The cyclone-fired boilers are very suitable for burning high-alkali content coal due to high slag capture rate and low flue gas dust content. However, NOx generation in cyclone-fired boilers is higher than that in other boiler types. In this work, the NOx generation characteristic of cyclone combustion was studied in a 100 kW cyclone combustion test bench. The results show that a strong reducing atmosphere is formed in cyclone barrel, and NOx generation is greatly inhibited in cyclone air-staging combustion. In cyclone barrel, NOx generation is high in the near-wall zone and low in the central zone. The central zone is the core region of NOx reduction. After the over fire air (OFA) injects into the burnout furnace, an obvious increase in NOx concentration is observed, which may be due to oxidation of char-N residue in char in burnout furnace.
Keywords cyclone combustion, NOx generation, air-staging combustion.