甲烷在氧化铁表面还原NO的特性与反应机理研究

NO reduction by methane over iron oxides and the mechanism

在程序控温电加热水平陶瓷管反应器中,在300~1 050℃,对N2气氛中甲烷在氧化铁（充分氧化后的铁丝网卷）表面还原NO的特性进行了实验研究,测试了NO脱除效率、CO生成量以及反应后铁样品表面组分和微观状态的变化特点,分析了甲烷在氧化铁表面还原NO的反应机理。在此基础上,在1 000℃时,对模拟烟气条件下甲烷在氧化铁表面还原NO的持久性进行了实验研究。结果表明,甲烷在氧化铁表面能够高效地还原NO。在N2气氛下,在850℃以上达到100%的NO脱除效率。在模拟烟气中,甲烷在氧化铁表面脱除NO的能力具有很好的持久性。实验结果表明,在1 000℃时,采用由体积分数为2.0%的O2、16.8%的CO2和524×10-6的NO,N2配平的模拟烟气,1.17%CH4能够在连续100 h内保持100%的NO脱除效率,而未出现下降的趋势。对反应机理的研究结果表明,甲烷在氧化铁表面还原NO的机理包括甲烷通过再燃机理还原NO以及甲烷通过在氧化铁表面还原氧化铁为金属铁、金属铁进而直接还原NO两种主要反应机理。其中,后者为主要反应机理。

NO reduction by methane over iron oxides（fully oxidized iron mesh roll） was experimentally investigated in an one-dimensional electrically heated temperature programmed ceramic tubular reactor at 300 ~ 1 050 ℃ in N 2 atmosphere.The NO reduction efficiency,CO formation,the components variation and microstructures of the iron sample after reaction w ere measured.The reaction mechanism of NO reduction by methane over iron oxides w as proposed.A durable NO reduction by methane over iron oxides in simulated flue gas w as conducted at 1 000 ℃.Results show ed that methane w as very effective to reduce NO over iron oxides.In N 2 atmosphere,100% NO reduction efficiency w as achieved w hen temperature w as above 850 ℃.In simulated flue gas,very good durable performance w as demonstrated.1.17% vol.methane could reduce 100% NO over 100 h at 1 000 ℃ in simulated flue gas w hich contained 2.0% O 2,16.8% CO 2 and 524×10-6NO in N 2 base.Research results on the mechanism show ed that NO w as reduced w ith methane via tw o major routes： one is by reburning w hile the other is methane reduced iron oxides to metallic iron through redox reactions and then NO w as reduced by metallic iron.The latter mechanism w as believed to play the major role of NO reduction.