Nucleation Behavior of Single-Gas Hydrates in the Batch-type Stirred Reactor and Their Promotion Effect with Ultrafine Bubbles: A Mini Review and Perspectives

Formation and dissociation processes of gas hydrates have been studied for managing the flow of natural gas and for developing new natural gas resources. Recently, such studies have also examined the unique properties of gas hydrates for use in industry, such as gas and energy storages. However, a large degree of supercooling (or supersaturation) and a long induction time are required to form gas hydrates even when their components (water and guest gas) are in hydrate-forming conditions. To overcome these obstacles, various formation-promoting technologies have been studied. In this mini review, we summarize the technologies for promoting the nucleation process in gas hydrate formation. We then focus on recent studies on the use of ultrafine bubbles (UFBs) to exploit the memory effect, which reduces the induction time. We add new data to clarify our experimental results on the formation of single-gas hydrate under an agitated environment and show that UFBs play an important role in promoting gas hydrate formation.