Rapid carbon-free iron ore reduction using an atmospheric pressure hydrogen microwave plasma

Abstract

CO2 emissions from steel production account for about 8% of the global anthropogenic CO2 emissions and the majority (over 70%) of these emissions occur during the reduction of iron ore to iron. Hence, the steel industry is striving to reduce its dependence on carbon-based energy sources and reducing agents, like the coke used in a traditional blast furnace. Approaches such as hydrogen-based direct reduction are being considered since they can drastically reduce the overall CO2 emissions of the steel-making process. Here, we report an electrified process for reducing iron ore particles using atmospheric pressure hydrogen plasma powered by microwave energy. The process has the potential to be entirely carbon-free and overcome common challenges of other hydrogen reduction approaches, including other plasma-based approaches. Relative reduction rates achieved are as high as 15.5% /s, on par or faster than the highest rates reported in the literature operating at lower temperatures and hydrogen concentrations. When compared to thermal reduction under otherwise close to identical conditions, the microwave plasma reduction is three to four times faster, suggesting the importance of plasma generated reactive species like atomic hydrogen. A promising mass scaling is observed, with increasing the mass load 50 times requiring only 7 times longer reaction, which points to a good potential for further scale-up of the technology.