Device and method for treating an exhaust gas containing particles

Abstract

A device for treating an exhaust gas containing particles includes: an exhaust gas line, an emission electrode and an electric supply line for the emission electrode. The electric supply line is at least partially surrounded by an electric insulator and the electric insulator has an outer diameter, the electric insulator extending from the exhaust gas line substantially in the direction of the longitudinal axis of the exhaust gas line. The outer diameter measures at most 20 mm in the terminal region towards the longitudinal axis.

Claims

1. A device (1) for treating an exhaust gas containing particles, comprising: an exhaust gas line (6) having a longitudinal axis (13); an emission electrode (2); an electrical supply line (3) configured to supply electricity to the emission electrode (2); a counter electrode (7) arranged inside the exhaust gas line (6); an electrical insulator (4) arranged inside the exhaust gas line (6) and spaced apart, with respect to the longitudinal axis, from the counter electrode (7), the electrical insulator (4) having an external diameter (12), wherein the electrical supply line (3) is enclosed at least in sections by the electrical insulator (4), wherein the electrical insulator (4) extends from the exhaust gas line (6) toward the longitudinal axis (13) in a direction orthogonal to a direction of the longitudinal axis (13) of the exhaust gas line (6), wherein the external diameter (12) is at most 20 mm in an end region (14) of the electrical insulator (4) proximate the longitudinal axis (13), and wherein a section of the electrical supply line (3) inside the exhaust gas line (6) and not enclosed by the electrical insulator (4) is oriented in the direction of the longitudinal axis (13) so as to project towards the counter electrode (7) such that application of electrical potential to the emission electrode (2) via the electrical supply line (3) generates an electric field between the emission electrode (2) and the counter electrode (7).

2. The device (1) as claimed in claim 1, wherein the external diameter (12) of the electrical insulator (4) is at most 20 mm over its entire length (15).

3. The device (1) as claimed in claim 1, wherein the electrical insulator (4) has a surface (5) against which the exhaust gas can flow, wherein the surface (5) is at most 500 mm.sup.2 in size.

4. The device (1) as claimed in claim 3, wherein the surface (5) is at least 50 mm.sup.2 in size.

5. The device (1) as claimed in claim 1, wherein: the electrical supply line (3) forms an intersection line (10) with the electrical insulator (4) inside the exhaust gas line (6), and a spacing (11) between the intersection line (10) and the exhaust gas line (6) is sufficiently large to prevent the occurrence of flashover during operation of said device at an applied voltage of 25 kV.

6. The device (1) as claimed in claim 5, wherein the spacing (11) between intersection line (10) and exhaust gas line (6) is at least 15 mm.

7. The device (1) as claimed in claim 1, wherein: the electrical supply line (3) has a honeycomb body (9) through which the exhaust gas can flow, and the electrical insulator (4) is arranged between the honeycomb body (9) and the exhaust gas line (6).

8. The device as claimed in claim 7, wherein the honeycomb body (9) is held in the exhaust gas line by a plurality of electrical insulators.

9. A method for treating an exhaust gas containing particles, in which the exhaust gas flows past an emission electrode (2) in an exhaust gas line (6) and an electrical supply line (3) configured to contact of the emission electrode (2) is enclosed at least in sections by an electrical insulator (4) having a surface (5), wherein a counter electrode (7) is arranged inside the exhaust gas line (6) and a section of the electrical supply line (3) inside the exhaust gas line (6) and not enclosed by the electrical insulator (4) is oriented in the direction of a longitudinal axis (13) of the exhaust gas line (6) so as to project towards the counter electrode (7), the method comprising: a) applying a high voltage to the emission electrode (2) to generate an electric field between the emission electrode (2) and the counter electrode (7) and a corona discharge; b) causing the exhaust gas to flow against the surface (5) of the electrical insulator (4); c) depositing particles on the surface (5); and d) combusting the deposited particles on an area of the surface (5) at most 500 mm.sup.2 in size.

10. The method as claimed in claim 9, wherein step d) further comprises increasing the applied high voltage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and the technical environment are explained hereafter as an example on the basis of the figures. It is to be noted that the figures show particularly preferred embodiment variants of the invention, but it is not restricted thereto. In the schematic figures:

(2) FIG. 1: shows an embodiment according to the invention of the device in a longitudinal section;

(3) FIG. 2: shows the embodiment according to FIG. 1 in a further longitudinal section;

(4) FIG. 3: shows a further embodiment of the device in a longitudinal section; and

(5) FIG. 4: shows a cross-sectional view of the embodiment according to FIG. 3.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(6) FIG. 1 and FIG. 2 schematically show a device 1 according to the invention in two longitudinal sections, which are orthogonal to one another, having an exhaust gas line 6, an emission electrode 2, and an electrical supply line 3. The exhaust gas line 6 has a longitudinal axis 13. The electrical supply line 3 is electrically conductively connected to a high-voltage source 8 and guided inside an insulator 4 through the exhaust gas line 6. The electrical supply line 3 is enclosed by the electrical insulator 4 at the feedthrough through the exhaust gas line 6. The electrical insulator 4 has an external diameter 12, a length 15, and an end region 14. The external diameter 12 is at most 20 mm in the end region 14. The surface of the insulator 4, which is in contact with the interior formed by the exhaust gas line 6, is identified as the surface 5 against which flow can occur. The surface 5 against which flow can occur is therefore the surface that can be in contact with the exhaust gas in operation, in particular also with cleaned insulator 4. The device 1 furthermore comprises a honeycomb body, which is used as a counter electrode 7. The electrical supply line 3 forms an intersection line 10 with the insulator 4. The spacing 11 from the intersection line 10 to the exhaust gas line 6 at least sufficiently large that no flashover occurs in operation using a voltage of 25 kV applied to the emission electrode 2. The spacing 11 is preferably at least 50 mm.

(7) In operation, the exhaust gas of an internal combustion engine, which contains particles, flows through the exhaust gas line 6, wherein the particles are ionized by a corona discharge generated using a high voltage at the emission electrode 2. An electrical field is generated by applying an electrical potential to the emission electrode 2 via the electrical supply line 3 in relation to the counter electrode 7 or exhaust gas line 6. In operation, soot particles are deposited on the surface 5 of the insulator 4 against which flow can occur. As soon as a continuous soot deposit has formed between the electrical supply line 3 and the exhaust gas line 6, a leakage current flows. When further soot particles have been deposited on the surface 5 against which flow can occur, such a large current flow thus occurs through the deposited particles that they combust, wherein the temperature of the soot is increased by the current flow.

(8) It can be seen in FIG. 2 that the surface 5 against which flow can occur substantially corresponds to an external lateral surface of a tube.

(9) FIGS. 3 and 4 show a further exemplary embodiment of a device 1 according to the invention in a longitudinal section and in a cross section, respectively. Only the differences in comparison to the embodiment shown in FIG. 1 will be described hereafter. In this embodiment, the electrical supply line 3 is formed by a honeycomb body 9 through which flow can occur. The electrical contacting of a plurality of emission electrodes 2 is therefore performed via the honeycomb body 9. The honeycomb body 9 is electrically insulated in relation to the exhaust gas line 6 via multiple electrical insulators 4 and is held thereby. The emission electrodes 2 are connected in an electrically conductive manner to the honeycomb body 9. The electrical field therefore forms between the emission electrodes 2 and the counter electrode 7.

(10) In the embodiment, the surface 5 against which flow can occur is formed by surfaces of the electrical insulators 4, which each have an external diameter 12. In this embodiment, the external diameter 12 of the electrical insulators is also selected so that combustion of the soot particles deposited thereon can be achieved by increasing the high voltage. In this case, a current flow through the deposited soot particles results in a temperature increase of the soot particles.

(11) Using the invention, long-term operation of a device 1 for treating an exhaust gas containing particles, in which the particles in the exhaust gas are ionized, is ensured. Reestablishing the insulation function of the electrical insulation can be ensured using simple, available structure by the invention.

(12) Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.