AdBlue is a crucial component in the Selective Catalytic Reduction (SCR) system, a technology widely used in diesel
engines to reduce harmful nitrogen oxide (NO?) emissions. This liquid solution is made up of 32.5% high-purity urea
and 67.5% deionized water. It is non-toxic, colorless, and safe to handle under proper conditions, playing a
significant role in helping vehicles meet stringent emission regulations.
How AdBlue Works in an SCR System
- Injection into the Exhaust Stream:AdBlue is stored in a dedicated tank on the vehicle and is
injected into the exhaust stream upstream of the SCR catalyst. The injection is precisely controlled to match engine
operating conditions and emission requirements.
- Thermal Decomposition:When exposed to the high temperatures of the exhaust gases, AdBlue decomposes
into ammonia (NH3) and carbon dioxide (CO2). This process is known as thermolysis and typically begins at around
180°C.
- Chemical Reaction in the Catalyst: The ammonia generated reacts with NO? in the SCR catalyst to form harmless nitrogen (N2) and water (H2O). Following chemical reactions take place:
- 4NO + 4NH3 + O2 → 4N2 + 6H2O
- 6NO2 + 8NH3 → 7N2 + 12H2O
- Mission Reduction: This reaction reduces NO? emissions by up to 90%, contributing significantly to cleaner exhaust output.
Challenges and Considerations
- Freezing and Storage: AdBlue freezes at -11°C, requiring heated tanks and lines in colder climates.
- Handling and Contamination: AdBlue must be stored in clean, non-metallic containers to avoid contamination, which can damage the SCR system.
AdBlue and Future Trends
With tightening emission regulations worldwide, AdBlue and SCR technology are increasingly vital. Ongoing research
focuses on enhancing catalyst efficiency, improving AdBlue dosing systems, and reducing system costs. By effectively
combining AdBlue with SCR technology, the automotive industry continues its progress toward achieving lower
emissions and a more sustainable future meeting futuristic stringent emission norms such as Euro 7, BS 7 etc.