Emission legislations for the light / medium and heavy duty vehicles are becoming more and more stringent worldwide. Tightening of NOx and Particulate Matter (PM) limits further from Euro III to Euro IV levels has provoked the need of either controlling NOx from the engine measures and use PM control after-treatment devices such as Partial Flow Filters, or, controlling PM from the engine measures and use NOx control devices such as Selective Catalytic Reduction (SCR) systems. Manufacturers have adopted different strategies, depending upon the suitability, cost factors, infrastructure development and ease of maintenance of these systems.
PM Metalit®, is a partial flow filter, which captures particulates coming out of the exhaust and re-generates on a continuous basis with the help of Nitrogen Dioxide (NO2) in the exhaust. As NO2 content is generally less in a typical exhaust of a diesel engine, a Diesel Oxidation Catalyst should be used before the PM Metalit®, in order to generate NO2 from the Nitrogen Oxide (NO) available in the exhaust. The PM Metalit® systems have been in use in Europe for various OEM and Aftermarket applications for quite some time.
India is poised to introduce Bharat Stage IV (Euro IV ) emission norms from year 2010 in all major cities. Along with this, the utmost required diesel fuel with 50 ppm sulphur will also be introduced across these selected cities. The NOx emission reduction from Bharat Stage III to Bharat Stage IV level may be possible through further engine optimisation or Exhaust Gas Recirculation (EGR) system optimization. For bringing down the particulate matter, partial flow PM Metalit® would be one of the options.
Details of the PM Metalit® system, along with some of the results obtained on various world-wide applications so far, are presented in this paper. The performance evaluation results obtained during the execution of application of these systems for one of the retrofiment programmes in Korea on light/ medium duty vehicles are also presented.