Measurements for the Dissociation Conditions of Methane Hydrate in the Presence of 1,3,5-Trioxane and Tetrahydrofurfuryl Alcohol
Date Issued
2010
Date
2010
Author(s)
Ko, Wei-Yi
Abstract
The thermodynamic properties of methane hydrate were measured with an apparatus which operated at high pressure and low temperature conditions. The liquid water-hydrate-vapor (Lw-H-V) three-phase dissociation temperatures and pressures for methane hydrate in the presence of additives were determined by employing the isochoric method. The certain additives to system of water + methane were investigated for their effects on the methane hydrate dissociation conditions. The motivation of this study was to establish the methane hydrate equilibrium database which could be applied on gas hydrate exploitation, storage and transportation. We hope the thermodynamic equilibrium data measured in this work can help for industrial design in the future.
In this work, 1,3,5-Trioxane and THFA were chosen as additives. The addition of 1,3,5-Trioxane in methane hydrate system shifted the original hydrate phase boundaries to lower pressure and higher temperature and thus the hydrate stability region was broadened, therefore it had a promotion effect on the formation of methane hydrate. Furthermore, the promotion effect increased when the concentration of 1,3,5-Trioxane in hydrate system increased. With the concentration of 15 wt% 1,3,5-Trioxane additive, the dissociation temperature increased about 13 K at a given pressure in comparison to that of pure water system. In addition, the methane hydrate dissociation conditions for brine systems with 3.5 wt% NaCl were also measured in this study with the addition of 1,3,5-Trioxane. The promotion effect for methane hydrate formation in brine environments was also observed with 1,3,5-Trioxane additive. The dissociation temperature increased about 12 K at most at a given pressure in comparison to that of pure water system. However, the promotion effect in the presence of 1,3,5-Trioxane in the salt system was less than that in the pure water system. On the other hand, the results of adding THFA showed the inhibition effect on the formation of methane hydrate. The addition of THFA in methane hydrate system shifted the original hydrate phase boundaries to higher pressure and lower temperature. Similarly, the inhibition effect increased when the concentration of THFA in hydrate system increased. The dissociation temperature decreased about 5 K at most at a given pressure in comparison to that of pure water system.
Subjects
Methane hydrate
isochoric method
dissociation condition
1,3,5-Trioxane
THFA
brine
Type
thesis
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