Rapid in-flight reduction of fine iron ore transported with CO, H2 and/or CH4 gas has been studied for direct use of fine iron ore in iron-making process. In this work, the mechanism and the kinetic of the reduction by CH4 gas were accurately investigated with spherical wustite fine particles. The spherical wüstite fine particle as fine iron ore was prepared to simplify the reduction rate analysis. Reduction temperature was varied from 1373 to 1573K. As the result, fractional reduction of spherical wüstite by CH4 gas reached over 80% at 1573K within 1 sec. From the cross section observation of the particle after reduction, it was found that the periphery of the wustite particle was metallized by reducing reaction and un-reacted wüstite core remained inside. Therefore, it was indicated that the reduction progressed topochemically in this experimental condition. In the reduction rate analysis, it was found out that the reduction rate by CH4 was higher than that by H2 or CO. From the carbon concentration analysis, it was found that the phase of the metallic shell during reduction was not only solid state but also liquid state. From the above-mentioned kinetic analysis, it was concluded that the reduction rate determining-step by CH4 was chemical reaction on Fe–FeO interface and the reduction of wüstite was preceded by the carbon dissolved into metallic shell from CH4 gas.
