Simultaneous Reduction of Diesel Particulate and NOx Using Oxygen-Poor Nonthermal Plasma Application

Simultaneous removal of NOx and PM (particulate matter) emitted from diesel engine is realized by the barrier-type packed-bed nonthermal plasma application driven by a pulse high voltage power supply under oxygen-poor condition. The packed pellets are BaTiO₃ particle having high dielectric constant (~10,000) and carbon particulate matter is loaded among the pellets. The NOx is reduced by N radicals and the PM is incinerated by oxygen radicals induced either by NOx or by O₃ reduction under elevated local temperature condition among pellets. It is confirmed from the photographs of the pellets that carbon soot is removed under oxygen poor condition and simultaneous removal of NOx and soot occurs. An optimal value for the mass of loaded soot exists, and when the loaded soot mass is larger than the threshold value, the strength of the nonthermal plasma induced by the partial discharge is too small to reduce the NOx and soot simultaneously. Under optimized plasma condition, energy efficiencies of 2.2 g/kWh for PM incineration and 4.3 g(NO₂) /kWh for NOx reduction are achieved in the experiment.