An Experimental and Theoretical Study of CO2 Hydrate Formation Systems

Fragkiskos Tzirakis

Research output: Book/ReportPh.D. thesis

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Abstract

Hydrate crystallization can become equally important carbon capture method provided that this technology undergoes further research. Toward this objective, this study tries to shed light on a quite new topic of research: hydrate promotion. Hydrate promotion implies the production of hydrate at lower pressures (and thus lower adjunctive capital/operational costs) by the use of special chemicals (promoters).
At first, extensive literature review has shown that both experimental data and modeling in this subject are imperative. Therefore, experimental data were produced and published (see Appendix E) using as promoters tetra-n-butyl ammonium salts of bromide, fluoride and cyclopentane in collaboration with MINESParisTech in France. These chemicals are well known for their reduction capabilities of hydrate formation pressure. The results are in good accordance with the literature. Moreover, the simultaneous combination of these chemicals achieved greater pressure reduction than if they were used separately. Then, experimental uncertainties were measured (for pressure/temperature transducers and gas chromatograph) and calculated (for the inserted quantities of water and chemicals). The uncertainties were at an acceptable level for all cases. A further evaluation of the experimental data, regarding their consistency, included the use of Clapeyron equation. It was shown that the results of this work and many of the systems from literature are quite satisfactory. Finally, the well-known van der Waals-Platteeuw hydrate model coupled with CPA EoS was used against experimental data as it was developed in CERE, DTU. The model predicted very satisfactory the CP results of this work and also other CO2+cyclolkane hydrate results from literature. This model´s consistency lies inter alia on the ground that fluid phases were modeled only with CPA EoS while correlations are utilized in current publications for the aqueous phase and an EoS for the hydrate phase.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages146
Publication statusPublished - 2016

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