Dry process for SO2 and NOx removal via gas-to-particle conversion with ozone and ammonia injection

Because of the stability of its production and cost-effectiveness, coal is expected to be a primary energy source in near future. However, SO2 and NOx emissions from the coal combustion have been considered a serious environmental issue in the last few decades; they react with water vapor and ammonia (NH3) in the atmosphere to form secondary aerosols. In this study, ozone (O-3) was injected to oxidize NO into NO2. Thereafter, NH3 was injected to convert SO2 into (NH4)(2)SO3 particles, which further reacted with NO2 to produce N-2 and (NH4)(2)SO4 particles. These reaction mechanisms were discussed employing different chemical analyses of the products. Moreover, the size of the product particles was analyzed by online particle size analysis and the scanning electron microscopy images. Further, the quantitative analysis of the product was performed by ion chromatography, and the atomic balance of sulfur was verified by gas analysis. A higher SO2 concentration increased the NOx removal efficiency because the product ((NH4)(2)SO3), which was obtained from SO2 removal, acted as a reactant for the removal of NOx. Therefore, a higher concentration of O-3 favored the improvement of the NOx removal efficiency since O-3 oxidizes NO into NO2, which reacts with (NH4)(2)SO3. Thus, the SO2 and NOx removal efficiencies were 93.6% and 69.6%, respectively, at SO2, NO, and O-3 concentrations of 900, 30, and 30 ppm, respectively.