還元褐鉄鉱のCO-H₂-H₂S混合ガスによる流動層中での炭化挙動:還元温度と炭化温度の影響

抄録

Iron ore particles of a limonite were completely reduced with H₂ at temperatures from 973 to 1273K in a laboratory scale fluidized bed. Then, at temperatures from 873 to 1073K, mainly at 973K, the reduced iron was exposed to H₂-H₂S mixtures (sulfur activity, a_s=0.5 or 0.1) for 3.6 ks and carbidized with 80%CO-H₂-H₂S mixtures at the atmospheric pressure. The integrated rate equation for first-order reaction, -ln(1-f_θ)=g(p_i, T)t; can be fitted very well to the carbidization curves. It is found that the carburization rate per reduced iron unit surface area g(p_i, T)/a_p⁰ slightly increases with increasing the reduction temperature. The value of g(p_i, T)/a_p⁰ decreases with increasing the specific surface area of reduced iron, a_p⁰, which increases with decreasing the reduction temperature, and increases with increasing the carbidization temperature. The specific surface area and sulfur content of the reduced iron does not largely change during most period of the carbidization, but both of them start simultaneously to increase just after free carbon deposition starts at the latest stage for the carbidization of reduced iron at 973K. The best temperatures for producing iron carbide are concluded to be 1123-1173K for reducing limonite iron ore and 973K for carbidizing the reduced iron.