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

A spiral Surface Dielectric Barrier Discharge reactor was employed to remove both NO and Hg from the flue gas. The effects of O-2 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/O-2/N-2. A desired NO conversion efficiency of 99.2% at 7 kV was obtained in the absence of O-2 with low energy cost. The presence of O-2 can suppress the reduction reaction while accelerating the oxidization of NO, consequently restraining the NO reduction to N-2 and promoting the NO2 generation. O-2 is necessary for the oxidation of Hg. At peak voltage of 7.0 kV, the Hg conversion reached above 94% at O-2 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. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.