Liquid phase compositions

Table 3 shows results obtained from a five-component, isothermal flash calculation. In this system there are two condensable components (acetone and benzene) and three noncondensable components (hydrogen, carbon monoxide, and methane). Henry s constants for each of the noncondensables were obtained from Equations (18-22) the simplifying assumption for dilute solutions [Equation (17)] was also used for each of the noncondensables. Activity coefficients for both condensable components were calculated with the UNIQUAC equation. For that calculation, all liquid-phase composition variables are on a solute-free basis the only required binary parameters are those for the acetone-benzene system. While no experimental data are available for comparison, the calculated results are probably reliable because all simplifying assumptions are reasonable the... 

Figure 7-2. Conjugate liquid phase compositions for water-acrylonitrile-acetonitrile system calculated with subroutine ELIPS for feeds shown by . ...

XM(I,2) cols 21-30 measured liquid-phase composition of component one (mole or weight fraction)... 

EVX(I,2) - ERROR VARRIANCE OF THF LIQUID-PHASE COMPOSITION MEASUREMENT. 

LILIK calculates liquid-liquid equilibrium ratios, K(I), for each component in a mixture of N components (N < 20) at specified temperature and liquid-phase compositions. 

Liquid phase compositions and phase ratios are calculated by Newton-Raphson iteration for given K values obtained from LILIK. K values are corrected by a linearly accelerated iteration over the phase compositions until a solution is obtained or until it is determined that calculations are too near the plait point for resolution. 

Equations (4.5) to (4.7) can now be solved to give expressions for the vapor- and liquid-phase compositions leaving the separator ... 

Outlined below are the steps required for of a X T.E calciilation of vapor-phase composition and pressure, given the liquid-phase composition and temperature. A choice must be made of an equation of state. Only the Soave/Redlich/Kwong and Peng/Robinson equations, as represented by Eqs. (4-230) and (4-231), are considered here. These two equations usually give comparable results. A choice must also be made of a two-parameter correlating expression to represent the liquid-phase composition dependence of for each pq binaiy. The Wilson, NRTL (with a fixed), and UNIQUAC equations are of general applicabihty for binary systems, the Margules and van Laar equations may also be used. The equation selected depends on evidence of its suitability to the particular system treated. Reasonable estimates of the parameters in the equation must also be known at the temperature of interest. These parameters are directly related to infinite-dilution values of the activity coefficients for each pq binaiy. 

In distillation operations, separation results from differences in vapor-and liquid-phase compositions arising from the partial vaporization of a hquid mixture or the partial condensation of a vapor mixture. The vapor phase becomes enriched in the more volatile components while the hquid phase is depleted of those same components. In many situations, however, the change in composition between the vapor and liquid phases in equihbrium becomes small (so-called pinched condition ), and a large number of successive partial vaporizations and partial condensations is required to achieve the desired separation. Alternatively, the vapor and liquid phases may have identical compositions, because of the formation of an azeotrope, and no separation by simple distillation is possible. 

Other initial conditions Initial liquid-phase compositions ... 

In order to allow integration of countercurrent relations like Eq. (23-93), point values of the mass-transfer coefficients and eqiiilibrium data are needed, over ranges of partial pressure and liquid-phase compositions. The same data are needed for the design of stirred tank performance. Then the conditions vary with time instead of position. Because of limited solubihty, gas/liquid reactions in stirred tanks usually are operated in semibatch fashion, with the liquid phase charged at once, then the gas phase introduced gradually over a period of time. CSTR operation rarely is feasible with such systems. 

Throughout this bocdt, several mass-exchange operations will be considered simultaneously. It is therefore necessary to use a unified terminology such that y is always the composition in die rich phase and x is the composition in the lean phase. The reader is cautioned here that tiiis terminology may be different ftom other literature, in which y is used for gas-phase composition and x is used for liquid-phase composition. 

Step 1. Assume the liquid phase composition or make an approximation. (If there is no guide, use the total feed composition.)... 

A minimum HETP or HTU represents a maximum separation efficiency with a representing the relative volatility, i.e., vapor and liquid phase compositions of the more volatile component in a binary system ... 

Total reflux for a symmetric separation. Note, the term symmetric separation is used here to mean that on a McCabe-Thiele diagram, the liquid phase compositions of the overhead product and bottom product are roughly equidistant from 0.5. 

The calculated and experimental gaseous and liquid phase compositions are shown in Figures 1 and 2 respectively. 

Figure 2. Experimental and predicted aqueous liquid phase compositions for the...

Nitrogen - Water System. The interaction parameters for the nitrogen - water system have been evaluated using the data of Wiebe and Gaddy (10), Paratella and Sagramora (Vj ), Rigby and Prausnitz (12)and O Sullivan and Smith (13). As with the two previous systems, only one constant interaction parameter was necessary to correlate the vapor phase composition while the interaction parameter for the aqueous liquid phase increased monotonically with temperature. A comparison of the calculated and experimental vapor phase and aqueous liquid phase compositions is given in Table I. 

Figure 3. Experimental and predicted vapor and aqueous liquid phase compositions for the carbon dioxide-water system ((-) P-R prediction data from Ref.

Figure 4. Experimental and predicted vapor and liquid phase compositions for...

Figure 3 shows the activity coefficient of HC1 in aqueous solution, p, as a function of liquid-phase composition for 10, 25 and 50°C. Experimental activity-coefficient data given by Harned and Owen (1J were used in conjunction with... 

The dominance of distillation-based methods for the separation of liquid mixtures makes a number of points about RCM and DRD significant. Residue curves trace the liquid-phase composition of a simple single-stage batch stillpot as a function of time. Residue curves also approximate the liquid composition profiles in continuous staged or packed distillation columns operating at infinite reflux and reboil ratios, and are also indicative of many aspects of the behavior of continuous columns operating at practical reflux ratios (12). 

Liquid Phase Composition Written as (Hg, ), , Liquidus Temperature in... 

The salt effect in the MeOH-EtOAc-CaC system can be explained by preferential solvation. As calcium chloride dissolves readily in methanol but only sparingly in ethyl acetate, it will be sufficient to consider the interaction between methanol molecules and calcium chloride molecules only in the MeOH-EtOAc solution. Referring again to Figure 2, the free methanol molecules which are not clustered with ethyl acetate increase linearly when the liquid-phase composition of methanol is above 0.333 in mole fraction. The solubility... 

The following is the prediction of vapor-liquid equilibrium composition when CaCl2 is added in 7.24 mol % to the ethyl acetate-ethanol system in which the liquid-phase composition of ethyl acetate is 0.502 in terms of mole fraction. 

The results of prediction over the entire range of liquid-phase composition are given in Table XII. The comparison of the prediction results with the observed values shown in the x-y diagram is shown in Figure 14. 

Equilibrium vapor condensate was analyzed by means of density measurement at 25.00° 0.02°C. An Ostwald pycnometer (capacity ca. 5 cm3) was used. Liquid phase composition was calculated by taking a material balance. In this case, the three moles of water present in trihydrous lithium perchlorate were considered water component. The accuracies of both compositions were 0.001 mole fraction. 

From experimental data for the ethanol-water system without salt, obtained at 700 and 760 mmHg, it can be seen that within this pressure range the effects of pressure on the equilibrium data are small enough to be within the experimental scatter. In fact, in previous works (8,11,12,13,18,19,23,24,27) there seems to be no clear difference between the equilibrium data at 700 and at 760 mmHg. Errors obtained in the determination of liquid and vapor compositions are approximately 0.05 wt % for the systems without salt. For salt-saturated systems, the same error prevails for the vapor phase, while the error is between 0.1 and 0.2 wt % for liquid phase compositions. The error for the boiling temperature is less than 0.1 °C for the systems without salt, but for saturated solutions the error is much greater from 0.2°C for nonconcentrated solutions to 3°C or more for highly concentrated solutions. 

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