| Reduction kinetics of synthetic hematite has been studied in hydrogen and carbon monoxide atmosphere. The morphology of reduced layer was throughly investigated by means of optical and electronic microscopic technique. A general kinetic formula incorporated with the morphology was suggested, and computer simulation of reduction kinetics was attempted. Results withdrawn from experiments are as follows; 1) At temperatures lower than 700℃, the reduction is controlled by the pore-diffusion process, while at higher temperatures by oxygen diffusion process through oxide matrix. It was also found that overall reduction rate of iron oxide was controlled by the reaction stage wustite to iron. 2) Relative size of pore as well as number play an important role in the reduction process. Those relations could be well expressed by Pepper`s empirical equation Δε∝t^0.4 where Δε and t are changes of porosity and reaction time, respectively. 3) The parallel kinetic model in which both chemical reaction and gaseous diffusion process proceed in a parallel fashion was found to be the most adequate one, describing for the present system. The model equation was solved by means of Runge Kutta method. For boundary conditions given, the model equation was proved to be satisfactory, especially in the reduction of iron oxide by hydrogen. |
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