Ammonia monitoring in exhaust gas based on wavelength modulated TDLAS near 1.5 μm

摘要

Summary form only given. In China, particulate pollution is a serious environment problem that is influencing air quality, regional and global climates, and human health. Emission of gaseous ammonia has long been known to play an important role in the air pollutants because of its contribution to secondary aerosol formation which is the major component of PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 micrometers). However, the source apportionment of atmospheric ammonia is still not clear. Additionally, ammonia has a short lifetime and very soluble in water. Therefore the efficiently monitoring of ammonia is of challenge. In this work tunable diode laser absorption spectroscopy (TDLAS) was adopted due to its great experimental simplicity, high spectral resolution, fast time response and high sensitivity.Furthermore,wavelength modulation spectroscopy was employed with second-harmonic detection (WMS-2f) to extend the detection limit of system. Absolute concentration can be derived with the normalization of the secondharmonic (2f) signal by the first-harmonic (1f) signal. Compared with conventional measurement strategy ammonia, usually measuring above 2 μm, this work present a near infrared measurement which has advantage of telecommunication band application and potential of instrumentation.