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Vapor-liquid equilibrium bubble pressure

The computer subroutines for calculation of vapor-liquid equilibrium separations, including determination of bubble-point and dew-point temperatures and pressures, are described and listed in this Appendix. These are source routines written in American National Standard FORTRAN (FORTRAN IV), ANSI X3.9-1978, and, as such, should be compatible with most computer systems with FORTRAN IV compilers. Approximate storage requirements for these subroutines are given in Appendix J their execution times are strongly dependent on the separations being calculated but can be estimated (CDC 6400) from the times given for the thermodynamic subroutines they call (essentially all computation effort is in these thermodynamic subroutines). [Pg.318]

Since the boiling point properties of the components in the mixture being separated are so critical to the distillation process, the vapor-liquid equilibrium (VLE) relationship is of importance. Specifically, it is the VLE data for a mixture which establishes the required height of a column for a desired degree of separation. Constant pressure VLE data is derived from boiling point diagrams, from which a VLE curve can be constructed like the one illustrated in Figure 9 for a binary mixture. The VLE plot shown expresses the bubble-point and the dew-point of a binary mixture at constant pressure. The curve is called the equilibrium line, and it describes the compositions of the liquid and vapor in equilibrium at a constant pressure condition. [Pg.172]

In most industrial processes coexisting phases are vapor and liquid, although liquid/liquid, vapor/solid, and liquid/solid systems are also encountered. In this chapter we present a general qualitative discussion of vapor/liquid phase behavior (Sec. 12.3) and describe the calculation of temperatures, pressures, and phase compositions for systems in vapor/liquid equilibrium (VLE) at low to moderate pressures (Sec. 12.4).t Comprehensive expositions are given of dew-point, bubble-point, and P, T-flash calculations. [Pg.471]

Experiments have shown that the bubbles are not always in thermodynamic equilibrium with the surrounding liquid i.e., the vapor inside the bubble is not necessarily at the same temperature as the liquid. Considering a spherical bubble as shown in Fig. 9-4, the pressure forces of the liquid and vapor must be balanced by the surface-tension force at the vapor-liquid interface. The pressure force acts on an area of nr2, and the surface tension acts on the interface length of 2irr. The force balance is... [Pg.502]

Related Calculations. The convergence-pressure K -value charts provide a useful andrapid graphical approach for phase-equilibrium calculations. The Natural Gas Processors Suppliers Association has published a very extensive set of charts showing the vapor-liquid equilibrium K values of each of the components methane to n-decane as functions of pressure, temperature, and convergence pressure. These charts are widely used in the petroleum industry. The procedure shown in this illustration can be used to perform similar calculations. See Examples 3.10 and 3.11 for straightforward calculation of dew points and bubble points, respectively. [Pg.65]

This would correspond to the bubble-point calculation as performed for vapor-liquid equilibrium, the object being to determine the temperature at a given pressure, or vice versa, whereby the first drop of vapor ensues from the vaporization of the liquid phase. That is, it would correspond to a point or locus of points on the saturated liquid curve. [Pg.687]

The essential features of vapor-liquid equilibrium (VLE) behavior are demonstrated by the simplest case isothermal VLE of a binary system at a temperature below the critical temperatures ofboth pure components. Forthis case ( subcritkaT VLE), each pure component has a well-defined vapor-liquid saturation pressure ff, and VLE Is possible for the foil range of liquid and vapor compositions xt and y,. Figure 1.5-1 ffiustrates several types of behavior shown by such systems. In each case, (he upper solid curve ( bubble curve ) represents states of saturated liquid (he lower solid curve ( dew curve ) represents states of saturated vtqtor. [Pg.34]

Column l. N = 20 and /= 11. The column has a partial condenser, and is to be operated at a reflux ratio Lul/Di = 4.0 at a pressure of 250 lb/in2 abs. The pressure drop across each plate is negligible. The feed enters the column as a liquid at its bubble point (551.56°R) at the column pressure. The boilup ratio of column 1 is to be selected such that the reboiler duty QRl of column 1 is equal to the condenser duty Qc2 of column 2. Use the vapor-liquid equilibrium and enthalpy data given in Tables B-l and B-2. Since the K values in Table B-l are at the base pressure of 300 lb in2 abs, approximate the K values at 250 lb/in2 abs as follows... [Pg.258]

The column has a total condenser which is to be operated at 40 mmHg. The pressure drop per stage may be taken to be 4.69 mmHg. The flow rate of the feed is 220.55 lb mol/h, and before entering the column, it is a liquid at its bubble-point temperature of 572°R at a pressure of 270 mmHg. The vapor-liquid equilibrium data and the enthalpy data are given in Tables B-3 and B-4. [Pg.305]

The column has a partial condenser which is to be operated at 300 lb/in2 abs. The distillate is removed as dewpoint vapor. The bottoms and the sidestream products are removed as bubble-point liquids. Feeds enter as liquids at their bubble point at the column pressure. Vapor-liquid equilibrium data and enthalpy data are given in Tables B-l and B-2. [Pg.323]

One method of removing a volatile contaminant from a liquid—for example, water— is by gas stripping, in which air or some other gas is bubbled through the liquid so that vapor-liquid equilibrium is achieved. If the contaminent is relatively volatile (as a result of a high value of its Henry s constant, vapor pressure, or activity coefficient), it will appear in the exiting air, and therefore its concentration in the remaining liquid is reduced. An example of this is given in the next illustration. [Pg.585]

At the lowest pressure in the figure, P = 0.133 bar, the vapor-liquid equilibrium curve intersects the liquid-liquid equilibrium curve. Consequently, at this pressure, depending on the temperature and composition, we may have only a liquid, two liquids, two liquids and a vapor, a vapor and a liquid, or only a vapor in equilibrium. The equilibrium state that does exist can be found by first determining whether the composition of the liquid is such that one or two liquid phases exist at the temperature chosen. Next, the bubble point temperature of the one or either of the two liquids present is determined (for example, from experimental data or from known vapor pressures and an activity coefficient model calculation). If the liquid-phase bubble point temperature is higher than the temperature of interest, then only a liquid or two liquids are present. If the bubble point temperature is lower, then depending on the composition, either a vapor, or. a vapor and a liquid are present. However, if the temperature of interest is equal to the bubble point temperature and the composition is in the range in which two liquids are present, then a vapor and two coexisting liquids will be in equilibrium. [Pg.630]

Figure 2.3-2 (a) Vapor-liquid equilibrium of the system C02-toluene at 311 K. Experimental bubble points (O) and dew points ( ) are shown as a function of the pertinent composition. The bubble and dew curves are calculated with the Peng-Robinson equation of state, (b) Percent volumetric expansion of the liquid phase in the system C02-toluene at 298 K as a function of pressure. The curve was calculated with the Peng-Robinson equation of state. [Pg.113]

Figure 11.2 Algorithm for using the gamma-phi method to solve multicomponent bubble-T problems in vapor-liquid equilibrium situations at low pressures [3]... Figure 11.2 Algorithm for using the gamma-phi method to solve multicomponent bubble-T problems in vapor-liquid equilibrium situations at low pressures [3]...
This linear relationship between the total pressure, P, and the mole fraction, x, of the most volatile species is a characteristic of Raoult s law, as shown in Figure 7.18a for the benzene-toluene mixture at 90°C. Note that the bubble-point curve (P-x) is linear between the vapor pressures of the pure species (at x, = 0, 1), and the dew-point curve (P-yJ lies below it. When the (x, yi) points are graphed at different pressures, the familiar vapor-liquid equilibrium curve is obtained, as shown in Figure 7.18b. Using McCabe-Thiele analysis, it is shown readily that for any feed composition, there are no limitations to the values of the mole fractions of the distillate and bottoms products from a distillation tower. [Pg.259]

Often the vapor-liquid equilibrium relations for a binary mixture of A and B are given as a boiling-point diagram shown in Fig. 11.1-1 for the system benzene (A)-toluene (B) at a total pressure of 101.32 kPa. The upper line is the saturated vapor line (the dew-point line) and the lower line is the saturated liquid line (the bubble-point line). The two-phase region is in the region between these two lines. [Pg.640]

As explained in Section 1.4, the enthalpy of a mixture is a function of temperature, pressure, and composition. These parameters determine the phase, so that, in vapor-liquid equilibrium calculations, the enthalpy is also implicitly a function of the phase. For a binary mixture at constant pressure, the equilibrium vapor and liquid temperatures vary with composition as represented by the dew point and bubble point curves (Figure 2.2). The enthalpy at each point may be plotted as a function of the composition, resulting in a saturated vapor enthalpy curve and a saturated liquid enthalpy curve, as shown in Figure 5.10. The composition is plotted as the mole fraction of the lighter component. [Pg.159]

Calculate the bubble point of the feed. This is done via procedures outlined in Section 3. In the present case, where both the vapor and liquid phases can be considered ideal, the vapor-liquid equilibrium ratio Ki equals vapor pressure of ith component divided by system pressure. The bubble point is found to be 94°C. At 40°C, then, the feed is subcooled 54°C. [Pg.350]

The most striking news that one learns when studying vapor-liquid phenomena is that not only does the vapor need to nucleate a liquid droplet to condense, but that also the liquid needs to nucleate a gas bubble to evaporate [24]. On the theoretical side, the simulation is made easier because the vapor is relatively simple to handle, on the experimental side, vapor pressure measurements in vapor-liquid equilibrium are fairly easy to perform. The Gibbs ensemble Monte Carlo method (Section 9.8) can be applied to the vapor-liquid equilibrium with considerable success vapor pressure curves, second virial coefficients, and other equilibrium properties can be calculated by molecular simulation, and, remarkably, good results can apparently be obtained by highly accurate ab initio quantum mechanical potentials [25a] or by simple empirical potentials [25b]. [Pg.341]

Boltzmann, L. 18. 19 Boltzmann constant 337 Boltzmann distribution law 514-23 bubble-pressure curve in vapor + liquid phase equilibrium 406... [Pg.655]

Let us consider a superheated liquid which has attained the limit of superheat and a vapor embryo forms in equilibrium with the liquid. The bubble radius is ro, the pressure in the bulk liquid is Pq, and the temperature is Tq. Assume the liquid is pure. [Pg.189]

These subroutines are used to calculate respectively, the bubble temperature of a liquid composition, dew temperature of a vapor composition, equilibrium temperature and composition of the phases produced by the flash of a particular stream at known values of total vapor and liquid, and the composition and amount of the phases produced by the flash of a particular stream at a known temperature. All are done at the column pressure which applies. [Pg.307]

If the pressure at the suction of the pump falls to its bubble or boiling point, the liquid will start to vaporize. This is called cavitation. A cavitating pump will have an erratically low discharge pressure and an erratically low flow. As shown in Fig. 23.5, the bubble-point pressure of the liquid, is the pressure in the vessel. We usually assume that the liquid in a drum is in equilibrium with the vapor. The vapor is then said to be at its dew point, while the liquid is said to be at its bubble point. [Pg.306]


See other pages where Vapor-liquid equilibrium bubble pressure is mentioned: [Pg.111]    [Pg.655]    [Pg.6]    [Pg.178]    [Pg.403]    [Pg.350]    [Pg.97]    [Pg.480]    [Pg.262]    [Pg.365]    [Pg.497]    [Pg.565]    [Pg.12]    [Pg.659]    [Pg.17]    [Pg.86]    [Pg.119]    [Pg.352]    [Pg.147]    [Pg.709]    [Pg.22]    [Pg.347]   
See also in sourсe #XX -- [ Pg.65 ]




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Vapor-liquid equilibrium equilibria

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