DE10140295B4 - Exhaust aftertreatment device for diesel engines - Google Patents

Abstract

Exhaust gas aftertreatment device for reducing particle and NO _x emissions in diesel engines, in which an SCR catalytic converter is connected after a controlled ammonia supply to a pre-catalyst used for particle oxidation and the formation of nitrogen oxide, characterized by a common housing (1) with an exhaust gas inlet (14) on one side and an exhaust gas outlet (15) on the other side, in which housing (1) is formed by chambers (2, 3, 4) sealed against one another by partition walls (16, 17) and a plurality of catalyst modules (5) are passed through these partition walls, the first section of which is a pre-cat element (51) with axial and / or radial inlet gas duct (511) and radial outlet gas duct (513) and the second section axially partitioned off against the pre-cat element (51) is an SCR cat element (52) with radial inlet gas duct ( 521) and axial and / or radial outlet gas guide (523), the inlet gas guide (511) of the pre-cat element (51) in a first chamber (2) with the exhaust gas inlet (14), the radial outlet gas duct (513) of the pre-cat element (51) and the radial inlet gas duct (521) of the SCR cat element (52) in a second Chamber (3), into which gaseous ammonia is fed, and the outlet gas duct (523) of the SCR cat element (52) are arranged in a third chamber (4) with the exhaust gas outlet (15).

Description

The invention relates to an exhaust gas aftertreatment device for reducing particulate and NO _x emissions in diesel engines, in particular for commercial vehicles, in which an SCR catalytic converter is used after a controlled ammonia supply, after a controlled ammonia supply, to a precatalyst used for particle oxidation and nitrogen oxide formation.

A method for reducing nitrogen oxides (NO _x ) on an SCR catalytic converter which is arranged in the exhaust line of a diesel engine with ammonia (NH ₃ ), which is preferably introduced into the exhaust gas stream upstream of the catalytic converter, is known, for example, from US Pat DE 197 20 209 C1 known. In particular, a controlled supply of ammonia is discussed here.

However, process principles for exhaust gas aftertreatment for the purpose of reducing particle and NO _x emissions in commercial vehicle diesel engines are also known, in which a pre-catalytic converter is provided in which reactive nitrogen oxide is generated, which accelerates the subsequent SCR reaction. Here, a corresponding pre-catalyst is used, which, in terms of the process, is followed by an external urea converter for generating ammonia, from which the ammonia generated is carried into the exhaust gas stream to the downstream SCR catalyst. (See reports on energy and process engineering BEV, series Heft 2001.1, editor Prof. Dr.-Ing. A. Leipertz, Erlangen 2001, published Essen March 13/14, 2001). Such a known exhaust gas aftertreatment device consists of several units that require a large amount of space or require a large overall length, which leads to design problems in corresponding commercial vehicles.

From the US 5829250 A An exhaust gas aftertreatment for reducing NOx emissions in these engines is known, in which an SCR catalytic converter is connected downstream of a reducing agent supply. In this document, a common housing of such a device is disclosed with an exhaust gas inlet on one side and an exhaust gas outlet on the other side. In this housing, mutually sealed chambers are formed by partitions. Several catalyst modules are passed through these partitions, the first section of which is a pre-cat element with axial inlet and outlet gas routing and the second section of which is an SCR catalytic converter element with axial inlet and outlet gas routing, the outlet gas duct of the pre-cat element in one first chamber with the exhaust gas inlet of the outlet gas duct of the pre-cat element and the inlet gas duct of the SCR-cat element in a second chamber and the gas outlet duct of the SCR-cat element are arranged in a third chamber.

Another generic device for reducing NO _x emissions is from the US 5367875 A known, which also includes a reduction in particle emissions. In this device, a pre-catalyst or an oxidation catalyst is connected upstream of the reducing agent supply and the SCR catalyst. The supply of reducing agent is controlled. The reducing agent is gaseous ammonia. The supply of this ammonia is arranged in the second chamber between the pre-cat element and the SCR-cat element.

The object of the invention is therein, an exhaust gas aftertreatment device of the type mentioned Kind in their overall length to optimize and create a corresponding unit.

The invention task is solved with an exhaust gas aftertreatment device with the features of Claim 1. In such a device according to the invention, the two Catalysts, the pre-catalyst and the SCR catalyst in preferably tubular Combined catalyst modules, preferably in multiple arrangement are housed in parallel in a common housing. By partitions are in the housing Chambers formed, being in the area of the transfer from the pre-catalyst escaping exhaust gas for entry into the SCR catalytic converter in Art a mixing chamber around the corresponding sections of the catalyst module around ammonia directly gaseous supplied becomes.

A preferred embodiment a catalyst module is proposed with claim 2. A such arrangement according to the invention of pre-cat element and SCR cat element leads to a short overall length and a particularly good mixture of the exiting from the pre-cat element Exhaust gas with the ammonia supplied in this mixing chamber and enables favorable inflow into the SCR cat element. The ammonia feed can preferably be correspondingly distributed in the mixing chamber in the form of an ammonia injection.

A radial inlet gas guide and Exit gas management is achieved by radially perforated pipe sections on the corresponding Place the cat module.

To impulse the rear wall of the housing in the area of the gas exits from the SCR catalytic converter through the exhaust gas to prevent, according to claims 5 and 6 suggested behind these cat elements with spacing baffle plates to provide a deflection of the exhaust gas flow in the corresponding Effect chamber. The exhaust gas flows out of this chamber through the corresponding one Gas leak in the back wall of the housing out.

Based on a principle shown embodiment the invention becomes closer explained. Show it:

1 : A longitudinal section through an exhaust gas aftertreatment device according to the invention with several catalyst modules and

2 : A basic perspective view of the arrangement of the catalyst modules in the housing, which is only partially shown.

The exhaust gas after-treatment shown shows a with the number 1 designated housing with a jacket 11 , a front wall 12 and a back wall 13 , In the area of the front wall 12 is with the digit 14 and the corresponding arrow indicates the exhaust gas inlet flowing in from the engine. The aftertreated exhaust gases appear on the rear wall 13 in the area of the exhaust outlet 15 out. Through the partition walls provided in the housing 16 and 17 are the chambers 2 . 3 and 4 formed, which are separated from each other.

A plurality of tubular catalyst modules arranged parallel to one another are with their corresponding sections through the intermediate walls 16 and 17 passed sealed. This catalyst module 5 consists of a first section, the pre-cat element 51 , in which a particle oxidation and the formation of nitrogen oxide takes place and a second section, the SCR cat element 52 in which the SCR reaction takes place after the addition of ammonia.

The tubular pre-cat element 51 has an axial and radial inlet gas guide 511 in the form of the correspondingly perforated inlet pipe section. These sections protrude from the front wall 12 of the housing 1 and the partition 16 formed chamber 2 , into which the exhaust gas inlet 14 the exhaust gas flows in. After the exhaust gas flows in through the inlet gas duct 511 the exhaust gas gets into the actual pre-catalytic converter 512 , emerges from the back and flows radially through the in the chamber 3 arranged section of the outlet gas duct 513 out. In this chamber 3 , the actual mixing chamber, is exhausted via the ammonia injection 6 leading to the outside via a supply line 61 is connected, admixed ammonia in gas form. This mixture then flows through the inlet gas duct 521 into the SCR cat element 52 , The respective tubular pre-cat element 51 is with a bevel cut and corresponding bulkhead 7 against the subsequent SCR cat element 52 partitioned off in the axial direction. The SCR-cat element therefore also has a corresponding oblique cut 52 at its inlet gas duct 521 on. About this inlet gas duct 521 the mixture of pretreated exhaust gas and ammonia flows to the actual SCR catalytic converter 522 in which the SCR reaction takes place.

The outlet gas duct 523 of the SCR cat element 52 is in the chamber 4 by the partition 17 and the back wall 13 is formed. The correspondingly treated exhaust gas exits both axially and partially radially. The axially flowing exhaust gas is against the baffle plates arranged at a distance 524 led and redirected. These baffles 54 are with webs arranged at a corresponding radial distance from one another 525 on the SCR cat element 52 held. Out of the chamber 4 the treated exhaust gas flows through the exhaust outlet 15 out of the housing 1 out, usually to a silencer system.

1

casing

11

coat

12

front wall

13

rear wall

14

exhaust inlet

15

exhaust outlet

16

partition

17

partition

2

chamber

3

chamber

4

chamber

5

catalyst module

51

Vorkatelement

511

Inlet gas guide

512

precatalyzer

513

Exit gas management

52

SCR Katelement

521

Inlet gas guide

522

SCR catalyst

523

Exit gas management

524

baffle plate

525

web

6

ammonia injection

61

supply

7

bulkhead

Claims (6)

Exhaust gas aftertreatment device for reducing particle and NO _x emissions in diesel engines, in which an SCR catalytic converter is connected downstream of a pre-catalytic converter which serves for particle oxidation and the formation of nitrogen oxide, after a controlled ammonia supply, characterized by a common housing ( 1 ) with an exhaust gas inlet ( 14 ) on one side and an exhaust outlet ( 15 ) on the other side, in which housing ( 1 ) through partitions ( 16 . 17 ) chambers sealed against each other ( 2 . 3 . 4 ) and several catalytic converter modules ( 5 ) are passed through, the first section of which each contains a pre-cat element ( 51 ) is with axial and / or radial inlet gas routing ( 511 ) and radial outlet gas flow ( 513 ) and their against the pre-cat element ( 51 ) axially partitioned second section an SCR cat element ( 52 ) with radial inlet gas supply ( 521 ) and axial and / or radial discharge gas routing ( 523 ) where the inlet gas duct ( 511 ) of the pre-cat element ( 51 ) in a first chamber ( 2 ) with the exhaust gas inlet ( 14 ), the radial exit gas tion ( 513 ) of the pre-cat element ( 51 ) and the radial inlet gas flow ( 521 ) of the SCR cat element ( 52 ) in a second chamber ( 3 ), into which gaseous ammonia is fed, and the outlet gas duct ( 523 ) of the SCR cat element ( 52 ) in a third chamber ( 4 ) with the exhaust outlet ( 15 ) are arranged. Device according to claim 1, characterized in that in each case the pre-cat element ( 51 ) with a bevel cut and corresponding bulkhead ( 7 ) against the subsequent SCR cat element ( 52 ) adjoins, this adjoining area with the radial outlet gas duct ( 513 ) of the pre-cat element ( 51 ) and the radial inlet gas duct ( 521 ) of the SCR cat element ( 52 ) in the second chamber ( 3 ) of the housing ( 1 ) is located. Device according to claim 1 or 2, characterized in that the ammonia feed in the second chamber ( 2 ) of the housing ( 1 ) as ammonia injection ( 6 ) is trained. Device according to claim 1, characterized in that the catalyst modules ( 5 ) are tubular and the inlet gas ducts ( 511 . 521 ) and the outlet gas ducts ( 513 . 523 ) are radially perforated. Device according to one of the preceding claims, characterized in that at a distance from the axial outlet gas guide ( 523 ) of the SCR cat element ( 52 ) one baffle plate ( 524 ) is arranged to redirect the exhaust gases emerging from the SCR catalytic element. Device according to claim 5, characterized in that the baffle plates ( 524 ) each with spaced webs ( 525 ) on the exit side of the SCR cat element ( 52 ) are arranged.