A cage-specific hydrate equilibrium model for robust predictions of industrially-relevant mixtures

Zhu, Danshi; Norris, Bruce; Aman, Zachary M.; May, Eric F.

doi:10.1039/d3cp01465g

Cited by 6 publications

(4 citation statements)

References 52 publications

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“…The cage-specific hydrate (CaSH) model adapts previous implementations of the vdW–P model to consider the unique guest–water KPPs of each cage type that can be present in structure I and II hydrates. The full details of this approach can be found in Zhu et al There are three KPPs: a c is the hard-core radius representing the closest distance of approach between the guest and a water molecule; σ is the distance where the net intermolecular potential is 0; and ϵ is an energy parameter representing maximum attractive intermolecular potential, which occurs at an intermolecular distance of 2 6 σ . Table lists the relevant KPPs for the gas hydrate formers considered in this work, including newly determined parameters for cyclopentane hydrates not published previously.…”

Section: Thermodynamic Modelingmentioning

confidence: 99%

“…No additional parameters are needed. We refer to Kontogeorgis et al , for the complete CPA-EOS modeling details and our previous work for the specific pure fluid parameters and binary interaction parameters employed.…”

Section: Thermodynamic Modelingmentioning

confidence: 99%

“…Recently, we improved on the vdW−P model of Ballard and Sloan 7−12 by removing the concept of multilayered shells and describing the guest−water interactions using Kihara potential parameters (KPPs) specific to each hydrate cage type. 13 Additionally, we incorporated the empty hydrate lattice model of Hielscher et al 14−16 into the model while using the cubic plus association equation of state (CPA-EOS) to describe the fluid phase in equilibrium with the hydrate. The resulting cage-specific hydrate (CaSH) model produces predictions of hydrate dissociation temperature as accurate as those from the models of Ballard and Sloan or the CPA-hydrate model implemented in MultiFlash 7.0 17 while reducing the number of adjustable parameters by 40% including fluid mixtures that contain THIs like MEG.…”

Section: Introductionmentioning

confidence: 99%

“…The first is the Gibbs energy change needed to form the empty hydrate lattice, while the other describes the Gibbs energy change caused by partial occupation of the hydrate lattice by guest gas molecules. Recently, we improved on the vdW–P model of Ballard and Sloan − by removing the concept of multilayered shells and describing the guest–water interactions using Kihara potential parameters (KPPs) specific to each hydrate cage type . Additionally, we incorporated the empty hydrate lattice model of Hielscher et al − into the model while using the cubic plus association equation of state (CPA-EOS) to describe the fluid phase in equilibrium with the hydrate.…”

Section: Introductionmentioning

confidence: 99%

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Cage-Specific Hydrate Equilibrium Electrolyte Model

Zhu,

May,

Norris

et al. 2024

Energy Fuels

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Understanding the stability of gas hydrates in aqueous electrolyte solutions is pivotal for industrial applications, particularly in oil and gas extraction and desalination processes. Many existing thermodynamic models, while predicting the influence of salts on hydrate dissociation temperatures, are often limited because they require numerous fitting parameters and, hence, are only tailored to specific hydrate systems. Here, we present a model for hydrate stability calculations with 40% fewer parameters but equivalent accuracy to existing approaches. This model has now been extended to include a physically based description of the impact of electrolyte solutions on hydrate equilibria. Utilizing an extended Debye−Huckel equation, we first accurately describe osmotic coefficients for 191 unique single strong electrolyte solutions. Zdanovskii's rule is then employed to predict osmotic coefficients in mixed electrolyte scenarios without any additional parameters. Finally, the predicted osmotic coefficients are used to correct water fugacities calculated via the cubic-plus-association equation of state. The resulting cage-specific hydrate equilibrium electrolyte (CaSH-e) model reliably describes multicomponent mixtures of hydrocarbon and aqueous compounds that include industrially important thermodynamic inhibitors such as methanol and monoethylene glycol. The CaSH-e model's performance is shown to either match or exceed that of current existing models, like CPA-hydrates in MultiFlash 7.0 (CPAHYD-MF) and the Ballard and Sloan model in CSMGem, particularly for chloride and bromide salt mixtures.

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