What is a Diesel Particulate Filter ?

A. What’s the issue with diesel particulate matter (DPM)?   Diesel particulate matter (DPM) is an exhaust-stream mix of diesel combustion by-products. At its base are particles of carbon and ash, also known as soot. Consisting mostly of unburned and incompletely oxidized lube oil and fuel, these carbonaceous particles cluster together and adsorb on their surface a sticky layer of liquid sulfate and heavy hydrocarbon. Although diesel particulate matter is very small in size (thinner than a strand of human hair).it has, in recent drawn the attention of agencies like the California Air Resource Board (CARB) and the Environmental Protection Agency (EPA). This is due to the fact that heavy-duty trucks and buses account for about one-third of NOx emissions and one-quarter of PM emissions from mobile sources. Both agencies understand the destructive nature of these particles on both human beings and our natural environment and have since instituted legislation to begin to regulate the levels of diesel particulate matter in our air.     B. Introduction     A Diesel Particulate Filter (DPF), also referred to as a soot trap, is a device designed to eliminate diesel engine smoke. Currently DPF’s are the most common method used to achieve a high level of particulate reduction, and these devices generally consist of a wall-flow type filter positioned in the exhaust system of a diesel vehicle. As the exhaust gases pass through the system, emissions of Particulate Matter (PM), Carbon monoxide (CO), and Hydrocarbons (HC) are trapped in the filter and reduced by more than 90%.   C. Technology   The DPF system consists of a filter encased in a stainless steel canister that is positioned in the exhaust stream and is designed to collect particulate emissions while allowing the exhaust gases to pass through the system as shown in the figure below.       1 | 2 | 3 | 4 | 5 | 6