JPH07116434A - Filter - Google Patents

Abstract

PURPOSE:To manufacture a thin-walled dust removing filter of high heat resistance and corrosion resistance usable in the corrosive atmosphere of high temperature with little pressure loss. CONSTITUTION:A filter is composed of a CVD coating layer of SiC, Si3N4, Al2O3 or C on the fiber surface of a fiber formed body of SiC, Si3N4, Al2O3 Al2O3.SiO2 or C and the surface of the fiber formed body is napped prior to forming the coating layer. The filter, therefore, is provided with superior heat resistance usable at the high temperature of 1000 deg.C or over. As the fiber formed body is used as a substrate, the thin-walled filter is provided with sufficient mechanical strength and large void content and with little pressure loss. The pressure loss is reduced further by napping. A coating layer of high purity, high corrosion resistance and high heat resistance is formed on the surface by means of the CVD process, and the filter can be used sufficiently in the corrosive atmosphere such as HCl at the high temperature.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

By the way, in the dust removal process of exhaust gas from a waste incinerator outlet, if the exhaust gas can be removed at a high temperature without being cooled, the exhaust gas is removed, and then heat exchange is performed to generate high temperature and high pressure steam in the boiler. And by using this for power generation, thermal energy can be effectively recovered as electrical energy. Therefore, from the viewpoint of exhaust heat recovery and effective use, it is necessary to remove the dust without cooling the exhaust gas. Therefore, the dust filter has a high heat resistant temperature and can be used at 1000 ° C. or higher. desired.

Further, since the exhaust gas of the refuse incinerator contains corrosive HCl and Cl ₂ , the dust-removing filter has not only a high heat-resistant temperature but also an excellent corrosion resistance at high temperatures. desired.

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

That is, when the pressure loss is large, it is necessary to reduce the passage velocity of the exhaust gas in order to reduce the pressure loss and enhance the dust removal efficiency. There is no choice but to transform.

Further, since the thick filter itself becomes bulky, it leads to an increase in size of the dust remover.

[0008]

Among the conventional filters, the glass fiber bag filter has a maximum operating temperature of 2
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 use.

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

In the honeycomb structure ceramic filter, the maximum operating temperature is not so high as 600 ° C. In addition, since it is made of sintered ceramic, it has a large wall thickness and a small porosity, which causes a large pressure loss. is there. Ceramic tube filters have a maximum operating temperature of 900-100
Although it is as high as 0 ° C., since it is made of sintered ceramic, it has a drawback that it is thick and has a large pressure loss, as described above.

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

Further, the ceramic filter by the CVD method currently under development has the drawbacks that it is thick, has a large pressure loss, and is high in cost.

As described above, the dust-removing filter, particularly the dust-removing exhaust gas-removing filter can be used even at a high temperature of 1000 ° C. or higher. In a corrosive atmosphere containing Cl ₂ or HCl,
And it can be used at high temperature. Thin, low pressure loss and miniaturization of dust remover. Such a condition is required, but the fact is that no filter that satisfies all such conditions has been provided so far.

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

[0015]

A filter according to claim 1 comprises:
Silicon Carbide (SiC), Silicon Nitride (Si ₃ N ₄ ), Alumina (Al ₂ O ₃ ), Alumina / Silica (Al ₂ O ₃ · S)
iO ₂ ) and carbon (C), the surface of the fiber of the fiber molded body composed of one or more fibers selected from the group consisting of silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), A filter comprising a coating layer formed by vapor deposition of one or more selected from the group consisting of alumina (Al ₂ O ₃ ) and carbon (C), wherein the fiber molding is the coating layer. Before the formation, the surface corresponding to the filter surface side is napped.

A filter according to a second aspect is the filter according to the first aspect, characterized in that the fiber molded body is formed by joining fibers with carbon or graphite.

The filter according to claim 3 is the filter according to claim 2, wherein the volume content of the fibers is 1 to 15%, the volume content of the coating layer is 2 to 15%, and the volume content of carbon or graphite for joining the fibers is The ratio is 2 to 20%, and the volume content of pores is 50 to 95%.

The present invention will be described in detail below according to the method for producing the filter of the present invention.

In order 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 fibers or C fibers.

This fiber molding is (i) a non-woven fabric of monofilaments having a length of 0.5 mm or more, preferably 1 to 5 mm. (Ii) a non-woven fabric of continuous monofilaments or yarns bundled with monofilaments. (iii) A nonwoven fabric-like molded product of the short fibers of (i) and the continuous single fibers of (ii) or a mixed fiber of yarns can be obtained. In addition, 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 dispersion of fibers in a resin into a mold, 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 needed in dispersing the fibers.

The fiber molded product thus obtained is a non-woven fabric-shaped fiber molded product in which carbon or graphite produced by carbonization or graphitization of resin is bonded to the contact points of the fibers.

The fiber molding according to the present invention can also be manufactured by depositing carbon on the surface of an aggregate of fibers by the CVD method and joining the contacts of the fibers with each other.

The method for producing a fiber molded body according to the present invention is not limited to the above method, but according to the above method for joining fibers with carbon or graphite, the CVD coating of the next step is reached. It is possible to easily manufacture a porous fiber molded body having a high porosity and being sufficiently resistant to handling.

The fiber molding according to the present invention may be a woven fabric of long fibers.

The filter of the present invention has a CV of SiC, Si ₃ N ₄ , Al ₂ O ₃ or C so that a predetermined proportion of pores remain on the fiber surface of the fiber molded body thus obtained.
D coating layer is formed.
It is characterized in that the fiber molded body is raised before the formation of the VD coating layer.

There is no particular limitation on the method of this raising treatment, but for example, the following method (a) or (b) can be adopted.

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

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

The nap raising process is performed on the surface which becomes the dust removing surface when used as a filter for dust removing processing, that is, the surface on the inflow side of the gas to be treated.

The filter of the present invention is manufactured by forming a CVD coating layer on the fiber molding thus treated for raising, and in the filter of the present invention,
The volume content of the fibers constituting the fiber molded body, carbon or graphite for joining the fibers, the CVD coating layer and the pores depends on its dust removal efficiency, pressure loss, heat resistance, mechanical properties, durability, etc. From the viewpoint, the following range is preferable.

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

(A) Bottomed or bottomless cylindrical shape (B) Bottomed or bottomless rectangular tube shape (C) Tapered in the length direction in (A) or (B) above (one end side) And the size of the cross section on the other end side is different) Note that the wall thickness t of the filter is √ (R / 30) <t with respect to the radius R of the filter in terms of pressure loss and backwash pressure resistance.
It is preferably <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), and the rectangular tubular filter (B).
Indicates the radius of the circumscribed circle of the inner wall, and the radius of the taper filter (C) in (A) and (B) above is the larger radius.

In the filter of the present invention, the material of the fiber forming the fibrous body and the material of the CVD coating layer may be the same or different, but when both are made of the same material, 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 removes dust from the exhaust gas from the refuse incinerator and the exhaust gas from the boiler outlet, removes the dust from the gas flowing into the furnace top pressure turbine of the steelmaking blast furnace, removes the dust from the blast furnace exhaust gas, etc. It can be used very effectively for dust removal.

[0036]

The filter of the present invention is made of SiC fiber, Si ₃ N ₄
SiC, Si ₃ on the fiber surface of the fiber, Al ₂ O ₃ fiber, Al ₂ O ₃ · SiO ₂ fiber or C fiber fiber molding
It is formed by forming a CVD coating layer of N ₄ , Al ₂ O ₃ or C, and is composed 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 higher.

Further, since the fiber molded body is used as the substrate, a filter having a sufficient mechanical strength even with a thin wall, a large porosity and a small pressure loss can be obtained. Moreover, since the surface of the fiber molded body is raised, the pressure loss can be further reduced. Therefore, it is possible to increase the passage speed of the gas to be treated to reduce the size of the dust removing device and the size of the induced draft fan (reduction of required power).

Furthermore, since a coating layer of 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.

According to the filter of the second aspect, handling in the CVD coating layer forming step becomes easy.

According to the filter of claim 3, there is provided a filter having a small pressure loss, excellent handleability, and capable of sufficiently withstanding repeated pressure pulses applied during backwashing and repeated heat and thermal shock. It

[0041]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 A SiC fiber having a length of 2 mm and a diameter of 8.5 μm was replaced with acetone:
It was dispersed in a mixed solution of phenol resin = 2: 1 (weight ratio), poured into a mold and cured by an autoclave treatment. The surface of this cured product was rubbed with # 120 sandpaper, and then heated at 900 ° C. in a nitrogen gas atmosphere to carbonize the resin. SiC thus obtained
By forming a SiC coating layer on the fiber surface of the fiber molded body by the CVD method, 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 surface 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% Porosity: 81% After applying the heat cycle shown in FIG. 2 and the pressure cycle shown in FIG. 3 to the obtained filter, respectively, Exhaust gas (temperature of about 150 ° C.) was treated and the pressure loss was compared and measured with and without dust load, and the results are shown in FIG.

Comparative Example 1 Commercially available glass fiber bag filter (inner diameter 115 mm,
For the outer diameter of 120 mm and the length of 1000 mm), comparative pressure loss measurement was carried out in the same manner as in Example 1, 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 nap treatment was not performed, and the comparative measurement of pressure loss was performed in the same manner. The results are shown in FIG.

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

Example 2 A nonwoven fabric made of SiC continuous fibers having a diameter of 11 μm was dispersed in a polyvinyl alcohol aqueous solution having a solid content of 6% by weight,
This was poured into a mold to be cured, and then heated at 900 ° C. in a nitrogen gas atmosphere to carbonize the polyvinyl alcohol. The surface of the thus obtained SiC fiber molded body was raised with a wire brush, and then a SiC coating layer was formed by the CVD method to manufacture a cylindrical filter having the 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% Porosity: 80% After applying the heat cycle shown in FIG. 2 and the pressure cycle shown in FIG. 3 to the obtained filter, respectively, Exhaust gas generated by incinerating the refuse incineration materials shown in Table 1 was subjected to dust removal treatment under the following conditions, and changes in pressure loss and changes in collection efficiency at that time are shown in FIGS. 5 and 6, respectively.

[0051]

[Table 1]

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

Example 3 A dust remover 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 the bottomed rectangular tube filter manufactured by the same method as in Example 1. And manufactured in Table 1 above.
Exhaust gas generated by incinerating the waste incineration product shown in was treated under the following dust removal conditions.

As a result, the collection efficiency of the filter was as high as 99.5% six months after the start of the treatment, and
The pressure loss could be suppressed to 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 dust collector outlet: 7 g / Nm ³ Comparative example 3 Commercially available Inconel bag filter (outer diameter 8.9 cm ×
A dust remover (outer diameter: 2.5 m x height: 13 m, total filtration area: 174 m ² ) using a bottomed cylindrical filter having a length of 1.0 m was used to perform dust removal treatment in the same manner as in Example 3. It was

As a result, the pressure loss is 0.4 m / per filtration rate.
In addition to being as high as 250 mmAq at min, the collection efficiency dropped to 75% after 6 months from the start of the treatment due to 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 even after half a year from 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 described in detail above, according to the filter of the present invention, it is excellent in heat resistance, corrosion resistance at high temperature, durability, pressure loss is extremely small and thinning is possible, and high efficiency treatment is achieved. And a filter effective for downsizing of dust removing equipment is provided.

According to the filter of the second aspect, handling in the CVD coating layer forming step becomes easy.

According to the filter of claim 3, there is provided a filter having a small pressure loss, excellent handleability, and capable of sufficiently withstanding repeated pressure pulses applied during backwashing and repeated heat and thermal shock. It

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

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing filters manufactured in Examples 1 and 2.

FIG. 2 is a graph showing heat cycle conditions applied to a filter in Examples 1 and 2.

FIG. 3 is a graph showing pressure cycle conditions with which a filter is loaded 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 changes in pressure loss in Example 2.

FIG. 6 is a graph showing changes in collection efficiency in Example 2.

[Explanation of symbols]

 1 Filter 1A Flange 1B Cylindrical 1C Bottom

Claims (3)

[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 the fiber molded body composed of at least one kind of fiber,
A filter having a coating layer formed by one or more kinds selected from the group consisting of silicon carbide, silicon nitride, alumina and carbon by a vapor deposition method, wherein the fibrous molded body is formed prior to forming the coating layer. A filter characterized in that the surface corresponding to the filter surface side is brushed. 2. The filter according to claim 1, wherein the fiber molded body is formed by bonding fibers with carbon or graphite. 3. The filter according to claim 2, wherein the volume content of the fibers is 1 to 15%, the volume content of the coating layer is 2 to 15%, and the volume content of carbon or graphite for joining the fibers is 2 to 20. %, And the volume content of pores is 50 to 95%.