Equilibria data sources

Source for liquid-liquid and vapor-liquid equilibrium data and vapor-pressure data. 

Data Source Equilibrium Constant (k) Mol.Vol. of Associate Density of Associate Molar Refractivity of Associate Refractive Index of Associate... 

There are numerous sources of phase equilibrium data available that serve as a database to those developing or improving equations of state. References to these databases are widely available. In addition, new data are added mainly through the Journal of Chemical and Engineering Data and the journal Fluid Phase Equilibria. Next, we give data for two systems so that the reader may practice the estimation methods discussed in this chapter. 

The most comprehensive source of equilibrium data for liquid-liquid systems is the DECHEMA data series, Sorensen and Arlt (1979). Equilibrium data for some systems is also given by Perry et al. (1997). 

Experimental vapor-liquid equilibrium data, Example 12.3. [Source Gmehling et al. (1981).]... 

Data at 25°C. Free energy of formation, equilibrium constants and re-lated data at 25°C exist for a wide range of minerals, other solids, gases and aqueous species, including ions and complexes (see later discussion on data sources). Availability of data at this reference temperature is usually not a major stumbling block. 

The calculational base consists of equilibrium relations and material and energy balances. Equilibrium data for many binary systems are available as tabulations of x vs. y at constant temperature or pressure or in graphical form as on Figure 13.4. Often they can be extended to other pressures or temperatures or expressed in mathematical form as explained in Section 13.1. Sources of equilibrium data are listed in the references. Graphical calculation of distillation problems often is the most convenient... 

We have looked at four KD equilibrium resources laboratory data, triangular equilibrium data from publications, Henry s law constants, and operating field data. All four are reliable data sources if applied with limitations as described. All can be applied to the rectangular equilibrium curve (the distribution coefficient equilibrium curve) as shown in Fig. 7.2, which includes a listing of laboratory data for the extraction process shown. Please notice the data table in the boxed area of columns... 

Figure 7.3 MTPlot72 equilibrium curve source data.

The LCM is a semi-theoretical model with a minimum number of adjustable parameters and is based on the Non-Random Two Liquid (NRTL) model for nonelectrolytes (20). The LCM does not have the inherent drawbacks of virial-expansion type equations as the modified Pitzer, and it proved to be more accurate than the Bromley method. Some advantages of the LCM are that the binary parameters are well defined, have weak temperature dependence, and can be regressed from various thermodynamic data sources. Additionally, the LCM does not require ion-pair equilibria to correct for activity coefficient prediction at higher ionic strengths. Thus, the LCM avoids defining, and ultimately solving, ion-pair activity coefficients and equilibrium expressions necessary in the Davies technique. Overall, the LCM appears to be the most suitable activity coefficient technique for aqueous solutions used in FGD hence, a data base and methods to use the LCM were developed. 

Equilibrium data have been obtained experimentally for many systems, and literature sources should be carefully checked before a decision is reached to perform an experimental measurement. The reader should also refer to published data banks from which parameters for the NRTL or UNIQUAC equations can be obtained. Recently, significant progress has been made in estimating equilibrium data by computer simulations of the molecular dynamics. 

Select the criterion to be used for thermodynamic consistency. Deviations from thermodynamic consistency arise as a result of experimental errors. Impurities in the samples used for vapor-liquid equilibrium measurements are often the source of error. A complete set of vapor-liquid equilibrium data includes temperature T. pressure P. liquid composition x, and vapor composition y,. Usual practice is to convert these data into activity coefficients by the following equation, which is a rearranged form of the equation that rigorously defines K values (i.e., defines the ratio y, /x, under Related Calculations in Example 3.1) ... 

Gas solubility has been treated extensively (7). Alethods for the prediction of phase equilibria and actual solubility data have been given (8,9) and correlations of the equilibrium K values of hydrocarbons have been developed and compiled (10). Several good sources for experimental information on gas— and vapor—liquid equilibrium data of nonideal systems are also available (6,11,12). 

Selection of Solubility Data Solubility values determine the liquid rate necessary for complete or economic solute recovery and so are essential to design. Equilibrium data generally will be found in one of three forms (1) solubility data ejq)ressed either as solubility in weight or mole percent or as Henrys-law coefficients, (2) pure-component vapor pressures, or (3) equilibrium distribution coefficients (K values). Data for specific systems may be found in Sec. 2 additional references to sources of data are presented in this section. 

The accuracy of calculated equilibrium states depends critically on the data sources used. Accurate predictions of heat capacities are often... 

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