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.