VOCs Emission Characteristics of DPF Regeneration in National VI Diesel Engine

The diesel particulate filter (DPF) is one of the necessary devices required for diesel engines to meet the National Ⅵ emission standards. In this study, its function is tested in bench experiments, showing that the emission of volatile organic compounds (VOCs) during the regeneration of DPF assisted by the oxidized catalytic converter (DOC) is significantly increased. The "calculation guide of air pollutant emission for road vehicles" formulated in 2014 did not take into account the impact of the DPF regeneration process on VOCs emission. The tail gas of the DPF regeneration process of the National Ⅵ diesel engine was collected in the bench test, and the VOCs in the exhaust gas were quantitatively analyzed by gas chromatography mass spectrometry. Results show that the VOC emissions in the DPF regeneration process increased significantly. The total amount of VOCs is four times that during non-regeneration, and the increase is 2419.6 μg·m-3. The VOCs emitted by DPF regeneration have the highest alkane content, followed by aromatic hydrocarbons, aldehydes and ketones, and olefins, which account for the total emission of VOCs, namely 42.5%, 29.7%, 24.9% and 2.9%, respectively. Using the generation potential of ozone and secondary organic aerogel to evaluate the atmospheric activity of VOCs, we found that the increased VOCs during DPF regeneration had a significant impact on the environment. The ozone and secondary organic aerosols generated by the increased VOCs were 4272.8 μg·m-3 and 9.0 μg·m-3, respectively. The aromatic hydrocarbons and alkanes contributed the most significantly to the ozone and secondary organic aerosols. Therefore, the impact of DPF regeneration on VOCs emissions from diesel engines should be considered. From the calculation, the VOCs emission factor of the DPF regeneration is 1.03 mg·(kW·h)-1, which can serve as a reference for the development of National Ⅵ diesel vehicle VOCs emission factors.