Comparison and Proposal for Light Duty Diesel (LDD) BS VI Solutions

The Indian government has announced that India will skip BS V legislation and move to BS VI from 2020. In order to meet this NOx emission standard, most vehicles will need to adopt either NOx Storage Catalyst (NSC) or Selective Catalytic Reduction (SCR). It is shown that these two devices have different NOx reduction temperature windows and different sulfur tolerance. In the LDD application, it is highly important to deal with NOx in the low temperature region directly after a cold start. NSC works in this region with better performance than SCR, but its sulfur tolerance is weaker than SCR. To improve the weakness in low temperature NOx control on SCR, SCRF^® which is SCR coated Diesel Particulate Filter (DPF) was developed and it demonstrated an advantage in light-off performance, due to the advantage in temperature conditions, by minimizing heat loss upstream of the SCR device. Referring to experience in the European market, various after-treatment systems were compared in terms of their NOx control ability and CO₂ emission. A Real Driving Emission (RDE) test will also be required directly after BS VI. One of the possible countermeasures in development is also introduced, and its effectiveness on controlling low temperature NOx with downstream catalyst devices is demonstrated.