NO/sub 3/ reduction for flue gas cleaning using wet-type plasma reactor

Fundamental characteristics of the flue gas cleaning for NO/sub x/ using the wet-type plasma reactor has been evaluated, with attention being laid on concentration of nitrate and ammonium ions in the liquid. The wet-type plasma reactor was a wire-cylinder, driven by square wave high voltage pulse. A thin liquid film was maintained on the inner wall of the reactor. In this reactor, discharge plasma oxidizes NO to NO/sub 2/, and NO/sub 2/ is dissolved into the liquid as HNO/sub 3/. Continuous absorption induces saturation and acidification of the liquid, inhibiting the absorption of NO/sub x/. Effect of the NH/sub 3/ addition for enhancement of NO/sub x/ removal has been experimentally confirmed. The NH/sub 3/ addition was effective for NO oxidation as well as NO/sub x/ absorption into the liquid, resulting in the increasing of NO/sub 2//sup -/ and NO/sub 3//sup +/ concentration in the liquid. With the presence of Fe ions in liquid exposed to the discharge plasma, reduction can be made from NO/sub 3//sup -/ to NH/sub 4//sup +/ through the oxidation of Fe/sup 2+/ to Fe/sup 3+/. The reductive reaction enhances the absorption of NO/sub x/. These results suggest the possibility of the continuous operation of the wet-type plasma reactor for NO/sub x/ removal without excess acidification of the absorbing water, nor feeding additives.