Reactivity influence on carbonaceous particle layer break-up and relocation events in O2-based model filter regeneration

Abstract

Understanding the influence of soot reactivity on layer break-up and particle structure detachment and transport during diesel particulate filter regeneration is essential for optimizing aftertreatment performance. Seven carbon blacks with differing reactivity were investigated as reactive particle model systems. The oxidation behavior was characterized by temperature-programmed oxidation, revealing a wide reactivity range, with the peak oxidation temperature spanning from 817 K for a propane-soot reference to 894-976 K for the carbon blacks. This paper examines the regeneration of a model filter channel in situ with high temporal and spatial resolution. The filter is loaded with 10 mg carbon black particles and then regenerated. The regeneration of the filter is analyzed by varying the particle system under constant regeneration conditions at a gas temperature of 823 K and a channel inlet gas velocity of 60 m/s. In addition, the layer height and temperature are varied for a selected carbon black, and a more reactive hydrocarbon mixture was added to the particle layer of the selected carbon black. In selected experiments high-speed imaging of the model filter channel enabled direct observation of layer break-up and particles detaching from the filters surface. Image-based analysis enables the quantification of the black surface area reduction and isolated particle structures. All carbon blacks showed a reaction of the carbonaceous particles, with little layer break-up and formation of isolated structures, as well as minimal detachment events (0-10 events per experiment). Introducing more reactive hydrocarbons to the particle layer markedly increased fragmentation and particle relocations to more than 500 events.