Study of nitrogen oxide absorption in the calcium sulfite slurry

摘要

Experiments were conducted using a bubbling reactor to investigate nitrogen oxide absorption in the calcium sulfite slurry. The effects of CaSO3 concentration, NO2/NO mole ratio and O-2 concentrations on NO2 and SO2 absorption efficiencies were investigated. Five types of additives, including MgSO4, Na2SO4, FeSO4, MgSO4/Na2SO4 and FeSO4/Na2SO4, had been evaluated for enhancing NO2 absorption in CaSO3 slurry. Results showed that CaSO3 concentration had significant impact on NO2 and SO2 absorption efficiencies, and the highest absorption efficiencies of SO2 and NO2 could reach about 99.5 and 75.0 %, respectively. Furthermore, the NO2 absorption was closely related to the NO2/NO mole ratio, and the existence of NO2 in flue gas may promote NO absorption. The presence of O-2 in simulated flue gas was disadvantage for NO (x) removal because it can oxidize sulfite to sulfate. It was worth pointing out that FeSO4/Na2SO4 was the best additive among those investigated additives, as the NO2 removal efficiency was significantly increased from 74.8 to 95.0 %. IC and in situ FTIR results suggest that the main products were NO3 (-) and NO2 (-) in liquid phase and N2O, N2O5 and HNO3 in gas phase during the CaSO3 absorption process.