Methane butane water system, phase

Figure 4. Predicted phase diagram of methane, butane water system at...

McKetta, J. J. Katz, D. L. Methane-72-butane-water system in two- and three-phase regions. Ind. En. Chem. 1948, 40, 853-863. 

Figure 4 shows the calculated phase relationships in the methane-butane-water ternary system (8) at two temperatures. The results shown in Figure 4 indicate that the equation of state predicts the bubble points well, but that the predicted dew points at the higher temperature may not be as accurate. 

Figures 8 and 9 illustrate the type of agreement that was obtained for the water content and the hydrocarbon distribution in both the hydrocarbon liquid and vapor phases for the methane n-butane-water system. It can be seen from Figure 8 that the predictions reproduce the water content very well at all temperatures. Figure 9 shows that the agreement between experimental and predicted hydrocarbon concentrations in the vapor and liquid phases is good at 100 F, although the agreements does not seem to be as good at 2220 F. The experimental data for 220 F may be open to question since the critical pressure for methane-n-butane mixtures at 220 F is reported to be about 1350 psia by Roberts et al (11). The experimental data of these authors on the methane-n-butane system at 220 F are Included for comparison. It seems doubtful that the presence of water in this system would increase the critical pressure to about 1550 psia as indicated by the three component data. In view of this, the predicted results are thought to be just as good at 220 F as at 100°F.

The interaction parameters for binary systems containing water with methane, ethane, propane, n-butane, n-pentane, n-hexane, n-octane, and benzene have been determined using data from the literature. The phase behavior of the paraffin - water systems can be represented very well using the modified procedure. However, the aromatic - water system can not be correlated satisfactorily. Possibly a differetn type of mixing rule will be required for the aromatic - water systems, although this has not as yet been explored. 

The three phase program was then evaluated by comparing predicted and experimental results for the methane-n-butane-water and n-butane-1 butene-water systems as reported by McKetta and Katz (,9) and Wehe and McKetta (1 ). 

For MeOH-salt systems, two other produeed water samples were used. The produced water samples were taken from the downstream of a pipeline that was inhibited with MeOH, and eontained multiple salts and an unknown amount of a CL The C-V device measured the first one (PWS-1) with 2.9 mass% of salts and 22.2 mass% of MeOH, and the second one (PWS-2) with 3.0 mass% of salts and 23.0 mass% of MeOH. For PWS-1, two hydrate phase boundaries were determined by the C-V deviee and the freezing point depression (FPD) method [14], for a typical natural gas that was composed of methane (88.3 mol%), ethane (5.4 mol%), propane (1.5 mol%), isobutene (0.2 mol%), normal butane (0.3 mol%), isopentane (0.1 mol%), normal pentane (0.09 mol%), nitrogen (2.39 mol%), carbon dioxide (1.72 mol%). For PWS-2 with the same natural gas, the C-V device determined the hydrate phase boimdary, and one hydrate... 

Figure 8. Water content of hydrogen-rich liquid and vapor in a three-phase system containing water, methane, and n-butane...

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