H2S水合物生长过程在线观测及拉曼光谱特征研究

Raman spectroscopic study of H2S hydrate online growth process

关键词:  H₂S水合物  拉曼光谱  生长过程  笼占有率  水合指数  结构演化

Key words:  H₂S hydrate  Raman spectroscopy  growth process  fractional occupancy  hydration number  structural evolution

摘要:

含硫天然气在低温高压下管输时,在管道中易形成含H₂S的混合气水合物,从而阻塞管道,腐蚀设备,影响采气系统的正常运行。了解H₂S水合物的生长速率对于天然气管道防堵具有一定的意义。同时,气体水合物具有储气能力,通过形成酸性气体水合物是储运和分离酸性气体的一种可行方法,获取H₂S水合物的笼占有率和水合指数有助于评估H₂S水合物的储气性能。基于熔融毛细硅管和在线观测系统,结合激光拉曼光谱技术,建立了H₂S水合物拉曼光谱分析与观测方法。显微观测了H₂S水合物的生长过程,证实了水合物生长主要受传质条件的控制,处于溶液中的H₂S水合物生长速率保持稳定；得到了H₂S水合物生长过程中拉曼光谱的变化信息,随着温度的降低,溶解态H₂S的S-H伸缩振动峰转变为H₂S水合物大笼和小笼中H₂S的S-H伸缩振动峰,液态水的O-H伸缩振动峰转变为水合物结构水O-H伸缩振动峰；通过拉曼光谱技术,证实常温下H₂S水合物为Ⅰ型水合物,并计算了大笼和小笼占有率分别为96.0%和80.9%,以及确定水合指数为6.23。H₂S水合物的高储气能力和稳定性为水合物法脱硫提供了有利支持。 

Abstract:

The gas mixture hydrates containing H₂S are easily formed while sour natural gas is transported in pipelines under low temperature and high pressure conditions. The formation of gas hydrates usually block pipelines and corrode equipment, thus affecting production of gas plants. Understanding the growth rate of H₂S hydrate has some significance for preventing natural gas pipelines from blocking. At the same time, gas hydrates can be considered as the storage media which can be used to store and transport and separate sour natural gas. It is conducive to evaluate the sorage capacity or H₂S hydrate by obtaining its fractional occupancy and hydration number. Based on the fused silica capillary tube and online observation system, combined with the in-situ Raman spectroscopy, a method of Raman spectroscopy analysis and online observation of H₂S hydrate was developed in this study. The growth process of H₂S hydrates were observed microscopically, and it was confirmed that hydrate growth was mainly controlled by mass transfer conditions, revealing that the growth rate of H₂S hydrate in solution. Characterizations of the Raman spectroscopy during the growth of H₂S hydrate were studied. With the decrease of temperature, the S-H stretching vibration band of H₂S dissolved in aqueous gradually turned into a double S-H stretching vibration bands of H₂S in hydrate phase, and liquid water O-H stretching vibration bands turned into structured water O-H stretching vibration bands. In addition, type Ⅰ of H₂S hydrate by Raman spectroscopy was identified. The fractional occupancy of big cage and small cage was 96.0% and 80.9% respectively, and hydration number was 6.23%. The high gas storage capacity and stability of H₂S hydrate provide a favorable support for hydrate desulfurization.