Reliable phase stability analysis for cubic equation of state models

Hua, James Z.; Brennecke, Joan F.; Stadtherr, Mark A.

doi:10.1016/0098-1354(96)00076-2

Cited by 50 publications

(44 citation statements)

References 14 publications

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“…However, the technique is general purpose and can be applied in connection with any model of the fluid phase. In addition to the solution of solid-fluid equilibrium problems, the methodology used here can also be applied to a wide variety of other problems in the modeling of phase behavior, 26,30,31,34,51 and in the solution of process modeling problems. 43 Table 1: Physical properties used in example problems.…”

Section: Discussionmentioning

confidence: 99%

Reliable Computation of High-Pressure Solid−Fluid Equilibrium

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Castier

et al. 2000

Ind. Eng. Chem. Res.

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The calculation of solid-fluid equilibrium at high pressure is important in the modeling and design of processes that use supercritical fluids to selectively extract solid solutes. We describe here a new method for reliably computing solid-fluid equilibrium at constant temperature and pressure, or for verifying the nonexistence of a solid-fluid equilibrium state at the given conditions. Difficulties that must be considered include the possibility of multiple roots to the equifugacity conditions, and multiple stationary points in the tangent plane distance analysis done for purposes of determining global phase stability. Somewhat surprisingly, these issues are often not dealt with by those who measure, model and compute high pressure solid-fluid equilibria, leading in some cases to incorrect or misinterpreted results. It is shown here how these difficulties can be addressed by using a methodology based on interval analysis, which can provide a mathematical and computational guarantee that the solid-fluid equilibrium problem is correctly solved. The technique is illustrated with several example problems in which the Peng-Robinson equation of state model is used.However, the methodology is general purpose and can be applied in connection with any model of the fluid phase.

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Section: Discussionmentioning

confidence: 99%

Reliable Computation of High-Pressure Solid−Fluid Equilibrium

Scurto

Castier

et al. 2000

Ind. Eng. Chem. Res.

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“…However, as noted above, knowledge of the stationary points may be useful for initializing the phase split computations, so we typically use IN/GB to find all the stationary points. These procedures are outlined in more detail by Xu et al 7 , and further details are given by Hua et al 34,35 and Schnepper and Stadtherr. 36 Properly implemented, the IN/GB technique provides the power to find, with mathematical and computational certainty, enclosures of all solutions of a system of nonlinear equations, or to determine with certainty that there are none, provided that initial upper and lower bounds are available for all variables.…”

Section: Interval Analysismentioning

confidence: 99%

Phase Behavior and Reliable Computation of High-Pressure Solid−Fluid Equilibrium with Cosolvents

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Brennecke

et al. 2003

Ind. Eng. Chem. Res.

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The identification of the correct, stable solution to a phase equilibrium problem, given a particular thermodynamic model, is essential for the design of separation processes.It is also important in the selection of an appropriate model to represent experimental data.The need for a completely reliable method to test for phase stability is particularly pressing when the number of phases likely to be present is not intuitive to the user, as is frequently the case with high-pressure systems. Previously, we have a presented a completely reliable computational technique, based on interval analysis, to correctly identify phase equilibrium and test for phase stability in binary solvent-solute systems, that include the possibility of a solid phase, using any of a variety of cubic equations of state as the thermodynamic model.Here we extend the methodology to include multicomponent solvent-solute-cosolvent systems where the likelihood of additional phase formation is even greater than in the binary case. Gaseous or liquid cosolvents are frequently used in supercritical fluid extraction processes, and are integral in processes such as the gas anti-solvent process (GAS) to precipitate uniform solid particles. Using several examples from the literature, we demonstrate how the new computational technique can be used to identify experimental data that may have been misinterpreted and to identify models that do not predict what the modeler intended.

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“…In this project we are developing and applying a new method, based on interval mathematics, that is capable of solving the phase stability and equilibrium problems with mathematical and computational certainty that the correct result has been obtained. In particular, in the first year of this project we have extended the applicability of the interval method to a wide variety of equation of state models (Hua et al, 1997a). This includes the Peng-Robinson equation, that can be used to predict solubilities of chelating agents and metal chelate compounds in supercritical CO 2 and CO 2 /cosolvent mixtures.…”

Section: Development Of a Completely Reliable Technique To Performmentioning

confidence: 99%