Evaluation of Biochar and Coke Blends for Slag Foaming Applications in Electric Arc Furnace Steelmaking

The electric arc furnace (EAF) is a promising approach to decarbonize the iron and steel industry. In EAF steelmaking, injecting carbon into the molten slag remains crucial for creating a foamy slag, which enhances the energy efficiency of the process and protects the furnace. Biochar (BC) has emerged as a potential alternative to traditional fossil carbon for slag foaming. However, fully replacing fossil carbon with BC poses technical challenges. In this study, the partial replacement of fossil carbon with BC is considered, in the form of a petroleum coke (petcoke) and BC blend. Interestingly, a blend of petcoke and BC matches or possibly outperforms either carbon type individually, due to a synergistic effect. Using an induction furnace to simulate EAF conditions, a synthetic slag is melted, and injection carbon is added into the slag layer. The slag foaming effectiveness of petcoke, BC, and three blend cases are studied. Thermogravimetric analysis reveals that the BC is more reactive with slag compared to petcoke, which leads to an initial high intensity of CO generation. However, the CO generation was not continuous or consistent. All experimental results are combined to propose a mechanistic description of the slag foaming behavior of BC blends.