Particulate filter

The particulate filter is a device able to cut the black fume (or fine particle) emissions of diesel engines. Diesel-powered cars, commercial vehicles and public transport vehicles are to a large extent responsible for atmospheric pollution which, especially in large urban centres, has now reached truly worrying levels. By fitting catalyst exhausts, a device for some years now installed on diesel engines, it has been possible to eliminate pollutant emissions in engine exhaust gases, but not black fumes or particulate. For the latter, particulate filters have recently been designed and launched on the market. Particulate filters, fitted on the exhaust lines of diesel engines, are able to considerably cut the emissions of fine particles in exhaust gases. The particulate filter is normally made with a steel casing inside which is housed a porous silicon carbide support, made with a special honeycomb structure, which represents the heart of particulate filters. The exhaust gases enter the filter and pass through the channels of the honeycomb support; the fine particles are trapped in the filter and then burned thanks to the high temperature of the exhaust gases. This process is called regeneration of the particulate filter and is crucial for preventing the filter from becoming blocked. The regeneration of particulate filters is often made easier by using a special additive, dosed in very small quantities in the fuel, but numerous methods and systems exist on the market for regenerating particulate filters. To achieve the best results as regards the cleansing of exhaust gases, particulate filters are normally fitted together with a catalyst able to eliminate the emission of carbon oxides and hydrocarbons. Modern cars are now all fitted with particulate filters, but these must also be fitted to older commercial vehicles, cars, public transport vehicles and operating machines.