Gas-Phase Reaction of NOX Formation in Oxyfuel Coal Combustion at Low Temperature

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• 作者：Ryo Yoshiie ; Takuya Kawamoto ; Daisuke Hasegawa ; Yasuaki Ueki ; Ichiro Naruse
• 刊名：Energy & Fuels
• 出版年：2011
• 出版时间：June 16, 2011
• 年：2011
• 卷：25
• 期：6
• 页码：2481-2486
• 全文大小：925K
• 年卷期：v.25,no.6(June 16, 2011)
• ISSN：1520-5029

文摘

Oxyfuel coal combustion with flue-gas recirculation is known to be one of the most promising methods for reducing CO₂ emissions from pulverized coal combustion power plants. In the oxyfuel system, the combustion atmosphere consists of only O₂ separated from air and flue gas recirculated from a stack. Therefore, the flue gas is dominated by CO₂ without any nitrogen. The most attractive potential aspect of oxyfuel coal combustion would be the ability to achieve a carbon capture and storage (CCS) system, which would be a 鈥渜uick-impact鈥?approach to reducing global CO₂ emissions. In the oxyfuel system, several minor components in the flue gases are also recirculated to the combustion zone, together with the CO₂. The effects of these additional impurities on the flue gas composition are one of our concerns. In this study, NO_X emissions were experimentally monitored in an oxyfuel coal combustion atmosphere. The effect of NO_X recirculation on NO_X formation in the combustion zone was investigated in particular. In addition, elementary reaction kinetics for NO_X formation was numerically analyzed under oxyfuel coal combustion conditions identical to the experiments. All experiments and numerical analyses were conducted at temperatures between 1073 K and 1223 K; these temperatures are relatively low, compared with various coal combustion conditions. In particular, this temperature range corresponds to fluidized-bed combustions. As a result, NO emissions under CO₂鈥揙₂ conditions were confirmed to be lower than those under 鈥渁ir鈥?conditions. In addition, the concentration of NO under oxyfuel conditions was unchanged by flue-gas recirculation. In contrast, the concentration of N₂O under CO₂鈥揙₂ conditions was higher than that under air conditions, and, furthermore, it was increased by flue-gas recirculation.