Method and exhaust treatment system for treatment of an exhaust gas stream

Patent metadata

Field	Value
Publication number	US-10837338-B2
Application number	US-201615750159-A
Country	US
Kind code	B2
Filing date	Aug 26, 2016
Priority date	Aug 27, 2015
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

Methods and systems are provided for treatment of an exhaust stream, comprising nitrogen oxides. The method comprises a first oxidation of compounds comprising one or more of nitrogen, carbon and hydrogen in the exhaust stream; and a control of a first supply of a first additive to the exhaust stream to prevent an accumulation of soot exceeding a soot threshold value in a catalytic filter. This soot threshold value depends at least on operating conditions for the combustion engine, which impact a level of a flow for the exhaust stream. A first reduction of nitrogen oxides is performed using reduction characteristics of a catalytic coating in the catalytic filter and the supplied first additive. Soot particles are caught and oxidized. A control of a second supply of a second additive is performed, following which a second reduction of nitrogen oxides is performed using the first and/or the second additive in a reduction catalyst device.

First claim

The invention claimed is:

1. A method for treatment of an exhaust stream from a combustion in a combustion engine in an exhaust treatment system, said method comprising:
a first oxidation of compounds comprising one or more of nitrogen, carbon and hydrogen in said exhaust stream using a first oxidation catalyst;
a regulation of a first supply of a first additive into said exhaust stream using a first dosage device in the exhaust treatment system, arranged downstream of said first oxidation catalyst, wherein application of said first supply is regulated to thereby prevent an accumulation of soot that exceeds a soot threshold value S th in a catalytic filter, arranged downstream of said first dosage device, wherein said soot threshold value S th is determined based on at least one or more operating conditions for said combustion engine, impacting a level of a flow for said exhaust stream;
a first reduction of nitrogen oxides NO x in said exhaust stream using reduction characteristics in an at least partly catalytic coating comprised in said catalytic filter, and using said first additive;
a catching and oxidizing of soot particles in said exhaust stream using said catalytic filter;
a regulation of a second supply of a second additive into said exhaust stream using a second dosage device, arranged downstream of said catalytic filter; and
a second reduction of nitrogen oxides NO x in said exhaust stream, using at least one of said first and said second additive in a reduction catalyst device, arranged downstream of said second dosage device.

2. The method according to claim 1 , wherein said regulation of said first supply is carried out based on said soot threshold value S th , to cause a soot oxidation in said catalytic filter based on nitrogen dioxide NO 2 .

3. The method according to claim 1 , wherein, except for time-limited special operating conditions instances for said combustion engine, said regulation of said first supply of said first additive is based on said soot threshold value S th , wherein said first supply of said first additive results in nitrogen dioxide NO 2 being supplied to said catalytic filter, wherein the nitrogen dioxide NO 2 is used to facilitate said oxidation of soot particles in said catalytic filter.

4. The method according to claim 3 , wherein said time-limited special operating conditions comprise transient operating conditions for said combustion engine.

5. The method according to claim 3 , wherein said time-limited special operating conditions comprise operating modes for which said first reduction of nitrogen oxides NO x is given a higher priority than said oxidation of soot particles.

6. The method according to claim 3 , wherein said time-limited special operating conditions comprise one or more of:
operating conditions in connection with an increased power output; or
operating conditions in connection with a cold start.

7. The method according to claim 1 , wherein said regulation of said first supply of said first additive is based on said soot threshold value S th , wherein said first supply of said first additive results in nitrogen dioxide NO 2 being supplied to said catalytic filter, wherein the nitrogen dioxide NO 2 is used to facilitate oxidation of soot particles in said catalytic filter.

8. The method according to claim 1 , wherein said one or several operating conditions for said combustion engine, impacting said level of said flow for said exhaust stream, comprises one or more from the group:
an engine speed for said combustion engine;
a torque emitted by said combustion engine;
a power output from said combustion engine;
an exhaust gas recirculation level (EGR-level) for said combustion engine;
a function for a gas exchange configuration used by said combustion engine;
a function for an exhaust brake acting on said exhaust stream;
a function for an inlet damper, which impacts an air intake to said combustion engine; or
a state for said combustion engine.

9. The method according to claim 1 , wherein a determination of said soot threshold value S th is determined based on said one or more operating conditions, in such a manner that said soot threshold value S th is allocated a smaller value for one or more operating conditions resulting in a higher level of said flow for said exhaust stream, and a greater value for one or more operating conditions, resulting in a lower level of said flow.

10. The method according to claim 1 , wherein said level for said flow for said exhaust stream is related to an impact that said accumulation of soot has on a fuel consumption for said combustion engine.

11. The method according to claim 10 , wherein said accumulation of soot has a greater impact on said fuel consumption at a high level for said flow for said exhaust stream than at a low level for said flow.

12. The method according to claim 1 , wherein said regulation of said first supply and/or said regulation of said second supply depends on additional operating conditions for said combustion engine comprising one or more in the group of:
a fuel type used to operate said combustion engine;
a used operating mode for said combustion engine; or
an altitude at which said combustion engine operates.

13. The method according to claim 1 , wherein a determination of said soot threshold value S th is also based on one or more operating conditions of the exhaust treatment system from the group of:
a state for said catalytic filter of the exhaust treatment system; or
a state for one or more other components in the exhaust treatment system.

14. The method according to claim 1 , wherein said regulation of said first supply and/or said regulation of said second supply depends on a total reduction of nitrogen oxides NO x for the exhaust treatment system.

15. The method according to claim 1 , wherein a determination of said soot threshold value S th is also based on one or more operating conditions for a vehicle comprising said combustion engine from the group of:
a weight for said vehicle;
a type of use of said vehicle; or
said vehicle being driven by a driver.

16. The method according to claim 1 , wherein a determination of said soot threshold value S th results in a soot threshold value S th that is smaller than a maximum physical filling level for said catalytic filter.

17. The method according to claim 1 , wherein said one or more operating conditions comprise one or more measured, modelled and/or predicted operating conditions.

18. The method according to claim 1 , wherein a second oxidation of one or more of nitrogen oxides NO x and incompletely oxidized carbon compounds in said exhaust stream is carried out using a second oxidation catalyst, which is arranged downstream of said catalytic filter and upstream of said second dosage device.

19. The method according to claim 1 , wherein said combustion engine is controlled to generate heat for heating of at least one of said first oxidation catalyst and said catalytic filter, to such an extent that said catalytic filter reaches a predetermined performance for conversion of nitrogen oxides NO x .

20. The method according to claim 1 , wherein at least one of said first supply of said first additive and said second supply of said second additive, using one of said first dosage device and said second dosage device, respectively, is regulated to increase to a level at which there is a risk of precipitates of said additive arising.

21. The method according to claim 1 , wherein at least one of

Assignees

• Scania Cv Ab

Inventors

• Nilsson Magnus

Classifications

• F01N3/023 Primary

  using means for regenerating the filters, e.g. by burning trapped particles · CPC title

• F01N3/106

  Auxiliary oxidation catalysts · CPC title

• B01D53/9495

  Controlling the catalytic process · CPC title

• F01N13/009

  having two or more separate purifying devices arranged in series · CPC title

• F01N11/007

  the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus · CPC title