Secondary nucleation in the formation of methane crystal hydrate

Makogon, Yuri F.; Мелихов, И. В.; Kozlovskaya, E. D.; Bozhevol’nov, V. E.

doi:10.1134/s0036024407100184

Cited by 10 publications

(6 citation statements)

References 5 publications

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“…On increasing supercooling (decreasing T ), the hydrate halo advances as an assemblage of small crystallites that nucleate at numerous locations at the halo front (secondary nucleation events), hence growing each to smaller size and giving rise to a smoother halo, similar to what is observed for hydrate polycrystalline crusts formed over water–guest interfaces. ,− , The hydrate halo grows closer to the glass wall, and the liquid water layer sandwiched between the halo and this wall is too thin to be visible under our microscope (see Figure ). However, due to the proper choice of capillary dimensions, the hydrate halo and the water layer cause a bright cusp on the inner wall (see above section “Glass Wettability and Thin Layers on the Glass”), so that their presence and lateral advance along the glass can be precisely monitored.…”

Section: Resultsmentioning

confidence: 53%

Roles of Wettability and Supercooling in the Spreading of Cyclopentane Hydrate over a Substrate

et al. 2017

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We use transmission optical microscopy to observe cyclopentane hydrate growth in sub-mm, open glass capillaries, mimicking cylindrical pores. The capillary is initially loaded with water and the guest fluid (cyclopentane) and thus possesses three menisci, that between water and cyclopentane (CP) in the middle and two menisci with the vapors at the ends. At temperatures T below the equilibrium temperature T ≈ 7 °C, the hydrate nucleates on the water-CP meniscus, rapidly coating it with an immobile, polycrystalline crust. Continued movement of the other two menisci provides insights into hydrate growth mechanisms, via the consumption and displacement of the fluids. On water-wet glass, the subsequent growth consists of a hydrate "halo" creeping with an underlying water layer on the glass on the CP side of the meniscus. Symmetrically, on CP-wet glass (silane-treated), a halo and a CP layer grow on the water side of the interface. No halo is observed on intermediate wet glass. The halo consists of an array of large monocrystals, over a thick water layer at low supercooling (ΔT = T - T below 5 K), and a finer, polycrystalline texture over a thinner water layer at higher ΔT. Furthermore, the velocity varies as ΔT, with α ≈ 2.7, making the early stages of growth very similar to gas hydrate crusts growing over water-guest interfaces. Beyond a length in the millimeter range, the halo and its water layer abruptly decelerate and thin down to submicron thickness. The halo passes through the meniscus with the vapor without slowing down or change of texture. A model of the mass balance of the fluids helps rationalize all of these observations.

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Section: Resultsmentioning

confidence: 53%

Roles of Wettability and Supercooling in the Spreading of Cyclopentane Hydrate over a Substrate

et al. 2017

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“…There have been many experiments and field studies conducted to understand the thermodynamics, − kinetics, − recovery, − and transportation − aspects of methane hydrate. In addition, molecular dynamics simulations are another powerful tool to investigate the thermophysical, structural, and dynamical properties of methane hydrate − and the formation, − dissociation, − and inhibition − mechanisms at the molecular scale.…”

Section: Introductionmentioning

confidence: 99%

“…1,[4][5][6] As a consequence, there is growing interest and research activity regarding its recovery [7][8][9][10][11][12] and related environmental and ecological impact. [13][14][15][16] There have been many experiments and field studies conducted to understand the thermodynamics, [17][18][19][20][21][22] kinetics, [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] recovery, [7][8][9][10][11][12] and transportation [39][40][41][42] aspects of methane hydrate. In addition, molecular dynamics simulations are another powerful tool to investigate the thermophysical, structural, and dynamical properties of methane hydrate [43][44][45]...…”

Section: Introductionmentioning

confidence: 99%

The Growth of Structure I Methane Hydrate from Molecular Dynamics Simulations

et al. 2010

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The key factors that affect the growth of methane hydrates are identified using molecular dynamics simulations. The three-phase molecular models consisting of methane gas, liquid water, and solid hydrate phase are used in this study. The melting temperatures of such a model at different pressures are found to be in good agreement with experiment. The growth rate of methane hydrate is found to be dominated by (1) the solubility of methane in the liquid phase, (2) the diffusivity of methane in water, and (3) the adsorption of methane by methane-filled incomplete water cages at the solid-liquid interface. The solubility, and hence the growth rate, increases with the partial pressure of methane in the vapor phase. The mass transport resistance from adsorption and the diffusion of methane are two competing factors, with the adsorption of methane at the interface found to be the rate-limiting step. The presence of a high concentration of incomplete clathrate hydrate cages presents strong affinity to dissolved methane at temperatures below the melting point. In addition to methane adsorption, water molecules must be expelled to form the complete clathrate cages. Both processes lead to a methane concentration minimum at 5-9 A in front of the growing interface. The methane concentration minimum provides the driving force for methane transport from the bulk to the interface. There are two types of solid layers of methane hydrate in the (1,0,0) direction. The growths of these layers are different, highly correlated, and affected by the methane concentration. A detailed mechanism of the layer growth is deduced from our simulations.

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“…The morphology of hydrate films formed from light hydrocarbons at high subcoolings has been often described as dendritic. , We observed methane + propane ( y CH 4 = 0.90) hydrate films with large, single grains at lower subcoolings changing to polycrystalline and finally to granular at higher subcoolings (Figure f–j). The growth of these hydrate films seemed to be dominated by a secondary nucleation mechanism , at Δ T sub = 3.0 K, therefore a highly packed, polycrystalline film is observed instead of a dendritic film. Propane hydrates did not evolve into dendrites or granular films, instead it formed blades that became densely packed and elongated at higher driving forces (Figure h).…”

Section: Resultsmentioning

confidence: 97%

Growth Mechanisms and Phase Equilibria of Propane and Methane + Propane Hydrates

Ovalle

Beltrán

2021

J. Chem. Eng. Data

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Gas hydrates of light hydrocarbons exhibit complex phase behavior, polymorphism, and diverse crystal morphology. We investigated phase equilibria and growth mechanisms of propane and methane + propane gas hydrates in the range of 0.25 to 2.1 MPa and 273.6 to 287.25 K. Clathrates formed from pure propane and the y CH4 = 0.90 methane + propane mixture exhibited similar morphologies at low subcoolings but differed considerably at higher subcoolings. The y CH4 = 0.98 methane + propane mixture formed crystals with radically different morphologies than those of pure propane and the y CH4 = 0.90 mixture. We report a new hydrate growth mechanism that proceeds via partial dissociation of the growing crystal in propane and propane + methane hydrates.

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Secondary nucleation in the formation of methane crystal hydrate

Cited by 10 publications

References 5 publications

Roles of Wettability and Supercooling in the Spreading of Cyclopentane Hydrate over a Substrate

Roles of Wettability and Supercooling in the Spreading of Cyclopentane Hydrate over a Substrate

The Growth of Structure I Methane Hydrate from Molecular Dynamics Simulations

Growth Mechanisms and Phase Equilibria of Propane and Methane + Propane Hydrates

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