Advanced kinetic modeling of Ruhrstahl–Heraeus decarburization: Comprehensive review and novel approach by coupling thermodynamics with tank-in-series reactor concept

: This work presents a reaction-site-based model for decarburization in Ruhrstahl–Heraeus (RH) vacuum degassing, a key secondary metallurgy process used to produce clean steels with very low dissolved gas and C contents. A review of experimental and modeling studies on vacuum decarburization provides the mechanistic basis and process parameters for the model. Four interacting reaction zones are considered: Ar bubbles, CO formation in the steel bulk, bath surface reactions, and droplet surface reactions. O 2 blowing and subsequent deoxidation by Al, Si, and Mn are also included. RH circulation and concentration gradients are represented using a tank-in-series concept instead of a single perfectly mixed volume. The coupled decarburization and deoxidation framework predicts the temporal and spatial evolution of steel composition during treatment and relates it to process conditions, including initial C content, O level, and vacuum performance. The model is validated using production data from twelve ultra-low carbon heats provided by voestalpine Stahl GmbH in Linz, Austria. For final C content, the RMSE and MAE are 7 ppm and 5 ppm, respectively; for O, they are 42 ppm and 31 ppm. Predicted Al additions for full deoxidation agree well with plant data, supporting the model’s use for RH process optimization.