What is the primary purpose of installing selective catalytic reduction (SCR) systems in power plants?

The primary purpose of installing Selective Catalytic Reduction (SCR) systems in power plants is to reduce emissions of nitrogen oxides (NOx) from the flue gas. NOx is a group of air pollutants, including nitrogen oxide (NO) and nitrogen dioxide (NO2), that contribute to the formation of smog, acid rain, and respiratory problems. SCR systems use a catalyst, typically made of titanium oxide, vanadium pentoxide, or zeolites, to promote the chemical reaction between NOx and a reducing agent, such as ammonia (NH3) or urea. This reaction converts NOx into nitrogen (N2) and water (H2O), which are harmless components of air. The SCR system is typically located downstream of the boiler and upstream of the air preheater, where the flue gas temperature is optimal for the catalytic reaction. By significantly reducing NOx emissions, SCR systems help power plants comply with air quality regulations and minimize their environmental impact.