Synergistic coke enhancement via thermal dissolution soluble fraction and hydrogen: a microstructure strategy for low-carbon blast furnace

The synergistic effects of thermal dissolution soluble fraction (TDSF) and hydrogen-rich atmospheres on quality and solution loss kinetics of cokes were investigated. By integrating crucible coking tests, structural characterizations (optical microscopy, Raman spectrometer, scanning electron microscopy, nitrogen physisorption), and shrinking core modeling, it is demonstrated that 5 wt.% TDSF incorporation reduces coke reactivity index (CRI) by 3.3% and enhances coke strength after reaction by 6.0% with the introduction of 10% H₂ into the gasifying atmosphere. TDSF-induced anisotropic graphitization fosters fibrous/leafiet microstructures, elevating optical texture index and reducing defect density. Hydrogen addition further suppresses CRI by lowering CO₂ partial pressure and blocking active sites via competitive adsorption, thus stabilizing pore structure. Kinetic analysis reveals dual gasification regimes: interfacial reaction dominates below 1323 K, transitioning to ash-layer diffusion limitation above 1373 K. Steam addition reduces activation energy by 41% via enhanced carbon-H₂O interactions, accelerating gasification rates compared to CO₂. Conversely, H2 elevates interfacial resistance by 25% through reversed water-gas shift reaction. TDSF increases pore tortuosity, raising diffusion activation energy by 6.8% and extending reaction layer thickness for stabilized conversion. Optimal performance is achieved at 1323-1373 K with 5 wt.% TDSF blending, balancing structural integrity and gasification efficiency. These findings establish a microstructure-mediated strategy for coke enhancement in hydrogen-enriched blast furnaces, advancing low-carbon ironmaking technologies.