5 October — More than hydrogen: steelmaking decarbonization with current and likely near-term technologies
Date: 5 October 2022
Time: 12:00pm ET
Location: Wean Hall 3701 & via Zoom
Speaker: Chris Pistorius
Topic: More than hydrogen: steelmaking decarbonization with current and likely near-term technologies
Abstract: Decarbonization of ironmaking and steelmaking would ultimately rely on electrification, through production of hydrogen or direct electrolysis. As the steel industry transitions to electrification, there are several potentially cost-effective options along the way. Maximizing electric arc furnace (EAF) steelmaking is one of these. For U.S. conditions, Scope 1 and 2 emissions from EAF steelmaking amount to approximately 300 kg CO2 per tonne crude steel; about half of this could be saved by using renewable electricity. The other half is from burning carbon in the furnace, which has the benefits of foaming the slag (increasing electrical efficiency and avoiding nitrogen pick-up) and providing some energy. For slag foaming, charcoal from waste wood is a potential replacement for fossil carbon. Scrap is the lowest-carbon raw material for EAF steelmaking, but increased concentration of copper is a source of concern. Direct-reduced iron (DRI), produced with gaseous reductants, is a viable source of clean iron units. When using natural gas, CO2 emissions from DRI production are approximately 600 kg per tonne Fe; this would decrease to near zero with green hydrogen. With increased DRI use, a concern is the increased slag volume from gangue in the DRI. The increased slag volume would increase the electrical energy consumption, and the use of lime and doloma (which have significant carbon intensities). However, there does not appear to be a specific strong cut-off value of the slag volume above which conventional EAF steelmaking would become unfeasible. The implication is that the required composition of “DRI-grade” pellets can be revisited.
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