Integrating a Top-Gas Recycling and CO2 Electrolysis Process for H-2-Rich Gas Injection and Reduce CO2 Emissions from an Ironmaking Blast Furnace

Introducing CO2 electrochemical conversion technology to the iron-making blast furnace not only reduces CO2 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 CO2 lean top gas and CO2 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 CO2 capture and conversion reduces CO2 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.