Direct absorption spectroscopy baseline fitting for blended absorption features.

Area of Science:

• Spectroscopy
• Analytical Chemistry
• Physical Chemistry

Background:

• Direct absorption spectroscopy is crucial for gas concentration measurements.
• Blended absorption features, caused by closely spaced lines or increased pressure, complicate spectral analysis.
• Accurate baseline determination is essential for reliable gas concentration quantification.

Purpose of the Study:

• To develop and validate a novel method for determining gas concentrations from blended absorption features using direct absorption spectroscopy.
• To address challenges in spectral analysis caused by overlapping absorption lines and elevated pressures.
• To provide a robust data analysis technique for complex spectral data.

Main Methods:

• Developed a blended-feature baseline fitting method using measured data and simulated fractional transmission.
• Validated the method with synthetic data.
• Applied the method to CO2 and H2O absorption lines in a heated static test cell and to flue gas emissions from a wood boiler.

Main Results:

• The method showed agreement within 1% with wavelength modulation spectroscopy measurements for CO2 and H2O.
• Analysis of flue gas emissions from a wood boiler yielded mean percent differences of 2.8% for CO and 5.8% for H2O compared to wavelength modulation spectroscopy.
• The technique effectively handles spectra with moderate feature blending, suitable for closely spaced absorption lines and moderate pressures.

Conclusions:

• The developed blended-feature baseline fitting method is a reliable approach for gas concentration determination using direct absorption spectroscopy.
• This method offers improved accuracy for spectral analysis in scenarios with moderate feature blending.
• The technique has practical applications in analyzing combustion system emissions and other complex gas mixtures.