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The emission standards are getting increasingly strict. This presents large engineering challenges. In Europe, commercial vehicle manufacturers can currently still choose between an SCR or diesel particulate filter system to meet the requirements of the currently applicable Euro 5 standard. In the USA, combined systems are already largely used, to meet EPA 10 requirements. In Europe, most manufacturers will also implement such systems when the Euro 6 standard comes into effect in 2013.
Combined exhaust aftertreatment systems consist of a diesel particulate filter and an SCR system, which means they can provide maximum reduction of the particulate and nitrogen oxide emissions whilst simultaneously muffling the sound.
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In the first cleaning phase, exhaust gases flow through the oxidation catalyst and the diesel particulate filter to reduce the soot particles. This cleaned exhaust gas flow to the second cleaning phase in the SCR catalyst, where the nitrogen oxides are reduced with the aid of the AdBlue/DEF reducing agent. Combined systems have to have a very compact design, because no additional space can be made available for them in the vehicle.
These forward-looking exhaust aftertreatment systems are already in use today, in public transport, which paves the way for future use in commercial vehicles.
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