A Percolating Path to Green Iron

ChemRxiv

Abstract

About 1.9 gigatonnes of steel is produced every year emitting 7\% (2.7 gigatonnes) of global CO$_2$ in the process. More than 50\% of the CO$_2$ emissions come from a single step of steelmaking, known as ironmaking. Hydrogen based direct reduction (HyDR) of iron oxide to iron has emerged as an emissions free ironmaking alternative. However multi-scale phenomena ranging from nanometers to meters inside HyDR reactors exhibit detrimental microstructure evolution which resists gaseous transport of H$_2$/H$_2$O, slows reaction rates and disrupts continuous reactor operation. To resolve the conundrum between atomic and reactor scales, we devise a percolation-theory model to reconcile nanoscale porosity with macroscopic properties relevant to reactor design models. Using synchrotron nano X-ray computed-tomography, we quantify the evolution of pores in iron oxide pellets, and demonstrate how nano-scale pore networks influence micro and macro-scale flow properties such as permeability, diffusivity and tortuosity. Our new modeling framework bridges the gap between scales and offers the criteria to accelerate HyDR by at least 5x via feedstock-reactor synergies based on percolation.

Authors 9

1. Subhechchha Paul
   Affiliation as printed

   stanford

2. Brinthan Kanesalingam

   Stanford University

   Affiliation as printed

   Stanford University

3. Yan Ma

   Max-Planck-Institut für Nachhaltige Materialien · Delft University of Technology

   Affiliation as printed

   Delft University of Technology

   Max Planck Institute for Sustainable Materials

4. Julie Villanova

   European Synchrotron Radiation Facility

   Affiliation as printed

   European Synchrotron Radiation Facility (ESRF)

5. Guillermo Carlos Requena Aachen

   Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) · RWTH Aachen University

   Affiliation as printed

   German Aerospace Center (DLR)

   RWTH-Aachen University

6. Stanley Chidubem Akpu

   Nnamdi Azikiwe University

   Affiliation as printed

   Nnamdi Azikiwe University

7. Dierk Raabe

   Max-Planck-Institut für Nachhaltige Materialien

   Affiliation as printed

   Max Planck Institute for Sustainable Materials

8. Ilenia Battiato

   Stanford University

   Affiliation as printed

   Stanford University

9. Leora E. Dresselhaus‐Marais

   Stanford University

   Affiliation as printed

   Stanford University