Experimental research on denitrification and elemental mercury removal by Surface Dielectric Barrier Discharge

Abstract

A spiral Surface Dielectric Barrier Discharge reactor was employed to remove both NO and Hg from the flue gas. The effects of O2 and peak voltage were extensively studied. Only NO, NO2 and N2O were observed using FTIR at the outlet of the reactor in the atmosphere of NO/O2/N2. A desired NO conversion efficiency of 99.2% at 7 kV was obtained in the absence of O2 with low energy cost. The presence of O2 can suppress the reduction reaction while accelerating the oxidization of NO, consequently restraining the NO reduction to N2 and promoting the NO2 generation. O2 is necessary for the oxidation of Hg. At peak voltage of 7.0 kV, the Hg conversion reached above 94% at O2 concentration higher than 4%. It decreased to lower than 55% at 3.5 kV. Different concentrations of CO2, C2H4, SO2, HCl and H2O were also introduced to study their effect on NO and Hg conversions. When the CO2 concentration was increased from 0% to 5 and 10%, the NO conversion decreased from 81.0% to 74.1% and 73.6% respectively. At peak voltage of 7 kV and 500 ppm and 1000 ppm of C2H4 were introduced, the NO conversion increased from 78.7% to 85.4% and 93.8% accordingly, while Hg removal efficiency declined. With HCl concentration increasing to 30 and 60 ppm, the Hg oxidation rate increased significantly to above 90% at peak voltage of 9 kV. A strong inhibition effect of SO2 and H2O on NO and Hg conversion were observed.