Effects of nanobubbles on methane hydrate dissociation

Effects of nanobubbles on methane hydrate dissociation: A molecular simulation study

Fang, B. (TU Delft Engineering Thermodynamics; China University of Geosciences)
Moultos, O. (TU Delft Engineering Thermodynamics)
Lü, Tao (China University of Geosciences; Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems,)
Sun, Jiaxin (China University of Geosciences)
Liu, Z. (China University of Geosciences)
Ning, Fulong (Qingdao National Laboratory for Marine Science and Technology; China University of Geosciences)
Vlugt, T.J.H. (TU Delft Engineering Thermodynamics)

2023

Hydrate dissociation is often accompanied by the formation of nanobubbles. Knowledge of the effects of nanobubbles on hydrate dissociation is essential for understanding the dynamic behavior of the hydrate phase change and improving the gas production efficiency. Here, molecular dynamics simulations were performed to study the methane hydrate dissociation kinetics with and without a pre-existing methane nanobubble. The results show that the hydrate cluster in the liquid phase dissociates layer-by-layer. This process is shown to be independent of the temperature and nanobubble presence at the simulation conditions. Hydrate dissociation does not always lead to nanobubble formation because the supersaturated methane solution can be stable for a long time. A steep methane concentration gradient was observed between the hydrate cluster surface and the methane nanobubble, which can enhance the directional migration of methane and effectively minimize the methane concentration in the liquid phase, thereby increasing the driving force for the hydrate dissociation. Our findings indicate that the presence of a nanobubble near the hydrate surface does not decrease the activation energy of hydrate dissociation, but it can increase the intrinsic decomposition rate. The average hydrate dissociation rate is linearly correlated with the mass flow rate towards the nanobubble. The mass flow rate is determined by the nanobubble size and hydrate-nanobubble distance. Our findings contribute to the fundamental understanding of the dissociation mechanism of gas hydrates in the liquid phase, which is crucial for the design and optimization of efficient gas hydrate production techniques.

http://resolver.tudelft.nl/uuid:289721dc-db65-400d-8f29-45b15903a1dd

https://doi.org/10.1016/j.fuel.2023.128230

0016-2361

Fuel: the science and technology of fuel and energy, 345

Institutional Repository

journal article

© 2023 B. Fang, O. Moultos, Tao Lü, Jiaxin Sun, Z. Liu, Fulong Ning, T.J.H. Vlugt