Numerical Study on Low and High Temperature Air Combustion Using Different Chemical Mechanism

The characteristics of NOx emission and combustion efficiency in the high temperature air combustion technology (HiTAC) were investigated numerically by different chemical mechanisms. Before considering HiTAC study, validation of numerical method, thermodynamic and transport relations and chemical mechanisms were investigated by a set of experimental results. Validation with a coflow flame showed a precise coincidence with experimental results. In this study both detailed and skeletal mechanisms were used to describe chemical reactions during combustion. Then, the concept of a HiTAC burner including heating a diluting of fresh air by flue gas was implemented in a two dimensional furnace model. Effects of temperature and O2 Concentration of preheated airflow on NOx emission from furnace were investigated. Numerical results show that thermal mechanism dominates NOx emission in HiTAC. If only the preheated air temperature is increased, NOx emission will rise significantly. However the combination of air preheating and flue gas recirculation not only improves the combustion efficiency, but also suppresses NOx emission in the combustion process. Also a new phenomenon was observed in NOx emission that only can be shown by detailed and skeletal mechanisms; if the maximum temperature of HiTAC flame decrease, the effect of thermal mechanism in NOx emission decreases and another NOx mechanism namely N2O-intermediate NOx becomes dominant.

کلیدواژه ها:

Flame ، High Temperature ، NOx ، Co-Flow ، Methane