Detector for detection of nitric oxide NO and ammonia NH3

摘要

The Nox emission of a Diesel engine may be substantially reduced by applying the SCR process. In this process, NH3 is injected into a catalyst through which the exhaust fumes are made to flow and in which the injected NH3 reacts with NO or NO2, forming nitrogen and water. As the exhaust fumes should not contain NO nor excess NH3, appropriate detectors are required to control NH3 leaks or to monitor or regulate the NH3 dosage. For that purpose, a nitrogen monoxide and ammonia detector contains an AlVO4 or FeVO4 thin layer as gas-sensitive element. The sensitivity to NO or NH3 of a vanadate layer produced by a special sputtering process is higher by several orders of magnitude than the transverse sensitivity to oxygen and hydrogen. The detector is not sensitive to methane, carbon monoxide and carbon dioxide. No masking effects occur, i.e. the sensitivity to NO and NH3 of the detector is not affected by the presence of other gasses. The invention is suitable as an air quality sensor, as a NH3 leak monitor and as a sensor for regulating a DENOx catalyst.