Quasi-simultaneous in-line flue gas monitoring of NO and NO₂ emissions at a caloric power plant employing mid-IR laser spectroscopy.

Two pulsed thermoelectrically cooled mid-infrared distributed feedback quantum cascade lasers (QCLs) were used for the quasi-simultaneous in-line determination of NO and NO2 at the caloric power plant Dürnrohr (Austria). The QCL beams were combined using a bifurcated hollow fiber, sent through the flue tube (inside diameter: 5.5 m), reflected by a retro-reflector and recorded using a fast thermoelectrically cooled mercury-cadmium-telluride detector.

Toward stand-off open-path measurements of NO and NO(2) in the sub-parts per million meter range using quantum cascade lasers (QCLs) in the intra-pulse absorption mode.

Two thermoelectrically cooled mid-infrared distributed feedback quantum cascade lasers operated in pulsed mode have been used for the quasi-simultaneous determination of NO and NO2 in the sub-parts per million meter (sub-ppm-m) range. Using a beam splitter, the beams of the two lasers were combined and sent to a retro-reflector. The returned light was recorded with a thermoelectrically cooled mercury cadmium telluride detector with a rise time of 4 ns.