Investigation of Tetrahydrofuran-CH<sub>4</sub> Hydrate Formation in Unstirred Conditions from a Different Perspective: Application to Solidified Natural Gas Storage
Bin‐Bin Ge, Dong‐Liang Zhong, Yiyu Lu, Xi‐Yue Li
Abstract
In this work, tetrahydrofuran (THF)-CH 4 hydrate formation in unstirred conditions was investigated using kinetic measurement, morphology observation, high pressure in situ Raman spectroscopy, and high-pressure DSC. The experiments were conducted at four THF concentrations (1.39, 2.78, 4.17, and 5.56 mol %) and a pressure of 6.0 MPa with the temperature ranging from 277.15 to 283.15 K. The results indicate that THF concentration is a key factor affecting THF-CH 4 hydrate formation. When increasing the THF concentration above 2.78 mol %, the emergence of channels on hydrates improved mass transfer for THF-CH 4 hydrate growth. The in situ Raman spectroscopy measurement shows that CH 4 and THF molecules fill the small and large cavities of the sII hydrate, respectively. With the increase of the THF concentration, more CH 4 molecules occupy the small cavities of the sII hydrate. In 2.78 and 4.17 mol % THF solutions, the coexistence of THF-CH 4 and CH 4 hydrates was determined while the temperature decreased to 277.15 K, and the gas consumption was 2.2 times larger than that obtained at 5.56 mol % THF. This finding suggests that forming two types of hydrates at a low THF concentration will be a viable means to increase the gas storage capacity.