Detailed Kinetic Modeling of Carbonaceous Nanoparticle Inception and Surface Growth during the Pyrolysis of C6H6 behind Shock Waves

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• 作者：J. Z. Wen ; M. J. Thomson ; M. F. Lightstone ; and S. N. Rogak
• 刊名：Energy & Fuels
• 出版年：2006
• 出版时间：March 2006
• 年：2006
• 卷：20
• 期：2
• 页码：547 - 559
• 全文大小：226K
• 年卷期：v.20,no.2(March 2006)
• ISSN：1520-5029

文摘

Soot formation in combustion processes is of significant interest due to its influences on both environmentalemissions and material synthesis (i.e., the synthesis of fullerences and carbon nanotubes). However, the inceptionprocess of the youngest carbonaceous nanoparticles from the gaseous phase is the most poorly understoodphenomenon in the study of soot kinetics at the current stage. Recently, researchers have found experimentallythe existence of transparent or semi-transparent carbonaceous particles (Krestinin, A. V. Combust. Flame 2000,121, 513-524) or nanoorganic carbon particles (D'Anna, A.; Rolando, A.; Allouis, C.; Minutolo, P.; D'Alessio,A. Proc. Combust. Inst. 2004, 30, 1449-1456) during soot nucleation, which have not been successfullyexplained by traditional polycyclic aromatic hydrocarbon (PAH) nucleation mechanisms. Most recently, amore detailed soot kinetic model (Vlasov, P. A.; Warnatz, J. Proc. Combust. Inst. 2002, 29, 2335-2341; Part2) has been implemented to predict soot formation behind shock waves and to describe the soot nucleation asa combined process of the fast polymerization of supersaturated polyyne vapor and the PAH growth. The lackof a detailed description of fractal particle structures in their aerosol dynamics model, however, restricted themodel's accuracy in predicting the particle coagulation rates and, hence, the particle sizes. In the current study,a new comprehensive kinetic model has been developed to describe soot chemical processes in a heterogeneousphase. The nucleation process is described by the formation of the soot precursors and the transformationfrom those precursors to solid soot particles. The precursors are represented by six sectional bins, which areformed through the detailed PAH nucleation mechanism and polyyne pathways, respectively. The gaseousreaction mechanism has been validated against measurements of polyynes and the C/C₂/C₃ carbon radicals.Finally, the aforementioned soot kinetic model has been implemented in an advanced aerosol dynamics modelto predict the main parameters of soot particle formation in the pyrolysis of C₆H₆/Ar mixture. This aerosoldynamics model includes the detailed description of the agglomerate structure of soot particles and calculatesthe particle coagulation rates according to their sizes and structures. The numerical simulation shows that,during the fuel pyrolysis behind shock waves, both PAH growth and polyynes polymerization play an importantrole during the soot nucleation process. And the polyynes surface growth model alone is able to predict sootyield as well as averaged particle diameter during the earlier stage of soot formation.