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

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