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Time‐lapse visualization of shrinking soot in diesel particulate filter during active‐regeneration using field emission scanning electron microscopy
Author(s) -
SRILOMSAK M.,
HANAMURA K.
Publication year - 2020
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/jmi.12905
Subject(s) - soot , scanning electron microscope , diesel particulate filter , materials science , chemical engineering , diesel exhaust , particle (ecology) , field emission gun , scanning mobility particle sizer , analytical chemistry (journal) , particulates , mineralogy , chemistry , diesel fuel , particle size , composite material , combustion , particle size distribution , chromatography , organic chemistry , oceanography , engineering , geology
Summary Regeneration of diesel particulate filter (DPF) is a complicated process due to its high operating temperature and associated oxidation of soot on the filter substrate. Several oxidation mechanisms of diesel soot have been proposed based on reaction kinetics, but more information about the oxidation phenomena is needed in a practical system, that is, soot oxidation on a DPF substrate. In this work, the DPF regeneration process was, for the first time, visualized at the particle scale ex‐situ , in time‐lapse series, using field emission scanning electron microscopy (FE‐SEM). Time‐lapse transformation of soot cake layer on a real DPF was followed from initiation through the complete regeneration process. In parallel, transformation of the soot primary particle diameter was directly measured using high‐resolution transmission electron microscopy. FE‐SEM visualization clearly showed shrinkage of the soot cake layer on the DPF wall as oxidation progressed. Furthermore, diameter distribution analysis revealed a trend of shrinkage of the nanoscale soot primary particles during oxidation, supporting the FE‐SEM observations of the micron‐scale shrinkage of the agglomerated soot cake layer. Fragmentation of the shrunken soot cake layer was also observed and is suspected to be a result of locally higher gas flow that depends on surface pore morphology of the filter substrate. Lay Description In this work, the DPF regeneration process was, for the first time, visualized at the particle scale ex‐situ, in time‐lapse series, using field emission scanning electron microscopy (FE‐SEM). Time‐lapse transformation of soot cake layer on a real DPF was followed from initiation through the complete regeneration process. In parallel, transformation of the soot primary particle diameter was directly measured using high resolution transmission electron microscopy. FE‐SEM visualization clearly showed shrinkage of the soot cake layer on the DPF wall as oxidation progressed. Furthermore, diameter distribution analysis revealed a trend of shrinkage of the nano‐scaled soot primary particles during oxidation, supporting the FE‐SEM observations of the shrinkage of the micron‐scale agglomerated soot cake layer. Fragmentation of the shrunken soot cake layer was also observed and is suspected to be a result of locally higher gas flow that depends on surface pore morphology of the filter substrate. Further detail mechanism about transformations of the soot cake layer was additionally discussed based on electrostatic attraction.