Dual path aftertreatment system and method utilizing fuel as an on-board reductant for NOx SCR

Patent metadata

Field	Value
Publication number	US-9765666-B2
Application number	US-201615018993-A
Country	US
Kind code	B2
Filing date	Feb 9, 2016
Priority date	Feb 11, 2015
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

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.

First claim

What is claimed is:

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, wherein the first set of cylinders comprises one half of the total cylinders of the engine, and the second set of cylinders comprises the other half of the total cylinders of the engine;
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; and
control 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;

wherein the first NOx storage and reduction catalyst in the first exhaust gas passageway comprises a first three-way catalyst (TWC) disposed upstream of a first combined TWC and lean NOx trap (TWLNT);
wherein the second NOx storage and reduction catalyst in the second exhaust gas passageway comprises a second TWC disposed upstream of a second combined TWC and TWLNT, and wherein the oxidation catalyst comprises an ammonia slip catalyst disposed upstream of a CO slip catalyst.

2. The system of claim 1 , wherein controlling the engine at the first period of time to produce the lean first exhaust gas stream and the rich second exhaust gas stream includes controlling the engine to combust lean fuel/air mixtures in the first set of cylinders and rich fuel/air mixtures in the second set of cylinders.

3. The system of claim 2 , wherein controlling the engine at the second period of time to produce the rich first exhaust gas stream and the lean second exhaust gas stream includes controlling the engine to combust rich fuel/air mixtures in the first set of cylinders and lean fuel/air mixtures in the second set of cylinders.

4. The system of claim 3 , wherein the rich fuel/air mixtures are richer than stoichiometric condition and the lean fuel/air mixtures and leaner than stoichiometric condition.

5. The system of claim 3 , wherein the total number of cylinders of the engine comprises four.

6. The system of claim 1 , wherein at a third period of time after the first period of time and before the second period of time, the controller is configured to control the engine to combust lean fuel/air mixtures in all cylinders thereby producing lean first and second exhaust gas streams during the third period.

7. The system of claim 1 , wherein at least a portion of the generated ammonia from the second exhaust gas passageway is stored on the SCR catalyst.

8. The system of claim 6 , wherein each of the first and second exhaust gas passageways include a first sensor configured to sense a parameter indicative of an amount of NOx in the respective passageways, and a second sensor configured to sense an amount of ammonia in the respective passageways.

9. The system of claim 8 , wherein the controller is configured to control the engine during the third period of time to produce the lean first and second exhaust gas streams in response to the sensed amount of ammonia and NOx.

10. The system of claim 9 , wherein the controller is configured to control the engine to transition from the control of the engine at the third period of time to the control of the engine at the second period of time in response to a determination based on input from the first and second sensors that an amount of ammonia stored on the SCR catalyst is below a predetermined threshold.

11. The system of claim 10 , wherein at a fourth period of time after the second period of time, the controller is configured to control the engine to combust lean fuel/air mixtures in all cylinders thereby producing lean first and second exhaust gas streams during the fourth period.

12. The system of claim 1 , wherein the SCR catalyst comprises a first SCR catalyst and a second SCR catalyst, the second SCR catalyst disposed downstream of the first SCR catalyst and upstream of the ammonia slip catalyst.

13. A method for utilizing fuel as an on-board reductant for selective catalytic reduction, the method comprising:
controlling an engine at a first period of time to combust a lean first fuel/air mixture in a first set of cylinders of the engine and produce a lean first exhaust gas stream, and to combust a rich second fuel/air mixture in a second set of cylinders of the engine and produce a rich second exhaust gas stream separate from the lean first exhaust stream, wherein the first set of cylinders comprises one half of the total cylinders of the engine, and the second set of cylinders comprises the other half of the total cylinders of the engine;
receiving the lean first exhaust gas stream in only a first exhaust gas passageway of a dual path aftertreatment system, the first exhaust gas passageway being fluidly coupled to only the first set of cylinders, and receiving the rich second exhaust gas stream in only a second exhaust gas passageway of the dual path aftertreatment system, the second exhaust gas passageway being fluidly coupled to only the second set of cylinders and separate from the first exhaust gas passageway, the first and second exhaust gas passageways including respective first and second NOx storage and reduction catalysts;
regenerating the second NOx storage and reduction catalyst with the rich second exhaust gas stream and generating ammonia;
combining the rich second exhaust gas stream having the generated ammonia and the le

Assignees

• Smith Michael A
• Dimaggio Craig L
• Wuttke Jeffrey P
• Brocker Andrew
• Hamilton Travis T
• Hardman Ken
• Baldwin-Squib Cody
• Fca Us Llc

Inventors

• Smith Michael A
• Dimaggio Craig L
• Wuttke Jeffrey P
• Brocker Andrew
• Hamilton Travis T
• Hardman Ken
• Baldwin-Squib Cody

Classifications

• F01N2430/06

  by varying fuel-air ratio, e.g. by enriching fuel-air mixture · CPC title

• F01N2430/02

  by cutting out a part of engine cylinders · CPC title

• F01N2900/1814

  Tank level · CPC title

• F01N2240/25

  an ammonia generator · CPC title

• F01N3/0814

  combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts · CPC title