甲烷在氧化铁表面还原NO的特性与反应机理研究

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 and the mechanism

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 N₂ atmosphere. The NO reduction efficiency, CO formation, the components variation and microstructures of the iron sample after reaction were measured. The reaction mechanism of NO reduction by methane over iron oxides was proposed. A durable NO reduction by methane over iron oxides in simulated flue gas was conducted at 1 000 ℃. Results showed that methane was very effective to reduce NO over iron oxides. In N₂ atmosphere, 100% NO reduction efficiency was achieved when temperature was above 850 ℃. In simulated flue gas, very good durable performance was demonstrated. 1.17% vol. methane could reduce 100% NO over 100 h at 1 000 ℃ in simulated flue gas which contained 2.0% O₂, 16.8% CO₂ and 524×10^-6 NO in N₂ base. Research results on the mechanism showed that NO was reduced with methane via two major routes: one is by reburning while the other is methane reduced iron oxides to metallic iron through redox reactions and then NO was reduced by metallic iron. The latter mechanism was believed to play the major role of NO reduction.