Electron beam treatment of lignite-burning flue gas with high concentrations of sulfur dioxide and water

Experiments were carried out to investigate the removals of SO2 and NOx from simulated lignite-burning flue gas containing SO2 (4800 ppm), NO (320 ppm) and H2O (22%) by electron beam irradiation. Removal efficiencies of SO2 and NOx were achieved to reach 97 and 88% at 70 degrees C, and 74 and 85% at 80 degrees C, respectively, with the dose of 10.3 kGy without NH3 leakage. The higher removal efficiencies of SO2 and NOx were observed in simulated lignite-burning flue gas than in coal-fired flue gas containing 800 ppm of SO2, 225 ppm of NO and 7.5% H2O at the same treatment condition. The higher removal efficiencies were attributed to the higher concentrations of SO2, H2O, and added NH3. Simulation calculations indicated that the higher concentrations of these components enhance the effective radical reactions to oxidize NO to form NO2 with HO2 radical, and to oxidize SO2 to form SO3 with OH radical and O-2. The reactions of NOx with N and NH2 radicals to produce N-2 and N2O also promote the NOx removal. By-product was determined to be the mixture of (NH4)(2)SO4 and NH4NO3 containing a small amount of H2SO4. (C) 1998 Elsevier Science Ltd. All rights reserved.