AU2006254533A1

AU2006254533A1 - Device and method for purification of exhaust gases from an internal combustion engine

Info

Publication number: AU2006254533A1
Application number: AU2006254533A
Authority: AU
Inventors: Matthias Boltze
Original assignee: Webasto SE
Current assignee: Enerday GmbH
Priority date: 2005-06-02
Filing date: 2006-06-01
Publication date: 2006-12-07
Anticipated expiration: 2026-06-01
Also published as: JP2008542606A; AU2006254533B2; KR100923521B1; DE102005025455B4; CN101273189A; KR20080015019A; EP1888889A1; DE102005025455A1; CA2611027A1; WO2006128449A1; US20090044519A1; AU2006254533A8; DE102005063323A1

Description

PUBLISHED SPECIFICATION VERIFICATION OF TRANSLATION I, ...Victor T. Smith... ..................... (insert translator's name) of ........... Artur-Kutscher-Platz 1, 80802 M0nchen, Germany........................ ................................................................................................. (translator's address) declare as follows: 1. That I am well acquainted with both the English and German languages, and 2. That the attached document is a true and correct translation made by me to the best of my knowledge and belief of: (a) The specification of International Bureau pamphlet numbered WO 2006/128449 International Application No. PCT/DE2006/000957 MuvdA ~A-i& ~c\k3V. 2-61 206-7 (Date) (Signature of Translator) (No witness required) - 1 PCT/DE2006/000957 Enerday GmbH 5 Device and method for emission control of an internal combustion engine 10 The invention relates to a device for emission control of an internal combustion engine including an exhaust tract comprising a NOx catalyst, and a reductant feeder de signed to deliver reductant to the exhaust tract upstream of the NOx catalyst. In addition the invention relates to 15 a method for emission control of an internal combustion engine wherein a NO catalyst provided in the exhaust tract is supplied with reductant. One problem associated with modern motor vehicles is the 20 emission of nitrous oxides (NOx) materializing in the combustion of gasoline or diesel in the engine, particu larly at high combustion chamber temperatures. To reduce NOx emissions catalyst systems are known for storing the NOx and reducing it to safe nitrogen. From the generic DE 25 102 33 66 5 Al it is already known for this purpose to inject reductant in the form of fuel into the exhaust tract upstream of the NOx catalyst. Instead of injecting pure fuel as is known from DE 102 33 66 5 Al use may be made of a reformate as the reductant. No matter what kind -2 of reductant is selected, it needs to be introduced into the exhaust tract in counteracting the fluctuating back pressure of the exhaust system. For this purpose prior art makes use of high-performance blowers, air compres 5 sors or injectors, all of which add to the costs and the nuisance of frequent servicing. The object of the present invention involves sophisticat ing generic devices and methods such that costly means 10 requiring frequent servicing for introducing the reduc tant in the exhaust tract counteracting the fluctuating back pressure of the exhaust system are now eliminated. This object is achieved by the features of the independ 15 ent claims. Advantageous aspects and further embodiments of the in vention read from the dependent claims. 20 The device in accordance with the invention is a sophis tication over generic prior art in that the reductant feeder comprises a reformer designed to react the gas exhausted by the engine and fuel into a reformate serving as the reductant. It is particularly with diesel engines 25 that the exhaust gas of the engine contains an apprecia ble proportion of oxygen which in addition to the fuel is feedstock for generating a reformate. When branching off this exhaust gas immediately downstream of the engine it has a corresponding high pressure level. Due to this high - 3 pressure level of the branched-off exhaust gas it is possible in accordance with the invention to introduce the reformate upstream of the NOx catalyst into the ex haust tract in thus eliminating costly means requiring 5 frequent servicing needed as in prior art to generate the pressure required to introduce the reformate. The branched-off exhaust gas and fuel are mixed in the re former and supplied to a reformer catalyst. In the subse quent reaction in the form of an exothermic partial oxi 10 dation a reformate gas having a proportion of the reduc ing gases hydrogen and carbon monoxide is generated. These gases are suitable for reducing the nitrous oxides in the NOx catalyst to safe nitrogen. 15 For the device in accordance with the invention it is considered to be particularly advantageous when it is provided for that the exhaust gas supplied to the re former is obtained via a exhaust tract branch-off dis posed directly downstream of the engine. Directly down 20 stream of the engine the exhaust gas pressure is high and thus well suited to introduce the reformate in counter acting the back pressure in the exhaust tract. In accordance with a preferred further embodiment of the 25 device in accordance with the invention it is provided for that the exhaust gas supplied to the reformer is obtained via a exhaust tract branch-off comprising an exhaust gas metering device. This exhaust gas metering device permits introducing the amount of exhaust gas as - 4 needed in each case to generate the reformate to be sup plied to the reformer. The exhaust gas metering device may work with open or closed loop control. 5 In conjunction with the arrangement as described above the exhaust gas metering device may comprise a valving apparatus. This valving apparatus may be, for example, a metering valve similar to a valve for returning the ex haust gas. 10 In addition or as an alternative thereto, it may be pro vided for in the device in accordance with the invention that the exhaust gas metering device comprises a blower which because of the high pressure level of the exhaust 15 gas supplied to the blower can be designed with a much lower power level than needed in prior art. The device in accordance with the invention can be so phisticated to advantage in that the exhaust gas supplied 20 to the reformer is obtained via a exhaust tract branch off disposed upstream of a further catalyst disposed upstream of the NOx catalyst. This further catalyst may be, for example, the main catalyst of the emission con trol system, the exhaust gas being obtained upstream of 25 the further catalyst and introduced into the NOx catalyst in the exhaust tract. At least in some aspects of the device in accordance with the invention it may be provided for that it comprises a - 5 fuel pump, designed to pump fuel from a fuel tank. The fuel pump may be in particular a fuel metering pump for pumping the fuel from the fuel tank in the amount as needed to generate the reformate in each case. This fuel 5 pump may also feature open or closed loop control. In accordance with yet another advantageous further em bodiment of the device in accordance with the invention it is provided for that the fuel is obtained from a fuel 10 line of the fuel system of the engine and that the fuel is supplied to the reformer via a fuel valving apparatus, the fuel line concerned may be, in particular, a pressur ized fuel line, for example a common rail return. The fuel valving apparatus may be, in particular, a fuel 15 metering valve which passes the amount of fuel as needed in each case to generate the reformate. This fuel valving apparatus may also feature open or closed loop control. The method in accordance with the invention is a sophis 20 tication over prior art in that use is made of reformate generated by a reformer as the reductant, the reformer generating the reformate from engine exhaust gas and fuel. This achievement has the same advantages and fea tures as recited for the device in accordance with the 25 invention and thus to avoid tedious repetition reference is made to the comments in conjunction with the device in accordance with the invention.

- 6 The same applies in accordance with the following pre ferred aspects of the method in accordance with the in vention, here too, reference being made to the comments in conjunction with the device in accordance with the 5 invention. In preferred aspects of the method in accordance with the invention it is provided for that the exhaust gas sup plied to the reformer is obtained via a exhaust tract 10 branch-off disposed directly downstream of the engine. It is likewise considered to be an advantage of the method in accordance with the invention that the exhaust gas supplied to the reformer is obtained via a exhaust 15 tract branch-off containing an exhaust gas metering de vice. In this arrangement it is considered to be an advantage that the exhaust gas metering device comprises a valving 20 apparatus. In addition to or as an alternative thereto it may be provided for that the exhaust gas metering device com prises a blower. 25 In certain aspects of the method in accordance with the invention it may be provided for that the exhaust gas supplied to the reformer is obtained via a exhaust tract -7 branch-off disposed at the input to a further catalyst disposed upstream of the NOx catalyst. In the method in accordance with the invention too, as 5 pects come into consideration in which it is provided for that a fuel pump is included, designed to pump fuel from a fuel tank. In this case it may be provided for in addition or as an 10 alternative thereto that the fuel is obtained from a fuel line of the fuel system of the engine and that the fuel is supplied to the reformer via a fuel valving apparatus. Of particularly advantage in the achievement in accor 15 dance with the invention is that it is independent of the exhaust back pressure of the exhaust system and thus of the load on the engine, because the reformer pressure is now always adapted to the level of the exhaust gas pres sure. In other words, via the reformer system the system 20 pressure is now always practically constant and independ ent of the load of the engine and exhaust back pressure. Preferred embodiments of the invention will now be ex plained by way of example with reference to the corre 25 sponding drawings in which FIG. 1 is a diagrammatic block diagram illustrating a first embodiment of the device in accordance with the invention suitable for implementing - 8 the method in accordance with the invention; and FIG. 2 is a diagrammatic block diagram illustrating a 5 second embodiment of the device in accordance with the invention likewise suitable for imple menting the method in accordance with the in vention. 10 Like components are identified in the drawings by like reference numerals as explained only once to avoid tedi ous repetition. Referring now to FIG. 1, there is illustrated how an 15 internal combustion engine 10 is assigned an exhaust tract 12 comprising a NOx catalyst 14 and a further cata lyst 24, the further catalyst 24 being the main catalyst. Disposed directly downstream of the engine 10 is a ex haust tract branch-off 20 connecting a reformer 18 via an 20 exhaust gas metering device 22. In the embodiment as shown in FIG. 1 the exhaust gas metering device 22 is formed by a exhaust gas metering valve. A fuel pump 26 is provided to supply the reformer 18 with fuel metered from a fuel tank 28. The exhaust tract branch-off 20, the 25 exhaust gas metering device 22, fuel pump 26 and reformer 18 all form together a reductant feeder. In the reformer 18 the branched-off exhaust gas and the fed fuel are mixed and supplied to a reformate catalyst (not shown) which is a component of the reformer 18. In the subse- - 9 quent reaction a gaseous reformate is generated contain ing a proportion of the reducing gases hydrogen and car bon monoxide. The reformate as generated this way is introduced into the exhaust tract 12 upstream of the NOx 5 catalyst 14. Because the reformer pressure is always adapted to the actual exhaust gas pressure no special means are needed to overcome the exhaust back pressure on introducing the reformate into the exhaust tract 12. Via the reformer 18 the system pressure is now by the 10 achievement in accordance with the invention practically constant and independent of the engine load and exhaust back pressure. Both the exhaust gas metering device 22 in the form of a metering valve as well as the fuel pump 26 can be operated with open or closed loop control. For 15 this purpose a controller (not shown) may be provided which is also capable of providing open or closed loop control of the other components of the reformer 18. Referring now to FIG. 2, there is illustrated a diagram 20 matic block diagram of a second embodiment of the device in accordance with the invention, likewise suitable for implementing the method in accordance with the invention. The embodiment as shown in FIG. 2 differs from the em bodiment as shown in FIG. 1 in that the exhaust gas me 25 tering device 22 is formed by a blower and that instead of a fuel pump a fuel valving apparatus 32 is provided. The blower forming the exhaust gas metering device 22 may be a relatively low power blower since the exhaust tract branch-off 20 is subjected to a high exhaust gas pres- - 10 sure. The fuel valving apparatus 32 is achieved by a fuel metering valve disposed between the fuel line 30 of the fuel system of the engine 10 and the reformer 18. The fuel line 30 of the fuel system of the engine 10 may be, 5 in particular, a fuel pressure line, for example a common rail return. This achievement is based on having discov ered that there is no need for a separate fuel pump when a sufficiently high fuel pressure is available anyway. 10 In the embodiment as shown in FIG. 2 too, a controller (not shown) may be provided for activating the corre sponding components as already explained in conjunction with with the comments as to FIG. 1. The advantage of operation independent of the exhaust back pressure and 15 engine load thus applies likewise to the embodiment as shown in FIG. 2. It will be appreciated, of course, that the exhaust gas metering device may also be formed in the embodiment as 20 shown in FIG. 2 too, by a valving apparatus; in the em bodiment as shown in FIG. 1 a blower can be put to use as an alternative. It is understood that the features of the invention as 25 disclosed in the above description, in the drawings and as claimed may be essential to achieving the invention both by themselves or in any combination.

- 11 List of reference numerals 5 10 engine 13 exhaust tract 14 NOx catalyst 16 reductant feeder 18 reformer 10 20 exhaust tract branch-off 22 exhaust gas metering device 24 further catalyst 26 fuel pump 28 fuel tank 15 30 fuel system line 32 fuel valving apparatus

Claims

2. The device as set forth in claim 1, characterized in 20 that the exhaust gas supplied to the reformer (18) is obtained via a exhaust tract branch-off (20) disposed directly downstream of the engine (10).
3. The device as set forth in claim 1 or 2, character 25 ized in that the exhaust gas supplied to the reformer (18) is obtained via a exhaust tract branch-off (20) comprising an exhaust gas metering device (22). - 13 4. The device as set forth in claim 3, characterized in that the exhaust gas metering device (22) comprises a valving apparatus. 5 5. The device as set forth in claim 3 or 4, character ized in that the exhaust gas metering device (22) com prises a blower.
6. The device as set forth in any of the preceding 10 claims, characterized in that the exhaust gas supplied to the reformer (18) is obtained via a exhaust tract branch off (20) disposed upstream of a further catalyst (24) disposed upstream of the NOx catalyst (14). 15 7. The device as set forth in any of the preceding claims, characterized in that it comprises a fuel pump (26), designed to pump fuel from a fuel tank (28).
8. The device as set forth in any of the preceding 20 claims, characterized in that the fuel is obtained from a fuel line of the fuel system of the engine and that the fuel is supplied to the reformer (18) via a fuel valving apparatus (32). 25 9. A method for emission control of an internal combus tion engine (10) wherein a NOx catalyst (14) provided in the exhaust tract (12) is supplied with reductant, char acterized in that use is made of reformate generated by a - 14 reformer (18) as reductant, the reformer (18) generating the reformate from the engine (10) exhaust gas and fuel.
10. The method as set forth in claim 9, characterized in 5 that the exhaust gas supplied to the reformer (18) is obtained via a exhaust tract branch-off (20) disposed directly downstream of the engine (10).
11. The method as set forth in claim 9 or 10, character 10 ized in that the exhaust gas supplied to the reformer (18) is obtained via a exhaust tract branch-off (20) containing an exhaust gas metering device (22).
12. The method as set forth in claim 11, characterized 15 in that the exhaust gas metering device (22) comprises a valving apparatus.
13. The method as set forth in claim 11 or 12, charac terized in that the exhaust gas metering device (22) 20 comprises a blower.
14. The method as set forth in any of the claims 9 to 13, characterized in that the exhaust gas supplied to the reformer (18) is obtained via a exhaust tract branch-off 25 (20) disposed upstream of a further catalyst (24) dis posed upstream of the NOx catalyst (14). - s15 15. The method as set forth in any of the claims 9 to 14, characterized in that the fuel supplied to the re former (18) is delivered by a fuel pump (26). 5 16. The method as set forth in any of the claims 9 to 15, characterized in that the fuel is obtained from a fuel line of the fuel system of the engine and that the fuel is supplied to the reformer (18) via a fuel valving apparatus (32).