Exhaust gas aftertreatment system
IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0150026
(2008-04-24)
|
등록번호 |
US-8176731
(2012-05-15)
|
우선권정보 |
DE-10 2007 019 460 (2007-04-25) |
발명자
/ 주소 |
- Döring, Andreas
- Jacob, Eberhard
|
출원인 / 주소 |
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
2 인용 특허 :
7 |
초록
▼
Exhaust gas aftertreatment system for internal combustion engines operated with a lean mixture, wherein nitrogen oxides are reduced by an SCR catalyst, and particulates are removed by a particle separator or filter. A thermolysis catalyst is located near the engine in the exhaust gas split stream do
Exhaust gas aftertreatment system for internal combustion engines operated with a lean mixture, wherein nitrogen oxides are reduced by an SCR catalyst, and particulates are removed by a particle separator or filter. A thermolysis catalyst is located near the engine in the exhaust gas split stream downstream of the supply point of the reducing agent. At temperatures above 135° C., this thermolysis catalyst vaporizes the water component of the aqueous urea solution. It contains a catalyst material that is thermally stable at exhaust gas temperatures occurring near the engine and preferentially reacts with the urea to form isocyanic acid. A hydrolysis catalyst is located in the exhaust gas stream downstream of the return of the split stream into the main stream of exhaust gas. The hydrolysis catalyst converts the isocyanic acid formed during thermolysis to ammonia and carbon dioxide using water vapor formed in the thermolysis catalyst.
대표청구항
▼
1. Exhaust gas aftertreatment system for reducing nitrogen oxides and particulates in a stream of exhaust gas from an internal combustion engines operated with a lean mixture, the system comprising: an oxidation catalyst arranged in a main stream of exhaust gas, the oxidation catalyst converting at
1. Exhaust gas aftertreatment system for reducing nitrogen oxides and particulates in a stream of exhaust gas from an internal combustion engines operated with a lean mixture, the system comprising: an oxidation catalyst arranged in a main stream of exhaust gas, the oxidation catalyst converting at least a portion of the nitric oxide present in the exhaust gas main stream to nitrogen dioxide,a reservoir containing a reducing agent comprising an aqueous urea solution;a metering device for metering the reducing agent into an exhaust gas split stream at a supply point parallel to the oxidation catalyst, wherein the exhaust gas split stream is split from the exhaust gas main stream upstream of the oxidation catalyst and returned to the exhaust gas main stream downstream of the oxidation catalyst, the reducing agent splitting off ammonia;a thermolysis catalyst located in the exhaust gas split stream downstream of the supply point of the reducing agent, the thermolysis catalyst reacting with the urea to form isocyanic acid and vaporizing the water component of the aqueous urea solution at an exhaust gas temperature above 135° C., the thermolysis catalyst being thermally stable at exhaust gas temperatures occurring near the engine;a hydrolysis catalyst located in the exhaust gas stream downstream of the return of the exhaust gas partial stream into the main stream of the exhaust gas, wherein the hydrolysis catalyst converts the isocyanic acid to ammonia and carbon dioxide with the aid of the water vapor formed in the thermolysis catalyst;a particle separator located in the exhaust gas stream downstream of the hydrolysis catalyst, the separator reacting with soot particles to form carbon monoxide, carbon dioxide, nitrogen, and nitric oxide by means of the nitrogen dioxideformed by the oxidation catalyst; andan SCR catalyst located downstream of the particle separator reducing the nitrogen oxides contained in the exhaust gas stream by selective catalytic reduction to nitrogen and water vapor using the ammonia formed by the hydrolysis catalyst. 2. The exhaust gas aftertreatment system of claim 1 wherein the thermolysis catalyst is resistant to the impact of droplets and is made of a material with greater thermal stability than the material of which the hydrolysis catalyst is made. 3. The exhaust gas aftertreatment system of claim 1 wherein the thermolysis catalyst contains at least one of titanium dioxide, silicon dioxide, aluminum oxide, tungsten oxide, and zeolite. 4. The exhaust gas aftertreatment system of claim 1 wherein the thermolysis catalyst has a porosity that promotes the evaporation of the water component of the aqueous urea solution. 5. The exhaust gas aftertreatment system of claim 1 wherein the hydrolysis catalyst comprises a carrier through which the exhaust gas can flow both in the main direction of flow of the exhaust gas and transverse to this direction in such a way that there is thorough mixing of the exhaust gas. 6. The exhaust gas aftertreatment system of claim 1 wherein the hydrolysis catalyst is coated with a washcoat containing at least one titanium dioxide, silicon dioxide, aluminum oxide, tungsten oxide, and zeolite. 7. The exhaust gas aftertreatment system of claim 1 wherein the hydrolysis catalyst has turbulence zones and low-flow zones with respect to the stream of exhaust gas, such that the hydrolysis catalyst deposits soot particles entrained with the stream of exhaust gas in the low-flow zones and reacts with them to form carbon monoxide, carbon dioxide, nitrogen, and nitric oxide with the aid of the nitrogen dioxide contained in the exhaust gas stream. 8. The exhaust gas aftertreatment system of claim 1 wherein titanium dioxide, the thermolysis catalyst containing a smaller fraction of titanium dioxide than the hydrolysis catalyst. 9. The exhaust gas aftertreatment system of claim 1 wherein the thermolysis catalyst and the hydrolysis catalyst both contain silicon dioxide, the thermolysis catalyst containing a higher fraction of silicon dioxide than the hydrolysis catalyst. 10. The exhaust gas aftertreatment of claim 1 wherein the thermolysis catalyst and the hydrolysis catalyst both contain anatase and rutile, the thermolysis catalyst containing one of a lower percentage of anatase and a higher percentage of rutile than the hydrolysis catalyst. 11. The exhaust gas aftertreatment system of claim 1 wherein at least one of: the percentage of anatase in the thermolysis catalyst is 0-30%;the percentage of rutile in the thermolysis catalyst is 8-80%; andthe percentage of silicon dioxide in the thermolysis catalyst is 30-100%. 12. The exhaust gas aftertreatment system of claim 1 wherein at least one of: the percentage of anatase in the hydrolysis catalyst is 50-80%;the percentage of rutile in the hydrolysis catalyst is 0-30%; andthe percentage of silicon dioxide in the hydrolysis catalyst is 20-60%.
이 특허에 인용된 특허 (7)
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Lewis, Jr.,Woodrow; van Nieuwstadt,Michiel J., Diesel aftertreatment systems.
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Zhicheng Hu ; Ronald M. Heck ; Rudolf M. Smaling ; Alan R. Amundsen, Engine exhaust treatment apparatus and method of use.
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Tennison, Paul Joseph; Laing, Paul M.; Lambert, Christine Kay; Hammerle, Robert Henry; Ruona, William Charles, Exhaust gas aftertreatment systems.
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Mathes, Wieland; M?ller, Raimund; Rusch, Klaus; Rusch, Petra Anette; Sigling, Ralf, Process and device for the selective catalytic reduction of nitrogen oxides in an oxygen-containing gaseous medium.
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Weitkamp Jens (Oldenburg DEX) Ernst Stefan (Stuttgart DEX) Rck Heinrich (Trostberg DEX) Scheinost Kurt (Trostberg DEX) Hammer Benedikt (Trostberg DEX) Goll Werner (Garching DEX) Michaud Horst (Trostb, Process for the production of cyanamide.
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Andreasson, Anders; Chandler, Guy Richard; Goersmann, Claus Friedrich; Warren, James Patrick, System for NOx reduction in exhaust gases.
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Cooper Barry J. (Radnor PA) Jung Hyun J. (Wayne PA) Thoss James E. (West Chester PA), Treatment of diesel exhaust gases.
이 특허를 인용한 특허 (2)
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Sarby, Håkan, Arrangement for injecting a reductant into an exhaust line of an internal combustion engine.
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Clayton, Jr., Robert D., System, apparatus, and method to address unwanted DEF-based deposits in diesel exhaust system.
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