DUAL PATH AFTERTREATMENT SYSTEM AND METHOD UTILIZING FUEL AS AN ON-BOARD REDUCTANT FOR NOx SCR

摘要

A system and method for utilizing fuel as an on-board reductant for selective catalytic reduction of NOx is provided and includes a controller for controlling an engine to produce a lean first exhaust stream and a rich second exhaust stream that are received in respective first and second passageways of a dual path aftertreatment system. The rich second exhaust stream reacts with NOx stored in a NOx storage and reduction catalyst of the second passageway to regenerate this catalyst and generate ammonia. The first exhaust stream and the second exhaust stream having the generated ammonia are combined in a downstream common passageway to form a combined lean exhaust gas stream where the ammonia carried therein is stored or used by an SCR catalyst of the common passageway for NOx reduction. The engine is subsequently controlled to produce a rich first exhaust stream and a lean second exhaust stream.

主权项

1. A system for utilizing fuel as an on-board reductant for selective catalytic reduction, the system comprising:
an engine including a first set of cylinders configured to produce a first exhaust gas stream and a second set of cylinders configured to produce a second exhaust stream separate from the first exhaust stream; a dual path aftertreatment system including:
a first exhaust gas passageway fluidly coupled to only the first set of cylinders so as to receive only the first exhaust stream, and a second exhaust gas passageway separate from the first exhaust gas passageway and fluidly coupled to only the second set of cylinders so as to receive only the second exhaust stream, the first and second exhaust gas passageways including respective first and second NOx storage and reduction catalysts;a common exhaust gas passageway coupled to the first and second exhaust gas passageways at a junction downstream of the respective NOx storage reduction catalysts, the common exhaust gas passageway including an oxidation catalyst downstream of an SCR catalyst and configured to receive the first and second exhaust gas streams to form a combined exhaust gas stream; and a controller in communication with the engine and configured to:
control the engine at a first period of time to produce a lean first exhaust gas stream and a rich second exhaust gas stream, wherein the second NOx storage and reduction catalyst facilitates a reaction with stored NOx and the rich second exhaust gas stream to regenerate the second NOx storage and reduction catalyst and generate ammonia, and wherein the combined exhaust gas stream at the first period of time includes the generated ammonia from the second exhaust gas passageway for storage or use by the SCR catalyst to reduce NOx; andcontrol the engine at a second period of time later than the first period of time to produce a rich first exhaust gas stream and a lean second exhaust gas stream, wherein the first NOx storage and reduction catalyst facilitates a reaction with stored NOx and the rich first exhaust gas stream to regenerate the first NOx storage and reduction catalyst and generate ammonia, and wherein the combined exhaust gas stream at the second period of time includes the generated ammonia from the first exhaust gas passageway for storage or use by the SCR catalyst to reduce NOx;wherein the controller is configured to control the engine at the first and second periods of time to maintain a net lean combined exhaust gas stream in the common exhaust gas passageway upstream of the SCR catalyst, thereby enabling the oxidation catalyst to oxidize HC and CO that are present in the respective combined exhaust gas streams from the respective rich exhaust gas streams.