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The development of optical measurement techniques for gas species and surface temperature on a planar SOFC methane-steam reformer Saunders, James Edward Appleby

Abstract

This thesis presents the development of an experimental apparatus and methods to allow the application of gaseous Raman spectroscopy to the challenging and original application of a small-scale, high-temperature methane/steam reformer developed to be representative of the technologies used in solid oxide fuel cell (SOFC) applications. The research is placed in the context of global energy trends and SOFC’s, with specific reference to the challenges related to directly internally reforming medium-temperature SOFC’s and the case for the development of non-intrusive measurement techniques for gas species and temperature is made. The practical aspects of the development of the broadband 308 nm Raman system are examined and previous works in this area are highlighted. The excitation light source is evaluated, the use of a liquid potassium hydrogen phthalate filter as a means to reduce Rayleigh line effects is demonstrated, and background fluorescence suppression through polarization of the 308 nm light source is presented. The arrangements of the experimental set-up, gas supply, metering, and humidification are shown, as are the optical arrangements for laser sheet formation and light collection. A description of the calibration experiments, procedures, and methodologies that are used to define the normalised relative differential Raman scattering cross sections of the major species of interest in this study is presented. The observation of an unexpected leakage of air into the reformer is described and a hypothesis is presented to explain the ingress of air. Finally, results are presented that describe the response of the optically-accessed reformer to variations in; operating temperature, humidification factor, total volume flow rate, methane volume flow rate, and the methane residency time within the reformer channel. From these results it was possible to conclude that increased reformer temperature increased reaction rate, increased gas residency time in the channel increased hydrogen production, and reactant streams with higher inlet mole fractions of methane resulting in increased reaction rates and amounts of hydrogen production. The performance of the reformer rig and the suitability of optical diagnostic techniques to the application of a SOFC scale reformer are discussed.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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