JPH1157355A - Ceramic filter and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve back washing efficiency regardless of the air passing pore diameter of a filter membrane layer. SOLUTION: A base material layer 2 composed mainly of a sintered compact of a ceramic particle such as silicon carbide particle having 300-400 μm particle diameter, the filter membrane layer 3 of a fine porous layer provided on the surface of the base material layer 2 and having 80-100 μm thickness and 15-25 μm average pore diameter and a ceraic particle forming many projections on the filter membrane layer 3 and 30-200 μm average particle diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic filter having excellent backwashing properties, and an improvement in a method for manufacturing the same.

[0002]

2. Description of the Related Art A ceramic filter installed in an exhaust gas purifying path for the purpose of filtering and removing dust is composed of ceramic particles of a material and a particle size corresponding to the purpose of use, which are similarly connected by a ceramic binder, and a myriad of pores communicating with the front and back. Is formed of a porous ceramic body. Ceramics for such applications include alumina ceramics, silicon carbide (S) having excellent wear resistance, heat resistance, chemical resistance, and the like.
iC) Ceramics are widely used.

FIG. 2 shows an example of such a ceramic filter. The ceramic filter has a cylindrical shape having an outer diameter of 60 mm × length of 1500 mm, and has a central shaft space 13 having an inner diameter of 40 mm. The thickness of this ceramic filter 1 is 10 mm
Is a substrate layer 11 obtained by sintering ceramic particles having a particle diameter of 100 to 500 μm,
It is a porous ceramic having a size of about 00 μm and is designed so that a sufficient mechanical strength as a ceramic filter can be obtained. On the surface of the base material layer 11, a thickness of 100
A filtration membrane layer 12 of about μm is formed.
The pore diameters of the myriad of filtration pores communicating with the front and back of are determined by the size of the filtration target. For example, if the object to be filtered is on the order of submicron, the filtration pore size of the filtration membrane layer 12 is about 0.5 μm.

In the ceramic filter 1 of this case, filtration is performed from the outside to the central axis space 13 via the filtration membrane layer 12, and as the filtration proceeds, filtration dust accumulates and the pressure difference between before and after the filter is increased. (Equivalent to pressure loss)
Rises. When this differential pressure reaches a certain upper limit,
A so-called backwashing operation is performed in which high-pressure air is repeatedly passed as a pulse in a direction opposite to the filtration direction, and the deposited filter dust is separated, dropped and removed.

[0005] Even if such a back washing operation is performed, fine dust clogging the filtration pores cannot be removed, and if the differential pressure does not recover to the initial low value, the clogging may occur. It is customary to replace it with a new one as its life. Then, in order to facilitate the backwashing operation, that is, to facilitate the removal of the filter-deposited dust, a method of setting the filtration pore diameter of the filtration membrane layer 12 of the ceramic filter small has been adopted.

As described above, when the filtration pore size is set to be small, the backwashing operation becomes somewhat easier, but the pressure loss must be increased, so that the frequency of backwashing becomes high. .

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to increase the backwashing efficiency irrespective of the filtration pore size of the filtration membrane layer. A ceramic filter having a novel structure is provided, and a method of manufacturing a ceramic filter having the novel structure is provided.

[0008]

Means for Solving the Problems A ceramic filter according to the present invention which has been made to solve the above problems, comprises a substrate layer,
It is characterized by comprising a filtration membrane layer provided on the surface and ceramic particles forming countless projections on the surface of the filtration membrane layer. The ceramic filter of the present invention is embodied in a form in which the ratio of the average particle diameter value b of the ceramic particles forming the projections to the average pore diameter value a of the filtration membrane layer is 2 or more. can do.

In the present invention, the combination b / a (μm) of the average pore diameter value a of the filtration membrane layer with the average particle diameter value b of the ceramic particles forming the projections is 50 to 50%.
200/15 to 25 (μm), or 30 to 80/0.
It can be embodied in a form of 3 to 5 (μm).

[0010] Further, the method for manufacturing a ceramic filter of the present invention, which has been made to solve the above-mentioned problem, comprises a step of coating a surface of a ceramic base material layer with a slurry for forming a filtration membrane layer, and then coating the surface with an average. Particle size 30-200
After the ceramic particles of μm are adhered, the particles are dried and sintered to form countless projections on the surface of the filtration membrane layer.

[0011]

Next, an embodiment of a ceramic filter and a method of manufacturing the same according to the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional illustration showing a model of a cross-sectional structure of the ceramic filter of the present invention. The ceramic filter of the present invention includes a base layer 2 and a filtration membrane layer 3 provided on the surface of the base layer 2. And a ceramic particle which forms countless projections 4 on the surface of the filtration membrane layer 3. Here, although the filtration membrane layer 3 is shown as a single layer, when the pore diameter is large and the pore diameter of the base material layer 2 is large, one or more intermediate filtration layers can be interposed.

In the case of a ceramic filter intended for ordinary dust (average particle size of 5 to 25 μm) generated in an incinerator, the base material layer 2 mainly includes ceramic particles having a particle size of 300 to 400 μm. Made of a sintered body of silicon carbide particles, for example, having an average pore diameter of 50 to 150 μm.
It has a series of vent holes that lead to countless front and back sides. The filtration membrane layer 3 provided on the surface of the base material layer 2 is formed by sintering finer particles made of the same material as the base material layer 2 and having a thickness of 80 mm.
It is composed of a microporous layer having a thickness of about 100 μm and an average pore size of 15 μm to 25 μm.

When the target dust is 5 μm or less and has a submicron size, the pore diameter of the base material layer 2 is 30 to 5 μm.
A microporous layer having a small diameter of about 0 μm and a pore size of 0.3 to 5 μm is formed as an average pore of the filtration membrane layer 3 which is a surface layer, and between the base layer 2 and the filtration membrane layer 3, Particle size 2
It is preferable that an intermediate filtration layer (not shown) of about 5 μm is interposed so that the size of pores changes stepwise.

The feature of the present invention resides in that the ceramic particles forming the countless projections 4 are fixed to the surface of the filtration membrane layer 3 at a certain interval. In this case, as ceramic particles for forming the projections 4, from the viewpoint of effectively improving the backwashing efficiency described below,
Preferably, the ratio b / a of the value b of the average particle diameter to the value a of the average pore diameter of the filtration membrane layer 3 is 2 or more. More preferably, the ratio b / a is 5 or more.

Further, in the present invention, the preferable size b of the ceramic particles for forming the projections 4 is shown in relation to the range of the average pore diameter a of the filtration membrane layer 3, and the combination b /
a (μm) is 50 to 200/15 to 25, or 30
８０80 / 0.3〜5. That is, the ceramic particles for forming projections have a suitable range in which the value of the average pore diameter of the filtration membrane layer 3 is adapted. At this time, the height of the protrusion 4 obtained naturally corresponds to about 1/2 to 2/3 of the size of one ceramic particle used, and the remainder is a portion embedded in the filtration membrane layer. Further, it is appropriate that the interval between the projections 4 is set to be about one ceramic particle used.

Next, Table 1 shows a comparison test result of the number of times of backwashing and the rate of air flow recovery between the ceramic filter having the countless projections 4 of the present invention and the conventional smooth ceramic filter. This test shows a case where simulated dust synthesized to have a composition similar to that of the collected ash from the ceramic filter of the actual machine was filtered.
It can be seen that, in the case of the embodiment of the present invention provided with the above, the rate of recovery of the ventilation rate is large and the cleaning effect is large in any backwashing. In addition, as a result of performing the filtration operation in the actual machine for a total of 800 hours and performing backwashing about 50 times, there was a difference of about 10% in the rate of air flow recovery.

[0017]

[Table 1] Note: Temperature indicates the filtration temperature of the ceramic filter.

Next, a method of manufacturing a ceramic filter according to the present invention will be described with reference to an embodiment of a SiC ceramic filter for ordinary dust in an incinerator. In this case, the base material layer is made of coarse SiC particles (average particle size of 350
μm) 60-70%, medium grain (average particle size 125 μm) 1
0 to 20%, fine particles (average particle size 1.5 μm) 15 to 25
% And a molding aid in a predetermined shape, for example, the above-mentioned cylindrical shape, and sintered at a high temperature of 2000 ° C. or higher.

The filtration membrane layer is composed of fine particles 1 of SiC particles.
(Average particle diameter 40 μm) 60 to 70%, fine particles 2 (average particle diameter 25 μm) 10 to 20%, fine particles (average particle diameter 1.5
A slurry having 15 to 25% of a molding aid added thereto is prepared, and the slurry is mechanically and spray-coated on the previously prepared cylindrical base material layer surface to a thickness of 80 to 100 μm.
coat m. In this case, the pore size of the obtained filtration layer is about 15 to 25 μm.
Layer or a plurality of intermediate pore size filtration layers,
It is preferable that the average pore diameter be reduced stepwise so that a target fine pore filtration layer is finally formed.

Then, in order to form projections on the coat layer, SiC particles having a relatively uniform particle size selected from the range of 30 to 200 μm are adhered by sand spray. It is preferable that dried SiC particles be adhered while the coating layer is kept sufficiently wet. By doing so, the SiC particles adhere to the surface of the coating layer in a single layer with a thickness of one particle,
Since extra particles do not adhere, orderly projections can be provided on the surface of the coat layer.

When it is desired to provide an appropriate interval between the projections, mechanical brushing may be performed to partially scrape off the attached particles. In the case where the ceramic particles are an oxide-based material, a flammable material having substantially the same size as the particles to be used, for example, particles of a synthetic resin are mixed, and adhered to the surface of the coat layer in the above-described procedure.
By burning the combustible material particles during subsequent sintering,
The space occupied by the space serves as a space, and an appropriate space can be provided between the projections.

After the projections are formed by the SiC particles in this way, the filter membrane layer is sufficiently dried, and the filtration membrane layer is sintered at a high temperature of 2000 ° C. or more to form filtration pores having an average pore diameter of 15 to 25 μm. This filtration membrane layer and the protruding portion can be firmly bonded to obtain a finished product. Thus, according to the present invention, a ceramic filter having a projection structure can be efficiently manufactured.

Here, the preferable particle size range of the SiC particles for forming the projections is 30 to 2 in accordance with the value of the average pore diameter of the filtration layer set in accordance with the particle size distribution of the object to be filtered.
What is necessary is just to select from the range of 00 micrometers. For example, the combination b / a (μm) of the average particle diameter b of the SiC particles and the average pore diameter a of the filtration membrane layer 3 is 50 to 200/15 to 25 (μm).
m) or a combination of 30 to 80 / 0.3 to 5 (μm) is practically appropriate, such as ease of production and backwashing efficiency. That is, the ceramic particles for forming projections have a suitable range in which the value of the average pore diameter of the filtration membrane layer 3 is adapted.

Next, the operation of the present invention will be described.
In the backwashing method using the ceramic filter of the present invention, as in the case of the ceramic filter described in detail above, a pulsed air current is supplied from the back surface side of the ceramic filter having ceramic particles forming countless projections on the surface of the filtration membrane layer. As the air flowing back through the filtration membrane layer is released to the surface, the deposition dust on the surface of the filtration membrane layer between the projections is peeled off, and at the same time, the filtration deposition dust covering between the projections is also pushed off. To remove.

It is considered that such a function is performed because the compressed state of the filter-deposited dust is alleviated by the presence of the ceramic particles of the present invention which form countless projections on the surface of the filter membrane layer. It is. To further explain this point, to observe the behavior of the filter sediment dust during the filtration operation of the ceramic filter of the present invention, as the filtration proceeds,
Although the dust to be filtered is deposited sequentially, the fine dust reaches the filter membrane layer between the protrusions and deposits,
Coarse dust is hindered by the projections and accumulates so as to cover the projections.

Therefore, in the case of a filter having no such projections, the dust deposited on the filtration membrane layer is further filled in a compressed state by the pressure at which the dust is accumulated. In such a case, dust accumulated on the filtration membrane layer as described above is alleviated by the projections so that the compressed state does not progress to a certain degree or more. Therefore, in the present invention, unlike the conventional case, the dust deposited on the filtration membrane layer is relatively easily separated and removed when subjected to backwashing.

[0027]

Since the present invention is configured as described above in detail, in the ceramic filter of the present invention, it is possible to increase the backwashing efficiency irrespective of the pore diameter of the filtration membrane layer. . Further, according to the method for manufacturing a ceramic filter of the present invention, a ceramic filter having the projection structure of the present invention can be efficiently manufactured. Therefore, the present invention has an extremely large industrial value as a ceramic filter and a method of manufacturing the same which have solved the conventional problems.

[Brief description of the drawings]

FIG. 1 is a conceptual cross-sectional view illustrating an embodiment of the present invention.

FIG. 2 is an external perspective view showing one example of a ceramic filter.

[Explanation of symbols]

1 ceramic filter, 2 substrate layer, 3 filtration membrane layer,
4 Projections.

Claims (4)

[Claims] 1. A substrate layer, a filtration membrane layer provided on the surface thereof,
And a ceramic filter comprising ceramic particles forming countless projections on the surface of the filtration membrane layer. 2. The ceramic filter according to claim 1, wherein the ratio of the average particle diameter value b of the ceramic particles forming the projection to the average pore diameter value a of the filtration membrane layer is 2 or more. 3. The combination b / a (μm) of the average pore diameter value a of the filtration membrane layer to the average particle diameter value b of the ceramic particles forming the projections is 50 to 200/15 to 2.
The ceramic filter according to claim 1, wherein the thickness of the ceramic filter is 5 (μm) or 30 to 80 / 0.3 to 5 (μm). 4. A slurry for forming a filtration membrane layer is coated on the surface of the ceramic base material layer, and ceramic particles having an average particle size of 30 to 200 μm are adhered to the surface, and then dried and sintered. And forming countless projections on the surface of the filtration membrane layer.