The diesel oxidation catalytic converter (DOC) has been extensively used by the underground mining industry to reduce exposure of workers to carbon monoxide (CO) and hydrocarbons (HC) emitted by diesel engines. The effects of those devices on the gaseous and diesel particulate matter emissions strongly depend on catalyst formulation. Recently, certain formulations of catalytic coatings used in DOCs marketed to underground mining were scrutinized for their potential to adversely affect emissions of the highly toxic compound, nitrogen dioxide (NO2). This study was conducted to get a better understanding of the effects that contemporary and emerging DOC technologies have on gaseous emissions. For test purposes, an EPA certified Tier 2 engine was retrofitted with two DOCs, one with a catalytic coating traditionally marketed to the underground mining industry (DOC 1), and the other with a novel coating designed to minimize undesirable NO2 emissions (DOC 2).
The evaluation was done for various steady-state engine operating conditions, generating exhaust with temperatures between 200 degrees C and 400 degrees C and one mining related transient cycle. Despite differences in catalyst formulations, both evaluated DOCs similarly reduced CO (63 to 98 %) and HC (16-32%) emissions. However, for the majority of test conditions, the NO2 emissions were found to be adversely affected by DOC 1.
Dramatic increases in NO2 emissions were observed at conditions that produced exhaust temperatures above 300 °C. Conversely, DOC 2 was found to favorably affect NO2 emissions for all test conditions. The findings of this study suggests that DOC catalyst formulations and systems can be successfully designed and optimized for underground mining applications to provide the desired reductions in CO and HC emissions without de novo generation of NO2 and in certain circumstances, provide a reduction in NO2 emissions.
Last Updated: 19/05/2020 01:13:54pm