SCR – a simple system

The Volvo SCR system consists in principle of an AdBlue tank positioned alongside the standard diesel tank, an AdBlue pump, an injector unit and an SCR catalytic converter. This means the engine itself is not really involved in the process - except for delivering optimal combustion levels:

AdBlue and the catalyst process

1 The AdBlue tank is placed  beside the vehicle's regular diesel fuel tank.

2. AdBlue is injected into the exhaust gases in the form of finely atomised spray. Precise metering ensures the optimum blend for every operating condition.

3. In the SCR catalytic converter, nitrogen oxide is transformed into harmless nitrogen gas and water. The catalytic converter is completely integrated into the silencer.

Easily fitted on the truck 
In comparison with diesel fuel, AdBlue does not take up a lot of space. With a 4% blend, 1000 litres of diesel fuel will require just 40 litres of AdBlue. The consumption of AdBlue always remains in fixed proportion to the consumption of diesel fuel. Tanks for AdBlue are available in various volumes from 50 to 140 litres. The tanks are made of aluminium or plastic.

AdBlue and the catalyst process
AdBlue consists of an ammonia reagent - urea - and water. The heat in the exhaust system converts the urea into ammonia (NH3) and carbon dioxide (CO2). It is the ammonia that is the active substance and the main ingredient in the ongoing process in the SCR catalytic converter. In the chemical-catalytic process that follows, the nitrogen oxides (NOx) are converted into nitrogen gas (N2) and water vapour (H2O). Nitrogen gas is a natural ingredient in the air we breathe. Any possible residues of ammonia are removed in the integrated Clean-Up catalytic converter.