Tracking Evolution of Reactive Species in Pellets During HyDR through combined X-ray and Neutron Imaging
9 affiliations
- 1Mechanical Engineering
- 2Stanford University
- 3Materials Science and Engineering
- 4Department of Mechanical and Aerospace Engineering
- 5Princeton University
- 6Andlinger Center for Energy and Environment
- 7PSI Center for Neutron and Muon Sciences, Forschungsstrasse 111, Villigen PSI, Switzerland, 5232
- 8Neutron Scattering Division, P.O. Box 2008, Oak Ridge, TN, USA, 37831
- 9SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, USA, 94025
Abstract
Steel production emits 3.6 Gtyr −1 of CO 2 , and the majority of these emissions come from a single step: ironmaking. Hydrogen-based direct reduction (HyDR) offers a lowemission alternative, producing H 2 O instead of CO 2 when operated with green H 2 . Though conceptualized in the 1930s, market adoption of HyDR remains limited due to reactor failures from sticking of iron-ore pellets. The sticking phenomenon is rooted in rate-limiting kinetics, where transport of reactive species competes with surface reaction to become the dominant process. We combine X-ray and neutron imaging to simultaneously resolve microscale pore network evolution and the spatial distribution of reactive species in two iron ore pellets, one non-fractured and one fractured, across three stages of reduction. We detect a consistent accumulation of hydrogenous species on the surface and interior of both pellets across all timepoints. Pellet pores > 10 2 µm, do not contribute to this accumulation, marking regions of efficient mass transport. Within the pellet interior, hydrogenous species are spotted in the pellet matrix and at pore boundaries. Isolated pore boundaries have up to 3× higher enrichment of hydrogenous species than the largest connected pore cluster, marking them as regions of poor mass transport. By quantifying permeability, diffusivity, and tortuosity, we show that improved bulk transport with reduction progress does not mitigate local trapping. Our findings connect hydrogenous species retention to pore network evolution and mass transport behavior. Insights from this study provide a basis for microstructural design strategies that could boost transport of reactive species and improve HyDR reactor performance.
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BibTeX
@misc{paul2026tracking,
title = {{Tracking Evolution of Reactive Species in Pellets During HyDR through combined X-ray and Neutron Imaging}},
author = {Subhechchha Paul and Zipeng Xu and Maha Yusuf and Zane Taylor and Anders Kaestner and Sergio Soria and Tz-En Chang and Jean-Christophe Bilheux and James Torres and Leora Dresselhaus-Marais},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008637/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008637/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Tracking Evolution of Reactive Species in Pellets During HyDR through combined X-ray and Neutron Imaging
AU - Subhechchha Paul
AU - Zipeng Xu
AU - Maha Yusuf
AU - Zane Taylor
AU - Anders Kaestner
AU - Sergio Soria
AU - Tz-En Chang
AU - Jean-Christophe Bilheux
AU - James Torres
AU - Leora Dresselhaus-Marais
PY - 2026
DA - 2026/09/10
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008637/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008637/v1
AB - Steel production emits 3.6 Gtyr −1 of CO 2 , and the majority of these emissions come from a single step: ironmaking. Hydrogen-based direct reduction (HyDR) offers a lowemission alternative, producing H 2 O instead of CO 2 when operated with green H 2 . Though conceptualized in the 1930s, market adoption of HyDR remains limited due to reactor failures from sticking of iron-ore pellets. The sticking phenomenon is rooted in rate-limiting kinetics, where transport of reactive species competes with surface reaction to become the dominant process. We combine X-ray and neutron imaging to simultaneously resolve microscale pore network evolution and the spatial distribution of reactive species in two iron ore pellets, one non-fractured and one fractured, across three stages of reduction. We detect a consistent accumulation of hydrogenous species on the surface and interior of both pellets across all timepoints. Pellet pores > 10 2 µm, do not contribute to this accumulation, marking regions of efficient mass transport. Within the pellet interior, hydrogenous species are spotted in the pellet matrix and at pore boundaries. Isolated pore boundaries have up to 3× higher enrichment of hydrogenous species than the largest connected pore cluster, marking them as regions of poor mass transport. By quantifying permeability, diffusivity, and tortuosity, we show that improved bulk transport with reduction progress does not mitigate local trapping. Our findings connect hydrogenous species retention to pore network evolution and mass transport behavior. Insights from this study provide a basis for microstructural design strategies that could boost transport of reactive species and improve HyDR reactor performance.
ER -