The Application of Diesel Particle Filters—From Past to Present and Beyond

Diesel particle filters are primarily applied to remove particulate matter from the exhaust gas of diesel engines. They have become a standard component in exhaust aftertreatment systems when it comes to meeting the latest legislative emission targets. In systems currently applied coated diesel particle filters represent one component among a few others. Filters are combined with diesel oxidation and SCR-catalysts in order to reduce particulate and gaseous emissions in one system. Based on a brief description of particulate traps, as applied in buses and diesel cars in the 1980s, historical engineering challenges of the application are highlighted. Material/coating durability aspects, the deposition of high amounts of ash, use of low quality fuel and exhaust temperature restrictions for soot removal, as they were given back in the 1980s, are outlined. The paper describes technological key enablers, such as the availability of low-sulphur diesel fuel, which allowed the integration of particle filters downstream of an oxidation catalyst (DOC). Functionally a continuous soot removal can be achieved, limiting the necessity of fuel-consuming active regeneration events. In addition the paper discusses sources of ash and how the application of low-ash oils can lower the amount of ash accumulated in the filter system significantly. Finally future challenges of the particle filter application as a standard component in aftertreatment systems of combustion engines are outlined. Among these are the reactivity of soot, originating from the use of alternative fuels as well as the use of fuel with higher Sulphur content.