Phase Equilibria of the Synthesized Ternary CH₄/CO₂/N₂ Mixed-Gas Hydrates in Tetrabutylammonium Bromide Aqueous Solutions at Different Concentrations

Abstract

Hydrate-based gas separation (HBGS) technology can effectively separate CH 4 and CO 2 in multicomponent gases. To provide the necessary basic data for the HBGS technology, the hydrate phase equilibrium conditions of a ternary gas mixture (CH 4 /CO 2 /N 2 = 0.5/0.4/0.1) were determined and compared in tetrabutylammonium bromide (TBAB) aqueous solutions with different mass fractions (0.05, 0.1, 0.2, and 0.4). The results indicated that all four concentrations of TBAB aqueous solution could shift the hydrate phase equilibrium conditions of the ternary gas mixture to higher temperatures and lower pressures; this influence was enhanced with higher TBAB concentrations. When the TBAB mass fraction was 0.4, under the same phase equilibrium pressure conditions, the phase equilibrium temperature increased by a range of approximately 9−14 K compared with that of a pure water system. Meanwhile, TBAB had a greater impact on the phase equilibrium conditions of hydrates containing larger proportions of CO 2 and CH 4 gas and a greater impact on the phase equilibrium conditions of CO 2 and CH 4 gas hydrates than on N 2 hydrate.

Hydrate Phase Equilibria of Ternary Gas Mixtures with Tetrabutylammonium Bromide and Cyclopentane

“…To determine the effect of the mixed gas additives, the hydrate phase equilibrium data were analyzed under different conditions (Figure ). As reliable experimental results were previously obtained using this experimental device, the accuracy of the equipment was not verified in this work.…”

“…The experiment was carried out on a self-made system. This device has been used and described in a prior literature report . The main component of the device is a high-pressure reactor with sight windows on both sides, with a mechanical stirring system placed inside the reactor.…”

“…This device has been used and described in a prior literature report. 38 The main component of the device is a high-pressure reactor with sight windows on both sides, with a mechanical stirring system placed inside the reactor. In addition, this experimental device includes a gas supply system (gas cylinder), vacuum system, gas pipelines, and data acquisition system.…”

Study of the Effect of Tetrabutylammonium Halide Aqueous Solutions on the Gas Storage of Methane and Carbon Dioxide

“…Deschamps and Dalmazzone found that high concentrations of TBA salts can enlarge the CH 4 /CO 2 hydrate stability zone [7]; however, these concentrations may be unfavorable for the separation of CO 2 from mixtures of gases [8]. It has been shown that the phase equilibrium temperature of gas captured from the semi-clathrate phase increased by a range of ~9-14 K compared to that of gas hydrate formed from a pure water system when the TBAB mass fraction was 0.4 [9]. Cryo-SEM images have shown that the specific surface area of the hydrate crystals significantly increased by adding TBAB, as compared to a pure water system [10].…”

Hydrate Phase Equilibrium Data of Dimethyl Ether in the Presence of Tetrahydrofuran, Tetra-n-butylammonium Bromide, and Cyclopentane

“…It can effectively improve the phase equilibrium temperature of a gas hydrate with the addition of a certain concentration of the TBAB aqueous solution under the condition of a same pressure . While Zang et al proposed that the effectiveness of the concentration increase under the phase equilibrium condition promotion for a CH 4 /CO 2 /N 2 ternary gas mixture hydrate is not obvious anymore. Liang and his team also confirmed that TBAB can increase the phase equilibrium temperature of the CO 2 hydrate under a certain pressure.…”