Inhibition methane hydrate

FIGURE 6.33 Data for structure H hydrates of methane with isopentane, neohexane, 2,3-dimethylbutane, and sodium chloride inhibition of hydrates of methane with isopentane, neohexane, and tert-butyl methyl ether. 

Figure 6.41 Methanol inhibition of simple methane hydrates.

Figure 6.44 Inhibition of simple methane hydrates with single and mixed electrolytes.

Frequently, hydrates become important in natural gas storage in salt caverns for peak shaving, or seasonal or diurnal volume averaging delivery of gases. The work by deRoo et al. (1983) discusses this process, regarding hydrate formation in high salt concentration, with their data provided in Chapter 6 on methane hydrate inhibited by sodium chloride. 

Some interesting simulations have been used to investigate crystallization and deposition processes, in order to obtain a fundamental understanding of how these processes can be inhibited. The inhibition of formation of waxes (mixtures of normal alkanes that form lamellar structures) was examined.302 Gas hydrate formation has been investigated, and it was demonstrated that inhibition of methane hydrate by a octomer of polyvinylpyrrolidone was able to be simulated,302 and simulations were used to assist in developing a new class of inhibitors of gas-hydrate formation.303... 

Models have been developed to evalnate natnral gas production from hydrates by both depressnrization and heating methods. There are three methods to obtain methane from gas hydrates (1) the depressurization method, (2) the thermal stimulation method, and (3) the chemical inhibition method. The thermal stimulation method and the chemical inhibitor injection method are both costly procedmes, whereas the depressurization method may prove useful when applied to more than one production. 

Figure 6.53 Methanol inhibition of methane + ethane hydrates.

Figure 6.55 Inhibition of methane + nitrogen hydrates with sodium chloride and magnesium chloride.

Naturally occurring clathrate hydrates are found in marine sediments and in permafrost. Because they contain a large amount of methane, they are thought to have potential as an unconventional energy resource. At the same time, however, clathrate hydrates are a serious problem for the gas and oil industries, because they form easily under suitable conditions at the sites of natural gas production, transportation, and processing. The inhibition and control of hydrates in pipelines adds tremendously to gas production costs. ... 

The presence of water, as mentioned earlier, can have several detrimental results among which is the formation of gas hydrates—snowlike, crystalline compounds composed of small amounts of methane, ethane, propane, or isobutane and water. The formation of these hydrates is aided by the presence of liquid water and areas of turbulence. The formation of these hydrates increases the pressure drop along the pipeline, thereby decreasing its capacity the presence of liquid water also can contribute to some corrosion. The formation and inhibition of these hydrates will be discussed in Section XII. In this section about gas treatment, the removal of hydrogen sulfide and other sulfide forms from the natural gas is discussed along with removal of carbon dioxide. A number of processes have been commercialized in this area and a few of them will be described here. 

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... 

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