JP2001246209A - Gas permeable member, method for manufacturing the same dust removing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas permeable member having gas cleaning function for detoxifying harmful gas, a method for manufacturing the same and a dust removing apparatus equipped with a gas cleaning filter including the gas permeable member. SOLUTION: The dust removing apparatus is equipped with the gas cleaning filter comprising the gas permeable member constituted of ceramic fibers between which metal oxide catalyst partiles are held.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas permeable member made of ceramic fiber carrying a catalyst, a method for producing the gas permeable member, and a dust removing device provided with a gas purifying filter including the gas permeable member. In particular, it allows permeation of flue gas containing harmful gases such as nitrogen oxides and organochlorine compounds,
A gas permeable body having a gas purifying function of decomposing and rendering harmless by the action of a supported catalyst, a method for producing the gas permeable body,
The present invention relates to a dust removal device provided with a gas purification filter including the gas permeable body.

[0002]

2. Description of the Related Art A dust remover equipped with a gas purifying element having a function of decomposing and purifying harmful gases such as nitrogen oxides and organochlorine compounds is a combustion facility that uses fossil fuels such as waste incinerators and coal. It is useful for decomposing and detoxifying nitrogen oxides and organochlorine compounds in flue gas discharged from various industrial furnaces for iron and metallurgy, cement firing furnaces, refractory firing furnaces, petroleum refining facilities, chemical plants, etc. is there.

[0003] Nitrogen oxides and PC contained in flue gas
Honeycomb is a well-known form of a catalyst carrier for decomposing organic chlorine compounds such as DD (polychlorinated dibenzodioxin) and PCDF (polychlorinated dibenzofuran). For example, with respect to nitrogen oxides, a honeycomb supporting a catalyst component is housed in a container, and in a cell of the honeycomb, a combustion exhaust gas containing ammonia previously injected is passed,
Many plants having a dust removing device that decomposes nitrogen oxides into nitrogen gas and water and renders them harmless have already been installed.

A catalyst element for decomposing a cyclic organic chlorine compound such as dioxin in a combustion exhaust gas discharged from an incineration plant is disclosed in, for example, JP-A-6-386.
There is an application in the gazette for the shape. These honeycombs have been manufactured by, for example, extruding a slurry-like material made of a metal oxide powder with a mold or the like, followed by a drying and firing process.

FIG. 5 shows a typical example of a honeycomb element. Commonly used honeycomb elements are, for example, those having a cell pitch of 5 mm and dimensions of about 200 mm, 200 mm, and 500 mm, respectively, in height, width, and height, respectively, but FIG. Above, it is typically 4 cells x 4 cells.

The honeycomb element 112 has one opening 113
From the combustion exhaust gas containing ammonia gas in the gas inflow direction 114 indicated by the arrow in the figure, and exposed to the gas passage wall surface in the cell or contacted with the catalyst at a depth of approximately 20 μm from the wall surface to oxidize nitrogen in the combustion exhaust gas. The thing is, by the action of the catalyst,
After being reduced to water and nitrogen gas, the gas is discharged from the other opening 115 of the gas inflow path of the honeycomb element 112 in a gas outflow direction 116 indicated by an arrow in the drawing.

However, among the nitrogen oxides in the combustion exhaust gas passing through the gas passage in the honeycomb element 112, a large amount of nitrogen oxides are discharged from the opening 115 without contacting the catalyst. The rate of reduction of nitrogen oxides per unit (denitration rate) remains at about 15 to 30%. Therefore,
It is general that the honeycomb group is configured in multiple stages to increase the denitration rate.

[0008]

However, in a conventional honeycomb supporting a catalyst component, a catalyst which plays a role of decomposing nitrogen oxides and organic chlorine compounds is dispersed and supported in these honeycombs. Most of the catalysts were buried in the honeycomb structure and did not function as a catalyst, except for the catalyst that was exposed on the wall of the gas flow path or was at a depth of about 20 μm from the flow path wall. .

Further, in the case of a conventional honeycomb supporting such a catalyst, even when a clean gas containing no dust, which has been removed in advance by a bag filter or the like, is allowed to pass through, a long period of time is required on the gas flow path wall surface of the honeycomb. It was necessary to secure a gas flow path cross-sectional area of at least about 3 mm x 3 mm in consideration of a decrease in the flow path cross-sectional area caused by the gradual accumulation of dust. In addition, dust accumulates on the gas flow path wall of the honeycomb, which covers the chemically active catalyst surface with dust, impeding contact between the gas and the catalyst, resulting in a decrease in catalyst performance. This requires periodic regeneration of the catalyst-carrying honeycomb or replacement with a new catalyst-carrying honeycomb.

Further, in a plant that does not have a dust removing means such as a bag filter on the upstream side of the gas, it usually has a gas flow area of about 10 mm × 10 mm in consideration of a reduction in the cross sectional area of the gas flow path due to adhesion of dust. Although a honeycomb is used, the specific surface area is smaller than that of a honeycomb that allows a clean gas to pass therethrough, and the apparatus is enlarged.

Further, in order to flow a gas containing a large amount of dust through the flow passage, a device for removing dust adhering to the surface of the flow passage is required. As in the case of the honeycomb which gradually accumulates on the flow path wall surface and allows the clean gas to pass through, it is necessary to periodically perform a honeycomb regeneration process or a replacement operation for a new honeycomb.

Accordingly, the present invention provides a gas purifying filter having a high functioning ratio of the supported catalyst, a long catalyst life, and a filter function for removing dust. It is an object of the present invention to provide a method for manufacturing a filter and a dust removing device provided with the gas purification filter.

[0013]

In order to achieve the above object, a gas permeable body 4 according to the first aspect of the present invention is composed of ceramic fibers 1 as shown in FIG. The metal oxide catalyst particles 3 are retained.

Since ceramic fibers holding metal oxide catalyst particles are provided, for example, a gas such as a combustion exhaust gas containing nitrogen oxides and organochlorine compounds flows through the ceramic fibers, and does not cause drifting. The dust contained in the gas is trapped on the gas inlet side wall of the gas permeable body and does not enter the inside of the gas permeable body 4, and the metal oxide catalyst particles dispersed and supported substantially uniformly are removed. Almost all can function effectively and, for example, nitrogen oxides and organochlorine compounds in a large amount of gas can be decomposed for a long time.

The gas permeable body according to the second aspect of the present invention
2. The gas permeable body according to claim 1, wherein the metal oxide catalyst particles have a titanium oxide carrier carrying a metal oxide containing at least one of tungsten trioxide and vanadium pentoxide as a main component.

Since the metal oxide is supported as described above,
In particular, nitrogen oxides and organochlorine compounds in the gas passing through the gas permeable body can be efficiently decomposed. Vanadium pentoxide or tungsten trioxide can be formed into a desired shape from a powdery state by using titanium oxide having an excellent affinity for them as a carrier, and can be firmly supported by the gas permeable body. Further, the metal oxide may contain tungsten trioxide and vanadium pentoxide as main components.

The gas permeable member according to the third aspect of the present invention
In the gas permeable body according to claim 1 or 2,
The average particle diameter of the metal oxide catalyst particles is 0.1 μm or more 2
0 μm or less.

Since the average particle diameter of the metal oxide catalyst particles is set as described above, the specific surface area of the particles in contact with the gas can be made sufficiently large.

According to a fourth aspect of the present invention, there is provided a gas permeable body according to any one of the first to third aspects, wherein the ceramic fibers are made of alumina, silica, magnesia, zirconia, The main component is at least one selected from the group consisting of silicon carbide and silicon nitride.

Since the ceramic fiber is constituted as described above, the gas permeable body is excellent in heat resistance and corrosion resistance, and can reduce the production cost.

The gas permeable body according to the invention according to claim 5 is
The gas permeable body according to any one of claims 1 to 4, wherein the porosity is 75% or more and 95% or less.

Since the porosity is 75% or more and 95% or less, a large amount of gas can be passed while minimizing the pressure drop while maintaining sufficient strength. Further, even if the amount of the metal oxide catalyst particles carried is large, the rise in pressure loss of the gas passing through the gas permeable body can be suppressed to be small.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a gas permeable body according to any one of the first to fifth aspects. In a metal sol solution containing at least one of silica sol and titanium sol,
The method is characterized in that the ceramic fibers and the metal oxide catalyst particles are dispersed, the solution is cast into a mold, dried, released from the mold, and further fired.

According to such a production method, the ceramic fibers can be firmly bonded to each other and the ceramic fibers and the catalyst particles, the strength (particularly, tension and shear) of the gas permeable body can be increased, and the life of the gas permeable body can be improved. Can be lengthened. Here, combining the ceramic fibers and the ceramic fiber and the catalyst particles means that the fibers are
This refers to, for example, bonding or sticking the fiber and the catalyst. Since the metal sol has viscosity, it has an action of bonding and sticking.

According to a seventh aspect of the present invention, there is provided a dust removing device including a gas purifying filter comprising the gas permeable body according to any one of the first to fifth aspects; A purifying filter having air permeability; configured to introduce dust-containing gas from one surface of the gas purifying filter, pass through the wall of the gas purifying filter, and take out clean gas from the other surface. .

The dust-containing gas is introduced from one side of the gas purifying filter and discharged from the other side, so that dust in the dust-containing gas can be removed. Furthermore, since the gas purifying filter is made of the gas permeable body according to any one of claims 1 to 5, for example, nitrogen oxides and organic chlorine in a large amount of corrosive dust-containing gas at high temperature. The compound can be efficiently decomposed for a long time, and the pressure drop of the dust-containing gas can be minimized.

According to an eighth aspect of the present invention, in the dust removing apparatus of the seventh aspect, the gas purification filter is formed in a hollow cylindrical shape; the one surface is an inner wall surface of the hollow cylinder, The other surface is an outer wall surface of the hollow cylinder.

Since the gas purifying filter is formed in a hollow cylindrical shape, the pressure at which dust gas is introduced can be increased. Further, if the dust gas is fed into the hollow portion, the feeding pressure of the dust gas can be further increased, and the dust collected and accumulated on the hollow inner wall surface of the gas purification filter can be easily removed.

According to a ninth aspect of the present invention, there is provided the dust removing apparatus according to the seventh or eighth aspect, further comprising a back washing means for removing dust adhering to the inner wall surface by back washing.

Since the backwash means is provided, the dust collected and deposited on the surface of the gas purification filter on which the gas is introduced is removed, thereby maintaining the dust removal ability and purification ability of the gas purification filter, An increase in pressure loss when passing through the gas purification filter can be prevented. The reverse cleaning refers to removing dust accumulated on the gas cleaning filter with a cleaning gas passing through the gas cleaning filter in a direction opposite to that of the dust-containing gas, and cleaning the gas purification filter.

The dust removing device according to the tenth aspect is the seventh aspect of the present invention.
The dust removal apparatus according to any one of claims 1 to 9, further comprising: an accumulation unit that is disposed vertically below the gas purification filter and accumulates dust removed from the dust-containing gas.

[0032] The dust removing apparatus according to the eleventh aspect is the seventh aspect.
The dust removal apparatus according to any one of claims 1 to 10, wherein the mass of the metal oxide catalyst particles is between 20 mass% and 60 mass% with respect to the total mass of the gas purification filter.

Since the mass of the metal oxide catalyst particles is between 20% by mass and 60% by mass with respect to the total mass of the gas purification filter, harmful substances in the dust-containing gas are maintained while maintaining the strength of the gas purification filter. The gas component sufficiently contacts the metal oxidation catalyst particles to purify the harmful gas.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding members are denoted by the same or similar reference numerals, and overlapping description will be omitted.

FIG. 1 shows a first embodiment of the present invention, a gas permeable body 4 made of ceramic fibers 1 carrying catalyst particles 3 as metal oxide catalyst particles of the present invention.
Note that both the ceramic fiber 1 and the catalyst particles 3 shown in the figure have a fiber diameter and an average particle diameter of at least 100 μm.
It is an aggregate in which the following microscopic substances are mixed and laminated in large quantities.Each single element is a microscopic substance that cannot be shown, but in consideration of convenience in describing the present invention, a large shape in illustration It is expressed in.

As shown in the figure, the gas permeable body 4 made of ceramic fibers 1 supporting catalyst particles 3 is preferably made of ceramic fibers having a fiber diameter of 1 μm to 10 μm and a fiber length of at least 10 mm. A ceramic fiber 1 occupying 50% or more of the entire ceramic fiber is composed of a fibrous formed body 2 bonded to each other. Fibrous molding 2
Is formed by forming the above-mentioned ceramic fibers into a thick nonwoven fabric.

The gas permeable member 4 has a porosity of 75% or more and 95% or more.
% Or less, and in the fibrous formed body 2 having a thickness of at least 10 mm or more, that is, a minimum thickness Tmin of 10 mm or more, vanadium pentoxide or tungsten trioxide or a compound of both. The catalyst particles 3 having an average particle diameter of 0.1 μm or more and 20 μm or less are dispersed and supported substantially uniformly.

Combustion containing nitrogen oxide or an organic chlorine compound such as PCDD (polychlorinated dibenzodioxin), PCDF (polychlorinated dibenzofuran), or both harmful gases from one wall surface of the gas permeable body 4, that is, the gas inlet surface 5. The exhaust gas is allowed to permeate in the direction indicated by the arrow in the figure, that is, in the gas inflow direction 6. The harmful substances contained in the flue gas are decomposed by the catalyst particles 3 and made harmless (the harmlessness is referred to as harmless in practice). In the direction indicated by the arrow in FIG.

The catalyst particles 3 contained in the ceramic fiber gas permeable body 4 supporting the catalyst are desirably contained in an amount of 20% by mass or more and 60% by mass or less based on the total mass of the gas permeable body 4. , 30 to 50% by mass.
The reason is that the ratio of the catalyst particles 3 in the gas permeable body 4 is 20%.
If the amount is less than 10% by mass, the nitrogen oxides and organochlorine compounds in the combustion exhaust gas flowing through the gas permeable body 4 do not sufficiently contact the catalyst particles 3 and are discharged without being sufficiently decomposed. is there. When the ratio of the catalyst particles 3 in the gas permeable body 4 exceeds 60% by mass, the ratio of the powdery substance in the fibrous formed body 2 made of the ceramic fibers 1 increases, and the strength of the gas permeable body 4 increases. Is undesirably reduced.

The gas permeable body 4 formed as described above is characterized in that the flue gas containing nitrogen oxides and the organochlorine compound emits fibrous material from one wall surface to the other wall surface, that is, from the gas inlet surface 5 to the gas outlet surface 7. Since the catalyst particles 3 flow through the inside of the molded body 2, almost all of the catalyst particles 3 dispersed and supported substantially uniformly inside the fibrous molded body 2 function effectively.

As in the prior art honeycomb, only the catalyst exposed on the wall surface and the catalyst from the wall surface to a depth of 20 μm function, and the nitrogen oxides and the organic chlorine compounds in the combustion exhaust gas passing through the honeycomb flow passage are removed. In contrast to the case where most are discharged without contacting the catalyst, in the gas permeable body 4 according to the embodiment of the present invention, nitrogen oxides and organic chlorine compounds contained in the exhaust gas are decomposed by contacting the catalyst particles 3. Opportunities are greatly increased. In other words, the gas permeable member 4 can decompose nitrogen oxides and organochlorine compounds equivalent to those of the honeycomb with a catalyst amount of about one third to one tenth of that required for the honeycomb. .

When the gas permeable member 4 formed as described above is used, dust contained in the flue gas is trapped at the gas inlet face 5 of the gas permeable member 4 and does not enter the gas permeable member 4. Therefore, as in the case of the honeycomb, the catalyst is covered with the dust by the dust accumulated on the wall surface and cut off from the gas,
The phenomenon that the function of the catalyst is deteriorated does not occur. Gas inlet surface 5
A filter element may be arranged for the purpose of trapping dust on the upstream side of the filter element, and the replacement period of only this filter element may be shortened.

The fibers constituting the gas permeable body 4 have any heat resistance of at least 500 ° C., have corrosion resistance to combustion exhaust gas, and can be any ceramic fiber as long as it can form a thick nonwoven fibrous formed body. Can be used. Ceramic fibers are alumina, silica,
The main component is at least one selected from the group consisting of magnesia, zirconia, silicon carbide, and silicon nitride. These ceramic fibers are excellent in heat resistance, corrosion resistance and marketability.

The catalyst particles 3 dispersed and supported on the gas permeable body 4 may be formed in advance into catalyst particles using titanium oxide as a carrier having an excellent affinity for vanadium pentoxide or tungsten trioxide. Good.

As a method for producing the ceramic fiber gas permeable body 4 in which the catalyst particles 3 are dispersed and supported, for example, a single component of a metal sol such as alumina sol, silica sol, titanium sol or a composite component thereof is used. And catalyst particles 3 in an aqueous solution comprising a surfactant such as starch.
While stirring and adding, the ceramic fibers are sequentially charged to form a slurry-like liquid mixture of the catalyst particles 3 and the ceramic fibers, and the ceramic fibers and the ceramic fibers and the catalyst particles 3 are adhered to each other. A molded product can be obtained by pouring into a mold through which the liquid component can be trapped and permeating the liquid component, forming the molded product, removing the molded product after the drying process, and performing a baking process.

Alternatively, more ceramic fibers are put into the mixed solution comprising the metal sol, the surfactant and the catalyst particles to form a plastic gel material comprising the catalyst particles and the ceramic fibers, and thereafter, extrusion molding or press molding. Then, a molded body may be obtained by performing a drying treatment and a baking treatment.

As described above, the gas permeable member 4 made of ceramic fiber carrying a catalyst, which is the first embodiment of the present invention, has many advantages as compared with the honeycomb catalyst carrying the prior art. Have.

FIG. 2 is a view showing a square plate-shaped gas permeable body 4 made of ceramic fiber carrying the catalyst according to the present invention shown in FIG.
2 shows a dust removing apparatus 11 using a gas purification filter 15 according to a second embodiment of the present invention, which is molded from the following. Dust remover 11
Not only removes dust, but also decomposes and purifies harmful gases such as nitrogen oxides and organic chlorine compounds.

The flue gas containing nitrogen oxides and organochlorine compounds passes through a gas duct 12 and passes through an ammonia injection valve.
The mixed gas is mixed with ammonia injected from 19, guided into the apparatus through a gas inlet 13, and a plurality of gas purification filters 15 manufactured by forming the gas permeable body 4 (see FIG. 1) according to the present invention into a plate shape. It passes in the gas inflow direction 14 indicated by the arrow in the figure. At this time, the nitrogen oxides and the organic chlorine compounds are decomposed and made harmless by the catalyst particles 3 (see FIG. 1) dispersed and supported inside the gas purification filter 15 and flow out of the gas purification filter 15. The detoxified gas that has flowed out of the gas purification filter 15 is discharged from a gas outlet 17 in a gas outflow direction 18 indicated by an arrow in the drawing via a gas collecting section 16.

When the dust removing device 11 is used only for decomposing the organic chlorine compound, it is not necessary to inject ammonia. The dust removal device 11 is a gas purification filter.
It has a container structure for storing 15.

The thickness of the gas purifying filter 15 formed of the gas permeable body according to the present invention in the gas flow direction is as follows:
In order to ensure a residence time in which the nitrogen oxides and the organochlorine compounds contained in the combustion exhaust gas can sufficiently contact the catalyst dispersed and supported in the gas purification filter 15, at least 10
It is desirable to set it to mm or more.

The gas temperature at the gas inlet 13 of the dust removing device 11 is 300 ° C., which is the temperature range in which the catalyst functions most efficiently.
It is desirable to control the temperature within a range of ± 150 ° C. Further, the sulfurous acid gas in the combustion exhaust gas is oxidized to sulfuric acid, and the ammonium sulfate salt generated by the reaction between the sulfuric acid and the injected ammonia poisons the catalyst. It is more preferable to set the temperature range to 250 ° C. or higher as a temperature range in which the possibility can be excluded.

The gas purifying filter 15 according to the present invention
Has a higher decomposition ability of nitrogen oxides and organochlorine compounds than a conventional honeycomb supporting a catalyst, and a single stage of the catalyst zone conventionally provided in a plurality of stages can exhibit its function sufficiently.

FIG. 3 shows a gas purifying filter 21 according to a third embodiment of the present invention, which comprises a gas permeable member made of ceramic fibers carrying a catalyst. Unlike the plate shape shown in FIG. Is formed into an open cylindrical shape.

The flue gas containing nitrogen oxides and organochlorine compounds flows from the gas inlet 22 in the gas inflow direction 23 indicated by the arrow in the figure, and from the inner wall surface 24 of the cylindrical wall to the outer wall surface 25 of the cylindrical wall. The nitrogen oxides and the organic chlorine compounds in the combustion exhaust gas are decomposed and made harmless by the catalyst dispersed and supported in the ceramic fibers constituting the cylinder, flowing in the gas outflow direction 26 indicated by the arrow in the figure. It flows out of the wall surface 25. In this case as well, in order to secure a residence time in which the catalyst can be sufficiently contacted with the catalyst dispersed and supported in the gas permeable body, it is desirable that the cylindrical shape has a thickness of at least 10 mm or more.

The gas purifying filter formed from the gas permeable body is a so-called candle type having a cylindrical shape, one end being open and the other end being closed. The open end is supported by a tube sheet, and the open end is opened. The structure may be such that the gas purifying filter is hung such that the portion is at the top and the closed end is at the bottom.

When the gas permeable body according to the present invention is formed into, for example, a plate shape as shown in FIG. 1, the same vertical, horizontal and horizontal dimensions as those of the honeycomb element 112 shown in FIG.
By setting the height dimension, the honeycomb of the existing denitration apparatus can be removed and replaced with the ceramic fiber gas permeable body according to the present invention. Since the gas permeable body thus replaced has a higher function of decomposing nitrogen oxides and organic chlorine compounds than the case of a honeycomb, even if the honeycomb group having a step configuration is, for example, a single-stage honeycomb group, a honeycomb having a three-stage configuration is used. The same or better resolution of nitrogen oxides and organochlorines as in the group is obtained.

Referring to FIG. 4, a dust removing device 31 according to a fourth embodiment of the present invention having a gas purifying filter 35 formed in a hollow cylindrical shape will be described. Inside the dust removing device 31, a gas permeable body 4 made of air-permeable ceramic fiber is provided.
30 hollow cylindrical gas purifying filters 35 formed from (see FIG. 1) are arranged in parallel with each other and vertically. Both ends of each gas purification filter 35 are supported by an upper tube sheet 47 and a lower tube sheet 48 also provided in the dust removing device 31. The support portions of the upper tube sheet 47 and the lower tube sheet 48 that support the gas purification filter 35 are sealed by an appropriate method.

The ceramic fiber 1 (see FIG. 1) used in the gas purifying filter 35 of the present invention is not particularly limited as long as it can be formed into a nonwoven fabric, but has heat resistance of about 500 ° C. and corrosion resistance to exhaust gas. This is preferable because the gas purification filter 35 has durability.

It is preferable from the viewpoint of corrosion resistance and availability if the material of the ceramic fiber 1 contains at least one selected from the group consisting of alumina, silica, magnesia, zirconia, silicon carbide and silicon nitride. Further, assuming that 50 to 100% of the total mass of the ceramic fiber 1 is in the range of 1 to 10 μm and the fiber length is 10 mm or more, when the gas purification filter 35 is formed, This is preferable because the strength of the gas purification filter 35 is increased.

Note that, between the ceramic fibers 1 constituting the gas purifying filter 35, tungsten trioxide using titanium oxide as a carrier is used with respect to the total mass of the gas purifying filter 35.
The catalyst particles 3 (see FIG. 1) as the metal oxide catalyst particles of the present invention, which are supported at 50% by mass, are held. The catalyst particles 3 preferably account for 20 to 60% by mass of the total mass of the gas purification filter 35. If the content is less than 20% by mass, harmful gas components (nitrogen oxides, organic chlorine compounds, hydrocarbons, carbon monoxide, etc.) in the dust-containing gas DG are reduced to 3
The harmful gas components pass through without contacting the satisfactorily, and are not preferable. On the other hand, 60% by mass
If the ratio exceeds the above range, the ratio of the ceramic fibers in the gas purification filter 35 decreases, and the strength of the gas purification filter 35 decreases, which is not preferable.

The catalyst particles 3 used in the gas purification filter 35 of the present embodiment need to be held between ceramic fibers. The catalyst particles 3 are appropriately selected according to the gas components contained in the dust-containing gas DG. For example, a metal oxide particle catalyst containing platinum or palladium is used to oxidize and render flammable components such as hydrocarbons and carbon monoxide in the dust-containing gas DG harmless. In particular, in dust removal equipment that treats dust-containing gas DG discharged from waste incineration equipment, etc.
When metal oxide catalyst particles are made of titanium oxide as a carrier and an oxide containing tungsten trioxide and / or vanadium pentoxide as a main component, dioxins can be decomposed and from the viewpoint of measures against dioxins. It is suitable.

The average particle size of the catalyst particles 3 is 0.1 to 20.
μm is preferred. When the average particle diameter of the catalyst particles 3 is less than 0.1 μm, the catalyst particles 3 supported between the ceramic fibers 1
Is not preferred because the amount of On the other hand, if the average particle diameter of the catalyst particles 3 exceeds 20 μm, the catalyst particles 3 are likely to settle when the gas purification filter 35 is manufactured via the slurry, and the catalyst particles 3 supported between the ceramic fibers 1
Is not preferred because the amount of

In the case of the present embodiment, as shown in the figure, a group of the gas purification filters 35 supported by the upper tube sheet 47 and the lower tube sheet 48 is arranged in one stage. By using a plurality of tube sheets 48, the gas purification filters 35 may be arranged in a plurality of stages vertically and vertically. Or
It can also be dealt with by appropriately changing the length, number, etc. of the gas purification filters 35. The apparatus outer wall 49 is provided with a gas inlet 33 into which the dust-containing gas DG enters and a gas outlet 37 through which the clean gas CG exits. Further, a dust hopper 50 as an accumulation means for accumulating dust 51 is attached to the lower tube sheet 48. A dust outlet 57 is attached to the bottom of the dust hopper.

In the case of the present embodiment, a gas purifying filter
35 is composed of 45% Al ₂ O _{3 and} 55% SiO ₂ with an average fiber diameter of
It is a non-woven fabric of ceramic fibers 1 having a length of 2 μm and a length of 10 mm. The gas purification filter 35 has an outer diameter of 17 cm and an inner diameter of 14 cm.
It is a hollow cylinder with a porosity of 90% and a length of 200 cm. As described above, 30 gas purification filters 35 are arranged in the dust removal device 31.

The porosity of the gas purification filter 35 is 75 to 95%.
This is preferable because the increase in pressure loss is small even if the amount of catalyst particles 3 carried is large. If the porosity of the gas purification filter 35 is less than 75%, the packing density of the ceramic fibers 1 per unit volume increases, so that the pressure loss of the gas passing through the wall of the gas purification filter 35 increases, (Not shown) requires a large-capacity blower (not shown), resulting in an increase in equipment costs and operating costs. On the other hand, if the porosity of the gas purification filter 35 exceeds 95%, the packing density of the ceramic fibers per unit volume becomes small, and the mechanical strength of the gas purification filter 35 becomes insufficient. There is a problem in point.

In the dust removing apparatus 31, the dust-containing gas DG is supplied to the gas inlet.
From 33, they are introduced into the inner wall surface 35A of each gas purification filter 35. Then, when entering the wall of the gas purification filter 35 through the inner wall surface 35A and exiting through the outer wall surface 35B, the dust 51 as dust on the inner wall surface 35A of the gas purification filter 35
(Unburned carbon, etc.) are collected. In this case, the large dust 51 falls downward due to inertia and gravity, and is collected in the dust hopper 50. In addition, many of the small dusts 51 aggregate and fall downward, but a part of the small dusts 51 is deposited on the inner wall surface 35A of the gas purification filter 35 (the deposited dust is not shown), and the gas passage pressure is reduced. Increase losses.

The dust removing device 31 includes a back washing device 52. The reverse cleaning device 52 includes a blower 53 for pumping a cleaning gas such as air or nitrogen gas, a tank 54 for storing the cleaning gas, and a gas outlet 37.
, And a cleaning gas supply line 56 connecting the nozzle 55 and the tank 54.

The dust 51 deposited on the inner wall surface 35A of the gas purification filter 35 can be removed by performing regular backwashing. In the backwashing, the cleaning gas is fed backflow pressure from the nozzle 55 of the gas outlet 37 and the inner wall surface 35 of the gas purification filter 35.
This is done by removing dust that has accumulated on A.
In the present embodiment, the pressure difference between the gas inlet 33 and the gas outlet 37 is
When 300 mmAq is exceeded, backwashing is performed by instantaneously feeding backwash gas under pressure.

Further, the harmful gas components contained in the dust-containing gas DG pass through the wall of the gas purification filter 35 from the inside to the outside, and the ceramic fibers of the gas purification filter 35
It is made harmless by contact with the catalyst particles 3 carried between the two. In the present dust removing device 31, the amount of the catalyst particles 3 carried is large, so that the catalytic action is maintained for a long time. The clean gas CG thus obtained flows out from the gas outlet 37.

In this embodiment, the gas throughput is about
700 Nm ³ / h, and the average filtered gas flow velocity on the wall of the gas purification filter 35 is about 1.75 cm / s. A combustion exhaust gas containing dioxin as a dust-containing gas was introduced into the dust removing device 31, and the dioxin concentration was measured. As a result, the gas inlet 33
Average dioxin concentration is 2ng-TEQ (TEQ is Toxic Equi
valents), the average dioxin concentration at the gas outlet 37 was confirmed to be 0.02 ng-TEQ, which was reduced to 1/100. Further, it was confirmed that dust contained in the combustion exhaust gas was captured and removed by the gas purification filter 35 and accumulated on the dust hopper 50.

The gas purifying filter of the dust removing apparatus 31 of the present embodiment is changed to a cordierite-based sintered body having a porosity of 40%, and the outer surface thereof has a different type (carrier) from that of the dust removing apparatus 31 of the present embodiment. The test was carried out with the same specifications as the dust removing device 31 of the present embodiment except that the catalyst supported different amounts (the same amount of titanium oxide) and different amounts (the same amount of titanium oxide). went. As a result, the gas processing amount was reduced to about 1 of the dust removal device 31 of the present embodiment. Further, the average dioxin concentration at the gas outlet 37 of the clean gas CG was also 1.6 ng-TEQ, and it was confirmed that the degree of harmful gas treatment was worse than that of the dust remover 31 of the present embodiment.

When there are a plurality of harmful gas components in the dust-containing gas DG handled by the dust removing apparatus 31 of the present embodiment, the main gas components are treated with the metal oxide catalyst particles of the gas purification filter 35. Alternatively, the remaining gas components may be processed by another gas processing device. For example, in dust-containing gas DG discharged from waste incineration facilities, etc., in addition to dioxins, NOX
If it is included, mainly dioxins are treated with metal oxide catalyst particles, and as an additional measure to further reduce the residual amount of NOX, an ammonia injection device is provided upstream of the gas inlet 33 and downstream of the gas outlet 37. Is also good.

As a method of manufacturing the gas purifying filter 35 made of the ceramic fiber 1 carrying the catalyst particles 3, a metal oxide is contained in a solution containing an inorganic adhesive, an organic binder, a surface treatment material and the like. A method for preparing a gas purification filter slurry by dispersing the catalyst particles 3 and ceramic fibers 1 of the product while dispersing them, pouring the slurry into a porous mold, drying, removing the mold from the mold, and firing. There is. The inorganic adhesive used to bond between the catalyst particles 3 and the ceramic fibers 1 and between the ceramic fibers 1 is not particularly limited. However, if a metal oxide gel is used, the catalyst function is not impaired and the gas purification filter is not damaged. This is preferable in that 35 can be molded.

According to the dust removing device 31, the dust containing gas DG is introduced into the gas purification filter 35. The introduction pressure of the dust-containing gas DG can be increased by introducing the dust-containing gas DG into the gas purification filter 35, and the dust collected on the inner wall surface 35A of the gas purification filter 35 can be removed. Becomes easier.

Since the dust removing device 31 can perform both dust removal and harmful gas treatment with one device, the installation space of the device can be saved as compared with a case where the dust removing device and the harmful gas treatment device are separately installed and operated. There is no need for piping to connect the devices, and the economic burden is small. In addition, operability and maintainability of the entire apparatus are improved as compared with the case where two apparatuses are operated.

Further, in the present dust removing device 31, the gas purification filter 35 is made of ceramic fibers 1 instead of a ceramic sintered body, so that the porosity of the gas purification filter 35 is increased to 75% or more and 95% or more. It can be:
Therefore, since the amount of catalyst can be increased while suppressing an increase in pressure loss, the ability to remove a large amount of gas and
It is possible to provide a dust removing device that is compatible with the ability to detoxify harmful gases contained in the dust containing gas DG.

[0078]

As described above, according to the gas permeable body of the present invention, the inside of the gas permeable body made of ceramic fibers holding the metal oxide catalyst particles is burned, for example, containing nitrogen oxides and organochlorine compounds. Since gas such as exhaust gas penetrates, almost all of the catalyst dispersed and supported inside the gas permeable body comes into contact with the gas without being cut off, and functions effectively. Also, it is possible to reduce nitrogen oxides and organic chlorine compounds in the combustion exhaust gas to a practically sufficient level.

Further, compared with the conventional type honeycomb supporting the catalyst, the combustion exhaust gas is allowed to pass through a relatively small volume, and the gas such as nitrogen oxides and organic chlorine compounds is decomposed more efficiently than before. Therefore, the size of the apparatus can be reduced, and in conjunction with the reduction in the amount of catalyst used, it greatly contributes to a reduction in the manufacturing cost of the apparatus.

The dust contained in the gas such as the combustion exhaust gas is trapped on the wall of the gas permeable body according to the present invention, and the dust does not penetrate inside the gas permeable body. As in the case of the honeycomb described above, the phenomenon that the catalyst is covered with the dust in the combustion exhaust gas and the catalytic function is not impaired does not occur, and the high catalytic function can be maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a perspective view of a plate-shaped ceramic fiber gas permeable body according to a first embodiment of the present invention.

FIG. 2 is a sectional view and a system diagram of an assembling step of a dust removing apparatus according to a second embodiment of the present invention in which a gas purifying filter made of a gas permeable body made of plate-like ceramic fiber of FIG. 1 is incorporated.

FIG. 3 is a perspective view of a cylindrical ceramic fiber gas permeable body having both ends open according to a third embodiment of the present invention.

FIG. 4 is an assembly step diagram and system diagram of a dust removal apparatus according to a fourth embodiment in which a gas purification filter formed of a ceramic fiber gas permeable body having a hollow cylindrical shape is incorporated.

FIG. 5 is a perspective view of a conventional honeycomb supporting a catalyst.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic fiber 2 Fibrous molded object 3 Catalyst particle 4 Gas permeable body 5 Gas inlet surface 6 Gas inflow direction 7 Gas outlet surface 8 Gas outflow direction 11, 31 Dust removal device 12 Gas duct 13, 33 Gas inlet 14 Gas inflow direction 15, 35 Gas purification filter 16 Gas collecting part 17, 37 Gas outlet 18 Gas outflow direction 19 Ammonia injection valve 21 Gas purification filter 22 Gas inlet part 23 Gas inflow direction 24 Inner wall surface 25 Outer wall surface 26 Gas outflow direction 47 Upper tube sheet 48 Lower part Tube plate 49 Outer wall of device 50 Dust hopper 51 Dust 52 Backwashing device 57 Dust outlet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 35/02 B01J 37/00 A 35/06 ZAB B01D 53/36 ZABC 37/00 104A 104B (72) Invention Person Masahiko Yamazaki 1-3-5 Jiyugaoka, Meguro-ku, Tokyo (72) Inventor Yoshihiko Goto 1-8-1 Shintoda, Hamamatsu-shi, Shizuoka F-term (reference) 4D019 AA01 BA05 BB06 BB10 BC07 CA03 CB02 CB06 4D048 AA06 AA14 AB03 BA01X BA01Y BA03X BA03Y BA06X BA07X BA07Y BA08X BA08Y BA10X BA10Y BA23X BA23Y BA27X BA27Y BA41X BA41Y BA46X BA46Y BB08 BB17 CC40 CD03 CD05 4D058 JA02 JA12 JB06 BA13 BAB BAA BAA BAA BAA BAA BAA BABA BB11B BB15A BB15B BC54A BC54B BC60A BC60B BD04A BD04B BD05A BD05B BD06A BD06B CA02 CA04 CA10 CA13 CA18 EA03X EA03Y EA09 EB18X EB18Y FA03 FA06 FB66

Claims (11)

[Claims] 1. A gas permeable material comprising ceramic fibers, wherein metal oxide catalyst particles are held between the ceramic fibers. 2. The gas according to claim 1, wherein the metal oxide catalyst particles have a titanium oxide carrier carrying a metal oxide containing at least one of tungsten trioxide and vanadium pentoxide as a main component. Transparent body. 3. An average particle diameter of said metal oxide catalyst particles is 3.
The gas permeable body according to claim 1, wherein the gas permeable body has a thickness of 0.1 μm or more and 20 μm or less. 4. The main component of the ceramic fiber is at least one selected from the group consisting of alumina, silica, magnesia, zirconia, silicon carbide, and silicon nitride.
The gas permeable body according to any one of claims 1 to 3. 5. A porosity of not less than 75% and not more than 95%.
The gas permeable body according to any one of claims 1 to 4. 6. The ceramic fiber and the metal oxide catalyst particles are dispersed in a metal sol solution containing at least one of alumina sol, silica sol and titanium sol, and then the solution is cast into a mold. The method for producing a gas permeable body according to any one of claims 1 to 5, wherein the mold is removed from the mold after drying, and further fired. 7. A gas purifying filter comprising the gas permeable body according to any one of claims 1 to 5; the gas purifying filter has air permeability; A dust removing device for introducing a dust-containing gas from one surface and passing the gas through the wall of the gas purification filter to remove a clean gas from the other surface; 8. The gas purifying filter is formed in a hollow cylindrical shape; the one surface is an inner wall surface of the hollow cylinder, and the other surface is an outer wall surface of the hollow cylinder; A dust remover as described. 9. The dust removing device according to claim 7, further comprising a back washing means for removing dust adhering to the inner wall surface by back washing. 10. A gas collecting means arranged vertically below the gas purifying filter and accumulating dust removed from the dust-containing gas.
The dust remover according to Item. 11. The mass of the metal oxide catalyst particles is between 20% by mass and 60% by mass with respect to the total mass of the gas purification filter;
The dust remover according to Item.