Semi-clathrate hydrate phase stability conditions for methane + TetraButylAmmonium Bromide (TBAB)/TetraButylAmmonium Acetate (TBAA) + water system: Experimental measurements and thermodynamic modeling

Abstract

One of the promising applications of clathrate/gas hydrates is the transport and storage of natural gas. Semi-clathrate hydrates have received more attention due to milder pressure/temperature stability conditions compared to ordinary clathrate hydrates. The most commonly reported semi-clathrate hydrates are formed from a combination of gas + water + quaternary ammonium salts. In this work, a total of 53 equilibrium data for semi-clathrate hydrates of methane + TetraButylAmmonium Bromide (TBAB)/TetraButylAmmonium Acetate (TBAA) aqueous solutions were experimentally measured. For TBAB, three concentrations including 0.0350, 0.0490, and 0.1500 mass fractions were used. For TBAA, a solution with a 0.0990 mass fraction was used. Additionally, the modified Chen–Guo model was applied to calculate the hydrate phase equilibrium conditions of methane + TBAB/TBAA aqueous solutions. The model can accurately calculate the aforementioned semi-clathrate hydrate phase equilibrium conditions with the Average Absolute Deviations ((AAD)T and (AAD)P) of 0.1 K and 0.08 MPa, respectively. The temperature increments for 0.0350, 0.0490, and 0.1500 mass fractions of TBAB are 7.7, 9.4, and 13.5 K, respectively. This value for 0.0990 mass fraction of TBAA is 6.2 K. Therefore, it is concluded that TBAB is a stronger hydrate promoter compared to TBAA.

Impacts of Triethylene Glycol and Polyvinyl Caprolactam on Dissociation Conditions and Complete Inhibition Region of Methane Hydrate

“…The solutions were provided by a gravitational method utilizing an electronic A&D balance with a precision of ±0.0001 in mass fraction (HR-200 laboratory balance, Japan). The preparation of the ultrapure water was carried out with the water purification system (M-UV-3, Zolalan Company, Iran). ,,,, Figure presents the experimental setup overview.…”

“…The initial pressure ranges were 31.13–70.55 bar. More details can be found elsewhere. ,,,,, The P - T uncertainties were estimated to be 0.1 K and 0.05 MPa, respectively (in the reproducibility of the data). The accuracy of the device for the methane hydrate dissociation point measurements was verified in the previous studies. , Figure presents the qualitative behavior of the experimental procedure.…”

“…The preparation of the ultrapure water was carried out with the water purification system (M-UV-3, Zolalan Company, Iran). 5,38,69,84,85 Figure 1 presents the experimental setup overview.…”

Experimental Measurement and Thermodynamic Modeling of Methane Hydrate Dissociation Conditions in the Presence of Diglycolamine Aqueous Solution

“…The hydrate dissociation point can be determined by visual observation using a sight glass or by monitoring the pressure–temperature plot via the isochoric pressure-search method. The details of the experimental setup and procedure have been presented in our previous studies. ,− At the beginning of each experiment, the deionized water was used to wash the cell and then dried out entirely. A 30 cm 3 aqueous solution of a given concentration was fed into the cell in each experimental run.…”

“…The details of the calculation procedure of the gas hydrate dissociation conditions are presented in the previous studies. 26,47,49 To calculate the water activity in the presence of DGA, three activity coefficient models, namely, the Wilson activity coefficient model, 43 the NRTL activity coefficient model, 43 and the UNIQUAC activity coefficient model, 43 are applied. All the aforementioned activity models benefit from the local composition concept, resulting in superior results in systems exhibiting nonrandom behavior and extreme nonidealities.…”