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Boletín de la Sociedad Geológica Mexicana
Print version ISSN 1405-3322
Abstract
MARTINEZ REYES, José; PEREZ, Renee J.; GONZALEZ PARTIDA, Eduardo and TINOCO MICHEL, Jorge A.. Equation for the Poynting correction in equilibrium thermodynamics between non-polar gas phases and aqueous systems: Application to the H2S-H2O-NaCl. Bol. Soc. Geol. Mex [online]. 2010, vol.62, n.2, pp.213-220. ISSN 1405-3322.
In this paper we used the semitheoretical expression for the partial molar volume at infinite dilution ofvolatile 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 (ΔG20). The mathematical equation is applicable to solutes whose β12 is known or can be estimated, in a temperature range of273.16 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.