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研究报告

苏亚欣,Benson B. Gathitu,Chen Weiyin.Fe₂O₃控制再燃脱硝中间产物HCN[J].环境科学学报,2011,31(6):1181-1186

Benson B. Gathitu
Department of Chemical Engineering, University of Mississippi, Oxford, MS 38677, USA

Chen Weiyin
Department of Chemical Engineering, University of Mississippi, Oxford, MS 38677, USA

摘要：再燃脱硝过程的中间产物HCN在燃尽过程的二次氧化对最终NO的脱除效率影响很大,有效控制HCN的转化对提高再燃脱硝的效率具有重要意义.以天然气和150目废轮胎粉为再燃燃料,利用模拟烟气在陶瓷管反应器中对典型条件下的再燃脱硝特性和中间产物HCN/NH₃的生成特性进行了实验研究.结果表明在典型的再燃条件下,随着再燃区空气系数的增大(再燃燃料的给料量减少),HCN的生成量逐渐下降,再燃过程生成的HCN的浓度远大于NH₃,表明HCN是主要的中间产物.进一步对HCN在不同温度下的分解特性以及在Fe₂O₃的催化作用下的还原特性进行了实验测试,发现Fe₂O₃能够有效地减少再燃过程HCN的生成,水蒸气和温度对Fe₂O₃的催化作用具有一定的影响.在再燃温度为1250 ℃,燃尽温度为1150 ℃,进口NO体积浓度为0.05%,烟气中水蒸气体积比为6.35%以及再燃段和燃尽段的空气系数分别为0.9和1.2条件下,当Fe的摩尔浓度为4000×10^-6时,废轮胎的再燃+燃尽脱硝效率达到88%.

Abstract：The re-oxidation of HCN during burnout strongly influences the final NO reduction efficiency by reburning. Effective control of HCN conversion is important to improve NO reduction efficiency. Natural gas and waste tire powders of 150-mesh were used as reburning fuel and experimental investigation of the reburning performance and HCN/NH₃ formation under typical reburning conditions were carried out with simulated flue gases in a ceramic reactor. Results showed that the amount of HCN decreased as the air/fuel ratio in the reburning zone increased. The HCN concentration was much more than that of NH₃ during reburning, which confirmed that HCN was the major intermediate product. Further experiments were conducted on the thermal decomposition of HCN and reduction of HCN catalysed by Fe₂O₃. Fe₂O₃ was effective in reducing the formation of HCN. Water vapor and temperature had an influence on Fe₂O₃ catalysis effectiveness. The NO reduction efficiency of 88% was achieved at a reburning temperature of 1250 ℃, burnout temperature of 1150 ℃, air/fuel ratio of reburning 0.9, air/fuel ratio of burnout zone 1.2, molar concentration of Fe 4000×10^-6 and volume fraction of water vapor in simulated flue gases 6.35%.