Opportunities to reduce energy consumption and CO₂ emissions from ironmaking blast furnace using CO₂ electrolysis to CO for carbon recycling

Abstract

The blast furnace (BF) ironmaking is an energy-intensive process and the largest source of CO₂ emissions in an integrated steel mill. We evaluated the potential energy, fresh coke savings and associated reductions in CO₂ emissions for a BF operation if some CO₂ in the BF gases were converted to CO using an electrochemical CO₂ conversion process and that CO was recycled to the BF. As an added benefit, the electrochemical process produces H₂ and O₂, which helps iron ores reduction and oxygen enrichment. This paper presents a mathematical model of BF that integrates CO₂ capture, CO₂ electrolysis, and gas injection. Our results show that integrating a CO₂ to CO electrolysis process in a traditional ironmaking plant could reduce coke consumption from 386 kg/tHM to 260 kg/tHM at a 9% oxygen enrichment rate. A maximum 40% reduction in the CO₂ emissions per ton of hot metal can be reached. However, the total energy consumption of the process increases when the CO₂ electrolysis unit is included. Consequently, realising these potential CO₂ savings requires the availability of zero-carbon electricity from renewable sources. Improvements in the selectivity and efficiency of the CO₂ electrolysis in the future may enhance the overall economics and efficiency of this process.