OCR Text |
Show achieved, parametric calculations were performed to examine the effects of the most important furnace design and operating parameters on the thermal performance of the system. Modeling Results and Discussion A summary of the modeling results for the Fuel Preheating and the Flame Zones is presented below. Fuel Preheat Zone The Fuel Preheat Zone of the high luminosity burner was modeled by a team at the University of Illinois at Chicago. Modeling consisted of calculating heat balances and kinetic mechanisms for the pyrolysis and combustion processes taking place in this part of the High Luminosity burner system. The kinetic mechanisms included 52 species and 76 pyrolysis reactions (including reactions leading to soot formation) along with 226 combustion reactions. The goals of the Fuel Preheat Zone modeling effort were: • to construct and operate a numerical model to explore the effects of preliminary heating on soot formation in the high luminosity burner, • to describe the mechanism of soot formation in a methane-oxygen flame and determine the key factors leading to high soot concentration and high luminosity in the flame, • to calculate optimal temperatures and residence times in the Fuel Preheat Zone for the most effective production of soot and highest luminosity in the Flame Zone. In this modeling effort, combustion of a fraction of the fuel methane was limited to producing a preheated methane (natural gas) temperature in the range of 900 to 1600 K (1160° to 2420°F). In the reaction pathways, the formation of amorphous carbon and carbon black was prohibited. The overall kinetic model was based on well known kinetic schemes with special attention paid to soot formation, the time evolution of soot particles, and soot oxidation in the Fuel Zone of the burner. The model consisted of: • pyrolysis and oxidation of non-aromatic species, • initial soot precursor formation from non-aromatic species, • polycyclic aromatic hydrocarbon growth, • soot particle nucleation through coalescence of polycyclic aromatic hydrocarbons, 7 |