Method and system for controlling nitrogen oxide emissions from a combustion engine

Patent metadata

Field	Value
Publication number	US-10260392-B2
Application number	US-201515120104-A
Country	US
Kind code	B2
Filing date	Feb 27, 2015
Priority date	Feb 28, 2014
Publication date	Apr 16, 2019
Grant date	Apr 16, 2019

Abstract

A treatment system for providing treatment of an exhaust stream comprising nitrogen oxides NO x , in which nitrogen monoxide NO and nitrogen dioxide NO 2 are comprised. When the exhaust stream passes through the treatment system, oxidation occurs of compounds comprising nitrogen, carbon and/or hydrogen. An amount of nitrogen oxides NO x reaching a reduction catalyst device downstream of the oxidizing component in the exhaust treatment system is reduced. A ratio (NO 2 /NO x ) det between an amount of nitrogen dioxide NO 2 reaching a reduction catalyst device and the amount of nitrogen oxides NO x reaching the reduction catalyst device is determined. An active control of at least one parameter related to the combustion engine is carried out, based on the determined ratio, so that the amount of nitrogen oxides NO x reaching the reduction catalyst device is increased, if the determined ratio (NO 2 /NO x ) det exceeds an upper threshold value (NO 2 /NO x ) threshold _ high .

First claim

The invention claimed is:

1. A method for treatment of an exhaust stream, resulting from a combustion in a combustion engine, passing through an exhaust treatment system, and comprising nitrogen oxides (NO x ), wherein said nitrogen oxides (NO x ) comprise nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ); said method comprising:
oxidizing compounds comprising one or several of nitrogen, carbon and hydrogen in said exhaust stream, wherein said oxidizing is carried out using at least one oxidizing component arranged in said exhaust treatment system;
reducing an amount of nitrogen oxides (NO x ) reaching a reduction catalyst device, which is arranged downstream of said oxidizing component in said exhaust treatment system, wherein said reduction is carried out through a catalytic reaction using an additive, and wherein said reducing uses reduction catalyst devices comprising:
a first reduction catalyst device arranged upstream of a particulate filter of said exhaust treatment system to provide a first impact on a first amount of nitrogen oxides reaching said first reduction catalyst device; and
a second reduction catalyst device arranged downstream of said particulate filter to provide a second impact on a second amount of nitrogen oxides reaching said second reduction catalyst device;

determining a value (NO 2 /NO x ) det for a ratio between an amount of nitrogen dioxide (NO 2 ) reaching said reduction catalyst device, and said amount of nitrogen oxide (NO x ) reaching said reduction catalyst device; and
actively controlling at least one parameter related to said combustion engine, based on said determined value (NO 2 /NO x ) det for said ratio, wherein said active control is carried out, so that said amount of nitrogen oxide (NO x ) reaching said reduction catalyst device is increased, when said determined value (NO 2 /NO x ) det for said ratio exceeds an upper threshold value (NO 2 /NO x ) threshold _ high ; (NO 2 /NO x ) det >(NO 2 /NO x ) threshold _ high .

2. The method according to claim 1 , wherein the increase of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device, during actively controlling, entails that said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is greater than an amount of nitrogen oxides (NO x ) comprised in said determined value (NO 2 /NO x ) det for said ratio.

3. The method according to claim 1 , wherein the increase of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device, during actively controlling, entails that said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device has a higher concentration of nitrogen oxides (NO x ) in said exhaust stream, than does a concentration of nitrogen oxides (NO x ) that corresponds to said determined value (NO 2 /NO x ) det for said ratio.

4. The method according to claim 1 , wherein said actively controlling further comprises actively controlling of said at least one parameter related to a combustion in said combustion engine, so that said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is reduced, when said determined value (NO 2 /NO x ) det for said ratio is smaller or equal to a lower threshold value (NO 2 /NO x ) threshold _ low , (NO 2 /NO x ) det ≤(NO 2 /NO x ) threshold _ low .

5. The method according to claim 4 , wherein the reduction of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device entails that said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is smaller than an amount of nitrogen oxides (NO x ) comprised in said determined value (NO 2 /NO x ) det for said ratio.

6. The method according to claim 4 , wherein the reduction of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device entails that said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device has a lower concentration of nitrogen oxides (NO x ) in said exhaust stream, compared to a concentration of nitrogen oxides (NO x ) that corresponds to said determined value (NO 2 /NO x ) det for said ratio.

7. The method according to claim 4 , wherein said lower threshold value (NO 2 /NO x ) threshold _ low has a value representing one of:
50%;
45%;
30%;
20%; and
10%.

8. The method according to claim 4 , wherein said lower threshold value (NO 2 /NO x ) threshold _ low has a value, which depends on a temperature over said reduction catalyst device.

9. The method according to claim 1 , wherein said upper threshold value (NO 2 /NO x ) threshold _ high has a value representing one of:
45%;
50%;
60%; and
>65%.

10. The method according to claim 1 , wherein said upper threshold value (NO 2 /NO x ) threshold _ low has a value, which depends on a temperature over said reduction catalyst device.

11. The method according to claim 1 , wherein said actively controlling of said at least one parameter comprises selecting at least one injection strategy for said combustion engine.

12. The method according to claim 11 , wherein said at least one injection strategy comprises controlling of a timing for an injection of fuel into respective cylinders in said combustion engine.

13. The method according to claim 12 , wherein an increase of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is achieved by advancing said timing for said injection.

14. The method according to claim 12 , wherein a reduction of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is achieved by delaying said timing for said injection.

15. The method according to claim 11 , wherein said at least one injection strategy comprises controlling an injection pressure for an injection of fuel into respective cylinders in said combustion engine.

16. The method according to claim 15 , wherein an increase of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is achieved by increasing said injection pressure.

17. The method according to claim 15 , wherein a reduction of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is achieved by reducing said injection pressure.

18. The method according to claim 11 , wherein said at least one injection strategy comprises controlling an injection phasing for an injection of fuel into respective cylinders in said combustion engine.

19. The method according to claim 18 , wherein an increase of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is achieved by controlling an injection phasing to achieve a relatively large pressure gradient.

20. The method according to claim 18 , wherein a reduction of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is achieved by controlling an injection phasing to achieve a relatively small pressure gradient.

21. The method according to claim 1 , wherein said actively controlling comprises control of a device for exhaust recirculation.

22. The method according to claim 21 , wherein an increase of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is achieved by reducing a fraction of said exhaust stream, which is recirculated through said device for exhaust recirculation.

23. The method according to claim 21 , wherein a reduction of said amount of nitrogen oxides (NO x ) reaching said reduction catalyst device is achieved by increasing a fraction of said e

Assignees

• Scania Cv Ab

Inventors

• Nilsson Magnus

Classifications

• B01D53/9477

  with catalysts positioned on separate bricks, e.g. exhaust systems · CPC title

• B01D2251/2062

  Ammonia · CPC title

• B01D2255/1021

  Platinum · CPC title

• B01D2255/904

  Multiple catalysts · CPC title

• B01D2251/2067

  Urea · CPC title