JPH0368411A - Cordierite-based gas filter and its production - Google Patents

Abstract

PURPOSE:To form the gas filter highly resistant to corrosion by providing a binding part consisting essentially of silica and alumina and having a specified content of lithium oxide in the cordierite-based aggregate with its apparent porosity and grain diameter specified. CONSTITUTION:More than 50wt.% cordierite-based aggregate having <=10% apparent porosity and >=74mum grain diameter and a raw powder for forming the binding part consisting of the powder contg. lithium oxide, clay and cordierite powder having <70mum grain diameter are mixed so that the lithium oxide content of the mixture is controlled to 0.05-1wt.% based on the total weight of the filter. An org. binder is then added to the mixture, and the mixture is formed and then calcined to obtain a cordierite-based gas filter. The aggregate is appropriately obtained by electrically melting a 2MgO.2Al2O3.5H2O composition, quenching the molten material and crystallizing the obtained glass by heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cordierite gas filter suitable as a gas filter, particularly a high-temperature gas filter, and a method for manufacturing the same.

[Technical Background] Ceramics are generally materials with excellent heat resistance and corrosion resistance, and are suitable as filter materials, and the use of ceramic gas filters has been expanding in recent years. Its uses range from pollution prevention and product quality improvement to energy conservation and coal energy development, and there are great expectations for the creation of reliable ceramic gas filters that can be used in harsh high-temperature environments. .

When ceramic filters are used to remove dust from high-temperature gases, rapid heating and cooling are often unavoidable, so a material that is resistant to thermal shock and has a low coefficient of thermal expansion is required for the filter.

Among the many types of ceramics, cordierite ceramics have considerable heat resistance, a low coefficient of thermal expansion, and are resistant to thermal shock.
Taking advantage of this property, high-temperature filters made of cordierite are being developed.

For example, JP-A-58-133810 discloses a cordierite honeycomb type filter and its manufacturing method, which is relatively suitable for removing particulates contained in diesel engine exhaust gas. A method of manufacturing 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.

Furthermore, 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 less likely to clog, for the purpose of removing dust from high-temperature dust-containing gas.

It is preferable for the filter to have a small ventilation pressure loss because it can handle a large amount of dust-containing gas, and for this purpose, it is better to have a large porosity.

However, there is a problem in that increasing the porosity significantly reduces the strength, so the common practice is to find a compromise and manufacture filters.

Alumina and silicon carbide, which have a relatively good track record as ceramic filters, have established uses as abrasives and abrasives. It can be used as a raw material and relatively easily produced with low ventilation pressure loss and practical strength.

These filters usually use glass or clay joints, but those with glass joints have a strength at 800°C that is 1/2 the strength at room temperature.
There is a problem in that the strength at high temperatures is low, such as a decrease of 1/3 or less, and the strength at room temperature is also low in those with clay joints.

On the other hand, commercially available synthetic cordierite usually has a high porosity, and even if a ceramic filter is prototyped using commercially available aggregate, the porosity will be large and the ventilation pressure loss will be large. If the porosity is increased to reduce the porosity, there is a problem that practical strength cannot be maintained.

In order to use cordierite filters for long periods of time in high-temperature and corrosive atmospheres, in order to ensure reliability, they must be strong not only at room temperature but also at high temperatures, have excellent thermal shock resistance, and be resistant to clogging. In addition to being difficult to clean and having low ventilation pressure loss, a ceramic filter is required that has excellent corrosion resistance, especially acid resistance, in order to remove dust from gases that contain corrosive substances such as NOx and SOx.

The purpose of the present invention is to solve the problems of the above-mentioned cordierite ceramic filters that the prior art had, to reduce the ventilation pressure loss of the filter, and to have heat resistance and practical strength. The present invention aims to provide a cordierite gas filter with excellent corrosivity and a method for manufacturing the same.

[Structure of the Invention] The present invention has been made to solve the above-mentioned problems, and the cordierite gas filter of the present invention has a filter of 50
It is composed of cordierite aggregate with a grain size of 74 μm or more and an apparent porosity of 10% or less, and a bonding part, and the main components of the bonding part are silica (Stow) and alumina (Altos). and lithium oxide (Li
, O) in an amount of 0.05 to 1 wt% based on the total weight.
It is characterized by containing.

In a preferred embodiment of the cordierite gas filter of the present invention, lithium oxide is contained in an amount of 0.2 to 0.6 wt% based on the weight of the entire filter.

In another preferred embodiment of the cordierite gas filter of the present invention, the cordierite aggregate is a cordierite aggregate crystallized from glass having an approximately cordierite composition (2MgO.2Al!015SiO3). It is.

In another preferred embodiment of the filter for cordierite gas of the present invention, the cordierite aggregate contains alumina sol, silica sol, titania sol, zirconia sol, or a mixture of two or more thereof. The material is impregnated with porosity and has an apparent porosity of 10% or less when fired.

In another preferred embodiment of the filter for cordierite gas of the present invention, the porosity of the filter material is 35% or more,
And the bending strength at 800°C is 75 Kg/cm2 or more.

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

In another preferred embodiment of the filter for cordierite gas of the present invention, the filter has a tubular shape with a wall thickness of 5 mm or more.

In the method for manufacturing a filter for cordierite gas of the present invention, 50 wt% or more of cordierite aggregate with an apparent porosity of 10% or less and a particle size of 74 μm or more and 590 μm or less is added to the cordierite aggregate, which is the weight of the entire filter. Powder containing lithium oxide, clay and cordierite powder with a particle size of less than 74 μm are mixed together to form a bonding powder raw material such that the lithium oxide content is 0.05 to 1 wt%. In a preferred embodiment of the method for manufacturing a filter for a carbonaceous gas of the present invention, the filter is formed by adding a binder and then molding and firing. The light aggregate consists of magnesia, alumina, and silica sand with a roughly cordierite composition (2MgO・2A1
10.・5SiO2), electrically melted, rapidly cooled to form glass, and then crystallized by heat treatment.

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

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

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

In another preferred embodiment of the method for producing a filter for cordierite gas of the present invention, the firing is carried out at a temperature of 1310 to 1380°C.
The test shall be carried out within the temperature range of

In the method for producing a filter for cordierite gas of the present invention, the apparent porosity of the cordierite aggregate used is 1 (1% or less) because it is effective for lowering the ventilation pressure loss of the filter. The apparent porosity is 10%.
This is because if it is more than that, the ventilation pressure loss will increase.

In addition, the apparent porosity of cordierite aggregate is 10%.
The following has the effect that the strength of the cordierite aggregate is increased, and as a result, the strength of the filter itself is also increased.

The reason for blending cordierite with a particle size of 74 μm or more (particle size that does not pass through a 200-mesh sieve) and 50 wt% or more of solid aggregate is that the aggregate with a particle size of 74 μm or more is a few μm.
This is because it is useful for forming pores of a size suitable for filters for gases of m or more, and blending 50 wt% or more of this is at least necessary to provide air permeability that allows use as a filter. This is to provide large pores, and if the aggregate with a particle size of 74 μm or more is less than 50 wt%,
This is not preferable because the shrinkage during firing becomes large, the filter is easily distorted during firing, the porosity becomes small, and the ventilation pressure loss becomes large.

Further, it is more preferable to mix 70 wt % or more of cordierite aggregate, as this reduces firing shrinkage, increases porosity, and reduces ventilation pressure loss.

Here, the residue is usually incorporated as a fine powder and forms the cordierite aggregate bond in the filter after firing.

This joint is sintered to provide strength, so its fire resistance is slightly lower than that of cordierite aggregate, and the coefficient of thermal expansion is lower than that of cordierite aggregate, so that the thermal stress that occurs between it and the aggregate does not become large. It is preferable to use something close to aggregate.

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

The reason why clay is blended into the powder raw material for forming the joint is that it contains alumina and silica as main components necessary for the joint, and at the same time is effective in improving moldability.

If the joint contains lithium oxide in addition to alumina and silica, glass will partially form during firing, resulting in a joint whose fire resistance is slightly lower than that of the aggregate, and whose coefficient of thermal expansion is close to that of the cordierite aggregate. By combining it with cordierite aggregate having a low porosity, it is possible to obtain a filter that maintains sufficient strength not only at room temperature but also at a high temperature of 800°C.

The content of lithium oxide (Litu) in the filter material is 0.05 to 1 wt% (1 to 1% as β spodumene)
20wt%) and 0.0
If it is less than 5wt%, a strong sintered body cannot be obtained;
% or more is not preferable because the heat resistance of the cordierite ceramic filter is impaired.

The reason why a filter that maintains its strength even at high temperatures is obtained by a bond containing lithium oxide (Li myo) is because cordierite and β-spodumene (Li20・AltO1
The correlation between 4SiO and 4SiO is complicated (Hiroshi Motoki).
Fine Ceramics P3101976 Gihodo) Although it is not clear, it is estimated as follows.

Alumina (A) containing lithium oxide (Limb) of the present invention
A considerable portion of the components of the bonding part of the filter, which are mainly composed of t*Om ) and silica (Sin, ), becomes vitrified during firing to form a strong bond between the aggregates. This glass contains most of lithium oxide and has a lower melting point than the aggregate, and crystals form in the glass when it is cooled afterwards.

The generated crystals have a low coefficient of thermal expansion, and the joint as a whole has a coefficient of thermal expansion close to that of cordierite aggregate. A cordierite ceramic filter with low residual strain caused by differential expansion and high strength at room temperature can be obtained.

Adding β-spodumene to the powder raw material that forms the joint is convenient for avoiding uneven distribution of lithium oxide, and even if β-spodumene remains in the filter material, it reduces the coefficient of thermal expansion of the entire joint. This is because the addition of cordierite powder is preferable to bring the coefficient of thermal expansion of the bonded portion close to that of the aggregate.

Furthermore, even at high temperatures of about 1000° C., the bonded portions have a relatively large amount of crystalline components, so the strength is maintained without softening.

The reason why it is preferable to use cordierite aggregate crystallized from glass in the method for manufacturing a cordierite gas filter of the present invention is that even though this aggregate requires an elaborate process, Because it is possible to obtain aggregate with a low coefficient of thermal expansion, and because the coefficient of thermal expansion is approximately % smaller than that of cordierite aggregate produced by normal firing, it is possible to obtain a cordierite filter material with a low coefficient of thermal expansion and particularly excellent thermal shock resistance. It is convenient because it provides a filter for elite gases, and the dense aggregate makes it a filter with excellent corrosion resistance.
This is because a cordierite gas filter suitable for use in a particularly harsh atmosphere at high temperatures can be manufactured.

Magnesia clinker, Bayer alumina, silica sand, etc. can be preferably used as raw materials for the cordierite aggregate crystallized from this glass. It is best to quickly cool the glass and then heat it to crystallize it.

As the synthetic cordierite aggregate, baked crystals made from talc, clay, and aluminum hydroxide are preferably used.

In order to obtain cordierite aggregates with an apparent porosity of 10% or less, it is economical to sufficiently sinter and compact the synthetic cordierite during the manufacturing stage of normal synthetic cordierite, and add zircon powder to improve sinterability. Raw materials with improved properties may also be used.

Commercially available synthetic cordierite usually has a porosity greater than 10% and cannot be used as is as an aggregate for the cordierite gas filter of the present invention.

For this reason, there is a method of re-firing to make it densified, but after various studies, we found that for aggregates whose apparent porosity is not so large, colloidal solutions such as alumina sol, silica sol, titania sol, and zirconia sol can be used to make cordierite bones. By impregnating the material, the apparent porosity of 10% or less can be converted to porosity, and if the porosity can be reduced to 10% or less, it can be used as the aggregate of the cordierite gas filter of the present invention without any problems. The manufactured filter has low ventilation pressure loss and high strength.

It is preferable to use reduced pressure to sufficiently impregnate the colloidal solution, and it is also possible to repeat the impregnation after drying the aggregate to further densify it.

For the purpose of the present invention, after impregnating aggregate with a colloidal solution, once the colloidal solution impregnated into cordierite aggregate is gelled or dried, it can be used as is as aggregate.

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

However, impregnating these colloid aqueous solutions after forming a tubular filter, for example, will block the pores in the filter that should be used as gas flow paths, resulting in a filter with a large ventilation pressure loss, which is not preferable.

The reason why the ventilation pressure loss decreases when the apparent porosity of the cordierite aggregate is set to 10% or less is presumed to be as follows.

First, the flow of gas passing through a ceramic filter is expressed by the equation (K
If the gas passing through the filter is a laminar flow, the ventilation pressure loss ΔP across the filter is expressed by the following equation (Fine
Particle Measure-went, C
1yde Orr Jr, et al, Chapter
er 7. TheMacmillan Co, Ne
w York 1959) @”'v”JgcL
/2μuL-)(ΔP/L) [t''/(1-E)
”] where Sv is the surface area per unit volume of the solid, g 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, and is the velocity in the filter. The length of the meandering capillary, ε, is the porosity, and approximately has a relationship of uC·(u/ε)(L, /L).

In other words, the ventilation pressure loss of gas passing through a filter can be approximated as being proportional to the square of the surface area of particles in a unit volume. Therefore, in order to reduce the ventilation pressure loss of a filter, it is necessary to increase the By reducing the surface area to the minimum necessary size, the ventilation pressure loss can be reduced.

In addition, in sintered bodies, when the apparent porosity is less than 10%, the air permeability becomes almost negligible and becomes small (Porous Materials, Kondo Ren-Mato, Gihodo Publishing Co., Ltd., 1973).
The pores in the particles whose porosity is 10% or less do not participate in ventilation and do not cause ventilation pressure loss.

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

In the case of a tubular body, the wall thickness of the gas filter is preferably 5 mm or more, since if the wall thickness is made too thin, it will be damaged by the gas pressure of backwashing due to repeated backwashing and regeneration.

In order to further improve air permeability and reduce ventilation pressure loss, it is best to mix into the raw material a pore-imparting material that is burned off during firing and forms pores. It is preferable to mix in coke powder, especially pitch coke powder, which is easy to obtain, is suitably hard, and does not adversely affect moldability.

The main purpose of mixing an organic binder into raw materials is to impart strength to the formed body, making it easier to mold, and to avoid damage when transporting the formed body. It also contributes to increasing porosity.

Isostatic press molding, semi-wet tamping molding, extrusion molding, etc. can be used as the filter molding method. Of these, isostatic press molding is a molding method that is conventionally suitable for manufacturing dense sintered bodies. Although there are no examples of it being used as a method for forming porous filters, it is possible to omit the drying process, it is possible to form large tubular filters, and the productivity is good, so it is suitable for manufacturing filters. is also a preferred molding method.

Firing is often carried out in a tunnel kiln, but a shuttle kiln may also be used, and the firing temperature range is 1310 to 1380.
It is preferable to set it as ℃.

If the firing temperature is lower than 1,310°C, the strength will be reduced due to insufficient sintering, and if it is higher than 1,380°C, the filter will deform due to its own weight during firing, and the porosity will decrease due to excessive sintering, which is not preferable.

The reason why the apparent porosity is set to 35% or more is because it is preferable to obtain practical air permeability as a filter.
The bending strength of 75 Kg/cm at 800°C is unprecedented for a cordierite trade ceramic filter with an apparent porosity of 35% or more.
This is because it is preferable in terms of improving the reliability of the filter.

However, when the thus obtained cordierite ceramic filter, which has high strength even at high temperatures, was actually used at high temperatures and its bending strength at room temperature was examined, it was found that the strength had decreased.

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 decreases due to some kind of tissue change in the joint.

ZrO* and/or Ti02I5I2 are added to this bond.
The purpose of adding these ingredients is to promote the crystallization of the joint by adding these components that act as crystal nuclei, and to crystallize the glass present in the joint during cooling during firing to create a stable state. It is something.

Due to the addition of these components, the presence of β-subodumene crystals was definitely 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 that without addition, but with addition A cordierite ceramic filter was obtained that exhibited stable strength and could be used repeatedly and reliably, without any tendency for strength to decrease during use, unlike those that do not.

Here, the amount of Zr0t and/or Ti0a added is preferably 0.5 to 12 wt%, particularly 1 to 10 wt% in total in the filter material, and if it is less than 0.5 wt%, the effect of stabilizing the strength is I didn't get much, and 12w
If it exceeds t%, the coefficient of thermal expansion of the filter becomes large, which impairs thermal shock resistance, which is not preferable.

The present invention will be further explained below with reference to Examples.

[Example] a, b, c as cordierite aggregates.

Seven types of d+er f+g were prepared.

a, magnesia, alumina and silica sand 2MgQ・2A
A mixture of I*015SiOs having a cordierite composition is electrically melted using a carbon electrode, and the melt is poured into water and rapidly cooled to form a cordierite composition glass, which is then taken out and crushed into granules. It was made of glass.

This was put on a trolley and passed through a tunnel kiln, which produced approximately 1,380
It was heat-treated at ℃ for 10 hours to crystallize it.

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

b, talc, clay, aluminum hydroxide and zircon fine powder as chemical components 2MgO・2AlzO* '5Si
A cordierite composition containing O□ as the main component and 3 wt% ZrO* was prepared, 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 kneaded. , extrusion molded into a rod-shaped body with an outer diameter of about 30 mm.

After drying the rod-shaped body, it is placed on a trolley and passed through a tunnel kiln.
The maximum temperature was maintained at 1360° C. for 10 hours to obtain synthetic cordierite. This is further crushed and classified, and 74 to 59
0 μm was taken out.

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

Fine powders of C1 talc, clay, and aluminum hydroxide are mixed to give a cordierite composition of approximately 2MgO・2A1tOs'5SiOi, and 2 parts by weight of methyl cellulose and an appropriate amount of water are added to 100 parts by weight of the raw raw material. was added, kneaded, and extruded into a rod-shaped body having an outer diameter of about 30+++n+.

After drying, it is placed on a trolley and passed through a tunnel kiln to a maximum of 136
The mixture was kept at 0°C for 10 hours to obtain synthetic cordierite.

This was further crushed and classified, and 74 to 590 micron shoes were taken out.

The average particle size of this aggregate is 250 μm, and the apparent porosity is 1.
It was 2%.

d. Commercially available synthetic cordierite aggregate was crushed and classified, and particles of 74 to 590 μm were taken out.

The average particle size of these coarse particles is 230μ, and the apparent porosity is 3.
It was 0%.

The cordierite aggregate obtained in steps e and c was impregnated with alumina sol, impregnated under reduced pressure, and dried. After heating this aggregate at 1000°C, the apparent porosity was 8%.

The cordierite aggregate obtained in f+g'c was impregnated with silica sol and titania sol under reduced pressure and dried.

After heating these aggregates at 1000°C, the apparent porosity was 7% and 8%, respectively.

β-spodumene powder was prepared as follows. 85 wt% and 15 wt% of waxite and lithium carbonate powder, respectively.
They were mixed at a ratio of wt%, and further mixed and pulverized using a wet method. After drying, this filter cake was baked at a temperature of 1150° C. in an electric furnace to synthesize β-spodumene, which was pulverized and passed through a 325 mesh sieve.

Using 8 to 7 types of cordierite aggregates, the first
A tubular cordierite gas filter was prototyped under the conditions shown in Tables 1 and 2.

In the Examples and Comparative Examples shown in Table 1, the effects of the porosity of the aggregate and the amount of aggregate mixed mainly on the filter characteristics were investigated.

In this example, in addition to 10% by weight of clay, 10 to 25% by weight of fine cordierite powder of the same material and 5% by weight of fine β-subodumene powder were added to the bonding part, and pores were added to 100 parts by weight of this mixture. The grain size of the material is 20~
25 parts by weight of 100 μm pitch coke powder were added, and 5 parts by weight of a 50 wt% aqueous solution of phenolic resin as an organic binder were added and mixed, dried at 110° C., and then crushed to obtain a granular raw material with a particle size of 3 mm or less.

Using this raw material, a tubular body having an outer diameter of about 170 mm and an inner diameter of about 1400 mm and a length of about 850 mm was formed using an isostatic press at a pressure of 1000 g/cm''.

This tubular molded body was heated to a maximum temperature of 1320°C for 5 minutes in an electric furnace.
After firing for several hours, a tubular cordierite filter was obtained.

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

The characteristics investigated for each tubular cordierite filter are also shown in Table 1.

In addition, for other Examples and Comparative Examples, tubular filters were experimentally produced under the same conditions as described above except for the conditions shown in Table 1, and their 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.

Further, the bending strength was measured by a three-point bending test using a 14×20×100 mm test piece with a distance between fulcrums of 7IIIffl.

Acid resistance was examined by changes in bending strength after immersion in IN HffiSO, aqueous solution for 72 hours at room temperature.

Furthermore, the dust removal performance was tested by dispersing Red Garlic powder dust with an average particle size of approximately 50 μm in the air to a concentration of 40 g/Nm using a backwash type dust removal test device, and reducing the ambient temperature to 30 g/Nm.
Assuming 0°C, the air passing through the filter speed is 5 cm/see.
Each test was conducted for 100 hours.

In addition, the particle size distribution of red iron powder is 1 μm or less.
%, 7 wt% for 1-111 μm, 35 wt% for 10-40 μm
wt%, 40-100μm is 46wt%, 100-80
0 μm was 11 wt%.

Table 2 examines the effect of changing the components of the joint on the material properties and filter properties of the filter. Conditions not shown in the table of filter manufacturing conditions are the same as those in the above examples. According to similar conditions.

In Comparative Example 5, the bentonite contains an alkaline component and is easily vitrified during firing, so that a strong filter was obtained at room temperature.

In Table 2, the amount of ZrO* and/or TiOa added is in parts by weight relative to 100 parts by weight of the total weight of aggregate and other binding components.

To check whether there is a decrease in strength during use, bending strength test pieces cut from ceramic filters are
After being kept in an electric furnace at 00°C for 24 hours, the bending strength at room temperature was measured.

As a result, although the initial strength of the ceramic filter with zirconia and/or titania added to the bonded portion was slightly lower, no decrease in strength was observed even after heat treatment.

[Effects of the Invention] The filter for cordierite gas of the present invention and the method for producing the same have excellent thermal shock resistance and corrosion resistance, low ventilation pressure loss, and high strength even at high temperatures of about 800°C. A cordierite gas filter suitable for gas dust removal and its manufacturing method were presented.

In the present invention, aggregate with a low porosity of 10% or less,
In particular, by using cordierite aggregate crystallized from glass, the ventilation pressure loss of the filter is reduced.
The combination of low-porosity aggregate and lithium oxide-containing joints results in high strength even with high porosity, which maintains this strength even at high temperatures, and provides excellent corrosion resistance, especially acid resistance. A filter for elite gases has been realized. The low ventilation pressure loss of the filter means that the processing capacity for dust-containing gas can be increased even with the same filter device, and the sufficient strength of the filter greatly reduces the risk of filter damage during installation and maintenance of the filter device. This has the effect of improving the reliability of the device.

In the cordierite gas filter of the present invention,
There was a tendency for the strength to decrease when used at high temperatures, but by adding Ties or Zr0t to the joint, the unstable glass phase in the joint is converted into crystals during firing, which reduces the tendency for the strength to decrease. No reliable filter could be improved.

Furthermore, it has become clear that silicon carbide filters, which are currently considered promising, suffer from oxidation due to water vapor contained in the combustion gas, leading to blockage of pores and increased ventilation pressure loss. However, the cordierite gas filter manufactured by the manufacturing method of the present invention has excellent durability in an acidic corrosive gas atmosphere containing water vapor, NOx, SOx, etc. such as coal combustion gas, and is suitable for power generation. It can be preferably used in fluidized bed boilers that burn coal, as well as in dust removal from synthesis gas in pressurized fluidized bed boilers and coal gasifiers.

The cordierite gas filter of the present invention can be widely used to remove dust from various high-temperature dust-containing gases discharged by industries that use high temperatures, and can recover thermal energy that could not be recovered due to dust and was wasted. This makes it possible to use them effectively.

In addition, it is easy to remove NOx and SQx from the removed high-temperature gas, and the separated dust is recovered in a dry state, making it easier to use it effectively.It has great industrial benefits. It is.

Claims (13)

[Claims] (1) Composed of cordierite aggregate of 50 wt% or more, with an apparent porosity of 10% or less and a particle size of 74 μm or more, and a bonding part, where the main component of the bonding part is silica (Si).
O_2) and alumina (Al_2O_3), and lithium oxide (LiO) is 0% of the weight of the entire filter.
．． A filter for cordierite gas characterized by containing 0.05 to 1 wt%. (2) The filter for cordierite gas according to claim 1, containing 0.2 to 0.6 wt% of lithium oxide based on the weight of the entire filter. (3) In claim 1 or 2, the cordierite aggregate has a generally cordierite composition (2MgO・2Al
A filter for cordierite gas, which is a cordierite aggregate crystallized from glass having _2O_3.5SiO_2). (4) In claim 1 or 2, the cordierite aggregate contains alumina sol,
A filter for cordierite gas which is impregnated with silica sol, titania sol, zirconia sol, or a mixture of two or more thereof, and has an apparent porosity of 10% or less when fired. (5) The filter for cordierite gas according to any one of claims 1 to 4, wherein the filter has a porosity of 35% or more and a bending strength at 800°C of 75 kg/cm^2 or more. (6) In any one of claims 1 to 5, in the joint portion, 0.5 to 12
A cordierite gas filter to which wt% of TiO_2 and/or ZrO_2 is added. (7) The filter for cordierite gas 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) 50 wt% or more of cordierite aggregate with an apparent porosity of 10% or less and a particle size of 74 μm or more,
Lithium oxide is 0.05% of the weight of the entire filter.
Powder containing lithium oxide, clay, and cordierite powder with a particle size of less than 74 μm are mixed together to form a bonding part, and an organic binder is added and molded so that the amount is ~1wt%. 1. A method for producing a filter for cordierite gas, the method comprising: (9) In claim 8, the cordierite aggregate with an apparent porosity of 10% or less is composed of magnesia, alumina, and silica sand with an approximately cordierite composition (2MgO・2A
1_2O_3・5SiO_3), electrically melted, rapidly cooled to form glass, and then crystallized by heat treatment. (10) The method for producing a filter for cordierite gas according to claim 8 or 9, wherein the powder containing lithium oxide is β-spodumene powder. (11) A method for manufacturing a cordierite gas filter according to any one of claims 8 to 11, wherein coke powder is mixed into the raw material as a pore-providing material that forms pores by burning and burning out. (12) Production of a cordierite gas filter according to any one of claims 8 to 11, wherein the filter is formed into a tubular shape by isostatic pressing using a metal core mold and a pipe-shaped rubber outer mold. Method. (13) The method for producing a cordierite gas filter according to any one of claims 8 to 12, wherein the firing is performed at 1310 to 1380°C.