Hilite SCR-System
The future stringent emission requirements for heavy duty diesel trucks in the USA, Europe and Japan will make it necessary to use an emission control system to reduce fuel consumption, NOx, CO and particulate matter.
For many years Hydraulik-Ring develops dosing systems and components for exhaust aftertreatment systems functioning according to the SCR-principle.
The components made by Hydraulik-Ring have been used successfully in series production for many years.
The requirements dosing systems must meet as to installation size, precise dosing and cost are constantly increasing.
With Hilite / Hydraulik-Ring you have a partner who offers optimal solutions for your application requirements.
Emission standards
Road traffic has a substantial part in global climate change. Especially heavy duty vehicles cause over 50% of the particulate and NOx emission.
Particularly Diesel engines emit eight to ten times more NOx than gasoline engines although in the average they are 10-25% less thursty and thus emit less CO2 (-11%). This positive effect is anulled by the emission of particulate matter (soot) and NOx.
In past years legislation has reacted with increasingly stricter emission standards especially for diesel powered vehicles.
- PM and NOx emission proportion of HD-trucks
Roadmap of emission standards
NOx - PM trade off
- Trade-off diagram
Measures which can be taken within the engine had to reduce fuel consumption and particulate matter, but at the same time the amount of NOx increases. Starting with Euro 5 we can only get Diesel engines clean by exhaust aftertreatment.During the aftertreatment particulate matter and NOx are reduced.
If in the opposite case NOx emission is reduced by measures inside the engine, e.g. EGR (exhaust gas recirculation) which lowers the combustion temparature the amount of particulate matter and fuel consumption increase.
The SCR-system solves this trade-off by reducing fuel consumption inspite of reduction of PM and NOx.
Chemical Processes in the SCR-System
- Chemical processes
In the SCR-process (Selective catalytic reduction) ammonia reacts, in a special catalyst at a certain temperature with the NOx in the exhaust fumes.
Since pure ammonia is a dangerous substance, we inject in the SCR-process a 32.5 % aqueous solution (AdBlue®) into the exhaust tract before it enters the SCR-catalyst. Ammonia is released by means of a hydrolytic
reaction and can react with the NOx in the SCR-catalyst. Hydrolysis is the splitting of a chemical compound by reaction with water. In this split one hydrogen atom goes to one “split-off piece“ and the remaining hydroxyl group goes to the other piece.
The quantity of the injected urea depends on the NOx emission of the engine and thus on the current engine speed and torque. Therefor it is indispensable to control the injection process exactly.
