Hydrate-Based Gas Storage Application Using Simulated Seawater in the Presence of a Co-Promoter: Morphology Investigation
Katipot Inkong, Viphada Yodpetch, Hari Prakash Veluswamy, Santi Kulprathipanja, Pramoch Rangsunvigit, Praveen Linga
Abstract
The hydrate morphology pattern plays a critical role in the reactor design for hydrate-based gas storage/separation technology. This work investigated the morphology of mixed methane–THF hydrate formation using salt water (3.5 wt % NaCl) instead of pure water at 288.2 K and 8 MPa. The result indicated that the nucleation occurred at the gas/liquid interface and then the hydrates grew along the wall of the crystallizer column. After a specific time interval, the hydrates gradually grew downward until they completely covered the bulk solution. This work applied 500 ppm of co-promoters, including sodium dodecyl sulfate (SDS) and three amino acids─valine, leucine, and methionine to improve the kinetics of mixed hydrate formation. The presence of SDS in the system resulted in distinct mixed hydrate formation patterns. After hydrate nucleation at the gas/liquid interface, most of the hydrates predominantly grew downward and enveloped the solution within a few minutes. Moreover, the mushy hydrates gradually transformed into stiff hydrates over time. Three amino acids resulted in the same hydrate patterns as those formed in the absence of a co-promoter, but the formation was completed more rapidly. The kinetic data indicated that using salt water for the formation of mixed methane–THF hydrates resulted in low hydrate formation kinetics. The presence of SDS significantly enhanced the kinetics of hydrate formation but decreased the final gas uptake by about one-half. Additionally, it was discovered that the presence of amino acids accelerated the hydrate formation kinetics while having a negligible effect on the final methane uptake.