Diesel Particulate Filters
Exhaust gas from diesel engines contains solids known as diesel particulate matter, which is hazardous to health. This particulate matter is largely comprised of carbon, but also contains hydrocarbons and a certain amount of metallic particles as a result of engine wear and the burning of lubricating oil. The role of a diesel particulate filter is to separate these from the exhaust gas stream.
However, the amount of particulate matter produced by even a modern diesel engine is quite significant, so the challenge is to prevent the filter from becoming blocked. One option is to simply throw the filter element away when it is dirty, and use of such disposable filters is often a viable option especially where the machine is only used intermittently. If an exhaust needs to be filtered on a long-term basis, then a means of periodically cleaning the filter (preferably without removing it from the engine) must be found.
Fortunately diesel particulate matter can be made to burn given the right conditions, producing mainly harmless carbon dioxide and water vapour as a result, so nearly all strategies for cleaning diesel particle filters in-situ rely on burning (or oxidation) for their effectiveness. The process of cleaning a diesel particulate filter is known as ‘regeneration’ and is the foremost consideration when deciding which type of system to install.