Excess Free Energies and Activity-Composition Relations for H{sub 2}O-CO{sub 2} Fluids at 400{degree}C and 1-4000 Bars
Experimentally determined excess molar volumes (V{sup ex}) for H{sub 2}O--CO{sub 2} fluids at 400{degree}C and 100-4000 bars have been used to calculate excess free energies (G{sup ex}) and activity-composition (a-X) relations for these mixtures. Excess free energies are continuously positive and asymmetric toward H{sub 2}O at all pressures up to 4000 bars, rising to peak values of approximately 1300, 1800, 2000 and 2100 J/mol at 500, 1000, 2000 and 4000 bars, respectively. Calculated activities for H{sub 2}O and CO{sub 2} vary correspondingly, increasing: substantially from 0 to 1000 bars, moderately from 1000 to 2000 bars, and slightly from 2000 to 4000 bars. In addition, because G{sup ex} is asymmetric toward H{sub 2}O at 400{degree}C and pressures up to at least 4000 bars, a-X relations for H{sub 2}O are distinctly different from a-X relations for CO{sub 2}. These results imply that H{sub 2}O--CO{sub 2} fluids are strongly nonideal at 400{degree}C and all pressures above approx. 300 bars, despite the fact that peak values for V{sup ex} decrease from approx. 50 cm{sup 3}/mol at 300 bars to approx. 1 cm{sup 3}/mol at 2000 bars, and remain small to pressures as high as 5000 bars. Excess free energies and a-X relations for H{sub 2}O--CO{sub 2} fluids at 400{degree}C and pressures up to 4000 bars calculated from semi-empirical equations of state generally suggest significantly smaller positive deviations from ideality.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 621562
- Report Number(s):
- CONF-9707107-1; ON: DE97008432; TRN: AD-a339 668
- Resource Relation:
- Conference: ISHR `97: 5th international symposium on hydrothermal reactions, Gatlinburg, TN (United States), 20-24 Jul 1997; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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