Simultaneous measurement of CO and CO2 at elevated temperatures by diode laser wavelength modulated spectroscopy

One single semiconductor distributed-feedback (DFB) laser is used to demonstrate the possibility of simultaneous measurements of CO and CO2 at elevated temperatures. Wavelength modulation spectroscopy with second-harmonic detection is used to improve the detection sensitivity and accuracy. The concentrations of CO and CO2 are determined from the WMS-1-normalized absorption-based WMS-2f signal peak heights of a proper line pair of CO and CO2 near 6357.814 cm−1 and 6357.312 cm−1, which are selected using some line-selection criterions for the target temperature range of 300–1000 K. The CO and CO2 concentrations measurements are within 2.86% and 2.69% of the expected values over the tested temperature range 300–1000 K. The minimum detectable concentrations of CO and CO2 at 1000 K are 250 ppm m and 280 ppm m respectively.

► Simultaneous detection of multiple gases with one single laser is demonstrated.
► A proper line pair of CO and CO2 is selected based on some selection criterions.
► The XCO and XCO2 measurements are within 2.86% and 2.69% of the expected values.
► The MDCs of CO and CO2 at 1000 K are 250 ppm m and 280 ppm m respectively.