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B. Lendl, W. Ritter:
"Photoacoustic Monitoring of Carbon Dioxide in a Biogas Matrix Using a Quantum Cascade Laser";
Poster: International Conference on Advanced Vibrational Spectroscopy, ICAVS 4, Corfu; 10.06.2006 - 15.06.2006.

We present an on-line sensor for biogas monitoring using mid-infrared quantum cascade laser (QCL) and photoacoustic (PA) detection. This sensor concept takes advantage of the inherent selectivity provided by mid-IR laser spectroscopy and the small gas volume required in photoacoustic spectroscopy allowing rapid response. Using a distributed feedback QCL emitting at 4,3 µm, the sensor concept as been successfully tested for carbon dioxide measurement under harsh conditions during biogas upgrade in a pilot plant. In this application a reliable and rapid gas sensor is required for process control to assure a continuous CO2 concentration below 2%. The obtained results compared favorably with a state of the art NDIR analyzer used as a reference with the distinct advantage of faster response times. Due to the generic nature of the developed PA-QCL sensor concept selective on-line measurement of other important analytes in biogas, such as NH3 and H2S are possible as well.