Hollow fiber membrane module for cross-flow filtration and method of operating the same

Abstract

A hollow fiber membrane module for cross-flow filtration of the present invention is made by filling a plurality of hollow fiber membranes in a container having a raw liquid inlet, a raw liquid outlet, and a filtrate outlet, in which the end portion on the raw liquid inlet side of the plurality of hollow fiber membranes is sealed, the end portion on the filtrate outlet side is open, at least the end portion on the filtrate outlet side has a packing portion fixed by an adhesive, the raw liquid side space and the filtrate side space in the container are separated by the plurality of hollow fiber membranes and the packing portion, the raw liquid side space is in contact with the outer surface of the hollow fiber membranes, the pure water permeation performance of the hollow fiber membranes is 2.0 m / hr or more and 20.0 m / hr or less, and the inner diameter Di of the hollow fiber membranes is 350 µm or more and 600 µm or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a hollow fiber membrane module for cross-flow filtration and a method for operating the same. BACKGROUND

[0002] Membrane filtration using a separation membrane is utilized in various fields such as water treatment fields of drinking water production, water purification treatment, or wastewater treatment, fermentation fields accompanying microorganisms, cultured cells, or food industry fields. Among them, membrane filtration using a hollow fiber membrane module is used in many fields because of a large amount of water to be treated, easy washing, and the like.

[0003] In the food industry field, the turbidity of the feed solution is often higher than that in the water treatment field, and in the full volume filtration operation that is often used in the water treatment field, clogging of the hollow fiber membrane, so-called fouling, rapidly progresses. Therefore, in the present application, cross-flow filtration operation that can further suppress fouling is performed. Cross-flow filtration operation is a method in which a portion of the feed solution is filtered while the total flow acts on the surface of the hollow fiber membrane. In this method, since the flow acts on the surface of the hollow fiber membrane, the operation can be performed while preventing the accumulation of turbidity on the surface of the hollow fiber membrane, so the fouling can be greatly reduced.

[0004] In general, in the filtration operation of a hollow fiber membrane module for outside pressure filtration, pressure loss occurs inside the hollow fiber due to the influence of the liquid passage resistance inside the hollow fiber, and thus a difference in the differential pressure between the membranes occurs in the axial direction of the hollow fiber membrane. In addition, in cross-flow filtration operation, in addition to the liquid passage resistance inside the hollow fiber membrane, pressure loss due to the flow of the feed solution occurs outside the hollow fiber membrane. Due to this pressure loss, there is a tendency that the differential pressure between the membranes on the feed solution inlet side of the hollow fiber membrane module becomes large and the differential pressure between the membranes on the filtrate outlet side becomes small. That is, the difference in the differential pressure between the membranes in the axial direction of the hollow fiber membrane becomes large. Furthermore, there is a case where, depending on the operation conditions, a reverse phenomenon occurs in which the pressure on the filtrate side near the filtrate outlet of the hollow fiber membrane becomes larger than that on the feed solution side, and the filtrate flows backward. In order to compensate for the amount of backward flow near the filtrate outlet, an excess amount is filtered near the feed solution inlet portion of the hollow fiber membrane. As a result, a difference in the filtration flux occurs in the axial direction of the hollow fiber membrane. In the case of operation in such a state, the development of fouling becomes faster at a portion where the filtration flux is fast, and the development of fouling becomes faster as a whole of the membrane module.

[0005] When the pollution reaches a certain state, the pollution is eliminated by means of liquid washing, but there is a problem that the liquid washing frequency becomes high due to the rapid development of the pollution. In the full volume filtration operation, the pressure loss inside the hollow fiber membrane is dominant, but in the cross flow filtration operation, in addition to the liquid passage resistance inside the hollow fiber membrane, pressure loss due to the flow of the raw liquid occurs outside the hollow fiber membrane. Therefore, depending on the operation conditions, the pressure on the filtrate side near the filtrate outlet of the hollow fiber membrane becomes greater than the pressure on the raw liquid side, and the reverse phenomenon occurs, and the filtrate flows backward. In order to compensate for the amount of backward flow near the filtrate outlet, an excess amount is filtered near the raw liquid inlet portion of the hollow fiber membrane. In the cross flow filtration operation, there are cases where the above-mentioned turbidity accumulation on the surface of the hollow fiber membrane due to the flow of the raw liquid is prevented, but there is also a phenomenon that the pollution of the raw liquid inlet portion becomes rapid due to the increase in the pressure loss on the raw liquid side, and as a result, there is a problem that the pollution of the entire module develops.

[0006] In Patent Literature 1, a method of providing a membrane module in which the water permeability of the open end side, which makes the filtration flux large, is made low, and the water permeability of the sealed end side, which makes the filtration flux small, is made high, is disclosed, and success is achieved in making the intermembrane differential pressure difference small. In Patent Literature 2, a method of suppressing the intermembrane differential pressure difference by changing the outer diameter, the inner diameter, and the membrane pressure in the axial direction of the hollow fiber membrane is disclosed.

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 04-11927

[0008] Patent Literature 2: Japanese Patent Application Laid-Open No. 07-96152

[0009] These methods require control of the performance of the membrane in the axial direction, but in order to manufacture such a membrane, the membrane manufacturing process becomes complicated and troublesome, and is not realistic. Therefore, a technique is desired which suppresses the reverse flow near the filtrate outlet of a general hollow fiber membrane having uniform performance in the axial direction. SUMMARY

[0010] Therefore, the object of the present application is to suppress the increase in the intermembrane differential pressure difference of the hollow fiber membrane and the reverse flow of the filtrate near the filtrate outlet due to the pressure loss on the raw liquid side accompanying the cross flow, and to reduce the development of membrane pollution.

[0011] In order to achieve the above object, the present application provides the following cross flow filtration hollow fiber membrane module and its operation method.

[0012] <1> A hollow fiber membrane module for cross-flow filtration, wherein the hollow fiber membrane module for cross-flow filtration is formed by filling a plurality of hollow fiber membranes in a container having at least a raw liquid inlet, a raw liquid outlet, and a filtrate outlet, characterized in that, in the plurality of hollow fiber membranes, the end on the side of the raw liquid inlet is sealed, the end on the side of the filtrate outlet is open, and at least the end on the side of the filtrate outlet has an injection portion fixed by an adhesive, the raw liquid side space in the container for connecting the raw liquid inlet and the raw liquid outlet, and the filtrate side space for connecting the filtrate outlet are separated by the plurality of hollow fiber membranes and the injection portion, the raw liquid side space is in contact with the outer surface of the hollow fiber membrane, and the pure water permeability K(m) of the hollow fiber membrane is... 3 / m 2 / hr / 50kPa) and the inner diameter D of the aforementioned hollow fiber membrane i (μm) satisfies the following requirements,

[0013] 2.0≤K≤20.0,

[0014] 350≤D i ≤600.

[0015] <2> The hollow fiber membrane module for cross-flow filtration described in <1> above is characterized in that the axial length L (m) of the hollow fiber membrane in contact with the raw liquid is 0.5≤L≤2.0.

[0016] <3> The hollow fiber membrane module for cross-flow filtration described in <1> or <2> above is characterized in that the outer diameter D of the hollow fiber membrane is... o (μm), fill rate M (%) and inner diameter D i (μm) satisfies the following relationship (2),

[0017] 0.33×D o -10×M+420≤D i ≤0.33×D o -10×M+550···(2).

[0018] <4> The hollow fiber membrane module for cross-flow filtration described in <3> above is characterized in that the aforementioned fill rate M (%) satisfies the following requirements:

[0019] 25≤M≤45.

[0020] <5> The hollow fiber membrane module for cross-flow filtration described in <3> or <4> above is characterized in that the aforementioned outer diameter D o (μm) satisfies the following requirements,

[0021] 850≤D o ≤1500.

[0022] The hollow fiber membrane module for cross-flow filtration according to any one of <1> to <6>, wherein the hollow fiber membrane has a membrane thickness D t (μm) relative to the inner diameter D i (μm) is 0.40 or more and less than 0.65. t / D i satisfies the following requirement,

[0023] 0.40≤D t / D i ≤0.65.

[0024] The hollow fiber membrane module for cross-flow filtration according to any one of <1> to <6>, wherein the hollow fiber membrane has a strength of 250 gf / root or more.

[0025] The hollow fiber membrane module for cross-flow filtration according to any one of <1> to <7>, wherein the hollow fiber membrane module has a feed inlet having a cross-sectional area S f relative to the flow path area S p inside the vessel is 0.35 or more. f / S p

[0026] A method for operating a hollow fiber membrane module, wherein the hollow fiber membrane module according to any one of <1> to <8> is used to perform cross-flow filtration in such a manner that the filtration flux J (m / d) and the cross-flow linear velocity v (m / s) satisfy the following requirement,

[0027] 0.5≤J≤2.0,

[0028] 1.0≤v≤1.8.

[0029] The method for operating a hollow fiber membrane module according to <9>, wherein the feed liquid is subjected to cross-flow filtration and has a turbidity of 20 NTU or more and a TOC concentration of 1000 mg / L or more.

[0030] The method for operating a hollow fiber membrane module according to <10>, wherein the filtrate has a turbidity of 10 NTU or more and a TOC concentration of 1000 mg / L or more.

[0031] The method for operating a hollow fiber membrane module according to any one of <9> to <11>, wherein the feed liquid has a viscosity of 2 mPa s or more.

[0032] Effects of the Invention

[0033] ​According to the present application, the backflow near the filtrate outlet during cross-flow filtration operation can be suppressed, and the membrane pressure difference in the axial direction of the hollow fiber membrane can be made small, and the development of contamination can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a schematic diagram showing one mode of the hollow fiber membrane module of the present application.

[0035] Figure 2 is a schematic flow chart showing one mode of the membrane filtration unit applying the full volume filtration operation.

[0036] Figure 3 is a schematic flow chart showing one mode of the membrane filtration unit applying the cross-flow filtration.

[0037] Figure 4 is a schematic flow chart showing another mode of the membrane filtration unit applying the cross-flow filtration.

[0038] Figure 5 is a schematic diagram showing a model for simulating the pressure distribution in the hollow fiber membrane module.

[0039] Figure 6 is a schematic flow chart showing one mode of the membrane filtration unit for verifying the simulation. DETAILED DESCRIPTION

[0040] Hereinafter, the embodiments of the present application will be explained in detail with reference to the drawings, but the present application is not limited at all by them.

[0041] In addition, in the present specification, "mass" is synonymous with "weight".

[0042] Figure 1 is a schematic diagram showing one mode of the cross-flow filtration hollow fiber membrane module (hereinafter, also referred to as the hollow fiber membrane module) of the present application. Hereinafter, in the present specification, the directions of "upper", "lower", and the like are based on the state shown in the drawing, and for the convenience, the upper side of the filtrate outlet 3 and the lower side of the raw material liquid inlet 2 are explained in the drawing. Figure 1

[0043] The cross-flow filtration hollow fiber membrane module 10 of the present application is filled with the hollow fiber membrane 5 in the container 1 having the raw material liquid inlet 2, the filtrate outlet 3, and the raw material liquid outlet 4. The both end portions of the hollow fiber membrane 5 are embedded in the first packing portion 8 and the second packing portion 9, and the first packing portion 8 and the second packing portion 9 are fixed to the container 1. The lower end portion of the hollow fiber membrane 5 embedded in the first packing portion 8 is sealed. In addition, the first packing portion 8 has a plurality of through-holes for passing the raw material liquid introduced from the raw material liquid inlet 2. On the other hand, the upper end portion of the hollow fiber membrane 5 embedded in the second packing portion 9 is embedded in the opened state. ​

[0044] The raw liquid inlet 2, the filtered liquid outlet 3, and the raw liquid outlet 4 are cylindrical nozzles that connect the container 1 and a pipe (not shown) and are fixed to the cylindrical container 1 in an open state. The raw liquid inlet 2 is connected to the lower end of the container 1, and the filtered liquid outlet 3 is connected to the upper end. The raw liquid outlet 4 is connected to the side of the container 1 and is provided near the second pouring portion 9. The materials thereof can be resin or metal.

[0045] The hollow fiber membrane 5 filled in the container 1 is a hollow fiber-shaped membrane composed of a high molecule having a liquid separation function. The hollow fiber membrane 5 is filled in a manner that the axial direction of the container 1 and the axial direction of the hollow fiber membrane 5 are parallel. The axial direction refers to the lengthwise direction of the container 1 and the lengthwise direction of the hollow fiber membrane 5.

[0046] The first pouring portion 8 and the second pouring portion 9 to which a plurality of hollow fiber membranes are fixed refer to portions in which the gaps between the bundled hollow fibers are filled with a so-called adhesive, that is, a pouring agent in which a pouring resin is a main component. The pouring portions are preferably formed at the end portions of the bundle of hollow fiber membranes.

[0047] As the main component of the pouring agent, a pouring resin excellent in adhesion to the hollow fiber membrane, heat resistance, and chemical durability is preferable. In addition, the pouring agent can include, for example, in addition to the pouring resin, an additive material such as silica, talc, mica, clay, calcium carbonate, glass, or rubber.

[0048] The first pouring portion 8 is formed at the raw liquid inlet side end portion of the hollow fiber membrane 5. The raw liquid inlet side end portion of the hollow fiber membrane 5 is sealed. The sealing refers to a state in which a liquid flowing inside the hollow fiber membrane 5 is not led out from the sealed end portion. The first pouring portion 8 is fixed to the container 1 but has a plurality of through-holes through which the raw liquid led from the raw liquid inlet 2 is introduced into the hollow fiber membrane 5. The shape and number of the through-holes are not specified, and are appropriately set in correspondence with the flow rate of the raw liquid passing therethrough so as to suppress the generation of resistance and flow unevenness.

[0049] The first pouring portion 8 can be positionally fixed in a manner that the first pouring portion 8 does not float due to the flow of the raw liquid, can be adhesively fixed to the container 1, or can be provided in a box structure that can be detached. The method of positional fixation is not particularly specified, and a structure that positionally fixes the container 1 and the first pouring portion 8, a structure that positionally fixes the second pouring portion 9 and the first pouring portion 8, or the like can be appropriately selected.

[0050] Further, the first perfusion portion 8 is not necessary as long as the raw material liquid introduction port side end portion of the hollow fiber membrane 5 is sealed, and it is also possible to be a free end not fixed by the perfusion agent instead of a so-called fixed end in which the bundle of hollow fiber membranes are fixed to each other by the perfusion agent. The free end refers to a state in which the hollow fiber membranes are not fixed to each other by the perfusion agent and can freely move. In this case, as a method of sealing the raw material liquid introduction port side end portion of the hollow fiber membrane 5, a method of sealing by injecting the perfusion agent into the hollow portion of the hollow fiber membrane 5, a method of sealing by welding the end portion by heat, or the like can be applied.

[0051] Next, the second perfusion portion 9 is formed at the filtrate lead-out port side end portion of the hollow fiber membrane 5 and is fixed in a state in which the filtrate lead-out port side end portion of the hollow fiber membrane 5 is open. The open state refers to a state in which the liquid flowing inside the hollow fiber membrane is led out from the open end portion.

[0052] The second perfusion portion 9 is fixed to the container 1, but as long as the raw material liquid and the filtrate can be liquid-tightly separated, it is also possible to be a configuration in which the second perfusion portion 9 and the container 1 are adhesively fixed or a so-called cartridge type in which the hollow fiber membrane can be attached and detached. In the case of the cartridge type, the second perfusion portion 9 and the container 1 can be connected via an O-ring or the like.

[0053] At the hollow fiber membrane module having the above configuration, the inside of the container 1 is separated into the raw material liquid side space 6 in which the raw material liquid is filled and the filtrate side space 7 in which the filtrate is filled by the hollow fiber membrane 5 and the second perfusion portion 9, the raw material liquid side space 6 is a space in contact with the outer surface of the hollow fiber membrane 5, and the filtrate side space 7 is a space in contact with the inner surface of the hollow fiber membrane 5.

[0054] The present application is an application applied to a so-called external pressure type hollow fiber membrane module in which the raw material liquid introduction port 2 and the raw material liquid lead-out port 4 are connected to the raw material liquid side space 6 and the filtrate lead-out port 3 is connected to the filtrate side space 7. As another way of the hollow fiber membrane module, an internal pressure type hollow fiber membrane module is exemplified, but the present application is not applied to the internal pressure type hollow fiber membrane module.

[0055] Next, a method of operating the hollow fiber membrane module indicated by Figure 2 and Figure 3 will be described. Figure 1

[0056] Figure 2 is a flowchart of the membrane filtration unit in which the full volume filtration operation is applied. The raw material liquid is supplied from the raw material liquid tank 12 to the container 1 by the supply pump 14. The raw material liquid introduced into the container 1 from the raw material liquid introduction port 2 passes through the raw material liquid side space 6 of the hollow fiber membrane 5 and is filtered by the hollow fiber membrane 5. Figure 1 ​The through hole of the first perfusion part 8 shown in the middle is supplied with liquid flow in parallel with the axial direction of the hollow fiber membrane 5 in the raw material side space 6. Thereafter, it is guided out from the container 1 via the raw material outlet 4. The guided-out raw material can be discharged to the outside of the system or can be returned to the raw material tank 12. After the raw material side space 6 is filled with raw material, in a state where the feed pump 14 is operated, the concentrated liquid valve 21 is closed and the filtered liquid valve 22 is opened, whereby the raw material is pressurized and the raw material is transferred to the filtered liquid side space 7 through the hollow fiber membrane 5. Thereafter, it passes through the inside of the hollow fiber membrane 5, passes through the end face of the opening of the second perfusion part 9, and is guided out from the filtered liquid outlet. The guided-out filtered liquid is delivered to the filtered liquid tank 13.

[0057] Such an operation method is called a full volume filtration operation. In the full volume filtration operation, the operation is performed in a manner that the filtration flow rate is constant as observed by the filtered liquid flow meter 32. At this time, the difference between the raw material inlet pressure PI observed by the raw material inlet pressure gauge 41 and the filtered liquid outlet pressure P3 observed by the filtered liquid outlet pressure gauge 43 is called the membrane differential pressure, and the operation is continued until the membrane differential pressure reaches a predetermined pressure.

[0058] In the full volume filtration operation, the flow in the raw material side space 6 is slow, and thus the pressure loss in the raw material side space 6 is very small. With respect to the inside of the hollow fiber membrane, the filtered liquid flows in a relatively fine flow path, and thus a pressure loss due to the liquid passage resistance is generated, but the pressure loss on the raw material side is small, and thus the membrane differential pressure difference in the axial direction of the hollow fiber membrane is small.

[0059] On the other hand, Figure 3 is a flowchart of a membrane filtration unit to which a cross flow filtration operation is applied. In the same manner as in the full volume filtration operation, raw material is supplied from the raw material tank 12 to the container 1 by the feed pump 14. The raw material guided into the container 1 from the raw material inlet 2 passes through Figure 1 The through hole of the first perfusion part 8 shown in the middle is supplied with liquid flow in parallel with the axial direction of the hollow fiber membrane 5 in the raw material side space 6. Thereafter, it is guided out from the container 1 via the raw material outlet 4.

[0060] The cross flow filtration operation is an operation method in which the circulation is performed at a flow rate of about 10 to 30 times the filtration flow rate, whereby the deposition of the membrane clogging components from the raw material on the membrane surface can be prevented due to the shearing effect of the flow, and stable filtration can be performed. It is an operation method that is particularly suitable for filtering raw material in which a large amount of clogging components are deposited on the membrane surface.

[0061] In the cross-flow filtration operation, the operation is also performed in a manner that the filtration flow rate is constant as observed by the filtrate flow meter 32. Further, the operation is performed in a manner that the circulation flow rate of the concentrate is also constant as observed by the concentrate flow meter 31. In the cross-flow filtration operation, the difference between the average of the raw liquid introduction pressure PI and the raw liquid discharge pressure P2 as observed by the raw liquid introduction pressure gauge 41 and the raw liquid discharge pressure gauge 42 and the filtrate discharge pressure P3 as observed by the filtrate discharge pressure gauge 43 is called the membrane differential pressure, and the operation is continued until the membrane differential pressure reaches a predetermined pressure.

[0062] Figure 4 A flow chart of another mode of the membrane filtration unit in which the cross-flow filtration operation is applied. In the cross-flow filtration operation, the amount of liquid circulated is large, and the pump power becomes large compared to the total filtration. Therefore, an operation method in which the circulation flow rate is made small by combining the feed pump 14 having a small flow rate and a large head and the circulation pump 15 having a large flow rate and a small head is also adopted. In this case, it is preferable to recycle a part or the whole of the raw liquid discharged from the raw liquid discharge port 4 to the piping between the feed pump 14 and the circulation pump 15. After the raw liquid side space 6 is filled with the raw liquid, in a state in which the feed pump 14 is operated, the opening of the concentrate valve 21 is reduced, and the filtrate valve 22 is opened, whereby the raw liquid is pressurized, and the raw liquid is transferred to the filtrate side space 7 through the hollow fiber membrane. Thereafter, the filtrate passes through the inside of the hollow fiber membrane, passes through the end face of the opening of the 2nd perfusion portion 9, and is discharged from the filtrate discharge port 3. The discharged filtrate is delivered to the filtrate tank 13.

[0063] In the cross-flow filtration operation, the flow in the raw liquid side space 6 is fast, and therefore the pressure loss of the raw liquid side space 6 becomes very large. The pressure loss also occurs in the inside of the hollow fiber membrane, but generally the pressure loss of the raw liquid side is large, and therefore the membrane differential pressure difference in the axial direction of the hollow fiber membrane becomes large compared to the total filtration operation. The pressure loss of the raw liquid side is large, and therefore the phenomenon in which the pressure of the filtrate on the filtrate discharge port 3 side of the hollow fiber membrane 5 is relatively high compared to the pressure of the raw liquid, that is, the inversion phenomenon occurs, and the problem of the backflow of the filtered liquid occurs. In order to compensate for the amount of the backflow of the filtrate, the excess amount of the liquid is filtered on the raw liquid introduction port 2 side of the hollow fiber membrane 5, and therefore becomes a factor that promotes the membrane pollution.

[0064] As a result of the intensive study on this problem, it was found that the pure water permeability K of the hollow fiber membrane 5 filled in the container 1 and the inner diameter D of the hollow fiber membrane 5 satisfy the following conditions. i The control is performed within the predetermined range, whereby the membrane differential pressure inversion on the filtrate discharge port 3 side at the time of the cross-flow filtration operation can be suppressed, and the membrane differential pressure difference in the axial direction of the hollow fiber membrane can be suppressed, and the invention of the present hollow fiber membrane module can be achieved.

[0065] The pure water permeability K (m 3 / m2 ( / hr / 50kPa) is 2.0≤K≤20.0, that is, 2.0m 3 / m 2 / hr / 50kPa and above and 20.0m 3 / m 2 / hr / below 50kPa. Pure water permeability K ratio 2.0m 3 / m 2 When the permeability K is low (50 kPa / hr, hereinafter referred to as m / hr), the filterability of the target liquid decreases. On the other hand, when the pure water permeability K is higher than 20.0 m / hr, the membrane pore size becomes larger, so the rejection rate of the components to be removed deteriorates, and there are cases where the membrane performance is not observed. The pure water permeability K is preferably 2.5 to 15.0 m / hr, more preferably 3.0 to 10.0 m / hr.

[0066] It was found that in such hollow fiber membrane modules, the inner diameter D of the hollow fiber membrane... i (μm) is set to 350≤D i The inner diameter is ≤600, meaning the range from 350μm to 600μm. This reduces the pressure difference between the feed liquid and filtrate sides during cross-flow filtration, suppressing backflow at the filtrate outlet and minimizing contamination. i When the diameter is larger than 600 μm, the intermembrane differential pressure on the feed inlet 2 side of the hollow fiber membrane 5 increases, leading to faster fouling. Inner diameter D i When the inner diameter is smaller than 350 μm, the pressure loss in the hollow section increases. Therefore, contrary to the case of a larger inner diameter, the intermembrane differential pressure on the filtrate outlet 3 side of the hollow fiber membrane 5 increases. Consequently, the axial intermembrane differential pressure of the hollow fiber membrane 5 increases, and fouling develops more rapidly. Regarding the inner diameter of the hollow fiber membrane, 400 μm to 550 μm is more preferably preferred. By controlling it within this range, the axial intermembrane differential pressure of the hollow fiber membrane can be suppressed while suppressing backflow of the filtrate, effectively reducing fouling.

[0067] The following information permeation performance (K) and inner diameter (D) of hollow fiber membranes are relevant. i The determination method is explained.

[0068] Regarding the pure water permeation performance K, a small module with an axial length of 0.1 m, consisting of three hollow fiber membranes, was fabricated for measurement. Under conditions of 25℃ and a filtration differential pressure of 18.6 kPa, the reverse osmosis membrane was used to filter the water at full external pressure for 10 minutes, and the permeation rate (m³) was calculated. 3 The transmittance (m) 3) based on the following formula (1) converted into a value per unit time (h) and effective membrane area (m 2 ) and multiplied by (50 / 18.6), thereby converted into a value under a pressure of 50 kPa, to thereby calculate the pure water permeation performance K. The effective membrane area is the area of the portion of the outer surface of the hollow fiber membrane 5 in the present application that is actually used for filtration.

[0069] K = permeation amount (m 3 ) / filtration time (hr) / effective membrane area (m 2 ) x (50 / 18.6)... (1)

[0070] The inner diameter D i (μm) of the hollow fiber membrane is measured by cutting the hollow fiber membrane with a single blade or the like in a plane perpendicular to the axial direction, observing the cross section by a microscope or the like, and measuring the diameter of the inner circle. In the case where the inner circle is flattened, the length of the portion where the diameter of the inner circle is the longest (major axis) and the length of the portion where the diameter of the inner circle is the shortest (minor axis) can be measured, and the average of the two is taken as the inner diameter D i . Preferably, the membrane can be arbitrarily cut from a plurality of hollow fiber membranes 5 filled in the vessel 1, and the average of the inner diameters of 10 or more hollow fiber membranes is used.

[0071] The pure water permeation performance K is preferably measured using the hollow fiber membrane before use, but can also be measured using a membrane in which the pure water permeation performance K is restored to 90% or more of the initial value by washing with a chemical solution or the like in the case of a hollow fiber membrane that is clogged due to use.

[0072] Next, in the hollow fiber membrane module for cross-flow filtration of the present application, the axial length L (m) of the hollow fiber membrane 5 is preferably in the range of 0.5 ≤ L ≤ 2.0, i.e., 0.5 m or more and 2.0 m or less. If the axial length L of the hollow fiber membrane 5 is less than 0.5 m, the membrane area per hollow fiber membrane module becomes small, and the number of hollow fiber membrane modules introduced into the filtration unit increases, so there is a case where the equipment cost and the operation power become high. On the other hand, if the axial length L of the hollow fiber membrane 5 exceeds 2.0 m, the pressure loss on the raw material side and the filtered liquid side becomes large, so there is a case where the inter-membrane pressure difference in the axial direction of the hollow fiber membrane further increases. The axial length L of the hollow fiber membrane 5 is preferably in the range of 0.7 m to 1.5 m, and further preferably in the range of 0.8 m to 1.2 m.

[0073] The axial length L refers to the length in the direction parallel to the vessel 1 of the portion of the hollow fiber membrane 5 that is actually used for filtration, i.e., the portion of the outer surface of the hollow fiber membrane 5 that contacts the raw material, in the state where the hollow fiber membrane 5 is filled in the vessel 1. Figure 1L is the length of the hollow fiber membrane 5 from the second perfusion portion side end surface of the first perfusion portion 8 to the first perfusion portion side end surface of the second perfusion portion 9. Here, the length of the hollow fiber membrane embedded in the first perfusion portion 8 and the second perfusion portion 9 is not considered.

[0074] In the case of the hollow fiber membrane module in which the hollow fiber membrane 5 is packed in a so-called U-shaped manner and embedded in a state in which both end portions are open at the second perfusion portion 9, the axial length L is half the length of the hollow fiber membrane actually used for filtration, that is, half the length of the fiber of the portion of the hollow fiber membrane in which the outer surface is in contact with the raw material liquid.

[0075] In the case in which the raw material liquid introduction portion side end portion of the hollow fiber membrane 5 is a free end without the first perfusion portion 8, the length of the free end from the portion in which sealing treatment based on an adhesive or heat is not performed to the raw material liquid introduction portion side end surface of the second perfusion portion 9.

[0076] Further, in the case in which the hollow fiber membrane 5 is crimped or twisted, the axial length L can also be measured as the length in the direction parallel to the container 1 of the portion of the hollow fiber membrane actually used for filtration, that is, the portion of the hollow fiber membrane in which the outer surface is in contact with the raw material liquid. As described above, the present application is a technology in which the pressure loss of the hollow portion is controlled to a predetermined range by the inner diameter D i , the axial length L, and the pure water permeation performance K of the hollow fiber membrane 5, the difference in pressure loss from the raw material liquid side is uniformized, and the inter-membrane pressure difference in the axial direction of the hollow fiber membrane 5 is reduced. In the case of the hollow fiber membrane module of the internal pressure type, the space in contact with the outer surface of the hollow fiber membrane is the filtrate side, so the effect according to the structure of the present application is not found. Therefore, it is a technology applied to the hollow fiber membrane module of the external pressure type.

[0077] Next, in the hollow fiber membrane module for cross-flow filtration of the present application, preferably, the outer diameter D o (μm) of the hollow fiber membrane, the packing ratio M (%) and the inner diameter D i (μm) satisfy the following relationship of Expression (2).

[0078] 0.33 x D o -10 x M + 420 ≤ D i ≤ 0.33 x D o -10 x M + 550 ··· (2)

[0079] In the hollow fiber membrane module in which the packing ratio M of the hollow fiber membrane is the same, the smaller the outer diameter D o of the hollow fiber membrane, the larger the membrane area in contact with the raw material liquid, so the pressure loss due to cross-flow flow increases. The present inventors found that the larger the pressure loss, the larger the pressure difference on the raw material liquid side in the axial direction of the hollow fiber membrane 5, but by making the inner diameter D ibecomes small, the liquid permeation resistance on the filtrate side of the hollow fiber membrane 5 increases, and thus the difference in pressure difference between the membrane on the raw material side and the membrane on the filtrate side can be suppressed.

[0080] Further, the outer diameter D o With the same hollow fiber membrane 5, the higher the packing ratio M, the larger the membrane area contacted by the raw material, and thus the pressure loss due to cross-flow flow increases. It was found that the larger the pressure loss, the larger the pressure difference on the raw material side in the axial direction of the hollow fiber membrane 5, but by making the inner diameter D i becomes small, the liquid permeation resistance on the filtrate side of the hollow fiber membrane 5 increases, and thus the difference in pressure difference between the membrane on the raw material side and the membrane on the filtrate side can be suppressed.

[0081] Thus, it is important that the inner diameter D i corresponding to the outer diameter D o and the packing ratio M be designed to be within an appropriate range. In the present application, it was found that under the conditions of general cross-flow filtration operation, the difference between the liquid permeation resistance inside the hollow fiber membrane 5 and the liquid permeation resistance on the raw material side can be suppressed, backflow can be suppressed, and the difference in pressure difference between the membranes in the axial direction of the hollow fiber membrane 5 can be suppressed. In addition, the conditions of general cross-flow filtration mean operation under the conditions of a filtration flux J (m / d) of 0.5 to 2.0 m / d and a cross-flow linear velocity v (m / s) of 0.5 to 2.0 m / s. However, depending on the viscosity of the raw material, the appropriate operation conditions can vary, and thus the present application is not limited thereto.

[0082] The packing ratio M (%) is the ratio of the cross-sectional area S1 of the container 1 when the central portion of the container 1 is cut in a plane perpendicular to the axial direction to the specific area S2 of the hollow fiber membrane 5, and is calculated according to the following formula (3).

[0083] [Formula 1]

[0084]

[0085] When there are components other than the container 1 and the hollow fiber membrane 5 in the cross-sectional area S1 of the container 1 when the central portion of the container 1 is cut in a plane perpendicular to the axial direction, the cross-sectional area S1 of the container 1 is calculated by subtracting the cross-sectional area of the component. That is, when the cross-sectional area of the component is S1', the packing ratio M is calculated according to the following formula (4).

[0086] [Formula 2]

[0087]

[0088] The filling rate M (%) is preferably 25 ≤ M ≤ 45, that is, preferably in the range of 25% to 45%. By controlling the filling rate M within 25% to 45%, the membrane area of ​​each module can be ensured, and the liquid flow resistance on the feed side can be reduced. The filling rate M is preferably 28% to 42%, and more preferably 30% to 40%.

[0089] Hollow fiber membrane outer diameter D o The measurement method and inner diameter D i The measurement method is the same: the hollow fiber membrane is cut in half with a single blade on a plane perpendicular to the axial direction, and the cross-section is observed using a microscope or other methods to determine the outer diameter. Outer diameter D o (μm) is preferably 850≤D o ≤1500, that is, preferably in the range of 850μm to 1500μm. This is achieved by adjusting the outer diameter D. o By controlling the membrane size between 850μm and 1500μm, the membrane area of ​​each module can be ensured, and the liquid flow resistance on the raw liquid side can be reduced.

[0090] Examples of polymers constituting the hollow fiber membrane 5 include polyethylene, ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomers, olefin polymers such as polypropylene or poly-4-methylpentene-1, fluoropolymers such as polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-ethylene copolymer or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, cellulose polymers such as cellulose acetate, polyvinyl chloride, acrylonitrile polymers, silicone polymers, polyamides, polyimides, polyethersulfone, polysulfone, polyphenylene ether, polyphenylene sulfide, polyarylates, polyetheretherketones, polyetherimides, polycarbonate, or polyvinyl alcohol polymers. To improve the heat resistance, physical strength, and chemical durability of the obtained hollow fiber membrane, fluoropolymers, polyethersulfone, or polysulfone are preferred. However, in hollow fiber membrane modules for cross-flow filtration where the membrane is subjected to heavy loads, fluoropolymers with excellent strength are preferred.

[0091] Cross-flow filtration is frequently used for treating highly turbid feed solutions. With smaller pore sizes, membrane clogging develops more rapidly. Therefore, the fractionation particle size φ of the hollow fiber membrane is preferably 0.1 μm or more. More preferably, it is 0.3 μm or more, and even more preferably 0.5 μm or more. On the other hand, when the fractionation particle size φ exceeds 2.0 μm, the removal rate of components that should be prevented decreases. Therefore, the fractionation particle size φ is preferably 2.0 μm or less, and even more preferably 1.5 μm or less.

[0092] The classification particle size φ can be measured by the following method. A small module identical to that used for measuring the pure water permeability K is prepared. Then, particles of polystyrene latex having uniform sizes are dispersed at a predetermined concentration to prepare a raw solution, and the particle concentration of the raw solution and the filtrate when the raw solution is filtered using the small module is measured. This is measured using polystyrene latex particles of various particle sizes, and the particle size at which the removal rate of the particles is 90% is set as the classification particle size φ.

[0093] At this time, the filtration is preferably performed by cross-flow filtration in order to suppress membrane clogging caused by the particles, and is preferably performed in a range where the filtration flux is 0.5 to 5 m / d and the cross-flow linear velocity is 0.5 to 5 m / s.

[0094] Hereinafter, the method for producing the hollow fiber membrane module of the present application will be described.

[0095] (Method for producing hollow fiber membrane)

[0096] As an example of the method for producing the hollow fiber membrane of the present application, a method for producing a hollow fiber membrane using a fluororesin-based polymer is described. As the method for producing a hollow fiber membrane using a fluororesin-based polymer, various methods such as a thermally induced phase separation method, a non-solvent induced phase separation method, and the like can be used. Hereinafter, a method using a thermally induced phase separation method is described.

[0097] A fluororesin-based polymer is dissolved in a poor solvent or a good solvent for the fluororesin-based polymer at a relatively high temperature of a crystallization temperature or higher, whereby a fluororesin-based polymer solution (i.e., a membrane-forming raw solution containing a fluororesin-based polymer) is prepared.

[0098] If the concentration of the polymer in the membrane-forming raw solution is high, a porous hollow fiber membrane having high strength is obtained. On the other hand, if the concentration of the polymer is low, the void fraction of the porous hollow fiber membrane becomes large, and the pure water permeability K is improved. Therefore, the concentration of the fluororesin-based polymer is preferably 20% by weight or more and 60% by weight or less, and more preferably 30% by weight or more and 50% by weight or less.

[0099] In the present specification, the poor solvent is a solvent that cannot dissolve 5% by weight or more of the fluororesin-based polymer at a low temperature of 60°C or lower, but can dissolve 5% by weight or more of the fluororesin-based polymer in a high temperature region of 60°C or higher and a temperature lower than the melting point of the fluororesin-based polymer (for example, about 178°C in the case where the polymer consists solely of a vinylidene fluoride monomer polymer). The good solvent is defined as a solvent that can dissolve 5% by weight or more of the fluororesin-based polymer in a low temperature region of less than 60°C, and the non-solvent is defined as a solvent that does not dissolve or swell the fluororesin-based polymer up to the melting point of the fluororesin-based polymer or the boiling point of the solvent.

[0100] Here, as the poor solvent of the fluorine resin-based polymer, cyclohexanone, isoforone, γ-butyrolactone, methyl isovaleryl ketone, propylene carbonate, dimethyl sulfoxide, and the like, and a mixture thereof can be exemplified. As the good solvent, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethyl urea, phosphoric acid trimethyl ester, and the like, and a mixture thereof can be exemplified. As the non-solvent, water, hexane, pentane, benzene, toluene, methanol, ethanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, a low-molecular-weight polyethylene glycol, and the like, aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic polyols, aromatic polyols, chlorinated hydrocarbons, or other chlorinated organic liquids, and a mixture thereof, and the like can be exemplified.

[0101] In the formation step of the hollow fiber, the hollow fiber is obtained from the film- forming dope solution containing the fluorine resin-based polymer by using a thermally induced phase separation method in which phase separation is induced by temperature change. In the thermally induced phase separation method, two kinds of phase separation methods are mainly used. One is a liquid-liquid phase separation method in which a polymer solution uniformly dissolved at a high temperature is separated into a polymer-rich phase and a polymer-lean phase due to a decrease in the solubility of the solution upon temperature decrease, and the structure is then fixed by crystallization. The other is a solid-liquid phase separation method in which a polymer solution uniformly dissolved at a high temperature is phase-separated into a polymer solid phase and a solvent phase by crystallization of the polymer upon temperature decrease.

[0102] In the former method, a three-dimensional mesh structure is mainly formed, and in the latter method, a spherical structure composed of a spherical organization is mainly formed. The production of the hollow fiber membrane of the present application is not particularly specified, but as the hollow fiber membrane for cross-flow filtration which requires strength, the latter phase separation method is preferably used. Thereby, the polymer concentration and the solvent which induce solid-liquid phase separation are selected.

[0103] As a specific method, the above-mentioned film-forming dope solution is ejected from the outer tube of a double-tube metal cap for spinning a porous hollow fiber membrane, and a hollow portion forming liquid is ejected from the inner tube of the double-tube metal cap. The thus-ejected film-forming dope solution is cooled and solidified in a cooling bath, whereby a porous hollow fiber membrane is obtained.

[0104] Next, the cooling bath for cooling the fluororesin-based polymer solution ejected from the metal cap is described. As the cooling bath, a mixed liquid composed of a poor solvent or a good solvent having a concentration of 50 to 95% by weight and a non-solvent having a concentration of 5 to 50% by weight is preferably used. Further, as the poor solvent, the same poor solvent as that of the polymer solution is preferably selected for use. Furthermore, as the hollow portion forming liquid, the same as the cooling bath, a mixed liquid composed of a poor solvent or a good solvent having a concentration of 50 to 95% by weight and a non-solvent having a concentration of 5 to 50% by weight is preferably used. Further, as the poor solvent, the same poor solvent as that of the polymer solution is preferably selected for use. The hollow fiber membrane composed of the fluororesin-based polymer obtained by the above method can be stretched. The stretching ratio and the stretching temperature are appropriately selected depending on the desired pore diameter, size, and pure water permeation performance.

[0105] In the case where the hollow fiber membrane filled in the hollow fiber membrane module of the present application is obtained, the inner and outer diameters of the hollow fiber membrane can be controlled mainly by controlling the cap diameter of the double-tube type metal cap, the ejection amount of the membrane-forming stock solution, and the hollow portion forming liquid. That is, the hollow fiber membrane having a large inner and outer diameter is obtained by using a double-tube type metal cap having a large diameter or increasing the ejection amount of the membrane-forming stock solution and the hollow portion forming liquid. Furthermore, the size can also be adjusted by changing the stretching ratio and the stretching temperature.

[0106] The pure water permeation performance K is mainly related to the pore diameter and the thickness of the obtained membrane. As for the pore diameter, it can be controlled by adjusting the coagulation conditions, the stretching conditions, and the like, for example, the pore diameter becomes large if the temperature of the raw material liquid in the gear pump is increased or the polymer concentration of the raw material liquid is decreased. The thickness can be controlled as described above by adjusting the cap diameter of the double-tube type metal cap, the ejection amount of the membrane-forming stock solution, and the hollow portion forming liquid, for example, by thinning the membrane by decreasing the ejection amount of the membrane-forming stock solution. By controlling the membrane-forming conditions as appropriate in this way, the pure water permeation performance K can be brought within the range of the present application.

[0107] Furthermore, as another mode of the hollow fiber membrane module of the present application, the ratio of the membrane thickness D t (μm) to the inner diameter D i (μm) is D t / D i is preferably 0.40 ≤ D t / D i ≤ 0.65, that is, it is preferably in the range of 0.40 or more and 0.65 or less.

[0108] Here, the membrane thickness D t (μm) is calculated from the outer diameter D o (μm) and the inner diameter D i (μm) of the hollow fiber membrane by the following formula (5).

[0109] Dt =(D o -D i ) / 2···(5)

[0110] That is, the film thickness D t Relative to inner diameter D i In cases where the membrane area is relatively small, increasing the membrane area leads to a higher fill rate and increased pressure loss on the feed side, thus failing to adequately secure the membrane area. On the other hand, the membrane thickness D... t Relative to inner diameter D i In larger cases, even with increased filler ratio, the increase in membrane area is relatively small. Membrane thickness D t Relative to inner diameter D i Within the range of 0.40 to 0.65, sufficient membrane area can be ensured, and the increase in pressure loss on the feed side can be suppressed, as well as the axial inter-membrane pressure difference of the hollow fiber membrane can be suppressed. (D) t / D i More preferably, it is 0.43 to 0.62, and even more preferably, it is 0.45 to 0.60.

[0111] Next, the hollow fiber membrane 5 used in this invention preferably has a strength of 250 gf / membrane or higher. As an example, in an external pressure cross-flow filtration system... Figure 1 As shown, after the raw liquid is introduced into the hollow fiber membrane module 1 through the raw liquid inlet 2, it is discharged through the raw liquid outlet 4. However, the liquid flow of the raw liquid rotates by 90° when discharged from the raw liquid outlet 4. Therefore, a shear force perpendicular to the length direction of the hollow fiber membrane 5 is applied to the hollow fiber membrane 5 near the raw liquid outlet 4.

[0112] It has been found that in this invention, the hollow fiber membrane 5 has a strength of 250 gf / piece or more, thereby being able to suppress fiber cutting, membrane damage, etc., relative to the shear caused by cross-flow velocity as envisioned in this application.

[0113] Strength refers to the load (gf) applied at the moment of fracture when the hollow fiber membrane 5 is stretched axially using a tensile testing machine or the like. The strength of the hollow fiber membrane 5 is preferably 400 gf / piece or more, and more preferably 600 gf / piece or more.

[0114] The method for determining strength is not particularly limited, but for example, a tensile testing machine can be used to change the specimen and perform more than 5 tests of stretching a specimen with a test length of 50 mm at a tensile speed of 50 mm / min, and the average value of the breaking strength and the average value of the breaking elongation can be obtained, thereby determining the strength.

[0115] (Fabrication of hollow fiber membrane modules)

[0116] The hollow fiber membrane module is classified into a container-integrated module in which the container 1 and the hollow fiber membrane 5 are fixed with an adhesive, and a cassette-type module in which the container 1 and the hollow fiber membrane 5 are not fixed with an adhesive and the hollow fiber membrane 5 can be attached to and detached from the container 1.

[0117] In the container-integrated module, the plurality of hollow fiber membranes 5 are inserted into the container 1, and the end portions of the hollow fiber membranes 5 and the container 1 are fixed with an adhesive. In the cassette-type module, the hollow fiber membranes are inserted into a dedicated jig or the like, and the membranes are adhered to each other with an adhesive without being fixed to the container 1.

[0118] In both of these methods, the hollow fiber membranes 5 are inserted into a fixing jig or a container or both, and an adhesive is flowed to fix them. As a method of filling an adhesive into the gap between the hollow fiber membranes, for example, a centrifugal filling method in which a perfusion agent is impregnated by centrifugal force, or a standing filling method in which an adhesive is impregnated by natural flow can be cited. In addition, the adhesive can be injected into a mold for injection molding to be filled into the gap between the hollow fiber membranes.

[0119] In the case where the end portion of the hollow fiber membrane fixed by the adhesive is open, the end portion of the hollow fiber membrane 5 is preliminarily sealed to be fixed by the adhesive so that the adhesive does not flow into the hollow portion of the hollow fiber membrane when the adhesive is flowed. As a method of sealing, a method of injecting an adhesive only into the hollow portion, fusion based on heat, a solvent, or the like can be cited. After the hollow fiber membrane 5 whose end portion is sealed by the adhesive is fixed, the other end side can be made open from the sealed portion by being cut in the direction of the cross section passing through the hollow fiber membrane 5. If the end portion of the hollow fiber membrane is not sealed and is fixed by the adhesive, the adhesive flows into the hollow portion of the hollow fiber membrane 5, so the end portion is sealed.

[0120] In the present application, a method of fixing both ends of the hollow fiber membrane 5 with an adhesive can also be employed, but the end portion on the side of the raw material liquid introduction port of the hollow fiber membrane 5 can also be provided as a free end that is not fixed with an adhesive.

[0121] In addition, with respect to the raw material liquid introduction port 2 connected to the container 1, in the case of the hollow fiber membrane module for cross-flow filtration of the present application, the ratio S f to the flow path area S p in the container 1 is preferably 0.35 or more. f / S p The ratio S

[0122] to the flow path area S f in the container 1 is preferably 0.35 or more.

[0123] The ratio S pS1 - S2 is the area of the cross-sectional area of the container 1 minus the exclusive area S2 of the hollow fiber membrane 5 when the central portion of the container 1 is cut in a plane perpendicular to the axial direction. The central portion of the container 1 refers to the central portion of the first and second perfusion portions 8 and 9 in the axial direction of the container 1.

[0124] The cross-sectional area S1 of the container 1 is the cross-sectional area of the space portion when the container 1 is cut in a cross section perpendicular to the axial direction of the hollow fiber membrane 5. In the case of the container 1 being cylindrical, the cross-sectional shape is circular, so the cross-sectional area of the inner circle is the cross-sectional area of the container 1.

[0125] The exclusive area S2 of the hollow fiber membrane 5 is the area of the hollow fiber membrane 5 when the hollow fiber membrane 5 is cut in a plane perpendicular to the axial direction of the hollow fiber membrane 5, assuming that the cross-sectional shape of the hollow fiber membrane 5 is a perfect circle. The exclusive area S2 of the hollow fiber membrane 5 is calculated by the following equation. o The calculated area of the circle is multiplied by the number N of the hollow fiber membranes filled in the container 1. In the case of the U-shaped, the number of the hollow fiber membranes is multiplied by 2 to calculate.

[0126] The amount of the raw material solution flowing in the container 1 in the cross-flow filtration is larger than that in the whole amount filtration, so the ratio S f / S p It is preferably 0.35 or more. The ratio S f / S p In the case where the ratio S f / S p It is preferably 0.5 or more, and further preferably 0.7 or more, whereby the pressure loss generated can be reduced.

[0127] Further, the cross-sectional area S c It is also preferably the cross-sectional area S c The ratio S p The ratio S c / S p It is 0.35 or more. The cross-sectional area S c is the area of the flow path portion when the raw material solution outlet 4 is cut in a plane perpendicular to the flow of the raw material solution, and is the area of the inner circle if the shape of the raw material solution outlet 4 is circular. The ratio S c / S p In the case where the ratio S c / S p It is preferably 0.5 or more, and further preferably 0.7 or more.

[0128] Further, in the case where the inner diameter of the container 1 is small, the raw material solution is likely to flow in the flow path area S pThe length of the boundary surface of contact becomes large, so the frictional resistance becomes large, and the pressure loss on the raw liquid side becomes large. In terms of suppressing the pressure loss on the raw liquid side, the inner diameter of the container 1 is preferably 50 mm or more, more preferably 80 mm or more, and further more preferably 100 mm or more.

[0129] (Method for operating a hollow fiber membrane module)

[0130] Next, a method for operating a hollow fiber membrane module according to the present application will be described in detail. Figure 3 Figure 4

[0131] In the cross-flow filtration operation, as shown in FIG. 1, the raw liquid is supplied from the raw liquid tank 12 to the container 1 by means of the supply pump 14, and the raw liquid side space 6 (refer to FIG. 2) is filled with the raw liquid. The raw liquid discharged from the raw liquid outlet 4 is circulated by flowing back to the raw liquid tank 12. The filtration liquid valve 22 is opened in this state, and thus the raw liquid is filtered and supplied to the filtration liquid tank 13. Figure 3 Figure 1 The filtration flow rate is adjusted by controlling the filtration liquid valve 22 in such a manner that the filtration liquid flow meter 32 is set to a predetermined flow rate. The circulation flow rate is adjusted by controlling the rotation speed of the supply pump 14 in such a manner that the concentrated liquid flow meter 31 is set to a predetermined flow rate.

[0132] On the other hand, the filtration unit shown in FIG. 3 is operated in such a manner that the raw liquid is supplied by means of the supply pump 14 and the circulation pump 15, and a part or all of the concentrated liquid is circulated by flowing back between the supply pump 14 and the circulation pump 15. The filtration flow rate is controlled by the supply pump 14 in such a manner that the filtration liquid flow meter 32 is set to a predetermined value, and the circulation flow rate is controlled by the circulation pump 15 in such a manner that the concentrated liquid flow meter 31 is set to a predetermined value.

[0133] Figure 4 The filtration unit shown in FIG. 3 is operated in such a manner that the raw liquid is supplied by means of the supply pump 14 and the circulation pump 15, and a part or all of the concentrated liquid is circulated by flowing back between the supply pump 14 and the circulation pump 15. The filtration flow rate is controlled by the supply pump 14 in such a manner that the filtration liquid flow meter 32 is set to a predetermined value, and the circulation flow rate is controlled by the circulation pump 15 in such a manner that the concentrated liquid flow meter 31 is set to a predetermined value.

[0134] At this time, the circulation flow rate V (m 3 / hr) and the filtration flow rate Q (m 3 / hr) are determined based on the set values of the cross-flow linear velocity v (m / s) and the filtration flux J (m / d) shown below.

[0135] The cross-flow linear velocity v is a value obtained by dividing the circulation flow rate by the flow path area S p in the container 1, and is calculated according to the following equation (6).

[0136] [Equation 3]

[0137]

[0138] The filtration flux J is a value obtained by dividing the filtration flow rate Q by the effective membrane area A (m 2 ) of the hollow fiber membrane 5, and is calculated according to the following equations (7) and (8). Here, D o ​​​​L is the outer diameter of the hollow fiber membrane (μm), L is the axial length of the hollow fiber membrane (m), and N is the number of hollow fiber membranes 5 inserted into the hollow fiber membrane module.

[0139] [Formula 4]

[0140]

[0141] In the hollow fiber membrane module for cross-flow filtration of the present invention, cross-flow filtration is performed in such a manner that the filtration flux J (m / d) and the cross-flow linear velocity v (m / s) satisfy the following requirements.

[0142] 0.5≤J≤2.0

[0143] 1.0 ≤ v ≤ 1.8

[0144] By controlling the filtration flux J within the range of 0.5 m / d to 2.0 m / d, the desired filtration flow rate can be ensured, and operation can be performed to suppress the development of fouling. Furthermore, by controlling the cross-flow velocity v to 1.0 m / s to 1.8 m / s, sufficient shear force is applied to remove fouling from the membrane surface while suppressing pressure loss on the feed side, thereby reducing the axial inter-membrane pressure differential of the hollow fiber membrane 5. The filtration flux J is preferably 0.8 to 1.8 m / d, more preferably 1.0 to 1.5 m / d. Furthermore, the cross-flow velocity v is preferably 1.2 to 1.7 m / s, more preferably 1.4 to 1.6 m / s.

[0145] (Pressure distribution simulation of hollow fiber membrane module)

[0146] In addition, to verify these effects, the pressure distribution within the hollow fiber membrane module was simulated, thus exploring the scope that could not be studied experimentally.

[0147] Figure 5 The text represents a summary of the model used for simulation. Figure 5 (a) represents the flow of a hollow fiber membrane, the raw liquid, and the filtrate. Figure 5 In the diagram, colored arrows represent the raw solution, and blank arrows represent the filtrate. The raw solution inlet end of the hollow fiber membrane 5 is set to n=0, and the filtrate outlet end is set to n=k. The raw solution inlet end of the hollow fiber membrane 5 is sealed, while the filtrate outlet end is open, allowing the filtrate to exit from all outlet ends. Figure 5 (b) represents the liquid flow in the micro-intervals n when the hollow fiber membrane 5 is gridded every Δl in the axial direction. n is an integer greater than or equal to 0, and k is a natural number greater than or equal to 1. The filtrate derived from micro-interval n-1 and the filtrate filtered by the membrane in micro-interval n are combined. As a result, the filtrate flow rate Q derived from micro-interval n is... i，nThe amount of filtrate derived from the microcell n-1 is set as Q i，n-1 The amount of filtrate filtered by the membrane in the microcell n is set as Q p，n The following equation (9) is satisfied when the amount of filtrate derived from the microcell n-1 is Q i， -1 is not present, Q i，0 = Q p，0 k is preferably 50 or more, and more preferably 100 or more. In addition, the length of the membrane from the raw solution introduction port side end to the microcell n is set as l n l0=0, and l k =L.

[0148] [Equation 5]

[0149] Q i，n = Q i，n-1 + Q p，n …(9)

[0150] The filtrate flow rate Q p，n in the microcell n is calculated according to the following equations (10) to (12) from the raw solution side pressure P o，n and the filtrate side pressure P i，n , the membrane area A n , the membrane filtration resistance R n , and the raw solution viscosity μ at the temperature at which filtration is performed. n The filtration flux J (= amount of permeation (m 3 ) / filtration time (hr) / effective membrane area (m 2 )) when the pure water permeation performance K is measured with a small module, the membrane inter-difference pressure ΔP m , and the viscosity μ are calculated, and at the initial stage of filtration, it is set to be the same in the axial direction of the hollow fiber membrane 5.

[0151] [Equation 6]

[0152]

[0153] A n = πD0Δl…(11)

[0154]

[0155] Regarding the raw solution side pressure P o，n in the microcell n, the raw solution introduction pressure P o，0 and the pressure loss ΔP0xl n due to cross-flow flow are considered.The following formula (13) is used for calculation. In reality, a portion of the original liquid is filtered by the membrane, so the circulating flow rate varies along the axis of the hollow fiber membrane 5. However, the filtered flow rate is relatively small compared to the circulating flow rate and can be ignored. Therefore, let ΔP be the pressure loss per unit length along the axial direction caused by the cross-flow in this model. o It is calculated to be constant regardless of location.

[0156] [Formula 7]

[0157] P o，n =P o,0 -ΔP o l n …(13)

[0158] Regarding the pressure loss ΔP per unit length o The flow path structure on the raw liquid side is complex, so based on the outer diameter D of the hollow fiber membrane 5... o Calculate the equivalent diameter D of the case where the original liquid side flow path is replaced by a circular tube, given the number N of hollow fiber membrane 5, etc. e The pressure loss ΔP is calculated according to the following formulas (14) to (16). o Additionally, ρ represents the density of the original solution, and D... c Let τ be the diameter of the inner circle of container 1, and τ be the shape correction factor for the original liquid side flow path.

[0159] [Formula 8]

[0160]

[0161] Regarding the filtrate-side pressure P in the infinitesimal interval n i，n The Reynolds number Re is calculated based on the pressure loss during flow inside the hollow fiber membrane 5. Here, the Reynolds number Re of the filtrate flowing inside the hollow fiber membrane 5 is calculated. i，n The pressure loss from the small interval n to the outlet end of the filtrate is calculated by integrating the pressure loss. The calculation method for the case where the internal flow is laminar is expressed in the following equations (17) to (18).

[0162] [Formula 9]

[0163]

[0164] For convenience, let's set it to P here. i，k =0, adjust P o，0 This results in the filtrate flow rate Q obtained from the hollow fiber membrane 5. i，k The pressure distribution on the feed liquid side and the filtrate side of the hollow fiber membrane 5 is calculated by satisfying the following equation (19). Additionally, J t This indicates the set filter flux.

[0165] [Formula 10]

[0166]

[0167] According to the pressure distribution thus calculated, the pressure on the feed solution side Pn in the minute interval n o， n and Pn+1 i，n is the difference between the pressures on the membrane surfaces in the interval, ΔPn m，n In the present application, it is preferable that ΔPn m，k > 0 at n = k when the module is operated under given conditions. It is more preferable that ΔPn m，k If ΔPn m，k / ΔPn+1 m，0 is less than zero, the filtrate passing through the hollow fiber membrane 5 temporarily flows back to the feed solution side, and the efficiency of filtration deteriorates. That is, an excess amount of filtrate is filtered in order to obtain a certain amount of filtrate.

[0168] More preferably, the size, packing ratio, operating conditions, etc. of the hollow fiber membrane module are controlled so that ΔPn m，k / ΔPn+1 m，0 is in the range of 0.1 to 5.0. If ΔPn m，0 / ΔPn+1 m，k is too high, the load on the end portion of the hollow fiber membrane 5 on the feed solution inlet side or the end portion on the filtrate outlet side becomes high, and clogging develops more quickly than usual. It is particularly preferable that ΔPn m，k / ΔPn+1 m， 0 be controlled to be in the range of 0.5 to 2.0.

[0169] The pressure distribution in the hollow fiber membrane module changes as filtration continues, but it is preferable that ΔPn m，k > 0 at the beginning of operation. In designing the hollow fiber membrane module, it is preferable that the size, performance, number of packing into the hollow fiber membrane module, and operating conditions of the hollow fiber membrane 5 be determined so that ΔPn m，k > 0 at the beginning of operation.

[0170] In the operation of the hollow fiber membrane module for cross-flow filtration in the present application, various feed solutions can be applied, but it is particularly suitable for a feed solution that needs to be operated at a relatively high cross-flow linear velocity.

[0171] As such a raw liquid, it is preferable that the turbidity be 20 NTU or more and the total organic carbon (TOC) concentration be 1000 mg / L or more. When such a raw liquid is filtered, the cross-flow flow caused by a slow cross-flow line velocity results in insufficient washing of the hollow fiber membrane surface. As a result, the development of clogging of the hollow fiber membrane becomes faster, and it is necessary to operate at a faster cross-flow line velocity. The turbidity is preferably 50 NTU or more, and preferably 100 NTU or more. Furthermore, the TOC concentration is preferably 5000 mg / L or more, and preferably 10000 mg / L or more. In addition, with respect to TOC, it is preferable that the raw liquid be composed of components that pass through the membrane as described later, and thus the upper limit of the TOC concentration is not particularly limited, but with respect to turbidity, the turbidity components accumulate within the module, and thus the operability deteriorates, and thus it is preferable that the turbidity be 100000 NTU or less.

[0172] As a method of measuring turbidity, it is not particularly limited as long as the value can be measured in NTU (Nephelometric Turbidity Unit) units, and various measuring devices can be used. As an example, a device that satisfies the requirements described in the drinking water test method is cited.

[0173] Furthermore, as a method of measuring the TOC concentration, the TC-IC method in which total carbon (TC) is subtracted from inorganic carbon (IC), the NPOC method in which a sample is aerated by adding oxygen, and the like can be used. Preferably, the TC-IC method is used in the case where the raw liquid includes a large amount of volatile organic carbon.

[0174] Furthermore, when such a raw liquid is filtered, it is preferable that the turbidity of the filtrate be 10 NTU or less and the TOC concentration be 1000 mg / L or more. That is, it is preferable that the raw liquid in which the components that constitute the TOC in the raw liquid are not components that are prevented by the membrane but also include components that pass through the membrane be subjected to the operation method of the present application. The components that pass through the membrane adhere to and accumulate on the membrane surface and inside the membrane, and the development of clogging of the hollow fiber membrane is promoted, but the clogging inside the membrane easily develops in the case where an excessively large filtration flux flows. By using the hollow fiber membrane module of the present application, it is possible to operate while suppressing the axial inter-membrane differential pressure difference, and thus it is possible to particularly suppress the flow of an excessively large filtration flux to the raw liquid inlet side end portion of the hollow fiber membrane 5, and it is possible to delay the development of clogging.

[0175] Furthermore, with respect to the viscosity of the raw liquid, it is preferable that the raw liquid whose viscosity during filtration operation is 2 mPa s or more be subjected to the operation. In the case where the viscosity of the raw liquid is high, the pressure loss on the raw liquid side also becomes high in correspondence with the viscosity, and thus the axial inter-membrane differential pressure difference of the hollow fiber membrane 5 easily occurs. By using the hollow fiber membrane module of the present application, it is possible to operate while suppressing the axial inter-membrane differential pressure difference even in a high-viscosity raw liquid.

[0176] There are no particular limitations on the method for measuring viscosity, but for a raw liquid whose viscosity varies with shear rate, it is preferable to measure the shear viscosity during filtration operation. Specifically, it is preferable to measure the viscosity at a shear rate during filtration operation, which can be achieved using a rheometer by measuring the shear viscosity at the temperature and applied shear rate during filtration operation. The shear rate can be calculated by multiplying the cross-flow velocity v during filtration operation by 2 (2v) and dividing by the equivalent diameter D of the flow path on the raw liquid side. e Calculated radius (=D) e / 2) to calculate.

[0177] Turbidity and viscosity vary with temperature, so it is preferable to measure turbidity and viscosity at the temperature during filtration.

[0178] Example

[0179] The present invention will now be illustrated with specific examples, but the invention is not limited to these examples. Furthermore, various parameters of the present invention were measured using the methods described above.

[0180] First, verify whether the simulation expressed in equations (9) to (19) above can accurately predict the pressure distribution of the actual hollow fiber membrane module to some extent.

[0181] (Refer to Example 1)

[0182] The verification used a small module approximately 1m in length. A fluorinated tubing with an inner diameter of 8mm was used as container 1, and a hollow fiber membrane with an outer diameter of 1190μm, an inner diameter of 720μm, and a pure water permeability of 3.2m / hr was used as hollow fiber membrane 5. Fifteen membranes were filled with the membrane, each with an axial length L of 1.1m, open at both ends. The fill rate M was 32%. Figure 6 As shown, the raw liquid inlet 2 and raw liquid outlet 4 are connected to the side of the tube. The raw liquid introduced through the raw liquid inlet 2 flows within the container 1 in a direction parallel to the axial direction of the hollow fiber membrane 5, and is discharged through the raw liquid outlet 4. At this time, the pressure measured by the raw liquid inlet pressure gauge 41 is set as the raw liquid inlet pressure P. o，0 The pressure measured by the original liquid export pressure gauge 42 is set as the original liquid export pressure P. o，k .

[0183] On the other hand, regarding the filtrate side, pressure gauges are connected to both ends of the opening, and the pressure measured by the filtrate outlet pressure gauge 43, which is connected to the filtrate tank 13, is set as the filtrate outlet pressure P. i，k The pressure measured by the pressure gauge 44, which is the filtrate introduced from the other end, is set as the filtrate introduction pressure P. i，0 .

[0184] In the hollow fiber membrane module 10 of this application, as Figure 1 As shown, the filtrate outlet end of the hollow fiber membrane 5 is open, while the inlet end is sealed. Therefore, P, as expressed in formula (18), cannot be actually measured. i，n The position where n=0 is the filtrate introduction pressure P. i，0 Therefore, for verification purposes in this simulation, a small module with openings at both ends was fabricated, and P was measured. i，0 In addition, P was measured. i，0 The space connected to the filtrate inlet pressure gauge 44 is sealed, and the filtrate is not discharged to the filtrate inlet pressure gauge 44 side, so the pressure distribution of the small module and the pressure distribution of the hollow fiber membrane module 10 are the same.

[0185] Filtration tests were conducted using this small module. A simulated solution of microbial fermentation broth was used for the stock solution. The viscosity of this simulated microbial fermentation broth was 2.4 mPa·s.

[0186] The prepared microbial fermentation broth was supplied to the small module via supply pump 14 for cross-flow filtration. The operating conditions were a filtration flux of 0.9 m³ / d and a cross-flow velocity of 1.5 m / s. Filtration was initiated under these conditions, and the pressures at the start of filtration were measured to calculate ΔP. m，0 ΔP m，k .

[0187] Furthermore, using equations (9) to (19), ΔP is calculated based on simulation. m，0 ΔP m，k The various parameters of the hollow fiber membrane 5 used in the fabrication of the simulation input miniature module. Additionally, regarding the filtrate discharge pressure P... o，k The values ​​were calculated using measurements obtained from tests on small modules. Furthermore, Δl was 10 mm, and the shape correction factor τ for the original liquid-side flow path was 1.5.

[0188] The measured values ​​and simulated values ​​were compared, and the results are shown in Table 1. ΔP m，0 There are slight differences, but they represent the same value, regarding ΔP. m，k Both are negative values, which can reproduce the phenomenon of reverse filtering.

[0189] (See Example 2 for reference)

[0190] Thirteen hollow fiber membranes 5, each with an outer diameter of 760 μm, an inner diameter of 540 μm, and a pure water permeability of 10.4 m / hr, were used. For container 1, fluorine tubing with an inner diameter of 6 mm was used to fabricate a small module. Otherwise, ΔP was measured using the same method as described in Reference Example 1. m，0 ΔP m，k For comparison, the fill rate M is 23%. The results are shown in Table 1, ΔPm，0 Slightly different, but indicates the same value, about ΔP m，k , both are positive values, can reproduce the phenomenon of inhibiting back filtration by making the inner diameter thin.

[0191] According to Reference Examples 1, 2, it can be confirmed that the present simulation can reproduce the pressure distribution of the hollow fiber membrane module, and therefore, regarding the inter-membrane differential pressure difference of the hollow fiber membrane 5 in the axial direction which is difficult to obtain data experimentally in the hollow fiber membrane module of the actual machine size, the result of the pressure distribution obtained by the simulation is indicated.

[0192] [Table 1]

[0193] Table 1

[0194]

[0195] (Example 1)

[0196] Production Figure 1 The outer pressure type hollow fiber membrane module described in the above was used to evaluate the filtration properties of a simulated liquid of a microbial fermentation broth.

[0197] The hollow fiber membrane used in the present hollow fiber membrane module was produced by the following method. First, a vinylidene fluoride homopolymer (KANEKA CORPORATION KF1300, weight average molecular weight: 417,000, number average molecular weight: 221,000) of 39% by weight and γ-butyrolactone of 61% by weight were dissolved at 150°C to obtain a polymer solution as a raw material liquid.

[0198] A device having a double-tube metal cap, a pipe connected to the metal cap, and two gear pumps disposed on the pipe was used for pressurization and ejection of the obtained polymer solution. The raw material liquid was pressurized to 2.5 MPa while being retained at 100-103°C for 15 seconds in the pipe between the gear pumps. Thereafter, the γ-butyrolactone 85% by weight aqueous solution was ejected from the inner pipe of the double-tube metal cap, and the raw material liquid was ejected from the outer pipe. The raw material liquid was retained in a cooling bath composed of the γ-butyrolactone 85% by weight aqueous solution at a temperature of 5°C for 20 seconds, and was solidified to obtain the hollow fiber membrane 5. Subsequently, the hollow fiber membrane obtained as described above was stretched 1.5 times in water at 95°C. The pure water permeation performance K of the obtained hollow fiber membrane was 4.5 m / hr, the inner diameter D i was 580 μm, the outer diameter D o was 1160 μm, and the strength was 560 gf / root. Regarding the strength, a tensile testing machine (TENSILON (registered trademark) / RTM-100, manufactured by TOYO BALLEN CO., LTD.) was used to perform a test of 5 times or more on a sample having a test length of 50 mm by changing the sample at a tensile speed of 50 mm / min in an atmosphere at 25°C, and the average value was calculated.

[0199] The obtained hollow fiber membrane 5 was cut to a length of 1.2 m, and dried after immersion in a 30 mass% glycerol aqueous solution for 1 hour. Thereafter, the end portion of the hollow fiber membrane on the filtrate outlet side was filled with a silicone adhesive (Dow Corning Toray Co., Ltd., SH850A / B, mixed so that the mass ratio of the two agents was 50:50).

[0200] Thereafter, as shown in Figure 1 , the aforementioned hollow fiber membrane 5 was filled in a container 1 (inner diameter 97.6 mm, length 1100 mm) so that the filled end portion on the filtrate outlet side was on the filtrate outlet 3 side. The filtrate outlet 3 side of the side surface of the container 1 was provided with a raw material liquid outlet 4.

[0201] Next, a first perfusion portion forming jig was installed on the raw material liquid inlet 2 side of the container 1, and a second perfusion portion forming jig was installed on the filtrate outlet 3 side. In order to open a through hole for introducing the raw material liquid into the raw material liquid side space 6 at the first perfusion portion forming jig, a pin having a diameter of 7 mm and a length of 100 mm was inserted in the same direction as the axial direction of the hollow fiber membrane 5.

[0202] As the perfusion agent, a bisphenol F type epoxy resin (Huntsman Co., Ltd., LST868-R14) and an aliphatic amine-based hardening agent (Huntsman Co., Ltd., LST868-H14) were mixed in a mass ratio of 100:30, and a total of 800 g (400 g per end) was put into a perfusion agent feeder.

[0203] Next, the centrifugal molding machine was rotated, and the perfusion agent was filled into the first perfusion portion forming jig and the second perfusion portion forming jig at both ends, and a first perfusion portion 8 and a second perfusion portion 9 were molded, and the perfusion agent was hardened. The temperature in the centrifugal molding machine was 35°C, the rotation speed was 300 rpm, and the centrifugation time was 5 hours.

[0204] After hardening, the first perfusion portion forming jig, the second perfusion portion forming jig, and the pin were extracted, and after hardening for 24 hours at room temperature, the end portion of the second perfusion portion 9 was cut with a sheet saw-type rotary blade, and the filtrate outlet side end surface of the hollow fiber membrane 5 was opened.

[0205] Next, a lower cap provided with the raw material liquid inlet 2 and an upper cap provided with the filtrate outlet 3 were installed at the container 1, and a hollow fiber membrane module was set. At this time, the axial length L of the hollow fiber membrane was 1.0 m, the packing ratio M was 34%, and the membrane area was 8.7 m 2 At this time, the inner diameter D i satisfied the following equation (2). In addition, the inner diameter of the raw material liquid inlet 2 was 59 mm, and the cross-sectional area S f of the raw material liquid inlet 2 was 0.028 m p 2. The ratio S f / Sp 0.55.

[0206] 0.33 x D o -10 x M + 420 < D i 0.33 x D o -10 x M + 550 (2)

[0207] Using the obtained hollow fiber membrane module, filtration was performed using a simulated liquid of a microbial fermentation broth. The simulated liquid of the microbial fermentation broth was prepared by previously adjusting distilled water to contain 1 wt% peptone and 2 wt% starch to make a stock solution. At this time, the viscosity of the simulated liquid was 2.4 mPa-s.

[0208] For the filtration test, the filtration unit represented by Figure 3 was used. The volume of the stock solution tank 12 was 200 L, and the stock solution was introduced into the hollow fiber membrane module by operating the feed pump 14, and a part of the stock solution was filtered, and the filtrate was supplied to the filtrate tank 13. The stock solution that was not filtered was entirely returned to the stock solution tank 1 from the stock solution outlet 4. As the filtration was continued, the simulated liquid of the microbial fermentation broth in the stock solution tank 12 decreased, so the operation was performed while replenishing the stock solution as necessary.

[0209] The filtration was performed while adjusting the filtration flux J to 1.0 m / d and the cross-flow linear velocity v to 1.5 m / s until the intermembrane pressure rose to 150 kPa. As a result, as shown in Table 2, the amount of the obtained filtrate was 0.17 m 3 / m 2 As a result, the turbidity of the filtrate was as low as 5.4 NTU in comparison with the turbidity of the stock solution of 250 NTU.

[0210] In addition, in parallel with the actual filtration test, a calculation based on the simulated pressure distribution in the module was performed. The calculation method was performed in the same manner as the method described in Reference Example 1. As a result, the ratio of the intermembrane pressure ΔP m，k at the end portion of the filtrate outlet side to the intermembrane pressure ΔP m，0 at the end portion of the stock solution inlet side, that is, ΔP m，k / ΔP m，0 was 0.005. From the results of the simulation, it was considered that backflow of the filtrate did not occur, but the difference in the intermembrane pressure in the axial direction of the hollow fiber membrane 5 was calculated to be slightly large.

[0211] (Example 2)

[0212] Except that the temperature of the raw material liquid was adjusted in the piping between the gear pumps, the ejection amount of the raw material liquid and the liquid in the hollow portion at the metal cap, the pure water permeation performance K of the hollow fiber membrane 5 was 4.3 m / hr, the inner diameter D i was 550 μm, and the outer diameter D oThe membrane was formed in the same manner as in Example 1 except that the hollow fiber membrane 5 had an outer diameter Do of 1080 μm, a tenacity of 480 gf / root, and the hollow fiber membrane module was produced in the same manner as in Example 1. At this time, the packing ratio M was 33%, the inner diameter D i satisfied the relationship of Equation (2). As a result, the membrane area was 9.4 m 2 .

[0213] The filtration test was also performed in the same manner as in Example 1, and the filtration test was performed until the differential pressure between the membranes rose to 150 kPa. As a result, as shown in Table 2, the obtained permeate amount was 0.21 m 3 / m 2 .

[0214] In addition, the calculation of the pressure distribution in the module based on the simulation was performed in the same manner as in Example 1. As a result, the differential pressure between the membranes ΔP m，k at the end portion on the permeate outlet side was 0.7 kPa, and the ratio of the differential pressure between the membranes ΔP m，0 at the end portion on the raw material inlet side, i.e., ΔP m，k / ΔP m，0 was 0.10. From the results of the simulation, it was considered that the backflow of the permeate did not occur, and the difference in the differential pressure between the membranes in the axial direction of the hollow fiber membrane 5 was small.

[0215] (Example 3)

[0216] The membrane was formed in the same manner as in Example 1 except that the raw material liquid temperature was adjusted in the piping between the gear pumps, the raw material liquid and the hollow portion forming liquid at the metal cap were adjusted, the pure water permeation performance K of the hollow fiber membrane 5 was 4.6 m / hr, the inner diameter Di was 500 μm, the outer diameter Do was 850 μm, and the tenacity was 260 gf / root. In addition, the hollow fiber membrane module was produced in the same manner as in Example 1. At this time, the packing ratio M was 29%, the inner diameter D i satisfied the relationship of Equation (2). As a result, the membrane area was 10.2 m 2 .

[0217] The filtration test was also performed in the same manner as in Example 1, and the filtration test was performed until the differential pressure between the membranes rose to 150 kPa. As a result, as shown in Table 2, the obtained permeate amount was 0.21 m 3 / m 2 .

[0218] In addition, the calculation of the pressure distribution in the module based on the simulation was performed in the same manner as in Example 1. As a result, the differential pressure between the membranes ΔP m，k at the end portion on the permeate outlet side was 0.9 kPa, and the ratio of the differential pressure between the membranes ΔP m，0 at the end portion on the raw material inlet side, i.e., ΔP m，k / ΔP m，0was 0.14. From the results of the simulation, it was considered that no backflow of the filtrate occurred, and the difference in the membrane pressure difference in the axial direction of the hollow fiber membrane 5 was small.

[0219] (Example 4)

[0220] The membrane was produced in the same manner as in Example 1, except that the temperature of the raw material liquid was adjusted in the piping between the gear pumps, the raw material liquid at the metal cap, and the discharge amount of the liquid forming the hollow portion, the pure water permeation performance K of the hollow fiber membrane 5 was 4.2 m / hr, the inner diameter Di was 450 μm, the outer diameter Do was 950 μm, and the strength was 390 gf / root. Further, with respect to the hollow fiber membrane module, it was produced in the same manner as in Example 1. At this time, the packing ratio M was 31%, the inner diameter D i satisfied the relationship of the equation (2). As a result, the membrane area was 9.8 m 2 .

[0221] The filtration test was also performed in the same manner as in Example 1, and the filtration test was performed until the membrane pressure difference rose to 150 kPa. As a result, the obtained amount of the filtrate was 0.22 m 3 / m 2 .

[0222] Further, the calculation of the pressure distribution in the module based on the simulation was performed in the same manner as in Example 1. As a result, the ratio of the membrane pressure difference ΔP m，k at the end portion of the filtrate discharge port side to the membrane pressure difference ΔP m，0 at the end portion of the raw liquid introduction port side, that is, ΔP m，k / ΔP m，0 was 1.01. From the results of the simulation, it was considered that no backflow of the filtrate occurred, and the difference in the membrane pressure difference in the axial direction of the hollow fiber membrane 5 was small.

[0223] (Example 5)

[0224] The membrane was produced in the same manner as in Example 1, except that the temperature of the raw material liquid was adjusted in the piping between the gear pumps, the raw material liquid at the metal cap, and the discharge amount of the liquid forming the hollow portion, the pure water permeation performance K of the hollow fiber membrane 5 was 3.9 m / hr, the inner diameter Di was 380 μm, the outer diameter Do was 880 μm, and the strength was 380 gf / root. Further, with respect to the hollow fiber membrane module, it was produced in the same manner as in Example 1. At this time, the packing ratio M was 30%, the inner diameter D i did not satisfy the relationship of the equation (2). As a result, the membrane area was 10.2 m 2 .

[0225] The filtration test was also performed in the same manner as in Example 1, and the filtration test was performed until the membrane pressure difference rose to 150 kPa. As a result, the obtained amount of the filtrate was 0.19 m 3 / m2 .

[0226] Further, the calculation of the pressure distribution in the module based on simulation was performed in the same manner as in Example 1. As a result, the ratio of the intermembrane pressure difference ΔP m，k at the end portion on the filtrate outlet side to the intermembrane pressure difference ΔP m，0 at the end portion on the raw material liquid inlet side, i.e., ΔP m，k / ΔP m，0 was 2.4. From the result of the simulation, it was considered that the backflow of the filtrate did not occur, but it was presumed that the intermembrane pressure difference in the axial direction of the hollow fiber membrane 5 was slightly large.

[0227] [Table 2]

[0228] Table 2

[0229]

[0230] (Example 6)

[0231] In addition to adjusting the raw material liquid temperature in the piping between the gear pumps, adjusting the raw material liquid at the metal cap, and the ejection amount of the hollow portion forming liquid, the pure water permeation performance K of the hollow fiber membrane 5 was 3.2 m / hr, the inner diameter Di was 550 μm, the outer diameter Do was 1070 μm, and the tenacity was 500 gf / root, the membrane was produced in the same manner as in Example 1. Further, with respect to the hollow fiber membrane module, it was produced in the same manner as in Example 1. At this time, the packing ratio M was 33%, the inner diameter D i satisfied the relationship of the equation (2). As a result, the membrane area was 9.1 m 2 .

[0232] With respect to the filtration test, it was also performed in the same manner as in Example 1, and the filtration test was performed until the intermembrane pressure difference rose to 150 kPa. As a result, as shown in Table 3, the obtained amount of the filtrate was 0.17 m 3 / m 2 .

[0233] Further, the calculation of the pressure distribution in the module based on simulation was performed in the same manner as in Example 1. As a result, the ratio of the intermembrane pressure difference ΔP m，k at the end portion on the filtrate outlet side to the intermembrane pressure difference ΔP m，0 at the end portion on the raw material liquid inlet side, i.e., ΔP m，k / ΔP m，0 was 0.08. From the result of the simulation, it was considered that the backflow of the filtrate did not occur, but it was presumed that the intermembrane pressure difference in the axial direction of the hollow fiber membrane 5 was slightly large.

[0234] (Example 7)

[0235] Example 1 except that the temperature of the raw material liquid was adjusted in the piping between the gear pumps, the raw material liquid at the metal cap, and the discharge amount of the liquid forming the hollow portion, the pure water permeation performance K of the hollow fiber membrane 5 was 2.5 m / hr, the inner diameter Di was 560 μm, the outer diameter Do was 1080 μm, and the strength was 650 gf / root. Further, with respect to the hollow fiber membrane module, the same method as in Example 1 was employed. At this time, the packing ratio M was 33%, the inner diameter D i satisfied the relationship of Equation (2). As a result, the membrane area was 9.4 m 2 .

[0236] With respect to the filtration test, the same method as in Example 1 was employed, and the filtration test was performed until the membrane interval differential pressure rose to 150 kPa. As a result, as shown in Table 3, the obtained filtrate amount was 0.16 m 3 / m 2 .

[0237] Further, the calculation of the pressure distribution in the module based on the simulation was performed in the same manner as in Example 1. As a result, the membrane interval differential pressure ΔP m，k at the end portion on the filtrate outlet side was 0.4 kPa, and the ratio of the membrane interval differential pressure ΔP m，0 at the end portion on the raw liquid inlet side, i.e., ΔP m，k / ΔP m，0 , was 0.05. From the results of the simulation, it was considered that the backflow of the filtrate did not occur, but it was presumed that the membrane interval differential pressure difference in the axial direction of the hollow fiber membrane 5 was slightly large.

[0238] (Example 8)

[0239] Example 1 except that the temperature of the raw material liquid was adjusted in the piping between the gear pumps, the raw material liquid at the metal cap, and the discharge amount of the liquid forming the hollow portion, the pure water permeation performance K of the hollow fiber membrane 5 was 2.0 m / hr, the inner diameter Di was 550 μm, the outer diameter Do was 1050 μm, and the strength was 800 gf / root. Further, with respect to the hollow fiber membrane module, the same method as in Example 1 was employed. At this time, the packing ratio M was 33%, the inner diameter D i satisfied the relationship of Equation (2). As a result, the membrane area was 9.2 m 2 .

[0240] With respect to the filtration test, the same method as in Example 1 was employed, and the filtration test was performed until the membrane interval differential pressure rose to 150 kPa. As a result, as shown in Table 3, the obtained filtrate amount was 0.15 m 3 / m 2 .

[0241] Further, the calculation of the pressure distribution in the module based on the simulation was performed in the same manner as in Example 1. As a result, the membrane interval differential pressure ΔPm，k The pressure difference ΔP between the membrane and the end of the inlet of the original solution is 0.6 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value is 0.06. Based on the simulation results, it is assumed that no backflow of the filtrate occurred, but it is estimated that the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 is slightly large.

[0242] (Example 9)

[0243] Filtration tests were conducted using the hollow fiber membrane module prepared in Example 2. The filtration tests were performed in the same manner as in Example 1, except that the crossflow velocity v was adjusted to 1.0 m / s. The results, as shown in Table 3, show that the obtained filtrate volume was 0.17 m³. 3 / m 2 .

[0244] Furthermore, the intra-module pressure distribution was calculated using the same method as in Example 1 based on simulation. The result showed that the inter-membrane differential pressure ΔP at the filtrate outlet end was... m，k The pressure difference ΔP between the membrane and the end of the inlet of the original solution is 2.8 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value is 0.63. Based on the simulation results, it is assumed that no backflow of the filtrate occurred, and the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 is small.

[0245] (Example 10)

[0246] Filtration tests were conducted using the hollow fiber membrane module prepared in Example 2. The filtration tests were performed in the same manner as in Example 1, except that the cross-flow velocity v was adjusted to 1.0 m / s and the filtration flux to 1.2 m / d. The results, as shown in Table 3, show that the obtained filtrate volume was 0.22 m³ / d. 3 / m 2 .

[0247] Furthermore, the intra-module pressure distribution was calculated using the same method as in Example 1 based on simulation. The result showed that the inter-membrane differential pressure ΔP at the filtrate outlet end was... m，k The pressure difference ΔP between the membrane and the end of the inlet of the original solution is 1.2 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value is 0.17. Based on the simulation results, it is assumed that no backflow of the filtrate occurred, and the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 is small.

[0248] [Table 3]

[0249] Table 3

[0250]

[0251] (Comparative Example 1)

[0252] In addition to adjusting the raw material liquid temperature in the piping between the gear pumps, adjusting the raw material liquid at the metal cap, and the discharge amount of the liquid forming the hollow portion, the pure water permeation performance K of the hollow fiber membrane 5 was 5.0 m / hr, the inner diameter Di was 700 μm, the outer diameter Do was 1140 μm, and the strength was 440 gf / root, the membrane was produced in the same manner as in Example 1. Further, with respect to the hollow fiber membrane module, it was produced in the same manner as in Example 1. At this time, the packing ratio M was 35%, the inner diameter D i did not satisfy the relationship of the formula (2). As a result, the membrane area was 9.1 m 2 .

[0253] With respect to the filtration test, it was also performed in the same manner as in Example 1, and the filtration test was performed until the intermembrane differential pressure rose to 150 kPa. As a result, as shown in Table 4, the obtained filtrate amount was 0.13 m 3 / m 2 .

[0254] Further, the calculation of the pressure distribution in the module based on the simulation was performed in the same manner as in Example 1. As a result, the intermembrane differential pressure ΔP m，k at the end portion of the filtrate discharge port side was -5.7 kPa, and the ratio of the intermembrane differential pressure ΔP m，0 at the end portion of the raw liquid inlet port side, that is, ΔP m，k / ΔP m，0 was -0.6. From the result of the simulation, it was considered that the backflow of the filtrate had occurred, and it was presumed that the intermembrane differential pressure difference in the axial direction of the hollow fiber membrane 5 was also large.

[0255] (Comparative Example 2)

[0256] In addition to adjusting the raw material liquid temperature in the piping between the gear pumps, adjusting the raw material liquid at the metal cap, and the discharge amount of the liquid forming the hollow portion, the pure water permeation performance K of the hollow fiber membrane 5 was 4.1 m / hr, the inner diameter Di was 630 μm, the outer diameter Do was 1130 μm, and the strength was 480 gf / root, the membrane was produced in the same manner as in Example 1. Further, with respect to the hollow fiber membrane module, it was produced in the same manner as in Example 1. At this time, the packing ratio M was 35%, the inner diameter D i did not satisfy the relationship of the formula (2). As a result, the membrane area was 9.3 m 2 .

[0257] With respect to the filtration test, it was also performed in the same manner as in Example 1, and the filtration test was performed until the intermembrane differential pressure rose to 150 kPa. As a result, as shown in Table 4, the obtained filtrate amount was 0.14 m 3 / m 2 .

[0258] Furthermore, the intra-module pressure distribution was calculated using the same method as in Example 1 based on simulation. The result showed that the inter-membrane differential pressure ΔP at the filtrate outlet end was... m，k The intermembrane pressure difference ΔP between the inlet and the end of the original solution is -3.4 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value is -0.4. Based on the simulation results, it is believed that backflow of the filtrate has occurred, and it is estimated that the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 is also relatively large.

[0259] (Comparative Example 3)

[0260] Except for adjusting the feed liquid temperature in the piping between the gear pumps, adjusting the feed liquid at the metal cap, and adjusting the ejection rate of the liquid formed in the hollow section, the hollow fiber membrane 5 was manufactured using the same method as in Example 1, with a pure water permeability K of 3.6 m / hr, an inner diameter Di of 330 μm, an outer diameter Do of 830 μm, and a strength of 320 gf / piece. Furthermore, the hollow fiber membrane module was manufactured using the same method as in Example 1. At this time, the fill rate M was 28%, and the inner diameter D... i The relationship in equation (2) is not satisfied. As a result, the membrane area is 10.1 m². 2 .

[0261] The filtration test was conducted using the same method as in Example 1, continuing until the intermembrane differential pressure rose to 150 kPa. The results, as shown in Table 4, were that the obtained filtrate volume was 0.14 m³. 3 / m 2 .

[0262] Furthermore, the intra-module pressure distribution was calculated using the same method as in Example 1 based on simulation. The result showed that the inter-membrane differential pressure ΔP at the filtrate outlet end was... m，k The pressure difference ΔP between the membrane and the end of the inlet of the original solution is 15.6 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value is 5.2. Based on the simulation results, it is assumed that no backflow of the filtrate occurred, but it is estimated that the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 is also relatively large.

[0263] (Comparative Example 4)

[0264] Filtration tests were conducted using the hollow fiber membrane module prepared in Example 2. The filtration tests were performed in the same manner as in Example 1, except that the crossflow velocity v was adjusted to 2.0 m / s. The results, as shown in Table 4, show that the obtained filtrate volume was 0.11 m³. 3 / m 2 .

[0265] Furthermore, the intra-module pressure distribution was calculated using the same method as in Example 1 based on simulation. The result showed that the inter-membrane differential pressure ΔP at the filtrate outlet end was... m，k The differential pressure ΔP between the membrane and the end of the inlet of the original solution is -1.4 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value is -0.2. Based on the simulation results, it is believed that backflow of the filtrate has occurred, and it is estimated that the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 is also relatively large. It is believed that the main reason for the increased pressure difference on the feed side is the higher velocity of the cross-flow lines.

[0266] (Comparative Example 5)

[0267] Filtration tests were conducted using the hollow fiber membrane module prepared in Example 2. The filtration tests were performed in the same manner as in Example 1, except that the crossflow velocity v was adjusted to 0.8 m / s. The results, as shown in Table 4, show that the obtained filtrate volume was 0.07 m³. 3 / m 2 .

[0268] Furthermore, the intra-module pressure distribution was calculated using the same method as in Example 1 based on simulation. The result showed that the inter-membrane differential pressure ΔP at the filtrate outlet end was... m，k The pressure difference ΔP between the membrane and the end of the inlet of the original solution is 3.7 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value is 1.1. Based on the simulation results, it is assumed that no backflow of the filtrate occurred, and the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 is also relatively small. However, it is believed that due to the low cross-flow velocity, the washing effect on the membrane surface is reduced, and the development of fouling is accelerated.

[0269] [Table 4]

[0270] Table 4

[0271]

[0272] (Comparative Example 6)

[0273] Except for adjusting the feed liquid temperature in the piping between the gear pumps, adjusting the feed liquid at the metal cap, and adjusting the ejection rate of the liquid formed in the hollow section, the hollow fiber membrane 5 was manufactured using the same method as in Example 1, with a pure water permeability K of 1.5 m / hr, an inner diameter Di of 540 μm, an outer diameter Do of 1070 μm, and a strength of 990 gf / piece. Furthermore, the hollow fiber membrane module was manufactured using the same method as in Example 1. At this time, the fill rate M was 33%, and the inner diameter D... i The relationship in equation (2) is satisfied. As a result, the membrane area is 9.4 m². 2 .

[0274] The filtration test was also performed in the same manner as in Example 1, and the filtration test was performed until the difference in pressure between the membranes rose to 150 kPa. As a result, as shown in Table 5, the obtained permeate amount was 0.09 m 3 / m 2 .

[0275] Furthermore, the calculation of the pressure distribution in the module based on simulation was performed in the same manner as in Example 1. As a result, the ratio of the difference in pressure between the membranes ΔP m，k at the end portion on the permeate outlet side to the difference in pressure between the membranes ΔP m，0 at the end portion on the feed inlet side, i.e., ΔP m，k / ΔP m，0 was 0.19. From the result of the simulation, it was considered that the backflow of the permeate did not occur, and it was presumed that the difference in pressure between the membranes in the axial direction of the hollow fiber membrane 5 was small, but as a result, the development of the contamination of the hollow fiber membrane was fast due to the low water permeability, and the obtained permeate amount was small.

[0276] (Comparative Example 7)

[0277] The membrane was formed in the same manner as in Example 1 except that the temperature of the raw material liquid was adjusted in the piping between the gear pumps, the ejection amount of the liquid forming the hollow portion at the metal cap, the pure water permeability K of the hollow fiber membrane 5 was 21.0 m / hr, the inner diameter Di was 590 μm, the outer diameter Do was 1040 μm, and the strength was 170 gf / root. Furthermore, the hollow fiber membrane module was produced in the same manner as in Example 1. At this time, the packing ratio M was 33%, the inner diameter D i did not satisfy the relationship of the equation (2). As a result, the membrane area was 9.4 m 2 .

[0278] The filtration test was also performed in the same manner as in Example 1, and the filtration test was performed until the difference in pressure between the membranes rose to 150 kPa. As a result, as shown in Table 5, the obtained permeate amount exceeded 0.30 m 3 / m 2 .

[0279] Furthermore, the calculation of the pressure distribution in the module based on simulation was performed in the same manner as in Example 1. As a result, the ratio of the difference in pressure between the membranes ΔP m，k at the end portion on the permeate outlet side to the difference in pressure between the membranes ΔP m，0 at the end portion on the feed inlet side, i.e., ΔP m，k / ΔP m，0The value was 0.25. Based on the simulation results, it was determined that backflow of the filtrate had occurred, and the axial intermembrane pressure differential of the hollow fiber membrane 5 was also relatively small. However, due to its high permeability, leakage of turbid components in the feed solution was confirmed. The result was that, compared to a feed solution turbidity of 250 NTU, the turbidity of the filtrate was as high as 15 NTU. Therefore, the barrier performance was insufficient. Furthermore, internal verification after operation revealed a break in the hollow fiber membrane 5. It was believed that the breakage was due to low strength and cross-flow.

[0280] [Table 5]

[0281] Table 5

[0282]

[0283] (Comparative Example 8)

[0284] The pressure distribution within the hollow fiber membrane module fabricated in Example 1 was calculated using simulation, assuming full-volume filtration operation without cross-flow filtration. The calculation method was the same as that described in Reference Example 1, except that the cross-flow velocity was set to zero.

[0285] The simulation results are shown in Table 6. The intermembrane differential pressure ΔP at the outlet side of the hollow fiber membrane 5 is... m，k The intermembrane pressure difference ΔP between the membrane and the end of the inlet of the original solution is 6.5 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value is 108.9. Since it is a full-volume filtration, the simulation results also indicate that no backflow of the filtrate occurred, but the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 is relatively large.

[0286] (Comparative Example 9)

[0287] The pressure distribution within the hollow fiber membrane module fabricated in Example 3 was calculated using simulation, assuming full-volume filtration operation without cross-flow filtration. The calculation method was the same as that described in Reference Example 1, except that the cross-flow velocity was set to zero.

[0288] The simulation results are shown in Table 6. The intermembrane differential pressure ΔP at the outlet side of the hollow fiber membrane 5 is... m，k The pressure difference ΔP between the membrane and the inlet side of the original solution is 7.4 kPa. m，0 The ratio is ΔP m，k / ΔP m，0 The value was 264.2. Since it was a full-volume filtration, the simulation results showed no backflow of the filtrate. However, the inter-membrane pressure difference along the axial direction of the hollow fiber membrane 5 was found to be large, which was worse than that of Comparative Example 8.

[0289] (Comparative Example 10)

[0290] The module pressure distribution in the case where the hollow fiber membrane module produced in Example 5 was operated without cross-flow filtration operation but with bulk filtration operation was calculated by simulation. The calculation method was performed in the same manner as the method described in Reference Example 1 except that the cross-flow linear velocity was made zero.

[0291] The result of the simulation is shown in Table 6, and the intermembrane differential pressure ΔP m，k of the filtrate outlet side end portion of the hollow fiber membrane 5 was 13.9 kPa, and the intermembrane differential pressure ΔP m，0 of the raw material inlet side end portion was 10.8 kPa. The ratio of the intermembrane differential pressure of the filtrate outlet side end portion to that of the raw material inlet side end portion, that is, ΔP m，k / ΔP m，0 was 13010.8. Since it was bulk filtration, backflow of the filtrate did not occur according to the result of the simulation, but it was calculated that the intermembrane differential pressure difference in the axial direction of the hollow fiber membrane 5 was large, and a tendency of deterioration compared to Comparative Example 9 was confirmed.

[0292] [Table 6]

[0293] Table 6

[0294]

[0295] According to the above results, it was predicted that the smaller the inner diameter, the more the intermembrane differential pressure difference in the axial direction was amplified, and the filtration performance deteriorated in bulk filtration operation, and on the contrary, by appropriately controlling the inner diameter in cross-flow filtration operation, the intermembrane differential pressure difference in the axial direction could be suppressed, and by suppressing the development of contamination, an effect of increasing the filtration capacity could be confirmed.

[0296] The present application has been described in detail by specific means, but it is obvious to those skilled in the art that various changes and modifications can be made without departing from the intent and scope of the present application. In addition, the present application is based on Japanese Patent Application (Japanese Patent Application No. 2020-112493) filed on June 30, 2020, which is incorporated by reference in its entirety.

[0297] Industrial applicability

[0298] The cross-flow filtration hollow fiber membrane module and the operation method thereof of the present application are preferably used for membrane filtration of raw materials in the field of water treatment such as drinking water production, water purification treatment, or wastewater treatment, the field of fermentation accompanying culture of microorganisms or cultured cells, the field of food industry, and the like.

[0299] Reference Signs List

[0300] 1 container

[0301] 2 raw material inlet

[0302] 3 filtrate outlet

[0303] 4 feed solution outlet

[0304] 5 hollow fiber membrane

[0305] 6 feed solution side space

[0306] 7 filtrate side space

[0307] 8 first perfusion portion

[0308] 9 second perfusion portion

[0309] 10 cross-flow filtration hollow fiber membrane module

[0310] 12 feed solution tank

[0311] 13 filtrate tank

[0312] 14 feed pump

[0313] 15 circulation pump

[0314] 21 concentrate valve

[0315] 22 filtrate valve

[0316] 31 concentrate flow meter

[0317] 32 filtrate flow meter

[0318] 41 feed solution inlet pressure gauge

[0319] 42 feed solution outlet pressure gauge

[0320] 43 filtrate outlet pressure gauge

[0321] 44 filtrate inlet pressure gauge

Claims

1. A hollow fiber membrane module for cross-flow filtration, the hollow fiber membrane module for cross-flow filtration being filled with a plurality of hollow fiber membranes in a vessel having at least a raw liquid inlet, a raw liquid outlet, and a filtered liquid outlet, characterized in that, in the plurality of hollow fiber membranes, an end portion on the raw liquid inlet side is sealed, and an end portion on the filtered liquid outlet side is open, and at least the end portion on the filtered liquid outlet side has a perfusion portion fixed by an adhesive, the raw liquid side space for connection of the raw liquid inlet and the raw liquid outlet, and the filtered liquid side space for connection of the filtered liquid outlet in the vessel are separated by the plurality of hollow fiber membranes and the perfusion portion, and the raw liquid side space is in contact with the outer surface of the hollow fiber membranes.

2. The hollow fiber membrane module for cross-flow filtration according to claim 1, characterized in that, the axial length L (m) of the hollow fiber membranes in contact with the raw liquid satisfies 0.5 ≤ L ≤ 2.

0.

3. The hollow fiber membrane module for cross-flow filtration according to claim 1 or 2, characterized in that, the packing ratio M (%) satisfies the following requirement, 0.5 ≤ M ≤ 0.

9. The pure water permeation performance K(m) of the aforementioned hollow fiber membrane 3 / m 2 / hr / 50kPa) and the inner diameter D of the aforementioned hollow fiber membrane i (μm) satisfies the following requirements, 2.0≤K≤20.0， 350≤D i ≤550， The outer diameter D of the aforementioned hollow fiber membrane o The hollow fiber membrane satisfies the following relationship of the outer diameter D (μm), the packing ratio M (%), and the inner diameter D (μm) of the hollow fiber membrane. i The hollow fiber membrane satisfies the following relationship of the outer diameter D (μm), the packing ratio M (%), and the inner diameter D (μm) of the hollow fiber membrane. 0.33 x D o -10 x M + 420 ≤ D i ≤ 0.33 x D o -10 x M + 550... (2).

4. The hollow fiber membrane module for cross-flow filtration according to claim 1 or 2, characterized in that, the number of hollow fiber membranes per unit volume V (m-1) satisfies the following requirement, 5000 ≤ V ≤ 20000.

5. The hollow fiber membrane module for cross-flow filtration according to claim 1 or 2, characterized in that, the number of hollow fiber membranes per unit area A (m-2) satisfies the following requirement, 1000 ≤ A ≤ 5000.

6. The hollow fiber membrane module for cross-flow filtration according to claim 1 or 2, characterized in that, the strength of the hollow fiber membranes is 250 gf / root or more.

7. The hollow fiber membrane module for cross-flow filtration according to claim 1 or 2, characterized in that, the number of hollow fiber membranes per unit length L (m-1) satisfies the following requirement, 1000 ≤ L ≤ 5000. 25≤M≤45。 8. A method for operating a hollow fiber membrane module, characterized in that, the hollow fiber membrane module for cross-flow filtration according to any one of claims 1 to 7 is used to perform cross-flow filtration in such a manner that the filtration flux J (m / d) and the cross-flow linear velocity v (m / s) satisfy the following requirement, 0.5 ≤ J / v ≤ 2.

0. The foregoing outer diameter D o The foregoing outer diameter D satisfies the following requirements, 850≤D o ≤1500。 9. The method for operating a hollow fiber membrane module according to claim 8, characterized in that, cross-flow filtration is performed on a raw liquid having a turbidity of 20 NTU or more and a TOC concentration of 1000 mg / L or more. The membrane thickness D of the aforementioned hollow fiber membrane t The ratio D of the aforementioned inner diameter D i (μm) relative to the aforementioned inner diameter D t / D i The following requirements are satisfied, 0.40 < D t / D i ≤0.

65.

10. The method for operating a hollow fiber membrane module according to claim 9, characterized in that, the filtered liquid has a turbidity of 10 NTU or more and a TOC concentration of 1000 mg / L or more.

11. The method for operating a hollow fiber membrane module according to any one of claims 8 to 10, characterized in that, cross-flow filtration is performed on a raw liquid having a viscosity of 2 mPa-s or more. ​ The cross-sectional area S of the aforementioned raw solution inlet f The ratio S of the cross-sectional area S of the aforementioned container to the cross-sectional area S of the flow path p f p is 0.35 or more.​​ ​ ​ 0.5≤J≤2.0， 1.0≤v≤1.8。 ​ ​ ​ ​ ​ ​

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