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甲烷水合物在冰粉石英砂混合物中的生成
其他题名Methane Hydrate Formation in a Mixed System of Ice Powders and Sand
黄雯
导师樊栓狮
2007-06-09
学位授予单位中国科学院广州能源研究所
学位授予地点广州能源研究所
学位名称硕士
关键词甲烷水合物 冰粉 石英砂 冰粉转化率 动力学模型
摘要天然气水合物作为一种储量巨大的潜在能源已经日益受到各国的重视,但目前的研究几乎都集中在海洋水合物,对多年冻土水合物几乎没有涉及。我国冻土专家在对青藏高原进行多年研究后认为,青藏高原羌塘盆地多年冻土区具备形成天然气水合物的温度和压力条件,可能蕴藏着大量天然气水合物。为了进一步深入研究多年冻土区天然气水合物形成及演化规律,评估青藏高原等地区天然气水合物可能的资源量,需要对冻土中水合物的生成动力学进行深入的研究。冻土中含多孔介质和冰,是多相混合体系,为了简化研究过程和便于分析,本文采用石英砂等单一多孔介质来研究天然气水合物在自然界中的形成过程。 本文在实验室现有实验设备的基础上改造的甲烷水合物高压生成实验台上进行了有关甲烷水合物在冰粉石英砂混合物中生成的初步实验研究。通过恒压预冷法探讨了环境温度、环境压力、砂冰总表面积比对甲烷水合物生成及生成过程中冰粉转化率的影响规律。 实验结果表明:甲烷水合物在冰粉石英砂混合物中生成时,(1)不存在成核诱导期。得到的实验样品为良好分散型水合物;(2)压力对反应中期冰粉的转化速度随压力的增大而指数级加快,对反应前期和反应后期冰粉的转化速度及最终的转化率影响不大;最终冰粉转化率均达60%左右;(3)反应持续时间随温度的增大而延长,263 K时反应持续了近100分钟,269 K时则持续了近150分钟,273 K时反应持续了近250分钟;冰粉转化率随温度的增大而升高,263 K时 约为42%,269 K时 约为51%,273 K时 约为60%;(4)反应初期冰粉转化率随砂冰总表面积比Ks的增大而增大,但Ks对反应初期持续时间没什么影响,均是30分钟左右;反应中期,反应持续时间随Ks值的增大而延长,但冰粉转化率上升值先升后降;反应后期,Ks值对冰粉转化率几乎没有影响。而最终冰粉转化率随砂冰总表面积比Ks的增大而升高,Ks值为0.00时,冰粉转化率只有32%;Ks值为0.33时,冰粉转化率有38%;Ks值为0.66时,冰粉转化率达到了44%;Ks值为1.32时,冰粉转化率则达到了51%;(5)石英砂的存在提高了冰粉转化速率,但降低了最终冰粉转化率。(6)探讨了冰粉石英砂混合物中甲烷水合物的生成机理,将反应过程分为两阶段:第一阶段为石英砂吸附转化阶段;第二阶段为甲烷气扩散控制阶段;(7) 在定压恒砂冰总表面积比的条件下,甲烷水合物在冰粉石英砂混合物中生成时,反应的第一阶段可以用数学表达式为: (1- )1/3= 1/2.1+1; 反应的第二阶段可以用数学表达式为: (1- )1/3= (t-t*)1/2+(1- *)1/3; 其中 *=34%。通过计算得到甲烷水合物生成的活化能约为70.1 KJ•mol-1。
其他摘要The natural gas hydrate attracts much concern from the countries all over the world as one of potential energy with large amounts of storage, however, the present researches are focused on hydrate in the sea, not involving the hydrate frozen soil hydrate.Through the researches lasting many years, experts on the frozen soil in our country predicts that the frozen soil area in the Qiangtang basin in Qinghai-Tibet Plain possesses the temperature and the pressure condition for the formation of natural gas hydrate, possibly contains large amount of natural gas hydrate resoures. In order to study the formation and the evolution rule for natural gas hydrate in frozen soil and to appraise the resource quantity of natural gas hydrate in the Qinghai-Tibet Plain, the hyrate formation kinetics in the frozen soil is need to be investigated.The frozen soil is the mixed system, contains the porous medium and the ice. In order to simplify the research process and the analysis, the single porous media such as the quartz sand is generally used to study on the formation process of natural gas hydrate in this work. In this thesis, a new equipment for the methane hydrate formation in high pressure was built, and the preliminary experimental investigation on the formation of methane hydrate in the mixture of ice powders and quartz sand was carried. The influence of the temperature, the pressure, the surface area ratio of ice powders to quartz sand on the formation of methane hydrate and the hydration rate of ice were investigated by the constant pressure and precooling method . The results shows that: (1) There is no induction period of nucleation in the formation of methane hydrate in a mixed system of ice powders and sand ,moreover the hydrate sample with good dispersion is obtained ; (2)The hydration velocity of the ice powders increases exponentially with increasing pressure in the middle period of reaction , the influence of pressure on the velocity of the ice powders reaction and the final hydration rate of ice is small in the earlier and later period of reaction, the final hydration rate of ice reaches about 60%; (3) The lasting reaction time increases with increasing the temperature.The reaction lasts about 100 minutes at 263 K, about 150 minutes at 269 K, and about 250 minutes at 273 K. The hydration rate of ice increases with increasing the temperature, the value is 42% at 263 K, 51% at 269 K, and 60% at 273 K; (4) The hydration rate of ice increases with increasing the surface area ratio of ice powders to quartz sand Ks in the initial period of reaction,however, Ks has no influence on the lasting time of the initial period of reaction, the lasting time is about 30 minutes.In the middle period of reaction, the lasting time ncreases with increasing Ks,however, the hydration rate of ice increases formerly and dereases later. In the later period of reaction, Ks has nearly no influence on the hydration rate of ice.However, the final hydration rate of ice increases with increasing the surface area ratio of ice powders to quartz sand Ks. When the Ks is 0.00, the hydration rate of ice is only 32%; When the Ks is 0.33, the hydration rate of ice is 38%; When the Ks is 0.66, the hydration rate of ice is 44%; When the Ks is 1.32, the hydration rate of ice can reach 51%; (5) The existence of quartz sand can enhance the velocity of the ice powders reaction, but reduce the final hydration rate of ice;(6)The formation mechanism of methane hydrate in a mixed system of ice powders and sand was discussed.The formation process can be divided into two stages: (I) quartz sand absorption and transfer stage, (II)methane diffusion-control stage;(7) In the formation process of methane hydrate in a mixed system of ice powders and sand under constant pressure the surface area ratio of ice powders to quartz sand, the first stage of reaction can be described by the mathematical expression: (1- )1/3= 1/2.1+1,and the second stage of reaction can be described as: (1- )1/3= (t-t*)1/2+(1- *)1/3, where *=34%. The activation energy of the formation of methane hydrate can be calculated, the value is about 70.1 KJ•mol-1.
页数77
语种中文
文献类型学位论文
条目标识符http://ir.giec.ac.cn/handle/344007/4021
专题中国科学院广州能源研究所
推荐引用方式
GB/T 7714
黄雯. 甲烷水合物在冰粉石英砂混合物中的生成[D]. 广州能源研究所. 中国科学院广州能源研究所,2007.
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