Bio-carbon - the key to fossil-free steel production in an electric arc furnace

Through a detailed study on the interaction of biochar’s with slag, metal, and lining when producing steel in the Electric Arc Furnace (EAF) the aim is to identify the impact from various biochar properties. To cope with the competition on available biochars, it is an advantage if biochar produced from less pure biomass can be used. The biochar functionality must include slag foaming, reduction, and energy supply, without impairing the steel quality.

Carbon is a crucial element in Electric Arc Furnace (EAF) steelmaking. By reducing iron oxides, it facilitates generating foamy slag, controls temperature, and supplies energy. Traditionally, fossil carbonaceous materials such as anthracite, metallurgical coke, pet coke, etc. have been the primary sources of carbon. However, the use of these fossil carbonaceous materials leads to fossil CO2 emissions from the EAF steelmaking process. To reach their efforts to reduce the fossil CO2 emission, the steelmaking industry must find potential renewable carbon sources to replace fossil materials.

"Biochar, which is carbon-neutral and has properties resembling fossil coals, is gaining momentum as the steel industry strives towards a carbon-neutral future. The research up to now has identified several factors that influence the functionality of biochar in steelmaking. Further studies are still required not only to enhance the understanding of identified parameters’ impact on slag-carbon interaction but also to assess the efficiency of Swedish biochars” says Lena Sundqvist Öqvist, Professor in Process metallurgy.

Through the FINAST project, the research at the Luleå University of Technology aims to identify and evaluate the factors that influence the interaction between the EAF slag formed when operating with carbon-free directly reduced iron (DRI) and potential fossil-free carbon sources, with a focus on biochar alternatives available in Sweden.

The laboratory experiments, supported by thermodynamic calculations using FactSage, are conducted in the process metallurgy laboratory at Luleå University of Technology (LTU), that is part of the division of Minerals and Metallurgical Engineering. The biochar required for the experimental work are supplied by the Energy technology group at LTU, and by domestic biochar producers. The research is conducted in collaboration with the industrial partner, SSAB.

“In addition to evaluating the biochar parameters, it is very important to understand the various slag compositional parameters on the slag-biochar interaction”, says Gangadharan Seenivasan, the PhD student performing the laboratory experiments to address the effect of slag compositional parameters on the slag foaming with the selected biochar, under the supervision of the professors Lena Sundqvist Öqvist, Hesham Ahmed, and Anton Andersson.

This project is particularly important for the green transition in the steel industry and is supported by the EU Just Transition Fund and the Swedish Agency for Economic and Regional Growth under grant number 20358499.