초록 ▼

A system for treating exhaust gases including NO, nitrogen and particulate matter comprises: a catalyst for generating NO 2 from the NO; a plasma generator for generating at least one of: (1) NO 2 from the NO or nitrogen or both; and (2) ozone; and a filter for trapping a desired proportion of the

A system for treating exhaust gases including NO, nitrogen and particulate matter comprises: a catalyst for generating NO 2 from the NO; a plasma generator for generating at least one of: (1) NO 2 from the NO or nitrogen or both; and (2) ozone; and a filter for trapping a desired proportion of the particulate matter which is combusted with at least one of NO 2 or ozone. Methods for increasing levels of NO 2 in an exhaust system to combust trapped particulate matter involve oxidising NO to NO 2 over an oxidation catalyst at an optimum temperature range and using a plasma generator to generate NO 2 from NO or N 2 . Reducing exhaust gas emissions is achieved by trapping the particulate matter and combusting it by reaction with NO 2 .

대표청구항 ▼

1. A system for treating exhaust gases including NO, nitrogen and particulate matter, which system comprising:(a) a catalyst for generating NO 2 from the NO;(b) a plasma generator for generating at least one of: (1) NO 2 from the NO or nitrogen or both; and (2) ozone;(c) a filter for trapping a de

1. A system for treating exhaust gases including NO, nitrogen and particulate matter, which system comprising:(a) a catalyst for generating NO 2 from the NO;(b) a plasma generator for generating at least one of: (1) NO 2 from the NO or nitrogen or both; and (2) ozone;(c) a filter for trapping a desired proportion of the particulate matter; and(d) a microprocessor for controlling the plasma generator to operate at exhaust gas temperatures over the oxidation catalyst of > about 400° C.,wherein trapped particulate matter is combusted by reaction with at least one of NO 2 or ozone. 2. A system according to claim 1, wherein the microprocessor further operates during engine conditions which are pre-determined to generate increased amounts of particulate matter. 3. A system according to claim 1, wherein the microprocessor further operates during low exhaust gas temperatures. 4. A system according to claim 3, wherein the microprocessor operates when the exhaust gas temperature over the oxidation catalyst is about <200° C. 5. A system according to claim 1, wherein the plasma generator is located upstream of the filter and all or a portion of the exhaust gases from the engine are passed therethrough. 6. A system according to claim 1, wherein the plasma generator is located downstream of the filter and all or a portion of the plasma-treated and filtered exhaust gases are recirculated to the upstream side of the filter. 7. A system according to claim 1, wherein a proportion of the exhaust gases are plasma treated and blended with untreated exhaust gases to create a desired blend of NO and NO 2 . 8. A system according to claim 1, further comprising means for removing or reducing NOx mounted downstream of the filter and plasma generator. 9. A system according to claim 8, wherein the means for removing or reducing NOx comprises a NOx trap. 10. A system according to claim 8, wherein the means for removing or reducing NOx comprises an SCR system. 11. A system according to claim 1, wherein the plasma generator comprises a piezoelectric device. 12. A system according to claim 1, wherein the microprocessor is comprised in an engine management unit. 13. A method of reducing exhaust gas emissions from lean burn engines, comprising oxidising NO in the exhaust gas to NO 2 over an oxidation catalyst at oxidation catalyst temperatures within an optimum oxidation catalyst temperature range and using a plasma generator to generate NO 2 from NO or N 2 in the exhaust gas or both at oxidation catalyst temperatures outside of the optimum oxidation catalyst temperature range trapping particulate matter on a filter and combusting the trapped particulate matter by reaction with NO 2 . 14. A method according to claim 13, wherein the optimum oxidation catalyst temperature range is from about 200° C. to about 400° C. 15. The method of claim 13, wherein the lean burn engine is a diesel engine. 16. A method of maintaining increased levels of NO 2 in exhaust gas over exhaust gas emitted from a lean burn engine independent of exhaust gas temperature, which NO 2 is for combusting particulate matter filtered from the exhaust gas, which method comprising oxidising NO in the exhaust gas to NO 2 over an oxidation catalyst at oxidation catalyst temperatures within an optimum oxidation catalyst temperature range and using a plasma generator to generate NO 2 from NO or N 2 in the exhaust gas or both at oxidation catalyst temperatures outside of the optimum oxidation catalyst temperature range. 17. A method according to claim 16, wherein the optimum oxidation catalyst temperature range is from about 200° C. to about 400° C. 18. The method of claim 16, wherein the lean burn engine is diesel engine. 19. A system for treating exhaust gases from diesel engines including NO, nitrogen and particulate matter, which system comprising:(a) a catalyst for generating NO 2 from the NO;(b) a plasma generator for generating at least one of: (1) NO 2 from the NO or nitrogen or both; and (2) ozone;(c) a microprocessor for controlling the plasma generator to operate at exhaust gas temperatures over the oxidation catalyst of > about 400°C.; and(d) a filter for trapping a desired proportion of the particulate matter,wherein trapped particulate matter is combusted by reaction with at least one of NO 2 or ozone. 20. A system according to claim 19, wherein the microprocessor further operates during engine conditions which are pre-determined to generate increased amounts of particulate matter. 21. A system according to claim 19, wherein the microprocessor further operates during low exhaust gas temperatures. 22. A system according to claim 21, wherein the microprocessor operates when the exhaust gas temperature over the oxidation catalyst is <200° C. 23. A system according to claim 19, wherein the plasma generator is located upstream of the filter and all or a portion of the exhaust gases from the engine are passed therethrough. 24. A system according to claim 19, wherein the plasma generator is located downstream of the filter and all or a portion of the plasma-treated and filtered exhaust gases are recirculated to the upstream side of the filter. 25. A system according to claim 19, wherein a proportion of the exhaust gases are plasma treated and blended with untreated exhaust gases to create a desired blend of NO and NO 2 . 26. A system according to claim 19, further comprising means for removing or reducing NOx mounted downstream of the filter and plasma generator. 27. A system according to claim 25, wherein the means for removing or reducing NOx comprises a NOx trap. 28. A system according to claim 25, wherein the means for removing or reducing NOx comprises an SCR system. 29. A system according to claim 19, wherein the plasma generator comprises a piezoelectric device. 30. A system according to claim 19, wherein the microprocessor is comprised in an engine management unit. 31. A method of increasing levels of NO 2 in an exhaust system to combust particulate matter trapped on a filter in the system, which system including an oxidation catalyst effective to oxidise NO to NO 2 over an optimum oxidation catalyst temperature, which method comprising using a plasma generator to generate additional NO 2 from one or both of NO and N 2 during engine conditions which are pre-determined to generate increased amounts of particulate matter when the oxidation catalyst temperature is within the optimum oxidation catalyst temperature range. 32. A method according to claim 31, wherein the optimum oxidation catalyst temperature range is from about 200° C. to about 400° C. 33. A system for treating exhaust gases including NO, nitrogen and particulate matter, which system comprising:(a) a catalyst for generating NO 2 from the NO;(b) a plasma generator for generating at least one of: (1) NO 2 from the NO or nitrogen or both; and (2) ozone plasma generator; and(c) a filter for trapping a desired proportion of the particulate matter, wherein trapped particulate matter is combusted by reaction with at least one of NO 2 or ozone and wherein the plasma generator is located downstream of the filter and all or a portion of the plasma-treated and filtered exhaust gases are recirculated to the upstream side of the filter. 34. A system for treating exhaust gases from diesel engines including NO, nitrogen and particulate matter, which system comprising:(a) a catalyst for generating NO 2 from the NO;(b) a plasma generator for generating at least one of: (1) NO 2 from the NO or nitrogen or both; and (2) ozone;(c) a filter for trapping a desired proportion of the particulate matter, wherein trapped particulate matter is combusted by reaction with at least one of NO 2 or ozone and wherein the plasma generator is located downstream of the filter and all or a portion of the plasma-treated and filtered exhaust gases are recirculated to the upstream side of th e filter. 35. A system for treating exhaust gases including NO, nitrogen and particulate matter, which system comprising:(a) a catalyst for generating NO 2 from the NO;(b) a plasma generator for generating at least one of: (1) NO 2 from the NO or nitrogen or both; and (2) ozone;(c) a filter for trapping a desired proportion of the particulate matter; and(d) a microprocessor for controlling the plasma generator to operate only at predetermined low and high exhaust gas temperatures,wherein trapped particulate matter is combusted by reaction with at least one of NO 2 or ozone.