System and methods for improved emission control of internal combustion engines

• US 20030101713A1
• Filed: 12/03/2002
• Published: 06/05/2003
• Est. Priority Date: 12/03/2001
• Status: Active Grant

• Current Assignee: International Engine Intellectual Property Company, LLC (Volkswagen AG)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Dalla Betta, Ralph, Cizeron, Joel
• Granted Patent: US 7,165,393 B2
• Time in Patent Office: Days
• US Class Current: 60/284
• CPC Class Codes: B01D 53/9431 Processes characterised by a specific device
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2240/20 a flow director or deflector
• CPC Class Codes: F01N 2240/30 a fuel reformer
• CPC Class Codes: F01N 2610/03 the substance being hydrocarbons, e.g. engine fuel
• CPC Class Codes: F01N 2610/04 the substance being hydrogen
• CPC Class Codes: F01N 2610/10 the substance being heated, e.g. by heating tank or supply line of the added substance
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0821 combined with particulate filters catalysed diesel particulate filters F01N3/035
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F01N 3/0871 Regulation of absorbents or adsorbents, e.g. purging by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235
• CPC Class Codes: F01N 3/2882 Catalytic reactors combined or associated with other devices, e.g. exhaust silencers or other exhaust purification devices combined with absorbents or adsorbents only F01N3/0814; combined with particulate filters F01N3/035
• CPC Class Codes: F01N 3/2892 Exhaust flow directors or the like, e.g. upstream of catalytic device

Abstract

The present invention provides systems and methods to improve the performance and emission control of internal combustion engines equipped with nitrogen oxides storage-reduction (“NSR”) emission control systems. The system comprises a NSR catalyst, a fuel processor located upstream of the NSR catalyst, and at least one fuel injection port. The fuel processor converts a fuel into a reducing gas mixture comprising CO and H₂. The reducing gas mixture is then fed into the NSR catalyst, where it regenerates the NSR adsorbent, reduces the NO_x to nitrogen, and optionally periodically desulfates the NSR catalyst. The fuel processor comprises one or more catalysts, which facilitate reactions such as combustion, partial oxidation, and/or reforming and help consume excess oxygen present in an engine exhaust stream. The methods of the present invention provide for NSR catalyst adsorbent regeneration. Control strategies are provided to control the system and methods of the invention.

Claims

1. A system for reducing NO_x in an exhaust stream containing excess O₂ comprising:

a NSR catalyst;

a fuel processor located at a position upstream of the NSR catalyst, comprising an inlet, an outlet, and at least one catalyst; and

at least one fuel injection port located upstream of the fuel processor catalyst, wherein fuel is injected into the fuel injection port and reacts on the fuel processor catalyst to rapidly increase the temperature of at least a portion of the fuel processor catalyst, and whereby at least a portion of the fuel is converted to H₂ and CO

2. The system of claim 1 further comprising a thermal mass having a heat capacity greater than that of the fuel processor.

3. The system of claim 2 wherein at least a portion of the thermal mass is selected from the group consisting of a PM filter, the fuel processor, the NSR catalyst, a monolithic structure having a heat capacity greater than that of the fuel processor, and combinations thereof.

4. The system of claim 3 wherein at least a portion of the thermal mass is a PM filter and at least a portion of the thermal mass is a monolithic structure having a heat capacity greater than that of the fuel processor.

5. The system of claim 1 further comprising a fuel preheater, wherein the fuel preheater is located at a position upstream of the fuel processor and downstream of the fuel injection port.

6. The system of claim 1 further comprising a fuel vaporizer, wherein the fuel vaporizer is located at a position upstream of the fuel processor and downstream of the fuel injection port.

7. The system of claim 1 further comprising a mixer, wherein the mixer is located at a position upstream of the fuel processor and downstream of the fuel injection port.

8. The system of claim 7 wherein the mixer is a static mixer.

9. The system of claim 7 wherein the mixer comprises a length of pipe, wherein the length of pipe has a L/D ratio greater than 5.

10. The system of claim 7 wherein at least a portion of the mixer is coated with a catalyst capable of oxidizing varnish or carbonaceous deposits.

11. The system of claim 1 further comprising a length of pipe, wherein the pipe is located at a position upstream of the fuel processor and downstream of the fuel injection port.

12. The system of claim 11 wherein the length of pipe is coated with a catalyst capable of oxidizing varnish or carbonaceous deposits.

13. The system of claim 1 further comprising a control system.

14. The system of claim 13 wherein the control system measures and regulates the fuel flow rate.

15. The system of claim 1 wherein the at least one catalyst of the fuel processor is a monolithic catalyst.

16. The system of claim 15 wherein the monolithic catalyst is constructed from a material selected from the group consisting of ceramic and metal.

17. The system of claim 15 wherein the monolithic catalyst has a wall thickness in the range of 10 to 500 microns.

18. The system of claim 1 wherein the fuel processor comprises at least two catalysts, wherein at least one catalyst is a reforming catalyst and at least one catalyst is an oxidation catalyst.

19. The system of claim 18 wherein the oxidation catalyst comprises elements selected from the group consisting of Groups VI, VII, VII, and IB of the periodic table of the elements, and combinations thereof.

20. The system of claim 19 wherein the oxidation catalyst comprises elements selected from the group consisting of Pd, Pt, Ir, Rh, Cu, Co, Fe, Ni, Ir, Cr, Mo, and combinations thereof.

21. The system of claim 19 wherein the reforming catalyst comprises elements selected from the group consisting of Ni, Rh, Pd, Pt, and combinations thereof.

22. The system of claim 18 wherein the at least two catalysts are in series.

23. The system of claim 18 wherein the at least two catalysts are in parallel.

24. The system of claim 1 wherein the NSR catalyst and the fuel processor are not located within a single housing structure.

25. The system of claim 1 wherein the NSR catalyst and the fuel processor are located within a single housing structure.

54. A method of controlling the system of claim 1, comprising the steps of:

initiating fuel flow into the fuel processor;

adjusting the fuel flow rate;

maintaining the fuel flow rate until the NSR catalyst is regenerated; and

terminating the fuel flow.

59. A method of controlling the method of claim 23 by estimating the NO_x saturation level of the NSR catalyst.

60. The method of claim 59 wherein the level of saturation is estimated using a NO_x sensor downstream of the NSR catalyst.

61. The method of claim 59 wherein the level of saturation is estimated using engine operating parameters that estimate the total amount of NO_x produced by the engine.

62. The method of claim 59 wherein the method of claim 23 is initiated when the NSR catalyst is estimated to be at a predetermined level of saturation.

26. A method of regenerating a NSR catalyst adsorbent comprising the steps of:

providing an engine exhaust stream comprising oxygen;

injecting fuel into a position upstream of a fuel processor, wherein the fuel processor comprises an inlet, an outlet, and at least one catalyst;

optionally mixing the exhaust stream with the fuel;

reacting the fuel and exhaust stream mixture within the at least one fuel processor catalyst to generate a reducing gas mixture comprising CO and H₂;

introducing the reducing gas mixture into a NSR catalyst having an adsorbent, whereby the adsorbent is regenerated by introduction of the reducing gas mixture.

27. The method of claim 26 wherein the exhaust stream is selected from the group consisting of compression ignition engine exhaust and lean burn spark ignited engine exhaust.

28. The method of claim 26 wherein the fuel comprises hydrocarbons.

29. The method of claim 28 wherein the fuel is selected from the group consisting of gasoline and diesel fuel.

30. The method of claim 26 wherein the fuel is vaporized prior to injection into the fuel injection port.

31. The method of claim 26 wherein the fuel is injected into the fuel injection port at an equivalence ratio greater than 1.

32. The method of claim 31 wherein the fuel is injected into the fuel injection port at an equivalence ratio from about 2 to about 5.

33. The method of claim 26 wherein at, least a portion of the fuel processor catalyst is heated to at least 500°

C.

34. The method of claim 33 wherein the time required to heat at least a portion of the catalyst to 500°

C. is less then 10 seconds.

35. The method of claim 26 wherein the NSR catalyst is regenerated by operating the fuel processor at an equivalence ratio from about 1.2 to about 7.

36. The method of claim 35 wherein the NSR catalyst is regenerated by operating the fuel processor at an equivalence ratio from about 2 to about 5.

37. The method of claim 26 wherein the oxygen concentration in the exhaust stream is less than 6%.

38. The method of claim 26 wherein the step of introducing the reducing gas mixture into the NSR catalyst further facilitates periodic desulfation of the NSR catalyst adsorbent.

39. The method of claim 26 further comprising the use of a control system.

40. The method of claim 26 wherein the fuel processor comprises at least two catalysts, at least one catalyst being a reforming catalyst and at least one catalyst being an oxidation catalyst.

41. The method of claim 26 wherein the fuel is injected intermittently.

55. A method of controlling the method of claim 26, comprising the steps of:

initiating the injection of fuel;

reducing the engine exhaust stream oxygen concentration;

adjusting the fuel flow rate;

maintaining the fuel flow rate until the NSR catalyst adsorbent is regenerated; and

terminating the fuel flow.

56. The method of claim 55 wherein the step of initiating the injection of fuel and the step of reducing the engine exhaust stream oxygen concentration occur simultaneously.

57. A method of controlling the method of claim 26 wherein the injection of fuel is controlled by controlling a variable selected from the group consisting of temperature at a desired location within the exhaust stream, oxygen concentration at a desired location within the exhaust stream, NO_x concentration at a desired location within the exhaust stream, total exhaust flow rate, and an engine operating parameter.

58. The method of claim 57 wherein the engine operating parameter is further selected from the group consisting of rpm, torque, turbocharger boost, EGR valve setting, and engine air flow.

42. A fuel processor unit for use with an engine exhaust stream comprising:

an inlet for receiving an engine exhaust stream comprising oxygen;

an outlet;

at least one catalyst; and

at least one fuel injection port, wherein the fuel injection port is located at a position upstream of the catalyst and facilitates the injection of fuel into the catalyst so that at least a portion of the fuel reacts on the catalyst to rapidly raise the temperature of at least a portion of the catalyst, and at least a portion of the fuel is converted to H₂ and CO.

43. The fuel processor unit of claim 42 wherein the exhaust stream is selected from the group consisting of compression ignition engine exhaust and lean burn spark ignited engine exhaust.

44. The fuel processor unit of claim 42 wherein at least a portion of the catalyst is heated to at least 500°

C.

45. The fuel processor unit of claim 44 wherein the time required to heat at least a portion of the catalyst to 500°

C. is less then 10 seconds.

46. The fuel processor unit of claim 42 further comprising a mixer, wherein the mixer is located downstream of the fuel injection port and upstream of the catalyst.

47. The fuel processor unit of claim 46 wherein the mixer is selected from the group consisting of a static mixer and a length of pipe.

48. The fuel processor unit of claim 42 further comprising at least two catalysts, wherein at least one catalyst is a reforming catalyst and at least one catalyst is an oxidation catalyst.

49. The fuel processor unit of claim 48 wherein the oxidation catalyst comprises elements selected from the group consisting of Groups VI, VII, VII and IB of the periodic table of the elements, and combinations thereof.

50. The fuel processor of claim 49 wherein the oxidation catalyst comprises elements selected from the group consisting of Pd, Pt, Ir, Rh, Cu, Co, Fe, Ni, Ir, Cr, Mo, and combinations thereof.

51. The fuel processor of claim 49 wherein the reforming catalyst comprises elements selected from the group consisting of Ni, Rh, Pd, Pt, and combinations thereof.

52. The fuel processor of claim 48 wherein the at least two catalysts are in series.

53. The fuel processor of claim 48 wherein the at least two catalysts are in parallel.