| Summary: | To understand the mercury speciation and mass flow in a full-scale bituminous coal-fired power plant equipped with a selective catalytic reduction (SCR) unit, an electrostatic precipitator (ESP), and a seawater flue gas desulfurization (SWFGD) scrubber, the evolution and emission of mercury was systematically measured and analyzed. The results showed that the elemental mercury (Hg0) was oxidized mainly through heterogeneous oxidation, especially in SCR, which transformed 57-64% of elemental mercury (Hg0) to oxidized mercury (Hg2+). It changed the concentrations of different mercury species and then increased the Hg2+ removal efficiencies of SWFGD, which ranged from 67 to 82%. A total of 8.24-11.54% of mercury was adsorbed by fly ash to form particulate-bound mercury (HgP) and subsequently removed by the ESP. Mass flow and mass distribution of mercury indicated that most mercury was removed and retained in the SWFGD. The heterogeneous oxidation of Hg0 in SCR and then absorption of Hg2+ by SWFGD significantly enhanced the mercury removal in the studied coal-fired power plant, although a part of Hg2+ absorbed in SWFGD was reduced and released back to the flue gas. Hg2+ was a little more than Hg0 in the flue gas emitted to the atmosphere. In addition, the SWFGD system without limestone addition may be beneficial for decreasing the re-emission of Hg0. The mercury emission factor at the power plant is 4.098 g/TJ, which is lower than that at other power plants without SCR. The configuration of SCR + ESP + SWFGD enhances the co-benefit mercury control. © 2017 American Chemical Society.
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