A Thermodynamic Model of the EAF Process for Stainless Steel

Abstract

A time-dependent thermochemical model has been developed for the electric arc furnace (EAF) process for stainless steel production. Time dependency is implemented by a stepwise input of energy and matter into an equilibrium reactor. The equilibrium calculations are performed using data from FACT-databases and implemented using the programming library ChemApp. The material input for the model was generated by reconciliation of industrial data and the energy input is approximated from the industrial data and scaled through an efficiency factor. The model is used to calculate the evolution of temperature and composition of gas, slag and metal phases with time. Agreement of the end composition in the metal phase with industrial data is good. In the slag phase, however, Cr, Fe, Mn and Si are oxidized significantly less than expected due to excess formation of CO-gas. The dynamics of the slag composition are examined in more detail. Here a fair agreement is reached for the main slag components. However, for Cr, Fe and Mn the model cannot predict the dynamics, which seem to be strongly kinetically controlled. The results of the equilibrium model can thus provide some insight into the kinetics of the process.

Determination of CaO–SiO2–MgO–Al2O3–CrOx Liquidus

“…Further, recycling of the slag requires mechanical and chemical stability, which also depend on the microstructure formed during cooling. Thermodynamic databases 6,7 may be used for process simulation 1,8,9 or for prediction of the microstructure after cooling 10 . However, uncertainty remains about the applicability of thermodynamic calculations in this important multicomponent slag system.…”

Experimental Determination of CaO–CrO–Cr2O3–MgO–SiO2 and Thermodynamic Modeling of the CrO–Cr2O3–MgO–SiO2 System

“…5,6 Magma streams or stainless-steel slags are complex multicomponent and multiphase materials, but when good thermodynamic descriptions are available, predictive tools can be developed. For instance, important processes in steel-making, such as chromium reduction, 7 slag solidification and modification, 8,9 or refractory degradation 10 may be modeled. By systematic analysis and evaluation of binary and ternary phase diagrams, such a thermodynamic description can be attained.…”

A Review of Mathematical Process Models for the Electric Arc Furnace Process

“…Some authors use a single parameter defined as the specific energy demand for each charged material and determine the progression of the meltdown according to the fraction of this energy that has been supplied up to the current point of time. [ 30,61,62 ] Shah et al [ 63 ] use a similar approach by dividing their pseudodynamic process model into predefined process steps that account first for the heating of the scrap to a certain temperature, then the melting, and for the final steps assume liquid steel for the calculation of chemical equilibrium. This simple energy balance approach is mainly used to determine the end of the meltdown and not to characterize the actual phenomena such as the change in geometry due to scrap melting and the resulting impact on heat flows.…”