Study on the prevention of face-plugging of diesel oxidation catalyst (DOC) 2018-32-0069
In order to resolve global atmospheric environmental problems, latest diesel engines for industrial machinery are required to reduce the emission of harmful gases such as carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx), and particulate matter (PM). For this reason, some of the diesel engines are equipped with exhaust gas treatment devices such as diesel particulate filter (DPF), diesel oxidation catalyst (DOC) and selective catalytic reduction (SCR) catalyst. However, such engine systems sometimes give rise to excessive back pressure increase and deterioration of the catalyst performance by the plugging of the inlet end face of DOC or DPF by soot when they are operated long under low load conditions. In order to resolve these problems, it is necessary for the system to be equipped with some additional devices to raise the exhaust gas temperature to a high level enough to burn out the soot. We attempt to resolve this plugging problem by improving DOC performance, not by additional devices.
In this study, we tried to identify the plugging material and also clarify the mechanism of plugging. For this purpose, we found the engine operating conditions which leads to the plugging and analyzed the components of exhaust gas under these conditions and soot which accumulated on the inlet end face of DOC. Also, we observed how the inlet end face was plugged as time went on, for DOC with different precious metal loadings. As a result, we found that the precious metal loading around the inlet end face had an influence on the extent of plugging. It was important to optimize the amount of precious metal.
Kota Nakano, Hiroaki Okano, Katsushi Inoue, Akira Obuchi PhD
KUBOTA Corporation, Nat'l Institute of AIST
SAE/JSAE Small Engine Technology Conference