DE10313704A1 - Exhaust gas purification device for vehicle engine comprises nitrogen oxides adsorber with adsorber channels connected in parallel - Google Patents

Abstract

Exhaust gas purification device comprises nitrogen oxides adsorber with adsorber channels connected in parallel. The nitrogen oxides-containing gas stream is fed to first part of adsorber channels and hydrogen-containing gas stream is fed to second part of adsorber channels. The adsorber channels assigned to first part and adsorber channels assigned to second part can be exchanged depending on the number of them.

Description

The present invention relates an emission control system for an internal combustion engine of a motor vehicle with the features of Preamble of claim 1.

An emission control system of this type is known from the published patent application DE 101 28 414 A1 known. This emission control system has an ammonia generating device, which is associated with a nitrogen oxide generator for generating nitrogen oxide from atmospheric nitrogen and a hydrogen generating unit for generating a hydrogen-containing gas and a nitrogen oxide reduction unit. From the latter, the nitrogen oxide produced is reduced using the hydrogen-containing gas to ammonia, which is supplied to the exhaust gas purification on the input side of an SCR catalyst (SCR = Selective Catalytic Reduction) the exhaust gas of an internal combustion engine. In this system, in addition to the reduction of nitrogen oxide to ammonia is simultaneously a reduction of remaining in the nitrogen oxide generation in the gas atmospheric oxygen with the reducing hydrogen-containing gas. For this purpose, a comparatively large amount of reducing agent is required because of the high oxygen content of the air, which is why the Ammoniakerzeugung with the in the DE 101 28 414 A1 disclosed ammonia generating device is relatively energy intensive. The ammonia production is also discontinuous, which complicates the need-based provision of ammonia.

The object of the invention is to provide a To specify an emission control system with an ammonia production facility, which in a simple manner a continuous and economic Generation of ammonia for emission control allows.

This task is performed by an emission control system solved with the features of claim 1.

The exhaust gas purification system according to the invention has an ammonia production facility with a nitrogen oxide adsorber, which is capable of nitrogen oxides from a nitric oxide supplied to it Separate gas stream and buffer. The ammonia production facility is also able to cached in the nitrogen oxide adsorber Nitric oxide with supplied At least partially convert hydrogen to ammonia. The emission control system according to the invention is characterized in that the nitrogen oxide adsorber of the ammonia generating device a large number of fluid parallel switched, preferably separated Adsorberkanäle, wherein a first portion of the adsorber channels of nitrogen oxide-containing gas stream supplied and a second portion of the adsorber channels is a hydrogen-containing Gas stream fed is. Furthermore, the adsorber channels associated with the first portion and the second portion associated adsorber channels in a predeterminable temporal dependence from the large number of adsorber channels selectable. The ammonia generating plant allows continuous production of ammonia by adding the first fraction the adsorber channels For some time charged with the nitric oxide-containing gas stream and then with the hydrogen-containing gas stream. Thereafter, another takes place Loading the first portion of the adsorber with the nitrogen oxide-containing gas stream. Conversely, the second share of Adsorberkanäle For some time, the hydrogen-containing gas stream is applied and subsequently stream with the nitrogen oxide gas. The first portion of Adsorberkanäle and the second portion of the adsorber channels So, in time, either a nitric oxide-containing gas stream or a hydrogen-containing gas stream supplied. As a proportion of Adsorberkanäle is here to understand a relative proportion with respect to the total existing adsorber channels.

When loading the adsorber with the usually oxidizing nitrogen oxide-containing gas stream this is the nitric oxide mostly or Completed deprived of the nitrogen oxide storage material by caching. After sufficient saturation the nitrogen oxide storage material of an adsorber channel of nitrogen oxides this is subjected to a reducing hydrogen-containing gas stream. This will release the cached nitrogen oxide caused. This is in the adsorber itself or in a flow downstream Reduction stage with the hydrogen at least partially reduced to ammonia. The corresponding adsorber channel is thus again for intermediate storage of nitric oxide available.

The ammonia production plant is preferably designed so that the with the nitrogen oxide-containing gas stream acted adsorber one make predetermined first proportion of total existing adsorber channels. In the same way, those with the hydrogen-containing gas stream include acted adsorber channels a predetermined second portion. The two parts complement each other preferably to 100% of the total existing adsorber channels. she can However, less than 100% amount, which has the consequence that a mathematically resulting third share of the total existing Adsorberkanäle temporarily neither of the nitric oxide-containing gas stream nor of the hydrogen-containing gas stream is flowed through and, for example with a purge gas rinsed can be.

The corresponding shares are preferred wise given by the constructive realization of the gas flow of the nitrogen oxide adsorber.

Because of that with the nitric oxide-containing gas stream acted adsorber channels and the acted upon by the hydrogen-containing gas stream adsorber in predeterminable temporal dependency from the large number of adsorber channels selectable are, a continuous ammonia production is possible.

The accumulation of nitrogen oxides in the adsorber channels leads to a cheap one ratio the re of the hydrogen oxidizing components nitrogen oxide and Oxygen, allowing an economic use of hydrogen and allows a high ammonia yield is. This is due to the predeterminable temporal selection of the respective Asorberkanal shares supported, which, for example, to the ammonia requirement for emission control can orient.

In an embodiment of the invention the variety of adsorber channels assigned exactly to a nitrogen oxide adsorber. The nitrogen oxide adsorber is preferably as cylindrical and with a nitrogen oxide storage material coated monolithic honeycomb body with round cross-section formed of the plurality of Adsorberkanäle in axial Direction is crossed. An education of the nitrogen oxide adsorber through a bed of coated moldings is also possible. Preferably, in this case, the adsorber channels are provided by suitable flow-guiding means, such as with the moldings filled and adjacent pods separated from each other. The individual flow channels formed as sleeves are to a cylindrical adsorber body combined with preferably also round cross-section.

In a further embodiment of the invention the time selection of the adsorber channels is carried out by a stationary gas supply and by a rotation of the nitrogen oxide adsorber about a parallel to Orientation of the flow channels arranged Axis. The fixed gas supply here refers to a flowed face of the Adsorber and relates to both the nitric oxide-containing gas stream as also the hydrogen-containing gas stream. This can be, for example by a stationary segment-like division of the streamed end face of the nitrogen oxide adsorber can be achieved. A first stationary segment is acted upon by nitrogen oxide-containing gas stream, a second stationary Segment is acted upon by the hydrogen-containing gas stream. The For example, segments can be be formed of corresponding sheet metal parts, which sufficient close to the Adsorberstirnfläche abut, in order to mix the gas streams at the location of the inflow in to avoid the adsorber. The nitrogen oxide adsorber either rotates continuously around its longitudinal axis or becomes discontinuous from time to time at an angle turned that the adsorber channels, which were impinged by the nitric oxide-containing gas before the rotation, after the rotation first no longer streamed to, from a purge gas stream or be flown by the hydrogen-containing gas stream. After another Rotation, preferably by the same angular amount, becomes the same Adsorber channels again streamed by the nitrogen oxide-containing gas stream or by a purge gas stream or flows through. The area proportions the segments can be different. With a uniform rotation of the adsorber becomes as determined by the larger segment area Part of the adsorber channels longer from respective gas stream acted as that of the smaller segment area associated Part of the adsorber channels.

Analogous to the above-mentioned embodiment takes place in a further embodiment of the invention, the temporal dependence the selection of adsorber channels by a non-moving nitrogen oxide adsorber and by a temporally location-dependent inflow of the nitrogen oxide adsorber. The location dependency refers here on the immovably arranged nitrogen oxide or on the be streamed Face. Advantageously, a rotating, segmental by appropriate flow split gas supply. The rotation can be continuous or discontinuous respectively. By this configuration are analogous to the above said embodiment the adsorber channels also in temporal change of nitric oxide-containing gas stream and acted upon by the hydrogen-containing gas stream.

In a further embodiment of the invention, the plurality of adsorber channels are assigned to at least two separate nitrogen oxide adsorbers and the time dependence of the selection of the adsorber channels is effected by an alternate selection of the at least two nitrogen oxide adsorbers. Thus, in each case one or more adsorbers are flowed through by the nitrogen oxide-containing gas stream, while the remaining part of the total existing adsorber is flowed through by the hydrogen-containing gas stream. If the nitrogen oxide storage capacity of the adsorber channels of an adsorber through which the nitrogen oxide-containing gas stream is exhausted, the gas streams are switched so that it is now acted upon by the hydrogen-containing gas stream and the nitrogen oxide temporarily stored in the asorber channels of this nitrogen oxide adsorber is released and at least partially reduced to ammonia. As a result, a regeneration of the adsorber takes place, so that it is then available again for a renewed intermediate storage of nitrogen oxides. Conversely, by the switching of the gas flows through a previously flowed through by the hydrogen-containing gas stream and thus regenerated with respect to its Nitrogenoxpeicherfähigkeit Nitric Oxide adsorber now flows through the nitrogen oxide-containing gas stream. By this configuration, a more continuous ammonia production process takes place. The gas flows can also be more uniform Be nature, which simplifies the process.

In a further embodiment of the invention is a nitrogen oxide generator for generating the ammonia generating device supplied nitrogen oxide-containing gas stream provided. This can be predominantly independently from internal combustion engine operation a demand-oriented amount of ammonia generated and provided for emission control.

In a further embodiment of the invention is the ammonia generating device supplied nitrogen oxide gas stream taken from the exhaust pipe of the internal combustion engine. In particular at a predominantly lean-burned internal combustion engine can so in the exhaust contained nitrogen oxide partly for ammonia production and thus at least partial removal of the rest of the internal combustion engine emitted nitrogen oxides are used. This eliminates one external generation of nitric oxide.

In a further embodiment of the invention is a fuel reformer for producing the ammonia generating device supplied Hydrogen provided. Preferably, the fuel reformer the fuel provided for operating the internal combustion engine subjected to thermal and / or catalytic reforming process, wherein a hydrogen-containing reducing reforming gas is generated, which the ammonia generating device to reduce nitrogen oxides Fed to ammonia becomes.

In a further embodiment of the invention is a water electrolysis unit for generating the ammonia generating device supplied hydrogen intended. This embodiment has the advantage that hydrogen is largely free of foreign gas and in concentrated Form can be provided for the reduction of nitrogen oxides. This results in a high yield of ammonia production.

The invention is based on the following of drawings and related Examples closer explained. It shows

1 1 is a schematic block diagram of an internal combustion engine having an exhaust gas purification system with a nitrogen oxide reduction catalytic converter in an exhaust gas line and with an associated ammonia generating device,

2 1 shows a schematic longitudinal section of a first embodiment of an ammonia generating device,

3 1 shows a schematic cross-section of a first embodiment of an ammonia generating device,

4 a schematic representation of another embodiment of an ammonia production plant.

According to 1 This is the example of the four-cylinder engine running here 1 discharged exhaust gas via an exhaust pipe 2 a nitrogen oxide reduction catalyst 3 fed. In the internal combustion engine 1 it is a predominantly lean-burn internal combustion engine, preferably a diesel engine. Furthermore, in a secondary branch of the exhaust pipe 2 an ammonia production facility 4 provided, of which ammonia-containing gas as a reducing agent for in the exhaust gas of the internal combustion engine 1 contained nitrogen oxides upstream of the nitrogen oxide reduction catalyst 3 the exhaust pipe 2 via a supply line 7 can be fed. The ammonia production facility 4 is capable of producing nitrogen oxides from a her via a first metering line 8th to separate supplied nitrogen oxide-containing gas stream and reduce to a buffer to ammonia. The nitrogen oxide freed gas stream is via a discharge line 10 discharged into the environment or back to the exhaust pipe 2 fed. The hydrogen used to reduce the cached nitrogen oxide is from a hydrogen source 6 provided and can the ammonia production plant 4 via a second feed line 9 be supplied.

As a source of hydrogen 6 For example, an elementary hydrogen storage or a water electrolysis unit may be provided. Preferably, the hydrogen source 6 but designed as a catalytic reformer, which is supplied with a fuel and air or lean exhaust gas. The reformer converts the supplied fuel into a hydrogen-containing gas in a catalytic reforming process. As the fuel is preferably for operating the internal combustion engine 1 used on board the associated motor vehicle available energy sources.

In the case of the ammonia production facility 4 supplied nitrogen oxide-containing gas stream is preferably a partial flow of the engine exhaust gas, which the exhaust pipe 2 upstream of the terminal of the ammonia plant 4 extracted ammonia-containing gas stream is removed. To provide the nitrogen oxide-containing gas stream, however, can also in 1 dotted shown separate nitrogen oxide generator 5 be provided. The production of nitrogen oxide in the nitrogen oxide generator 5 is carried out by reaction of nitrogen with oxygen, which is preferably made possible by an electric arc or by another suitable process, such as a plasma process. As educt gas this comes air or the lean, oxygen-containing exhaust gas of the internal combustion engine in question.

Preferably, the nitrogen oxide reduction catalyst 3 designed as a so-called SCR catalyst. This allows with the aid of the reducing agent ammonia under oxidizing conditions, a selective reduction of the nitrogen oxides contained in the engine exhaust gas.

It is understood that the in 1 schematically shown further arrangement, not shown here for clarity, components are assigned, or may be assigned. These include control devices for controlling the operation of the internal combustion engine 1 and the ammonia production facility 4 , the nitric oxide generator 5 and the hydrogen source 6 as well as also to be provided switching and conveying elements such as valves or pumps.

Furthermore, in the exhaust pipe 2 be arranged cleaning additional components such as a particulate filter or other catalytic units. Thus, it may be advantageous, in addition to the nitrogen oxide reduction catalyst 3 to provide an oxidation catalyst, a three-way catalyst and / or a nitrogen oxide storage catalyst, with which further exhaust gas cleaning functions can be performed.

In particular, it is advantageous upstream of the point of addition of the ammonia-containing gas stream in the exhaust pipe 2 to provide a nitrogen oxide storage catalyst. This stores at a lean operation of the internal combustion engine 1 the nitrogen oxides contained in the exhaust gas. The increasing slip of nitrogen oxides from the nitrogen oxide storage catalyst which accompanies the increasing exhaustion of the nitrogen oxide storage capacity can then be effected at the downstream nitrogen oxide reduction catalyst by means of the ammonia supplied by the ammonia generating device 3 be implemented. In this way, the low-consumption lean operating phases of the internal combustion engine can 1 last for a long time. The ammonia requirement is relatively low for such a type of exhaust gas purification system, which is why the components used for ammonia production can be made relatively small.

The regeneration of the nitrogen oxide storage catalyst by brief fat operation of the internal combustion engine 1 can be used for additional production of ammonia. This may be in the nitrogen oxide storage catalyst or in a three-way catalyst carried out in this regard, which may be upstream of the nitrogen oxide storage catalyst or between the nitrogen oxide storage catalyst and the nitrogen oxide reduction catalyst 3 in the exhaust pipe 2 can be arranged.

It is also advantageous to use a nitrogen oxide storage catalyst downstream of the nitrogen oxide reduction catalyst 3 to arrange in the exhaust pipe. By the supply of ammonia from the ammonia production facility 4 to the nitrogen oxide reduction catalyst 3 a part of the nitrogen oxide contained in the combustion exhaust gas is removed. Because of the reduced nitrogen oxide content, therefore, the downstream nitrogen oxide storage catalyst remains receptive to nitrogen oxides for a long time, so that the fuel-efficient lean operating phases of the internal combustion engine 1 can last long.

With reference to 2 and 3 will be described in more detail below on a first preferred embodiment of the ammonia generating device 4 received. In this case, matching features are designated by identical reference symbols. The ammonia production facility 4 has a nitrogen oxide adsorber 41 on, which is designed as a cylindrical honeycomb body with a circular cross-section. This is in the longitudinal direction of a plurality of flow-parallel connected and separate Adsorberkanäle 42 traversed. The adsorber channels 42 are coated with a nitrogen oxide storage material. Depending on the nature of the nitrogen oxide storage material, the nitrogen oxide storage can be effected by chemisorption, adsorption or by absorption or by a combination of the processes mentioned. Preferably, a nitrogen oxide storage material is used, which contains alkali earth alkaline and / or cerium compounds and the storage of the nitrogen oxide is carried out by nitrate formation.

In 2 is the ammonia production facility 4 shown schematically in longitudinal section. The nitrogen oxide adsorber 41 is in a housing 43 accommodated. About the first metering line 8th is the nitrogen oxide-containing gas stream in the housing 43 guided. About the second feed line 9 Hydrogen is supplied in the form of a hydrogen-containing gas stream. The second feed line 9 is on the outlet side to a circle segment 44 extended so that a corresponding circle segment 44 the face of the nitrogen oxide adsorber 41 has flowed from the supplied hydrogen-containing gas stream. The in 3 schematically illustrated cross-section along the cross-sectional line AA in 2 clarifies the facts. The segment-like extended outlet side of the second feed line 9 lies on the front side of the nitrogen oxide adsorber 41 On the other hand, apart from a more negligible leakage, the hydrogen-containing gas stream only flows into the within the segment 44 ending adsorber channels 42 flows. The other adsorber channels 42 in contrast, the nitrogen oxide-containing gas stream is supplied.

Due to the azimuthal extent of the circle segment 44 respectively. 45 is therefore on the one hand a first portion of the total existing adsorber channels 42 given to which the nitric oxide-containing gas stream is supplied and on the other hand given a second portion to which the hydrogen-containing gas stream is supplied.

Analogous to the gas inlet designed on the inlet side, the gas outlet on the outlet side is the ammonia generating device 4 designed. About the out of the case 43 guided discharge line 10 the gas stream which is largely freed of nitrogen oxides on its flow path along the first portion of the adsorber channels is removed.

By a drive, not shown, either the segment-like extended lines 9 and 7 synchronous or the nitrogen oxide adsorber about 41 around the central longitudinal axis of the nitrogen oxide adsorber 41 be rotated continuously or discontinuously. As a consequence thereof, in a manner dependent on the time course of the rotation, the first portion and the second portion of the total existing adsorber channels become 42 respectively assigned adsorber selected.

Thus, after a certain depletion of the nitrogen oxide storage capacity of their nitrogen oxide storage coating has occurred, the adsorber channels, which were initially charged with the nitrogen oxide-containing gas stream, are charged with the hydrogen-containing gas stream. In the reducing atmosphere of the gas stream containing hydrogen, a release of the cached nitrogen oxides takes place, as a result of which the nitrogen oxide storage material is regenerated with regard to its absorption capacity for nitrogen oxides. In a suitably designed, for example noble metal doped coating of the adsorber channels 42 , During the release of cached nitrogen oxides at the same time their reduction to ammonia, so that via the supply line 7 the exhaust pipe 2 Ammonia can be supplied.

Parallel to the process described As a result of the described rotation, the adsorber channels, the first subjected to the hydrogen-containing gas stream and thus regenerated were charged again with the nitric oxide-containing gas stream. In this way, there is a continuous production of ammonia in high yield with simultaneous effective use of the reducing agent Hydrogen.

The rotational speed or the frequency of the rotational movement are suitably tuned to the current demand for ammonia. Accordingly, the sizes of the nitrogen oxide-containing gas stream or of the hydrogen-containing gas stream are likewise adapted to the current ammonia requirement. Furthermore, the sizes of the segments 44 . 45 be suitably selected in the sense of an appropriate litigation.

With a continuous rotation of the segments 44 . 45 or of the nitrogen oxide adsorber 41 it is expedient that the acted upon by the nitrogen oxide-containing gas stream segment 45 a larger angle range comprises than the acted upon with the hydrogen-containing gas stream segment 44 , Every single adsorber channel 42 As a result, the nitrogen oxide-containing gas stream flows through it longer than from the hydrogen-containing gas stream. Accordingly, it is expedient that in a discontinuous made by 180 degrees rotation, the segments 44 . 45 are made the same size.

As an alternative to the described embodiment, the adsorber channels 42 also be coated with a non-noble nitrogen oxide storage material, by which the reduction of released nitric oxide to ammonia can not be catalyzed. In this case, the ammonia generating facility 4 a catalytic reduction stage, not shown, which is connected downstream of the nitrogen oxide adsorber. The nitrogen oxides released during the exposure to the hydrogen-containing gas are in this case fed to this reduction stage where they are reduced to ammonia and the generated ammonia of the exhaust gas line 2 fed. This embodiment has the advantage that in each case with regard to nitrogen oxide storage and nitrogen oxide reduction specially optimized materials can be used.

In 4 is another embodiment of an ammonia generating device 4 shown schematically, with respect to the 1 to 3 Matching features are provided with identical reference numerals. The ammonia production facility 4 Here, by way of example, has three nitrogen oxide adsorbers 41a . 41b . 41c on, each analogous to that in 2 illustrated adsorber are executed. The large number of adsorber channels for the intermediate storage of nitrogen oxides is therefore based on these nitrogen oxide adsorbers 41a . 41b . 41c divided up. About a respective input side provided switching valve 46 Any nitric oxide adsorber can optionally via the first metering line 8th with the nitrogen oxide-containing gas stream or via the second metering line 9 be acted upon with the hydrogen-containing gas stream. Accordingly, provided on the output side switching valves 47 the nitrogen oxide adsorber 41a . 41b . 41c with the to the exhaust pipe 2 leading supply line 7 for generated ammonia or with the discharge line 10 connectable. The changeover valves 46 and 47 are operated coordinated. In the in 4 shown position are the nitrogen oxide adsorber 41a and 41b in a nitrogen oxide adsorption mode and are charged by nitrogen oxide-containing gas. The nitrogen oxide adsorber 41c is in contrast in a regeneration mode and is acted upon by the hydrogen-containing gas. A possible mode of operation may now be that after a presettable period of time, a valve switch is made such that the nitrogen oxide adsorber 41b and 41c be operated in the adsorption mode and the nitrogen oxide adsorber 41a is operated in regeneration mode. Analogously, it is possible to cyclically switch on after further predeterminable times such that in each case one nitrogen oxide adsorber is regenerated, while the other two nitrogen oxide adsorbers are operated in the adsorption mode. Of course, a meaningful synchronous switching of the output-side changeover valves 47 ,

As described above, the nitrogen oxide adsorbers operated in the adsorption mode remove nitrogen oxides from the respectively supplied nitrogen oxide-containing gas stream and temporarily store them. In the regeneration mode, the cached nitrogen oxides are released again and reduced to ammonia. Depending on the design of the nitrogen oxide storage material, this can be done according to the above explanations in the supply line 7 switched separate reduction stage may be provided.

Of course it is possible that Make changes in another way or in a different order, especially when a different number of nitrogen oxide adsorbers are provided is what is also readily possible.

The above-described embodiments of an ammonia generating device can be supplemented by further components. In particular, it may be expedient to bring about a suitable temperature control of the components or gas flows by means of heaters or heat exchangers. For example, in the case of a hydrogen source designed as a reformer 6 a heat exchange between the hot hydrogen-containing reforming gas and the nitrogen oxide adsorber supplied nitrogen oxide gas may be provided. It can also be advantageous to provide a desulfurization device with which the gases fed to the nitrogen oxide adsorbers are desulfurized. In this way, poisoning or deactivation of the usually sulfur-sensitive nitrogen oxide storage materials can be prevented. For example, such a desulfurization device in the first feed line 8th and / or in the second feed line 9 be inserted. Likewise, the as the source of hydrogen 6 fuel supplied by a liquid sulfur desulfurization. This is particularly advantageous when using usually sulfur-containing diesel fuel.

Claims (9)

Emission control system for an internal combustion engine of a motor vehicle with an ammonia generating device and arranged in an exhaust pipe of the engine nitrogen oxide reduction catalyst, the ammonia generated by the ammonia generating means ammonia can be supplied, wherein the ammonia generating device is disposed outside the exhaust pipe and - has a nitrogen oxide, which is capable of nitrogen oxides separating and buffering the nitrogen oxide-containing gas stream supplied to the ammonia generating device - and at least partially converting the nitrogen oxide temporarily stored in the nitrogen oxide adsorber into ammonia, characterized in that the nitrogen oxide adsorber has a multiplicity of adsorber channels connected in parallel, wherein the nitrogen oxide-containing gas stream can be fed to a first portion of the adsorber channels and - a second portion of the adsorber channels a hydrogen-containing Gas stream can be fed, and the adsorber channels associated with the first portion and the adsorber channels associated with the second portion can be selected from the plurality of adsorber channels in a predeterminable time dependence. Exhaust gas purification system according to claim 1, characterized that the plurality of adsorber channels exactly one nitrogen oxide adsorber assigned. Emission control system according to claim 2, characterized in that that the temporal dependency the selection of adsorber channels by a stationary gas supply and by a rotation of the nitrogen oxide adsorber around a parallel to the alignment of the adsorber arranged axis takes place. Emission control system according to claim 2, characterized in that that the temporal dependency the selection of adsorber channels by a non-moving nitrogen oxide adsorber and by a temporally location-dependent inflow of the nitrogen oxide adsorber. Exhaust gas purification system according to claim 1, characterized that the plurality of Adsorberkanäle at least two separate Nitrogen adsorbers are assigned and the time dependence the selection of adsorber channels by an alternate selection of at least two nitrogen oxide adsorber he follows. Emission control system according to one of the preceding Claims, characterized in that a nitrogen oxide generator for generating the nitrogen oxide-containing gas stream supplied to the ammonia generating device is provided. Emission control system according to one of claims 1 to 6, characterized in that the ammonia generating device added nitric oxide-containing Gas flow is taken from the exhaust pipe of the internal combustion engine. Emission control system according to one of the preceding Claims, characterized in that a fuel reformer for generating provided to the ammonia generating means supplied hydrogen is. Emission control system according to one of the preceding Claims, characterized in that a water electrolysis unit for Generation of the ammonia generating means supplied hydrogen is provided.