Application of a Diesel Fuel Processor to Single Leg NOx Adsorber Systems

Lean NOx adsorber systems are one of the primary candidate technologies for the control of NOx from diesel engines to meet the 2007-2010 US emissions regulations. Several of the technical challenges facing this technology are regeneration at low exhaust temperatures and the efficient use of diesel fuel to minimize fuel penalty. Recent reports have shown that “reactive” reductants such as H₂, CO and oxygenated species can regenerate NO_x traps more rapidly and at lower temperatures. A diesel fuel processor system has been developed and tested in a single leg NOx adsorber configuration on a diesel engine test stand. During NO_x adsorber regeneration, this fuel processor system reduces the exhaust O₂ level to zero and efficiently processes the diesel fuel to H₂ and CO. Combined with a NO_x adsorber catalyst, this system has demonstrated NO_x reduction above 90%, regeneration of the NO_x adsorber with H₂/CO pulses as short as 1 second and fuel penalties in the 3 to 4% range at 50% load. This fuel processor system can also be used to provide the desulfation cycle required with sulfur containing fuels as well as providing thermal management for PM filter regeneration.