Comparison of CO2 capture economics for iron and steel mills

Abstract

One of the largest energy consuming manufacturing industries in the world is the iron and steel industry which emits almost 5% of the total world CO2 emissions. Previous studies examining the application of CO2 capture at iron and steel mills evaluated capture at conventional and Corex iron and steel mills. This study extends the analysis to include Hismelt, Midrex and the mini mill. In the first part of our study, we present a high level scoping assessment of the opportunities for implementing CO2 capture at existing direct atmospheric CO2 emission points. Implementing CO2 capture using commercial MEA solvent at a conventional iron and steel mill costs from A$ 80 to A$ 250 per tonne of CO2 avoided. Estimated costs to capture from the existing point sources at the Hismelt and Corex iron and steel mills also range from A$ 80 to A$ 250 per tonne of CO2 avoided. At a direct reduction iron process such as Midrex, the cost of CO2 capture from the process stack gas is estimated at about A$ 90 per tonne of CO2 avoided. A cost of approximately A$ 110 to A$ 130 per tonne of CO2 avoided is estimated to capture from the EAF unit of the steel production route for the Midrex and mini mill processes.Alternatively, CO2 can also be captured where it is produced from processes such as the blast furnace or reduction vessel. Although these streams contain a high level of CO2, they are used as a low-grade fuel throughout the plant and the produced CO2 is vented elsewhere. This study also estimates the cost of capturing the CO2 before further combustion and venting. The costs are estimated for the conventional iron and steel mill blast furnace, the top gas recycling blast furnace (TGRBF), Hismelt and Corex reduction vessel gases. Capture using MEA solvent absorption, the costs range from A$ 65 to almost A$ 80 per tonne CO2 avoided. Using Vacuum Pressure Swing Adsorption technology in place of MEA solvent absorption, the capture costs for these gases reduce by approximately 25–40%.