Measurement of Dioxin and Furan Emissions during Transient and Multi-Mode Engine Operation

This study analyzed the impact of transient and multi-mode engine conditions on emissions of dioxins and furans from a variety of diesel aftertreatment configurations. Exhaust aftertreatment systems included combinations of diesel oxidation catalyst, diesel particulate filter, and either Cu/zeolite or Fe/zeolite selective catalytic reduction catalyst. EPA method TO-9A was modified for proportional exhaust gas sampling, whereas EPA method 0023A was modified for raw exhaust gas sampling. Dioxin and furan emissions were first measured with modified method TO-9A during Federal Test Procedure transient cycles, but no toxic dioxins or furans were detected. Measurements were then taken with modified method 0023A during Ramped Mode Cycles-Supplemental Emissions Test experiments. Because more rigorous pre-cleaning and sample extraction procedures were used with this method and lower detection limits were achieved by the analytical laboratory, some dioxin and furan congeners were detected. Results from modified method 0023A showed that there was no statistical difference in dioxin and furan emissions from the same aftertreatment system containing either a Cu/zeolite or Fe/zeolite SCR system. Overall, this study showed that toxic equivalency quotient emissions of dioxins and furans from both aftertreatment configurations under transient and multi-mode cycles were negligible in comparison to EPA mandated emission levels from other sources such as waste incinerators.