NH 3 line broadening coefficients and intensities measurement and impurities determination in emerging applications: CCUS, Biomethane and H 2 .

A mid-infrared quantum cascade laser (Mid-IR QCL) coupled with a Single Pass Cell and a Multi Pass Cell, was utilized to measure ammonia (NH ₃ ) absorption spectroscopic parameters and determine NH ₃ impurities toward three emerging applications. We for the first time measured the pressure broadening coefficients perturbed by Air, O ₂ , N ₂ , He, CO ₂ , CH ₄ , and H ₂ and the line intensities of six NH ₃ transition lines near 1084.6 cm ^-1 . The measured NH ₃ -He, NH ₃ -Air, and NH ₃ -CO ₂ broadening coefficients align with HITRAN database, while NH ₃ -H ₂ coefficients exhibit a maximum discrepancy of 46 %. Deviations between the measured line intensities and HITRAN database are minimal. Nevertheless, the uncertainties of line intensities have been significantly reduced from 20 % in HITRAN to below 3 %. The newly measured line parameters are utilized to address NH ₃ impurity requirements outlined in CCUS (ISO 27913:2016), Biomethane (EN 16723:2016), and H ₂ (ISO 14687:2019) standards. Based on the concept of optical gas standard (OGS), the NH ₃ impurity detection requirements in all three standards have been fulfilled with an uncertainty of 1.35 %. The precision of the NH ₃ -OGS is 800 part per trillion (ppt) with an integration time of 100 s. The repeatability of the NH ₃ -OGS is 130 ppt for a continuous measurement time of 48 min. Notably, the NH ₃ -OGS effectively addresses the highly nonlinear adsorption-desorption dynamics, underscoring the potential of OGS as a calibration-free and SI-traceable metrological gas analysis instrument.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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