A thermodynamic model is introduced to describe equilibrium conditions of gas hydrates formed from mixtures of CO2, N2 and H2O. The model employs the van der Waals and Platteeuw (vdW–P) solid solution theory and a modified version of cubic-plus-association equation of state that uses the Peng–Robinson equation of state for physical interactions (PR–CPA) to describe hydrate and fluid phases, respectively. When not available elsewhere, the model parameters are determined as part of this work. Pure component parameters for N2 were calculated by fitting of the PR–CPA parameters to vapor pressures and saturated liquid densities. Moreover, solubility data for N2 in pure water are used to fit the binary interaction parameter for the N2–H2O system. Finally, Kihara cell potential parameters are obtained by regressing the model to the hydrate dissociation pressures of mixed hydrates. The model is validated with available experimental data in terms of equilibrium dissociation pressure and hydrate composition. Results reveal that the model is capable of describing equilibrium conditions with high accuracy. In addition to the equilibrium dissociation pressure, the model is able to predict hydrate compositions with satisfactory accuracy compared to other models, although such data were not utilized as reference data in the fitting procedure. Due to disparity amongst various data sets for the studied system, it is difficult to find unequivocally a model that perform better for all data sets. However, the introduced model shows more accurate results for most data sets and obtains satisfactory agreement in the rest. Additionally, the presented model predicts the structural transition boundary better than other similar models.

中文翻译：

---

CO2捕集气体水合物系统相平衡的热力学模拟研究

引入了热力学模型来描述由 CO2、N2 和 H2O 的混合物形成的气体水合物的平衡条件。该模型采用 van der Waals 和 Platteeuw (vdW-P) 固溶体理论以及使用 Peng-Robinson 物理相互作用状态方程 (PR-CPA) 描述水合物的三次加缔合状态方程的修改版本和流体相，分别。当其他地方不可用时，模型参数被确定为这项工作的一部分。N2 的纯组分参数通过将 PR-CPA 参数拟合到蒸气压和饱和液体密度来计算。此外，N2 在纯水中的溶解度数据用于拟合 N2-H2O 系统的二元相互作用参数。最后，Kihara 电池电位参数是通过将模型回归到混合水合物的水合物分解压力来获得的。该模型通过可用的实验数据在平衡解离压力和水合物组成方面得到验证。结果表明，该模型能够高精度地描述平衡条件。除了平衡解离压力之外，与其他模型相比，该模型还能够以令人满意的精度预测水合物成分，尽管这些数据在拟合过程中并未用作参考数据。由于所研究系统的各种数据集之间存在差异，因此很难明确找到对所有数据集都表现更好的模型。然而，引入的模型对大多数数据集显示出更准确的结果，并在其余数据集上获得令人满意的一致性。此外，所提出的模型比其他类似模型更好地预测了结构过渡边界。