Aftertreatment System Solutions (2) for a Diesel/HVO Engine and a SI Gas Engine were thought after.
1.Characteristics and specifications of EAS for stoichiometric gas combustion concept with biomethane:
AVL described the development and layout of an exhaust aftertreatment system for a stoichiometric gas engine developed in WP4 of LONGRUN in deliverable 2.6. The report includes measurements from on a synthetic gas test bench, modelling of reaction kinetics and the layout of the exhaust aftertreatment system.
At start of the work the LONGRUN emission targets for gas engines were discussed. The contractually agreed target for NOx (30% reduction based on EURO VI = 0,32 g/kWh) was considerably lowered to 0,1 g/kWh (referring to a combined WHTC cold/ warm).
Two aftertreatment system configurations were investigated in detail:
1st EAS concept: a main three-way catalyst (TWC) and coated CNG particulate filter (CPF)
With the chosen engine-out emission traces of a WHTC, the tailpipe brake-specific NOx and the tailpipe average NH3 targets were not met. Both an improved cold start and lambda control had to be applied to meet the targets.
2nd EAS concept: close-coupled three-way catalyst (ccTWC), a main three-way catalyst (TWC), and a coated CNG particulate filter (CPF)
This concept uses a small close coupled TWC and a main TWC. The volumes of both these TWCs are equal to the TWC volume of the 1st concept. The purpose of this TWC split is to gain advantage in their overall light-off performance due to the higher exhaust temperature at the close-coupled TWC position. With this system, CO and CH4 emissions can be significantly reduced compared to the 1st EAS concept. NOx emissions in the cold WHTC are approximately 30% lower when using the 2nd EAS concept, while hot emissions remain on a similar level. This leads to overall reduced NOx emissions for the 2nd EAS concept. N2O emissions increase in the 2nd EAS concept as a side effect of increased NOx conversion. NH3 emissions are slightly lower when using the 2nd EAS concept. Still, to meet the LONGRUN project targets also for the 2nd EAS concept an improved cold start and lambda control had to be applied to meet the targets.
2.Characteristics and specifications of EAS for engines operated with Diesel fuel and Diesel and renewable fuels in Dual-Fuel operation
The deliverable report 2.7 describes the development and layout of an exhaust aftertreatment system for engines operated with Diesel fuel and optionally with blends of Hydrogenated Vegetable Oil (HVO).
At start of the work the LONGRUN emission targets were discussed and considerably aggravated for NOx and N2O. The revised targets have been based on an initial proposal from CLOVE, Oct 2020. Thus, the limit for NOx was set to 80 mg/kWh and the limit for N2O to 35 mg/kWh. Both limits refer to combined WHTC (cold/ warm). In terms of NOx, this represents a reduction compared to the current EURO VI limit by approximately 83 %. While N2O is not yet regulated in the European legislation, in US there is a limit of 100 mg/bhp-hr in the combined FTP cold/hot meaning that the LONGRUN target of 35 mg/kWh is a ~75 % reduction compared to the current US legislation.
The investigation of the optimum aftertreatment system architecture started with an experience-based assessment of 26 system configurations together with UMICORE and VOLVO who are partners of WP2, Sub-Task ST2.3.2.
Five architectures were selected for detailed investigations. Vanadium and copper-based SCR technology was used in the simulation study. While state-of-the-art Cu-SCR kinetics were taken from the AVL model database, Umicore provided syngas measurement data of the V-SCR technology. Based on this syngas data a corresponding simulation model was set up in AVL CruiseM™.
Lowest NOx and N2O emissions have been predicted with exhaust aftertreatment system configurations with two SCR-stages. The introduction of an electrical heater shows high potential to reduce emissions right after cold start. The use of Vanadium-based SCR technology is mandatory in view of N2O emission compliance.
For more information, please contact Georg Kaufmann, AVL;
You may also download LONGRUN_Advisory_Board_Meeting_Nov2022_EATS_AVL from 21 Nov. 2022