A modified Peng–Robinson equation of state for phase equilibrium calculation of liquefied, synthetic natural gas, and gas condensate mixtures

Abstract

A modified Peng-Robinson equation of state, MPR2 EOS, is introduced by incorporating a new alpha function and a temperature dependent function for covolume, b. The modified cubic EOS has three input per each substance: critical temperature, critical pressure, and acentric factor. The coefficients of temperature dependence of the alpha and beta functions, relating to the parameters a and b of the new cubic EOS, are obtained by simultaneous fitting of saturated experimental vapour pressure and liquid density data for several pure components. The percent absolute average deviation (AAD%) of 1.38, 4.80 and 2.89 are obtained to correlation of the saturation vapour pressure, liquid density and vapour volume, respectively. Also the ADD% of 2.575 is computed for prediction of saturation enthalpy of vapourisation of the pure compounds. For calculation of phase equilibrium of mixture, the modified PR EOS is used for prediction of liquid density of the LNG mixtures. Also the new EOS is applied for construction of the phase envelop of synthetic natural gas, SNG, mixtures and calculation vapour-liquid equilibria of gas condensates. The results demonstrate that the new MPR2 EOS can be used for calculation of vapour-liquid equilibrium of pure components and mixtures with good accuracy.Uneéquation de Peng-Robinson modifiée de l'Etat, EOS MPR2, est introduit en intégrant une fonction nouvelle alpha et une fonction dépendant de la température de covolume, b. L'EOS modification de cube a trois entrées pour chaque substance: la température critique, pression critique et le facteur acentrique. Les coefficients de dépendance de la température des fonctions alpha et bêta, relatives aux paramètres a et b de l'EOS nouveaux cubes, sont obtenus par montage simultané de données expérimentales de plusieurs composants pursà saturation. L'écart moyen absolu pour cent (AAD%) de 1,35, 3,09 et 2,22 sont obtenusà la corrélation de la pression de vapeur saturante, la densité du liquide et le volume de vapeur, respectivement. Aussi l'ADD de 2,21% est calculé pour la prévision de la saturation et de l'enthalpie de vaporisation des composés purs. L'EOS modifiée pour le calcul deséquilibres entre phases de mélange est utilisé pour la prédiction de la densité de liquides, des mélanges de GNL. Aussi l'EOS MPR2 nouvelle méthode est appliquée pour la construction de la phase de l'enveloppe de gaz naturel de synthèse, SNG, des mélanges. Les résultats démontrent que l'EOS MPR2 nouvelle peutêtre utilisé pour le calcul de l'équilibre liquide-vapeur des corps purs et mélanges avec une bonne précision.

On the Calculation of the Second Virial Coefficient of Pure Polar and Non-Polar Gases Using van der Waals and Dieterici Models; Temperature-Dependence Covolume Parameter

“…For example, van der Waals himself in 1913 had already pointed out that b could not be an entirely density-independence . Also, kinetic theory of gases suggests that the parameter b should be a function of temperature [24,25], it has been taken as a temperature dependent parameter in recent studies [26][27][28].…”

Valorization of Sewage Sludge via Gasification and Transportation of Compressed Syngas

“…Figure 2 presents the list of modeled syngas compositions (minimum and maximum values) with the scope of application of the GERG-2008 method. This creates a need to determine a new approach in the determination of the syngas compressibility coefficient that will make it possible to calculate this value for the syngas for the obtained ranges of constituents (those are values obtained for the gasification of SS under conditions mentioned in Table 3 and are the result of this work): In addition to the methods mentioned above dedicated to NG, other methods for determining the gas state, including syngas (e.g., the Redlich-Kwong equation, the Peng-Robinson equation, and others) [37,40] are known. Those methods rely on values of critical properties (critical temperature and critical pressure) of analyzed gas, which often requires to apply several mixing rules based on the gas composition.…”

“…• the analyzed gas is treated as a mixture of one-component real gases, • this model does not take into account phase changes occurring as a result of gas heating or compression, • it is assumed that in the tested range the mixture is in a gaseous or supercritical state, • compressibility factor values for mono-component gases are determined for a specific gas state, which corresponds to the modeled state of syngas, • the gas analyzed under STP conditions behaves like an ideal gas. In addition to the methods mentioned above dedicated to NG, other methods for determining the gas state, including syngas (e.g., the Redlich-Kwong equation, the Peng-Robinson equation, and others) [37,40] are known. Those methods rely on values of critical properties (critical temperature and critical pressure) of analyzed gas, which often requires to apply several mixing rules based on the gas composition.…”

Studies about an Equation of State for Pure Associated Fluids: Temperature Dependent Co-Volume Accounting a Physically Consistent Repulsive Term

“…Another way to improve phase equilibria representation considers the co-volume parameter (represented by b) to be temperature dependent. Fuller (Fuller, 1976), (Haman et al, 1977, Ravagnani and D'Ávila (Ravagnani & D'Avila, 1985), and Toghiani and Viswanath (Toghiani & Viswanath, 1986) proposed modifications of the SRK EOS considering the b parameter temperature dependent; (Xu & Sandler, 1987), (Nasrifar & Moshfeghian, 2001), and (Haghtalab et al 2011) proposed the b parameter to be temperature dependent for the PR EOS. All work showed that the agreement between experimental data and those calculated from equations of state was enhanced with b(Tr).…”