Evolution of particulate matter deposited in the DPF channel during low-temperature regeneration by non-thermal plasma

Abstract

In this paper, diesel particulate filters (DPFs) were regenerated at a low temperature (100 °C) using a non-thermal plasma (NTP) injection system. The physical and chemical characteristics of the particles deposited at different regeneration stages, such as their macromorphology, microstructure, oxidation activity, surface functional groups, and soluble organic fraction, were analyzed. The results showed that when NTP flowed through the DPF, the deposited particles were oxidized, decomposed, and then removed from the channels. The soot cake dispersed into blocks from an initially dense morphology and gradually shrank until it disappeared. The residual ash lost the initial spherical structure of the carbonaceous particulate matter (PM). The weak part of the flocculant structure of PM broke first during the oxidation of NTP active substances and decomposed into a chain structure. As DPF regeneration proceeded, O atoms were continuously bonded into the PM to form oxidation intermediate products that contained C-O, C=O, and other functional groups, which improved the PM oxidation activity. Changes in the physical and chemical properties of PM at the DPF regeneration interface were more significant than those at the most downstream sampling position. The high carbon atom fraction in the soluble organic fraction (SOF) decreased, and the DPF regeneration by NTP involved the continuous removal of carbon atoms.