High-Temperature Phase Equilibria for Asymmetric Mixtures of Helium + m-Xylene and Nitrogen + m-Xylene

Lin, Ho-mu; Lee, Ming-Jer; Lee, Rong-Jwyn

doi:10.1021/ie00039a046

Cited by 8 publications

(12 citation statements)

References 15 publications

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“…12−15 In practice, to compensate for this limitation, binary interaction parameters between quantum gases and other compounds tend to be set much larger than normal. 16,17 As discussed by Prausnitz and co-workers 13,14 and recognized much earlier, 12 the corresponding states approach works well for classical gases but fails for gases whose critical properties are influenced by quantum phenomena. This problem is most severe for helium because it has one of the lowest critical temperatures of any gas (5.1953 K).…”

Section: ■ Introductionmentioning

confidence: 94%

“…They reported that they could obtain reasonable agreement only between the equations of state and the available pTxy data by employing "extraordinarily large (close to or greater than unity)" binary interaction parameters, 27 in some cases reaching 1.9. 16 It should be noted that there is sentiment in the literature that values of binary interaction parameters greater than unity are physically unrealistic: Ashour et al claim that values greater than unity violate the postulates of the kinetic theory of gases (ref 28, p 47). On the other hand, Jaubert and co-workers, whose "predictive" Peng−Robinson equation involves temperature-dependent binary interaction parameters exceeding 1.5, 9,22 are convinced that this is not a problem as long as the overall attractive contribution from intermolecular forces remains positive (ref 22, p 67).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Helium is an outlier in this regard. Compared to the classical gases, helium and other quantum gases (H 2 , its isotopic variations, and neon) do not conform well with the law of corresponding states. − In practice, to compensate for this limitation, binary interaction parameters between quantum gases and other compounds tend to be set much larger than normal. , …”

Section: Introductionmentioning

confidence: 99%

“…Although natural gas is composed predominantly of methane, heavy compounds possessing high boiling-point temperatures may also be present in gas mixtures, either due to natural occurrence or as chemical additives. Binary mixtures of helium with heavy compounds including paraffins, aromatic hydrocarbons, , and fatty alcohols were investigated by Lee and co-workers to test the Soave–Redlich–Kwong and Peng–Robinson cubic equations of state at high reduced temperatures. They reported that they could obtain reasonable agreement only between the equations of state and the available pTxy data by employing “extraordinarily large (close to or greater than unity)” binary interaction parameters, in some cases reaching 1.9 .…”

Section: Introductionmentioning

confidence: 99%

“…Binary mixtures of helium with heavy compounds including paraffins, aromatic hydrocarbons, , and fatty alcohols were investigated by Lee and co-workers to test the Soave–Redlich–Kwong and Peng–Robinson cubic equations of state at high reduced temperatures. They reported that they could obtain reasonable agreement only between the equations of state and the available pTxy data by employing “extraordinarily large (close to or greater than unity)” binary interaction parameters, in some cases reaching 1.9 . It should be noted that there is sentiment in the literature that values of binary interaction parameters greater than unity are physically unrealistic: Ashour et al claim that values greater than unity violate the postulates of the kinetic theory of gases (ref , p 47).…”

Section: Introductionmentioning

confidence: 99%

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Effective Critical Constants for Helium for Use in Equations of State for Natural Gas Mixtures

2017

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Most of the world’s helium supply is obtained by the cryogenic distillation of natural gas. Modeling the distillation conditions requires equations of state capable of predicting vapor–liquid equilibria over wide ranges of conditions. Equations of state, including cubic equations and multiparameter Helmholtz models, depend on the critical properties of pure substances for predicting various properties of multicomponent fluid mixtures. Predictions for helium are problematic as its critical point (5.195 K, 0.2275 MPa) is influenced strongly by quantum effects; large, empirical interaction parameters tend to be used in equations of state to compensate for these effects. Prausnitz and co-workers proposed an alternative approach using effective critical constants for quantum gases but demonstrated it for only three helium-containing binary mixtures. Here, we demonstrate that the use of an effective critical point at (11.73 K, 0.568 MPa) for helium substantially improves the prediction of VLE by the Peng–Robinson equation of state for 15 binary and 2 ternary mixtures, including the major components of natural gas. This effective critical point for helium was selected from a critical analysis of pTxy data for the (methane + helium) binary. The effective critical constants for helium are compatible with an acentric factor near zero, as expected for a small spherical molecule and similar to the acentric factors of heavy noble gases. The possibility of applying this approach to address recognized limitations of the GERG-2008 equation of state is discussed.

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