Dissolution of Carbon-Containing Species in CaO–SiO₂–Al₂O₃ Slag

Abstract

The acceleration of the carburizing and melting processes in reduced iron is critical for reducing energy consumption and CO₂ emissions produced by the steel industry. The aims of the study were to clarify the carbon dissolution reactions and diffusion processes in molten slag. A combined approach utilizing Raman spectroscopy and XPS was employed to investigate the relationship between carbon-containing species and slag composition in the CaO–SiO₂–Al₂O₃ slag system. The Raman spectra indicated that carbon dissolved in slag in the form of carbides, carbonates, and graphitic structures. The proportion of carbide ions in the slag increased from 64.2% to 74.7%, and the proportion of graphitic structures decreased from 19.7% to 7.4% as the slag’s basicity increased. The carbon dissolution mechanism in slag involved the reaction of carbon with dissolved oxide ions and oxygen-containing anions in the slag. This formed carbon-containing species such as CO₃²⁻, C₂²⁻, and graphitic structures that diffused in the slag and subsequently underwent carburization and deposition at the iron interface.