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Dear Fellow Fluid-Inclusionists,
I need to compute fugacity of CO2 in a H2O-CO2-NaCL fluid with XCO2=0.2033, and about 6 eq.wt% NaCl (XNaCl = 0.0187) at 250 C and 200 to 400 bars. The system is in the field of immiscibility of the CO2-H2O-NaCl system.
The EOS given by Bowers and Helgeson (1983) is for higher T and P. An EOS based on correspondance states for CO2-H2O-NaCl has been given by Duan, Moller and Weare (1995) which is valid up to 300 C. The computation is however not easy. Others (as I understand) only deal with the CO2-H2O system.
I request members for literature/suggestions for the calculation. An explicit answer to the question is also welcome.
Hari Shankar Pandalai Department of Earth Sciences Indian Institute of Technology Powai, Mumbai 400076 India
Tel. Off. : (+91) (22) 5767265 Dept.: (+91) (22) 5767251 Res. : (+91) (22) 5770148 Fax Dept.: (+91) (22) 5767253 IIT : (+91) (22) 5783480 e-mail : pandalai@geos.iitb.ernet.in, pandalai@zircon.geos.iitb.ernet.in
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If you are referring to the paper of Duan et al. 1995 (Equation of state prediction of phase equilibria and volumtric properties), you are not quite right that the equation is valid up to 300 C. Rather the original formulation on which the paper is based (Anderko and Pitzer, 1993) treats the system only above 300 deg. so that all NaCl can be assumed to be associated and can behave as hard spheres. I think, you can calculate the fugacity coefficient, hence the fugacity, through the DMW equation. I myself have never computed the fugacity coefficient because I have not needed to do it. Correct me if I am wrong.
Regards.
Panigrahi
M.K.Panigrahi Department of Geology & Geophysics I.I.T., Kharagpur (WB) 721302 India
Fax: (91) 3222 55303
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Dr. Panigrahi was right.
The computer program EOSNHC that Dr. Duan gave me in 1995 was based on the paper by Duan, Moller, and Weare (GCA, 59, 2869-2882, 1995) for the system NaCl-H2O-CO2 for T=300-1000 C, and P=0-6000 bar, NaCl=0-30 wt% (or up to 50 wt% with less accuracy).
I believe the program is still available from Duan (<duan@chem.ucsd.edu>), who is traveling in China, and will be back at UCSD soon.
Regards,
I-Ming Chou
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I-Ming Chou Address: 954 National Center U.S. Geological Survey Reston, VA 20192 U.S.A.
Phone: +1 (703)648-6169 Fax: +1 (703)648-6383 or +1 (703) 648-6252 E-mail: imchou@usgs.gov
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