Morphological Investigations of Methane−Hydrate Films Formed on a Glass Surface

Beltrán, Juan G.; Servio, Phillip

doi:10.1021/cg1003098

Cited by 67 publications

(77 citation statements)

References 35 publications

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“…Individual grain size decreases with increasing subcooling, and therefore grain density is lower towards higher temperatures. The latter agrees with previous work done for pure methane hydrate . Both systems B and C exhibited a change in crystal habit toward lower subcoolings (Figure ).…”

Section: Resultssupporting

confidence: 56%

“…The latter agrees with previous work done for pure methane hydrate. [14,24,25] Both systems B and C exhibited a change in crystal habit toward lower subcoolings ( Figure 5). For the system containing Inhibitor B, this transition was evident at ΔT sub = 2.2 K, whereas for system C the transition was observed at ΔT sub = 1.4 K. This dependence of the crystal habit on subcooling, namely the density of grains, ridges, and dendrites, has been reported for several KHIs and THIs, although the particular morphologies are different in each case.…”

Section: Exptmentioning

confidence: 99%

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Assessment of commercial hydrate inhibitors using the 3‐in‐1 method

et al. 2019

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Phase equilibria, kinetics, and morphology studies of gas hydrates require separate pieces of equipment and experimentation times in the order of days. Recently, we designed a reactor that allows for tight control of the crystallization temperature. Coupled with a novel method, this reactor can screen the crystal morphology, phase equilibria, and apparent kinetics of gas hydrates. Compared to traditional multi‐trial methods, the main advantage of this method is that only a single experiment, completed in the order of hours, is required to assess: (a) the change in hydrate growth velocity with respect to temperature, (b) the HLV equilibrium temperature at the experimental pressure, and (c) the change in crystal morphology with respect to driving force. Using this 3‐in‐1 method, methane hydrate growth and dissociation was studied in the presence of four commercial inhibitors. Phase equilibria, kinetics, and morphology were obtained for all hydrate systems with inhibitors. The standard uncertainty for the HLV equilibrium temperature was 0.05 K and for pressure 0.005 MPa. The apparent rates of growth were measured for all systems (standard uncertainty was 0.008 mm · s−1) and the difference between the inhibited systems and the pure system was very clear. Crystal habits varied considerably among inhibitors and radically with respect to the uninhibited system. Overall, we present an innovative technology to assess the morphology, kinetics, and thermodynamics of hydrate forming systems with a single apparatus. Furthermore, with little time investment, small sample sizes can be used to obtain replicates with minimum temperature and pressure uncertainties.

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Section: Resultssupporting

confidence: 56%

Section: Exptmentioning

confidence: 99%

Assessment of commercial hydrate inhibitors using the 3‐in‐1 method

et al. 2019

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“…Otherwise, a system may be in a metastable state from seconds to hours/days because nucleation of the hydrates is a stochastic process. Because the effect of the "memory" on the crystal growth behavior was concerned as observed on the crystal morphology of the hydrate formed on the liquid water wetting the glass surface, [21] we performed some experiments without the memory effect and confirmed that the results were identical with those with the memory effect.…”

Section: Methodsmentioning

confidence: 56%

Crystal Growth of Clathrate Hydrate in Gas/Liquid/Liquid System: Variations in Crystal‐Growth Behavior

Ishida¹,

Sakemoto²,

Ohmura³

2011

Chemistry A European J

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This paper reports the visual observations of the formation and growth of structure-II hydrate crystals on a water droplet partially immersed in liquid cyclopentane and exposed to difluoromethane gas. Each of the experiments was performed under prescribed temperature and pressure conditions in the range from 281.7 to 297.0 K and from 0.12 to 1.10 MPa in order to investigate the effect of the driving force for the hydrate crystal growth. The experiments were conducted at 25 different temperature-pressure conditions. It was found that the behavior of the hydrate crystal growth in this three-component system can be classified into three modes, which we called "cover", "expansion" and "line", depending on the temperature and pressure. The descriptions of the three types are summarized as follows. "COVER": Hydrate crystals first formed on the water-droplet surface and then grew to form a polycrystalline layer covering the surface. After complete surface coverage, no more hydrate growth and little change in the shape of the hydrate-covered water droplet were observed. "EXPANSION": Like "cover", the first crystals were observed on the water-droplet surface. They grew not only along the surface, but also toward the gas phase, and then continued to grow for more than several tens of minutes after complete coverage. "LINE": Unlike the other two modes, hydrate crystals first formed at the three-phase interfacial line and grew along this line. The shape of the hydrate crystals eventually became like a doughnut, since the center of the water droplet collapsed when they grew.

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“…The presence of MEG had a dramatic effect on halo propagation. Previous studies [31,32] had reported smooth halos, but never the three-dimensional faceted habit observed in Figure 4. The results observed in Figure 4 were highly reproducible as shown in Figure 5.…”

Section: Water + Ch 4 + Meg (W Meg = 10%)mentioning

confidence: 65%

A 3-In-1 Approach to Evaluate Gas Hydrate Inhibitors

2019

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With a single apparatus and very short experimentation times, we have assessed phase equilibria, apparent kinetics and morphology of methane gas hydrates in the presence of thermodynamic inhibitors ethane-1,2-diol (MEG) and sodium chloride (NaCl); and kinetic hydrate inhibitor polyvinyl-pyrrolidone (PVP). Tight, local temperature control produced highly repeatable crystal morphologies in constant temperature systems and in systems subject to fixed temperature gradients. Hydrate-Liquid-Vapor (HLV) equilibrium points were obtained with minimal temperature and pressure uncertainties (u T avg = 0.13 K and u p = 0.005 MPa). By applying a temperature gradient during hydrate formation, it was possible to study multiple subcoolings with a single experiment. Hydrate growth velocities were determined both under temperature gradients and under constant temperature growth. It was found that both NaCl and MEG act as kinetic inhibitors at the studied concentrations. Finally, insights on the mechanism of action of classical inhibitors are presented.

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Morphological Investigations of Methane−Hydrate Films Formed on a Glass Surface

Cited by 67 publications

References 35 publications

Assessment of commercial hydrate inhibitors using the 3‐in‐1 method

Assessment of commercial hydrate inhibitors using the 3‐in‐1 method

Crystal Growth of Clathrate Hydrate in Gas/Liquid/Liquid System: Variations in Crystal‐Growth Behavior

A 3-In-1 Approach to Evaluate Gas Hydrate Inhibitors

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