| In order to accurately measure the NH3 concentration on-line to help reduce ammonia leak, to determine the optimal amount of ammonia injected, while controlling the spatial distribution of ammonia to reduce NOx emissions. This paper mainly in the conditions of ammonia slip of power plant SCR devices flue gas, using tunable diode laser absorption spectroscopy and wavelength modulation method for measuring the ammonia concentration of ammonia at low concentration and high temperature. And explore the influence of particulate matter to measurements of ammonia. At last, design and site installation of ammonia on-line measurement measuring gun, realize continuous online measurement.This paper choose wavelength of 2.25nm tunable laser, using wavelength modulation methods, to explore the influence of modulation voltage and modulation frequency. At the same time meet the high SNR and high second harmonic peak condition, select the best modulation voltage and the modulation frequency. At low concentrations (less than 1ppm) of NH3 concentration, and measurement results were evaluated. Meanwhile, in order to eliminate temperature change on NH3 concentration measurements. For temperature-dependent second harmonic polynomial fitting peak three times to give the empirical formula temperature correction, and the measurement results were analyzed at different temperatures. In order to eliminate particulate matter measuring the impact of the gas concentration, according to the principle of the extinction method by measuring the laser intensity due to attenuation caused by scattering particle method, enabling on-line measurement of particle concentration. For the actual measurement site environment, design and site installation of ammonia on-line measurement measuring gun in a power plant in Jiaxing, realize ammonia slip on-line continuous measurement, and research change of ammonia slip concentration when the spray ammonia flow changes in the boiler back pass. |
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