Current advances in slag foaming processes toward reduced CO2 emission for electric arc furnace steelmaking

Electric arc furnace (EAF) steelmaking offers significant advantages in terms of low CO₂ emissions, making it a promising avenue for achieving carbon peaking and carbon neutrality in the iron and steel industry. However, the conventional slag foaming practice through injection of fossil-based carbon (coal and coke) and oxygen still contributes most direct CO₂ emissions to EAF steelmaking. Development of low-fossil carbon even fossil carbon-free slag foaming technology has presented a new opportunity to further decrease the CO₂ emissions of EAFs. The present review systematically delves into the current advancements in EAF slag foaming processes to inspire and give valuable insights on near-zero CO₂ emission slag foaming technology. The foaming slag theory and evaluation models were first summarized. And then the strengths and weaknesses of most of distinct slag foaming processes, namely the conventional carbon-oxygen injection slag foaming process, the slag foaming process utilizing waste plastics and rubber, biomass chars, carbonates and nitrates, and the exogenous gas injection slag foaming process, were reviewed and analyzed from perspectives of foamy mechanism and performance, reduction of CO₂, industrial application and challenge. In general, the carbon-free exogenous gas injection or combined injection with biomass char exhibit the most promising potential among these slag foaming processes in terms of great CO₂ reduction and even near-zero CO₂ emission. Ultimately, the future prospects surrounding the development directions and industrial application challenge of low-CO₂ and near-zero CO₂ emission slag foaming technology were discussed and summarized.