Abstract
An analyzer for measuring NH3 emitted from a combustion process has been developed based on a simple non-dispersive infrared (NDIR) technique because of its cost-effective benefit. The weakness of the NDIR analyzer due to interference and zero-drift has been overcome. A least-interfering bandpass filter (BPF) was found and manufactured to compensate for the interfering effects of gases emitted from a combustion process (e.g., CO, NOx, SO2, CO2, H2O, HCl, formaldehyde, acetaldehyde and toluene). It was found that there was no significant interference in the least-interfering BPF with respect to gases of concern. Measurement errors by the analyzer were less than 2.5% in a range of 1 to 10 ppmv of NH3 compared to a standard method when the compound was measured in complicated mixing gases. For the zero-drift, using BPFs with identical center wavelength with respect to different incident infrared intensity was found to help minimize the zero-drift of the NDIR analyzer. As a result, the analyzer could cut approximately 19% of zero-drift caused by the aging effect of both IR source and detector. It suggests that the analyzer could be applied for measuring NH3 emitted from combustion processes with good accuracy and reproducibility.
Highlights
Ammonia (NH3, CAS number 7664-41-7) is a colorless gas with a pungent smell [1].NH3 has adverse effects on human health
An NH3 non-dispersive infrared (NDIR) analyzer has been developed with negligible zero-drift and high accuracy
To compensate for interference effects and to improve the accuracy of the analyzer, a least-interfering bandpass filter (BPF) was made based on information in the HITRAN database of CO, NO, NO2, SO2, CO2, H2 O, formaldehyde, acetaldehyde and toluene
Summary
Ammonia (NH3 , CAS number 7664-41-7) is a colorless gas with a pungent smell [1].NH3 has adverse effects on human health. NH3 exposure causes coughing, wheezing, and shortness of breath [2]. Inhalation of over 10,000 ppm of NH3 can cause death [2]. The continuous monitoring of NH3 emitted from combustion processes is a pivotal issue to control the emission of NH3 , especially from industrial and traffic emission sources. The measurement of air pollutants is useful for emission inventories. Governments can find significant sources of air pollutants from the emission inventory for environmental policy action [11]. The emission inventory is an input for mathematical models used to predict the formation of secondary air pollutants in the atmosphere [3,4,5,6,7,8,9]. The accuracy of measurement data is an important issue
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