SCR (Selective Catalytic Reduction) is one of the best available technologies for NOx reduction in industrial processes.

Selective Catalytic Reduction (SCR) is an advanced emission control technology designed to significantly reduce nitrogen oxides (NOx) in exhaust gases generated by industrial and other processes.

The operation of SCR is based on the selective chemical conversion of NOx into nitrogen (N2) and water (H2O) through a catalytic reaction. In general it works by:

• Injection of a reducing agent and mixing in the SCR reactor: In the Selective Catalytic Reduction process, a reducing agent is injected into the exhaust gas, most commonly ammonia (NH3) or urea (CO(NH2)2) depending on the specific application and conditions. The gases with the reducing agent are mixed in an SCR reactor. It is important to achieve a uniform mixing of the reducing agent with the pollutant gases.
  
  
• Catalytic reaction: In the presence of a specific catalyst, usually a zeolite or a metal-based material, a chemical reaction is initiated. The catalyst accelerates the selective conversion of NOx into nitrogen (N2) and water (H2O) through the following chemical reaction:
  
  

4NO + 4NH3 → 4N2 + 6H2O

• NOx removal: As a result of the catalytic reaction, NOx is converted into nitrogen and water, which significantly reduces NOx emissions in the exhaust gas. Nitrogen and water are non-harmful products that can be safely released into the environment.
  
  

An SCR can operate over a wide temperature range, between 200°C and 450°C, and achieve reduction efficiencies of up to 90%.