping Yang ; Hanping Chen
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：November 19, 2015
• 年：2015
• 卷：29
• 期：11
• 页码：7474-7482
• 全文大小：591K
• ISSN：1520-5029

文摘

To understand the effect of CO₂ on fuel N evolution during rapid coal pyrolysis, pyrolysis/gasification of EH lignite and HL bituminous coal were carried out in a suspension-bed reactor under N₂ or CO₂ atmosphere. The chemical and physical structures of the chars were measured by Fourier transform infrared spectrometry and X-ray diffractometry. The results show that higher temperature is favorable for the evolution of HCN and NH₃. Thermally stable quaternary N is believed to be the important intermediate for the formation of NH₃. The presence of CO₂ can promote HCN and NH₃ generation through the creation of H radicals and the cracking of N-containing groups. However, the HCN yields of HL coal pyrolyzed in CO₂ at 700 and 800 掳C are lower than that in N₂, and a similar result was obtained for EH coal at 1000 掳C, which are caused by the blocking effect of CO₂ and the reaction of HCN with CO₂, respectively. Structural analyses of the chars show that in the initial stage of coal pyrolysis/gasification, CO₂ can suppress the polymerization of aliphatic chains and more H is retained as 鈭扖H₂ or 鈭扖H₃ in chars. Subsequently, gasification of CO₂ with the rich aliphatic chains is helpful to produce abundant H radicals for the formation of NH₃.