HWAHAK KONGHAK, Vol.18, No.1, 21-29, February, 1980
산화철 환원반응속도의 수학적 해석
A Mathematical Analysis of Reduction Rate of Iron Oxide
초록
수소에 의한 다공질산화철의 환원반응의 율속단계를 고찰하기 위하여 총괄반응속도식을 전개하였다. 총괄속도식은 산화철입자 표면에서의 기체의 경막물질이동, 환원철층에서의 기체확산 및 미반응 각계면에서의 화학반응을 동시에 생각하였다. 전개한 속도식에 문헌에 실린 실험데이타를 적용하여 환원속도의 율속단계를 고찰하였다. 그 결과 반응온도와 압력에 따라 약간의 차이는 있으나, 입자직경이 1 cm이하인 산화철입자에 있어서는 계면화학반응이 환원속도의 율속단계이나 그 이상에서는 환원철층내의 기체확산이 율속단계임을 알 수 있었으며, 입자표면에서의 경막물질이동속도는 무시될 정도였다.
또한 이러한 수학적 해석으로부터 산화철 환원속도에 대하여 계면반응영향보다 확산영향이 더 커지는 입자직경범위를 정확히 알 수 있었다.
또한 이러한 수학적 해석으로부터 산화철 환원속도에 대하여 계면반응영향보다 확산영향이 더 커지는 입자직경범위를 정확히 알 수 있었다.
A general rate expression based on a proposed reaction model has been developed to describe the rate-controlling process in reduction of porous iron oxide with hydrogen. Transport fluxes in the external boundary layer and the porous iron layer and kinetic flux at the unreduced core surface are considered simultaneously in driving the rate equation in gaseous reduction of iron oxide.
Quoting the experimental data appeared on the literatures, the developed rate equation was examined to consider the rate-controlling step for the reduction of iron oxide. Such analysis showed that the interface reaction is the controlling step for the particle sizes smaller than about 1 cm in diameter, while the gaseous diffusion is the controlling step for the larger particles. It was found that mass transfer of gas to the surface on the reduction rate can be neglected.
From the mathematical analysis on the reduction rate of iron oxide, the range of particle sizes in which the effect of the diffusion rate is greater than that of the interface reaction rate was also determined.
Quoting the experimental data appeared on the literatures, the developed rate equation was examined to consider the rate-controlling step for the reduction of iron oxide. Such analysis showed that the interface reaction is the controlling step for the particle sizes smaller than about 1 cm in diameter, while the gaseous diffusion is the controlling step for the larger particles. It was found that mass transfer of gas to the surface on the reduction rate can be neglected.
From the mathematical analysis on the reduction rate of iron oxide, the range of particle sizes in which the effect of the diffusion rate is greater than that of the interface reaction rate was also determined.