Discharge plasma treatment for NOx reduction from diesel engine exhaust: a laboratory investigation

A detailed study on the removal of oxides of nitrogen (NO_x ) with and without the presence of carbonaceous soot in a stationary diesel engine exhaust was carried out using pulsed electrical discharges/catalyst/adsorbent processes. The processes were separately studied first and then the cascaded processes namely plasma-catalyst and plasma-adsorbent were examined. To investigate the effect of carbonaceous soot on the plasma treatment process, the filtered and unfiltered exhaust was treated by plasma separately. In the cascaded plasma-catalyst process, the plasma treating filtered exhaust was cascaded with a reduction catalyst V₂O₅/TiO₂ using ammonia as reducing agent and in the cascaded plasma-adsorbent process, the plasma treating unfiltered (raw) exhaust was cascaded with adsorbents (MS-13X/activated alumina/activated charcoal). The enhanced NO_x removal efficiency of plasma process in the presence of soot is identified, possible pathways are summarized and the results of the cascaded processes are discussed in detail