Integrating a Top-Gas Recycling and CO(2) Electrolysis Process for H(2)-Rich Gas Injection and Reduce CO(2) Emissions from an Ironmaking Blast Furnace

Introducing CO(2) electrochemical conversion technology to the iron-making blast furnace not only reduces CO(2) emissions, but also produces H(2) as a byproduct that can be used as an auxiliary reductant to further decrease carbon consumption and emissions. With adequate H(2) supply to the blast furnace, the injection of H(2) is limited because of the disadvantageous thermodynamic characteristics of the H(2) reduction reaction in the blast furnace. This paper presents thermodynamic analysis of H(2) behaviour at different stages with the thermal requirement consideration of an iron-making blast furnace. The effect of injecting CO(2) lean top gas and CO(2) conversion products H(2)–CO gas through the raceway and/or shaft tuyeres are investigated under different operating conditions. H(2) utilisation efficiency and corresponding injection volume are studied by considering different reduction stages. The relationship between H(2) injection and coke rate is established. Injecting 7.9–10.9 m(3)/tHM of H(2) saved 1 kg/tHM coke rate, depending on injection position. Compared with the traditional blast furnace, injecting 80 m(3)/tHM of H(2) with a medium oxygen enrichment rate (9%) and integrating CO(2) capture and conversion reduces CO(2) emissions from 534 to 278 m(3)/tHM. However, increasing the hydrogen injection amount causes this iron-making process to consume more energy than a traditional blast furnace does.