Abstract
Using a thermobalance, an industrial hematite pellet was reacted with pressurized H2-CO gas mixtures at temperatures of 9731073K to produce more effectively an iron carbide pellet. H2S of low pressures unable to form FeS was added to the mixtures not to precipitate soot. Gas pressurization to 5 atm enhanced iron carbidization rates a few times more than those under 1 atm. This carbidization occurred as soon as metallic iron was formed on the outer surface of pellet even when unreduced iron oxides remained inside, finally leading iron percarbide χ(FeχC, Monoclinic), not θ(Fe3C, Orthorhombic) as final products. During a moderate period, 4 phases of θ, Fe, FeO, and Fe3O4 existed macro-topochemically in turn from the outer layer. The lower temperature and the more gas pressure, the higher the iron carbidization rates. The minimum sulfur content in carbides was as low as 0.012 mass% S. Carbidization rates of a reduced iron pellet were analysed by an unreacted core model to investigate this process.
