JP2006247540A - Hollow fiber membrane module and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow fiber membrane module having an improved gas dispersion property during air cleaning and an operation method of the hollow fiber membrane module capable of efficient cleaning. <P>SOLUTION: The hollow fiber membrane module comprises an adhered and fixed portion in which a hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes is adhered to and bundled on at least one end thereof, and a through-hole consisting of a hollow tube in the axial direction of the hollow fiber membrane module is provided in the adhered and fixed portion, wherein the diameter of circle that is equivalent to an internal diameter of the hollow tube is 0.1 to 0.8 mm, and the hollow tube protrudes upward on the axis of the hollow fiber membrane module relative to the adhered and fixed portion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a structure and operating method of a hollow fiber membrane module, and more particularly to a method of air washing and a plurality of through holes provided in an adhesive fixing portion of the hollow fiber membrane.

  The membrane separation method has features such as energy saving, space saving, labor saving, and product quality improvement, and therefore, its use in various fields is expanding. For example, microfiltration membranes and ultrafiltration membranes can be applied to water purification processes for producing industrial water and tap water from river water, groundwater and sewage treated water.

  However, when raw water is filtered through a membrane, the removal object such as turbidity and organic matter contained in the raw water accumulates on the membrane surface, and the membrane clogging phenomenon occurs. become unable. Therefore, it is necessary to wash the membrane in order to maintain the membrane filtration performance. There are two types of membrane cleaning: back-flow cleaning in which membrane filtered water flows backward from the secondary side of the membrane, and air cleaning to remove gas from the membrane by supplying gas. Air washing is an effective means for removing turbidity accumulated in the hollow fiber membrane, and is indispensable for stably performing the filtration operation of the hollow fiber membrane.

Generally, a hollow fiber membrane module contains a hollow fiber membrane bundle in which approximately several hundred to several tens of thousands of hollow fiber membranes are bundled, and at least one end of the hollow fiber membrane bundle is bonded and fixed with resin. It is configured. For example, Patent Document 1 discloses a module in which both ends of a hollow fiber membrane bundle are bonded and fixed, and a plurality of through holes of 2 to 30 mm are provided in one adhesive fixing portion. It serves as a supply port, a gas supply port for cleaning, and a suspended material discharge port. The gas passes through the through-hole and shakes the hollow fiber membrane to peel off and remove the turbidity. However, during operation, turbidity accumulates in the upper part of the through hole, and part of the through hole is blocked, resulting in poor gas dispersibility, so that part of the hollow fiber membrane module is washed with air. Therefore, there is a problem that the filtration performance of the hollow fiber membrane module is lowered. In order to solve such a problem, Patent Document 2 discloses that a gas supply nozzle is disposed at the lower part of the hollow fiber membrane module and individually controlled to improve gas dispersibility, and gas is fed into the entire hollow fiber membrane module. A method is described. However, in this method, it is necessary to provide a complicated nozzle for each module, and there is a problem that the cost is very high.
JP-A-9-220446 JP-A-10-94720

  An object of the present invention is to provide a hollow fiber membrane module with improved gas dispersibility during air cleaning and a method of operating the hollow fiber membrane module that enables efficient cleaning.

  The present invention for solving the above-described problems has the following characteristics.

  (1) It has an adhesive fixing part in which at least one end of a hollow fiber membrane bundle composed of a plurality of hollow fiber membranes is adhered and focused, and the adhesive fixing part is a hollow tube in the axial direction of the hollow fiber membrane module. A hollow fiber membrane module provided with a configured through-hole, wherein a circle equivalent inner diameter of the hollow tube inner diameter is 0.1 to 0.8 mm, and the hollow tube is attached to the adhesive fixing portion. On the other hand, the hollow fiber membrane module protrudes upward with respect to the hollow fiber membrane module axis.

  (2) The hollow fiber membrane module according to (1), wherein the hollow tube is made of substantially the same material as the hollow fiber membrane.

  (3) A cross section of the hollow tube made of substantially the same material as the hollow fiber membrane has substantially the same shape as a cross section of the hollow fiber membrane forming the hollow fiber membrane bundle. (2) The hollow fiber membrane module according to the above.

  (4) A method for operating the hollow fiber membrane module according to any one of (1) to (3), wherein a gas is supplied to a hollow tube formed in the hollow fiber membrane module to wash the hollow fiber membrane A method for operating a hollow fiber membrane module, wherein the pressure loss of the gas supplied to the hollow tube is 20 to 300 kPa.

  According to the present invention, as described below, it is possible to provide a low-cost module with improved gas dispersibility during air cleaning.

  BEST MODE FOR CARRYING OUT THE INVENTION The best embodiment of the present invention will be described below with reference to the drawings, taking as an example a hollow fiber membrane module applied as a clean water filtration device. However, the present invention is not limited to the embodiments described below.

  FIG. 1 is a schematic cross-sectional view of a hollow fiber membrane module according to the present invention. In this hollow fiber membrane module, a hollow fiber membrane bundle 2 in which hundreds to tens of thousands of hollow fiber membranes are bundled and arranged in a fixed length is accommodated in a cylindrical case 3, and both ends are bonded and fixed portions 4a. 4b is bonded and focused, and is fixed in the cylindrical case 3. A portion between the adhesive fixing portions that is not adhesively fixed by the adhesive fixing portions 4a and 4b is a filtration region portion.

  The material of the hollow fiber membrane constituting the hollow fiber membrane bundle 2 is not particularly limited and is not particularly limited as long as it is a porous hollow fiber membrane, but polyethylene, polypropylene, polyacrylonitrile, ethylene-tetrafluoroethylene copolymer, poly Chlorotrifluoroethylene, polytetrafluoroethylene, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and chlorotrifluoroethylene-ethylene copolymer, polyfluoride It is preferable to contain at least one selected from the group consisting of vinylidene, polysulfone, cellulose acetate, polyvinyl alcohol, polyethersulfone, ceramics, and other inorganic materials. Vinylidene Preferably, polyacrylonitrile are preferable from the viewpoint of high high stain resistance hydrophilic.

  The hollow fiber membrane preferably has an outer diameter in the range of 0.3 to 2 mm. This is because if the outer diameter of the hollow fiber membrane is too small, the hollow fiber membrane breaks during handling of the hollow membrane when manufacturing the hollow fiber membrane module, and during filtration and washing when using the hollow fiber membrane module. This is because there is a problem such as damage, and conversely, if the outer diameter is too large, the number of hollow fiber membranes that can be inserted into a cylindrical case of the same size is reduced and the filtration area is reduced. The hollow fiber membrane preferably has a thickness in the range of 0.1 to 0.9 mm. This is because when the film thickness is too small, especially in the case of an external pressure type hollow fiber membrane module, there is a problem such as the film breaking due to pressure, and conversely, if the film thickness is large, there is a problem such as pressure loss and increase in raw material cost Because there is.

  In the hollow fiber membrane, at the filtrate water outlet / backwash water inlet 5 side, only the hollow fiber membranes are bonded and fixed by the adhesive fixing portion 4a, and the end surfaces of the hollow fiber membranes are opened. On the other hand, on the gas supply chamber 6 side, the adhesive fixing portion 4b penetrates to the inside of the hollow fiber membrane so that the hollow fiber membranes are bonded and fixed together and the end surface of the hollow fiber membrane is also sealed. On the gas supply chamber 6 side, a plurality of through-holes penetrating in the axial direction of the hollow fiber membrane module are provided in the adhesive fixing portion 4b which has been bonded and solidified, and these through holes are located on the module axis of the adhesive fixing portion 4b. It is constituted by a hollow tube 8 protruding in the direction. For the adhesive fixing portions 4a and 4b for bonding and fixing the hollow fiber membrane bundle, it is preferable to use a polymer material such as an epoxy resin, a urethane resin, or an epoxy acrylate resin that is a general-purpose product and is inexpensive and does not affect the water quality. .

  Examples of the material of the cylindrical case 3 include polyolefins such as polyethylene, polypropylene and polybutene, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), ethylene tetrafluoride / hexafluoropropylene (FEP), ethylene Fluororesin such as ethylene tetrafluoride (ETFE), ethylene trifluoride chloride (PCTFE), ethylene trifluoroethylene chloride (ECTFE), vinylidene fluoride (PVDF), and polyvinyl chloride, polyvinylidene chloride, etc. Chlorine resin, polysulfone resin, polyethersulfone resin, polyallylsulfone resin, polyphenyl ether resin, acrylonitrile-butadiene-styrene copolymer resin (ABS), acrylonitrile-styrene copolymer resin, polyphenylene sulfide Resins, polyamide resins, polycarbonate resins, polyether ketone resins, polyether ether ketone resins, and the like are used alone or in combination. In addition to resins, aluminum, stainless steel, and the like are preferable, and composite materials such as a resin-metal composite, glass fiber reinforced resin, and carbon fiber reinforced resin can be used. The cylindrical case 3 is preferably a net-like structure in the case of an immersion type module, and is preferably a pressure resistant pipe having a pressure resistance corresponding to the operating pressure in the case of a pressure type module.

  In one embodiment according to the present invention, at the time of air cleaning, gas is fed from a gas supply port 7 to the gas supply chamber 6 below the adhesive fixing portion 4b by a compressor or the like, and the gas passes through the hollow tube 8 to pass through the hollow fiber membrane bundle 2 Is sent to. In the present invention, by making the inner diameter of the hollow tube 8 smaller than that of the conventional through hole, the pressure loss when the gas actively flows can be increased to make the gas flow uniform. When normal membrane filtration is carried out for a long period of time, turbidity accumulates in the upper part of the through hole and in the hollow fiber membrane in the vicinity thereof, and water and gas hardly flow through a part of the through hole. In particular, since gas is much less viscous than water, when such a phenomenon occurs, the gas flows only through the through-holes where no turbidity is accumulated. Then, in the hollow fiber membrane above the through hole where the gas flow has deteriorated, turbidity is further accumulated. By repeating this, a through hole in which almost no gas flows and a through hole in which a large amount of gas flows are formed. In such a state, not only in the vicinity of the through hole, but also in the hollow fiber membrane of the entire module, a portion where turbidity is accumulated and a portion where it is not formed are formed, and the performance of the membrane module is drastically lowered. In addition, if the membrane filling rate is uneven in the adhesive fixing portion of the hollow fiber membrane at the time of module creation, the tendency becomes more prominent.

  The equivalent circular diameter of the inner diameter of the hollow tube 8 needs to be 0.1 to 0.8 mm. If this is larger than 0.8 mm, it is difficult to sufficiently increase the pressure loss of the gas flowing through the through hole in the appropriate gas flow rate range per module during air cleaning, and the number of holes per module decreases. This is because it is difficult to send gas uniformly to the entire module. On the other hand, if it is smaller than 0.1 mm, a very large number of hollow tubes are required in order to flow an appropriate gas flow rate, which increases the cost of module creation and makes it impossible to obtain a sufficient gas flow rate per module. Because. For the above reason, it is preferable that the circle equivalent equivalent diameter of the through hole is 0.2 to 0.6 mm. Here, the equivalent circular diameter of the inner diameter of the hollow tube refers to the diameter of the circle when the shape of the inner diameter cross section is replaced with a circle having the same area.

  The cross-sectional shape of the hollow tube 8 may be any shape such as a circle, an ellipse, or a polygon, but a circle is preferable from the viewpoint of cost reduction. The arrangement of the plurality of through-holes is arbitrary, such as the positions of the vertices of many equilateral triangles, the positions of the intersections of the radial lines and concentric circles, the positions of the lattice-shaped intersections, etc. If there is a variation, the portion where the interval is larger than the others is likely to be a staying portion, so it is preferable to make the interval equal so that there is no great difference in the interval.

  The pressure loss of the gas flowing through the hollow tube 8 is preferably 20 kPa to 300 kPa. This is because a pressure of 20 kPa or more is necessary for air to flow uniformly from the entire through-hole even when turbidity is accumulated in the hollow fiber membrane above the hollow tube during air cleaning. Also, pressures higher than 300 kPa are not preferable because the pressure resistance of the members and the adhesive fixing parts is required, and the cost of the module becomes high, and if the pressure is too high, the power consumption of the compressor increases. The pressure loss is preferably 50 kPa or more from the viewpoint of removing raw water flowing back to the hollow tube 8 during filtration and preventing clogging of the hollow tube. Here, the pressure loss of the gas flowing through the hollow tube is a pressure loss that occurs when the gas flows through the hollow tube during air cleaning, and the gas supply chamber 6 and the adhesive fixing portion 4b upper raw water side during air cleaning. It is calculated | required by measuring the differential pressure | voltage.

  Conventionally, as a method of creating a through-hole in the adhesive fixing portion 4b, a rod-like material that does not adhere to the adhesive when the hollow fiber membrane bundle is focused and fixed is inserted into the adhesive fixing portion, and the adhesive solidifies. It has been common practice to create a through hole by removing. However, when the number of through-holes increases, the work of removing the rod-like object becomes complicated when producing by the above method, and the production becomes difficult. Therefore, the present invention has proposed a method of forming the through hole by embedding a hollow tube in the adhesive fixing portion. Here, the hollow tube refers to a hollow resinous or stainless steel tube, hose, tube, or hollow fiber having both ends opened. When the hollow tube is made of substantially the same material as the hollow fiber membrane, it is easy to create an adhesive fixing part, no new member is required, and other members when the module is discarded Is preferable because it is easy to sort.

  Further, when the cross section of the hollow tube made of the substantially same material has substantially the same shape as the cross section of the hollow fiber membrane forming the hollow fiber membrane bundle, it is easy to bond and fix the module. Since a surplus portion of the hollow fiber membrane that is produced at the time of production can be used, it is preferable in that a new member is not required. Here, the cross section of the hollow tube made of the substantially same material is substantially the same in shape of the cross section of the hollow fiber membrane forming the hollow fiber membrane bundle. There is no restriction | limiting about the length of the longitudinal direction of a hollow fiber membrane, It means that only cross-sectional shape is substantially the same. The cross-sectional shapes being substantially identical to each other preferably means that the cross-sectional shapes are mutually congruent, but it does not impair the gist that the remaining portion of the hollow fiber membrane that was produced at the time of module creation can be used. For example, they are all assumed to have substantially the same cross-sectional shape. For example, even if each cross-sectional shape does not necessarily look the same in appearance, each outer diameter and each inner diameter are substantially the same, or each outer circumference length and each thickness is substantially the same. In other words, it is determined that the cross-sectional shapes are substantially the same.

  When creating a through-hole with a hollow tube, it is possible to easily obtain the necessary pressure loss by protruding upward from the adhesive fixing part 4b with respect to the hollow fiber membrane module axis, and the upper part of the adhesive fixing part 4b accumulates. It is possible to uniformly clean the entire membrane module without being affected by turbidity. The hollow tube is preferably protruded from 0.5 cm to 20 cm from the upper end surface of the adhesive fixing portion 4b. This is because if it is shorter than 0.5 cm, it is easily affected by the turbidity accumulated in the upper part of the adhesive fixing part 4b, and the adhesive may enter the hollow tube when the adhesive fixing part is created, thereby blocking the hollow tube. This is because if the length is longer than 20 cm, the hollow tube may be bent or entangled. Since the hollow tube above the adhesive fixing part 4b rubs against the hollow fiber membrane during air cleaning and may damage the hollow fiber membrane, it is preferable that the hollow tube is made of a material having the same or soft hardness as the hollow fiber membrane. . A detailed view of the vicinity of the hollow tube 8 of the adhesive fixing portion 4b is shown in FIG. In this case, since the gas A is supplied from the gas supply port 7 and is supplied to the membrane module from the upper part of the turbidity 13 through the hollow tube 8, the gas A is uniformly supplied to the entire module without being affected by the accumulation of turbidity. Can be supplied. For this reason, the hollow tube is preferably projected 2 cm to 10 cm from the upper end surface of the adhesive fixing portion 4b.

  FIG. 2 shows an example of a pressurized hollow fiber membrane module according to the present invention. In the present invention, since the through-hole is small, it is difficult to efficiently flow water through the through-hole. Therefore, the gas supply chamber 6 below the through-hole is used only for sending the air cleaning gas. However, since a reverse flow of the raw water can be considered, it is preferable to provide a drain port 12 for draining the gas supply chamber 6. And it is preferable if the raw water inlet / drain outlet 10 is provided in the upper part of the through hole so that the raw water is supplied and the turbid waste water is discharged.

  The operation method will be described with reference to FIG. 2. 1) A filtration step in which raw water is introduced from the raw water inlet / drain outlet 10 and filtered through the hollow fiber membrane bundle 2 to extract permeate from the filtrate outlet / backwash water inlet 5. 2) (1) Air cleaning for removing accumulated substances adhering to the surface of the hollow fiber membrane by stopping the supply of raw water and introducing gas from the gas supply port 7 at the lower part of the hollow fiber membrane module; (2) Reverse flow cleaning that reversely flows from the filtered water outlet / backwash water inlet 5 by pumping the filtered water from the direction opposite to the filtration direction of the hollow fiber membrane, and (3) turbidity that has been peeled off by these air cleaning and backflow cleaning In order to efficiently discharge outside the module system, all or a part of the module is discharged outside the module system from the raw water inlet / drain outlet 10 or (4) a certain amount of raw water from the raw water inlet / drain outlet 10 By supplying turbidity from gas / backwash outlet 9 Method for performing flushing to push out like, consisting of cleaning process combination.

  Even when the hollow tube 8 is clogged with turbidity, it is possible to remove the clogging by applying pressure to the gas supply chamber 6 below the hollow tube 8 with gas. Even when clogging that cannot be removed still occurs, clogging can be suppressed by removing the lower member of the hollow tube 8 and cleaning the through hole.

The gas flow rate varies depending on the size of the horizontal cross-sectional area of the membrane module, the vertical length, and the hollow fiber membrane diameter, but usually 70 to 400 m ³ / (m ² · h) (atmospheric pressure) per horizontal cross-sectional area of the membrane module The standard) is preferable. According to the present invention, since the gas is uniformly dispersed and the cleaning efficiency of the module is increased, the gas flow rate can be reduced as compared with the conventional case. For this reason, it is possible to greatly reduce the deterioration of the film performance caused by rubbing the film surface and turbidity by air cleaning.

  Here, the membrane module is preferably an external pressure type. There is no problem even if it is a full-volume filtration type module or a cross-flow filtration type module, but a full-volume filtration type module is preferred from the viewpoint of low energy consumption. Further, although it may be a pressure type module or a submerged type module, the submerged type suction filtration method is preferably a submerged type module because raw water is less likely to flow back into the gas supply chamber 6. . The filtration flow rate control method for the hollow fiber membrane module can be either constant flow filtration or constant pressure filtration. However, the method using constant flow filtration is preferred because of the ease of controlling the amount of filtered water produced. Is preferred.

  The gas used for air cleaning is generally air sent by an air blower or compressor, but oxygen, nitrogen or ozone gas can be used, providing sufficient pressure and being inexpensive. In this respect, compressed air using a compressor is preferable.

Example 1
A bundle of hollow fiber membranes consisting of 3,500 polyacrylonitrile porous hollow fiber membranes with an outer diameter of 680 μm, an inner diameter of 400 μm, and an average pore diameter of 0.01 μm is bundled and inserted into a rigid vinyl chloride pipe housing with an inner diameter of 104 mm, and both ends are bonded with urethane. A hollow fiber membrane module having a length of 1100 mm and a membrane area of 12 m ² as shown in FIG. 2 was prepared by fixing with an agent and cutting one end of the adhesive fixing portion to open the inside of the hollow fiber membrane. The length of the through-hole of the adhesive fixing part 4b is determined by arranging the hollow fiber membrane cut into 12 cm evenly on the 12 module lower adhesive fixing part before fixing the adhesive, and then cutting off by 2 cm after adhesive fixing. A module having a hollow fiber through-hole protruding at 10 cm and 3 cm above the upper end surface of the adhesive fixing portion 4b was prepared. The pressure difference between the gas supply chamber 6 and the upper part of the adhesive fixing part 4b at the time of air cleaning was 50 kPa to 100 kPa. An experiment was conducted under the following conditions using one pressure-type hollow fiber membrane module.

The raw water is bentonite 10 mg / L and humic acid 5 mg / L added to the lake water. Filtration flow rate is 1.5 m ³ / (m ² · d). 0.0m ³ / (m ² · d) for 30 seconds, air cleaning at 20L / min for 60 seconds, all the water on the raw water side in the membrane module is discharged, and the raw water side in the membrane module is fully filled with raw water for cleaning The process was performed and the cycle which returns to the filtration process again was repeated. In the initial stage of operation, the film differential pressure was 30 kPa at 25 ° C. temperature correction differential pressure, and after one month operation, the film differential pressure was stable at 50 kPa at 25 ° C. temperature correction differential pressure.

(Comparative Example 1)
In the module of Example 1, the same experiment was performed as a module in which only 12 through holes having a diameter of 8 mm were opened. The pressure difference between the gas supply chamber 6 and the through-hole upper raw water side during air cleaning was 1 kPa or less. In the initial stage of operation, the membrane differential pressure was 30 kPa at 25 ° C. temperature correction differential pressure, but thereafter the membrane filtration differential pressure gradually increased, and after 3 weeks the membrane differential pressure reached 150 kPa at 25 ° C. temperature correction differential pressure. . When the hollow fiber membrane module was disassembled and observed after the operation was completed, a lot of mud adhered to a part of the membrane module, and a portion where air cleaning was not effectively performed was observed.

  The present invention relates to a water treatment method using a filtration membrane module for a water purification process. More specifically, the present invention relates to a water treatment method using a filtration membrane module used for water purification treatment of industrial water or tap water, sewage treatment, industrial wastewater treatment, and the like, but the present invention is not limited thereto.

It is a schematic longitudinal cross-sectional view which shows an example of the hollow fiber membrane module which concerns on this invention. It is a schematic longitudinal cross-sectional view which shows an example of the pressurization type hollow fiber membrane module which concerns on this invention. It is a schematic sectional drawing which shows the detail of the lower through-hole vicinity of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane module 2 Hollow fiber membrane bundle 3 Cylindrical case 4a, 4b Adhesive fixing part 5 Filtrated water outlet / backwash water inlet 6 Gas supply chamber 7 Gas supply port 8 Hollow tube (through hole)
9 Gas / backwash outlet 10 Raw water inlet / drain outlet 11 Pressure-resistant cylindrical case 12 Drain port 13 Turbidity

Claims (4)

It has an adhesive fixing part in which at least one end of a hollow fiber membrane bundle made of a plurality of hollow fiber membranes is bonded and focused, and the adhesive fixing part is configured by a hollow tube in the axial direction of the hollow fiber membrane module A hollow fiber membrane module provided with a through-hole, wherein a circle equivalent inner diameter of the hollow tube inner diameter is 0.1 to 0.8 mm, and the hollow tube is hollow with respect to the adhesive fixing portion. A hollow fiber membrane module characterized by protruding upward with respect to the yarn membrane module axis. The hollow fiber membrane module according to claim 1, wherein the hollow tube is made of substantially the same material as the hollow fiber membrane. 3. The cross section of the hollow tube made of substantially the same material as the hollow fiber membrane has substantially the same shape as the cross section of the hollow fiber membrane forming the hollow fiber membrane bundle. The hollow fiber membrane module described. The operation method of the hollow fiber membrane module according to any one of claims 1 to 3, wherein the hollow fiber membrane is washed by supplying gas to a hollow tube formed in the hollow fiber membrane module. A method for operating a hollow fiber membrane module, wherein the pressure loss of the gas supplied to the hollow tube is 20 to 300 kPa.

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