1. Diesel Exhaust Particulate Characterization - Influence on DPF Regeneration Performance -
D. Foster, T. Root, T. Kawai, E. Wirojsakunchai, E. Schroeder, N. Schmidt, C. Kolodziej, R. Yapaulo
Procedure
Objective: In addition to filling performance the regeneration behavior of various DPFs with different collected soot is examined to better understand the mechanisms involved.
Lab Setup:
Kinetic Parameter Estimation
Internal thermocouples are used to get temperature distribution
The DPF is then divided into several individual “reactors” with minimal thermal gradients
The rate constant as an Arrhenius expression
DPFs are exposed to controlled temperature ramp and gas-phase emissions are monitored
Good fit with experimental data
The measured emissions are a convolution
of the emissions from the smaller
reaction volumes
Soot oxidation occurs in two distinct events:
Catalytic oxidation at low temps (~300 °C)  LT Peak
Thermal (carbon) oxidation (500 – 600 °C)  HT Peak
Temperature Ramp: Room T to 700 °C (6.67 °C/min)
Results
Applying Kinetic Parameters to in-situ Regeneration
Conclusions
For a given substrate the LT and HT kinetic parameters are similar
LT soot is characterized by tight catalyst contact
HT soot oxidation is not affected by the catalyst (loose contact)
Mode 3, Catalyzed Cordierite, LT & HT
Conceptual Model of Regeneration
Stage 1: High filtration efficiency (intact soot cake)
Stage 2: Decreasing filtration efficiency (transition)
Stage 3: Low filtration efficiency (clean DPF)
Activation Energies [kJ/mol]
Catalyzed Cordierite
Mode 4 (HT)
111 ± 2.1
Mode 4 (LT)
43.9 ± 1.6
Mode 3 (HT)
109 ± 1.4
Mode 3 (LT)
42.2 ± 1.3
Mode 5 (HT)
125 ± 2.1
Mode 5 (LT)
46.5 ± 7.2
Catalyzed SiC
195 ± 3.6
44.5 ± 1.32
Bare Cordierite (No LT reaction observed)
190 ± 3.3
Washcoated Cordierite (No LT reaction)
128 ± 4.1
Mode 3, Catalyzed Cordierite, LT
LT and HT soot contribute to filtration efficiency and pressure drop in different ways
LT soot does not significantly increase pressure drop or filtration efficiency (during both filling and regeneration)
Oxy – acetylene Burner setup
In – situ regeneration results in high thermal gradients and non-homogeneous soot oxidation rates
Pressure drop and filtration efficiency correlate well with the amount of HT soot remaining in the filter
Mode 3, Catalyzed Cordierite, HT