JP3003475B2 - 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). alumina (Al 2 _{O 3)} and a one or more filter obtained by forming a coating layer by vapor deposition is selected from the group consisting of carbon (C), the fiber molded article, the coating Prior to layer formation, the surface corresponding to the filter surface side is brushed , and the fibers are made of carbon or
It is characterized by being joined by graphite .

[0016]

According to a second aspect of the present invention, there is provided the filter according to the first aspect , wherein the volume content of the fiber is 1 to 15%, the volume content of the coating layer is 2 to 15%, and the volume content of the carbon or graphite for bonding the fiber. The ratio is 2 to 20%, and the volume content of pores is 50 to 95%.

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 molded article is (i) a non-woven fabric formed of a single fiber having a length of 0.5 mm or more, preferably 1 to 5 mm. (Ii) a non-woven fabric formed of a continuous single fiber or a yarn obtained by bundling single fibers. (iii) A nonwoven fabric formed of the short fibers of (i) and the continuous single fibers of (ii) or the mixed fibers of yarns can be provided. In the above (i) to (iii), the fiber diameter is preferably about 5 to 20 μm.

Such a fiber molded article can be produced, for example, by pouring a resin in which fibers are dispersed in a resin, curing the resin, and then carbonizing (or graphitizing) the resin. In this case, a phenol resin, an epoxy resin, polyvinyl alcohol, or the like can be used as the resin, and an organic solvent or water is further used as necessary for dispersion of the fibers.

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

The fiber molded article according to the present invention can also be manufactured by depositing carbon on the surface of the aggregate of fibers by a CVD method, and joining the contacts of the fibers with the deposited carbon.

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 fiber molded article according to the present invention may be a long-fiber woven fabric.

The filter according to 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 thus obtained.
D coating layer is formed.
Prior to the formation of the VD coating layer, it is characterized in that the fiber molded body is raised.

There is no particular limitation on the method of raising the hair. For example, the following method (a) or (b) can be adopted.

(A) When the above-mentioned fiber-dispersed resin solution is cured and carbonized to produce a fiber molded body, the surface of the cured cured body is rubbed and rubbed with a sandpaper, a wire brush or the like.

(B) When the fiber-dispersed resin solution is cured and carbonized to produce a fiber molded body, the surface of the carbonized molded body is rubbed and rubbed with sandpaper, a wire brush or the like.

The brushing process is performed on the side which becomes the dust removing surface when the filter is used in the dust removing process, that is, the surface on the inflow side of the gas to be treated.

The filter of the present invention is produced by forming a CVD coating layer on the fiber molded body subjected to the raising treatment as described above.
The fibers constituting the fiber molded body, the carbon or graphite for bonding the fibers, the volume content of the above-mentioned CVD coating layer and the pores, such as dust removal efficiency, pressure loss, heat resistance, mechanical properties, durability, etc. From the viewpoint, it is preferable to be in the following range.

Fiber: 1 to 15% Carbon or graphite: 2 to 20% CVD coating layer: 2 to 15% Voids: 50 to 95% The shape of the filter of the present invention is not particularly limited. The following shapes (A) to (C) are preferable in order to reduce the loss and increase the durability against pressure during backwashing (removal of accumulated dust) of the filter.

(A) Bottomed or non-bottomed cylindrical shape (B) Bottomed or non-bottomed rectangular cylindrical shape (C) Tapered lengthwise in (A) or (B) above (one end side) And the other end side has a different cross-sectional size). The wall thickness t of the filter is, from the viewpoint of pressure loss and anti-backwash pressure, relative 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. In addition, since the surface of the fiber molded body is raised, the pressure loss can be further reduced. For this reason, it is possible to increase the passing speed of the gas to be treated, thereby reducing the size of the dust removing device and the induction exhaust fan (reducing the required power).

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.
, The 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 SiC fiber having a length of 2 mm and a diameter of 8.5 μm was treated with acetone:
It was dispersed in a mixture of phenol resin = 2: 1 (weight ratio), poured into a mold, and cured by autoclaving. After rubbing the surface of the cured product with # 120 sandpaper, the resin was carbonized by heating at 900 ° C. in a nitrogen gas atmosphere. SiC thus obtained
An SiC coating layer is formed on the fiber surface of the fiber molded body by a CVD method, and the cross-sectional shape and dimensions shown in FIG.
A cylindrical filter 1 including a flange portion 1A, a cylindrical portion 1B, and a bottom portion 1C was manufactured.

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

SiC fiber: 7% Carbon: 2% SiC coating layer: 10% Voids: 81% After the obtained filter was subjected to the heat cycle shown in FIG. 2 and the pressure cycle shown in FIG. 3, respectively, Exhaust gas (temperature of about 150 ° C.) was processed, and pressure loss was compared and measured with respect to the presence or absence of dust load. The results are shown in FIG.

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.

Comparative Example 2 A filter was manufactured in the same manner as in Example 1 except that the raising treatment was not performed, and a comparative measurement of the pressure loss was similarly performed. 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 nonwoven fabric made of continuous SiC fibers having a diameter of 11 μm was dispersed in an aqueous solution of polyvinyl alcohol having a solid content of 6% by weight.
This was poured into a mold and cured, and then heated at 900 ° C. in a nitrogen gas atmosphere to carbonize the polyvinyl alcohol. The surface of the SiC fiber molded body thus obtained was brushed with a wire brush, and then a SiC coating layer was formed by a CVD method to produce a cylindrical filter having a cross-sectional shape and dimensions shown in FIG.

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

SiC fiber: 9% Carbon: 3% SiC coating layer: 8% Voids: 80% The obtained filter was subjected to a thermal cycle shown in FIG. 2 and a pressure cycle shown in FIG. 3, respectively. Exhaust gas generated by incineration of the incinerated garbage shown in Table 1 was subjected to dust removal treatment under the following conditions, and the change in pressure loss and the change in collection efficiency at that time are shown in FIGS. 5 and 6, respectively.

[0051]

[Table 1]

Exhaust gas amount at dust removal conditions : 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 this, it is clear that dust removal can be stably performed over a long period of time with a small pressure loss and a high collection efficiency.

Example 3 A dust filter having an outer dimension of 3 m × 4.3 m × 1.5 m and a total filtration area of 174 m ² was prepared using a bottomed rectangular tube filter manufactured in the same manner as in Example 1. And the above Table 1
Exhaust gas generated by incineration of the garbage incineration shown in Table 2 was treated under the following dust removal conditions.

As a result, the collection efficiency of the filter was remarkably high at 99.5% even six months after the start of the treatment.
The pressure loss was as low as 95 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 3 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.

Comparative Example 4 A filter was manufactured in the same manner as in Example 3 except that the raising treatment was not performed, and the dust removal treatment was performed in the same manner. The collection efficiency of the filter was 99 months after the start of the treatment. Although it was remarkably high at 0.5%, the pressure loss was 125 mmAq at a filtration speed of 4 m / min, which was slightly higher than that of Example 3.

[0058]

As detailed above, according to the present invention, according to the filter of the present invention, heat resistance, corrosion resistance at high temperatures, excellent durability, yet allows the pressure loss is extremely small and thin, or
In addition, handling in a CVD coating layer forming process
A filter that is easy to perform and 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 at the time of backwashing and the repetition of heat and thermal shock. You.

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 Examples 1 and 2.

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]

 1 Filter 1A Flange 1B Cylindrical 1C Bottom

──────────────────────────────────────────────────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. One or two selected from the group consisting of silicon carbide, silicon nitride, alumina, alumina / silica and carbon.
On the fiber surface of a fiber molded body composed of at least one kind of fiber,
Silicon carbide, silicon nitride, a one or filter obtained by forming a coating layer by two or more vapor deposition is selected from the group consisting of alumina and carbon, the fiber preform is in the coating layer formed Previously, the surface corresponding to the filter surface side was brushed , and the fibers were carbon or carbon.
Is a filter characterized by being bonded with graphite . 2. The filter according to claim 1 , wherein the volume content of the fiber is 1 to 15%, the volume content of the coating layer is 2 to 15%, and the volume content of carbon or graphite joining the fibers is 2 to 20%. %, And the volume content of pores is 50 to 95%.