Identification of Main Reaction Path of Soot Formation from Primary Pyrolysis Products in Coal Gasification

AbstractIn coal gasification, soot forms from volatile matter (VM) and it influences the gasification efficiency. Recently, biomass or plastic wastes with higher VM than coal are used for gasification processes and the importance of soot is increasing. For predicting soot formation, elementary step models are often used. However, defining main reaction paths is difficult because the models include huge species and reactions. In this study, the polyaromatic hydrocarbon formation path was analyzed via an elementary step-like model with 257 species and 1107 reactions to understand soot formation. The main reaction paths were extracted. Initially, 257 species were classified into non-aromatic species, one-ring, two-ring, and three- or more-ring aromatics. Ten species in each group with high maximum concentrations were considered as the major species. The reactions were extracted as follows: extracting reactions according to their contribution to the major species mass balance; adding fast reactions; and identifying the main reaction path. Consequently, the main reaction path extracted (MRE) model for the combustor condition was reduced to under 100 reactions for two kinds of conditions. Simulation of coal gasification reaction with the MRE model successfully described soot formation behavior in experiments with a drop tube furnace.