SOOT AND TAR PRODUCTION IN A JET-STIRRED PLUG-FLOW REACTOR SYSTEM - HIGH AND LOW C2H2 CONCENTRATION ENVIRONMENTS

We demonstrate that carbon molecular weight growth chemistry can conti nue to occur when polycyclic aromatic hydrocarbons (PAH), produced by localized fuel rich pockets within an incinerator, disperse into the n ear-stoichiometric bulk flow characteristic of the unit. Naphthalene, a model PAH, was added to a near-stoichiometric (phi = 1.2) post-flame combustion flow produced by premixed C2H4/O-2/N-2/Air combustion in a jet-stirred/plug-flow reactor system (JSR/PFR), and the results compa red against those from a fuel rich (phi = 2.2) post-flame combustion f low without naphthalene addition. In both experiments, the PFR was sam pled for soot (CH2Cl2 insolubles), tar (CH2Cl2 solubles; PAH), C2H2 an d other light gases. The results indicate that naphthalene addition to the phi = 1.2 flow produces PAH in the naphthalene (MW = 128) to cycl openta[cd]pyrene (MW = 226) fraction at exactly the same total mass co ncentration as observed in the phi = 2.2 flow without naphthalene addi tion. Similarly, the rate of growth of soot mass is approximately the same in both cases. In contrast, the concentration of high molecular w eight PAH (PAH > MW 226) produced is 3 times less, and that of C2H2 is 100 to 600 times less in the phi = 1.2 flow with C10H8 addition than in the phi = 2.2 flow without C10H8 addition. These data suggest that under our reactor conditions, PAH in the 128 to 226 amu molecular weig ht range are more important contributors to the soot growth process th an either C2H2 or high molecular weight PAH.