Gas monitoring instruments and systems for DeNOx process control - Air and Climate

In most combustion process atmospheric nitrogen reacts with oxygen in high temperature conditions to produce nitrogen oxides (NOx). Total NOx production is the sum of nitrogen monoxide NO and nitrogen dioxide NO2. The emissions of these gases are controlled through setting of emission limit values (ELVs) for power plants.

The amount of nitrogen oxides in the flue or exhaust gas can be be effectively reduced from stack gases by reacting them with ammonia NH3 in high temperature. Ammonia reacts with both nitrogen monoxide NO and nitrogen dioxide NO2 to produce molecular nitrogen N2 and water vapor H2O. This results in a need to measure ammonia gas in power plants. Release of ammonia gas is controlled by environmental authorities through setting of an emission limit value. The ammonia reagent is costly, and excessive ammonia use increases salt formation. This can lead to blocked heat exchangers, which further may lead to increased downtime for the power plant.

A clear need for measurement systems to monitor ammonia continuously at power plants with DeNOx scrubbers exists. With Gasmet™ FTIR Gas Analyzer solutions, it is possible to measure most gas emission components needing continuous monitoring at a power plant, including gaseous ammonia NH3, nitrogen oxide NOx, sulfur dioxide SO2, and several other typical emissions components. Our Continuous Emissions Monitoring System II (Gasmet™ CEMS II) can be used both on the process side to monitor the untreated raw gases, and at the stack to measure the amount of NOx in the flue gas.