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。     

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。     

Kinetics of gas hydrate formation from mixtures of methane and ethane

Experimental data on the kinetics of formation of gas hydrates from three mixtures of gaseous methane and ethane are reported. the experiments were conducted in a semi-batch stirred tank reactor at temperatures from 273 to 284 K and of pressures from 0.68 to 5.60 MPa. An intrinsic kinetic model for the growth of the gas hydrate is proposed. It is extension of the model for pure component hydrate formation. The model is based on the crystallization theory coupled with the two-film theory for the gas absorption into the liquid phase. the model does not contain any adjustable parameters. The kinetic rate constants which appear in the model are those obtained previously from pure component formation data. The results indicate that the formation rate is proportional to a lienar combination of the differences in the fugacities of the dissolved gases and their three-phase equilibrium fugacities at the experimental temperature. The effect of the mixture composition is taken into account indirectly through the computation of the three-phase equilibrium conditions and of the fugacities. the total gas consumption rate is proportional to the second moment of the particle size distribution.     

冰-气生成天然气水合物的动力学研究

对由冰生成天然气水合物过程中的过饱和度和过冷度的作用进行了实验研究。结果表明 ,较大的过饱和度和过冷度提高了生成水合物的含气率 ,同时反应还存在一个最佳反应时间。提出冰转化为水合物的过程是一个包括气体的外扩散、产物层内扩散以及界面反应的过程     

机械扰动强化气体水合物快速生成研究进展

气体水合物技术在天然气固态储运、CO₂捕获与封存等领域具有广阔的应用前景。高效快速制备水合物是水合物应用技术产业化的关键技术之一。从成核机理、相平衡、传热和传质等角度简述了气体水合物快速生成机理,回顾了常见的搅拌、喷淋和鼓泡等机械扰动强化气体水合物快速生成方法的基本原理和特性。依据强化传质传热领域内的新进展,进一步阐述了新型机械扰动强化气体水合物快速生成方法的基本原理和特性,重点综述了流化床、超声波、超重力、撞击流等技术的研究进展。从耗气率、水合物生成速率、总能耗、气体转化率等角度分析评价了各种机械扰动强化气体水合物快速生成方法的优缺点。总体来说,目前各种机械扰动强化气体水合物生成技术仍处于实验室阶段,传统的搅拌、喷淋和鼓泡强化技术生成速率较低;新型的流化床、超声波、超重力和撞击流等技术也存在各种不同的缺点,有待进一步优化改进。同时指出探究微观成核机理、开发新型易固液分离的气体水合物生成系统以及构建水合物反应器评价体系等是未来气体水合物快速生成相关研究中需要进一步解决的问题。     

气体水合物抑制剂的研制与性能评价

针对海洋深水钻井过程中气体水合物的形成严重影响钻井作业的顺利进行等问题,室内经过大量的优选实验,采用甲基丙烯酸乙酯和N-乙烯基吡咯烷酮作为单体,并对单体比例、引发剂、反应温度及反应时间等综合因素进行分析,研制出低剂量气体水合物抑制剂HLA。通过四氢呋喃(THF)测试法和水合物生成模拟实验装置评价其效果,实验结果表明:盐类气体水合物抑制剂能使形成气体水合物的温度和压力条件得到改变,此外还可以有效的抑制气体水合物的形成;低剂量气体水合物抑制剂HLA能使水合物的形成速率得到有效降低,使形成水合物晶核的诱导时间得到一定的延长,使晶体的聚集过程得到一定的改变,但并不能从实际上改变气体水合物形成的相平衡。     

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.     

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.     

Specific features of the formation of gas hydrates during the injection of a cold gas into a porous medium saturated with a gas and water

A mathematical model of the process of the formation of gas hydrates in a porous medium during the injection of a cold gas is presented. The cases where hydrate formation is limited by the kinetics of the process and heat and mass transfer in a porous medium are considered. The influence of the initial parameters of the porous medium and the intensity of the gas injection on the dynamics of the processes of hydrate formation is studied. The critical conditions that separate the different modes of hydrate formation are found.     

Metastable state of gas hydrate during decomposition: A novel phenomenon

Natural gas hydrates are solid compounds with cage-like structures formed by gas and water. An intriguing phenomenon that gas hydrates can dissociate at a low rate below the ice freezing point has been viewed as the metastability of hydrate. The mechanisms of hydrate metastability have been widely studied, and many mechanisms were proposed involving the self-preservation effect, supercooled water-gas-hydrate metastable equilibrium, and supersaturated liquid–gas-hydrate system etc. The metastable state of hydrate could be of crucial significance in the kinetics of hydrate formation and decomposition, heat and mass transfer during gas production processes, and the application of hydrate-based technique involving desalination, energy storage and transportation, and gas separation and sequestration. Few researches have systematically considered this phenomenon, and its mechanism remains unclear.In this work, various mechanisms and hypothesis explaining the metastable state of gas hydrates were introduced and discussed. Further studies are still required to reveal the intrinsic nature of this metastable state of gas hydrate,and this work could give some implications on the existing theory and current status of relevant efforts.     

天然气水合物形成与生长影响因素综述

天然气水合物(NGH)是水分子和天然气分子形成的一种复杂的笼型晶体,其在油气管道输送、天然气储存和制冷等行业中都具有重要的研究意义和利用价值,但天然气水合物的形成是一个多组分、多阶段的复杂过程,不同因素对于天然气水合物形成和生长的影响尚有待明确。本文介绍了天然气水合物形成的物理过程以及水合物成核的3种机理假说;详细梳理了基质两亲性、添加剂、多孔介质环境和杂质、液体组成、温度压力以及流动条件等因素对于天然气水合物形成和生长的影响,并对其作了简要分析。同时指出,原油组成对于水合物抑制效果的定量化、蜡晶结构对于水合物形成过程中传质和传热的影响以及微观化的动力学抑制剂抑制机理等都是水合物相关研究中需要进一步深入探究和明确的问题。     

木里冻土区天然气水合物形成条件及特征

祁连山木里冻土区是第一个发现天然气水合物的中纬度高山冻土区,与国外发现的冻土区天然气水合物相比,祁连山木里冻土区天然气水合物具有埋深浅、冻土层薄、重烃气体组分高等特征。气体碳氢同位素分析显示,区域内气体来源主要以油型气为主,并在局部伴有煤型气。分析了木里冻土区天然气水合物形成的主要影响因素,冻土层特征和气体组分对冻土区天然气水合物形成的影响较大,富含重烃等气体组分更有利于该地区天然气水合物的成藏,而纯甲烷气体在该地区不易形成天然气水合物。天然气水合物储集层段主要以粉砂岩、油页岩、泥岩和细砂岩为主,并且泥岩和油页岩占90%以上,岩石裂缝较发育,以裂隙型天然气水合物为主要赋存类型。初步认为木里冻土区天然气水合物为下部热解气在断层等构造通道作用下运移而形成的一种重烃气体组分热解气-低温冷冻-地层型为主的动态成藏。     

Thermodynamic consistency test for experimental data of water content of methane

Accurate knowledge of the water content of natural gases is an important factor to estimate the gas hydrate, ice, and condensed water formation conditions. However, the experimental data regarding the water content of gases in equilibrium with the gas hydrate, ice, or liquid water (near gas hydrate or ice formation region) are limited. This is partly because of the fact that concentration of water in the gaseous phase in equilibrium with gas hydrate, ice or liquid water (near gas hydrate or ice formation region) is very low considering that reaching the equilibrium conditions near and inside gas hydrate or ice formation region is time consuming process. The measurement difficulties may consequently result in generating unreliable experimental data. This work aims at performing a thermodynamic consistency test based on area approach to study the reliability of some experimental data reported in the literature on the water content of methane (the main component of natural gases) in equilibrium with the gas hydrate, ice, or liquid water (near gas hydrate or ice formation region). A discussion is made on the studied experimental data according to the performed consistency test. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

表面活性剂在瓦斯水合物生成过程中的热力学作用

在实验研究基础上,结合表面活性剂水溶液中瓦斯水合物生成微观机理,提出了表面活性剂改变水合物生成热力学条件物理作用假说,认为表面活性剂胶束对溶于其中的气体分子和吸附于其周围的水分子的束缚作用,相当于降低了体系的温度.利用T40（0.001 mol·L^-1）、T40（0.002 mol·L^-1）、T40/T80（0.001 mol·L^-1）分别组成的3种气 液 煤 水合物反应体系实验测定了水合物生成时的相平衡参数,与同样温度和压力条件下相平衡计算值比较,结果表明,表面活性剂的加入有效地改变了水合物生成的热力学条件.例如,在T40/T80（0.001 mol·L^-1）实验体系中,当压力为22.67 MPa时,水合物生成相平衡温度为22.6℃,比纯水中提高2.1℃.     

含环戊烷体系中二氧化碳水合物形成分解热特性

水合物法分离捕集二氧化碳（CO₂）是实现碳减排的重要技术。然而,受制于气体水合物形成分解微观机理的不明确,水合物形成速度慢及气体消耗量低两个关键问题还未得到解决,气体水合物CO₂分离捕集技术还未得到商业应用。为了揭示气体水合物形成微观机理,本研究利用激光Raman光谱仪对不同实验条件下生成的CO₂水合物进行测试,详细分析了生成的气体水合物的Raman峰,利用低温高压差式扫描量热仪（DSC）对含环戊烷（CP）体系中CO₂水合物形成分解进行热表征。研究发现,恒容条件下,初始压力为2.5MPa时,气体消耗量为0.0187 mol/mol,CO₂的Raman峰出现在1276.3 cm^-1和1379.6 cm^-1;初始压力为5.0MPa时,气体消耗量为0.744mol/mol,CO₂的Raman峰出现在1276.1 cm^-1和1379.6 cm^-1。CO₂水合物形成分解热结果表明,一方面,随着操作温度、压力条件的变化,形成水合物的种类与结构发生改变;另一方面,对于相同初始体系,最终形成的水合物不是单一的,而是多种水合物共存。此研究结果为进一步理清气体水合物形成微观机理提供了理论基础和重要的科学依据。     

Methane Hydrate Formation and Dissociation in the presence of Bentonite Clay Suspension

The present work reports the effect of bentonite clay on methane hydrate formation and dissociation in synthetic seawater of salinity 3.55 % of total dissolved salts. Extensive observations of pressure‐temperature equilibrium during formation and decomposition of methane hydrate under different conditions have been made. It is observed that phase equilibrium conditions of hydrate are affected on changing the concentration of bentonite clay in synthetic seawater. Induction time for hydrate nucleation has been measured under different concentrations of clay and subcooling conditions. The presence of bentonite clay in synthetic seawater reduces the induction time of hydrate formation. Enthalpy of hydrate dissociation is calculated by Clausius‐Clapeyron equation using measured phase equilibrium data. The amount of gas consumed during hydrate formation has been calculated using real gas equation. It is found that a larger amount of gas is consumed upon addition of bentonite clay in synthetic seawater.     

Kinetics of formation of carbon dioxide clathrate hydrates

The new experimental apparatus capable of observing the clathrate hydrate formation kinetics was developed in this study. Experimental data on the kinetics of carbon dioxide hydrate formation were carefully measured. The experiments were carried out in a semi-batch stirred tank reactor with stirring rate of 500 rpm at three different temperatures between 275.2 and 279.2 K and at pressures ranging from 2.0 to 3.5 MPa. The kinetic model was adopted to predict the growth of hydrates with only one adjustable parameter which represented the rate constant for the hydrate particle growth. The model was based on the crystallization theory coupled with the two-film theory for gas absorption into the liquid phase. The model predictions matched the experimental data very well with the largest deviation of 7.18%, which is within experimental error range. This study is the first for the kinetic data of carbon dioxide hydrate formation and important in developing carbon dioxide fixation process using clathrate hydrate phenomenon.     

油藏流体中H型水合物生成条件的计算

1 INTRODUCTION Gas hydrates are serious problems in the petroleum and petrochemical industries since it may cause the plugging of production facilities and trans- portation pipelines during gas and oil production. It is known to all that gas hydrates have three poten- tial hydrate formation structures: structure- structure- and structure-H (SH). The two for- mer structures have been studied extensively and their phase equilibrium conditions are well characterized. For a long time, molecu…     

Growth kinetics of hydrate formation from water–hydrocarbon system

Gas hydrates have drawn global attentions in the past decades as potential energy resources. It should be noted that there are a variety of possible applications of hydrate-based technologies, including natural gas storage, gas transportation, separation of gas mixture, and seawater desalination. These applications have been critically challenged by insufficient understanding of hydrate formation kinetics. In this work, the literatures on growth kinetic behaviors of hydrate formation from water-hydrocarbon were systematically reviewed. The hydrate crystal growth, hydrate film growth and macroscopic hydrate formation in water system were reviewed, respectively. Firstly, the hydrate crystal growth was analyzed with respect to different positions, such as gas/liquid interface, liquid–liquid interface and gas–liquid–liquid system. Secondly, experimental and modeling studies on the growth of hydrate film at the interfaces between guest phase and water phase were categorized into two groups of lateral growth and thickening growth considering the differences in growth rates. Thirdly, we summarized the promoters and inhibitors reported (biological or chemical, liquid or solid and hydrophobic or hydrophilic) and analyzed the mechanisms affecting hydrate formation in bulk water system. Knowledge gaps and suggestions for further studies on hydrate formation kinetic behaviors are presented.     

The initial stage of hydrate formation in liquid volume on impurity particles upon contact of gas and water

A concept and appropriate theoretical construction have been proposed to describe initial stage of hydrate layer formation at the interface between water and hydrate-forming gas. The model presented indicates that this stage (or induction period) is accompanied by the dissolution of gas in water, as well as the formation and growth of hydrate in the bulk zone on impurity particles near the contact boundary. An analytical solution was obtained for the characteristic time during which the volume content of the hydrate phase at the contact boundary reaches one and, thus, nuclei form as a film prior to a hydrate layer at the gas–water boundary. This characteristic time is accepted as the induction time. According to the obtained formula, the induction period depends inversely on static pressure and in inverse two-thirds proportion on the number of impurity particles per unit volume of water. The problem of the formation and growth of hydrate at the interface between the hydrate layer and aqueous gas solution has been considered and solved. The temperature fields caused by heat generated during hydrate formation on the contact surface of hydrate massif and gas solution are analyzed.