乙烷在金属铁表面还原NO的实验研究

温度300~1 100 ℃时,由程序控温电加热水平陶瓷管反应器在N₂气氛和模拟气氛下,对乙烷在金属铁表面还原NO的特性进行了实验研究。结果表明,乙烷在金属铁表面能够高效地还原NO。在N₂气氛中,温度高于900 ℃时,乙烷在金属铁表面的脱硝效率超过95%。在模拟烟气条件下,当温度超过900 ℃,且过量空气系数小于1.0时,乙烷在金属铁表面还原NO的效率能够达到90%以上。相同条件下,乙烷在金属铁表面脱硝效率高于甲烷的脱硝效率。SO₂对乙烷在金属铁表面还原NO的效率影响可以忽略。对反应后的铁样品的组分进行了XRD表征,在此基础上对反应机理进行了分析。结果表明,在模拟烟气条件下NO的还原通过乙烷的再燃脱硝和金属铁直接还原两个机理完成。金属铁直接还原NO时生成的氧化铁则被乙烷还原为金属铁,从而使得金属铁能够持续对NO进行直接还原。乙烷再燃还原NO的中间产物HCN被氧化铁氧化为N₂,同时氧化铁也被HCN还原为金属铁。这一过程增强了NO的持续还原反应,同时避免了在燃尽时HCN二次氧化重新生成NO,从而保证了较高的NO还原效率。

Experimental study of NO reduction by ethane over iron

NO reduction by ethane over iron was experimentally investigated in a one-dimensional temperature- programmed ceramic tubular reactor at 300~1 100 ℃ in nitrogen and simulated flue gas atmospheres. The results show that ethane can effectively reduce NO to N₂ over the surface of metallic iron. In N₂ atmosphere, more than 95% of NO is reduced by ethane over metallic iron when the temperature is higher than 900 ℃. In simulated flue gas atmosphere, more than 90% of NO is reduced by ethane over metallic iron above 900 ℃ when the excess air ratio is lower than 1.0. Under the same conditions, NO reduction by ethane over iron is higher than that by methane. The effect of SO₂ in simulated flue gas on NO reduction can be ignored. The iron samples were characterized with respect to their composition by XRD after reaction, and on this basis the reaction mechanism was further analyzed. There are two mechanisms for NO reduction, i.e., the reburning of ethane and direct reduction by iron. The iron is oxidized to iron oxides after reducing NO and then ethane reduces the iron oxides to metallic iron, leading to the sustainable and durable reduction of NO by iron. Meanwhile, NO is reduced by ethane through reburning to from the intermediate HCN that could be oxidized to N₂ by iron oxide, furthermore the iron oxides are reduced to iron simultaneously. This process enhances the NO reduction and prevents the additional NO formation due to the oxidization of HCN during burnout, leading to a high NO reduction efficiency.