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。     

注乙二醇溶液分解甲烷水合物的实验研究

在甲烷水合物一维分解模拟系统上,进行了模拟注乙二醇溶液分解甲烷水合物的实验研究。使用甲烷气体与纯水在一定温度、压力条件下,在沉积物中合成水合物。通过以不同速率注入不同浓度的乙二醇溶液,研究了化学法分解水合物过程中甲烷气体和水生产规律。实验结果表明,水合物分解产出甲烷气体的过程主要分为4个阶段：初始注入段、化学剂稀释段、水合物分解段和残余气体产出段。整个分解过程中,水的生产速率几乎保持恒定。通过对实验结果的能量分析表明,本实验条件下分解综合效率在0.20～0.88之间,并且受注入速率和化学剂浓度影响。在恒定注入速率条件下,分解效率在化学剂质量分数为60%时达到最大值。     

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。     

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。     

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。     

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。     

甲烷水合物在纯水中的生成动力学

The kinetic behavior of methane hydrate formation in pure water was investigated.12 sets of experimental data on methane hydrate formation were determined at temperatures ranging from 273.65 to 276.15K and pressures ranging from 4.47 to 8.47MPa.The duration of three stages in methane hydrate formation,known as the dissolution,nucleation and growth periods,that are lacking in open literature,was obtained.The effect of pressure and temperature on the kinetics of methane hydrate formation was also studied.     

甲烷水合物在纯水和抑制剂体系中的生成动力学

Kinetic data of methane hydrate formation in the presence of pure water,brines with single salt and mixed salts,and aqueous solutions of ethylene glycol(EG) and salt EG were measured.A new kinetic model of hydrate formation for the methane water systems was developed based on a four-step formation mechanism and reaction kinetic approach.The proposed kinetic model predicts the kinetic behavior of methane hydrate formation in pure water with good accuracy.The feasibility of extending the kenetic model of salt(s) and EG containing systems was explored.     

甲烷水合物的研究和开发

介绍了甲烷水合物的结构、相平衡性质和在自然界的赋存情况,以及为开采甲烷水合物而进行的钻探和深海开发技术,并探讨了开发甲烷水合物中的环境保护问题.     

温度对多孔介质中甲烷水合物生成过程的影响

采用自行设计的实验装置,分别进行了0℃以上(274.7 K)、0℃附近(272.8±0.5 K)和0℃以下(267.4 K)3种不同温度下,在20～40日石英砂中甲烷水合物的生成实验.结果表明甲烷水合物在0℃以上生成比较快;在0℃附近储气量大,水合物在整个砂层中的分布比较均匀.针对实验结果,本文提出了水合物在三种不同温度下的生成机理.     

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.     

Experimental verification of anomalous chloride enrichment related to methane hydrate formation in deep‐sea sediments

Anomalous chloride concentration enrichment has been detected in marine sediments comprising methane hydrates (MHs). In this study, we designed an electric circuit system linked to the high‐pressure resistance cell in which the chloride ion concentration can be directly measured within reliable accuracy under in situ conditions of the deep‐sea floor pressure and temperature. Chloride concentration increased under a fast MH formation rate, but no noticeable concentration change was detected under a relatively low‐rate. Furthermore, we suggested that the MH formation rate must be maintained at least ～10² mol m^?2 yr^?1 so as to efficiently enrich chlorides and retain the acquired chlorinity. The present experimental system dose not fully reflect the relatively minor effective variables such as vertical advections in real system, but the results seem to be sufficient for revealing chloride enrichment phenomena induced by fast MH formation rate with free methane gas. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

EFFECT OF DIFFERENT OPERATION METHODS ON METHANE HYDRATE FORMATION

Three experiments of static state storage method, low-temperature and constant-pressure storage method and low-temperature and constant-pressure storage method were carried out to investigate which method was best in gas hydrate. The relationships of hydrate rate, capacity and liquid temperature versus time were derived and three results were contrasted. The experimental results show lowtemperature and constant-pressure method is better than the other two methods because it's operation period is shorter and storage capacity is larger than the other two. Low-temperature and constant-pressure method is the best method. So new method will be new research objective.     

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。     

Intensification and kinetics of methane hydrate formation under heat removal by phase change of n‐tetradecane

A method of direct heat removal resulting from the phase change of n‐tetradecane was used to intensify the heat transfer during hydrate formation. The growth rates of methane hydrate in aqueous slurries containing 25–45 wt % of solid n‐tetradecane were investigated at pressures between 4.70 and 6.46 MPa (gauge) and near the fusion point of solid n‐tetradecane. Methane hydrate growth started at a practically constant rate, which became variable after a sudden increase. Two rate laws were established to correlate with the experimental data for the constant and variable rate stages. The methane hydrate growth rates achieved with solid n‐tetradecane were significantly enhanced compared with those obtained under indirect heat removal. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3441–3450, 2015     

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。     

环戊烷-甲烷水合物生成过程的温度特性

研究了环戊烷-甲烷水合物生成过程中的温度变化,分析了体系的热量损失。在不同初始温度(4℃、8℃和12℃)、压力(2MPa、4MPa、6MPa、8MPa和10MPa)和进气方式(一次性进气、连续进气和间歇进气)的条件下,测定了釜内温度,对比了以上各因素对釜内最高温度(T_max)与釜内最大温升(ΔT_max)的影响。实验表明,T_max主要受压力和进气方式影响,初始温度对其影响不明显;ΔT_max受初始温度、压力和进气方式影响显著。在间歇进气方式下,初始温度越低、压力越高,ΔT_max越大。其中,在初始温度为4℃、压力为10MPa、进气时间间隔为30min的间歇进气方式下,ΔT_max可达16.5℃。此外,由热量分析发现,体系的主要热量损耗表现为体系向环境中的散热。因此,提高保温层的绝热性能,有利于提高水合物生成热的热量有效利用率。