Chapter 4:
From Phases to Method (Models) Selection
Abstract
Read the abstractTable of contents
See the table of contentsList of examples
- 4-1: Calculation of the condensation enthalpy of the acetone + water mixture with NRTL at a given pressure (1 bar)
- 4-2: Distribution coefficients in an ideal mixture (propane + n-pentane)
- 4-3: Comparison of phase envelope predictions for the ethane + n-pentane mixture
- 4-4: Behaviour of a methane + n-decane mixture and its models
- 4-5: Behaviour of the benzene + n-hexane mixture and its models
- 4-6: Calculation of the eutectic of para- and ortho-xylene
- 4-7: Comparison of experimental values and different model with H2 + n-hexane mixture
- 4-8: Prediction of a heteroazeotrope with total liquid immiscibility
- 4-9: Formation of hydrates
- 4-10: Example of a vapour-liquid-liquid equilibrium of an acid gas system in the presence of water
- 4-11: VLE and LLE calculation of the methanol + n-hexane mixture
Example 4-9: Formation of hydrates
To illustrate the fact that various model can lead to the same description of thermodynamic behaviour, figure 1 shows the pressure dissociation curve of methane hydrates as a function of temperature. Two models are compared with data of Verma (1974)[1]. Both models use the Kihara parameters in the Van der Waals and Platteeuw theory, but for the vapour phase, Parrish and Prausnitz use a modified Redlich-Kwong equation of state (EoS), while Youssef et al. employ the Cubic plus Association (CPA) EoS that explicitly takes into account the association of water by hydrogen bouding.
Figure 1: Dissociation conditions in PT diagram for methane hydrate (solid curve by Parrish and Prausnitz, 1972 [2]; dashed curve by Youssef et al. 2009[3]).
References
[1] VERMA V.K., Gas Hydrates from liquid Hydrocarbon-Water Systems, 1974.
[2] PARRISH W.R., PRAUSNITZ J.M., Dissociation Pressure of Gas Hydrates Formed by Gas Mixtures, Industrial & Engineering Chemistry Process Design and Development, 1972, 11, n°1, p. 26-35. http://dx.doi.org/10.1021/i260041a006
[3] YOUSSEF Z., BARREAU A., MOUGIN P., JOSE J., MOKBEL I., Measurements of Hydrate Dissociation Temperature of Methane, Ethane, and CO2 in the Absence of Any Aqueous Phase and Prediction with the Cubic Plus Association Equation of State, Industrial & Engineering Chemistry Research, 2009, 48, n°8, p. 4045-4050. http://dx.doi.org/10.1021/ie801351e