Diesel particluate filters

General information

During the combustion of diesel fuel, substances of different types and form are produced. The work of a cold engine is usually accompanied by emissions of white or blue smoke formed droplets of unburned or partially oxidized hydrocarbons, and the emissions of aldehydes whose presence in the exhaust gas is easily recognized by their characteristic smell. In the exhaust of diesel engines there are not only gaseous but also solid substances, the dimensions of which are comparable to the size of dust particles. These formations, generally termed as “particles” are considered to be harmful to human health and polluting environment.

Reducing emissions of soot particles is today one of the biggest challenges in the field of diesel engines exhaust gas cleaning. In addition to measures to reduce soot formation during the combustion of fuel directly in the engine, special attention is paid to gas filtration at its exhaust.

An effective way of cleaning gases from soot particles is their detention by means of special filters. The most widely used are the systems consisting of oxidizing type converter and diesel particulate filter. For example, Volkswagen Group has developed a particulate filter with a catalytic coating, which combines in a single package a filter with converter. In addition it allows almost continuously to burn the detained soot without adding special additives to the fuel. The latter property is achieved using a specially designed filter, and as a result of its maximum approach to the engine.

Figure 1 Diesel particluate filter

The invention relates to a catalytic filter for cleaning exhaust gases of diesel engines. This is a particle filter for the treatment of exhaust gases of diesel engines with an inlet side and an outlet side for the exhaust gas and the axial length, covered with the first catalyst that as the catalytically active component comprises platinum group metals on the carrier materials, wherein the carrier materials for platinum group metals were selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, cerium oxide, and mixtures thereof, or mixed oxides. The first catalyst further comprises at least one zeolite for the accumulation of hydrocarbons from the inlet side. The particulate filter is coated on the part of the length with the second catalyst, which does not contain zeolite. Both catalysts are applied to the particulate filter in the form of a slurry coating. This filter is used to reduce carbon monoxide, hydrocarbons and soot particles in the exhaust gases of diesel engines. This filter improves the conversion of hydrocarbons to carbon monoxide.

Particulate filters can filter particles shaped components of exhaust gases, especially the soot particles from the exhaust gases of internal combustion engines and, thus, prevent their emission into the atmosphere. In principle, for this purpose we can use both surface filters, and filters with high permeability of filter material. Surface filters are made of ceramic materials, such as silicon carbide, Cordero, aluminum titanate or mullite. With these filters filtration of up …
Posted by: Amira Smale

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