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Catalytic converter gets the pollution out of diesel engines
September 08, 2004In 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.
Zero emission for combustion engines is long term objective
PSI scientists have now developed a practicable SCR catalytic converter that disposes over 90% of the nitrogen oxides in exhaust gases. Kroecher describes the PSI advantages over other SCR prototypes: "Our converter has minimal dimensions and can prevent the escape of ammonia generated during the reaction, thanks to an ingenious regulating system." To optimise the nitrogen oxide dismantling, the amount of urea added adapts continuously to different drive phases. "Our regulator system all but anticipates the engine activity and can therefore react fast enough to changes", says Kroecher.
With the nitrogen oxide output going down the problem with harmful soot particles from diesel engines will also be defused. While diesel engines could be tuned to a low soot production, this will however increase the nitrogen oxides. The new SCR catalytic converter strongly reduces this drawback. PSI researchers want to achieve even more. Kroecher: "In the long run, we're working on zero-emission concepts, in order to develop combustion types creating no other pollutants than carbon dioxide."
The work on the SCR catalytic converter was carried out together with industry partners and with the support of the Swiss Federal Office of Energy. The Measurement and Control Laboratory at the Swiss Federal Institute of Technology (ETH) in Zurich developed the advanced catalytic converter process strategy. Commercial products based on the PSI know-how will be introduced to the market in the near future.
Paul Scherrer Institut (PSI)
Zero emission for combustion engines is long term objective
PSI scientists have now developed a practicable SCR catalytic converter that disposes over 90% of the nitrogen oxides in exhaust gases. Kroecher describes the PSI advantages over other SCR prototypes: "Our converter has minimal dimensions and can prevent the escape of ammonia generated during the reaction, thanks to an ingenious regulating system." To optimise the nitrogen oxide dismantling, the amount of urea added adapts continuously to different drive phases. "Our regulator system all but anticipates the engine activity and can therefore react fast enough to changes", says Kroecher.
With the nitrogen oxide output going down the problem with harmful soot particles from diesel engines will also be defused. While diesel engines could be tuned to a low soot production, this will however increase the nitrogen oxides. The new SCR catalytic converter strongly reduces this drawback. PSI researchers want to achieve even more. Kroecher: "In the long run, we're working on zero-emission concepts, in order to develop combustion types creating no other pollutants than carbon dioxide."
The work on the SCR catalytic converter was carried out together with industry partners and with the support of the Swiss Federal Office of Energy. The Measurement and Control Laboratory at the Swiss Federal Institute of Technology (ETH) in Zurich developed the advanced catalytic converter process strategy. Commercial products based on the PSI know-how will be introduced to the market in the near future.
Paul Scherrer Institut (PSI)
Ozone Current Events and Ozone News RSSWildfires Cause Ozone Pollution to Violate Health Standards, New Study Shows
Wildfires can boost ozone pollution to levels that violate U.S. health standards, a new study concludes.
2008 ozone hole larger than last year
The 2008 ozone hole - a thinning in the ozone layer over Antarctica - is larger both in size and ozone loss than 2007 but is not as large as 2006.
International Field Campaign examines impact of beetle kill on Rocky Mountain weather, air quality
Mountain pine beetles appear to be doing more than killing large swaths of forests in the Rocky Mountains. Scientists suspect they are also altering local weather patterns and air quality.
Pine Bark Beetles Affecting More than Forests
Pine bark beetles appear to be doing more than killing large swaths of forests in the Rocky Mountains. Scientists suspect they are also altering local weather patterns and air quality.
IMPACTS: On the Threshold of Abrupt Climate Changes
Abrupt climate change is a potential menace that hasn't received much attention. That's about to change. Through its Climate Change Prediction Program, the U.S. Department of Energy's Office of Biological and Environmental Research (OBER) recently launched IMPACTS - Investigation of the Magnitudes and Probabilities of Abrupt Climate Transitions - a program led by William Collins of Berkeley Lab's Earth Sciences Division (ESD) that brings together six national laboratories to attack the problem of abrupt climate change, or ACC.
Pollution, everyday allergens, may be sources of laryngitis
Everyday exposure to environmental tobacco smoke, allergens, and air pollution may be the root of chronic cases of laryngitis, says new research presented at the 2008 American Academy of Otolaryngology - Head and Neck Surgery Foundation (AAO-HNSF) Annual Meeting & OTO EXPO in Chicago, IL.
Breaking harmful bonds
Everybody loves the way breakfast eggs conveniently slide off of Teflon without leaving any pesky pieces of egg in the pan. Indeed, the carbon-fluorine bond at the heart of Teflon cookware is so helpful we also use it in clothing, lubricants, refrigerants, anesthetics, semiconductors, and even blood substitutes.
Even seaweeds get sunburned
It is red, it burns and itches: a sunburn on our skin. However, too much sun is not only bad for humans. Many plants react sensitively to an increased dose of ultraviolet radiation, too. Yet they are dependent on sunlight.
Drier, warmer springs in US Southwest stem from human-caused changes in winds
Human-driven changes in the westerly winds are bringing hotter and drier springs to the American Southwest, according to new research from The University of Arizona in Tucson.
Newly detected air pollutant mimics damaging effects of cigarette smoke
A previously unrecognized group of air pollutants could have effects remarkably similar to harmful substances found in tobacco smoke, Louisiana scientists are reporting in a study scheduled for presentation today at the 236th National Meeting of the American Chemical Society.
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