Effects of fly ash on the oxidation of mercury during post-combustion conditions
Mercury emissions from coal-fired power plants pose impact on human health. The emissions will be regulated in the near future. Mercury speciation in flue gas has an important effect on the efficiency of mercury emission control devices. This study focuses on the role of fly ash on the oxidation of Hg 0 in bench-scale simulated flue gas environment and in laboratory-scale coal combustion flue gas environment. The effects of flue gas matrices, temperature, fly ash mineralogy and morphology on the oxidation of Hg0 are studied. Conclusions are drawn based on the testing results: (1) Mercury chemistry is very complex in flue gas. (2) The presence of fly ash is critical for heterogeneous Hg0 oxidation. (3) The flue gas components, including NO2, HCl, NO and SO2, have strong effects on the potential of whole fly ashes to oxidize Hg0. (4) Fly ash specific surface area appears to have a determining effect on Hg0 heterogeneous oxidation.