Investigation of (H2–H2O) partial pressure on the gas-based reduction of fine iron ore in mixed gases (H2–H2O–CO–CO2–N2)

Abstract

The escalating demand for sustainable, green practices in the steel industry have accentuated the necessity of low-carbon technologies. One of the methods for CO2 mitigation is utilization of H2 in ironmaking process instead of CO-based reducing condition. This research focuses on understanding the utilization of H2 in CO-based iron making process, with an emphasis on the impact of the (H2 + H2O) partial pressure in mixed gases (H2–H2O–CO–CO2) with 10 vol% N2. To control the reducing conditions, the dimensionless indicators denoted oxidation strength (OS, (PH2O+PCO2)/(PH2+PH2O+PCO+PCO2)) and (H2 + H2O) partial pressure in H2–H2O–CO–CO2 (H, (PH2+PH2O)/(PH2+PH2O+PCO+PCO2)) were employed. Based on the reduction behavior and the kinetics analysis, the rate-controlling step of fine iron ore is mixed controlled reaction. It was revealed that a higher H and a lower OS correlate with the promoted internal diffusion of reducing gas and enhanced driving force for reduction, respectively. These characteristics facilitate the reduction rate. Also, reduction rate increased with higher temperature. As a results, the highest rate constant was 0.1863/min at temperature, OS, and H of 1273 K, 0.10, and 0.40. The lowest rate constant was 0.0433/min at temperature, OS, and H of 1073 K, 0.20, and 0.20. The apparent activation energy was calculated to be between 20 and 40 kJ/mol. Additionally, scanning electron microscopy and X-ray diffraction were utilized to analyze the variations in morphological characteristic based on reduction degree and (H2 + H2O) partial pressure in in H2–H2O–CO–CO2 with 10 vol% N2.

Keywords

• CO2 mitigation
• Direct reduced iron (DRI)
• Fine iron ore
• Hydrogen reduction
• Reduction behavior