A thermodynamic model to predict the aqueous solubility of hydrocarbon mixtures at two-phase hydrate-liquid water equilibrium

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• 作者：Srinath C. Velaga^a ; ^b ; ^{SVelaga@mix.wvu.edu" class="auth_mail" title="E-mail the corresponding author} ; Jonathan S. Levine^b ; ^{Jonathan.Levine@netl.doe.gov" class="auth_mail" title="E-mail the corresponding author} ; Robert P. Warzinski^b ; ^{Robert.Warzinski@netl.doe.gov" class="auth_mail" title="E-mail the corresponding author} ; Brian J. Anderson^a ; ^b ; ^{Brian.Anderson@mail.wvu.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Gas hydrates ; Aqueous solubility of hydrocarbon mixtures ; Hydrate cage occupancy ; Hydrate-liquid water two-phase thermodynamic equilibrium ; Deep sea hydrates
• 刊名：Fluid Phase Equilibria
• 出版年：2016
• 出版时间：25 April 2016
• 年：2016
• 卷：414
• 期：Complete
• 页码：75-87
• 全文大小：1508 K

文摘

Understanding the fate and transport of hydrocarbons and hydrocarbon mixtures in the deep sea and underlying sediments requires accurate determination of the two-phase hydrate (H)-liquid water (L_w) thermodynamic equilibrium in the absence of a free gas phase. In addition to controlling hydrate formation directly from the aqueous phase, the H-L_w equilibrium provides the aqueous solubility of dissolving hydrate. The aqueous solubility of hydrocarbon mixture at H-L_w equilibrium was calculated based on the van der Waals and Platteeuw statistical thermodynamic model and the Holder model. Langmuir constants were calculated from cell potential parameters obtained from ab initio intermolecular potentials and thus the model contains no fitting parameters. The model accurately predicts pure methane, ethane, and propane experimental H-L_w equilibrium solubility data, including new data provided here for methane. We present hydrocarbon solubilities in water and seawater at H-L_w equilibrium at deep sea conditions for both methane and a thermogenic mixture based on the methane–ethane–propane ratio from the 2010 Macondo oil spill. We also present model predictions of the proportion of occupied large and small cages at H-L_w equilibrium for both systems, as well as hydrocarbon ratios in the hydrate phase for the thermogenic mixture.