Simultaneous removal of SO2, NO and Hg0 using an enhanced gas phase UV-AOP method

The core for simultaneous removal of SO2, NO and Hg-0 is the oxidation of NO and Hg-0. Radical induced oxidation of NO and Hg-0 is considered to be the most efficient method. We develop a novel gas phase advanced oxidation process (AOP) of UV-Heat/H2O2-NaClO2 to simultaneously remove SO2, NO and Hg-0 due to a great synergism between H2O2 and NaClO2 under thermal and ultraviolet (UV) co-catalysis. The results indicated that the SO2 removal was always good, while the removal of NO and Hg-0 was affected by NaClO2 and UV. Higher catalytic temperature and longer flue gas residence time favored the removal of NO and Hg-0. The presence of SO2 and NO facilitated Hg-0 removal. Kinetics analyses were conducted to provide the reaction rate of removal of NO and Hg-0 under different conditions. X-ray photoelectron spectroscopy (XPS) revealed the product composition as Cl-, Hg2+, NO3- and SO42-. Electron spin resonance (ESR) tests confirmed the generation of HO. Cost analyses demonstrated the better cost performance of the proposed method compared to SCR-ACI combined method. HO center dot and ClO2 were proved to be the main oxidant. The reaction mechanism for removal of NO and Hg-0 by using UV-Heat/H2O2-NaClO2 were proposed finally.