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| Johnson Matthey continuously regenerating trap being evaluated at the University of Minnesota |
Background
The diesel particulate filter has been shown to reduce the amount of diesel particulate matter (DPM) emitted from diesel-powered vehicles effectively. However, the mining industry has voiced concern regarding the amount of maintenance required to institute a diesel particulate filter program. A major issue is the necessity to clean accumulated DPM from the filter. At high exhaust temperatures, DPM can be removed through combustion often initiated by a catalyst, a process known as regeneration. However, using a catalyst for regeneration often leads to the release of excessive quantities of nitrogen dioxide (NO2). This is a concern because NO2 is a very toxic gas that affects the throat and lungs. It is a fast-acting substance having a ceiling value of only five parts per million parts of air. To supply the mining industry with a diesel particulate filter that both effectively reduces DPM emissions and allows for low-temperature natural regeneration, NIOSH is working with Johnson Matthey, Inc., of Taylor, MI, to develop and test a continuously regenerating trap with NO2 control. This device continuously regenerates the filter medium with NO2, which is produced by a catalyst positioned directly upstream of the filter. NO2 is effective in catalyzing low-temperature DPM combustion soot that has accumulated on the DPF. The continuously regenerating trap system is currently used in road vehicles. A problem with NO2 slip, the process whereby NO2 is emitted from an exhaust pipe, has prevented this technology from being used in underground mines. To solve NO2 slip, Johnson-Matthey has developed a NO2 control that is currently being tested under a NIOSH contract at the University of Minnesota’s Center for Diesel Research in Minneapolis, MN.
Potential Outcome
If successful, this system will give the mining industry a diesel particulate filter that will be simple to install and use for at least 250 hours, or the period between normal engine maintenance. This should solve one of industry’s major problems relative to instituting a filter program. Successful development of this continuously regenerating trap will directly relate to lower DPM exposures for miners. Research at the University of Minnesota should be completed by late 2006, and if successful, followed by in-mine tests of the system in a U.S. metal/nonmetal mine (under the Metal/Nonmetal Diesel Partnership) in 2007. Results should be published and available to the industry in late 2007.