Simultaneous removal of NO and SO₂ from flue gas by Fe^IIEDTA/sodium dithionite solutions

Abstract

BACKGROUND The SO2 and NO emitted from coal‐fired power plants have caused serious air pollution in China. FeIIEDTA complexation technology is one of the most promising processes to realize the simultaneous removal of SO2 and NO. However, FeIIEDTA is easily oxidized to FeIIIEDTA, causing loss of activity, which limits its further application. To solve this problem, sodium dithionite (SD) combined with FeIIEDTA was used for the simultaneous removal of SO2 and NO. RESULTS Results showed that the SO2 removal efficiencies were ≈92–99% in all experiments, whereas the NO removal fluctuated substantially under different operating conditions. Specifically, SD can markedly improve NO removal efficiency, and the optimal FeIIEDTA:SD ratio was 3 mmol L–1:0.026 mol L–1. With increasing temperature, pH value, SO2 concentration or O2 concentration, the NO removal efficiency increased first and then decreased. As the NO concentration increased, the NO removal efficiency continually decreased. Finally, based on the analysis of different ion concentrations, the main products were identified as sulfite, sulfate, ammonium, nitrite and nitrate. CONCLUSION The synergistic mechanism of SD and FeIIEDTA on SO2 and NO was investigated. SD can regenerate FeIIEDTA solution by reducing FeIIIEDTA and FeIIEDTA‐NO. These fundamental findings can offer valuable guidance for industrial denitrification and desulfurization by mixed FeIIEDTA and SD systems. © 2019 Society of Chemical Industry