Proceedings PaperContinuous multicomponent stack gas analyzer using ultraviolet-photodiode-array spectroscopy
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Ammonia injection is frequently used to reduce emissions of nitrogen oxides from modern combustion plant. Accurate measurements of ammonia and nitric oxide are therefore required to ensure optimum operation of the NOx control system. Measurements of sulphur dioxide are also required to ensure compliance with legislation in most countries. An extractive analytical system has been developed for continuous measurements of ammonia, nitric oxide and sulphur dioxide concentrations in stack gases based on an ultraviolet spectrometer using a photodiode array detector operating in the 200nm region. The use of the photodiode array spectrometer enables the system to have a fast response time while maintaining excellent wavelength stability and reliability, since there are no moving parts in the main optical system. A high temperature sampling system is coupled to a hot sample cell to ensure that there is no degradation of the sample prior to measurement. Tests in the laboratory and at a combustion plant in Europe have shown practical detection limits of 1ppm for all of the target gases.