102 resultados para hydrate
Resumo:
提出制冷剂气体水合物在纳米流体中快速生成的设想,通过HFC134a气体水合物在纳米铜流体(由0.04%的十二烷基苯磺酸钠(SDBS)水溶液和名义直径为25nm的纳米铜粒子组成)中的生成实验验证了此设想.实验结果表明,与去离子水中HFC134a气体水合物的生成过程相比,纳米铜流体中SDBS是造成HFC134a气体水合物诱导时问明显缩短的主要原因,而纳米铜粒子对诱导时间的影响不大;纳米铜流体中SDBS的乳化作用和纳米铜粒子大比表面积大大促进了HFC134a在水中的溶解;纳米铜粒子的加入明显加强了HFC134a气体水合物生成过程中的传热传质,随着纳米铜粒子数的增加,HFC134a气体水合物生成过程明显缩短.
An idea was presumed that the refrigerant gas hydrate could be formed rapidly in nanofluids, so that subsequent experiments were carried on the HFC134a gas hydrate formation process in the nanofluid comprised of 0. 04% sodium dodecylbenzenesulfonate-6solution(SDBS) and nano-copper particles of 25 nm in nominal diameter. The results indicated that, compared with the formation process of HFC134a hydrate in deionized water, the addition of 0.04 % SDBS resulted in much more reduction of induction time of HFC134a gas hydrate than the addition nano-copper did in the nanofluids. The emulation of SDBS and great specific surface of nano-copper particles greatly improved the solubility of HFC134a in water, and the formation process of HFC134a gas hydrate decreased with the mass fraction of nano-copper in nanofluid due to that the addition of nano-copper enhanced the heat and mass transfer of formation of HFC134a gas hydrate.
Resumo:
用分子动力学模拟方法研究甲烷水合物热激法分解,系统地研究注入340 K液态水的结构Ⅰ型甲烷水合物的分解机理.模拟显示水合物表层水分子与高温液态水分子接触获得热能,分子运动激烈,摆脱水分子间的氢键束缚,笼状结构被破坏.甲烷分子获得热能从笼中挣脱,向外体系扩散.热能通过分子碰撞从外层传递给内层水分子,水合物逐层分解.对比注入277K液态水体系模拟结果,得出热激法促进水合物分解.
Thermal stimulation on dissociation of methane hydrate was investigated with molecular dynamics simulation. The dissociation mechanism of methane hydrate with structure Ⅰ was investigated systematically by injecting heated, liquid water of 340 K. The results showed that when the water molecules on hydrate surface are made in contact with high temperature liquid water, they obtain heat energy, and with the obtained energy the water molecules move intensively, breaking the hydrogen bond between water molecules, and destroy the clathrate structure. In addition, methane molecules that have obtained heat energy, break away from the clathrate and diffuse into liquid. Due to heat energy being transferred into inside layer from outside layer through collision between molecules, the hydrate is dissociated layer by layer. Comparing the effects of liquid water with different temperatures of 340 and 277 K on hydrate dissociation, it is concluded that the thermal stimulation promotes dissociation of the hydrate.
Resumo:
用分子动力学(MD)模拟方法系统研究了结构Ⅰ型(SⅠ)和结构H型(SH)氢气水合物中氢气的占据情况并确定了氢气水合物的稳定结构:SⅠ水合物氢气分子数小胞中为2,大胞中为3;SH水合物氢气分子数小胞中为2,中胞中为2,大胞中为11.分析了稳定情况下水合物各胞腔内氢气分子之间的径向分布函数(RDF),得出了氢气分子在各胞腔内的稳定位置.由稳定位置得到了稳定结构下氢气水合物的储氢质量分数:SⅠ为5.085%,SH为6.467%.与实验对比得出结论:SH水合物稳定结构下的储氢能力最强.
Resumo:
实验研究了添加剂对甲烷气体水合物形成过程的影响。发现微量的表面活性剂降低了甲烷气体水合物在静止反应器中形成的诱导时间,并使水合物快速形成和生长,提高了水合物形成过程中的填充密度。阴离子表面活性剂(十二烷基硫酸钠)对水合物生长的促进作用比非离子表面活性剂(烷基多糖苷)强。液态烃环戊烷降低了水合物形成的诱导时间,但环戊烷不能提高水合物的填充密度。
The effect of additives on methane gas hydrate formation was tested. The induction time of methane hydrate formation was reduced, gas hydrate could grow rapidly, and the methane consumption was improved during hydrate formation in a quiescent cell with micella surfactants. The effect of an anionic surfactant ( sodium dodecyl sulfate) on gas hydrate formation is more pronounced compared to a nonionic surfactant (dodecyl polysaccharide glycoside). Cyclopentane reduced the induction time of hydrate formation, but could not improve the methane consumption during gas hydrate formation in a quiescent cell.
Resumo:
化石燃料的燃烧是百余年来大气中二氧化碳(CO2)浓度增加的主要原因。CO2的收集和处置则是抑制这一趋势的有效途径。本文通过对现有收集利用和处置技术的分析,认为火电厂是收集CO2的重点考虑对象;CO2用于三次采油及天然气回收在技术上和经济上比较可行;蓄水层储气前景广阔值得研究;深海处置有待进一步探索;CO2用于置换开采天然气水合物也是很有前景的方案。
The burning of fossil fuel is the primary cause to have the concentration of carbon dioxide(CO2) in atmosphere increased during the past more than a hundred of years,and the capture and disposal of CO2 is an effective method to control its rising tendency.By analysis of the current capture and disposal technologies of CO2,it is concluded that firepower plants are the key targets to capture CO2.The paper also puts forth that tertiary oil recovery and natural gas recovery with CO2 are feasible both technologically and economically;storage of CO2 in saline aquifer is a method of nice foreground and deserves to be researched; disposal of CO2 in deep seafloor will be further investigated;and displacement of gas hydrate with CO2 is a tempting programme also.
Resumo:
介绍了近年来CO2置换开采天然气水合物技术的研究进展;论述了CO2与天然气水合物中CH4置换反应在热力学上的可能性;认为正确理解置换反应机理、探索新的反应技术并提高反应速率是置换开采技术走向产业化的关键。
This paper introduces the advancement in research on replacement of CH4 from hydrate with CO2, and discusses the thermodynamic feasibility of replacment reaction between CO2 and CH4 hydrate, and points out that correct understanding of the replacement mechanism, new reaction techniques and higher reaction rate will be the key to commercial application.
Resumo:
Hydrate equilibrium data of the CH4 + tetra-n-butyl ammonium bromide (TBAB) + water have been measured by using the isothermal pressure search method for four components of TBAB aqueous solutions. The three-phase equilibrium lines obtained in the present study are shifted to the low-temperature or high-pressure side from that of the stoichiometric TBAB solution. Moreover, methane uptake into semi-clathrates is confirmed by a shift in the clathrate regions when methane is present. The experiments are carried out in the pressure range of (0.5 to 11) MPa and in the temperature range of (281.15 to 295.15) K.
Resumo:
The methane hydration process is investigated in a semi-continuous stirred tank reactor. Liquid temperatures and reaction rates without stirrer are compared with those occurring with stirrer, while at the same time better stirring conditions of the methane hydration process are given by the experiments. Some basic data of fluid mechanics, for example, stirring Reynolds number, Froucle number and stirrer power, are calculated during the methane hydration process, which can be applied to evaluate stirrer capacity and provide some basic data for a scaled up reactor. Based on experiment and calculations in this work, some conclusions are drawn. First, the stirrer has great influence on the methane hydration process. Batch stirring is helpful to improve the mass transfer and heat transfer performances of the methane hydration process. Second, induction time can be shortened effectively by use of the stirrer. Third, in this paper, the appropriate stirring velocity and stirring time were 320 rpm and 30 min, respectively, at 5.0 MPa, for which the storage capacity and reaction time were 159.1 V/V and 370 min, respectively. Under the condition of the on-flow state, the initial stirring Reynolds number of the fluid and the stirring power were 12,150 and 0.54 W, respectively. Fourth, some suggestions, for example, the use of another type of stirrer or some baffles, are proposed to accelerate the methane hydration process. Comparing with literature data, higher storage capacity and hydration rate are achieved in this work. Moreover, some fluid mechanics parameters are calculated, which can provide some references to engineering application.
Resumo:
利用研制的天然气水合物沉积物合成及力学性质一体化试验设备,以粉细砂土作为土骨架,分别对冰沉积物以及对四氢呋喃(THF)、二氧化碳(CO_2)和甲烷3种水合物沉积物进行了室内合成和三轴剪切试验,分析和比较了这4种沉积物样品的应力-应变和强度特性,初步探究了冰和不同气体在水合物沉积物强度中所起的作用. 试验结果表明:4种沉积物均表现为塑性破坏;围压越大,水合物沉积物强度越高;在水合物含量相同条件下,不同气体水合物会使水合物沉积物的强度不同
Resumo:
沉积物水合物在热源周围的分解范围是水合物热开采以及相关灾害分析的重要基础数据.该文针对平面内边界有恒温热源的水合物热分解范围问题进行了理论分析和四氢呋喃水合物沉积物模型实验,并将两者结果进行了对比.结果表明:沉积物水合物最大分解范围主要取决于热源与环境温度的温差;热源周围水合物热分解最大范围的理论值与实验值接近,误差小于5%
Resumo:
建立了降压法开采水合物藏数学模型, 考虑了气-水-水合物-冰相多相渗流、水合物相变及分解动力学过程、冰-水相变、热传导、对流过程、渗透率变化等对于水合物分解的影响. 三维水合物藏模拟表明:在开采前期阶段, 可采用降压法, 但随着储层能量消耗, 产气速度下降很快, 需转变开采方式. 分析了一些主要参数, 如孔隙度、渗透率、饱和度、压力等对水合物开采的影响.
Resumo:
A set of bimetallic Pt-Ru catalysts prepared by co-impregnation of carbon black with ruthenium(III) chloride hydrate and hydrogen hexachloroplatinate(IV) hydrate were investigated by temperature-programmed reduction (TPR), chemisorption of hydrogen, transmission electron microscopy (TEM), microcalorimetry of adsorbed CO and a structure-sensitive reaction (n-hexane conversion). The results showed that the volumetric capacities for CO and H-2 adsorption is influenced in the bimetallic Pt-Ru catalysts by the formation of a Pt-Ru alloy. The n-hexane reaction revealed that the reaction mechanism for the pure Pt catalyst mainly occurs via cyclic isomerization and aromatization due to the presence of bigger Pt surface ensembles, whereas the Pt-Ru catalysts exhibited predominantly bond-shift isomerization by the diluting effect of Ru metal addition. The differential heats of CO chemisorption on Pt-Ru catalysts fell between the two monometallic Pt and Ru catalysts extremes. (C) 2004 Elsevier B.V. All rights reserved.
Resumo:
Sheaflike terbium phosphate hydrate hierarchical architectures composed of filamentary nanorods have been fabricated by a hydrothermal method. The X-ray diffraction patterns and thermogravimetric/differential thermal analysis investigations reveal that the obtained terbium phosphate hydrate has a structural formula of TbPO4 center dot H2O, which can be readily indexed to the hexagonal phase GdPO4 center dot nH(2)O in JCPDS file 39-0232. The evolution of the morphology of the products has been investigated in detail. It is found that the addition of CTAB and Na2H2L (disodium ethylenediamine tetraacetate) plays an important role in controlling the final morphology of the products. A possible formation mechanism of the sheaflike architectures was proposed according to the experimental results and analysis. In addition, the phase structure of the product changes to monoclinic phase when it is annealed at 750 degrees C for 2 h in N-2-H-2 atmosphere. Tetragonal chase TbPO4 can be obtained when annealed temperature increases to 1150 degrees C.
Resumo:
The adsorbed kinetics, proton transportation in electrochemical redox process of 4-pyridyl hydroquinone (4PHQ) self-assembled monolayer (SAM) modified Pt electrode were studied by electrochemical quartz crystal microbalance (EQCM) in situ. It proved that the electrode was modified by a monolayer and underwent a rapid electron transfer. It was a slow adsorbed kinetic process. The ion transfer in the electrochemical redox at the SAM-modified electrode surface mainly involved into the hydrate hydrogen ion.
Resumo:
The reaction of diglycolic acid, O(CH2CO2H)(2), with Cu(NO3)(2) . H2O and lanthanoid nitrate hydrate produces a series of novel Ln-Cu mixed metal complexes, [Ln(2)CU(3){O(CH2CO2)(2)}(6)]. nH(2)O (Ln = La, Nd, n = 9; Ln = Er, n = 6), which have been characterized by elemental analysis, i.r. spectroscopy, magnetic measurements and X-ray crystallography. The Ln(3+) and Cu2+ ions are connected by the carboxylate groups of the ligands, resulting in the formation of a complicated network.