Effect of circulating ash from CFB boilers on NO and N2O emission

Abstract

NO and N 2 O emissions from circulating fluidized bed (CFB) boilers are determined by their formation and destruction rates in the furnace. The effect of circulating ash from a CFB boiler on NO and N 2 O emissions were investigated in a laboratory-scale fluidized bed reactor. The results show that the residue char in circulating ash and the CO generated from the char play an important role in NO reduction and N 2 O formation; however, active components of circulating ash such as CaO, Fe 2 O 3 accelerate the decomposition of N 2 O. Experiment was also conducted on a 75 t/h CFB boiler fueled with the mixture of anthracite and biomass. The lower residue carbon content of circulating ash in this experiment is lower; therefore, the reacting rate of NO deoxidize is limited. This result verified the conclusion of laboratory research.

NOx Emission from a Circulating Fluidized Bed Boiler Cofiring Coal and Corn Stalk Pellets

“…The SiO 2 , Al 2 O 3 , CaO, and Fe 2 O 3 contents are shown in Figure . It can be seen that the ash of CSP-A and CSP-B are rich in CaO, which is believed to be an active catalyst for NH 3 oxidation. ,,− While the rice husk ash used in the previous study was rich in SiO 2 , it lacked CaO, so the value of R NC decreased as the rice husk mixing ratio decreased.…”

“…Some ash compositions may act as a catalyst in the formation of NO x precursors and NO formation. − It was found that the interaction of ash could increase the yield of NH 3 and decrease the yield of HCN . The ash compositions of the coal and biomass used in present experiments and the similar rice husk as that used in the referred study were analyzed via XRD.…”