JPH0779935B2 - Cordierite gas filter and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a filter for cordierite-like gas, which is suitable as a filter for gas, particularly at high temperature, and a method for producing the same.

[Background of the Technology] Ceramics are generally excellent in heat resistance and corrosion resistance and are suitable as filter materials. In recent years, the use of ceramic gas filters is expanding. Its uses extend to the prevention of pollution and the improvement of product quality, as well as the development of energy conservation and coal energy, and great expectations are placed on the realization of a reliable ceramics gas filter that can be used in high-temperature severe environments. There is.

When a ceramics filter is used for dust removal of high-temperature gas, rapid heating and rapid cooling are often inevitable, so a material having a small coefficient of thermal expansion that is resistant to thermal shock is required for the filter.

Among the many types of ceramics, cordierite-based ceramics have considerable heat resistance, a small coefficient of thermal expansion, and are strong against thermal shock.
Utilizing this characteristic, a high temperature filter using cordierite has been developed.

For example, Japanese Patent Application Laid-Open No. 58-133810 discloses a cordierite honeycomb type filter and a method for producing the same, which is relatively suitable for removing fine particles contained in exhaust gas of a diesel engine. A method for producing a cordierite filter having a large average pore size is disclosed, and it is shown that a lithium oxide component is added for the purpose of forming relatively large pores.

Further, the present applicant has previously proposed, in Japanese Patent Laid-Open No. 63-31517, a tubular cordierite filter having a pore size distribution that is unlikely to be clogged, for the purpose of removing dust from high-temperature dust-containing gas.

As the filter, a filter having a small ventilation pressure loss is preferable because a large processing capacity of dust-containing gas can be obtained, and for this purpose, a higher porosity is better.

However, when the porosity is increased, there is a problem that the strength is remarkably reduced, and it is a general method to find a compromise and manufacture the filter.

For alumina and silicon carbide, which have a relatively good track record as ceramics filters, their use as abrasives and abrasives has been established for these materials. It is relatively easy to make a material that is used as a raw material and has a small ventilation pressure loss and a strength that is at a practical level.

In these filters, a vitreous or clay joint is usually used, but a vitreous joint has a high-temperature strength such as a strength at 800 ° C that falls to 1/3 or less of room temperature strength. However, those having a bond portion made of clay have a problem that the strength at room temperature is also low.

On the other hand, commercially available synthetic cordierite usually has a large porosity, and even if a commercially available aggregate is obtained and a ceramic filter is trial-produced, the porosity is large and the ventilation pressure loss is large. However, if the porosity is increased to reduce the value of p, the practical strength cannot be maintained.

In order to use the cordierite filter for a long time in a high temperature and corrosive atmosphere, in order to ensure reliability, it has high strength not only at room temperature but also at high temperature, has excellent thermal shock resistance, and is not clogged. In addition to being difficult and having a small ventilation pressure loss, a gas that contains corrosive substances such as NOx and SOx is removed, so a ceramic filter with excellent corrosion resistance, especially acid resistance is required.

The object of the present invention is to solve the above-mentioned problems of the cordierite ceramics filter that the prior art had, reduce the ventilation pressure loss of the filter, have heat resistance and practical strength, and An object of the present invention is to provide a cordierite gas filter having excellent corrosiveness and a method for producing the same.

[Configuration of Invention] The present invention has been made to solve the above-mentioned problems, and a filter for cordierite-like gas according to the present invention is
74μ particle size with an apparent porosity of 10% or less with 50wt% or more
It is composed of m or more cordierite aggregate and a joint part, and the main components of the joint part are silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), and lithium oxide (Li ₂ O) It is characterized by containing 0.05 to 1 wt% with respect to the weight.

In a preferred embodiment of the cordierite gas filter of the present invention, lithium oxide is used for the weight of the entire filter.
Contains 0.2 to 0.6 wt%.

In another preferred embodiment of the cordierite gas filter of the present invention, the cordierite aggregate is a cordierite crystallized from glass having a generally cordierite composition (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ). It is a light aggregate.

In another preferred embodiment of the filter for cordierite gas of the present invention, the cordierite aggregate is the cordierite aggregate, and alumina sol, silica sol, cyania sol, zirconia sol, or a mixed liquid of two or more thereof. Is impregnated with it, and has an apparent porosity of 10% or less when fired.

In another preferred embodiment of the cordierite gas filter of the present invention, the porosity of the filter material is 35% or more, and the bending strength at 800 ° C. is 75 Kg / cm ² or more.

In another preferred embodiment of the cordierite gas filter of the present invention, 0.5 to 12 wt% of TiO ₂ and / or ZrO ₂ relative to the weight of the entire filter is added to the joint portion.

In another preferred embodiment of the cordierite gas filter of the present invention, the shape of the filter is a tubular body having a wall thickness of 5 mm or more.

In the method for producing a cordierite gas filter of the present invention, the cordierite aggregate having a particle size of 74 μm or more and 590 μm or less and having an apparent porosity of 10% or less is oxidized by the weight of the entire filter. Lithium is 0.05
~ 1wt%, powders containing lithium oxide, clay and powder raw material forming a joint part containing a mixture of clay and cordierite powder having a particle size smaller than 74 μm are mixed together,
It is characterized in that an organic binder is added and the mixture is molded and fired.

In a preferred embodiment of the method for producing a cordierite gas filter of the present invention, the apparent porosity is 10% or less of cordierite aggregate, magnesia, alumina and silica sand are generally cordierite composition (2MgO.2Al ₂ O ₃ · 5SiO ₂₎
It was prepared by blending so as to obtain the following, electrically fused, rapidly cooled into glass, and crystallized by heat treatment.

In another preferred embodiment of the method for producing a cordierite gas filter of the present invention, the powder containing lithium oxide is β
It is spodumene powder.

In another preferred embodiment of the method for producing a cordierite gas filter of the present invention, coke powder is mixed as a pore-forming material that forms pores by burning and burning in the raw material.

In another preferred embodiment of the method for producing a cordierite gas filter of the present invention, the filter is molded by an isostatic press using a metal core mold and a pipe-shaped rubber outer mold, and molded into a tubular shape.

In another preferred embodiment of the method for producing the cordierite gas filter of the present invention, the firing is performed in a temperature range of 1310 to 1380 ° C.

In the method for producing a filter for cordierite gas of the present invention, the reason for setting the apparent porosity of the cordierite aggregate used to be 10% or less is that it is effective for reducing the ventilation pressure loss of the filter, This is because if the apparent porosity is 10% or more, the ventilation pressure loss increases.

Further, by setting the apparent porosity of the cordierite aggregate to 10% or less, the strength of the cordierite aggregate is increased, and as a result, the strength of the filter itself is also increased.

The reason why 50 wt% or more of cordierite aggregate with a particle size of 74 μm or more (particle size that does not pass through the 200 mesh of the sieve) is blended is that the aggregate with a particle size of 74 μm or more is suitable for a gas filter of several μm or more. This is because it is useful for forming pores of a size, and the content of 50 wt% or more is to provide at least the pores necessary to provide air permeability that enables use as a filter. When the content of the aggregate having a particle size of 74 μm or more is 50 wt% or less, the shrinkage during firing becomes large, the filter is easily distorted during firing, the porosity becomes small, and the ventilation pressure loss becomes large, which is not preferable.

Further, it is more preferable that the cordierite aggregate is blended in an amount of 70 wt% or more because firing shrinkage is reduced, porosity is increased, and ventilation pressure loss is reduced.

The balance here is usually compounded as a fine powder, which forms the bond of the cordierite aggregate in the filter after firing.

This joint has a slightly lower fire resistance than cordierite aggregate because it is sintered to give strength, and its coefficient of thermal expansion is cordierite so that the thermal stress generated between it and the aggregate does not become large. It is preferably close to aggregate.

In order to increase the strength of the filter material, it is preferable that the joint portion has a composition such that glass is partially formed during firing.

The reason why the clay is blended in the powder raw material for forming the bonding portion is that it contains alumina and silica as the main components necessary for the bonding portion as the main components, and at the same time has the effect of improving the moldability.

When lithium oxide is included in the joint part in addition to alumina and silica, glass is partially formed during firing, the fire resistance is a little smaller than that of the aggregate, and the thermal expansion coefficient is close to that of the cordierite of the aggregate. Therefore, by combining with a cordierite aggregate having a low porosity, it is possible to obtain an effect that a filter having sufficient strength can be obtained not only at room temperature but also at a high temperature of 800 ° C.

The content of lithium oxide (Li ₂ O) in the filter material is 0.05
1 wt% (corresponding to blending 1 to 20 wt% as β-spodumene). If 0.05 wt% or less, a strong sintered body cannot be obtained, and if it is 1 wt% or more, cordierite ceramic filter. The heat resistance of is impaired, which is not preferable.

The reason why a filter containing lithium oxide (Li ₂ O) provides a filter that retains its strength even at high temperatures is because the phase between cordierite and β-spodumene (Li ₂ O ・ Al ₂ O ₃・ 4SiO ₂ ) It is not clear due to the complicated relationship (Yoichi Mogi P310 1976 Gihodo), but it is estimated as follows.

Alumina (Al ₂ O 3) containing lithium oxide (Li ₂ O) of the present invention
₂ O ₃ ) and silica (SiO ₂ ) as the main components of the filter joint part vitrify during firing and a strong bond occurs between the aggregates. This glass contains most of lithium oxide and has a lower melting point than the aggregate,
Crystals are formed in the glass by subsequent cooling.

The generated crystals have a low coefficient of thermal expansion, and the joint as a whole has a coefficient of thermal expansion similar to that of cordierite aggregate, and even when cooled to room temperature, the heat between the aggregate and the aggregate is high. A cordierite ceramic filter having a small residual strain caused by a difference in expansion and a large strength at room temperature can be obtained.

It is convenient to add β-spodumene to the powder raw material forming the joint to avoid uneven distribution of lithium oxide, and even if β-spodumene remains in the filter material as it is, the coefficient of thermal expansion of the entire joint is small. This is because the addition of cordierite powder is preferable for bringing the thermal expansion coefficient of the joint close to the thermal expansion coefficient of the aggregate.

Further, even at a high temperature of about 1000 ° C., since it is a bonded portion having a relatively large amount of crystal components, the strength is maintained without being softened.

In the method for producing the filter for a cordierite gas of the present invention, it is preferable to use the cordierite aggregate crystallized from glass even if the aggregate requires an elaborate official regulation. Since the aggregate with a low coefficient of expansion can be obtained and the coefficient of thermal expansion is about 1/2 of that of cordierite-based aggregate by ordinary firing, the coefficient of thermal expansion of the filter material is small and the thermal shock resistance is particularly excellent. It is convenient because a filter for cordierite gas can be obtained.
Because the aggregate is strict, it becomes a filter excellent in corrosion resistance, and it is possible to manufacture a filter for cordierite gas suitable for use in a high temperature and particularly severe atmosphere.

As a raw material of the cordierite aggregate crystallized from this glass, magnesia clinker, Bayer alumina, silica sand and the like can be preferably used, and the production thereof is described, for example, in Japanese Patent Publication
As disclosed in 57-20269, it is preferable to heat-treat what is once rapidly cooled into glass to be crystallized.

As the synthetic cordierite aggregate, a sintered product made from talc, clay and aluminum hydroxide can be preferably used.

In order to obtain a cordierite aggregate with an apparent porosity of 10% or less, it is economical to fully bake it in the usual synthetic cordierite production stage. Zircon powder is added to improve the sintering property. Improved raw materials may be used.

Most commercially available synthetic cordierite has a porosity of more than 10% and cannot be used as it is as an aggregate of the cordierite gas filter of the present invention.

Therefore, there is also a method of densification by firing again, but as a result of various investigations, in aggregates with apparently low porosity, colloidal solutions such as alumina sol, silica sol, titania sol, zirconia sol are used as cordierite aggregates. By impregnation, it is possible to convert to an apparent porosity of 10% or less, and if the porosity can be 10% or less, it can be used without any problem as an aggregate of the cordierite gas filter of the present invention, and the manufactured filter is Vent pressure loss is small and strength is high.

It is preferable to use reduced pressure to sufficiently impregnate the colloidal solution, and it is also possible to further impregnate the aggregate after it is dried and further densified.

For the purpose of the present invention, after the aggregate is impregnated with the colloid solution, the colloid solution impregnated with the cordierite aggregate is once gelled or dried and can be directly used as the aggregate.

In the cordierite gas filter of the present invention, the condition that the apparent porosity of the aggregate is 10% or less needs to be achieved in the state after firing.

However, for example, when the colloidal aqueous solution is impregnated after being formed into a tubular filter, the pores to be used as gas flow passages in the filter are blocked, and the filter has a large ventilation pressure loss, which is not preferable.

It is speculated that the reason why the ventilation pressure loss becomes smaller when the apparent porosity of the cordierite aggregate is 10% or less is as follows.

First, a gas flow passing through a ceramic filter expresses a fluid flow passing through a packed bed of powder (Ko
If the gas passing through the filter is laminar, the ventilation pressure loss ΔP across the filter is expressed by the following equation (Fine Particle Measurem).
ent, Clyde Orr Jr.et al, Chapter 7, The Macmillan Co.
New York 1959).

S _v ² = (g _c L / 2 μuL _e ) (ΔP / L) [ε ² / (1-ε) ² ] where S _v is the surface area of the solid per unit volume, g _c
Is the gravitational constant, L is the thickness of the filter, μ is the viscosity of the gas, u
Is the apparent velocity of the gas, L _e is the length of the meandering capillary in the filter, ε is the porosity, and approximately has a relation of u _c = (u / ε) (L _e / L).

That is, the ventilation pressure loss of the gas passing through the filter can be approximated to be proportional to the square of the surface area of the particles in the unit volume. Therefore, in order to reduce the ventilation pressure loss of the filter, the particles in the unit volume formed in the filter can be reduced. Venting pressure loss can be reduced by making the surface area of the sheet to the necessary minimum size.

In addition, in the sintered body, when the apparent porosity becomes 10% or less, the air permeability becomes almost negligible (porous material, Renichi Kondo, edited by Gihodo Publishing Co., Ltd. 1973), so the porosity increases.
The pores within the particles of 10% or less do not participate in ventilation and do not cause a pressure loss of ventilation.

That is, it is considered that the ventilation pressure loss is mainly determined by the surface area formed in the tissue between the surface of the aggregate and the aggregate, so that the filter having the small ventilation pressure loss can be manufactured.

For the gas filter, the wall thickness is preferably 5 mm or more in the case of a tubular body, because if the wall thickness is made too thin, it will be damaged by the gas pressure of the backwash because of repeated backwash regeneration.

In order to further improve the air permeability and reduce the air pressure loss, it is preferable to mix the raw material with a pore-forming material that burns out during firing and forms pores. It is preferable to mix coke powder, particularly pick coke powder, which is easy to obtain and is reasonably hard and does not adversely affect moldability.

The main purpose of mixing the organic binder in the raw material is to give strength to the green molded body to facilitate molding and avoid damage when carrying the green molded body. It also contributes to the increase in porosity.

As a filter molding method, isostatic press molding, semi-wet tamping molding, extrusion molding, etc. can be adopted. Of these, isostatic press molding is a molding method that is conventionally suitable for producing a dense sintered body. It has been used as a filter, but there is no example used as a method for forming a porous filter.However, it is possible to omit the drying step, it is also possible to form a large tubular filter, and it has good productivity. Is also a preferable molding method.

Firing is often performed using a Tonel kiln, but a shuttle kiln or the like may be used, and the firing temperature range is preferably 1310 to 1380 ° C.

If the firing temperature is lower than 1310 ° C, the strength will be insufficient due to insufficient sintering, and if it is higher than 1380 ° C, it will be deformed due to the weight of the filter during sintering, or the porosity will be decreased due to excessive sintering, which is not preferable. .

The reason for setting the apparent porosity to 35% or more is that it is preferable for obtaining practical air permeability as a filter.
The value of the bending strength of 75 kg / cm ^{2 at} 0 ° C is unprecedented in a cordierite ceramics filter having an apparent porosity of 35% or more, and is preferable in terms of improving filter reliability. .

The cordierite ceramics filter thus obtained, which has a high strength even at a high temperature, however, was found to have decreased in strength when examined at room temperature after being actually used at a high temperature.

The reason for this is not clear at present, but when there is a decrease in strength, the presence of β-spodumene crystals in the bond was detected by X-ray powder diffraction. That is, it is considered that the strength is reduced due to some structural change in the joint.

Addition of ZrO ₂ and / or TiO ₂ components to this bond part promotes crystallization of the bond part by adding these components that can become crystal nuclei, and the glass present in the bond part is crystallized during cooling during firing. It aims to be stable and stable.

After addition of these components, the presence of β-spodumene crystals was confirmed by X-ray powder diffraction in the bonded part of the filter after firing, and as a result, the initial strength was slightly sacrificed compared to the one without addition. A cordierite-based ceramic filter was obtained which did not show a tendency of strength decrease during use like the ones not using it, showed stable strength, and could be used repeatedly and reliably.

Here, the added amount of ZrO ₂ and / or TiO ₂ is preferably 0.5 to 12 wt%, particularly preferably 1 to 10 wt% in the total amount in the filter material, and if 0.5 wt% or less, the effect of stabilizing the strength is almost the same. If it is not obtained, and if it is 12 wt% or more, the coefficient of thermal expansion of the filter becomes large and the thermal shock resistance is impaired, which is not preferable.

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

[Example] Seven types of a, b, c, d, e, f, and g were prepared as cordierite aggregates.

a. Magnesia, alumina and shaped sand 2MgO ・ 2Al ₂ O ₃・ 5S
A mixture of iO ₂ and cordierite was electromelted using a carbon electrode, and the melt was poured into water and rapidly cooled to obtain glass with a cordierite composition. It was glass.

Put this on a trolley and pass through the tunnel kiln at about 1380 ℃
It was crystallized by heat treatment for 10 hours.

This was further crushed and classified, and 74 to 590 μm was taken out.
The average particle size of this aggregate is 270 μm and the apparent porosity is 3%.
Met.

b.Talc, clay, aluminum hydroxide and fine powder of zircon as the chemical components, 2MgO ・ 2Al ₂ O ₃・ 5SiO ₂ as the main component, 3
A cordierite composition containing wt% ZrO ₂ was added, and 2 parts by weight of methyl cellulose and an appropriate amount of water were added to 100 parts by weight of the prepared raw material, and the mixture was kneaded to form a rod-shaped body having an outer diameter of about 30 mm. Was extruded.

After drying the rod, put it on the trolley and pass it through the tunnel kiln.
The product was kept at the maximum temperature of 1360 ° C for 10 hours to obtain synthetic cordierite. This was further pulverized and classified, and 74 to 590 μm was taken out.

The average particle size of this aggregate is 265 μm and the apparent porosity is 7%.
Met.

c. Mostly talc, clay and aluminum hydroxide fine powder
2MgO ・ 2A1 ₂ O ₃・ 5SiO ₂ was prepared to have a cordierite composition, and 2 parts by weight of methyl cellulose and an appropriate amount of water were added to 100 parts by weight of the raw compounded material and kneaded to obtain an outer diameter of about
It was extruded into a rod of 30 mm.

After drying, put it on the trolley and pass it through the tunnel kiln.
It was held at 10 ° C for 10 hours to obtain a synthetic cordierite. This was further pulverized and classified, and 74 to 590 μm was taken out.

The average particle size of this aggregate is 250 μm and the apparent porosity is 12%.
Met.

d. A commercially available synthetic cordierite aggregate was crushed and classified, and 74 to 590 μm was taken out.

The average particle size of this coarse particle is 230μ, and the apparent porosity is 30%.
Met.

The cordierite aggregate obtained in ec was impregnated with alumina sol, impregnated under reduced pressure, and dried. 1000 this aggregate
The apparent porosity after heating at ℃ was 8%.

The cordierite aggregates obtained by f and gc were impregnated with silica sol and titania sol under reduced pressure and dried.

The apparent porosities after heating these aggregates at 1000 ° C. were 7% and 8%, respectively.

The β-spodumene powder was prepared as follows. Wax stone and lithium carbonate powder were mixed at a ratio of 85 wt% and 15 wt%, respectively, and further wet-mixed and pulverized. The filter cake was dried and then calcined in an electric furnace at a temperature of 1150 ° C. to synthesize β-spodumene, which was finely pulverized and passed through a 325 mesh sieve.

Using 7 kinds of cordierite aggregates a to g,
Under the conditions shown in Tables and Table 2, tubular tubular cordierite gas filters were manufactured.

In Examples and Comparative Examples of Table 1, the effects of the filter characteristics on the degree of porosity of the aggregate and the amount of the aggregate compounded are mainly examined.

In this example, 10% by weight of clay in addition to 10 to 25% by weight of fine powder of cordierite and 5% by weight of fine powder of β-spodumene were used in the joint part, and 100 parts by weight of this mixture was provided with porosity. 25 parts by weight of pitch coke powder having a particle size of 20 to 100 μ is added as a material, and 5 parts by weight of a 50 wt% aqueous solution of a phenol resin is added as an organic binder and mixed at 110 ° C.
After that, it was crushed and crushed to obtain a granular raw material having a particle size of 3 mm or less.

This raw material is used in an isostatic press at 1000 Kg / cm ₂
The outer diameter is about 170 mm, the inner diameter is about 140 mm, and the length is about 850 m.
A tubular body of m was molded.

The tubular molded body was fired in an electric furnace at a maximum temperature of 1320 ° C. for 5 hours to obtain a tubular cordierite filter.

When firing was carried out in a tunnel kiln, a filter in a similar sintered state was obtained when fired at about 1350 ° C.

The properties examined for each tubular cordierite filter are also shown in Table 1. Also, for the other Examples and Comparative Examples, tubular filters were manufactured under the same conditions as described above except for the conditions shown in Table 1, and the characteristics are shown in Table 1.

Here, the apparent porosity was measured by a water immersion method, and the average pore diameter was measured by a mercury porosimeter.

The bending strength was measured by a 14 × 20 × 100 mm test piece in a 3-point bending test with a fulcrum distance of 70 mm.

The acid resistance was investigated by the change in bending strength after immersing in IN H ₂ SO ₄ aqueous solution for 72 hours at room temperature.

For dust removal performance, dust of red iron oxide powder with an average particle size of about 50 μm was dispersed in air to a concentration of 40 g / Nm ³ using a backwash type dust removal tester, the ambient temperature was set to 300 ° C, and the air filter was used. The test was conducted for 100 hours at a passing speed of 5 cm / sec.

The particle size distribution of red iron oxide powder is 1 wt% below 1 μm,
1-10 μm is 7 wt%, 10-40 μm is 35 wt%, 40-100 μm
Was 46 wt% and 100 to 800 μm was 11 wt%.

Table 2 shows the effect of changing the composition of the coupling portion on the material characteristics and filter characteristics of the filter, and the conditions not shown in the inner table of the manufacturing conditions of the filter are the same as those in the above embodiment. Under similar conditions.

In Comparative Example 5, bentonite contains an alkaline component and easily vitrifies during firing, so that a filter having strength at room temperature is obtained.

In Table ₂ , the added amount of ZrO ₂ and / or TiO ₂ is expressed as parts by weight, which is a ratio with respect to 100 parts by weight of the total weight of the aggregate and other binding components.

As a method of checking whether strength has decreased during use, bend strength test pieces cut from a ceramics filter at 1000 ° C.
After holding in the electric furnace for 24 hours, the bending strength at room temperature was measured.

As a result, although the ceramic filter to which zirconia and / or titania was added in the joint had a little small initial strength, no decrease in strength was observed even after the heat treatment.

[Advantages of the Invention] According to the cordierite gas filter and the method for producing the same of the present invention, the thermal shock resistance and the corrosion resistance are excellent, the ventilation pressure loss is small, and the strength is high even at a high temperature of about 800 ° C, particularly at a high temperature. A cordierite gas filter suitable for dust removal of gas and a method for manufacturing the same have been shown.

In the present invention, an aggregate having a low porosity of 10% or less, particularly by using a cordierite aggregate crystallized from glass, the ventilation pressure loss of the filter is reduced, and the aggregate has a low porosity. By combining with a bonding part containing lithium oxide, a filter for cordierite-like gas that has high strength even with high porosity, retains this strength even at high temperatures, and has excellent corrosion resistance, especially acid resistance was realized. . Since the ventilation pressure loss of the filter is small, it is possible to increase the processing capacity of dust-containing gas even with the same filter device.
Since the strength of the filter is sufficient, the damage of the filter during installation and maintenance of the filter device is significantly reduced, and the reliability of the device is improved.

In the cordierite gas filter of the present invention,
Although the strength tended to decrease when used at high temperatures, the addition of TiO ₂ or ZrO ₂ in the bond converts the unstable glass phase in the bond into crystals during firing, resulting in a decrease in strength. The trend could be improved to a reliable filter.

Furthermore, it has been clarified that the silicon carbide-based filter, which is currently promising, has problems such as the pores being clogged by the oxidation of water vapor contained in the combustion gas and the ventilation pressure loss becoming large. However, the cordierite gas filter according to the production method of the present invention has excellent durability in an acidic corrosive gas atmosphere containing steam such as combustion gas of coal, NOx and SOx, and for power generation. It can be preferably used for a fluidized bed boiler that burns coal, a pressurized fluidized bed boiler, and dust removal of synthetic gas by a coal gasification furnace.

The cordierite gas filter of the present invention can be widely used for dust removal of various high-temperature dust-containing gases emitted by industries that use high temperatures, and can recover the thermal energy that cannot be recovered because it conventionally contains dust. It enables effective use.

In addition, NOx and SOx can be easily removed from the dust-free high-temperature gas, and the separated dust can also be collected in a dry state, making it easy to effectively use it. Is.

Claims (14)

[Claims] 1. A cordierite aggregate having an apparent porosity of 10% or less and a particle diameter of 74 μm or more and a bonding part, and the main component of the bonding part is silica (SiO ₂ ). Alumina (Al ₂ O ₃ ) and lithium oxide (Li ₂ O)
A filter for cordierite gas, characterized by containing 0.05 to 1 wt% of the total weight of the filter. 2. The filter for cordierite-based gas according to claim 1, which contains lithium oxide in an amount of 0.2 to 0.6 wt% with respect to the total weight of the filter. 3. The cordierite aggregate according to claim 1 or 2, wherein the cordierite aggregate has a cordierite composition (2MgO.2Al ₂ O ₃
A filter for cordierite gas, which is a cordierite aggregate crystallized from glass having 5SiO ₂ ). 4. The cordierite aggregate according to claim 1 or 2, wherein the cordierite aggregate is impregnated with an alumina sol, a silica sol, a titania sol, a zirconia sol, or a mixed solution of two or more of these. And
A cordierite gas filter which has an apparent porosity of 1% or less when fired. 5. A cordierite gas filter according to claim 1, wherein the porosity of the filter is 35% or more and the bending strength at 800 ° C. is 75 kg / cm ² or more. 6. The weight of the filter as a whole according to any one of claims 1 to 5, which is 0.5 to 12 w.
A filter for cordierite gas, to which t% TiO ₂ and / or ZrO ₂ is added. 7. The cordierite gas filter according to any one of claims 1 to 6, wherein the filter is a tubular body having a wall thickness of 5 mm or more. 8. A cordierite aggregate having a particle size of 74 μm or more and an apparent porosity of 10% or less of 50 wt% or more, and 0.05 to 1 wt% of lithium oxide relative to the weight of the entire filter.
So that the powder containing lithium oxide, clay, and the powder raw material that forms the bonding part in which the clay and the cordierite powder with a particle size of less than 74 μm are mixed together are mixed, an organic binder is added, and the mixture is molded and fired. A method for manufacturing a filter for cordierite gas, comprising: 9. The cordierite-based aggregate having an apparent porosity of 10% or less according to claim 8, wherein magnesia, alumina, and silica sand have a cordierite composition (2MgO.2Al ₂ O ₃
• A method for producing a filter for cordierite-like gas, which is prepared by blending so as to be 5SiO ₂ ), electromelting, rapidly cooling to glass, and crystallizing by heat treatment. 10. The method for producing a cordierite gas filter according to claim 8, wherein the powder containing lithium oxide is β-spodumene powder. 11. The method according to any one of claims 8 to 10,
A method for producing a filter for cordierite gas, which comprises mixing coke powder as a pore-forming material for forming pores in a raw material by burning and burning. 12. The method according to any one of claims 8 to 11,
The filter is molded by an isostatic press using a metal core mold and a pipe-shaped rubber outer mold, and firing is performed at 1310 to 13
A method for producing a filter for cordierite gas at 80 ° C. 13. An apparent composition comprising 50 wt% or more of cordierite aggregate having a particle size of 74 μm or more and crystallized from glass having a generally cordierite composition, and a joint portion containing silica and alumina as main components. A cordierite gas filter, which has a porosity of 35% or more and a bending strength at 800 ° C of 75 kg / cm ² or more. 14. A cordierite aggregate having a particle size of 74 μm or more crystallized from a glass having a generally cordierite composition, and a powder raw material for forming a bonding part finer than 74 μm and containing silica and alumina as a main component. , A granular raw material containing a pore-forming material that forms pores by burning and burning, and an organic binder are filled in a molding die composed of a metal core die and a pipe-shaped rubber outer die, and isostatic A method for producing a filter for cordierite-like gas, which comprises forming the material into a tubular shape by pressing and then firing at 1310 to 1380 ° C.