Heavy Duty Diesel Engine Emission Control to Meet BS VI Regulations 2017-26-0125

The next generation advanced emission regulations have been proposed for the Indian heavy duty automotive industry for implementation from 2020. These BS VI emission regulations will require both advanced NO_x control as well as advanced PM (Particulate Matter) control along with Particle Number limitations. This will require implementation of full DPF (Diesel Particulate Filter) and simultaneous NO_x control using SCR technologies.

DPF technologies have already been successfully implemented in Euro VI and US 10 HDD systems. These systems use low temperature NO₂ based passive DPF regeneration as well as high temperature oxygen based active DPF regeneration. Effective DPF and DOC designs are essential to enable successful DPF regeneration (minimize soot loading in the DPF) while operating HDD vehicles under transient conditions. DOC designs are optimized to oxidize engine out NO into NO₂, which helps with passive DPF regeneration. In addition, effective DOC design is also needed to enable exotherm generation (>600°C) by combusting fuel/HC dosed in the exhaust to allow active DPF regeneration. DOC and DPF work in tandem to minimize high soot loading in the DPF while continuously carrying out PM and PN control.

For advanced NO_x control, Selective Catalytic Reduction (SCR) is being used as the principal method. A variety of SCR catalysts have been developed over the years for effective NO_x reduction. These include vanadium based catalysts and advanced zeolite based catalysts, in different emission control systems. Vanadium SCR catalysts have demonstrated high performance and excellent durability to <600°C operation, in such Euro VI systems where passive DPF regeneration is preferred. For systems with high temperature active DPF regeneration, either Cu-zeolite based or Fe-zeolite based SCR systems have been successfully used due to their high temperature durability (>600°C). In addition, a suitably designed Ammonia Slip Catalyst (ASC) is used to minimize the emission of unused NH₃.

In this presentation, an overview of various DOC, DPF and SCR catalyst technologies and their applications will be discussed, with respect to their implementation for BS VI HDD regulations.