Experimental Study of Mixed Gas Hydrates from Gas Feed Containing CH4, CO2 and N2: Phase Equilibrium in the Presence of Excess Water and Gas Exchange

Abstract

This article presents gas hydrate experimental measurements for mixtures containing methane (CH 4 ), carbon dioxide (CO 2 ) and nitrogen (N 2 ) with the aim to better understand the impact of water (H 2 O) on the phase equilibrium. Some of these phase equilibrium experiments were carried out with a very high water-to-gas ratio that shifts the gas hydrate dissociation points to higher pressures. This is due to the significantly different solubilities of the different guest molecules in liquid H 2 O. A second experiment focused on CH 4 -CO 2 exchange between the hydrate and the vapor phases at moderate pressures. The results show a high retention of CO 2 in the gas hydrate phase with small pressure variations within the first hours. However, for our system containing 10.2 g of H 2 O full conversion of the CH 4 hydrate grains to CO 2 hydrate is estimated to require 40 days. This delay is attributed to the shrinking core effect, where initially an outer layer of CO 2 -rich hydrate is formed that effectively slows down the further gas exchange between the vapor phase and the inner core of the CH 4 -rich hydrate grain.

Recent Advances in Experimental Measurements of Mixed-Gas Three-Phase Hydrate Equilibria for Gas Mixture Separation and Energy-Related Applications

“…The related issues of the particular field experiment, however, at the laboratory scale were discussed by Schicks et al For that particular case, it is important to have available three-phase equilibrium data for the ternary mixture CH 4 + CO 2 + N 2 . Such experimental measurements have been reported by Lim et al, Legoix et al, and Mu and von Solms …”

“…The related issues of the particular field experiment, however, at the laboratory scale were discussed by Schicks et al 327 For that particular case, it is important to have available three-phase equilibrium data for the ternary mixture CH 4 + CO 2 + N 2 . Such experimental measurements have been reported by Lim et al, 209 Legoix et al, 67 and Mu and von Solms. 150 (iv) Finally, Fan and Guo 47 considered the use of various CO 2 -rich mixtures (including the ternary CO 2 + CH 4 + N 2 ) for processes related to enhanced oil recovery (EOR) and reported three-phase equilibria data that correspond to conditions that are related to the transportation of the CO 2 mixture.…”

Evaluation of a Simplified Model for Three-Phase Equilibrium Calculations of Mixed Gas Hydrates

“…Only a few exceptions to the aforementioned rule have been identified. Namely, the experimental data of Obanijesu et al [148] and Legoix et al [117,151] have % AAD values in the range 30-60% (see Figure S2b and Tables in Section S4 of the Supplementary Material). Given that the calculations (LI or CSMGem) for the other experimental data sets result in % AADs with significantly lower values, this could lead to the conclusion that the three particular data sets may have problematic experimental measurements that could be resolved by performing additional experimental measurements under similar conditions.…”

Polyhydroxybutyrate Production from Methane and Carbon Dioxide by a Syntrophic Consortium of Methanotrophs with Oxygenic Photogranules without an External Oxygen Supply

“…DH-1 and M. trichosporium OB3b strains were cultivated with OPGs to achieve simultaneous consumption of the CH 4 /CO 2 mixture. During the first few days of cultivation, CH 4 consumption was higher than CO 2 consumption in both cases, even though the aqueous solubility of CO 2 is known to be higher than that of CH 4 [ 34 ], which can be attributed to the higher growth rate of methanotrophs compared to phototrophs in OPGs, resulting in an imbalance between CO 2 production by methanotrophs and CO 2 consumption by phototrophs, and thus a significant decrease in the proportion of CO 2 in the headspace was not observed. After that, the growth rate of phototrophs increased, resulting in concurrent consumption of the CH 4 /CO 2 mixture ( Figure 1 a,c).…”