Carbidization Behavior of Reduced Limonite Iron Ore with CO-H_2-H_2 S Mixtures in Fluidized Bed: Influence of Reduction Temperature and Carbidization Temperature

摘要

Iron ore particles of a limonite were completely reduced with H_2 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 H_2-H_2 S mixtures (sulfur activity, a_s = 0.5 or 0.1) for 3.6 ks and carbidized with 80 percent CO-H_2-H_ S mixtures at the atmospheric pressure. The integrated rate equation for first-order reaction, - ln (j - f #theta#)=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~o_p slightly increases with increasing reduction temperature. The value of g(p_i, T)/~0_p decreases with increasing the specific surface area of reduced iron, a~0_p, 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 car-bidizing the reduced iron.