甲烷水合物生成和分解的实验研究

利用水合物法实现对天然气的工业储运,需要提高水合物的储气量并解决水合物的分解速度问题。为此,文章研究了在十二烷基硫酸钠(SDS)体系中,甲烷水合物的储气量和在冰点以下的常压分解规律。研究发现,SDS浓度为650 mg/L时甲烷水合物储气量达到最高值,约为170 V/V。分解温度为268.2~272.2 K区域内,甲烷水合物的分解速率随温度的降低而降低;在268.2 K时,甲烷水合物分解速率最低。     

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。     

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。     

气液比对表面活性剂复配促进甲烷水合物生成影响

气液比作为影响天然气水合物快速、大量生成的关键因素,有必要对其深入研究。利用天然气水合物装置,设定初始压力为6 MPa,温度为275.15 K,研究了十二烷基硫酸钠(SDS)与烷基多糖苷(APG1214)复配溶液体系在不同气液比条件下对天然气水合物生成影响。结果表明,合理的选取气液比能增强水合物的储气能力以及生成速率,4.00为其最佳气液比,最终储气密度可达到110.2(V/V),实验初始气液比的大小会影响水合物的生成过程,增加气液比能增加水合物的生成速率。因此,合理地将表面活性剂复配以及选取气液比,可显著提高水合物生成速率与储气能力。     

水合物法储存乙烯实验研究

提出了以水合物法储运乙烯,选用阴离子表面活性剂十二烷基硫酸钠(SDS)作为乙烯水合物的生成促进剂进行实验研究,考察了SDS对乙烯水合物生成的促进作用以及乙烯水合物在低温下的热稳定性。结果表明:SDS对乙烯水合物的生成速率和储气密度都有较大提高,对其促进原因进行了初步分析;实验测定乙烯水合物在263～269K的分解平衡压力范围是0.244～0.460MPa,在263～271K进行常压分解时,其分解率随温度升高而升高,在温度低于267K时,乙烯水合物的平衡分解率将降到23.7％以下,其中263K的分解率为5.6％。     

甲烷-叔丁胺-水体系中水合物的生成过程

利用恒压预冷法研究了不同反应物量(30.0,100.0g)、不同压力(2.50,3.50,4.50 MPa)、温度为6℃时无搅拌甲烷-叔丁胺-水体系中水合物的生成过程.实验结果表明,水合物在此体系中的生成形态为浆状;CH4水合反应速率随压力升高而增大;当初始反应物量较少(30.0g)时,甲烷储气量(标准状态下水合物中甲烷与初始反应物的体积比)随压力升高而增大不明显(3.50 MPa时为3.0 mL/mL,4.50 MPa时为3.1 mL/mL),当初始反应物量较多(100.0g)时,甲烷储气量随压力升高反而降低(由2.50 MPa时的5.4 mL/mL变为4.50 MPa时的0.9 mL/mL);反应过程中可能同时生成了纯叔丁胺结构的Ⅵ型和甲烷/叔丁胺结构的Ⅱ型两种水合物,且Ⅵ型与Ⅱ型量比在反应后期比前期大;甲烷与浓度为9.3%(mol)的叔丁胺溶液生成的水合物中甲烷储气量较低(最高5.4 mL/mL).通过分析甲烷-叔丁胺-水体系中水合物的生成过程,认为其可能包括反应分子接触聚集、水合物骨架形成和水合物晶体增长等3个步骤.     

复配体系下酸碱度对甲烷水合物生成的影响

1 m~3甲烷水合物分解后释放0.8 m~3的水和172 m~3的甲烷,燃烧时产生的高热量和低污染使其是理想的烃类能源。但是,其储气量少、诱导时间长等问题,使水合物技术难以在工业上大范围使用。文中使用4 mm氧化铝颗粒,并将其与十二烷基硫酸钠(SDS)溶液混合。研究在275.15 K和7 MPa的条件下,通过改变酸碱度来观察水合物的生成情况,并以双电层理论为基础进行分析。研究表明:在此复配环境下,存在着最佳的酸碱度促进甲烷水合物的生成。在pH=4的情况下,水合物的储气密度和气体消耗量达到最大,储气密度为301.4 mol/mol,气体消耗量为0.538 mol。且无论酸碱度如何都不改变水合物的生成位置。同时酸碱度的改变,减少了水合物生成过程中的诱导时间。     

天然烟浸滤液水合物法储甲烷动力学研究

水合物法储存天然气被公认为是一种极具潜力的高效储气技术。如何加速水合物生成,又能保证水合促进材料绿色环保,是水合固气技术实用化的关键。本文利用天然烟丝和烟末浸泡滤液在8.0 MPa和274.2 K的实验条件下进行静态水合储甲烷实验,研究甲烷水合物在烟滤液中的生成动力学特性。实验结果表明,水-烟质量比(液固比)为5～100的滤液与表面活性剂溶液性质相似,其表面张力比纯水下降36.7%～47.5%,甲烷水合物在该天然活性溶液中能快速生成。烟丝滤液中活性物含量明显低于烟末滤液,低液固比时,烟丝溶液有更高的水合储气量和储气速率;高液固比时,烟末滤液则表现出更优的水合储气性能,尤其在液固比为50时,烟末滤液中水合物储气量高达118.5 mmol·mol^-1,储气速率达2.98 mmol·mol^-1·min^-1。     

高含水油包水乳液的水合物储气性能研究

油包水乳液是近年来新兴的一种水合强化材料,具有良好的水合储气潜力,但是为了保证乳液的稳定性,通常所用的油包水乳液含水量不超过50%。然而水合物的储气量与水含量密切相关,因此高含水的油包水乳液更具有应用前景。对含水量超过50%的油包水乳液进行了水合物的储甲烷研究,考察了乳化剂用量、初始压力及搅拌速率对储气性能的影响,最后考察了乳液的循环储气能力。结果表明：含水量超过55%后,含水量的增加会造成乳液液滴的增大,储气量的降低。乳液含水量为55%,复合乳化剂Span80 / Tween80（m_Tween80∶m_Span80=0.783∶1）用量5%（质量）（以水量为基准）的乳液最适合水合储气;初始压力的增加有利于水合储气性能的提高,但压力过高会造成水合物壳的快速形成,从而降低整体储气能力;适宜的搅拌速率有利于水合物的生成,过快或过慢都会引起水合速率的下降。本实验中最佳的乳液水合储气条件为：温度274.15 K、反应釜中气水体积比10∶1、甲烷初始压力6 MPa、搅拌速率700 r/min,在此条件下,储气量可达141.42 L 气/L 水。在此条件下进行循环储气实验证明该乳液具有良好的循环利用性,四次循环中储气量均在130 L 气/L 水以上。研究结果可为天然气储运以及含烃混合气分离提供技术参考。     

表面活性剂吸附对促进甲烷水合物生成效果的影响

基于表面活性剂固-液界面吸附理论,在无搅拌条件下研究了十二烷基硫酸钠（SDS（、脂肪醇聚乙烯醚硫酸钠（AES（、脂肪醇聚乙烯醚（AEO（3种表面活性剂在不锈钢反应釜中对甲烷水合物生成的促进效果。结果表明：水合物的生成形态与表面活性剂吸附金属表面形态有良好的对应关系;SDS与AES在金属表面的吸附作用可使水合物成核速率提高,成核位置增多。由于AEO不能在金属壁面发生吸附,导致对水合物生成促进效果降低,在浓度为300 mg·L^-1的SDS、AES和AEO溶液中,水合物储气密度及平均储气速率分别为131.4、128.3、12.3（体积比（和5.8、7.6、0.07 mmol·min^-1;逐步提高SDS溶液浓度（80~1200 mg·L^-1（和AES溶液浓度（60~1350 mg·L^-1（,水合物储气密度首先增大然后减小,储气速率线性增大。因此,合理选择表面活性剂种类及浓度,可显著促进水合物生成。     

EXPERIMENTAL INVESTIGATION ON GAS HYDRATE FORMATION IN PRESENCE OF ADDITIVE COMPONENTS

Additives were used to increase gas hydrate formation rate and storage capacity. Experimental tests of methane hydrate formation were carried out in surfactant water solutions in a high-pressure cell. Sodium dodecyl sulfate (SDS) and alkyl polysaccharide glycoside (APG) were used to increase hydrate formation. The effect of SDS on hydrate formation is more pronounced compared APG. Cyclopentane (CP) also improves hydrate formation rates while it cannot increase methane gas storage capacity.     

Effect of different surfactants on methane hydrate formation rate, stability and storage capacity

The effects of anionic surfactants sodium dodecyl sulfate (SDS) and linear alkyl benzene sulfonate (LABS), cationic surfactant cetyl trimethyl ammonium bromide (CTAB) and non-ionic surfactant ethoxylated nonylphenol (ENP) on the formation, dissociation and storage capacity of methane hydrate have been investigated. Each surfactant was tested with 3 concentrations 300, 500 and 1000 ppm and it has been found that SDS, when prepared with these three concentrations speeds up the hydrate formation rate effectively. LABS increases the hydrate formation rate at 500 and 1000 ppm but decreases it at 300 ppm. CTAB and ENP have promotion effect on hydrate formation rate at 1000 ppm but decrease it at 300 and 500 ppm. Hydrate stability tests have been performed at three temperatures 268.2, 270.2 and 272.2 K with and without surfactant promoters. The results show that all tested additives increase the dissociation rate of methane hydrate below the ice point. CTAB has the minimum and LABS the maximum effect on the methane hydrate dissociation rate. Experimental results on hydrate gas content revealed that maximum storage capacity of 165 V/V is obtained with 1000 ppm of CTAB in water.     

Induction time,storage capacity,and rate of methane hydrate formation in the presence of SDS and silver nanoparticles

In this communication, the kinetic parameters of methane hydrate formation (induction time, quantity and rate of gas uptake, storage capacity (SC), and apparent rate constant) in the presence of sodium dodecyl sulfate (SDS), synthetized silver nanoparticles (SNPs), and mixture of SDS?+?SNPs have been studied. Experimental measurements were performed at temperature of 273.65?K and initial pressure of 7?MPa in a 460?cm³ stirred batch reactor. Our results show that adding SDS, SNPs and their mixture increases the quantity of gas uptake, water to hydrate conversion, and SC of methane hydrate formation, noticeably. Using 300?ppm SDS increases the SC and the quantity of methane uptake 615, and 770%, respectively, compared with pure water. Investigating the hydrate growth rate at the start of hydrate formation process shows that, using SNPs, SDS, and their mixture increases the initial apparent rate constant of hydrate rate, considerably. Our results show that the system of methane?+?water?+?SDS 500?ppm?+?SNPs 45?µM represents the maximum value of initial apparent rate constant, compared with other tested systems.     

A型分子筛对甲烷水合物生成的影响

The porous medium has an important effect on hydrate formation. In this paper, the formation process and the gas storage capacity of the methane hydrate were investigated with A-type zeolite and Sodium Dodecyl Sulfate (SDS) existing in the system. The results show that A-type zeolite can influence methane hydrate formation. At the temperature of 273.5 K and pressure of 8.3 MPa, the distilled water with A-type zeolite can form methane hydrate with gaseous methane in 12 hours. The formation process of the system with A-type zeolite was quite steady and the amount of A-type zeolite can influence the gas storage capacity significantly. The adding of A-type zeolite with 0.067 g•(g water)－1 into 2×10－3 g•g－1 SDS-water solution can increase the gas storage capacity, and the maxi-mum increase rate was 31%. Simultaneously the promotion effect on hydrate formation of 3A-type zeolite is much more obvious than that of 5A-type zeolite when the water adding amounts are 0.033 g•g－1 and 0.067 g•g－1 at the experimental conditions.     

X射线衍射分析聚乙烯吡咯烷酮对水合物分解过程的影响

深水油气资源的勘探开发以及开采过程中的环保要求,使得天然气水合物动力学抑制剂使用不可避免,含动力学抑制剂的分解研究对水合物生成后的解堵具有重要的指导意义。本文在高压反应釜内采用甲烷和丙烷混合气,合成天然气水合物,并用X射线粉晶衍射仪分析了含动力学抑制剂聚乙烯吡咯烷酮的水合物分解过程。结果显示甲烷和丙烷气体会形成SⅡ型水合物,但伴随有SⅠ型甲烷水合物的生成;添加动力学抑制剂后,水合物的分解速率变慢,在-60℃,添加0.5%的聚乙烯吡咯烷酮后,分解起始的20 min内,无抑制剂体系水合物分解可达69%,而在含抑制剂体系分解约18%;SⅡ型甲烷丙烷混合气水合物分解过程中晶胞各晶面分解速率相同,没有偏好性,水合物笼作为一个整体分解,添加抑制剂不改变这种分解方式,仍以整体分解。     

Effect of surfactant on the formation and dissociation kinetic behavior of methane hydrate

The effects of anionic surfactant sodium dodecyl sulfate (SDS) on the formation/dissociation kinetic behaviors of methane hydrate have been studied experimentally, with an emphasis put on dissociation kinetic behavior below ice point. The experimental results on hydrate formation show that the formation rates of methane hydrate could be speeded up by adding SDS to water and a critical SDS concentration of 650 ppm corresponding to a maximum storage capacity of 170V/V is determined. The SDS concentrations are fixed at this value in preparing hydrate samples for all dissociation tests. The dissociation experiments have been performed in two ways, at atmospheric pressure where the dissociation rates are determined by measuring the accumulative evolved gas volume, and in a closed system where the dissociation rates are determined by measuring the increasing system pressure profiles. For comparison, the dissociation tests with respect to two different cases, with and without the presence of SDS, are done in parallel. The results from tests in the first way show that the presence of SDS increases the dissociation rate of methane hydrate in whole temperature region below ice point. The results for the second way are somewhat different. The presence of SDS increases the dissociation rate and meta-stable system pressure in temperature region lower than . But when temperature is equal to or higher than , SDS speeds up the dissociation process only in beginning period, it turns to suppress the dissociation of methane hydrate several hours later and leads to a lower meta-stable system pressure compared with the case of without SDS. The experiments in closed system also demonstrate that the dissociating system approaches a meta-stable state with a pressure much lower than equilibrium dissociation pressure.     

甲烷水合物分解动力学

根据两种测量水合物分解动力学的方法———恒定分解压力法及压力变化法 ,采用气体水合物静力学实验装置测定了甲烷水合物的分解动力学数据 .由建立的分解动力学模型计算了甲烷水合物的分解速率 ,较好地拟合了所测得的实验数据 .实验数据验证了分解速率和水合物平衡压力下的逸度与实验压力下的逸度之差有关 ,计算的分解活化能为 73.3kJ·mol^-1(甲烷 ) .     

Enhanced hydrate formation under mild conditions using a novel spiral-agitated reactor

Hydrate-based solidified natural gas (SNG) technology provides a promising approach to store and transport natural gas, but demanding formation conditions and low methane storage capacity limit its application. Here, we presented a novel spiral-agitated reactor, and hydrate formation in pure water and amino acid systems was evaluated. It is worth to highlight that spiral agitation significantly enhances initial hydrate grow kinetics, and satisfied methane uptake of 134.9 V/V was obtained under a mild condition (4.3 MPa, 275.15 K, and 30 rpm). Impressively, when amino acids were introduced, late hydrate growth was greatly improved because of secondary uptake, and a large methane uptake (145.97 V/V) was obtained under a milder condition (3.8 MPa, 275.15 K, and 60 rpm), which increases by 82.97% comparing to that in pure water systems. These findings provide a new insight (synergistic effect of spiral agitation and amino acids) on enhanced hydrate production under extremely mild conditions.     

水合物法分离低浓度煤层气中的甲烷

向模拟煤层气(13.11vol% CH4+86.89vol% N2)中添加5.8mol%四氢呋喃(THF)?0.03mol%十二烷基硫酸钠(SDS)促进剂溶液分离提纯煤层气,考察了压力、温度、反应时间对气体消耗量、反应速率、分解气中甲烷浓度、甲烷回收率和甲烷分离因子的影响,采用色谱分析法分别测定了CH4在剩余气相和分解气相中的浓度。结果表明,压力增加,CH4回收率增大,CH4分离因子增大,CH4分离效果越好;温度是影响甲烷分离因子的关键因素,温度降低,氮气和甲烷竞争进入水合物晶体中,导致水合物相中甲烷浓度降低;温度升高有利于提高水合物对甲烷的选择性。甲烷回收效率最高可达98.65%,分离因子最大为14.83。随反应时间增加,分解气中CH4浓度升高。