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FUNDAMENTALS OF MERCURY SPECIATION AND CONTROL IN COAL-FIRED BOILERS
Citation:
Ghroishi, S. B. FUNDAMENTALS OF MERCURY SPECIATION AND CONTROL IN COAL-FIRED BOILERS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-98/014 (NTIS PB98-127095), 1998.
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Description:
The report describes the progress of an experimental investigation of the speciation of mercury in simulated coal combustion flue gasses. The effects of flue gas parameters and coal fly ash on the oxidation of elemental mercury (Hgo) in the presence of hydrogen chloride (HCl) in a simulated post-combustion region, including the baghouse portion of air pollution control systems, were studied using a bench-scale setup. Results of the gas-phase experiments indicate that the in-flight, post-combustion oxidation of Hgo in the presence of HCl in a simulated flue gas is slow and proceeds at measurable rates only at high temperatures (> 700 C) and high HCl concentrations (>200 ppmv). The presence of sulfur dioxide (SO2) and water vapor in the simulated flue gas significantly inhibits the gas-phase oxidation of Hgo in the presence of HCl. However, results of a preliminary investigation indicate that the gas-phase reaction of Hgo with chlorine (Cl2) proceeds rapidly, suggesting that Cl2 is a more active chlorinating agent than HCl. The effects of the coal fly ash component and its composition were investigated using a fixed bed of model fly ashes. The primary focus was to evaluate the catalytic activity of major mineral constituents of coal fly ashes. Copper and iron oxides were the only two components that exhibited significant catalytic activity toward surface-mediated oxidation of Hgo.