The EPA challenge is to further reduce NOx from diesel engine exhaust. Volvo has chosen to eliminate NOx using the proven and highly efficient process of SCR: Selective Catalytic Reduction. Volvo engines with SCR technology have near-zero emissions with less fuel consumption.
Volvo's technique for further reduction of NOx is through the aftertreatment of engine exhaust. If NOx gases are selectively eliminated in a downstream aftertreatment chamber, the level of NOx produced by the engine can be significantly higher. This approach allows the engine to be retuned for maximum fuel efficiency.
SCR requires a catalytic converter into which is injected Diesel Exhaust Fluid (DEF). The primary component of DEF is water; the active organic component is urea.
Urea is a nitrogen compound that turns to ammonia when heated. When a urea-and-water solution is injected into the exhaust stream and passed over a catalyst, the urea reacts with the NOx to form nitrogen and water vapor -- two clean and harmless components of the air we breathe.
The basic elements of the Volvo SCR system:
- SCR catalyst aftertreatment chamber
- DEF tank
- Pump & lines
- Heating system
- Control & monitoring system