Semester

Fall

Date of Graduation

2003

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Hisashi O. Kono.

Abstract

Natural gas hydrates (NGH) are crystalline compounds that consist of water and natural gas (NG) molecules. By hydrogen bonds, water molecules form a regular lattice structure containing many cavities. NG molecules occupy the cavities, and therefore stabilize the cavities. NGH are considered to be one of the most potential alternative world energy resources. The applications of NGH in other fields, such as NG purification, storage, and transportation, are also possible. To obtain the full benefits of all the possible applications of NGH, a full understanding of the kinetics of NGH formation is needed.;Strictly speaking, the experimental works of reproducible intrinsic chemical reaction rate constants of NGH formations have not yet been reported. It has been because the control of the interfacial surface areas among the three phases of gas, liquid, and solid involved in the reaction, i.e. NG in gas phase, water in liquid phase, and NGH in solid phase was experimentally difficult during the progress of water-NG conversion into NGH.;In this dissertation, a new experimental method and analysis to determine the intrinsic reaction rate constants of methane gas hydrate (MGH) and propane gas hydrate (PGH) formations are reported. The important aspect of the novel experimental method is the control on the interfacial surface area in the heterogeneous reacting system. The control was achieved using a well-defined specific particle packing structure consisting of spherical, uniform-sized inert particles (e.g. glass beads). The defined packing structure gave reproducible interfacial boundary area of the heterogeneous reacting systems, and the interfacial boundary area can be modeled using simple geometry.;Data showed that initial pressures and glass bead sizes did not affect the reaction rate constants. The data gave the value of K = (1.89 +/- 0.16) x 10-6 m/s for MGH formation and K = (2.25 +/- 0.53) x 10-6 m/s for PGH formation. Compared to the mass transfer coefficients of methane/propane in water (l) film kL (approximately 10 -5 m/s), the values of K are significantly smaller for both MGH and PGH formations. Hence, the intrinsic reaction rate constants (kr) of MGH and PGH formations were practically represented by the observed K.

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