Investigation of the induction time for THF hydrate formation in porous media

• Six test tubes as reactors experimented to verify the randomness of induction time.
• Memory effect and a high driving force can help reduce the induction time.
• Greater subcooling decreases induction time to a point with little effect thereafter.
• Sufficiently small support pore size can significantly reduce induction time.
• Reaction condition control eliminates the stochastic character of hydrate formation.

The induction time of hydrate formation is an important parameter during gas exploitation, which allows secondary natural gas hydrates to form, and in the improvement of hydrate-based technologies. The effects of the memory effect, subcooling, and the particle size of the porous media on the induction time for tetrahydrofuran (THF) hydrate formation were investigated in this study. Six test tubes were used as reactors when forming the hydrates in porous media. The experimental results indicated that that the memory effect and the use of extreme sub-cooling as a strong driving force can reduce the induction time effectively. Extreme sub-cooling can strengthen the driving force for hydrate formation. The relationship between the induction time and subcooling is less pronounced when the THF hydrate forms from hydrate-dissociated water. The average induction time for the formation of the THF hydrate from hydrate-dissociated water was 27.5 min in BZ-06 when using a 3 mol % THF solution. The induction time can be controlled easily when the driving force increases to a threshold value. The average induction time decreases as the particle size increases. Porous media with larger particle sizes can control the induction time and reduce the stochastic nature of the induction time.