(9c) Soot Formation Pathways From A Coal Tar Surrogate Under Coal Gasification Conditions

Coal pyrolysis in the early stages of pressurized coal gasification forms tar and light hydrocarbon gases. Coal tar forms soot a high temperatures and fuel-rich conditions. Elevated pressure decreases tar yield but enhances conversion of tar and other hydrocarbons to soot. The formation of soot during coal gasification causes substantial heat losses due to radiative heat transfer. Therefore, an understanding of soot formation kinetics is a valuable tool for the design of coal gasification systems. Soot formation studies were conducted using an atmospheric flat flame burner and a pressurized flat flame burner. Fuel-rich flame conditions were used to prevent oxidation of the soot. A soot precursor, 2,6-dimethylnaphthalene, was selected for study as a representative surrogate for coal tar. The temperature, pressure, and residence time were experimental variables in the process of soot formation from this compound. 13-C NMR and mass spectroscopy is used to determine the structures present in the soot formed. This information was used to propose reaction pathways for soot formation from coal tar.