气体水合物技术在天然气水合物开采

1、摘 要气体水合物技术在天然气水合物开采、蓄冷、二氧化碳分离及深海储藏、气体储运、海水淡化等领域具有潜在的广阔应用前景。气体水合物技术的应用与气体水合物生成驱动力、生成速率、生成过程等生成动力学基础问题密切相关。目前，国内外气体水合物生成动力学的研究尚处于初级阶段，气体水合物生成过程中生成驱动力存在许多争议。本文在分析与比较前人气体水合物生成驱动力公式的基础上，选择摩尔吉布斯自由能变表征气体水合物生成驱动力，并对气体水合物生成过程中生成驱动力做了初步研究，具体研究内容和结果如下：（1）通过计算等温条件下纯水中纯组分气体（甲烷、乙烷、丙烷、二氧化碳和硫化氢）的生成驱动力和3.5%NaCl溶液中甲烷

2、和二氧化碳水合物生成驱动力，理论分析二氧化碳置换海底甲烷气体的动力学可行性，并就压力、温度等参数对气体水合物生成驱动力的影响做了定量分析。结果表明：气液系统水合反应摩尔吉布斯自由能变随压力的增大非线性减小，即单位压力的增加对生成驱动力的贡献不一样，压力对甲烷和二氧化碳水合物生成驱动力的影响可分为两个阶段。（2）利用自行设计的一套可视化实验装置观测了丙烷水合物在纯水、1950 ppm十二烷基硫酸钠（SDS）溶液、400ppm十二烷基苯磺酸钠（SDBS）溶液中的生长过程，研究了水合反应中压力、温度、水合物的生长厚度、反应速率、生成驱动力等参数变化。通过对比纯水和表面活性剂溶液中的水合物生成实验，发

3、现有/无表面活性剂溶液中的水合物生成情况有很大区别：无表面活性剂存在时，水合物首先在两相界面生成，水合反应缓慢且不充分；添加表面活性剂后，水合物生长速度加快，水合物完全生成。显然，表面活性剂可以有效的降低水合反应物两相界面张力，减小了气液界面的比表面积，使气体分子更容易进入液相中，促进了气体水合物的生成。（3）根据理论计算得到的驱动力数值与实验所得的水合反应速率数据，拟合以常数、幂函数和双曲线函数的线性组合函数表征的气液系统水合物生成动力学模型。纯水中气-液界面上水合物层的厚度呈阶梯性生长，水合反应速率与驱动力都存在先增长后保持稳定的趋势，并且两者随着反应的进行呈常数、幂函数和双曲线函数的线性

4、组合拟合函数趋势变化。本文认为静态条件下水合物生长缓慢且不充分并且水合物在生长后期存在稳定阶段的原因取决于铠甲效应、水合反应相变热以及压力对一定温度和容积条件的气液系统水合物结晶过程影响的综合效果。本文的创新点和意义在于：（1）首次得到以摩尔吉布斯自由能变表征的静态条件下气液系统丙烷水合反应驱动力数据；（2）首次得到了丙烷水合物层生长过程中温度、压力、厚度，水合反应速率及生成驱动力等动力学重要参数，并拟合气液系统中丙烷水合物生长动力学模型；力学生长啊e formation driving force ormation in （3）归纳并完善静态条件下气体水合物生长规律，补充静态条件下纯水中水合

5、物生长过程中存在稳定阶段。 气液系统水合反应规律为界面水合反应和水合物技术工业化应用的研究提供了一定的理论基础，具有极大地参考意义。关键词：气体水合物；生成动力学；驱动力；丙烷；气液系统AbstractThe technology of gas hydrate has extensive application foreground in the fields of gas hydrate exploitation, store up cool,carbon dioxide storage deposited in seabed, natural gas transportation by t

6、he form of solid, sea aqueous solution desalination and other areas of industry. The application of gas hydrate is tight related to formation driving force, formation velocity and other foundation problem.Presently, the research of gas hydrate kinetics still at primary state.There are many disputes

7、on the question of driving force. This passage characterizes driving force of gas hydrate formation by the use of molar Gibbs free energy difference, preliminary study formation driving force during gas hydrte growth. Material contents and results as follow:(1) It gets the driving force of gas hydra

8、te formation of simple component gas (methane, ethane, propane, carbon dioxide and sulfureted hydrogen) and methane and carbon dioxide in 3.5% sodium chloride solution in pure aqueous solution on the condition of isothermal. It analyses theoretically kinetic feasibility, which using carbon dioxide s

9、ubstitute methane in seabed. It also quantitative analyses the impacts of pressure and temperature on driving force of hydrate reaction. The results indicates that molar Gibbs free energy difference of hydrate reaction does not minish with pressure as linearity for gas and liquid system. The gradien

10、t of molar Gibbs free energy difference changes along with pressure increase.That is the contribution of increase of unit pressure for driving force has changed. It can be plot out two trends for methane and carbon dioxide hydrate formation driving force.(2)It observes the hydrate growth process for

11、 gas and liquid system, taking propane for example, using a suit of experiment installation and experiment measure, which designed by self. The experiment proceed in pure water，sodium dodecyl sulfate of 1950ppm, sodium dodecyl benzene sulfonate of 400ppm. It attends the changing of pressure and temp

12、erature during the whole reaction and important parameters of thickness, reaction velocity, driving force etc. There is great difference on hydrate interface formation reaction if surface active agent exist.When there is not surface active agent, hydrate formation just happen at the interface layer.

13、 Hydrate reaction slow and insufficiency. When appending surface active agent, it grows mass hydrate and reaction thoroughly. It forms solid hydrate entirety indeed. By all appearances, surface active agent can reduce interfacial tension of two kinds of reactant, minish specific suiface area between

14、 interface of gas and liquid effectively, which make gas molecule enter into liquid phase easily, promote hydrate formation.The thickness of gas and liquid interface hydrate layer growth as ladder in pure water. )e question of ollow:ce during gas hydrte growth.(3)It fits kinetics model using linear

15、combines function of constant, power function and hyperbolic function, based on academic calculation numerical value of driving force and hydrate reaction velocity from experiment. The thickness of hydrate layer growth as ladder.There are both increase firstly then keep steady on hydrate reaction ve

16、locity and driving force. They both change as linear combine function of constant, power function and hyperbolic function during reaction.It believes that the reason of hydrate growth slowly and insufficiency at state of static lie on the compositive effect of loricae effect, heat of transformation

17、of hydrated reaction, the influence of pressure on hydrate crystal process in gasous-liquid system with a given condition of temperature and pressure.The innovation point and significance is:(1)The data of hydrate reaction driving force at static state of gas and liquid system were obtained for the

18、first time, which using mol Gibbs free energy change express;(2) The important dynamics parameters of temperature, pressure, thickness, hydrate reaction velocity and driving force during process of peopane hydrate layer growth were obtained for the first time. It fits propane hydrate growth dynamics model of gas and liquid system;(3) The gas hydrate growth disciplinarian at static state was concluded and perfected. It renews that thereis tranquilization phase in hydrate growth process at static state in pure water。The law of hydrate r