Abstract
The paper describes a photoacoustic spectrometer for detection of NH3 in power plant emission with a detection limit below 1 ppm. The radiation source is a tunable CO2 waveguide laser, and detection is performed at reduced pressure, where the vibration-rotation lines of NH3 are essentially Doppler broadened. Immunity against interference is ensured by recording a characteristic spectral profile, and problems associated with the high concentration of CO2, and the associated line center absorption are eliminated by utilizing the effect of kinetic cooling on the photoacoustic phase. A computerized spectrometer has been constructed and tested under realistic conditions at a Danish power plant operating a test facility for selective non-catalytic reduction of NO x . Results of this field test are given.
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Supported by the Danish Science Research Councils under grants no. 5.17.4.6.19 and 5.17.4.1.23 and by ELSAM
Chr. F. Rovsing A/S