Life cycle assessment of blast furnace carbon footprint under different oxygen-enrichment rates

Oxygen-enriched blast technology for blast furnaces is widely used for its significant energy-saving and carbon-reduction potential. By injecting oxygen-enriched air and coal powder into blast furnaces, it raises the theoretical combustion temperature at the tuyere. This boosts coal injection rates, cuts coke consumption, and reduces the coke ratio while increasing output. However, its actual impact on fuel ratios and CO₂ emissions needs further study. A life cycle assessment model was built for blast furnace hot metal to explore the environmental and carbon footprint impacts of oxygen-enriched coal injection. The characterization results of different impact categories show diverse trends. Greenhouse gas emissions slightly increase, while toxic pollutant emissions decrease. When the oxygen-enrichment rate rises from 5.58% to 8.10%, the life cycle CO₂ emissions of hot metal increase from 1656.2 to 1698.1 kg/t (a 2.52% rise). In the production phase, CO₂ emissions from the blast furnace process rise from 749.1 to 798.6 kg/t, while those from the coking process fall from 172.7 to 168.3 kg/t. Sintering emissions also decrease. During the upstream stages and transportation process, indirect emissions from coal combustion rise, while the benefits derived from by-products diminish.