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Decontamination plasma way: Would a future solution? (Inspired by The Research, February 1999)

Keywords: treatment, exhaust, pollution, plasmas catalyst.

The gaseous emissions from diesel engines are more severely limited by European standards. To achieve compliance, new technologies are developed.

For trucks, there are high-performance catalysts such as those where ammonia from urea hydrolyzed, acts as reducing agent. But they must operate at elevated temperatures, generally above 200 ° C. Now, these temperatures are not reached by the exhaust gases from cars during startup or urban journeys.

This catalyst developed by Siemens is composed of electrodes between which a plasma is created. It measures about 20 6 cm long cm in diameter. (Photo Siemens, II / 98).

Unless you use an additional warming of gas, which would be very expensive energy, the solution requires further purification path. To do this, the Siemens Group in collaboration with the German Ministry of Research, has developed a plasma phase catalysis process.

Reduction of nitrogen oxides in exhaust gas 220 ° C of a diesel engine through a dielectric plasma discharges and

The principle of contacting the exhaust gas with a plasma with high energy electrons will initiate on the one hand, the oxidation of carbon compounds to carbon dioxide and water and, on the other hand, reduction of nitrogen oxides of nitrogen. The plasma is obtained only by causing a brief electric discharge (a few nanoseconds) within the gas. But the effectiveness of this method considerably decreases the water content and oxygen becomes large, the reduction of nitrogen oxides then being very disadvantaged.

Reduction of NOx according to the technology used.

To remedy this problem, the researchers placed the system in series with a conventional catalyst such as those mentioned above. They observed that through this association, it was operating at temperatures below 200 ° C. For example, the reduction of oxides is evaluated 60% if the temperature is only 100 ° C. The quantity of urea to be hydrolyzed is also much lower in these conditions. The first tests are conducted at the University of Erlangen. The time required to develop prototypes, and develop an effective diet to ensure the landfill is estimated at six or seven. To learn more about this technology, visit the Siemens website

always ongoing research

Despite the date of this article, 1999, searches are still ongoing especially at CNRS, here is a summary document: Remediation of waste gases by Plasma (CNRS and GREMI)

The French manufacturers Renault and PSA récement co-filed a patent entitled: non-thermal plasma reactor and motor vehicle exhaust line including this reactor

Position papers:

- Original article Siemens (German)
- Remediation of waste gases by Plasma (for the GREMI, Orléans University and CNRS)
- Patent PSA-Renault (download reserved for members)
- Visit GREMI Site


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