Effect of Ore Types and Temperature on Sticking and Flowability of Direct Reduced Iron in a Hydrogen Fluidized Bed Reduction

Abstract Hydrogen ( $${\hbox {H}}_{{2}}$$ H 2 )-based fluidized bed reduction is a promising route for carbon-neutral ironmaking, but defluidization caused by interparticle sticking of $${\hbox {H}}_{{2}}$$ H 2 -Direct Reduced Iron (DRI) remains a major challenge. The present study examines the influence of sticking behavior and flowability on fluidized bed stability during $${\hbox {H}}_{{2}}$$ H 2 reduction. Experiments with hematite- and goethite-based ores revealed distinct fluidization behaviors. The hematite-based ore exhibited defluidization at 750 $$^{\circ }$$ ∘ C to 850 $$^{\circ }$$ ∘ C due to whisker-induced Fe layer formation, while the hematite-goethite-mixed ore remained stable without whisker formation. Quantitative rheological analysis confirmed that defluidization correlated with a transition from “Easy-Flowing” to “Cohesive” regime when interparticle cohesion exceeded a critical threshold. To prevent the defluidization, ore blending strategies were explored as a mean to satisfy the rheological properties identified in the present study. A 20 pct blending of hematite-goethite-mixed ore effectively ensured “Easy-Flowing” regime and lowered the chance of cohesion below the critical value, ensuring stable fluidization. These findings provide key insights into the sticking mechanisms of $${\hbox {H}}_{{2}}$$ H 2 -DRI and highlight the critical powder characteristics necessary to achieve a stable and efficient $${\hbox {H}}_{{2}}$$ H 2 reduction process.