Abstract
Air-staged and flue gas recycle (FGC) combustion are important technologies to reduce NOx emissions. This study explores FGC ratios on the NOx formation in the primary combustion zone under air-staged combustion for a HT-NR3 swirl burner at different air excess coefficients. The coal combustion characteristics including gas velocity, temperature, gas components and NOx emission under different FGC ratios were analyzed. The results show that higher the FGC ratio will larger the gas temperature decrease and lower the NOx emission. Combined FGC technology with lower air excess coefficients technology, the NOx emission at outlet of furnace will be further reduced. When the air consumption excess coefficient is 0.8 with FGC ratio 20%, the NOx concentration at the furnace outlet will decrease from 208ppm to 138ppm, lower 33.6%.
Highlights
HT-NR3 low-nitrogen swirl burner [1,2,3,4] and flue gas recycle technology [5,6,7,8] are both widely used to reduce NOx emission
Wang et al [10] studied coal combustion under different cycle rates by numerical simulation, the results show that the combustion temperature and ignition position of pulverized coal are affected by the cycle rate
Li [11] conducted a study on a 30 t/h high-efficiency pulverized coal double-cylinder chamber fired industrial boiler, and the results showed that with the increase of the FGC ratio, the NOx reduction is 17%
Summary
HT-NR3 low-nitrogen swirl burner [1,2,3,4] and flue gas recycle technology [5,6,7,8] are both widely used to reduce NOx emission. Hu[9] numerically simulated the combustion process and NOx emission characteristics of a tangentially fired boiler, the calculation results showed that, with flue gas recycle, a lower average temperature and maximum temperature in the furnace will be obtained. It can be seen that the temperature in the center zone of the furnace is lower, while the gas temperature around the center flow is higher.
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