Assessment of Diesel Particulate Control—Direct and Catalytic Oxidation

The technology for disposal of diesel particulate by oxidation is discussed. Properties of typical diesel particulate are given, including the size (on the order of 0.1 μm diameter) and the presence of a portion extractable with an organic solvent. Available reaction rate data are used to derive particle lifetimes at various temperatures; these exceed likely exhaust system residence times. The use of catalysts to increase oxidation rates and lower ignition temperatures is discussed. Small amounts of many metals increase the rate of oxidation and lower the ignition temperature. Chemical reactor theory is used to derive ignition and operational characteristics of trap/oxidizers. Special note is taken of the tendency of these devices to go rapidly from a cold unignited state to an ignited state close to the adiabatic flame temperature of the fuel. Design techniques to ameliorate undesirable temperature excursions are presented.