Modified SPHCT equation of state for improved predictions of equilibrium and volumetric properties of pure fluids

Shaver, R.D.; Robinson, Robert L.; Gasem, K.A.M.

doi:10.1016/0378-3812(95)02698-e

Cited by 9 publications

(8 citation statements)

References 32 publications

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“…When the relative change of compressibility factor with a previous iteration was smaller than 1.0x10 -8 , the iterations were terminated. This solution algorithm is more robust than that introduced by Shaver and coworkers [24].…”

Section: The Various Data Sets Used In This Workmentioning

confidence: 86%

“…In addition, the high sensitivity of the calculated properties to T * , as discussed by Shaver and coworkers [24], suggests that improvement in EOS predictions can be achieved by modifying the temperature dependence of the attractive term. A modified form for the radial distribution function of Equations (5) and (6) is…”

Section: Modification Of the Attractive Termmentioning

confidence: 94%

“…As such the attractive term of this equation, similar to other EOSs, contains several assumptions, which simplify its temperature and density dependence [5,7,13,24]. In this study, we have sought a greater flexibility in the structural and temperature dependence of the attractive term.…”

Section: Modification Of the Attractive Termmentioning

confidence: 99%

“…However, since both equations are based on molecule-molecule interactions, their application to asymmetric mixtures has not been as favorable [13,24].…”

Section: Introductionmentioning

confidence: 99%

“…They replaced the attraction term of the PHCT equation with the local composition model of Lee et al [16]. This equation has a comparable predictive capability to the SRK and PR equations in representing the phase behavior of simple molecules, and has a better capability for handling some asymmetric mixtures [13,24]. Although this equation has the advantages of a segment-interaction model, it suffers from several shortcomings, as we have described previously.…”

Section: Introductionmentioning

confidence: 99%

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Phase Behavior of Light Gases in Hydrocarbon and Aqueous Solvents

Gasem¹,

Robinson²

1998

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Under previous support from the Department of Energy, an experimental facility has been established and operated to measure valuable vapor-liquid equilibrium data for systems of interest in the production and processing of coal fluids. To facilitate the development and testing of models for prediction of the phase behavior for such systems, we have acquired substantial amounts of data on the equilibrium phase compositions for binary mixtures of heavy hydrocarbon solvents with a variety of supercritical solutes, including hydrogen, methane, ethane, carbon monoxide, and carbon dioxide.The present project focuses on measuring the phase behavior of light gases and water in Fischer-Tropsch (F-T) type solvents at conditions encountered in indirect liquefaction processes and evaluating and developing theoretically-based correlating frameworks to predict the phase behavior of such systems. Specific goals of the proposed work include (a) developing a state-ofthe-art experimental facility to permit highly accurate measurements of equilibrium phase compositions (solubilities) of challenging F-T systems, (b) measuring these properties for systematically-selected binary, ternary and molten F-T wax mixtures to provide critically needed input data for correlation development, (c) developing and testing models suitable for describing the phase behavior of such mixtures, and (d) presenting the modeling results in generalized, practical formats suitable for use in process engineering calculations.During the present period, the Park-Gasem-Robinson (PGR) equation of state (EOS) has been modified to improve its volumetric and equilibrium predictions. Specifically, the attractive term of the PGR equation was modified to enhance the flexibility of the model, and a new expression was developed for the temperature dependence of the attractive term in this segmentsegment interaction model.The predictive capability of the modified PGR EOS for vapor pressure, and saturated liquid and vapor densities was evaluated for selected normal paraffins, normal alkenes, cycloparaffins, light aromatics, argon, carbon dioxide and water. The generalized EOS constants and substance-specific characteristic parameters in the modified PGR EOS were obtained from the pure component vapor pressures, and saturated liquid and vapor molar volumes. The calculated phase properties were compared to those of the Peng-Robinson (PR), the simplified-perturbedhard-chain theory (SPHCT) and the original PGR equations. Generally, the performance of the proposed EOS was better than the PR, SPHCT and original PGR equations in predicting the pure fluid properties (%AAD of 1.3, 2.8 and 3.7 for vapor pressure, saturated liquid and vapor densities, respectively).A manuscript we have prepared for publication is attached in lieu of detailed technical information. EXECUTIVE SUMMARYThe Park-Gasem-Robinson (PGR) equation of state (EOS) has been modified to improve its volumetric and equilibrium predictions. Specifically, the attractive term of the PGR equation was modified to...

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Section: The Various Data Sets Used In This Workmentioning

confidence: 86%

Section: Modification Of the Attractive Termmentioning

confidence: 94%

Section: Modification Of the Attractive Termmentioning

confidence: 99%

“…However, since both equations are based on molecule-molecule interactions, their application to asymmetric mixtures has not been as favorable [13,24].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase Behavior of Light Gases in Hydrocarbon and Aqueous Solvents

Gasem¹,

Robinson²

1998

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Improving the simplified‐perturbed‐hard‐chain theory equation of state using a new non‐attracting hard‐sphere equation

2000

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Since Carnahan and Starling (1 969) formulated their hard-sphere equation of state, it has been used as the model of repulsion behavior in different equations of state. Carnahan and Starling (1972) showed the advantages of using their hard-sphere equation as the repulsion term in the van Since the development of the SPHCT equation of state, it was the subject of several research projects, i.e., Peters et al. In spite of the wide usage of the Carnahan and Starling (1969) equation of state, it suffers from the shortcoming associated with the close-packed limit. In fact, like many other hard-sphere equations of state proposed in the literature, the Carnahan and Starling ( 1 969) equation of state fails to satisfy the close-packed limit by predicting a finite value at this limit. Iglesias-Silva and Hall (1994) and Khoshkbarchi and Vera (1 997) attempted to solve this deficiency by introducing new hardsphere equations of state. Although the introduced hard-sphere equations of state satisfy the close-packed limit and show the same accuracy as the Carnahan and Starling ( 1 969) equation of state for low and moderate reduced densities, they are relatively complex. They are polynomial ratios with different orders in the numerator and denominator.This work introduces a new non-attracting hard-sphere equation of state. It satisfies the ideal gas and close-packed limits. It is, however, simpler than the expression given by Carnahan and Starling (1969

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