Kinetics of hydrogen reduction of Brazilian hematite in a micro-fluidized bed

Abstract

Substituting hydrogen utilization for coke consumption is the main research field for the development of iron and steel manufacturing. Understanding the reaction kinetics of the reduction of hematite by hydrogen is essential for the rational utilization of hydrogen resources and the development of corresponding technologies. In the present study, the reduction process of Brazilian hematite with hydrogen (volume concentration from 10% to 25%) was conducted in a micro-fluidized bed at 600–800 °C. Results indicated that the external diffusion could be eliminated as the gas flow rate is higher than 400 mL/min (at NTP). The reaction rate of the reduction of hematite increased with increasing temperature and inlet H2 concentration. In order to analyze the multistep reaction kinetics, a multistep analysis method, which could be used to divide the reduction of hematite into three stages, was established and verified by various detections of reaction products. The reaction rates of Fe2O3→Fe3O4, as the conversion X is less than 0.11, and Fe3O4→FeO were controlled by phase boundary, and then progressively transformed into gas internal diffusion for FeO→Fe. The apparent activation energies of Fe2O3→Fe3O4, Fe3O4→FeO, and FeO→Fe were determined as 13.01–21.23 kJ/mol, 26.51 ± 0.56 kJ/mol, and 11.46 ± 0.10 kJ/mol, respectively.