Stability of Cementite under CO–CO₂–H₂ Gas Mixture at 1200 K

Abstract

Suppression of CO₂ discharged from iron and steelmaking companies is an example of the biggest issues for the protection of global environment and sustainable growth of steelmaking industry. One of the efforts made to decrease the emission of CO₂ in ironmaking process is blowing of hydrogen gas into blast furnace. Hydrogen gas can reduce iron oxide and form harmless H₂O. Cementite (Fe₃C) may be formed by introduction of hydrogen into blast furnace and play an important role on carburization and smelting behavior of reduced iron.
In the present work, Fe₃C sample was held at 1200 K under various CO–CO₂–H₂ gas mixtures to clarify the stability of Fe₃C phase. It was confirmed that metastable Fe₃C phase will decompose into Fe and C, and FeO will form under high CO₂ partial pressure. Also, it was found that existence of H₂ will suppress decomposition of Fe₃C. It was confirmed that CO₂ gas will be continuously converted into CO by C formed by decomposition of Fe₃C.