KINETIC-ANALYSIS ON CO REDUCTION OF WUSTI TE PRIOR TO IRON METAL FORMATION BY MIXED CONTROL MODEL

Dense wustite plates have been reduced at 1273K with CO-CO2 gas mixtur e which has a chemical potential to form metallic iron. In early stage oi the reduction, no formation of metallic iron was observed and only the composition of the wustite changed. The composition change was fo llowed by the changes of the lattice parameter and the mass of the sam ple. 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-alpha/Ks). Pco (kg-oxygen/m(2) . s) where Ks and alpha are the Pco(2)/Pco ratio in the gas mixture in equi librium 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 X 10(-10). Ks(0.34)(k g-oxygen/m(2) . s . Pa). On the other hand, the inter-diffusion coeffi cient ($) over tilde D was independent of the iron ion vacancy concent ration y and was estimated as ($) over tilde D = 5.4 X 10(-10)(m(2)/s) at 1273K. The iron ion concentration profile, estimated from the latt ice parameter, and the mass change of the reduced wustite were explain ed reasonably by the model.