基于Raman光谱技术的瓦斯混合气水合过程定量分析

Quantitative Analysis of the Hydration Process of Mine Gas Mixture Based on Raman Spectroscopy

瓦斯水合物微观晶体结构研究对水合分离技术具有重要理论意义。利用Raman光谱技术对三种含高浓度CO2瓦斯混合气水合反应过程进行在线观测,并对水合物相Raman光谱图进行分析,获取了瓦斯水合物不同生长阶段大、小孔穴占有率,同时利用van der Waals与Platteeuw热力学统计模型间接获得水合指数等晶体结构信息。结果表明,瓦斯水合物孔穴占有率及水合指数在水合物不同生长阶段未发生较大变化,水合物相中大孔穴几乎被客体分子填满,CO2与CH4分子共同占据大孔穴,但CO2占绝大多数,达到78.58%-94.09%,CH4分子仅为4.52%-19.12%,这主要是由于两种分子间存在竞争关系且气样中CO2浓度明显高于CH4,大孔穴占有率维持在97.70%-98.68%;小孔穴占有率为17.93%-82.41%,占有率普遍偏低,且仅有CH4分子;随气样中CH4浓度增加,CH4在大、小孔穴中的占有率均有所增加,且CH4分子在大孔穴中的占有率均明显低于在小孔穴中占有率;水合物生长不同阶段水合指数为6.13-7.33,随气样中CH4浓度的增加,小孔穴占有率有所增加,致使水合指数随之降低;由于瓦斯水合物生长分布不均匀,三种气样对应的不同生长阶段水合指数均呈不规则变化。

The research on micro crystal structure of mine gas hydrate is especially significant for the technology of gas hydrate separation.Using Raman spectroscopy to observe hydration process of 3kinds of mine gas mixture on line which contains high concentration of carbon dioxide,this experiment obtained the information of the hydrate crystals including large and small cage occupancy.Meanwhile obtained the hydration number indirectly based on the statistical thermodynamic model of van der Waals and Platteeuw.The results show that cage occupancy and hydration number of mine gas hydrates change little during different growth stages.The large cages of hydrate phases are nearly full occupied by carbon dioxide and methane molecules together,with the occupancy ratios between 97.70% and 98.68%.Most of the guest molecules in large cages is carbon dioxide（78.58%-94.09%）and only a few（4.52%-19.12%）is filled with methane,it is because carbon dioxide concentration in the gas sample is higher than methane and there is competition between them.However the small cage occupancy ratios is generally low in the range from 17.93%to 82.41%,and the guest molecules are all methane.With the increase of methane concentration in gas sample,the cage occupancy both large and small which methane occupied has increased,meanwhile the large cage occupancy which methane occupied is lower than small cage.The hydration numbers of mine gas hydrate during different growth stages are between 6.13 and 7.33.Small cage occupancy has increased with the increase of methane concentration,this lead to hydration number decreases.Because of the uneven distribution of hydrate growth,the hydration numbers of 3kinds of gas samples show irregular change during different growth stages.