Research Progress on Fe-Loaded Biochar for Promoting the Co-Combustion of Coke Breeze

Abstract

Coke breeze remains an indispensable solid fuel in iron ore sintering and several high-temperature metallurgical combustion systems, but its high ignition temperature, poor burnout, and coupled CO/NOx emissions constrain clean and low-carbon utilization. Biochar derived from biomass is a promising partial substitute because of its renewable carbon origin, developed pore structure, and relatively high intrinsic reactivity. However, the rapid combustion of biochar, the large difference in mineral composition relative to coke breeze, and instability under harsh thermal conditions often limit its direct use. Fe loading provides a practical route to integrate fuel substitution with catalytic promotion. Recent studies on coal/biochar co-combustion, coke combustion catalysis, Fe-loaded char catalysts, and iron ore sintering indicate that Fe-loaded biochar can improve oxygen transfer, construct Fe-O-C interfacial active sites, accelerate the oxidation and gasification of carbon, and promote heterogeneous NO reduction while suppressing incomplete combustion. This review summarizes recent progress in feedstock selection, preparation methods, structure-property relationships, combustion and kinetic behavior, interfacial mechanisms, ash transformation, deactivation, and engineering prospects of Fe-loaded biochar for coke-breeze co-combustion. Particular attention is paid to the synergy among Fe redox cycles, alkali/alkaline-earth metals, and defect-rich carbon matrices. Finally, major knowledge gaps are identified, including the lack of in situ evidence under realistic heating rates, scale bridging from thermogravimetric tests to packed beds, and long-term stability evaluation in real metallurgical atmospheres.