Simultaneous Removal of NOX and Particles from Diesel Engine Exhaust Using Plasma and Oxidative Catalyst

Abstract

In this study, performance of a coaxial-type packed -bed plasma reactor was investigated for simultaneous removal of NO x and diesel exhaust particles (DEP) from diesel exhaust. The plasma reactor was a concentric cylinder with a single layer of catalytic pellets (gamma-alumina or Pt-alumina) set between electrodes. Pulsed square high voltage was used. 6.0 L/min of diesel engine exhaust was used as the test gas, and space velocity was 36,000 hr - 1 in this plasma reactor. The pressure drop across the reactor was about 380-540 Pa. Experiment was carried out under rich oxygen gas conditions (13-15%) and low temperature (423K). The DEP was collected by the catalytic pellets. NO was oxidized to NO 2 in the plasma and adsorbed by the catalytic pellets along with DEP. Exposing the catalysts to the pulsed plasma, collected DEP was continuously oxidized to CO 2 . More than 95% of DEP (including sub-nano size particles) from diesel exhaust was collected and oxidized using plasma and catalyst. At the same time, NO x and hydrocarbon were converted into N 2 , CO 2 and H 2 O. 73% removal rate of NO x was obtained in the test at low energy 43 J/L (44 eV/molecule NO). We found simultaneous removal effect continued for 20-30 minutes after switching off the plasma.