Generation of micro- and nano-bubbles in water by dissociation of gas hydrates

Uchida, Tsutomu; Yamazaki, Kenji; Gohara, Kazutoshi

doi:10.1007/s11814-016-0032-7

Cited by 77 publications

(106 citation statements)

References 27 publications

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“…Since the decomposition behavior is largely governed by the supersaturation of melt water in the vicinity to GH surface, the differences in the solubility and diffusion coefficients will influence the shape of the compositional gradient, but the phenomena are expected to be qualitatively the same. Indeed, molecular dynamics and electron microscopic work on methane hydrate decomposition have repeatedly observed the formation of nano‐ to micro‐ scale gas bubbles which may be the vesicles for the metastable enrichments in the liquid state [ Bagherzadeh et al ., ; Uchida et al ., , ]. Persistence and size of such nano‐bubbles is likely to be somewhat different for Xe and CH 4 systems.…”

Section: Discussionmentioning

confidence: 99%

Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix

Yang

Falenty

Chaouachi

et al. 2016

Geochem. Geophys. Geosyst.

198

109

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In-situ synchrotron X-ray computed microtomography with sub-micrometer voxel size was used to study the decomposition of gas hydrates in a sedimentary matrix. Xenon-hydrate was used instead of methane hydrate to enhance the absorption contrast. The microstructural features of the decomposition process were elucidated indicating that the decomposition starts at the hydrate-gas interface; it does not proceed at the contacts with quartz grains. Melt water accumulates at retreating hydrate surface. The decomposition is not homogeneous and the decomposition rates depend on the distance of the hydrate surface to the gas phase indicating a diffusion-limitation of the gas transport through the water phase. Gas is found to be metastably enriched in the water phase with a concentration decreasing away from the hydrate-water interface. The initial decomposition process facilitates redistribution of fluid phases in the pore space and local reformation of gas hydrates. The observations allow also rationalizing earlier conjectures from experiments with low spatial resolutions and suggest that the hydrate-sediment assemblies remain intact until the hydrate spacers between sediment grains finally collapse; possible effects on mechanical stability and permeability are discussed. The resulting time resolved characteristics of gas hydrate decomposition and the influence of melt water on the reaction rate are of importance for a suggested gas recovery from marine sediments by depressurization.

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Section: Discussionmentioning

confidence: 99%

Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix

Yang

Falenty

Chaouachi

et al. 2016

Geochem. Geophys. Geosyst.

198

109

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“…Because of the short standing time, the existing gas in the water phase before reformation cannot completely strip the water phase. 56 The stored gas would promote hydrate reformation. 58 Combining Figure 6 and Table 2, it can be found that the induction time at the 1 °C test temperature in the first formation was shorter than those at 3 and 5 °C.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Uchida et al have found that the storage period of 200 min is most conducive to the hydrate reformation. 24,56 The test temperatures of hydrate formation were 1, 3, and 5 °C.…”

Section: Methodsmentioning

confidence: 99%

Cyclic Formation Stability of 1,1,1,2-Tetrafluoroethane Hydrate in Different SDS Solution Systems and Dissociation Characteristics Using Thermal Stimulation Combined with Depressurization

et al. 2019

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Cold storage using hydrates for cooling is a high-efficiency technology. However, this technology suffers from problems such as the stochastic nature of hydrate nucleation, cyclic hydrate formation instability, and a low cold discharge rate. To solve these problems, it is necessary to further clarify the characteristics of hydrate formation and dissociation in different systems. First, a comparative experimental study in pure water and sodium dodecyl sulfate (SDS) solution systems was conducted to explore the influence of SDS on the morphology of the hydrate and the time needed for its formation under visualization conditions. Subsequently, the cyclic hydrate formation stability was investigated at different test temperatures with two types of SDS solution systems—with or without a porous medium. The induction time, full time, and energy consumption time ratio of the first hydrate formation process and the cyclic hydrate reformation process were analyzed. Finally, thermal stimulation combined with depressurization was used to intensify hydrate dissociation compared with single thermal stimulation. The results showed that the growth morphology of hydrate and the time required for its formation in the SDS solution system were obviously different than those in pure water. In addition, the calculation and comparison results revealed that the induction time and full time of cyclic hydrate reformation were shorter and the energy consumption time ratio was smaller in the porous medium. The results indicated that a porous medium could improve the cyclic hydrate formation process by making it more stable and by decreasing time and energy costs. Thermal stimulation combined with depressurization at different backpressures (0.1, 0.2, 0.3, and 0.4 MPa) effectively promoted the decomposition of hydrates, and with the decrease in backpressure, the dissociation time decreased gradually. At a backpressure of 0.1 MPa, the dissociation time was reduced by 150 min. The experimental results presented the formation and dissociation characteristics of 1,1,1,2-tetrafluoroethane hydrates in different systems, which could accelerate the application of gas hydrates in cold storage.

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“…However, various substances readily accumulate at the interface [ 7 ], as shown by the impurity deposits in Figure 1 , and such a change at the interface should decrease the air/water interfacial tension. As a result, the actual internal pressure would be lower than that predicted by use of the air/water interfacial tension of bulk water [ 16 ]. Therefore, the bubble internal pressure in an actual solution should be smaller than that estimated from Equation (2).…”

Section: Resultsmentioning

confidence: 99%

“…We just briefly describe the sample-preparation for the freeze-fracture replicas and TEM observations here as the details are described in [ 6 , 7 , 16 ]. Each frozen sample (at liquid nitrogen temperature) is placed in a freeze-etching device (JEOL, Tokyo, Japan, type JFD-9010), and fractured by a knife edge in a vacuum chamber at a temperature of about 150 K and a pressure of about 10 −5 Pa.…”

Section: Methodsmentioning

confidence: 99%

Ultra-Fine Bubble Distributions in a Plant Factory Observed by Transmission Electron Microscope with a Freeze-Fracture Replica Technique

et al. 2018

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Water containing ultra-fine bubbles (UFB) may promote plant growth. But, as UFBs are too small to distinguish from other impurities in a nutrient solution, it is not known if UFBs survive transport from the water source to the rhizosphere. Here we use the freeze-fracture replica method and a transmission electron microscope (TEM) to observe UFBs in the nutrient solutions used in a crop-growing system known as a plant factory. In this factory, TEM images taken from various points in the supply line indicate that the concentration of UFBs in the nutrient solution is conserved, starting from their addition to the nutrient solution in the buffer tank, through the peat-moss layer, all the way to the rhizosphere. Measurements also show that a thin film formed on the surface of UFBs in the nutrient solution, with greater film thickness at the rhizosphere. This film is considered to be made from the accumulation of impurities coming from solute and the peat-moss layer.

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Generation of micro- and nano-bubbles in water by dissociation of gas hydrates

Cited by 77 publications

References 27 publications

Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix

Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix

Cyclic Formation Stability of 1,1,1,2-Tetrafluoroethane Hydrate in Different SDS Solution Systems and Dissociation Characteristics Using Thermal Stimulation Combined with Depressurization

Ultra-Fine Bubble Distributions in a Plant Factory Observed by Transmission Electron Microscope with a Freeze-Fracture Replica Technique

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