Continuous NO and NH3 measurements in deNOx installations

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:560481

Wisker, S M; Bay, W; Masterson, J S

The ammonia (NH{sub 3})/aqueous urea injection concept has been used extensively as a secondary deNO{sub x} method for many years. The basic technology involves spraying ammonia or aqueous urea into the flue gas either over a catalyst or in a temperature zone, encouraging the oxides of nitrogen to dissociate into atomic nitrogen and water vapor. Although this injection results in a beneficial reduction in NO{sub x}, it comes with its own set of drawbacks. At some point, additional NH{sub 3} will no longer react with NO{sub x} and will pass, or {open_quotes}slip{close_quotes} by the catalyst and/or temperature zone. This is commonly termed {open_quotes}ammonia slip.{close_quotes} Monitoring this {open_quotes}slip{close_quotes} is an important control parameter for any deNO{sub x} system, given the costs of commercially available ammonia and the fact that ammonia is defined as a pollutant by many of the regulatory authorities. Plant attempt to operate with the lowest {open_quotes}slip{close_quotes} possible while maintaining an acceptable deNO{sub x} effect. In addition, ammonia is an aggressive and elusive substance, proving very difficult to measure in a flue gas scenario. It partitions with particulate material and also forms a variety of salts with other flue gas constituents. This requires the gas measurement close to the secondary deNO{sub x} process. This cost, along with the detrimental physical and environmental effects of ammonia, make {open_quotes}ammonia slip{close_quotes} control important, thus the focus of this paper.

• OSTI ID: 560481
• Report Number(s): CONF-961232--
• Country of Publication: United States
• Language: English

Related Subjects

20 FOSSIL-FUELED POWER PLANTS
AIR POLLUTION CONTROL
AMMONIA
FLUE GAS
FOSSIL-FUEL POWER PLANTS
MONITORING
NITROGEN OXIDES
SPECTROMETERS