DE102006030175B4 - Exhaust after-treatment device of an internal combustion engine with a device for generating ammonia - Google Patents

Abstract

Exhaust after-treatment device of an internal combustion engine, in particular of a motor vehicle, with at least one SCR catalyst in the exhaust line and a device for generating ammonia with an outside of the exhaust line arranged ammonia reactor, the urea in solid form, for. As urea pellets, or liquid form such as a urea water solution from a reservoir can be supplied by means of a metering device and in which the urea is converted in a thermal process in the presence of water vapor in ammonia, which flows into the exhaust line upstream of the / the SCR catalyst (EN) can be fed, characterized in that in the ammonia reactor (11) generated ammonia or ammonia-containing gas mixture fed to the ammonia reactor (11) downstream metering device (19) and by means of this time and quantity exactly on the engine operating condition generated exhaust gas in the sense of a 100% conversion within the running in the / the SCR catalyst (s) (21) catalytic process in the exhaust pipe (15) can be fed, said control-relevant organs (38, 40) of the metering device (19) are controlled by commands from a computer-aided electronic control unit (ECU), whereby ...

Description

The invention relates to an exhaust aftertreatment device of an internal combustion engine, in particular of a motor vehicle, having features as indicated in the preamble of claim 1.

From the DE 10 2004 042 225 A1 For example, an apparatus and method for producing ammonia from solid urea, namely urea pellets, is known. For this purpose, an ammonia reactor is provided, which is inside or outside an exhaust pipe z. B. an internal combustion engine is arranged. The exhaust gas generated in the ammonia reactor is fed from a reactor-internal outlet chamber directly via a feed line in the exhaust line upstream of an SCR catalyst.

As an alternative to the urea solid is at one of the EP 1085939 B1 known device used a urea water solution for the production of ammonia in an ammonia reactor. Again, the generated ammonia from a reactor-internal outlet chamber is fed directly via a feed line in the exhaust line upstream of an SCR catalyst.

Furthermore, from the DE 103 42 003 A1 an exhaust aftertreatment device of an internal combustion engine known, with an SCR catalyst in the exhaust line and a device for generating ammonia with an arranged outside the exhaust line ammonia reactor, the urea in liquid form such as a urea water solution from a reservoir can be fed by means of a metering device and in which Urea in a thermal process in ammonia is convertible, which is fed into the exhaust line in terms of flow in front of the SCR catalyst.

One of the apparatus for producing ammonia according to the DE 10 2004 042 225 A1 similar device is also from the DE 102 06 028 A1 known. Here, too, urea pellets or prills are converted into ammonia in an ammonia reactor. This is fed from an outlet zone of the ammonia reactor via a feed line and a nozzle in an exhaust pipe coming from the engine upstream of an SCR catalyst.

Also from the DE 199 60 976 A1 a device for the production of ammonia is known, from which the generated ammonia is fed via a feed line into an exhaust pipe coming from the engine upstream of an SCR catalyst.

All known devices of the aforementioned type have the disadvantage, namely that in certain operating states of the internal combustion engine an overproduction of ammonia is unavoidable, which results from the inaccuracy of the metering of the urea and a non-utilization of the excess ammonia in the SCR catalyst ( en) and thus has an ammonia slip result. In order to remedy this undesirable but hardly avoidable problem and to prevent the escape of ammonia into the atmosphere, so far output of the SCR catalyst (s) or subsequently to these ammonia barrier catalysts are provided. These take up space and cause considerable additional costs.

It is accordingly an object of the invention to remedy the described problem of ammonia slip in a different way than by providing Ammoniaksperrkatalysatoren.

This object is achieved in an exhaust aftertreatment device of the generic type by the invention specified in the characterizing part of claim 1.

Advantageous embodiments of this solution are characterized in the subclaims.

In the solution according to the invention, in contrast to previously not the dosage of urea solid or urea water solution, but the dosage of the ammonia produced from this starting material by means of the ammonia reactor perfected while the output of the ammonia reactor given ammonia or the gas mixture containing a Supplied metering and fed by means of this needs in the exhaust gas flow in front of the SCR catalyst (s). This is done by commands of a computer-aided working electronic control and control unit, with which the control-relevant organs of the metering device are acted upon. The metering device may have a metering valve, but also a buffer memory, which communicates via a connecting channel with the output of the ammonia reactor given outlet chamber and in which an overproduction or deliberately generated supply of ammonia is temporarily stored. The feed of the ammonia or the gas mixture containing this can be supported by a built-in the connecting channel feed pump. The metered addition of the ammonia or the gas mixture containing this in the exhaust line via a metering with the built-shut-off / metering valve, which is preferably controlled by the electronic control and control unit. This works on the basis of stored motor and / or driving operation data, maps and / or characteristics as well as actual operating values and controls the operation depending on the result of executed nominal-actual comparisons the urea metering device and ammonia metering device and optionally other facilities. By means of the control and control unit, the ammonia is adjusted in terms of time and quantity to the extent that this gas can be converted without residue into another gas mixture which can be discharged into the atmosphere without harmful effects in the context of its intended use for NO _x reduction in the SCR catalyst.

For the sake of completeness, there is also the DE 103 26 055 A1 mentioned, from which an exhaust aftertreatment device of an internal combustion engine, in particular of a motor vehicle is known, in which produced with the aid of a fuel cell fuel system produced electricity and the resulting reformate or fuel cell exhaust gas of a treatment device can be fed, by means of which a generation of ammonia. This ammonia treatment device is connected via a line with a arranged in the exhaust pipe of the engine reduction catalyst in combination. This line is connected to a metering device and optionally a buffer, via which organs the ammonia produced is fed to the reduction catalyst. However, nothing is said about a regulation and control of this ammonia dosing. In this respect, the solution according to the invention, on the other hand, also provides a technical teaching which remedies the problem described above.

Further, not yet mentioned features of the invention will become apparent from the following description of some embodiments thereof with reference to the drawing. In the drawing show:

1 schematically a first embodiment of the device according to the invention, in the solid urea z. B. is used in the form of urea pellets as ammonia supplier,

2 schematically an alternative solution for a subsection of the device according to 1 .

3 1 schematically shows a further embodiment of the device according to the invention, in which a urea-water solution is used as an ammonia supplier,

4 . 5 and 6 one embodiment of the dosing device according to the invention.

In the figures, the same or corresponding parts / components are marked with the same reference numerals.

In 1 is with 1 a reservoir for solid urea pellets called. These urea pellets are preferably prefabricated as urea granules in the form of equal sized balls with a diameter of a few tenths of a millimeter to several millimeters. The urea pellets are in a pantry 2 internally of the storage container 1 storable as bulk material and in the latter via a closable filling opening 3 fillable. The pantry 2 tapers in a funnel shape 4 to an outlet 5 out. At the outlet 5 closes a pellet metering device 6 and to these in turn a pellet accelerator 7 at. At the exit 8th closes a pellet shot channel 9 An in a room or a zone 10 in a reactor for ammonia production opens. The latter is hereinafter ammonia reactor 11 called. This points in the area of the room or the zone 10 a arranged at the end of the free firing range pellet baffle 12 on. Furthermore, the ammonia reactor 11 a urea evaporation device 13 and in the example shown, subsequently a hydrolysis catalyst 14 on. In the pellet shot channel 9 is - preferably moved close to its reactor-side end / exit - a shut-off 1.9 , for example, gate valve, built by commands - see arrow 9.2 - An electronic control and electronic control unit ECU is controlled and is only switched to open or forward position when a promotion of urea pellets is to take place, so both the pellet metering device 7 as well as the pellet accelerator 8th operate. As soon as pellet dosing no longer occurs, the obturator 1.9 switched into shut-off position, so that then no hot gases in the shut-off part of the firing channel 9 can penetrate. With 15 In the individual exemplary embodiments, an exhaust gas line is designated which discharges the exhaust gas of an internal combustion engine which can be treated with the aid of the ammonia produced. The storage tank 1 , the metering device 6 and the pellet accelerator 7 can be the same or similar as the corresponding components according to the DE 10 2004 042 225 A1 be known apparatus for ammonia production. The storage tank 1 is preferably arranged and designed so that in his room 2 stockpiled urea pellets by gravity out of it and out through the pellet outlet 5 in the metering device 6 reach. This has an electric motor 6a drivable mechanical conveyor and an outlet 6b on top of which the required urea pellets in the pellet accelerator 7 reach. This has internally one by an electric motor 7a powered pellet accelerator, by means of which each fed urea pellet can be accelerated to a speed of the order of up to 100 m / sec and then via the outlet 8th in the firing channel 9 and about this continued in the Ammonia reactor 11 is einschießbar. The operation of both electric motors 6a respectively. 7a is via associated electrical control lines 1.6 respectively. 7.1 from the electronic control unit ECU forth according to needs controllable. The ammonia reactor 11 is outside the exhaust pipe 15 arranged at a suitable location.

The ammonia reactor 11 has an outer housing 16 in which within the room or the zone 10 the urea evaporator 13 z. B. in the form of a cylindrical heating tube and in the rear of the pellet baffle wall 12 is arranged so that the gas mixture produced on the outside past her to the subsequent hydrolysis 14 can flow. This extends over the entire cross section of the outer housing 16 , Flowwise after the hydrolysis catalyst 14 is in the case 16 of the ammonia reactor 11 an outlet chamber 17 from which the generated, ammonia-containing gas mixture via a connecting channel 18 a downstream metering device according to the invention 19 can be fed. This is discussed in more detail later. To the metering device 19 At the end a dosing line closes 20 on, in the exhaust pipe 15 leads and there spaced fluidly before at least one in the exhaust pipe 15 built-in SCR catalyst 21 in a mixing zone 22 in which the supplied ammonia-containing gas mixture before entering the SCR catalyst (s) 21 is intimately mixable with the exhaust gas. For ammonia production in the ammonia reactor 11 In addition to the urea, water or water vapor is necessary in order to be able to chemically treat the harmful isocyanic acid which forms during the thermolysis of the urea particles accordingly. The necessary water can z. B. directly into the room or the zone 10 be metered. Alternatively and preferably, however, the residual water vapor content of the exhaust gas is used as a water vapor supplier, for which in the case of 1 and 2 an exhaust partial flow from the exhaust pipe 15 via a branching off this supply line 23 into the room or the zone 10 of the ammonia reactor 11 is fed, in demand-controlled amount via a control of the control electronics via the control line 1.24 correspondingly adjusted control valve 24 ,

In case of 2 is the ammonia reactor 11 between the two sections 1.23 . 2.23 installed an exhaust gas bypass line. This branches with her section 1.23 at a branch point 1.15 from the exhaust pipe 15 flows and flows in the direction of the ammonia reactor 11 with her section 2.23 at 2.15 back into the exhaust pipe 15 one.

In this case, the bypass line section is used 1.23 similar to the feed line 23 in case of 1 for supplying a partial exhaust gas stream into the ammonia reactor 11 which partial exhaust stream is also used here with its residual water vapor content as a water supplier to the resulting in the evaporation of urea in addition to ammonia harmful isocyanic acid then in the hydrolysis 14 chemically convert to ammonia and carbon dioxide. The amount of partial exhaust gas flow is about one in the region of the input 15 the exhaust bypass line 1.23 arranged shut-off / throttle 24 adjustable, which can take a shut-off position and different sized open positions and by a servomotor 24a which is able to actuate its commands via the control line 1.24 from the control unit ECU. The bypass line section 2.23 is the outlet of the outlet chamber 17 through a shut-off / throttle 25 shut-off or switchable to passage, by means of a servomotor 26 , which also sends its control commands from the electronic control unit ECU via a control line 1.26 receives. With the shut-off / throttle valve 25 is also in their range of motion from the outlet chamber 17 branching connection channel 18 to the metering device 19 taxable and registrable. In this way, it is possible to produce the ammonia-containing gas mixture produced in the ammonia reactor either via the metering device according to the invention 19 or directly over the bypass line section 2.23 in the exhaust pipe 15 feed.

The latter has the advantage that even in case of failure or malfunction of the metering device 19 an injection of the generated ammonia gas mixture in the exhaust pipe 15 is possible.

The embodiment of 3 differs from that according to 1 only partially due to the use of another ammonia supplier, namely a urea water solution. This is in a HWL tank 27 storable and out of this by means of a metering device 28 giving their commands via control line 1.28 from the electronic control unit ECU, via a nozzle 29 into the room or the zone 10 of the ammonia reactor can be fed. The baffle 12 , as in 1 . 2 is not required here, otherwise the ammonia reactor 11 according to 3 be the same or similar to that of 1 . 2 , In 3 is also exemplified, such as SCR catalysts 21 can be flowed through in parallel in a silencer 30 are housed. This has a housing 31 , a gas-tight partition 32 , a non-gas-tight retaining wall 33 , an exhaust gas inlet pipe 34 and an exhaust tailpipe 35 on. The SCR catalysts 21 are with their enclosures as modules through the two walls 32 . 33 held in mounting position. The partition 32 separates the interior of the muffler 30 in an exhaust gas inlet space 36 into the exhaust gas inlet pipe 34 opens, and an exhaust gas exhaust space 37 , in the after flowing through the SCR catalysts 21 cleaned exhaust gas exits and from these via the tailpipe 35 is discharged into the atmosphere.

The following is on the production of ammonia with the devices according to 1 to 3 shortly received.

In the case of the examples according to 1 . 2 are the urea pellets from the reservoir 1 by means of the metering device 6 in controlled amount / number taken and the pellet accelerator 7 transported. With this, each supplied urea pellet is internally accelerated mechanically to a high speed, then at this speed in the outlet side subsequent firing channel 9 and via this further into the ammonia reactor 11 shot down where it is at the end of the firing range at the local pellets baffle wall 12 is crushed into a variety of fragments. These pellets fragments are immediately thereafter by means of the urea evaporation device 13 converted at temperatures up to about 550 ° C in a ammonia (NH ₃ ) and isocyanic acid (HNCO) containing gas mixture. This is then combined with water vapor, resulting in the case shown from the residual water vapor content in the exhaust gas of the internal combustion engine, through the hydrolysis 14 passed, wherein the isocyanic acid is converted into ammonia and carbon dioxide. At the end of this process is the output of the hydrolysis catalyst 14 in the outlet room 17 of the ammonia reactor 11 a gas mixture containing ammonia, which is then fed to its further intended use.

In case of 3 is the urea water solution by means of the metering device 28 over the nozzle 29 into the room or the zone 10 of the ammonia reactor 11 injected and therein by means of the evaporation device 13 converted at temperatures up to about 550 ° C in a ammonia (NH ₃ ) and isocyanic acid (HNCO) containing gas mixture. The further procedure is then the same as in the case of 1 . 2 ,

According to the invention that in the ammonia reactor 11 produced ammonia or ammonia-containing gas mixture by means of the metering device 19 in the exhaust pipe 15 fed.

Below is on various design options and functionalities of the metering device 19 discussed in more detail.

To the dosing device 19 generally leads to the connection channel 18 back and forth of the metering device 19 the dosing line goes 20 starting in the exhaust pipe 15 , there in the mixing zone 22 opens.

The metering device 19 generally has a metering valve 38 on. In addition, the metering device can be a buffer memory 39 for an intermediate storage of the ammonia reactor 11 from its outlet chamber 17 over the connection channel 18 have supplied ammonia or the ammonia-containing gas mixture. Furthermore, the metering device 19 one in the connection channel 18 built-in, the promotion and compression of the in the cache 39 feeding gas serving feed pump 40 exhibit. The metering valve 39 is in the case of 4 at the beginning with the connection channel 18 and in the case of 5 . 6 at the beginning via a connection channel 41 with the exit 42 of the buffer memory 39 connected. At the outlet of the metering valve 38 the dosing line closes 20 at. The metering valve 38 can z. B. be formed by an electromagnetically actuated shut-off / passage valve or by an electromechanically adjustable in its passage cross-section (also lockable) throttle valve. The cache 39 According to its design, it can either have a space-fixed, predetermined receiving volume or a spatially variable receiving volume, in particular under pressure, for the gas to be injected. The metering valve 38 is via a control line 38/1 controlled by the electronic control unit ECU. Also, the operation of the feed pump 40 - If available - such as their on and off times, speed or power, is preferably through the control and control unit ECU via a control line 40/1 controlled.

As for the functionality of the metering device according to the invention 19 As far as the aim is that with her the ammonia or the ammonia-containing gas mixture produced in the ammonia reactor time and volume exactly to the engine operating incidental exhaust gas into the exhaust pipe 15 can be fed, in the sense or with the aim of a 100% conversion of the ammonia during the in the / the catalyst (s) 21 ongoing catalytic process.

The electronic control and control unit operates on the basis of stored engine and / or driving operation data, maps and / or characteristics and recorded operating and exhaust gas actual values. The latter are using sensors 43 captured and via control lines 43/1 supplied to the control and control unit ECU and compared by this with the stored setpoint values. The result is always an on-demand operation of the relevant for the dosage of urea or urea water solution organs 6 . 6a ; 7 . 7a ; 9a 28, as well as the organs involved in the production of ammonia 13 . 24 as well as the control-relevant parts 38 . 40 the metering device 19 realized. The operation of the relevant for the dosage of urea or urea water solution organs 6 . 6a ; 7 . 7a ; 9a . 28 by the control and control unit ECU exactly to the operational demand for ammonia, also with regard to a possible temporary storage of the same in the buffer memory 39 Voted. A possible temporary overproduction of ammonia and its storage in the buffer memory 39 During certain engine operating phases then allows due to the high availability and a particularly sensitive metering of ammonia in the exhaust pipe 15 ,

Claims (6)

Exhaust after-treatment device of an internal combustion engine, in particular of a motor vehicle, with at least one SCR catalyst in the exhaust line and a device for generating ammonia with an outside of the exhaust line arranged ammonia reactor, the urea in solid form, for. As urea pellets, or liquid form such as a urea water solution from a reservoir can be supplied by means of a metering device and in which the urea is converted in a thermal process in the presence of water vapor in ammonia, which flows into the exhaust line upstream of the / the SCR catalyst (en), characterized in that in the ammonia reactor ( 11 ) produced ammonia or ammonia-containing gas mixture of the ammonia reactor ( 11 ) downstream metering device ( 19 ) can be supplied and by means of this exactly in terms of time and quantity produced by the engine operating conditionally exhaust gas in the sense of a 100% conversion within the in the SCR catalyst (s) ( 21 ) running catalytic process in the exhaust pipe ( 15 ), whereby control-relevant bodies ( 38 . 40 ) of the metering device ( 19 ) are controlled by commands of a computer-aided operating electronic control unit (ECU), wherein further output of the ammonia reactor ( 11 ) an outlet space ( 17 ), from which a connection channel ( 18 ) to the dosing device ( 19 ), and the output of the metering device ( 19 ) a dosing line ( 20 ) going into the exhaust pipe ( 15 ) and there in a flow before the SCR catalyst (s) ( 21 ) given mixing zone ( 22 ), that the dosage device further comprises - a buffer memory ( 39 ) for intermediate storage of the ammonia reactor ( 11 ) via the connection channel ( 18 ) supplied ammonia or ammonia-containing gas mixture, and - one in the connecting channel ( 18 ), the extraction and compression of the buffer ( 39 ) to be introduced ammonia or ammonia-containing gas mixture serving pump ( 40 ), and - a metering valve ( 38 ), which at the beginning via a connecting channel ( 41 ) with the buffer memory ( 39 ) communicates and at the output the dosing line ( 20 ). Exhaust after-treatment device according to claim 1, characterized in that the metering valve ( 38 ) is formed by an electromagnetically actuated shut-off / passage valve. Exhaust after-treatment device according to claim 1, characterized in that the metering valve ( 38 ) is formed by an electronically adjustable in its passage cross-section throttle valve. Exhaust after-treatment device according to claim 1, characterized in that the buffer memory ( 39 ) has a space fixed predetermined recording volume. Exhaust after-treatment device according to claim 1, characterized in that the buffer memory ( 39 ) has a spatially variable, in particular under pressure increasing receiving volume. Exhaust gas aftertreatment device according to claim 1, characterized in that the electronic control and control unit (ECU) based on stored motor and / or driving operation data, characteristics and / or characteristics as well as detected operating and exhaust gas actual values works and the result of target / actual Value comparison according to the operation of the relevant organs for the dosing of the urea or urea 6 . 6a ; 7 . 7a ; 1.9 ; 28 ), and the organs involved in the production of ammonia ( 13 . 24 ) as well as the management-relevant bodies ( 38 . 40 ) of the metering device ( 19 ) exactly coordinated with each other controls.

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