Hg0 emission from coal-fired flue gas has become a great public concern due to its hazards for human health and ecosystem. The wet oxidation has received wide attention in the removal of Hg0 because of its low cost and synergy with other processes. A series of oxidants (KMnO4, H2O2, NaClO2, NaClO, K2S2O8 and, K2FeO4) were selected in this study to remove Hg0 from simulated flue gas in a packed tower, and the composite oxidant NaClO/NaClO2 showed a better removal efficiency. Thermodynamic analysis on Hg0 removal with composite oxidants was carried out, and experimental results indicated that the removal efficiency reached 94% at the reaction temperature of 50 Â°C. The physicochemical characteristics of solid products were studied through SEM (scanning electron microscopy) and XRD (X-ray diffraction), and the amount of mercury was detected by AAS (atomic absorption spectrophotometry). Results showed that 23% of Hg0 was oxidized and transferred into the gypsum in the form of compounds, while 77% was oxidized into Hg2 in the absorption solution. The findings of this research might provide a practical reference for promoting the removal of Hg0 from coal fired flue gas by NaClO/NaClO2 with limestone in industrial application.
Keywords coal fired flue gas, Hg0 removal, wet oxidation, complex oxidants