JPH1089050A - Filter device for exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the scavenging efficiency of a particulate matter while retaining low pressure loss, and also prevent damage when a filter is regenerated, by mutually laminating a metallic mesh part and an alumina ceramic mesh part consisting of yarn of alumina fiber, and intermittently energizing and heating the metallic mesh part. SOLUTION: This filter device is equiped with alumina ceramic mesh parts 11 consisting of a Fe-Cr-Al alloy and alumina ceramic mesh parts 12 consisting of yarn of alumina long fiber whose fiber diameter is in the range of from ϕ5 micron to ϕ15 micron, and these metallic mesh parts 11 and alumina ceramic mesh parts 12 are mutually overlapped so as to form a filter part main body. Voltage applying terminals are connected to both ends of the metallic mesh parts 11, and the metallic mesh parts 11 themselves are energized and heated by applying voltage to these terminals. That is, an electric heater is formed from the metallic mesh parts 11 themselves, and particulate matters scavenged by Joule heat by this energization are burnt and eliminated so as to regenerate a filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an automobile, a railway,
The present invention relates to an exhaust gas filter device that collects and processes particulate matter mainly discharged from a diesel engine used in ships, construction machines, power generation, and the like.

[0002]

2. Description of the Related Art Exhaust gas discharged from a diesel engine contains SOF (H) as unburned exhaust material such as soot, fuel and lubricating oil of carbon alone, which is called dry soot.
C), sulfate containing water (H ₂ SO ₄ H ₂ O),
Inorganic substances in fuel, such as metal abrasion powder generated from engine parts, are contained as particulate matter.

It has been pointed out that the black smoke composed of these particulate matter pollutes the environment and may have a bad influence on the human body, and technology for preventing emission to the atmosphere has been actively developed. I have.

[0004] As this discharge prevention technology, there are a technology based on engine improvement such as high-pressure fuel injection and a post-treatment technology.
Although the engine improvement technology is becoming quite successful in constant load operation, it has many problems when a variety of loads such as automobiles are applied. Therefore, development of a post-processing technique such as removal of particulate matter by a filter is desired.

In addition, conventional particle substances (particle diameter: 0.1 to 1)
As a filter for trapping the dust and removing the clogging, a combination of a ceramic monolith filter 1 made of cordierite and an electric heater 2 or a burner shown in FIGS. 4 and 5 is often used. Are known. This monolith filter 1 exhibits characteristics favorable as a filter, that is, high collection efficiency and low pressure loss.

As shown in FIGS. 4 and 5, this monolithic filter 1 has a number of cells which are sealed by an opening 3 on one side and a ceramic sealing material 4 on the other side and surrounded by microporous partition walls 5. Has a honeycomb structure. The plugs are alternately arranged for adjacent cells.
Therefore, the gas containing particulate matter enters the filter through the opening 3 for each cell, but the filter outlet is connected to the plugging material 4.
The exhaust gas flows from the fine holes of the partition wall 5 to the adjacent cells and is discharged out of the filter.
Since the fine pores of the partition 5 have a size similar to that of the particulate matter, the particulate matter in the exhaust gas is
By filtration. This trapping mechanism is called the blocking effect.

Furthermore, low pressure losses are achieved by having a very large number of micropores and at the same time having a large surface area.

The need to remove filter clogging, referred to as regeneration, is for the following reasons. As the filter is used, particulate matter gradually fills the pores, increasing pressure drop. This pressure loss acts as a back pressure on the engine, and as a result, the fuel efficiency is deteriorated and the output is reduced.

In the case of the monolith filter 1, regeneration is often performed by heating. For example, the clogged monolith filter 1 is heated by an electric heater 2 or a burner arranged on the upstream side of the exhaust gas as shown in FIG. 4 to ignite particulate matter such as soot, which is a combustible substance, and the combustion causes soot. It is done by baking. That is, it is carried out by thermal oxidative decomposition to change to CO ₂ or H ₂ O.

[0010]

However, the conventional ceramic monolith filter 1 has the following problems. First, due to filtration and collection by the fine pores of the partition walls 5, metal abrasion powder that cannot be thermally oxidized and decomposed and ash composed of inorganic substances remaining after combustion remain in the pores even after regeneration,
It is difficult to remove. Therefore, the filter for collecting and filtering the fine pores has a limit in the reproducibility of repetition, and eventually becomes unusable due to clogging. In addition, if the filter is replaced, the cost becomes high, and the replacement operation is troublesome.

Second, since the monolith filter 1 is made of ceramic and has a structure having a large number of fine holes, the mechanical strength is low. For this reason, cracks are likely to occur in the filter due to thermal fatigue due to the occurrence of non-uniform distribution of the temperature in the filter during the regeneration combustion process.

Third, at the time of regeneration, the ceramic filter is liable to be damaged by soot or abnormal high-temperature combustion of SOF. The regeneration of the monolithic filter 1 is performed by igniting soot or SOF collected on the front surface of the filter by an electric heater 2 or a burner disposed on the exhaust gas upstream side of the filter, and then burning in the filter downstream from the exhaust gas upstream side. Achieved by communicating to At this time, the temperature becomes higher toward the downstream side due to the heat of reaction due to combustion. Furthermore, due to the presence of the plug 4 shown in FIG. 4, the particulate matter is trapped in the exhaust gas downstream in the monolith filter 1, and combustion during regeneration becomes more intense in the downstream. On the downstream side, there is a case where the temperature becomes high such that the melting point of cordierite ceramic exceeds about 1200 ° C. Filter erosion is likely to occur in such cases.

The present invention has been made to solve the conventional problems as described above, and can improve the collection efficiency of particulate matter while maintaining a low pressure loss, as well as filter clogging and filter fatigue due to thermal fatigue. An object of the present invention is to provide a filter device for exhaust gas which can prevent destruction and melting damage at the time of regeneration of a filter.

[0014]

To achieve the above object,
The exhaust gas filter device according to the invention of claim 1 is
A metal mesh portion and an alumina ceramic mesh portion made of an alumina fiber yarn are stacked on each other, installed in an exhaust gas passage, and intermittently energized and heated in the metal mesh portion.

According to a second aspect of the present invention, there is provided a filter device for exhaust gas, wherein the metal mesh portion is provided on the exhaust gas inflow side centered on a laminate of the metal mesh portion and the alumina ceramic mesh portion. When the pressure loss or the pressure difference generated between the outflow sides exceeds a set value, the heating is performed.

According to a third aspect of the present invention, in the exhaust gas filter device, the metal mesh portion is made of Fe-Cr.
-An aluminum alloy.

Further, the exhaust gas filter device according to the invention of claim 4 is provided with a pressure loss detecting means between the inflow side and the outflow side of the exhaust gas.

Further, in the exhaust gas filter device according to the present invention, the metal mesh portion may have a mesh roughness of ♯30 to ♯180 and a wire diameter of Φ
0.3 mm to Φ0.05 mm, mesh size is set to 0.55 mm to 0.09 mm, and the alumina ceramic mesh portion has a mesh roughness of ♯3 to ♯1 per plain weave.
5. The yarn diameter is Φ0.5mm to Φ1.5mm, and the mesh size is 7.
It is a yarn of alumina long fiber of 96 mm to 0.19 mm.

According to a sixth aspect of the present invention, in the exhaust gas filter device, the mesh roughness of the metal mesh portion and the alumina ceramic mesh portion changes from coarse to dense from the upstream side to the downstream side of the exhaust gas. It is intended to be.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing an exhaust gas filter device according to the present invention. In FIG. 1, reference numeral 11 denotes a metal mesh portion made of an Fe-Cr-Al-based alloy, which is made of one or more metal meshes. Become
Mesh roughness is $ 30 to $ 18 per piece of plain weave
0, the wire diameter is 0.3 mm to 0.05 mm, and the opening is 0.55 mm to 0.09 mm. As the Fe-Cr-Al-based alloy forming the metal mesh,
Examples of the components shown in Table 1 can be given.

[0021]

[Table 1]

Reference numeral 12 denotes a fiber diameter of Φ5 μm to Φ1.
An alumina ceramic mesh portion made of a yarn of 5 micron alumina long fiber, which is made of one or more alumina ceramic meshes, and has a mesh roughness of from about 3 to about 15, and a yarn of a yarn, per plain weave. Diameter φ0.5mm ~ φ1.5mm, opening 7.96mm ~
0.19 mm. As the alumina ceramic forming the alumina ceramic mesh, those having the components shown in Table 2 can be exemplified.

[0023]

[Table 2]

The metal mesh portion 11 and the alumina ceramic mesh portion 12 are alternately overlapped (laminated) to form a filter main body, and the mesh roughness of each of them is determined on the upstream side of the exhaust gas (on the engine side). ) From downstream to coarse.

Further, terminals for voltage application are connected to both ends of each of the metal mesh portions 11, and by applying a voltage to these terminals, the metal mesh portions 11 themselves can be energized and heated. .

Further, the number of layers of the metal mesh portion 11 and the alumina ceramic mesh portion 12 and the cross-sectional area (pressure receiving area) of the filter receiving the exhaust gas are determined by the displacement of the target engine, the allowable filter size, the pressure loss and the target. The appropriate value differs depending on the collection efficiency and the like, and cannot be shown unconditionally. This is because there is a contradiction that the trapping efficiency is improved with an increase in the number of layers, but the pressure loss is worse with an increase in the number of layers. However, as a guide, the initial pressure loss is 8KP
The number of stacked layers and the pressure receiving area are selected to be not more than a and the collection efficiency to be 30% or more.

Further, the electric heater of the present invention is made of Fe-Cr-
The metal mesh part 11 itself made of an Al-based alloy is heated by Joule heat generated by energizing the metal mesh. That is, the electric heater of the present invention is a planar heater that also serves as a collection filter.
The alumina ceramic mesh portion 12 also functions as an insulating layer of the heater.

The structure in which the metal mesh portion 11 and the alumina ceramic mesh portion 12 are combined and the metal mesh portion 11 is used as an electric heater achieves a high collection efficiency and a low pressure loss. To solve.

First, with respect to (A) collection efficiency, pressure loss and prevention of clogging during regeneration, the filter device of the present invention
Both the e-Cr-Al-based alloy and alumina have a small aperture of 0.09 mm and 0.19 mm, respectively, which are considerably larger than the particulate matter. Therefore,
Whereas a conventional monolith filter has a main trapping mechanism of a shielding effect, in the present invention, when a gas flow changes direction due to the presence of a mesh line, an inertial force acting on a particle having a mass causes a particle to be removed. The main mechanism is that of inertial collection, in which a collision occurs with a line.

In this inertial collection, the collection efficiency of very small particles and the collection efficiency per unit thickness is small, but the size of the openings is made wider than the size of the collected material as in the present invention. In this case, there is an advantage that clogging is not easily performed. This means that the increase in pressure loss is small even if the number of stacked layers is increased to increase the collection efficiency.

Further, metal abrasion powder and ash remaining after the regeneration do not block the pores of the mesh. Therefore, there is no need to replace the filter due to clogging during regeneration even during long-term use.

Next, regarding (B) prevention of filter destruction due to thermal fatigue, during regeneration, the heat of reaction generated when soot or SOF undergoes thermal oxidative decomposition is large, and in some cases, the combustion temperature may reach 1200 ° C. is there. Therefore, a material having high heat resistance and high-temperature oxidizing property is required for the filter material. For this purpose, oxide ceramics such as alumina and cordierite are most suitable. However, an integrated structure such as a monolith filter is liable to cause thermal fatigue failure due to uneven distribution of strain and insufficient toughness of ceramic.

In the present invention, the filter structure is made of a mesh made of fibrous alumina ceramic, thereby avoiding thermal fatigue fracture while maintaining heat resistance and high-temperature oxidizing property. That is, in the mesh structure, the fibers are not bonded to each other but are merely bundled, so that the unevenness of the strain can be easily reduced.

However, if the filter is constituted only by the alumina ceramic mesh 12, the rigidity is too small and the filter vibrates due to the pulsation of the exhaust gas, so that a problem such as applying a large back pressure to the engine occurs. Therefore, for the purpose of increasing the rigidity of the entire filter, the alumina ceramic mesh is formed of a highly rigid metal mesh portion 11.
(Fe-Cr-Al alloy).

The metal mesh portion 11 is made of Fe-Cr-A
The choice of an l-based alloy is for two reasons. The first reason is that F
This is because the e-Cr-Al-based alloy has excellent heat resistance and high-temperature oxidation property. The second reason is that the Fe-Cr-Al-based alloy is an electric heating material, that is, a material itself of an electric heater, and this mesh is used as an electric heater for regeneration. Further, needless to say, the Fe-Cr-Al-based alloy is superior in toughness as compared with ceramic, and the metal mesh is excellent in thermal fatigue resistance due to the adoption of the mesh structure.

(C) Regarding the prevention of filter erosion, combining the metal mesh portion 11 and the alumina ceramic mesh portion 12 and using the metal mesh portion 11 as an electric heater is also effective in preventing the filter erosion. large. One cause of the erosion of the monolith filter is that a large amount of combustible particulate matter is trapped in the filter on the downstream side of the exhaust gas where the heat of reaction is stored, so that the combustion is intense on the downstream side.

In the present invention, the roughness of the mesh is changed from coarse to dense from upstream to downstream of the exhaust gas.
This allows the collection of combustible particulate matter to be averaged over the entire filter. Therefore, it is possible to lower the combustion temperature in the downstream filter, and to prevent the filter from being damaged.

Further, since the metal mesh portion 11 is a heater which can be energized, it can be heated at an arbitrary place in the filter, and the control of combustion becomes extremely easy. Depending on the case, it is also possible to heat the filter downstream or from the center or to heat the entire filter simultaneously.

Next, the case where the trapping property of the filter according to the present invention is tested by a measuring device as shown in FIG. 2 will be described. Here, a 0.25 liter diesel engine 13 is used as the particulate matter generator. The engine load at this time is 2 kw · h at 3000 rpm.

The metal mesh portion 11 in the filter device 14
And the alumina ceramic mesh part 12 has a diameter of 68 m.
m, and the laminated structure has an Fe-Cr-Al-based metal mesh portion 11 having a mesh roughness of ♯30 and a wire diameter of ｍｍ0.3 mm from the exhaust gas upstream, a mesh roughness of ♯6, and a wire diameter of １．０1.0 m.
m alumina ceramic mesh parts 12 are alternately superimposed, and then the mesh roughness is 35 and the wire diameter is 0.26.
mm Fe-Cr-Al metal mesh portion 11 and 40 alumina ceramic mesh portions 12 having a mesh roughness of ♯9 and a wire diameter of Φ1.0 mm are alternately superimposed on each other. , F with wire diameter Φ0.26mm
e-Cr-Al based metal mesh part 11 and mesh roughness 粗
11. Forty wire alumina ceramic mesh parts 12 having a wire diameter of 1.0 mm are alternately stacked.

As the electric heater for regeneration, the first, second, and third meshes of Fe—C
A current of 1 A per wire is applied to the r-Al-based metal mesh portion 11. At this time, the heater reaches 900 ° C. in about 5 minutes. The trapping performance of the filter measured by this measuring device is
The particulate matter concentrations of the exhaust gas entering the filter and the exhaust gas exiting the filter are measured by a Bosch-type smoke meter 16 and can be grasped by comparing the measurement results. The clogging of the filter is caused by the pressure difference before and after the filter. Alternatively, the pressure loss can be obtained by measuring the pressure loss by a pressure loss detecting means 15 such as a manometer. Then, a heating power supply is connected to the metal mesh portion, and when the pressure difference or the pressure loss measured by the pressure loss detection means 15 exceeds a set value, the heating power supply is controlled by the control section and turned on. When the metal mesh portion is turned on, the metal mesh portion is energized to perform a heat regeneration process.

Therefore, according to the measuring device, as shown in FIG. 3, in the present invention, the trapping efficiency and the pressure loss of the particulate matter by the filter device are shown by the change at every measuring time.

Here, the collection efficiency is defined by dividing the difference between the value of the smoke meter of the exhaust gas entering the filter and the value of the exhaust gas leaving the filter by the value of the exhaust gas entering the filter. The trapping efficiency is about 40% at first, but then shows 60% to 80%, indicating that the filter has sufficient performance as a particulate matter trapping filter. The pressure loss gradually increases with the passage of the measurement time, which means that the collection is proceeding smoothly.

FIG. 3 shows changes in the collection efficiency and the pressure loss after the regeneration, and shows the same changes after the regeneration as before the regeneration. Then, this reproduction process is performed, for example, as shown in FIG.
It is performed when the pressure loss detected by a manometer as a pressure loss detecting means as shown in has reached 20 KPa,
The metal mesh, which also served as a filter, reached about 900 ° C. by the 5-minute energization, and the collected particulate matter started burning, and this burning was completed in about 15 to 20 minutes. At this point, the pressure loss of the filter shows an almost initial value of 5 KPa, which indicates that the particulate matter collected by all the filters was thermally decomposed and the regeneration was completely and automatically performed.

In the above embodiment, the metal mesh No. 1 shown in Table 1 was used. The Fe-Cr-Al-based alloy of No. 1 was used as an alumina ceramic mesh in No. 1 shown in Table 2. One alumina ceramic was used. In addition, No. 1 shown in Table 1 2-No. No. 4 Fe-Cr-Al alloy and No. 4 shown in Table 2. 2-No. Alumina ceramic No. 5 can also be used sufficiently, and both are heat-resistant. Further, the metal mesh is required to be able to cope with a heat cycle (fluctuation in temperature) because the exhaust gas temperature fluctuates depending on the displacement of the engine, the compression ratio, the number of revolutions, and the like.
The metal mesh of the Fe-Cr-Al-based alloy exemplified in
It meets these requirements and is effective and can be provided.

[0046]

As described above, according to the first aspect of the present invention, the metal mesh portion and the alumina ceramic mesh portion made of the alumina fiber yarn are laminated on each other and installed in the exhaust gas passage. The section is configured to be heated intermittently, so the collection efficiency of particulate matter can be increased while maintaining a low pressure loss, and at the time of filter clogging, filter destruction due to thermal fatigue, and filter regeneration Thus, the effect of preventing erosion in the above can be obtained.

According to the second aspect of the present invention, a pressure loss is generated between the inflow side and the outflow side of the exhaust gas around the laminate of the metal mesh part and the alumina ceramic mesh part. Or, when the pressure difference exceeds the set value, it is configured to conduct electricity and heat.
By detecting that the metal mesh portion and the alumina ceramic mesh portion have been clogged by the particulate matter in a predetermined state, an effect is obtained that the clogged material can be automatically incinerated and removed.

According to the third aspect of the present invention, since the metal mesh portion is made of an Fe—Cr—Al alloy,
The metal mesh part can be used as a filter for trapping particulate matter, etc., and can also be used as a heater to heat and incinerate the collected material, resulting in a smaller filter device and lower cost. Is obtained.

According to the fourth aspect of the present invention, the pressure loss detecting means is provided between the inflow side and the outflow side of the exhaust gas. The effect is obtained that the heating current supply to the metal mesh part can be automated.

According to the fifth aspect of the present invention, the metal mesh portion has a mesh roughness of $ 30 per plain weave.
♯180, the wire diameter is Φ0.3mm to Φ0.05mm, the aperture is 0.55mm to 0.09mm, and the alumina ceramic mesh portion has a mesh roughness of ♯3 to ♯15 per plain weave. Yarn diameter is Φ0.5mm ~ Φ1.5
mm and an opening of 7.96 mm to 0.19 mm made of alumina long fiber yarn, it is possible to obtain an effect that optimum filter efficiency and incineration and removal of particulate matter can be realized.

According to the sixth aspect of the present invention, the mesh roughness of the metal mesh portion and the alumina ceramic mesh portion is configured to vary from coarse to dense from the upstream side to the downstream side of the exhaust gas. The trapping of particulate matter can be averaged over the entire filter, thereby preventing an increase in combustion temperature in the downstream filter, and the effect of preventing erosion of the filter can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a main part showing an exhaust gas filter device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a measuring device used to measure the trapping characteristics of the exhaust gas filter device of the present invention.

FIG. 3 is a characteristic diagram showing a trapping characteristic and a pressure loss characteristic of the exhaust gas filter device of the present invention.

FIG. 4 is a sectional view showing a conventional filter device.

5 is a front view of the exhaust gas filter device shown in FIG.

[Explanation of symbols]

 11 Metal mesh part 12 Alumina ceramic mesh part

Claims (6)

[Claims] 1. A metal mesh portion and an alumina ceramic mesh portion made of an alumina fiber yarn are laminated on each other, installed in an exhaust gas passage, and intermittently heated by heating the metal mesh portion. Exhaust gas filter device. 2. A pressure loss or a pressure difference generated between an inflow side and an outflow side of the exhaust gas around a laminate of the metal mesh part and the alumina ceramic mesh part exceeds a set value. The exhaust gas filter device according to claim 1, wherein the filter is heated when energized. 3. The method according to claim 2, wherein the metal mesh part is Fe—Cr—A.
The exhaust gas filter device according to claim 1, wherein the filter device is made of an l-based alloy. 4. The exhaust gas filter device according to claim 1, wherein a pressure loss detecting means is provided between the exhaust gas inflow side and the exhaust gas outflow side. 5. The metal mesh part has a mesh roughness of from about 30 to about 180 and a wire diameter of about 0.3 per plain weave.
mm to Φ0.05mm, with an aperture of 0.55mm to 0.5mm.
09 mm, the alumina ceramic mesh portion has a mesh roughness of ♯3 to ♯15, a yarn diameter of Φ0.5 mm to Φ1.5 mm, and an aperture of 7.96 m per plain weave.
The exhaust gas filter device according to claim 1, wherein the filter device is made of an alumina long fiber yarn having a length of m to 0.19 mm. 6. The exhaust gas according to claim 1, wherein the mesh roughness of the metal mesh portion and the alumina ceramic mesh portion is changed from coarse to dense from upstream to downstream of the exhaust gas. Filter device for gas.