JP2017070915A - Washing method of hollow fiber membrane module and filtration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a washing method of a hollow fiber membrane module and a filtration device where stable continuous filtration operation can be performed with high washing performance and for a long term compared to the conventional one and the miniaturization of the device can be performed.SOLUTION: A washing method of a hollow fiber membrane module is implemented in a filtration device equipped with a hollow fiber membrane module 1 provided with spaces at a stock solution side B and a filtrate side A. The washing method of the hollow fiber membrane module includes: a chemical injection step injecting a chemical into a filtrate existing in the space at the filtrate side A; and a pressurizing step where the filtrate after being injected with the chemical is pressurized by a gas having smaller pressure than pressure when the gas is discharged from the stock solution side B in a state of being filled with a stock solution in the space at the stock solution side B and the filtrate is pushed out to the space at the stock solution side B from the space at the filtrate side A via a hollow fiber membrane 4.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for cleaning a hollow fiber membrane module and a filtration device.

  In recent years, the development of separation technology using hollow fiber membranes has progressed, and it is widely used for various applications including water filtration. However, in the process of filtration with a hollow fiber membrane, solid matter such as suspended solids in a stock solution called SS adheres to the surface of the hollow fiber membrane or enters into the micropores to cause membrane clogging. When the transmembrane pressure increases, and the membrane clogging further proceeds, the permeation flux decreases. Therefore, in order to continue the filtration operation stably over a long period of time, it is indispensable to develop a method for washing the hollow fiber membrane and a method for operating the filtration device in washing simultaneously with setting of the filtration conditions.

  Conventionally, various methods have been proposed as cleaning methods for hollow fiber membrane modules, and these can be broadly classified into physical cleaning methods and chemical cleaning methods.

  As a physical cleaning method, a liquid backwashing method for passing a liquid such as water or filtered water from the filtrate side to the stock solution side, a gas backwashing method for passing a pressurized gas from the filtrate side to the stock solution side (Patent Document 1, Patent Document 2 etc.), a variety of methods such as a bubbling method in which bubbles are ejected from the bottom of a module on the stock solution side, an ultrasonic method, and the like have been proposed. Further, as a chemical cleaning method, a method is known in which a deposit is dissolved or decomposed with a chemical solution such as an acid, an alkaline aqueous solution, an oxidizing agent, or a cleaning agent.

  In general, when a conventionally known physical cleaning method is used, the cleaning effect is not always satisfactory. For example, when the filtration process and the cleaning process are continuously operated by sequence control or the like, it is several days to several months. There was a problem that the permeation flux was greatly reduced. In order to solve this problem, Patent Document 3 proposes a physical cleaning method in which a gas having a pressure smaller than the pressure at which the gas is released from the raw liquid side of the hollow fiber membrane is introduced from the filtrate side of the hollow fiber membrane. . Patent Document 4 proposes a liquid backwashing method using membrane filtered water into which a chemical solution has been injected.

JP-A-53-108882 Japanese translation of PCT publication 1-500732 Japanese Patent Laid-Open No. 10-286441 JP-A-11-009973

  By using the physical cleaning methods of Patent Document 3 and Patent Document 4, filtration of a stock solution in which membrane clogging is unlikely to occur by filtration, or filtration with a low filtration flux, which is a filtration flow rate per unit membrane area, is performed for a long time. Continuous filtration operation becomes possible. However, in Patent Document 3, since the cleaning ability is insufficient, in filtration of a stock solution in which membrane clogging is likely to occur, or in filtration with a high filtration flux, the hollow fiber membrane is gradually clogged, resulting in a difference between the membranes. In many cases, it is difficult to continue the filtration operation due to an increase in pressure or a decrease in filtration flux. Therefore, it is necessary to develop an effective cleaning method in order to enable continuous filtration operation for a long period of time in filtration of a stock solution in which membrane clogging is likely to occur, or in filtration with a high filtration flux.

  Moreover, in patent document 4, since it is necessary to supply a lot of backwashing water in order to fully wash | clean the whole hollow fiber membrane, it is liquid-fed to the tank for storing a lot of backwashing water, or a hollow fiber membrane module Therefore, it is difficult to reduce the size of the apparatus.

  An object of the present invention is to provide a cleaning method and a filtration device for a hollow fiber membrane module that have a higher cleaning ability than that of the prior art and that enable a continuous filtration operation for a long period of time and that can reduce the size of the device. There is.

  The washing method and filtration device for a hollow fiber membrane module of the present invention that solves the above problems have the following characteristics.

  (1) The method for cleaning a hollow fiber membrane module of the present invention is a method for cleaning a hollow fiber membrane module that is carried out by a filtration apparatus including a hollow fiber membrane module provided with a space on the stock solution side and the filtrate side. The hollow fiber membrane module cleaning method includes a chemical solution injection step of injecting a chemical solution into the filtrate existing in the filtrate side space, and gas is released from the stock solution side in a state where the stock solution is filled in the space on the stock solution side. Pressurizing the filtrate after injection of the chemical solution with a gas having a pressure lower than the pressure to push the filtrate from the filtrate side space to the stock solution side space through a hollow fiber membrane.

  (2) The method for cleaning the hollow fiber membrane module may further include a gas cleaning step of cleaning the stock solution side of the hollow fiber membrane module with gas after the pressurizing step.

  (3) The method for cleaning the hollow fiber membrane module may further include an immersing step of immersing the hollow fiber membrane in the liquid into which the chemical solution is injected between the pressurizing step and the gas cleaning step.

  (4) The method for cleaning the hollow fiber membrane module includes a water filling step for filling the stock solution in a space on the stock solution side of the hollow fiber membrane module after the pressurizing step and before the gas cleaning step, and the gas cleaning. After the step, a drainage step of discharging the liquid in the hollow fiber membrane module out of the system may be further provided. A cleaning cycle in which the water filling step, the gas cleaning step, and the drainage step are sequentially performed may be repeated.

  (5) In the above-described method for cleaning a hollow fiber membrane module, in the pressurizing step, the filtrate after chemical injection may be pressurized with a gas having a pressure of 0.1 MPa to 0.5 MPa.

  (6) The method for cleaning the hollow fiber membrane module may be carried out by an external pressure filtration type filtration device in which a stock solution is supplied to the outer surface side of the hollow fiber membrane and the filtrate is taken out from the inner surface side of the hollow fiber membrane. .

  (7) In the method for cleaning a hollow fiber membrane module, as the hollow fiber membrane module, the upper ends of the hollow fiber membrane bundles are fixed together and the lower ends are sealed in a state where the hollow fiber membranes are not fixed one by one A free type hollow fiber membrane module may be used.

  (8) The filtration device of the present invention comprises a hollow fiber membrane module provided with a stock solution side and a filtrate side space, a liquid feed pump that supplies the stock solution to the stock solution side space, and a chemical solution in the filtrate side space. The operation of the chemical supply device to be supplied, the gas supply device for supplying the gas for pressurizing the filtrate existing in the filtrate side space to the space, the liquid feed pump, the chemical supply device and the gas supply device A control device for controlling. The control device uses a gas having a pressure smaller than a pressure at which a chemical solution is injected into the filtrate existing in the filtrate side space and the gas is discharged from the stock solution side in a state where the stock solution is filled in the space on the stock solution side. The operations of the liquid feed pump, the chemical solution supply device, and the gas supply device are controlled so that the filtrate after the chemical solution is injected is pressurized.

  (9) In the above filtration device, the hollow fiber membrane module is a single-end free type hollow fiber in which the upper ends of the hollow fiber membrane bundle are fixed together and the lower ends are sealed in a state where the hollow fiber membranes are not fixed one by one. It may be a membrane module.

  The reason why the cleaning method and the filtration device for the hollow fiber membrane module of the present invention exhibit an excellent effect as compared with the prior art will be described below using the external pressure filtration method shown in FIGS. 1 and 2 as an example.

  FIG. 1 shows the flow of the filtrate in a cross-sectional view along the length direction of the hollow fiber membrane in liquid backwashing using the filtrate. FIG. 1 shows a case where a filtrate is caused to flow using a pump on the filtrate side (inner surface side) of a one-end free type hollow fiber membrane sealed without fixing one end. FIG. 2 shows the length of the hollow fiber membrane when the filtrate is pressurized with a gas having a pressure smaller than the pressure at which the gas is released from the stock solution side in a state where the liquid is filled on the stock solution side of the hollow fiber membrane. The flow of the filtrate in the cross sectional view along the direction is shown. FIG. 2 shows a case where compressed gas is introduced into the filtrate side of the one-end free type hollow fiber membrane using a compressor. In FIG. 1 and FIG. 2, the arrow from the inside of the hollow fiber membrane toward the outside indicates the filtrate flowing out from the filtrate side inside the hollow fiber membrane through the wall surface of the hollow fiber membrane to the stock side outside the hollow fiber membrane, The length of this arrow represents the magnitude of the flow rate of the filtrate.

  As schematically shown in FIG. 1, the filtrate introduced to the inner surface side of the hollow fiber membrane flows preferentially through the wall surface of the hollow fiber membrane from the vicinity of the permeate introduction portion where the pressure loss is small. Therefore, in many cases, the filtrate that is sufficient to wash the membrane does not flow to the end portion of the hollow fiber where the pressure loss is large. On the other hand, as schematically shown in FIGS. 2a to 2d, a gas having a pressure smaller than the pressure at which the gas is discharged from the stock solution side in a state where the liquid is filled on the stock solution side of the hollow fiber membrane is used. When backwashing is performed, the liquid level of the filtrate inside the hollow fiber membrane is sequentially lowered by the pressurized gas. At this time, since the vicinity of the liquid surface with a small pressure loss is preferentially backwashed, as the liquid surface of the filtrate inside the hollow fiber membrane decreases, from the permeate introduction part to the end part of the hollow fiber membrane The whole is washed uniformly. Further, after the washing with the filtrate is completed, the hollow fiber membrane is pressurized with gas from the inside and receives a force to expand outward, and the hollow fiber membrane expands as indicated by a broken line in FIG. At this time, the SS component adhering to the outside of the hollow fiber membrane is peeled off or cracked, and the SS component is likely to fall off in the gas washing step performed after the pressurizing step. From the above, according to backwashing using a gas having a pressure smaller than the pressure at which the gas is discharged from the stock solution side in a state where the liquid is filled on the stock solution side of the hollow fiber membrane, the reverse described with reference to FIG. Unlike washing, the entire hollow fiber membrane can be washed uniformly, and an excellent washing effect is exhibited.

  In the cleaning method and the filtration device of the hollow fiber membrane module of the present invention, the chemical solution is injected into the filtrate remaining in the filtrate side space of the hollow fiber membrane module after filtration, and the stock solution is filled in the stock solution side space. By extruding the filtrate after injecting the chemical solution to the stock solution side with a gas having a pressure smaller than the pressure at which the gas is released from the side, and performing backwashing, an organic substance adhering to the hollow fiber membrane is exhibited at the same time, Inorganic substances and the like can be dissolved or decomposed and removed, and a cleaning effect that is remarkably superior to conventional cleaning methods is exhibited.

  Moreover, in the cleaning method and filtration device of the hollow fiber membrane module of the present invention, by pressurizing with a gas having a pressure smaller than the pressure at which the gas is discharged from the stock solution side in a state where the stock solution is filled in the stock solution side space, As described with reference to FIGS. 2A to 2D, the entire hollow fiber membrane can be uniformly washed with a decrease in the liquid level by a small amount of filtrate remaining in the filtrate side space. Therefore, unlike the conventional case, a tank for storing a large amount of backwash water becomes unnecessary, and the apparatus can be miniaturized. Moreover, the usage-amount of the chemical | medical solution inject | poured into this can also be reduced by reducing the usage-amount of backwash water.

  According to the present invention, it is possible to provide a cleaning method and a filtering device for a hollow fiber membrane module that have a high cleaning capability and enable a continuous filtration operation for a long period of time and that can be downsized.

It is the figure which showed typically the flow of the filtrate in the backwashing using a filtrate. It is the figure which showed typically the flow of the filtrate in the backwashing using the gas of a pressure smaller than the pressure from which the gas is discharge | released from the stock solution side of a hollow fiber membrane. It is a figure which shows an example of the hollow fiber membrane module used for the filtration apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the filtration apparatus which concerns on embodiment of this invention. It is a figure which shows the basic driving | operation program of the filtration apparatus shown in FIG.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

(Filtering device)
First, an example of the filtration device 10 of the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram illustrating an example of an external pressure type hollow fiber membrane module 1 used in the filtration device 10 of the present embodiment. FIG. 4 is a schematic configuration diagram illustrating an example of the filtration device 10 using the hollow fiber membrane module 1.

  The filtration device 10 is an external pressure filtration type filtration device in which a stock solution is supplied to the outer surface side of the hollow fiber membrane 4 (hollow fiber membrane element) and the filtrate is taken out from the inner surface side of the hollow fiber membrane 4. The filtration device 10 includes a hollow fiber membrane module 1 provided with a space on the stock solution side B and a filtrate side A, a liquid feed pump 29 that supplies the stock solution to a space on the stock solution side B of the hollow fiber membrane module 1, and a hollow fiber membrane. An air compressor 30 (gas supply device) that supplies gas to the stock solution side B and filtrate side A spaces of the module 1, and a chemical solution injection pump 32 (chemical solution supply) that injects the chemical solution to the filtrate side A space of the hollow fiber membrane module 1 Device) and a control device 40.

  The inside of the hollow fiber membrane module 1 is partitioned by the bonded end 2 so that the upper part is a space on the filtrate side A and the lower part is a stock solution side B. A filtrate side pipe 51 is connected to the filtrate side A, and the filtrate side pipe 51 is provided with a filtrate outlet 5, a pressurized gas inlet 6, and a chemical liquid inlet 11. The stock solution side B is provided with a gas discharge port 8 and a stock solution side piping 52, and the stock solution side piping 52 is provided with a stock solution introduction port 7, a gas introduction port 9, and a stock solution drain port 12. A plurality of hollow fiber membranes 4 are arranged in the space on the stock solution side B, and an aeration member 13 is arranged below the hollow fiber membrane 4. The stock solution introduced into the space on the stock solution side B from the stock solution introduction port 7 passes through the wall surface of the hollow fiber membrane 4 and is led to the space on the filtrate side A as a filtrate.

  The liquid feed pump 29 is connected to the stock solution introduction port 7 via a stock solution introduction pipe 41. The stock solution introduction pipe 41 is provided with a stock solution inlet valve 21 for switching between the flow and shut-off of the stock solution in the pipe. The liquid feed pump 29 supplies the undiluted solution to the space on the undiluted solution side B via the undiluted solution introduction pipe 41.

  The air compressor 30 is connected to the pressurized gas inlet 6 via the first gas inlet pipe 42 and is connected to the gas inlet 9 via the second gas inlet pipe 43. The air compressor 30 pressurizes the filtrate present in the space by supplying the pressurized gas to the space on the filtrate side A via the first gas introduction pipe 42. Moreover, the air compressor 30 supplies the pressurized gas to the space on the stock solution side B through the second gas introduction pipe 43 to perform gas cleaning (bubbling) of the stock solution existing in the space. In addition, the gas supply apparatus in this invention is not restricted to the air compressor 30, What is necessary is just an apparatus which has the structure which can supply pressurized gas.

  The chemical solution injection pump 32 is connected to the chemical solution injection port 11 via a chemical solution injection pipe 44. The chemical solution injection pump 32 injects the chemical solution into the filtrate remaining in the filtrate side A space via the chemical solution injection pipe 44. Examples of the chemical liquid include an oxidizing agent, an acid, an alkali, and the like, and can be appropriately selected and injected according to the properties of the stock solution and the filtration behavior. The chemical solution injection pump 32 may have injection means capable of injecting one type of chemical solution, or may have injection means capable of injecting a plurality of types of chemical solutions. In addition, the chemical solution supply device in the present invention is not limited to the chemical solution injection pump 32, and any chemical solution may be used as long as the chemical solution can be supplied to the filtrate side A space.

  The control device 40 controls the drive of each device of the liquid feed pump 29, the air compressor 30, and the chemical solution injection pump 32, and controls the opening / closing operation of each valve. The control device 40 is configured by, for example, a personal computer. The control device 40 includes a storage unit in which sequence information of each step (water filling, filtration, chemical injection, pressurization, gas washing, drainage, etc.) sequentially executed in the filtration process is stored, and each device according to the sequence information. And a controller for controlling the opening and closing operation of the valve.

(Hollow fiber membrane)
Next, the hollow fiber membrane 4 used in the filtration device 10 will be described in detail.

  The hollow fiber membrane 4 used in the present embodiment includes a polysulfone resin hydrophilized with a polyvinyl alcohol resin, a polyvinylidene fluoride resin, a polysulfone resin injected with a hydrophilic polymer, and a polyvinylidene fluoride resin. Resin, polyvinyl alcohol-based resin, polyacrylonitrile-based resin, cellulose acetate-based resin, and hydrophilic materials such as polyethylene-based resin that have been hydrophilized have high hydrophilicity, so that SS components are difficult to adhere and adhere to. However, a hollow fiber membrane made of another material can also be used. For example, it is composed of organic polymer materials such as polyolefin, polysulfone, polyethersulfone, cellulose acetate, polyvinylidene fluoride, polyperfluoroethylene, polymethacrylate, polyester, and polyamide. Hollow fiber membranes, hollow fiber membranes made of inorganic materials such as ceramics, and the like can be selected according to use conditions, desired filtration performance, and the like. Here, a hollow fiber membrane comprising a polysulfone resin hydrophilized with a polyvinyl alcohol resin, a polyvinylidene fluoride resin, a polysulfone resin injected with a hydrophilic polymer, a polyvinylidene fluoride resin, and a polyvinyl alcohol resin. Is particularly preferable because it is excellent not only in the above-described hydrophilicity but also in heat resistance. When an organic polymer material is used, it may be a copolymer obtained by copolymerizing other components in an amount of 30 mol% or less, or a blend of other materials in an amount of 30 wt% or less.

  When an organic polymer hollow fiber membrane is used, the method for producing the hollow fiber membrane is not particularly limited, and a method appropriately selected from known methods depending on the characteristics of the material and the desired hollow fiber membrane performance Can be selected. Generally, a melt spinning method, a wet spinning method, a dry wet spinning method, or the like is employed. Further, from the viewpoint of water permeability, the hollow fiber membrane preferably has an inclined structure having a dense layer and a support layer. However, since hollow fibers generally produced by melt spinning have a symmetric structure, the dry and wet spinning method It is preferable to produce by a phase change method such as

  The pore diameter of the hollow fiber membrane 4 used in the present embodiment is not particularly limited, but being within a range of 0.001 to 5 microns has high water permeability and is less likely to reduce filtration efficiency. preferable. Here, the pore diameter refers to the particle diameter of a reference material from which 90% is excluded when various reference substances with known particle diameters such as colloidal silica, emulsion, and latex are filtered through a hollow fiber membrane. The pore diameter is preferably uniform. With an ultrafiltration membrane, it is impossible to determine the pore size based on the particle size of the reference material as described above. However, when a similar measurement is performed using a protein with a known molecular weight, Those having a molecular weight of 3000 or more are preferred.

  From the viewpoint of the mechanical properties of the hollow fiber membrane and the membrane area as a module, the outer diameter of the hollow fiber membrane 4 is preferably set in the range of 200 to 30000 microns, and is set in the range of 500 to 2000 microns. More preferably. Similarly, the thickness of the hollow fiber membrane 4 is preferably set within a range of 100 to 600 microns.

  In this embodiment, the hollow fiber membrane 4 is modularized and used for filtration as shown in FIG. The form of the module can be appropriately selected according to the filtration method, filtration conditions, washing method, and the like, and the hollow fiber membrane module may be configured by mounting one or a plurality of hollow fiber membranes. As the form of the module, for example, a bundle of dozens to hundreds of thousands of hollow fiber membranes is made into a U-shape in the module, one end of the hollow fiber bundle is collectively sealed with an appropriate sealing material, Examples include one in which one end of a hollow fiber bundle is sealed in a state where it is not fixed one by one with a suitable sealing material (free state), and one in which both ends of the hollow fiber bundle are opened. Further, the form of the hollow fiber membrane module is not particularly limited, and may be, for example, a cylindrical shape or a screen shape. In this embodiment, since the effect of cleaning the membrane surface with gas is extremely high, the upper ends of the hollow fiber membrane bundles are fixed together and the lower ends are sealed in a state where the hollow fiber membranes are not fixed one by one (free state). It is particularly preferable to use the “one end free type” hollow fiber membrane module 1.

  Examples of the filtration method using the hollow fiber membrane module 1 include external pressure total filtration, external pressure circulation filtration, internal pressure total filtration, and internal pressure circulation filtration, and can be appropriately selected according to desired treatment conditions and treatment performance. . From the viewpoint of membrane life, a circulation system capable of performing filtration and cleaning of the membrane surface at the same time is preferable, and from the viewpoint of facility simplicity, installation cost, and operation cost, a total filtration system is preferable. In the present embodiment, when the membrane surface is cleaned with gas, a cleaning effect is produced by rubbing the hollow fiber membranes, so that the stock solution is supplied to the outer surface side of the hollow fiber membrane 4 and the hollow fiber membrane 4 An external pressure filtration method in which the filtrate is taken out from the inner surface side is preferable.

(Washing method for hollow fiber membrane module)
Next, a filtration operation by the filtration device 10 and a method for cleaning the hollow fiber membrane module according to the present embodiment performed during the operation will be described with reference to FIGS. FIG. 5 shows the correlation between each process and the open / closed state of the operation valve in the basic operation method of the filtration device 10 shown in FIG. A circle in FIG. 5 means that the corresponding valve is open.

  First, a water filling step (before filtration) is performed. In this step, the gas discharge port valve 24 and the stock solution inlet valve 21 are opened by the control device 40 from the state where all the valves of the filtration device 10 are closed, and the liquid feed pump 29 is operated. Thereby, the stock solution is introduced from the feed pump 29 into the space on the stock solution side B of the hollow fiber membrane module 1, and the lower portion of the filtration container 25 is filled with the stock solution.

  Next, a filtration step is performed. In this step, after the stock solution overflows from the gas outlet 8 (gas outlet valve 24), the filtrate outlet valve 23 is opened by the control device 40 and the gas outlet valve 24 is closed. Then, the liquid filled in the space on the stock solution side B passes through the wall surface from the outer surface side of the hollow fiber membrane 4 to permeate the inner surface side and is taken out as a filtrate.

  In this filtration step, the SS component adheres to the outer surface of the hollow fiber membrane 4 as the filtration time elapses, thereby reducing the filtration capacity. Therefore, after the said filtration process is implemented for a fixed time, the hollow fiber membrane module 1 is wash | cleaned with the washing | cleaning method of the hollow fiber membrane module which concerns on this embodiment demonstrated below.

  First, a chemical solution injection step is performed. In this step, after the feed pump 29 is stopped, the stock solution inlet valve 21 and the filtrate outlet valve 23 are closed, and the filtration is stopped. Then, the gas outlet valve 24 is opened by the control device 40, and the chemical solution injection pump 32 is operated for a predetermined time in this state. Thereby, the chemical solution is injected from the chemical solution injection pump 32 into the filtrate remaining in the filtrate side A space of the hollow fiber membrane module 1.

  Examples of the chemical solution include an oxidizing agent, an acid, an alkali, and the like, and a preferable one is injected according to the properties of the stock solution and the filtration behavior. Moreover, what combined several types of chemical | medical solution may be inject | poured. The concentration of the chemical solution can be changed according to the nature of the stock solution, the degree of membrane blockage, the frequency of backwashing with the chemical solution, etc., but it should be in a range where deterioration of the hollow fiber membrane and performance degradation do not occur Is preferred. Further, when the hollow fiber membrane module 1 is washed a plurality of times during the filtration operation, different types of chemical solutions may be used in turn for each time.

  Next, a pressurization process is implemented. In this step, the control device 40 opens the stock solution outlet valve 27 and the pressurized gas inlet valve 22 and operates the air compressor 30. As a result, the pressurized gas is introduced into the space on the filtrate side A of the filtration container 25 (the space on the filtrate side A of the hollow fiber membrane module 1) from the pressurized gas introduction port 6, and the filtrate after the chemical solution injection is added by the gas. Pressed. Then, the filtrate enters the region on the inner surface side of the hollow fiber membrane 4 from the space on the filtrate side A, and is pushed out to the space on the stock solution side B through the wall surface of the hollow fiber membrane 4. At this time, a part of the stock solution filled in the space on the stock solution side B is discharged out of the system from the stock solution drain 12 (stock solution outlet valve 27). In this manner, the hollow fiber membrane 4 is backwashed with the filtrate into which the chemical solution has been injected. Thereafter, the pressure in the space on the filtrate side A of the hollow fiber membrane module 1 is lowered by opening the filtrate side pressure release valve 31.

  In this pressurizing step, the filtrate after the injection of the chemical solution is pressurized in a state in which the space on the stock solution side B of the hollow fiber membrane module 1 is filled, so that the filtrate is on the filtrate side A of the hollow fiber membrane module 1. It is extruded from the space into the space on the stock solution side B through the hollow fiber membrane. The pressurization is performed by a gas having a pressure smaller than the pressure at which the gas is released from the stock solution side B. At this time, the hollow fiber membrane 4 is back-washed in the process in which the filtrate filled in the filtrate side piping 51 and the filtrate side A space of the hollow fiber membrane module 1 is pushed out into the stock solution side B space. In the present embodiment, as described with reference to FIGS. 2A to 2D, the hollow fiber membrane 4 is formed by gradually decreasing the liquid level of the filtrate toward the end on the inner surface side of the hollow fiber membrane 4. The whole in the length direction can be cleaned uniformly. In addition, you may increase the quantity of the filtrate used for backwashing by providing the tank for storing a filtrate in the middle of the filtrate side piping 51. FIG.

  Examples of the gas used in the pressurizing step include air and nitrogen, and the pressure is selected within a range not exceeding the burst pressure of the hollow fiber membrane 4. When the burst pressure of the hollow fiber membrane 4 is greater than 0.5 MPa, the pressure of the pressurized gas is preferably in the range of 0.10 MPa to 0.50 MPa, and in the range of 0.15 MPa to 0.30 MPa. More preferably, it is within.

  The execution time of the pressurization step needs to be set to a time longer than the time at which the filtrate remaining in the filtrate side A of the hollow fiber membrane module 1 can be completely discharged or replaced, but per unit time of the pressurized gas It differs depending on the amount of introduction and the volume of the space on the filtrate side A of the hollow fiber membrane module 1. The pressurization time needs to be set in consideration of the volume inside the hollow fiber membrane 4.

Next, an immersion process is performed. In this process, in order to enhance the membrane cleaning effect with chemicals,
After the liquid is injected into the space on the stock solution side B by the pressurizing step, the hollow fiber membrane 4 is immersed in the liquid after the liquid is injected for a predetermined time. The implementation time of the dipping process is appropriately changed according to the type of chemical solution, the nature of the stock solution, and the degree of membrane clogging. As the immersion time increases, the cleaning effect by the chemical solution increases, but on the other hand, the operation rate of the filtration operation decreases. Therefore, the immersion time is preferably 60 minutes or less, and more preferably 30 minutes or less. In addition, the said immersion process is not an essential process and may be omitted.

  Next, a water filling step (before washing) is performed. In this step, in order to raise the liquid level in the space on the stock solution side B, which has been lowered in the pressurizing step, the gas discharge port valve 24 and the stock solution inlet valve 21 are opened by the control device 40 and the feed pump 29 is operated. As a result, the stock solution is filled in the space on the stock solution side B of the hollow fiber membrane module 1. Then, after the stock solution overflows from the gas discharge port 8 (gas discharge port valve 24), the liquid feed pump 29 is stopped, the stock solution introduction port valve 21 is closed, and the supply of the stock solution is stopped.

  Next, a gas cleaning process is performed. In this step, in a state where the stock solution side B of the hollow fiber membrane module 1 is filled with liquid, the control device 40 opens the gas inlet valve 28 and the air compressor 30 operates. Then, gas is supplied from the air compressor 30 to the space on the stock solution side B. Thereby, bubbles are generated in the liquid filled in the space on the stock solution side B, and the surface of the hollow fiber membrane 4 is washed for a predetermined time by the bubbles.

In this gas cleaning step, a gas such as air or nitrogen is supplied to the space on the stock solution side B. The amount of gas supply at this time is not particularly limited, but from the viewpoint of enhancing the membrane cleaning effect and reducing the risk of membrane breakage, it is within the range of 5 to 1000 normal liters per hour per 1 m ² of the hollow fiber membrane. It is preferable to be within a range of 10 to 500 normal liters / hour. In the one-end free type hollow fiber membrane module 1 used in the present embodiment, SS peeled off from the hollow fiber membrane 4 is easily discharged, and the membrane cleaning effect by gas becomes extremely high.

  Next, a drainage process is performed. In this step, the control device 40 closes the gas inlet valve 28 and opens the stock solution outlet valve 27. Thereby, the liquid in the hollow fiber membrane module 1 (stock solution filled in the space on the stock solution side B) is discharged out of the system.

  In this embodiment, after the completion of the pressurizing step, a cleaning cycle in which the water filling step (before cleaning), the gas cleaning step, and the draining step are sequentially performed may be repeated a predetermined number of times. This washing cycle is performed in order to reliably discharge the chemical solution injected into the hollow fiber membrane module 1 out of the system. The number of repetitions of the cleaning cycle can be changed according to the type and concentration of the chemical solution, and is preferably set to the number of times that the chemical solution does not remain in the hollow fiber membrane module 1. After the washing of the hollow fiber membrane module 1 is completed as described above, the filtration operation is resumed by returning to the water filling step (before filtration) and the filtration step again.

  In the above-described embodiment, a series of steps such as filtration, injection of a chemical solution into the filtrate, pressurization with gas, and gas cleaning can be performed by sequence control using the control device 40. For example, after performing the filtration process for a certain time, the hollow fiber membrane is back-washed by the chemical solution injection process and the pressurization process, and then the washing cycle including the gas washing process and the draining process is repeated once to several times. Each step may be performed automatically and continuously.

  The cleaning method of the hollow fiber membrane module of the present embodiment, in which the cleaning effect superior to the conventional cleaning method is expressed regardless of the material constituting the hollow fiber membrane and the shape of the module, is extremely wide use. It is possible to perform stable filtration continuously for a long period of time with a permeation flux higher than that of the prior art. For example, in the food industry field, sterilization / turbidity / iron removal / manganese removal of raw water, sterilization / fine particle removal / recovery of washing water, sterilization / fine particle removal of natural water, sterilization / purification of soy sauce, Sterilization and purification, vinegar sterilization and purification, mirin purification and seasoning sterilization and purification, product recovery from brewing and folding, sugar solution sterilization and fine particle removal and purification, honey purification, enzyme and protein Purification / concentration, fermentation solution purification, protein recovery from cheese poye, production of high protein milk by milk concentration, protein recovery from fishery processing wastewater, fish protein concentration, meat protein recovery from meat processing waste , Separation of red blood cells from pig blood, concentration and purification of albumin and globulin in blood, recovery and purification of bioactive substances from soybean whey, protein recovery from soybean broth, removal of oily protein toxins and protein concentration, potato Starch industrial waste Recovery of useful proteins from, recovery and purification of the natural pigments can be used in applications such as the purification of fermentation liquid by the recovery of bacterial cells and metabolites. Also, in the medical field, pure water used as a stock solution, pretreatment of ultrapure water production equipment, pyrogen removal of backwash water, injection water production, dialysis water production, dialysate purification, vaccines / enzymes / viruses / nucleic acids / proteins It can be used for applications such as separation / concentration / purification of hormones, purification of hormones, production of artificial blood, concentration and purification of polysaccharides, sterilization of hospital hand washing water, and sterilization of surgical instrument washing water. In the electronics industry, reverse osmosis membrane pretreatment, ultrapure water final filter, ultrapure water use point filter, ultrapure water unit built-in filter, cleaning water particulate removal, polishing wastewater recovery, dicing wastewater It can be used for purposes such as recovery. Also, in the chemical industry, paint concentration / recovery, oil separation / recovery, emulsion separation / recovery, colloid separation / recovery, fine powder washing and purification, washing water particulate removal, plating solution purification, electrodialysis It can be used for purposes such as pre-processing. In the field of textile and dyeing processing, it can be used for applications such as closing PVA desizing drainage, recovery and reuse of textile processing oil, recovery of lanolin from hair washing wastewater, and recovery of sericin from silk processing wastewater. is there. In the steel and machining field, barrel polishing wastewater recovery, buffing wastewater recovery, rolling oil wastewater treatment, water-soluble cutting oil wastewater treatment, animal and vegetable oil processing wastewater treatment, degreasing wastewater, It can be used for applications such as recovery, removal of rinse water emulsion / rinse water recovery, and removal of inks from screen plate cleaning agents.

(Other embodiments)
In the filtration device 10 of the above embodiment, a plurality of hollow fiber membrane modules 1 may be arranged in parallel in the filtration container 25 so as to share the stock solution introduction port 7, the filtrate outlet 5 and the stock solution discharge port 12. In this case, the chemical solution injection port 11 may be provided on the filtrate side A of each hollow fiber membrane module 1, or one chemical solution injection port 11 may be provided on the shared filtrate outlet 5.

  In the cleaning method of the above-described embodiment, the chemical solution may be supplied to the stock solution side B of the hollow fiber membrane module 1 after backwashing, and organic substances and inorganic substances attached to the hollow fiber membrane 4 may be dissolved and removed. Here, as a chemical cleaning method, a method of treating with an alkali or an oxidizing agent such as an aqueous sodium hydroxide solution to remove organic substances or inorganic materials, a method of treating with an acid such as an acid aqueous solution to remove metals There is a method of treating with a cleaning agent, or a method of continuously carrying out a combination thereof, whereby the hollow fiber membrane 4 can be regenerated. The type and concentration of the chemical solution can be changed according to the nature of the stock solution and the degree of membrane clogging, and are preferably selected so that the hollow fiber membrane 4 is not deteriorated or deteriorated in performance. When the same chemical solution as that used for backwashing is used, it is preferable to use a chemical solution having a higher concentration than that for backwashing from the viewpoint of enhancing the cleaning effect.

  In the cleaning method of the above embodiment, when the filtration process is restarted after cleaning the hollow fiber membrane module with chemical solution injection, sequence control may be performed so that the filtrate is discarded until a predetermined time has elapsed from the start of filtration. At this time, it is preferable that the time for discarding the filtrate is set to a time at which no chemical is mixed in the filtrate.

  In the cleaning method of the above embodiment, a step of cleaning the surface of the hollow fiber membrane 4 and the inside of the hollow fiber membrane module 1 by repeating drain discharge and water filling or a flushing cleaning step may be additionally performed as necessary. Good.

  In the cleaning method of the above embodiment, the filtration operation is continued while alternately repeating the filtration step and the cleaning step without chemical solution injection, and the membrane is clogged when the number of repetitions of the filtration step and the cleaning step reaches a certain value. In the case where the value becomes larger, a cleaning process with chemical solution injection may be performed. And after the washing | cleaning process accompanied by chemical | medical solution injection | pouring is completed, the washing | cleaning process not accompanied by a filtration process and chemical | medical solution injection | pouring may be repeated again. By such a so-called select switch system, it is possible to continue the filtration operation stably for a long period of time. Here, it is preferable that the frequency of the cleaning process involving the chemical solution injection is low because the operation rate of the filtration operation is high and the amount of the chemical solution used is also small. However, if the degree of progress of film clogging increases, the cleaning effect by the chemical solution decreases, so it is important to manage the execution frequency within an appropriate range. For example, after repeating the filtration step and the washing step without chemical solution injection 10 to 1000 times, or at the timing when the transmembrane pressure difference reaches a predetermined value or more set in the range of 50 to 100 kPa, the chemical solution injection is accompanied. A washing step is preferably performed.

  Moreover, it is not limited to the sequence control by the control apparatus 40, The said control apparatus 40 is abbreviate | omitted, and an operator is so that each process, such as a chemical | medical solution injection | pouring process, a pressurization process, an immersion process, and a gas washing process, may be implemented in order. The valve switching operation may be performed manually.

(Example)
Examples of the present invention will be described below. From the results of the following examples and comparative examples, it becomes clear that stable filtration operation can be performed for a long time in the present invention.

<Example 1>
As the hollow fiber membrane module, a hollow fiber membrane made of a polyvinylidene fluoride resin hydrophilized with polyvinyl alcohol and having an average pore diameter of 0.02 microns was used. This hollow fiber membrane module is a one-end free type and has a membrane area of 42 m ² .

  Lake water was used as a stock solution, and a constant flow rate filtration was performed under the condition of a flow rate of 3000 L / h using a hollow fiber membrane module by an external pressure total filtration method. And the washing | cleaning process was implemented once every 15 minutes of filtration processes. By the sequence control, a filtration process and a cleaning process cycle (80 times) without chemical liquid injection and a filtration process and a cleaning process cycle (single time) with chemical liquid injection were alternately performed.

  In the washing process not involving the injection of the chemical solution, a pressurizing process in which a pressurized operation is performed for 10 seconds by sending compressed air having a pressure of 0.2 MPa from the filtrate side of the hollow fiber membrane module to pressurize the inside of the hollow fiber membrane module, Depressurizing step for lowering the pressure, filling step for filling the undiluted solution on the undiluted solution side, a gas washing step for blowing air from the lower portion on the undiluted solution side of the hollow fiber membrane module at a flow rate of 1700 NL / h for 60 seconds, The drainage process to discharge was performed. Further, in the washing step involving the injection of the chemical solution, after injecting sodium hypochlorite so that the effective chlorine concentration becomes 100 mg / L with respect to the liquid on the filtrate side of the hollow fiber membrane module, The extraction process was performed. Next, an immersion process was performed in which the chemical solution and the film deposit were reacted by allowing to stand for 10 minutes. Then, the washing cycle in which the water filling step, the gas washing step, and the drainage step were sequentially performed was repeated 10 times.

  When the filtration operation was continued for 77 days under the above conditions, there was no fluctuation in the transmembrane pressure difference that was an indicator of membrane blockage, and a stable filtration operation was possible.

<Comparative Example 1>
The lake water is used as the stock solution in the same manner as in Example 1, and the constant flow filtration is performed under the condition of a flow rate of 3000 L / h by the external pressure total filtration method using the hollow fiber membrane module, and the washing step is performed once every 15 minutes of the filtration step. Carried out. By the sequence control, the operation was performed under the condition that only the cycle of the filtration process and the cleaning process without chemical solution injection was repeated. That is, unlike the above-described Example 1, the cleaning process with chemical injection was not performed. Other conditions were the same as in Example 1.

  When the filtration operation was continued for 8 days under the above conditions, the transmembrane pressure difference increased by a total of 8.7 kPa, and membrane clogging gradually occurred as the operation continued.

  In Comparative Example 1, membrane clogging occurred in a short period due to the continuation of filtration operation, whereas in Example 1, stable filtration operation was possible over a long period without increasing the transmembrane pressure difference. . Therefore, it has been found that by using the method for cleaning a hollow fiber membrane module of the present invention, a continuous filtration operation can be stably performed over a long period of time.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane module, A Filtrate side, B Stock solution side, 4 Hollow fiber membrane, 10 Filtration apparatus, 29 Liquid feed pump, 30 Air compressor (gas supply apparatus), 32 Chemical liquid injection pump (chemical liquid supply apparatus), 40 Control apparatus

Claims (9)

A method for cleaning a hollow fiber membrane module, which is carried out by a filtration apparatus including a hollow fiber membrane module provided with a space on a stock solution side and a filtrate side,
A chemical injection step of injecting a chemical into the filtrate present in the filtrate-side space;
The filtrate is injected from the space on the filtrate side by pressurizing the filtrate after injecting the chemical with a gas having a pressure smaller than the pressure at which the gas is released from the stock solution side in a state where the space on the stock solution side is filled with the stock solution. A method of cleaning the hollow fiber membrane module, comprising: a pressurizing step of pushing the hollow fiber membrane into the space on the stock solution side.   The method for cleaning a hollow fiber membrane module according to claim 1, further comprising a gas cleaning step of cleaning the stock solution side of the hollow fiber membrane module with a gas after the pressurizing step.   The method for cleaning a hollow fiber membrane module according to claim 2, further comprising an immersion step of immersing the hollow fiber membrane in a liquid into which a chemical solution is injected between the pressurizing step and the gas cleaning step. After the pressurizing step and before the gas washing step, a water filling step for filling the stock solution in the space on the stock solution side of the hollow fiber membrane module;
After the gas washing step, further comprising a drainage step of discharging the liquid in the hollow fiber membrane module out of the system,
The method for cleaning a hollow fiber membrane module according to claim 2 or 3, wherein a cleaning cycle in which the water filling step, the gas cleaning step, and the drainage step are sequentially performed is repeated.   The method for cleaning a hollow fiber membrane module according to any one of claims 1 to 4, wherein in the pressurizing step, the filtrate after chemical injection is pressurized with a gas having a pressure of 0.1 MPa to 0.5 MPa. .   The hollow according to any one of claims 1 to 5, which is carried out in an external pressure filtration type filtration device in which a stock solution is supplied to the outer surface side of the hollow fiber membrane and the filtrate is taken out from the inner surface side of the hollow fiber membrane. Cleaning method for thread membrane module.   The hollow fiber membrane module is a one-end free type hollow fiber membrane module in which the upper ends of the hollow fiber membrane bundles are fixed together and the lower ends are sealed in a state where the hollow fiber membranes are not fixed one by one. The washing | cleaning method of the hollow fiber membrane module of any one of 1-6. A hollow fiber membrane module provided with a space on the stock solution side and the filtrate side;
A liquid feed pump for supplying the stock solution to the space on the stock solution side;
A chemical supply device for supplying a chemical to the filtrate side space;
A gas supply device for supplying a gas for pressurizing the filtrate present in the filtrate side space to the space;
A control device for controlling the operation of the liquid feed pump, the chemical liquid supply device and the gas supply device,
The control device uses a gas having a pressure smaller than a pressure at which a chemical solution is injected into the filtrate existing in the filtrate side space and the gas is discharged from the stock solution side in a state where the stock solution is filled in the space on the stock solution side. A filtration device that controls operations of the liquid feed pump, the chemical solution supply device, and the gas supply device so that the filtrate after the chemical solution is injected is pressurized.   The hollow fiber membrane module is a one-end free type hollow fiber membrane module in which the upper ends of the hollow fiber membrane bundle are fixed together and the lower ends are sealed in a state where the hollow fiber membranes are not fixed one by one. The filtration apparatus as described in.

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