KINETIC ANALYSIS OF HYDROGEN REDUCTION OF VARIOUS HEMATITE PELLETS ON THE BASIS OF THE MULTI-STAGE ZONE-REACTION MODELS.

Hydrogen reduction of various hematite pellets (firing temperature, 1100 degree -1300 degree C; slag content, 0-10 wt%; basicity, (wt% CaO)/(wt% SiO//2) equals 0-2; total porosity, 0. 05-0. 45; reduction temperature, 800 degree -1000 degree C) is analyzed using the multi-stage zone-reaction model (MSZR1 model) and that with solid-state diffusion of oxygen dissolved in iron (MSZR2 model). In pellets having wustite particles encircled with dense iron (particle E), reduction curves and boundary radii calculated using the MSZR2 model agree with experimental data up to the final stage of reduction. In pellets having almost no particle E, the results calculated by the MSZR1 model agree with experimental data. It is confirmed that the reduction rate in the final stage varies according to the amount and diameter of particle E and reduction temperature. Expressions for chemical-reaction rate constants and effective diffusivities are presented as functions of temperature and porosity, respectively.