凹凸棒石体系下CO2水合物生成动力学实验

油气生产、储运及CO₂管道输送的过程中易生成CO₂水合物,添加抑制剂是预防CO₂水合物生成的有效手段。为解决CO₂水合物堵塞问题,本文采用超声波处理后的凹凸棒石作为抑制剂,利用可视化高压反应釜实验装置,在初始条件3 MPa和2℃下,研究了添加浓度为0、0.05mg/mL、0.30mg/mL、0.50mg/mL、0.75mg/mL、1.00mg/mL和1.50 mg/mL的凹凸棒石对CO₂水合物生成动力学的影响。用压力变化法测定了水合物生成诱导时间,用动力学模型计算了水合物生成量,并分析了凹凸棒石影响CO₂水合物生成的微观机理。实验结果表明凹凸棒石能延长CO₂水合物生成诱导时间,浓度为0.75mg/mL时作用效果最佳,较纯水体系CO₂水合物生成诱导时间延长了200%;凹凸棒石能减少CO₂水合物的生成量,浓度为1.5mg/mL时作用效果最佳,与纯水体系相比减少了12.8%。凹凸棒石抑制水合物生成的微观机理主要是由于其独特的选择吸附性以及对传质传热的阻碍。研究表明以凹凸棒石作为CO₂水合物抑制剂效果良好,能有效延长其诱导时间,兼具经济性和环境友好的特点。     

13X分子筛耦合四丁基溴化铵促进剂作用下CO2/H2水合物形成动力学

水合物法捕集CO₂技术因其清洁环保、工艺简单等优点成为研究热点。但气液传热传质速度慢导致的形成速率慢、储气能力低等关键问题亟待解决。利用13X分子筛耦合四丁基溴化铵（TBAB）促进剂在279.15～280.65K、3.0～6.0MPa研究了CO₂/H₂（39.8% CO₂/60.2% H₂）水合物的形成过程的压降曲线和气体消耗量,并对比分析了TBAB浓度、压力对其促进效果的影响。实验结果表明,与采用搅拌方式的TBAB/CO₂/H₂水合物形成过程相比,13X分子筛可显著提高TBAB/CO₂/H₂水合物的压降速率和气体消耗量。在279.15K、3.0MPa,随着TBAB溶液浓度增大,CO₂/H₂水合物形成过程的气体消耗量先增大后减小;而当温压条件为280.65K、3.0MPa时,气体消耗量随耦合促进剂中TBAB浓度变化仍遵循类似规律。此外,13X分子筛耦合TBAB促进剂对CO₂/H₂水合物压降速率和气体消耗量的影响随着实验压力升高而升高。     

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。     

水合物法分离二氧化碳的研究现状

介绍了利用水合物法从火力发电厂排放的烟气和从整体煤气化联合循环发电系统（IGCC）合成气中分离二氧化碳（CO₂）的研究及发展现状,包括水合物形成促进剂和添加剂的选择,水合物分离捕集工艺以及成本核算。TBAB和THF在研究中证明能有效地提高水合物形成速度、降低反应压力、提高CO₂的分离捕集效率。在此基础上,提出了不同的分离捕集工艺,这些工艺都是以水合物法分离为主,结合化学吸附法或者膜分离法而展开。通过与传统的化学吸附法的成本核算做比较,发现水合物法分离捕集每吨CO₂的成本约为USD 26,比化学吸附法要便宜约31%,并且随着水合物法研究的进一步深入,水合物法分离捕集CO₂的成本还可能进一步降低,显示了未来的工业应用中有光明的前景。     

撞击流式反应器内水合物法分离沼气中CO2研究

实验考察了撞击流式反应釜内水合物法分离沼气中CO₂的特性。选取纯水和十二烷基硫酸钠（SDS）两个不同的体系，考察了水合物生成过程中压力、温度、撞击强度的影响。实验结果表明在纯水体系和SDS体系下压力的升高均有利于水合物的快速生成，但并不利于沼气中的二氧化碳捕集；实验通过改变撞击流式反应器的撞击强度发现，当撞击强度为0.128时，CO₂分离因子(S.F.)在纯水和SDS两种体系下均达到最大，纯水体系下S.F.的最大值为138.9，SDS体系下S.F.的最大值为64.5；实验结果表明添加剂SDS可以促进水合物的生成，最适宜的浓度为600 mg/L，此时耗气量、CO₂水合率S.Fr.(CO₂)和CH₄水合率S.Fr.(CH₄)达到最大，但SDS对CH₄水合物生成过程的促进作用大于CO₂水合物，反而不利于CO₂的分离，降低CO₂的分离因子。     

基于化学亲和力模型的水合物生成动力学

水合物生成促进及动力学模型是水合物利用技术的关键问题。本文回顾了水合物生成促进技术的发展，实验研究了氧化石墨烯（GO）与十二烷基硫酸钠（SDS）复配促进剂体系下CO₂水合物的生成动力学，揭示了不同浓度对水合物生成时间、耗气的影响规律。研究结果表明，在GO与SDS复配体系下，CO₂水合物生成速度加快，诱导时间和生成时间缩短，耗气量增大。得出最佳复配浓度为0.005%GO+0.2%SDS，与纯水和单一0.005%GO体系相比，水合物的生成时间分别缩短69.7%和12.2%，耗气量提高11.24%和3.2%。建立了该体系下CO₂水合物生成化学亲和力模型，并从模型角度研究了GO与SDS复配比例、温度和压力对化学亲和力模型参数的影响。利用Matlab对模型编程计算并与实验结果进行了对比分析，吻合很好。通过研究认为，化学亲和力模型可准确预测复配体系水合物的生成。     

水逸度模型预测THF添加剂体系下气体水合物相平衡

加入添加剂降低水合物生成压力是当前水合物法分离混合气体研究热点。本研究以水的逸度模型为基础, 结合PRSV2 状态方程研究了CH₄、O₂、N₂ 及其混合气体水合物在纯水体系下的相平衡条件;通过UNIFAC 基团 贡献法对添加剂四氢呋喃(THF)水溶液进行基团划分,计算该体系下液相各组分的活度,理论研究了添加剂 THF 对气体水合物相平衡条件的影响;结果表明在相应的温度范围内,与其他模型相比,在纯水体系下该模型 预测精度较高,在THF 水溶液体系下该模型对单组分和双组分气体的预测精度平均相对误差在7%左右,随着 THF 浓度增加,气体水合物相平衡压力的降低幅度减小;当THF 摩尔分数达到6%时,对气体水合物相平衡影 响达到最大。相关研究结果为混合气体的大规模工业提纯分离提供了理论基础。     

季铵盐类化合物水合分离烟道气中CO2的实验研究

利用季铵盐类化合物[四丁基溴化铵（TBAB）、四丁基氟化铵（TBAF）]作为热力学促进剂对CO₂（9.06%,摩尔分数）+N₂（90.94%,摩尔分数）混合气体进行水合分离实验。结果表明：在279.15 K、2.0 MPa下,0.293% TBAF溶液中,CO₂能够在水合物相中富集到37.73%（摩尔分数）,分离因子13.23,回收率28.44%。TBAF对CO₂的富集程度和分离效果要优于TBAB。同时将实验结果与文献中季铵盐类化合物以及同样实验条件下四氢呋喃（THF）水合分离实验结果进行比较,发现本实验的分离效果要低于文献中CO₂-N₂-TBAB体系,分离因子高于同样实验条件下CO₂-N₂-THF体系,但回收率低于CO₂-N₂-THF体系。     

油水乳液分离沼气实验研究

研究了柴油-水乳液体系在水合物生成条件下对沼气（CO₂/CH₄）中CO₂的捕集能力。阻聚剂Span20被加入到乳液中以分散水滴和水合物颗粒。综合考虑了温度、原料气组成、压力和乳液含水率对柴油-水乳液体系分离能力的影响。从实验结果可以看出,吸收-水合耦合分离效果明显优于单独的吸收分离,且分离平衡后,浆液中水合物分散均匀,流动性良好。乳液体系分离能力在一定范围内随着温度降低和含水率的增加而增强。综合考虑乳液分离能力和流动特性表明,温度270.15～272.15 K,体系含水率 20%～25%（vol）和初始推动力为3.2 MPa左右时为最合适的分离条件,在对应条件下经过两级模拟分离,气相中CO₂浓度能从31%（mol）降到近10%（mol）,超过87%（mol）的CO₂被水合物浆液捕集。     

碳纳米材料促进气体水合物生成动力学研究进展

从碳纳米材料对气体水合物生成动力学影响方面进行详细综述,分别针对原始碳纳米材料、非共价修饰和共价修饰的碳纳米材料对水合物诱导时间、气体消耗量、生成速率和生长周期等参数影响展开介绍。重点分析了纳米材料添加浓度对水合物生产动力学及混合气中CO₂分离效果的影响。对非共价修饰纳米材料,分别从表面活性剂改性与聚合物改性两方面阐述了其对水合物生成动力学特性的影响。在共价修饰方面,对氧化还原修饰、纳米金属离子修饰后纳米材料的稳定性及水合物的生成特性进行了分析。提出现阶段碳纳米材料促进水合物生成的关键问题应从合成纳米材料的稳定分散性、合成材料的循环使用性能两方面进行突破的建议。     

Progress of Gas Hydrate Studies in China

A brief overview is given on the gas hydrate-related research activities carried out by Chinese researchers in the past 15 years. The content involves: (1) Historical review. Introducing the gas hydrate research history in China; (2) Gas hydrate research groups in China. There are nearly 20 groups engaged in gas hydrate research now; (3) Present studies. Including fundamental studies, status of the exploration of natural gas hydrate resources in the South China Sea region, and development of hydrate-based new techniques; (4) Future development.     

甲烷水合物分解实验

在体积10 L的静态反应器中研究了水合物分解动力学,考察了储存温度和水合物量等因素对水合物分解的影响。实验结果表明,水合物在273.15 K以下时存在一种异常的自我保护效应,其在268.05 K时分解速度最慢;而水合物的储运压力与储罐中的水合物量有关,当储罐容积一定时,分解压力随着储罐中水合物量的增加而增加,但水合物的分解百分比随着水合物量的增加而减少;最后提出了在一定压力下储运水合物的方法。以期为水合物法固态储存气体技术的工业化应用提供实验数据和理论依据。     

The gas-adsorption mechanism of kinetic hydrate inhibitors

Molecular dynamics was employed to study the inhibition mechanism of vinyl lactam-based kinetic hydrate inhibitors (KHIs). By comparing the inhibition functions of the same KHIs at different initial locations, we found that the KHI molecules on the surface of hydrate nuclei could obviously prolong the hydrate induction time and exhibited the best inhibition effect. The impacts of KHIs on the methane migration and the arrangement of H₂O molecules were analyzed at the molecular level. A gas-adsorbing mechanism for KHIs (i.e., the KHIs with an excellent gas adsorption ability could reduce the supersaturation of methane in the aqueous solution, reinforce the migration resistance of methane to the nucleus, and further inhibit the hydrate growth) was proposed. In addition, the conformations of KHI polymer molecules in the aqueous solution are closely related to their inhibitory effect, that is, stretched skeletons and well-organized structures would maximize their inhibitory effect.     

Fundamental challenges to methane recovery from gas hydrates

The growing use of natural gas, cleanest of all available fossils fuels, is already raising concern regarding the long-term supply of this precious resource. The amount of methane in gas hydrates is much greater than all other presently known sources of methane. This paper describes some fundamental challenges, the location, magnitude, and feasibility of recovery, which must be addressed to recover methane from dispersed hydrate sources. For methane recovery, we briefly describe kinetic models of methane hydrate decomposition for temperature and pressure conditions that mimic in situ methane hydrate stability. We also propose the catalytic role of sediment impurities, if any, in inducing nucleation sites for hydrate formation. The availability of plentiful methane is important to avoid future energy crises, such as that which crippled the world economy three decades ago.     

New approach for evaluating the risk of hydrate formation during transport of hydrocarbon hydrate formers of sI and sII

Classical industrial hydrate risk evaluation schemes are commonly based on water dew-point calculation. This method ignores another (new) route to hydrate formation based on adsorption of water onto rusty surfaces. Maximum allowable water contents in pure and mixtures of hydrate formers of Structures I and II hydrocarbons to avoid the risk of hydrate nucleation during pipeline transport have been studied using both the dew-point method and the new approach of adsorption of water onto hematite (rust). The estimates from this study suggest that the new approach (adsorption of water onto the rusty internal walls of pipelines and equipment) dominates. Thus, this approach could have an impact on designing natural gas dehydration systems. Free energy analysis has also been performed to show which molecule forms hydrate first based on the combined first and second laws of thermodynamics in terms of Gibbs free energy. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1097–1110, 2019     

An investigation into the laboratory method for the evaluation of the performance of kinetic hydrate inhibitors using superheated gas hydrates

Kinetic hydrate inhibitors (KHIs) are used to prevent gas hydrate formation in gas and oilfield operations. Recently, a new KHI test method was reported in which hydrates are formed and re-melted just above the equilibrium temperature, before the fluids are re-cooled and the performance of the chemical as a KHI is determined. The method, which we have called the superheated hydrate test method, is claimed to be more reliable for KHI ranking in small equipment, giving less scattering in the hold time data due to avoiding the stochastic nature of the first hydrate formation. We have independently investigated this superheated hydrate test method in steel and sapphire autoclave tests using a gas mixture forming Structure II hydrates and a liquid hydrocarbon phase, which was necessary for satisfactory results. Our results indicate that hold times are shorter than using non-superheated hydrate test methods, but they are more reproducible with less scattering. The reduced scattering occurs in isothermal or slow ramping experiments even when the hydrates are melted at more than 10 °C above the equilibrium temperature (T_eq). However, if a rapid cooling method is used, the improved reproducibility is retained when melting hydrate at 2.4 °C above T_eq but lost when warming to 8.4 °C above T_eq. Using the ramping test method, most, but not all the KHIs tested agreed with the same performance ranking obtained using traditional non-superheated hydrate test methods. This may be related to the variation in the dissociation temperature of gas hydrates with different KHIs and different KHI inhibition mechanisms. Results also varied between different size autoclave equipments.     

天然气水合物的生成机理与防治研究

概述了天然气水合物的分子结构,分析了天然气水合物的生成条件,总结了天然气水合物生成的概念模型,研究了天然气水合物的防治方法:物理方法和化学方法。其中物理方法包括:加热法,脱水法,降压法,清管法;化学方法包括:添加热力学抑制,动力学抑制剂以及水合物浆输送技术。提出了今后的研究重点和方向。     

水基钻井液中天然气水合物形成的研究进展

依据水基钻井液中天然气水合物生成的相关研究,结合理论与实践,介绍了一些钻井液处理剂对水合物生成的影响,重点概述了水基钻井液对天然气水合物生成的抑制效应,并简要说明了水合物抑制剂在钻井液中应用的相关研究。     

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     

Gas hydrate concentration measurements on sucrose solutions using a new pilot test rig

A new 750 cm³ pilot test rig based on the “isochoric pressure method” was designed and commissioned for the hydrate measurements to concentrate sucrose solutions. The reactor included an improved agitation system and enabled sampling of the sucrose solutions. The experimental method was validated be performing dissociation measurements for the CO₂ + water system. Gas hydrate kinetic and sampling data were measured for the CO₂ + sucrose solutions at sucrose concentrations between (12–60) ^oBrix, within the temperature range of (274.65–276.15) K and at pressures up to 3.70 MPa. Results showed that sucrose is a kinetic inhibitor. The data were modeled to obtain hydrate formation rate, storage capacity, gas consumption and apparent rate constant. Stage-wise concentration measurements were performed with reactor conditions at 274.65 K, 3.70 MPa and 130 rpm mixer speed with liquid sample withdrawal. A final sucrose product of approximately 60 ^oBrix was obtained.