• Journal of Industrial Technology
• /
• v.40 no.1
• /
• pp.25-32
• /
• 2020

In this study, the effects of thermodynamic hydrate inhibitors on hydrate formation and dissociation behaviors were identified. The nucleation and growth of CP hydrate in the presence of methanol were monitored by optical microscope. Cyclopentane was used to demonstrate the oil phase in the pipeline in this study. Hydrate morphology, required time for hydrate formation, hydrate dissociation temperature were also identified by experiments. With the addition of methanol in water solution, the hydrate nucleation as well as hydrate growth were delayed. Moreover, hydrate morphology was also varied with the addition of methanol. Hydrate formation and dissociation temperature also decrease as the concentration of methanol increases.

• Neonatal Medicine
• /
• v.18 no.1
• /
• pp.130-136
• /
• 2011

Purpose: Chloral hydrate is a common drug frequently used for procedural sedation. But data on chloral hydrate use in the newborns are limited. This study examined the frequency of adverse effects of chloral hydrate and factors related to the adverse effects. We also examined if there were additional adverse effects when an additional sedative was used. Methods: The medical records of 104 patients admitted to neonatal intensive care unit of Seoul St. Mary's Hospital from March 2010 to February 2011 who used chloral hydrate for procedural sedation were retrospectively reviewed. Results: Adverse effects after administration of chloral hydrate were noted in 41.3% of the 104 patients. The adverse events included oxygen desaturation (18.8%), increase in apneic episodes (17.5%), increase in bradycardia (10%), and feeding intolerance (3.8%). Using oxygen at the time of chloral hydrate administration was independently associated with adverse effects (odds ratio [OR], 10.911: 95% confidence interval [CI], 2.082-57.178) and with the necessity for an additional sedative after administration of chloral hydrate (OR, 4.151: 95% CI, 1.455-11.840). Using one additional sedative agent after chloral hydrate showed no difference in adverse effects except feeding intolerance. Conclusion: Patients dependent on oxygen at the time of chloral hydrate administration may were found to be at higher risk for adverse effect of chloral hydrate and for an additional sedative. When an additional sedative is needed, it could be used with monitoring feeding intolerance after chloral hydrate administration.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.188-191
• /
• 2008

There have been many methods for producing natural gas from gas hydrate reservoirs in permafrost and sea floor sediments. It is well knownthat the depressurization should be a best option for Class 1 gas hydrate deposit, which is composed of tow layers: hydrate bearing layer and an underlying free gas. However many of gas hydrate reservoirs in sea floor sediments are classified as Class 2 that is composed of gas hydrate layer and mobile water, and Class 3 that is a single gas hydrate layer. The most appropriate production methods among the present methods such as thermal stimulation, inhibitor injection, and controlled oxidation are still under development with considering the gas hydrate reservoir characteristics. In East Sea of Korea, it is presumed that the thick fractured shale deposits could be Class 2 or 3, which is similar to the gas hydrate discovered offshore India. Therefore it is needed to evaluate the possible production methods for economic production of natural gas from gas hydrate reservoir. Here we would like to present the production of natural gas from gas hydrate deposit in East Sea with industrial flue gases from steel company, refineries, and other sources. The existing industrial complex in Gyeongbuk province is not far from gas hydrate reservoir of East Sea, thus the carbon dioxide in flue gas could be used to replace methane in gas hydrate. This approach is attractive due to the suggestion of natural gas productionby use of industrial flue gas, which contribute to the reduction of carbon dioxide emission in industrial complex. As a feasibility study, we did the NMR experiments to study the replacement reaction of carbon dioxide with methane in gas hydrate cages. The in-situ NMR measurement suggeststhat 42% of methane in hydrate cages have been replaced by carbon dioxide and nitrogen in preliminary test. Further studies are presented to evaluate the replacement ratio of methane hydrate at corresponding flue gas concentration.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.425-428
• /
• 2006

Natural gas hydrate has been a major problem for its plugging nature in the pipeline. With the demand of deep-water production, the importance of flow assurance technology, preventing hydrate, asphaltene and wax in the pipeline becomes bigger Kinetic models combined with the flow simulator are being developed to explain the nature of hydrate plug formation in the pipeline. To simulate the hydrate plug formation, each stage including the nucleation, growth and agglomeration should be considered. The hydrate nucleation is known to be stochastic and is believed hard to be predicted. Recent publications showed hydrate growth and agglomeration can be observed rigorously using a particle size analyzer. However properties of the hydrate should be investigated to model the growth and agglomeration. The attractive force between hydrate particles, supposed to be the capillary force, was revealed to be stochastic. Alternative way to model the hydrate agglomeration is to simulate by the discrete element method. Those parameters, particle size distribution, attractive force, and growth rate are embedded into the kinetic model which is combined Into the flow simulator. When compared with the flowloop experimental data, hydrate kinetic model combined into a flow simulator showed good results. With the early results, the hydrate kinetic model is promising but needs more efforts to improve it.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.11a
• /
• pp.47-49
• /
• 2006

The Sea of Okhotsk is the unique area providing the highest methane production rate of the northern hemisphere. The area of focused fluid venting offshore the NE Sakhalin continental slope was investigated during the CHAOS (Hydro-Carbon Hydrate Accumulations in the Okhotsk Sea) expeditions onboard of RV "Akademik Lavrentyev" In 2003, 2005 and 2006. The International Research Project CHAOS (Russia-Korea-Japan) aimed at the study of gas hydrate formation processes associated with the fluid venting in the Sea of Okhotsk. Several new gas hydrate accumulations were discovered during the cruise. Hydrate-associated structures have been named as KOPRI, VNIIOKeangeologia, POI and KIT (the names of cruise participant institutes) Some of hydrate-bearing cores contain big amount of gas hydrates: massive gas hydrate layers (up to 35cm thick) were recovered. The shallowest submarine gas hydrate accumulations in the world (at the depth less then 400m) were discovered during the cruise.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.549-552
• /
• 2009

Methane hydrate is crystalline ice-like compounds which formed methane gas enters within water molecules composed cavity at specially temperature and pressure condition, and water molecule and each other from physically-bond. $1m^3$ hydrate of pure methane can be decomposed to the maximum of $172m^3$ at standard condition. If these characteristics of hydrate are reversely utilized, natural gas is fixed into water in the form of hydrate solid. Therefore the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18~24% less than the liquefied transportation. However, when methane hydrate is formed artificially, the amount of consumed gas is relatively low due to a slow reaction rate between water and methane gas. In this study, for the better hydrate reaction rate, there is make nano fluid using ultrasonic dispersion of carbon nano tube. and then, Experiment with hydrate formation by nano fluid and methane gas reaction. The results show that when the carbon nano tubes of 0.004 wt% was added to pure water, the amount of consumed gas was about 300% higher than that in pure water and the hydrate formation time decreased.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.151-151
• /
• 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
• /
• 2005.06a
• /
• pp.663-666
• /
• 2005

Gas hydrates are ice-like compounds that form at the low temperature and high pressure conditions common in shallow marine sediments at water depths greater than 300-500 m when concentrations of methane and other hydrocarbon gases exceed saturation. Estimates of the total mass of methane carbon that resides in this reservoir vary widely. While there is general agreement that gas hydrate is a significant component of the global near-surface carbon budget, there is considerable controversy about whether it has the potential to be a major source of fossil fuel in the future and whether periods of global climate change in the past can be attributed to destabilization of this reservoir. Also essentially unknown is the interaction between gas hydrate and the subsurface biosphere. ODP Leg 204 was designed to address these questions by determining the distribution, amount and rate of formation of gas hydrate within an accretionary ridge and adjacent basin and the sources of gas for forming hydrate. Additional objectives included identification of geologic proxies for past gas hydrate occurrence and calibration of remote sensing techniques to quantify the in situ amount of gas hydrate that can be used to improve estimates where no boreholes exist. Leg 204 also provided an opportunity to test several new techniques for sampling, preserving and measuring gas hydrates. During ODP Leg 204, nine sites were drilled and cored on southern Hydrate Ridge, a topographic high in the accretionary complex of the Cascadia subduction zone, located approximately 80km west of Newport, Oregon. Previous studies of southern Hydrate Ridge had documented the presence of seafloor gas vents, outcrops of massive gas hydrate, and a pinnacle' of authigenic carbonate near the summit. Deep-towed sidescan data show an approximately $300\times500m$ area of relatively high acoustic backscatter that indicates the extent of seafloor venting. Elsewhere on southern Hydrate Ridge, the seafloor is covered with low reflectivity sediment, but the presence of a regional bottom-simulating seismic reflection (BSR) suggests that gas hydrate is widespread. The sites that were drilled and cored during ODP Leg 204 can be grouped into three end-member environments basedon the seismic data. Sites 1244 through 1247 characterize the flanks of southern Hydrate Ridge. Sites 1248-1250 characterize the summit in the region of active seafloor venting. Sites 1251 and 1252 characterize the slope basin east of Hydrate Ridge, which is a region of rapid sedimentation, in contrast to the erosional environment of Hydrate Ridge. Site 1252 was located on the flank of a secondary anticline and is the only site where no BSR is observed.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.407-409
• /
• 2006

Geochemical analyses carried out on samples collected from cores on and near the southern smit of Hydrate Ridge have advanced understanding by providing a clear contrast of the two major modes of marine gas hydrate occurrence. High concentrations (15%-40% of pore space) of gas hydrate occurring at shallow depths (0-40 mbsf) on and near the southern summit are fed by gas migrating from depths of as much as 2km within the accretionary prism. This gas carries a characteristic minor component of C2-C5 thermogenic hydrocarbons that enable tracing of migration pathways and may stabilize the occurrence of some structure II gas hydrate. A structure II wet gas hydrate that is stable to greater depths and temperatures than structure I methane hydrate may account for the deeper, faint second bottom simulating reflection (BSR2) that occurs on the seaward side of the ridge. The wet gas is migrating In an ash/turbidite layer that intersects the base of gas hydrate stability on the seaward side of and directly beneath the southern summit of Hydrate Ridge. The high gas saturation (>65%) of the pore space within this layer could create a two-phase (gas + solid) system that would enable free gas to move vertically upward through the gas hydrate stability zone. Away from the summit of the ridge there is no apparent influx of the gas seeping from depth and sediments are characterized by the normal sequence of early diagenetic processes involving anaerobic oxidation of sedimentary organic matter, initially linked to the reduction of sulfate and later continued by means of carbonate reduction leading to the formation of microbial methane.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.410-411
• /
• 2006

On the continental margins and in permafrost regions, natural gas, which has been expected to replace petroleum energy, exists In solid hydrate farm. World hydrate reserves Including natural gas are estimated at about twice as much as the energy contained In total fossil fuel reserves. Because of its vast quantities, the efficient recovery of natural gas from natural gas hydrate becomes the most important factor on evaluating the economic feasibility in the sense of commercialization. It has been noted that carbon dioxide, one of the well-known green house gases, possibly can be stored in the ocean floor as a carbon dioxide hydrate. If the natural gas hydrate could be converted into carbon dioxide hydrate, natural gas hydrate deposits would serve as energy sources as well as carbon dioxide storage sites in the deep ocean sediments. In this study, we first attempted to examine the real swapping phenomenon occurring between guest molecules and various structures of gas hydrate through spectroscopic identification such as NMR spectroscopy.