Evelyne Rauzy

A consistent correction for Redlich-Kwong-Soave volumes

Abstract If the volumetric and phase behaviour of a fluid mixture is calculated by means of an equation of state, certain translations along the volume axis may be effected that leave the predicted phase equilibrium conditions unchanged. This property may be exploited in the form at a consistent correction to improve volume estimations by the Redlich-Kwong-Soave method. Applications of this improved method to pure liquids, mixtures of liquids or gases, and petroleum fluids show that markedly superior volume estimations are obtained, except in the neighbourhood of the pure-component critical points; nonetheless, critical volumes for mixtures can be estimated correctly.

Excess functions and equations of state

Abstract In an extension of the development originally presented by Vidal, the connection between excess functions and equations of state is established by equating excess functions derived from the Guggenheims quasi-lattice theory to expressions derived from equations of state. The zeroth approximation of that theory is shown to be compatible with the classical van der Waals mixing rules, which may be a starting point for interesting methods founded on excess functions for correlating and predicting thermodynamic properties of fluids.

Group-contribution equation of state for correlating and predicting thermodynamic properties of weakly polar and non-associating mixtures: Binary and multicomponent systems

Abstract Abdoul W., Rauzy E. and Peneloux A., 1991. Group-contribution equation of state for correlating and predicting thermodynamic properties of weakly polar and non-associating mixtures. Binary and multicomponent systems. Fluid Phase Equilibria, 68: 47-102. The applicability of the “Guggenheim quasi-lattice excess function equation of state” formalism is tested through a zeroth approximation group-contribution model and a Peng-Robinson-type equation of state. The temperature-dependent correlations of the group-contribution model are derived from low-pressure excess enthalpy (HE) and vaporliquid equilibrium (VLE) binary data and are then extended to the prediction of high-pressure vapor-liquid equilibria of mixtures of weakly polar and non-associating compounds (i.e. hydrocarbons, CO2, H2S, N2). The numbers of binary systems, data sets and determinations used in the development and testing of the method are 169, 805 and 10634 for low-pressure VLE; 282, 789 and 11308 for HE; and 163, 1329 and 12272 for high-pressure VLE, respectively. The average relative deviation with experiment in bubble-point pressure is 1% and the average absolute deviation in vapor-phase composition is 0.005 for low-pressure VLE data. Heat effects are well reproduced with average deviations of 12 J for 7009 determinations of binaries with HE less than 300 J and 5.5% for 4299 determinations of binaries with higher HE. Owing to a term accounting for chain-length effects, the accuracy of the prediction of high-pressure VLE is not deteriorated by the group-contribution approach (average deviations of 3% in bubble-point pressure, 0.0103 in vapor-phase composition). Thus, in addition to its predictive power, the method is found to be an improvement over the classical Peng-Robinson procedure with constant binary interaction parameters, especially for mixtures of molecules of different sizes.

Vapor pressures of 12 alkylcyclohexanes, cyclopentane, butylcyclopentane and trans-decahydronaphthalene down to 0.5 Pa. Experimental results, correlation and prediction by an equation of state

Abstract Several improvements of the static device developed by the authors for measuring low vapor pressures are described: 1. a installation of a supplementary pressure gauge allowing the extension of the measurement range up to 200 kPa 2. b modification of the measurement cell in order to have a good degassing of the compounds (important step in low vapor pressure measurements). The apparatus was used to measure vapor pressure (0.5 Pa to 200 kPa) of 12 alkylcyclohexanes, cyclopentane, butylcyclopentane and trans-decahydronaphthalene. The experimental results correlated using Wagners equation are in good agreement with the available literature data. Experimental vapor pressures were then represented and predicted satisfactorily with a modified version of the Peng-Robinson equation of state in which the different parameters were expressed in terms of a group contribution method.

Low vapor pressures of 12 aromatic hydrocarbons. Experimental and calculated data using a group contribution method

As an extension to our previous work carried out on the measurements of vapor pressures for cycloalkanes [I. Mokbel, E. Rauzy, H. Loiseleur, C. Berro, J. Jose, Fluid Phase Equilibria, 108 (1995) 103] and polycyclic aromatic hydrocarbons [I. Mokbel, T. Guetachew, J. Jose, Eldata, Int. Electron. J. Phys. Chem. Data (1995) 167] we have performed a similar study for 12 aromatic hydrocarbons in the range 1 Pa to 200 kPa. The experimental results correlated with Wagners equation are in a good agreement with the available literature data. Experimental vapor pressures were then represented and predicted with a group contribution method.

Representation and prediction of thermophysical properties of heavy hydrocarbons

Abstract Thermophysical properties (vapor pressures, saturated liquid densities, heats of vaporization and saturated liquid heat capacities) of a wide variety of hydrocarbons present in petroleum fluids are calculated with a Peng-Robinson type equation of state. The form of the temperature dependent parameter found by Carrier et al. (1988) is slightly modified. Each component is characterized by three parameters: the normal boiling absolute temperature, the pseudocovolume and the shape parameter, both calculated by a Bondi-like group contribution method. A consistent correction which improves volumetric estimations is also developed using a group contribution model. The proposed approach yields good representation of pure component saturated properties.

Water dew points of binary nitrogen+water and propane+water mixtures. Measurement and correlation

Abstract A water dew point generation bench has been built and tested. Experimental measurements of dew point for binary nitrogen+water and propane+water were carried out between 1.01×105 Pa and 109.61×105 Pa and temperatures from 249.80 to 283.93 K. An excess function–equation of state method reproduces quite accurately the experimental curves independently of the pressure range.

Experimental vapour pressures of 13 secondary and tertiary alcohols—correlation and prediction by a group contribution method

Abstract Vapour pressures were measured using the static method for thirteen secondary and tertiary alcohols over the pressure range of 0.2 to 2000 Pa. Antoine equations are given in addition to the experimental values. A modified Peng–Robinson equation of state in which the covolume and attractive term were calculated by a group-contribution method was developed for primary alcohols. The proposed model leads to good results and is applied to secondary and tertiary alcohols.

Dew points of ternary methane+ethane+butane and quaternary methane+ethane+butane+water mixtures: measurement and correlation

Abstract Dew points for ternary methane+ethane+butane and quaternary methane+ethane+butane+water mixtures were determined experimentally between 4.77×105 and 99.45×105 Pa and at temperatures from 250.92 to 288.54 K. The experimental dew point curves of the mixtures with water were reproduced quite accurately with an excess function–equation of state method, independent of the temperature and pressure ranges.

Vapour-liquid equilibria calculations for normal fluid systems using a new cubic equation of state

Abstract Freze, R., Chevalier, J.-L., Peneloux, A. and Rauzy, E., 1983. Vapour-liquid equilibria calculations for normal fluid systems using a new cubic equation of state. Fluid Phase Equilibria, 15: 33–66. A new cubic equation of state is presented with a pseudocritical compressibility factor taken as substance-dependent. This equation leads to good phase-behaviour prediction for normal fluid mixtures up to the critical state, even in the case of binary systems involving a light and a heavy alkane, for which the equations of Redlich-Kwong-Soave and Peng-Robinson give poor results. With the volume correction proposed by Peneloux et al., this method also gives good estimates of the volumetric properties of pure compounds and mixtures, except in the neighbourhood of the pure-component critical points.