Gases phase diagrams

Figure A2.5.3. Typical liquid-gas phase diagram (temperature T versus mole fraction v at constant pressure) for a two-component system in which both the liquid and the gas are ideal mixtures. Note the extent of the two-phase liquid-gas region. The dashed vertical line is the direction x = 1/2) along which the fiinctions in figure A2.5.5 are detemiined.

Figure A2.5.5. Phase diagrams for two-eomponent systems with deviations from ideal behaviour (temperature T versus mole fraetion v at eonstant pressure). Liquid-gas phase diagrams with maximum (a) and minimum (b) boiling mixtures (azeotropes), (e) Liquid-liquid phase separation, with a eoexistenee eurve and a eritieal point.

Fig. 17 Section of Ca-Au Ga phase diagram showing the distribution of 1/0, 1/1, 2/1 ACs in samples that were slowly cooled from 800°C and annealed at 500°C. Note that the i-QC is obtained only in quenched samples near CaAujGaj (marked by the arrow)...

Pu-Ga phase diagram, 29 684. See also Plutonium- gallium alloys PULEG (/-Pulegone, /-menthol from, 24 523... 

Figure 5.16. Two versions of the Pu-Ga phase diagram as reported, according to Hecker and Timofeeva (2000), by Peterson and Kassner (1988) and by Chebotarev etal. (1975). According to the first version the fee 6-Pu phase is retained at room temperature for Ga concentrations included between approximately 2 at.% and 9 at.%. According to the second version the S-Pu phase undergoes (below 100°C) a eutectoid decomposition to the a-Pu phase plus Pu3Ga. Both diagrams were extrapolations to equilibrium.

The third type of reservoir fluid we will consider is retrograde gas. Retrograde Gas Phase Diagram... 

Retrograde Gas Phase Diagram — Field Identification of Retrograde Gases — Laboratory Analysis of Retrograde Gases — Comments... 

Wet Gas Phase Diagram — Comments — Field Identification of Wet Gases... 

Here we derive Eq. (7.2.14) on the basis of somewhat tortuous thermodynamic arguments. An alternative, simpler procedure is provided in the next section, but the present method is instructive and included for that reason. We base our considerations on the portion of the liquid-gas phase diagram very close to the critical point, shown in Fig. 7.3.1. One of the two isotherms is taken at the critical temperature Tc the other, at a lower temperature T very close to Tc. We investigate... 

There exist two variants of the Sc-Ga phase diagram in the literature. The first one was reported by Markiv et al. (1977) who investigated only 13 binary alloys within... 

Aging experiments have also been conducted on the Ni-Ga alloys at temperatures in the range 600 to 800 °C. So far we have not observed the precipitation of the solid solution phase, which indicates that the y solvus in this alloy system does not have the necessary negative slope in the Ni-Ga phase diagram. 

Fig. 7.3 Pressure range of adsorption at constant temperature in the liquid-gas phase diagram of the adsorptive. The pressure cannot exceed the saturated vapour pressure ps of the fluid at the adsorption temperature Tads...

Using this mixture as an example, consider starting at pressure A and isothermally reducing the pressure to point D on the diagram. At point A the mixture exists entirely in the liquid phase. When the pressure drops to point B, the first bubble of gas is evolved, and this will be a bubble of the lighter component, ethane. As the pressure continues to drop, the gas phase will acquire more of the heavier component and hence the liquid volume decreases. At point C, the last drop of liquid remaining will be composed of the heavier component, which itself will vaporise as the dew point is crossed, so that below... 

A volatile oil contains a relatively large fraction of lighter and intermediate oomponents which vaporise easily. With a small drop in pressure below the bubble point, the relative amount of liquid to gas in the two-phase mixture drops rapidly, as shown in the phase diagram by the wide spacing of the iso-vol lines. At reservoir pressures below the bubble point, gas is released In the reservoir, and Is known as solution gas, since above the bubble point this gas was contained in solution. Some of this liberated gas will flow towards the producing wells, while some will remain in the reservoir and migrate towards the crest of the structure to form a secondary gas cap. 

Black oils are a common category of reservoir fluids, and are similar to volatile oils in behaviour, except that they contain a lower fraction of volatile components and therefore require a much larger pressure drop below the bubble point before significant volumes of gas are released from solution. This is reflected by the position of the iso-vol lines in the phase diagram, where the lines of low liquid percentage are grouped around the dew point line. 

When oil and gas are produced simultaneously into a separator a certain amount (mass fraction) of each component (e.g. butane) will be in the vapour phase and the rest in the liquid phase. This can be described using phase diagrams (such as those described in section 4.2) which describe the behaviour of multi-component mixtures at various temperatures and pressures. However to determine how much of each component goes into the gas or liquid phase the equilibrium constants (or equilibrium vapour liquid ratios) K must be known. 

Figure A2.5.1. Schematic phase diagram (pressure p versus temperature 7) for a typical one-component substance. The full lines mark the transitions from one phase to another (g, gas liquid s, solid). The liquid-gas line (the vapour pressure curve) ends at a critical point (c). The dotted line is a constant pressure line. The dashed lines represent metastable extensions of the stable phases.

Phase transitions in binary systems, nomially measured at constant pressure and composition, usually do not take place entirely at a single temperature, but rather extend over a finite but nonzero temperature range. Figure A2.5.3 shows a temperature-mole fraction T, x) phase diagram for one of the simplest of such examples, vaporization of an ideal liquid mixture to an ideal gas mixture, all at a fixed pressure, (e.g. 1 atm). Because there is an additional composition variable, the sample path shown in tlie figure is not only at constant pressure, but also at a constant total mole fraction, here chosen to be v = 1/2. 

Figure A2.5.10. Phase diagram for the van der Waals fluid, shown as reduced temperature versus reduced density p. . The region under the smooth coexistence curve is a two-phase liquid-gas region as indicated by the horizontal tie-lines. The critical point at the top of the curve has the coordinates (1,1). The dashed line is the diameter, and the dotted curve is the spinodal curve.

With these simplifications, and with various values of the as and bs, van Laar (1906-1910) calculated a wide variety of phase diagrams, detennining critical lines, some of which passed continuously from liquid-liquid critical points to liquid-gas critical points. Unfortunately, he could only solve the difficult coupled equations by hand and he restricted his calculations to the geometric mean assumption for a to equation (A2.5.10)). For a variety of reasons, partly due to the eclipse of the van der Waals equation, this extensive work was largely ignored for decades. 

Figure A3.8.1 A schematic diagram of the PMF along the reaction coordinate for an isomerizing solute in the gas phase (frill curve) and in solution (broken curve). Note the modification of the barrier height, the well positions, and the reaction free energy due to the interaction with the solvent.

Fig. 3. Vapor—liquid-phase diagram for the HCl—H2 O system (5) where (-) represents the demarcation between the two-phase region and the gas...

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