Gas hydrate equilibria for CO2–N2 and CO2–CH4 gas mixtures—Experimental studies and thermodynamic modelling

Abstract

International audienceIn this paper, a set of experimental data on the phase equilibrium of gas hydrates in the presence of binary gas mixtures comprising CO2 is presented. The procedure established allows for the determination of both the composition of the gas phase as well as the hydrate phase without the need to sample the hydrate. The experimental results obtained in these measurements have been described by means of the classical model of van der Waals and Platteeuw. The values of internal parameters of the reference state and the Kihara parameters have been re-discussed and their interdependency is pointed. Finally the new set of parameters is validated against experimental data from other sources available in the literature, or invalidated against other sources. Finally, we conclude on the difference of experimental data between laboratories. The differences are not on the classical (pressure, temperature, gas composition) data which appear equivalent between laboratories. The difference stands on the measurement composition of the hydrate phase

Clathrate Hydrate Equilibrium Data for the Gas Mixture of Carbon Dioxide and Nitrogen in the Presence of an Emulsion of Cyclopentane in Water

“…In addition to the experimental data, Figure 9 shows corresponding curves calculated via a simulation for the system without cyclopentane, i.e. for the system {H 2 O + CO 2 + N 2 }, by means of the in-house programme "GasHyDyn" 23 at four different temperatures T. It can be seen in Figure 9 that the carbon dioxide selectivity in the mixed CO 2 + N 2 + CP hydrates is significantly increased compared to the theoretical selectivity of the gas hydrates without any promoter. For example, the mole fraction of CO 2 relative to the system {CO 2 + N 2 } present in the hydrate phase Experimental data presented by Li et al 22 for mixed CO 2 + N 2 + CP hydrates are added in Figure 9.…”

“…Via this change in tracer concentration, the water consumption could be estimated. 23,24 Estimation of the solubility of carbon dioxide in the emulsion…”

“…23,25 Mixed CO 2 + N 2 + CP hydrates were obtained by establishing hydrate forming state conditions in the reactor which was initially filled with a Initially, the reactor containing the empty Pyrex cell was closed and evacuated. The reactor was flushed three to four times with the first gas (CO 2 or N 2 ) to erase any trace of other gases before it was filled with the considered gas to the desired pressure.…”

“…Initially, Henry's constants of CO 2 in water, in cyclopentane as well as in a CP-in-water emulsion at several total mass fractions of p are compared to corresponding results obtained from a simulation using our in house-software "GasHyDyn" on the ternary system {H 2 O + CO 2 + N 2 } without CP 23 . Finally, the benefit of using cyclopentane in mixed CO 2 +N 2 +CP hydrates for lowering the equilibrium pressure is quantified and the gas storage capacity GSC is calculated.…”

Phase equilibrium measurements for clathrate hydrates of flue gas (CO2+N2+O2) in the presence of tetra-n-butyl ammonium bromide or tri-n-butylphosphine oxide

“…CO 2 hydrate is one of gas hydrates that are inclusion compounds with cages formed by the hydrogen-bonded water molecules and guest species [13]. One can employ the differences in the hydrate phase equilibrium conditions of CO 2 [14], O 2 [15] and N 2 [15] to selectively engage CO 2 into the cages of hydrate [16] while leaving other gas molecules behind. However, gas hydrate formation in water generally requires high working pressure; there is a need for lowering the pressure requirement in order to improve the process safety and lower the cost.…”