Optimum regeneration of diesel particulate filters and NOx traps using fuel reformers

Abstract

Pollution control apparatus. An exhaust aftertreatment unit is fitted to the exhaust of an internal combustion engine and a fuel reformer provides hydrogen rich gas in an optimal way to the aftertreatment unit to regenerate the aftertreatment unit. It is preferred that the hydrogen rich gas be provided only to a portion of the aftertreatment unit at any time to regenerate that portion. Stored hydrogen may be used.

Description

BACKGROUND OF THE INVENTION [0001] This invention relates to pollution control apparatus and more particularly to the regeneration of diesel particulate filters and NOx traps using fuel reformers. [0002] Diesel engines have several advantages over other types of internal combustion engines such as durability, high efficiency, and low hydrocarbon and CO emissions. On the other hand, diesel engines have high emissions of NOx and particulates. Concerns about the adverse air quality effects of NOx and particulates have resulted in a United States requirement for large reductions of these pollutants by 2010. Recently there has also been the additional concern about the possibility that soot emission contributes significantly to global warming. [0003] Diesel particulate filter (DPF) technology has been developed to control particulates. Diesel particulate filters trap soot but require periodic regeneration to purge the filters thus to allow them to continue to trap soot without building u...

AI Technical Summary

Benefits of technology

[0012] In yet another embodiment the aftertreatment unit comprises a carousel containing a plurality of particulate filter cartridges or NOx trap cartridges. In this embodiment, at least one of the particulate filter cartridges or NOx trap cartridges receives the hydrogen rich gas for regeneration and at the same time at least another cartridge receives the engine exhaust. In a preferred embodiment the hydrogen rich gas mixes with exhaust gas upstream of the particulate filter whereby particulates combust with free oxygen in the exhaust gas. In another embodiment, hydrogen rich gas does not mix with the exhaust gas upstream of a NOx trap whereby a reducing environment required for regeneration is provided with a minimum fuel penalty, while the engine is operating in a lean mode (with excess oxygen).

Problems solved by technology

On the other hand, diesel engines have high emissions of NOx and particulates.

It is deemed unlikely that passive means of regeneration can be robust enough over wide ranges of vehicle operation to be effective.

For either a catalytic or non-catalytic system to work, however, it is necessary to generate a self-supporting burn in the filter.

It is difficult to meet all of these requirements.

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