Raman spectroscopy studies of combustion-related microparticles

摘要

Abstract: ion 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 SO$-2$/ 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 SO$-2$/ show the formation of CaSO$-3$/ and CaSO$-4$/ 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.!19