EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In the present work, the state of steelmaking slags and their dephosphorization potential is re-evaluated using a computational thermodynamics approach. The thermodynamic simulations are carried out by coupling a newly developed thermodynamic database BOFdePhos to the software package FactSage TM. The non-ideal associate solution model is used for the description of the Gibbs energy of the liquid phase and the Compound Energy Formalism (CEF) for the description of the Gibbs energy of the solid solution phases, while the solid stoichiometric compounds are treated with simple temperature-dependent Gibbs energy functions.

The results indicate that steelmaking slags are heterogeneous for a large part of the blowing process, and are mostly saturated with silicates and/or with monoxide phases. The type and amount of solid phases is a strong function of the temperature, the oxidation state of FeOx, as well as the content of minor oxides such as MgO-, MnO- and Al2O3-content. The overall phosphorus distribution ratio Lp, between the heterogeneous slag and the liquid Fe solution, increased considerably when the solid phase 2CaO.SiO2-3CaO.P2O5 (C2S_C3P) was present while other phases such as 3CaO.SiO2, CaO-ss, and MgO-ss had a negative effect. Based on those findings, a new slag target region for achieving optimal dephosphorization results is suggested for the industrial process.