Solubility of NaCl in CO2 at high pressure and temperature: First experimental measurements

摘要

NaCl solubility in gaseous carbon dioxide has been measured in the pressure range from 30 to 70 MPa at 623 and 673 K. Our originally-designed high pressure apparatus allows in situ sampling of a portion of the fluid phase for chemical analysis. The results indicate that the solubility of NaCl increases with both temperature and pressure, and is about 4-5 orders of magnitude higher than saturated NaCl pressure values at the same temperature conditions (6.02 x 10(-12) at 623 K and 1.51 x 10 at 673 K). It is also 1-2 orders of magnitude greater than predictions according to the Equation of State of the ternary H2O-CO2-NaCl system by Duan, Moeller and Weare [Duan, Z., Moller, N., and Weare, J. H. (1995) Equation of state for the NaCl-H2O-CO2 system: prediction of phase equilibria and volumetric properties. Geochim. Cosmochim. Acta 59, 2869] and has the opposite pressure dependence. The activity values of NaCl in the vapor phase, calculated from the experiments (with pure molten NaCl as a standard state in the vapor), have been fitted to the Darken Quadratic Formalism: RT In a(NaCl,v) = RT In x(NaCl),(v).x(NaCl,v)+ B-NaCl,v(G) where, x(NaCl,v) is mole the fraction of NaCl in the vapor phase, W-NaCl-Co2(G) = (1936.3 - 43.669 - P) x 10(6), B-NaCl-CO2(G) = 106 G, 83, 754 - 420.1 - P, where P is the pressure in MPa and T the absolute temperature. Caution should be exerted While extrapolating this empirical equation far beyond the experimental P-T-compositional range. (C) 2007 Elsevier Ltd. All rights reserved.