Kinetic analysis of iron ore powder reaction with hydrogen–carbon monoxide

Iron ore powder was isothermally reduced at 1023–1373 K with hydrogen/carbon monoxide gas mixture (from 0vol%H₂/100vol%CO to 100vol%H₂/0vol%CO). Results indicated that the whole reduction process could be divided into two parts that proceed in series. The first part represents a double-step reduction (Fe₂O₃→Fe₃O₄→FeO), in which the kinetic condition is more feasible compared with that in the second part representing a single-step reduction (FeO→Fe). The influence of hydrogen partial pressure on the reduction rate gradually increases as the reaction proceeds. The average reduction rate of hematite ore with pure hydrogen is about three and four times higher than that with pure carbon monoxide at 1173 and 1373 K, respectively. In addition, the logarithm of the average rate is linear to the composition of the gas mixture. Hydrogen can prominently promote carbon deposition to about 30% at 1023 K. The apparent activation energy of the reduction stage increases from about 35.0 to 45.4 kJ/mol with the increase in hydrogen content from 20vol% to 100vol%. This finding reveals that the possible rate-controlling step at this stage is the combined gas diffusion and interfacial chemical reaction.