Table I.

Critical comparison of representative coke-reduction routes according to coke function, carbon-saving role, and industrial limitations

Strategy	Main coke function targeted	Carbon-saving role	Key industrial limitation
Low-rank coal/semi-coke	Chemical demand reduction	Partial fossil carbon substitution	High reactivity; weak hot strength
Biomass/biochar/bio-coke	Chemical demand reduction	Lower net fossil CO2 input	Supply limitation, quality variation, weak structural role
Carbon-bearing wastes/by-products	Chemical demand reduction	Waste carbon recovery	Impurity accumulation, slag chemistry, permeability
Auxiliary fuel injection (especially PCI)	Chemical demand reduction	Reduces coke as fuel and reductant	Combustion efficiency, raceway stability, thermal balance
H2-rich gas injection	Chemical demand reduction	Lowers carbon-based reduction demand	H2 cost, thermal balance, H2O-induced coke degradation
Hot-blast temperature, oxygen enrichment, and high-pressure operation	Chemical demand reduction	Indirect coke saving	Limited by furnace stability and operating window
Top-gas recycling/oxygen blast furnace	Chemical demand reduction	High CO2-reduction potential	CO2 separation, O2 demand, energy penalty, system integration
Burden and furnace structure optimization	Indirect reduction of structural demand	Maintains permeability at lower coke rate	Ore quality, softening-melting control
CO2-to-CO conversion	Chemical demand reduction	Reuses captured CO2 as reducing gas	Conversion efficiency, energy demand, reactor integration
Load-bearing packed-bed materials	Direct structural support	Potential structural coke replacement	Slag attack, abrasion, cost, recyclability, large-scale supply