JP2008161799A - Manufacturing method of ceramic filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a ceramic filter which can form a filter membrane with uniform membrane thickness across the entire length of the ceramic filter. <P>SOLUTION: This manufacturing method is to manufacture the ceramic filter with the filter membrane formed on the inner wall surface of each through hole 3 of a long porous support 4 having one or more through holes 3 reaching from one end surface 1 to the other end surface 2, both being opposed to each other. The porous support 4 is set sideways inside a vacuum chamber 10 and the outer peripheral surface 5 of the porous support 4 is vacuum-sucked while feeding a membrane-forming slurry into each through hole 3 from one end surface 1 to the other end surface 2. Thus, the membrane is formed by stacking a membrane forming substance contained in the membrane forming slurry on the inner wall surface of each through hole 3, and thereafter, draining, drying and calcining the surplus slurry. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a ceramic filter used for liquid and gas filtration in technical fields such as sewage treatment, clean water treatment, and industrial use.

  Ceramic filters are widely used in technical fields such as sewage treatment, water treatment, and industrial use because they are excellent in physical strength, chemical strength, durability, and the like. In many cases, in order to improve both the filtration accuracy and the filtration flow rate, a structure in which a ceramic filtration membrane is formed on the inner wall surface of the flow path formed in the ceramic porous support is adopted. One or more through-holes reaching from one end surface to the other end surface are formed in a cylindrical or prismatic porous support, and these through-holes are used as liquid channels to be filtered. A ceramic filter having a tube structure or a monolith structure as a filtering surface is generally used.

  In order to manufacture such a ceramic filter, as shown in Patent Document 1, a filtration film-forming method is known in which a porous support body in which a through-hole is formed is erected inside a vacuum chamber. In this method, a film-forming slurry containing a film-forming substance is fed into the through hole from the lower side of the porous support to fill the inside, and the vacuum chamber is decompressed to make the film-forming slurry porous. In this method, the film-forming substance in the film-forming slurry is deposited on the inner wall surface of each through-hole. After a predetermined amount of the film-forming substance is deposited, excess film-forming slurry in the porous support is drained downward, and dried and fired.

  Such a filtration film-forming method makes it easy to fill the entire through-hole of the porous support with the film-forming slurry, enables film formation without any pinholes, and eliminates sludge on the lower side of the porous support. Due to its simplicity, it has become a standard method for manufacturing ceramic filters. However, in recent years, the length of the ceramic filter has become longer than 800 mm due to an increase in filtration capacity, so the head difference between the upper and lower portions of the film-forming slurry filled in the through holes of the porous support is low. As a result, the thickness of the lower filtration membrane becomes 10 μm or more thicker than that of the upper filtration membrane. In the case of a ceramic filter having a length of less than 500 mm, the head difference is small and the film thickness difference between the upper and lower sides is several μm.

  In such a ceramic filter in which the thickness of the filtration membrane is different between the upper and lower parts of the porous support, the amount of filtration at the thin portion is large during actual use, the amount of filtration at the thick portion is small, and filtration is not effective. Uniformity occurs. Also, when backwashing is performed, the pressure loss is low in the thin portion, so that the backwash water is concentrated and the backwashing is not performed uniformly.

  In addition, the thin part has a large filtration flow rate, but the filtration accuracy may be reduced. To avoid this problem, setting the overall film thickness to a large value will reduce the amount of water permeation or the pore diameter of the channel. This causes problems such as decreasing the size of the cake and making it difficult to discharge the cake during backwashing.

Therefore, after the first film formation, a method of reducing the difference between the upper and lower film thickness by reversing the upper and lower sides of the porous support and performing the film formation again was studied, but it requires many times as many steps as before. Therefore, it was unsuitable for manufacturing mass-produced products.
Japanese Patent Publication No. 63-66566

  The present invention solves the above-mentioned conventional problems, and even when the ceramic filter is a long product having a length of 800 mm or more, it is possible to form a filtration membrane having a uniform film thickness over the entire length of the ceramic filter by the filtration film-forming method. An object of the present invention is to provide a method for producing a ceramic filter.

  In order to solve the above-mentioned problems, the present invention provides a porous support having one or more through-holes that are cylindrical or prismatic and extend from one end face to the other end face, and each through-hole. A ceramic filter having a filtration membrane formed on the inner wall surface of the substrate, wherein a long porous support is horizontally placed inside a vacuum chamber, and a membrane-forming slurry is passed from one end surface to the other. While feeding liquid to the inside of each through-hole toward the end surface, the outer peripheral surface of the porous support is vacuum-sucked to deposit a film-forming substance in the film-forming slurry on the inner wall surface of each through-hole to form a film. Then, after surplus film-forming slurry is discharged, the whole is dried and fired.

  In the method for producing a ceramic filter of the present invention, film formation can be performed while rotating the porous support around an axis parallel to the through-hole inside the vacuum chamber. Moreover, it is preferable that the angle with respect to the horizontal surface of the porous support body placed horizontally inside the vacuum chamber is within a range of −30 ° to + 30 °. In addition, when the excess film-forming slurry is discharged, the inside of the porous support can be blown from one end face, and the porous support is inclined only when the excess film-forming slurry is discharged. Can be made. The porous support may have a tube structure with one through hole or a monolith structure with a plurality of through holes.

  According to the method for producing a ceramic filter of the present invention, a long porous support is horizontally placed inside a vacuum chamber, and a film-forming slurry is sent from one end face to the other end face into each through hole. While the liquid is being drawn, the outer peripheral surface of the porous support is vacuum-sucked to deposit the film-forming substance in the film-forming slurry on the inner wall surface of each through-hole. A head difference does not occur, and even a long porous support having a length of 800 mm or more can form a filtration membrane having a uniform film thickness by a single film formation.

  According to the method for producing a ceramic filter of the present invention, since the porous support is horizontally placed inside the vacuum chamber to form a film, no head difference occurs in the axial direction parallel to the through hole. Microscopically, a slight head difference occurs in the radial direction. Therefore, if the film is formed while rotating the porous support around the axis parallel to the through-hole in the vacuum chamber as in the invention of claim 2, the difference in thickness in the radial direction can be eliminated. it can. However, if the rotational speed is increased, centrifugal force is generated, and the film thickness on the outer peripheral side tends to increase. Therefore, it is preferable that the rotational speed is 10 rpm or less.

  The method for producing a ceramic filter of the present invention is a method in which a porous support is horizontally placed inside a vacuum chamber to form a film. In order to eliminate the difference in film thickness of the filtration membrane, the porous support is penetrated. The axis parallel to the hole is preferably horizontal. However, in a completely horizontal state, the operation of draining excess film-forming slurry from the inside of the through-hole becomes difficult to perform as compared with the conventional vertical placement method. The quality support can be tilted within a range of ± 30 ° with respect to the horizontal plane. With this degree of inclination, the difference in film thickness is about a few μm, which is not a big problem, and it is easy to drain mud.

  As described above, the method for producing a ceramic filter of the present invention is a method in which a porous support is horizontally placed inside a vacuum chamber to form a film. Hateful. Therefore, a method of air-blowing the inside of the porous support from one end face at the time of drainage can be adopted as in claim 4. If air blow is performed, mud discharge is completed in a very short time, and productivity can be improved. Further, as in claim 5, if the film formation is performed in a horizontal support state and the porous support is inclined only when the excess film forming slurry is discharged, the mud is discharged without causing a difference in film thickness. Can be promoted.

  Embodiments of the present invention will be described below. An example of a ceramic filter manufactured by the method of the present invention is shown in FIG. The ceramic filter of FIG. 1 has a cylindrical shape having a large number of through holes 3 extending from one end surface 1 to the other end surface 2. The diameter is, for example, 100 mm, and the length is 1000 mm. Use in which a filtration membrane is formed on the inner wall surface of each through-hole 3 formed in the porous support 4, membrane filtration is performed using each through-hole 3 as a raw water flow path, and filtered water is taken out from the outer peripheral surface 5 of the ceramic filter. The law is normal.

  FIG. 2 shows an outline of the apparatus used in the present invention. In FIG. 2, 10 is a horizontally long vacuum chamber, and cylindrical holders 11 and 12 for holding both ends of the porous support 4 from the outer periphery are provided on both left and right ends thereof. The porous support 4 is horizontally placed inside the vacuum chamber 10 and is held by the cylindrical holders 11 and 12 with both ends sealed by an O-ring 21 or the like. In FIG. 2, the porous support 4 is held between the cylindrical holders 11 and 12 with the axis thereof being horizontal, but can be inclined within a range of ± 30 ° with respect to the horizontal plane as described above. In the case of inclining, in this embodiment, the right cylindrical holder 11 is inclined downward.

  In this embodiment, the cylindrical holders 11 and 12 are rotatable with respect to the fixed headers 13 and 14. When the cylindrical holder 11 is rotated by the motor 15, the cylindrical holder that holds the other end of the porous support 4. 12 can also follow and rotate. A vacuum pump 16 is connected to the upper portion of the vacuum chamber 10 via a valve V4, and the inside of the vacuum chamber 10 can be decompressed.

  A film forming slurry tank 17 stores the film forming slurry. As a film-forming slurry, a slurry in which ceramic particles as a film-forming substance are dispersed in a dispersion medium such as water and a sintering aid, an organic binder, a pH adjuster, a surfactant, etc. are added as necessary is used. It is done. The particle size of the ceramic particles is selected depending on the intended use of the filter and is, for example, about 1 to 5 μm. The size of the ceramic particles constituting the porous support 4 is also selected according to the selected ceramic particles as the film-forming substance, and is, for example, 10 to 50 μm. The material of these ceramic particles is not particularly limited, and for example, alumina, mullite, cordierite, silicon carbide and the like can be used.

  Reference numeral 18 denotes a liquid feed pump, which sends the film-forming slurry in the film-forming slurry tank 17 to the cylindrical holder 11 through the valve V1, and sends the liquid from one end face 1 of the porous support 4 to the inside of each through hole 3. can do. The film-forming slurry that has flowed out from the other end face 2 of the porous support 4 returns to the film-forming slurry tank 17 via the cylindrical holder 12, the valve V7, and the return pipe 19.

  In addition, 20 is a filtration drainage tank installed in the lower part of the vacuum chamber 10, The upper space is connected to the vacuum pump 16 via the valve | bulb V4 as shown with a broken line. A valve V5 disposed adjacent to the valve V4 is a valve for communicating the inside of the vacuum chamber 10 with the outside air. Further, a valve V6 provided in the fixed header 14 is a valve for performing air blow at the time of discharging mud.

Below, the manufacturing method of the ceramic filter of this invention is demonstrated.
First, as shown in FIG. 2, the porous support 4 provided with a large number of through-holes 3 is set in the horizontal state inside the vacuum chamber 10, and the vacuum pump 16 is turned on while the valve V4 is closed. And the cylindrical holder 11 is rotated with the motor 15, and the porous support body 4 is rotated around an axis line.

  Further, the valve V1 and the valve V7 are opened and the liquid feed pump 18 is operated, so that the film-forming slurry in the film-forming slurry tank 17 flows from one end face of the porous support 4 to the other end face of each through-hole 3. Deliver liquid inside. At this time, the valve V2 is closed. Since the film-forming slurry that has passed through the inside of the porous support 4 returns to the film-forming slurry tank 17 via the return pipe 19, the film-forming slurry is between the inside of the porous support 4 and the film-forming slurry tank 17. Will be circulated.

  When the film-forming slurry fills the inside of each through-hole 3 of the porous support 4, the valve V4 is opened and the inside of the vacuum chamber 10 is decompressed. The film-forming slurry is sucked from the inside of each through-hole 3 toward the outer peripheral surface 5 of the porous support 4, and the film-forming substance that is a solid content in the film-forming slurry is deposited on the inner wall surface of each through-hole 3. On the other hand, moisture or the like, which is a liquid component in the film-forming slurry, is discharged from the outer peripheral surface 5 of the porous support 4 and collected in the filtration drainage tank 20 via the valve V3. In this way, film formation is performed for a predetermined time, for example, for 2 to 3 minutes. When the filtered wastewater reaches a specified amount, the liquid feed pump 18 is stopped and the valve V1 is closed.

  Thereafter, when the valve V2 is opened and left, surplus film-forming slurry is discharged from the inside of each through-hole 3 into the filtration drainage tank 20. However, when the porous support 4 is installed horizontally and the mud does not proceed as it is, the valve V7 is closed, the valve V6 is opened, and the air blow B is blown into the porous support 4 from one end face. , Forced to drain. Thereafter, the valve V7 is opened and the valve V6 is closed. Note that the porous support 4 may be installed horizontally during the film forming operation, and the entire vacuum chamber 10 may be raised at a necessary angle during the mud discharge operation to promote the mud discharge.

  As described above, in the present invention, the porous support 4 is horizontally placed to form a film, so that a head difference does not occur depending on the position in the axial direction, and a substantially uniform film thickness is formed over the entire length. Further, as in this embodiment, the film forming operation is performed while gently rotating the porous support 4 at a speed that does not generate centrifugal force, thereby eliminating the difference in film thickness in the radial direction of the porous support 4. Can do. After draining the excess film-forming slurry, the valve V4 is closed and the valve V5 is opened to return the interior of the vacuum chamber 10 to atmospheric pressure, and the porous support 4 is taken out to the outside, followed by drying and firing by a conventional method. Thus, a ceramic filter is obtained.

  The ceramic filter manufactured by the method of the present invention has a filter membrane having a uniform film thickness over the entire length even when the ceramic filter is a long product having a length of 800 mm or more. In this case, the maximum film thickness difference is 3 μm or less. Accordingly, it is possible to prevent uneven filtration and poor backwashing caused by a difference in the thickness of the filtration membrane, such as a ceramic filter manufactured by a conventional method.

It is a perspective view which shows an example of a ceramic filter. It is sectional drawing which shows the outline | summary of the apparatus used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 One end surface 2 The other end surface 3 Through-hole 4 Porous support body 5 Outer peripheral surface 10 Vacuum chamber 11 Tubular holder 12 Tubular holder 13 Fixed header 14 Fixed header 15 Motor 16 Vacuum pump 17 Film-forming slurry tank 18 Liquid feeding pump 19 Return pipe 20 Filtration drain tank 21 O-ring

Claims (6)

  A ceramic comprising a porous support having one or more through-holes that are cylindrical or prismatic and extend from one end face to the other end face, and a filtration membrane formed on the inner wall surface of each through-hole A method of manufacturing a filter, in which a long porous support is placed horizontally in a vacuum chamber, and a film-forming slurry is fed from one end face toward the other end face into each through hole. In addition, the outer peripheral surface of the porous support is vacuum-sucked to deposit a film-forming substance in the film-forming slurry on the inner wall surface of each through-hole to form a film, and then the excess film-forming slurry is drained, A method for producing a ceramic filter, wherein the whole is dried and fired.   2. The method for producing a ceramic filter according to claim 1, wherein the film formation is performed while rotating the porous support around an axis parallel to the through hole inside the vacuum chamber.   3. The method for producing a ceramic filter according to claim 1, wherein an angle of the porous support placed horizontally inside the vacuum chamber with respect to a horizontal plane is within a range of −30 ° to + 30 °.   4. The method for producing a ceramic filter according to claim 3, wherein when the excess film-forming slurry is discharged, the inside of the porous support is blown from one end face.   The method for producing a ceramic filter according to any one of claims 1 to 4, wherein the porous support is inclined only when the excess film-forming slurry is discharged.   The method for producing a ceramic filter according to claim 1, wherein the porous support has a plurality of through holes.

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