Critical evaluation and optimization of the thermodynamic properties of liquid tin solutions
- PDF / 1,684,819 Bytes
- 19 Pages / 612 x 792 pts (letter) Page_size
- 26 Downloads / 208 Views
1.
INTRODUCTION
IN the production of plate glass by the float glass process, the molten glass cools while being drawn across the surface of a large pool of molten tin. It is important to be able to calculate the distribution of elements (impurities and additions) between the molten tin and glass phases, as well as to predict interactions with the gas phase and the precipitation of solid inclusions. To this end, the technique of global Gibbs energy minimization can be used to calculate the conditions for thermodynamic equilibrium. Several software packages are available to perform such calculations, such as the F*A*C*T (Facility for the Analysis of Chemical Thermodynamics) system developed in the authors' laboratory.t~ These programs require databases for the thermodynamic properties of the phases. The present article reports on the development of a thermodynamic database for 18 solute elements in molten Sn. The database should prove useful not only in calculations involving the float glass process, but also in other processes involving molten tin such as smelting operations. All available thermodynamic and phase equilibrium data were first collected for the binary and ternary systems of these elements with Sn. A technique of least-squares optimization was then used to obtain polynomial expressions for the excess Gibbs energies as functions of composition and temperature for all binary systems. These expressions are the best optimized Gibbs energy functions which are consistent with the data. In some binary systems, data were critically evaluated over the entire composition range so that the polynomial expansions apply to the entire system. In other systems, only the Sn-rich region was critically
MARIE-CLAUDE HEUZEY, formerly Undergraduate Student, Department of Metallurgy and Materials Engineering, Centre de Recherche en Calcul Thermochimique, Ecole Polytechnique, is Researcher, is with Hydro-Qu6bec, Varennes, PQ, Canada J3X 1SI. ARTHUR D. PELTON, Professor, is with the Department of Metallurgy and Materials Engineering, Centre de Recherche en Calcut Thermochimique (Center for Research in Computational Thermochemistry), Ecole Polytechnique, Montr6al, PQ, Canada H3C 3A7. Manuscript submitted April 13, 1995. 810--VOLUME 27B, OCTOBER 1996
evaluated. For the multicomponent solution of several solutes in molten Sn, solute-solute interaction terms in the polynomial expansion were evaluated from ternary data where available, or were estimated when data were lacking. In cases of strong solute-solute interactions, the existence of associated complexes in solution was postulated. The optimized excess Gibbs energies are presented as polynomial expansions and also in the form of "interaction parameters." The data were represented over as wide a temperature range as possible, but particular attention was given to the range from 600~ to 1100 ~ The article begins with a summary of the polynomial expansions and the thermodynamic relationships. The equivalence of the polynomial representation and the modified interaction parame
Data Loading...
