Review

Key measurement technologies for direct reduction ironmaking

TMT Tapping Measuring Technology S.à r.l., 32, rue d‘Alsace, Luxembourg 1122, Luxembourg

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Received: 29 August 2025
Accepted: 14 April 2026

Abstract

This work presents novel online in situ measurement technologies for real-time monitoring of gas utilization and metallization degree. A laser-based in situ gas spectrometer is used to measure all relevant gases – hydrogen, nitrogen, and water vapor – in 4 s, with an accuracy of 0.2 vol%. This instrument accurately measures H₂O, which is a process gas and poses a challenge for conventional technologies in conjunction with high H₂ content. An electromagnetic metallization degree sensor is used to identify the metallized iron components in the pellets, such as iron and iron carbide, via magnetic susceptibility and temperature. This measurement is validated with real material, enabling rapid and in-the-field feedback on the actual reduction grade of the material. The measuring solutions can be integrated into the direct reduction process using proven TMT probe solutions.