Device and method for impacting the amount of nitrogen oxides in exhaust gases from an internal combustion engine

Patent metadata

Field	Value
Publication number	US-10267198-B2
Application number	US-201515120107-A
Country	US
Kind code	B2
Filing date	Feb 27, 2015
Priority date	Feb 28, 2014
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

A method and an exhaust treatment system are provided for treatment of an exhaust stream that comprises nitrogen oxides NO x . The method comprises using a first slip-catalyst SC 1 , arranged at a first device to create a first impact on a first amount of nitrogen oxides NO x _ 1 An NO x -storing catalyst may store nitrogen oxides NO x . The first slip-catalyst SC 1 may reduce nitrogen oxides NO x , and/or oxidize potential additive in the exhaust stream. This first impact is actively controlled, based on the first amount of nitrogen oxides NO x _ 1 reaching the first device. The method also comprises a second impact on a second amount of nitrogen oxides NO x _ 2 reaching a second device. The active control of the first impact may be by active control of the dosage of additive at the first device, and/or through an active control of an exhaust environment, for example, a temperature for the exhaust stream.

First claim

The invention claimed is:

1. A method for treatment of an exhaust stream, resulting from a combustion in a combustion engine, wherein the exhaust stream comprises nitrogen oxides (NO x ), comprising nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ), said method comprising:
performing, under active control, a first reduction of a first amount of nitrogen oxides (NO x _ 1 ) reaching a first device, arranged in said exhaust treatment system using at least a first slip-catalyst (SC 1 ) comprised in said first device, wherein said first slip-catalyst (SC 1 ) carries out primarily a reduction of nitrogen oxides (NO x ) and secondarily an oxidation of potential additive in said exhaust stream, so that performing said first reduction is actively controlled based at least on said first amount of nitrogen oxides (NO x _ 1 ) reaching said first device; and
performing a second reduction of a second amount of nitrogen oxides (NO x _ 2 ) reaching a second device, arranged downstream of said first device, in order to reduce said second amount of nitrogen oxides (NO x _ 2 ).

2. The method according to claim 1 , wherein said treatment of said exhaust stream also comprises oxidizing one or more of nitrogen oxide (NO) and incompletely oxidized carbon compounds, in said exhaust stream, wherein said oxidation occurs at least in one substrate with oxidizing coating, arranged downstream of said first device.

3. The method according to claim 1 , further comprising:
supplying a first additive into said exhaust stream upstream of said first device; and
said performing a first reduction comprises performing a first reduction of said first amount of nitrogen oxides (NO x _ 1 ), with a first selective catalytic reduction catalyst (SCR 1 ) prior to said primary reduction of nitrogen oxides (NO x ), and said secondary oxidation of potential additive in said exhaust stream with said first slip-catalyst (SC 1 ).

4. The method according to claim 3 , wherein said performing a first reduction is also actively controlled based on a coverage degree for additive for said first selective catalytic reduction catalyst (SCR 1 ), and/or for said first slip-catalyst (SC 1 ).

5. The method according to claim 3 , wherein said performing a first reduction is also actively controlled based on at least one catalytic characteristic for said first device.

6. The method according to claim 3 , wherein said performing a first reduction is also actively controlled based on a temperature for said first selective catalytic reduction catalyst T SCR1 , and/or for said first slip-catalyst T SC1 .

7. The method according to claim 3 , wherein said performing a first reduction is also actively controlled based on how much of said first amount of nitrogen oxides (NO x _ 1 ) that can be stored, and/or reduced, by said first device.

8. The method according to claim 3 , wherein said supplying a first additive into said exhaust stream comprising supplying said first additive such that a coverage degree for said first additive in said first selective catalytic reduction catalyst (SCR 1 ) exceeds a value for a maximum coverage degree for additive in said first selective catalytic reduction catalyst (SCR 1 ).

9. The method according to claim 3 , wherein said supplying a first additive into said exhaust stream results in a slip of additive out from said first selective catalytic reduction catalyst (SCR 1 ).

10. The method according to claim 9 , wherein said slip of additive out of said first selective catalytic reduction catalyst (SCR 1 ) is substantially stored and/or oxidized in said first slip-catalyst (SC 1 ).

11. The method according to claim 10 , wherein said supplying a first additive into said exhaust stream is reduced such that a coverage degree for said first selective catalytic reduction catalyst (SCR 1 ) drops, when a coverage degree for said first additive in said first slip-catalyst (SC 1 ) exceeds a value for a maximum coverage degree for additives in said first slip-catalyst (SC 1 ).

12. The method according to claim 3 , further comprising:
storing of nitrogen oxides (NO x ) with a NO x -storing catalyst (NCC), arranged upstream of said first selective catalytic reduction catalyst (SCR 1 ), prior to said performing a first reduction of said first amount of nitrogen oxides (NO x _ 1 ) with a first selective catalytic reduction catalyst (SCR 1 ).

13. The method according to claim 3 , further comprises:
following said reduction of nitrogen oxides (NO x ), and/or oxidation of potential additive, in said exhaust stream with said first slip-catalyst (SC 1 ), storing nitrogen oxides (NO x ) with a NO x -storing catalyst (NCC) arranged downstream of said first slip-catalyst (SCR 1 ).

14. The method according to claim 3 , wherein said performing a first reduction is also actively controlled based on a coverage degree of nitrogen oxides (NO x ) in a NO x -storing catalyst (NCC) included in said first device.

15. The method according to claim 1 , wherein said performing a first reduction further comprises storing nitrogen oxides (NO x ) with a NOx-storing catalyst (NCC).

16. The method according to claim 1 , wherein said performing a first reduction is also actively controlled based on a determined value (NO 2 _ 2 /NO x _ 2 ) det for a second ratio between a second amount of nitrogen dioxide (NO 2 _ 2 ), and said second amount of nitrogen oxides (NO x _ 2 ) reaching said second device.

17. The method according to claim 16 , wherein said performing a first reduction reduces a value (NO 2 _ 2 /NO x _ 2 ) for said second ratio, wherein said reducing is achieved by increasing said second amount of nitrogen oxides (NO x _ 2 ).

18. The method according to claim 17 , wherein said reducing of said value (NO 2 _ 2 /NO x _ 2 ) for said second ratio is achieved by active control of said performing a first reduction of said first amount of nitrogen oxides (NO x _ 1 ) so that there is reduced reduction of said first amount of nitrogen oxides (NO x _ 1 ) in said first device, so that said second amount of nitrogen oxides (NO x _ 2 ) increases.

19. The method according to claim 16 , further comprising:
supplying a first additive into said exhaust stream upstream of said first device, wherein said first supply is based on said determined value (NO 2 _ 2 /NO x _ 2 ) det for said second ratio, so that a high determined value (NO 2 _ 2 /NO x _ 2 ) det for said second ratio results in supply of less additive, than what a low determined value (NO 2 _ 2 /NO x _ 2 ) det results in.

20. The method according to claim 19 , wherein said first supply of additive is reduced, if said determined value (NO 2 _ 2 /NO x _ 2 ) det for said second ratio is greater than an upper threshold value (NO 2 _ 2 /NO x _ 2 ) threshold _ high , (NO 2 _ 2 /NO x _ 2 ) det >(NO 2 _ 2 /NO x _ 2 ) threshold _ high .

21. The method according to claim 20 , wherein said upper threshold value (NO 2 _ 2 /NO x _ 2 ) threshold _ high has a value that depends on one or more of:
catalytic characteristics for said first device;
catalytic characteristics for said second device
a catalyst type for said first device;
a catalyst type for said second device;
a temperature interval within which said first device is active;
a temperature interval within which said second device is active;
a coverage degree of additive for said first device;
a coverage degree of addi

Assignees

• Scania Cv Ab

Inventors

• Nilsson Magnus
• Birgersson Henrik

Classifications

• B01D53/9477

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• B01D2251/2062

  Ammonia · CPC title

• B01D2255/1021

  Platinum · CPC title

• B01D2255/904

  Multiple catalysts · CPC title

• B01D2251/2067

  Urea · CPC title