How much can we further reduce the amount of NOx in the exhaust by uing a SCR (with urea) ?
Post combustion NOx control technologies such as selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR), in addition to primary control measures can potentially reduce NOx in the exhaust to adhere to the compliance standards. Oxides of nitrogen (NOx) are among the major pollutants responsible for both smog and acid rain, formation of secondary particulate matter (PM) and ground level ozone and thus is a health concern.
SCR proves to be one of the best way to reduce NOx emission from an engine.
The NOx reduction in a SCR system depends upon the catalyst used, Flow rate of Urea, Temperature Maintained.
Few researches have claimed to reduce NOx by 70%-85%, while using Diesel and Bio oils.
A fundamental aspect of Diesel combustion is the emission from the engine of oxides of nitrogen and particulate matter, both very difficult to eliminate together in the combustion chamber.
Diesel fuel contains neither nitrogen nor oxygen and so NOx creation results from chemical changes to combustion air due to the high cylinder pressures and temperatures experienced during the combustion process. In cylinder NOx reduction techniques involve measures to reduce maximum cylinder temperatures and pressures that, paradoxically, increase the creation of particulate matter and reduce combustion efficiency resulting in increased fuel consumption. Once the need for exhaust after-treatment is accepted, it is clearly necessary to make the system work as hard as possible in order to not compromise the engine combustion process.
The choice can be made to reduce particulate matter to the absolute minimum, allowing engine-out NOx emissions to increase due to the improved combustion efficiency resulting from this measure.
The “SCR Only” technology in the exhaust system allows the NOx reduction to be made. The modest engine-out PM emissions can be brought to the necessary levels using a full-flow Diesel Particulate filter that will achieve continuous regeneration due to the high exhaust NOx levels and the high gas temperature. Forced filter regeneration may not be necessary under normal circumstances.
A new generation Zeolite based compact SCR after-treatment system with all integrated components can be designed to optimise layout and minimise weight impact, resulting in a single, simple box shaped system that includes DOC (Diesel Oxidant Catalyst), DPF (Diesel Particulate Filter), SCR (Selective Catalytic Reduction) and CUC (Clean-Up Catalyst).
All these components can be installed with extreme compactness, achieving superior conversion efficiencies for all pollutants. In the very same box the AdBlue injection/mixing devices, as well as all exhaust gas sensors needed for the after-treatment management, are required to be carefully integrated.
This allows the entire exhaust after-treatment to be contained in a compact, fully enclosed structure thereby not impeding body building or chassis equipment mounting activities.
More in detail tailpipe emission reduction levels can potentially be achieved with a robust engineering margin by means of innovative design and accurate testing and modelling activities.
The result could be a perfect tuning of DOC, DPF, SCR and CUC coatings to grant maximum conversion efficiency without significant ageing for the full vehicle life. A clear-cut design of inlet and outlet substrate areas allows for the complete exploitation of the catalyst installation in its confined volume, including the AdBlue injection area with controlled turbulence and optimised thermal insulation. This guarantees perfect AdBlue aerosol mixing and urea hydrolysis prior to reaching the SCR. With precise positioning of exhaust gas sensors, a rapid and precise monitoring of all catalytic substrates and on-going chemical reactions is thus possible to achieve.
- Badges
- Science topic
- Similar topics
- Linguistics
- Composition Studies
- Publication