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Selective Catalytic Reduction

Coal-fired utilities in the Ohio River Valley have recently been required to greatly reduce nitrogen oxide (NOx) emissions. Coal-fired power plants in Kentucky are in the process of installing selective catalytic reduction (SCR) technology at several power plants in order to comply with these emission regulations. SCR works by injecting ammonia into the flue-gas stream, which then passes over a special catalyst reducing the NOx in the flue gas to elemental nitrogen and water. Although SCR is very effective in controlling NOx emissions, the catalysts can be easily damaged, or even incapacitated, by elevated percentages of certain elements in the flue-gas stream, namely arsenic. As such, the amount of arsenic in utility feed coal is of great concern. A cooperative program with the USGS is currently underway to better understand the origin and distribution of arsenic in Appalachian coal beds.