Are there any cheap NOx reduction methods to reduce NOx emissions from IC engines. As SCR methods are costly and consume more fuel to have after burning in the exhaust port.
It is important for this topic to differentiate between internal techniques and after treatment techniques. As far as I know internal techniques will have big problems to meet the actual and future NOx emission regulations.
The second commonly used after treatment system (beside SCR) is the lean NOx trap (LNT). Here NOx is adsorbed at the catalyst during lean phase (normal) and is reduced during short fat phases. In recent publications you will find an interesting approach of combining LNT and SCR, where no (or at least less) urea dosage is needed.
I have attached several reviews/papers dealing with different DeNOx/NOx abetment/Denitrification/... systems.
Article Trends in NO abatement: A review
Article Catalytic NOx Abatement Systems for Mobile Sources: From Thr...
Article Engines and exhaust after treatment systems for future autom...
Chapter Improvement of Performance and Emission Characteristics of D...
Article Vehicular Emissions in Review
Article Development of Di-Air - A New Diesel deNOx System by Adsorbe...
Article Review of Vehicular Emissions Trends
Article Experimental Investigation of Combined LNT + SCR Diesel Exha...
Article Review of Diesel Emissions and Control
Article Impact of Combination of EGR, SCR, and DPF Technologies for ...
The after treatment techniques are more expensive than internal techniques.
An Hybrid EGR System can be a cheap solution for NOx reduction in small turbocharged Diesel engine.
Article Hybrid EGR and turbocharging systems control for low NOX and...
Unfortunately there is no really objective and complete comparison of internal and after treatment systems regarding effect and costs (but the 2012 ICCT report: "Estimated Cost of Emission Reduction Technologies for Light-Duty Vehicles" gives a try).
As far as I know it is really hard (up to impossible) to meet the EURO VI only with internal techniques, without fundamental changes of the whole engine especially the burning chamber. But with high effort it could be done by internal techniques/EGR (see attached papers). Actual there is only a very small segment of diesel vehicles (7% in EU, no data for US) which is not equipped with after treatment systems (see "European vehicle market statistics, 2015/2016", ICCT -> link).
http://www.theicct.org/sites/default/files/publications/ICCT_LDVcostsreport_2012.pdf
http://www.theicct.org/sites/default/files/publications/ICCT_EU-pocketbook_2015.pdf
Article Strategies for emission control in diesel engine to meet Euro VI
Article Estimated Cost of Emission Control Technologies for Light-Du...
Thank you all for responding and spending your valuable time in replying my question.
The thing I want to mention is ... all the proposed solutions above are known to me. I am looking for cutting edge technologies under development or any other chemical reaction sort of techniques not just confined to IC engines, but consider my questions as a air purification technologies context rather than confining it to only IC engines internal and external treatments.
Waiting for your response... Thank you all.
Low cost is not always the cheapest over the lifetime of the engine. This is why many heavy-duty commercial engines use SCR - the added additional cost is worth the fuel savings in the long run.
One cheap method is to instruct the operators not to idle the engines when not necessary - you would be surprised how many diesel engines are idled without the need to have them running.
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