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Hydrogen-based Direct Reduction of Industrial...
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Hydrogen-based Direct Reduction of Industrial Hematite Pellets: An Experimental Investigation and Reaction Modeling

Abstract

This study investigates the kinetics of iron ore reduction using hydrogen gas, a critical step towards achieving a sustainable steel industry. Despite extensive studies, considerable discrepancies remain in interpreting the kinetics of iron oxide reduction, primarily due to variations in experimental methods, modeling assumptions, and material properties. A comprehensive approach that integrates kinetic analysis with detailed microstructural characterization is essential to address these complexities. To this end, a three-interface shrinking core model (SCM), consistent with physics-based principles and microstructural observations, is employed to describe the reduction process. This model accounts for multiple chemical reactions occurring at distinct interfaces within a solid particle. Isothermal reduction experiments were conducted at 800 ℃ using a custom-built thermogravimetric setup. Two types of industrial hematite pellets were studied: DR-grade (~68% Fe) and BF-grade (~65% Fe). Partial reduction experiments revealed the formation of distinct phase layers-iron, wüstite, and magnetite-progressing from the outer surface of the pellet towards its core. The chemical and phase compositions of the layers were confirmed using EDS and EBSD. SCM was validated against the experimental data and showed good agreement. Further model evaluation involved tracking the growth of the iron layer and comparing it with the FeO→Fe interface movement, which demonstrated a close match between microstructural observations and model predictions. These findings suggest that the model accurately incorporates multiple reaction steps, their respective kinetic parameters, driving forces, and the associated transport phenomena.

Authors

Zakeri A; Coley KS; Tafaghodi L

Pagination

pp. 1012-1017

Publication Date

January 1, 2025

Conference proceedings

Proceedings Icsti 2025 10th International Congress on the Science and Technology of Ironmaking

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