by Amanda Gogates, Cascade Global Product Manager, Emerson
Nitrogen oxides are powerful pollutants that can cause smog and acid rain and contribute to the development of tropospheric ozone. It’s critical to control nitrogen oxide (NOx) emissions to protect the environment and meet environmental regulatory requirements. NOx occurs as a result of combustion occurring in the presence of nitrogen and results from combustion processes in turbines, crackers, combustion engines, boilers, and other locations within a plant.
Ammonia can be used to react with NOx at high temperatures in order to turn it into molecular nitrogen and water vapor. Both selective catalytic and selective non-catalytic reduction (SCR and SNCR) are techniques used worldwide to remove NOx in DeNOx reactors.
However, this process can result in a byproduct of unreacted ammonia, or ammonia slip. Operators must use the precise amount of ammonia since either too much or too little can be problematic. Not enough ammonia will result in emissions, while too much ammonia can lead to waste.
As a result, continuous measurement and monitoring of ammonia slip is needed. However, such measurement can be challenging, especially in high-dust, high-temperature environments.