Throughout the world, regulations on gases emitted by internal combustion engines are increasingly stringent, with the aim of minimizing emissions to values close to zero, regardless of the type of fuel used. In order to do this, sophisticated technologies must be adopted to check combustion, together with post-treatment systems of the most complex exhaust gases.
The measures adopted for the combustion can very well reduce emissions, but at the risk of penalizing other engine performances: silent operation, specific power and fuel consumption.
Instead, post-treatment technologies of exhaust gases can make it possible to overcome this conflict.
Modern diesel engines, with fuel injection systems such as Common Rail have NOx emissions that are 95% lower than the engines produced in the early 1990s.
The post-treatment system called Selective Catalytic Reduction (SCR) allows a further reduction in NOx levels of up to 95 %. The SCR calls for the injection of a liquid reducing agent in the exhaust gases by using the FreeNOx system developed by Magneti Marelli. The reducing agent is a solution of 32.5% urea in water (generically called AdBlue or Diesel Exhaust Fluid, DEF), stored in a separate tank on the vehicle. In order to reduce the NOx, the reducing agent is pressurized and injected in suitable quantities in the engine exhaust gases, upstream the SCR catalytic converter. Through a process of thermolysis and hydrolysis, NH3 ammonia is released from the solution and reacts with the NOx in the SCR catalytic converter, turning them into nitrogen and water.
The urea solution dosing system was developed by Magneti Marelli Powertrain starting from 2007, for applications on both light and heavy vehicles, on and off-road.
The system is aimed at applications that have to satisfy Tier2 Bin5 (U.S.) and Euro 6 (EU) requirements for light and heavy vehicles, and STAGE4/TIER 4 Final (EU/U.S.) requirements for off-road applications, and it is suited for both original equipment and retrofit applications.
The Magneti Marelli FreeNOx system consists of the following devices:
The following components complete the management system of the SCR catalytic converter:
Through its business lines, Magneti Marelli is able to supply a complete SCR system that includes, in addition to the reagent control and injection devices (Magneti Marelli - Powertrain), the exhaust line with the SCR catalytic converter (Magneti Marelli - Exhaust Systems), and the storage tank for the urea solution (Magneti Marelli - Plastics).
This way, Magneti Marelli can provide a technical solution optimized with respect to the customer’s needs, both under a technical and system cost standpoint.