JPH06317140A - Filter for collecting particulate in exhaust gas - Google Patents

Abstract

PURPOSE:To provide a filter which is structurally stable and excellent in electrical independence by mounting a conductive filtering plate on the mounting portion of an insulative support while leaving part of an opening uncovered, and attaching electrodes to the conductive filtering plate, and stacking these members inside an outer tube. CONSTITUTION:An insulative support 31 is molded into e.g. a rectangular shape and has an opening 33 formed at its center portion as seen from the direction of circulation of exhaust gas, with a mounting portion 32 of a prescribed width formed around the opening. A conductive filtering plate 34 is mounted on the mounting portion 32 of the insulative support 31 with part of the opening 33 left uncovered. Electrodes 35 are disposed in two portions, each with an overlap with the conductive filtering plate 34, and are integrally secured to the insulative support 31. A number of such assemblies are rotated by e.g. 180 degrees without making the openings 33 overlap one another, and are stacked one atop another inside an outer tube 41 made by e.g. a steel pipe. A filter is thus obtained which is structurally stable and excellent in the electrical independence of its conductive filtering plate 34.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Gas emitted from diesel vehicles is soot-like carbonaceous fine particles (hereinafter abbreviated as "fine particles")
This reduction is one of the important issues to be solved at an early stage in global environmental problems. The present invention is
The present invention relates to a method and a filter for removing fine particles contained in a gas discharged from an internal combustion engine such as a diesel engine.

[0002]

2. Description of the Related Art Conventionally, a ceramic honeycomb structure has been mainly studied as a filter for collecting fine particles in a gas discharged from a diesel engine vehicle (Japanese Patent Laid-Open No. 57-7216). Here, the honeycomb structure is a structure having a plurality of through holes divided by partition walls and capable of taking a large filtration area per unit volume. For collecting fine particles of diesel vehicle exhaust gas, the cell density is 10 to 15 cells / cm ² , and the total number of cells is 1500 to ²
500, partition wall thickness 0.3-0.5 mm, filtration area about 1.5
cm ² is illustrated.

To regenerate a honeycomb structure in which fine particles are collected, the whole or a part of the honeycomb structure is heated to 600 ° C.
A method of igniting fine particles by applying the above high heat and burning and removing them is mainly studied, and exhaust gas is continuously treated by repeating collection and regeneration. In this method, the honeycomb structure having extremely thin partition walls and a large number of cells as described above is required to have a property of withstanding a high temperature when fine particles burn and a property of withstanding repeated temperature fluctuations. .

However, since the partition wall as described above is thin,
It is extremely difficult to manufacture a honeycomb structure with a large filtration area without containing defects such as pinholes, and moreover cracks occur in the partition walls of the honeycomb structure when burning fine particles or in the course of repeated temperature fluctuations. However, there was a problem in productivity and reliability that the collection efficiency was significantly reduced. Further, in the case of regenerating the filter, in the system in which exhaust gas is circulated to collect fine particles and regenerate, since the exhaust gas temperature is about 150 to 350 ° C., which is considerably lower than the combustible temperature of the fine particles, the fine particles burn out even if ignited. There is a problem that combustion cannot be continued up to this point and a fire is lost on the way. For this reason, there is a problem that it is necessary to adopt a method in which two filters are provided in series and one filter is used during regeneration, so that collection and regeneration are repeated alternately. There is a big problem that it becomes expensive. Furthermore,
It was also necessary to incorporate an emergency measure in the equipment, in which fine particles abnormally accumulated, the filter was blocked, and the exhaust gas flow path was blocked.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to solve these drawbacks of the prior art, and has a simple structure, high durability, and low electric capacity required for filter regeneration. A filter for collecting fine particles is provided.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to an outer cylinder, a plurality of stackable insulative supports having an opening in the outer cylinder and a mounting portion for a conductive filter plate, and a plurality of stackable insulating supports. A conductive filter plate attached to the insulating support, leaving a part
And a filter for collecting fine particles in exhaust gas, which is configured to include an electrode attached to the conductive filter plate, and further, the electrode is used as the conductive filter plate at the mounting portion of the conductive filter plate of the insulating support. It is an attached filter for collecting fine particles.

The present invention uses a plurality of stackable insulative supports having openings and attachments for conductive filter plates. The shape of the insulative support is not particularly limited, but a square shape as shown in FIG. 1, a circular shape as shown in FIG. Here, the opening of the insulating support (11 in the figure,
21) means a portion through which exhaust gas can pass without an insulating support material that blocks the flow of exhaust gas in a state where the insulating support is attached inside the outer cylinder, and preferably, FIG.
2 surrounded by an insulative support material.
A conductive filter plate is attached to this opening in a state of being shielded while leaving a part of the opening. The attachment part (12, 22 in the figure) of the conductive filter plate is at least 3 times the conductive filter plate.
It means a strip-shaped region in contact with a width of not less than mm, preferably a width of 5 to 30 mm, and is preferably electrically conductive by means of a bolt and a nut as means for fixing the electrically conductive filter plate to the insulative support at the mounting portion. It has a hole through which a bolt for attaching the filter plate to the insulating support is inserted.

Stackable means that two or more insulative supports can be structurally stacked, and two or more insulative supports can be structurally stacked without special means for fixing the insulative supports to the outer cylinder. It means that the state in which the insulating supports are stacked in the outer cylinder is stable as a structure. In this sense, the plurality of insulating supports to be stacked have substantially the same shape, and it is preferable that the portions in contact with each other in the stacked state are in contact with each other with as little gap as possible, and the contact portions are as flat as possible. Is preferred. The total area including the opening of the insulating support as viewed from the flow direction of the exhaust gas is not particularly limited, but 10 to 2000 cm ² is appropriate for diesel passenger cars, and more suitably 4
It is 0 to 700 cm ² . The area of the opening viewed from the flow direction of the exhaust gas is 50 to 99% of this area, preferably 70
Occupy ~ 95%. The height of the insulating support is not particularly limited, but is preferably 5 to 100 mm, more preferably 10 to 50 mm.

The material of the insulating support is not particularly limited, but may be alumina, mullite, cordierite,
A wide range can be selected from quartz, silicon nitride, boron nitride, various heat resistant glasses, etc., and molded sintered bodies of these can be preferably used.

The conductive filter plate used in the present invention is required to have the property of being heated to at least 550 ° C. or higher, preferably 650 ° C. or higher by energizing it. In addition, if there is a pressure difference between the front and back surfaces of the conductive filter plate, the gas must pass through the conductive filter plate and pass through, but must have the property of trapping fine particles. The conductive filter plate having such properties, nickel, chromium, iron, aluminum, a porous body of a conductive heat-resistant alloy produced from cobalt, molybdenum disilicide, tungsten disilicide, zirconia,
It can be formed from a porous body of a conductive ceramic such as silicon carbide, boron carbide or lanthanum chromite, and has a porosity of at least 20% or more, preferably 30 to 80.
%, The average pore diameter is at least 0.1 μm or more, preferably 1 to 100 μm, and more preferably 10 to 60 μm. The shape of the conductive filter plate is not particularly limited, but it is selected from a wide range such as a square shape, a circular shape, an elliptical shape or the like according to the shape of the insulating support.
Although the size of the conductive filter plate varies depending on the amount of exhaust gas to be treated, the size of the conductive filter plate is at least 30% or more, preferably 60 to 98% of the area of the opening of the insulating support. That is, the area of the opening of the insulating support viewed from the flow direction of the exhaust gas is at least less than 70%, preferably 2 to 40%. A suitable one-sided area viewed from the flow direction of the exhaust gas is about 10 to 1500 cm ² , preferably about 30 to 600 cm ² . The thickness of the conductive filter plate is selected depending on the porosity and strength,
5 mm is preferable.

An opening left as a part of the state where the conductive filter plate is attached to the opening of the insulating support (eg, 33 in the figure,
The position of 53) may be any position such as the central portion and the edge of the filter plate. However, when stacking with the conductive filter plate attached to the insulating support, the opening is in the exhaust gas flow direction. It is preferable from the viewpoint of the collection efficiency of fine particles that they are stacked by rotating, for example, 90 degrees or 180 degrees so that they do not overlap.

The number of conductive filter plates attached to the insulating support is selected in consideration of the collection efficiency to be achieved and the pressure loss of exhaust gas, but is usually 3 to 300, and more suitably 5
~ 50 sheets.

It is necessary to attach at least two electrodes for electric heating to each conductive filter plate. Here, when attaching the electrodes to the conductive filter plate, the electrodes are attached to the conductive filter plate mounting portion of the insulating support. A method of attaching electrodes, that is, a method of integrally mounting the conductive filter plate and the electrode on the insulating support body with bolts and nuts in a state of being superposed at the conductive filter plate mounting portion of the insulating support body, It is preferable because of the stability of the structure of the filter and the ease of manufacturing. Lead wires for energization from a power source are connected to the electrodes. As an example, the lead wires pass through the respective electrode holes provided in the outer cylinder and are guided to the electrodes from the power supply.

The filter of the present invention can be assembled, for example, by
Place the insulating support with the conductive filter plate and the electrode inside the outer cylinder, connect the lead wire to the electrode, and then stack the insulating support with the conductive filter plate and the electrode on top of the electrode. It can be performed by repeating a predetermined number of steps such as connecting a lead wire to.

[0015]

The filter for collecting fine particles of the present invention partially uses the pressure difference between the front and back surfaces of the filter plate generated in the process of the exhaust gas flowing through the flow path blocked by the conductive filter plate while leaving a part of the filter. It is a filter suitable for achieving a high collection rate by repeating the operation of collecting fine particles in the exhaust gas of a plurality of times continuously, and by attaching electrodes to each conductive filtration plate, each conductive filtration It is a filter that can heat and regenerate the plate independently.

Therefore, in this system, each conductive filter plate needs to be arranged in a state where there is substantially no electrical connection with other conductive filter plates or outer cylinders. Further, the conductive filter plate needs to be arranged in the outer cylinder so as to be structurally stable when mounted on a traveling diesel vehicle. To solve this problem, the present invention achieves substantial insulation from the outer cylinder and other conductive filter plates by attaching the conductive filter plate to the insulating support provided with the mounting portion of the conductive filter plate. Furthermore, structural stability is achieved by making this insulating support a stackable structure. That is, by mounting each conductive filter plate on an insulative support that can be stacked in the outer cylinder and therefore has a substantially stable structure in the outer cylinder and dispose in the outer cylinder, conductive filtration is performed. The non-contact between the outer casing of the plate and the other conductive filter plate is ensured, and the insulating support is substantially structurally stable in the outer casing. The attached electrode can be a stable structure as a whole.

The present invention will be specifically described below with reference to examples.

【Example】

Example 1 As an insulating support, a rectangular alumina sintered body having a shape as shown in FIG. 1, a flat conductive filter plate, and an electrode were used as a filter member, and these were assembled as shown in FIG. The size of the insulating support 31 is 11 cm × 11 cm × height 3 c
m, the wall thickness was 3 mm. The opening of the insulative support was located in the center of the insulative support as viewed from the direction of exhaust gas flow, had a size of 10 cm × 10 cm, and had a conductive filter plate mounting portion 32 with a width of 7 mm around it. . Further, mounting holes having a diameter of 2 mm were provided at intervals of 8 mm at the center of the width of the mounting portion of the conductive filter plate. The density of the alumina sintered body 31 is 3.85 g / cm ^3, which is 97% of the theoretical density.
Met.

10.6 cm × 8 as the conductive filter plate 34
A silicon carbide based porous material having a size of cm × 2 mm in thickness was used. The silicon carbide based porous material had a density of 1.54 g / cm ³ , a porosity of 52% and an average pore diameter of 28 μm. This conductive filter plate is arranged on the insulating support in the state shown in FIG. 3, and holes are provided in the conductive filter plate 34 in accordance with the positions of the mounting holes of the mounting portion 32 of the insulating support. A bolt made of heat-resistant stainless alloy was passed through the hole and fixed integrally with the bolt and nut. The electrode 35 has a width of 3 mm and a length of 8
A heat-resistant stainless alloy having a thickness of 1 cm and a thickness of 1 mm was placed on the conductive filter plate at two positions as shown in FIG. 3, and fixed with bolts and nuts integrally with the insulating support. With the conductive filter plate and the electrode attached to the insulating support, the opening 33 of the insulating support which is not shielded by the conductive filter plate is 2
It was cm × 10 cm.

In this way, 15 sets of insulating supports to which conductive filter plates and electrodes were attached were prepared, and the inner dimensions were 11.1 cm × 11.1 cm, the wall thickness was 2 mm, and the length was 5 mm.
The steel tube 41 having a rectangular column shape of 0 cm was rotated by 180 degrees one by one so that the openings would not overlap with each other, and the tubes were stacked as shown in FIG. A lead wire for energization was attached to each electrode through the steel tube. An insulating material was placed around the through-hole of the steel tube to prevent conduction between the lead wire and the steel tube.

The filter thus constructed was installed in an automobile equipped with a diesel engine having a displacement of 2500 cc, the exhaust gas was guided to the filter, and a particulate collection test was conducted under an actual running condition for 100 hours. Run about 50k
The speed was set to m / h, and an electric power of 1 kw was sequentially supplied to each of the conductive filter plates for 10 minutes while guiding the exhaust gas to the filter to intermittently heat and regenerate the filter. A smoke meter and a pressure gauge for measuring the concentration of fine particles in the exhaust gas were installed both before and after the filter, and continuous measurement was performed. As a result, the collection rate of fine particles by the filter is 8
3 to 88%, the pressure loss in the filter is 0.53
It was ˜0.57 kg / cm ² , and no problem that hinders continuous collection of fine particles was observed.

Example 2 A circular mullite sintered body 51 having a shape as shown in FIG. 2 as an insulating support, a notched disk-shaped conductive filter plate 54, and an electrode 55 were used as members of a filter. Was assembled as shown in FIG. The diameter of the insulating support is 12c
m, the height was 3 cm, and the wall thickness was 2 mm. The opening of the insulative support is located in the center of the insulative support as seen from the flow direction of the exhaust gas, and has a diameter of 10 cm and a circumference of 8 m.
It had a conductive filter plate mounting portion 52 of m width. In addition, a diameter of 2 mm is provided at the center of the width of the mounting portion 52 of the conductive filter plate.
mm mounting holes were provided at 8 mm intervals. The density of the mullite sintered body 51 was 2.88 g / cm ³ , which was 95% of the theoretical density.

Diameter 11.4c as the conductive filter plate 54
m, minimum width 6.4 cm (there are two notches with a width of 2.5 cm as shown in FIG. 5), and a thickness of 1.5 mm of molybdenum disilicide porous body (porosity 46%, average pore diameter 37 μm). )
Was used. This conductive filter plate was placed on the insulating support in the state shown in FIG. 5, and fixed in the same manner as in Example 1 by using bolts and nuts made of heat-resistant stainless alloy. Further, an arc-shaped heat-resistant stainless alloy having a width of 5 mm and a wall thickness of 1 mm is used for the electrode 55, and the electrodes are arranged at two positions in a state of being overlapped with the conductive filter plate at the mounting portion of the conductive filter plate as shown in FIG. It was fixed with bolts and nuts integrally with the flexible support. With the conductive filter plate and the electrodes attached to the insulating support, the maximum width in the center direction of the circle of the opening 53 of the insulating support not shielded by the conductive filter plate was 1.8 cm.

In this way, 20 sets of the electrically insulating supports to which the conductive filter plate and the electrodes are attached are prepared.
It was placed in a cylindrical steel tube having a length of 2 cm, a wall thickness of 2 mm, and a length of 70 cm, rotating 90 degrees one by one so that the openings would not overlap. A lead wire for energization was attached to each electrode through the steel tube. An insulating material was placed around the through-hole of the steel tube to prevent conduction between the lead wire and the steel tube. The filter thus constructed was installed in a vehicle equipped with a diesel engine in the same manner as in Example 1, and a particulate collection test was conducted under actual running conditions for 100 hours. While guiding the exhaust gas to the filter, electric power of 1 kw was sequentially supplied to each conductive filter plate for 10 minutes to intermittently heat and regenerate the filter. A smoke meter and a pressure gauge for measuring the concentration of fine particles in the exhaust gas were installed both before and after the filter, and continuous measurement was performed.

As a result, the collection rate of fine particles by the filter is 88 to 91%, and the pressure loss in the filter is 0.57 to 0.61 kg / cm ^2, which is an obstacle to continuing the collection of fine particles. No such problem was seen.

[0025]

EFFECT OF THE INVENTION By using a plurality of stackable insulative supports having an opening and a mounting part of the conductive filter plate, structurally stable and reliable electrical independence of the conductive filter plate is obtained. A highly efficient filter can be provided.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of the structure of an insulating support.

FIG. 2 is a schematic view showing an example of the structure of an insulating support.

FIG. 3 is a schematic view showing a state in which a conductive filter plate and electrodes are attached to an insulating support.

FIG. 4 is a schematic view of a cross section of a filter in a direction parallel to the flow of exhaust gas.

FIG. 5 is a schematic view showing a state in which a conductive filter plate and electrodes are attached to an insulating support.

[Explanation of symbols]

 11 ... Insulating support opening 12 ... Attachment part of conductive filter plate 34 ... Conductive filter plate 35 ... Electrode 41 ... Steel tube

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[Procedure amendment]

[Submission date] September 21, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction content]

[0001]

[Industrial application] Gas emitted from diesel vehicles is soot-like carbonaceous fine particles (hereinafter abbreviated as "fine particles")
This is one of the important issues to be solved at an early stage in global environmental problems. The present invention is
The present invention relates to a filter for removing fine particles contained in gas discharged from an internal combustion engine such as a diesel engine.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Conventionally, a ceramic honeycomb structure has been mainly studied as a filter for collecting fine particles in a gas discharged from a diesel engine vehicle (Japanese Patent Laid-Open No. 57-7216). Here, the honeycomb structure is divided by partition walls, and one end portion has an alternating positional relationship.
It is a structure that has a large number of closed cells and can have a large filtration area per unit volume. For collecting fine particles of exhaust gas from diesel vehicles, the cell density is 10
15 cells / cm ² , total number of cells 1500 to 2500, partition wall thickness 0.3 to 0.5 mm, and filtration area of about 1.5 m ² are exemplified.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

The material of the insulating support is not particularly limited, but may be alumina, mullite, cordierite,
A wide range of materials can be selected from quartz, silicon nitride, boron nitride, various heat resistant glasses, etc., and molded sintered bodies thereof can be preferably used. Also, spray an insulating ceramic material onto the metal.
Material, or contact between the support and the conductive filter plate
Insulating packing etc. is interposed in the part
It is also possible to adopt a structure that ensures sufficient insulation.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

An opening left as a part of the state where the conductive filter plate is attached to the opening of the insulating support (eg, 33 in the figure,
The position of 53) is an arbitrary position such as the central part and the edge of the filter plate.
May be at, but in stacking in a state of mounting a conductive filtration plate insulating support, so that the opening does not overlap in the flow direction of the exhaust gas, for example 90 degrees, be stacked rotated 180 degrees such It is preferable from the viewpoint of the collection efficiency of fine particles.

Claims (2)

[Claims] 1. An outer cylinder, a plurality of stackable insulative supports having an opening and an attachment portion of a conductive filter plate in the outer cylinder, and the insulating property with a part of the front opening left. A filter for collecting fine particles in exhaust gas, comprising a conductive filter plate attached to a support and an electrode attached to the conductive filter plate. 2. The filter according to claim 1, wherein the electrode is attached to the conductive filter plate at a portion of the insulating support where the conductive filter plate is attached.