Numerical analysis of blast furnace decarbonized gas for coke replacement in an oxygen-enriched blast furnace

The blast furnace decarbonized gas (BFDG) is a high-quality gas abundant in carbon monoxide (CO) and containing only minor amounts of carbon dioxide (CO₂). Its injection into the blast furnace (BF) presents a viable strategy for lowering fuel consumption and reducing CO₂ emissions, which contributes to the mitigation of the greenhouse effect. In this paper, through the thermal balance analysis of coke and BFDG in oxygen-enriched blast furnaces, where the blast contains 50 pct oxygen, a numerical model of the replacement ratio (RR) for BFDG to replace coke was established, and the theoretical calculation formula of RR was derived. The results show that under the normal operation conditions of the oxygen-enriched blast furnace, the RR of BFDG to coke is 0.167 kg/Nm³. Further analysis evaluated how the RR was affected by variations in the volume fractions of CO, H₂, and CO₂ in BFDG, as well as by oxygen enrichment rate, coke carbon content, and top gas temperature. Based on the model, carbon emissions were estimated at 786.7 kg/t of iron produced. Finally, the RR was verified through the actual operation data of the factory, the results confirmed that the model has good reliability and applicability.