Abstract
In a previous paper, the present authors proposed a method of analysis for the reduction of iron-oxide pellets with hydrogen by the mixed-control mechanism of the intraparticle diffusion and the chemical reaction which involved the adsorption terms. This method has been applied to many experimental data on pellets reduced with hydrogen or a hydrogen-nitrogen mixture at 500° or 550°C. The reduction rate with the mixed gas is not proportional to the partial pressure of hydrogen. The degree of the reduction rate decreases more than that of the pressure.
In the case of the reducing gas diluted with an inert gas, the intraparticle diffusion coefficient is estimated from the concept of equimolal counter diffusion in three components and the apparent rate constant of the chemical reaction is presumed by adopting Thiele’s model at the reacting zone. When the diffusion resistance is relatively small, the above coefficients are given by Eqs. (14) and (21).
These equations have been applied to the data of reduction using nitrogen as diluent. As shown in Figs. 6 and 7, the calculated values of the diffusion and reaction coefficients coincide fairy well with the experimental values.
