(210f) A New Uneven Dielectric Barrier Discharge Reactor for Removal of Diesel Particulate Matter

It is desirable to change mobiles powered by gasoline to those by diesel to reduce the emission of the greenhouse gas CO₂, as the energy efficiency of mobiles powered by diesel is better than those by gasoline. Unfortunately, the emission of harmful particulate matter (PM) and nitrogen oxides (NOx) from diesel mobiles is a problem; innovative after-treatment systems for removals of diesel PM and NOx are required. The authors have developed an uneven dielectric barrier discharge (DBD) reactor driven by a pulse power supply [1]. The PM removal efficiency was 0.085 g/kWh/discharge-layer. For the practical application of this uneven DBD reactor, it is required to improve the reactor structure and PM removal efficiency further. In this study, a new type of uneven DBD reactor is developed. 　The new uneven DBD reactor basically consists of 72 pieces of flat alumina plates (99.5% purity, 149x149x1.0 mm³) and 37 pieces of flat aluminum plates (130x130x0.8mm³). Several parallel grooves are engraved on one side of each alumina plate. Each flat aluminum plate is sandwiched by two alumina plates with their flat sides. Each two alumina plates of grooves on their surfaces are assembled face to face between which quartz fiber ribbons are inserted to form discharge spaces. The flat aluminum plates are alternately connected to the output side and earth terminal of a high-voltage pulse power supply. Exhaust gases from a diesel engine were introduced to the discharge spaces of the new uneven DBD reactor under the condition of 70 km/h constant speed running. PM emission rates were measured using a diesel particulate monitor (TEOM 1105, Thermo Electron Corporation) by sampling an exhaust gas from the outlet of the new uneven DBD reactor. The PM removal efficiency was calculated from the difference of PM emission rates with or without plasma discharges. The PM removal efficiency was improved to 0.13g/kWh/discharge-layer (1.5 times as many as that using the previously developed uneven DBD reactor [1]). The pressure loss in the new DBD reactor has also been improved. The PM in the exhaust gases was removed by electrostatic precipitation and by oxidation/combustion with activated oxygen species produced by plasma discharges when exhaust gases are introduced into the discharge spaces. The detail mechanisms of plasma PM removal and the further development of this technology will be discussed.

This work was supported by the New Energy and Industrial Technology Development Organization, Japan

[1] Yao S, Fushimi C, Madokoro K, Yamada K. Uneven dielectric barrier discharge reactors for diesel particulate matter removal. Plasma Chemistry and Plasma Processing. 2006;26:481-493.