Sintered spheres of reagent grade hematite and particles of vermilion ore were reduced by carbon monoxide-carbon dioxide mixtures over the temperature range 820° to 920°C. If all the weight loss were assumed to occur at a single hematite-iron interface, then the early stages of reduction could be correlated by a series combination of the individual resistances due to boundary-layer transport, transport through the reduced iron shell, and interfacial chemical reaction. Sintering and cracking affected the reduction at later stages. Particle reducibility, measured as rate of weight loss, was independent of particle porosity.
Packed beds of similar sized vermilion ore particles were reduced with carbon monoxide-carbon dioxide mixtures at temperatures between 820° and 920°C. Barner's and Spitzer's methods of estimating fixed-bed reduction rates and exit gas compositions were modified to include the multiple-step, single-particle kinetic models. The resulting predictions of fractional reduction agreed closely with the present data; however, theoretical and experimental exit gas compositions differed considerably.