Thermodynamic and kinetic properties of gas hydrate phase transition from formation to decomposition with applications: A review

Gas hydrates phase transition is crucial for energy exploitation, natural gas transportation and CO₂ capture storage fields. This review introduces the characteristics of gas hydrate in phase transition process including the thermodynamic and kinetic characters, the dissociation and reformation characters, and the promotion methods. The phase equilibrium conditions of gas hydrate determine its thermal properties, but some accurate statistical studies are needed to obtain a variety of phase equilibrium experimental results in the future. In addition, it is necessary to quantify the factors of hydrate nucleation and provide an accurate induction time prediction model due to the randomness of the nucleation process. In hydrate exploitation applications, the depressurization and heat injection methods may be hindered due to the limitation of temperature, pressure, inhibitor and heat transfer characteristic. It will cause the hydrate reformation phenomenon and further influence the hydrate exploitation efficiency. Controlling the hydrate exploitation process requires a more systematic combination of decomposition methods, and further proving the influence factors such as memory effect and nanobubbles for the hydrate reformation. Besides, the promotion for gas hydrate phase transition also has been studied to make the hydrate rapid formation in the industrial fields come true. Stirring, spraying, bubbling method and additives are available for the promotion. However, the energy cost and efficiency improvement of hydrate formation promotion process need to be further studied. At last, several gas hydrate applications are proposed, including CO₂ capture and sequestration, natural gas storage, seawater desalination, cold storage, mixed gas separation and sewage treatment. This review presents an overall analysis of gas hydrate phase transition from characteristics to applications and contributes a reference for future development in hydrate technology.