Direct measurements of the interactions between clathrate hydrate particles and water droplets

Liu, Chenwei; Li, Mingzhong; Zhang, Guodong; Koh, Carolyn A.

doi:10.1039/c5cp02247a

Cited by 46 publications

(56 citation statements)

References 29 publications

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“…This occurs because the droplet is forced to change its shape at the last stages of coalescence, which is consistent with the interpretation of experimental data. 55 Qualitatively, the features just described are common in all simulated force -distance profiles obtained for the bare or the coated droplets, although different surfactants are considered. Some differences are however observed.…”

Section: A Hydrate Particle -Droplet Coalescencementioning

confidence: 88%

“…Long-range corrections to electrostatic interactions were treated using the Particle Mesh Ewald (PME) method. 47 The simulated temperature was maintained at We conducted steered MD simulations to mimic the hydrate coalescence as investigated by recent experimental approaches; [51][52][53][54][55] in our simulations the droplet was pulled towards the hydrate particle, which was maintained fixed. We used a harmonic spring with a force constant of 3000 kJ/mol.nm 2 tethered to the center of mass (COM) of the droplet.…”

Section: Simulation Methodologymentioning

confidence: 99%

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Molecular mechanisms responsible for hydrate anti-agglomerant performance

Phan

Bui

Acosta

et al. 2016

Phys. Chem. Chem. Phys.

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Steered and equilibrium molecular dynamics simulations were employed to study the coalescence of a sI hydrate particle and a water droplet within a hydrocarbon mixture. The size of both the hydrate particle and the water droplet is comparable to that of the aqueous core in reverse micelles. The simulations were repeated in the presence of various quaternary ammonium chloride surfactants. We investigated the effects due to different groups on the quaternary head group (e.g. methyl vs. butyl groups), as well as different hydrophobic tail lengths (e.g. n-hexadecyl vs. n-dodecyl tails) on the surfactants' ability to prevent coalescence. Visual inspection of sequences of simulation snapshots indicates that when the water droplet is not covered by surfactants it is more likely to approach the hydrate particle, penetrate the protective surfactant film, reach the hydrate surface, and coalesce with the hydrate than when surfactants are present on both surfaces. Force-distance profiles obtained from steered molecular dynamics simulations and free energy profiles obtained from umbrella sampling suggest that surfactants with butyl tripods on the quaternary head group and hydrophobic tails with size similar to the solvent molecules can act as effective anti-agglomerants. These results qualitatively agree with macroscopic experimental observations. The simulation results provide additional insights, which could be useful in flow assurance applications: the butyl tripod provides adhesion between surfactants and hydrates; when the length of the surfactant tail is compatible with that of the hydrocarbon in the liquid phase a protective film can form on the hydrate; however, once a molecularly thin chain of water molecules forms through the anti-agglomerant film, connecting the water droplet and the hydrate, water flows to the hydrate and coalescence is inevitable.

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Section: A Hydrate Particle -Droplet Coalescencementioning

confidence: 88%

Section: Simulation Methodologymentioning

confidence: 99%

Molecular mechanisms responsible for hydrate anti-agglomerant performance

Phan

Bui

Acosta

et al. 2016

Phys. Chem. Chem. Phys.

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“…Span 80 has a hydrophilic-lipophilic balance (HLB) value of 4.3, which is considered as an oil soluble surfactant that can promote the formation of water-in-oil emulsion. Span 80 has been used as a hydrate anti-agglomerant in labroratory researches [19,20]. In this study, the synergistic effect between AA and Span 80 is observed.…”

Section: Performance Of Compounded Anti-agglomerantsmentioning

confidence: 71%

Study on the Synergistic Properties of Two Nonionic Natural Gas Hydrate Anti-agglomerants Via Rocking Cell Tests

Dong¹

2017

IJEPE

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The application of anti-agglomerants (AAs) is becoming attractive due to effectiveness at low dosage and high subcooling. However, limited attention has been paid to the synergism effect between different AAs to increase their performance. In this study, anti-agglomeration performance of single and compounded chemical additives using a sapphire rocking cell is evaluated. The experimental results show that cocamidopropyl dimethylamine (AA) combined with sorbitan monooleate (Span 80) exhibits good anti-agglomeration performance. A compounded anti-agglomeration mechanism, in which Span 80 promotes the dispersion of water droplet in the oil phase before the formation of hydrates and AA prevents the agglomeration of hydrate particles formed from water droplets, is proposed. The physical appearance of the octane/brine/AAs mixtures has been studied and related to the anti-agglomeration performance of the AAs.

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“…5,6 In some cases, the amount and type of hydrate accumulation may lead to a blockage that completely disrupts flow. [7][8][9] These blockages are not only costly and hazardous to remove, but also lead to significant losses in production due to downtime. Thus, gas hydrate is considered the major flow assurance challenge in the production of oil and gas.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of hydrate formation and deposition under pseudo multiphase flow

2017

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Gas hydrate formation is considered one of the major challenges in the flow assurance of deepwater oil and gas pipelines, as their blockage by hydrate can lead to significant production/economic loss and safety risk. Understanding the hydrate formation and deposition processes can improve the management methods in field development and production. This study used a high‐pressure rocking cell to simulate multiphase flow conditions to visually investigate the hydrate formation and deposition from an oil‐gas‐water system. The changing hydrate morphologies, flow pattern and particle distribution during hydrate formation were studied and a conceptual model was proposed. The relative motion of hydrates to the cell wall and the final morphology of the hydrate chunks are found to be two critical parameters for evaluating hydrate deposition characteristics in the flow system. Five types of hydrate deposition morphologies are observed and these are correlated to the hydrate porosity. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4136–4146, 2017

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Direct measurements of the interactions between clathrate hydrate particles and water droplets

Cited by 46 publications

References 29 publications

Molecular mechanisms responsible for hydrate anti-agglomerant performance

Molecular mechanisms responsible for hydrate anti-agglomerant performance

Study on the Synergistic Properties of Two Nonionic Natural Gas Hydrate Anti-agglomerants Via Rocking Cell Tests

Dynamics of hydrate formation and deposition under pseudo multiphase flow

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