Simultaneous removal of NO{sub}x and particles from diesel engine exhaust using plasma and oxidative catalyst

摘要

In this study, performance of a coaxial-type, packed-bed plasma reactor was investigated for simultaneous removal of NO{sub}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{sup}(-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{sub}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{sub}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{sub}x and hydrocarbon were converted into N{sub}2, CO{sub}2 and H{sub}2O. 73% removal rate of NO{sub}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.