MS Defense: Hao-Wei Wu
Kinetics of Soot Oxidation by NO2
Department of Mechanical Engineering
Advisor: Professor Heejung Jung
Abstract: Soot is a byproduct of incomplete combustion of hydrocarbon fuels. When it is emitted to the ambient air, it is considered as a pollutant, and it can cause health hazard once inhaled into human bodies. Soot also contributes to global warming positively and negatively due to its strong light absorption characteristics and its ability to form cloud condensation nuclei. A Diesel Particulate Filter (DPF) is designed to trap soot particles emitted from diesel engines. Soot oxidation is a very important process in regenerating the DPF. The investigation on soot oxidation is done mostly under air environment with O2, H2O or NOx as oxidant, and prior research showed that small amount of NOx in the environment enhances the oxidation process. This paper focused on the soot oxidation with NO2 in N2 environments to study influence of NO2 on soot oxidation. The kinetics of soot oxidation with NO2 is investigated using the High Temperature Oxidation Tandem Differential Mobility Analysis (HTO-TDMA) with soot being oxidized in a laminar flow reactor. Soot oxidation depends on different factors such as NO2 concentrations, reactor temperature, and different residence time for the soot oxidation. Soot particles are considered non-volatile, however, they may contain more volatile organic components depending on flame conditions such as air/fuel ratios and particle size. A thermal-optical analysis of soot particles generated from diffusion flame in this study showed that about 40% of these particles consisted of organic carbon (OC), while the remaining 60% was elemental carbon (EC) for the mobility size of 40nm. The effect of the organic carbon on the soot oxidation is reduced by passing these particles through a catalytic stripper to remove OC. The data showed that the oxidation rate increased with the increase of the NO2 concentration and reactor temperature. This thesis presents kinetic parameters of soot oxidation under N2 environment with NO2 concentration in the range of 0 - 800ppm.