Follow-up Research on Simultaneous Removal of NO and SO₂ by Wet Scrubbing NaClO Solution Combined In Situ with Ozone Oxidation: Performance and Mechanism

Abstract

Previous work proposed a one-stage wet scrubbing in situ combined with O 3 oxidation for simultaneous removal of NO and SO 2 from flue gas, and the results showed that wet scrubbing combined in situ with O 3 injection could effectively improve O 3 oxidant utilization efficiency. In this work, a follow-up research work was carried out to further explore the synergistic effect of dual oxidants of NaClO in the liquid phase and O 3 in gas phase. The synergistic effects of O 3 /NO molar ratio and NaClO concentration in the circulating scrubbing solution on NO x removal performance was investigated systematically. The results showed that when molar ratio of O 3 /NO was 0.5 and NaClO concentration was 25 mM, NO could be oxidized completely and averaged NO x removal efficiency exceeded 70%. NO x concentrations in outlet gas and anion compositions in the scrubbed solution were analyzed, and the possible reaction paths of wet scrubbing NaClO solution in situ with O 3 injection in denitration process were also discussed. When the solution pH was around 6, a relative balance between NO x oxidation and absorption might be achieved, resulting in a high NO x removal efficiency. The temperature of inlet flue gas imposed little impact on NO x removal efficiency due to the quick and efficient cooling effect by wet scrubbing. The increase of initial SO 2 concentration led to a slight increase of NO x removal efficiency from 70 to 73.5%. A complete removal of SO 2 could be achieved, but coexisting SO 2 in flue gas would consume NaClO oxidant and shorten the reaction duration.