SCR stands for Selective Catalytic Reduction. It is an advanced emissions control technology used in power plants, industrial processes, and vehicles to reduce nitrogen oxide (NOx) emissions.

In SCR systems, a reductant agent, typically an ammonia-based compound called urea or AdBlue, is injected into the exhaust stream of a combustion process. The exhaust gases containing NOx then pass through a catalyst bed, where a chemical reaction takes place between the NOx and the reductant. This reaction converts the harmful NOx gases into harmless nitrogen (N2) and water (H2O) vapor.

The SCR process relies on the use of a catalyst, usually made of a metal such as titanium or vanadium, which facilitates the reaction between the NOx and the reductant. The catalyst promotes the conversion of NOx into nitrogen and water at relatively low temperatures, typically between 200-500°C.

SCR technology offers several advantages in reducing NOx emissions. It can achieve high removal efficiency, typically up to 90% or more, making it effective in meeting stringent emission regulations. It also works across a wide range of operating conditions, ensuring consistent emission control. Additionally, SCR systems can be retrofitted to existing equipment and vehicles, providing a viable solution for reducing emissions from older sources.

Overall, SCR is a widely adopted and proven technology for reducing NOx emissions, contributing to improved air quality and environmental sustainability.