JPS58174216A - Filter for removing combustible fine particle - Google Patents

Abstract

PURPOSE:To remove filtered combustible fine particles efficiently by burning them while keeping the high filtering capacity of a filter, by applying an electric current to the filter's own body to generate heat. CONSTITUTION:A filter is formed by filling a passage 6 with filtering bodies 3 without leaving any gap, and a heat-generating electrically-conductive ceramic material, etc. is used for a constituent component of the body 3 as well as that of a wall body 2. An incineration of carbon is profitably performed at lower temperature by depositing the body 3 on a catalytic metal 7 such as platinum, rhodium, and palladium. Both electrodes 4 and 5 are formed at both ends of opened outlet and inlet ports of the passage 6 of the filter 1 in a honeycomb- shaped construction body consisting of the wall bodies 2. As the electrodes 4 and 5 are not provided to the end surfaces of the body 3, they have lattice shapes, respectively. Materials used for the electrodes consist essentially of metallic powder such platinum, nickel, and cobalt, and powder of silicon, etc., is added as required.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filter device for removing combustible particulates contained in gas, particularly combustible particulates such as carbon contained in exhaust gas from automobiles, and more specifically relates to a filter itself. The present invention relates to a filter that efficiently burns and removes filtered combustible particulates while maintaining filterability by applying electricity to generate heat.

Conventionally, it has been proposed to use a filter in the exhaust system or exhaust recirculation system in order to remove carbon particulates contained in the exhaust gas of a car engine as a pollution control measure. There was a problem that this caused clogging and pressure loss. To solve this problem, it is possible to heat the particulate trapping part of the filter by combining a heater such as a nichrome wire or a heat-generating metal layer with electricity, or by injecting fuel into the particulate part and heating it with the combustion heat of the fuel, or by using a high-voltage electrode. Methods have been used to prevent clogging, such as installing a filter and heating it with a spark discharge, or using a carbon III-filtered filter and heating it by passing electricity through the carbon fiber to incinerate the h-bon particles and prevent clogging. .

However, when using nichrome wire, etc., the heat generating area is small, resulting in poor energy efficiency, and it is also time-consuming to attach it to the filter.When installing a heat generating wire, it must be thin so as not to interfere with filtration. They had to be installed in a small area, were not energy efficient, were time-consuming to install, and were thin wires, so there was a risk of wire breakage due to oxidative corrosion. In addition, if the underbody temperature does not go well due to the cooling effect of exhaust gas, stop the engine and then
It has also become necessary to burn off the carbon particles that have accumulated in the filter. Additionally, fuel injection and high-pressure discharge methods require extremely complex equipment, consume large amounts of energy, cause fuel fire problems, and damage filters from discharge; It had the disadvantage that it itself was destroyed by combustion.

In view of the above problems, as a result of intensive research, the present inventors found that
This is a completed filter that solves the above problems.

That is, the gist of the present invention is that a skeleton-type filter body having a filtration effect is filled in the passages of a honeycomb-like structure that forms a group of passages through a combination of electrically conductive and heat-generating walls. This is a characteristic feature of the filter for removing combustible particulates.

Here, the skeleton-type filter body refers to a porous material that is felt-like, woven-fabric-like, or spongy-like and has a function of filtering particulates in exhaust gas.

Next, embodiments of the filter for removing combustible particulates according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a first embodiment of the filter of the present invention, FIG. 2 is a side view thereof, and FIG. 3 is a partially cutaway perspective view thereof.

Reference numeral 1 represents a filter for removing combustible particles, 2 represents an electrically conductive heat generating wall, 3 represents a skeleton type filter, and 4 and 5 represent electrodes.

Here, the walls 2 are sufficiently dense and usually extremely airtight, and are formed by combining them so as to surround the passage 6 from four directions, so that the passage 6, which has a rectangular column shape as a whole, is stacked regularly as shown in Fig. 2. It is structured in a honeycomb-like structure. The material for the wall body 2 can be used as long as it generates heat through electricity and is heat resistant, but it is generally made of silicon carbide or molybdenum disilicide as a main component, with alumina, silica, etc. added as necessary. It will be done.

The filter body 3 is formed so that the passage 6 is filled with 5rlIJ, and its constituent components can be the same heat-generating conductive ceramic material as the wall body 2, but other materials include alumina, aluminum titanate, Non-conductive oxides such as mullite and cordierite can also be used as main components or additives.

It is advantageous if this filter body 3 supports a catalytic metal such as platinum, rhodium, palladium, etc., since carbon can be incinerated at a lower temperature.

The electrodes 4.5 are formed at both ends of the filter 1, in which the outlet and inlet of the passage 6 are open, within the honeycomb-like structure consisting of the wall body 2. Since both electrodes 4.5 are not provided on the end face of the filter body 3, they have a lattice shape as shown in FIG. The material used is one whose main component is metal powder such as platinum, nickel, or cobalt, with powder of silicon or the like added as necessary.

The filter of the first embodiment having the structure as described above is manufactured, for example, by the following method.

First, to manufacture a honeycomb structure, for example, the following procedure is performed. In addition to the main ingredients such as silicon carbide or molybdenum disilicide, fine raw material powders such as alumina and silica, organic binders such as sodium alginate, ammonium alginate, and polyvinyl alcohol, and solvents such as water and ethyl alcohol are added and kneaded. An integrated structure is created by making a compound and extruding it through a die consisting of many slits so that the cross-sectional shape of the through hole forms a polygon such as a triangle, square, or hexagon, or a predetermined shape such as a circle or an ellipse. A raw honeycomb-like structure can be obtained by cutting the long material into a required length.

Further, the shape of the passage 6 of the honeycomb structure can be selected from various shapes such as a square prism, a hexagonal prism, and a triangular prism.

Next, in order to form the filter body 3 in the passages 6 of the honeycomb-like structure, a raw ceramic paste whose composition is blended to form a skeleton-type filter body is applied to the honeycomb-like structure by firing. After the passage 6 is filled, heating and baking may be performed.For example, a raw material solution of soft urethane foam such as polyol and polyisocyanate is added to and mixed with a ceramic raw material powder mixed with a dispersion medium and a binder as necessary. This may be achieved by injecting the foamed material into the passage 6, forming a green ceramic foam in the passage 6 by the foaming reaction of the resulting isocyanate, and then drying and firing. In addition, a plastic foam already formed in the same shape as the passage 6 may be impregnated with a slurry-like mixture of ceramic raw materials, a dispersion medium, a binder, etc., and then inserted into the passage 6 and heated and fired after drying. Accordingly, the filter body 3 can also be formed within the passage 6.

In this case, by changing the thickness of the holes in the foam, the holes in the filter body 3 can be made smaller continuously in the direction of gas flow, and as a result, the air can be distributed more uniformly in the filter body. Fine particles can be dispersed and captured, making incineration processing more efficient.

To form the electrode 4.5 on the end face of the honeycomb structure,
After applying a paste prepared by adding and blending the required amount of dispersion medium, binder, etc. to the metal powder as described above to the end face of the raw or sintered honeycomb-like structure by printing, etc., simultaneously when firing the entire filter, Or, separately, it is made by firing.

The filter of the first embodiment described above has a rectangular parallelepiped shape,
Depending on where the filter of the present invention is applied, various shapes, such as a cylindrical shape, a triangular prism shape, a hexagonal prism shape, etc., can be adopted.

If the filter of the first embodiment is used to remove combustible particulates from gas, for example, when gas to be filtered enters from direction F on the left side in FIG. As a result, fine particles in the gas are dispersed and captured in the filter body.The fine particles thus captured are transferred to the electrode 4.5.
When energized, electricity mainly flows through the wall 2 of the honeycomb-like structure, causing the wall 2 to stably generate heat, which is then conducted to the filter 3 to raise the deposits above the ignition point. It heats up, burns and disappears.

This energizing heat-generating incineration process can be performed at the same time as the filtration process by simply passing electricity between the electrodes, so there is no need to remove the filter and incinerate it, and no clogging occurs even when used for a long time. Further, the electrodes are positioned not only at the ends of the honeycomb-like structure as described above in the gas flow direction, but also at the ends of the peripheral walls 7 of the filter parallel to the gas flow direction, relative to each other, as shown in FIG. electrodes 9 on each side.
10 may be provided and electricity may be applied between them to cause the wall body 2 to generate heat.

The shape of the above filter has a wall thickness of 0°211
- 1111 passages of 12 m - 5 - 1 width 2 - - 5 mm are common.

Next, as a second embodiment, FIGS. 5 and 6 show an example of a cylindrical filter according to the present invention applied to an exhaust pipe or an exhaust gas recirculation pipe of a self-help engine.

FIG. 5 is a partial sectional view, and FIG. 6 is a side view.

Here, 11 represents the filter for removing combustible particulates of the second embodiment, 12 represents an electrically conductive heat-generating wall, 13 represents a skeleton type filter, and 14 and 15 represent electrodes. Electrode 14.15
Conductive wires 16 and 17 are brazed to each other at portions 18 and 19, and insulated to outer cylinder 22 through insulators 20 and 21.
being led to the outside of The conducting wire 16 is connected to one pole of the electrode E via a switch 23, and is grounded to the vehicle body between the power source E and the switch 23. On the other hand, the conductor 17
is connected to the other pole of the electric HIE. In this configuration, connecting the filter 11, the conductive wires 16, 17, the switch 23, and the electric wire 11E constitutes a heating circuit.

Further, the filter 11 is housed in a ceramic insulating cylinder 24 and inserted into the outer cylinder 22 in an insulated and tight state.
The flange 25 of the joint pipe 25 that is connected to the flange 22b of 22
Due to the pressing force of a spring member 27 disposed between the insulation ring 26 and the insulation ring 26, the filter 11 is moved through the insulation ring 26.
The insulating cylinder 24 is supported by being urged by the locking portions 24a of the outer cylinder 24, and further by being urged in the direction of the locking protrusions 22a provided inside the outer cylinder 22.

The outer cylinder 22 may be a part of the exhaust pipe or the exhaust gas recirculation pipe, or it may be formed independently as the outer cylinder of the filter for removing combustible particulates of the present invention and incorporated into the exhaust pipe or the exhaust gas recirculation pipe. When this @@ is attached, the upstream side F of the exhaust gas is the exhaust manifold side, and the downstream side B is the exhaust port side. On the other hand, when this device is attached to the exhaust gas recirculation pipe, the upstream side F of the exhaust gas is the exhaust manifold side, and the downstream side B is the intake manifold side.

In the above configuration, the exhaust gas containing carbon particles from the engine passes through the exhaust manifold as it is, and flows from the upstream direction F to the filter 1 as shown by the dotted line.
1 and flows into the filter body 13, where most of the carbon fine particles contained in the exhaust gas are captured by the pores in the filter body 13. After that, the exhaust gas is filtered through filter 1
1 and goes in the direction 8 of the downstream exhaust port. In other words, the carbon particles in the exhaust gas are dispersed and remain in the filter body 13 of the filter 11.

At this time, by turning on the switch 23, the electrodes 14.1561 at both ends of the filter 11 are energized.
The wall 12 of the filter 11, which is energized and generates heat, generates heat.

As a result, the heat of the wall body 12 is conducted to the filter body 13, and the carbon particulates are ignited and burned, thereby preventing the filter body 13 from becoming clogged.

As detailed above, the present invention provides a filter for removing combustible particulates, in which a skeleton-type filter body having a filtration action is provided in the passages of a honeycomb-like structure that forms a group of passages through which a combination of electrically conductive and heat-generating walls is formed. By filling the filter, the strength of the entire filter is increased by the honeycomb structure, which prevents a decrease in yield due to breakage of the filter during housing. Ru. Moreover, since heat is generated in the honeycomb-like structure, the heat generation can be freely adjusted by selecting the wall thickness of the honeycomb-like structure as appropriate for extrusion molding, for example, and uniform molding is easy. ,
It is easy to maintain quality such as uniform heating performance, and it is possible to increase the yield of high-quality filters that do not cause cracks due to partial heat generation, etc.
*Can be done.

Furthermore, in the filter of the present invention, since the surface area of the heat generating portion is small relative to the volume, the oxidation resistance can be greatly improved. Furthermore, since the filter body does not particularly require electrical conductivity, it has the advantage that valuable materials such as alumina and cordierite can also be used. In addition, the filter of the present invention has a compact shape because the honeycomb structure contributes to both reinforcement of the filter itself and stable heat generation as described above, and is completely integrated with the filter body. It is possible to provide both the effects of trapping and incinerating particulates, which are the performances required for a filter for removing combustible particulates.

Next, the method for manufacturing the filter of the present invention will be described using examples.

Production Example-1 β-8iC (average particle size 0.3μ) 100 parts (lI parts, same hereinafter) Ba0 0.25 parts Phenol tree If 6 parts Ethyl alcohol
100 parts or more of the ingredients were mixed in a ball mill for 3 hours, then dried and pulverized to obtain a formulation containing silicon carbide as the main component.

Next, the components of the above-mentioned formulation (100 parts, polyurethane resin, 7 parts, dimethylformamide (DMF>20 parts) or more were sufficiently kneaded in a kneader, and then extruded to obtain a raw honeycomb-like structure.Separately, β- 8iC (average particle size 0.3μ) 100 parts 8
40 0.25 parts Phenol resin 6 parts Soft urethane foam stock solution (Polyester@) 100 parts or more of the ingredients were thoroughly kneaded using a kneader, and 30 parts of soft urethane foam stock solution (Isocyanate solution) was added.
The mixture was mixed and stirred for 5 seconds, and poured into a mold into which the raw honeycomb structure had been previously inserted to cause a foaming reaction. 12
The bales were removed from the mold for 0 seconds to obtain a foamed body integrated with a honeycomb structure. This was held in vacuum at 800'C for 1 hour to blow off the polyurethane resin and other organic substances.

Further, this structure was sintered at 1950'C in an argon stream for 1 hour to perform secondary firing, and then secondary firing was performed at 1950'C in 1 atm nitrogen gas for 3 hours to make it flammable. A filter for removing particulates was obtained. The honeycomb-like structure of this filter has 22-square columnar passages arranged in an orderly manner vertically and horizontally. was.

At both ends of the above filter on the passage entrance and exit side, 5ic10
~90 It amount% and the balance at least 2 of Fe, Nl, Co
Electrodes were prepared by applying a paste containing a powder of a composition consisting of a mixture of at least one species and firing it in a non-oxidizing atmosphere at a temperature of 1100 to 1 aoo'c, and an electric heat generation incineration experiment of carbon fine particles was conducted as described below. Ta.

When a voltage of 24 V was applied between both electrodes of the filter provided with the above electrodes, the voltage was 0.250 before carbon particles were attached. When this was attached to the exhaust muff of a diesel engine, more than 50% of carbon particles were filtered out. It reached saturation at about 1 o'clock, so 2
When 4V was applied between both electrodes, the voltage increased to 600' in about 30 seconds.
C, the carbon ms ended in about 2 minutes from the start of current application, the carbon particles completely disappeared, and the filtration function of the filter returned to its original state.

l1fI practical example-2 Cordierite 100811 soft urethane foam stock solution (polyester liquid) 100 parts or more and component F were sufficiently kneaded in a kneader i, then 30 parts of soft urethane foam stock solution was added and mixed and stirred for 5 seconds. ,
Separately, a raw honeycomb structure formed in the same manner as in Example 1 was placed in Ar gas at 1950℃ for 60 minutes.
1 mm and then heated to 1950℃ in Nz gas at RL pressure (F).
The product that had been secondarily fired for 3 hours was inserted into a mold, and the above-mentioned stirred mixture was then poured into it to cause a foaming reaction. 120
After a few seconds, it was taken out of the mold to obtain a foam that was integrated with the honeycomb structure. This was heated in the atmosphere at 500°C for 6 hours to remove polyurethane resin and other substances, and then fired in N2 gas at 1350°C for 1 hour to obtain a filter for removing combustible particles. This filter has a pore diameter of 0.
The shape was the same as Production Example-1 except that the amount was 7 mg1.

Electrodes were provided on the above filter in the same manner as in Manufacturing Example 1, and an electric heat generation incineration experiment of carbon fine particles was conducted as described below.

When a voltage of 24 V was applied between both electrodes of the filter provided with the above electrodes, the voltage was 0.350. In addition, the removal effect of carbon fine particles was the same as in Production Example 1, but in Production Example 2.
It took 7 seconds to reach 600° C. by applying a voltage of 4 V, and it took about 30 seconds for the carbon to burn and completely disappear.

Production Example-3 Polycarbosilane 100 parts β-8iC
(Average grain! 0.3μ) 35 parts DMF
After sufficiently kneading the above ingredients in a kneader, the honeycomb-like structure obtained in the same manner as in Production Example-1 was preheated in A gas at 1950°C for 60 minutes.
The mixture was press-fitted into the product which was subjected to secondary firing at 1950°C for 3 hours in N2 gas at 1 atm, and then placed in the atmosphere for 8 hours.
It was thoroughly dried at 0°C.

The above dried product was baked at 1250° C. for 1 hour tm in a vacuum. At this time, the polycarbosilane decomposed and chemically reacted with SiC, thereby obtaining a filter with a skeleton structure. The diameter of the pores of the filter body of this filter is 5 to 50μ
Met.

Electrodes were provided on the above filter in the same manner as in Manufacturing Example 1, and an electric heat generation incineration experiment of carbon fine particles was conducted as described below.

When a voltage of 24V was applied between both electrodes of the filter, the voltage was 0.250. The carbon particulate removal effect is
When installed on the exhaust muffler of a diesel engine,
More than 70% of the carbon particles were filtered out. The saturation state was reached in about 1 hour, so when 24V was applied between both electrodes, the temperature reached 600°C in 30 seconds, and the combustion of carbon ended in about 2 minutes from the start of current application, and the carbon particles completely disappeared. , the filter's filtration function has been restored.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a rectangular parallelepiped filter according to the first embodiment of the present invention, Fig. 2 is a front view thereof, Fig. 3 is a partially cutaway perspective view thereof, and Fig. 48 is an embodiment in which the positions of the electrodes are changed. FIG. 5 is a cross-sectional view of a cylindrical filter according to a second embodiment of the present invention applied to an exhaust pipe or exhaust gas recirculation pipe of an automobile engine.
FIG. 6 shows its side view. 1.8.11...Flammable particulate removal filter 2.1
2... Current-carrying heat-generating wall 3.13... Skeleton filter body 4.5.9.10.14, 15... Electrode 6... Passage agent Tsutomu Adachi, patent attorney Figure 1 Figure 3

Claims (1)

[Scope of Claims] 1. A honeycomb-like structure that forms a group of passages through a combination of electrically conductive and heat-generating walls, and the passages are filled with a skeleton-type filter having a filtration effect. Filter for removing combustible particles. 2. The honeycomb-like structure is made of ceramic whose main component is silicon carbide, and the skeleton filter body is made of one or more selected from silicon carbide, alumina, titanium sapon aluminum, mullite, or cordierite as its main component. The filter for removing combustible particulates according to claim 1, which is made of ceramic. 3. The filter for removing combustible particulates according to claim 1, wherein the skeleton filter body supports a combustion catalyst.