Experimental Determination of Slag Emissivities for Enhanced Slag Control by Infrared-Based Systems

For today's high-quality steel production, good control of slag composition is essential in secondary steelmaking. However, the conventional slag analysis practice, involving sampling, sample preparation, and analysis, is very time-consuming. This work is the first step toward an investigation of infrared (IR)-based systems and can be used for online slag composition monitoring using the principle that different slag compositions have different emissivities in the IR wavelength range. Therefore, this work experimentally determines emissivity values of slags as a function of composition at steelmaking temperature, since available data for slags are very limited in the literature. The emissivities of three different slag compositions belonging to the Al2O3-CaO-SiO2-MgO system are investigated at 1773 K. The investigated emissivities are in the range of 0.75-0.87, with the best repeatability seen in the slag which is fully liquid at 1773 K. Variations in emissivities are observed within the other slags due to the presence of solid phases. Although the data clearly indicate a difference of emissivities as a function of slag composition, further experiments must be performed to evaluate the emissivities of other characteristic slags at different temperatures in order to further assess the applicability of IR-based systems for slag composition control. This article addresses the need for comprehensive slag emissivity data as a first step toward assessing the applicability of infrared (IR)-based systems in online control of slag composition via laboratory-scale experiments. Results reveal the dependence of emissivity on composition, with further insights into the influence of solid-phase precipitates on the surface conditions of slags.image (c) 2024 WILEY-VCH GmbH