EP1321643A1 - Device and method for after-treatment of exhaust gases - Google Patents

Abstract

The exhaust gas treatment device has a reduction stage (14) for nitrous oxides inserted in the exhaust gas line (16) close to the engine (1), upstream of a device (24,26) for removal of particles and nitrous oxides. The reduction stage is heated by the engine exhaust gases, for reduction of nitrous oxides in engine operating conditions in which the subsequent device is non-operational, e.g. at low engine loadings or revs. <??>An Independent claim for a method for treatment of diesel engine exhaust gases is also included.

Description

State of the art

The invention is based on an arrangement or one Process for the treatment of exhaust gases, in particular one Diesel engine, according to the genre of the independent Expectations. DE 199 21 974 already has one Device for reducing harmful components in the Exhaust gas from an internal combustion engine is known, in which one Particulate filter is arranged downstream of a storage catalytic converter. This can lead to a cold start in particular of the engine and / or at low engine load or low Speeds of the motor insufficient efficiency Denitrification of the exhaust gas can be achieved.

Advantages of the invention

The arrangement according to the invention or the one according to the invention Process with the characteristic features of the independent In contrast, claims have the advantage that regardless of the operating situation of the internal combustion engine high Efficiencies in the denitrification of the exhaust gas can be achieved can. Here, a device of the arrangement takes over Denitrification, especially when the engine is warm or when medium and high speeds or engine loads, while the upstream means advantageously denitrification especially at low load and / or low speed the internal combustion engine guaranteed. So that can especially for internal combustion engines with self- or Compression ignition (diesel process) the EURO 5 emissions standards or the requirements on the US market for SULEV applications be fulfilled.

By those listed in the dependent claims Measures are advantageous training and Improvements in the independent claims specified arrangement or the specified method possible.

If the agent is dimensioned in a suitable manner, then the means and the furnishings complement each other in an ideal way Way, also with regard to soot oxidation, so that Combined exhaust aftertreatment system for simultaneous High reduction of nitrogen oxide and particle emissions Efficiency in denitrification achieved a safe Soot oxidation ensures and thermal damage the system components, especially the agent, safely can be prevented.

It is particularly advantageous between the agent and the To provide an auxiliary arrangement, with whose help a tool to support exhaust aftertreatment in the device can be supplied to the exhaust system. This Auxiliary arrangement advantageously enables Particle filter regeneration or regeneration and / or Desulfation of a denitrification catalyst Facility. This can be done easily by feeding an appropriate amount of an auxiliary, i.e. through a operation of an aid supply unit as required, depending on the desired measure (Particulate filter regeneration, regeneration of the Denitrification catalyst or desulfation of Denitrification catalyst) happen.

It is also advantageous to provide one Oxidation catalyst or an electrically heated (Oxidation) catalyst, which works the way support supplied aids in a suitable manner can.

Fuel, in particular, can also be obtained in a simple manner Diesel fuel, used as an aid. The also enables the regeneration of the Particulate filter or for regeneration / desulfation of the denitrification catalyst of the facility required Conditions not only through the auxiliary arrangement need to be adjusted, but additional motor Interventions are possible, provided they are the means to Do not endanger the reduction of nitrogen oxides. It can in particular be provided over a moderate Late adjustment of the start of injection in the Internal combustion engine already part of the temperature increase to achieve so that the fuel supply on the Auxiliary arrangement quasi as a fine-tuning over the Oxidation catalyst achieved an additional exotherm, so to ensure that those for Diesel particle filter regeneration required temperature is achieved. This has the additional advantage that the Process of fuel injection into the Internal combustion engine can be designed more freely, as a finely optimized post-motor fuel supply the optimal Setting the conditions for exhaust gas aftertreatment guaranteed.

drawing

Embodiments of the invention are in the drawing shown and in the description below explained. 1 shows a first embodiment and Figure 2 shows a second embodiment.

Description of the embodiments

Figure 1 shows a diesel engine 1, the an exhaust manifold 3 and an exhaust gas turbocharger 5 with an arrangement 2 for exhaust gas aftertreatment is connected. The connected to the exhaust gas turbocharger 5 near the engine exhaust pipe 10 leads to one designed as a storage catalytic converter Denitrification catalyst 14. A middle exhaust pipe 16 connects the denitrification catalyst 14 with one Oxidation catalyst 20. An auxiliary supply unit 18 to supply fuel to the exhaust tract is on the middle exhaust pipe 16 introduced so that fuel behind the denitrification catalyst 14 and before Catalyst 20 can be introduced into the arrangement 2. An exhaust gas connection line 22 leads from Oxidation catalyst 20 to a particulate filter 24. Ein Denitrification catalyst 26 in the form of a Storage catalytic converter immediately follows that Particle filter 24; the exit of the Denitrification catalyst 26 is not one with one Exhaust pipe 28 shown in more detail connected.

The storage catalysts 14 and 26 are used for temporary Storage of the nitrogen oxides contained in the exhaust gas. in the so-called regeneration operation by a internal engine and / or a post engine supply of Desorb fuel that is introduced into the exhaust system the nitrogen oxides and are reduced to nitrogen. The Particle filter 24 is used to separate the particles a filtering medium. At times a regeneration of the Particle filter take place in which the settled solid or soot particles oxidized to carbon dioxide or carbon monoxide become. The storage catalytic converter 14 near the engine reaches after the optimum operating temperature quickly when the engine is started. They are in the position close to the engine in the exhaust system Exhaust gas temperatures so high that immediately after Starting the engine high NOx sales rates can be achieved. Thermal damage to the near-engine nitrogen oxide storage catalytic converter 14 will avoid the Exhaust gas temperature via a corresponding control of the Check the fuel supply to the engine so that the near-engine nitrogen oxide storage catalytic converter 14 harmful Exhaust temperatures cannot be reached. The for the Regeneration and desulfation of the storage catalytic converter 14 required conditions are about motor Interventions shown. In front of the particle filter 24 and him following second nitrogen oxide storage catalyst 26 is located a fuel supply unit 18 and a Oxidation catalytic converter 20, which is controlled by suitable control in different operating modes can be used. In a first mode is via the fuel supply unit 18 hydrocarbons in one Amount supplied that with sufficient remaining Residual oxygen content via the oxidation catalyst Temperature increase in the exhaust gas is achieved, which is sufficient is to regenerate the particle filter. In a second Mode are hydrocarbons in such an amount supplied that over the oxidation catalyst reducing atmosphere is generated, so that on the absorbed second nitrogen oxide storage catalyst 26 Nitrogen oxides can be desorbed and reduced to nitrogen. In A third mode uses hydrocarbons in one such amount timed so that the for a desulfation of the second nitrogen oxide storage catalyst 26 required temperature and the required reducing or alternating reducing / oxidizing atmosphere is represented.

The storage catalytic converter 14 close to the engine can be of its size be dimensioned so small that it from medium Engine load, or from medium engine speeds, due to the then high space velocities of the exhaust gas only stores little or no nitrogen oxides. The below these conditions the storage catalytic converter 14 near the engine Passing nitrogen oxides represent the particulate filter Soot oxidation using nitrogen dioxide is available, whereby the required conversion of nitrogen monoxide too Nitrogen dioxide either on the particle filter upstream oxidation catalytic converter or in the particle filter itself (if it is coated catalytically) can. Because in this process via the particle filter Nitrogen oxides are not reduced, are behind Particulate filters still nitrogen oxides in the following second nitrogen oxide storage catalyst 26 can be stored. So get at low load or low The engine speeds up the nitrogen oxides only up to the first storage catalytic converter near the engine, while at medium or high loads or speeds only in the particle filter downstream storage catalyst can be stored. The soot particles become independent of the operating situation stored in the particle filter 24.

In a further alternative embodiment, the Regeneration of the particle filter by adding a catalytic additive to diesel fuel get supported. The additive supply can be in the normally provided fuel tank or else after-engine into the exhaust system. It is also possible, only the fuel that over the Aid supply unit 18 in the exhaust tract is introduced to add an additive.

In a further alternative embodiment, the Connection line 22 the output of a secondary air pump be attached to the intended desulfation clocked is operated to be bold together with the then set exhaust gas an oscillation of the lambda value around the To achieve value 1 (so-called "Lambda wobble").

Figure 2 shows an alternative arrangement 21 to Exhaust aftertreatment, which also has a Exhaust gas turbocharger 5 and an exhaust manifold 3 with a Diesel engine 1 is connected. Same or Similar components as in Figure 1 are the same Provide reference numerals and will not be repeated described. In contrast to Figure 1, the arrangement 2 an integrated exhaust gas aftertreatment 30, in which is a denitrification catalyst and a diesel particulate filter are integrated on a ceramic block. Unit 30 therefore takes over the function of separately in Figure 1 executed units 24 and 26. It is also in the Unit 30 of the denitrification catalyst to the particle filter downstream.

The mode of operation is the same as that in FIG. 1 . described The use of an integrated Exhaust aftertreatment unit 30 enables a compact, space-saving arrangement and enables, for example, behind the oxidation catalyst 20 several Denitrification catalysts and particle filters in alternate order.

As an alternative to an oxidation catalyst 20 (as well in Figure 1) a heatable catalyst or a heated oxidation catalyst can be used. As Aid supply unit 18 can be, for example Arrangement used as in the German Patent application with the file number 44 36 415.6 described is.

Claims (18)

Arrangement for the aftertreatment of exhaust gases, in particular a diesel internal combustion engine, with a device for removing particles and nitrogen oxides, the exhaust gases being able to flow through the device, characterized in that upstream of the device (24, 26; 30), an exhaust gas line (16, 22) means (14) connected to the device for reducing nitrogen oxides can be arranged close to the internal combustion engine, so that the agent can be heated more strongly by the exhaust gases compared to the device and thus the agent can reduce nitrogen oxides in operating situations of the internal combustion engine in which the device does this does not become active, especially at low load and / or low engine speed. Arrangement according to claim 1, characterized in that the means is dimensioned such that it is outside its working range from medium engine speeds or from medium engine load and allows the nitrogen oxides to pass so that they are available to the device for particle removal. Arrangement according to claim 1 or 2, characterized in that an auxiliary arrangement (18, 20) is provided between the means (14) and the device (24, 26; 30), the auxiliary arrangement having an auxiliary supply unit (18) for supply an aid to support exhaust gas aftertreatment in the facility (24, 26; 30). Arrangement according to claim 3, characterized in that the auxiliary supply unit (18) can supply fuel. Arrangement according to claim 3 or 4, characterized in that the auxiliary arrangement (18, 20) has a catalyst downstream of the auxiliary supply unit (18), in particular an oxidation catalyst or an electrically heatable catalyst, optionally an electrically heatable oxidation catalyst, to support an at least partially Burning the aid. Arrangement according to one of the preceding claims, characterized in that the means (14) is a denitrification catalyst, in particular a storage catalyst. Arrangement according to one of the preceding claims, characterized in that the device (24, 26; 30) comprises a particle filter (24), in particular a catalytically coated particle filter. Arrangement according to one of the preceding claims, characterized in that the device (24, 26; 30) contains a denitrification catalyst (26), in particular a storage catalyst. Arrangement according to claims 7 and 8, characterized in that the particle filter and the denitrification catalyst of the device (30) are integrated on a block, in particular on a ceramic block. Process for the aftertreatment of exhaust gases, in particular a diesel internal combustion engine, in which the exhaust gases flow through a device for the removal of particles and nitrogen oxides, characterized in that the exhaust gases, before entering the device (24, 26; 30), initially with a means (14) for Reduction of nitrogen oxides interact and then pass through an exhaust pipe (16, 22) leading to the device, so that the exhaust gases heat the medium more than the device and thus the medium can reduce nitrogen oxides in operating situations of the internal combustion engine in which the device does not become active for this purpose, especially at low load and / or low engine speed. A method according to claim 10, characterized in that the means is dimensioned such that it is outside its working range from medium engine speeds or from medium engine load and allows the nitrogen oxides to pass so that they are available to the device for particle removal. Method according to claim 10 or 11, characterized in that an auxiliary means for supporting the exhaust gas aftertreatment in the device (24, 26; 30) is supplied to the exhaust gases in the region of the exhaust pipe (16, 22). A method according to claim 12, characterized in that fuel is used as an aid. A method according to claim 12 or 13, characterized in that an at least partial combustion of the auxiliary is supported catalytically. Method according to one of the preceding method claims, characterized in that a denitrification catalyst, in particular a storage catalyst, is used as the means (14). Method according to one of the preceding method claims, characterized in that the device (24, 26; 30) comprises a particle filter (24), in particular a catalytically coated particle filter. Method according to one of the preceding claims, characterized in that the device (24, 26; 30) contains a denitrification catalyst (26), in particular a storage catalyst. Method according to claims 16 and 17, characterized in that the particle filter and the denitrification catalyst of the device (30) are integrated on a block, in particular on a ceramic block.

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