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.