When pressure is less than the critical pressures of both components, the bubble-point and dew-point lines join at the vapor pressures of the pure components at either side of the diagram. When the pressure exceeds the critical pressure of one of the components, the bubble-point line and the dew-point line join at a critical point. For instance, a mixture of 98 mole percent methane and 2 mole percent ethane has a critical temperature of minus 110°F at a critical pressure of 700 psia. [Pg.72]

EXAMPLE 2-3 Determine the critical temperature and critical pressure of a mixture of50.02 mole percent methane and 49.98 mole percent ethane. Also determine the bubble-point pressure and dew-point pressure of this mixture at 20°F. [Pg.64]

When the temperature exceeds the critical temperature of one component, the saturation envelope does not go all the way across the diagram rather, the dew-point and bubble-point lines join at a critical point. For instance, when the critical temperature of a mixture of methane and ethane is minus 100°F, the critical pressure is 750 psia, and the composition of the critical mixture is 95 mole percent methane and 5 mole percent ethane. [Pg.71]

Figure 7. Dependence of the rate constant (k ) on pressure for the Diels-Alder reaction in CO2(1) + hexane(2) mixture at 318.15 K. P-o, Pc and P denote tlie dew point, critical point, and bubble point, respectively. |

Figure 2-27 gives the saturation envelope for mixtures of methane, propane, and n-pentane at the same temperature as Figure 2-26 but at a higher pressure. The bubble-point and dew-point lines join at a critical point. The critical point gives the composition of the mixture, which has a critical pressure of 1500 psia and a critical temperature of 160°F. [Pg.77]

However, unlike the case for the pure fluid, this inflection point is not the real mi.xture critical point. The mixture critical point is the point of intersection of the dew point and bubble point curves, and this must be determined from phase equilibrium calculations, more complicated mixture stability conditions, or experiment, not simply from the criterion for mechanical stability as for a pure fluid. [Pg.568]

When the two components are mixed together (say in a mixture of 10% ethane, 90% n-heptane) the bubble point curve and the dew point curve no longer coincide, and a two-phase envelope appears. Within this two-phase region, a mixture of liquid and gas exist, with both components being present in each phase in proportions dictated by the exact temperature and pressure, i.e. the composition of the liquid and gas phases within the two-phase envelope are not constant. The mixture has its own critical point C g. [Pg.100]

Above this pressure, dot 6, all mixtures of methane and propane are single phase. Thus only the methane-n-pentane binaries have two-phase behavior, and only the methane-n-pentane side of the ternary diagram can show a bubble point and a dew point. The bubble-point and dewpoint lines of the saturation envelope do not intercept another side of the diagram, rather the two lines join at a critical point, i.e., the composition of the three-component mixture that has a critical pressure of 1500 psia at 160°F. [Pg.79]

The definition of the critical point as applied to a pure substance does not apply to a two-component mixture. In a two-component mixture, liquid and gas can coexist at temperatures and pressures above the critical point, Notice that the saturation envelope exists at temperatures higher than the critical temperature and at pressures higher than the critical pressure. We see now that the definition of the critical point is simply the point at which the bubble-point line and the dew-point line join. A more rigorous definition of the critical point is that it is the point at which all properties of the liquid and the gas become identical. [Pg.63]

Because the law of rectilinear diameters does not hold for mixtures, the critical volumes of mixtures are very difficult to determine accurately. However, if the maxcondentherm and maxcondenbar are fairly similar (not more than 1 K different in their temperatures) use of the law appears to lead to reasonable values of the critical volume. The law cannot be recast by substituting pressure in place of temperature as suggested by Kaminiski and Toriumi. The only reliable method of obtaining the critical volume of a mixture is to extrapolate the bubble-point volume and dew-point volume to the critical point. [Pg.82]

When the proportions of a mixture are varied, the plait point changes. For a two-substance mixture, a curve plotted through the plait points at different proportions will terminate at either end in the critical points of the pure substances. At other points in the graph of state, the compositions of the two phases are not identical, producing two curves—a bubble point curve and a dew point curve. (See Fig. 4-13.) [Pg.63]

In Fig. 3.3a, we present the Txy diagram for binary mixtures of cyclohexane and toluene at a pressure of 1 atm, which is below the critical pressure of both pure species. Point A denotes the boiling temperature of pure toluene, and point C is the boiling temperature of pure cyclohexane. Connecting these two points are two curves that form the two-phase envelope. The upper curve (with the open symbols) is the dew point curve, and the lower curve (with the filled symbols) is the bubble point line. [Pg.27]

The condition at which the liquid just begins to form is called the dew point. The condition at which the vapor just begins to form is called the bubble point. A curve can be plotted showing the temperature and pressure at which a mixture just begins to liquefy. Such a curve is called a dew-point curve or dew-point locus. A similar curve can be constructed for the bubble point. The phase envelope is the combined loci of the bubble and dew points, which intersect at a critical point. The phase envelope maps out the regions where the various phases exist. [Pg.73]

To examine gle at elevated pressures we return to Figure 4.10. At T, which is below the critical temperature of both A and B, the bubble- and dew-point curves both start at the low-pressure end at the vapor pressure of B, which is the less volatile component. At higher pressure, the two curves diverge and finally both end at the vapor pressure of A, the more volatile component. At T2, which is between the critical temperatures of A and B, the bubble- and dew-point curves at the low-pressure end stiU start at the vapor pressure of B, but at the higher-pressure side they meet at the mixture critical state. The critical points of mixtures of varying composition form the mixture critical loci, a space curve that connects the critical states of A and B. [Pg.292]

In P-T projections, the composition axis is collapsed into the pressure-temperature plane. The vapor pressure curve for component A is labeled LV(A) and that for component B is labeled LV(B). These curves terminate at the component critical points (L = V) designated as hollow circles. In Fig. 2, dew pressure and bubble pressure curves for an intermediate composition x intersect at a point on the (L = V) critical locus where the liquid and vapor phases become critically identical. Normally, dew and bubble pressure curves are not shown in projections. They are shown here so that the construction of the related P-x at fixed T, and T-x at fixed P, phase diagrams is clearly illustrated. Each critical point on the critical locus corresponds to a fixed composition. Points close to the critical point of component A are critical points for mixtures with high concentrations of A, whereas points closer to the critical point of [Pg.2068]

© 2019 chempedia.info