Abstract
As a fundamental study for clarifying the reduction phenomena of sintered iron ore in a blast furnace, iron oxide (H) and quaternary calcium ferrite (Cf) were prepared and its kinetic behavior at the final stage of reduction with CO–CO2 gas mixture was studied.
Reduction rate increased with increasing reduction temperature. Besides, it increased with increasing partial pressure of CO gas. Influence of gas composition on reduction rate is much larger than reduction temperature.
From comparisons of weight loss curves of H samples with that of Cf samples, reduction rate of H samples were faster than that of Cf samples in the same conditions.
Reduction reaction of H and Cf samples proceeded topochemically at higher temperature (1100°C), and proceeded non-topochemically at lower temperature (<1000°C). Besides, the reduction reaction of samples used CO rich gas proceeded topochemically. Structure of iron layer in H samples were different for temperature and gas composition. On the other hand, structure of iron layer in Cf samples were almost the same in all conditions.
Reduction data were analyzed by one interface unreacted core model, chemical reaction rate content kc and effective diffusion coefficient in product layer De were determined. The values of kc had Arrhenius-type temperature dependence, and were approximately same tendency except for Cf samples in near equilibriums gas compositions. The values of De obtained from Cf samples were approximately constant in all conditions.
