Citation:

Lee*, C, R K. Srivastava*, S. B. Ghorishi, J. Karwowski, T. W. Hastings, AND Hirschi. EFFECT OF SCR CATALYST ON MERCURY SPECIATION. Presented at Combined Power Plant Air Pollutant Control Mega Symposium, Washington, DC, August 30 - September 02, 2004.

Impact/Purpose:

To inform the public.

Description:

A pilot-scale research study was conducted to investigate the effect of selective catalytic reduction (SCR) on elemental mercury speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois bituminous coals and one Powder River Basin (PRB) coal were tested in a pilot scale combuster. The SCR catalyst induced high oxidation of elemental mercury, decreasing the percentage of elemental mercury at the outlet of the SCR to values below 12% for the three Illinois coal tests. The PRB coal test indicated a low oxidation of mercury by the SCR catalyst with the percentage of elemental mercury decreasing from about 96% to about 80% at the outlet. The test indicates a strong coal-type dependant effect of SCR on promoting mercury oxidation. The results also suggest the viability of reducing mercury emissions using SCR systems in Illinois bituminous coal-fired boilers that are equipped with FGD systems. SCR applications on PRB coal-fired boilers equipped with FGD systems may not achieve increased mercury removal. The coal type dependence of mercury speciation observed in this study is consistent with the available field data.
Bench-scale tests of the oxidation of elemental mercury with simulated coal combustion flue gases were conducted on fresh and field aged SCR catalyst samples. The effect of space velocity on the oxidation of elemental mercury was also studied. Data reflect that the SCR catalyst used for bituminous coal firing showed no apparent aging effect as relates to oxidizing elemental mercury. Space velocity seems to have a significant effect on mercury oxidation, suggesting a heterogeneous mechanism is involved in the oxidation.

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