IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0204634
(2011-08-05)
|
등록번호 |
US-8480986
(2013-07-09)
|
우선권정보 |
GB-9802504.2 (1998-02-06) |
발명자
/ 주소 |
- Andreasson, Anders
- Chandler, Guy Richard
- Goersmann, Claus Friedrich
- Warren, James Patrick
- Huethwohl, Georg
|
출원인 / 주소 |
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
5 인용 특허 :
41 |
초록
A system for NOx reduction in combustion gases, especially from diesel engines, incorporates an oxidation catalyst to convert at least a portion of NO to NO2, tparticulate filter, a source of reductant such as NH3 and an SCR catalyst. Considerable improvements in NOx conversion are observed.
대표청구항
▼
1. A method of reducing particulates and NOx in an exhaust gas stream of a diesel engine, comprising: (1) converting at least a portion of the NO in the gas stream to NO2 on an oxidation catalyst; (2) passing the gas stream through a particulate trap to trap at least a portion of the particulates fr
1. A method of reducing particulates and NOx in an exhaust gas stream of a diesel engine, comprising: (1) converting at least a portion of the NO in the gas stream to NO2 on an oxidation catalyst; (2) passing the gas stream through a particulate trap to trap at least a portion of the particulates from the gas stream; (3) reducing the proportion of NO2 in the gas stream by combusting a portion of the trapped particulates in the presence of NO2; (4) adding reductant fluid to the gas stream to form a mixed composition; and (5) passing the mixed composition over the SCR catalyst under NOx reduction conditions. 2. The method of claim 1, wherein: the ratio of NO to NO2 in the gas stream, prior to adding the reductant fluid, is from about 4:1 to about 1:3 by volume. 3. The method of claim 1, wherein: the particulate trap comprises a wall-flow filter. 4. A method of reducing particulates and NOx in an exhaust gas stream of a diesel engine, comprising: (1) converting at least a portion of the NO in the gas stream to NO2 on an oxidation catalyst; (2) passing the converted gas stream through a particulate trap to trap at least a portion of the particulates from the gas stream; (3) reducing the proportion of NO2 in the converted gas stream by combusting a portion of the trapped particulates in the-presence of NO2; (4) adding reductant fluid to the gas stream to form a gas mixture; and (5) passing the gas mixture over the SCR catalyst under NOx reduction conditions. 5. The method of claim 4, wherein: the ratio of NO to NO2 in the gas stream, prior to adding the reductant fluid, is from about 4:1 to about 1:3 by volume. 6. The method of claim 4, wherein: the particulate trap comprises a wall-flow filter. 7. The method of claim 1, wherein the reductant fluid is selected from the group consisting of ammonia, ammonium carbamate and urea. 8. The method of claim 1, wherein the reductant fluid in NH3. 9. The method of claim 1, wherein the reductant fluid in urea. 10. The method of claim 1, wherein the reductant fluid being added to the gas stream prior to entering the SCR catalyst is urea. 11. The method of claim 1, wherein the oxidation catalyst is a platinum catalyst carried on a through-flow honeycomb support. 12. The method of claim 1, wherein the gas stream is cooled before reaching the SCR catalyst. 13. The method of claim 1, wherein the NO to NO2 ratio of the gas mixture is adjusted to a level pre-determined to be optimum for the SCR catalyst, by oxidation of NO over the oxidation catalyst. 14. The method of claim 11, wherein the NO to NO2 ratio of the gas mixture is adjusted to a level pre-determined to be optimum for the SCR catalyst, by oxidation of NO over the oxidation catalyst. 15. The method of claim 14, wherein the ratio of NO:NO2 leaving the oxidation catalyst is adjusted to about 4:3. 16. The method of claim 1, wherein the SCR catalyst is maintained at a temperature from 160° C. to 450° C. 17. The method of claim 1, wherein the SCR catalyst includes a component selected from the group consisting of a transition metal and a rare-earth metal. 18. The method of claim 1, wherein the SCR catalyst is selected from the group consisting of transition metal/zeolite catalysts, rare earth-based catalysts and transition metal catalysts. 19. The method of claim 1, wherein the SCR catalyst comprises a transition metal/zeolite catalyst. 20. The method of claim 1, further comprising the step of contacting the gas mixture leaving the SCR catalyst with a clean-up catalyst to remove NH3 or derivatives thereof. 21. The method of claim 1, wherein the space velocity of the exhaust gas over the SCR catalyst is in the range 40,000 to 70,000 h−1. 22. The method of claim 1, wherein the particulates are removed without causing accumulation and resulting blockage and back pressure problems. 23. The method of claim 1, wherein the particles are removed from the particulate trap by combustion in the presence of NO2. 24. The method of claim 1, wherein the particulate trap is manufactured from ceramic. 25. The method of claim 1, wherein the particulate trap is manufactured from woven knitted heat resistant fabrics. 26. The method of claim 1, wherein the particulate trap is manufactured from non-woven heat resistant fabrics. 27. The method of claim 1, wherein the gas stream comprises exhaust from a heavy duty diesel engine. 28. The method of claim 1, wherein the gas stream comprises exhaust from a light duty diesel engine. 29. The method of claim 1, wherein NH3 or derivatives thereof which pass unreacted or as by-products through the SCR catalyst are removed by means of a clean-up catalyst arranged downstream of the SCR catalyst. 30. The method of claim 4, wherein the reductant fluid is selected from the group consisting of ammonia, ammonium carbamate and urea. 31. The method of claim 4, wherein the reductant fluid is NH3. 32. The method of claim 4, wherein the reductant fluid is urea. 33. The method of claim 4, wherein the reductant fluid being added to the gas stream prior to entering the SCR catalyst is urea. 34. The method of claim 4, wherein the oxidation catalyst is a platinum catalyst carried on a through-flow honeycomb support. 35. The method of claim 4, wherein the gas stream is cooled before reaching the SCR catalyst. 36. The method of claim 4, wherein the NO to NO2 ratio of the gas mixture is adjusted to a level pre-determined to be optimum for the SCR catalyst, by oxidation of NO over the oxidation catalyst. 37. The method of claim 34, wherein the NO to NO2 ratio of the gas mixture is adjusted to a level pre-determined to be optimum for the SCR catalyst, by oxidation of NO over the oxidation catalyst. 38. The method of claim 37, wherein the ratio of NO:NO2 leaving the oxidation catalyst is adjusted to about 4:3. 39. The method of claim 4, wherein the SCR catalyst is maintained at a temperature from 160° C. to 450° C. 40. The method of claim 4, wherein the SCR catalyst includes a component selected from the group consisting of a transition metal and a rare-earth metal. 41. The method of claim 4, wherein the SCR catalyst is selected from the group consisting of transition metal/zeolite catalysts, rare earth-based catalysts and transition metal catalysts. 42. The method of claim 4, wherein the SCR catalyst comprises a transition metal/zeolite catalyst. 43. The method of claim 4, further comprising the step of contacting the gas mixture leaving the SCR catalyst with a clean-up catalyst to remove NH3 or derivatives thereof. 44. The method of claim 4, wherein the space velocity of the exhaust gas over the SCR catalyst is in the range 40,000 to 70,000 h−1. 45. The method of claim 4, wherein the particulates are removed without causing accumulation and resulting blockage and back pressure problems. 46. The method of claim 4, wherein the particles are removed from the particulate trap by combustion in the presence of NO2. 47. The method of claim 4, wherein the particulate trap is manufactured from ceramic. 48. The method of claim 4, wherein the particulate trap is manufactured from woven knitted heat resistant fabrics. 49. The method of claim 4, wherein the particulate trap is manufactured from non-woven heat resistant fabrics. 50. The method of claim 4, wherein the gas stream comprises exhaust from a heavy duty diesel engine. 51. The method of claim 4, wherein the gas stream comprises exhaust from a light duty diesel engine. 52. The method of claim 4, wherein NH3 or derivatives thereof which pass unreacted or as by-products through the SCR catalyst are removed by means of a clean-up catalyst arranged downstream of the SCR catalyst.
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