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1.
Thermal property measurements of natural gas hydrates in various sediment mixtures are necessary to describe heat transfer
to surroundings during well boring and gas production. An apparatus for measuring thermal diffusivity in various mixtures
of hydrates with sediment has been constructed. The apparatus uses a new method for determining thermal diffusivity that has
advantages over the von Herzen and Maxwell probe method. The new experiment is simple and inexpensive to construct and appears
to be much more accurate than the ±30% reported for an earlier probe. The thermal diffusivity of ice has been measured to
determine the uncertainty of the technique, i.e., within ±6% with a 95% confidence level. The thermal diffusivity for pure
methane hydrate at various temperatures is reported.
Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A. 相似文献
2.
Ekta Chaturvedi Krishan Patidar Madhukar Srungavarapu Sukumar Laik Ajay Mandal 《Advanced Powder Technology》2018,29(4):1025-1034
Huge amount of gas hydrate deposits are identified in deep marine sediments, which may be considered as a future source of energy. Since carbonate is one of the major components of marine sediments, in the present study attention has been given to characterize methane hydrate formation and dissociation in presence of calcium carbonate. Experiments were performed with 0%, 2%, 4%, 6% and 10% by weight of calcium carbonate in distilled water. Extensive investigations have been done on pressure-temperature equilibrium behavior of hydrate formation and dissociation at varying concentrations of calcium carbonate. Hydrate formation rate was found to vary with concentration of calcium carbonate as the solubility of calcium carbonate in water is controlled by the presence of simultaneous chemical equilibria involving a high number of species like Ca2+, CO32?, HCO3?, CO2, etc. Induction time for hydrate formation has also been measured at different concentrations of carbonate. Nucleation point for the hydrate formation was observed to be slightly higher at higher concentration of calcium carbonate due to increased heat absorption. Dissociation enthalpy of hydrates was calculated by using Clausius-Clapeyron at different measured conditions. Moles consumption of methane gas during hydrate formation at different concentrations of carbonate was measured using real gas equation and found to be minimum at 10?wt%. 相似文献
3.
《Advanced Powder Technology》2014,25(4):1227-1233
This paper reports an experimental study of the kinetics of methane hydrate formation in the presence of ionic surfactants with equal carbon chain length, such as sodium dodecyl sulfate (SDS), dodecylamine hydrochloride (DAH), dodecyltrimethylammonium chloride (DTAC) and N-dodecylpropane-1,3-diamine hydrochloride (DN2Cl). Methane hydrates were formed at 274 K with incipient gas pressure of 15 MPa in an unstirred isochoric/isothermal reactor containing aqueous solutions at different initial surfactant loadings. It was found that addition of DTAC had little effect on methane hydrate formation whereas SDS, DAH, and DN2Cl had pronounced promoting effects. This result coincides with the fact that the Krafft point of DTAC is below 273 K and those of SDS, DAH, and DN2Cl are near room temperature. At a given initial surfactant loading, the effectiveness of the surfactants for reducing the induction time of methane hydrate formation followed the order of SDS > DAH > DN2Cl. SDS also gave higher hydrate growth rates than DAH and DN2Cl. At 1000 and 2000 ppm, however, DN2Cl gave slightly higher final methane uptake than SDS. It was also found that during the nucleation or induction period, addition of SDS, DAH and DN2Cl instead of DTAC, considerably reduced methane mole fraction in the liquid phase. Possible promotion mechanisms of surfactants during the hydrate nucleation period were discussed. 相似文献
4.
Sanehiro Muromachi Hiroyuki Miyamoto Ryo Ohmura 《International Journal of Thermophysics》2017,38(12):173
Semiclathrate hydrates are water-based host-guest compounds formed from aqueous solutions of ionic guest substances. These materials can greatly moderate formation pressures and temperatures from canonical gas hydrates. This is a significant advantage for industrial applications such as gas separation and storage. \(\hbox {N}_{2}\) gas is a major component contained in various flue gases and is usually mixed with \(\hbox {CO}_{2}\). Semiclathrate hydrates can separate these gases under moderate thermodynamic conditions. Tetra-n-butylammonium bromide (TBAB) is a widely used ionic guest substance. To develop the application technologies and their theoretical models, solubility data of \(\hbox {N}_{2}\) gas in TBAB aqueous solutions are required. In this study, we report \(\hbox {N}_{2}\) gas solubility measured by an absolute gravimetric method for the semiclathrate hydrate formation system of \(\hbox {TBAB} + \hbox {H}_{2}\hbox {O} + \hbox {N}_{2}\). The measurement pressures, temperatures and TBAB mass fractions were 3 MPa, 5 MPa and 7 MPa, 292.15 K, 302.15 K and 307.15 K, and 0 (pure water), 0.10, 0.20, 0.32 and 0.40, respectively. The uncertainties were 0.056 MPa, 0.44 K and 0.00012 in mole fraction. Although the technical difficulty lays on measurements of small \(\hbox {N}_{2}\) gas solubility by the absolute gravimetric method, our data implied the unique gas dissolution property of aqueous TBAB solution depending on the TBAB concentration. The aqueous TBAB solutions with mass fractions of 0.10 and 0.20 had similar \(\hbox {N}_{2}\) gas solubility as that in pure water. With higher mass fractions, 0.32 and 0.40, the \(\hbox {N}_{2}\) gas solubility slightly increased from that in pure water, which implies the salting-in effect of TBAB. 相似文献
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Hossein Sojoudi Matthew R. Walsh Karen K. Gleason Gareth H. McKinley 《Advanced Materials Interfaces》2015,2(6)
The formation and accumulation of clathrate hydrates inside oil and gas pipelines cause severe problems in deep‐sea oil/gas operations. In the present work, durable and mechanically robust bilayer poly‐divinyl benzene/poly(perfluorodecylacrylate) coatings are developed using initiated chemical vapor deposition (iCVD) to reduce the adhesion strength of hydrates to underlying substrates (silicon and steel). Tetrahydrofuran (THF) dissolved in water with a wt% concentration of 0–70 is used to study the formation of hydrates and their adhesion strength. Goniometric measurements of the THF–water droplets on the substrates exhibit a reduction in advancing and receding contact angles with an increase in the THF concentration. The strength of hydrate adhesion experiences a tenfold reduction when substrates are coated with these iCVD polymers: from 1050 ± 250 kPa on bare silicon to 128 ± 100 kPa on coated silicon and from 1130 ± 185 kPa on bare steel to 153 ± 86 kPa on coated steel. The impact of subcooling temperature and time on the adhesion strength of hydrate on substrates is also studied. The results of this work suggest that the THF–water mixture repellency of a given substrate can be utilized to assess its hydrate‐phobic behavior; hence, it opens a pathway for studying hydrate‐phobicity. 相似文献
8.
Experiments on fast nucleation and growth of HCFC141b gas hydrate in static water columns 总被引:3,自引:0,他引:3
Jinping Li Kaihua Guo Deqing Liang Ruzhu Wang 《International Journal of Refrigeration》2004,27(8):793-939
A major technical issue in the realization of refrigerants gas hydrates energy storage systems is to develop a practical means for rapid hydrate formation. In this paper, the nucleation and growth processes of HCFC141b (CH3CCl2F, HCFC141b) gas hydrate in a column of water added with 0.038 wt% sodium dodecylbenzenesulfonate-6 and with a metal rod which was placed in the center of the column has been studied. The water solution column, in a cylindrical glass container, was placed in a thermostatic bath ranged 274.15–280.15 K and under atmospheric pressure. The experimental results show that, comparing to that of pure water and HCFC141b system, the properly placed metal rods combined with proper amount of sodium dodecylbenzenesulfonate-6 considerably promotes the hydrate formation speed and reduces the nucleation time. The growth rate of HCFC141b hydrate is significantly effected by the surrounding bath temperature and the formation can be finished in 8 h with a short nucleation time when the bath temperature ranged 274.15–279.15 K and the iron rod penetrating the interface between the water solution and liquid HCFC141b. The experimental results suggest a new way for fast formation of gas hydrates. 相似文献
9.
H. J. M. Hanley G. J. Meyers J. W. White E. D. Sloan 《International Journal of Thermophysics》1989,10(4):903-909
Melting points for the tetrahydrofuran/D2O hydrate in equilibrium with the airsaturated liquid at atmospheric pressure are reported. The melting points were measured by monitoring the absorbance of the solution. Overall, the meltingpoint phase boundary curve is about 2.5 K greater than the corresponding curve for the H2O hydrate, with a congruent melting temperature of 281±0.5 K at a D2O mole fraction of 0.936. The phase boundary is predicted to within 5% if the assumption is made that the THF occupancy in the D2O and H2O hydrates is the same. We measure an occupancy of 99.9%. The chemical potential of the empty lattice in D2O is estimated to be 5% greater than in H2O. 相似文献
10.
本文基于压缩式循环原理,采用水冷式直接接触式蓄冷系统,研究了不同充注压力(3.5、3.6、3.7、3.8、3.9、4.0 MPa)和不同质量浓度(0.3、0.5、0.7、0.9 g/L)的十二烷基硫酸钠(SDS)溶液中,CO2水合物的生成特性和蓄冷特性。根据实验数据对蓄冷量、蓄冷速率和CO2水合物生成质量进行计算,结果表明:与未添加SDS的溶液相比,含有不同质量浓度的SDS溶液中,系统的预冷时间和蓄冷时间均缩短,水合物生成质量、总蓄冷量及平均蓄冷速率均有所提升,且随着充注压力的不断提高,系统的蓄冷性能也不断加强。当充注压力为4.0 MPa,SDS溶液质量浓度为0.5 g/L时,预冷时间(5.58 min)和蓄冷时间(10.92 min)达到最短。此时,系统的总蓄冷量(4021.2 kJ)、潜热蓄冷量(2476.8 kJ)、CO2水合物生成质量(4.95 kg)及平均蓄冷速率(6.14 kW)均达到最大值,即系统蓄冷能力达到最强,说明SDS对于本系统的CO2水合物蓄冷性能具有明显的强化效果。 相似文献
11.
随着海底矿物开采越来越普遍,技术人员面对越来越复杂的钻探技术挑战。特别是极端条件下的深海开采,开采矿产之前,要先处理好表层的可燃冰。通过PVT仪器直接目测来观察气体水合物的形成是一种比较常用的方法。通过记录测量过程中的温压变化来确定气体水合物的形成热力学条件。但是笨重的PVT仪使得实验受限制,并且实验过程中不能有固体微粒出现。本文通过微量热法来确定水合物的成分,研究形成及分解机理,测量比热容。为了满足高压微量热试验需求,法国塞塔拉姆公司特别提出了完全革新的测试手段(法国石油学会专利技术),运用高压MICRODSC来建立气体水合物的形成热力学模型及生成动力学理论,表征水合物相变与时间、温度、压力的对应关系。MicroDSCVII是研究气体水合的专业高压微量热仪,一经推出就广受好评,样品量为0.7ml的全新样品池,并可与专业的高压控制面板相接,最大压力可以达到1000bars,温度范围为-45℃andl20℃。目前,高压MicroDSCVII已经被运用于各种条件下的气体水合物研究,诸如:气体水合物的形成机理,特别是甲烷气体水合物的研究;气体水合物在海底沉积物中的成藏机理;石油开采中水合物形成的抑制;天然气运输及储存过程中气体水合物的形成;冷藏过程中的气体水合的形成及分解等。 相似文献
12.
Isothermal composition measurements for both the equilibrium liquid and vapour phases have been determined for the nitrogen + methane system at eight temperatures between 112.00 and 180.00 K, and at pressures from 1 to 49 atm (1 to 50 bar). The internal consistency of these data is checked by comparing experimental and calculated thermodynamically consistent vapour phase compositions. Derived Henry's constants are used to provide a comparison between these data and those of other investigators. 相似文献
13.
A theoretical model of a single gas bubble rising in open water is considered. It is revealed that methane bubble rising is accompanied by the formation of the hydration shell on its surface under the thermobaric conditions of the stability of hydrates. Numerical solutions for two limiting cases were obtained and analyzed, when the formation rate of the hydrated crust on the bubble surface is limited by the intensity of heat removal released in the process of hydrate formation by the surrounding liquid or the diffusion resistance of the gas hydrate crust to the transfer of hydrate-forming components. The comparison of numerical results with experimental data showed that the scheme of the diffusion transfer of hydrate-forming components through the crust describes most adequately the process of the growth of the gas hydrate particle observed in experiments of methane bubbles rising in sea water. It is established that argon bubble rising under the corresponding thermobaric conditions can occur without the formation of the hydrate on its surface. The migration of the gas bubble is accompanied by its dissolution in water. Numerical estimates for the values of the argon diffusion coefficient in water and reduced diffusion coefficients of gas (methane) and water through the hydrate crust are obtained from the conditions of matching theoretical and experimental data from the change of the argon bubble radius and the gas hydrate particle. 相似文献
14.
Consideration is given to the possibility of using crystalline hydrates as a source of water, on whose evaporation most of
the heat passing to the protected surface is expended. A version of the thermal protection based on silica fabric, whose pores
are partly filled with a crystalline hydrate, is studied. Test results are presented. Experimental data are analyzed.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 75–79, January–February, 2000. 相似文献
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Hydration and microstructural characteristics of mixtures containing C3A and CaSO4.2H2O (0, 12.5, 25%) with or without addition of CaCO3 (0, 12.5, 25%) are followed by X-ray diffraction, differential scanning calorimetry, differential thermogravimetry, scanning
electron microscopy and conduction calorimetry. Depending on the length of hydration, products formed at different periods
from 5 min to 3 days consisted of hexagonal calcium aluminate hydrate, cubic calcium aluminate hydrate, calcium monocarboaluminate
hydrate, etrringite, calcium monosulfoaluminate hydrate and possibly a solid solution of hexagonal calcium aluminate hydrate
with monocarbo-and sulfo-aluminate hydrates.
Calcium carbonate retards or suppresses the formation of the cubic aluminate hydrate in the hydration of C3A. It accelerates formation of ettringite and its conversion to the monosulfoaluminate phase when added to the C3A+gypsum+H2O mixture.
Résumé On étudie l’hydratation et les caractéristiques de la microstructure de mélanges renfermant du C3A et du CaSO4.2H2O (0, 12,5 et 25% avec ou sans addition de CaCO3 (0, 12,5 et 25%) à l’aide de la diffraction X, de la calorimétrie par balayage différentiel, la thermogra-vimétrie différentielle, la microscopie électronique à balayage et la calorimétrie par conduction. Selon la durée de l’hydration, il se forme à différents intervalles allant de 5 minutes à 3 jours de l’hydrate d’aluminate de calcium hexagonal, de l’hydrate d’aluminate de calcium cubique, de l’hydrate de monocarboaluminate de calcium, de l’ettringite, de l’hydrate de monosulfoaluminate de calcium et parfois une solution solide d’hydrate d’aluminate de calcium hexagonal avec hydrate de monocarbo et sulfoaluminate. Le carbonate de calcium retarde ou empêche la formation d’hydrate d’aluminate cubique dans l’hydratation de C3A. Il accélère la formation d’ettringite et sa conversion en phase monosulfoaluminate lorsqu’il s’ajoute au mélange C3A+platre+H2O.相似文献
17.
气体水合及其在空调蓄冷技术中的应用 总被引:15,自引:1,他引:14
本文概述了气体水合“暖冰”蓄冷这一技术的研究发展现状,简明地介绍了气体水合现象和水合物的晶体结构、热力学性质、形成条件,影响稳定性和生成速度等的因素,以及混合气体水合物的特点,阐述了气体水合物作为空调蓄冷材料的优越性和在蓄冷技术中的应用方式,并指出了气体水合蓄冷技术研究发展的一些关键问题及该技术的应用前景。 相似文献
18.
Some current challenges in clathrate hydrate science: Nucleation,decomposition and the memory effect
《Current Opinion in Solid State & Materials Science》2016,20(6):344-351
Among outstanding issues still to be understood regarding the clathrate hydrates are the mechanism of the processes involved in the formation and decomposition of clathrates: nucleation, decomposition, and the memory effect during reformation. The latter involves the shorter induction times required for solutions of decomposed hydrate to nucleate as compared to those for freshly prepared solutions. The formation of the clathrate hydrate phases of insoluble gases in water is accompanied by a ∼6000 fold concentration of the gas content in the solid phase compared to the aqueous phase from which it forms. The nucleation mechanism for the solid hydrate which allows the delivery of such high concentration of gas and water in one location has been the subject of much experimental and computational study. While these studies have improved our understanding of the nucleation process, many unknown aspects remain. These developments are described in this Opinion. 相似文献
19.
There is substantial evidence that the oceans of the world will pose the most important challenges in the area of hydrate formation. This work indicates three areas of concern for hydrate formation in the ocean: (1) deposits of natural gas in ocean hydrates, which will serve as an energy resource and environmental concern in the next tnillenium, (2) a recent proposal for the ocean storage of carbon dioxide in the form of hydrates, and (3) the prevention of hydrate formation in ocean pipelines. To address such applications, fundamental knowledge on the site of hydrate formation was determined. Results are presented for quiescent, high-pressure experiments done in a sapphire tube to determine the site of hydrate formation in deionized water and in mixtures with amorphous silica and sodium dodecyl sulfate. Visual (microscope aided) results are presented for formation with a typical gas mixture and with carbon dioxide.Invited paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, USA. 相似文献
20.
从万金塔二氧化碳气田向气站内输送原料二氧化碳过程中,经常发生二氧化碳与水形成水合物堵塞输气管道的现象,给二氧化碳的净化提纯生产带来不利的影响。研究人员在参阅相关文献的基础上,提出应用统计热力学方法来求取二氧化碳形成水合物的具体条件,并且基于实践的基础上分析了防止水合物形成的预防方法,对二氧化碳气田的开发具有一定的借鉴意义。 相似文献