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In underground noncoal mines the emission of nitrogen dioxide (NO2) in the exhaust of a diesel engine is more important than the emission of nitrogen oxide (NO) because of the much lower permissible exposure limit for NO2. Consequently, the tendency of aftertreatment devices such as oxidation catalytic converters (OCCs) to oxidize NO to NO2 is counterproductive. The U.S. Bureau of Mines (USBM) is investigating the effects of OCCs upon NO2 emission by using a Fourier Transform Infrared (FTIR) exhaust gas analyzer to compare the concentration of NO2 in diesel exhaust upstream and downstream of the OCC. We find that some OCCs increase the concentration of NO2 much more than others, and that over some temperature ranges the aftertreatment results in an apparent decrease in NO2 concentration.

The U.S. Bureau of Mines is conducting laboratory evaluations of the effectiveness of oxidation catalytic converters (OCC's) for application on diesel engines used in underground mines. The composition of the exhaust emitted from a diesel engine depends critically upon the fuel-to-air ratio (F/A). The F/A changes significantly with altitude, requiring regulatory derating of engines used at altitudes above 0.30 km (1000 ft). It is important to evaluate exhaust control devices for application on mining vehicles at various altitudes because mines are located at a wide range of elevations. The objective of this work is to determine the characteristics and performance of an OCC at various altitudes as well as investigate an altitude simulation technique used in a laboratory setting.