Clathrate‐hydrate formation by water spraying onto a porous metal plate exuding a hydrophobic liquid coolant

A novel technique for producing a clathrate hydrate from a gaseous guest substance was devised and experimentally tested. This technique employs a horizontally oriented spray nozzle and a vertically oriented porous metal plate placed in opposition to each other in a guest‐gas phase. Water is sprayed onto the plate while a precooled hydrophobic liquid coolant is seeping out of the plate to form a continuous film flowing down the plate surface. The coolant film is expected to sweep the heat released by hydrate formation away from the plate surface and, at the same time, to prevent the hydrate crystals from agglomerating on the surface thereby hindering the successive contact of the water spray with the coolant. A series of experiments has been performed to reveal the behavior of hydrate formation in the above scheme of guest‐gas/water/coolant contact operations. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Intensification and kinetics of methane hydrate formation under heat removal by phase change of n‐tetradecane

A method of direct heat removal resulting from the phase change of n‐tetradecane was used to intensify the heat transfer during hydrate formation. The growth rates of methane hydrate in aqueous slurries containing 25–45 wt % of solid n‐tetradecane were investigated at pressures between 4.70 and 6.46 MPa (gauge) and near the fusion point of solid n‐tetradecane. Methane hydrate growth started at a practically constant rate, which became variable after a sudden increase. Two rate laws were established to correlate with the experimental data for the constant and variable rate stages. The methane hydrate growth rates achieved with solid n‐tetradecane were significantly enhanced compared with those obtained under indirect heat removal. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3441–3450, 2015     

水合物浆体在水平细管中的流动相变换热

实验测量了质量分数为0~19.2%的TBAB水合物浆体在恒热流条件下在小管径内流动时的流动传热特性。利用数值计算获得管内浆体的沿程温度分布,在此基础上得到水合物浆体在小管径内的强制对流传热特性。结果表明加热功率对小管径管道中的浆体传热特性有较大影响;在层流状态下,流速对传热系数的影响相比紊流时要小。在实验数据基础上总结出了TBAB水合物浆体在小管径管内的对流换热经验关联式。     

气体水合物形成的热力学与动力学研究进展

气体水合物形成过程中涉及复杂的热力学和动力学问题.本文对水合物热力学理论模型、水合物生成动力学机理等方面的研究成果和最新进展进行了综述.热力学方面重点介绍了基于等温吸附理论 (van der Waals-Platteeuw模型)和基于双过程水合物生成机理(Chen-Guo模型)的相平衡热力学模型,同时介绍水合物结构及其转变方面的最新研究成果.动力学方面介绍了成簇成核、界面成核等成核机理模型以及成核后的水合物生长机理.另外还述及了目前水合物热力学和动力学研究中所涉及的微观、亚微观和宏观测量方法.针对目前水合物热力学和动力学研究中存在的问题,对未来的发展方向和重点提出了建议.     

Modelling and experimental study of hydrate formation kinetics of natural gas‐water‐surfactant system in a multi‐tube bubble column reactor

To promote the heat and mass transfer during the hydrate formation process, an internal spiral‐grooved tube (ISGT) was proposed as the reaction tube in a large‐scale multi‐tube bubble column reactor with external slurry circulation. In order to investigate such multi‐component gas (natural gas)‐water‐surfactant systems during the hydrate formation process in the ISGT, based on the solute permeation model and Kolmogorov isotropic turbulence theory, a CFD method combined with the population balance model (PBM) was utilized to simulate gas‐liquid mass transfer coefficient. Then, the hydrate formation kinetics model in ISGT was modelled based on the model proposed by Kashchiev and Firoozabadi. The hydrate formation experiments were carried out in the multi‐tube bubble column reactor at six different pressure‐temperature‐circulating flow velocities of piston pump regimes to investigate the actual formation process of natural gas hydrate. The experimental results were then used to finetune the optimized parameters to facilitate accurate model predictions.     

Diffusion‐limited kinetics modeling of one‐step polyimide formation

A diffusion‐limited kinetic model was developed to describe the imidization of one‐step polythioetherimide formation based on an endgroup diffusion model. The changes of conversion and viscosity during the imidization were monitored with thermogravimetric analysis and dynamic stress rheometry, respectively. It was observed that the imidization rate began to decelerate after a fast early stage, whereas the viscosity in the system increased dramatically after a period of low value. Amic acid and imide formations concurrently take place in the one‐step polyimide formation, but the formation of amic acid is much slower than that of imide and is the rate‐limiting step of imidization. When a second‐order kinetic model was used to describe the imidization, the effect of viscosity on the diffusion resistance of reactive groups needed to be included. In order to predict the change of viscosity during the imidization, the Lipshitz‐Macosko model was modified and introduced into the diffusion‐limited kinetic model by the Stokes‐Einstein equation. The comparison of the modeled results with experimental data indicated that the diffusion‐limited kinetic model and the modified Lipshitz‐Macosko model were able to efficiently predict the changes of conversion and viscosity with temperature and time during the one‐step polythioetherimide formation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2052–2059, 2001     

SDS对甲烷水合物生成动力学和微观结构的影响

表面活性剂是促进水合物生成的有效手段之一。在高压反应釜中研究了十二烷基硫酸钠（SDS）对水合物生成过程的动力学影响,利用XRD和拉曼光谱探究了SDS存在条件下水合物的微观结构。宏观结果表明SDS缩短了诱导时间,加快了水合物生长速率。微观结果表明SDS没有影响sI型水合物的晶型结构,晶面间距与理想sI型水合物及纯水甲烷对比误差在千分之几。水合物中甲烷在大笼小笼中的拉曼位移分别为2904和2915 cm^-1,SDS没有改变大笼小笼结构。大笼绝对占有率（q_L）接近饱和时,SDS可以进一步提高小笼绝对占有率（q_S）,从微观角度证明了SDS可以减少水合数,提高储气率。     

Accelerated methane storage in clathrate hydrates using surfactantstabilized suspension with graphite nanoparticles

In this study, enhanced kinetics of methane hydrate formation in the sodium dodecyl sulfate(SDS) solution with different concentrations of suspended graphite nanoparticles(GNPs) were investigated at 6.1–9.0 MPa and 274.15 K. The GNPs with rough surfaces and excellent thermal conductivity not only provided a considerable number of microsites for hydrate nucleation but also facilitated the fast hydrate heat transfer in the suspension system. At a relatively low pressure of 6.1 MPa, the suspension with 0.4 wt% of GNPs exhibited the minimum induction time of 22 min and maximum methane uptake of 126.1 cm~3·cm~(-3). However, the methane storage performances of the suspensions with higher and lower concentrations of GNPs were not satisfactory. At the applied pressure, the temperature increase arising from the hydrate heat in the suspension system with the optimized concentration(0.4 wt%) of GNPs was more significant than that in the traditional SDS solution. Furthermore,compared with those of the system without GNPs, enhanced hydration rate and storage capacity were achieved in the suspensions with GNPs, and the storage capacities were increased by 3.9%–17.0%. The promotion effect of GNPs on gas hydrate formation at low pressure is much more obvious than that at high pressure.     

操作工况对酸性天然气水合物生成动力学的影响分析

水合物的快速生成受诸多因素的影响,操作工况是其主要的影响因素之一。以67.7%CH4+32.3%CO2（摩尔分数）混合气为例模拟酸性天然气,采用自行设计的水合物动力学实验装置,分别对初始压力为3.0 MPa、3.5 MPa、4.2 MPa、5.0 MPa和实验温度分别为1.42 ℃、3.27 ℃、5.48 ℃、7.45 ℃时的水合物生成动力学进行实验研究。定义诱导期、平衡总耗时、生长速率为水合物动力学评价指标,指标通过分析水合物生成过程中的压力及气相组成变化得到,进而综合分析了操作工况对酸性天然气水合物生成动力学的影响。实验结果表明：初始压力越高,实验温度越低,水合物平衡时气相CO2的浓度越低,水合物的生成量和生长速率越大;此外,初始压力对体系诱导期影响不够显著,而操作温度的降低可以明显缩短体系诱导期。     

冰点以下多孔介质中气体水合物的生成动力学研究进展

青藏高原冻土区储存着大量的天然气水合物资源,CO₂置换开采冻土区的天然气水合物可实现天然气水合物的安全开采和温室气体CO₂的地层封存。冰点以下多孔介质中气体水合物的生成动力学,是冻土区天然气水合物置换开采研究领域的难点和热点问题。本文全面综述了冰点以下多孔介质中气体水合物的生成动力学研究进展,讨论了不同体系冰点以下多孔介质中气体水合物的形成机理及其生成特性;详述了冰生成水合物机理及其冰粉/多孔介质体系中气体水合物的生成特性,分析了冰点以下多孔介质中气体水合物生成动力学研究尚待完善和改进的地方。最后本文指出冰点以下多孔介质中水合物的生成过程是由传热、传质等多种因素所控制,揭示不同过程的主导因素及其影响规律是今后研究的重点方向。目前对冰点以下多孔介质中水合物的生成特性及机理的认识尚未成熟,仍需深入研究。     

乙烯水合物膜生长动力学

利用显微放大技术测定了不同温度(274.1～280.1 K)、压力(0.80～4.38 MPa)下乙烯水合物膜在乙烯气泡表面生长的动力学数据,采用量纲1 Gibbs自由能差作为推动力对数据进行关联建模,得到了乙烯水合物膜生长动力学模型,并回归出乙烯水合物膜生长表观活化能为61.23 kJ·mol^-1,指前因子为6.76×10¹¹mm²·s^-1,同时,考察了在不同温度下压力对乙烯水合物膜生长速率的影响.     

泡沫铜强化甲烷水合物生成动力学实验研究

提高水合物生成速率和储气密度对天然气水合物技术应用非常重要。将三种孔密度的泡沫铜（CF）分别浸入十二烷基硫酸钠（SDS）溶液中构建水合储气强化体系,在高压静态反应釜中研究泡沫金属对甲烷水合物生成动力学特性。实验结果表明,泡沫铜骨架能为水合物生成提供充足的结晶点,同时可作为水合物生长过程水合热迁移的“高速公路”。甲烷水合物在SDS/CF体系中可快速生成,最大水合储气速率分布在19.24~21.04 mmol·mol^-1·min^-1之间,其中添加15 PPI泡沫铜的SDS溶液储气量最高（139 mmol·mol^-1）,且达到最大储气量90%所用时间最短（10.1 min）。在6.0~8.0 MPa压力下,相比SDS溶液,添加15 PPI泡沫铜的SDS溶液储气量提高了8.8%~35.6%,储气速率提高了4.7%~40.4%;特别在压力为5.0 MPa时,该孔密度SDS/CF体系储气量甚至比SDS溶液增加13倍,储气速率增加16倍。     

螺旋内槽管内天然气-水-表面活性剂体系的水合物生成动力学计算

针对多组分气体（天然气）-水-表面活性剂体系在螺旋内槽管内的水合物生成过程,首先采用CFD方法结合群体平衡模型（PBM）,基于溶质渗透模型和Kolmogorov各向同性湍流理论对螺旋内槽管内气液传质系数进行了模拟;其次基于Kashchiev和Firoozabadi的经典水合物成核和生长理论,将其体系从单组分-水系统扩展到多组分气体（天然气-水-十二烷基硫酸钠）系统,同时结合经典结晶理论利用传质系数对水合物生长模型进行了修正,建立了适用于螺旋内槽管流动体系内天然气水合物生成动力学模型。通过模拟计算,获得不同水合物生产条件下天然气在水中的平均传质系数;进而利用Microsoft Visual C++编程计算得到不同条件下水合物生成动力学数据,在考察范围内,天然气水合物的成核速率随着反应体系有效表面能的增大而锐减,而水合物生成驱动力和生长速率未受影响,同时水合物生长速率随着流速和反应压力的增大及温度的降低而增大,成核速率随着压力的增大和温度的降低而增大。     

玉米棒+四氢呋喃对IGCC合成气水合物生成动力学的影响

为了明确玉米棒颗粒与四氢呋喃(THF)对整体煤气化联合循环(IGCC)合成气气体水合物生成的协同作用,在温度276.15K、初始压力为6.0MPa的静态反应条件下,通过实验研究了玉米棒颗粒+THF溶液体系中气体水合物的生成动力学过程,并确定了不同THF浓度溶液条件下水合物的生成诱导时间、气体消耗量、CO₂分离效率及水合物的晶体结构。实验结果表明:玉米棒的存在会延长实验的稳定时间,且其压降幅度相较于不含玉米棒颗粒的体系更高;无论是否含玉米棒颗粒,诱导时间均在180s以内,且随着THF浓度上升到摩尔分数4.0%和5.6%,二者的诱导时间变得非常接近;玉米棒颗粒存在时,THF溶液的浓度越大,气体消耗量达到最终气体消耗量90%的时间则越短,且在相同THF浓度下,其所获得的气体消耗量和CO₂分离效率普遍比纯THF溶液体系高,这意味着玉米棒颗粒的存在提高了THF溶液对CO₂的分离效果。同时,微观结构分析表明无论是否含有玉米棒颗粒,THF溶液体系中所生成的IGCC合成气气体水合物的结构均为sⅡ型,纯水体系中生成的IGCC合成气气体水合...     

Comparative study of hydrogen,argon, and xenon uptake into a propane hydrate

The rate of absorption of hydrogen, argon, and xenon into a Type II propane clathrate hydrate has been studied. The propane hydrate is synthesized from 250‐μm ice grains, is estimated to have a porosity of 65% and has roughly the consistency of chalk. Hydrogen is rapidly absorbed by the hydrate sample and approaches the equilibrium vapor pressure in an hour before a very slow residual absorption process ensues. For an initial hydrogen pressure of 1.5 MPa, about 4.5% of the available 5¹² cages are occupied by hydrogen after 1 h, and 4.9% after 18 h. In contrast, for both argon and xenon significantly more gas is absorbed by the hydrate but at a much slower rate: about 5% as fast for xenon and 1% as fast for argon. We conclude that hydrogen readily diffuses through the propane hydrate microcrystal structure, while argon and xenon are probably absorbed by growing new double hydrate while consuming the propane hydrate. Although considerably higher pressures would be required to store significant quantities of hydrogen in propane hydrate, it appears that the crystal can be loaded and emptied in relatively short times. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

甲烷-四氢呋喃-水体系水合物生成动力学的实验和模型化研究

研究了透明鼓泡塔中含促进剂四氢呋喃（THF）体系中甲烷水合物的生成动力学.分别考察了进气速率、温度、压力、水合物体积分数对甲烷消耗速率的影响.根据Chen-Guo水合物生成机理,采用基础水合物生成反应的量纲1 Gibbs自由焓变-ΔG/RT作为反应的推动力,建立了水合物生成动力学模型,模型中考虑了体系温度、压力和气液接触比表面积的影响.把模型应用于甲烷气体消耗速率的计算,其模型预算结果与实验数据吻合良好,实验结果和反应动力学模型将有助于工业水合反应器的设计和操作条件的设定.     

天然气水合物储运技术中水合物反应器的研究进展

可观的储气率与自保效应的存在使得天然气水合物能作为一种天然气储运的方式,并且在与其他如液化天然气、压缩天然气储运方式比较时有着自己独到的优势。但由于针对水合物储运的研究起步较晚,利用水合物储运天然气的技术尚未成熟。尤其是在水合物反应器的研究上,生成水合物的速率较低,无法达到工业生产所需要的水平。本文通过调研国内外文献与专利等资料,介绍了国内外天然气水合物储运技术发展状况,简述了水合物生成强化的物理化学手段与机械手段,详述了搅拌式等传统天然气水合物反应器与管式、超重力式等新型天然气水合物反应器的结构与工作原理。根据现有水合物反应器的特点与存在的问题,对水合物反应器的研究方向提出建议：未来应当加快对喷淋式、超重力式与流化床式反应器的放大研究,加快针对不同物理强化手段与机械强化手段的协同作用研究,建立起以天然气储运为目的的水合物反应器评价体系。