Step-wise Reduction of Hematite Pellets with CO-CO₂ Gas Mixtures

A series of reduction experiments was made in which hematite pellets were reduced stop-wise from Fe2O3 to Fe3O4, Fe3O4 to FexO, and finally FexO to Fe by CO-CO2 mixtures of appropriate compositions in the temperature range from 800 to 1050°C. The hematite pellets were made of pyrite cinder and the porosity was approximately 13%. Experimental data for each reduction step were analyzed in terms of the mixedcontrol kinetics based on the isothermal unreacted-core model.The results obtained are summarized as follows:(1) Rate constants for the reduction steps of Fe2O3 to Fe3O4, Fe3O4 to FexO, and FexO to Fe are expressed, respectively, by following equations:kcm=exp (7.768-18.92×103/RT) (cm/sec)kcw=exp (12.18-28.80×103/RT) (cm/m)kcFe=exp (12.70-29.91×103/RT) (cm/sec)(2) Labyrinth factors of the reduction product layers of Fe3O4, FexO, and Fe are expressed, respectively. by following equations:log10ξm-0.382×10-2T-5.352 (-)log10ξw=0.159×10-2T-2.467 (-)log10ξFe-0.124×10-2T-1.734 (T≥1 173K) (-)log10ξFe-0.102×10-1T-12.25 (T<1 173K) (-)(3) Reduction curves calculated for each reduction step by using the rate parameters based on the unreacted-core model are in satisfactory agreement with experiments.