WO2000032911A1

WO2000032911A1 - Device and method for the cleaning of exhaust gas from an internal combustion engine

Info

Publication number: WO2000032911A1
Application number: PCT/EP1999/008670
Authority: WO
Inventors: Rolf Bosse
Original assignee: Volkswagen Aktiengesellschaft
Priority date: 1998-11-28
Filing date: 1999-11-11
Publication date: 2000-06-08
Also published as: DE19855092A1; DE19855092B4

Abstract

The invention relates to a device for cleaning exhaust gas of an internal combustion engine comprising an NOx accumulating catalyst and particle filters. Said device comprises n ≥ 2 sections, where n is an integer and each section is provided with at least one particle filter element and at least one NOx accumulating catalyst element. Said elements are thermally coupled. In a preferred embodiment, each section comprises exactly one particle filter element and one NOx accumulating catalyst element. The sections or particle filter elements are provided with heating devices. Said particle filter elements may have an ignition device. The respective NOx accumulating catalyst element is heated to a temperature exceeding the desulfurisation temperature during a regeneration phase by the burn-off of the filter particles of a particle filter element.

Description

Device and method for cleaning the exhaust gas of a

Internal combustion engine

The invention relates to a device and a method for cleaning the exhaust gas of an internal combustion engine, the cleaning device having a NOx storage catalytic converter and a particle filter.

Exhaust gas cleaning devices are known, in particular for diesel injection engines which can be operated in lean operation and which have a NOx storage catalytic converter and an upstream particle filter. In the functional operation of the exhaust gas purification device, the exhaust gas flow brings sulfur to the NOx storage catalytic converter, which was in the fuel used and adversely affects the absorption capacity of the NOx storage catalytic converter. In technical jargon one speaks of a poisoning of the catalyst by the sulfur. The sulfates formed can be converted again at elevated exhaust gas temperatures. This measure can be carried out in an exhaust gas cleaning device of an internal combustion engine, in which a heating device is provided for heating the NOx storage catalytic converter to a de-sulfation temperature. With such a device, the sulfates formed during the functional operation of the NOx storage catalytic converter can be converted again during a heating-up time interval, so that the poisoning is reversible overall.

To reach the desulphation temperature, an electrical heating device can be provided, which can be put into operation by means of a control or regulating device. However, this leads to increased energy consumption. It can be expected that because of the relatively large and comparatively cool exhaust gas mass flows, very high electrical currents, e.g. B. in the partial load range above 500 A at 14.4 volts are required, which can hardly be provided by the electrical system of a motor vehicle, in particular a car.

The invention has for its object to provide a device and a method with which the exhaust gas purification can be carried out with less energy. This object is solved by the features of claim 1 or 12. Preferred embodiments of the invention are the subject of the dependent claims.

The device according to the invention for cleaning the exhaust gas of an internal combustion engine with a NOx storage catalyst and particle filter has n> 2 sections, where n is a natural number, and each section has at least one particle filter element and at least one NOx storage catalyst element, the at least one particle filter element and that at least one NOx storage catalyst element are thermally coupled.

Each section preferably has exactly one particle filter element and one NOx storage catalytic converter element, it being possible for the sections to be layered or arranged sequentially. Furthermore, the sections can be longitudinal or transverse sections or coaxially inserted parts and can be arranged and / or shaped in segments.

Each section preferably has a heating device, wherein each particle filter element (PE) and / or NOx storage catalyst element (KE) can have a separate heating device. Furthermore, an ignition element, for example a glow ignition, can be provided for each particle filter element in order to initiate the combustion of the filter particles, which are soot particles, which accumulate in the particle filter element.

Furthermore, an electronic control or regulating device can be provided which regulates the heating device of each section or particle filter element and / or NOx storage catalytic converter element and, if present, the ignition elements of the particle filter elements in a specific sequence in each case during a NOx regeneration process.

An initiation of the burn-up can also be effected by regulating the heating device of the particle filter element concerned in such a way that the flame temperature of the filter particles is exceeded, the electronic control device preferably switching on the heating devices of the particle filter elements concerned before the initiation of a NOx regeneration process. To increase the heat coupling between the sections, the device is arranged in a corresponding housing.

In the method according to the invention for cleaning the exhaust gas of an internal combustion engine with a device according to the invention, during a NOx regeneration of the device, de-sulfation of at least one section of the device is carried out by causing the filter particles to burn off in the at least one particle filter element of the section. To cause the filter particles to burn up, the corresponding particle filter element can be heated to the flame temperature of the filter particles. It is also possible to initiate the erosion via an ignition device. Furthermore, the ignition of the filter particles can be started before the NOx regeneration is initiated.

In the method according to the invention, less energy is required, since the energy for heating the NOx storage catalyst arrangement is obtained by burning off the filter particles and only energy is required for igniting the filter particles, for which less energy is required. This makes it possible to draw the required energy from the vehicle's electrical system, and conventional electrical system equipment can be used without being overloaded.

Due to the possibility for the desulfation to ignite and heat up the sections of the NOx storage catalytic converter arrangement in succession, an even lower energy output is required for each partial heating.

The sections of the cleaning device which are preferably identical in terms of their energy consumption or also structurally identical can be designed so large in terms of their energy consumption that they can be supplied by the vehicle electrical system in each case without problems and without overloading.

In the context of the invention, the sections can be longitudinal or transverse sections, wherein they can only be defined by the space section that can be heated with the associated heating device or by a separate component.

Preferred embodiments of the invention are explained in more detail below with reference to the drawings. Show it Figure 1 shows a first embodiment of the device according to the invention in a perspective and schematic representation.

2 shows a second embodiment of the device according to the invention in cross-sectional representation; and

Fig. 3 shows a third embodiment of the device according to the invention in

Cross-sectional representation.

The exhaust gas cleaning device or NOx storage catalytic converter, generally designated 1, is part of an exhaust gas cleaning system (not shown further) and is located in the exhaust gas system of an internal combustion engine, in particular a diesel engine, which is preferably an injection internal combustion engine which is operated with gasoline or diesel fuel can. The catalytic converter 1 is arranged in the flow path of the exhaust gas of the exhaust system, i.e. in its exhaust pipe.

The catalyst 1 has several, more precisely at least two sections 1a, 1b,

1c, with each section 1a, 1b, 1c ... at least one

Storage catalyst element KE and at least one particle filter PF. The

Sections 1a, 1b, 1c can each be heated individually by means of a heating device (not shown), wherein each particle filter element (PF) and each NOx storage catalyst element (KE) can also be provided with a respective separate heating device. Furthermore, the particle filter PF can be arranged upstream or downstream of the storage catalyst element KE in the flow direction 4 of the exhaust gas.

In the embodiment according to FIG. 1, sections 1a, 1b, 1c of the

Storage catalytic converter 1 around longitudinal sections, which are arranged axially one behind the other in the flow direction 4 of the exhaust gases, wherein in the area of sections 1a,

1b, 1c results in an axial flow direction 4. That or that

Storage catalyst elements KE and particle filter PF can be disc-shaped parts.

In the embodiment according to FIG. 2, in which the same or comparable parts are provided with the same reference numerals, the one or more storage catalytic converter elements KE and particle filter PF are annular parts which are arranged coaxially surrounding one another in a ring are. In this embodiment, the flow direction in the region of the sections 1a, 1b, 1c is directed radially inwards or radially outwards.

3, sections 1a, 1b, 1c are concerned

Cross sections of the storage catalytic converter 1, preferably in the form of segments or pie-shaped cutouts. With this configuration, the direction of flow in the region of the sections 1a, 1b, 1c can be directed in the circumferential direction.

In order to obtain a good thermal coupling, the one or more storage catalyst elements KE and particle filter PF should not only be accommodated in one housing (not shown), but should be layered or arranged sequentially, so that a good thermal coupling between the storage catalyst elements KE and the particle filter PF given is.

Each particle filter element PF of a section 1a, 1b, 1c can also have one

Have ignition device that initiates the burning of the filter particles of a particle filter element PF. However, it is also possible to use the appropriate heating device for this purpose.

The number n of preferably identical sections 1a, 1b, 1c is equal to or greater than 2. Two or more, e.g. 16, sections 1a, 1b, 1c may be provided.

The heating devices and / or ignition devices are set in operation by a control or regulating device. The heating and / or ignition functions of all sections 1a, 1b, 1c can be put into operation simultaneously or in a specific order.

In the functional mode of the NOx storage catalytic converter arrangement 2, NOx is deposited on the surface of the catalytic converter when the internal combustion engine is lean. A regeneration process of the storage catalytic converter 1 must therefore be carried out at regular intervals, which takes place with reducing, stoichiometric or slightly lean exhaust gas.

According to the invention, for the desulfurization of the storage catalytic converter 1, its sections 1a, 1b, 1c are at the same time or at certain time intervals subsequently heated to the desulfation temperature in each case in a NOx regeneration process.

The heating of the sections 1a, 1b, 1c to the de-sulfation temperature is ignited and the subsequent combustion of the filter particles

Particle filter element of the corresponding section 1a, 1b, 1c When the filter particles are burned, so much heat is generated that the associated section 1a, 1b, 1c i.e. the associated NOx storage catalyst element KE is heated to the increased desulfation temperature, as a result of which the NOx storage catalyst element KE is desulfated. In this case, electrical energy is only required during ignition, which can be removed from the vehicle electrical system due to the relatively small amount.

In the case of a heating of the sections 1a, which is not simultaneous but one after the other,

1b, 1c, the time intervals between these partial de-sulfations are determined such that all sections 1a, 1b, 1c ... and thus the storage catalyst 1 as a whole are desulfurized before its NOx absorption capacity is significantly impaired or fails. Due to the still lower required heating power, an on-board electrical system of the associated vehicle can be used with even lower performance

Serve as a source of energy. Since the sections 1a, 1b, 1c in their entirety the

Form storage catalyst 1, after n de-sulfation processes according to the invention, the storage catalyst 1 has been completely heated to the de-sulfation temperature and de-sulfated.

The ignition of the burn-off of a section 1a, 1b, 1c can take place before one

Start initiation of NOx regeneration. Because of the reduction in the cooling effect due to the partial throttling as soon as NOx regeneration is initiated, energization is preferred to be carried out during this initiation phase.

The de-sulfation can be carried out at the de-sulfation temperature of the exhaust gas and in a reducing, stoichiometric or slightly lean environment. REFERENCES LIST

KE NOx storage catalyst element

PE particle filter element

1a, 1b, 1c section

1 NOx storage catalyst device

2 flow direction

Claims

PATE NTAN S PRU CHE

1. A device for cleaning the exhaust gas of an internal combustion engine with NOx storage catalyst and particle filter, characterized in that the

Device n> 2 sections (1a, 1b, 1c), where n is a natural

Is a number, and each section has at least one particle filter element (PF) and at least one NOx storage catalyst element (KE), the at least one particle filter element (PF) and the at least one NOx storage catalyst element (KE) being thermally coupled.

2. Device according to claim 1, characterized in that each section (1a, 1b, 1c) has exactly one particle filter element (PF) and a NOx storage catalyst element (KE)

3. Device according to claim 1 or claim 2, characterized in that the sections (1a, 1, 1c) are layered or arranged sequentially.

4. Device according to one of the preceding claims, characterized in that the sections (1a, 1b, 1c) are longitudinal or transverse sections or coaxially nested parts.

5. The device according to claim 4, characterized in that the sections (1a, 1b, 1c) are arranged and / or shaped in segments.

6. Device according to one of the preceding claims, characterized in that each particle filter element (PF) and / or NOx storage catalyst element (KE) has a heating device.

7. The device according to claim 6, characterized in that a control device is provided which regulates the heating device of each particle filter element (PE) and / or NOx storage catalyst element (KE) in a certain order in each case in a NOx regeneration process.

8. The device according to claim 7, characterized in that the heating device of the particle filter element concerned is controlled so that the ignition temperature of the filter particles is exceeded.

9. The device according to claim 6 or 7, characterized in that each particle filter element (PF) has an ignition device.

10. The device according to claim 9, characterized in that the ignition devices are controlled by the control device.

11. The device according to any one of claims 7 to 10, characterized in that the electronic control device controls the heating devices and / or ignition devices of the particle filter elements (PE) concerned before the initiation of a NOx regeneration process.

12. A method for cleaning the exhaust gas of an internal combustion engine with a device according to one of the preceding claims, characterized in that during a NOx regeneration of the device a desulfation of at least a portion (1a, 1b, 1c ...) of the device is carried out is achieved by causing the filter particles to burn up in the at least one particle filter element (PE) of the section (1a, 1b, 1c ...).

13. The method according to claim 12, characterized in that the particle filter element (PE) is heated to the ignition temperature of the filter particles.

14. The method according to any one of claims 12 or 13, characterized in that the filter particles are ignited before the initiation of NOx regeneration.