8 September 2004
Sweden’s Emission Technology Group (ETG) has launched new urea-SCR retrofit system for the control of NOx emissions from heavy-duty engines. The system enables existing, Euro III and older diesel powered trucks, buses and machinery to achieve Euro V emission levels for all regulated pollutants.
The new system includes two major components: (1) a new type of catalytic particulate filter (which was launched by ETG earlier this year), which reduces PM emissions by over 90%, and (2) an SCR catalyst that reduces NOx by about 80%. The system is controlled using a feed-forward strategy, based on an exhaust NOx sensor signal.
The SCR (selective catalytic reduction) technology involves adding the right amount of urea—which acts as the NOx reductant—upstream of the catalyst. The urea reacts over the catalyst with nitrogen oxides to form nitrogen, carbon dioxide and water. Urea solutions (trade name “AdBlue”) will be ultimately available at most fuel stations throughout Europe, as a number of manufacturers of heavy-duty diesel engines have chosen SCR technology to meet Euro IV (2005) and/or Euro V (2008) emission standards.
In the ETG system, nitric oxide discharged from the engine is measured continuously using a sensor, and the correct amount of urea is automatically added. This strategy allows, among other benefits, to apply the system to different engines without the need for engine emission mapping or other expensive adaptations.
The SCR system is also equipped with a remote monitoring using GSM/GPRS, so the company’s technicians can follow the system and suggest service measures to the customer if necessary. One of the first customers was Connex, who tested the new system on urban buses in Växjö, Sweden.
ETG has tested the system at the AVL MTC laboratory, seeking an approval under the Swedish Environmental Zones program. In measurements performed on a bus with a Euro III engine, CO emissions were reduced by 94%, HC by 100% (removed below detection limit), PM by 93%, and NOx by 81%.