动力学水合物促进剂研究进展

动力学水合物促进剂是实现水合物法(NGH)储运天然气技术大规模工业化应用的关键。首先简单介绍了NGH技术与其它常规储气相比时的技术特点和优势,其次从表面活性剂类、氨基酸类、淀粉和聚合物类和纳米流体类等系统调研了动力学水合物促进剂的最新研究进展,最后分析认为氨基酸类促进剂的促进机理及纳米流体颗粒对水合物生成动力学的影响等方面应为日后该领域的研究重点。     

动力学水合物促进剂研究进展

动力学水合物促进剂是实现水合物法(NGH)储运天然气技术大规模工业化应用的关键。首先简单介绍了NGH技术与其它常规储气相比时的技术特点和优势,其次从表面活性剂类、氨基酸类、淀粉和聚合物类和纳米流体类等系统调研了动力学水合物促进剂的最新研究进展,最后分析认为氨基酸类促进剂的促进机理及纳米流体颗粒对水合物生成动力学的影响等方面应为日后该领域的研究重点。     

水合物形成促进剂研究进展

添加促进剂是高效制备水合物的研究热点,促进剂及其添加量对水合物生成效果至关重要。本文主要从热力学促进剂和动力学促进剂两大类型进行分析：总结了可溶水相热力学促进剂和不可溶水相热力学促进剂的浓度对水合物形成相平衡的影响;从表面活性剂、纳米粒子和相变材料等添加剂,阐述了动力学促进剂添加量对水合物生成诱导时间、储气量和生成速率等方面的影响。促进剂都存在最佳浓度的添加量,并且不同类型促进剂复配更有利于水合物生成。目前添加促进剂后水合物形成机理的研究大多从宏观现象推测,部分学者通过拉曼光谱、X射线衍射和显微观察探索分析促进剂对水合物形成的微观影响,这方面研究有待于进一步开展。添加量作为水合物形成促进剂的重要指标,研究者应得到水合物形成促进剂的最佳浓度与所研究对象的关联性。     

水合物法提纯沼气技术研究进展

沼气是一种重要的可再生能源,对沼气进行充分高值利用对于缓解我国能源需求和环境压力具有重要意义。沼气在高值利用前必须进行脱碳提纯处理,本文介绍了一种可用于沼气提纯的新技术--水合物分离技术。介绍了水合物分离技术的基本理论,调研总结了水合物法提纯沼气和可用于沼气体系（CH₄/CO₂）的水合物分离技术研究进展,包括相平衡研究、热力学促进剂、动力学促进剂、机械强化、外场强化、添加多孔介质/纳米流体等和采用油/水乳液促进技术,并对各种水合物分离促进技术进行了分析：相平衡研究为水合物法提纯沼气提供了理论基础;合理地选用热力学和动力学促进剂能够有效改善气体水合物相平衡条件,促进水合物生成,增加储气效果和提高分离效率;机械强化及外场作用通过强化水合反应过程的传质传热效果促进水合物生成;添加多孔介质和纳米流体等能够增大气液接触面积,对水合过程发挥促进作用;采用油/水乳液不但能够强化气液接触,而且微乳状态下的水合物具有很好的流动性,具有良好工业应用前景。最后对水合物法提纯沼气技术进行了展望,水合物提纯沼气研究虽处在起步阶段,但随着研究的不断深入,该技术凭借操作条件温和,对原料气要求低,并且具有操作简单灵活、安全性高、环保无污染等优点,必将在我国沼气产业发展过程中发挥作用。     

气体水合物高效生成、分离与储存一体化技术研究

基于水合物的固体天然气(solidified natural gas, SNG)技术为天然气储存提供了一种新型、高效途径,但水合物的高压生成环境限制了其分离与储存,进而制约了水合物的连续制备,而强化水合物的生长动力学,实现水合物高效生成、分离与储存是该技术应用的关键。提出了一种新型螺旋搅拌反应装置,实现了水合物生成、分离与储存一体化,并通过乳液聚合法制备了—SO₃^-@PSNS与—COO^-@PSNS两种纳米促进剂,强化了后期水合物生长动力学,进而实现了水合物高效制备。研究表明,在较温和条件下(5 MPa,275.15 K,30 r/min),纳米促进剂与螺旋搅拌协同作用大幅强化了水合效率,在—SO₃^-@PSNS与—COO^-@PSNS体系,水合物诱导时间分别为1.59和6.48 min,水合物储气量高达128.38 m³/m³,且与—COO^-@PSNS相比,—SO₃     

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。     

卵磷脂对甲烷水合物形成的影响

建立了用于测定卵磷脂(lecithin)对钻井液中水合物形成影响的实验装置及方法,以理解化学添加剂卵磷脂对北极Cascade地区钻井过程中水合物层的稳定作用。本研究旨在理解卵磷脂对纯水中甲烷水合物形成热力学和动力学的影响。结果表明，卵磷脂基本上不影响甲烷水合物生成的热力学条件，但当卵磷脂在水中的浓度超过0.003 g·g^-1时，它会影响甲烷水合物的生成速度和数量,是很好的水合物生成动力学促进剂。     

二氧化碳水合物动力学促进剂研究进展

利用水合物法捕获二氧化碳是当今世界的研究热点,但其应用受到了水合物的生成条件苛刻、生成速率缓慢等问题的限制,故需要利用特定促进剂来改善水合物法分离气体的性能。本文从动力学促进剂对二氧化碳水合物生成的影响效果和促进机理两个方面的研究进展进行了分析和介绍：在影响效果方面,主要阐述了不同类型动力学促进剂对水合物生成产生不同的影响以及在高浓度时对水合物生成产生的抑制作用,并分别分析了其原因;在促进机理方面,总结了国内外各学者的研究成果,并指出现有各种关于动力学促进剂促进机理的理论存在的不足。此外,还提出了未来关于二氧化碳水合物动力学促进剂的发展方向：一是着重研究动力学促进剂对水合物生成促进效果与其含有基团的关系;二是目前关于动力学促进剂促进水合物生成机理还没有统一定论,这可能是由于目前的研究主要集中在促进剂对水合物外部形态的改变而未探讨促进剂对水合物内部结构的改变,因此促进剂对水合物内部结构的改变上需进一步研究。     

多孔介质中CO2-CH4水合物置换的影响因素及强化机理研究进展

天然气水合物因其储量巨大、清洁无污染而成为未来最具潜力的清洁能源之一，CO₂置换法可实现天然气水合物的安全开采和温室气体的地层封存。然而，多孔介质中CO₂-CH₄水合物的置换过程存在反应周期长、速率慢、效率低等特点，已成为制约天然气水合物高效开采的瓶颈问题。本文全面综述了多孔介质体系中CO₂-CH₄水合物的置换特性，分析了CO₂-CH₄水合物的置换机理及其动力学过程。在此基础上，详述了不同因素对多孔介质中CO₂-CH₄水合物置换效率的影响规律及强化机理，包括热刺激、置换压力、小分子气体、化学添加剂等的作用机理及其规律。最后指出了多孔介质体系中CO₂-CH₄水合物置换过程强化技术存在的不足和未来的发展方向。对多孔介质体系中CO₂-CH₄水合物置换过程的强化机理及其动力学机制的认识仍需进一步研究。     

介观尺度下甲烷水合物合成特性研究

为研究介观尺度下甲烷水合物的生成速率及储气量等特性,选用介孔分子筛SBA-15为多孔介质,并添加热力学促进剂THF、TBAB和表面活性剂SDS以提高水合反应速率。水合物生成实验在定容恒温条件下进行,压力选取2. 0 MPa和1. 8MPa,温度选取282. 15 K和279. 15 K。实验结果表明,在添加剂的共同作用下,介观尺度下水合物合成速率得到显著提高;反应过程中温度波动较小,最大为0. 6 K,表明其具有良好的传热性;在水合物储气量方面,实验中最大储气量达到45. 826 mmol(10 m L水),降温、增压能够提高水合物储气量;同时高压和低温能够有效地提高介观尺度下水合反应速率,最高生成速率达到2. 335 mmol/min;在促进水合物生成、提高水合物储气能力、加快水合物反应速率方面THF均优于TBAB。     

Evaluation on the natural gas hydrate formation process

Gas hydrates have endowed with great potential in gas storage, and rapid formation of gas hydrates is critical to use this novel technology. This work evaluated the natural gas hydrate formation process, which was compared from six parameters, including conversion of water to hydrate, storage capacity, the rate of hydrate formation, space velocity (SV) of hydrate reaction, energy consumption and hydrate removal. The literature was selected by analyzing and comparing these six parameters mentioned above, meanwhile placing emphasis on the three parameters of storage capacity, the rate of hydrate formation and space velocity of hydrate reaction. Through analysis and comparison, four conclusions could be obtained as follows. Firstly, the overall performance of the stirring process and the spraying process were better than other processes after analyzing the six parameters. Secondly, the additive types, the reactor structure and the reactor size had influence on the natural gas hydrate formation process. Thirdly, the energy consumption via reciprocating impact in the hydrate formation process was higher than that via stirring, spraying and static higee. Finally, it was one key for hydrate removal to realize the hydrate industrial production.     

笼型水合物为能源化工带来新机遇

笼型水合物是利用水分子通过氢键作用构建的笼型结构对甲烷等能源气体进行存储和提取,具有高安全性、高储存容量、温和储存条件、环境友好等优点。天然气水合物是传统能源和绿色能源之间的桥梁燃料,已成为世界各国科学家竞相研究开发的热点。本文综述了笼型水合物在能源与环境、流动安全、工程应用三个方面的研究成果,涵盖了固化天然气（SNG）、CO₂捕获和气体分离、蓄冷、海水淡化、汽车燃料以及制氢与储氢等能量转换、能量储存的领域。文章指出大力发展笼型水合物衍生技术,实现提取甲烷同时捕获二氧化碳,有助于实现碳中和的目标。阐述了笼型水合物生成依赖于其自身的热力学相平衡条件、反应过程的动力学性质及传递过程强化,从生成到分解的过程主要包括溶解、成核、生长、晶裂和解吸等一系列步骤,过程的微观机理复杂。展望了利用多尺度方法研究水合物生成的微观结构、界面现象、宏观应用和作用机理,有助于扩展化学工程的原理和知识,对开发能源化工领域新材料新工艺也有裨益,从而促进能源化工的发展。     

低剂量超吸水树脂溶液微滴中甲烷水合物生成动力学

高储气密度水合物的快速生成对气体水合物技术应用至关重要。将水与疏水性气相纳米二氧化硅和低剂量［0.1%~1.0%（质量）］的超吸水树脂在搅拌器中高速混合分散，制备出一种超吸水树脂改性的干水。该改性干水实质上是由高分子聚合物支撑且可自由流动的分散微滴堆。在8.0 MPa和274.2 K条件下，研究该改性微滴中甲烷水合物生成动力学特性。结果表明，松散的聚合物微滴极大地改善了液相连续水比表面积，为气体扩散至微滴表面提供了丰富的通道。水合物在聚合物微滴中快速生成，储气速率可达5.15~8.78 cm³·g^-1·min^-1，储气量高达158.0~175.0 cm³·g^-1。质量分数为0.3%的微滴表现出最快储存速率和最高储气量，且其循环水合储气过程中前6次储气量均超过120 cm³·g^-1。研究结果对水合物储运天然气技术规模化应用有一定的参考价值。     

低剂量超吸水树脂溶液微滴中甲烷水合物生成动力学

高储气密度水合物的快速生成对气体水合物技术应用至关重要。将水与疏水性气相纳米二氧化硅和低剂量［0.1%~1.0%（质量）］的超吸水树脂在搅拌器中高速混合分散,制备出一种超吸水树脂改性的干水。该改性干水实质上是由高分子聚合物支撑且可自由流动的分散微滴堆。在8.0 MPa和274.2 K条件下,研究该改性微滴中甲烷水合物生成动力学特性。结果表明,松散的聚合物微滴极大地改善了液相连续水比表面积,为气体扩散至微滴表面提供了丰富的通道。水合物在聚合物微滴中快速生成,储气速率可达5.15~8.78 cm³·g^-1·min^-1,储气量高达158.0~175.0 cm³·g^-1。质量分数为0.3%的微滴表现出最快储存速率和最高储气量,且其循环水合储气过程中前6次储气量均超过120 cm³·g^-1。研究结果对水合物储运天然气技术规模化应用有一定的参考价值。     

水合物利用技术应用进展

过去的几十年中,对于水合物的研究不单单集中在抑制天然气水合物的生成上,基于水合物的生成利用技术也得到了广泛的研究。基于水合物的生成利用技术是环保和可持续的新技术,利用不同气体生成水合物相平衡条件的差异,可用于气体分离、置换开采。由于水合物具有较高的气体浓度,可用于气体的存储。利用水合物较高的化解潜热,可将其用于蓄冷。本文综述了国内外水合物技术的研究应用现状,分析了水合物技术在气体分离与存储、溶液浓缩分离、蓄冷、二氧化碳（CO₂）置换开采等领域有前景的研究方向。但是其水合反应速率慢、生成压力高、后期分离困难,极大地限制了水合物利用技术的工业应用。展望了水合物技术未来的研究发展方向,开发安全、高效和环保的水合物促进剂,开发高效水合物反应设备,开发连续水合物工艺,以便早日实现工业应用。     

Mechanism of methane hydrate formation in the presence of hollow silica

Methane hydrates are studied extensively as a prospective medium for storing and transporting natural gas due to their inherent advantages, including high volumetric energy storage density, being environmentally benign and extremely safe method compared to conventional compression and liquefaction methods. Enhanced formation kinetics of methane hydrates has been reported in hollow silica due to the increased gas/liquid contact surface area available for efficient conversion of water to hydrates. This work elucidates the mechanism of methane hydrate formation in light weight hollow silica. Hollow silica-to-water ratio was varied and its effect on the methane hydrate formation/dissociation morphology was observed. There exists a critical hollow silica-to-water ratio (1 : 6) beyond which the hydrates preferentially crystallize on the top of the bed by drawing water from the interstitial pores, whereas below this ratio the hydrate formation occurs within the bed between inter-particular spaces of hollow silica. Due to the very low bulk density, a small fraction of hollow silica was observed to be displaced from the bed during the hydrate formation above the critical hollow silica to water ratio.     

Experimental study on the scale-up effect of gas storage in the form of hydrate in a quiescent reactor

This paper presents the experimental study on the scale-up effect of natural gas storage in the form of hydrates in a quiescent reactor. The hydrate formation experiments with respect to gas storage in the presence of sodium dodecyl sulfate (SDS) were initially performed in a 10 L reactor to study the scale-up effect by adjusting the mass of water loaded. The results demonstrated that the scale-up effect was very obvious, i.e., the specific hydrate formation rate, the moles of gas consumed per unit mass of water and time, decreased rapidly with the increasing mass of water loaded in the reactor. A multi-deck cell-type vessel was devised as the internals of the reactor to eliminate the scale-up effect, where water was loaded in each cell of the vessel instead of being loaded in the reactor directly and the hydrate formed in all cells of the vessel simultaneously. A double-deck cell-type vessel was set-up and a series of hydrate formation experiments were performed to study the influence of the number of deck and the size of each cell upon the specific formation rate and the storage capacity. The experimental results proved the feasibility of the multi-deck cell-type vessel. The influence of water quality was also studied and the results demonstrated that tap water could be used instead of the expensive distilled water in the formation of hydrates and the most suitable concentration of SDS in tap water was 2000 mg/L.     

STUDY FOR NATURAL GAS HYDRATE CONVERSED FROM ICE

Natural gas hydrates are crystalline clathrate compounds composed of water and gases of small molecular diameters that can be used for storage and transport of natural gas as a novel method. In the paper a series of experiments of aspects and kinetics for hydrate formed from natural gas and ice were carried out on the industrial small scale production apparatus. The experimental results show that formation conditions of hydrate conversed from ice are independent of induction time, and bigger degrees of supersaturation and supercooling improved the driving force and advanced the hydrate formation. Superpressure is also favorable for ice particle conversion to hydrate. In addition, it was found there have an optimal reaction time during hydrate formation.     

Investigation on the effect of oxalic acid,succinic acid and aspartic acid on the gas hydrate formation kinetics

Gas hydrate reserves are potential source of clean energy having low molecular weight hydrocarbons trapped in water cages. In this work, we report how organic compounds of different chain lengths and hydrophilicities when used in small concentration may modify hydrate growth and either act as hydrate inhibitors or promoters. Hydrate promoters foster the hydrate growth kinetics and are used in novel applications such as methane storage as solidified natural gas, desalination of sea water and gas separation. On the other hand, gas hydrate inhibitors are used in oil and gas pipelines to alter the rate at which gas hydrate nucleates and grows. Inhibitors such as methanol and ethanol which form strong hydrogen bond with water have been traditionally used as hydrate inhibitors. However, due to relatively high volatility a significant portion of these inhibitors ends up in gas stream and brings further complexity to the safe transportation of natural gas. In this study, organic additives such as oxalic acid, succinic acid and L-aspartic acid (all three) having—COOH group(s) with aspartic acid having an additional—NH₂ group, are investigated for gas hydrate promotion/inhibition behavior. These compounds are polar in nature and thus have significant solubility in liquid water; the presence of weak acidic and water loving (carboxylic/amine groups) moieties makes these organic acids an excellent candidate for further study. This study would pave ways to identify a novel(read better) promoter/inhibitor for gas hydrate formation. Suitable thermodynamic conditions were generated in a stirred tank reactor coupled with cooling system; comparison of gas hydrate formation kinetics with and without additives were carried out to identify the effect of these acids on the formation and growth of hydrates. The possible mechanisms by which these additives inhibit or promote the hydrate growth are also discussed.