As a fundamental study for clarifying the reduction phenomena of sintered ore in a blast furnace, mixtures of iron oxide and quaternary calcium ferrite (Cf) were prepared and its kinetic behavior at the final stage of reduction with CO gas was studied. Reduction rate increased with increasing reduction temperature regardless of mineral ratio. Influence of mineral ratio were small and reduction rate were similar in every sample at 1000°C and above. While at 900°C and below, reduction rate increased with increaseng amount of Cf. The reason thought to be due to that the dense iron layer on surface of iron oxide particle inhibits the reduction at inner phase. Reduction reaction proceeded topochemically at higher temperature. On the other hand, reduction reaction did not proceed topochemically at lower temperature. Besides reduction reaction of rich Cf samples proceeded topochemically. Reduction data were analyzed based on the two interface unreacted core model, effective diffusion coefficient in outer layer and inner layer were determined. Reduction curves calculated by using the rate parameters obtained by the analysis agreed with observed data very well at 1000°C and above. Therefore reduction rate of two minerals mixture sample can be analyzed based on the two interface unreacted core model above 1000°C.
