A Fast Start-Up On-Board Diesel Fuel Reformer for NOx Trap Regeneration and Desulfation

This paper describes recent progress in our program to develop an emissions technology allowing diesel engines to meet the upcoming 2007/2010 regulations for NOx. At the heart of this technology is the ArvinMeritor Diesel Fuel Reformer that reforms the fuel, on-demand, on-board a vehicle. The fuel reformer uses plasma to partially oxidize a mixture of diesel fuel and air creating a highly reducing mixture of Hydrogen and Carbon monoxide. In a previous publication, we have demonstrated that using a reformate rich in H₂ and CO to regenerate a NOx trap is highly advantageous compared to vaporized diesel fuel used conventionally. In this paper we present results and a strategy for performing desulfation of the traps using the fuel reformer. In contrast to vaporized diesel, which requires very high temperatures that fall outside the normal exhaust operating temperatures for diesel engines, desulfation was achieved at temperatures lower by more than 100 °C using the Plasma Fuel Reformer. This is likely to provide substantial durability benefits for the NOx traps, a major hurdle remaining in the commercialization of that technology. A lower temperature that falls within the normal engine operating range also provides an effective desulfation strategy including the possibility of some desulfation occurring simultaneously with regeneration. In this paper, we also present experimental results on the fuel reformer including hydrogen yield, soot production, start-up time and durability. The fuel reformer is capable of reaching up to 90-100% of the theoretically possible hydrogen yield at a range of fuel flow rates when used in conjunction with a downstream catalyst. The soot production is minimal both upstream (<20 mg/m3) and downstream (<5 mg/m3) of the catalyst, while the start-up time required to reach 90% of the maximum hydrogen output is around 10 seconds. The system has been operated for more than 3000 cycles without any noticeable performance degradation.