Method and apparatus for no2-based regeneration of diesel particulate filters using recirculated NOX

Abstract

In a method for performing NO2-based regeneration of a diese! particulate filter (DPF) using recirculated NOx, the DPF is regenerated by oxidizing soot in the DPF with NO2 so that CO, CO2, and NO are formed, at least some NOx is recirculated from a takeoff point to a point upstream of the takeoff point. NO2 can be formed by reacting the recirculated NO with 02. During regeneration of the DPF, at least some of the NO2 that oxidizes soot in the DPF is recirculated ISI 02 or formed from recirculated NO that is reacted with 02 to form NO2. An exhaust aftertreatment system for performing NO2-based regeneration of a diesel particulate filter (DPF) using recirculated NOx is also disclosed.

Description

[0001]The present application is related to commonly assigned, copending application Ser. No. ______ (Attorney Docket No 000009-260) entitled METHOD AND APPARATUS FOR REGENERATING A CATALYZED DIESEL PARTICULATE FILTER (DPF) VIA ACTIVE NO2-BASED REGENERATION WITH ENHANCED EFFECTIVE NO2 SUPPLY, filed on the same date as the present application, and claims the benefit of U.S. Provisional Application 61 / 063,900, filed Feb. 7, 2009, entitled METHOD FOR MAXIMIZING SOOT REDUCTION CAPACITY OF NO2 REACTANT FOR ACTIVE NO2 REGENERATION OF PARTICULATE FILTER.BACKGROUND AND SUMMARY[0002]The invention relates to methods and apparatus for regeneration of diesel particulate filters (DPFs), that is, removal of accumulated particulate matter or soot from the DPF, and more particularly to methods and apparatus involving an oxidation reaction with NO2.[0003]The most common method for removal of soot from a DPF is oxidation of the trapped soot to produce gaseous products (CO2 and CO) which can pass thro...

AI Technical Summary

Benefits of technology

[0004]Presently known and implemented solutions for DPF regeneration comprise active O2-based regeneration systems, passive NO2-based regeneration systems, or a combination thereof. Active O2-based regeneration systems raise the temperature of the reactants, through a variety of methods, in order to establish and sustain an O2 / soot reaction. During active O2-based regenerations, substantially all soot removal is via reaction with O2. Passive NO2-based systems use catalyzing agents to form NO2 from NO already present in the exhaust gas, typically in an oxidation catalyst upstream of the DPF, and to reduce the activation energy required for a NO2 / soot reaction to occur at temperature levels achievable in some portion of the normal engine, operation range without active thermal management of the reactants.

Problems solved by technology

The primary limitation of passive NO2-based regeneration is its inability to guarantee adequate regeneration of the DPF in all applications.

The primary limitations of O2-based regenerations are lower maximum DPF soot loading levels, which must be observed, and a significantly higher temperature requirement than is necessary for NO2-based regeneration.

The higher temperature requirement, as well as the need for more frequent regenerations, can lead to deterioration in the performance and durability of all affected exhaust aftertreatment devices, including those downstream of the soot filtration and regeneration components, such as an SCR system.

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