SCR+ASC Performance During a Period of Late Diesel Injection for DPF Regeneration

More efficient removal of nitrogen oxides and particulate matter from off-road diesel engines is needed for the future emission requirements (CARB Tier 5). The dual-SCR system is proposed to enhance low-temperature performance by adding a second SCR catalyst near the engine, in addition to the main SCR catalyst located after the diesel oxidation catalyst (DOC) and particulate filter (DPF). However, the regular regeneration of the DPF must be taken care of by injecting diesel fuel so that the excess hydrocarbon that ends up in the DOC+DPF oxidizes the carbon-containing particles at high temperatures. This study used late diesel injection during the DPF regeneration period of a high-speed, common-rail diesel engine. In addition to the US EPA Tier 4F compatible off-road engine, the experimental setup included the exhaust aftertreatment system (SCR, DOC, DPF) installed into the insulated exhaust line in laboratory environment. Steady-state experiments were conducted to assess how late diesel injection affects vanadium-SCR and ammonia slip catalyst performance, with the SCR inlet temperatures from 250 to 400 °C. The study´s overall conclusion is that the late diesel injection strategy through a vanadium-ccSCR catalyst is viable for particulate filter regeneration only when SCR inlet temperatures are sufficiently high (≥ 320 °C).