High resolution quantitative multi-species hydrocarbon gas sensing with a cw external cavity quantum cascade laser based spectrometer in the 6–11 μm range

Abstract

We report multi-species spectroscopy of hydrocarbons with a continuous wave external-cavity quantum cascade laser (EC-QCL) based spectrometer providing tunability from 6-11 µm to measure direct absorption spectra of the first 7 alkanes and their mixtures. The gas spectra where acquired in the range from 1440-1480 cm -1 at reduced pressure of 50 mbar and at a temperature of 323 K. By linearization of the measured wavelengths with a custom-made highly temperature stable air spaced etalon high spectral accuracy of ±0.001 cm -1 is achieved for the whole spectral range. The simultaneous high resolution of 0.001 cm -1 yields spectra of unprecedented richness of detail for the heavier alkanes (C3 − C5) and allows the discrimination of narrow spectral features for the lighter ones (C1 − C2). Thereby, the measured spectra reveal the influences of collisional broadening effects among the measured species. Quantitative spectroscopic multi-species gas sensing relies on the comprehension of the extent of spectral broadening. Studying the spectral broadening in combination with highly accurate reference spectra is mandatory for highly sensitive and specific multi-species gas analyzers. The quantitative results that can be obtained with our approach are presented for an exemplary calibrated mixture of all 7 components and reveals an absolute accuracy below 0.5 vol% for the determination of the mole fraction of each gas.

Interband Cascade Laser Arrays for Simultaneous and Selective Analysis of C1–C5 Hydrocarbons in Petrochemical Industry

“…Tunable laser spectroscopy (TLS) has become a powerful technique for analyzing components both in liquids 1 and in gas mixtures. 2,3 The major benefits of this technique are the real-time measurement speed, its high sensitivity, and selectivity. 4 TLS sensor systems can be built in a maintenance-free fashion without the need for additional calibration or alignment after initial deployment.…”

Selective H2 sensing using lanthanum doped zinc oxide thin film: A study of temperature dependence H2 sensing effect on carrier reversal activity

“…Recently, there are various reports that highlighted the inevitability of the gas sensors at different fields of applications. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] However, gas sensors are extremely necessary for the early detection of gas leakage. Compared to other gas species, detection of hydrogen is highly desirable as H 2 leakage is harmful to human safety and can be flammable and explosive when mixed with air.…”