A comprehensive, semidetailed kinetic scheme describing hydrocarbon oxidation is applied to the simulation of premixed, rich, sooting, ethylene laminar flames. The main goal of this work is to investigate the soot precursor and aromatic pathways under different operative conditions in terms of temperatures and feed composition. The modeling computations are in good agreement with the experimental data and are also comparable with predictions of different kinetic schemes present in the literature. The recombination reactions of resonantly stabilized radicals (such as propargyl) and C2H2 addition on linear dehydrogenated molecules (C4Hx) are taken into account to explain formation of the first aromatic ring. Two major channels of benzene and polycyclic aromatic hydrocarbon (PAH) formation are observed in the conditions under analysis. The former, which is not included in previous literature schemes, is faster and occurs first (where the conversion is still low). It is governed by ethylene and vinyl radical, which, through butadiene and butenyl radicals, explain the formation of cyclopentadiene and through further successive additions give rise to benzene and styrene. This mechanism should be the starting point for the initial formation of heavy highly hydrogenated compounds. Acetylene and resonantly stabilized radicals are mainly responsible for the successive aromatic growth. The study of such pathways is also important for the analysis of low NOx burners and new process alternatives, such as recirculating flue gases, where pollutant emission reductions are pursued by the use of low-temperature flames. The comparisons with experimental data for pure ethylene pyrolysis at lower temperatures (1100 K) confirms the validity of the assumed mechanism.
The kinetic modeling of soot precursors in ethylene flames
FARAVELLI, TIZIANO;RANZI, ELISEO MARIA
1998-01-01
Abstract
A comprehensive, semidetailed kinetic scheme describing hydrocarbon oxidation is applied to the simulation of premixed, rich, sooting, ethylene laminar flames. The main goal of this work is to investigate the soot precursor and aromatic pathways under different operative conditions in terms of temperatures and feed composition. The modeling computations are in good agreement with the experimental data and are also comparable with predictions of different kinetic schemes present in the literature. The recombination reactions of resonantly stabilized radicals (such as propargyl) and C2H2 addition on linear dehydrogenated molecules (C4Hx) are taken into account to explain formation of the first aromatic ring. Two major channels of benzene and polycyclic aromatic hydrocarbon (PAH) formation are observed in the conditions under analysis. The former, which is not included in previous literature schemes, is faster and occurs first (where the conversion is still low). It is governed by ethylene and vinyl radical, which, through butadiene and butenyl radicals, explain the formation of cyclopentadiene and through further successive additions give rise to benzene and styrene. This mechanism should be the starting point for the initial formation of heavy highly hydrogenated compounds. Acetylene and resonantly stabilized radicals are mainly responsible for the successive aromatic growth. The study of such pathways is also important for the analysis of low NOx burners and new process alternatives, such as recirculating flue gases, where pollutant emission reductions are pursued by the use of low-temperature flames. The comparisons with experimental data for pure ethylene pyrolysis at lower temperatures (1100 K) confirms the validity of the assumed mechanism.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
