The spatial heterogeneity effects on dTDLAS-based CO sensor for industrial emission monitoring applications

Accurate measurement of emissions to the atmosphere is vital to control and reduce air pollution. Industry needs to measure and report emissions for regulatory purposes including assessing stack emissions against concentration limit values. IMPRESS 1 and IMPRESS 2 projects [1] go beyond state of the art in measuring the emissions of critical pollutants with lower emission limit values, requiring detection limits and uncertainties unachievable with current Standard Reference Methods, enabling traceability and directly traceable measurements. Laser-based optical gas sensors provide powerful tools for industrial emission monitoring.Tunable diode laser absorption spectroscopy (TDLAS) is frequently used in science and industry for online and in situ gas analysis. We present our direct TDLAS (dTDLAS) method for absolute gas concentration measurement [2]. Note that the TDLAS is one of the line-of-sight (LOS) absorption spectroscopy techniques, and its application is normally limited to uniform conditions with constant or negligible temperature and/or concentration gradients along the LOS. However, in many applications, for example, combustion diagnostic and cross-stack emission measurements, temperature and concentration gradients along the LOS may occur. In those scenarios, special care should be taken to spectral fitting, line width and concentration quantification [3].This contribution covers a 4.6 μm EC-QCL based TDLAS CO spectrometer. The two gas cells configuration enables to investigate the heterogeneity effects on dTDLAS applications. The CO concentration and line width were measured under different heterogeneous conditions and compared to those under uniform settings. Currently the dTDLAS method is implemented for HCl measurements as a principle technique for cross-stack emission control.The research was supported by IMPRESS2 within EMPIR. The EMPIR initiative is co-funded by the European Union’s Horizon 2020 research and innovation programme and the EMPIR Participating States.

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