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MERCURY OXIDATION PROMOTED BY A SELECTIVE CATALYTIC REDUCTION CATALYST UNDER SIMULATED POWDER RIVER BASIN COAL COMBUSTION CONDITIONS
Citation:
LEE, C., S. D. SERRE, Y. ZHAO, S. LEE, AND T. W. HASTINGS. MERCURY OXIDATION PROMOTED BY A SELECTIVE CATALYTIC REDUCTION CATALYST UNDER SIMULATED POWDER RIVER BASIN COAL COMBUSTION CONDITIONS. 10.3155-1047-3289.58, T. Keener, G. Hidy (ed.), JOURNAL OF AIR AND WASTE MANAGEMENT. Air & Waste Management Association, Pittsburgh, PA, 58(4):484-493, (2008).
Impact/Purpose:
Journal article
Description:
A bench-scale reactor consisting of a natural gas burner and an electrically heated reactor housing a selective catalytic reduction (SCR) catalyst was constructed for studying elemental mercury oxidation under SCR conditions. A low sulfur Power River Basin (PRB) coal combustion fly ash was injected into the entrained-flow reactor along with sulfur dioxide, nitrogen oxides, hydrogen chloride and trace elemental mercury. It was observed that hydrogen chloride provides the source of chlorine for elemental mercury oxidation under simulated PRB coal-fired SCR conditions. The decrease in elemental mercury mass balance closure across the catalyst with decreasing hydrogen chloride concentration suggests that transient mercury capture on the SCR catalyst occurred during the short test exposure periods and that the outlet speciation observed may not be representative of steady-state operation at longer exposure times. Increasing the space velocity and operating temperature of the SCR led to less elemental mercury oxidized. Introduction of PRB coal fly ash resulted in slightly decreased outlet oxidized mercury as a percentage of total inlet mercury and correspondingly resulted in an incremental increase in mercury capture. The injection of ammonia for nitrogen oxide reduction by SCR was found to have a strong effect to decrease mercury oxidation. The observations suggest that elemental mercury oxidation may occur near th exit region of commercial SCR reactors. Passage of flue gas through SCR systems without ammonia injection, such as during the non-ozone season, may also impact mercury speciation and capture in the flue gas.
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MERCURY OXIDATION PROMOTED BY A SELECTIVE CATALYTIC REDUCTION CATALYST UNDER SIMULATED POWDER RIVER BASIN COAL COMBUSTION CONDITIONS