Composition vapor

A component in a vapor mixture exhibits nonideal behavior as a result of molecular interactions only when these interactions are very wea)c or very infrequent is ideal behavior approached. The fugacity coefficient (fi is a measure of nonideality and a departure of < ) from unity is a measure of the extent to which a molecule i interacts with its neighbors. The fugacity coefficient depends on pressure, temperature, and vapor composition this dependence, in the moderate pressure region covered by the truncated virial equation, is usually as follows ... 

Subroutine VPLQK. VPLQK calculates K factors (K = for given values of pressure, temperature, liquid and vapor compositions, and the adjustable parameters. The K factors are calculated from the following relation (Prausnitz, 1969) ... 

Subroutine MULLER. MULLER iteratively solves the equilibrium relations and computes the equilibrium vapor composition when organic acids are present. These compositions are used by subroutine PHIS2 to calculate fugacity coefficients by the chemical theory. 

SDZ(I) cols 31-40 standard deviation of vapor composition measurement... 

THIS SECTION CALCULATES THE VAPOR COMPOSITION AND PRESSURE CORRESPONDING TO A GIVEN LIQUID COMPOSITION AND TEMPERATURE. 

VALIK calculates vapor-liquid vaporization equilibrium ratios, K(I), for each component in a mixture of N components (N 20) at specified liquid composition, vapor composition, temperature, and pressure. 

VAPOR COMPOSITIONS Z. ENTH RETURNS ERE=0 UNLESS BINARY DATA ARE... 

ZT,ZJ Temporary true vapor composition estimates. k6 True vapor composition estimate flag (0 = a priori ... 

ZO(I) Vector (length 20) of true vapor compositions from previous iteration (I = 1, N). 

FOR NO PREVIOUS PHI VALUES AVAILABLE (KO = 0) MAKE FIRST ESTIMATES OF ACTUAL VAPOR COMPOSITION... 

Y(I) vector of estimated equilibrium the vapor composition (mole fraction) if known (I = 1, N) otherwise can be any vector not summing to 1. 

BUDET calculates the bubble-point temperature or dew-point temperature for a mixture of N components (N < 20) at specified pressure and liquid or vapor composition. The subroutine also furnishes the composition of the incipient vapor or liquid and the vaporization equilibrium ratios. 

FOR NO ESTIMATE OF INCIPIENT VAPOR COMPOSITION SET EQUAL TO FEED... 

Hydrogen Chloride—Water System. Hydrogen chloride is highly soluble in water and this aqueous solution does not obey Henry s law at ah concentrations. Solubhity data are summarized in Table 5. The relationship between the pressure and vapor composition of unsaturated aqueous hydrochloric acid solutions is given in Reference 12. The vapor—Hquid equiHbria for the water—hydrogen chloride system at pressures up to 1632 kPa and at temperatures ranging from —10 to +70° C are documented in Reference 13. 

Refrigerant mixtures are divided into two categories, azeotropes and zeotropes. The 500-series refrigerants are classified as azeotropes, since the vapor composition is identical to the Hquid composition at a given pressure. The 400-series refrigerants are classified as zeotropes, because the equiUbrium... 

For ease of presentation and understanding, the initial discussion of distillation processes involves binary systems. Fxamining the binary boiling point (Fig. la) and phase (Fig. lb) diagrams, the enrichment from Hquid composition Xj to vapor composition represents a theoretical step, or equiHbrium stage. 

Calculate the vapor composition in equihbrium with the Hquid feed. From equation 2a and for x = 0.60 mol fraction ... 

The typical phase equiHbrium problem eacouatered ia distiHatioa is to calculate the boiling temperature and the vapor composition ia equiHbrium with a Hquid phase of specified composition at a givea pressure. If the Hquid phase separates, thea the problem is to calculate the boiling temperature and the compositions of the two equiHbrium Hquid phases plus the coexistiag vapor phase at the specified overall Hquid compositioa. Robust and practical numerical methods have been devised for solving this problem (95—97) and have become the recommended techniques (98,99). 

Fig. 19. Separation of ethanol and water from an ethanol—water—benzene mixture. Bottoms and are water, B is ethanol, (a) Kubierschky three-column sequence where columns 1, 2, and 3 represent the preconcentration, azeotropic, and entrainer recovery columns, respectively, (b) Material balance lines from the azeotropic and the entrainer recovery columns, A and E, respectively, where represents the overall vapor composition from the azeo-column, 2 1SP Hquid in equiUbrium with overhead vapor composition from the azeo-column, Xj, distillate composition from entrainer...

FIG. 2-10 Enthalpy-concentration diagram for aqueous ethyl alcohol. Reference states Enthalpies of hquid water and ethyl alcohol at 0 C are zero. NOTE In order to interpolate equilihrium compositions, a vertical may he erected from any liquid composition on the hoihug hue and its intersection with the auxihary hue determined. A horizontal from this intersection will estahhsh the equihhrium vapor composition on the dew hue. (Bosnjakovic, Techuische Thermo-dynamik, T. Steinkopff, Leipzig, 1935. )... 

The two degrees of freedom for this system may be satisfied by setting T and P, or T and t/j, or P and a-j, or Xi and i/i, and so on, at fixed values. Thus, for equilibrium at a particular T and P, this state (if possible at all) exists only at one liquid and one vapor composition. Once the two degrees of freedom are used up, no further specification is possible that would restrict the phase-rule variables. For example, one cannot m addition require that the system form an azeotrope (assuming this possible), for this requires Xi = i/i, an equation not taken into account in the derivation of the phase rule. Thus, the requirement that the system form an azeotrope imposes a special constraint and reduces the number of degrees of freedom to one. 

The data-reduction procedure just desciiDed provides parameters in the correlating equation for g that make the 8g residuals scatter about zero. This is usually accomphshed by finding the parameters that minimize the sum of squares of the residuals. Once these parameters are found, they can be used for the calculation of derived values of both the pressure P and the vapor composition y. Equation (4-282) is solved for yjP and written for species 1 and for species 2. Adding the two equations gives... 

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