JP3003474B2 - filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter for removing dust in high-temperature gas such as exhaust gas from a refuse incinerator, exhaust gas from a boiler, gas flowing into a furnace top pressure turbine of a steelmaking blast furnace, or exhaust gas from a blast furnace. About.

[0002]

2. Description of the Related Art Conventionally, as a filter for removing dust from various kinds of exhaust gas, a bag filter made of glass fiber, a bag filter made of metal, a ceramic filter having a honeycomb structure, a ceramic tube filter and the like have been provided. Further, ceramic filters formed by a chemical vapor deposition method (CVD method) are being developed.

[0003] By the way, if it is possible to remove dust at a high temperature without cooling the exhaust gas in the dust removal treatment of the exhaust gas from a garbage incinerator, heat is exchanged after removing the exhaust gas, and high-temperature, high-pressure steam is passed through a boiler. By using this for power generation, heat energy can be effectively recovered as electric energy. Therefore, from the viewpoint of exhaust heat recovery and effective utilization, it is necessary to remove dust without cooling the exhaust gas. Therefore, the dust removal filter has a high heat-resistant temperature and can be used at 1000 ° C. or higher. desired.

[0004] Further, since the corrosive HCl and Cl ₂ are contained in the exhaust gas of the garbage incinerator, the filter for dust removal is not only high in heat resistance temperature but also excellent in corrosion resistance at high temperature. desired.

Further, in order to improve the processing efficiency and reduce the size of the dust remover, it is desired that the pressure loss is small and the thickness of the filter is small.

That is, when the pressure loss is large, it is necessary to lower the passage velocity of the exhaust gas in order to reduce the pressure loss and increase the dust removal efficiency. I have to change.

[0007] Further, the thick filter itself becomes bulky, which leads to an increase in the size of the dust remover.

[0008]

Among the conventional filters, the bag filter made of glass fiber has a maximum operating temperature of two.
The temperature is about 50 to 300 ° C., and in order to use this bag filter for dust removal of high-temperature exhaust gas, it is necessary to cool the high-temperature exhaust gas, which is disadvantageous in terms of exhaust heat recovery and effective utilization.

Although the maximum operating temperature of a metal (Inconel) bag filter is 870 ° C., which is higher than that of a glass fiber bag filter, it has a problem in corrosion resistance and cannot be used for dust removal of corrosive gas. There are drawbacks.

[0010] Honeycomb-structured ceramic filters have the drawback that the maximum operating temperature is not so high as 600 ° C, and because they are made of sintered ceramic, they are thick and have a low porosity, so that pressure loss is large. is there. Ceramic tube filters have a maximum operating temperature of 900 to 100
Although it is as high as 0 ° C., since it is made of sintered ceramic, it has the disadvantage that it is thick and has a large pressure loss as described above.

Moreover, the existing ceramic filter is Si
Since it is made of O ₂ or Al ₂ O ₃ , it cannot cope with dust removal of exhaust gas which is highly corrosive at high temperatures.

Further, the ceramic filter manufactured by the CVD method, which is currently under development, has disadvantages in that it is thick, has a large pressure loss, and is expensive.

As described above, a filter for removing dust, particularly a filter for removing exhaust gas from refuse incineration, can be used even at a high temperature of 1000 ° C. or more. In a corrosive atmosphere containing Cl ₂ or HCl,
And it can be used at high temperatures. It is thin, has low pressure loss, and can be miniaturized. Such a condition is required, but a filter that satisfies all such conditions has not been provided so far.

The present invention solves the above-mentioned conventional problems and provides a thin filter for dust removal which has high heat resistance and corrosion resistance which can be used even in a high-temperature corrosive atmosphere, and has a small pressure loss and a small thickness. Aim.

[0015]

According to the first aspect of the present invention, there is provided a filter comprising:
Silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), alumina (Al ₂ O ₃ ), alumina silica (Al ₂ O ₃ .S)
silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), on the fiber surface of a fiber molded body composed of one or more fibers selected from the group consisting of iO ₂ ) and carbon (C). A filter formed by forming one or two or more coating layers formed by a vapor deposition method selected from the group consisting of alumina (Al ₂ O ₃ ) and carbon (C). A first fiber layer constituting a surface side;
A second fiber layer provided on the back side of the fiber layer, wherein the first fiber layer is a layer in which fibers are gathered in a nonwoven fabric, and the second fiber layer is a layer of a woven fabric of fibers. or Ri assembly layer der chopped yarn and fiber molding is a fiber carbon
Alternatively, it is characterized by being joined by graphite .

[0016]

[0017] according to claim 2 filter, the filter of claim 1, 1-10% volume content of fibers in the formed surface layer with a first fiber layer, the volume content of the coating layer is 2-20% The volume content of carbon or graphite joining fibers is 1 to 20%, the volume content of pores is 50 to 96%, and the volume content of fibers of the base layer composed of the second fiber layer is 5 to 5%. 20%, the volume content of the coating layer is 5 to 20
%, The volume content of carbon or graphite joining the fibers is 1 to 2
0% and the volume content of pores is 40 to 89%.

Hereinafter, the present invention will be described in detail according to the filter manufacturing method of the present invention.

To manufacture the filter of the present invention, first,
SiC fiber, Si ₃ N ₄ fiber, Al ₂ O ₃ fiber, Al ₂
A fiber molded body is manufactured using O ₃ · SiO ₂ fiber or C fiber.

The fibrous formed body is made up of a first fiber layer and a second
It has a laminated structure composed of a fiber layer.

First fiber layer (i) Single-fiber non-woven aggregate layer having a length of at least 0.5 mm, preferably 1 to 5 mm (ii) Non-woven non-woven aggregate layer of continuous single fibers or yarns bundled with single fibers Or (iii) a non-woven aggregate layer of the short fiber of (i) and the continuous fiber of (ii) or the mixed fiber of yarn, the second fiber layer (a) a layer in which a plurality of woven fabrics of fibers are laminated, or (b) An aggregated layer of chopped yarn having a length of 1 mm or more, preferably 5 to 25 mm. In the above (i) to (iii) and (a) to (b), the single fiber diameter is preferably about 5 to 20 μm. . In (b), the chopped yarn preferably has about 500 to 2,000 such single fibers converged.

Such a fiber molded article is, for example, a two-layered cloth-like article formed by laminating a woven fabric of fibers and impregnating the resin with one side and spraying short fibers together with the resin by a spray-up method. After winding the cloth body around a mold, vacuum forming is performed. Then, after hardening, it can be manufactured by carbonizing (or graphitizing) the resin.

[0023] Further, after an assembly of chopped yarns impregnated with a resin is wound around a mold, a nonwoven fabric of continuous fibers impregnated with the resin is wound around the surface, and after curing, the resin is carbonized (or carbonized). (Graphitization).

In this case, the resin is a phenol resin,
Epoxy resin, polyvinyl alcohol, or the like can be used, and the resin used may be the same or different between the first fiber layer and the second fiber layer. In using the resin, an organic solvent or water is further used as necessary.

The fiber molded body obtained in this manner is a fiber molded body in which carbon or graphite produced by carbonizing or graphitizing a resin is joined to the contacts of fibers.

Further, in the fiber molded article according to the present invention, by depositing carbon on the surface of the laminate of the first fiber layer and the second fiber layer by the CVD method, the contacts of the fibers are joined by the deposited carbon. It can also be manufactured.

The production method of the present invention to such a fibrous form but not in any way limited to the above method, the present invention, for joining the fibers with carbon or graphite, up to the CVD coating of the next step It is possible to easily produce a porous fiber molded body having sufficient porosity that can withstand handling sufficiently.

The fibers of the first fiber layer and the fibers of the second fiber layer constituting the fiber molded body may be of the same material or of different materials. By using this, generation of stress due to a difference in thermal expansion is prevented, which is advantageous for use at higher temperatures.

The filter of the present invention has a CV of SiC, Si ₃ N ₄ , Al ₂ O ₃ or C such that a predetermined ratio of pores remains on the fiber surface of the fiber molded product obtained in this manner.
Manufactured by forming a D coating layer.

In the filter of the present invention, the fibers constituting the fiber molded body, carbon or graphite for bonding the fibers,
The above-mentioned volume content of the CVD coating layer and the voids corresponds to the surface layer corresponding to the first fiber layer and the second fiber layer in terms of dust removal efficiency, pressure loss, heat resistance, mechanical properties, durability and the like. It is preferable that the respective base layers have the following ranges.

Surface layer fiber: 1 to 10% Carbon or graphite: 1 to 20% CVD coating layer: 2 to 20% Void: 50 to 96% Base layer fiber: 5 to 20% Carbon or graphite: 1 to 20% CVD Coating layer: 5 to 20% Void: 40 to 89% The thickness of each of the surface layer and the base layer is 0.5 to
It is preferably 5 mm and the base layer 1 to 10 mm.

The shape of the filter of the present invention is not particularly limited. However, in order to reduce the pressure loss and to increase the durability against pressure during backwashing (removal of accumulated dust) of the filter, the following is required. (A) to (C).

(A) A bottomed or non-bottomed cylindrical shape (B) A bottomed or non-bottomed rectangular tube shape (C) Tapered in the longitudinal direction in (A) or (B) above (one end and other The thickness t of the filter is determined by the following formula from the viewpoint of pressure loss and anti-backwash pressure with respect to the radius R of the filter: √ (R / 30) <t
Preferably, it is <15 mm. Here, the radius R of the filter means the inner radius of the cylindrical filter (A) (the average inner radius if it is not a perfect circle), the rectangular cylindrical filter (B)
In this case, the radius of the circumscribed circle of the inner wall and the radius of the tapered filter (C) in (A) and (B) above are the larger ones.

In the filter of the present invention, the fiber material constituting the fiber molded body and the material of the CVD coating layer may be the same or different. The generation of stress due to the difference in thermal expansion is prevented, which is advantageous for use at higher temperatures.

The filter of the present invention is useful for removing high-temperature, corrosive gases such as dust from exhaust gas from the garbage incinerator and exhaust gas from the boiler, dust from the gas flowing into the furnace top pressure turbine of a blast furnace for steelmaking, and dust from the blast furnace exhaust gas. It can be used very effectively for dust removal.

[0036]

The filter of the present invention is composed of SiC fiber, Si ₃ N ₄
Fibers, the Al ₂ O ₃ fibers, Al ₂ O ₃ · SiO ₂ fibers or fiber surface of the fiber molded body of C fibers, SiC, Si ₃
It is formed by forming a CVD coating layer of N ₄ , Al ₂ O ₃ or C, and is made of only a high heat-resistant material, so that it has excellent heat resistance that can be used even at a high temperature of 1000 ° C. or more.

Further, since the fibrous formed body is used as the base, a filter having a sufficient mechanical strength even with a small thickness, a large porosity and a small pressure loss can be obtained. Moreover, since the fiber molded body has a laminated structure of the first fiber layer and the second fiber layer, the following operation and effect can be obtained. That is, the surface layer on the filter dust removal side can be efficiently removed with a small pressure loss by the nonwoven fabric-like aggregate layer of the fibers of the first fiber layer. On the other hand, the woven fabric of fibers of the second fiber layer or the aggregate of chopped yarns enables the base layer of the filter to effectively function as a reinforcing layer of the surface layer, has excellent handling properties, and is capable of reducing pressure pulses and thermal stress applied during backwashing. A high-strength filter that is sufficiently resistant to repetition is provided. In addition, a chopped yarn or a woven fabric can form a layer having sufficiently high mechanical strength even if the porosity is increased, and is effective in reducing pressure loss.

Further, since a coating layer having high purity, high corrosion resistance and high heat resistance is formed on the surface by the CVD method, it can be sufficiently used even in a corrosive atmosphere such as HCl at a high temperature.

In addition, the fiber of the fiber molded body is made of carbon or graphite.
In this case, handling in the CVD coating layer forming step is facilitated.

According to the filter of the second aspect , there is provided a filter which has a small pressure loss, is excellent in handleability, and can sufficiently withstand the repetition of the pressure pulse applied at the time of backwashing and the repetition of heat and thermal shock. You.

[0041]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 A laminate of 8 plain woven cloths of SiC fibers having a diameter of 11 μm (thickness: 2 mm) was acetone: phenol resin = 2: 1.
(Weight ratio) of the resin solution. On one surface of the resin-impregnated laminate, SiC fibers having a length of 2 mm and a diameter of 8.5 μm are sprayed together with the same resin liquid as described above by a spray-up method, then wound around a mold, and formed by a vacuum bag method ( The pressure was 200 torr). Then, it is cured in an autoclave, and then 900 ° C. in a nitrogen gas atmosphere.
And carbonized the resin. An SiC coating layer is formed on the fiber surface of the SiC fiber molded body thus obtained by the CVD method, and is composed of a flange portion 1A, a cylindrical portion 1B, and a bottom portion 1C having the cross-sectional shape and dimensions shown in FIG. Thus, a cylindrical filter 1 having a laminated structure of the surface layer 1a and the base layer 1b was manufactured.

The volume content of the components of each layer of the obtained filter is as follows.

Surface layer SiC fiber: 5% Carbon: 2% SiC coating layer: 10% Voids: 83% Base layer SiC fiber: 15% Carbon: 5% SiC coating layer: 15% Voids: 65% The thickness of 1a was 1 mm, and the thickness of base layer 1b was 1.5 mm.

After loading the obtained filter with the heat cycle shown in FIG. 2 and the pressure cycle shown in FIG. 3, respectively, the exhaust gas (at a temperature of about 150 ° C.) is treated to reduce the pressure loss with respect to the presence or absence of dust load. Compare and measure the results
Shown in the figure.

Comparative Example 1 A commercially available glass fiber bag filter (inner diameter 115 mm,
Comparative measurement of pressure loss was carried out in the same manner as in Example 1 for an outer diameter of 120 mm and a length of 1000 mm), and the results are shown in FIG.

It is apparent from FIG. 4 that the filter of the present invention has a small pressure loss and can perform an efficient dust removal process even when the dust load is large.

Example 2 A 3 mm thick chopped yarn compact (diameter 11 μm) impregnated with an aqueous solution of polyvinyl alcohol having a solid content of 8% by weight.
12m long yarn with 800 m of SiC fibers converged
m is formed by shaping the chopped yarn cut into pieces by the SMC method) into a mold at 40 ° C., 300 torr.
After drying in vacuum, acetone: phenol =
One layer of 3 mm thick felt (felt made of continuous fiber of 11 μm diameter SiC fibers) impregnated with a 2: 1 (weight ratio) resin liquid was wound. Then, after hardening in an autoclave, the resin was heated at 900 ° C. in a nitrogen gas atmosphere to carbonize the resin. The Si thus obtained
A SiC coating layer is formed on the fiber surface of the C fiber molded body by a CVD method, and is composed of a flange portion 1A, a cylindrical portion 1B, and a bottom portion 1C having a cross-sectional shape and dimensions shown in FIG. Was manufactured.

The volume content of the components of each layer of the obtained filter is as follows.

Surface layer SiC fiber: 3% Carbon: 2% SiC coating layer: 8% Void: 86% Base layer SiC fiber: 15% Carbon: 5% SiC coating layer: 6% Void: 74% The thickness of 1a was 1.5 mm, and the thickness of base layer 1b was 2.5 mm.

After applying the heat cycle shown in FIG. 2 and the pressure cycle shown in FIG. 3 to the obtained filter, respectively, the exhaust gas generated by incinerating the incinerated garbage shown in Table 1 is subjected to dust removal under the following conditions. The change in pressure loss and the change in collection efficiency at that time are shown in FIGS. 5 and 6, respectively.

[0052]

[Table 1]

Dust removal conditions Exhaust gas amount: 1200 m ³ / hr (at 825 ° C.) Exhaust gas temperature: 1000 to 1050 ° C. Dust type: incineration ash Dust concentration: 5 g / Nm ³ Dust load: about 300 g / m ² · hr Filtration speed: 3.9 m / min (at 1025 ° C.) Number of filters: 28 (filtration area: about 5.1 m ² ) Reproduction method: pulse air (timer control: about 3 minute intervals) From FIGS. 5 and 6, the filter of the present invention is shown. According to the results, it is clear that dust can be stably removed over a long period of time with a small pressure loss and a high collection efficiency.

Example 3 Using a bottomed rectangular cylindrical filter manufactured in the same manner as in Example 1, the outer dimensions were 2.4 m × 4.3 m × 1.5.
A dust filter having a height of m and a total filtration area of 174 m ² was manufactured, and the exhaust gas generated by burning the incinerated waste shown in Table 1 was treated under the following dust removal conditions.

As a result, the collection efficiency of the filter was as high as 99.5% even six months after the start of the treatment.
The pressure loss was as low as 105 mmAq at a filtration speed of 4 m / min, and high efficiency treatment was possible.

Dust Removal Conditions Exhaust gas amount: 9700 Nm ³ / hr Treatment temperature: 900 ° C. Dust concentration at the outlet of the dust remover: 7 g / Nm ³ Comparative Example 2 A commercially available bag filter made of Inconel (outer diameter 8.9 cm ×
A dust remover (outer diameter 2.5 m × height 13 m, total filtration area 174 m ² ) using a bottomed cylindrical filter having a length of 1.0 m was subjected to dust removal treatment in the same manner as in Example 3. Was.

As a result, the pressure loss was 0.4 m / filtration speed.
The min. efficiency was as high as 250 mmAq, and the collection efficiency was reduced to 75% six months after the start of the treatment due to the corrosion deterioration of the filter.

[0058]

As described above in detail, according to the filter of the present invention, heat resistance, corrosion resistance at high temperatures, excellent durability, yet allows the pressure loss is small and thin, also, CV
Easy handling in D coating layer formation process
In addition, a filter that is effective for high-efficiency processing and miniaturization of dust removal equipment is provided.

[0059]

According to the filter of the second aspect , there is provided a filter which has a small pressure loss, is excellent in handleability, and can sufficiently withstand the repetition of the pressure pulse applied during the backwashing and the repetition of the thermal shock.

According to the filter of the present invention, it is possible to recover and reuse thermal energy by directly removing dust from the high-temperature exhaust gas without cooling it.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a filter manufactured in Examples 1 and 2.

FIG. 2 is a graph showing thermal cycle conditions applied to filters in Examples 1 and 2.

FIG. 3 is a graph showing pressure cycle conditions applied to filters in Examples 1 and 2.

FIG. 4 is a graph showing the results of Example 1 and Comparative Example 1.

FIG. 5 is a graph showing a change in pressure loss in Example 2.

FIG. 6 is a graph showing a change in trapping efficiency in Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filter 1A Flange part 1B Cylindrical part 1C Bottom part 1a Surface layer 1b Base layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 39/00-39/20

Claims (2)

(57) [Claims] 1. Silicon carbide, silicon nitride, alumina, aluminum
One or two selected from the group consisting of silica and carbon
On the fiber surface of a fiber molded body composed of at least one kind of fiber,
From the group consisting of silicon carbide, silicon nitride, alumina and carbon
One or more selected coatings by vapor deposition
A fibrous body, wherein the fibrous formed body comprises a first fiber constituting a surface side of the filter.
A fiber layer and a second fiber layer provided on the back side of the first fiber layer
And wherein the first fiber layer is a layer in which fibers are gathered in a nonwoven fabric form.,
2 The fiber layer is a woven layer of fibers or a collection of chopped yarns
In layersAnd In addition, the fiber molded body is formed by bonding fibers with carbon or graphite.
To A filter, characterized in that: 2. The filter according to claim 1 , wherein the volume content of the fibers in the surface layer composed of the first fiber layer is 1 to 10.
%, The volume content of the coating layer is 2 to 20%, the volume content of the carbon or graphite joining the fibers is 1 to 20%, and the volume content of the pores is 50 to 96%. The volume content of the fibers in the base layer to be composed is 5 to 20%, the volume content of the coating layer is 5 to 20%, the volume content of the carbon or graphite joining the fibers is 1 to 20%, and the volume content of the pores A filter having a ratio of 40 to 89%.