The Induction Time of Hydrate Formation From a Carbon Dioxide-Methane Gas Mixture

Mohammadi, Abolfazl; Manteghian, Mehrdad

doi:10.1080/10916466.2011.615367

Cited by 12 publications

(6 citation statements)

References 14 publications

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“…These observations indicate that a higher y CO2 (CO 2 composition in gas mixture) can destabilize the nanobubbles and lead to a higher gas concentration in solution and a shorter induction time. This is in line with experimental studies, in which the induction time of hydrate formation decreased while hydrate growth rate increased upon increasing CO 2 composition in the CH 4 /CO 2 gas mixture. , Nevertheless, we find that the trend of induction time does not simply follow the trend of gas mole fraction in water, and that the induction times in run 1 and run 2 are different. These observations clearly show the stochastic nature of nucleation.…”

Section: Resultssupporting

confidence: 92%

Molecular Insights into the Nucleation and Growth of CH₄ and CO₂ Mixed Hydrates from Microsecond Simulations

Gupta

Linga

et al. 2016

J. Phys. Chem. C

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Hydrates of CH4/CO2 gas mixture are widely involved in hydrate-based applications, such as CH4/CO2 separation and exchange in exploitation of natural gas hydrate resource; nevertheless, their formation mechanisms remain elusive. In this study, microsecond simulations are performed to investigate the nucleation and growth of CH4/CO2 mixed hydrates from two-phase systems of water and CH4/CO2 gas mixture. The simulation results show that CH4-occupied small 512 cages initiates hydrate nucleation in a local liquid phase with a high gas concentration, where CO2 and CH4 cooperatively adsorb to hydrogen-bonded water rings toward hydrate-like ordering and cage formation. The difference in hydrophobicity between CH4 and CO2 affects the stability of nanobubbles of CH4/CO2 gas mixture in water and nucleation rate, and a high content (>75%) of CO2 accelerates nucleation due to its high solubility. The formation kinetics reveals the preferential uptake of CH4 into CH4/CO2 mixed hydrates during nucleation and the transition from fast to slow growth due to the rapid conversion of free water into hydrates. After hydrate growth, most water molecules in the systems are converted to CH4/CO2 mixed hydrates, composed of standard cages (512, 51262, 51263, and 51264) and metastable cages (4151062, 4151063, and 4151064). In these incipient hydrates, gas molecules always prefer to occupy the size-fitting cages, i.e., CH4 in 512, 4151062, 51262 cages and CO2 in 4151062, 51262, respectively. Interestingly, the abundance of 4151062 metastable cages (especially those CO2 occupied), with a size between those of small 512 and large 51262 cages, suggests their important role in the formation of incipient CH4/CO2 mixed hydrates. Multiple pathways are observed for the nucleation of CH4/CO2 mixed hydrates. In most of the systems, amorphous hydrates are formed with small sI and sII motifs exhibiting short-range orders, while only one system grows into partially ordered solids containing a large sI domain with long-range order spanning the whole simulation box. From bottom-up, this simulation study reveals the complex interplay between gas and water molecules at the condition of hydrate formation, and provides microscopic insights into the nucleation and growth of CH4/CO2 mixed hydrates.

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Section: Resultssupporting

confidence: 92%

Molecular Insights into the Nucleation and Growth of CH₄ and CO₂ Mixed Hydrates from Microsecond Simulations

Gupta

Linga

et al. 2016

J. Phys. Chem. C

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“…Many researchers have studied the hydrate induction time for gases in pure water. ,,,, The main influencing factors are subcooling, driving force, memory effect, stirring rate, and gas composition. ,− However, hydrate formation in crude oil or in water-in-oil emulsion may not be the same as the process in pure water, as for example there will be differences in the heat and mass transfer. − So it is essential to study the hydrate induction time in water-in-oil emulsion.…”

Section: Introductionmentioning

confidence: 99%

Induction Time of Hydrate Formation in Water-in-Oil Emulsions

Zheng

Huang

Wang

et al. 2017

Ind. Eng. Chem. Res.

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Blockage of pipelines due to hydrate formation is a major problem for subsea flow assurance. Induction time for hydrate formation from the multiphase system within a pipeline is a critical parameter to determine whether hydrates may form at a given time. In this work, the induction time for hydrate formation in water-in-oil emulsions was investigated under different conditions. For this purpose, an autoclave with an online viscometer was designed and built. Based on the viscosity variation observed in the experiments during hydrate formation, a new avenue for defining induction time is proposed, which should be more convenient for determining the hydrate formation time in some pipelines. As hydrate formation in emulsions is more complicated than in pure water, the effects of several factors were considered in this study, including water cut of the emulsions, shear rate, driving force, and memory effect. Additionally, wax precipitation is also a common problem in subsea pipelines and can impact flow assurance when hydrate formation and wax precipitation both occur. Consequently, the effect of wax solid particles on hydrate formation was also considered in this work. The presence of wax particles is observed to impede hydrate formation. In this work, it is determined from induction time that the hydrate formation is initiated at the water–oil surface for water-in-oil emulsion. Moreover, the memory effect can shorten induction times of hydrate formation due to the remaining small CO2 bubbles at the surface of water droplets.

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“…The induction time ( t induction ) describes the inhibitor’s ability to delay hydrate nucleation process before visible hydrate growth occurs [ 62 , 63 ]. It is the time required to form a detectable hydrate phase volume [ 64 , 65 , 66 ]. Nevertheless, the induction period is often defined as a probabilistic phenomenon because of the non-stochiometric existence of hydrate formation.…”

Section: Methodsmentioning

confidence: 99%

Kinetic Behavior of Quaternary Ammonium Hydroxides in Mixed Methane and Carbon Dioxide Hydrates

et al. 2021

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This study evaluates the kinetic hydrate inhibition (KHI) performance of four quaternary ammonium hydroxides (QAH) on mixed CH4 + CO2 hydrate systems. The studied QAHs are; tetraethylammonium hydroxide (TEAOH), tetrabutylammonium hydroxide (TBAOH), tetramethylammonium hydroxide (TMAOH), and tetrapropylammonium hydroxide (TPrAOH). The test was performed in a high-pressure hydrate reactor at temperatures of 274.0 K and 277.0 K, and a concentration of 1 wt.% using the isochoric cooling method. The kinetics results suggest that all the QAHs potentially delayed mixed CH4 + CO2 hydrates formation due to their steric hindrance abilities. The presence of QAHs reduced hydrate formation risk than the conventional hydrate inhibitor, PVP, at higher subcooling conditions. The findings indicate that increasing QAHs alkyl chain lengths increase their kinetic hydrate inhibition efficacies due to better surface adsorption abilities. QAHs with longer chain lengths have lesser amounts of solute particles to prevent hydrate formation. The outcomes of this study contribute significantly to current efforts to control gas hydrate formation in offshore petroleum pipelines.

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The Induction Time of Hydrate Formation From a Carbon Dioxide-Methane Gas Mixture

Cited by 12 publications

References 14 publications

Molecular Insights into the Nucleation and Growth of CH₄ and CO₂ Mixed Hydrates from Microsecond Simulations

Molecular Insights into the Nucleation and Growth of CH₄ and CO₂ Mixed Hydrates from Microsecond Simulations

Induction Time of Hydrate Formation in Water-in-Oil Emulsions

Kinetic Behavior of Quaternary Ammonium Hydroxides in Mixed Methane and Carbon Dioxide Hydrates

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The Induction Time of Hydrate Formation From a Carbon Dioxide-Methane Gas Mixture

Cited by 12 publications

References 14 publications

Molecular Insights into the Nucleation and Growth of CH4 and CO2 Mixed Hydrates from Microsecond Simulations

Molecular Insights into the Nucleation and Growth of CH4 and CO2 Mixed Hydrates from Microsecond Simulations

Induction Time of Hydrate Formation in Water-in-Oil Emulsions

Kinetic Behavior of Quaternary Ammonium Hydroxides in Mixed Methane and Carbon Dioxide Hydrates

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Molecular Insights into the Nucleation and Growth of CH₄ and CO₂ Mixed Hydrates from Microsecond Simulations

Molecular Insights into the Nucleation and Growth of CH₄ and CO₂ Mixed Hydrates from Microsecond Simulations