DE102014221322A1 - Exhaust treatment device for an exhaust system of an internal combustion engine - Google Patents

Abstract

An exhaust gas treatment device for an exhaust system (16) of an internal combustion engine (12) is described which can be used in motor vehicles (10). The exhaust gas treatment device comprises a metering element (20) for introducing a reducing agent for nitrogen oxides into the exhaust system (16), an SCR catalyst (24) arranged downstream of the metering element (20) in the exhaust system (16) for the selective catalytic reduction of nitrogen oxides, a passive one Mixing element (22), which is arranged in direct fluid communication upstream of the SCR catalyst (24), and arranged in direct fluidic connection downstream of the SCR catalyst (24) in the exhaust system particulate filter (26) with oxidation-catalytically active coating.

Description

The invention relates to an exhaust gas treatment device for an exhaust system of an internal combustion engine having the features according to the preamble of claim 1. Furthermore, the invention relates to an internal combustion engine and a motor vehicle with such an exhaust gas treatment device.

The chemical conversion of hydrocarbons in an internal combustion engine may produce undesirable combustion products. So that they do not completely enter the environment, the exhaust gas of the internal combustion engine is passed through an exhaust gas treatment device, in which undesirable combustion products react at least partially with the aid of catalytically active substances to other chemical products. For example, the nitrogen oxide and soot-containing exhaust gas of an internal combustion engine, in particular a diesel engine, with added reducing agent and a nitrogen oxide reduction catalyst together with a particulate filter can be cleaned so that legal emission standards, which define a maximum concentration of undesirable combustion products, are met. For the future, it is to be expected that the legally standardized maximum concentrations will be further reduced, while at the same time the exhaust gas back pressure caused by the components of the exhaust gas treatment device should be as low as possible in order to minimize consumption as well. Therefore, there is a continuing need for technical improvements.

From the document EP 2 138 681 A1 For example, a method and apparatus for purifying diesel exhaust from a turbocharged engine is known. The device includes in the flow direction of the exhaust gas, a metering device for a reducing agent (ammonia or an ammonia-releasing compound), a catalyst for selective catalytic reduction (SCR catalyst), an oxidation catalyst and a diesel particulate filter. In one embodiment, the diesel particulate filter has an oxidation-catalytically active coating. The reducing agent passes through the turbine of the turbocharger, so that, on the one hand, a hydrolysis of the reducing agent and, on the other hand, an almost complete homogenization of the reducing agent and the exhaust gas takes place.

The document DE 10 2009 014 361 A1 concerns an exhaust gas treatment device for an internal combustion engine in a vehicle and a method for operating an exhaust gas treatment device, wherein the exhaust gas treatment device comprises an SCR catalytic converter for reducing nitrogen oxides in the exhaust gas. By means of a metering device, a reducing agent upstream of a turbine is introduced into the exhaust gas, so that the turbine provides for an efficient mixing of the reducing agent with exhaust gas. Upstream of the point of introduction, an oxidation catalyst is arranged. In front of the turbine, a mixing element may additionally be arranged.

In the document US 2011/0020201 A1 For example, a plurality of arrangements of exhaust treatment devices having a transition metal-stabilized oxygen storage catalyst will be described. Among other things, a class of arrangements for a diesel engine with an oxidation catalyst is shown upstream of upstream and upstream downstream of several additional components upstream or downstream. The components are in particular a diesel particle filter, a metering device for a reducing agent and a selective catalytic reduction catalyst.

Against this background, it is an object of the present invention to provide an exhaust gas treatment device with a selective catalytic reduction upstream of an oxidation of undesirable combustion products in a simple structure.

This object is achieved by an exhaust gas treatment device for an exhaust system of an internal combustion engine with the features of claim 1. Advantageous developments of the invention are characterized in the dependent claims.

An exhaust gas treatment device according to the invention for an exhaust system of an internal combustion engine comprises a metering element for introducing a reducing agent for nitrogen oxides in the exhaust system, a downstream of the metering in the exhaust system arranged SCR catalyst for the selective catalytic reduction of nitrogen oxides and in direct fluidic connection downstream of the SCR catalyst in the exhaust system arranged particulate filter with oxidation-catalytically active coating. In direct fluidic connection upstream of the SCR catalyst, a passive mixing element is arranged.

In the manner according to the invention, to use a passive mixing element, it is advantageously achieved that the exhaust backpressure is tolerable only slightly, preferably not increased.

The selective catalytic reduction of nitrogen oxides can take place by means of a catalytically active surface for the reduction of nitrogen oxides (NO _x ) in the gas stream to nitrogen (N ₂ ) of the SCR catalyst. The reducing agent can For example, be ammonia (NH ₃ ), urea or an ammonia precursor. The reducing agent may be in an aqueous solution.

The term "in direct fluidic connection" is understood to mean that no further exhaust-gas treatment components, in particular catalytically active exhaust-gas treatment components, are arranged in the fluidic connection in the exhaust system between the two exhaust-gas treatment components in fluid communication. A direct fluidic connection may also be referred to as an immediate fluidic connection. Short is also spoken of directly downstream / downstream and from directly upstream / upstream.

In further developments of the exhaust gas treatment device according to the invention, the SCR catalytic converter may have one or more uncoated gas flow paths. In particular in its input region for the exhaust gas, the SCR catalyst may have a coating active for the catalytic hydrolysis of the reducing agent. It may also be at least partially in the SCR catalyst also uncoated or not catalytically active coated areas.

In a preferred embodiment, the passive mixing element of the exhaust gas treatment device according to the invention is arranged in direct fluidic connection downstream of the metering element. This measure contributes to a compact construction of the exhaust gas treatment device.

In one group of embodiments, the exhaust gas treatment device according to the invention is used in an exhaust system of an internal combustion engine which has at least one turbine, in particular exactly one turbine, in the exhaust system. In these embodiments, the metering element is located downstream of exactly one turbine or all turbines in the exhaust system. In particular, the metering element may preferably be arranged in direct fluidic connection downstream of exactly one turbine or all turbines in the exhaust system. In other words, the exhaust gas treatment device according to the invention is arranged in a section of the exhaust system in which there is a lower pressure than the pressure of the section located immediately downstream of the combustion chamber. Thus, an exhaust backpressure inducing influence in the high pressure section is avoided.

A particularly advantageous development of the exhaust gas treatment device according to the invention is that the particle filter with oxidation-catalytically active coating additionally has a further catalytically active coating for the selective catalytic reduction of nitrogen oxides. As a result, the particulate filter additionally has a blocking function for preventing the exit of reducing agent from the exhaust system.

In a particularly preferred embodiment, the exhaust gas treatment device is arranged close to the engine. In the context of the present invention, the term "close to the engine / internal combustion engine" is understood to mean a distance between the cylinder outlet of the internal combustion engine and the end face of the exhaust gas treatment system of at most 120 cm, in particular at most 100 cm, preferably at most 80 cm. In a concrete embodiment, the distance is about 75 cm. A close-coupled arrangement means, in particular, that the exhaust system is arranged in the engine compartment and / or accommodated on the internal combustion engine ("closed-coupled"). In this way, the waste heat of the internal combustion engine can be used to achieve the operating temperatures of the catalysts in the exhaust gas treatment plant.

In addition, or alternatively to the features described above, flow directions with mutually different orientations may be present in the exhaust gas treatment device. In the exhaust gas treatment device, a first flow direction through the SCR catalytic converter for selective catalytic reduction of nitrogen oxides and a second flow direction through downstream in direct fluid communication of the SCR catalyst arranged particulate filter have different orientations from each other. In particular, the orientations may be substantially antiparallel or opposite to each other. This measure represents a further contribution to a compact construction of the exhaust gas treatment device.

In addition, in further developments of the exhaust gas treatment device, one or more further exhaust gas treatment components can be arranged downstream of the particle filter. Specifically, the one or more further exhaust treatment components may be one or more of the following: SCR catalyst (SCR), metering element, oxidation catalyst (OC), particulate filter (PF), partial oxidation catalyst (CPO), ammonia oxidation catalyst (AMOX). These additional components assist in the chemical reaction of the undesirable chemical combustion products. A readjustment of the further exhaust gas components downstream of the SCR catalytic converter and of the particulate filter has, inter alia, the advantage that the SCR catalytic converter is arranged as close as possible to the combustion chambers of the internal combustion engine ("first catalytic component"), so that the thermal energy of the exhaust gas is the SCR -Catalyst can heat up as quickly as possible and bring to working temperature.

In the context of the inventive idea is also an internal combustion engine, in particular for a motor vehicle. An internal combustion engine according to the invention is characterized by an exhaust gas treatment device, in particular exhaust gas treatment device arranged close to the engine / internal combustion engine, with features or feature combinations according to this representation, the internal combustion engine being self-igniting. Advantageous embodiments of the internal combustion engine can be charged or rechargeable by means of one or more charging devices, for example an exhaust gas turbocharger or an electrically driven supercharger, and / or have one or more exhaust gas recirculations, for example a low-pressure exhaust gas recirculation or a high-pressure exhaust gas recirculation. The internal combustion engine according to the invention may be part of an engine of a motor vehicle or represent the engine of a motor vehicle.

A motor vehicle according to the invention comprises an exhaust gas treatment device according to the invention with one or more features according to this representation. The motor vehicle is in particular a trackless land vehicle, preferably a wheeled vehicle, for example a passenger car or a truck.

Further advantages and advantageous embodiments and developments of the invention will be described with reference to the following description with reference to the figures. It shows in detail:

1 a topology of a preferred embodiment of an exhaust gas treatment device according to the invention for an exhaust system of an internal combustion engine, and

2 a schematic representation of the preferred embodiment of 1 close to the engine.

The 1 shows a topology of a preferred embodiment of an exhaust gas treatment device according to the invention for an exhaust system 16 an internal combustion engine 12 in a motor vehicle 10 , The internal combustion engine 12 is preferably self-igniting and / or works by a diesel combustion process. It has a motor in this preferred embodiment 14 which is rechargeable. Such embodiments may also have at least one exhaust gas recirculation. The exhaust system 16 is the engine 14 the internal combustion engine 12 downstream: In the exhaust system 16 enters the exhaust of the engine 14 , In its flow direction, the exhaust gas first passes through a turbine 18 a charging group of the engine 14 , In other words, the internal combustion engine 12 includes a turbocharger, especially in this specific embodiment exactly one turbocharger. The turbine 18 does not drive one in the 1 shown compressor for compressing the engine 14 supplied fresh gas, which may also be proportionately mixed with recirculated exhaust gas or will be mixed, before there is a combustion chamber of the engine 14 reached. In addition, one or more additional compressors may be present. The one or more further compressors are preferably electrically driven.

In direct fluidic connection downstream (directly downstream) of the turbine 18 the exhaust system has a metering element 20 for introducing a reducing agent for nitrogen oxides in the exhaust system 16 on. So that the reducing agent introduced into the exhaust gas mixes as homogeneously as possible with the exhaust gas, according to the invention directly downstream of the metering element 20 a passive mixing element 22 arranged. Suitable passive mixing elements are, for example, in the previously filed document DE 10 2014 201 586.3 and the documents cited therein. The entire disclosure content of the document DE 10 2014 201 586.3 is incorporated herein by reference.

Immediately downstream of the passive mixing element 22 is inventively in the exhaust system 16 an SCR catalyst 24 for the selective catalytic reduction of nitrogen oxides. The SCR catalyst 24 Downstream downstream is a particle filter 26 with oxidation-catalytically active coating. Finally, the exhaust gas purification device comprises directly downstream of the particulate filter 26 in the exhaust system 16 another exhaust treatment component 28 In concrete terms, this is another SCR catalyst and / or an ammonia oxidation catalyst (barrier catalyst). In this way, an olfactory impairment by leaking ammonia is advantageously prevented.

In the 2 is schematically the preferred embodiment of 1 shown in a close-coupled arrangement. Identical components are provided with the same reference numerals. With reference to the 1 described topology is geometrically implemented in this arrangement to the effect that the exhaust system 16 a diversion between the SCR catalyst 24 and the particulate filter 26 having. In the section of the diversion points the exhaust system 16 no components of the exhaust gas treatment device according to the invention. It is a 180 degree turnaround. In other words, first the exhaust gas flows through the exhaust system 16 in a first flow direction and passes the turbine 18 , the dosing element 20 and the passive mixing element 24 , After the diversion, the exhaust gas passes the particle filter 26 in a second flow direction. In the case of an embodiment of the internal combustion engine with an exhaust gas recirculation, a (low-pressure) exhaust gas recirculation branches off downstream of the particle filter.

The first and second flow directions are oriented substantially antiparallel to each other. In this way, a compact close-coupled arrangement of the exhaust gas treatment device of the exhaust system is achieved, at the same time there is the lowest possible exhaust backpressure in the exhaust system. The schematically illustrated arrangement is received on the exhaust side of the engine of the internal combustion engine.

Such a close-coupled arrangement, for example, in the documents EP 2 305 991 B1 and WO 2013/026533 A2 described. The entire disclosure content of the documents EP 2 305 991 B1 and WO 2013/026533 A2 is incorporated herein by reference.

Further exhaust treatment components, in particular a blocking catalyst, are remote from the engine in this embodiment, specifically arranged on the underbody of the motor vehicle.

LIST OF REFERENCE NUMBERS

10

motor vehicle

12

Internal combustion engine

14

engine

16

exhaust system

18

turbine

20

metering

22

passive mixing element

24

SCR catalyst

26

Particle filter with oxidation-catalytically active coating

28

further exhaust treatment components

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 2138681 A1 [0003]
• DE 102009014361 A1 [0004]
• US 2011/0020201 A1 [0005]
• DE 102014201586 [0025, 0025]
• EP 2305991 B1 [0029, 0029]
• WO 2013/026533 A2 [0029, 0029]

Claims (10)

Exhaust treatment device for an exhaust system ( 16 ) an internal combustion engine ( 12 ), with a metering element ( 20 ) for introducing a reducing agent for nitrogen oxides into the exhaust system ( 16 ), one downstream of the dosing element ( 20 ) in the exhaust system ( 16 ) arranged SCR catalyst ( 24 ) for the selective catalytic reduction of nitrogen oxides and one in direct fluidic connection downstream of the SCR catalyst ( 24 ) arranged in the exhaust system particulate filter ( 26 ) with an oxidation-catalytically active coating, characterized by a passive mixing element ( 22 ) which is in direct fluidic connection upstream of the SCR catalyst ( 24 ) is arranged. Exhaust treatment device according to claim 1, characterized in that the passive mixing element ( 22 ) in direct fluidic connection downstream of the metering element ( 20 ) is arranged. Exhaust treatment device according to claim 1 or 2, wherein the internal combustion engine ( 12 ) at least one turbine ( 18 ) in the exhaust system ( 16 ), characterized in that the dosing element ( 20 ) downstream of exactly one turbine ( 18 ) or all turbines ( 18 ) in the exhaust system ( 16 ) is arranged. Exhaust treatment device according to one of claims 1 to 3, characterized in that the particulate filter ( 26 ) with oxidation-catalytically active coating additionally has a further catalytically active coating for the selective catalytic reduction of nitrogen oxides.  Exhaust treatment device according to one of claims 1 to 4, characterized by a close-coupled arrangement. Exhaust treatment device according to one of claims 1 to 5, characterized in that a first flow direction through the SCR catalyst ( 24 ) for the selective catalytic reduction of nitrogen oxides and a second flow direction through the in direct fluidic connection downstream of the SCR catalyst ( 24 ) arranged particulate filter ( 26 ) have mutually different orientations. Exhaust treatment device according to one of claims 1 to 6, characterized in that downstream of the particulate filter ( 26 ) one or more further exhaust treatment components ( 28 ) are arranged. Exhaust treatment device according to claim 7, characterized in that the one or more further exhaust gas treatment components ( 28 ) one or more of the following group are: SCR catalyst (SCR), dosing element, oxidation catalyst (OC), particulate filter (PF), partial oxidation catalyst (CPO), ammonia oxidation catalyst (AMOX). Internal combustion engine ( 12 ), characterized by an exhaust gas treatment device according to one of claims 1 to 8, wherein the internal combustion engine ( 12 ) is self-igniting. Motor vehicle ( 10 ), characterized by an exhaust gas treatment device according to one of claims 1 to 8.

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