Abstract Although salt ions severely distort the gas hydrate lattice, this phenomenon is poorly realized in the existing statistical thermodynamics models. We propose a mechanistic model by addressing a novel concept of instability in the hydrate-water film arising due to salt exclusion. The consequent water reorientation in the unstable lattice due to excluded ions is described in terms of the stress buildup in the hydrate lattice using Poirier’s theory of crystal creep. Tolman’s theory is reworked to account for the combined influence of guest and salt concentration on the surface energy of the phases in contact. Together with an empirical conformational term, the three phase hydrate equilibrium is modelled. To describe the liquid phase non-ideality, the UNIQUAC and Pitzer activity coefficient models are combined. For vapour phase, Patel and Teja equation of state is used, whereas for hydrate phase, Klauda and Sandler model is utilized. The particle swarm optimization is hybridized with simplex search algorithm to identify the model parameters. The proposed thermo-physical hydrate model exhibits an improved performance over the existing models, which is quantified in terms of absolute average relative deviation (AARD) with respect to the experimental data.

中文翻译：

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深入了解气体水合物的热物理：电解质存在下的三相平衡

摘要 尽管盐离子严重扭曲了天然气水合物的晶格，但现有的统计热力学模型对这种现象的认识很差。我们通过解决由于盐排斥而引起的水合物-水膜不稳定的新概念提出了一个机械模型。使用 Poirier 的晶体蠕变理论，根据水合物晶格中的应力积累描述了由于被排除的离子而导致的不稳定晶格中的水重新定向。Tolman 的理论被重新设计以解释客体和盐浓度对接触相的表面能的综合影响。与经验构象项一起，对三相水合物平衡进行建模。为了描述液相的非理想性，结合了 UNIQUAC 和 Pitzer 活度系数模型。对于气相，使用 Patel 和 Teja 状态方程，而对于水合物相，使用 Klauda 和 Sandler 模型。粒子群优化与单纯形搜索算法混合以识别模型参数。所提出的热物理水合物模型表现出优于现有模型的性能，其根据相对于实验数据的绝对平均相对偏差 (AARD) 进行量化。