Diesel NOx aftertreatment by combined process using temperature swing adsorption, nonthermal plasma, and NOx recirculation: NOx removal accelerated by conversion of NO to NO2

• Nonthermal plasma, temperature swing adsorption, and NOx recirculation are combined.
• NOx treatment efficiency is greatly improved by the conversion of NO to NO2 prior to adsorption with the small increase in adsorbent as compared to the original system.
• NOx treatment with extremely high energy efficiency is carried out.

NOx emitted from a stationary diesel engine generator was treated with a hybrid system that achieves NOx reduction by means of nonthermal plasma (NTP) and temperature swing adsorption (TSA) driven by engine waste heat. TSA produces a low-volume gas mixture of N2 and highly concentrated NOx, which is effectively reduced by NTP treatment. The performance of NOx treatment is enhanced by the re-injection of the concentrated NOx into the engine intake. In this study, in particular, an oxidation catalyst was placed before the adsorber to enhance the adsorption of NOx by converting NO to NO2, with the aim of achieving a higher removal efficiency with a low adsorbent volume. The results show that it is possible for the treatment system to be downsized using the oxidation catalyst. The system's energy efficiency (the ratio of the amount of NOx to the input electrical energy) ranges from 260 to 304 g(NO2)/kWh.