Effects of ash composition and ash stack heights on soot deposition and oxidation processes in catalytic diesel particulate filter

TLDR: In this paper, the influence of ash stack height on the soot deposition and regeneration processes is studied. But the authors focus on the degradation of the CDPF catalytic layer.

Abstract: In order to provide the theorical basis for regeneration strategy and solid catalytic reaction of catalytic diesel particulate filter (CDPF), the effects of ash composition and ash stack heights on soot deposition and oxidation processes in CDPF are investigated. The MgO ash nanoparticles have an inert effect on soot oxidation process through a series of thermogravimetric experiments. Based on the visualized single-channel bench, the influence of ash stack height on the soot deposition and regeneration processes is studied. The deposition process of soot particles on the CDPF slice without ash is divided into three stages, including depth filtration, transitional filtration and soot cake formation stages. When the ash stack height is 15 μm, there are only transitional filtration and soot cake formation stages. Then, only soot cake formation stage remains when the height increases to 30 μm. During the regeneration process, the pressure drop mainly has three linear decline stages, the oxidation rates of which are 0.77, 1.78 and 0.54 Pa/s, respectively. When the ash stack height increases from 0 to 30 μm, the oxidation rate of soot layer during Ⅱ-regeneration stage decreases from 1.78 to 0.51 Pa/s. The oxidation rate is 0.51 Pa/s at 30 μm ash stack height, which is close to the 0.55 Pa/s oxidation rate of the clean DPF sample. Consequently, around 30 μm ash stack height is the limit distance of back-diffusion of active oxygen molecules, which leads to the failure of the CDPF catalytic layer.