Abstract Metastable clathrate hydrates are a promising energy source in the shallow geosphere and present challenges in flow assurance, energy storage, and carbon capture sequestration. While they have been widely studied, little pertinent data is available for common propane hydrates concerning hydrate phase composition, nor its volume or the amount of converted water. This was the initial motivation for our work. Therefore, with a novel technique, propane hydrate composition and volume were measured dynamically at non-equilibrium conditions over time and at the final states for slow and quick rates of crystallization. Surprisingly, equilibrium pressure, hydrate volume and composition are different according to crystallization rate. The hydrate volume and water conversion in the quick crystallization process were larger. Moreover, at a slow crystallization rate, in a hydrocarbon mixture, enclathration of propane is more considerable and the hydrate crystals appear to be more homogeneous. Furthermore, the hydrate crystallization of a gas mixture is closer to the thermodynamic equilibrium at slow crystallization rates where the impact of kinetics is slight. A new compilation of propane Kihara parameters was presented. Unlike methane, ethane and carbon dioxide, for propane we strongly recommend two Kihara parameters, one for pure and the other for mixtures of propane. A thermodynamic model based on classical van der Waals and Platteuw model was also used to investigate the effects of kinetics. The simulation results have a satisfactory accordance with the experimental data from literature to predict the hydrate equilibrium pressure. The consequence of this research could have a substantial impact on design calculations in which the assumption of thermodynamic equilibrium are done. For instance, at present there would be excess hydrates volume estimations for pipe-lines, equilibrium conditions in energy storage and transportation or carbon capture sequestration and thus increase expenses or loss of productivity where propane is concerned.

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研究非平衡条件和最终状态下涉及丙烷的混合天然气水合物的新方法：实验研究和建模

摘要 亚稳态包合物水合物是浅层地圈中一种很有前景的能源，在流动保证、能量储存和碳捕获封存方面面临挑战。虽然它们已被广泛研究，但关于水合物相组成、体积或转化水量的常见丙烷水合物的相关数据很少。这是我们工作的最初动机。因此，使用一种新技术，丙烷水合物的组成和体积在非平衡条件下随时间的推移以及在缓慢和快速结晶速率的最终状态下动态测量。令人惊讶的是，平衡压力、水合物体积和组成根据结晶速率而不同。快速结晶过程中的水合物体积和水转化率较大。而且，在较慢的结晶速度下，在烃混合物中，丙烷的包合更显着，水合物晶体看起来更均匀。此外，在缓慢的结晶速率下，气体混合物的水合物结晶更接近热力学平衡，其中动力学的影响很小。提出了丙烷 Kihara 参数的新汇编。与甲烷、乙烷和二氧化碳不同，对于丙烷，我们强烈推荐两个 Kihara 参数，一个用于纯丙烷，另一个用于丙烷混合物。基于经典范德华和普拉特模型的热力学模型也用于研究动力学的影响。模拟结果与文献中预测水合物平衡压力的实验数据具有较好的一致性。这项研究的结果可能会对进行热力学平衡假设的设计计算产生重大影响。例如，目前对于管道、能量储存和运输中的平衡条件或碳捕获封存会存在过量的水合物体积估计，从而增加丙烷方面的费用或生产力损失。