Continuous Infrared Analysis of N2O in Combustion Products

Nitrous oxide (N₂O) levels in the atmosphere are increasing, potentially contributing to the greenhouse effect and depletion of stratospheric ozone. From a limited data base, combustion sources have been identified as a major anthropogenic source of N₂O. However, the existing data base (obtained by traditional grab sampling techniques followed by gas chromatographic analysis) is in question due to the discovery of a sampling artifact. A continuous on-line N₂O analyzer would enable and facilitate the accurate characterization of combustion sources over a range of operating conditions, and also aid in the development of an appropriate sampling technique. This paper addresses the development of a continuous measurement technique, and the evaluation and initial use of a field prototype continuous N₂O analyzer developed at the UCI Combustion Laboratory in cooperation with a major instrument manufacturer. The analyzer is capable of measuring N₂O levels down to a few ppm. The analyzer has been evaluated and used to study the N₂O emissions from a pulverized coal-fired boiler. The N₂O levels found with the analyzer are substantially lower than levels previously attributed to such sources. Initial N₂O measurements made with the analyzer suggest that N₂O levels are not a substantial fraction of the NO_X levels, as previously suggested.