FGD and DeNOx
NEWSLETTER       

                                                                                                           May 2003
                                                                                                             No. 301

European Prescription for U.S. SCR

A European SCR consultant, well familiar with the experience of the many electric utility owners of high-dust SCR systems retrofitted in Europe in the 1980s, would be expected to prescribe the following special provisions for a typical high-sulfur, low-ash, United States coal-fired unit according to Bill Ellison and Helmut Weiler:

·     A catalyst with a low SO₂-to-SO₃ conver­sion rate, i.e., less than 0.4 percent

·     Ammonia injection upstream of the econo­mizer

·     Alkali injection upstream of the air prehea­ter

·     Enameled heating plates on the flue gas side of the air preheater extending  up to 2/3 of the plate height

·     Protection against corrosion of the casing and rotor structure on the cold side of the air preheater

·     Adequate means for optimizing soot blowing action within the air preheater

·     Limiting of design ammonia-slip to no more than 2 ppm, particularly where SO₃ generation was already a problem

·     Measuring daily the ammonia content of the flyash.

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