Hou Guodong, Liang Deqing, Li Xiaosen
Department of Thermal Science and Energy Engineering, University of Science and Technology of China Hefei 230027 China.
Key Laboratory of Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences Guangzhou 510640 People's Republic of China
RSC Adv. 2018 Nov 27;8(69):39511-39519. doi: 10.1039/c8ra07215a. eCollection 2018 Nov 23.
Gas hydrates might cause a potential safety hazard in subsea flow assurance. Anti-agglomeration is a promising approach to keep subsea oil and gas pipelines free from hydrate risks. Effective anti-agglomerants could prevent hydrate agglomeration of small crystallites by lowering the capillary force between hydrate particles. Biosurfactants are widely known for their eco-friendly nature. In this work, -octane, water and methane were used as hydrate-forming ingredients to examine the effectiveness of rhamnolipid. Our investigation was carried out at constant high pressure (10 MPa) with different water cuts, subcooling degrees and rhamnolipid mass fractions. Three agglomeration states of hydrate were observed in a high-pressure visual autoclave apparatus. Torque measurements showed that rhamnolipid could effectively prevent hydrate agglomeration with a concentration of 0.5 wt%. In addition, the structural characteristics and morphology of hydrate were observed by use of powder X-ray diffraction, Raman spectroscopy and cryo-scanning electron microscopy. We noticed that the introduction of rhamnolipid had no effect on hydrate structure, but it could increase the large and small cavity ratio value and hydration number. Through the microscopic images, we inferred that rhamnolipid could make the surface of hydrate smooth, which resulted in a more ordered surface.
天然气水合物可能会在海底流动保障方面引发潜在的安全隐患。抗团聚是一种有望使海底油气管道免受水合物风险影响的方法。有效的抗团聚剂可以通过降低水合物颗粒之间的毛细力来防止小晶粒的水合物团聚。生物表面活性剂因其环保特性而广为人知。在这项工作中，使用正辛烷、水和甲烷作为水合物形成成分来检验鼠李糖脂的有效性。我们的研究在恒定高压（10兆帕）下进行，改变含水率、过冷度和鼠李糖脂质量分数。在高压可视高压釜装置中观察到了水合物的三种团聚状态。扭矩测量表明，鼠李糖脂在浓度为0.5重量%时能有效防止水合物团聚。此外，通过粉末X射线衍射、拉曼光谱和低温扫描电子显微镜观察了水合物的结构特征和形态。我们注意到鼠李糖脂的引入对水合物结构没有影响，但它可以增加大、小腔比值和水合数。通过微观图像，我们推断鼠李糖脂可以使水合物表面光滑，从而形成更有序的表面。
