Method and apparatus for a selective catalytic reduction system

Patent metadata

Field	Value
Publication number	US-11215098-B2
Application number	US-201716464336-A
Country	US
Kind code	B2
Filing date	Dec 11, 2017
Priority date	Dec 21, 2016
Publication date	Jan 4, 2022
Grant date	Jan 4, 2022

Abstract

Selective catalytic reduction (SCR) systems are known and are generally included in the exhaust systems of diesel engines in order to treat the exhaust gases of such engines. Such systems typically involve the introduction of a diesel exhaust fluid (DEF) into exhaust gas flowing in an exhaust passage of an engine. DEF dosing systems are limited by the amounts of DEF that can be delivered without deposits forming on surfaces of the aftertreatment system. An impaction device is dosed with DEF at a first rate based on a set of characteristics of the SCR system. A second set of characteristics, such as an available storage capacity for DEF, is determined based on a set of criteria, such as a decomposition rate of DEF. Based on the second set of characteristics, the DEF dosing rate is changed to a second rate. The dosing rate is reverted to the first rate after a second set of criteria, e.g. a lower threshold of available storage for DEF, are fulfilled.

First claim

The invention claimed is:

1. A method for a catalytic system comprising a hydrolysis catalyst, comprising:
dosing the hydrolysis catalyst with Diesel Exhaust Fluid (DEF) at a first rate based on a first set of characteristics;
determining a second set of characteristics of the hydrolysis catalyst based on a first set of criteria;
changing the first rate to a second rate based on the second set of characteristics; and
reverting the dosing rate to the first rate based on a second set of criteria, wherein the second rate is larger than the first rate and larger than a decomposition rate of DEF on the surface of the hydrolysis catalyst.

2. The method according to claim 1 , wherein the second set of characteristics comprises an available storage capacity of the hydrolysis catalyst.

3. The method according to claim 2 , wherein the dosing rate is changed to the second rate when a threshold of available storage is reached.

4. The method according to claim 1 , wherein the first set of criteria comprises an initial storage capacity of the hydrolysis catalyst and the decomposition rate of DEF on the surface of the hydrolysis catalyst.

5. The method according to claim 4 , wherein the decomposition rate of DEF is derived based on a state of an exhaust system.

6. The method according to claim 1 , wherein the step of changing the dosing rate to a second rate further comprises determining a value for the second rate based on the first set of criteria.

7. The method according to claim 1 , wherein the step of changing the dosing rate to a second rate further comprises determining a dosage time period for dosing the hydrolysis catalyst at the second rate.

8. The method according to claim 1 , wherein the second set of criteria comprises a lower threshold of available storage for DEF on the surface of the hydrolysis catalyst.

9. The method according to claim 1 , wherein the first set of characteristics comprises an effective residence time of DEF on the surface of the hydrolysis catalyst.

10. The method according to claim 9 , wherein the first rate is set so as to cause the effective residence time of DEF to be substantially zero.

11. The method according to claim 1 , wherein the first set of characteristics comprises at least one of: the decomposition rate of DEF on the surface of the hydrolysis catalyst; a temperature of exhaust; and a flow rate of the exhaust.

12. A selective catalytic reduction system for treating exhaust gas in an exhaust passage, the system comprising:
hydrolysis catalyst;
a DEF dosing unit configured to inject DEF onto the hydrolysis catalyst; and
a controller configured to carry out a method for the catalytic reduction system, the method comprising:
dosing the hydrolysis catalyst with Diesel Exhaust Fluid (DEF) at a first rate based on a first set of characteristics,
determining a second set of characteristics of the hydrolysis catalyst based on a first set of criteria,
changing the dosing rate to a second rate based on the second set of characteristics, and
reverting the dosing rate to the first rate based on a second set of criteria, wherein the second rate is larger than the first rate and larger than a decomposition rate of DEF on the surface of the hydrolysis catalyst.

13. A controller comprising a computer program product containing one or more sequences of machine-readable instructions for performing a method for a catalytic system, the method comprising:
dosing a hydrolysis catalyst with Diesel Exhaust Fluid (DEF) at a first rate based on a first set of characteristics,
determining a second set of characteristics of the hydrolysis catalyst based on a first set of criteria,
changing the dosing rate to a second rate based on the second set of characteristics, and
reverting the dosing rate to the first rate based on a second set of criteria,

wherein the second rate is larger than the first rate and larger than a decomposition rate of DEF on the surface of the hydrolysis catalyst.

Assignees

• Perkins Engines Co Ltd

Inventors

• Eden Alexis
• Shead Leo
• Silver Ronald
• Reid Ben
• Hargrave Graham
• Gaynor Paul
• Lockyer Thomas

Classifications

• F01N2610/14

  Arrangements for the supply of substances, e.g. conduits · CPC title

• F01N3/208 Primary

  Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent · CPC title

• Y02T10/12

  Improving ICE efficiencies · CPC title

• F01N2610/02

  the substance being ammonia or urea · CPC title

• F01N2610/03

  the substance being hydrocarbons, e.g. engine fuel · CPC title