In the near future the usual summer ozone peaks exceeding the allowed threshold may be a thing of the past: the Paul Scherrer Institute (PSI) in Switzerland has developed a new type of catalytic conversion system, which filters nearly all nitrogen oxides out of diesel exhaust gases using a refined control technology. This eliminates the main cause of summer ozone build-up. The process requires a non-toxic urea solution, which future diesel engine commercial vehicles can take with them in a separate refillable tank.
Diesel engines are looked upon as relatively economic and environment-friendly, because they have a better fuel efficiency than gasoline engines. But burning diesel also has a grave disadvantage: it produces nitrogen oxides, which enhance the build-up of hazardous ozone during periods of high solar radiation. “In the end, diesel engines today are the main cause for high ozone values during summer”, says Oliver Kroecher, Exhaust Gas Aftertreatment Group Manager at PSI. Already by 2005, exhaust gas standards for diesel engines are to be tightened massively throughout Europe. And further steps reducing the threshold are planned.
To comply with the new threshold values engine manufacturers are now focussing on the so-called SCR (Selective Catalytic Reduction) technology. Here nitrogen oxides are transformed into nitrogen and water vapour using a catalytic converter and by adding a harmless urea solution. This compelling principle could establish itself in the foreseeable future in all commercial diesel-powered commercial vehicles. In future drivers should get used to refilling an additional urea tank.
Beat Gerber | alfa
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