Due to the influence of combustion temperature, excess air coefficient and fuel characteristics, for ordinary fuel coal, NOx in the flue gas of CFB boiler is less than 300mg/Nm3, which can be denitrified by SNCR method (selective non-catalytic reduction) with denitrification efficiency up to 60%.
Ammonia liquid is sprayed into the high temperature area of the furnace for selective reaction with NOx, and the reducing agent NH3 is SNCR reacted with NOx in the flue gas to produce N2 and H2O. This method takes the furnace as the reactor.
Generally, the reactor is set in the flue between the economizer and the air preheater. Under the action of the catalyst, the molar ratio of NH3 and NOX is controlled at 1.1 ~ 1.5 for the reaction within the temperature range of 300 ℃ ~ 420 ℃. The denitration rate can reach more than 96%.
Basic reaction equation:
4 NO + 4 NH3 + O2 = 4 N2 + 6 H2O
6 NO2 + 8 NH3 = 7 N2 + 12 H2O