JP3448246B2 - Bag filter and exhaust gas purification method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to various incinerators such as an urban refuse incinerator, an industrial waste incinerator, a sludge incinerator, and the like.
Regarding technology for purifying exhaust gas discharged from thermal decomposition furnaces, melting furnaces, etc., especially halogenated aromatic compounds such as nitrogen oxides and dioxins contained in the exhaust gas, highly condensed aromatic hydrocarbons, and environmental hormones The present invention relates to a bag filter for detoxifying individually or simultaneously and an exhaust gas purification method using the bag filter.

[0002]

BACKGROUND ART Generally, in order to remove dust components contained in exhaust gas, a bag filter as shown in FIG. 2 is used.
Removing dust. Conventionally, this bag filter is loaded with a denitration catalyst to remove harmful substances (soot dust, hydrogen chloride,
Techniques for removing sulfur oxides, nitrogen oxides, dioxins, mercury, etc. have been proposed (JP-A-7-204466).
(See Japanese Patent Publication).

FIG. 2 is a system diagram of a fuel exhaust gas treating apparatus using the bag filter according to the above proposal. FIG. 3 is a schematic diagram of a bag filter. As shown in FIG. 2, the flue gas treatment apparatus includes a slaked lime supply device 13 that supplies slaked lime 12 to an exhaust gas 11 by a blower 13a, and an exhaust gas 1 from which hydrogen chloride, sulfur oxides, etc. have been removed by a neutralization reaction of the slaked lime.
1. A dust collector 19 having a reducing agent supply device 15 for supplying a reducing agent 14 of nitrogen oxides to the No. 1 by a pump 15a, and a bag filter body 17 carrying a denitration catalyst for forming an adhesion layer 16 shown in FIG. It consists of and. Here, as shown in FIG. 3, the bag filter main body 17 forms the adhesion layer 16 to remove the dust component 11a as a result of the dust component 11a and the slaked lime 12 in the exhaust gas 11 adhering thereto. Then, as shown in FIG. 3, the reducing agent 1
The exhaust gas 11 added with ammonia which is 4 is the adhesion layer 1
6 and the bag filter main body 17 are passed through to reduce and remove nitrogen oxides (NOx) in the exhaust gas, and the purified exhaust gas 2
It is released to the atmosphere as 0. The dust component adhering to the bag filter body 17 is discharged from the ash discharging device 21 provided in the lower part of the dust collecting device 19 shown in FIG. is doing.

Here, as a catalyst for decomposing the denitration catalyst for removing the harmful substances, a catalyst having titania (TiO ₂ ) as a carrier and vanadium pentoxide (V ₂ O ₅ ) as an active component is used. ing.

An example of the conventional method for producing the denitration catalyst will be described below. First, a solution of titanium sulfate or titanium chloride, which is a raw material of TiO ₂ as a carrier of a catalyst, is hydrolyzed by heating or neutralized with NH ₃ or the like to be precipitated, and the obtained hydrous titanium oxide is 400 to 600. By heat-treating at about ℃, TiO ₂ as a catalyst carrier is obtained.
Next, a raw material solution such as an ammonium salt of V ₂ O ₅ as an active ingredient is mixed with TiO _2, and after mixing, it is formed into a honeycomb shape or the like and fired at 450 to 550 ° C.

The catalyst thus obtained has a small specific surface area of about 50 to 68 m ² / g, and its activity at a low temperature of 200 ° C. or lower is remarkably reduced. In the present situation, by reheating the exhaust gas, the decomposition treatment is performed at 200 ° C. or higher even when the exhaust gas is loaded on the bag filter body.

Further, dioxins are thermally decomposed at high temperature in an incinerator, but when passing through a gas cooling device and dust-removed by a dust remover, dioxins are regenerated in a low temperature region of 400 ° C. or lower. It may be a problem.

Conventionally, exhaust gas is passed through a dust remover (for example, a bag filter), then through a catalyst device, and then dioxins are separately removed by a denitration catalyst, but the device is simplified. Therefore, there is a demand for development of a technique for removing dioxins in exhaust gas with high efficiency together with removal of dust components, and for example, securing 0.1 ng-TEQ / Nm ³ which is the emission regulation value of the Ministry of Health and Welfare.

On the other hand, in the decomposition of the above-mentioned harmful substances contained in the exhaust gas such as dioxins, for example, titania (TiO ₂ ) is used as a carrier, and vanadium pentoxide (V ₂ O ₅ ) and tungsten trioxide (WO) are used as active components. It has been proposed to treat exhaust gas using a catalyst carrying ₃ ) and ₃ ).

The conventional technique disclosed in Japanese Patent Laid-Open No. 2-35914 is a titanium oxide carrier having vanadium pentoxide and tungsten trioxide supported as a catalyst (TiO ₂
60% by weight, V ₂ O ₅ 4% by weight, WO ₃ 3.5% by weight)
However, since the decomposition rate of dioxins is 50% or less and the decomposition efficiency is poor, the decomposition efficiency of dioxins is low even when loaded on the bag filter body, There is a demand for further high decomposition efficiency of dioxins and the like.

In view of the above problems, the present invention improves denitration activity in a low temperature range of 200 ° C. or lower (particularly 150 ° C. or lower), and decomposition activity of harmful substances such as dioxins and highly condensed aromatic hydrocarbons and environmental hormones. An object of the present invention is to provide a bag filter and an exhaust gas purification method for simultaneously removing soot dust and gaseous harmful substances (such as dioxins) from exhaust gas.

[0012]

[Means for Solving the Problems ] The above-mentioned problems are solved.
Therefore, a first invention is a bag filter for purifying dust components in exhaust gas, which has an X-ray diffraction pattern shown in the following "Table 3 " and has a molar ratio of oxides in a dehydrated state. expressed _{in, (1 ± 0.8) R 2} O · [aM 2
O ₃ · bM′O · cAl ₂ O ₃ ] · ySiO ₂ (in the above formula,
R is an alkali metal ion and / or hydrogen ion, M is VI
Group II elements, rare earth elements, titanium, vanadium, chromium,
At least one element ion selected from the group consisting of niobium, antimony, and gallium, M ′ is an alkaline earth metal ion of magnesium, calcium, strontium, or barium, a> 0, 20> b ≧ 0, a + c = 1 ,
V> Mn, Co, Fe, Cu, Ag, Pt, P is added to the crystalline silicate having the chemical formula of 3000>y> 11).
It is characterized in that it carries a dioxin catalyst comprising at least one metal selected from the group consisting of d, Ru, Ir, Rh, and Au.

[Table 3]

The second invention is characterized in that, in the first invention, the specific surface area of the decomposition catalyst is 90 m ² / g or more.

A third aspect of the present invention is an exhaust gas purification method using a bag filter for purifying dust components in exhaust gas, in which a dioxin decomposition catalyst is carried on a bag filter main body made of chemically-synthesized felt fibers. In the exhaust gas purification method of decomposing and denitrifying dioxins together with the removal of dust components in the exhaust gas, the catalyst has the X-ray diffraction pattern shown in "Table 4 " below, and the moles of oxides in the dehydrated state are Expressed as a ratio , (1 ± 0.
8) R ₂ O ・ [aM ₂ O ₃・ bM'O ・ cAl ₂ O ₃ ] ・ y
SiO ₂ (in the above formula, R is an alkali metal ion and / or hydrogen ion, M is a Group VIII element, a rare earth element, titanium,
At least one element ion selected from the group consisting of vanadium, chromium, niobium, antimony, and gallium, M ′ is an alkaline earth metal ion of magnesium, calcium, strontium, or barium, a> 0, 20
> B ≧ 0, a + c = 1, 3000>y> 11), V, Mn, Co, F is added to the crystalline silicate having the chemical formula.
e, Cu, Ag, Pt, Pd, Ru, Ir, Rh, Au
The catalyst is characterized by supporting at least one metal selected from the group consisting of

[Table 4]

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below, but the present invention is not limited thereto.

FIG. 1 shows an example of a bag filter according to this embodiment. As shown in FIG. 1, a bag filter 100 according to the present embodiment is a bag filter that purifies dust components in exhaust gas discharged from, for example, an incinerator, a pyrolysis furnace, a melting furnace, and the like, and is a chemically synthesized fiber. A bag filter main body 101 made by weaving in a felt shape carries a dioxin decomposition catalyst 102.

In the present invention, the dioxin decomposition catalyst (hereinafter, also simply referred to as "decomposition catalyst") 102 is
It can be exemplified the following catalysts.

The dioxin-decomposing catalyst 102 according to the present embodiment has an X-ray diffraction pattern shown in the following "Table 5 ", and is expressed by the molar ratio of oxides in the dehydrated state to (1 ± 0.8) R ₂ O ・ [aM ₂ O ₃・ bM '
O.cAl ₂ O ₃ ] .ySiO ₂ (wherein R is an alkali metal ion and / or a hydrogen ion, M is a group VIII element, a rare earth element, titanium, vanadium, chromium, niobium, antimony and gallium. At least one elemental ion selected, M'is magnesium,
Alkaline earth metal ions of calcium, strontium and barium, a> 0, 20> b ≧ 0, a + c = 1, 30
00>y> 11) to a crystalline silicate having a chemical formula of V, Mn, Co, Fe, Cu, Ag, Pt, Pd,
It is a catalyst that carries at least one metal selected from the group consisting of Ru, Ir, Rh, and Au.

[Table 5]

Further, the exhaust gas purification method according to the present embodiment is provided with a bag 102 carrying a catalyst 102 capable of decomposing by contacting with a harmful substance contained in the exhaust gas and decomposing it.
A method using the filter body 102, wherein the catalyst 10
2 has the X-ray diffraction pattern shown in the above "Table 5 " and is expressed by the molar ratio of the oxide in the dehydrated state, and is (1 ± 0.8) R ₂ O. [aM ₂ O _3. bM'O
cAl ₂ O ₃ ] .ySiO ₂ (wherein R is an alkali metal ion and / or hydrogen ion, M is selected from the group consisting of Group VIII elements, rare earth elements, titanium, vanadium, chromium, niobium, antimony and gallium. Or at least one elemental ion, M ′ is an alkaline earth metal ion of magnesium, calcium, strontium, or barium, a> 0, 20> b ≧ 0, a + c = 1, 3000> y
> 11) to a crystalline silicate having the chemical formula
Mn, Co, Fe, Cu, Ag, Pt, Pd, Ru, I
It carries at least one metal selected from the group consisting of r, Rh and Au .

The components and composition ratio of the catalyst composition according to the present invention are not particularly limited, but as a typical example, the catalyst components (V, M) are added to 100 parts by weight of the crystalline silicate.
n, Co, Fe, Cu, Ag, Pt, Pd, Ru, I
r, Rh, Au) may be appropriately prepared so as to have catalytic activity. For example, when V is used as a catalyst component, for example, vanadium pentoxide is used in an amount of 0.001 to 5 parts by weight in a one-component system, and 0.00005 parts by weight or more in a system of two or more components, thereby sufficiently expressing the activity. can do.

To carry the above-mentioned catalyst component on the bag filter body, the filter cloth for the bag filter is dipped in a slurry containing the catalyst powder, the catalyst powder is carried on the filter cloth, drained, dried and fired. Obtained.

The above-mentioned oxidation catalyst has a specific surface area of 90 m ² / g or more, preferably 90 m ² / g or more, when it is used as a catalyst loaded on a bag filter for treating exhaust gas from an incinerator.
It is preferably about 200 m ² / g. This is because when the specific surface area exceeds 200 m ² / g, the specific surface area decreases due to the growth of particles in the temperature range of 200 ° C. when treating the exhaust gas, the thermal stability is poor and the activity decreases, and the long-term This is because it cannot be used stably over a period of time. On the other hand, if the specific surface area is less than 90 m ² / g, the activity at 200 ° C. or lower remarkably decreases as in the conventional case, which is not preferable.

The supported amount of the above catalyst is preferably 1 to 500 g / m ² . If it is less than 1 g / m ² , the decomposition performance of dioxins is insufficient, while 500 g / m 2
If it exceeds ² , it is not preferable because the pressure loss of the exhaust gas increases. As the chemically synthesized fiber used for the bag filter body, polyimide-based, polyphenylene sulfide-based, polyfluoroethylene-based, and polyester-based fibers can be used. The loading can be carried inside or on the surface of the bag filter body.

The catalyst used for treating the exhaust gas may be in any shape integrally molded such as pellet, plate, cylinder, corrugated, and honeycomb. Of course, it is preferable to increase the contact area with the gas,
Depending on the packing density of the powdery catalyst, the back pressure of exhaust gas flow increases, which is not preferable. As a countermeasure against this, it is particularly preferable to use, for example, a honeycomb-shaped molded body obtained by compressing the powder to a predetermined density without excessively reducing the specific surface area. When the bag filter contains a catalyst component and both dust removal and catalyst decomposition are performed, a method of coating the powder component of the catalyst on the bag filter can also be adopted.

Here, the harmful substances in the exhaust gas decomposed by the catalyst of the present invention are not only nitrogen oxides but also harmful halogenated aromas represented by dioxins and PXB (X represents halogen). It refers to harmful substances such as group compounds and highly condensed aromatic hydrocarbons, but is not limited to these as long as they are harmful substances (or environmental hormones) in exhaust gas that can be decomposed by the oxidation catalytic action of the present invention.

The aromatic halogen compounds contained in the ash and soil to be decomposed in the present invention are limited to harmful substances represented by dioxins and PCBs (eg, environmental hormones). is not. Here, the dioxins are a general term for polyhalogenated dibenzo-p-dioxins (PXDDs) and polyhalogenated dibenzofurans (PXDFs) (X represents halogen), and halogen compounds and certain organic compounds. It is said that a small amount is generated when a halogen compound is burned. Depending on the number of halogens there are monohalides to octahalides, of which dibenzo-p-dioxin tetrachloride (T ₄ CDD) is known to be the most toxic. As the harmful halogenated aromatic compound, in addition to dioxins, various organic halogen compounds as precursors thereof (for example, aromatic compounds such as phenol and benzene (for example, halogenated benzenes,
It contains halogenated phenols, halogenated toluene, etc.), halogenated alkyl compounds, etc.) and needs to be removed from the ash. That is, dioxins represent not only chlorinated dioxins but also halogenated dioxins such as brominated dioxins. In addition, PXBs (polyhalogenated biphenyls) is a general term for compounds in which several halogen atoms are added to biphenyl. Although there are isomers depending on the number of halogen substitutions and the substitution position, in the case of PCB (polychlorinated biphenyls) , 2,6-dichlorobiphenyl, 2,2'-dichlorobiphenyl, 2,3,5-trichlorobiphenyl, etc. are typical ones, which are highly toxic and may cause dioxins when incinerated. Known as a thing and needs to be removed from the ash. Needless to say, the PXBs also include the coplanar PXB.

The high-condensation aromatic hydrocarbon is a general term for polynuclear aromatic compounds, may contain one or more OH groups, is recognized as a carcinogen, and needs to be removed from the exhaust gas. .

Further, in many manufacturing processes, exhaust gas containing, in addition to soot and dust, a gaseous organic compound such as formaldehyde, benzene or phenol may be generated. These organic compounds are also environmental pollutants and significantly impair human health, and thus need to be removed from exhaust gas.

The nitrogen oxides to be treated in the present invention usually mean NO and NO ₂ as well as a mixture thereof.
Also called NOx. However, in addition to these, the NOx often contains unstable nitrogen oxides of various oxidation numbers. Therefore, x is not particularly limited, but is usually a value of 1-2. It is said that it becomes nitric acid, nitrous acid, etc. in rainwater, etc., or NO is one of the main causative substances of photochemical smog, and is a compound harmful to the human body.

By using the bag filter according to the present invention, harmful substances such as the above-mentioned harmful substances such as nitrogen oxides, halogenated aromatic compounds and highly condensed aromatic hydrocarbons and gaseous organic compounds can be contacted. It can be decomposed and treated to be harmless .

Regarding nitrogen oxides, a basic substance (for example, ammonia) is allowed to exist on the upstream side of the dust collector equipped with the bag filter main body carrying the catalyst of the present invention, and the detoxification treatment is simultaneously performed by the reduction reaction. It can be carried out.

Now, an exhaust gas treatment system using the bag filter of the present invention will be described with reference to FIG.

As shown in FIG. 2, the temperature of the exhaust gas discharged from the combustion furnace is reduced to 100 to 200 ° C., and the required amount of slaked lime is supplied from the slaked lime supply device 13 as a neutralizing agent.
Hydrogen chloride in the exhaust gas 11 due to the neutralization reaction of this slaked lime,
Part of the sulfur oxide and the like is removed.

In the exhaust gas 11 from which part of hydrogen chloride, sulfur oxides, etc. in the exhaust gas 11 has been removed, a reducing agent (N
A required amount of H ₃ ) 14 is supplied from the reducing agent supply device 15, and the supplied exhaust gas containing the neutralizing agent and the reducing agent is introduced into the filter type dust collecting device 19.

In the dust collector 19, as shown in FIG. 1, on the upstream surface of the felt-like bag filter body 101, into which the exhaust gas containing the neutralizing agent and the reducing gas is introduced and which carries the catalyst for decomposing harmful substances. An adhesion layer 103 formed of soot dust and a neutralizing agent is formed on the surface. When the exhaust gas 11 passes through the adhesion layer 103, hydrogen chloride, sulfur oxides, etc. remaining in the exhaust gas 11 react with slaked lime to be absorbed and removed, and soot is also removed by the filtering effect. The exhaust gas 11 thus passing through the adhesion layer 103 is introduced into the bag filter body 101 together with ammonia as a reducing agent, and the dioxins in the exhaust gas are decomposed and removed by the dioxins decomposition catalyst, and the nitrogen oxides have a denitrification function. As a result, the exhaust gas 20 that has been reduced and removed by ammonia and has been cleaned is released to the outside.

Since the thickness of the adhering layer 103 adhering to the upstream side of the bag filter main body 102 gradually increases, back pressure and back washing should be appropriately performed every predetermined period so as not to become too thick. Alternatively, the ash discharging device 2 provided below the dust collector 19 by removing the adhesion layer 103 by an operation such as vibration
It is discharged by 1 and treated separately.

In the bag filter according to the present invention, the catalyst for decomposing harmful substances is carried on the bag filter body 101 which is constructed by weaving chemically synthetic fibers into a felt shape, so that the catalyst holding power is increased and the bag filter body is It is possible to prevent the deterioration of the catalytic function by supporting the catalyst.

Since the bag filter body 101 is made of felt-like synthetic fibers , it has good surface filtration performance, low pressure loss value, and high flow rate filtration. . Further, in cleaning by washing with water, cleaning with a chemical solution, and regeneration of the catalyst, there is no reduction in strength due to openings or the like like those obtained by weaving glass fibers into a cloth shape. Therefore, the bag filter can have a long catalyst life, can be regenerated and used for a long time, and can significantly reduce the renewal cost.

Example 1 Water glass No. 1 (SiO ₂ : 30%): 5616 g was added to water:
It was dissolved in 5429 g, and this solution was designated as solution A. on the other hand,
Water: 4175 g, aluminum sulfate: 718.9 g, ferric chloride: 110 g, calcium acetate: 47.2 g, sodium chloride: 262 g and concentrated hydrochloric acid: 2020 g were mixed and dissolved, and this solution was designated as solution B. Solution A and Solution B
Is supplied at a constant ratio to generate a precipitate, which is sufficiently stirred to p
A slurry of H: 8.0 was obtained. This slurry was charged into a 20 liter autoclave, 500 g of tetrapropylammonium bromide was further added, hydrothermal synthesis was carried out at 160 ° C. for 72 hours, after synthesis was washed with water, dried, and further calcined at 500 ° C. for 3 hours to crystallize. A sex silicate 1 was obtained. This crystalline silicate 1 has a molar ratio of oxide (excluding water of crystallization) of 0.5Na ₂ O.0.5H ₂ O. [0.8A
l ₂ O ₃ · 0.2Fe ₂ O ₃ · 0.25CaO] · 25
It was represented by the composition formula of SiO ₂ , and the crystal structure was as shown in Table 5 above by X-ray diffraction.

The above crystalline silicate 1 was treated with 4N NH ₄ C.
1 aqueous solution was stirred at 40 ° C. for 3 hours to carry out NH ₄ ion exchange. It was washed after ion exchange, dried at 100 ° C. for 24 hours, and then calcined at 400 ° C. for 3 hours to obtain H-type crystalline silicate 1.

To the H-type crystalline silicate, an ammonium metavanadate aqueous solution, a manganese nitrate aqueous solution, a cobalt nitrate aqueous solution, a copper nitrate aqueous solution silver nitrate, a chloroplatinic acid aqueous solution, a palladium nitrate aqueous solution, a ruthenium chloride aqueous solution, respectively,
Impregnated with iridium chloride aqueous solution and rhodium chloride aqueous solution,
After evaporating to dryness, it was calcined at 500 ° C. for 3 hours to obtain a powder catalyst.

3 wt% of V ₂ O ₅ , 3 wt% of MnO ₂ and 3 wt of Co ₃ O ₄ were added to the obtained powder catalyst.
%, CuO 3 wt%, AgO 3 wt%, Pt 1 w
t%, Pd 1 wt%, Ru 1 wt%, Ir 1 wt
% And Rh of 1 wt% were respectively supported to obtain a powder catalyst.

This powder catalyst was made into a slurry and supported on each bag filter body to obtain a bag filter. The bag filter of Example 1 was capable of denitration with high efficiency while decomposing dioxins.

[0044]

According to the present invention, the dust component in the exhaust gas can be removed, and at the same time, the dioxins can be decomposed and denitrified, and the exhaust gas treatment apparatus can be simplified.

Further, by supporting a catalyst for decomposing harmful substances on a bag filter body made of chemically-synthesized felt in a felt shape, the catalyst performance is extended and the bag filter body is washed with water, with a chemical solution and when the catalyst is regenerated. It is possible to prevent a decrease in strength, and it is possible to reduce the renewal cost by using it for a long period of time.

Further, since the felt-like bag filter body is adopted, the surface filterability is good, the pressure loss value is low, and high flow rate filtration can be supported, and the dust collector can be made compact. be able to.

In addition, unlike the conventional catalysts supporting a simple NOx removal catalyst, all the catalysts supported on the bag filter body of the present invention have a high decomposition efficiency of dioxins even at low temperatures, and are downstream of the dust collector. Exhaust gas can be purified without separately providing a decomposition device for dioxins and the like.

[Brief description of drawings]

FIG. 1 shows a schematic diagram of a bag filter according to the present embodiment.

FIG. 2 is a system diagram of a fuel exhaust gas treatment device using a bag filter.

FIG. 3 is a schematic diagram of a conventional bag filter.

[Explanation of symbols]

11 exhaust gas 12 slaked lime 13 Slaked lime supply device 14 Reducing agent 15 Reductant supply device 16 Adhesive layer 17 Bag filter body 19 Dust collector 20 Purified exhaust gas 21 Ash discharge device 100 bug filters 101 Bag filter body 102 catalyst 103 Adhesion layer

Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI B01J 23/42 B01J 29/72 A 23/89 29/78 A 29/72 32/00 29/78 B01D 53/36 ZABG 32/00 104B F23J 15/00 F23J 15/00 J (72) Inventor Mamoru Shioki 12 Nishiki-cho, Naka-ku, Yokohama-shi, Kanagawa Mitsubishi Heavy Industries, Ltd. Yokohama Works (72) Hideaki Oyamatsu, 4-chome, Sugita, Isogo-ku, Yokohama, Kanagawa No. 25 within ICT Corporation (56) References JP-A-10-180039 (JP, A) JP-A-11-253970 (JP, A) JP-A-11-156192 (JP, A) ( 58) Fields investigated (Int.Cl. ⁷ , DB name) B01D 39/00-39/20

Claims (3)

(57) [Claims] 1. A bag filter for purifying dust components in the exhaust gas, has an X-ray diffraction pattern shown in the following "Table 1", expressed in terms of mole ratios of oxides in the dehydrated state, ( 1 ± 0.8) R ₂ O ・ [aM ₂ O ₃・ bM'O ・ cAl ₂
O ₃ ] .ySiO ₂ (wherein R is an alkali metal ion and / or hydrogen ion, M is at least selected from the group consisting of Group VIII elements, rare earth elements, titanium, vanadium, chromium, niobium, antimony and gallium. One or more elemental ions, M '
Is an alkaline earth metal ion of magnesium, calcium, strontium or barium, a> 0, 20> b ≧ 0,
a + c = 1, 3000>y> 11) to a crystalline silicate having a chemical formula of V, Mn, Co, Fe, Cu, A
A bag filter comprising a dioxin catalyst carrying at least one metal selected from the group consisting of g, Pt, Pd, Ru, Ir, Rh and Au. [Table 1] 2. The bag filter according to claim 1, wherein the decomposition catalyst has a specific surface area of 90 m ² / g or more. 3. A method for purifying exhaust gas using a bag filter for purifying dust components in exhaust gas, which comprises supporting a dioxin-decomposing catalyst on a bag filter body made by weaving chemically-synthesized fibers in a felt shape, and dust components in exhaust gas. In the exhaust gas purification method of decomposing and denitration of dioxins together with the removal of the above, the catalyst has an X-ray diffraction pattern shown in "Table 2" below, and is expressed by a molar ratio of oxides in a dehydrated state , (1 ± 0.8) R ₂ O ・ [aM ₂ O ₃・ bM'O ・ cAl ₂
O ₃ ] .ySiO ₂ (wherein R is an alkali metal ion and / or hydrogen ion, M is at least selected from the group consisting of Group VIII elements, rare earth elements, titanium, vanadium, chromium, niobium, antimony and gallium. One or more elemental ions, M '
Is an alkaline earth metal ion of magnesium, calcium, strontium or barium, a> 0, 20> b ≧ 0,
a + c = 1, 3000>y> 11) to a crystalline silicate having a chemical formula of V, Mn, Co, Fe, Cu, A
An exhaust gas purification method, which is a catalyst comprising at least one metal selected from the group consisting of g, Pt, Pd, Ru, Ir, Rh, and Au. [Table 2]