JP2002045627A - Dust collecting filter made of ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dust filter having high heat resistance and corrosion resistance against alkali metals, or the like, low pressure drop and high degree of freedom of design. SOLUTION: This dust filter made of ceramic has a three dimensional skeleton structure formed by bonding alumina fibers with an inorganic binder and the alumina fiber contains >=70 wt.% Al2O3 and the inorganic binder is one or more kinds selected from titania sol, alumina sol and zirconia sol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic dust filter for removing dust from high-temperature gas, and more particularly to a ceramic dust filter excellent in corrosion resistance to corrosive substances such as alkali metal compounds in high-temperature gas. It is.

[0002]

2. Description of the Related Art In recent years, from the viewpoints of environmental problems and energy saving, it has been desired to disseminate technologies for generating electric power by using thermal energy of high-temperature exhaust gas generated in a garbage incinerator and for performing district heating and cooling. The utilization of the heat energy of the exhaust gas is usually performed by introducing the exhaust gas into a heat exchanger and collecting it. Therefore, in order to use the heat energy of the exhaust gas with high efficiency, it is preferable that the exhaust gas can be introduced into the heat exchanger at a high temperature. Here, as the heat exchanger, usually, in order to increase the heat exchange efficiency, a metal material having high heat conductivity such as stainless steel of high chromium and high nickel is used, and a large number of fins are formed or thin tubes are densely formed. The thing of the arrangement structure is used.

However, municipal waste generally contains sodium, potassium, calcium, chloride and the like. For this reason, in the exhaust gas from the refuse incinerator, dust containing compounds such as the above sodium, for example, alkali metal salts, alkaline earth metal salts, iron chloride and the like (hereinafter, also referred to as “alkali metal salts and the like”). It is contained in large quantities.

Therefore, if the exhaust gas is directly introduced into the heat exchanger, a large amount of dust easily adheres to the fins or clogs the thin tubes. Also, alkali metal salts and the like in the exhaust gas dust,
At a high temperature of about 700 ° C. or higher, the activity tends to increase due to melting, and the can body of a heat exchanger made of high chromium high nickel stainless steel or the like is easily corroded. For this reason, in order to introduce the exhaust gas into the heat exchanger at a high temperature in order to increase the thermal efficiency, the dust containing the alkali metal salt or the like in the exhaust gas is sufficiently removed by a dust collection filter before being introduced into the heat exchanger. There is a need.

[0005] The dust collection filter used here is required to have sufficient dust removal performance and small pressure loss.
Heat resistance of about 700 ° C. or more is required. Further, when alkali metal salts and the like in the dust react with the filter in the temperature range, the filter is deteriorated or deteriorated, resulting in an increase in pressure loss and a decrease in strength. The high-pressure air) makes it difficult to be removed and maintenance becomes difficult. Accordingly, the dust collection filter is required to have a property that does not easily react with an alkali metal salt or the like (hereinafter, also referred to as “corrosion resistance to an alkali metal or the like”). Furthermore, the required dust removal performance and pressure drop value also differ depending on the scale and method of the incinerator,
It is desired that the dust collection filter has a high degree of design freedom in which the dust removal performance, the pressure loss value, and the like can be easily changed according to each filter.

To solve these problems, Japanese Patent Application Laid-Open No. 63-723 discloses
No. 17 discloses a high temperature bag filter composed of at least 85% by weight of TiO ₂ (titania) fiber, and JP-A-63-72319 discloses at least 85% by weight.
High temperature filters composed of a porous sintered body composed of TiO _{2 by} weight are disclosed. These filters can remove dust containing an alkali metal salt even at a high temperature of about 950 ° C. Since the alkali metal salt contained in the dust thus produced does not firmly adhere to the filter, it can be easily removed.

[0007]

However, in the invention described in Japanese Patent Application Laid-Open No. 63-72317, since it is difficult to convert titania into fibers, the diameter and fiber size of the titania fibers are adjusted to adjust pressure loss and the like. It is more difficult to change the length, and there is a problem that the degree of freedom in design is low. Further, in the invention described in JP-A-63-72319, there is a problem that the pressure loss is likely to be high because a porous sintered body of titania is used.

Accordingly, it is an object of the present invention to provide a dust collection filter having high heat resistance, high corrosion resistance to alkali metals and the like, low pressure loss and high design flexibility.

[0009]

Under such circumstances, the present inventors have conducted intensive studies and found that the content of Al ₂ O ₃ was 7
A ceramic dust filter having a three-dimensional skeleton structure in which 0% by weight or more of alumina fibers are bonded with a specific inorganic binder has high heat resistance, high corrosion resistance to alkali metals, etc., low pressure loss, and freedom of design. The present inventors have found that a dust collection filter having a high density can be obtained, and have completed the present invention.

That is, the present invention is a ceramic dust filter having a three-dimensional skeleton structure in which alumina fibers are bonded with an inorganic binder, wherein the alumina fibers have an Al ₂ O ₃ content of 70% by weight or more, The inorganic binder is one or more selected from titania sol, alumina sol, and zirconia sol, and provides a ceramic dust filter.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The ceramic dust filter according to the present invention is a ceramic dust filter having a three-dimensional skeletal structure in which specific alumina fibers are bonded with a specific inorganic binder.

The alumina fibers used in the present invention include those having an Al ₂ O ₃ content of usually 70% by weight or more, preferably 90% by weight or more. It is preferable that the content of Al ₂ O ₃ in the alumina fiber is within the above range, since the corrosion resistance to alkali metals and the like is increased.

The component other than Al ₂ O ₃ in the alumina fiber is not particularly limited.
O ₂ ). When silica is contained in a certain amount, the corrosion resistance of alumina fibers to alkali metals and the like is slightly reduced, but the flexibility of the fibers is improved,
It is preferable because the spolling property and flexibility of the filter are improved. The content of silica is usually 30% by weight or less, preferably 10% by weight or less, more preferably 3 to 7% by weight, and still more preferably 4 to 6% by weight in the alumina fiber.

Therefore, the corrosion resistance to alkali metals and the like is low.
As an alumina fiber that is both high and excellent in flexibility,
Normal Al_TwoO_ThreeContent 70% by weight or more and SiO_TwoContained
30% by weight or less, preferably Al_TwoO_ThreeContent 90 weight
% Or more and SiO_TwoContent of 10% by weight or less, more preferred
Or Al_TwoO_ThreeContent of 93 to 97% by weight and SiO _Two
Content of 3 to 7% by weight, more preferably Al_TwoO_ThreeContained
94-96% by weight and SiO_TwoContent of 4-6% by weight
Things.

The alumina fiber has a fiber diameter of usually 0.5 to
It is 10 μm, preferably 1 to 5 μm. The fiber length is not particularly limited since it may be appropriately selected according to the dust removal performance and pressure loss value of the designed filter, but may be, for example, 50 μm to 30 mm. In the present invention, the alumina fibers can be used alone or in combination of two or more.

Generally, in a dust filter, the fiber diameter and fiber length of the fibers used greatly affect the determination of dust removal performance, pressure loss value, and the like. In the present invention, however, alumina fibers that are easily fiberized are used. Therefore, it is easy to adjust the fiber diameter and the fiber length, and thereby, the degree of freedom in designing the dust removal performance and the pressure loss value of the dust collecting filter is high.

The inorganic binder used in the present invention includes one or more selected from titania sol, alumina sol and zirconia sol. Titania, alumina, and zirconia obtained from these sols have high corrosion resistance to alkali metals and the like, and thus do not have low corrosion resistance to alkali metals and the like unlike filters using colloidal silica as an inorganic binder. Among the above sols, titania sol is preferable because of its low wettability with alkali metal salts and alkaline earth metal salts.

The ceramic dust filter according to the present invention has a three-dimensional skeletal structure in which the alumina fibers are bonded with the inorganic binder. The shape of the ceramic dust filter is not particularly limited, and examples thereof include a plate shape, a rectangular parallelepiped shape, a cylindrical shape, and a candle shape.

The ceramic dust filter according to the present invention is characterized in that at least a gas introduction part on the surface of the above-mentioned ceramic dust filter has at least one selected from oxide ceramics other than silica, carbide ceramics, nitride ceramics and cermet. It is preferable that a coating layer to which particles of at least one species are adhered is formed. Here, the gas introduction part refers to a part of the surface of the ceramic dust filter where exhaust gas (gas to be treated) is introduced into the filter when the ceramic dust filter is actually used.
The surface of the ceramic dust filter refers to the outer surface of the ceramic dust filter. For example, when the filter is cylindrical, it refers to the outer peripheral surface, the inner peripheral surface, and the upper and lower bottom surfaces. Therefore, when the ceramic dust filter is cylindrical, the gas introduction part is formed, for example, on a part or all of the outer peripheral surface.

The coating layer may be formed on the surface of the ceramic dust filter other than the gas introduction portion in addition to the gas introduction portion on the surface of the ceramic dust filter.
Further, the particles may be attached to the surface of alumina fibers or the surface of a cured inorganic binder inside the ceramic dust filter.

Among the particles forming the coating layer, other than silica
Examples of oxide ceramics include spinel (M
gAl_TwoO_Four); MnAl_TwoO_Four, CoAl_TwoO_Four, M
gCr_TwoO_FourOxides with a spinel structure such as
AB as a genus atom_TwoO _FourType compound); alumina,
Examples include titania and zirconia. Carbide ceramic
For example, Al-Mg-C ceramics
Is mentioned. As nitride ceramics, for example,
Al-N ceramics, Si-N ceramics, etc.
No. As the cermet, for example, TiC-N
i-type cermet, Al_TwoO_Three-Cr cermets and others
I can do it.

Since the particles forming the coating layer have high corrosion resistance to alkali metals and the like, the formation of the coating layer increases the corrosion resistance of the ceramic dust filter to alkali metals and the like. In addition, among the above particles, spinel and oxide having a spinel structure are preferable because they have particularly high corrosion resistance to alkali metals and the like.

The particle size of the particles forming the coating layer may be selected so as not to fill the openings according to the openings formed by the alumina fibers or the inorganic binder in the three-dimensional skeleton structure. Although not limited, for example, 0.5 to
It may be 300 μm. When the particles are attached to the surface of a cured product of an alumina fiber or an inorganic binder inside the ceramic dust filter, the particle diameter is usually 0.01 to 0.1 μm.

The coating layer is a sintered body of the particles or a binder of the particles with an inorganic binder having high corrosion resistance to alkali metals and the like. Examples of the inorganic binder used here include, for example, the same ones as those described above used for binding the alumina fibers, and specifically, one or more selected from titania sol, alumina sol, and zirconia sol Two or more types are exemplified.

The thickness of the coating layer is usually from 25 to 500 μm. When the particles are adhered to the surface of a cured product of an alumina fiber or an inorganic binder inside the ceramic dust filter, the thickness of the layer composed of the adhered particles is usually 0.01 to 1 μm. When the thickness of the layer is within the above range, alumina fibers and the like are preferable because corrosion resistance to alkali metals and the like is increased while maintaining flexibility.

The density, porosity, pressure loss and the like of the ceramic dust collecting filter according to the present invention are not particularly limited as long as they are appropriately selected according to the filter to be designed. cm ³ , porosity 80-95
% And a pressure drop of 50 m / s at a flow rate of 0.05 m / s.
The pressure may be 0 to 1500 Pa.

Next, an example of a method for manufacturing the above ceramic dust filter will be described. First, a slurry is obtained by blending alumina fibers, an inorganic binder and an appropriate amount of water, and the slurry is dewatered and formed to form a fibrous formed body composed of alumina fibers having a predetermined shape and an inorganic binder. The compounding ratio of the alumina fiber and the inorganic binder in the slurry is usually 20:80 to 90:10, preferably 65:35 to 45:55 by weight ratio (alumina fiber: inorganic binder).

The obtained molded body is dried or, if necessary, further calcined to remove water. As a drying condition, for example, a method of performing the drying at a temperature of 105 ° C. for 12 hours may be mentioned. The firing conditions include, for example, a temperature of 50.
A method of performing the reaction at 0 to 1500 ° C. for usually 1 hour or more, preferably for about 3 hours is mentioned. When this moisture is removed, the inorganic binder is hardened, and the ceramic dust filter according to the present invention is obtained.

In the ceramic dust filter according to the present invention, for example, the following operation is performed in order to further form a coating layer if necessary. First, a dispersion of particles forming a coating layer is prepared. The dispersion may be a dispersion in which only the particles are dispersed in a dispersion medium, but if the particles are hardly sinterable, the dispersion is added with an inorganic binder having a high corrosion resistance to alkali metals and the like to form a colloid solution. It is preferable to disperse the particles so that the particles can be easily attached to the molded body.

Next, the dispersion liquid is applied or sprayed on the surface of the obtained ceramic dust filter, or a part or the whole of the molded body is immersed in the dispersion liquid to disperse the dispersion liquid in the molded body. Make contact. When the ceramic dust filter and the dispersion liquid are brought into contact, the ceramic dust filter may be in any state of an unfired dried body or a fired body. In the case where the dispersion is brought into contact with the dried product, it may be further baked after the contact. afterwards,
The ceramic dust filter is dried and fired to form a coating layer to obtain a ceramic dust filter.

The ceramic dust filter according to the present invention can be used, for example, as a dust filter for removing dust containing alkali metal salts and the like contained in exhaust gas from garbage incinerators and the like.

[0032]

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 First, Al_TwoO_ThreeContent 95% by weight, SiO_TwoContent 5
Weight%, average fiber diameter 3 μm, average fiber length 500 μm
0.6 parts by weight of luminous fiber, 30% by weight of titania component
0.4 parts by weight of titania sol and 99 parts of water
Parts by weight and mixed with the slurry shown in Table 1
Got Lee. Next, the slurry was subjected to dehydration molding to obtain an outer diameter of 18 mm.
0mm, inner diameter 150mm, length 1000mm, wall thickness 15mm
After obtaining a cylindrical molded body, the molded body was heated at 105 ° C. for 12 hours.
Dried under the following conditions, and having a hollow portion 12 shown in FIG.
A molded body 11 was obtained. Next, a spinel having an average particle size of 80 μm
(MgAl_TwoO_Four) 34 parts by weight of particles were titania component 30
66% by weight of titania sol (1% in terms of titania)
(9.8 parts by weight).
0.3 g / cm on the outer peripheral surface of form 11^TwoAfter applying in the amount of
After drying at 05 ° C. for 12 hours,
At 3 ° C. for 3 hours.
A Lamix dust filter 10 was obtained. Ceramics collection
The dust filter 10 has a spinel (MgAl_Two
O _Four) Having a thickness of 150 to 200 μm
Had been formed. The ceramic dust filter 10
The entire outer peripheral surface on which the coating layer 13 is formed corresponds to the gas introduction part
The exhaust gas is discharged as shown by arrow 21 in FIG.
Introduced into the mixed dust filter 10 and the filter 1
0, after passing through the inside and being subjected to dust collection,
As shown by a mark 22, the ceramic dust filter 10 is discharged.
Will be issued. About the obtained ceramic dust filter
The pressure loss was measured under the following conditions. Also obtained
The ceramic dust filter is contacted with municipal waste incineration ash.
The temperature was raised to 800 ° C. and kept for 12 hours.
And those held for 100 hours were produced. Then this
In order to remove the incinerated ash adhering to
From the inner surface to the outer surface of the mixed dust filter
Reverse injection of pulse air for 0.5 seconds at a pressure of 10,000 Pa
did. Ceramics collection after holding for 12 hours after reverse injection
The surface of the dust filter and the ceramic after holding for 100 hours
The surface of the dust collection filter is subjected to EDX analysis under the following conditions.
(Energy dispersive X-ray analysis)
Check the amount of impurities (compound of Na, K and Ca)
Was. Table 2 shows the results.・ Measurement conditions of pressure loss: Ceramic dust filter 1
The flow velocity from the outer surface of the filter to the outer surface of the filter is 0.05m /
s.
Difference between the pressure near the air inlet inside the filter 10 and the atmospheric pressure
Was read with a differential pressure gauge to determine the pressure loss.・ Measurement conditions for EDX analysis: EDX analyzer (Oxfu
Link / IS manufactured by Ford Instruments Co., Ltd.
IS 300 series) and a ceramic dust filter
Arbitrarily select 20 measurement points on the Luther surface,
These measurement points were subjected to EDX analysis at a magnification of 1000 times. The analysis
Then, after calculating the total weight (1) of Na, K and Ca,
The total weight (1) is divided by the total weight (2) other than Na and the like.
The amount of impurities on the surface of the ceramic dust filter
% By weight. The evaluation criteria are shown below. (Evaluation Criteria) A: The impurity amount is 5% by weight or less at all measurement points. ：: Impurity amount is 10% by weight or less at all measurement points. Δ: Impurity amount is 15% by weight or less at all measurement points. ×: The impurity amount exceeds 15% by weight at any of the measurement points.
You.

[0034]

[Table 1] * In the table, units are parts by weight.

[0035]

[Table 2]

Example 2 As shown in Table 1, Al ₂ O ₃ was used instead of alumina fiber.
A ceramic dust filter was obtained and subjected to EDX analysis in the same manner as in Example 1 except that a mullite fiber having a content of 72% by weight, a SiO ₂ content of 28% by weight, an average fiber diameter of 3 μm, and an average fiber length of 500 μm was used. . Table 2 shows the results.

Comparative Example 1 As shown in Table 1, Al ₂ O ₃ was used instead of alumina fiber.
A ceramic dust filter was obtained and subjected to EDX analysis in the same manner as in Example 1 except that ceramic fibers having a content of 50% by weight, a SiO ₂ content of 50% by weight, an average fiber diameter of 3 μm, and an average fiber length of 500 μm were used. Table 2 shows the results.

Example 3 As shown in Table 1, a ceramic dust filter was obtained in the same manner as in Example 1 except that a zirconia sol having a zirconia component of 20% by weight was used instead of the titania sol.
X analysis was performed. Table 2 shows the results.

Example 4 As shown in Table 1, a ceramic dust filter was obtained and subjected to EDX analysis in the same manner as in Example 1 except that an alumina sol having an alumina component of 20% by weight was used instead of the titania sol. Table 2 shows the results.

Comparative Example 2 As shown in Table 1, silica component 3 was used in place of titania sol.
Example 1 except that 0% by weight of colloidal silica was used.
A ceramic dust filter is obtained in the same manner as
analyzed. Table 2 shows the results.

[0041]

[Table 3] * In the table, units are parts by weight.

Example 5 As shown in Table 3, a ceramic dust filter was obtained and subjected to EDX analysis in the same manner as in Example 1 except that no coating layer was formed without using a coating layer dispersion. Table 4 shows the results.

Comparative Example 3 As shown in Table 3, a ceramic dust filter was obtained and subjected to EDX analysis in the same manner as in Comparative Example 1, except that the coating layer was not formed without using the coating layer dispersion liquid. Table 4 shows the results.

Reference Example 1 Pressure loss was measured in the same manner as in Example 1 for a sintered filter element made of a cordierite powder sintered body. Table 4 shows the results.

[0045]

[Table 4]

From the results of Examples 1 and 2 and Comparative Example 1, it can be seen that impurities are less likely to adhere to the ceramic dust filter using the alumina fiber, the mullite fiber, and the ceramic fiber in the order of the former. Further, from the results of Examples 1, 3, 4 and Comparative Example 2, it can be seen that when titania sol, zirconia sol, and alumina sol are used as the inorganic binder, impurities are less likely to adhere to the filter than when colloidal silica is used. Example 1,
From the results of Example 5, Comparative Example 4, and Reference Example 1, it can be understood that the ceramic dust filter using the inorganic fibers has a smaller pressure loss than the dust filter using the sintered body.
From the results of Example 1, Example 5, and Comparative Example 3, alumina fibers and titania sol produced a fibrous molded body,
If a coating layer made of spinel powder is formed on the surface,
It can be seen that the amount of impurities attached to the filter can be reduced.

[0047]

The ceramic dust filter according to the present invention has high heat resistance, high corrosion resistance to alkali metals and the like, low pressure loss, and high design flexibility. In particular, regarding the degree of design freedom, since the filter is made of a porous molded body using alumina fibers, by controlling the fiber size and the amount of the binder, various pressure loss is low and dust removal performance is high. This is preferable because a ceramic dust filter can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is an example of a fibrous formed body.

FIG. 2 is an example of a ceramic dust filter according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 ceramic dust filter 11 fibrous formed body 12 hollow portion 13 coating layer 21, 22 flow of exhaust gas

Continued on the front page (72) Inventor Takashi Onoe 1-8-1 Shintoda, Hamamatsu-shi, Shizuoka Nichias F-term in Hamamatsu Research Laboratory Co., Ltd.

Claims (5)

[Claims] 1. Alumina fiber bonded with an inorganic binder
Ceramic Dust Filler with Improved 3D Skeleton Structure
The alumina fiber is Al_TwoO _ThreeContent
Is 70% by weight or more, and the inorganic binder is titaniazo.
1 selected from sol, alumina sol and zirconia sol
Ceramics, characterized by being of at least one kind
Dust filter. 2. The ceramic dust filter according to claim 1, wherein the alumina fiber has an Al ₂ O ₃ content of 90% by weight or more. 3. The ceramic dust filter according to claim 1, wherein the inorganic binder is a titania sol. 4. A particle made of one or more selected from oxide ceramics other than silica, carbide ceramics, nitride ceramics, and cermet is attached to at least a gas introduction portion on the surface of the ceramic dust filter. The ceramic dust filter according to any one of claims 1 to 3, wherein a coating layer is formed. 5. The ceramic dust filter according to claim 4, wherein the oxide ceramic other than silica is an oxide ceramic having a spinel type crystal structure.