Thermodynamic Modeling of Hydrogen Hydrate Formation with and without Help Molecules

Ghorbanzadeh, Maryam | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41221 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Taghikhani, Vahid; Ghotbi, Siroos
  7. Abstract:
  8. In this study equilibrium condition of pure hydrogen hydrates is determined with Lee-Holder model. Two hydrogen molecules and four hydrogen molecules encaged in the small and large cavities respectively. Langmuir constant of hydrogen is calculated with the Exp-6 potential. Lee et al. reported parameter of this model by integrating ab initio calculation with classical statistical thermodynamics. This model reasonably predicts dissociation pressures of hydrogen hydrates.Calculated reference parameters are used in modeling of binary hydrogen hydrates. Lattice distortion model is used for modeling of binary hydrogen hydrates with tetrahydrofuran (THF) as a promoter. Cavity radius and parameters of reference chemical potential are determined using the Zele – Lee – Holder model. Five different thermodynamic models for correlating the fugacity of water and THF in liquid phase in equilibrium with hydrogen hydrate phase, based on the van der Waals–Platteeuw (vdW-P) statistical thermodynamic model are used. The studied models in liquid phase are NRTL excess Gibbs energy, Peng-Robinson (PR) equation of state (PR EOS), Peng-Robinson-Steryjek-Vera with the Wong-Sandler mixing rule (PRSV-WS), Dashtizadeh EOS (DPTG), and Ghotbi-Vera Simple SAFT (GV-SSAFT) EOS. The results show that the GV-SSAFT model correlates more accurately the experimental dissociation pressure of binary hydrogen hydrate. Additionally, hydrogen storage capacity of binary hydrogen hydrates is calculated. Calculated hydrogen storage capacity of pure and binary hydrogen hydrates is 4wt% and 2wt% respectively
  9. Keywords:
  10. Hydrate Phase Equilibrium ; Hydrate Dissociation Pressure ; Hydrogen Hydrate ; Hydrogen-Tetrahydrofuran Hydrate

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