| Ex-situ transmission measurements of the optical properties as a function of residence time in the post-combustion gasses of a flat flame reactor have been obtained for three types of coal-derived soot, for propane soot, and for acetylene soot. Data were measured by suspending soot in a heptane/surfactant solution and measuring transmission through a liquid cell using an FT-IR spectrometer. Data have been corrected for scattering using Mie theory calculations and particle size data obtained by Photon Correlation Spectroscopy. Comparisons with previous research for propane soot indicate agreement in the near-infrared. Discrepancies at higher wavelengths are thought to be caused by differences in soot sampling and measurement techniques. Data show that while the optical properties of coal-derived soot and soot from propane and acetylene have the same range of values for the absorption index, trends with residence time are virtually opposite. Chemical composition data are presented for carbon, hydrogen, nitrogen, sulfur, and oxygen by difference. Chemical compositions show trends of decreasing carbon content with increasing residence time in the post flame environment. This phenomena indicates that either the soot is being attacked by radicals and undergoing partial gasification, or there is deposition of ash on the maturing soot particles. There is a correlation between the C/H ratios and the absorption index for coal-derived soot. |
