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The effect of non-thermal plasma technology for particulate matter removal and nitrogen oxide emission reduction from diesel exhaust has been investigated. A sample of exhaust was cooled to the ambient temperature and passed through a dielectric barrier discharge reactor. This reactor was employed for producing plasma inside the diesel exhaust. A range of discharge powers by varying the applied voltage from 7.5 to 13.5 kV (peak-peak) at a frequency of 50 Hz has been evaluated during the experiments. Regarding the NO x emission concentration, the maximum removal efficiency has been achieved at energy density of 27 J/L. Soot, soluble organic fraction and sulphate components of diesel particulate matter have been analysed separately, and the consequence of plasma exposure on particle size distribution on both the nucleation and accumulation modes has been studied. Plasma was found to be very effective for soot removal, and it could approach complete removal efficiency for accumulation mode particles. However, when applied voltage approached 12 kV, the total number of nucleation mode particles increased by a factor of 50 times higher than the total particle numbers at the reactor inlet. This increase in nucleation mode particles increased even more when applied voltage was set at 13.5 kV.

A DeNO x process using a DC corona discharge was investigated experimentally. A mixture system of N 2 =O 2 =NO was used as a test gas. The compositions such as NO, NO 2 , N 2 O and so on were analyzed with Fourier transform infrared spectroscopy and an NO x meter. It was found that the characteristics of NO removal by corona discharge differed remarkably whether or not oxygen exists in the mixture. In regard to the spectrum of light emission from the corona discharge in N 2 atmosphere or N 2 =O 2 mixture, some N 2 bands were detected. N 2 dissociation into atomic N and N 2 radical in the corona discharge field was conjectured. Furthermore, ozone was yielded by the corona discharge in the case of the N 2 =O 2 mixture. Ozone gas from an ozonizer was added into the N 2 =O 2 mixture without corona discharge to investigate the effect of O 3 on the characteristics of NO x removal by corona discharge. In the case of the N 2 =NO mixture, the process of NO reduction was mainly controlled by N 2 radicals excited by the corona discharge. On the other hand, in the case of the N 2 =O 2 =NO mixture, NO was oxidized by ozone generated from the corona discharge and converted to NO 2 and N 2 O 5 .