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Communication Dans Un Congrès Année : 2014

Online gas monitoring by using raman spectroscopy

Résumé

The objective of this study was to investigate the viability of Raman spectrometry to continuously monitor various gases and gas mixtures. Complex gaseous samples, measured at atmospheric pressure, containing N2, CO2, CO, O2 gases and H2O vapor in a 1,1,1,2-tetrafluoroethane (F134a or Forane) gas matrix, were selected for analysis.. The capability of using an optimized AirHeadTM process Raman probe manufactured by Kaiser Optical Systems (Kaiser) to provide high sensitive gas-phase Raman detection and quantification is reported in this paper. Raman spectroscopy, in which light is scattered from a molecule following photoexcitation that induces a change in polarization of the molecule, can provide “fingerprint” information about specific molecules since each molecule has its own set of vibrational modes. One of the advantages of using Raman spectroscopy for gas detection is being able to measure homonuclear diatomic species such as nitrogen, oxygen, and hydrogen, as well as other molecular gas species including water vapor, and hydrocarbons. Raman spectra of gases and gas mixtures were obtained by using a RamanRxn4TM gas-phase analyzer (Kaiser), with 532 nm laser excitation. A Raman probe (AirHeadTM) connected by optical fibers to the Raman analyzer allowed measurement to be made directly on the gas circuit through a specially built gas-cell. This Raman gas-cell is based on a multi-reflection scattering amplification concept, where the laser is reflected on mirrors. Raman backscattering amplification is collected through the sapphire window and transmitted by the Raman probe head and the optical fibers to the spectrometer. For the quantitative study, Raman spectra of mixtures with known gas concentrations (vol.%) containing (i) Forane (5%-95%) in N2, (ii) CO2(0.2%-6%), CO(0.2%-6%), O2(0.2%-1.33%) in Forane matrix (33%) in N2 and (iii) H2O vapor (0.2%-1%) in Forane matrix (60%) in N2, were analyzed by using univariate modeling, and a calibration curve for each gas (Forane, CO2, CO, O2 and H2O) was obtained. To validate these regression models (after calibration), complex mixtures containing all gases with various concentrations were analyzed. The signal stability was also studied by looking at concentrations evolution with time. In this study, we have demonstrated that a Raman analyzer equipped with an optimized gas-phase AirHeadTM probeis a powerful tool for high sensitive gas-phase detection and quantification.
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Dates et versions

hal-01108320 , version 1 (22-01-2015)

Identifiants

  • HAL Id : hal-01108320 , version 1

Citer

Yamina Ouabbas, Hervé Lucas, Jean-Paul Viricelle, Sandra Grimaldi, Béatrice Allard-Breton. Online gas monitoring by using raman spectroscopy. Nextlab, Apr 2014, Rueil-Malmaison, France. ⟨hal-01108320⟩
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