Trace Elements in West Virginia Coals

ARSENIC (As)

Arsenic is an especially toxic, Clean Air Act, Title III Hazardous Air Pollutant element in West Virginia coals and is of important environmental and economic concern.

Geologic Occurrence: Arsenic occurs in coal primarily within pyrite (FeS₂) and arsenopyrite (FeAsS) ¹.  Because pyrite is far more abundant than arsenopyrite in coal, most arsenic is in solid solution within pyrite in small amounts ² .  Arsenic is highest in coals of the Conemaugh Group and is highest in parts of the state where these coals are present. The Harlem, Elk Lick and Mahoning coals of Tucker, Mineral and Grant counties contain the highest arsenic averages (see cautionary notes page).  These coals have not historically been mined because of they are thin and not laterally extensive, and as such are not economically important (see the historic Conemaugh production).Whole coal As averaged 17.13 ppm in West Virginia coals and correlated statistically only with total sulfur and mercury.

Economic Impact: Arsenic in coal is of great importance to Selective Catalytic Reduction (SCR) for NO_x control. In SCR systems, ammonia vapor or urea is used as the reducing agent and is injected into the flue gas stream, passing over a catalyst. NO_x emission reductions over 80-90% are achieved. The very expensive catalysts can be severely degraded by arsenic poisoning, therefore the abundance of arsenic in the coal burned is of great importance ³.

Environmental Impact: Important natural sources of atmospheric As include volcanic eruptions, which contribute 22% of the total atmospheric arsenic. Coal combustion contributes 1.8% of the total emissions, which is the same amount as wood combustion ⁴.  During coal combustion, fly ash concentrates As several hundred times, thereby reducing atmospheric emissions ⁵.

References:
    1.  Finkelman, et al, (1979)
    2.  Minkin, J.A., et al., (1984)
    3.  IEA Coal Research Centre
    4.  Walsh, et al., (1979)
    5.  Swaine, D.J., (1990)
 

Page last revised: January 23, 2006

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