Marie-Aline Van Ende

A Critical Evaluation and Thermodynamic Optimization of the CaO-CaF2 System

A critical evaluation and thermodynamic optimization of all the available literature experimental data of the CaO-CaF2 system was conducted to obtain a set of thermodynamic functions which can reproduce all available and reliable experimental phase diagrams and thermodynamic data. The liquid solution was described using the Modified Quasichemical Model which assumes the mixing of O2 and F− in the pseudo anionic sublattice and CaF2 solid solution was described using the compound energy formalism. The discrepancies in the CaO and CaF2 liquidii among the available experimental data were resolved. The recent experimental data on the solubility of CaO in solid CaF2 phase were well reproduced, which is critical to explain the eutectic temperature of the system.

A Kinetic Ladle Furnace Process Simulation Model: Effective Equilibrium Reaction Zone Model Using FactSage Macro Processing

The ladle furnace (LF) is widely used in the secondary steelmaking process in particular for the de-sulfurization, alloying, and reheating of liquid steel prior to the casting process. The Effective Equilibrium Reaction Zone model using the FactSage macro processing code was applied to develop a kinetic LF process model. The slag/metal interactions, flux additions to slag, various metallic additions to steel, and arcing in the LF process were taken into account to describe the variations of chemistry and temperature of steel and slag. The LF operation data for several steel grades from different plants were accurately described using the present kinetic model.

Thermodynamic optimization of the Dy–Nd–Fe–B system and application in the recovery and recycling of rare earth metals from NdFeB magnet

A critical evaluation and optimization of all reliable experimental thermodynamic properties and phase diagram data of the Dy–Nd–Fe–B system has been performed to obtain the best set of model parameters to describe the Gibbs energy of all phases in the system. Thermodynamic models with optimized model parameters can be used to predict unexplored phase diagrams and complex thermodynamic equilibria. The thermodynamic database of the Mg–Dy–Nd–Fe–B system was prepared by integrating the present model parameters to the FactSage light alloy database (FTlite) and was applied to perform comprehensive thermodynamic analyses of the selective extraction and purification process of Nd and Dy from the NdFeB permanent magnet scrap using molten Mg. Essential process parameters such as temperature, magnet to solvent ratio, vacuum pressure, heat requirement, etc. are determined in order to maximize the selective extraction of the RE metal from the magnet scrap and produce an RE alloy with low impurity content.

Chapter 5.4 – Process Modeling

Computational thermodynamic database combined with reaction kinetics are the ultimate tool to simulate complex multicomponent and multiphase processes. The general approach consists in breaking down the process in a series of small reactors or reaction zones, defining the inputs and outputs for each of them, specifying the connection between reactors, defining the reaction mechanisms taking place in the reactors and writing appropriate kinetic equations as a function of process parameters. This approach requires a deep understanding of the different reactions taking place during the process and provides an important tool for the analysis of plant problems. In this chapter, several ferrous and nonferrous process applications modeled with thermochemical programs will be investigated. The emphasis will be given to the method developed to model the process. Thermodynamic databases applied in Gibbs energy minimization codes combined with reaction kinetics are the ultimate tool to simulate complex multicomponent and multiphase processes. The general approach consists in breaking down the process into a series of small reactors or reaction zones, defining the inputs and outputs for each of them, specifying the connection between reactors, defining the reaction mechanisms taking place in the reactors, and writing appropriate kinetic equations as a function of process parameters. This approach requires a deep understanding of the different reactions taking place during the process, but then provides an important tool for the analysis of plant problems, the optimization of existing processes, and even the derivation of new process variants or design of completely new processes. In this chapter, several ferrous and nonferrous process applications modeled with thermochemical programs will be discussed. The emphasis will be given to the method developed to model the process.

Corrosion Behavior of Various Steels by AZ31 Magnesium Melt

During the production of magnesium and its alloys, the melt is in contact with steel at various stages of the process. Steel can be eroded and corroded through chemical reactions with molten magnesium and the protective gases such as SF6 or SO2. The dissolution rate and corrosion mechanism of steels in molten magnesium were investigated by the rotating cylinder method. The corrosion behavior of four steel grades, i.e. high carbon and low carbon steel, stainless steel 316 and 400 were examined for AZ31 melt under N2-l% SF6 gas atmosphere. The corrosion rates were found to be different depending on steel grades. It is found that the corrosion mechanism of steels in magnesium melts involves a two-stage process consisting of oxidation of Fe and its reduction by magnesium melt.