Kinetic Analysis on CO Reduction of Wustite Prior to Iron Metal Formation by Mixed Control Model

Abstract

Dense wustite plates have been reduced at 1273K with CO-CO₂ gas mixture which has a chemical potential to form metallic iron. In early stage of the reduction, no formation of metallic iron was observed and only the composition of the wustite changed. The composition change was followed by the changes of the lattice parameter and the mass of the sample. A mixed chemical reaction/solid state diffusion limited model was applied to the reduction rate. The reduction rate r was expressed by the following equation, r=k'·(1-α/Ks)·Pco(kg-oxygen/m²·s)
where Ks and α are the Pco₂/Pco ratio in the gas mixture in equilibrium with the surface wustite and that in the reducing gas mixture, respectively. The apparent chemical reaction rate constant k' changed with Ks and was expressed as follows, k'=1.18×10^-10·Ks^0.34(kg-oxygen/m²·s·Pa).
On the other hand, the inter-diffusion coefficient D was independent of the iron ion vacancy concentration y and was estimated as D=5.4×10^-10(m^2/s) at 1273K. The iron ion concentration profile, estimated from the lattice parameter, and the mass change of the reduced wustite were explained reasonably by the model.