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Many diesel engines have to work at load profiles which, due to the low exhaust gas temperatures, necessitate active regeneration procedures to ensure continued engine operation and the reliability of the particulate filter. An active regeneration may be initiated via inner engine measures such as late injection. However, due to high maintenance interval and run time requirements for non-road applications the combustion of soot accumulated in the diesel particulate filter (DPF) often is realized via downstream processes. Known methods for this purpose are burner systems, systems based on downstream hydrocarbon injection (HCI) and subsequent hydrocarbon (HC)-conversion due to a catalyst or a combination of both. This paper describes an autarkic system using two-stage electro-thermal-supported hydrocarbon conversion. This system is capable to regenerate a DPF within the entire engine operating range and it is less complex than flame burner systems.

For the regeneration of diesel particulate filters with oxygen, temperatures above 550°C are normally required. The increase of the exhaust gas temperature to temperatures above 500°C demands a large amount of energy, so that strategies to reduce the regeneration temperature have to be considered. One option is the injection of a catalyst, which reduces the required regeneration temperature. Hence, a system was developed at HJS Emission Technology GmbH to inject catalyst-precursor into the exhaust gas pipe, whereby the catalysts are generated due to decomposition of the precursor in the hot exhaust gas. A technique based on the calculation of apparent activation energies was developed to characterize the soot combustion on the filter. In the first step metal oxide catalysts, like cerium(IV)oxide, manganese-oxide and iron(III)oxide were investigated after injection of their nitrate precursors dissolved in water.