Study on the effect of electrode configurations on nox removal from diesel engine exhaust

The electrical discharge phenomenon is ubiquitous in various fields of engineering to solve some complex and complicated problems. Applications of electrical discharges also include environmental remediation techniques such as water and air pollution treatments. This paper deals with the application of electrical discharge in non-thermal plasma based depollution of diesel engine exhaust. Experiments are conducted to know the effect of electrode configuration on NO_X removal efficiency. A high voltage AC test set is used as a source for the power required for the plasma reactor. The dielectric barrier discharge technique is used to dissociate the exhaust gas molecules into radicals, which further cause a number of chemical reactions to take place so that the harmful pollutants would get removed or converted into harmless gases. Two cylindrical discharge electrodes with diameters 3 mm and 5 mm, respectively, and one square electrode with a diagonal of 5 mm are tested as high voltage electrodes. Results are discussed considering three cases; in each case, removal of NO_X with one particular discharge electrode is analyzed. As the energy consumed to remove the NO_X is a major consideration, the specific energy (J/L) delivered by the source as well as the energy cost (eV/mol) are calculated for all the cases. A comparison is made among the results to determine the best electrode configuration with respect to DeNO_X efficiency, specific energy consumption and energy cost. The square electrode is found to be the best among the test electrodes, which has removed 84% of NO_X from the exhaust at a specific energy of 51.45 J/L. The energy cost in this case is 54.07 eV/NO_X.