Numerical Simulation of Nucleation Process of Clathrate Hydrates.

Ota, Masahiro; Qi, Yingxia

doi:10.1299/jsmeb.43.719

Cited by 21 publications

(9 citation statements)

References 12 publications

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“…The molecular mechanism of hydrate formation was investigated by using molecular dynamics simulations conducted at various temperatures under constant NVT conditions 18–20. This revealed that type 1 methane hydrate is more stably formed below 275 K. Although it can also be formed up to 300 K, it cannot be formed at 350 K. The crystal structure of hydrate type 1 generated by our simulations is in very good agreement with that measured by Hollander and Jeffery 6.…”

Section: Discussionsupporting

confidence: 82%

Visualization of Molecular Dynamics by Simulation

Ota

2002

Annals of the New York Academy of Sciences

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The mechanism of formation of methane hydrate is investigated here at a molecular level. The key to whether or not methane hydrates can be formed is the stability of the hydrate structure. This paper deals with a computer simulation of methane hydrate type 1 formation by a molecular dynamics method and an accurate description of the crystal structure. Computer simulation results show that very stable type 1 methane hydrates can be formed below 275 K, in which 46 water and 8 methane molecules are contained in a single cubic unit cell of length 12.0 A. Above 275 K, the stability of the hydrates increasingly degrades, logarithmically as a power function, up to 300 K, with no stability at 350 K. Pressure, as a parameter of formation conditions, increases with temperature and becomes tremendously high at 350 K. Hydrates with various hydration numbers (at least one guest molecule in a small cage) have roughly the same degree of stability, but higher pressures are required for hydrates with fewer guest molecules. Empty hydrates dissolve above 275 K.

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Section: Discussionsupporting

confidence: 82%

Visualization of Molecular Dynamics by Simulation

Ota

2002

Annals of the New York Academy of Sciences

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“…In the molecular dynamics simulation for the hydrate structure-I (20), (21) Table 3. From this table we can remark that the CO 2 hydrate structure simulated in this study is in good agreement with the MD simulation.…”

Section: Hydrate Structuresmentioning

confidence: 99%

“…5 Seeing the radial distribution function it is understood that our results are higher than the MD simulation results for the first and second peaks. Molecular dynamics simulation (20) was carried out for the radial distribution of methane-methane molecules and it was found that the methane molecules were separated by 6. To investigate the influence of hydration number on the structural nature between guest molecule-guest molecule radial distribution functions of CO 2 So, it may be said that the hydrate structures are main- …”

Section: Hydrate Structuresmentioning

confidence: 99%

Monte Carlo Approach to Structure and Thermodynamic Property of CO2 Hydrate

Ota

Ferdows

2005

JSME international journal. Ser. B, Fluids and thermal engineer

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Monte Carlo simulations have been carried out for the clathrate hydrate of CO 2 hydrates. In this study, we investigate the structure and statistical thermodynamic property of CO 2 hydrates at temperatures ranging from 150 to 288 [K] and at a pressure of up to 50 [MPa] under constant temperature and pressure conditions. We have found that the hydrate structure can be maintained at approximately 283 [K]. The thermodynamic property of density reflects the cage occupancy of the guest molecules and enthalpy increases with increasing temperature. Through our MC simulations, we also clarified hydrate and nonhydrate dividing lines by comparing them with other researchers' experimental results.

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“…A chemical potential driving force between the solution and the hydrate phase is required to initiate the formation of the first hydrate building blocks; it depends on the degree of sub-cooling, pressure and water content which in turn influence how quickly hydrates form after sub-cooling (Hobbs 1974). This has been shown by Christiansen and Sloan (1994) and in simulations (Ota and Qi 2000). The presence of impurities and the introduction of mechanical agitation stimulate formation and the nucleation rate reduce the degree of sub-cooling required for the time required for hydrate formation to induce (Dai et al 2014).…”

Section: Formation Vs Dissociationmentioning

confidence: 78%

Gas hydrate formation and dissociation numerical modelling with nitrogen and carbon dioxide

Smith

Barifcani

Pack³

2015

Journal of Natural Gas Science and Engineering

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This work aims at providing experimental data for various methane-based hydrates, namely nitrogen and carbon dioxide gas mixtures with varying concentrations to provide an empirically based hydrate equilibrium model. Acquired using a sapphire pressurevolumetemperature (PVT) cell, this data is used as the foundation for the derivation of a model able to calculate the equilibrium temperature of a nitrogen and/or carbon dioxide diluted methane gas is accomplished. There are several theoretical predictive models used in software which can provide hydrate formation and equilibrium data, however theoretical models appear to outnumber experimental data and empirical models for which a comparison can be made.The effect of nitrogen and carbon dioxide, an inhibitor and promotor respectively, on methane hydrate formation and dissociation and their associated pressure and temperature conditions are explored. The hydrate profiles for various gas mixtures containing the gases mentioned are presented at pressures ranging between 40-180 bara. These hydrate profiles and the model presented were compared to those predicted by hydrate computational software and experimental data from other studies for verification. The derived model proved to be reliable when applied to various gas mixtures at different pressure conditions and was consistent when compared to computational software based on theoretical models.Consistency of methane hydrate formation data was compared to dissociation data proved that the formation temperature is not an accurate representation of the equilibrium temperature. A simple statistical measure revealed the dissociation temperature measurements to be more precise and agreed to a much larger degree with literature.

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Numerical Simulation of Nucleation Process of Clathrate Hydrates.

Cited by 21 publications

References 12 publications

Visualization of Molecular Dynamics by Simulation

Visualization of Molecular Dynamics by Simulation

Monte Carlo Approach to Structure and Thermodynamic Property of CO2 Hydrate

Gas hydrate formation and dissociation numerical modelling with nitrogen and carbon dioxide

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