Diesel Particulate Filter Regeneration Strategies: Study of Hydrogen Addition on Biodiesel Fuelled Engines

The diesel particulate filter (DPF) has attracted considerable attention for the reduction of particulate emissions to meet strict forthcoming emission regulations. The advantages associated with the current commercial diesel oxidation catalyst (DOC) have been implemented and combined with that of the diesel particulate filter for overall improvement in filtration and oxidation efficiencies. This study has been extended to include regeneration of the DPF, with the main focus being on the impact of hydrogen on the DOC performance by means of actual exhaust gas from a diesel engine operating on diesel, biodiesel (RME), and low temperature Fischer–Tropsch (LTFT) synthetic diesel (GTL). This technique is a key element for continuous DPF regeneration at low temperatures. A DOC has the ability to effectively oxidize hydrocarbon and carbon monoxide, as well as enhance the NO2 concentration with increased hydrogen concentration from 0 to 3000 ppm. However, hydrogen addition without the use of a DOC had no significant benefit for DPF regeneration. The combustion of different fuels illustrated in terms of NO2 formation (specifically NO2/NO ratio) over the DOC followed the order RME > GTL > diesel, which represented the ability of DPF regeneration activity in the presence of hydrogen (3000 ppm).