A novel exhaust aftertreatment technology for the simultaneous elimination of NO, NO2 and NH3 of pilot-diesel-ignited ammonia engines based on the active exhaust diversion

Abstract

The significant release of nitrogen oxides, coupled with the emissions of unburned ammonia in ammonia engines, poses a considerable threat to the environment and hinders the widespread adoption of these engines. In this study, a novel exhaust aftertreatment technology was first proposed to eliminate NO, NO₂ and NH₃ simultaneously in the ammonia-diesel dual-fuel engine without additional reductant. Based on the conventional diesel engine aftertreatment system, which consisted of the diesel oxidation catalyst (DOC), diesel particulate filter (DPF), selective catalytic reduction (SCR), and ammonia slip catalyst (ASC), a bypass tube was integrated into the system. Besides, two electrical valves were installed at the inlet of the bypass tube and the DOC, respectively. By manipulating the valves, the exhaust gas flow could be directed either through the DOC, DPF, SCR, and ASC, or alternatively, it can be redirected straight from the bypass tube to the SCR and ASC. The DOC helped to reduce a portion of the NH₃ emissions, while the remaining NH₃ from the bypass tube reacted with nitrogen oxides in the SCR. Experimental results showed that in this design, NH₃, NO and NO₂ emissions can be nearly eliminated simultaneously with the 40 %, 60 % and 80 % ammonia energetic ratios. However, when the exhaust gas passes through the oxidation catalyst, the NH₃ is oxidized into the N₂O, while the existing aftertreatment devices cannot effectively solve the N₂O, leading to an increment of the final N₂O emissions.