• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.268-275
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• 2008

The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.268-275
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• 2008

The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.391-394
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• 2006

Growth characteristics of methane-propane clathrate hydrate, growing under different undercooling conditions, was investigated. After the water within pressurized vessel was fully saturated with guest gas molecules by agitation, medium was rapidly undercooled and maintained at the constant temperature. The growth of hydrate was always Initiated with film formations at the upper bounding surface of liquid pool. The visual observation using microscope revealed detailed features of subsequent crystal nucleation, migration, growth and interference occurring within liquid pool. A number of small crystals ascended and settled at the hydrate film. When undercooling was small $({\Delta}T=3.2K)$, some of the settled crystals slowly grew into faceted columns. As the undercooling increased, the downward growth of crystals underneath the hydrate film became dendritic and occurred with greater rate and with finer arm spacing. The shapes of the floating crystals were diverse and included octahedron and triangular or hexagonal platelet When the undercooling was small, the octahedral crystals were found dominant. As the undercooling increased, the shape of the floating crystals also became dendritic. The detailed characteristics of floating crystals were reported in this study.

• 신재생에너지
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• 제2권2호
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• pp.94-101
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• 2006

[ $1m^3$ ] solid hydrate contains up to $200m^3$ of natural gas, depending on pressure and temperature. Such large volume of natural gas hydrate can be utilized to store and transport large quantity of natural gas in a stable condition. So, in the present investigation, experiments carried out for the formation of natural gas hydrate governed by pressure, temperature, and gas compositions, etc.. The results show that the equilibrium pressure of structure II natural gas hydrate) is approximately 65% lower and the solubility is approximately three times higher than structure I methane hydrate). Also, the subcooling conditions of the structure I and II must be above 9K and 11K in order to form hydrate rapidly regardless of gas components, but the pressure increase is more advantageous than the temperature decrease in order to increase the gas consumption. And utilizing nozzles for spraying water in the form of droplets into the natural gas dramatically reduces the hydrate formation time and increases its solubility at the same time.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.399-402
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• 2006

[ $1m^3$ ] solid hydrate contains up to $200m^3$ of natural gas, depending on pressure and temperature. Such large volume of natural gas hydrate can be utilized to store and transport large quantity of natural gas in a stable condition. So, in the present investigation, experiments carried out for the formation of natural gas hydrate governed by pressure, temperature, and gas compositions, etc.. The results show that the equilibrium pressure of structure II natural gas hydrate (is approximately 65% lower and the solubility is approximately three times higher than structure I methane hydrate). Also, the subcooling conditions of the structure I and II must be above 9K and 11K in order to form hydrate rapidly regardless of gas components, but the pressure increase is more advantageous than the temperature decrease in order to increase the gas consumption. And utilizing nozzles for spraying water in the form of droplets into the natural gas dramatically reduces the hydrate formation time and increases its solubility at the same time.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.151-151
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• 2011

Large amounts of natural gas, mainly methane, in the form of hydrates are stored on continental margins. When gas hydrates are dissociated by any environmental trigger, generation of excess pore pressure due to released free gas may cause sediment deformation and weakening. Hence, damage on offshore structures or submarine landslide can occur by gas hydrate dissociation. Therefore, geotechnical stability of gas hydrate bearing sediments is in need to be securely assessed. However, geotechnical characteristics of gas hydrates bearing sediments including small-strain elastic moduli have been poorly identified. Synthesizing gas hydrate in natural seabed sediment specimen, which is mainly composed of silty-to-clayey soils, has been hardly attempted due to their low permeability. Moreover, it has been known that hydrate loci in pore spaces and heterogeneity of hydrate growth in specimen scale play a critical role in determining physical properties of hydrate bearing sediments. In the presented study, we synthesized gas hydrate containing sediments in an instrumented oedometric cell. Geotechnical and geophysical properties of gas hydrate bearing sediments including compressibility, small-strain elastic moduli, elastic wave, and electrical resistivity are determined by wave-based techniques during loading and unloading processes. Significant changes in volume change, elastic wave, and electrical resistivity have been observed during formation and dissociation of gas hydrate. Experimental results and analyses reveal that geotechnical properties of gas hydrates bearing sediments are highly governed by hydrate saturation, effective stress, void ratio, and soil types as well as morphological feature of hydrate formation in sediments.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.192-195
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• 2008

Conventional gas deposits consist of pressurized gas held in porous and permeable reservoir rocks and its recovery takes place where the natural pressure of the gas reservoir forces gas to the surface. But gas hydrate is a crystalline solid, its prospects require reservoir rock properties approprate porosity, permeability with mapping of temperature and pressure conditions to define the hydrate stability zone. In this study, we have carried out to investigate the dissociation characteristics of methane hydrates and the productivities of dissociated gas and water with depressurization scheme. Also, it has been conducted the flowing behavior of the dissociated gas and water in porous rock and the efficiency of the production.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.890-893
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• 2012

가스 하이드레이트란 물이 형성하는 수소 결합의 격자 구조 내로 저분자량의 기체 분자가 포집되며 형성하는 결정성 화합물이다. 가스 하이드레이트는 작은 고체 부피 내에 막대한 양의 기체 분자를 저장할 수 있다는 특징으로 인해 에너지 가스의 수송/저장 매체로 주목받고 있다. 또한 심해저와 영구 동토지역에 천연적으로 형성되어 부존되어 있는 막대한 양의 천연가스 하이드레이트를 미래 청정 에너지원으로 활용하기 위한 연구도 진행 중에 있다. 본 연구에서는 천연가스의 수송/저장 매체로 가스 하이드레이트의 활용 가능성을 확인하기 위하여, 메탄, 에탄, 프로판이 각각 90.0, 7.0, 3.0 mol% 포함된 합성 천연가스를 사용하여 가스 하이드레이트 형성과 형성시의 거동 변화를 측정하였다. 268 K 및 50 bar의 조건에서 형성된 천연가스 하이드레이트 시료에 대해 고체상 NMR 및 고분해능 분말 XRD 분석을 통하여 시료의 결정 구조 확인 및 미세 분자 거동을 확인하였다. 실험 결과를 통해 형성된 천연가스 하이드레이트는 구조-II인 것을 확인하였으며, 구조-II의 두 가지 동공 중 작은 동공은 메탄이, 그리고 큰 동공은 메탄, 에탄, 프로판 모든 성분들이 포집되어 있음을 알 수 있었다. 또한 NMR 분광 분석법과 기체 크로마토그래피를 사용하여 기체 및 고체 조성을 분석한 결과, 천연가스의 성분별 포집도에 차이가 있는 것을 알 수 있었는데, 순수한 기체를 기준으로 하였을 때 가스 하이드레이트를 더 잘 형성할 수 있는 프로판, 에탄, 메탄의 순으로 포집 경향이 나타남을 알 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.196-199
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• 2008

In this study, gas hydrate production has been followed using swapping method to investigate the effect of injection rate of flue gas and soaking period in unconsolidated artificial sand sample. The results shows that recovery factor of methane gas decreases with increasing the injection rate of flue gas. This indicates that the velocity of flue gas in porous media may act as kinds of inhibitor for production of hydrate. Also recovery factor increases with increasing the soaking time.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.241-246
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• 2000

Gas hydrates are solid solutions when water molecules are linked through hydrogen bondin create host lattice cavities that can enclose a large variety of guest gas molecules. The natural hydrate crystal may exist at low temperature above the normal freezing point of water and pressure greater than about 30 bars. A lot of quantities of natural gas hydrates exists in the ear many production schemes are being studied. In the present investigation, depressurization method considered to predict the production of gas and the simulation of the two phase flow - gas and - in porous media is being carried out. The simulation show about the fluid flow in porous have a variety of applications in industry. Results provide the appearance of gas and water prod the pressure profile, the saturation of gas/ water/ hydrates profiles and the location of the pl front.