Improving the Accuracy of Gas Hydrate Dissociation Point Measurements

Tohidi, Bahman; Burgass, Rhoderick William; Danesh, Ali; Ostergaard, Kasper Korsholm; Todd, Adrian Christopher

doi:10.1111/j.1749-6632.2000.tb06846.x

Cited by 358 publications

(433 citation statements)

References 6 publications

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“…The pressure drop indicates the formation of gas hydrates. A heating procedure [49], with step-wise temperature increments of 0.5 K every 2 h was used to monitor the p-T of dissociation of mixed gas hydrates. This experimental setup and procedure employed to measure phase equilibrium with the Titanium pressure cell was validated by measuring HVLE data of pure CH 4 and pure H 2 O.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2018

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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.

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Section: Methodsmentioning

confidence: 99%

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

et al. 2018

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“…H 2 O was injected afterwards, and the temperature was reduced to 276.85 K to allow the formation of gas hydrates. An isochoric stepwise heating procedure [44] with temperature increments of 0.5 K every 5 h was applied to determine the hydrate dissociation conditions. The composition of the CO 2 -rich liquid phase was measured by discrete sampling during gas hydrate formation and dissociation.…”

Section: Methodsmentioning

confidence: 99%

Phase Equilibria of the CH4-CO2 Binary and the CH4-CO2-H2O Ternary Mixtures in the Presence of a CO2-Rich Liquid Phase

et al. 2017

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Abstract:The knowledge of the phase behavior of carbon dioxide (CO 2 )-rich mixtures is a key factor to understand the chemistry and migration of natural volcanic CO 2 seeps in the marine environment, as well as to develop engineering processes for CO 2 sequestration coupled to methane (CH 4 ) production from gas hydrate deposits. In both cases, it is important to gain insights into the interactions of the CO 2 -rich phase-liquid or gas-with the aqueous medium (H 2 O) in the pore space below the seafloor or in the ocean. Thus, the CH 4 -CO 2 binary and CH 4 -CO 2 -H 2 O ternary mixtures were investigated at relevant pressure and temperature conditions. The solubility of CH 4 in liquid CO 2 (vapor-liquid equilibrium) was determined in laboratory experiments and then modelled with the Soave-Redlich-Kwong equation of state (EoS) consisting of an optimized binary interaction parameter k ij(CH 4 -CO 2 ) = 1.32 × 10 −3 × T − 0.251 describing the non-ideality of the mixture. The hydrate-liquid-liquid equilibrium (HLLE) was measured in addition to the composition of the CO 2 -rich fluid phase in the presence of H 2 O. In contrast to the behavior in the presence of vapor, gas hydrates become more stable when increasing the CH 4 content, and the relative proportion of CH 4 to CO 2 decreases in the CO 2 -rich phase after gas hydrate formation.

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“…In practice, it took several hours, before stable values of temperature, pressure and gas composition were obtained and to be certain that equilibrium was attained. 25 As long as cyclopentane was not completely consumed during the mixed hydrate phase formation, the equilibrium stages, visualised in Figure 7, were independent of the overall cyclopentane composition.…”

Section: Hydrate Crystallisation Proceduresmentioning

confidence: 97%

“…The dissociation of the hydrate phase was performed by means of an isochoric procedure in which the reactor was heated in increments of ∆T = 1 K. 1,23,25 Each of the incremental increases in temperature was accompanied by a simultaneous increase in pressure which was caused by the liberation of gas during the hydrate dissociation ( Figure 7). After several hours, constant values for T and p were approached, indicating that thermodynamic equilibrium was attained.…”

Section: Hydrate Crystallisation Proceduresmentioning

confidence: 99%

“…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.…”

Section: Hydrate Crystallisation Proceduresmentioning

confidence: 99%

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

et al. 2014

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hydrate equilibrium data for gas mixture of carbon dioxide and nitrogen in the presence of an emulsion of cyclopentane in water.. Journal of Chemical and Engineering Data, American Chemical Society, 2014, 59 (3) ABSTRACTCarbon dioxide and nitrogen gas separation is achieved through clathrate hydrate formation in the presence of cyclopentane. A phase diagram is presented in which the mole fraction of CO 2 in the gas phase is plotted against the mole fraction of CO 2 in the carbon dioxide + nitrogen + cyclopentane mixed hydrate phase, both defined with respect to total amount of CO 2 and N 2 in the respective phase. The curve is plotted for temperatures ranging from 283.5 K to 287.5 K and pressures from 0.76 MPa to 2.23 MPa. The results show that the carbon dioxide selectivity is moderately enhanced when cyclopentane is present in the mixed hydrate phase. Carbon dioxide could be enriched in the hydrate phase by attaining a mole fraction of up to 0.937 when the corresponding mole fraction in the gas mixture amounts to 0.507. When compared to the three phase hydrate-aqueous liquid-vapour equilibrium in the ternary system 2 {water +carbon dioxide + nitrogen}, the equilibrium pressure of the mixed hydrate is reduced by 0.95 up to 0.97. The gas storage capacity approaches 40 m 3 gas.m -3 of hydrate. This value turns out to be roughly constant and independent of the gas composition and the operating conditions.

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Improving the Accuracy of Gas Hydrate Dissociation Point Measurements

Cited by 358 publications

References 6 publications

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

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

Phase Equilibria of the CH4-CO2 Binary and the CH4-CO2-H2O Ternary Mixtures in the Presence of a CO2-Rich Liquid Phase

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

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