The back diffusion of catalysts on the oxidation characteristics of particle layer during the CDPF active regeneration process

Abstract

Pressure drop is an important parameter in the regeneration process of diesel particulate filter (DPF) and catalyzed DPF (CDPF). It indicates the overall oxidation status of the particle layer on the filter channel, while the thickness change of the particle layer reflects the structure change of the particle layer on the wall surface. This research systematically investigates the effect of catalyst back diffusion on particle layer oxidation characteristics during the CDPF activity regeneration process based on pressure drop and thickness change. The experimental results show that the pressure drop of different thickness particle layers on the CDPF filter during regeneration exhibits a three-stage trend with the back diffusion effect of catalysts. When the particle layer deposition thickness is less than 80 μm, the pressure drop rate is the highest in the second stage and the beneficial effect of back diffusion in promoting the oxidation of carbon black particles leads to a significantly higher pressure drop rate in the second stage of CDPF than DPF. When the particle layer thickness exceeds 80 μm, the diameter of the effective airflow micropores (effective flow pores) inside the particle layer gradually decreases, resulting in a lower pressure drop rate in the second stage of CDPF compared to DPF. However, the duration of CDPF in the second stage is longer, leading to a shorter duration of CDPF in the third stage and a smaller total pressure drop value. The study also elucidates a time delay in the initiation of pressure drop and thickness reduction in CDPF, which is significantly smaller than the DPF’s if deposition thickness exceeds 193 μm. This phenomenon is attributed to the catalyst-induced simultaneous oxidation at both the top and bottom of the particle layer. These findings have increased the subtle understanding of the catalytic role in regulating the pressure drop and thickness of the particulate filter during regeneration. This study provides a theoretical basis for elucidating the impact of reverse diffusion of catalysts on the oxidation characteristics of particle layers and lays a research foundation for a deeper understanding of the active regeneration process of CDPF.