Detailed modeling of PAH and soot formation in a laminar premixed benzene/oxygen/argon low-pressure flame Henning Richter a,b, * , Silvia Granata a,c , William H. Green a , Jack B. Howard a,b a Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA b Nano-C, Inc., Westwood, MA 02090, USA c CMIC Department, Politecnico di Milano, 20133 Milan, Italy Abstract Combustion-generated polycyclic aromatic hydrocarbons (PAH) and soot particles are of significant environmental concern whereas controlled combustion is of increasing interest for the synthesis of carbo- naceous nanostructures such as fullerenic material. Improved understanding of chemical and physical pro- cesses involved in PAH and soot formation is required to correlate operating conditions with emission characteristics. A detailed kinetic model describing the formation and consumption of PAH and soot in fuel-rich hydrocarbon combustion has been developed. Using a sectional approach, large PAH and carbo- naceous particles with diameters of up to 70 nm are defined as classes (BINs) covering given mass ranges. Numbers of carbon and hydrogen atoms corresponding to their average masses are assigned to each BIN, accounting for a decrease in H/C ratios with increasing particle size. The model has been successfully tested for a rich premixed benzene/oxygen/argon flame (/ = 2.4, 10% argon, v = 25 cm s 1 , 5.33 kPa). Model predictions are compared with published experimental data including mole fraction profiles of individual PAH and concentration as well as number density profiles of soot. Reactions of PAH radicals with PAH and between PAH radicals were found to be the dominant pathway to soot nuclei. Surface growth contrib- utes 75% to the final particle mass, and reaction of acetylene with particle radicals is the major growth pathway. Surface growth reactions are involved in PAH depletion in the postflame zone. Particle coagu- lation involving BINs and BIN radicals significantly contributes to the formation of progressively larger particles whereas oxidation by OH plays a non-negligible role in their depletion. Ó 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Soot; PAH; Modeling; Benzene; Combustion 1. Introduction Many large-scale uses of combustion including transportation, power generation, and waste incineration are major sources of airborne species of significant health concerns such as soot particles and polycyclic aromatic hydrocarbons 1540-7489/$ - see front matter Ó 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.proci.2004.08.088 * Corresponding author. Fax: +1 781 407 9419. E-mail address: richter@mit.edu (H. Richter). Proceedings of the Combustion Institute 30 (2005) 1397–1405 www.elsevier.com/locate/proci Proceedings of the Combustion Institute