Phase equilibria high pressure

Charlu T. V., Newton R. C., and Kleppa O. J. (1978). Enthalpy of formation of lime silicates by high temperature calorimetry, with discussion of high pressure phase equilibrium. Geochim. Cosmochim. Acta, 42 367-375. 

In this chapter the basic concepts on high-pressure phase equilibrium are introduced. Phenomenological behaviour, experimental methods and theoretical modelling are briefly described in order to give a general overview of the problematic. References are given to more detailed treatments for the different subjects in order to help the reader to go deeply into them. 

Information about experimental solubility and equilibrium data are important, even when complex mixtures are extracted. Reviews of high-pressure phase-equilibrium data have been published by several authors, for example, by Knapp et al. [38] covering the period 1900 to 1980, by Fomari et al. [39] covering 1978 to 1987, and by Dohm and Brunner [40], between 1988 to 1993. 

To address these limitations to the commercial evaluation and implementation of C02 as a substitute solvent, we (1) present a methodology to measure and model high-pressure phase behavior of C02-based reaction systems using minimal experimental data and (2) present a new computational technique for high-pressure phase equilibrium calculations that provides a guarantee of the correct solution to the flash problem. 

We have applied a global optimization technique, based on interval analysis, to the high-pressure phase equilibrium problem (INTFLASH). It does not require any initial guesses and is guaranteed, both mathematically and computationally, to converge to the correct solution. The interval analysis method and its application to phase equilibria using equation-of-state... 

Previous work in the area of high-pressure phase equilibrium of aqueous solutions of organic compounds with supercritical fluids... 

A recirculation apparatus for the determination of high pressure phase equilibrium data for mixtures of water, polar organic liquids and supercritical fluids was constructed and operated for binary and ternary systems with supercritical carbon dioxide. 

The schematic diagram of the high-pressure vapor-liquid equilibrium circulation-type apparatus is shown in Fig.l. The main piece of the equipment is a high-pressure phase equilibrium cell of approximately 100 cm3. The apparatus includes a compressed-air actuated piston-pump that allows to circulate one or both phases to bring the vapor and liquid in close contact with each other. This pump, the cell and all the related valves were placed in a constant-temperature water bath to have and to keep uniformely the desired temperature. 

Gros HP, Bottini SB, Brignole EA. High pressure phase equilibrium modeling of mixtures containing associated compounds and gases. Fluid Phase Equilibria 1997 139 75-87. 

Wohlfarth, Ch., P. Wagner, D. Glindemann, M. Vblkner, and M. T. Ratzsch. 1984. The high pressure phase equilibrium in the system ethylene -H vinyl acetate + ethylene-vinyl acetate copolymer. Acta Polymerica. 35 498-503. 

The discussion of the previous section was concerned with low-pressure vapor-liquid equilibria and involved the use of activity coefficient models. Here we are interested in high-pressure phase equilibrium in fluids in which both phases are describable by equations of state, that is, the cj -4> method. One example of the type of data we are interested in describing (or predicting) is shown in Fig. 10.3-1 for the ethane-propylene system. There we see the liquid (bubble point) and vapor (dew point) curves for this system at three different isotherms. At each temperature the coexisting vapor and liquid. phases have the same pressure and thus are joined by horizontal tie lines, only one of... 

It should be evident from the examples in Chapters 10, 11, and 12 that the evaluation of species fugacities or partial molar Gibbs energies (or chemical potentials) is central to any phase equilibrium calculation. Two different fugacity descriptions have been used, equations of. state and activity coefficient models. Both have adjustable parameters. If the values of these adjustable parameters are known or can be estimated, the phase equilibrium state may be predicted. Equally important, however, is the observation that measured phase equilibria can be used to obtain these parameters. For example, in Sec. 10.2 we demonstrated how activity coefficients could be computed directly from P-T-x-y data and how activity coefficient models could be fit to such data. Similarly, in Sec. 10.3 we pointed out how fitting equation-of-state predictions to experimental high-pressure phase equilibrium data could be used to obtain a best-fit value of the binary interaction parameter.. /"... 

High-pressure phase equilibrium (HPPE) measurements... 

Henry s constant, 4 High-pressure phase equilibrium experimental data, 259-352 experimental methods, 5... 

RAE Ratzsch, M.T., Wagner, P., Wohlfarth, C., and Heise, D., High-pressure phase equilibrium studies in mixtures of ethylene and (ethylene-vinyl acetate) copolymers. Part 1. Dependence on vinyl acetate content of copolymers (Ger.), cto Polym., 33, 463, 1982. 

Excess Gibbs energy Excess enthalpy Excess volume High-pressure phase equilibrium and critical properties... 

The high-pressure phase-equilibrium references contain a wide variety of studies of fluid-phase equilibria. References have only been included if they give some values above 1.5 MPa. The actual variables studied are noted and short explanatory comments on the nature of the system or results are occasionally given. 

HIGH-PRESSURE PHASE EQUILIBRIUM (HPPE) DATA OF AQUEOUS POLYMER SOLUTIONS... 

The Supplement will be divided again into the seven chapters as used before in the former Handbook. (1) Introduction, (2) Vapor-Liqitid Equilibrium (VLE) Data of Aqueous Polymer Solutions, (3) Liquid-Liquid Eqitilibriitm (LLE) Data of Aqueous Polymer Solutions, (4) High-Pressure Phase Equilibrium (HPPE) Data of Aqueous Polymer Solutions, (5) Enthalpy Changes for Aqueous Polymer Solutions, (6) PVT Data of Polymers and Aqueous Polymer Solutions, and (7) Second Virial Coefficients (A2) of Aqueous Polymer Solutions. Finally, appendices quickly route the user to the desired data sets. 

Kiamos, A.A., High-Pressure Phase-Equilibrium Studies of Polymer-Solvent-Supercritical Fluid Mixtures, Masters Essay, The Johns Hopkins University, 1992. 

The spinodal curve and the critical points (including multiple critical points) only depend on few moments of the molar-mass distribution of the polydisperse system while the cloud-point curve the shadow curve and the coexistence curves are strongly influenced by the whole curvature of the distribution function. The methods used that include the real molar-mass distribution or an assumed analytical distribution replaced by several hundred discrete components have been reviewed by Kamide. In the 1980s continuous thermodynamics was applied, for example, by Ratzsch and Kehlen to calculate the phase equilibrium of a solution of polyethene in supercritical ethene as a function of pressures at T= 403.15 K. The Flory s model was used with an equation of state to describe the poly-dispersity of polyethene with a a Wesslau distribution. Ratzsch and Wohlfarth applied continuous thermodynamics to the high-pressure phase equilibrium of ethene [ethylene]-I-poly(but-3-enoic acid ethene) [poly(ethylene-co-vinylace-tate)] and to the corresponding quasiternary system including ethenyl ethanoate [vinylacetate]. In addition to Flory s equation of state Ratzsch and Wohlfarth also tested the Schotte model as a suitable means to describe the phase equilibrium neglecting the polydispersity with respect to chemical composition of the... 

Table 2.1 High-pressure phase equilibrium material properties and transport data in corresponding phase state.

Kodama, D. Sato, R. Haneda, A. Kato, M. High-pressure phase equilibrium for ethylene + ethanol at 283.65 K. L Chem. Eng. Data 2005, 50, 122-124. 

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