Second and Third Virial Coefficients for Methane + Ethane and Methane + Ethane + Carbon Dioxide at (300 and 320) K

Abstract

Measurements of pVT made using the Burnett technique at (300 and 320) K are reported for methane, ethane, three x 1 methane + (1 − x 1) ethane mixtures with x 1 = 0.30623, 0.49971, and 0.70090, and two x 1 methane + x 2 ethane + (1 − x 1 − x 2) carbon dioxide mixtures with x 1 = 0.32125, x 2 = 0.34099 and x 1 = 0.24759, x 2 = 0.56013. Second virial coefficients have been calculated from these results for the pure fluids, and the binary and ternary mixtures. Cross second and third virial coefficients have been derived, including the cross third virial coefficient which describes the simultaneous unlike interaction between methane, ethane, and carbon dioxide. The experimental results were used to test an approximation to the virial equation which greatly simplifies calculations for multicomponent mixtures and which requires only experimental virial coefficients for binary mixtures. Values calculated using the model agree with experimental values within the estimated uncertainties. The results are compared with literature values, where available.

Second and third virial coefficients for (methane + ethane + carbon dioxide)

“…a Calculated from the GERG correlations. b Calculated using GERG correlations for pure component virial coefficients and unlike interaction coefficients from the study by Hou et al (2) second virial coefficients calculated from the GERG correlations and the combination of GERG correlations for pure component coefficients and Hou et al values for unlikeinteraction coefficients. There is also agreement, within experimental uncertainty, between both sets of calculated values and the experimental measurements from this study.…”

“…The δC i j values were calculated using equation (1) The calculated values at T = (300 and 320) K are taken from Hou et al (2) assuming that the composition of the mixture at T = 300 K is the same as the composition at T = 303.15 K for the present study and that the composition at T = 320 K is the same as that at T = 323.15 K. There are no experimental results available at these temperatures in the present study. …”

“…The only previously reported measurements on this ternary system were by Hou et al (2) in 1996 who measured mixture compression factors for two different mixture compositions at T = 300 K and T = 320 K. As full an understanding as possible of this mixture is important, because many natural gases, including the predominant New Zealand natural gas supplied from the Maui field, contain the three components. This study extends the temperature range of the ternary system measurements as well as providing a comparison between ternary measurements using a Burnett apparatus, in the Hou et al study, and measurements made by the direct method.…”

Partial Pressures in Thermodynamics of Classical Fluid Mixtures

“…For the calculation of thermodynamic partial pressures in gas mixtures we used a ternary mixture of methane, ethane and carbon dioxide at 320 K and at pressures up to 10 MPa. The state equation of this mixture, determined by (Hou et al 1996), permits the calculation of thermodynamic partial pressures, as well as of the classical partial pressures of types A and B. For the calculation of thermodynamic partial pressures in liquid mixtures we used a water solution of lithium hydroxide, for which densities as a function of mass fractions were given by (Söhnel and Novotný 1983) at 20 °C and atmospheric pressure.…”

“…All results are presented in Tables 1-4 and Figures 1 and 2 below. For the ternary gas mixture CH 4 (1)-C 2 H 6 (2)-CO 2 (3), the state equation (Hou et al 1996) takes the form of the following virial equation for pressure P as a function of molar volume V:…”