SENSOR FOR ONLINE IN-SITU MEASUREMENT OF SOOT CONCENTRATION IN FLUE-GASES

A new potentiometric soot sensor for in situ application based on a po rous zirconia solid electrolyte has been developed. Its mode of operat ion has been evaluated in a test facility with test gas of various soo t concentrations. Stationary soot concentrations in the test gas rangi ng from 0 to 90 mg/m3 could be produced with the help of an aerosol ge nerator. The sensor signal was found to be in the range of 0 to 60 mV with higher sensitivity at low soot concentrations (<30 mg/m3) and app roaching saturation at concentrations >70 mg/m2. Sensitivity and respo nse time were found to be inversely temperature dependent: higher temp erature results in a faster response, but a lower sensitivity. Sensiti vity in the low concentration range is increased when the gas atmosphe re contains less O2 than air and the saturation of the sensor signal a ppears already at some 30 mg/m3 in this case. Non-combustible particul ates do not contribute to the sensor signal. The working principle of the sensor can be understood by a first-order model assuming an equili brium between adsorption and burn-off of soot particulates at the work ing electrode, and regarding the sensor as a network of distributed e. m.f. sources.