JP3071218B2 - Ceramic filter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a ceramic filter for separating and capturing a solid in a gas or a liquid.

[Prior art and problems] As is well known, a porous ceramics separation membrane used for a semiconductor process in-line gas filter or the like includes:
Alumina asymmetric membranes are used. This material is
Since it was originally developed for gas separation of uranium raw materials, it started with a simple shape, that is, a single tube shape, in order to ensure reliability in a large plant. Extrusion molding is suitable as a method for forming this single tube, and a lotus root-shaped tube developed later is also made by a similar molding technique.

By the way, in both the single tube and the lotus root tube, the separation membrane is formed inside the hole. Here, the separation membrane has the same chemical composition as the support, and is formed by sintering a powder having a small particle size.

[Problems to be Solved by the Invention] However, both the single tube and the lotus root tube,
The overall shape is made of a support material that has a strong function, and the separation membrane is formed inside the single tube or inside the hole of the lotus root tube, so the membrane is smaller than the volume of the entire ceramic membrane material. It is difficult to increase the area. Therefore, in order to secure the membrane area, the ceramic membrane material becomes large, and as a result, the membrane module becomes large, and eventually the separation device must be large.

Also, the ceramic film material in the form of a tube defines the concept of a ceramic module. That is,
Basically, a module with a length of less than 1 m was used, and a small membrane module was made by cutting a tube into a membrane material, and attached a casing, gasket, etc. Therefore, the minimum diameter of the module was limited by the thickness of the ceramic tube.

The present invention has been made in view of the above circumstances, and has a pore diameter smaller than the pore diameter of the porous ceramic support on the surface of the skeleton excluding a part of the porous ceramic support having a three-dimensional network structure. A plurality of ceramic membranes having the following structure are formed, and the pore diameter is gradually reduced from the inside to the surface of the ceramic membrane formed from the ceramic support toward the surface of the multilayered ceramic membrane. It is an object of the present invention to provide a ceramic filter capable of increasing a film area.

[Means for Solving the Problems] The present invention provides a porous ceramic support having a three-dimensional network structure on a surface of a skeleton excluding a part of the porous ceramic support having a pore size smaller than the pore size of the porous ceramic support. The ceramic filter is characterized in that a plurality of ceramic membranes having a plurality of layers are formed, and the pore diameter is gradually reduced from the inside to the surface from the inside of the ceramic support toward the surface of the ceramic membrane formed with the plurality of layers. .

In the present invention, in order to form a porous ceramic support into a three-dimensional network structure, a technique of foaming a ceramic slurry to form a foam is used. According to this technique, it is difficult for defects to be introduced into the network ceramics. Further, when forming a film on the surface of the support having a three-dimensional network structure, in order to avoid occurrence of defects such as pinholes in the film, the ceramic foam molded body is treated with a solvent that dissolves a binder, Alternatively, it is preferable that the cross section of the ceramic constituting the mesh is made substantially circular by dipping in a thin ceramic slip after calcination. Note that a ceramic support having a three-dimensional network structure usually has a ceramic slip attached to the surface of a polyurethane foam or the like to form a molded body, which is then fired to burn off the urethane foam to form only the ceramic support. Is formed. However, according to this technique, the place where the urethane was present becomes a hole, significantly reducing the strength of the network, and has many micro cracks generated when the ceramic slip attached to the urethane surface dries and shrinks. Gases generated when urethane is decomposed have many defects such as cracks in the mesh, which is not preferable.

In the present invention, the reason why the ceramic support is made porous is to make the inside of the ceramic support constituting the network a flow path of the fluid after filtration. Further, the material of the ceramic support having the mesh shape is determined based on the strength and the permeation resistance of the fluid.

In the present invention, it is also effective to combine a mesh-like ceramic with a bone-like structure having a large flow path for collecting and flowing the fluid flowing through the network-like structure, in order to increase the membrane area per unit area. For example, thin channels such as the vasculature of an animal or leaves of a plant are collected into a thick channel.

In the present invention, in order to combine the mesh-like porous ceramics with the bone-like porous ceramics, the bone-like porous ceramics material is previously molded by pressure molding or other methods, processed, calcined, and after bubbling. It is possible by a method such as insertion into an undried foam and integration. Alternatively, a separately molded foam compact and a bone compact may be processed and calcined, assembled, and joined with a slurry for forming foam.

In the present invention, as a method of introducing communicating pores having a low permeation resistance into the ceramic support, particles having a relatively large particle size and fine powder are blended, and the particles having a large particle size are deformed during sintering. It may be a method utilizing the property of being difficult to introduce pores between large particles, or may be another method.

In the present invention, as a means for forming a ceramic film having a pore diameter smaller than the pore diameter of the porous ceramic on the surface of the porous ceramic support, a known immersion method, that is, fine ceramic particles forming the ceramic is used. This is possible by immersing the ceramic support in the suspended liquid, absorbing the liquid in the porous support, and attaching the suspended ceramic fine particles to the surface of the support. Here, in order for the ceramic fine particles to adhere to the surface of the support, the relative relationship between the pore diameter of the support and the diameter of the fine particles is important. If the diameter of the fine particles is too small, they will penetrate into the support. Further, the fine particle layer attached to the support surface can be heated and baked on the support.
The baking conditions are determined in consideration of the degree of particle growth of the fine particles and the baking strength. Specifically, as the baking temperature increases, the particle growth progresses, the pore diameter of the film due to the fine particles increases, and the baking strength to the support increases. on the other hand,
If the baking temperature is too high, shrinkage of the film proceeds, and ground cracks occur on the film surface.

Incidentally, the ceramic filter according to the present invention, the surface of the porous ceramic support having a three-dimensional network structure,
A configuration in which a ceramic film having a diameter smaller than the pore diameter of the porous ceramic is formed may be used. Further, in the ceramic filter, the porous ceramic support having a three-dimensional network structure has a bone-like structure made of the same material as the network structure and having a thickness larger than a skeleton portion of the network structure. The structure and the inside of the bone-like structure may integrally communicate with each other, and a filter membrane may be formed on a part or all of the surface of the ceramic filter formed on the surface of the mesh structure and the bone-like structure. .

[Operation] According to the present invention, a ceramics filter capable of increasing the film area per unit area is obtained.

Example An example of the present invention will be described below.

(1) Agitated foaming; 90 parts by weight of alumina particles having an average particle diameter of 20 μm, and a primary particle diameter of 0.
10 parts by weight of 2 μm high-purity alumina powder, 50 parts by weight of ion-exchanged water, 5 parts by weight of methylcellulose as a binder, 5 parts by weight of ammonium stearate as a foam stabilizer, and 0.5 parts by weight of a dispersant ammonium polyacrylate are placed in a stirrer. It was charged and stirred and foamed.

(2) Formation of a round bar; 90 parts by weight of alumina particles having an average particle size of 20 μm, and a primary particle size of 0.
10 parts by weight of 2 μm high-purity alumina powder, 20 parts by weight of ion-exchanged water, and 5 parts by weight of methylcellulose as a binder were mixed with a crusher, granulated through a 40-mesh nylon sieve, and dried to obtain a granulated powder. . Next, 50 kg / c
Pressure molding was performed at a pressure of m ² to obtain a 50 mm × 50 mm × 5 mm plate-like molded body. Next, the molded body was heated in the air at 1200 ° C. for one hour to obtain a calcined body, which was then machined to obtain a 4 × 40
mm round bar.

(3) Formation of support; The round bar was inserted into the foam and dried at the same time. Next, this dried body was processed into a rod shape of 10φ × 40 mm. At this time, the axis center of the calcined body of φ4 was set as the processing center. Next, the processed body was fired in air at 1200 ° C. for 1 hour, and then fired in a hydrogen atmosphere at 1900 ° C. for 2 hours to obtain a support. As shown in FIG. 1, the support has a thick bone-like structure 1 having a diameter of 3.9 mm at the center and a thickness of 0.3 mm around the bone structure 1.
And a mesh structure 2 having a cell diameter of 1 mm is surrounded. The ceramic material had a porosity of 30% and a pore diameter of 10 μm. FIG. 2 is a sectional view taken along line XX of FIG. 1, and FIG. 3 is a partially enlarged view of FIG. In the figure, the film 3 is formed on one end (X) side of the bone-like structure portion 1, and the film is not formed on the other end (Y). Reference numeral 4 denotes a film on the surface of the network structure 2 which communicates with the film 5 on the surface of the bone structure 1. The inside of the network structure 2 is a porous body having large pores.

Next, the support was immersed in a slip obtained by dispersing 3 parts by weight of high-purity alumina powder having a primary particle diameter of 1 μm and an average particle diameter of aggregates of 3 μm in 100 parts by weight of ion-exchanged water. Dried. This was baked in air at 1500 ° C. for 2 hours to obtain a support (film-formed body) on which a single layer of film was formed.

Next, the above-mentioned film-formed body was immersed in a slip obtained by dispersing 1 part by weight of high-purity alumina powder having a primary particle diameter of 0.2 μm and an average particle diameter of aggregates of 1 μm in 100 parts by weight of ion-exchanged water, and then dried. Baking in air at 1200 ° C. for 2 hours. Subsequently, the end of the bone-like structure 1 was processed with a diamond grinder to remove the film portion at the end of the bone-like structure 1. Subsequently, ceramics were fixed to a stainless steel tube having an inner diameter of 12 mm using a Teflon gasket. The space introduced from one of the stainless steel tubes was connected to the outer space of the ceramic, and the other was connected to the inner space of the tube from which the membrane had been removed, to form a filter module.

The outer diameter of this module is φ15mm, length 50mm, volume 9c
m ³ and a membrane area of 238 cm ² . In contrast, the conventional filter module has an outer diameter of 50 mm, a length of 70 mm, and a volume of 137 c.
m ³ , and the membrane area was 143 cm ² .

It should be noted that the present invention is not limited to alumina ceramics, but can also be made of ceramics of other components made by molding and sintering a granular material. For example, the ceramic material may be an oxide such as silica, zirconia, spinel, or mullite, or a non-oxide such as silicon nitride or silicon carbide.

[Effects of the Invention] As described above in detail, according to the present invention, the surface of the skeleton excluding a part of the porous ceramic support having a three-dimensional network structure is larger than the pore diameter of the porous ceramic support. By adopting a structure in which a plurality of ceramic films having a small pore diameter are formed, and the pore diameter gradually decreases from the inside to the surface from the inside of the ceramic support toward the surface of the ceramic film formed of the plurality of layers, A ceramic filter capable of increasing the membrane area per unit area can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a support according to one embodiment of the present invention, FIG. 2 is a sectional view taken along line XX of FIG. 1, and FIG. 3 is a partially enlarged view of FIG. 1 ... bone-like structure part, 2 ... mesh-like structure part, 3, 4, 5 ... membrane.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadayoshi Muto 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. Hadano Plant (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 39/20

Claims (1)

(57) [Claims] 1. A plurality of ceramic films having pore diameters smaller than the pore diameter of the porous ceramics support are formed on the surface of the skeleton excluding a part of the porous ceramics support having a three-dimensional network structure. A ceramic filter, characterized in that the pore diameter gradually decreases from the inside toward the surface of the ceramic film having a plurality of layers formed from the inside of the ceramic support.