DE10162383A1 - Arrangement and method for the treatment of exhaust gases - Google Patents

Abstract

An arrangement and a method for the aftertreatment of exhaust gases, in particular a diesel internal combustion engine, are proposed, in which a device (24, 26; 30) for removing particles and nitrogen oxides is connected upstream via an exhaust pipe (16, 22) to the device ( 24, 26; 30) connected means (14) for reducing nitrogen oxides near the internal combustion engine is used. This means (14) ensures a reduction of nitrogen oxides in operating situations of the internal combustion engine in which the device (24, 26; 30) is not active for this purpose, in particular when the internal combustion engine has a low load and / or a low speed.

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 and the method according to the invention with the characterizing features of the independent claims have the advantage that high efficiencies in denitrification of the exhaust gas can be achieved regardless of the operating situation of the internal combustion engine. Here, a device of the arrangement takes over the denitrification, particularly when the engine is warm or at medium and high speeds or engine loads, while the upstream means advantageously ensures denitrification, in particular at low load and / or low speed of the internal combustion engine. This means that the EURO 5 emissions standards and the requirements for SULEV applications on the US market can be met, particularly for combustion engines with auto-ignition or compression ignition (diesel process).

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. H. through a appropriate operation of an auxiliary Feed unit, 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 shown in the drawing and explained in more detail in the following description. In the drawings Fig. 1 shows a first embodiment and Fig. 2 shows a second embodiment.

Description of the embodiments

Fig. 1 shows a diesel engine 1, which is connected via an exhaust manifold 3 and an exhaust gas turbocharger 5 with an arrangement 2 for exhaust gas treatment. The exhaust pipe 10 close to the engine connected to the exhaust gas turbocharger 5 leads to a denitrification catalytic converter 14 designed as a storage catalytic converter. A middle exhaust pipe 16 connects the denitrification catalytic converter 14 to an oxidation catalytic converter 20 . An auxiliary supply unit 18 for supplying fuel to the exhaust tract is introduced on the central exhaust line 16 , so that fuel can be introduced into the arrangement 2 downstream of the denitrification catalytic converter 14 and upstream of the catalytic converter 20 . An exhaust gas connection line 22 leads from the oxidation catalytic converter 20 to a particle filter 24 . A denitrification catalytic converter 26 in the form of a storage catalytic converter directly adjoins the particle filter 24 ; the outlet of the denitrification catalytic converter 26 is connected to an exhaust pipe 28 leading to a muffler, not shown.

The storage catalytic converters 14 and 26 serve for the temporary storage of the nitrogen oxides contained in the exhaust gas. In the so-called regeneration mode, which is introduced into the exhaust tract by an internal engine and / or a post-engine supply of fuel, the nitrogen oxides desorb and are reduced to nitrogen. The particle filter 24 serves to separate the particles through a filtering medium. At times, the particle filter must be regenerated, in which the deposited solid or soot particles are oxidized to carbon dioxide or carbon monoxide. The storage catalytic converter 14 near the engine quickly reaches its optimum operating temperature after an engine start. In the position close to the engine in the exhaust system, the exhaust gas temperatures are so high that high NOx conversion rates can be achieved immediately after the engine is started. In order to avoid thermal damage to the nitrogen oxide storage catalytic converter 14 close to the engine, the exhaust gas temperature is controlled via a corresponding control of the fuel supply to the engine in such a way that harmful exhaust gas temperatures are not reached for the nitrogen oxide storage catalytic converter 14 close to the engine. The conditions required for the regeneration and desulfation of the storage catalytic converter 14 are represented by engine interventions. In front of the particle filter 24 and the second nitrogen oxide storage catalytic converter 26 following it there is a fuel supply unit 18 and an oxidation catalytic converter 20 which can be used in various operating modes by suitable control. In a first mode, hydrocarbons are supplied via the fuel supply unit 18 in such an amount that, with a sufficient residual oxygen content remaining, an increase in temperature in the exhaust gas which is sufficient to regenerate the particle filter is achieved via the oxidation catalytic converter. In a second mode, hydrocarbons are supplied in such an amount that a reducing atmosphere is generated via the oxidation catalyst, so that the nitrogen oxides absorbed on the second nitrogen oxide storage catalyst 26 are desorbed and reduced to nitrogen. In a third mode, hydrocarbons are supplied in such an amount in a time-controlled manner that the temperature required for desulfating the second nitrogen oxide storage catalytic converter 26 and the required reducing or alternately reducing / oxidizing atmosphere are shown.

The size of the storage catalytic converter 14 close to the engine can be dimensioned so small that it stores little or no nitrogen oxides from an average engine load or from an average engine speed due to the then high space velocities of the exhaust gas. The nitrogen oxides passing through the storage catalytic converter 14 close to the engine under these conditions are available to the particle filter for soot oxidation by means of nitrogen dioxide, and the required conversion of nitrogen monoxide to nitrogen dioxide can take place either on the oxidation catalytic converter upstream of the particle filter or in the particle filter itself (if it is catalytically coated). Since nitrogen oxides are not reduced in this process via the particle filter, nitrogen oxides are still present behind the particle filters and are stored in the subsequent second nitrogen oxide storage catalytic converter 26 . Thus, at low load or low engine speeds, the nitrogen oxides only reach the first storage catalytic converter near the engine, while at medium or high loads or engine speeds they are only stored in the storage catalytic converter downstream of the particle filter. Regardless of the operating situation, the soot particles are stored in the particle filter 24 .

In a further alternative embodiment, the regeneration of the particle filter can be supported by adding a catalytically active additive to the diesel fuel. The additive can be fed into the normally provided fuel tank or into the exhaust system using the engine. It is also possible to add an additive only to the fuel that is introduced into the exhaust tract via the auxiliary supply unit 18 .

In a further alternative embodiment, the output of a secondary air pump can be attached to the connecting line 22 , which is operated in a clocked manner when desulfation is provided, in order to achieve an oscillation of the lambda value by the value 1 together with the exhaust gas which is then set to be rich (so-called "lambda wobble"").

Fig. 2 shows an alternative arrangement 21 for exhaust gas treatment, which is also connected via an exhaust gas turbocharger 5 and an exhaust manifold 3 is connected to a diesel internal combustion engine 1. The same or similar components as in Fig. 1 are given the same reference numerals and will not be described again. In contrast to FIG. 1, the arrangement according to FIG. 2 has an integrated exhaust gas aftertreatment 30 in which a denitrification catalyst and a diesel particle filter are integrated on a ceramic block. The unit 30 thus takes over the function of the units 24 and 26 which are designed separately in FIG. 1. In this case, the denitrification catalyst is also arranged downstream of the particle filter in the unit 30 .

The mode of operation is the same as that described in FIG. 1. The use of an integrated exhaust gas aftertreatment unit 30 enables a compact, space-saving arrangement and makes it possible, for example, to arrange a plurality of denitrification catalysts and particle filters in alternating order behind the oxidation catalytic converter 20 .

As an alternative to an oxidation catalytic converter 20 , a heatable catalytic converter or also a heatable oxidation catalytic converter can be used (as also in FIG. 1). An arrangement such as is described in the German patent application with the file number 44 36 415.6 can be used, for example, as the auxiliary supply unit 18 .

Claims (18)

1. 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 near 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 not become active for this purpose, in particular at low load and / or low engine speed. 2. Arrangement according to claim 1, characterized in that the mean is dimensioned so that it starts from the middle Engine speeds or from an average engine load is outside his work area and the nitrogen oxides lets pass so that they are the facility for Particle removal is available. 3. 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 ), wherein the auxiliary arrangement has an auxiliary supply unit ( 18 ) to supply an auxiliary device to support the exhaust gas aftertreatment in the device ( 24 , 26 ; 30 ). 4. Arrangement according to claim 3, characterized in that the auxiliary supply unit ( 18 ) can supply fuel. 5. Arrangement according to claim 3 or 4, characterized in that the auxiliary arrangement ( 18 , 20 ) one of the auxiliary supply unit ( 18 ) downstream catalyst, in particular an oxidation catalyst or an electrically heated catalyst, optionally an electrically heated oxidation catalyst, to support one at least partial combustion of the aid. 6. Arrangement according to one of the preceding claims, characterized in that the means ( 14 ) is a denitrification catalyst, in particular a storage catalyst. 7. 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. 8. 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. 9. Arrangement according to claim 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. 10. A method for the aftertreatment of exhaust gases, in particular a diesel internal combustion engine, in which the exhaust gases flow through a device for removing particles and nitrogen oxides, characterized in that the exhaust gases first enter the device ( 24 , 26 ; 30 ) with a means ( 14 ) interact to reduce nitrogen oxides 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 is not active for this purpose is, especially at low load and / or low speed of the internal combustion engine. 11. The method according to claim 10, characterized in that the mean is dimensioned so that it starts from the middle Engine speeds or from an average engine load is outside his work area and the nitrogen oxides lets pass so that they are the facility for Particle removal is available. 12. The method according to claim 10 or 11, characterized in that the exhaust gases in the region of the exhaust pipe ( 16 , 22 ) is supplied with an aid to support the exhaust gas aftertreatment in the device ( 24 , 26 ; 30 ). 13. The method according to claim 12, characterized in that fuel is used as an aid. 14. The method according to claim 12 or 13, characterized characterized in that an at least partial combustion of the Aid is supported catalytically. 15. The method according to any one of the preceding method claims, characterized in that a denitrification catalyst, in particular a storage catalyst, is used as the means ( 14 ). 16. The method according to any 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. 17. The method according to any one of the preceding claims, characterized in that the device ( 24 , 26 ; 30 ) contains a denitrification catalyst ( 26 ), in particular a storage catalyst. 18. The method according to claim 16 and 17, characterized in that the particle filter and the denitrification catalyst of the device ( 30 ) on a block, in particular on a ceramic block, are integrated.