--> Non-Equilibrium Nature of Hydrates in Sediments and Consequences for Choices of Ways to Produce Hydrates Safely and Economically Feasible

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Non-Equilibrium Nature of Hydrates in Sediments and Consequences for Choices of Ways to Produce Hydrates Safely and Economically Feasible

Abstract

Hydrates can form from many different phases. The most commonly investigated is hydrate formation from gas or liquid hydrate former phase and a free water phase. But hydrate can form from dissolved solution of hydrate former in water and solid surfaces provide several possible routes to hydrate formation and dissociation. Various routes to hydrate formation leads to several hydrate phases with varying degrees of thermodynamic stability. Thermodynamic equilibrium is impossible and the balance between thermodynamics of each phase transition (formation or dissociation), and the associated mass- and heat-transport processes needed to make the phase transition possible is implicitly linked. Hydrate phase transitions are also very fast and on nano-scale in times and space if thermodynamic driving force is sufficient bur rarely exceeds microscale. It is therefore important to distinguish between the two physically well-defined processes of nucleation and growth, and the more complex onset of massive growth (induction time). Various processes can lead to extreme rate limitations and lead to misunderstood nucleation times. Various aspects of these issues are discussed with a focus on developing efficient ways to produce hydrates.