An efficient model for the prediction of CO2 hydrate phase stability conditions in the presence of inhibitors and their mixtures

Avula, Venkata Ramana; Gardas, Ramesh L.; Sangwai, Jitendra S.

doi:10.1016/j.jct.2015.01.009

Cited by 46 publications

(26 citation statements)

References 30 publications

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“…The hydrate–liquid water–gas/vapor phase equilibrium conditions are often predicted by equating the fugacity of water in the hydrate phase

f_{w}^{H}

, in the liquid water phase

f_{w}^{L}

, and in the vapor/gas phase

f_{w}^{normalv true/ normalg}

f_{w}^{H} = f_{w}^{L} = f_{w}^{normalv true/ normalg}

where w is water, H is hydrate, L is liquid, g is gas, and f is fugacity.…”

Section: Model Developmentmentioning

confidence: 99%

“…The fugacity of empty hydrate lattice

f_{w}^{MT}

can be given by the following Eqn :

f_{w}^{MT} = P_{w}^{MT} φ_{w}^{MT} exp \int_{P_{normalw}^{MT}}^{P} ((), \frac{v_{normalw}^{MT} d P}{italicRT})

where P is pressure and

v_{w}^{MT}

is the vapor pressure of water in empty hydrate lattice.

φ_{w}^{MT}

stands for the fugacity coefficient of water in empty hydrate phase, and because the vapor pressure of water phase is negligible,

v_{w}^{MT}

can be assumed to be pressure‐independent.…”

Section: Model Developmentmentioning

confidence: 99%

“…The change in chemical potential in the hydrate phase can be written as follows :

\frac{μ_{w}^{H} - μ_{w}^{MT}}{RT} = {\sum_{i} ln ((), 1 + C_{ij} f_{j})}^{- v_{i}^{'}}

where

v_{i}^{'}

is the number of cavities of type i per water molecule in a unit hydrate cell, C ij represents the Langmuir adsorption constant for hydrate former's interaction with each type of hydrate cavity, and f j is the fugacity of the hydrate former.…”

Section: Model Developmentmentioning

confidence: 99%

“…For dodecahedral cages,

C_{small} = \frac{A_{italicij}}{T} exp ((), \frac{B_{ij}}{T})

tetrakaidecahedra cages,

C_{large 1} = \frac{C_{italicij}}{T} exp ((), \frac{D_{ij}}{T}) ((), 1 + \frac{{italicew}_{normalp}}{T^{2}})

pentakaidecahedra cages,

C_{large 2} = \frac{f_{italicij}}{T} exp ((), \frac{g_{ij}}{T}) ((), 1 + \frac{{italicuw}_{normalp}}{T^{2}})

where w p is the weight fraction of the promoter (TBAB) and A ij – B ij are the adjustable parameters from our earlier report for CO 2 hydrate engaged in small cages (see Table ). C ij , D ij , f ij , g ij , e , and u are new adjustable parameters.…”

Section: Model Developmentmentioning

confidence: 99%

“…The fugacity of hydrate former in the vapor/gas phase can be evaluated from PR‐EoS . In this work, the effect of the promoter (TBAB) in vapor/gas phase is neglected because of its nonvolatility.…”

Section: Model Developmentmentioning

confidence: 99%

See 4 more Smart Citations

Thermodynamic modeling of phase equilibrium of carbon dioxide clathrate hydrate in aqueous solutions of promoters and inhibitors suitable for gas separation

Avula

Gupta

Gardas

et al. 2017

Asia-Pacific J Chem Eng

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Gas hydrates of CO 2 in the presence of tetra-n-alkyl ammonium bromide (TBAB) and tetrahydrofuran (THF) show potential applications for storage. Prediction of the phase behavior of these systems is an important precursor for their successful application. In this work, a thermodynamic model is developed to predict phase equilibrium of CO 2 hydrates in the presence of TBAB and THF aqueous solutions. In this work, the van der Waals and Platteeuw model is used to model the hydrate phase stability. The fugacity of hydrate former and that of water is calculated from the Peng-Robinson equation of state and the Pitzer-Mayorga-Zavitsas hydration (PMZH) model for TBAB and nonrandom two-liquid (NRTL) models for the THF system. Further, the vapor pressure of water in the empty hydrate as well as Langmuir adsorption constants has been expressed in terms of concentration of the promoter. The model predictions is compared with available experimental data on the phase equilibrium of CO 2 hydrates in the presence of TBAB and THF aqueous solution and are found to be in good agreement. Then, the developed model is also applied for the prediction of phase equilibrium conditions of the semiclathrate hydrates of CO 2 in the presence of TBAB + NaCl solution. The developed model is found to interpret the promotion effects of both TBAB (with or without NaCl) and THF on phase stability conditions of CO 2 hydrate. The overall average absolute deviation in pressure has been perceived to be within 3.6% for TBAB and 7.7% for TBAB + NaCl both with PMZH model and 6.9% for THF systems with NRTL model.

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“…The hydrate–liquid water–gas/vapor phase equilibrium conditions are often predicted by equating the fugacity of water in the hydrate phase