Green Ironmaking at Higher H₂ Pressure: Reduction Kinetics and Microstructure Formation During Hydrogen-Based Direct...

Area of Science:

• Materials Science
• Chemical Engineering
• Metallurgy

Background:

• Hydrogen-based direct reduction (HyDR) is a promising sustainable ironmaking technology to mitigate CO2 emissions in the steel industry.
• Current commercial HyDR processes operate at elevated pressures, but the specific influence of H2 pressure on reduction kinetics and microstructure is not fully understood.

Purpose of the Study:

• To investigate the effect of varying H2 pressures on the reduction kinetics of hematite pellets.
• To analyze the microstructural evolution of iron ore pellets under different H2 pressures during direct reduction.
• To provide insights for optimizing HyDR processes and furnace design.

Main Methods:

• Reduction experiments were conducted on hematite pellets using pure H2 at 700 °C under static (1, 10, 100 bar) and dynamic (1.3, 50 bar) gas conditions.
• X-ray diffraction (XRD) was used to analyze the phase composition of reduced pellets.
• Scanning electron microscopy with electron backscatter diffraction (SEM-EBSD) was employed for detailed microstructural characterization.

Main Results:

• H2 pressure was found to critically influence the reduction kinetics and the resulting sponge iron microstructure.
• Specific pressure-dependent changes in reduction rates and microstructural features were observed.
• The study provides quantitative data on the role of H2 pressure in hematite reduction.

Conclusions:

• H2 pressure is a crucial parameter that needs careful control in hydrogen-based direct reduction processes.
• The findings offer a basis for optimizing HyDR furnace design and operational parameters for enhanced efficiency and sustainability.
• Further research can leverage these insights to advance low-CO2 steelmaking technologies.