Synergistic gas–slag scheme to mitigate CO2 emissions from the steel industry

Improving the sustainability of the steel industry requires decarbonization strategies that are both technically and economically viable. The recovery of both material and heat on site is a promising approach but largely unexplored. Here we propose a scheme integrating heat recovery, carbon mineralization and the use of slag in cement production, along with the blast-furnace injection of hydrogen from off-gas. The proposed scheme, based on the synergistic use of coke oven gas and slag, can reduce CO2 emissions by 48% compared to the conventional approach. When coupled with an external gas supply from coal gasification or biomass pyrolysis, CO2 emissions can drop by 63% and 92%, respectively. The cost of avoiding CO2 emissions could be less than half the cost of conventional industrial capture and could be offset by the projected carbon price by 2030. For the steel industry in China, we find that the scheme is applicable to over 46% of existing steel mills, resulting in 16 provinces meeting the 2 °C target and 19 provinces surpassing the 50% national mitigation target. Overall, we have shown how a minor reconfiguration of the steel production process could substantially improve the sustainability of the steel industry.