Simultaneous Removal of NO and SO2 via an Integrated System of Nonthermal Plasma Combined with Catalytic Oxidation and Wet Electrostatic Precipitator

An integrated system of dielectric barrier discharge (DBD) combined with MnCu/Ti catalyst and wet electrostatic precipitator (DBD–catalyst–WESP) was constructed for simultaneous removal of SO2 and NO. The removal mechanism and the effects of special energy density (SED) and initial concentrations of NO and SO2 on oxidation efficiency were investigated. Experimental results showed that compared with Mn/Ti and Cu/Ti, the MnCu/Ti catalyst exhibited a higher dispersion of active constituents and has more catalytic oxidation active substances. The removal efficiencies of NO and SO2 in the DBD-catalyst system increased with increasing SED (15–275 J/L), and the lower the initial concentration was, the higher were the simultaneous removal efficiencies of NO and SO2. The competitive relationship between the removal of NO and SO2 was clarified. Compared with the DBD–catalyst system, the DBD–catalyst–WESP system significantly improved the simultaneous removal efficiencies of NO and SO2. With low initial concentrations (200 mg/m3 NO and 1000 mg/m3 SO2), the simultaneous removal efficiencies in DBD–catalyst–WESP reached the highest values (93.4% for NO and 100% for SO2) at SED = 275 J/L. According to ion chromatography measurements, the DBD–catalyst oxidation products were NO2 and SO3. Most of the oxidation products were captured and converted into nitrate ions and sulfate ions in WESP.