Abstract
Emission of nitrogen oxides (NOx) and soot particles during the combustion of biomass fuels and municipal solid waste is a major environmental issue. Hydrogen cyanide (HCN) and acetylene (C2H2) are important precursors of NOx and soot particles, respectively. In the current work, infrared tunable diode laser absorption spectroscopy (IR-TDLAS), as a non-intrusive in situ technique, was applied to quantitatively measure HCN and C2H2 in a combustion environment. The P(11e) line of the first overtone vibrational band v1 of HCN at 6484.78 cm−1 and the P(27e) line of the v1 + v3 combination band of C2H2 at 6484.03 cm−1 were selected. However, the infrared absorption of the ubiquitous water vapor in the combustion environment brings great uncertainty to the measurement. To obtain accurate temperature-dependent water spectra between 6483.8 and 6485.8 cm−1, a homogenous hot gas environment with controllable temperatures varying from 1100 to 1950 K provided by a laminar flame was employed to perform systematic IR-TDLAS measurements. By fitting the obtained water spectra, water interference to the HCN and C2H2 measurement was sufficiently mitigated and the concentrations of HCN and C2H2 were obtained. The technique was applied to simultaneously measure the temporally resolved release of HCN and C2H2 over burning nylon 66 strips in a hot oxidizing environment of 1790 K.
Highlights
The combustion of biomass fuels and municipal solid waste is an important fossil-free energy sector providing heat and power
Soot particles during combustion is seen as a major environmental issue
Due to the lack of proper electronic transitions in the UV/visible spectral regions, the detection of Hydrogen cyanide (HCN) in a combustion environment is mainly focused on using the absorption lines in the infrared region
Summary
The combustion of biomass fuels and municipal solid waste is an important fossil-free energy sector providing heat and power. To fully understand the NOx and soot particle formation process in various combustion environments, reliable measurements of HCN and C2 H2 are essential. Considering that both HCN and C2 H2 will be consumed downstream, nonintrusive in situ laser-based techniques are preferred. Using the same absorption line, Hot et al [2] achieved quantitative in situ measurements of HCN released from burning straw pellets at atmospheric pressure using mid-infrared degenerate four-wave mixing (IR-DFWM). Goldman et al [3] reported HCN measurement in low-pressure flames using fiber laser intracavity absorption spectroscopy (FLICAS), probing the first overtone vibrational band at around 1.5 μm. Ex situ measurements of HCN in flames were reported by Gersen et al [4], using wavelength
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