Deciphering Temperature‐Dependent Synergistic Mechanisms in Ammonia‐Mediated Iron‐Ore Reduction: Kinetic Optimization for Carbon‐Neutral Steelmaking

This study examines the direct reduction of iron ore using ammonia as a low‐carbon alternative to coke‐dependent blast furnaces in steelmaking. Experimental and thermogravimetric analyses of goethite (H1) and vanadium‐titanium ore (H2) reveal temperature‐dependent NH 3 synergies. H1 undergoes complete reduction at 900 °C with 5% NH 3 , while reduction at 700 °C requires 30% NH 3 . High temperatures (>850 °C) favor direct formation of Fe over Fe 3 O 4 /Fe 4 N intermediates, while crystalline water removal at 500 °C impedes reduction through steam generation. Kinetic analysis shows that the reduction degree of H1 is 20% higher than that of H2 at 950 °C/60% NH 3 . This can be explained by the porous structure of H1, unlike the dense Ti–Fe lattice in H2, where TiO 2 induces steric hindrance. The R1 kinetic model [ G ( α ) = −ln(1 − α )] effectively describes the reduction process, demonstrating a linear relationship between the reaction degree and NH 3 partial pressure. Specifically, increasing NH 3 concentration from 40% to 60% boosts degree constants by 48.4–60.4%. The findings position ammonia as a viable candidate for decarbonizing ironmaking, providing critical insights for optimizing reduction parameters and promoting sustainable steel production through fossil fuel substitution. Overall, this work addresses a critical knowledge gap in low‐carbon metallurgy and suggests actionable strategies for industry implementation.