JP2001079321A - Honeycomb filter for dust collection and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a honeycomb filter capable of easily producing the honeycomb filter having a high capturing efficiency and low pressure loss with a simple device, moreover capable of producing many filters in uniform quality. SOLUTION: In the production method of a dust collecting honeycomb filter in which porous film is formed on the surface of the honeycomb porous base material, film is formed by supplying the slurry prepared from the aggregate particle whose 50% particle size (D50: μm) is >=2/3 times and not larger than the average pore diameter (P: μm) of the porous base material and whose particle distribution is within the range of the formula D50/(D50-D10)>=1.5 (where, D50 is 50% particle size (μm) and D10 is 10% particle size (μm) to the inside of a cell of the porous base material and the film is burned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a dust collecting honeycomb filter used for removing dust and the like in a gas to be treated, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A honeycomb filter is a dust collecting filter for removing dust and the like in a gas to be treated, and recovers products from a high-temperature gas in a wide range of fields such as chemical, electric power, steel and automobile-related industries. Or used to purify exhaust gas.

In general, as shown in FIG. 2, in a honeycomb filter, a large number of cells 23 are formed in a honeycomb-shaped porous body, and the ends of the large number of cells 23 on the inlet side B and the outlet side C are one cell. It has a structure sealed alternately every time. According to such a filter 21, by sending the gas to be treated including dust and the like into the cell 23 from the inlet side B,
Dust and the like larger than the pore diameter of the porous body are trapped in the pores of the cell wall 22, so that only the gas component that permeates the cell wall 22 can be collected from the outlet side C.

[0004] In the honeycomb filter, in addition to the high efficiency of capturing dust and the like, it is necessary to reduce the pressure loss when the gas to be processed permeates the filter and to improve the processing capacity. A structure in which a porous film having a smaller pore diameter than the porous substrate is formed on the surface of the material is employed. With such a structure, dust and the like are trapped exclusively in the porous film, so that by appropriately designing the pore size of the porous film, the dust and the like trapping efficiency can be improved, and By increasing the pore diameter of the porous substrate, the pressure loss of the entire filter can be reduced.

In the honeycomb filter having the above structure, for example, one end side of a porous base material in which pores are saturated with a liquid is decompressed,
A dynamic pressure vacuum method for supplying a slurry containing aggregate particles from the other end side (Japanese Patent Application Laid-Open No. 61-238315). Water is applied after the ceramic powder is adhered to the surface of the porous substrate in an air stream. Air flow coating method (Japanese Patent Laid-Open No. 10-249124), a slurry containing aggregate particles is brought into contact with and held on the surface of a porous substrate, and then a slurry injection / discharge method is performed. A dipping method in which the slurry containing the aggregate particles is immersed in a slurry containing the aggregate particles, a slurry direct filtration method in which the slurry containing the aggregate particles is supplied to each cell of the porous substrate, and the water in the slurry is removed through the porous substrate. Thus, a film can be formed on the surface of a honeycomb-shaped porous base material, and then fired to produce the film.

[0006]

However, the above-mentioned manufacturing methods have problems in manufacturing or in the quality of manufactured filters, and none of these methods can be said to be sufficient. For example, when the dynamic pressure vacuum method is applied to a substrate having a complicated shape such as a honeycomb structure, a complicated apparatus is required, and there is a problem in terms of production efficiency and production cost. In addition, in the airflow coating method, since the ceramic particles adhere to the substrate in an aggregated state, the average pore diameter of the porous film becomes large, and it is difficult to realize high trapping efficiency.

On the other hand, the slurry injection / discharge method and the dipping method have a problem that the capture efficiency and the degree of pressure loss vary between filters due to the difficulty in controlling the thickness of the porous film. there were. In the slurry direct filtration method, aggregate particles having a small average particle diameter (specifically,
When the slurry prepared from the aggregate particles having an average pore diameter of less than 2/3 of the base material) is to be formed into a film, the aggregate particles penetrate into the pores of the base material. There is a problem that a mixed layer of both having a dense structure is formed between them, and the pressure loss of the filter increases.

The present invention has been made in view of the above-described problems of the related art, and an object of the present invention is to provide a honeycomb filter having a high trapping efficiency and a small pressure loss by using a simple device. It is an object of the present invention to provide a method of manufacturing a honeycomb filter which can be easily manufactured and can manufacture a large number of filters with uniform quality.

[0009]

Means for Solving the Problems As a result of intensive studies by the present inventors, in the slurry direct filtration method, a slurry prepared from aggregate particles having an average particle diameter and a particle size distribution within a predetermined range is used. The present inventors have found that the above-mentioned problems of the prior art can be solved by forming a film, and completed the present invention.

[0010] That is, according to the present invention, a dust-collecting honeycomb in which at least one porous film having a smaller pore size than the porous substrate is formed on the surface of the honeycomb-shaped porous substrate. A method for producing a filter, wherein a 50% particle diameter (D ₅₀ : μm) is at least 2/3 times the average pore diameter (P: μm) of the porous substrate inside the cells of the porous substrate, A slurry prepared from aggregate particles having a particle size distribution of not more than 1 and having a particle size distribution in the range of the following formula (1) is supplied, and moisture in the slurry is allowed to pass through the pores of the porous substrate. A method for manufacturing a dust-collecting honeycomb filter, characterized by forming a film by removing the film and then firing the film, is provided. D ₅₀ / (D ₅₀ −D ₁₀ ) ≧ 1.5 (1) (However, D ₅₀ : 50% particle diameter (μm), D ₁₀ : 10% particle diameter (μm))

Further, according to the present invention, a honeycomb for dust collection, wherein at least one layer of a porous film having a smaller pore diameter than that of the porous substrate is formed on the surface of the honeycomb-shaped porous substrate. In the filter, the first porous membrane among the porous membranes has a 50% particle diameter (D ₅₀ : μm) which is 2/3 times the average pore diameter (P: μm) of the porous substrate. It is characterized in that the particle size distribution is not more than 1 time, the particle size distribution is constituted by aggregate particles within the range of the following formula (1), and the average film thickness is 3 times or more of the 50% particle diameter. The present invention provides a dust collecting honeycomb filter. D ₅₀ / (D ₅₀ −D ₁₀ ) ≧ 1.5 (1) (However, D ₅₀ : 50% particle diameter (μm), D ₁₀ : 10% particle diameter (μm))

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for manufacturing a honeycomb filter for dust collection according to the present invention, in a slurry direct filtration method, a film is formed by using a slurry prepared from aggregate particles having a predetermined average particle diameter and particle size distribution. It is characterized by performing. According to such a method, a honeycomb filter having a high capture efficiency and a small pressure loss can be easily manufactured with a simple device,
Further, it is possible to manufacture a large number of filters with uniform quality. Hereinafter, the production method of the present invention will be described in more detail.

The production method of the present invention is a slurry film forming method for forming a porous film on a surface of a porous substrate (hereinafter, simply referred to as “substrate”).
A slurry direct filtration method is employed in which a slurry containing aggregate particles is supplied, and water in the slurry is removed by passing through the pores of the base material to form a film. The slurry direct filtration method can be carried out with a simple apparatus as shown in FIG. 1 even for a substrate having a complicated shape such as a honeycomb shape. This is because it is superior to other methods in that the thickness of the film can be easily controlled and a large number of filters can be manufactured with uniform quality.

However, in the conventional slurry direct filtration method, when an attempt is made to form a film of a slurry prepared from aggregate particles having a small average particle diameter, the aggregate particles penetrate into pores of the base material, and the base material and the base material are mixed with each other. There is a problem that a mixed layer of both having a dense structure is formed between the porous membrane and the porous membrane, and the pressure loss of the filter increases. Therefore, in the production method of the present invention, a film is formed using a slurry prepared from aggregate particles having a predetermined average particle diameter and a predetermined particle size distribution.

First, in the production method of the present invention, the average particle diameter of the aggregate particles for preparing the slurry, that is, the 50% particle diameter (D ₅₀ : μm) is 2 times the average pore diameter (P: μm) of the base material. It is necessary to be at least / 3 times and at most 1 time.

By setting the 50% particle diameter of the aggregate particles to be at least 2/3 times the average pore diameter of the base material, the aggregate particles hardly enter the pores of the base material. As in the method, a mixed layer of both having a dense structure is formed between the base material and the porous membrane, and it is possible to prevent the pressure loss of the filter from increasing. On the other hand, since the 50% particle diameter of the aggregate particles is not more than one time the average pore diameter of the base material, the pore diameter of the porous film formed on the base material surface does not become unnecessarily large, and dust and the like are trapped. There is no loss in efficiency.

Further, when the 50% particle diameter of the aggregate particles is within the above range, the balance between the settling property of the slurry and the adhesion of the particles to the base material becomes good, so that the thickness of the porous membrane is increased. This is also preferable in that it is possible to make the filter constant and to make the capture efficiency and the degree of pressure loss uniform between filters. In order to balance the pressure loss of the filter and the trapping efficiency of dust and the like at a higher level, it is necessary to use 5% of aggregate particles.
The 0% particle size is at least 4/5 times the average pore size of the substrate,
It is preferred to be 7 times or less.

In the manufacturing method of the present invention,
The 50% particle diameter of the aggregate particles for preparing the rally is within the above range.
In addition, the particle size distribution of the aggregate particles is within a predetermined range.
Must be within enclosure. Specifically, the aggregate particles
50% particle size (D ₅₀: Μm) and 10% particle diameter (D_Ten: Μ
m) must satisfy the relationship of the following equation (1). D₅₀/ (D₅₀-D_Ten) ≧ 1.5 (1)

The reason for defining not only the 50% particle size but also the particle size distribution of the aggregate particles is that even if the 50% particle size is within the above-mentioned range, the particle size distribution is broad and contains many fine components. This is because, in such a case, the pressure loss of the filter may increase as in the case where the 50% particle size is less than 2/3 of the average pore size of the base material. The smaller the value of D ₅₀ / (D ₅₀ -D ₁₀ ) used as an index in the present invention, the broader the particle size distribution is.
If the value is less than the above, the pressure loss of the filter increases, which causes a problem in use of the filter. When the particle size distribution of the aggregate particles does not satisfy the above conditions, it is possible to adjust the particle size distribution to a predetermined particle size by performing a conventionally known classification process such as elutriation, cyclone, and sizer.

In the present invention, 50% particle size and 10%
The particle size is determined by the Stokes liquid layer sedimentation method,
X-ray transmission type particle size distribution analyzer (for example, SEDIGRAPH 5000-02 manufactured by Shimadzu Corporation) which performs detection by a line transmission method.
Shape, etc.). According to the X-ray transmission type particle size distribution measuring device, the particle size corresponding to the accumulated weight% settled is directly displayed by the particle size distribution curve, so that the 50% particle size and the 10% particle size can be measured relatively easily. For example, FIG. 3 shows a particle size distribution curve obtained by measuring the particle size distribution of aggregate particles before classification and the particle size distribution after classification by elutriation using an X-ray transmission type particle size distribution analyzer. It can be confirmed that the treatment increases the particle size by 10% (that is, decreases the fine particle component) and sharpens the particle size distribution.

In the production method of the present invention, conditions other than the 50% particle diameter and the particle size distribution of the aggregate particles are not particularly limited, but the concentration of the aggregate particles in the slurry is 0.5% by weight or more. In the range of less than 0% by weight, and more preferably in the range of 0.8% by weight or more and 1.5% by weight, the balance between the settling property of the slurry and the adhesion of the particles to the substrate is improved. preferable. Further, if the volume of the slurry used for film formation is less than three times the total volume of the cell on which the porous film is to be formed, there is a problem that a film thickness difference occurs inside the cell.
If it exceeds twice, the amount of slurry becomes large and the operation becomes difficult. Therefore, the total volume of the cells is preferably 3 times or more and 6 times or less.

The production method of the present invention is based on the assumption that the first porous film is formed on the base material. However, the formation of the second and subsequent porous films is not limited to the first porous film. After baking, it can be performed in the same manner as described above. In this case, the 50% particle diameter of the aggregate particles contained in the slurry used for forming the (n + 1) th layer is set to be not less than 2/3 times and not more than 1 time of the average pore diameter of the nth layer porous film. It is preferable that the particle size distribution of the aggregate particles satisfies the relationship of the following expression (1). D ₅₀ / (D ₅₀ −D ₁₀ ) ≧ 1.5 (1)

In the filter of the present invention, at least one porous film having a smaller pore size than the base material is formed on the surface of the honeycomb base material. Then, the first porous film among the porous films formed on the surface of the base material (ie, the first porous film)
The 50% particle diameter (D ₅₀ : μm) of the aggregate particles constituting the porous membrane which is in direct contact with the substrate surface is 2/3 times or more and 1 time or less of the average pore diameter (P: μm) of the substrate. And an aggregate particle having a particle size distribution in the range of the following formula (1). D ₅₀ / (D ₅₀ −D ₁₀ ) ≧ 1.5 (1)

In such a filter, since the inside of the pores of the substrate is not closed by fine particles and a porous film having an appropriate pore diameter is formed on the surface of the substrate, the trapping efficiency is high and the pressure is high. This is useful in that the loss can be reduced.

In the filter of the present invention, 1
Although only the relationship between the porous membrane of the layer and the substrate is specified,
It is preferable that the same relationship is satisfied for the second and subsequent porous films. That is, the 50% particle diameter of the aggregate particles constituting the (n + 1) th layer porous membrane is not less than 2/3 times and not more than 1 time of the average pore diameter of the nth layer porous membrane. It is preferable that the particle size distribution satisfies the relationship of the following expression (1). D ₅₀ / (D ₅₀ −D ₁₀ ) ≧ 1.5 (1)

In the filter of the present invention, the 50% particle size and the particle size distribution of the aggregate particles of the porous membrane satisfy the above conditions, and the average thickness of the first porous membrane is It is necessary that the particle diameter is at least three times the 50% particle diameter of the film itself. This is because if the ratio is less than three times, the capture efficiency may decrease. The other conditions are not particularly limited, but the average thickness of the first porous film is preferably 7 times or less the 50% particle diameter of the aggregate particles constituting the porous film, and preferably 5 times or less. It is more preferable that the number be twice or less. This is because if the thickness of the porous membrane is made larger than necessary, the pressure loss of the filter may increase even if the 50% particle size and the particle size distribution of the aggregate particles of the porous membrane are specified.

[0027]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to these examples.

In Examples 1 to 5 and Comparative Examples 1 to 13, a slurry was formed on the surface of the honeycomb-shaped base material and fired, whereby a porous film having a smaller pore diameter than the base material was obtained. The formed honeycomb filter for dust collection was manufactured.

(Substrate) Cordierite is used as the substrate.
Consisting of: average pore diameter 15 μm, size 150 mm × 1
In the longitudinal direction of the porous body of 50 mm x 500 mm, the cell wall
1.3mm thick, 10mm x 10mm cross section square
A large number of cells are formed, and as shown in FIG.
A structure in which one end and the other end of a cell are alternately sealed for each cell
The ones having were used. Should form a porous film of the substrate
Total cell volume is 3692cm ^ThreeMet.

(Porous Membrane) The porous membrane was formed by forming a slurry on the inner surface of the cell of the above-mentioned base material and firing the slurry. The thickness of the porous film was controlled by the slurry concentration described later, and a porous film having three average thicknesses of 20 μm, 30 μm, and 50 μm was formed.

Each of the aggregate particles is made of cordierite and has a 50% particle diameter of 2 μm, which is an average pore diameter of the base material of 15 μm.
The ones that were / 3 times or more and 1 times or less were used. The slurry was prepared by adjusting the weight ratio of the aggregate particles, the organic binder, and the water to 5
1: 0.005: 99 for 0 μm, 0.6: 0.003: 99.4 for 30 μm, 0.4: 0.002: 99.6 for 20 μm The mixture was stirred and mixed with a homomixer. The volume of the slurry used for the film formation was set to three times the total volume of the cells for forming the porous film, which was 3692 cm ³ .

The slurry was formed by a slurry direct filtration method using the processing apparatus 4 shown in FIG. In the treatment device 4, the slurry 8, which has been adjusted to a uniform concentration in the slurry tank 6 by the stirring action of the magnet stirrer 5,
, Slurry injection tool 3, mounting jig 2
Is supplied from the cell opening on the inlet side of the substrate 1 to the inside of the cell, and is filtered by the cell walls of the substrate 1 to form a film. That is, since the outlet side of the cell is sealed, the water in the slurry permeates through the cell wall of each cell and flows out into the adjacent cell, while the aggregate particles in the slurry adhere to the inner surface of the cell. By doing so, film formation proceeds.

At this time, the supply amount of the slurry 8 is monitored by a liquid level gauge 7 provided in the slurry tank 6.
When the supply amount reaches a predetermined value, the supply of the slurry 8 is automatically stopped. Next, the film formation is completed by inverting the base material 1 and discharging the filtered water flowing into the adjacent cell from the cell opening on the outlet side. The film is dried and 13
By firing at 50 ° C. for 2 hours to form a porous film, a honeycomb filter was obtained. The total area of the formed porous film was 17172 cm ² .

[0034] (Example 1, Comparative Example 1-2) using the slurry values were prepared from the aggregate particles is 1.765 of D ₅₀ / is an indicator of the particle size distribution (D ₅₀ -D ₁₀₎ formed The membrane was made.

[0035] (Example 2, Comparative Example 3-4) formed by using the slurry values were prepared from the aggregate particles is 1.729 of an indicator of the particle size distribution _{D 50 / (D 50 -D 10} ) The membrane was made.

[0036] (Example 3, Comparative Example 5-6) formed by using the slurry values were prepared from the aggregate particles is 1.708 of an indicator of the particle size distribution _{D 50 / (D 50 -D 10} ) The membrane was made.

[0037] (Example 4, Comparative Example 7-8) formed by using the slurry values were prepared from the aggregate particles is 1.630 of an indicator of the particle size distribution _{D 50 / (D 50 -D 10} ) The membrane was made.

[0038] (Example 5, Comparative Example 9-10) formed using a slurry values were prepared from the aggregate particles is 1.592 of an indicator of the particle size distribution _{D 50 / (D 50 -D 10} ) The membrane was made.

The value of (Comparative Example 11 to 13) is an indicator of the particle size distribution _{D 50 / (D 50 -D 10} ) was subjected to film formation using a slurry prepared from the aggregate particles is 1.487 .

(Evaluation Method) Examples 1 to 5 and Comparative Examples 1 to
With respect to the 13 honeycomb filters, pressure loss and trapping efficiency were evaluated by the following methods. The results are shown in Table 1 and FIG.

(1) Pressure loss The pressure loss of the filter was evaluated based on the differential pressure generated in the porous membrane of the filter (hereinafter, referred to as "transmembrane pressure"). The base material inlet side and outlet when air at normal temperature was previously passed through the base material before forming the porous membrane at a flow rate (m ³ / min) of 1 (m / min) per filtration area (m ² ). The pressure difference (mmAq) between the filter inlet side and the filter outlet side is measured for the filters of Examples and Comparative Examples in the same manner. The value obtained by subtracting the pressure difference was used as the transmembrane pressure difference (mmAq) of the filter. Normally, transmembrane pressure is 35mmA
If the value exceeds q, the pressure loss of the filter increases and exceeds the allowable differential pressure, which is not preferable.

(2) Capture Efficiency Assuming that the particle density on the filter inlet side is 6250 (particles / m ³ ), air containing dioctyl phthalate particles having a 50% particle diameter of 0.2 μm is used as a filter in Examples and Comparative Examples. And the particle density (particles / m ³ ) at the outlet of the filter was measured, and the value obtained from the following equation (2) was taken as the trapping efficiency (%). Usually, if the trapping efficiency is less than 80%, the amount of dust leaking increases, and the dust collection performance is undesirably reduced. Capture efficiency (%) = 1− (exit particle density / inlet particle density) (2)

(Others) Although not shown in Table 1, the thickness of the porous film was measured at a plurality of positions of one filter, and the uniformity of the thickness of the porous film was determined from the degree of the variation. , Manufactured many filters under the same conditions,
The pressure loss and trapping efficiency of each filter were measured, and the stability of the characteristics of the porous membrane was evaluated based on the degree of variation. As a result, the honeycomb filters of Examples 1 to 5 and Comparative Examples 1 to 13 all showed good results in terms of the uniformity of the thickness of the porous film and the stability of the characteristics of the porous film.

[0044]

[Table 1]

(Results) As shown in Table 1, Examples 1 to 5
Both filters showed good results in both the capture efficiency and the transmembrane pressure. On the other hand, although the filter of Comparative Example 11 had good capture efficiency, it had a problem in that the transmembrane pressure was as high as 38 mmAq, the pressure loss of the filter increased, and exceeded the allowable differential pressure. Further, the filters of Comparative Examples 1 to 10 and 12 to 13 in which the average thickness of the porous membrane is less than three times the 50% particle diameter of the aggregate particles are good in terms of the transmembrane pressure, but the capture efficiency is low. This was reduced to less than 80%, which was problematic in terms of dust collection performance.

[0046]

According to the manufacturing method of the present invention, it is possible to easily manufacture a honeycomb filter having a high trapping efficiency and a small pressure loss with a simple device, and to manufacture a large number of filters with uniform quality. Is possible. Further, the honeycomb filter of the present invention has a high trapping efficiency and a small pressure loss. Therefore, the honeycomb filter is widely used as a dust collecting filter for removing dust and the like in a gas to be treated, such as chemical, electric power, steel, and automobile-related industries. In various fields, it can be suitably used for product recovery from high-temperature gas and exhaust gas purification.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of a method for manufacturing a honeycomb filter for dust collection of the present invention.

FIG. 2 is a perspective view showing a general configuration of a honeycomb filter.

FIG. 3 is a graph showing a particle size distribution curve measured by an X-ray particle size distribution measuring device.

FIG. 4 is a graph showing the relationship between the particle size distribution and the transmembrane pressure difference.

[Explanation of symbols]

1: porous substrate, 2: mounting jig, 3: slurry injecting tool,
4 ... Treatment apparatus, 5 ... Magnet stirrer, 6 ... Slurry tank, 7 ... Level gauge, 8 ... Slurry, 9 ... Piping, 21 ...
Honeycomb filter, 22 ... cell wall, 23 ... cell.

Claims (2)

[Claims] 1. A method for manufacturing a dust-collecting honeycomb filter, comprising a honeycomb-shaped porous substrate and at least one porous film having a smaller pore size than the porous substrate formed on the surface of the honeycomb substrate. The inside of the cell of the porous substrate, the 50% particle diameter (D ₅₀ : μm) is 2/3 times or more and 1 time or less of the average pore diameter (P: μm) of the porous substrate. ,
Further, a slurry prepared from aggregate particles having a particle size distribution within the range of the following formula (1) is supplied, and water in the slurry is removed by permeating the pores of the porous substrate to form a film. And then calcining the honeycomb filter for dust collection. D ₅₀ / (D ₅₀ −D ₁₀ ) ≧ 1.5 (1) (However, D ₅₀ : 50% particle diameter (μm), D ₁₀ : 10% particle diameter (μm)) 2. A honeycomb filter for dust collection, wherein at least one porous film having a smaller pore size than that of the porous substrate is formed on a surface of the honeycomb-shaped porous substrate, The first porous membrane of the porous membrane has a 50% particle diameter (D ₅₀ : μm) of 2/3 times or more and 1 time or less of the average pore diameter (P: μm) of the porous substrate. So,
A honeycomb filter for dust collection, comprising an aggregate particle having a particle size distribution within the range of the following formula (1), and having an average thickness of three times or more of the 50% particle diameter. D ₅₀ / (D ₅₀ −D ₁₀ ) ≧ 1.5 (1) (However, D ₅₀ : 50% particle diameter (μm), D ₁₀ : 10% particle diameter (μm))