Host: The Japan Society of Mechanical Engineers
Name : International Conference on Power Engineering-2021(ICOPE-2021)
Date : October 17, 2021 - October 21, 2021
The NO-reburning technology can significantly reduce the NOx emission during combustion. Although substantial progress has been made for NO-reburning chemistry in conventional flame combustion, the homogeneous NO-reburning mechanism in flameless combustion has not been systematically investigated. This paper performs a detailed comparative study between flameless combustion and conventional swirl flame combustion for NO-reburning by both experiments and numerical simulations. The finite-rate reaction is modeled by the eddy dissipation concept combustion model coupled with a well-developed skeletal mechanism for NO-reburning and the simulations are validated with experiments. To insulate the effect of NO formation, substantial amount of NO is added to the initial fuel and thus the NO-reburning can be investigated by assessing the NO reduction during combustion. For both flameless and swirl flame combustion, the initial addition of NO significantly increases the furnace temperature and the NO emission. Interestingly, the present study for the first time found that flameless combustion can increase the NO-reburning reaction by 30%, relative to the swirl flame combustion. The reaction pathway of the NO-reburning during flameless combustion is also analyzed. Moreover, with the equivalence ratio (Φ) increasing from 0.7 to 0.9, it is found that Φ plays an insignificant role in the NO-reburning during flameless combustion, although the CO formation is rapidly increased to extremely high when Φ > 0.83. Therefore, to minimize both the emissions of NO and CO and the exhaust gas flow rate in flameless combustion, an optimal Φ is found and this optimal Φ is about 0.83 for the present study. The present study reports the advantage of flameless combustion using low preheating temperature air for significant NO reduction by reburning and provides new fundamental understandings of the NO-reburning mechanism.
