流動層での予備還元鉄鉱石とCO-H2-H2S混合ガスの反応による炭化鉄の生成:還元率の影響

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In our previous studies of the iron carbide formation, the iron ore particles were completely reduced to metallic iron and then the reduced iron was carburized with CO-H_2-H_2S mixtures. However, the reactivity of the reduced iron seems to definitely influence the rate of the iron carbide formation. Therefore, in this study, at the atmospheric pressure and 873K, iron ore particles of hematite were first reduced to various reduction degrees with 50% N_2-H_2-H_2S mixture and second exposed to CO-H_2-H_2S mixtures with α_s=0.5. The remained iron oxides are reduced and then the fresh reduced iron ore of somewhat low sulfur contents is immediately carburized. It was experimentally confirmed that the lower the pre-reduction degree, the faster the carburization rate and the easier the formation of Fe_5C_2 and free carbon. The recommended condition for the fast and stable carbide formation is to be a low pre-reduction degree and the CO-H_2-H_2S mixtures containing less than 60% CO. From the microscopic observation of cross sections of samples, a new knowledge was obtained that the remained wustite and reduced iron are open to the reaction gas access through the pore of particles.
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