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

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 zerocarbon 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.

Automated summary

This study evaluates the potential energy savings and CO2 emissions reductions by converting CO2 in blast furnace gases to CO using an electrochemical process and recycling it back to the furnace. Modeling results show that introducing CO2 electrolysis can reduce coke consumption to 260 kg/tHM and achieve up to 40% reduction in CO2 emissions per ton of hot metal. However, realizing these savings requires zero-carbon electricity and improvements in the efficiency and selectivity of CO2 electrolysis.