Effect of CO/CH₄ on Redox of Iron during NO Reduction by XRD/SEM

Abstract

NO reduction by iron was conducted in a one-dimensional ceramic tubular reactor at 300 - 1100 °C with simulated flue gas of 0.05% NO in N2base. The evolution of metallic iron was investigated by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) methods. The effect of reducing gases including CO and CH4was analyzed on the redox of iron. Results showed that metallic iron was oxidized to its oxides after the reaction with NO. In N2atmosphere, Fe3O4was the major iron oxide at 550 °C and Fe2O3was the major iron oxide at 1100 °C. SEM image of the iron sample surface showed that the iron surface was smooth and dense after the iron reduced NO at 550 °C, however, the iron surface became porous after the iron reduced NO at 1100 °C. Reducing gas CO could reduce iron oxides to metallic iron. XRD result showed that a little FeO was found but metallic iron was still the dominant component of the iron sample after the reaction with NO in CO atmosphere. CO was not effective to maintain a durable NO reduction efficiency in simulated flue gas atmosphere while CH4was very effective. XRD result of the iron sample after the 100 hours durable test at 1050°C when 1.17% CH4was added into the simulated flue gas showed that the iron was not fully oxidized during the durable reaction.

Investigations of the reduction of NO to N2 by reaction with Fe under fuel-rich and oxidative atmosphere

“…Hayhurst and Lawrence speculated that the iron oxide is mainly FeO, with a small amount of Fe 2 O 3 [19]. Su et al [20,21] found that iron oxides content depended on temperature range. They concluded that Fe 3 O 4 was the major iron oxide at 550°C and Fe 2 O 3 was the major iron oxide at 1,100°C.…”