DE102004043931B4 - exhaust treatment device - Google Patents

Abstract

Exhaust after-treatment device (1) for diesel engines, in particular, with a soot particle filter (5) for removing soot particles from the exhaust gas and an SCR catalytic converter (6) connected downstream of the soot particle filter (5), wherein the soot particle filter (5) and the SCR catalytic converter (6) a common housing (2) are arranged, wherein further in the housing (2) between an exhaust gas outlet of the particulate filter (5) and an exhaust gas inlet of the SCR catalyst (6) has a mixing chamber (12) with a Reduktionsmitteldosiereinrichtung (14) for metering reducing agent in the exhaust gas flow is provided,
wherein in the mixing chamber (12) an exhaust gas guide plate (16) is arranged to guide the exhaust stream, and
wherein the mixing chamber (12) is arranged in an end-side section of the housing (2),
characterized,
that the mixing chamber (12) is delimited by a bottom wall (4) and an intermediate wall (9) arranged inside the housing (2), and
the exhaust gas guide plate (16), together with the bottom wall (4), the intermediate wall (9) and a jacket (3) of the housing (2) delimiting the mixing chamber, delimits a channel in the mixing chamber (12) which forms a reaction zone (15) ,

Description

The invention relates to an exhaust aftertreatment device for diesel engines in particular with an element for removing soot particles from the exhaust gas and an element downstream SCR catalyst having the features of the preamble of claim 1.

An exhaust aftertreatment device of the generic type is known from DE 101 40 295 A1 known. To eliminate the soot particles, an oxidation catalyst is used, to which an SCR catalyst is connected downstream to reduce nitrogen oxides. Both catalyst elements are arranged in a common housing, wherein a mixing chamber is provided for the flow of the exhaust gas from the oxidation catalyst into the SCR catalyst between the two catalyst elements. Furthermore, an ammonia feed device, via which ammonia is added to the exhaust gas, opens into the mixing chamber. At the outlet of the oxidation catalyst is an exhaust baffle, from which the exhaust gas is passed into the mixing chamber.

The disadvantage is that within the mixing chamber, a homogeneous distribution of the ammonia in the exhaust stream is not possible. Furthermore, uniform loading of the catalyst modules with exhaust gas due to a disordered flow of exhaust gas in the mixing chamber is not possible.

From the document WO 2003/036056 A1 the features of the preamble of independent claim 1 are known. Next teaches this document to provide rod-shaped bluff body in a mixing chamber, which cause additional turbulence of the exhaust stream.

The document DE 100 42 542 A1 teaches providing a mixing chamber between an exhaust gas outlet of a particulate filter and an exhaust gas inlet of an SCR catalyst.

The invention has for its object to improve the generic exhaust aftertreatment device such that in addition to a simplified elimination of the soot particles optimal mixing of supplied reducing agent and exhaust gas in the mixing chamber and a uniform application of the catalyst modules are achieved in a compact design of the device.

The above object is achieved by the combination of the features of independent claim 1. Preferred developments can be found in the subclaims.

According to the invention, an exhaust gas guide plate is provided in the mixing chamber which, together with a bottom wall, an intermediate wall and a jacket of a housing delimiting the mixing chamber, defines a channel which forms a reaction path.

The exhaust aftertreatment device according to the invention has the advantage that the soot particles are eliminated from the exhaust gas flow in a simple mechanical manner. Furthermore, the reaction path created in the mixing chamber by the exhaust gas guide has the advantage of an ordered overflow of the exhaust gas from the soot particle filter into the SCR catalytic converter, whereby a uniform admission of the individual catalyst modules is achieved. In addition, the reducing agent introduced into the exhaust gas flow can be evenly distributed in the exhaust gas flow through the created reaction path, which favors the reaction in the SCR catalytic converter and achieves the best possible nitrogen oxide reduction.

Finally, it is still advantageous that the placement of the soot filter and SCR catalyst in the housing itself is not hindered by the arrangement of the mixing chamber in an end portion of the housing and also a longest possible reaction path can be realized.

Further advantageous embodiments of the invention will become apparent from the dependent claims.

Reference to an embodiment shown in the drawing, the invention will be explained in more detail below.

Showing:

1 the mixing chamber with the reaction path according to the invention in a perspective front view and

2 the exhaust aftertreatment device in a partial side view.

The illustrated exhaust aftertreatment device 1 comprises an approximately cuboid, rounded at the corners housing 2 with a coat 3 attached to its longitudinal ends by bottom walls, of which the bottom wall 4 is shown is closed. Other forms of housing 2 However, are also conceivable within the scope of the invention.

Inside the case 2 are in an upper area a soot particle filter 5 and below that is an SCR catalyst 6 arranged. During the soot particle filter 5 has an approximately rectangular cross-section and with its longitudinal sides transverse to a housing high axis 7 (lying) installed is, the SCR catalyst consists of several circular cylindrical catalyst modules 6a to 6e , which are arranged side by side and in two layers one above the other. Both the soot particle filter 5 as well as the catalyst modules 6a to 6e extend in the longitudinal direction of the housing 2 parallel to a housing longitudinal axis 8th , By this arrangement of soot particle filter 5 and SCR catalyst 6 results in a compact design.

Other forms and arrangements of soot particle filters are also within the scope of the invention 5 and SCR catalyst 6 possible.

In the case 2 are intermediate walls at a distance from the floor walls 9 and 10 used by the soot particle filter 5 and the SCR catalyst 6 guided and stored at the same time. Further storage can be done on the bottom walls.

The exhaust gases leaving the diesel engine reach the inflow section of the soot particle filter in the region of the bottom wall (not shown) 5 , flow through it in the direction of the arrow and leave it through the outlet openings 11 ,

According to the invention, the outlet openings are now 11 in a mixing chamber 12 arranged in an end region of the housing 2 from the bottom wall 4 and the partition 9 is limited. That from the outlet openings 11 into the mixing chamber 12 Entering and freed from soot particles exhaust gas can here to the SCR catalyst 6 overflow, with its inlets 13 into the mixing chamber 12 protrudes. The implementation of soot particle filter 5 and catalyst modules 6a to 6e through the partition 9 in a sealed form, to avoid a false flow.

To reduce the nitrogen in the SCR catalyst 6 a reducing agent, preferably ammonia or more preferably urea-water solution, must be supplied to the exhaust gas. This is done by a metering device 14 in the mixing chamber 12 , By means of which the reducing agent is introduced into the exhaust gas stream. Regarding an optimal reaction in the SCR catalyst 6 on the one hand the best possible distribution of the reducing agent in the exhaust gas and on the other hand in the case of urea-water solution as a reducing agent whose complete hydrolysis with the release of ammonia necessary.

According to the invention, this is achieved in that of the soot particle filter 5 exiting exhaust gas over a relatively long reaction distance 15 from the outlet openings 11 out to the entrance openings 13 in the SCR catalyst 6 to be led. This reaction path is formed or limited 15 through an exhaust baffle 16 that in the mixing chamber 12 between exhaust soot filter 5 and the SCR catalyst 6 is built in and away from the bottom wall 4 to the intermediate wall 9 extends.

As 1 shows, has the exhaust baffle 16 an approximately S-shaped form, through which a meandering course of the reaction path substantially 15 results.

In detail is off 1 to recognize that entry into the reaction path 15 a first part 17 the exhaust baffle 16 forms, which laterally and with distance from the soot particle filter 5 directly on the coat 3 along to about half the height of the particulate filter 5 expands. To the section 17 closes with a bow another section 18 which extends substantially across the width of the housing 2 between the soot particle filter 5 and the SCR catalyst 6 extends. This section 18 sits down with a bow in a distance laterally along the mantle 3 about vertically extending intermediate piece 19 Continue with a bow in one to the bottom of the coat 3 spaced wall section 20 passes. This wall section 20 extends - like the section 18 - Over the width of the housing substantially 2 and enters with an approximately semicircular arc in between the two layers of the catalyst modules 6a . 6b . 6c and 6d . 6e to the periphery of the catalyst module 6e reaching tail 21 above.

The exhaust baffle 16 thus limited together with the coat 3 , the bottom wall 4 and the partition 9 a channel that controls the reaction path 15 forms. In conjunction with the radially directed outlet openings 11 in the soot particle filter 5 this results in a transverse to the longitudinal axis 8th directed flow, with much of the reaction path 15 on the coat 3 along leads.

To ensure the most uniform possible flow velocity in the reaction zone 15 to reach, are the individual sections of Abgasleitbleches 16 preferably aligned so that the cross-section of the channel, starting from the inlet region on the soot particle filter 5 to the mouth area on the catalyst module 6d constantly rejuvenated.

It is likewise advantageous if the reaction section is in the region of the metering device 14 and in particular in the area of the reducing agent outlet, it is similar to a Venturi nozzle. This allows a further improved mixing of the reducing agent with the exhaust gases or a further improved urea hydrolysis and thus a further improved exhaust gas purification.

According to 1 is the metering device 14 at the transition between section 18 and intermediate piece 19 , Of course, another arrangement, such as in the inlet region of the reaction zone 15 conceivable.

Claims (10)

Exhaust aftertreatment device ( 1 ) for in particular diesel engines with a soot particle filter ( 5 ) for removing soot particles from the exhaust gas and a soot particle filter ( 5 ) downstream SCR catalyst ( 6 ), wherein the particulate filter ( 5 ) and the SCR catalyst ( 6 ) in a common housing ( 2 ) are arranged, wherein further in the housing ( 2 ) between an exhaust gas outlet of the soot particle filter ( 5 ) and an exhaust gas inlet of the SCR catalyst ( 6 ) a mixing chamber ( 12 ) with a reducing agent dosing device ( 14 ) is provided for metering of reducing agent in the exhaust stream, wherein in the mixing chamber ( 12 ) an exhaust baffle ( 16 ) is arranged to guide the exhaust stream, and wherein the mixing chamber ( 12 ) in an end portion of the housing ( 2 ), characterized in that the mixing chamber ( 12 ) from a bottom wall ( 4 ) as well as one within the housing ( 2 ) arranged intermediate wall ( 9 ) is limited, and that the exhaust baffle ( 16 ) together with the bottom wall ( 4 ), the intermediate wall ( 9 ) and a jacket bounding the mixing chamber ( 3 ) of the housing ( 2 ) in the mixing chamber ( 12 ) defines a channel having a reaction path ( 15 ). Exhaust after-treatment device according to claim 1, wherein the soot particle filter ( 5 ) and the SCR catalyst ( 6 ) are arranged parallel to each other. Exhaust after-treatment device according to one of the preceding claims, wherein the soot particle filter ( 5 ) with its outflow end through the partition wall ( 9 ) through into the mixing chamber ( 12 ) and radially directed outlet openings ( 11 ) for the flow of the exhaust gas into the mixing chamber ( 12 ) having. Exhaust after-treatment device according to one of the preceding claims, wherein the exhaust gas guide plate ( 16 ) for forming a meandering reaction path ( 15 ) is bent several times. Exhaust after-treatment device according to one of the preceding claims, wherein the SCR catalyst ( 6 ) from a plurality of tubular catalyst modules ( 6a to 6e ) in the housing ( 2 ) are arranged running parallel to each other in the longitudinal direction, and that the reaction distance ( 15 ) from the exhaust baffle ( 16 ) is shaped such that the catalyst modules ( 6a to 6e ) are applied successively. Exhaust after-treatment device according to one of the preceding claims, wherein the reducing agent metering device ( 14 ) at the beginning of the reaction zone ( 15 ) is arranged. Exhaust after-treatment device according to one of the preceding claims, wherein the reducing agent metering device ( 14 ) is designed for the controlled supply of ammonia or urea-water solution in the exhaust gas stream. Exhaust gas aftertreatment device according to one of the preceding claims, wherein the course of the exhaust gas guide plate ( 16 ) shaped reaction section ( 15 ) starting from the soot particle filter ( 5 ) rejuvenates. Exhaust gas aftertreatment device according to one of the preceding claims, wherein the course of the exhaust gas guide plate ( 16 ) shaped reaction section ( 15 ) in the area of the reducing agent metering device ( 14 ) is executed narrowed. Exhaust after-treatment device according to one of the preceding claims, wherein the exhaust gas guide plate ( 16 ) is punched.

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