Continuous Emissions Monitoring
History
The first continuous emission monitoring requirements in the US were promulgated for fossil fuel-fired steam generators in December 1971. In 1974, Germany passed the Federal Immission Control Law that included requirements for continuous emission monitoring. However, the CEM industry did not begin to develop until after October 6, 1975, when the US EPA established performance specification for CEMS and required their installation in a limited number of sources.
Extractive System
Extractive systems were the first type of CEMS developed for continuous emissions monitoring. Two types of extractive systems
- fully extractive, source-level systems
- dilution systems.
There are three types of source-level extractive systems:
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hot/wet system. it uses a heated line to transport the flue gas to an analyzer that incorporates a sample cell heated above the flue gas temperature. The gas delivered to the analyzer are both hot and wet. The particulate matter needs to be removed with a course filters located at the probe.
- cool/dry systems with conditioning at the probe.
- cool/dry systems with conditioning at the CEMS shelter
Gas is conditioned before it enters the analyzer. The gas temperature is reduced to ambient temperature temperature and moisture is removed.