DE102011117104A1 - Internal combustion engine comprises exhaust gas recirculation system with exhaust pipe, which is fluidically connected with internal combustion engine, where exhaust gas treatment device is fluidically connected to exhaust gas line - Google Patents

Abstract

The internal combustion engine (1) comprises an exhaust gas recirculation system with an exhaust pipe (2), which is fluidically connected with the internal combustion engine. An exhaust gas treatment device (4) is fluidically connected to the exhaust gas line, which comprises an exhaust gas heating unit (5) in the exhaust pipe in flow direction (3) of the exhaust gas. A secondary auxiliary medium introducing unit (11) is arranged in the exhaust gas heating unit upstream to a diesel oxidation catalytic converter (6).

Description

The invention relates to an internal combustion engine having an exhaust gas aftertreatment system having the features of the preamble of claim 1.

In the course of compliance with legal requirements to minimize exhaust emissions from internal combustion engines, these are increasingly equipped with an exhaust aftertreatment (AGN) device. Such AGN devices usually consist of one or more catalytic converters and / or filters, which are arranged in an exhaust pipe of the internal combustion engine. In addition, one or more devices for introducing auxiliary agents into the exhaust gas in the exhaust gas line are or are usually still in front of the above mentioned. Catalytic converters and / or filters arranged. These aids have in conjunction with the catalytic converters reducing effect on the nitrogen oxides contained in the exhaust gas, or they serve to heat the exhaust gas to burn soot particles in the filter. The catalytic converters and their function are known from the prior art. Examples include diesel oxidation catalysts (DOC), catalysts for selective catalytic reduction (SCR catalysts) and ammonia blocking catalysts (blocking catalysts). The filters are usually diesel particulate filters (DPF) and / or diesel particulate traps. Auxiliaries are, for example, a urea water solution, solid urea, gaseous ammonia and hydrocarbons. For these aids to develop their full effect, they must completely vaporize in the exhaust gas and distribute as evenly as possible over the cross section of the exhaust pipe. The aids evaporate completely as long as the exhaust gas is hot, in which they are introduced. Hot exhaust gas is available in full load operation of the internal combustion engine. However, many internal combustion engines are used in applications that allow only a small proportion of full load in the overall operation. The predominant proportion of load adjusts itself in the middle and lower load range. Consequently, the exhaust gas temperature is relatively low, with the result that the introduced aids evaporate only poorly and can not fully develop their effect. This may be the case in particular with engines with exhaust gas recirculation (EGR).

From the Scriptures US 2008/0202101 A1 It is known to arrange in the exhaust pipe upstream of the means for introducing an auxiliary means for heating the exhaust gas. This means for heating the exhaust gas comprises a burner and this downstream arranged a DOC. The burner is operated, for example, with fuel. The DOC oxidizes z. B. contained in the exhaust incompletely burned soot particles, hydrocarbons, carbon monoxide, o. Ä., But also nitrogen monoxide to nitrogen dioxide. In this oxidation, heat is generated, which, together with the heat of the burner, raises the exhaust gas to a temperature that facilitates the evaporation of the introduced auxiliary.

The disadvantage of this is that the burner is technically very complex with its own ignition system, which is prone to failure and takes a grollen space. This is where the invention starts.

The object of the invention is to heat the exhaust gas of an internal combustion engine, namely with exhaust gas recirculation, on the one hand to achieve optimal evaporation and uniform distribution of an introduced auxiliary in an exhaust pipe, on the other hand to achieve rapid heating of downstream exhaust gas catalysts and filters in order thus to realize in total optimum conversion rates of the introduced auxiliary to minimize exhaust emissions.

The solution is carried out with an internal combustion engine with the features of claim 1. Advantageous embodiments of the invention are illustrated in the subclaims.

The invention relates to an internal combustion engine with exhaust gas recirculation with a fluidly connected to the internal combustion engine exhaust pipe to the fluidically an exhaust aftertreatment device is connected, which comprises means for heating the exhaust gas in the exhaust pipe in the flow direction of the exhaust gas, said means for heating the exhaust gas, a first diesel oxidation catalyst comprises, the exhaust gas aftertreatment device downstream of the means for heating the exhaust gas in the exhaust pipe comprises means for introducing a first aid, subsequently comprising a first SCR catalyst and a diesel particulate filter and then comprises a barrier catalyst. In this case, a device for introducing a second auxiliary agent is arranged in the device for heating the exhaust gas upstream of the first diesel oxidation catalyst. The advantage of this invention is that the introduced second aid oxidizes at the downstream first diesel oxidation catalyst and thereby generates heat which heats the exhaust gas and hence the further downstream adjuvants and catalysts or diesel particulate filters to an optimum temperature. The oxidation of the second aid is flameless and uniform on the surface of the diesel oxidation catalyst. This results in a continuous and over the cross section of the diesel oxidation catalyst uniform heat transfer to the exhaust gas. Due to the flameless oxidation no harmful pressure pulsations of the exhaust gas, which the subsequent catalysts or diesel particulate filter over longer Would damage the deadline. In addition, no burner is needed, which generates only bundled heat, so that the following components only selectively heated and thus can lead to thermal stresses in these. In addition, the burner requires a large space of a compact design. In addition, it can cause high maintenance costs due to susceptibility.

According to a preferred embodiment of the invention, the device for heating the exhaust gas in the exhaust pipe is arranged directly after the internal combustion engine. The direct arrangement after the internal combustion engine, d. H. without further intermediate exhaust aftertreatment devices o. a. Components, apart from exhaust gas turbines, which constitute heat sinks, advantageously enables a largely heat loss-free flow of the exhaust gas into the exhaust aftertreatment device according to the invention. As a result, relatively little of the second aid is needed to increase the temperature of the exhaust gas. This is resource-saving and financially beneficial.

According to a further preferred embodiment of the invention, the first SCR catalytic converter and the diesel particulate filter are arranged in a common housing. The advantage of this compact design is rapid heating of SCR catalytic converter and diesel particulate filter. This results in short reaction times to load changes of the internal combustion engine and low heat losses due to heat radiation, which in turn means only a small consumption of the second auxiliary means for heating the exhaust gas. Advantageously, this embodiment also allows a cost and space-saving design.

According to a further preferred embodiment of the invention, the first SCR catalyst is applied as a corresponding coating on the diesel particulate filter. This embodiment allows a very compact design and a very rapid heating of the diesel particulate filter. The compactness requires only small heat losses due to heat radiation. This means that for heating the diesel particulate filter by the hot exhaust gas, the consumption of the second auxiliary is only low. The coating on the diesel particulate filter also allows a free choice of the position of the coating. Thus, it is possible to apply the coating at the exhaust gas inlet, exhaust gas outlet, in the middle or in several sections of the diesel particulate filter to z. B. exploit optimal temperature conditions. Advantageously, this embodiment also allows a cost and space-saving design.

According to a further preferred embodiment of the invention, at least one second SCR catalytic converter is arranged downstream of the common housing of the first SCR catalytic converter and diesel particle filter and upstream of the barrier catalytic converter.

According to a further preferred embodiment of the invention, a second SCR catalyst is arranged downstream of the example coated diesel particulate filter and upstream of the barrier catalyst. As an advantage of a second SCR catalyst is thus a larger overall effective surface of the SCR catalysts of the AGN device can be displayed. This is particularly important if the coating of the diesel particulate filter with a corresponding first SCR coating for nitrogen oxide reduction is insufficient. Furthermore, a second SCR catalytic converter has the advantage of designing it by selecting a corresponding material from the prior art for a reduction of nitrogen oxide in a temperature range other than the first SCR catalytic converter, in order to achieve optimum nitrogen oxide reduction overall in a larger temperature range.

According to a further preferred embodiment of the invention, a second diesel oxidation catalyst takes over the function of the blocking catalyst. The advantage of the second diesel oxidation catalyst is that it is not designed exclusively for the oxidation of ammonia not consumed in the exhaust gas purification process, but additionally oxidizes unreacted hydrocarbons and carbon monoxide in the upstream exhaust gas purification process.

According to a further preferred embodiment of the invention, the first SCR catalyst and the barrier catalyst are applied as appropriate coatings on the diesel particulate filter. This embodiment allows a very compact design and a very rapid heating of the diesel particulate filter, including the coatings. The compactness requires only small heat losses due to heat radiation. This means that for heating the diesel particulate filter by the hot exhaust gas, the consumption of the second auxiliary is only low. The coating on the diesel particulate filter also allows a free choice of the position of the coatings. So it is possible to apply the coatings, for example, the exhaust gas inlet, exhaust gas outlet, in the middle or in several sections of the diesel particulate filter to z. B. exploit optimal temperature conditions. Advantageously, this embodiment also allows a cost and space-saving design.

According to a further preferred embodiment of the invention, the first aid is a urea water solution and / or solid urea and / or or ammonia gas and / or a hydrocarbon and / or a mixture of hydrocarbons.

According to a further preferred embodiment of the invention, the second auxiliary is a hydrocarbon or a mixture of hydrocarbons.

Embodiments of the invention are illustrated in the drawings and will be described in more detail below.

Show it:

1 a schematic representation of an internal combustion engine with exhaust gas recirculation with a connected to the engine exhaust pipe to which an exhaust aftertreatment device is connected according to a first embodiment of the invention;

2 a schematic representation of an internal combustion engine with exhaust gas recirculation with an internal combustion engine connected to the exhaust pipe to which an exhaust aftertreatment device, with a second SCR catalyst and a second Dieseloxidationskatalysator which replaces a barrier catalyst is connected, according to another embodiment of the invention;

3 a schematic representation of an internal combustion engine with exhaust gas recirculation with a connected to the engine exhaust pipe to which an exhaust aftertreatment device with a diesel particulate filter with SCR and barrier catalyst coatings is connected, according to another embodiment of the invention.

1 shows a schematic representation of an internal combustion engine 1 with exhaust gas recirculation with one with the internal combustion engine 1 fluidically connected exhaust pipe 2 , at the fluidic an exhaust aftertreatment (AGN) device 4 connected. The exhaust gas recirculation of the internal combustion engine 1 works, for example, according to the principle of the dispenser cylinder concept, which after DE 199 60 998 C1 known from the prior art and is not shown here. Other concepts for exhaust gas recirculation are also conceivable. Not shown are one or more of the internal combustion engine 1 arranged exhaust gas turbocharger, of an exhaust gas of the internal combustion engine 1 be traversed before this exhaust gas into the exhaust pipe 2 flows. Subsequently, the exhaust gas flows directly into the AGN device described below 4 , This means that between the above-mentioned exhaust gas turbocharger (s) and the AGN device 4 except the exhaust pipe 2 no other AGN devices or other components are arranged, which constitute heat sinks. The AGN facility 4 includes in the flow direction 3 the exhaust gas means 5 for heating the exhaust gas, hereinafter a device 7 for introducing a first aid, this subsequently a first SCR catalyst 8th and a diesel particulate filter 9 and to this then a blocking catalyst 10 , The device 5 for heating the exhaust gas comprises in the flow direction 3 An institution 11 for introducing a second auxiliary agent, for example a hydrocarbon, which is introduced into the exhaust gas. This second aid oxidizes with residual oxygen in the exhaust gas at the downstream first diesel oxidation catalyst 6 and heats the exhaust gas by an exothermic reaction. In the hot exhaust gas is through the device 7 introduced for introducing a first aid, for example, a urea water solution. The urea water solution evaporates in the hot exhaust gas and decomposes into ammonia, among other things. Optimum conditions for evaporation and decomposition of the urea water solution are at exhaust gas temperatures above 350 ° C, in full load operation of the internal combustion engine 1 prevail or in the middle and lower load range by the introduction of the second aid in the above device 5 be achieved to heat the exhaust gas. The liberated ammonia is reduced in the subsequent first SCR catalyst 8th in the exhaust gas contained nitrogen oxides. A regeneration of the diesel particulate filter 9 takes place through its cyclical heating. This is done by introducing appropriate amounts of the hydrocarbon into the exhaust gas in the device 11 for introducing a second auxiliary agent and the subsequent oxidation in the first diesel oxidation catalyst 6 , whereby the exhaust gas and thus the diesel particulate filter 9 is heated. For this purpose, so much hydrocarbon is introduced that this in the first diesel oxidation catalyst 6 can not completely oxidize and the remaining residual hydrocarbons in, possibly coated with precious metals, diesel particulate filter 9 oxidize and additionally heat and regenerate it by the exothermic reaction. The subsequent barrier catalyst 10 Oxidized in the exhaust possibly existing ammonia, which in the previous first SCR catalyst 8th was not oxidized. As a result, a so-called. Ammoniakschlupf by the AGN device 4 through into the environment.

2 shows how 1 the schematic representation of an internal combustion engine 1 with exhaust gas recirculation with the following differences: On the diesel particulate filter 9 In this arrangement, a coating is applied, which performs the function of in 1 described first SCR catalyst 8th takes over. This results in a compact and space-saving arrangement. Below the diesel particulate filter 9 is a second SCR catalyst 12 arranged. As an advantage of a second SCR catalyst 12 is a larger whole Effective surface of the SCR catalysts 8th and 12 the AGN facility 4 represented. This is particularly important if the coating of the diesel particulate filter 9 with the corresponding first SCR coating 8th insufficient for nitrogen oxide reduction. Next offers the second SCR catalyst 12 the advantage of this by selecting a corresponding material from the prior art to a nitrogen oxide reduction in a different temperature range than the first SCR catalyst 8th be interpreted in order to achieve a total of a larger temperature range optimal nitrogen oxide reduction. Following the second SCR catalyst 12 is a second diesel oxidation catalyst 13 arranged. The second diesel oxidation catalyst 13 is not designed exclusively for the oxidation of ammonia not used in the exhaust gas purification process, but additionally oxidizes unreacted hydrocarbons and carbon monoxide in the upstream exhaust gas purification process.

3 shows how 1 and 2 the schematic representation of an internal combustion engine 1 with exhaust gas recirculation. Here are on the diesel particulate filter 9 the first SCR catalyst 8th and the barrier catalyst 10 applied as appropriate coatings. This embodiment allows a very compact design and thus a very rapid heating of the diesel particulate filter 9 including the coatings.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

exhaust pipe

3

Flow direction exhaust gas

4

exhaust treatment device

5

Device for heating the exhaust gas

6

first diesel oxidation catalyst

7

Device for introducing a first aid

8th

first SCR catalyst

9

diesel particulate Filter

10

blocking catalytic converter

11

Device for introducing a second aid

12

second SCR catalyst

13

second diesel oxidation catalyst

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

• US 2008/0202101 A1 [0003]
• DE 19960998 C1 [0022]

Claims (10)

Internal combustion engine ( 1 ) with exhaust gas recirculation with one with the internal combustion engine ( 1 ) fluidly connected exhaust pipe ( 2 ), at the fluidically an exhaust aftertreatment device ( 4 ), which in the exhaust pipe ( 2 ) in the flow direction ( 3 ) of the exhaust gas is a device ( 5 ) for heating the exhaust gas, this device ( 5 ) for heating the exhaust gas, a first diesel oxidation catalyst ( 6 ), the exhaust aftertreatment device ( 4 ) following the establishment ( 5 ) for heating the exhaust gas in the exhaust pipe ( 2 ) An institution ( 7 ) for introducing a first auxiliary, then a first SCR catalyst ( 8th ) and a diesel particulate filter ( 9 ) and to this then a blocking catalyst ( 10 ), characterized in that in the device ( 5 ) for heating the exhaust gas upstream of the first diesel oxidation catalyst ( 6 ) An institution ( 11 ) is arranged for introducing a second auxiliary means. Internal combustion engine according to claim 1, characterized in that the device ( 5 ) for heating the exhaust gas in the exhaust pipe ( 2 ) directly after the internal combustion engine ( 1 ) is arranged. Internal combustion engine according to claims 1 or 2, characterized in that the first SCR catalytic converter ( 8th ) and the diesel particulate filter ( 9 ) are arranged in a common housing. Internal combustion engine according to one of claims 1 to 3, characterized in that the first SCR catalytic converter ( 8th ) as a coating on the diesel particulate filter ( 9 ) is applied. Internal combustion engine according to claims 3 or 4, characterized in that downstream of the common housing of the first SCR catalyst ( 8th ) and diesel particulate filter ( 9 ) and upstream of the barrier catalyst ( 10 ) a second SCR catalyst ( 12 ) is arranged. Internal combustion engine according to one of claims 1 to 4, characterized in that downstream of the diesel particulate filter ( 9 ) and upstream of the barrier catalyst ( 10 ) a second SCR catalyst ( 12 ) is arranged. Internal combustion engine according to one or more of claims 1 to 6, characterized in that a second Dieseloxidationskatatysator ( 13 ) assumes the function of a blocking catalytic converter. Internal combustion engine according to claim 1 or 2, characterized in that the first SCR catalytic converter ( 8th ) and the blocking catalyst ( 10 ) as corresponding coatings on the diesel particulate filter ( 9 ) are applied. Internal combustion engine according to one or more of claims 1 to 8, characterized in that the first aid is a urea water solution and / or solid urea and / or ammonia gas and / or a hydrocarbon and / or a mixture of hydrocarbons. Internal combustion engine according to one or more of claims 1 to 9, characterized in that the second aid is a hydrocarbon or a mixture of hydrocarbons.

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