Methane vapor pressure

In Figure 4 for Pocahontas coal the methane isotherms at —195°, —78°, 0°, 30°, and 50°C., determined in the sequence indicated, are shown as solid curves, and the isotherms at 0°, —78° and —195°C. after the initial sequence are shown as dashed curves. For the Pittsburgh coal, only the isotherms in a rising series of temperatures were determined (Figure 5). Figures 4 and 5 show a plot of methane isotherms at —195°C. on a relative pressure basis (pressure of methane/vapor pressure) because the vapor pressure is only about 10 torr. Isotherms determined at —195°C. represent metastable equilibrium and those at 30°, 50°, and possibly 0°C. equilibrium. Adsorption was... 

The Reid vapor pressure is generally barely different from the true vapor pressure at 37.8°C if the light gas content —methane, ethane, propane, and butane— of the sample is small, which is usually the case with petroleum products. The differences are greater for those products containing large quantities of dissolved gases such as the crude oils shown in Table 4.13. 

Gas can be condensed by (a) mechanically refrigerating it, (b) compressing and expanding it, using turboexpanders, or, (c) pressure effects such as by Joule-Thomson cooling and overcoming the vapor pressure. The liquefaction of methane can involve all three of these effects. These effects can be separately evaluated to show the effectiveness of each in producing liquid. 

The vapor pressure of a compound is important in determining the upper limit of its concentration in the atmosphere. High vapor pressures will permit higher concentrations than low vapor pressures. Examples of organic compounds are methane and benzo[fl]pyrene. Methane, with a relatively high vapor pressure, is always present as a gas in the atmosphere in contrast, benzo[fl]pyrene, with a relatively low vapor pres.surc, is. id-... 

Typically, the liquid out the bottom of the tower must meet a specified vapor pressure. The tower must be designed to maximize the molecules of intermediate components in the liquid without exceeding the vapor pressure specification. This is accomplished by driving the maximum number of molecules of methane and ethane out of the liquid and keeping a.s much of the heavier ends as possible from going out with the gas. 

Dr. Blum As a further comment on pressure optimization, and as it relates to our system, I think the response of the slurry methanation system to pressure is somewhat different from that of dry methanation. It relates to the ability of the catalyst to methanate a given amount of gas. In our system, the effective pressure is the total pressure minus the vapor pressure of the liquid phase. This doesn t hold for the standard methanation catalyst in the dry system. There is a different pressure relationship so the optimum just might not work quite the same way. 

A sample of methane gas was collected over water at 35°C. The sample was found to have a total pressure of 756 mm Hg. Determine the partial pressure of the methane gas in the sample (vapor pressure of water at 35°C is 41 mm Hg). 

Table 13.1). In the solid P(CH4) > P(CD4) but the curves cross below the melting point and the vapor pressure IE for the liquids is inverse (Pd > Ph). For water and methane Tc > Tc, but for water Pc > Pc and for methane Pc < Pc- As always, the primes designate the lighter isotopomer. At LV coexistence pliq(D20) < Pliq(H20) at all temperatures (remember the p s are molar, not mass, densities). For methane pliq(CD4) < pLiq(CH4) only at high temperature. At lower temperatures Pliq(CH4) < pliq(CD4). The critical density of H20 is greater than D20, but for methane pc(CH4) < pc(CD4). Isotope effects are large in the hydrogen and helium systems and pLIQ/ < pLiQ and P > P across the liquid range. Pc < Pc and pc < pc for both pairs. Vapor pressure and molar volume IE s are discussed in the context of the statistical theory of isotope effects in condensed phases in Chapters 5 and 12, respectively. The CS treatment in this chapter offers an alternative description.

Vapor pressure of crude oils is primarily influenced by the presence or absence of light and intermediate hydrocarbons, particularly methane. Methane has much more effect than the same quantity of ethane, ethane more than propane, etc. The composition of a crude oil having a vapor pressure of 10 ... 

It can be seen that while this particular crude oil contains over 95t by volume pentanes and heavier, these constituents only contribute about 201 to the vapor pressure. Most of the vapor pressure of this oil is contributed by the propane and butanes, since it contains very little methane and ethane. This oil stream is the product of an extremely selective separation process. Crude oil streams, unless they have "weathered" in an open tank for some period of time,... 

Figure 2-15 shows phase data for eight mixtures of methane and ethane, along with the vapor-pressure lines for pure methane and pure ethane.3 Again, observe that the saturation envelope of each of the mixtures lies between the vapor pressure lines of the two pure substances and that the critical pressures of the mixtures lie well above the critical pressures of the pure components. The dashed line is the locus of critical points of mixtures of methane and ethane. 

The edge of the diagram labeled 100 mole percent methane represents vapor pressures of methane. The edge of the diagram labeled zero mole percent methane gives vapor pressures of ethane. 

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. 

At atmospheric pressure, all mixtures of these components will be gas. See Figure 2-28(1). The temperature is well above the critical temperature of methane, and atmospheric pressure is well below the vapor pressures of propane and n-pentane at 160°F. 

Consider a pressure above the vapor pressure of n-pentane and below vapor pressure of propane, for instance, 200 psia. See dot 2 on Figure 2-29 and Figure 2-28(2). All mixtures of methane and propane are gas. Both the methane-n-pentane binary and the propane-n-pentane binary are in their two-phase regions. Their bubble-point and dew-point compositions appear along the sides of the ternary diagram as the ends of the bubble-point and dew-point lines of the ternary mixtures. 

Fig. 2-29. Vapor pressures of methane, propane, and n-pentane with critical loci of binary mixtures. (The numbered points correspond to the diagram numbers on Figure 2-28.)...

At pressures above the vapor pressure of propane and less than the critical locus of mixtures of methane and n-pentane, for instance 500 psia, dot 4, the methane-propane and methane-n-pentane binaries exhibit two-phase behavior, and propane-n-pentane mixtures are all liquid. Thus the saturation envelope appears as in Figure 2-28 (4). 

The densities of methane liquid and gas in equilibrium along the vapor-pressure line are given below. Estimate the density of methane at its critical point of - 116.7°F. 

Third, a pure compound does not have a vapor pressure at temperatures above its critical temperature. Thus, these equations are limited to temperatures less than the critical temperature of the most volatile component in the mixture. For example, if methane is a component of the mixture, Equations 12-6 and 12-7 cannot be applied at temperatures above — 116°F. 

VOLATILE ORGANIC COMPOUNDS. Any hydiocaibon, except methane and ethane, with vapor pressure to or greater than 0,1 inmHg,... 

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