How does a Diesel particulate filter work
There are two types of Particulate filters: Open and closed.
The Open type works comparable to a catalytic converter. The exhaust gas is lead down a substrate of hundres of tiny channels. The channels are coated with catalytic material that incinerates the particles when they get into contact. The efficiency of an open type filter is up to 50% reduction of particulate matter (PM), but the particulate number (PN) is nearly unaffected.
The closed type filter is usually made up from highly porous ceramics or metal. Just as the open type filter, the exhaust gas is lead down the tiny channels, but this time every second channel is blocked which forces the exhaust gas to penetrate the walls between the channels to continue. In this process the particles are trapped in the filter, and a closed filter always removes at least 90% of particulate matter (PM) and particulate number (PN) – Dinex DiSiC ceramic filters guarantees a removal rate of at least 99%.
A closed filter must be regenerated frequently. This means that the trapped matter is incinerated and reduced to soot which takes up only a fraction of the space. Regeneration is triggered when the filter reaches a proper temperature, and depending on the driving pattern of the vehicle, various technologies are used for regeneration. But at some time (dependable also on driving pattern) the filter must be cleaned in order to prevent the filter to be blocked by soot, which will cause to excessive back pressure in the exhaust system. Cleaning should be done only by trained personnel using proper equipment, as the soot is extremely hazardous.