The Experts below are selected from a list of 60825 Experts worldwide ranked by ideXlab platform
Yongwon Seo - One of the best experts on this subject based on the ideXlab platform.
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Formation and dissociation behaviors of SF6 Hydrates in the presence of a surfactant and an antifoaming agent for Hydrate-based greenhouse gas (SF6) separation
Chemical Engineering Journal, 2020Co-Authors: Yongwon SeoAbstract:Abstract Sulfur hexafluoride (SF6), the most potent greenhouse gas, should be separated from gas mixtures for recycling and for mitigation of global warming. In this study, the formation and dissociation behaviors of SF6 Hydrates in the presence of a surfactant (sodium dodecyl sulfate, SDS) and an antifoaming agent (antifoam A concentrate, AAC) were investigated, with a primary focus on kinetic, spectroscopic, and morphological analyses for Hydrate-based SF6 separation. The optimum concentrations of SDS and AAC for SF6 Hydrates were found to be 250 ppm and 1,500 ppm, respectively. The structure of SF6 Hydrates in the presence of SDS and AAC was identified as structure II, indicating that SDS and AAC had no impact on Hydrate structure. The formation behaviors of SF6 Hydrates were thoroughly examined through gas uptake measurements, visual observation, and in-situ Raman spectroscopy. The addition of SDS 250 ppm significantly accelerated the formation rate of SF6 Hydrate and the additional injection of AAC did not inhibit the promoting effect of SDS. Visual observation, temperature profiles, and volume of retrieved gas during the dissociation of SF6 Hydrates clearly demonstrated that SDS also had a promoting effect on SF6 Hydrate dissociation and its effect was slightly diminished with the addition of AAC, although AAC showed a powerful defoaming effect during the dissociation of SF6 Hydrates. The experimental results obtained in this study will be very useful for accelerating the formation rate of SF6 Hydrates using SDS and for solving the foaming problem using AAC in the design and operation of the gas Hydrate-based SF6 separation process.
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A novel discovery of a gaseous sH clathrate Hydrate former
Chemical Engineering Journal, 2019Co-Authors: Eunae Kim, Yongwon SeoAbstract:Abstract No gaseous guests have ever been discovered that can form sH clathrate Hydrates. Herein, we show that a large molecular fluorinated gas (octafluorocyclobutane, c-C4F8), can stabilize the crystal structure of sH clathrate Hydrate by occupying large (51268) cages. The inclusion of c-C4F8 molecules in sH clathrate Hydrate in the presence of CH4 molecules was clearly demonstrated through three-phase (clathrate Hydrate (H) – liquid water (LW) – vapor (V)) equilibria, powder X-ray diffraction (PXRD) and 13C NMR spectroscopy. The discovery of a gaseous sH former, c-C4F8, contributes to broadening clathrate Hydrate science and engineering by expanding target components for sH clathrate Hydrates, and also offers excellent potential in various applications of sH clathrate Hydrates, especially in clathrate Hydrate-based gas separation.
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isostructural and cage specific replacement occurring in sii Hydrate with external co2 n2 gas and its implications for natural gas production and co2 storage
Applied Energy, 2016Co-Authors: Youngju Seo, Jaehyoung Lee, Seongmin Park, Hyery Kang, Yunho Ahn, Dongwook Lim, Sejoon Kim, Joo Yong Lee, Taewoong Ahn, Yongwon SeoAbstract:A replacement technique has been regarded as a promising strategy for both CH4 exploitation from gas Hydrates and CO2 sequestration into deep-ocean reservoirs. Most research has been focused on replacement reactions that occur in sI Hydrates due to their prevalence in natural gas Hydrates. However, sII Hydrates in nature have been also discovered in some regions, and the replacement mechanism in sII Hydrates significantly differs from that in sI Hydrates. In this study, we have intensively investigated the replacement reaction of sII (C3H8+CH4) Hydrate by externally injecting CO2/N2 (50:50) gas mixture with a primary focus on powder X-ray diffraction, Raman spectroscopy, NMR spectroscopy, and gas chromatography analyses. In particular, it was firstly confirmed that there was no structural transformation during the replacement of C3H8+CH4 Hydrate with CO2/N2 gas injection, indicating that sII Hydrate decomposition followed by sI Hydrate formation did not occur. Furthermore, the cage-specific replacement pattern of the C3H8+CH4 Hydrate revealed that CH4 replacement with N2 in the small cages of sII was more significant than C3H8 replacement with CO2 in the large cages of sII. The total extent of the replacement for the C3H8+CH4 Hydrate was cross-checked by NMR and GC analyses and found to be approximately 54%. Compared to the replacement for CH4 Hydrate with CO2/N2 gas, the lower extent of the replacement for the C3H8+CH4 Hydrate with CO2/N2 gas was attributable to the persistent presence of C3H8 in the large cages and the lower content of N2 in the feed gas. The structural sustainability and cage-specific replacement observed in the C3H8+CH4 Hydrate with external CO2/N2 gas will have significant implications for suggesting target gas Hydrate reservoirs and understanding the precise nature of guest exchange in gas Hydrates for both safe natural gas production and long-term CO2 sequestration.
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Accurate measurement of phase equilibria and dissociation enthalpies of HFC-134a Hydrates in the presence of NaCl for potential application in desalination
Korean Journal of Chemical Engineering, 2016Co-Authors: Dongyoung Lee, Yohan Lee, Seungmin Lee, Wonjung Choi, Yongwon SeoAbstract:Phase equilibria, structure identification, and dissociation enthalpies of HFC-134a Hydrates in the presence of NaCl are investigated for potential application in desalination. To verify the influence of NaCl on the thermodynamic Hydrate stability of the HFC-134a Hydrate, the three-phase (Hydrate (H) - liquid water (LW) - vapor (V)) equilibria of the HFC-134a+NaCl (0, 3.5, and 8.0 wt%)+water systems are measured by both a conventional isochoric (pVT) method and a stepwise differential scanning calorimeter (DSC) method. Both pVT and DSC methods demonstrate reliable and consistent Hydrate phase equilibrium points of the HFC-134a Hydrates in the presence of NaCl. The HFC-134a Hydrate is identified as sII via powder X-ray diffraction. The dissociation enthalpies (ΔHd) of the HFC-134a Hydrates in the presence of NaCl are also measured with a high pressure micro-differential scanning calorimeter. The salinity results in significant thermodynamic inhibition of the HFC-134a Hydrates, whereas it has little effect on the dissociation enthalpy of the HFC-134a Hydrates. The experimental results obtained in this study can be utilized as foundational data for the Hydrate-based desalination process.
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ch4 recovery and co2 sequestration using flue gas in natural gas Hydrates as revealed by a micro differential scanning calorimeter
Applied Energy, 2015Co-Authors: Yohan Lee, Jaehyoung Lee, Huen Lee, Yunju Kim, Yongwon SeoAbstract:The CH4–flue gas replacement in naturally occurring gas Hydrates has attracted significant attention due to its potential as a method of exploitation of clean energy and sequestration of CO2. In the replacement process, the thermodynamic and structural properties of the mixed gas Hydrates are critical factors to predict the heat flow in the Hydrate-bearing sediments and the heat required for Hydrate dissociation, and to evaluate the CO2 storage capacity of Hydrate reservoirs. In this study, the 13C NMR and gas composition analyses confirmed that the preferential enclathration of N2 molecules in small 512 cages of structure I Hydrates improved the extent of the CH4 recovery. A high pressure micro-differential scanning calorimeter (HP μ-DSC) provided reliable Hydrate stability conditions and heat of dissociation values in the porous silica gels after the replacement, which confirmed that CH4 in the Hydrates was successfully replaced with flue gas. A heat flow change associated with the dissociation and formation of Hydrates was not noticeable during the CH4–flue gas replacement. Therefore, this study reveals that CH4–flue gas swapping occurs without structural transitions and significant Hydrate dissociations.
Yohan Lee - One of the best experts on this subject based on the ideXlab platform.
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Accurate measurement of phase equilibria and dissociation enthalpies of HFC-134a Hydrates in the presence of NaCl for potential application in desalination
Korean Journal of Chemical Engineering, 2016Co-Authors: Dongyoung Lee, Yohan Lee, Seungmin Lee, Wonjung Choi, Yongwon SeoAbstract:Phase equilibria, structure identification, and dissociation enthalpies of HFC-134a Hydrates in the presence of NaCl are investigated for potential application in desalination. To verify the influence of NaCl on the thermodynamic Hydrate stability of the HFC-134a Hydrate, the three-phase (Hydrate (H) - liquid water (LW) - vapor (V)) equilibria of the HFC-134a+NaCl (0, 3.5, and 8.0 wt%)+water systems are measured by both a conventional isochoric (pVT) method and a stepwise differential scanning calorimeter (DSC) method. Both pVT and DSC methods demonstrate reliable and consistent Hydrate phase equilibrium points of the HFC-134a Hydrates in the presence of NaCl. The HFC-134a Hydrate is identified as sII via powder X-ray diffraction. The dissociation enthalpies (ΔHd) of the HFC-134a Hydrates in the presence of NaCl are also measured with a high pressure micro-differential scanning calorimeter. The salinity results in significant thermodynamic inhibition of the HFC-134a Hydrates, whereas it has little effect on the dissociation enthalpy of the HFC-134a Hydrates. The experimental results obtained in this study can be utilized as foundational data for the Hydrate-based desalination process.
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ch4 recovery and co2 sequestration using flue gas in natural gas Hydrates as revealed by a micro differential scanning calorimeter
Applied Energy, 2015Co-Authors: Yohan Lee, Jaehyoung Lee, Huen Lee, Yunju Kim, Yongwon SeoAbstract:The CH4–flue gas replacement in naturally occurring gas Hydrates has attracted significant attention due to its potential as a method of exploitation of clean energy and sequestration of CO2. In the replacement process, the thermodynamic and structural properties of the mixed gas Hydrates are critical factors to predict the heat flow in the Hydrate-bearing sediments and the heat required for Hydrate dissociation, and to evaluate the CO2 storage capacity of Hydrate reservoirs. In this study, the 13C NMR and gas composition analyses confirmed that the preferential enclathration of N2 molecules in small 512 cages of structure I Hydrates improved the extent of the CH4 recovery. A high pressure micro-differential scanning calorimeter (HP μ-DSC) provided reliable Hydrate stability conditions and heat of dissociation values in the porous silica gels after the replacement, which confirmed that CH4 in the Hydrates was successfully replaced with flue gas. A heat flow change associated with the dissociation and formation of Hydrates was not noticeable during the CH4–flue gas replacement. Therefore, this study reveals that CH4–flue gas swapping occurs without structural transitions and significant Hydrate dissociations.
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structure identification and dissociation enthalpy measurements of the co2 n2 Hydrates for their application to co2 capture and storage
Chemical Engineering Journal, 2014Co-Authors: Yohan Lee, Seungmin Lee, Jaehyoung Lee, Yongwon SeoAbstract:Abstract In this study, the mixed gas Hydrates formed from the flue gas mixtures of CO 2 + N 2 have been investigated with a primary focus on the structure identification and the dissociation enthalpy measurements. The stability conditions of the CO 2 + N 2 gas Hydrates are determined using an isochoric (PVT) method and a differential scanning calorimeter (DSC). It is found from the comparison of the Hydrate phase equilibrium data measured using two methods that the DSC can be effectively used as an alternative method for measuring the stability conditions of the CO 2 + N 2 gas Hydrates. The microscopic analyses, such as powder X-ray diffraction and Raman spectroscopy, demonstrated that the gas mixtures of CO 2 + N 2 form a structure I Hydrate and that the structural transition does not occur in the range of the flue gas composition. To reveal the dissociation behavior of the mixed gas Hydrates, the dissociation enthalpies of the CO 2 + N 2 gas Hydrates have been measured using a micro-differential scanning calorimeter (μ-DSC). The dissociation heats of the CO 2 + N 2 gas Hydrates increased with an increase of the CO 2 composition in the Hydrate phase. The experimental results obtained in this study provide the thermodynamic and physical background required to estimate the heat liberated or absorbed during Hydrate formation and dissociation and to predict the operation conditions for the gas Hydrate-based CO 2 capture and storage process.
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experimental verification of methane carbon dioxide replacement in natural gas Hydrates using a differential scanning calorimeter
Environmental Science & Technology, 2013Co-Authors: Seungmin Lee, Yohan Lee, Jaehyoung Lee, Huen Lee, Yongwon SeoAbstract:The methane (CH4) – carbon dioxide (CO2) swapping phenomenon in naturally occurring gas Hydrates is regarded as an attractive method of CO2 sequestration and CH4 recovery. In this study, a high pressure microdifferential scanning calorimeter (HP μ-DSC) was used to monitor and quantify the CH4 – CO2 replacement in the gas Hydrate structure. The HP μ-DSC provided reliable measurements of the Hydrate dissociation equilibrium and Hydrate heat of dissociation for the pure and mixed gas Hydrates. The Hydrate dissociation equilibrium data obtained from the endothermic thermograms of the replaced gas Hydrates indicate that at least 60% of CH4 is recoverable after reaction with CO2, which is consistent with the result obtained via direct dissociation of the replaced gas Hydrates. The heat of dissociation values of the CH4 + CO2 Hydrates were between that of the pure CH4 Hydrate and that of the pure CO2 Hydrate, and the values increased as the CO2 compositions in the Hydrate phase increased. By monitoring the heat ...
Jaehyoung Lee - One of the best experts on this subject based on the ideXlab platform.
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isostructural and cage specific replacement occurring in sii Hydrate with external co2 n2 gas and its implications for natural gas production and co2 storage
Applied Energy, 2016Co-Authors: Youngju Seo, Jaehyoung Lee, Seongmin Park, Hyery Kang, Yunho Ahn, Dongwook Lim, Sejoon Kim, Joo Yong Lee, Taewoong Ahn, Yongwon SeoAbstract:A replacement technique has been regarded as a promising strategy for both CH4 exploitation from gas Hydrates and CO2 sequestration into deep-ocean reservoirs. Most research has been focused on replacement reactions that occur in sI Hydrates due to their prevalence in natural gas Hydrates. However, sII Hydrates in nature have been also discovered in some regions, and the replacement mechanism in sII Hydrates significantly differs from that in sI Hydrates. In this study, we have intensively investigated the replacement reaction of sII (C3H8+CH4) Hydrate by externally injecting CO2/N2 (50:50) gas mixture with a primary focus on powder X-ray diffraction, Raman spectroscopy, NMR spectroscopy, and gas chromatography analyses. In particular, it was firstly confirmed that there was no structural transformation during the replacement of C3H8+CH4 Hydrate with CO2/N2 gas injection, indicating that sII Hydrate decomposition followed by sI Hydrate formation did not occur. Furthermore, the cage-specific replacement pattern of the C3H8+CH4 Hydrate revealed that CH4 replacement with N2 in the small cages of sII was more significant than C3H8 replacement with CO2 in the large cages of sII. The total extent of the replacement for the C3H8+CH4 Hydrate was cross-checked by NMR and GC analyses and found to be approximately 54%. Compared to the replacement for CH4 Hydrate with CO2/N2 gas, the lower extent of the replacement for the C3H8+CH4 Hydrate with CO2/N2 gas was attributable to the persistent presence of C3H8 in the large cages and the lower content of N2 in the feed gas. The structural sustainability and cage-specific replacement observed in the C3H8+CH4 Hydrate with external CO2/N2 gas will have significant implications for suggesting target gas Hydrate reservoirs and understanding the precise nature of guest exchange in gas Hydrates for both safe natural gas production and long-term CO2 sequestration.
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ch4 recovery and co2 sequestration using flue gas in natural gas Hydrates as revealed by a micro differential scanning calorimeter
Applied Energy, 2015Co-Authors: Yohan Lee, Jaehyoung Lee, Huen Lee, Yunju Kim, Yongwon SeoAbstract:The CH4–flue gas replacement in naturally occurring gas Hydrates has attracted significant attention due to its potential as a method of exploitation of clean energy and sequestration of CO2. In the replacement process, the thermodynamic and structural properties of the mixed gas Hydrates are critical factors to predict the heat flow in the Hydrate-bearing sediments and the heat required for Hydrate dissociation, and to evaluate the CO2 storage capacity of Hydrate reservoirs. In this study, the 13C NMR and gas composition analyses confirmed that the preferential enclathration of N2 molecules in small 512 cages of structure I Hydrates improved the extent of the CH4 recovery. A high pressure micro-differential scanning calorimeter (HP μ-DSC) provided reliable Hydrate stability conditions and heat of dissociation values in the porous silica gels after the replacement, which confirmed that CH4 in the Hydrates was successfully replaced with flue gas. A heat flow change associated with the dissociation and formation of Hydrates was not noticeable during the CH4–flue gas replacement. Therefore, this study reveals that CH4–flue gas swapping occurs without structural transitions and significant Hydrate dissociations.
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structure identification and dissociation enthalpy measurements of the co2 n2 Hydrates for their application to co2 capture and storage
Chemical Engineering Journal, 2014Co-Authors: Yohan Lee, Seungmin Lee, Jaehyoung Lee, Yongwon SeoAbstract:Abstract In this study, the mixed gas Hydrates formed from the flue gas mixtures of CO 2 + N 2 have been investigated with a primary focus on the structure identification and the dissociation enthalpy measurements. The stability conditions of the CO 2 + N 2 gas Hydrates are determined using an isochoric (PVT) method and a differential scanning calorimeter (DSC). It is found from the comparison of the Hydrate phase equilibrium data measured using two methods that the DSC can be effectively used as an alternative method for measuring the stability conditions of the CO 2 + N 2 gas Hydrates. The microscopic analyses, such as powder X-ray diffraction and Raman spectroscopy, demonstrated that the gas mixtures of CO 2 + N 2 form a structure I Hydrate and that the structural transition does not occur in the range of the flue gas composition. To reveal the dissociation behavior of the mixed gas Hydrates, the dissociation enthalpies of the CO 2 + N 2 gas Hydrates have been measured using a micro-differential scanning calorimeter (μ-DSC). The dissociation heats of the CO 2 + N 2 gas Hydrates increased with an increase of the CO 2 composition in the Hydrate phase. The experimental results obtained in this study provide the thermodynamic and physical background required to estimate the heat liberated or absorbed during Hydrate formation and dissociation and to predict the operation conditions for the gas Hydrate-based CO 2 capture and storage process.
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experimental verification of methane carbon dioxide replacement in natural gas Hydrates using a differential scanning calorimeter
Environmental Science & Technology, 2013Co-Authors: Seungmin Lee, Yohan Lee, Jaehyoung Lee, Huen Lee, Yongwon SeoAbstract:The methane (CH4) – carbon dioxide (CO2) swapping phenomenon in naturally occurring gas Hydrates is regarded as an attractive method of CO2 sequestration and CH4 recovery. In this study, a high pressure microdifferential scanning calorimeter (HP μ-DSC) was used to monitor and quantify the CH4 – CO2 replacement in the gas Hydrate structure. The HP μ-DSC provided reliable measurements of the Hydrate dissociation equilibrium and Hydrate heat of dissociation for the pure and mixed gas Hydrates. The Hydrate dissociation equilibrium data obtained from the endothermic thermograms of the replaced gas Hydrates indicate that at least 60% of CH4 is recoverable after reaction with CO2, which is consistent with the result obtained via direct dissociation of the replaced gas Hydrates. The heat of dissociation values of the CH4 + CO2 Hydrates were between that of the pure CH4 Hydrate and that of the pure CO2 Hydrate, and the values increased as the CO2 compositions in the Hydrate phase increased. By monitoring the heat ...
Jiho Yoon - One of the best experts on this subject based on the ideXlab platform.
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phase equilibrium studies of tetrahydrofuran thf ch4 thf co2 ch4 co2 and thf co2 ch4 Hydrates
Journal of Chemical & Engineering Data, 2012Co-Authors: Taro Kawamura, Yoshitaka Yamamoto, Jiho YoonAbstract:The Hydrate phase equilibrium behaviors of tetrahydrofuran (THF) + CH4, THF + CO2, CH4 + CO2, and THF + CO2 + CH4 were investigated over wide ranges of temperature, pressure, and concentration. The dissociation conditions of THF + CH4 and THF + CO2 Hydrates were shifted to lower pressures and higher temperatures from the dissociation boundaries of pure CH4 and pure CO2 Hydrates. X-ray diffraction results revealed that the CH4 + CO2 and THF + CO2 + CH4 Hydrates prepared from a CH4/CO2 (50:50) gas mixture formed structure I and II clathrate Hydrates, respectively. Raman measurements provided detailed information regarding the cage occupancy of CH4 and CO2 molecules encaged in the Hydrate frameworks. For the CH4 + CO2 Hydrates, the concentrations of CO2 in the Hydrate phase were higher than those in the vapor phase. In contrast, for the THF + CO2 + CH4 Hydrates, the concentrations of CO2 in the Hydrate phase were lower than those in the vapor phase.
Jiro Nagao - One of the best experts on this subject based on the ideXlab platform.
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effective control of gas Hydrate dissociation above the melting point of ice
Physical Chemistry Chemical Physics, 2011Co-Authors: Masato Kida, Hideo Narita, Yusuke Jin, Jiro NagaoAbstract:Direct measurements of the dissociation behaviors of pure methane and ethane Hydrates trapped in sintered tetrahydrofuran Hydrate through a temperature ramping method showed that the tetrahydrofuran Hydrate controls dissociation of the gas Hydrates under thermodynamic instability at temperatures above the melting point of ice.
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dissociation behavior of c2h6 Hydrate at temperatures below the ice point melting to liquid water followed by ice nucleation
Journal of Physical Chemistry A, 2011Co-Authors: Hiroshi Ohno, Hideo Narita, Ikumi Oyabu, Yoshinori Iizuka, Takeo Hondoh, Jiro NagaoAbstract:The dissociation of C2H6 Hydrate particles by slow depressurization at temperatures slightly below the ice melting point was studied using optical microscopy and Raman spectroscopy. Visual observations and Raman measurements revealed that ethane Hydrates can be present as a metastable state at pressures lower than the dissociation pressures of the three components: ice, Hydrate, and free gas. However, they decompose into liquid water and gas phases once the system pressure drops to the equilibrium boundary for supercooled water, Hydrate, and free gas. Structural analyses of obtained Raman spectra indicate that structures of the metastable Hydrates and liquid water from the Hydrate decay are fundamentally identical to those of the stable Hydrates and supercooled water without experience of the hydration. These results imply a considerably high energy barrier for the direct Hydrate-to-ice transition. Water solidification, probably induced by dynamic nucleation, was also observed during melting.
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numerical analysis of the dissociation experiment of naturally occurring gas Hydrate in sediment cores obtained at the eastern nankai trough japan
Energy & Fuels, 2010Co-Authors: Yoshihiro Konno, Hiroyuki Oyama, Jiro Nagao, Yoshihiro Masuda, Masanori KuriharaAbstract:Oceanic gas Hydrate deposits at high saturations have been found within continuous thick sands in areas such as the Eastern Nankai Trough and the Gulf of Mexico. The recent discovery of these deposits has stimulated research and development programs exploring the use of gas Hydrates as energy resources. Because the permeability of Hydrate-bearing sediments is a crucial factor for successful gas production from oceanic Hydrate reservoirs, the permeability of these sediments and the dissociation process of Hydrates should be investigated using Hydrate cores obtained at these oceanic Hydrate reservoirs. In this study, to investigate the permeability of actual Hydrate-bearing sediments and the dissociation process of Hydrates by a depressurization method, a numerical simulation was conducted using a state-of-the-art Hydrate reservoir simulator. A dissociation experiment of Hydrate-bearing sandy cores obtained from turbidite sediments at the Eastern Nankai Trough was analyzed. By choosing appropriate model par...
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phase diagram latent heat and specific heat of tbab semiclathrate Hydrate crystals
Fluid Phase Equilibria, 2005Co-Authors: Hiroyuki Oyama, Satoshi Takeya, Wataru Shimada, Takao Ebinuma, Yasushi Kamata, Tsutomu Uchida, Jiro Nagao, Hideo NaritaAbstract:Tetra-n-butyl ammonium bromide (TBAB) is a tetra-alkylammonium salt, that forms two types of semiclathrate Hydrate. At atmospheric pressure, the melting points are between room temperature and freezing point of water. There are some useful applications of the semiclathrate, for example using as a heat transport medium and gas separator, but there are little knowledge about TBAB Hydrates characteristics. In this paper, some thermal properties of TBAB semiclathrate Hydrate are reported. We determined the phase diagram of semiclathrate Hydrate nucleation under the condition of atmospheric pressure, latent and specific heats capacity of TBAB semiclathrate Hydrate. From the phase diagram, the congruent melting points of two TBAB Hydrates were determined. Using above results, we obtained the hydration numbers of two type TBAB Hydrates.
