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.     

天然气水合物生成条件的测定和计算

利用全透明蓝宝石水合物静力学实验装置,测定了4种塔里木油田天然气在纯水中的水合物生成条件.将Chen-Guo 水合物模型应用于天然气水合物生成条件的计算,实验测定的4种天然气水合物生成条件的计算结果和实验结果符合得很好.     

氨水在冰粉法合成甲烷水合物中的作用

利用冰粉法在低温高压冰态环境中合成甲烷水合物,通过压缩因子修正理想气体消耗量的PVT理论研究甲烷水合物饱和度随着氨水体积的变化规律,进而探索液态氨与固体甲烷水合物的作用关系。结果表明,在冰粉直径为200μm,温度为-4℃,甲烷气体压力为4.7MPa的条件下,随着氨水体积从0mL增加到24mL,甲烷水合物饱和度从3.8%降低到0.3%,起到了抑制生成甲烷水合物作用。研究为完善冻土带天然气水合物的性质及其开发利用提供了依据。     

含(CH4+CO2+H2S)酸性天然气水合物形成条件实验与计算

采用高压全透明蓝宝石水合物相平衡装置,测定了(CH₄+CO₂+H₂S)三元酸性天然气在纯水条件下的水合物生成条件数据.实验温度范围为274.2～299.7 K,压力范围为0.58～8.68 MPa.混合物气体中H₂S和CO₂的浓度分别为 4.95%（mol）～26.62％（mol）和6.81%（mol）～10.77%（mol）.采用Chen-Guo水合物模型对实验数据进行了计算,结果表明,在不同的H₂S浓度下,Chen-Guo水合物模型的预测精度优于CSMHYD 模型.随着H₂S浓度的增加,计算的绝对偏差增大.针对H₂S浓度较高［＞10％（mol）］的体系,该两种水合物模型均有待改进.     

基于不同状态方程预测气体水合物相平衡条件

气相逸度的计算结果会直接影响气体水合物相平衡条件的预测精度。基于Chen-Guo模型,选取RK、SRK、PR以及PT四种状态方程计算逸度,分别对甲烷、乙烷以及二氧化碳三种不同气体水合物在不同温度范围内的相平衡条件进行计算。结果表明:纯水条件下,RK方程最适合预测甲烷水合物相平衡条件,而PR方程更适合预测乙烷及二氧化碳水合物相平衡条件;对于冰中,SRK方程适合预测甲烷水合物的相平衡条件,PR方程适合预测乙烷水合物的,而RK方程更适合二氧化碳水合物的;对于甲烷水合物,低于218.2 K的预测是导致模型预测精度偏低的原因;对于乙烷水合物,需要提高低于230.2 K的预测精度;对二氧化碳水合物而言,提高对低于270.7K的预测可以进一步提高模型预测精度。     

基于不同状态方程预测气体水合物相平衡条件

气相逸度的计算结果会直接影响气体水合物相平衡条件的预测精度。基于Chen-Guo模型,选取RK、SRK、PR以及PT四种状态方程计算逸度,分别对甲烷、乙烷以及二氧化碳三种不同气体水合物在不同温度范围内的相平衡条件进行计算。结果表明：纯水条件下,RK方程最适合预测甲烷水合物相平衡条件,而PR方程更适合预测乙烷及二氧化碳水合物相平衡条件;对于冰中,SRK方程适合预测甲烷水合物的相平衡条件,PR方程适合预测乙烷水合物的,而RK方程更适合二氧化碳水合物的;对于甲烷水合物,低于218.2 K的预测是导致模型预测精度偏低的原因;对于乙烷水合物,需要提高低于230.2 K的预测精度;对二氧化碳水合物而言,提高对低于270.7 K的预测可以进一步提高模型预测精度。     

含氢气体水合物生成条件的测定和计算

利用全透明蓝宝石水合物静力学实验装置测定了12组含氢气体混合物（包括5个二元系、4个三元系和3个四元系）在纯水中的水合物生成条件.将Chen-Guo水合物模型应用于含氢体系水合物生成条件的计算,计算中选用PR状态方程以及刘昆元和汪文川提出的混合规则计算含氢气体混合物的组分逸度系数,并对混合规则中的二元交互作用参数进行了重新回归.实验测定的12组含氢气体混合物水合物生成条件的计算结果和实验结果符合得很好.     

十二烷基硫酸钠(SDS)对甲烷水合物膜生长动力学的影响

采用水中悬浮单个气泡法测定了不同温度（273.4～279.4K）和压力（3.60～11.90MPa）下甲烷在含SDS水溶液中的水合物膜生长动力学数据,并应用Chen-Guo模型中的无因次Gibbs自由能差作为推动力（-△G/（RT））对实验数据进行关联,得到了一个较为简单的数学模型。由实验数据回归出不同SDS浓度下的甲烷水合物膜生长动力学的反应级数,并根据模型回归的参数和Arrhenius方程计算出甲烷水合物膜生长表观活化能及指前因子,同时也讨论了SDS对甲烷水合物膜生长速率的影响。     

管道中天然气水合物的预测

管道中天然气水合物的预测是为了找到天然气水合物生成条件,以便及早的发现水合物的生成,防止水合物聚集堵塞管道,造成不必要的经济损失与安全事故。介绍了图解法、相平衡常数法、热力学统计法、预测模型,并重点介绍了预测模型如VDW-P型天然气水合物预测模型、Chen-Guo预测模型、含抑制剂体系的水合物预测模型等,以期为今后的研究提供参考。     

SDS体系下甲烷水合物生成条件预测模型

以van der Walls-Platteeuw模型为基础,采用划分基团贡献的思想利用UNIFAC法和Aasberg-Petersen模型分别计算十二烷基硫酸钠(SDS)中不同基团对水的活度系数贡献值,建立了SDS体系下甲烷水合物生成条件预测模型。经实验验证,预测最大误差不超过5%,平均误差在3%以内,改进后的模型良好的可靠性可为水合物动力学研究提供准确的相平衡数据。通过模型计算,发现相对比纯水,SDS会影响水的活度明显改善水合物生成条件。当浓度在0.001 5 mol/L时效果最好,超过0.002 mol/L时,反而会提高水合物生成条件抑制水合物生成。     

石英砂中甲烷溶解运移体系水合物生成与聚集实验分析

建立了可模拟海底天然气水合物形成环境的大型三维成藏实验模拟装置,其主体高压反应釜内径500 mm,高1000 mm。在此基础上,采用填砂模型,进行了甲烷溶解运移体系下甲烷水合物生成与聚集过程的实验模拟分析。实验流程为：甲烷溶解于NaCl溶液中,再泵送进入高压反应釜,在沉积层中渗流并生成甲烷水合物。通过30个电阻率传感器监测甲烷水合物的生成和聚集过程。实验结果表明,甲烷溶解运移体系下甲烷水合物生成之后首先分散在溶液中,当溶液的总甲烷浓度（溶解的甲烷及水合物分散相中的甲烷）达到操作条件下盐溶液体系甲烷饱和溶解度后,甲烷水合物从溶液中析出。电阻率分布实验结果表明,析出甲烷水合物的聚集区域受溶液流动控制。     

Equilibrium and Kinetic Properties of Methane Hydrate

During methane dissolution in water in a closed space, the pressure varies exponentially with time until the formation of methane hydrate. A model of this process is proposed that fits experimental data well. The methane concentration at the onset of hydrate formation is calculated as a function of temperature and pressure.     

利用吸收-水合耦合法从氨弛放气中回收氢气的研究(英文)

In this work, the absorption-hydration hybrid method was used to recover (hydrogen + nitrogen) from (hydrogen + nitrogen + methane + argon) tail gas mixtures of synthetic ammonia plant through hydrate forma-tion/dissociation. A high-pressure reactor with magnetic stirrer was used to study the separation efficiency. The in-fluences of the concentration of anti-agglomerant, temperature, pressure, initial gas-liquid volume ratio, and oil-water volume ratio on the separation efficiency were systematically investigated in the presence of tetrahydro-furan (THF). Anti-agglomerant was used to disperse hydrate particles into the condensate phase for water-in-oil emulsion system. Since nitrogen is the material for ammonia production, the objective production in our separation process is (hydrogen + nitrogen). Our experimental results show that by adopting appropriate operating conditions, high concentration of (hydrogen + nitrogen) can be obtained using the proposed technology based on forming hydrate.     

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。     

Kinetics of carbon dioxide and methane hydrate formation

Experimental data on the kinetics of carbon dioxide hydrate formation and its solubility in distilled water are reported. The experiments were carried out in a semi-batch stirred tank reactor at nominal temperatures of 274, 276 and 278 K and at pressure ranging from 1.59 to 2.79 MPa for the kinetics experiments and at pressure ranging from 0.89 to 2.09 MPa for the solubility experiments. A minor inconsistency in the kinetic model developed by Englezos et al. (1987a) was removed and the model was modified to determine the intrinsic kinetic rate constant for carbon dioxide hydrate formation. The same model was also used to re-determine the intrinsic kinetic rate constant for methane hydrate formation. The model is based on the crystallization theory coupled with the two-film theory for gas absorption in the liquid phase. The Henry's constant (H) and apparent dissolution rate constant (K_La) required in the model were determined using the experimental solubility data. The kinetic model describes the experimental data very well. The kinetic rate constant obtained for the carbon dioxide hydrate formation was found to be higher than that for methane.     

甲烷与冰快速形成天然气水合物的影响因素研究

设计了冰-气生成天然气水合物的实验装置,对由冰和甲烷反应生成天然气水合物的影响因素进行实验研究。结果表明,压力越高,温度越低,冰粒越小,越有利于水合物的生成,促进水合物快速形成的搅拌速度和促进剂浓度最佳值分别是800 r/min和800 mg/L。     

离子对甲烷水合物相平衡的影响

自由水盐度直接影响水合物的生成和分解,为了充分研究自由水盐度对甲烷水合物相平衡的影响,本文利用正交实验设计方法研究了不同离子组成和浓度条件下多孔介质中水合物形成与分解特性。运用正交法研究水合物可减少实验次数、缩短实验周期。甲烷水合物相平衡点通过定容压力搜索法测得。与纯水体系相比,添加离子后相同压力条件下甲烷水合物的平衡温度降低,并且随着离子浓度的增加,平衡温度进一步降低。方差分析证明阳离子中Mg²⁺对水合物平衡影响最显著;极差分析结果表明,阳离子的影响程度从大到小依次为Mg²⁺、Ca²⁺、Na⁺、K⁺。SO^2-₄、CO^2-₃、Cl^-三种阴离子浓度对水合物相平衡点影响均显著。水合物诱导时间变化无明显规律,受离子种类、浓度影响不显著。     

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.     

石英砂粒径大小对甲烷水合物形成及分布的影响

为了研究不同粒径多孔介质体系中甲烷水合物的形成,本文采用粒径分别为0.075~0.5mm、0.5~1mm、1~2mm和2~3mm的石英砂作为多孔介质,在初始压力7.0MPa、温度0.5℃条件下进行水合物形成实验并进行取样观察、分层分解,得出不同粒径大小石英砂中甲烷水合物形成及分布的特征。结果表明：随着石英砂粒径的增大,石英砂砂体中的水合物形成量和初始水合物形成速率在逐渐减小;在粒径为0.075~0.5mm、1~2mm和2~3mm石英砂中,充气过程中水合物便开始形成,且并未出现明显的水合物大量形成阶段,而在粒径为0.5~1mm石英砂体系中出现了水合物大量形成的阶段;通过计算发现,0.5~1mm石英砂体系的气体消耗量最大,为0.47mol,2~3mm石英砂体系的气体消耗量最小,仅为0.05mol;在这4种粒径的石英砂体表面的甲烷水合物主要以分散状均匀分布于颗粒之间或胶结成块,但这一观察结果与通过分解的方法所得到的石英砂上部水合物形成量大于下部的结果存在差异;重复实验也发现,仅在粒径为0.5~1mm石英砂顶部出现了水合物大量富集的现象,因此推断认为在一定粒径的介质体系同时上部存在较大空隙时,水合物有可能会在空隙中大量富集存在。这一实验结果对自然环境中水合物的赋存区域及形态的预测具有一定的参考价值。     

0℃以下含SDS的甲烷水合物生成方式及过程对其分解速率的影响

The dissociation rates of methane hydrates formed with and without the presence of sodium dodecyl sulfate(methane-SDS hydrates),were measured under atmospheric pressure and temperatures below ice point to investigate the influence of the hydrate production conditions and manners upon its dissociation kinetic behavior.The experimental results demonstrated that the dissociation rate of methane hydrate below ice point is strongly dependent on the manners of hydrate formation and processing.The dissociation rate of hydrate formed quiescently was lower than that of hydrate formed with stirring;the dissociation rate of hydrate formed at lower pressure was higher than that of hydrate formed at higher pressure;the compaction of hydrate after its formation lowered its stability,i.e.,increased its dissociation rate.The stability of hydrate could be increased by prolonging the time period for which hydrate was held at formation temperature and pressure before it was cooled down,or by prolonging the time period for which hydrate was held at dissociation temperature and formation pressure before it was depressurized to atmospheric pressure.It was found that the dissociation rate of methane hydrate varied with the temperature(ranging from 245.2 to 272.2 K) anomalously as reported on the dissociation of methane hydrate without the presence of surfactant as kinetic promoter.The dissociation rate at 268 K was found to be the lowest when the manners and conditions at which hydrates were formed and processed were fixed.