Analysis of collaborative carbon reduction technology in hydrogen-based shaft furnace-blast furnace coupled production

The steel industry is fundamental sector of the national economy and also the largest carbon emitting industry in the manufacturing sector. Under the background of China's carbon peak and carbon neutrality goals, the steel industry faces urgent need for large scale deep carbon reduction. Hydrogen metallurgy, through replacing carbon with hydrogen, has become the most effective pathway to achieve deep decarbonization in the steel industry. Domestic trials of technologies such as hydrogen-based shaft furnace direct reduction and hydrogen rich blast furnace ironmaking have been conducted and have achieved significant carbon reduction effects. However, the current development of hydrogen metallurgy technology still faces the bottleneck of high cost of hydrogen rich reducing gas and the difficulty of coordinating carbon reduction with cost reduction. To address this challenge, this paper proposed a synergistic carbon reduction process coupling hydrogen-based shaft furnace and blast furnace production, taking into account China's energy structure and resource characteristics. This process fully utilized the respective smelting advantages of the hydrogen-based shaft furnace and the blast furnace while avoiding the economic disadvantage of the electric furnace melting separation step for direct reduced iron, thereby reducing production costs while achieving carbon reduction. A multi zone constrained mathematical model of the coupled hydrogen-based shaft furnace and blast furnace process was developed to systematically analyze the effects of three different reducing gas sources, namely natural gas, coke oven gas, and pure hydrogen, on the shaft furnace direct reduction process and the subsequent blast furnace smelting of direct reduced iron. The calculation results indicate that under current technical and market conditions, the coke oven gas shaft furnace and blast furnace coupled process is the most suitable technical route for promoting large scale low carbon metallurgy in Chinese steel enterprises. In this process, the optimal metallization rate of direct reduced iron in the shaft furnace direct reduction stage is approximately 90%, the coke oven gas consumption per ton of hot metal is 400 m³（normal state）, and the blast furnace fuel rate is 285 kg/t （including a coke rate of 165 kg/t）. The CO₂ emission per ton of hot metal in the coupled process is 1 090 kg, which is 30% lower than that of the conventional blast furnace process. The fuel cost per ton of hot metal is 601 yuan, which is 21% lower than that of the conventional blast furnace process.