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24 May 1993 Raman spectroscopy studies of combustion-related microparticles
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Proceedings Volume 1862, Laser Applications in Combustion and Combustion Diagnostics; (1993)
Event: OE/LASE'93: Optics, Electro-Optics, and Laser Applications in Scienceand Engineering, 1993, Los Angeles, CA, United States
Combustion processes may involve a variety of particles in the micrometer size range. Such microparticles include coal macerals, and the processes can generate particulate matter via the production of flyash, soot, or condensables. In addition, sorbent microparticles can be added to a combustor such as the fluidized bed coal combustor to remove hydrogen sulfide and/or sulfur dioxide, the so-called dry-scrubbing process of desulfurization. In this study, inelastic light scattering and infrared laser heating techniques were developed and used to follow chemical changes in single microparticles levitated electrodynamically. The reactions between CaO and CuO sorbent particles with SO2 were explored, coal macerals were characterized by inelastic scattering, and the effects of heating on a black carbonaceous microparticle were examined. Raman spectra obtained for CaO/Ca(OH)2 particles levitated in a stream of oxygen and SO2 show the formation of CaSO3 and CaSO4 upon heating. The uptake of water by the sorbent leads to fluorescence, which can mask the Raman spectrum. Single vitrinite and liptinite macerals are shown to have significantly different spectra, the latter being dominated by fluorescence. Heating and inelastic scattering measurements performed using fructose microspheres as a model carbonaceous blackbody show large changes in the particle due to pyrolysis. The apparatus, procedures and experimental results are presented together with a discussion of the problems and limitations associated with laser heating of levitated microparticles.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Scot D. Rassat, Theresa M. Allen, and E. James Davis "Raman spectroscopy studies of combustion-related microparticles", Proc. SPIE 1862, Laser Applications in Combustion and Combustion Diagnostics, (24 May 1993);

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