Simultaneous Removal of PM and NOx in Combustion Exhaust Gas by Non-thermal Plasma

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Electrical discharge process using corona is effective in reducing particulate matter(PM), nitrogen oxides(NOx) and total hydrocarbon(THC) contained in diesel engine exhaust. We experimentally evaluate the application of DC corona discharge reactor to reduce the PM, NOx and THC from diesel exhaust. Particulate trapping in a corona reactor can be accomplished by electrostatic precipitation. The accumulated PM on a nichrome electrode of reactor can be regenerated by the controlled burning process. In a corona reactor, NO is oxidized to NO_2 and NO_2 reacts with H_2O contained in exhaust. NOx decreases as a result of HNO_3 formation in a reactor, and successively HNO_3 is neutralized on the filter paper contained alkali. A corona reactor consists of cylindrically-shaped outer electrode made of stainless steel and central electrode made of rolled nichrome wire. In this study, the effects of corona voltage, current and the space velocity of reactor on soot collection efficiency, NOx removal rate and THC reduction rate are investigated. Also discussed is the particle size distribution of soot collected by a reactor.The conclusions are summarized as follows ;(1)A corona discharge reactor is capable of reducing diesel particulate matter PM, nitrogen oxides NOx and total hydrocarbon THC levels simultaneously.(2)The soot collection efficiency of 45-95% is obtained at a corona input power of 5-10W (1-5kV), under the space velocity of 9200-29500/h, while the NOx removal rate of 2-10%, THC reduction rate of about 15% are observed.(3)Particulate trapping of fine-particles less than 1μm, which has harmful effects on the human body, can be accomplished by corona discharge process.