Boletín de la Sociedad Geológica Mexicana   Volumen 62, núm. 2, 2010, p. 213-220 http://dx.doi.org/10.18268/BSGM2010v62n2a2

Ecuación para la Corrección Poynting en Termodinámica de Equilibrio de Fases Gases no Polares-Sistemas Acuosos. Aplicación al Sistema H₂S-H₂O-NaCl

José Martínez Reyes^1,*, Renee J. Pérez^2,3, Eduardo González Partida¹, Jorge A. Tinoco Michel¹

¹ Centro de Geociencias, Universidad Nacional Autónoma de México Campo de Juriquilla, Qro., México, apartado postal 76230.
² Department of Chemical and Petroleum Engineering, University of Calgary, 500 University Drive, Calgary Alberta, Canada, T2N 1N4.
³ ExxonMobil Upstream Research Company 3120 Buffalo Speedway, Houston, TX 77098.

^*This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

In this paper we used the semitheoretical expression for the partial molar volume at infinite dilution of volatile aqueous non-electrolyte solute (V₂⁰), developed by Plyasunov et al. (2000b) in order to propose a new equation for Poynting correction. The mathematical formula V₂⁰ considers as variables the density and isothermal compressibility of the solvent, as well as the second cross solvent-solute virial coefficient (β₁₂) and the second virial coefficient of pure solvent (β₁₁).

The equation was integrated analytically with respect to pressure using some auxiliary correlations found in the literature, and thereby obtain a mathematical expression of the isothermal pressure increment of the standard (infinite dilution) Gibbs energy (or chemical potential) of the solute (∆G₂⁰). The mathematical equation is applicable to solutes whose β₁₂ is known or can be estimated, in a temperature range of 273.16 K to 647 K, values of pressure up to 2 kbar and brines with ionic strength equal to 6 m NaCl. The expression fits the experimental data very well, as shown for the H₂S-H₂O-NaCl system (with maximum deviation of 7%), through a thermodynamic model that uses this formula proposal coupled with the Law of Henry and the Soave-Redlich-Kwong equation of state for modeling the liquid-vapor phase equilibria. Similarly, we propose an alternative expression for calculating V₂⁰ (with similar values of maximum deviation).

Keywords: thermodynamic modeling, Poynting correction.