Abstract The accurate estimation of CO 2 sequestration potential in deep saline aquifers requires the knowledge of CO 2 solubility in brine, thus placing importance on reliable thermodynamic models that account for the effect of different salts and their mixtures over wide ranges of pressure, temperature and salt concentration. Most literature investigated CO 2 solubility in a single-salt solution as a replacement of real saline water, which may significantly overestimate CO 2 sequestration potential through solubility trapping. In order to accurately estimate CO 2 sequestration potential over geological conditions, the Peng-Robinson Cubic-Plus-Association (PR-CPA) equation of state (EOS) is used in this study to model both aqueous and nonaqueous phases. A promising flash technique at given moles, volume and temperature, known as NVT flash, is employed and the salting-out effect is reproduced by correcting the chemical potential of aqueous nonelectrolyte components. To represent real saline environments, five salts are considered, including sodium chloride (NaCl), potassium chloride (KCl), calcium chloride ( CaCl 2 ), magnesium chloride ( MgCl 2 ) and sodium sulfate ( Na 2 SO 4 ). With taking into account the electrostatic contribution caused by salts, the combination of the salt-based PR-CPA EOS and NVT flash accurately models the solubility behavior of CO 2 in mixed-salt solutions and the numerical results agree with experimental data very well. Moreover, the proposed CPA model exhibits neck-to-neck accuracy to the more sophisticated electrolyte CPA EOS, thus making it promising to accurately estimate carbon sequestration potential in saline aquifers through solubility trapping.

中文翻译：

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使用 NVT flash 和cubic-Plus-association 状态方程对CO2 在盐水中的溶解度进行热力学建模

摘要 深部咸水层中 CO 2 封存潜力的准确估计需要了解 CO 2 在盐水中的溶解度，因此重视可靠的热力学模型，该模型考虑不同盐类及其混合物在很宽的压力、温度和盐度范围内的影响。专注。大多数文献研究了 CO 2 在单一盐溶液中的溶解度，以替代真正的盐水，这可能会显着高估通过溶解度捕获的 CO 2 封存潜力。为了准确估计地质条件下的 CO 2 封存潜力，本研究中使用 Peng-Robinson Cubic-Plus-Association (PR-CPA) 状态方程 (EOS) 来模拟水相和非水相。在给定的摩尔数、体积和温度下，一种很有前途的闪光技术，称为 NVT 闪光，并通过校正水性非电解质组分的化学势来重现盐析效应。为了代表真实的盐水环境，考虑了五种盐，包括氯化钠 (NaCl)、氯化钾 (KCl)、氯化钙 (CaCl 2 )、氯化镁 (MgCl 2 ) 和硫酸钠 (Na 2 SO 4 )。考虑到盐引起的静电贡献，盐基PR-CPA EOS和NVT闪光的组合准确模拟了CO 2 在混合盐溶液中的溶解行为，数值结果与实验数据非常吻合。此外，所提出的 CPA 模型显示出与更复杂的电解质 CPA EOS 并驾齐驱的精度，从而有望通过溶解度捕获准确估计盐水含水层中的碳封存潜力。