Pilot-Scale Aftertreatment Using Nonthermal Plasma Reduction of Adsorbed NOx in Marine Diesel-Engine Exhaust Gas

Regulations governing marine diesel engine NO_x emissions have recently become more stringent. As it is difficult to fulfill these requirements by combustion improvements alone, effective aftertreatment technologies are needed to achieve efficient NO_x reductions. In this study, we develop an effective NO_x-reduction aftertreatment system for a marine diesel engine that employs combined nonthermal plasma (NTP) and adsorption. Compared with selective catalytic reduction, the proposed technology offers the advantages of not requiring a urea solution or harmful heavy-metal catalysts and low operating temperatures of less than 150 °C. The NO_x reduction comprises repeated adsorption and desorption flow processes using NTP combined with NO_x adsorbents made of MnO_x–CuO. High concentrations of NO_x are treated by NTP after NO_x adsorption and desorption, and this aftertreatment system demonstrates excellent energy efficiencies of 161 g(NO₂)/kWh, which fulfills the most recent International Maritime Organization emission NO_x standards in the Tier II–III regulations for 2016 and requires only 4.3 % of the engine output power.