DE102015015973A1 - Exhaust after-treatment device for an internal combustion engine of a motor vehicle - Google Patents

Abstract

The invention relates to an exhaust aftertreatment device (10) for an internal combustion engine of a motor vehicle, comprising at least one exhaust gas passage (14) through which exhaust gas of the internal combustion engine is provided, with a metering device (18) by means of which at least one supply point (20) comprises a reducing agent for de-stoking the exhaust gas the exhaust duct (14) can be introduced, and with at least one downstream of the feed point (20) arranged catalyst (22) for Entsticken the exhaust gas, wherein the exhaust passage (14) comprises a supply (20) and up to an upstream of the catalyst ( 22) and downstream of the feed point (20) or downstream of an optional element (28) arranged terminal (32) extending processing region (30), which is at least partially formed by a wall (36) of a non-catalytic ceramic material.

Description

The invention relates to an exhaust aftertreatment device for an internal combustion engine of a motor vehicle according to the preamble of patent claim 1.

Such exhaust aftertreatment devices for internal combustion engines of motor vehicles are already well known from the general state of the art. The exhaust gas aftertreatment device comprises at least one exhaust gas passage through which exhaust gas of the internal combustion engine can flow, and a metering device, by means of which a reducing agent for removing the exhaust gas into the exhaust gas channel and thus into the exhaust gas flowing through the exhaust gas channel can be introduced at at least one feed point. Further, at least one catalyst is provided for Entsticken the exhaust gas, wherein the catalyst is arranged downstream of the feed point. In particular, the catalyst is an SCR catalyst (SCR-selective catalytic reduction), wherein by means of the SCR catalyst, in particular in the SCR catalyst, a reaction, in particular a chemical reaction, is effected, within whose scope at least constituents of the reducing agent with nitrogen oxides contained in the exhaust gas (NO _x ) to react with water and nitrogen. As a result, nitrogen oxides contained in the exhaust gas can be reduced, which is also referred to as de-staking or denoxing of the exhaust gas.

This means that the reducing agent and the catalyst serve to de-stench the exhaust gas. This is understood to mean that the exhaust gas of the internal combustion engine designed, for example, as a diesel engine may contain nitrogen oxides (NO _x ) which are at least partially removed or eliminated with the aid of the reducing agent. Here, the nitrogen oxides, for example, with ammonia (NH ₃ ) from the reducing agent to nitrogen and react with water. This reaction takes place in the context of a selective catalytic reduction (SCR), in particular in the catalyst which can be flowed through by the exhaust gas mixed with the reducing agent and which can be a component of the exhaust gas aftertreatment device.

Usually, the reducing agent is an aqueous solution, in particular an aqueous urea solution, which is introduced into the exhaust gas channel, in particular injected, for example by means of the metering device. It has been found that by introducing the reducing agent into the exhaust gas channel deposits and in particular urea deposits can occur in the interior of the exhaust gas aftertreatment device, in particular in the interior of an exhaust gas guide element delimiting the exhaust gas channel.

Further, the EP 1 676 985 A1 an exhaust gas aftertreatment device for an internal combustion engine, with an SCR catalyst for Entsticken exhaust gas of the internal combustion engine.

In addition, the disclosed FR 2 731 746 A1 an exhaust guide element for guiding exhaust gas of an internal combustion engine. Also the US 2010/0005791 A1 discloses an exhaust aftertreatment device for an internal combustion engine.

Object of the present invention is to develop an exhaust aftertreatment device of the type mentioned in such a way that deposits that result from the introduction of the reducing agent in the exhaust passage can be kept at least low.

This object is achieved by an exhaust gas aftertreatment device having the features of patent claim 1. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims.

In order to develop an exhaust aftertreatment device specified in the preamble of claim 1 type such that deposits resulting from the introduction of the reducing agent in the exhaust duct can be kept at least low, it is provided according to the invention that the exhaust duct comprising a feed point and up to a processing area extending upstream of the catalyst and located downstream of the feed point, which is thus arranged upstream of the example of an SCR catalyst catalyst, wherein the treatment area is at least partially formed by a wall of a non-catalytic, ceramic material. This means that the exhaust gas channel is formed at least in a longitudinal region arranged upstream of the catalyst through the wall of the non-catalytic, ceramic material. It is provided, for example, that the wall is formed by a coating which is applied to a base body, which is formed from a different material from the non-catalytic, ceramic material. The wall of the non-catalytic, ceramic material prevents excessive adhesion of deposits, particularly urea deposits, and by-products, so that excessive deposits resulting from the reducing agent inside the exhaust aftertreatment device can be avoided.

By the non-catalytic material is meant that the material is catalytically ineffective is or does not act catalytically and thus does not cause or support a reaction of nitrogen oxides contained in the exhaust gas with constituents contained in the reducing agent, in particular in contrast to the catalyst.

Characterized in that the wall of the non-catalytic, ceramic material delimits at least the length range of the exhaust passage, the exhaust gas flowing through the exhaust gas flow along the wall and thereby touch the wall, so that the wall of the exhaust gas and thus the metered into the exhaust reducing agent directly exposed. However, since the wall is formed of the non-catalytic ceramic material, excessive deposits on the wall can be avoided. Furthermore, a surface finish of the wall can be created such that the amount of reducing agent to be introduced into the exhaust gas can be kept low even at low temperatures while at the same time realizing a sufficient effective denitrification of the exhaust gas.

By using the wall of the non-catalytic ceramic material, it is possible to prevent excessive adhesion of urea deposits and by-products both in areas located close to the feed point and in areas far from the feed point. to avoid. As a result, particularly high amounts of the reducing agent can be introduced into the exhaust gas, without causing excessive deposits, so that a particularly high efficiency in terms of denitrification of the exhaust gas and a particularly high efficiency of the internal combustion engine can be realized.

In order to keep the costs of the exhaust aftertreatment device particularly low, the wall is preferably formed by the previously described coating, which is thus designed as non-catalytic or catalytically non-effective, ceramic coating, which prevents urea deposits and deposits of secondary products. This makes it possible, in particular, to realize a particularly large angle at which the reducing agent is introduced into the exhaust gas duct by means of the metering device in an area arranged close to the supply point and / or in a region encompassing the supply point, so that respective diameters of drops of the Reducing agent can be kept very low. The aforementioned angle is also referred to as spray angle. This embodiment is based on the finding that small diameters of the drops of the reducing agent lead to a particularly advantageous evaporation of the reducing agent. In other words, smaller diameters of the droplets lead to a better evaporation of an amount of reducing agent introduced into the exhaust gas duct by means of the metering device, whereby excessive cooling of wall regions bounding the exhaust duct can be avoided.

Since in the exhaust gas aftertreatment device according to the invention deposits that result from the introduction of the reducing agent into the exhaust duct can be kept at least low, the fuel consumption of the internal combustion engine can be kept low, since additional regeneration processes to dissolve deposits are no longer required.

The non-catalytic, ceramic material is selected in particular according to thermal aspects and addition aspects, in particular in conjunction with the reducing agent used. When using several or different reducing agents, in particular in different, several areas, the wall, in particular depending on the reducing agent used, consist of different, ceramic and non-catalytic materials.

Further, it is possible to form the wall by a solid component formed of the non-catalytic ceramic material and not by a coating of a component. Under the non-catalytic, ceramic material or the wall is to be understood that the material is not an active material and therefore not the exhaust aftertreatment, but purely the prevention of deposits or deposits is used.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the figure description and / or alone in the single figure can be used not only in the respectively indicated combination but also in other combinations or alone, without the frame to leave the invention.

The drawing shows in the single FIGURE is a schematic sectional view of an exhaust aftertreatment device for an internal combustion engine of a motor vehicle, wherein at least one wall of a non-catalytic, ceramic material is formed, by means of which by introducing a reducing agent caused deposits can be kept at least low.

The single FIGURE shows a schematic sectional view of a whole 10 designated exhaust aftertreatment device for an internal combustion engine of a motor vehicle. The internal combustion engine is designed for example as a diesel engine and serves to drive the motor vehicle. The exhaust aftertreatment device 10 comprises at least one exhaust gas guide element 12 , which is also referred to as an exhaust pipe and an exhaust gas flow through the exhaust gas of the internal combustion engine 14 having. The flow of exhaust gas through the exhaust duct 14 is in the figure by an arrow 16 illustrated.

The exhaust aftertreatment device 10 further comprises a metering device 18 , which is also referred to as nozzle. By means of the metering device 18 is at least one feed point 20 a reducing agent in the exhaust passage 14 and thus into the exhaust duct 14 flowing exhaust gas introduced, in particular einspritzbar. The reducing agent serves to Entsticken the exhaust gas. This means that with the aid of the reducing agent in the exhaust gas contained nitrogen oxides (NO _x ) are at least partially removed from the exhaust gas. The reducing agent is for example an aqueous urea solution, from which in the exhaust gas channel 14 after introduction into the exhaust gas duct 14 Ammonia (NH ₃ ) is released. The nitrogen oxides contained in the exhaust gas can react with the ammonia as part of a selective catalytic reduction (SCR) to nitrogen and water.

The exhaust aftertreatment device 10 also includes one as SCR catalyst 22 formed catalyst, which in the flow direction of the exhaust gas through the exhaust passage 14 downstream of the feed point 20 is arranged. The exhaust aftertreatment device 10 may further comprise a particulate filter, not shown in the figure, which, for example, in the flow direction of the exhaust gas through the exhaust passage 14 upstream of the feed point 20 or as an SCR coated particulate filter (SCRf / SDPF) downstream of the feed point 20 is arranged. Since the internal combustion engine is designed here as a diesel engine, the particulate filter is, for example, a diesel particulate filter (DPF).

By means of the SCR catalyst 22 , which can be flowed through by the exhaust gas and the reducing agent metered or introduced into the exhaust gas, the selective catalytic reduction is effected or supported. The SCR catalyst 22 thus comprises a catalytic material, that is a catalytically active material, which causes or supports the SCR.

From the Fig. It can be seen that the reducing agent to form a jet in the exhaust passage 14 is introduced, the jet as a spray 24 referred to as. The spray 24 is for example at least substantially conical or has a conical shape, the central axis in the Fig. Shown by a dotted line and with 26 is designated. The central axis 26 is, for example, an imaginary straight line, which coincides with an injection direction into which the reducing agent by means of the metering device 18 at the feed station 20 in the exhaust duct 14 introduced and injected in particular. This means that the spray 24 along the injection direction and thus along the central axis 26 from the metering device 18 spreads away. The metering device 18 is thus a device for metering a reducing agent, in particular for metering urea-containing solutions for Entsticken the exhaust gas.

Downstream of the feed point 20 and upstream of the SCR catalyst 22 is at least one element in the illustrated embodiment 28 arranged, which is for example a mixing and evaporation element. This element 28 but is optional for the general embodiment of the inventive idea and can thus be absent in other embodiments, not shown. An arrangement of the element 28 can be provided, but not necessarily. By means of the element 28 For example, a particularly advantageous mixing of the exhaust gas with the metered reducing agent is effected. Alternatively or additionally, by means of the element 28 an evaporation of the metered reducing agent can be effected so that a particularly advantageous mixing of the reducing agent can be represented by means of the exhaust gas. Alternatively or additionally, the element 28 designed as a flow-guiding element for guiding or guiding the exhaust gas, so that a particularly favorable flow of the exhaust gas through the exhaust duct 14 can be realized.

The exhaust duct 14 has a treatment area 30 on, which is also referred to as a preparation route. From the Fig. It can be seen that the treatment area 30 in the flow direction of the exhaust gas to before the SCR catalyst 22 extends while the feeder 20 includes. This means that the feed point 20 Part of the treatment area 30 which is up to an upstream of the SCR catalyst 22 and downstream of the feed point 20 arranged terminal 32 extends. This means that the treatment area 30 until ahead of the SCR catalyst 22 or its catalytically effective range, but does not extend beyond, so that the SCR catalyst 22 or its catalytically active area is not part of the treatment area 30 is. Below the catalytic effective range of the SCR catalyst 22 is the area to understand which the SCR effects or supports. From the Fig. It can be seen that the treatment area 30 also upstream of the feed point 20 arranged length range 34 the exhaust duct 14 includes.

In order now excessive, from the introduction of the reducing agent in the exhaust duct 14 resulting deposits, especially urea deposits, to avoid, is the treatment area 30 at least partially through a wall 36 formed from a non-catalytic, ceramic material. This means that the wall 36 is formed from a catalytically inactive or catalytically non-effective material. By this is meant that the material from which the wall 36 is formed, does not participate in the exhaust aftertreatment or does not cause or support the SCR. The treatment area shown in the figure 30 is thus a possible area in which the exhaust duct 14 may be limited or formed by a wall of a ceramic, non-catalytic material, thereby to avoid urea deposits and deposits of secondary products of urea or to keep it particularly low. It was found that through the use of the wall 36 the adhesion of such deposits in the exhaust aftertreatment device 10 at least can be reduced.

An area in which the wall 36 is arranged of the ceramic, non-catalytic material, can be kept to a minimum, so that, for example, only a direct impact surface or contact surface of the spray 24 through the wall 36 is formed. This can be through the wall 36 For example, a baffle or the like may be formed, on which the spray 24 is sprayed when introducing the reducing agent. Furthermore, it is conceivable, an entire, the exhaust duct 14 limiting surface from the nozzle to the flow direction of the exhaust gas to the SCR catalyst 22 or its catalytically active material through the wall 36 to build.

The treatment area 30 extends advantageously so far upstream of the feed 20 as a reducing agent for Entsticken the exhaust gas through the feed 20 in the exhaust duct 14 can be introduced. As a result, it can be prevented or at least reduced that the reduction agent, which is introduced into the exhaust gas channel, is introduced 14 upstream of the feed point 20 on the wall 36 meets, can settle there.

The wall 36 thus serves to at least keep deposits that may result from the introduction of the reducing agent, wherein the wall 36 may also be formed from a different material of a ceramic material. However, it has surprisingly been found that urea deposits can be kept particularly low, in particular by the use of ceramic materials. The wall 36 is for example by a solid component, in particular by the exhaust gas guide element 12 , educated. Alternatively, it is conceivable that the wall 36 is formed by a coating which is applied to a base body. This main body is formed, for example, from a different material from the non-catalytic, ceramic material, said main body, for example, by the exhaust pipe (exhaust guide element 12 ) can be formed by itself. This means that the exhaust pipe itself may be ceramic coated, the ceramic coating up to active exhaust aftertreatment areas, in particular the SCR catalyst 22 , can pull. In other words, the exhaust pipe can be up to the SCR catalyst 22 be coated. Under the SCR catalyst 22 is a component to understand, which is catalytically effective and causes or supports the SCR. In other words, the SCR catalyst 22 a component with at least one with respect to the SCR catalytically active material.

The element 28 , which in the illustrated embodiment in the treatment area 30 is arranged and supports the preparation of the reducing agent in the exhaust gas is advantageously at least partially formed from a non-catalytic ceramic material. Here, the element 28 if it is arranged in one embodiment, either completely formed of the non-catalytic ceramic material or of a base body formed of a material different from the non-catalytic ceramic material, on which the non-catalytic, ceramic material is applied as a coating. It is essential, above all, that the possible contact surface with the reducing agent consists of the non-catalytic, ceramic material.

The element 28 Here, the preparation by mixing or mixing of the exhaust gas flow with the reducing agent or by evaporation of the reducing agent support, wherein the element 28 For example, has a shape for guiding the exhaust stream.

LIST OF REFERENCE NUMBERS

10

exhaust treatment device

12

Exhaust guide element

14

exhaust duct

16

arrow

18

metering

20

induct

22

SCR catalyst

24

spray

26

central axis

28

element

30

treatment area

32

terminal

34

length range

36

wall

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1676985 A1 [0005]
• FR 2731746 A1 [0006]
• US 2010/0005791 A1 [0006]

Claims (7)

Exhaust aftertreatment device ( 10 ) for an internal combustion engine of a motor vehicle, with at least one exhaust gas of the internal combustion engine through-flowable exhaust gas channel ( 14 ), with a metering device ( 18 ), by means of which at at least one feed point ( 20 ) a reducing agent for Entsticken the exhaust gas in the exhaust passage ( 14 ) and at least one downstream of the feed point ( 20 ) arranged catalyst ( 22 ) for de-stoking the exhaust gas, characterized in that the exhaust duct ( 14 ) one the Zuführstelle ( 20 ) and up to an upstream of the catalyst ( 22 ) and downstream of the feed point ( 20 ) terminal ( 32 ) ( 30 ), which at least partially by a wall ( 36 ) is formed of a non-catalytic, ceramic material. Exhaust aftertreatment device ( 10 ) according to claim 1, characterized in that the wall ( 36 ) is formed by a coating which is applied to a base body, which is formed of a different material from the non-catalytic, ceramic material. Exhaust aftertreatment device ( 10 ) according to claim 1 or 2, characterized in that the downstream of the feed point ( 20 ) terminal ( 32 ) of the extending processing area ( 30 ) directly in front of the catalyst ( 22 ) is arranged. Exhaust aftertreatment device ( 10 ) according to one of the preceding claims, characterized in that the treatment area ( 30 ) also at least as far upstream of the feed point ( 20 ), such as a reducing agent for de-stoking the exhaust gas through the supply ( 20 ) in the exhaust duct ( 14 ) can be introduced. Exhaust aftertreatment device ( 10 ) according to one of the preceding claims, characterized in that in the treatment area ( 30 ) an element ( 28 ) is arranged to support the processing, which is at least partially formed of a non-catalytic ceramic material. Exhaust aftertreatment device ( 10 ) according to claim 5, characterized in that the non-catalytic, ceramic element ( 28 ) is formed by a coating which is applied to a base body, which is formed of a different material from the non-catalytic, ceramic material. Exhaust aftertreatment device ( 10 ) according to one of the preceding claims, characterized in that the non-catalytic, ceramic material of the wall ( 36 ) and / or the element ( 28 ) in the treatment area ( 30 ) is arranged substantially in the region of a possible impact surface or contact surface of a metering of the reducing agent for Entsticken the exhaust gas.

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