Research and development of key equipment and engineering applications for direct reduction in pure hydrogen shaft furnace

The steel industry is the sector with the highest industrial carbon emissions nationwide. To achieve carbon neutrality, it is imperative to develop non-blast furnace ironmaking technologies. These represent green processes that help the steel industry improve its product and energy structure, reduce CO₂ emissions, and promote sustainable development. Hydrogen-based shaft furnace direct reduction, as the dominant direct reduction process, especially when combined with pure hydrogen metallurgy using upstream renewable energy sources, can play a key role in enabling near-zero carbon emissions in the steel industry. Based on the current development status of gas-based shaft furnaces both domestically and internationally, the technical issues of pure hydrogen reduction processes that require resolution are described in detail. The development of key equipment for pure hydrogen shaft furnaces is identified as particularly urgent. Given that pure hydrogen shaft furnace equipment technology is still in its infancy worldwide, available references and practical experience are extremely limited. After several years of technical research, the first demonstration line of pure hydrogen shaft furnace direct reduction developed by China Iron and Steel Research Institute Group (CISRI) was successfully commissioned. Breakthroughs were achieved in several areas, including pure hydrogen single-medium reduction and cooling of metallized pellets, high-temperature resistant and hydrogen corrosion-resistant discharge systems, modular regenerative high-temperature hydrogen electric heaters, dynamic sealing at the transmission joint of the shaft furnace, and high-temperature hydrogen multi-gradient adaptive injection systems. Verification tests using iron ore and vanadium-titanium magnetite confirmed that the developed process and equipment are safe and reliable. The experimental results show that, with a hydrogen heating temperature of 1 000-1 050 ℃ and a furnace pressure of 0.30-0.35 MPa, the metallization rates of iron oxide pellets and vanadium-titanium magnetite pellets after pure hydrogen reduction exceed 96% and 93%, respectively. The powdering rate passing through a 5 mm sieve is below 6% in all cases. Under the condition of unrecovered off-gas hydrogen, the hydrogen consumption per ton of reduced iron is approximately 10% higher than the theoretical value. The total electricity consumption for hydrogen heating and auxiliary systems is 873.7 kW·h per ton of reduced iron. On this basis, the research, development, and design of large-scale pure hydrogen shaft furnaces and associated equipment have been carried out. The 300 000 t and 600 000 t capacity pure hydrogen shaft furnaces currently under development are in the phase of engineering implementation.