The research on NOx formation in MILD combustion of primary combustion gas in waste incinerator

The flame structure and NOx formation of the inversed diffusion flame (IDF) and MILD combustion formed in the secondary combustion area of waste incinerator were experimentally investigated in order to clarify the NOx generation mechanism in the waste incinerator. The flame structure of secondary combustion near the nozzle exit was characterized by visualization, OH planar laser induced fluorescence (PLIF), and temperature distribution. Besides, ammonia was used as the additives in fuel for understanding the effects of flame structure on NOx formation. The amount of NOx in the exhaust was sampled and analyzed. Results showed that both the IDF and the MILD combustion were successfully formed under the same volume flow rate of oxidizer at the nozzle exit. In the case of MILD combustion without ammonia, the NOx concentration in the exhaust gas was lower than that in IDF without ammonia because the temperature of MILD combustion was more uniform and lower. On the other hand, MILD combustion with ammonia showed higher NOx concentration than that of IDF with ammonia because the spatially homogeneous reaction region was formed in the condition of MILD combustion.