Effect of water vapor on the hydrogen reduction of iron oxide pellets

Abstract

The aim of this thesis was to perform isothermal and non-isothermal hydrogen reduction experiments of iron oxide pellets, and to investigate the effect of water vapor in reducing gas. Based on the results of isothermal experiments, kinetic parameters were fitted into mathematical models found in the literature. It was also considered how the results could be applied in practical direct reduction processes. In the theory part, practical direct reduction processes and hydrogen reduction of iron oxides were introduced. Information was collected on the rate and mechanism of hydrogen reduction of iron oxides and experimental parameters were determined for the experiments: temperature range (Isothermal: 800 °C, 900 °C and 1000 °C. Non-isothermal: 150-1000 °C), water vapor content (10 %, 20 % and 30 %), gas flow rate (2000 ml/min) and pellet mass (6 g). Additionally, the kinetic models to be used (Jander, R3, A3 and A4) were decided. The experimental part includes H2/H2O reduction (STA), characterization (FESEM), and kinetic model fitting. It was observed that as the temperature increased, the reduction rate increased and as the amount of water vapor increased, the degree of reduction decreased. Based on the TGA curves and model fitting, it was found that the effect of water vapor on the kinetics is more significant in the latter stage of the reduction (from magnetite to metallic iron). These findings clarify the role of water vapor in the hydrogen reduction of iron oxide pellets and provide valuable information for the optimization of reduction processes in industrial applications.