5 August 2002
Lubrizol’s Engine Control Systems (ECS) division announced that its Cattrap™ passively regenerating diesel particulate filter (DPF), a subject to emission tests by the US Mine Safety & Health Administration (MSHA), was found to be the only catalyzed DPF tested not to promote the formation of nitrogen dioxide (NO2).
MSHA has recently completed laboratory tests of a number of DPF systems from different manufacturers to establish their impact on NO2 emissions. The tests were conducted in conjunction with the MSHA diesel regulation for underground coal mines, which requires that mines retrofit existing engines with emission controls to meet a diesel particulate matter (PM) emission standard of 2.5 g/hr, effective (for nonpermissible engines) 19 July 2003. It was found that all platinum-based DPFs increased NO2 emissions to levels that might require significantly increased ventilation rates to meet MSHA exposure limits for NO2.
Commercially launched in 1991, especially for mining applications, the ECS Cattrap™ employs a base metal catalyst which facilitates passive regeneration without promoting NO2 formation. The tests, conducted over the ISO-8178 8 mode test cycle on a Deutz F6L912W test engine, showed an overall PM filtration efficiency of 88% for the Cattrap™ using 500 ppm sulfur fuel.
Based on the test results, MSHA instructed mines not to use platinum-based DPFs which increase NO2 concentrations, as shown in the listing of PM control technologies posted on the MSHA web site. At this time, the ECS Cattrap™ is the only allowed passively regenerated filter technology.
Most emission control manufacturers are currently offering platinum-based catalysts in their DPF systems, which are believed to provide the most effective support of filter regeneration. However, these catalysts oxidize a portion of the engine-out nitric oxide (NO) to NO2, which is a compound characterized by higher chemical and biological activity, and much lower occupational exposure limits than those for NO. The findings by MSHA, as well as NO2 limits from particulate filters established by California, will require that catalysts of less NO2 activity are developed for mining and certain other markets, or else actively regenerated filters be used.