Showing papers by "Arthur D. Pelton published in 2009"

FactSage thermochemical software and databases - recent developments

Abstract: FactSage® was introduced in 2001 as the fusion of the F*A*C*T/FACT-Win and ChemSage thermochemical packages. The FactSage package runs on a PC operating under Microsoft Windows® and consists of a series of information, database, calculation and manipulation modules that enable one to access and manipulate pure substances and solution databases. With the various modules one can perform a wide variety of thermochemical calculations and generate tables, graphs and figures of interest to chemical and physical metallurgists, chemical engineers, corrosion engineers, inorganic chemists, geochemists, ceramists, electrochemists, environmentalists, etc. This paper presents a summary of the recent developments in the FactSage thermochemical software and databases. In the article, emphasis is placed on the new databases and the calculation and manipulation of phase diagrams and complex phase equilibria.

Thermodynamic Model and Database for Sulfides Dissolved in Molten Oxide Slags

Abstract: A thermodynamic model has been developed in the framework of the modified quasichemical model in the quadruplet approximation to permit the calculation of solubilities of various gaseous species (sulfide, sulfate, nitride, carbide, water, etc.) in molten slags. The model calculates the solubilities solely from knowledge of the thermodynamic activities of the component oxides and the Gibbs energies of the pure liquid components (oxides, sulfides, sulfates, etc.). In the current article, it is shown that solubilities of sulfur as sulfide in Al2O3-CaO-FeO-Fe2O3-MgO-MnO-SiO2-TiO2-Ti2O3 multicomponent slags, which are predicted from the current model with no adjustable model parameters, are in good agreement with all available experimental data. The article also provides a thorough review of experimental sulfide capacity data for this system. The model applies at all compositions from pure oxides to pure sulfides and from basic to acidic slags. By coupling this database with other evaluated databases, such as those for molten metal and gaseous phases, and with general software for Gibbs energy minimization, practically important slag/metal/gas/solid equilibria can be computed such as S-distribution ratios.

Thermodynamic Modeling of the Al2O3–Ti2O3–TiO2 System and Its Applications to the Fe–Al–Ti–O Inclusion Diagram

Abstract: All available thermodynamic and phase diagram data have been critically evaluated and optimized for the liquid slag phase and for all solid phases at 1 bar pressure from 298 K to above the liquidus temperatures for the systems Al2O3–TiO2, Al2O3–Ti2O3, and Al2O3–Ti2O3–TiO2, and a database of model parameters has been prepared. The Modified Quasichemical Model was employed for the molten oxide phase. The thermodynamic modeling predicts the existence of a liquid oxide Al2O3–Ti2O3–TiO2 phase at secondary steelmaking conditions. The database was used to calculate the inclusion diagram for Al–Ti deoxidation at 1600°C.

Thermodynamic Assessment of the Al-Mn and Mg-Al-Mn Systems

Abstract: The binary Al-Mn system has been critically evaluated based upon available phase equilibrium and thermodynamic data, and optimized model parameters have been obtained giving the Gibbs energies of all phases as functions of temperature and composition. The liquid solution has been modeled with the modified quasichemical model to account for short-range ordering. The results have been combined with those of our previous optimizations of the Al-Mg and Mg-Mn systems to evaluate and optimize the Mg-Al-Mn system. All available data for the ternary system are reproduced with only one small ternary model parameter for the liquid phase.

Thermodynamic assessment of the Ce–Si, Y–Si, Mg–Ce–Si and Mg–Y–Si systems

Abstract: The binary Ce – Si and Y – Si systems have been critically evaluated based upon available phase equilibrium and thermodynamic data, and optimized model parameters have been obtained giving the Gibbs energies of all phases as functions of temperature and composition. The liquid solution has been modeled with the Modified Quasichemical Model to account for the short-range ordering. The results have been combined with those of our previous optimizations of the Mg – Si, Mg – Ce and Mg – Y systems to predict the phase diagrams of the Mg – Ce – Si and Mg – Y – Si systems. The predictions have been compared with available data.

Thermodynamic and volumetric databases and software for magnesium alloys

Abstract: Extensive databases for the thermodynamic and volumetric properties of magnesium alloys have been prepared by critical evaluation, modeling, and optimization of available data. Software has been developed to access the databases to calculate equilibrium phase diagrams, heat effects, etc., and to follow the course of equilibrium or Scheil-Gulliver cooling, calculating not only the amounts of the individual phases, but also of the microstructural constituents.

A condensation model for the formation of chondrules in enstatite chondrites

Abstract: It is proposed that the chondrules in enstatite chondrites formed near the Sun from rain-like supercooled liquid silicate droplets and condensed Fe-Ni alloys in thermodynamic equilibrium with a slowly cooling nebula. FeO formed and dissolved in the droplets in an initial stage when the nucleation of iron was blocked, and was later mostly reduced to unalloyed Fe. At high temperatures, the silicate droplets contained high concentrations of the less volatile components CaO and Al2O3. At somewhat lower temperatures the equilibrium MgO content of the droplets was relatively high. As cooling progressed, some droplets gravitated toward the Sun, and moved in other directions, depleting the region in CaO, Al2O3, and MgO and accounting for the relatively low observed CaO/SiO2, Al2O3/ SiO2, and MgO/SiO2 ratios in enstatite chondrites. At approximately 1400 K, the remaining supercooled silicate droplets crystallized to form MgSiO3 (enstatite) with small amounts of olivine and a high-SiO2 liquid phase which became the mesostases. The high enstatite content is the result of the supercooled chondrules crystallizing at a relatively low temperature and relatively high total pressure. Finally, FeS formed at temperatures below 680 K by reaction of the condensed Fe with H2S. All calculations were performed with the evaluated optimized thermodynamic databases of the FactSage thermodynamic computer system. The thermodynamic properties of compounds and solutions in these databases were optimized completely independently of any meteoritic data. Agreement of the model with observed bulk and phase compositions of enstatite chondrules is very good and is generally within experimental error limits for all components and phases.

Thermodynamic modelling of the A12O3-CaO-FeO-Fe2O3-PbO-SiO2-ZnO system with addition of K and Na with metallurgical applications

Abstract: Computerized thermodynamic databases for the slag and solid oxide phases in the Al2O3CaO-FeO-Fe2O3-PbO-SiO2-ZnO system have been developed by critical evaluation/optimization of all available phase equilibrium and thermodynamic data. The database contains parameters of models for molten slag and solid oxide solutions such as spinel, melilite, olivine, monoxide (wustite, lime), corundum (hematite), etc. The polynomial and sublattice models were used for the solid solutions in this study. The modified quasichemical model was used for the liquid phase. Model parameters are derived by the optimization process to reproduce all thermodynamic and phase equilibrium data within experimental error limits. All binary, ternary and higher order sub-systems were optimised to obtain a self-consistent set of model parameters. This resulted in a significant improvement in the predictive ability of the computer model. The models permit extrapolation into regions of temperature and composition where experimental data are not available. The thermodynamic database is being extended to describe the effects of K and Na oxides – details of the recent thermodynamic optimisation of the Al2O3-Na2O-SiO2 system are presented. The thermodynamic databases are automatically accessed by user-friendly FactSage software that calculates complex multi-component multi-phase equilibria involving simultaneously slag, metal, solid and gas phases over wide ranges of temperatures and oxygen partial pressures. Industrial applications of the databases for the lead / zinc and iron metallurgical processes are discussed.

Thermodynamic modeling of dilute components in multicomponent solutions

Abstract: Those performing applied calculations with thermodynamic database computing systems often find that an essential component of a particular solution phase is missing from the database Provided that one is interested only in dilute solutions of this component, and only over a relatively narrow concentration range of the major components, the solution can often be treated with acceptable accuracy for practical purposes by assuming that the activity coefficient of the dilute component is constant, independent of composition over the composition range of interest (Henry’s Law) It is shown that, in this case, the only required model parameter, apart from the constant activity coefficient γ , is a constant ν , defined as the total number of independent species, not already present in the solvent solution, into which the dilute component dissociates That is, the equation for the chemical potential of the dilute component is independent of the model used for the solution in the database Consequently, simple software can be written permitting one to add dilute species to existing solution databases, while performing calculations, by supplying values only of the constants γ and ν A sample application is given of the calculation of Fe3+/Fe2+ and Cu2+/Cu+ redox ratios in a 9-component glass melt