Читать книгу Continuous Emission Monitoring - James A. Jahnke - Страница 118

The majority of instruments used in CEM systems are based on principles associated with the interaction of light with matter. Opacity monitors measure the effects of light scattering and absorption; a nondispersive infrared analyzer measures the amount of light absorbed by a pollutant molecule; and a chemiluminescence analyzer senses the light emitted in a chemical reaction. One could treat the operation of CEM system analyzers as “black boxes” that give out answers, but an understanding of their operation is necessary to properly apply an analyzer for monitoring at a source. Although some techniques will work well in a given application, other techniques will have problems in the same application. Also, for proper evaluation of system performance, a knowledge of how an analyzer works is essential to understand the effects of interferences, temperature, pressure, and so on. This understanding will be developed by first reviewing some of the basic properties of light and how these properties can be applied to measure pollutant gas concentrations.