Simultaneous removal of sulfur dioxide and nitric oxide from gas streams via combined plasma photolysis

The concept of applying Dielectric Barrier Discharge (DBD) and Combined Plasma Photolysis (CPP) to simultaneously remove SO{dollar}sb2{dollar} and NO from simulated flue gas streams has been evaluated with a laboratory-scale reactor. CPP relies on DBD to generate gas phase radicals which oxidize SO{dollar}sb2{dollar} and NO to form H{dollar}sb2{dollar}SO{dollar}sb4{dollar} and HNO{dollar}sb3{dollar}, respectively. UV irradiation is applied to photolyze O{dollar}sb3{dollar} to enhance OH generation. The resulting compounds can then be chemically neutralized with NH{dollar}sb3sb{lcub}rm (g){rcub}{dollar} and removed from the gas stream by an aerosol particle removal device. Experimental results indicate that the SO{dollar}sb2{dollar} and NO removal efficiencies with DBDs are sensitive to (H{dollar}sb2{dollar}0{dollar}sb{lcub}rm (g){rcub}{dollar}), (O{dollar}sb2{dollar}), (CO{dollar}sb2{dollar}), and the temperature of the gas stream. When a sufficient voltage is applied to generate the plasma, both SO{dollar}sb2{dollar} and NO removal efficiencies increase with increasing (H{dollar}sb2{dollar}O{dollar}sb{lcub}rm (g){rcub}{dollar}). For the gas streams with same gas composition, SO{dollar}sb2{dollar} and NO removal efficiencies increases with increasing temperature as a result of higher reduced electric field (E/N). With sufficient (H{dollar}sb2{dollar}O{dollar}sb{lcub}rm (g){rcub}{dollar}), SO{dollar}sb2{dollar} removal efficiency increases with increasing (O{dollar}sb2{dollar}) as a result of more OH radicals. In contrast, there is an optimal (O{dollar}sb2{dollar}) which maximizes NO removal for a specific (H{dollar}sb2{dollar}O{dollar}sb{lcub}rm (g){rcub}{dollar}) in the gas stream. Electronegative gases like CO{dollar}sb2{dollar} tend to decrease both SO{dollar}sb2{dollar} and NO removal efficiencies. Injection of NH{dollar}sb3sb{lcub}rm (g){rcub}{dollar} into the gas stream significantly increases SO{dollar}sb2{dollar} removal efficiency due to the thermal reactions between SO{dollar}sb2{dollar} and NH{dollar}sb3sb{lcub}rm (g){rcub}{dollar}, while injection of NH{dollar}sb3sb{lcub}rm (g){rcub}{dollar} does not appreciably change NO removal efficiency with DBDs. Without NH{dollar}sb3sb{lcub}rm (g){rcub}{dollar} injection, 95% NO and 32% SO{dollar}sb2{dollar} are simultaneously removed with DBDs for the gas stream with composition of NO/SO{dollar}sb2{dollar}/O{dollar}sb2{dollar}/CO{dollar}sb2{dollar}/H{dollar}sb2{dollar}O{dollar}sb{lcub}rm (g){rcub}{dollar}/N{dollar}sb2{dollar} = 0.025/0.1/6/12/15/66.875 % by volume at 160{dollar}spcirc{dollar}C. SO{dollar}sb2{dollar} removal efficiency achieved by DBDs can be enhanced by UV irradiation. Conversely, UV irradiation decreases NO removal efficiency achieved by DBDs due to the regeneration of NO caused by the UV photolysis of NO{dollar}sb2{dollar} and HNO{dollar}sb3sb{lcub}rm (g){rcub}{dollar}.