Santiago, Chile Retrofit Results In

Since 2006 the United States Environmental Protection Agency (USEPA), through the PCFV Clearing-House, has supported the Chilean environment agency CONAMA in the design and implementation of a heavy duty diesel vehicle retrofit project in Santiago.

Ten municipal service trucks (waste, delivery and construction) were retrofit with particle filters to assess their potential for reducing pollutants (especially particulates) when combined with low-sulphur diesel fuel (50 ppm or less). A number of diesel particle filter technologies were used in the testing, and the results of the project are now available on the PCFV website (Spanish language only, English version to be uploaded soon).

The results for high and medium temperature exhaust motors show a 95% reduction in carbon monoxide, 97% reduction in hydrocarbons, a 90% drop in particle mass, and a 99.9% reduction in ultra fine particles when using a continuously regenerating particulate filter.

Over one million new passenger vehicles have been equipped with diesel particulate filters (DPFs) in Europe since mid-2000. Starting in 2007, every new diesel passenger vehicle and heavy-duty on-road diesel vehicle sold in the U.S. and Canada will be equipped with a high-efficiency DPF. From 1 September 2007 all new diesel cars and vans in the European Union will have to be equipped with DPFs. DPFs are currently being retrofitted on some older engines as well. Over 200,000 on-road heavy-duty vehicles worldwide have been retrofitted with DPFs. DPFs are quite effective and have reliably demonstrated over 95% reduction in particulate emissions, in addition to providing effective control of CO and HC emissions, reducing these emissions by 90 to 99% and 58 to 82% respectively.

However, sulphur in fuel greatly reduces their efficiency. High levels of sulphur can render the DPF ineffective or even stop the engine due to unacceptable backpressure. DPFs should not be used with fuel sulphur levels greater than 50 ppm. Also, low sulphur engine oils should be used. Studies show that DPFs achieved greater efficiency and required less frequent regeneration when combined with fuel sulphur levels of 15 ppm or below. The US, EU, and Japan have decided to limit sulphur in diesel to 15 ppm or less to ensure optimal functioning of DPFs.

The PCFV Sulphur Working Group report explains that DPFs are positioned in the exhaust system to collect a significant fraction of the small particulates in the exhaust while allowing other exhaust gases to pass through the system. Since the collected particulate builds up over time, the DPF has been designed to automatically clean or "regenerate" the particle trap. This is accomplished by oxidizing or combusting the collected particulates using higher temperature exhaust. Some DPFs incorporate a catalyst into the DPF, which lowers the ignition temperature needed to oxidize the collected particles (catalyzed DPF or CDPF).