Hydrogen-based direct reduction of steel by-product mill scale
(2026) International Journal of Hydrogen Energy — Vol. 221, p. 154185 (2026)
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- Authors
Stevens, Nicole 
Hessels, Conrad
- Abstract
- Hydrogen-based direct reduction (HyDR) of mill scale is a promising process for transitioning the steel industry towards more sustainable production. Previous studies focused on high temperature reduction of mill scale in shaft furnace, but sintering issues are encountered. To mitigate this problem, the reduction of mill scale particles was investigated at lower temperatures (400 °C-700 °C). Reduction experiments were conducted in a thermog-ravimetric analyzer (TGA) using pure hydrogen, both with and without pre-oxidation stage conducted between 700 °C and 900 °C and coupled with microstructure characterization. The highest reduction rate is obtained at 500 °C after pre-oxidation at 800 °C, governed by mixed phase boundary and 2D nucleation and growth mechanisms. Without pre-oxidation, unstable wüstite decomposes into Fe and Fe 3 O 4 as analyzed under both neutral and reducing atmosphere following a 1D nucleation and growth mechanism, while magnetite reduction to iron is governed by a phase boundary-limited mechanism.
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Citations
Kuypers, B., Stevens, N., Hessels, C., Jacques, P., Finotello, G., & Choisez, L. (2026). Hydrogen-based direct reduction of steel by-product mill scale. International Journal of Hydrogen Energy, 221, 154185. https://doi.org/10.1016/j.ijhydene.2026.154185 (Original work published 2026)