Development of a Negligible Zero-Drift NDIR Analyzer for Measuring NH3 Emitted from an Urban Household Solid Waste Incinerator

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.

Automated summary

A new NH3 analyzer based on NDIR technique has been developed to measure emissions from combustion processes effectively and cost-efficiently. By using a least-interfering BPF, interference and zero-drift issues have been successfully overcome, leading to measurement errors less than 2.5% and a 19% reduction in zero-drift for accurate and reproducible NH3 measurements.