JP2001046818A - Ceramic filter element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve characteristics such as strength, corrosion resistance, thermal impact resistance, and the like, while pressure loss and capturing performance of a ceramic filter element are maintained. SOLUTION: In a ceramic filter element wherein a filter layer comprising ceramics is formed on a substrate comprising a ceramic fiber, the substrate comprises principally a mullite long filter woven by a filament winding method, a pitch between respective adjoining long fiber bundles in a structure of the woven layer is wider than the width of the long fiber bundle, and the porosity of the substrate is 40-70 vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous ceramic filter element for removing dust from a high-temperature combustion gas and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, pressurized fluidized bed boilers (PFBC) and coal gasification combined cycle power generation (IGCC) using coal as fuel have been developed.
Is being developed. However, since all of these use coal as fuel, dust is generated, and it is necessary to remove the dust. In addition, since dust is mixed in a high-temperature gas, the filter must be able to withstand high temperatures. A porous ceramic filter element has been used to satisfy such requirements.

For example, in a dust removal system 1 used in a coal gasifier as shown in FIG. 1, a high-temperature gas inflow path 2 into which gas is introduced and a high-temperature gas outflow path 3 through which gas is discharged. , A plurality of ceramic filter elements 4 attached to the tube sheet 5 are installed inside,
The dust hopper 6 is attached to the lower part of a casing having an inverted conical shape.

When the coal gas flowing from the hot gas inflow path 2 passes through the ceramic filter element 4,
The dust contained in the coal gas is removed, the purified gas is discharged from the high-temperature gas outflow passage 3, and the dust is collected by the dust hopper 6. In addition, if this collecting operation is continuously performed for a long time, dust accumulates on the surface of the ceramic filter and the air flow resistance increases, so that the collecting efficiency is greatly reduced. Therefore, the pressure difference between the hot gas inflow path 2 and the hot gas outflow path 3 is sensed by the differential pressure gauge 9, and when the pressure difference reaches a certain value or more, the backwash tank 7 and the backwash valve 8 reverse the flow of the coal gas. The direction of the backwash air is blown out, and the dust accumulated on the surface of the ceramic filter element is blown off to recover the collection efficiency.

Conventionally, a ceramic filter element having a predetermined particle size is added to a ceramic filter element in such a high-temperature gas dedusting system by adding a clay mineral or a material having a lower melting point than the ceramic powder of the base material as a binder. A monolithic porous ceramic produced by firing into a filter shape and firing at a firing temperature near the softening of the binder has been used. Particularly, from the viewpoints of chemical stability and thermal shock resistance, porous monolithic ceramic materials made of cordierite or SiC have been often used.

[0006]

However, the monolithic ceramic filter is a porous material obtained by hardening ceramic powder with a binder, and has a strength of only about 10 MPa in a structure having a porosity of 50%.

In the PFBC pilot plant, when switching from light oil combustion to coal combustion at the time of boiler startup,
When the load fluctuates or when the fuel is suddenly stopped, the balance between the combustion air and the fuel is lost, and the amount of unburned fuel is generated due to a temporary lack of oxygen. The unburned components fly to the ceramic filter and accumulate. This unburned portion remains accumulated in the filter while the amount of oxygen is insufficient, but the combustion state of the boiler stabilizes and the oxygen concentration of the filter increases. This causes a temperature difference and damages the filter element.

[0008] In addition, when dust is removed, the filter is exposed to a high temperature of 500 ° C to 900 ° C. However, since the surface of the filter is rapidly cooled by the injection of the backwash air flow, the low-strength monolithic ceramic filter is damaged by thermal shock. Resulting in.
In addition, there is also a problem in that the filter element comes into contact with another element and is damaged when the filter element is replaced.

Therefore, the ceramic filter element and the method of manufacturing the same according to the present invention maintain strength and pressure while maintaining pressure loss and trapping performance of the ceramic filter element.
The purpose is to improve properties such as corrosion resistance and thermal shock resistance.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the inventors have attempted to produce a porous filter material having high strength by using various structural members. As a result, a high strength and highly reliable porous material is used as compared to a monolithic ceramic filter material by using a ceramic long fiber material with high strength as the base material of the ceramic filter and applying a filtration membrane as a filter layer on the surface. A ceramic filter material was obtained.

According to a first aspect of the present invention, there is provided a ceramic filter element in which a filter layer made of ceramic is formed on a base made of ceramic fibers. In addition, the porosity of the substrate is 40 to 70% by volume.

The mullite filament used in the present invention is woven by a filament winding method, and the pitch between adjacent filament bundles in the woven layer structure is preferably wider than the width of the filament bundle. Further, the mullite filament used in the present invention is bound and solidified by a bonding portion mainly composed of mullite obtained by impregnating and firing alumina sol and silica sol, and the zirconia content in the bonding portion is less than 20% by weight. preferable.

The filter layer used in the present invention is composed of a powder mainly composed of mullite having an average particle size of 5 to 100 μm, and equimolar amounts of calcia (CaO) and zirconia (Zr).
O ₂ ), and the content of the calcia (CaO) and zirconia (ZrO ₂ ) is 1 to the mullite powder.
It is preferably formed by firing a mixture that is 20% by weight.

In the method for producing a ceramics filter of the present invention, a filter mainly comprising mullite filaments is impregnated with alumina sol and silica sol,
A step of forming a substrate by baking at a temperature of ° C .; and a step of forming a filter layer made of ceramic on the substrate.

Further, the method for producing a ceramic filter according to the present invention comprises a step of forming a base material mainly composed of mullite filaments, wherein the base material comprises mullite, calcium zirconate and 0.1 to 20% by weight based on the mullite. Of kaolinite from 1100 ° C. to 1300
And forming a filter layer by baking at a temperature of ℃.

In the present invention, a method of manufacturing a ceramic filter in which one of the filter base materials is sealed includes a step of preparing a filter base material by forming a filter layer made of ceramic on a base material made of ceramic fibers; A step of applying a mixture of mullite, calcium zirconate and kaolinite to at least one of a base material or a one-end sealing material for sealing one open portion of the filter base material and connecting both, and the filter base material and one end Baking a product connected to the sealing material.

In the present invention, strength and thermal shock resistance can be maintained even in a ceramic filter element having a porosity of 40 to 70% by volume by using mullite long fibers as a base material of the ceramic filter element.

Further, a predetermined porosity is ensured by weaving by a filament winding method and by making the pitch between adjacent long fiber bundles in the structure of the woven layer wider than the long fiber bundle width. be able to.

The mullite filaments used in the present invention are impregnated with alumina sol and silica sol and fired to obtain
By forming the bonding portion mainly composed of mullite, it is possible to form a substrate having higher strength. By including less than 20% of zirconia in such a joint, alkali resistance can be improved.

By using mullite powder having an average particle size of 5 to 100 μm for forming the filter layer used in the present invention, the pore size can be adjusted according to the target particle size of the dust-removed particles. In addition, calcia and zirconia are equimolar and 1 to 20% by weight based on the mullite powder.
, The heat resistance and alkali resistance can be improved.

In the present invention, mullite filaments are impregnated with alumina sol and silica sol at 1150 ° C.
By firing at 〜1300 ° C., a substrate having high strength can be produced.

In the present invention, when the filter layer is formed, by adding 0.1 to 20% by weight of kaolinite to the mullite powder, the mullite powder can be relatively easily solidified, and the melting point can be reduced. Clogging of the filter due to the above can be suppressed.

Further, in the ceramic filter element of the present invention, the filter base material and the one-end sealing material are fired and joined to one composed of mullite, calcium zirconate and kaolinite, thereby joining the filter base material with the one-end sealing material. The stopper can be sufficiently integrated.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Ceramic long fiber materials include various materials such as silica fiber, alumina fiber, SiC fiber and mullite fiber. When used as a material for a filter element, they have excellent heat resistance and alkali resistance. It is necessary to have a low thermal expansion property capable of withstanding a thermal stress load such as back washing. When a porous body is made of a long fiber material, the pore diameter and the porosity of the filter substrate are controlled by the arrangement of the long fibers, so that it is necessary to regularly arrange the long fibers. In addition, select a material that does not cause a decrease in strength at high temperatures and has excellent alkali resistance as a binder for solidifying a long fiber filter base material to maintain its shape and for binding powder as a filter layer. There is a need.

That is, a ceramic filter element according to the present invention is a ceramic filter element in which a ceramic filter layer is formed on a ceramic fiber base material, wherein the base material is mainly composed of mullite filaments and the pores of the base material are Rate is 40-70
% By volume.

The mullite filament used in the present invention is woven by a filament winding method, and the pitch between adjacent filament bundles in the structure of the woven layer is larger than the width of the filament bundle. preferable.

The mullite filament material has a room temperature strength of 2 GPa.
Although the heat resistance is extremely high and the heat resistance is inferior to the alumina fiber and the SiC fiber, the strength deterioration is relatively small up to 1200 ° C. Further, since mullite long fiber is a material having low thermal expansion, it is strong against a rapid temperature change such as backwashing and washing, and is excellent as a material for a filter base material for high-temperature dust removal. Therefore, in the present invention, the strength of the ceramic filter element is improved by using the mullite long fiber for the ceramic filter element while maintaining the porosity of 40 to 70% by volume so as not to cause a pressure loss.

When a porous filter substrate is formed from such a long-fiber material, the voids woven by long fiber bundles become pores inside the filter substrate. It is conceivable that the pore size varies and the porosity becomes uneven depending on the location of the filter substrate, and that when used as a filter substrate, a difference in aeration pressure loss occurs at each location in the filter element and the filter element may be damaged in some cases. Therefore, it is necessary to control the pore diameter and the pore distribution in the filter element by selecting the fiber weaving method and controlling the fiber bundle pitch and the weaving angle θ.

In the present invention, it is preferable to use a filament winding method as a weaving method capable of controlling the void diameter and the void distribution. The filament winding method is a method of producing a fibrous structure by winding a bundle of long fibers around a rotating core, and the weaving angle with the rotation axis can be determined by the traverse speed of the fibers.

When stress is generated in the filter element structural member during operation of the dust removal system, "stress in the longitudinal axis direction of the filter / stress in the circumferential direction of the filter" is determined by the weaving angle θ.
Is expressed as cos ² θ / sin ² θ, so that the stress generated in the filter element can be borne by controlling the weaving angle θ.

In the filament winding method, in order to produce a porous base material having uniform void shape and uniform void distribution woven together by fibers, it is necessary to control not only the weaving angle but also the fiber bundle pitch. There is. In the filament winding method, there are several winding patterns such as split winding, sequential winding, and random winding. In each of the patterns, the fiber bundles are arranged at a regular pitch under a certain weaving angle θ. When a fiber having a fiber bundle width W is woven at an orientation angle θ in a one-layer structure, the fiber bundle pitch P is equal to W / cos θ to completely cover the surface of the core with the fiber. To be. However, in this structure, since the fibers are densely arranged, the number of voids through which the gas passes is reduced, and the porosity is also reduced, so that the gas ventilation pressure loss is increased and the collection efficiency is reduced. Therefore, voids are formed by making W / cos θ larger than the fiber bundle width W. When the filter element material is made of a long fiber material, 1.5 ≦ P /
Control is performed so that (W / cos θ) ≦ 8. P / (W
(/ Cos θ) is smaller than 1.5, the porosity is reduced and the ventilation pressure loss is increased. When P / (W / cos θ) is larger than 8, the porosity of the filter element substrate itself is increased and the pore diameter is also increased. The strength of the filter substrate is greatly reduced.

Preferably, the porosity is about 50% and the average pore diameter is 100 to 40 by controlling the fiber bundle pitch P so that P / (W / cos θ) is in the range of 2 to 6.
A filter substrate having a low pressure loss of 0 μm can be produced.

The mullite filament used in the present invention has a diameter of 5 to 200 μm and a length of 1 mm.
It is preferable to use the above continuous fibers.

FIG. 2 shows an example of the core used in the present invention. As shown in FIG. 2A, a core shaft 11 for rotating the core 10 is provided on a center axis of the core 10, and a filament bundle 12 is formed on the surface of the core 10 at a weaving angle θ. I will be attracted. In addition, as shown in FIG. 2B, a gap 13 exists between the filament bundles 12. Here, P represents a fiber bundle pitch, and W represents a fiber bundle width.

The ceramic filter element according to the present invention is a ceramic filter element comprising a base material formed of ceramic fibers and a filter layer formed of ceramic powder, wherein the mullite filament as a base material is used. Bonded and solidified by a substantially mullite bonding portion formed by impregnating and firing alumina sol and silica sol, and 2
It is characterized by containing less than 0% by weight of zirconia. Preferably, the base material is fired in a temperature range of 1150 ° C to 1300 ° C. By baking in such a temperature range, the bonding portion can be made to have higher strength mullite. The reason why the joining portion is made of mullite made of the same material as the long fiber is to reduce a mismatch due to a difference in thermal expansion between the long fiber and the joining portion.

A porous substrate made of mullite long fiber is prepared by impregnating a long fiber with a mixture of alumina sol and silica sol, and baking and solidifying the mixture. As a method of impregnation, when weaving by filament winding, there is a method of weaving while impregnating the fiber, and a method of forming a porous substrate by filament winding, and then dipping and impregnating a sol mixture. In both cases, uniform impregnation is relatively easy. Crystallization of a mixture of alumina sol and silica sol into mullite can be performed at a low temperature of about 1200 ° C.

In general, mullite is a high melting point material. Therefore, when impregnating and baking and solidifying powder, mullite must be sintered at a high temperature of 1400 ° C. or more. As a result, the strength of the substrate deteriorates. However, by impregnating and firing alumina sol and silica sol, low-temperature firing becomes possible, and deterioration in the strength of mullite fibers can be minimized. The reason why the firing temperature is set to 1150 ° C. or higher is that when firing at a temperature lower than 1150 ° C., an amorphous material is formed, so that the strength of the bonding portion is low and the strength reliability as a filter element structure is reduced. Because. The firing temperature is 1300 ° C
The reason for this is that if the heat treatment is performed at a temperature exceeding 1300 ° C., the crystal structure of the mullite long fiber is enlarged, leading to a large decrease in strength.

It is preferable that such a mullite bonding portion contains zirconia in a range of less than 20%. By including zirconia in the bonding portion as described above, alkali resistance can be improved. High temperature dust filters are exposed to corrosive environments, especially sodium,
It may be eroded by alkali vapor such as potassium. Mullite itself is a chemically stable material, but the silica component in the mullite may react with an alkali metal to form a low-melting compound such as sodium silicate.
Therefore, in the present invention, by containing zirconia excellent in corrosion resistance to alkali in the mullite bonding portion,
The alkali resistance of the joint can be improved. In the present invention, the zirconia content of the mullite joint is 20
The reason for the content being less than% by weight is that if the content is more than that, cracks are formed due to the difference in thermal expansion between mullite and zirconia, and the strength of the filter substrate is reduced.

However, since the melting point of zirconia is higher than the melting point of mullite, it must be 1500 ° C. or higher to impregnate and solidify the powder by firing, which lowers the strength of the mullite filament. However, a zirconia sol that can be combined with other materials and fired at a low temperature has recently been developed. Therefore, in the present invention, it is preferable to use this zirconia sol.

Further, the filter layer of the ceramic filter element according to the present invention has an average particle size of 5 to 100 μm.
m, mainly composed of mullite, and equimolar calcia (CaO) and zirconia (ZrO ₂ ), wherein the content of the calcia (CaO) and zirconia (ZrO ₂ ) is based on the mullite powder forming the filter layer. 1
Preferably, it is formed by firing a mixture of about 20 wt%. The equimolar mixture of calcia and zirconia is preferably calcium zirconate. The filter layer of the present invention is obtained by adding 0.1 to 20% by weight of kaolinite to mullite powder which is a constituent material of the filter layer.
It is preferably formed by baking at 00 ° C to 1300 ° C.

Particle size of mullite powder as filter layer
IGCC, PFBC
The particle size of the dust discharged by
Wide and filter layer suitable for the target particle size
This is to enable various adjustments of the pore diameter. Ma
Calcia (CaO) and zirconia (ZrO)_Two)
Equimolar each, and said calcia (CaO) and jill
Konia (ZrO_Two) Content forms a filter layer
The reason that the content is 1 to 20% by weight based on the mullite powder is as follows.
This is for generating calcium zirconate. This
Calcium ruconate is mullite powder as filter layer
Used to join the ends. Zirconic acid as binder
The reason why calcium is used is that the calcium component is
Alumina, silica content and high melting point glassy or anodic
Luteite (CaAl_Two・ Si_TwoO ₈)
It is for improving heat resistance by forming. As described above
Calcia (CaO) and zirconia (ZrO_Two) Amount
The specified ones are calcia (CaO) and zirconia (Z
rO_TwoIf the content of) is less than 1% by weight, the filter membrane is used.
Difficult to solidify all mullite powder, 20% by weight
Exceeding the thermal expansion coefficient difference between mullite and zirconia
Cracks are likely to occur due to
This is because the light powder is likely to fall off.

In the method for producing a ceramic filter of the present invention, a filter mainly composed of mullite filaments is impregnated with alumina sol and silica sol,
And a step of forming a filter layer made of ceramic on the base material.

By doing so, the mullite long fiber used for the base material is bonded and solidified, and the strength of the ceramic filter element can be improved.

Another method for producing the ceramic filter element of the present invention comprises a step of forming a base material mainly composed of mullite filaments, and the step of forming a base material comprising mullite, calcium zirconate and 0.1 to 20 wt. A mixture consisting of 1% by weight of kaolinite is added and 1100
Baking at a temperature of from 1 ° C. to 1300 ° C. to form a filter layer.

Calcium zirconate is used to bind mullite powder as a filter layer, and kaolinite is used for low-temperature firing. The reason for using calcium zirconate as a binder is that the calcium component forms a high-melting glassy or crystalline compound such as anorthite (CaAl ₂ · Si ₂ O ₈ ) with alumina and silica of kaolinite to improve heat resistance. It is to improve. The addition amount of the calcium zirconate is preferably 1 to 20% by weight based on the mullite powder as the filter membrane. If it is less than 1% by weight, it is difficult to solidify the mullite powder as a filter membrane, and if it exceeds 20% by weight, cracks are likely to occur due to the difference in thermal expansion coefficient between mullite and zirconia, and the mullite powder as a filter membrane will fall off. This is because it becomes easier. The amount of kaolinite is preferably 0.1 to 20% by weight based on the mullite powder as the filter layer. This is because if the amount of kaolinite is less than 0.1% by weight, it is difficult to solidify the mullite powder as a filter membrane, and if it exceeds 20% by weight, the bonding portion will have a low melting point. In this case, if the filter element is continuously used at a high temperature, dust is fused to the filter membrane and clogging occurs, and the collecting performance of the filter element cannot be recovered even by the backwashing, and as a result, the life of the element is shortened. Would. The firing of such a filter layer is preferably performed at 1100 ° C to 1300 ° C. If the temperature is lower than 1100 ° C., sintering and solidification of the mullite powder is not sufficiently performed, and the mullite powder becomes a very brittle material.
If the temperature exceeds ℃, sintering causes densification to proceed and pores become small. As further densification progresses,
Due to sintering shrinkage, countless cracks are generated on the surface of the filter base material, making it impossible to form a filter layer and deteriorating the fiber strength of the base material. In the present invention, by baking within the above range, a filter film having a low shrinkage rate can be fired and solidified, and a decrease in strength of the mullite long fiber as a filter substrate can be minimized.

Further, the ceramic filter element according to the present invention has a structure in which one end of the filter is sealed with a mullite sealing material, and the filter substrate and the sealing material are made of mullite, calcium zirconate and kaolinite. The mixture is integrated by coating and firing.

By using a mullite material as the sealing material, a difference in thermal expansion coefficient between the sealing material and the filter substrate can be minimized, and a filter having excellent strength can be manufactured. Further, by using a mixture of mullite, calcium zirconate and kaolinite as a coating material for integrating the sealing material and the filter substrate, a ceramic filter element having excellent heat resistance and strength can be produced. .

FIG. 3 shows a specific example of a ceramic filter element having one end sealed according to the present invention. FIG. 3A shows a structure in which both the filter base material 14 and the one-end sealing material 15 are joined to each other with a step provided therebetween. FIG. 3b shows one end sealing material 15
Are provided with a step only at the joint of the filter substrate 14 and joined to the filter base material 14. FIG. 3C shows a case where the one-end sealing material 15 is inserted into the inside of the filter base material 14 and sealed.
The above is a specific example of the present invention, and the embodiment of the present invention does not necessarily need to be the above embodiment.

Hereinafter, the ceramic filter element and the method of manufacturing the same according to the present invention will be specifically described.

[0050]

EXAMPLES [First Embodiment] In the first embodiment, the relationship between the porosity and the strength was compared.

Example 1 A ceramic filter element was manufactured using a core as shown in FIG. The core has a diameter of 50 mm, a shaft is attached to the end face of the core, and the fiber is wound by rotating. The yarn used was a mullite long fiber (Toshiba Monoflux Co., Ltd.) made of 3840 bundles of 10 μm diameter fibers. The fiber bundle width W per yarn is 1 mm. The fiber orientation angle θ was 60 °, and the fiber bundle was woven by the filament winding method in 16 divisions per layer so that the fiber bundle pitch was 10 mm. Ten layers were woven in the same pattern as the number of laminations. In this case, P / (W
/ Cos θ) is 5.

Comparative Example 1 Using the same core and fiber as in Example 1, a fiber orientation angle of 60
° and a fiber bundle pitch of 2 mm, and woven by a filament winding method at 80 divisions per layer. Ten layers were woven in the same pattern as the number of laminations. In this case, P /
(W / cos θ) is 1.

Comparative Example 2 Using the same core and fiber as in Example 1, a fiber orientation angle of 60 was used.
° and a fiber bundle pitch of 20 mm, and woven by a filament winddig method in 8 divisions per layer. Ten layers were woven in the same pattern as the number of laminations. In this case, P /
(W / cos θ) is 10.

Next, alumina sol and silica sol were added to the structures of Example 1 and Comparative Examples 1 and 2 in a molar ratio of solid content of 3:
2 and impregnated. After drying, in the air,
The substrate was fired at a temperature rising rate of 50 ° C./h at 1200 ° C. for 2 hours to prepare a substrate. Further, 5 parts by weight of calcium zirconate and 5 parts by weight of kaolinite are added as binders to mullite powder having an average particle size of 35 μm to form a filter layer on the surface of the base material, and mixed with a pot roller. The slurry was applied. After drying this substrate, it was fired at 1150 ° C. for 4 hours at a temperature increase rate of 100 ° C./h to produce a ceramic filter element.

As for the evaluation of the filter, the porosity and average pore diameter were evaluated by a mercury porosimeter, and a C-ring compression test was performed by cutting a ring-shaped test piece.

Table 1 shows the measurement results of the porosity, the average pore diameter of the substrate, and the strength. In addition, the measurement results of monolithic cordierite as a comparative material are also shown.

[0057]

[Table 1]

The material of Comparative Example 1 has a high strength and a high reliability as a structural material, but has a small pore diameter, a high air pressure loss, and has a problem in terms of function in continuous use as a filter, and is suitable as a filter material. Absent. In Comparative Example 2, the porosity was too high and the strength was low, and the reliability as a structural member was low. On the other hand, it was confirmed that Example 1 had the same function (pore diameter, porosity) as a cordierite ceramic and a filter, and was very excellent as a porous material because of its high strength. Was.

[Second Embodiment] In the second embodiment, the effect of the amount of zirconia and the sintering temperature on the mullite long fiber composite was examined.

Example 2 The same mullite fiber as that in Embodiment 1 was used for evaluating the material properties. Weave the fibers into a 12 yarn / inch cloth,
After cutting into a 50 mm square, 10 sheets were laminated. After mixing the alumina sol and the silica sol so that the solid content molar ratio was 3: 2, zirconia sol was added at 10% by weight in terms of solid content to impregnate the cloth fibers. Then, after drying, it was baked in the air at 1200 ° C. for 2 hours at a temperature rising rate of 50 ° C./h.

Comparative Example 3 An impregnated cloth was produced in the same manner as in Example 2, and then fired in the air at 1100 ° C. for 2 hours and 1350 ° C. for 2 hours at a heating rate of 50 ° C./h.

Comparative Example 4 In the same manner as in Example 2, fibers were woven into a cloth of 12 yarns / inch, cut into 50 mm squares, and laminated into 10 sheets. After mixing the alumina sol and the silica sol so that the solid content molar ratio was 3: 2, zirconia sol was added at 30% by weight in terms of solid content, and the cloth fibers were impregnated. Then, after drying, 1100 ° C. for 2 hours at a temperature increase rate of 50 ° C./h in the air, 12
It baked at 00 degreeC-2h and 1300 degreeC-2h.

From the structures of Example 2 and Comparative Examples 3 and 4, strip-shaped test pieces were cut out and subjected to a bending test at 1000 ° C. Furthermore, the sample was exposed to the atmosphere at 1000 ° C. for 100 hours, and the flexural strength at 1000 ° C. after thermal degradation was measured. Table 2 shows the measurement results of strength before and after thermal deterioration.

[0064]

[Table 2]

In the sintered bodies of Comparative Examples 3 and 4 at 1350 ° C., the crystal structure of the mullite filaments was enlarged, and the strength was much lower than the strength characteristics of the mullite filaments themselves. The 1100 ° C. sintered bodies of Comparative Example 3 and Comparative Example 4 had a strength of about 50 MPa, were less thermally degraded, and were higher in strength than a porous body of a monolithic material, but had a high temperature because the binder was not completely crystallized. Under the alkaline corrosion environment, the strength deteriorated easily. 12 of Comparative Example 4
The strength of the 00 ° C. sintered body before the heat deterioration test was as high as about 140 MPa, but after the heat deterioration test, the strength was sharply reduced to 以下 or less. Further, observation by SEM revealed that countless cracks were formed in the joint. This is considered to be because cracks were generated due to a difference in thermal expansion due to a large content of zirconia. On the other hand, in Example 2, the strength was about 130 MPa, and it was confirmed that thermal deterioration did not occur.

[Third Embodiment] In the third embodiment, the material characteristics of a filter film as a filter material were evaluated.

Example 3 5 parts by weight of calcium zirconate and 5 parts by weight of kaolinite were added to mullite powder having an average particle diameter of 35 μm, and water was added so that the slurry concentration became 60%, followed by mixing with a pot roller for 4 hours. After vacuum degassing, by the slurry casting method,
A 50 mm square molded body was produced. After drying, heating rate 10
A test piece was prepared by firing at 0 ° C./h at 1150 ° C. for 4 hours.

Comparative Example 5 A 50 mm square molded body was produced in the same manner as in Example 3, dried, and heated at a rate of 100 ° C./h at 1050 ° C.-4.
for 1 h at 1350 ° C. to produce a test piece.

Comparative Example 6 25 parts by weight of calcium zirconate and 5 parts by weight of kaolinite were added to mullite powder having an average particle size of 35 μm, water was added so that the slurry concentration became 60%, and the mixture was mixed for 4 hours with a pop roller. After vacuum degassing, by the slurry casting method,
A 50 mm square molded body was produced. After drying, heating rate 10
A test piece was prepared by firing at 0 ° C./h at 1150 ° C. for 4 h and at 1350 ° C. for 4 h.

Comparative Example 7 5 parts by weight of calcium zirconate and 25 parts by weight of kaolinite were added to mullite powder having an average particle diameter of 35 μm, and water was added so that the slurry concentration became 60%, followed by mixing with a pot roller for 4 hours. After vacuum degassing, a 50 mm square molded body was produced by a slurry casting method. After drying, the specimen was fired at a heating rate of 100 ° C./h at 1150 ° C. for 4 hours to produce a test piece.

The dimensions of the structures of Example 3 and Comparative Examples 5, 6, and 7 were measured, and the shrinkage rates before and after firing and solidification were measured. Then, strip-shaped test pieces were cut out and subjected to a bending test at 1000 ° C. Carried out. Furthermore, the sample was exposed to the atmosphere at 1000 ° C. for 100 hours, and the flexural strength at 1000 ° C. after thermal degradation was measured. Further, as a function evaluation of the filtration membrane, the porosity and the average pore diameter were measured by a mercury porosimeter.

Table 3 shows the measurement results of the porosity, the pore diameter, the shrinkage, and the bending strength.

[0073]

[Table 3]

The sintered body at 1050 ° C. of Comparative Example 5 had a porosity,
Although the pore size can fulfill the function as a filter membrane, the strength as a structural material is insufficient due to insufficient calcination and solidification, and the filter layer peels off during high-temperature gas dedusting, so reliability is high. Became poor. Although the sintered bodies at 1350 ° C. of Comparative Examples 5 and 6 have advanced sintering and have high strength as a structural material, the porosity as a filter layer is high for separating dust of several microns such as coal ash. It was too small, leading to an increase in pressure loss and a significant decrease in trapping performance, and it was not possible to exhibit a sufficient function as a filter membrane. 1150 ° C of Comparative Example 6
The sintered body was greatly deteriorated in strength, and when observed with a SEM, numerous microcracks were present on the surface of the porous body, which was unsuitable as a filter film. The 1150 ° C. sintered body of Comparative Example 7 had insufficient high-temperature strength due to softening of the vitreous joint, and was unsuitable as a filter film. On the other hand, in Example 3, the porosity and the pore diameter were able to sufficiently function as a filter layer, and the strength was not reduced by thermal deterioration, and the firing shrinkage was extremely small. The integration with the material was sufficiently possible, and it was confirmed that it was suitable as a filter membrane.

[Fourth Embodiment] In the fourth embodiment, when a candle type filter structure was used, the difference in strength due to the sealing method of one end of the filter element was evaluated.

Example 4 As shown in FIG. 3, an attempt was made to integrate a filter substrate and a mullite one-end sealing material. A slurry in which 10% by weight of calcium zirconate and 15% by weight of kaolinite were added to the mullite powder was applied to the one-end sealing material, and then fitted into the base material, fired at 1150 ° C. for 4 hours, and integration was attempted. Then, a heat cycle from normal temperature to 1000 ° C. is performed for 5
It was performed 0 times and observed.

According to the observation results, there is no particular crack at the joint between the filter substrate and the one-end sealing material.
It was confirmed that the filter substrate and the one-end sealing material were sufficiently integrated. Therefore, it can be seen that the ceramic filter element composed of the filter base material and the one-end sealing material integrated by such a method has no cracks or the like and is excellent in reliability.

[0078]

As described above, according to the ceramic filter element and the method of manufacturing the same according to the present invention, it is possible to improve properties such as strength, corrosion resistance and thermal shock resistance while maintaining pressure loss and trapping performance. Thus, it is possible to provide a ceramic filter element having excellent characteristics as compared with a monolithic ceramic filter element.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a high-temperature gas dedusting system.

FIG. 2 is a woven structure of a long fiber material according to the present invention and an enlarged view thereof.

FIG. 3 is a cross-sectional view showing a specific example of a ceramic filter element with one end sealed according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot gas dust removal system 2 Hot gas inflow path 3 Hot gas outflow path 4 Ceramic filter element 5 Tube sheet 6 Dust hopper 7 Backwash tank 8 Backwash valve 9 Differential pressure gauge 10 Core 11 Core rotation shaft 12 Filament bundle 13 Air gap Part 14 Filter base material 15 One-end sealing material

Continuation of the front page (72) Inventor Makoto Ikeda 7-1, Nisshincho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture F-term in Toshiba Electronics Engineering Co., Ltd. 4D019 AA01 BA05 BA06 BA07 BB02 BB07 BC20 BD01 CA03 CB06 DA02

Claims (7)

[Claims] 1. A ceramic filter element in which a filter layer made of ceramic is formed on a base made of ceramic fibers, wherein the base is mainly made of mullite filaments, and the porosity of the base is 40 to 70% by volume. A ceramic filter element, characterized in that: 2. The mullite filaments are woven by a filament winding method, and the pitch between adjacent filament bundles in the woven layer structure is wider than the filament width. Item 7. A ceramic filter element according to Item 1. 3. The mullite filaments are bonded and solidified by a bonding portion mainly composed of mullite obtained by impregnating and firing alumina sol and silica sol, and the zirconia content in the bonding portion is less than 20% by weight. The ceramic filter element according to claim 1, wherein 4. The filter layer has an average particle size of 5-10.
0 μm powder consisting mainly of mullite and equimolar
Calcia (CaO) and zirconia (ZrO _Two)
And calcia (CaO) and zirconia (Zr
O_Two) Is 1 to 20 weights with respect to the mullite powder.
% Formed by firing the mixture which is
The ceramic filter according to claim 1, wherein
Rement. 5. A material mainly composed of long mullite fibers impregnated with alumina sol and silica sol,
A method for manufacturing a ceramic filter element, comprising: a step of forming a base material by firing at 1300 ° C .; and a step of forming a filter layer made of ceramic on the base material. 6. A step of forming a base material mainly composed of mullite filaments, and adding a mixture of mullite, calcium zirconate and 0.1 to 20% by weight of kaolinite to the mullite to the base material. Baking at 1100 ° C. to 1300 ° C. to form a filter layer. 7. A step of forming a filter substrate by forming a filter layer made of ceramic on a substrate made of ceramic fibers, and one end for sealing the filter substrate or one open portion of the filter substrate. A step of applying a mixture comprising mullite, calcium zirconate and kaolinite to at least one of the sealing materials and connecting them, and a step of firing the filter base and the one-end sealing material connected to each other. A method for manufacturing a ceramic filter element, comprising: