水合物法提纯低浓度煤层气的实验研究

发布时间：2018-08-17 15:21

【摘要】：我国煤层气资源储量丰富,但开发利用效率较低,尤其是低浓度煤层气,造成了巨大的资源浪费和严重的环境污染。提高煤层气的利用效率已成为能源领域迫切需要解决的一个关键问题。气体水合物是由水分子和气体分子在一定的温度和压力条件下形成的结晶状化合物。不同气体分子形成水合物的相平衡条件不同,是水合物法分离混合气体的理论基础。利用水合物法提纯低浓度煤层气具有广阔的应用前景,近年来受到国内外学者的普遍关注。但是水合物结晶时间过长、生成水合物的温度和压力条件苛刻、甲烷回收率不高是该方法目前需解决的关键科学问题。针对这些关键科学问题,本文在溶液搅拌体系、石英砂体系、煤炭颗粒体系开展了水合物法分离低浓度煤层气(30.0 mol%CH4,60.0 mol%N2,10.0 mol%O2)的实验研究,重点研究了表面活性剂、多孔介质饱和度等因素对气体消耗量、水合物生成速率、CH4回收率等参数的影响关系,主要获得以下几点结论:①采用观察法测定了低浓度煤层气在1.0 mol%THF溶液中生成水合物的相平衡条件。与纯水体系的相平衡数据对比发现,促进剂四氢呋喃(THF)大大降低了低浓度煤层气生成水合物的相平衡压力。②根据测定的相平衡数据,在THF溶液搅拌体系与THF/SDS溶液搅拌体系开展了低浓度煤层气提浓的动力学实验研究。研究结果表明,表面活性剂SDS能有效缩短水合物的结晶诱导时间,促进水合物快速生成,并提高CH4回收率与分离效率。③在石英砂体系开展了动力学实验研究。通过研究发现,与THF/SDS溶液体系相比,低浓度煤层气在石英砂体系的结晶诱导时间明显缩短,水合物生成速率更快,但气体消耗量和CH4回收率较低。④在煤炭颗粒体系开展了低浓度煤层气的分离动力学实验。实验结果表明,煤炭颗粒对CH4气体具有较强的吸附作用,极大的缩短了气体水合物的生成过程。煤炭颗粒的饱和度越小,气体消耗量和气体消耗速率越大。比较溶液体系、石英砂体系、煤炭颗粒体系的实验结果,我们发现THF/SDS溶液搅拌体系获得的CH4气体回收率最高(40%),水合物分解气中CH4浓度从30mol%升至50mol%。当煤炭颗粒的饱和度为40%时,在其吸附-水合反应的共同作用下,水合物的结晶诱导时间最短,气体消耗量和气体消耗速率最大。
[Abstract]:China is rich in CBM resources, but the efficiency of exploitation and utilization is relatively low, especially the low concentration of CBM, which results in a huge waste of resources and serious environmental pollution. Improving the utilization efficiency of coalbed methane (CBM) has become a key problem in energy field. Gas hydrate is a crystalline compound formed by water molecule and gas molecule under certain temperature and pressure. The phase equilibrium conditions of hydrate formation by different gas molecules are different, which is the theoretical basis for the separation of mixed gases by hydrate method. The application of hydrate method in the purification of low concentration coalbed methane (CBM) has a broad application prospect, which has attracted widespread attention of scholars at home and abroad in recent years. However, the key scientific problems need to be solved at present are the excessive crystallization time of hydrate, the harsh temperature and pressure conditions for hydrate formation, and the low recovery rate of methane. In view of these key scientific problems, the separation of low concentration coalbed methane (30.0 mol Ch _ 4 and 60.0 mol N _ 210.0 mol%O2) by hydrate method has been carried out in the solution agitating system, quartz sand system and coal particle system, with emphasis on the study of surfactants. The effect of saturation of porous media on gas consumption, hydrate formation rate and Ch _ 4 recovery rate, etc. The main conclusions are as follows: 1. The phase equilibrium conditions for the formation of hydrate from low concentration coalbed methane in 1. 0 mol%THF solution were determined by using the observation method. Comparing with the phase equilibrium data of pure water system, it is found that the accelerator tetrahydrofuran (THF) greatly reduces the phase equilibrium pressure of the formation of hydrate from low concentration coalbed methane according to the measured phase equilibrium data. The kinetics of coal bed methane (CBM) concentration in THF solution stirring system and THF/SDS solution stirring system was studied. The results show that surfactant SDS can effectively shorten the induction time of hydrate crystallization, promote the rapid formation of hydrate, and improve the recovery rate and separation efficiency of CH4 in quartz sand system. It is found that the crystallization induction time of low concentration coalbed methane in quartz sand system is shorter than that of THF/SDS solution system, and the rate of hydrate formation is faster than that of THF/SDS solution system. However, gas consumption and CH4 recovery were lower. 4. 4. The separation kinetics experiments of coal bed methane with low concentration were carried out in coal particle system. The experimental results show that coal particles have strong adsorption on CH4 gas and greatly shorten the gas hydrate formation process. The smaller the saturation of coal particles, the greater the gas consumption and gas consumption rate. Comparing the experimental results of solution system, quartz sand system and coal particle system, we found that the recovery rate of CH4 gas in THF/SDS solution agitation system was the highest (40%), and the concentration of CH4 in hydrate decomposition gas increased from 30 mol% to 50 mol%. When the saturation of coal particles is 40, the crystallization induction time of hydrate is the shortest, and the gas consumption and gas consumption rate are the largest under the combined action of adsorption-hydration reaction.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD845

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