Application note DeNox
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Application Note All Rights Reserved, Copyright © December 2015, NEO Monitors AS Continuous Ammonia monitoring in DeNOx Processes Emissions from combustion processes contain gases which are harmful to the environment. Some of these gases include Nitric Oxides (NOx). For environmental reasons the reduction of NOx emissions is very important and is regulated by government in many countries. A common method used to reduce emissions of NOx is the injection of NH3 or Urea. Controlling and monitoring the NH3 ­concentration is important to optimize the NOx reduction efficiency, and to minimize NH3 emissions. PROCESS: In ­power plants NOx reduction, referred to as DeNOx, is typically achieved by selective catalytic reduction (SCR) or selective non-­ catalytic reduction (SNCR). Ammonia is injected into the gas flow to react with NO to form H2O and N2. The excess ammonia (NH3) in the off gas is called NH3 slip. Ammonia is typically measured after the injection point (1) downstream from the catalysts (SCR). It’s important that the measurement be accurate, fast and reliable. Since ammonia is considered to be toxic, the emission to air is also measured in the stack (2). High sensitivity and high reliability are required. TYPICAL PROCESS DATA NH3 concentration 0-15 ppm (SCR), 0-50ppm (SNCR) H2O content 10 –30% Temperature 200-400 °C Pressure atmospheric Optical path length 1-6 meter Fig 1: NH3 measurement points (1) and (2) in a typical DeNOx process NEO Monitors as • A subsidiary of Norsk Elektro Optikk • Prost Stabels vei 22 • N-2019 Skedsmokorset, Norway Phone +47 67 97 47 00 • www.n

The accurate measurement of Ammonia slip and emissions to the atmosphere are of concern for the operators of DeNOx process due to the following reasons: • Minimize the NH3 slip to reduce maintenance due to the deposition, plugging and ­potential corrosion. The solution is LaserGasTM II NH3 analyzer. With the fast response time and high reliability is a perfect solution to control the injection of NH3. With a high sensitivity, the LaserGasTM II is the best option for measuring low concentrations of NH3. Typical applications include is in-situ measurement for Continuous Emission Monitoring...