Kinetic analysis of spherical Wüstite reduction transported with CH₄ gas

Rapid in-flight reduction of fine iron ore transported with CO, H ₂ 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 wüstite fine particles. The spherical wiistite fine particle as fine iron ore was prepared to simplify the reduction rate analysis. Reduction temperature was varied from 1 373 to 1 573 K. As the result, fractional reduction of spherical wüstite by CH₄ gas reached over 80% at 1573 K within 1s. From the cross section observation of the particle after reduction, it was found that the periphery of the wüstite 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.