JP6374291B2 - Hollow fiber membrane module - Google Patents

Description

  The present invention relates to a hollow fiber membrane module.

  Separation technology using hollow fiber membranes has advantages such as downsizing of the apparatus, so various fields, for example, water treatment fields such as water purification treatment, drinking water production, industrial water production and wastewater treatment, food industry field, And widely used in the pharmaceutical manufacturing field. Among these, for example, in the field of water treatment, attention is paid to the fact that treated water with good water quality can be obtained at a relatively low cost by using a separation technique using a hollow fiber membrane. Furthermore, such a separation technique using a hollow fiber membrane is expected to expand in application, scale, etc., and development of a lower cost system is desired.

  Further, in the separation technique using hollow fibers, generally, a hollow fiber membrane module obtained by modularizing a plurality of hollow fiber membranes is often used. And the apparatus for implementing the isolation | separation technique using a hollow fiber membrane is requested | required of size reduction for the reduction of initial cost, the space saving of installation space, etc. In order to contribute to the downsizing of the device, the hollow fiber membrane module provided in the device is required to increase the permeation flux that is the permeation rate per unit membrane area. The permeation flux of the hollow fiber membrane module is a value obtained by dividing the permeation rate that can be filtered by one hollow fiber membrane module by the total area of the hollow fiber membranes provided in the hollow fiber membrane module. That is, the permeation flux in the case of allowing water to permeate through the hollow fiber membrane module is the permeation rate of water passing through the hollow fiber membrane per unit membrane area. In particular, it is required to increase the permeation flux in fields where it is necessary to filter water with a large amount of turbid components, for example, filtration of surface water and underground water in the water supply field, and water recovery in the factory. Yes.

  Moreover, the membrane filtration method using a hollow fiber membrane increases the amount of foulant which is a turbid component deposited on the surface or inside of the hollow fiber membrane as the filtration time increases. The foulant deposited on the hollow fiber membrane becomes filtration resistance and causes fouling, which is a phenomenon that the filtration efficiency is lowered. For this reason, when filtering the liquid to be treated over a long period of time using a hollow fiber membrane, the hollow fiber membrane is backwashed, so-called backwashed, to periodically remove the foulant deposited on the hollow fiber membrane. It may be possible to do so.

  Non-Patent Document 1 discloses that the membrane area can be reduced when the permeation flux is increased. On the other hand, when the permeation flux is increased, the number of times of washing such as the number of times of washing increases due to an increase in the amount of foulant per unit time and an increase in transmembrane pressure difference. It is disclosed. From this, it is also disclosed that increasing the permeation flux is not necessarily advantageous for long-term operation.

  Patent Document 1 is made of polyvinylidene fluoride resin, has a porosity of 40 to 90%, does not substantially contain 10 μm or more of microvoids inside, and has an average pore size of the surface layer of 0.05 μm or more and less than 5 μm, Moreover, it has a three-dimensional network structure composed of homogeneous communication holes having a ratio of the average pore diameter of the surface layer to the average pore diameter of the membrane cross section of 0.5 to 2.0, and the ratio of the maximum pore diameter to the average pore diameter is 1. A porous membrane made of polyvinylidene fluoride resin having a pore size distribution of 2 to 2.5 is described. According to Patent Document 1, it is disclosed that a polyvinylidene fluoride porous membrane having excellent permeation performance can be obtained.

  In addition, as a method for cleaning a porous film such as the polyvinylidene fluoride porous film described in Patent Document 1, a film cleaning method described in Patent Document 2 is described.

  Patent Document 2 describes a membrane cleaning method in which, in a porous membrane cleaning method, backwashing is performed with water containing an acid in a direction opposite to the filtration direction, followed by backwashing with water containing an oxidizing agent. ing. Patent Document 2 also discloses a membrane cleaning method in which a backwashing is performed with water containing an oxidant and then backwashing with water containing an acid in a direction opposite to the filtration direction in the porous membrane cleaning method. Have been described. Furthermore, in the cited document 2, it is also described that bubbles are introduced into the raw water side of the membrane simultaneously with the above-described backwashing to swing the membrane.

JP-A-3-215535 JP 2001-70763 A

Shinichi Minegishi, Yoshinori Watanabe, “Proceedings of the Sanitation Symposium”, 2001, Vol. 9, p. 194-196 Jian PENG, Gaogao XUE, “Journal of systems, cybernetics and informations”, 2006, Vol. 4, No. 1, p. 47-52

  According to Patent Document 2, it is possible to effectively wash the porous membrane described in Patent Document 1, and as a result, it is possible to maintain a high membrane filtration flow rate over a long period of time. It is disclosed.

  However, using only the membrane cleaning method described in Patent Document 2 may not allow suitable filtration to be continued for a long period of time depending on the porous membrane used.

  In addition, such a method merely maintains a high permeation flux by dropping the foulant deposited on the surface or inside of the membrane by pressing the force. For this reason, the apparatus provided with the hollow fiber membrane module may become large, and operation cost may increase. Furthermore, the hollow fiber membrane itself needs to be excellent in strength, chemical resistance and the like in order to cope with cleaning by force pushing, and the hollow fiber membrane that can be used is limited.

  This invention is made | formed in view of this situation, Comprising: It aims at providing the hollow fiber membrane module which not only is excellent in a fractionation characteristic but can maintain the outstanding permeation | permeation performance over a long period of time.

  The present inventors paid attention to the fact that Darcy's formula expressed by the following formula (1) holds in the filtration of a solution containing a turbid component (see, for example, Non-Patent Document 2).

u represents the permeation flux (m / day), ΔP represents the transmembrane pressure difference, μ represents the viscosity of the liquid to be treated, and Rm, Rp, and Rc represent the passage resistances, respectively. Rm represents the passage resistance of the membrane itself, Rp represents the passage resistance due to deposition of turbid components on the membrane surface, and Rc represents the passage resistance due to deposition of turbid components inside the membrane, that is, inside the pores. Indicates.

  The inventors of the present invention first focused on the following points regarding the above formula (1). From this equation (1), it can be seen that the permeation flux u is proportional to the transmembrane pressure difference ΔP and inversely proportional to the sum of the viscosity μ of the liquid to be treated and the passage resistances Rm, Rp, and Rc. The viscosity μ of the liquid to be treated is usually almost constant, and it can be seen that it is difficult to control by devising the configuration of the hollow fiber membrane module. For example, when filtration of surface water and underground water in the field of clean water is assumed, the viscosity μ is considered to be constant due to the filtered aqueous state.

  In view of the above points, the present inventors focused on the fact that increasing the permeation flux u can be realized by increasing the transmembrane pressure difference ΔP, and studied this. For example, in the membrane filtration method, it was considered that the permeation flux u can be increased by increasing the pressure on the secondary side of the membrane.

  However, according to studies by the present inventors, it has been found that when the transmembrane pressure difference ΔP is increased and the permeation flux u is increased, the filtration efficiency is significantly reduced.

  The present inventors considered this as follows. First, during membrane filtration, the amount of foulant, which is a turbid component that accumulates on the surface and inside of the hollow fiber membrane, increases, and since the transmembrane pressure difference ΔP is high, the force that the foulant is pressed against the hollow fiber membrane I guessed it would be stronger. In that case, it was presumed that the foulant easily adheres to the surface or inside of the hollow fiber membrane. As a result, it has been inferred that the foulant deposited on the hollow fiber membrane is likely to cause fouling, which is a phenomenon in which the filtration resistance is lowered and the filtration efficiency is reduced as described above. Moreover, in order to remove this foulant, it is conceivable that the hollow fiber membrane is backwashed, that is, so-called backwashing, but since the foulant is fixed to the hollow fiber membrane, the effect of removing the foulant is reduced. I guessed it could happen. Then, we thought that fouling could occur more prominently. From these facts, it was speculated that when the transmembrane pressure difference ΔP was increased, as a result, the reduction of the filtration efficiency became remarkable.

  Further, in the study in Non-Patent Document 1, when the permeation flux is increased, if the transmembrane pressure difference ΔP is increased, the effect of backwashing is reduced as described above. It was not noticed that the decrease.

  Therefore, the present inventors pay attention not only to the level of the permeation flux but also the transmembrane differential pressure, and even if the fractionation characteristics are excellent, the permeation flux is reduced to the transmembrane differential pressure. It is found that a hollow fiber membrane module capable of maintaining excellent permeation performance over a long period of time can be obtained by configuring the hollow fiber membrane module so that the value divided by is within an appropriate range. I arrived at the idea.

  The hollow fiber membrane module which concerns on 1 aspect of this invention is a hollow fiber membrane module by which the some hollow fiber membrane was accommodated in the housing | casing, Comprising: The fraction particle diameter of the said hollow fiber membrane is 0.001-0. The value obtained by dividing the permeation flux when pure water permeates through the hollow fiber membrane module by the transmembrane differential pressure is 0.2 to 1.5 m / day / kPa.

  According to such a configuration, it is possible to provide a hollow fiber membrane module that not only has excellent fractionation characteristics but also can maintain excellent permeation performance over a long period of time. This is considered to be due to the following.

  First, since the hollow fiber membrane provided in the hollow fiber membrane module has a fractional particle diameter of 0.001 to 0.5 μm, it has excellent fractionation characteristics. In the case of a hollow fiber membrane having such excellent fractionation characteristics, since the pores existing on the membrane surface and in the membrane are relatively small, the permeation flux is sufficiently increased unless the transmembrane pressure difference is relatively high. There is a tendency to not be able to. Even a hollow fiber membrane module having a hollow fiber membrane having such a fractional particle diameter is a value obtained by dividing the permeation flux when pure water permeates through the hollow fiber membrane module by the transmembrane differential pressure. The hollow fiber membrane to be accommodated in the housing so that a certain module permeability coefficient is 0.2 to 1.5 m / day / kPa, permeability performance, length in the longitudinal direction (fiber direction), outer diameter, inner diameter, Further, by adjusting the properties of the film thickness, the number of hollow fiber membranes accommodated in the housing, etc., a high permeation flux can be realized without increasing the transmembrane pressure difference more than necessary. In addition, since a high permeation flux can be maintained without increasing the transmembrane pressure difference more than necessary, it is considered that the reduction in filtration efficiency due to the increase in the transmembrane pressure pressure as described above can be suppressed. It is done. Therefore, according to the above configuration, it is considered that not only the fractionation characteristics are excellent, but also excellent transmission performance can be maintained over a long period of time.

  In the hollow fiber membrane module, the total cross-sectional area of the plurality of hollow fiber membranes (the hollow fiber membrane occupies the area (inner area) of the cross section perpendicular to the longitudinal direction of the hollow fiber membrane in the housing) The ratio of (total area) is preferably 10 to 65%.

  According to such a configuration, excellent transmission performance can be maintained over a longer period. This is considered to be due to the following.

  The ratio is the ratio of the total area occupied by the hollow fiber membrane to the inner area of the housing, that is, the filling rate. When the filling rate is within the above range, the module transmission coefficient is considered to be easily within the above range. Specifically, when the filling rate is within the above range, a space that exists between the hollow fiber membranes suitably exists, and a hollow that is accommodated in the casing while suppressing a decrease in permeation performance of each hollow fiber membrane is suppressed. It is thought that the total area of the yarn membrane can be increased. From this, since it is possible to maintain a higher permeation flux without increasing the transmembrane pressure difference more than necessary, the above-described reduction in the filtration efficiency due to the increased transmembrane pressure difference is further suppressed. It is thought that you can. Therefore, it is considered that not only the fractionation characteristics are excellent, but also excellent transmission performance can be maintained over a longer period.

  In the hollow fiber membrane module, the effective length of the hollow fiber membrane is preferably 0.3 to 2 m.

  According to such a configuration, excellent transmission performance can be maintained over a longer period. This is considered to be due to the following.

  If the effective length of the hollow fiber membrane is within the above range, it is considered that the module permeability coefficient easily falls within the above range. Specifically, when the effective length is within the above range, pressure loss when the liquid to be treated flows through the hollow fiber membrane can be suppressed while preventing fouling from being reduced due to the hollow fiber membrane being too short. it is conceivable that. Therefore, it is considered that not only the fractionation characteristics are excellent, but also excellent transmission performance can be maintained over a longer period.

In the hollow fiber membrane module, the hollow fiber membrane preferably has a pure water permeation amount of 3000 to 40000 L / m ² / hour at a transmembrane pressure difference of 0.1 MPa.

  According to such a configuration, excellent transmission performance can be maintained over a longer period. This is considered to be due to the following.

  The permeation amount of pure water at a transmembrane differential pressure of 0.1 MPa of the hollow fiber membrane is a single yarn permeation amount, which indicates the permeation performance of the hollow fiber membrane alone. The single yarn water permeability is a value measured using a hollow fiber membrane having a length of 20 cm. If the permeation performance of the single hollow fiber membrane is as described above, it is considered that the module permeation coefficient, which is the permeation coefficient of a hollow fiber membrane module including a plurality of hollow fiber membranes, easily falls within the above range. Therefore, it is considered that not only the fractionation characteristics are excellent, but also excellent transmission performance can be maintained over a longer period.

  In the hollow fiber membrane module, it is preferable that an outer diameter of the hollow fiber membrane is 0.8 to 5 mm and an inner diameter of the hollow fiber membrane is 0.5 to 3 m.

  According to such a configuration, excellent transmission performance can be maintained over a longer period. This is considered to be due to the following.

  When the size of the hollow fiber membrane is an outer diameter and an inner diameter within the above range, it is considered that the module permeability coefficient easily enters the above range. Specifically, when the outer diameter of the hollow fiber membrane is within the above range, it is considered that the number accommodated in the housing can be made appropriate while suppressing a decrease in the strength of the hollow fiber membrane. Moreover, it is thought that the pressure loss at the time of a to-be-processed liquid flowing through a hollow fiber membrane can be suppressed, suppressing the fracture | rupture of a hollow fiber membrane as the internal diameter of a hollow fiber membrane is in the said range. Therefore, it is considered that not only the fractionation characteristics are excellent, but also excellent transmission performance can be maintained over a longer period.

  In the hollow fiber membrane module, it is preferable that the hollow fiber membrane includes a vinylidene fluoride resin, is hydrophilic, and has holes on the outer surface smaller than holes on the inner surface.

  According to such a configuration, in filtration using an aqueous medium as the liquid to be treated, not only the fractionation characteristics are excellent, but also excellent permeation performance can be maintained over a long period of time. This is considered to be due to the following.

  First, since the hollow fiber membrane provided in the hollow fiber membrane module is a hydrophilic hollow fiber membrane containing a vinylidene fluoride resin, it is suitable for filtration using an aqueous medium as a liquid to be treated, such as water treatment. Filtration resistance is obtained.

  In addition, since the hollow fiber membrane has pores present on the outer surface smaller than those present on the inner surface, a dense layered portion considered to be involved in the fractionation characteristics and other relatively large pores are formed. It is thought that the part etc. were formed. For this reason, it is considered that the hollow fiber membrane not only has excellent fractionation characteristics, but also has excellent permeation performance.

  From the above, in filtration using an aqueous medium as the liquid to be treated, it is considered that not only the fractionation characteristics are excellent, but also excellent permeation performance can be maintained over a long period of time. Furthermore, since this hollow fiber membrane is hydrophilic, it is considered that the hollow fiber membrane is highly resistant to dirt. That is, this hollow fiber membrane is considered to be excellent in stain resistance.

  The present invention has been made in view of such circumstances, and can provide a hollow fiber membrane module that not only has excellent fractionation characteristics but also can maintain excellent permeation performance over a long period of time.

FIG. 1 is a schematic diagram illustrating an example of a hollow fiber membrane module according to an embodiment of the present invention. FIG. 2 is a schematic view showing another example of the hollow fiber membrane module according to the embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of the hollow fiber membrane module shown in FIG. FIG. 4 is a partial perspective view of the hollow fiber membrane provided in the hollow fiber membrane module according to the embodiment of the present invention. FIG. 5 is a schematic diagram illustrating an example of a hollow fiber membrane molding nozzle used when manufacturing a hollow fiber membrane included in a hollow fiber membrane module according to an embodiment of the present invention. 6 is a view showing a scanning electron micrograph of a cross section of the hollow fiber membrane according to Example 1. FIG. 7 is a view showing a scanning electron micrograph of the outer peripheral surface of the hollow fiber membrane according to Example 1. FIG. FIG. 8 is a view showing a scanning electron micrograph of the inner peripheral surface of the hollow fiber membrane according to Example 1. FIG.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  The hollow fiber membrane module which concerns on one Embodiment of this invention is a hollow fiber membrane module with which the several hollow fiber membrane was accommodated in the housing | casing. That is, it is a hollow fiber membrane module comprising a plurality of hollow fiber membranes and a housing that accommodates the plurality of hollow fiber membranes.

  In addition, as the hollow fiber membrane module, specifically, a hollow fiber membrane module in which each hollow fiber membrane is sealed in the housing with a sealing agent or the like with the hollow interior of each hollow fiber membrane open. Etc. In such a hollow fiber membrane module, since the hollow fiber membrane is sealed in the housing, the hollow fiber membrane is liquid-tightly fixed to the housing. Further, in the hollow fiber membrane module, each of the hollow fiber membranes and the casing may be directly bonded and sealed with a sealing agent, or each hollow fiber membrane may be sealed in a cylindrical case with the sealing agent. The hollow fiber membranes and the casing may be sealed by bonding and fixing the cylindrical case to the casing. In addition, the hollow fiber membrane module, for example, bundles a predetermined number of hollow fiber membranes, cuts the hollow fiber membrane bundle into a predetermined length, accommodates (fills) in a predetermined shape housing, It is obtained by fixing to the housing with a sealant containing a thermosetting resin such as polyurethane resin or epoxy resin. Examples of the hollow fiber membrane module include a hollow fiber membrane module shown in FIG.

  As shown in FIG. 1, the hollow fiber membrane module 30 includes a housing 31, a plurality of hollow fiber membranes 32, an inlet 35, and an outlet 36. The casing 31 is not particularly limited as long as it can be used as a casing of a hollow fiber membrane module. Specifically, cylindrical bodies, such as cylindrical shape, etc. are mentioned. The plurality of hollow fiber membranes 32 are fixed to the casing 31 with the upper end portion 33 opening the hollow portion and the lower end portion 34 sealing the hollow portion. . The casing 31 is provided with an inlet 35 for introducing the liquid to be processed into the casing 31 on the lower end 34 side of the plurality of hollow fiber membranes 32. In addition, the housing 31 includes a discharge port 36 through which the liquid to be treated passes through each hollow fiber membrane 32 and leads to the filtered liquid on the upper end 33 side of the plurality of hollow fiber membranes 32. The hollow fiber membrane module 30 is incorporated in a membrane filtration device, and the liquid to be filtered filtered by the hollow fiber membrane 32 is led out from the outlet port 36 by introducing the liquid to be treated from the inlet port 35. The hollow fiber membrane module 30 may include an air vent 37 for discharging the air introduced into the housing 31 to the outside of the housing 31. Moreover, in the membrane filtration method using such a hollow fiber membrane module, a to-be-processed liquid permeate | transmits toward the inner surface from the outer surface of a hollow fiber membrane, and a to-be-processed liquid is filtered. Therefore, the outer surface side of the hollow fiber membrane is also called a primary side, and the inner surface side is also called a secondary side.

  In addition, as described above, the hollow fiber membrane module has one end of the hollow fiber membrane that is open-fixed and the other end is sealed. However, the present invention is not limited to this, for example, both ends of the hollow fiber membrane as described later. The opening may be fixed.

  As shown in FIG. 2, the hollow fiber membrane module 40 includes a housing 41, a plurality of hollow fiber membranes 42, an inlet 45, and an outlet 46. The casing 41 is not particularly limited as long as it can be used as the casing of the hollow fiber membrane module, similarly to the casing 31. The plurality of hollow fiber membranes 42 have the upper end 43 and the lower end 44 fixed to the casing 41 with the upper end 43 and the lower end 44 both open to the hollow. And the housing | casing 41 is provided with the inlet 45 which introduces a to-be-processed liquid in the housing | casing 41 in the longitudinal direction (fiber direction) center part of the hollow fiber membrane 42 of the side surface. In addition, the casing 41 has outlets 46 through which the liquid to be treated permeates the hollow fiber membranes 44 is led out on both the upper end 43 side and the lower end 44 side of the plurality of hollow fiber membranes 32. Prepare. Examples of the hollow fiber membrane module include those in which both ends of such a hollow fiber membrane are fixed to be open.

  As described above, the hollow fiber membrane module according to the present embodiment is a hollow fiber membrane module in which a plurality of hollow fiber membranes are accommodated in a housing, and the hollow fiber membrane to be accommodated has a fractional particle diameter. A hollow fiber membrane having a diameter of 0.001 to 0.5 μm is used. Then, the hollow fiber membrane module accommodates the hollow fiber membrane, and a value obtained by dividing the permeation flux when the pure water permeates through the hollow fiber membrane module by the transmembrane differential pressure (module permeability coefficient), 0.2 to 1.5 m / day / kPa. Further, this hollow fiber membrane module accommodates hollow fiber membranes having a fractional particle diameter of 0.001 to 0.5 μm, and the arrangement method of the hollow fiber membranes is particularly limited as long as the module permeability coefficient is within the above range. Not.

  First, the value obtained by dividing the permeation flux when pure water permeates through the hollow fiber membrane module by the transmembrane differential pressure is measured as follows, for example.

First, for example, when a hollow fiber membrane module as shown in FIG. 1 is used and pure water is allowed to permeate in a state set to have a predetermined transmembrane pressure difference, the pure water permeation amount of one module (m ³ / day). Specifically, a hollow fiber membrane module as shown in FIG. 1 is used, the air vent 37 is closed, water is introduced from the inlet 35, and the internal pressure becomes a value at which the transmembrane pressure difference becomes a predetermined value. The amount of water coming out from the outlet 36 is measured. The transmembrane pressure difference is preferably set to be 0.01 to 0.1 MPa. For example, in this embodiment, it is set to 0.02 MPa. Then, the permeation flux (m / day) was calculated by dividing the amount of water permeation (m ³ / day) by the total membrane area (m ² ) of the hollow fiber membranes provided in one module. This permeation flux (m / day) is divided by the transmembrane pressure. The value thus obtained is also referred to as a module transmission coefficient k.

This module transmission coefficient k is a numerical value related to the passage resistance (Rm, Rp, Rc) and the viscosity μ of the liquid to be treated in the Darcy equation represented by the above equation (1). It is a value when the numerical value of is regarded as a constant. The module transmission coefficient k is considered as follows. When the water permeation amount is measured using pure water, Rp and Rc are foulant-derived passage resistances, and therefore the change can be ignored. Also, the viscosity μ is always constant since the liquid to be treated is pure water, and the change can be ignored. Thus, the module transmission coefficient k is a value that depends on the passage resistance Rm. This can be considered as the passage resistance of the hollow fiber membrane itself, for example, when measured using one 20 cm hollow fiber membrane. That is, when measuring the permeation amount of pure water (single yarn permeation amount) (LMH: L / m ² / hour) of the hollow fiber membrane, for example, the permeation amount of pure water at a transmembrane pressure difference of 0.1 MPa, etc. The same can be considered.

  However, in the case of a hollow fiber membrane module that is actually used industrially, the pressure loss when water flows through the gap between the hollow fiber membrane and the hollow fiber membrane, or the pressure loss when water flows through the hollow portion of the hollow fiber membrane The resistance value (passage resistance) as a hollow fiber membrane module due to the above becomes so high that it cannot be ignored. For this reason, the present inventors paid attention to the module permeability coefficient k considering such a resistance value as a hollow fiber membrane module. That is, if the module permeability coefficient k is small, the inclination of the permeation flux u with respect to the transmembrane differential pressure ΔP is small, and in order to increase the permeation flux u, it is necessary to make the transmembrane differential pressure relatively high. There is. On the other hand, when the module permeability coefficient k is large, the gradient of the permeation flux u with respect to the transmembrane differential pressure ΔP is large, and when increasing the permeation flux u, the transmembrane differential pressure is set at a relatively low pressure. It is enough. From this, it is preferable that a hollow fiber membrane module having a large module permeability coefficient k is obtained even if a hollow fiber membrane having excellent fractionation characteristics is provided.

  And as for the hollow fiber membrane with which the above hollow fiber membrane modules are equipped, the fraction particle diameter is 0.001-0.5 micrometer, It is preferable that it is 0.01-0.3 micrometer, 0.02 More preferably, it is -0.2 micrometer. This fractionated particle size refers to the particle size of the smallest particle that can prevent passage of the hollow fiber membrane, and specifically includes, for example, a particle size that provides a blocking rate of 90% by the hollow fiber membrane. Such a fractional particle size is preferably as small as possible, but in order to maintain excellent transmission performance, the limit is about 0.001 μm. For this reason, the minimum value of the fractional particle diameter is about 0.001 μm, and is preferably about 0.01 μm from the viewpoint of transmission performance. In addition, if the fractional particle diameter of the hollow fiber membrane is too large, even if the permeation performance is increased, the fractionation characteristics are lowered, and the application range to be removed tends to be narrowed. From this, when the particle diameter of the hollow fiber membrane is within the above range, excellent fractionation characteristics can be exhibited while suppressing a decrease in permeation performance.

  Moreover, the applicable range of the hollow fiber membrane varies depending on the fractional particle diameter. Specifically, if the fractional particle size is 0.05 to 0.1 μm, it can be applied to the removal of microorganisms and viruses as a microfiltration membrane. Moreover, if a fraction particle diameter is 0.001-0.01 micrometer, it can apply to removal of a micropathogenic microbe and protein as an ultrafiltration membrane. Moreover, if a fraction particle diameter is 0.002 micrometer or less, it can apply to desalination etc. as a reverse osmosis membrane.

  From the above, the hollow fiber membrane module according to this embodiment can exhibit excellent permeation performance while having excellent fractionation characteristics that can be applied to the removal of microorganisms and viruses as a microfiltration membrane.

  As described above, the hollow fiber membrane provided in the hollow fiber membrane module has excellent fractionation characteristics. In the case of a hollow fiber membrane having such excellent fractionation characteristics, since the pores existing on the membrane surface and in the membrane are relatively small, the permeation flux is sufficiently increased unless the transmembrane pressure difference is relatively high. There is a tendency to not be able to. Even a hollow fiber membrane module having a hollow fiber membrane having such a fractional particle diameter is a value obtained by dividing the permeation flux when pure water permeates through the hollow fiber membrane module by the transmembrane differential pressure. When a certain module permeability coefficient k is 0.2 to 1.5 m / day / kPa, a high permeation flux can be realized without increasing the transmembrane pressure difference more than necessary. The module permeability coefficient k is 0.2 to 1.5 m / day / kPa, preferably 0.2 to 1 m / day / kPa, and 0.3 to 0.6 m / day / kPa. It is more preferable. That is, the properties of the permeation performance, the length in the longitudinal direction, the outer diameter, the inner diameter, and the film thickness of the hollow fiber membrane to be filled in the housing so that the module permeability coefficient k falls within the above range, and the housing By adjusting the number of hollow fiber membranes to be filled in the membrane, a high permeation flux can be realized without increasing the transmembrane pressure difference more than necessary. On the other hand, when the module permeability coefficient k is too large, for example, it is constituted by a hollow fiber membrane in which the amount of single-fiber water permeability is too large, so that the fractionation performance of the hollow fiber membrane is low and practical enough for filtration. There is a tendency not to get sex. Or, in the hollow fiber membrane module, due to the low filling rate of the hollow fiber membrane or the short effective length of the hollow fiber membrane, a practically sufficient amount of water cannot be obtained as the hollow fiber membrane module, and the permeation There is a tendency that the cost reduction effect due to the flux improvement cannot be obtained sufficiently. For example, if the effective length of the hollow fiber membrane is too short, the permeation flux can be increased, but since the hollow fiber membrane module is also small, the total area of the hollow fiber membrane is reduced, and the actual amount of treated water is small. There is a tendency to become. Further, when the module permeability coefficient k is too small, when the permeation flux is increased, the transmembrane pressure difference tends to increase, and the fouling suppression effect due to the suppression of the differential pressure increase tends to be difficult to obtain. .

  From the above, the hollow fiber membrane module according to this embodiment can maintain a high permeation flux without unnecessarily increasing the transmembrane pressure difference, so that the filtration efficiency is improved by increasing the transmembrane pressure difference. It is considered that the decrease can be suppressed. Therefore, it is considered that this hollow fiber membrane module not only has excellent fractionation characteristics but also can maintain excellent permeation performance over a long period of time.

  Further, when the permeation flux is increased, the recoverability due to physical backwashing tends to decrease due to an increase in transmembrane pressure difference. On the other hand, in the hollow fiber membrane module according to the present embodiment, it is not necessary to increase the transmembrane differential pressure more than necessary in order to increase the permeation flux, and the foulant is pressed against the hollow fiber membrane to be fixed. It is thought that this can be suppressed and an excellent fouling suppression effect can be exhibited.

  In the hollow fiber membrane module, the filling rate of the hollow fiber membrane is preferably 10 to 65%, more preferably 10 to 60%, and further preferably 20 to 55%. If the filling rate is too low, the water permeability tends to be too small even if the module permeability coefficient is high. Moreover, when the said filling rate is too high, there exists a tendency for a module permeability coefficient to become difficult to be in the said range, and to suppress the fall of filtration efficiency over a long period of time. Therefore, when the filling factor is within the above range, the module permeability coefficient is easily within the above range, and thus excellent transmission performance can be maintained over a longer period.

The filling rate of the hollow fiber membrane is the ratio of the total cross-sectional area of the plurality of hollow fiber membranes to the area of the cross section perpendicular to the longitudinal direction (fiber direction) of the hollow fiber membrane inside the housing. Specifically, as shown in FIG. 3, the total cross-sectional area of the plurality of hollow fiber membranes 32 with respect to the area of the cross section perpendicular to the longitudinal direction (fiber direction) of the hollow fiber membrane 32 in the hollow portion of the casing 31. Ratio. The cross-sectional area of the hollow fiber membrane 32 is not a cross-sectional area of the hollow portion but a cross-sectional area including the membrane itself, and is a cross-sectional area calculated from the outer diameter of the hollow fiber membrane 32. And the calculation method of the said filling rate is the product of the number (the number) of the hollow fiber membranes accommodated in the said housing | casing 31, and the cross-sectional area (m < ² > / piece) of one said hollow fiber membrane 32, for example. That is, by dividing the area occupied by the hollow fiber membrane 32 in the casing 31 by the area calculated from the inner diameter of the casing 31, that is, the inner area of the casing 31, the filling rate Can be calculated. FIG. 3 is a schematic cross-sectional view of the hollow fiber membrane module shown in FIG.

  Moreover, the housing | casing with which the said hollow fiber membrane module is equipped will not be specifically limited if it can be used as a housing | casing of a hollow fiber membrane module as mentioned above. Moreover, it is preferable that the internal diameter of the said housing | casing is 10-200 cm, It is more preferable that it is 10-100 cm, It is further more preferable that it is 10-50 cm. Further, the height of the casing is preferably 0.3 to 3 m, more preferably 0.3 to 2 m, and further preferably 0.5 to 1.5 m. When this housing is too large, the handleability is poor and the cost for maintenance tends to increase. In addition, if this casing is too small, a practically sufficient flow rate cannot be secured, and as a result, a large number of hollow fiber membrane modules are prepared, which increases the cost of both equipment and operation. Tend.

  Next, the hollow fiber membrane provided in the hollow fiber membrane module will be described.

  The hollow fiber membrane is not particularly limited as long as it is a hollow fiber membrane that can be made into the hollow fiber membrane module by housing it in a housing.

  Moreover, it is preferable that the said hollow fiber membrane is a hollow fiber membrane which shows hydrophilic property. Such a hollow fiber membrane is considered to have high resistance to dirt. This is considered to be due to the following. As a foulant which is a turbid component deposited on the surface or inside of the hollow fiber membrane, there are many hydrophobic organic substances. In particular, when this hollow fiber membrane is used for filtration using an aqueous medium as a liquid to be treated, such as water treatment, the foulant is often a hydrophobic organic substance. The hydrophilicity of the hollow fiber membrane can suppress the deposition of this hydrophobic organic substance on the hollow fiber membrane rather than the hydrophobicity. From this, it is considered that the hollow fiber membrane is improved in contamination resistance by being hydrophilic. Furthermore, when this hollow fiber membrane is used for filtration using an aqueous medium as a liquid to be treated, such as water treatment, the water permeability of the hollow fiber membrane can be increased and the filtration resistance can be lowered.

  The degree of hydrophilicity of the hollow fiber membrane is not particularly limited as long as it shows hydrophilicity. For example, the hydrophilicity of the hollow fiber membrane includes hydrophilicity to the extent that the stain resistance is enhanced by the hydrophilicity. Further, the degree of hydrophilicity of the hollow fiber membrane is evaluated by the ratio of the water permeability (dry water permeability) in the dry state to the water permeability (wet water permeability) in the wet state (dry water permeability / wet water permeability). It is possible.

The dry water permeability is the water permeability of the hollow fiber membrane in a dry state, and is, for example, the water permeability at a transmembrane differential pressure of 100 kPa. More specifically, the amount of water permeation measured by the following method can be mentioned. First, the hollow fiber membrane which is a measurement object is dried. The drying is not particularly limited as long as the hollow fiber membrane can be dried, and examples thereof include drying for 24 hours in a 60 ° C. constant temperature dryer. Using the hollow fiber membrane module in which one end of the hollow fiber membrane in the dry state is sealed, pure water is used as raw water, and the external pressure is filtered under the conditions of a filtration pressure of 100 kPa and a temperature of 25 ° C. Measure. From the measured water permeability, the water permeability (L / m ² / hour) at a transmembrane differential pressure of 100 kPa (0.1 MPa) is obtained in terms of the water permeability per unit membrane area, unit time, and unit pressure.

Next, the wet water permeation amount is the water permeation amount of the hollow fiber membrane in a wet state, for example, the water permeation amount at a transmembrane differential pressure of 100 kPa (0.1 MPa). More specifically, the amount of water permeation measured by the following method can be mentioned. First, a hollow fiber membrane as a measurement object is immersed in a 50% by mass aqueous solution of ethanol for 15 minutes, and then subjected to a wet treatment such as washing with pure water for 15 minutes. Except for using this wet-treated hollow fiber membrane in place of the dry hollow fiber membrane, the water permeability at a transmembrane differential pressure of 100 kPa (0.1 MPa) was determined in the same manner as the dry water permeability measurement method. L / m ² / hour).

  The ratio of the water permeability (dry water permeability) in the dry state to the water permeability (wet water permeability) in the wet state (dry water permeability / wet water permeability) is determined from each water permeability obtained as described above. calculate. In addition, as for dry water permeability and wet water permeability, the value etc. which measured using the hollow fiber membrane of length 20cm etc. are mentioned, for example.

  The hollow fiber membrane is preferably hydrophilic so that the ratio obtained as described above is 40% or more. Further, this ratio is more preferably 60% or more, and further preferably 80% or more. In addition, if the hollow fiber membrane in a dry state is immediately wetted when touched with water, the ratio is 100%. For this reason, the upper limit of the ratio is 100%. Therefore, the ratio is preferably 40 to 100%, more preferably 60 to 100%, and still more preferably 80 to 100%. If the hydrophilicity is too low, the effect exhibited by the hollow fiber membrane being hydrophilic tends to be insufficient. That is, the contamination resistance tends to be low.

Further, the hollow fiber membrane preferably has a single yarn permeation amount which is a water permeation amount at a transmembrane differential pressure of 0.1 MPa, that is, a wet water permeation amount of 3000 to 40000 L / m ² / hour, preferably 3000 to 30000 L / hour. m ² / hour is more preferable, and 3500 to 15000 L / m ² / hour is more preferable. If the amount of water permeation is too small, the permeation performance tends to be inferior, which can be a factor for reducing the module permeability. Moreover, when there is too much water permeability, there exists a tendency for a fractionation characteristic to fall. From this, if the amount of water permeation is within the above range, a hollow fiber membrane having better permeation performance and fractionation characteristics can be obtained.

  Moreover, the said hollow fiber membrane may raise the hydrophilicity of the material which comprises a hollow fiber membrane, and may make a hydrophobic hollow fiber membrane hydrophilic by the hydrophilization process. Further, in order to increase the hydrophilicity of the material constituting the hollow fiber membrane, it may be produced from a material exhibiting hydrophilicity as a raw material of the hollow fiber membrane. For example, the hollow fiber membrane is composed mainly of a hydrophilic resin. What is necessary is just to manufacture. The hydrophilic treatment is not particularly limited as long as the treatment can make the hollow fiber membrane hydrophilic. For example, a method of impregnating a hollow fiber membrane with a hydrophilic resin can be used.

  The hydrophilic resin is not particularly limited as long as it is a hydrophilic resin that can be included in the hollow fiber membrane. Examples of the hydrophilic resin include polyvinyl alcohol, polyethylene vinyl alcohol, polyethylene glycol, cellulose, cellulose acetate, polyvinyl pyrrolidone, a copolymer of vinyl pyrrolidone and vinyl acetate, and a copolymer of vinyl pyrrolidone and vinyl caprolactam. Can be mentioned. As said hydrophilic resin, the resin of the said illustration may be used independently, and may be used in combination of 2 or more type.

  In addition to the method of impregnating the hollow fiber membrane with a hydrophilic resin, the hydrophilic treatment includes a method of immersing the hollow fiber membrane in glycerin, ethylene glycol, a surfactant or the like. By this method, the hydrophilicity of the hollow fiber membrane may be imparted.

  Moreover, it is preferable that the hole which exists in the outer surface (outer peripheral surface) of the said hollow fiber membrane is smaller than the hole which exists in an inner surface (inner peripheral surface). The hollow fiber membrane is more preferably an inclined structure that gradually decreases from the inner surface to the outer surface so that the holes existing on the outer surface are smaller than the holes existing on the inner surface. . In this way, when the pores existing on the outer surface are smaller than the pores existing on the inner surface, a dense layered portion considered to be involved in the fractionation characteristics is formed near the outer surface, and the other portions are compared with It is considered that a portion where a large pore is formed is formed. From this, it is considered that the hollow fiber membrane not only has excellent fractionation characteristics but also has excellent permeation performance.

  The resin contained in the hollow fiber membrane is not particularly limited as long as it can be used as a material for the hollow fiber membrane. The hollow fiber membrane may contain a hydrophilic resin. As described above, the hollow fiber membrane may be hydrophilic by containing a hydrophilic resin as the resin constituting the hollow fiber membrane. Examples of the hydrophilic resin include the resins described above, and examples include polyvinyl alcohol, polyethylene vinyl alcohol, and cellulose acetate. Further, as described above, the hollow fiber membrane may be rendered hydrophilic by a hydrophilization treatment, and in that case, other than a hydrophilic resin can be used. As the resin contained in the hollow fiber membrane, in addition to the hydrophilic resin, for example, a fluorine-based resin such as polyvinylidene fluoride resin such as polyvinylidene fluoride, a tetrafluoroethylene polymer, and an ethylene / chlorotrifluoroethylene copolymer. Examples thereof include resins, polymethyl methacryl, polymethyl acryl, polyurethane, and epoxy resins. As said resin, the resin of the said illustration may be used independently and may be used in combination of 2 or more type. Moreover, as said resin, a fluororesin is preferable and vinylidene fluoride resin is more preferable from a viewpoint that sufficient intensity | strength and the outstanding chemical resistance can be maintained among resin of the said illustration. The hollow fiber membrane has hydrophilicity as described above. From this, when the said hollow fiber membrane contains fluorine-type resins, such as a vinylidene fluoride type resin, since there exists a tendency for hydrophobicity to become high, it is preferable to give a hydrophilic treatment to a hollow fiber membrane. By performing the hydrophilization treatment in this way, even if a fluorine-based resin is used as the resin, hydrophilicity can be exhibited. Further, by including the fluorine-based resin, sufficient strength and excellent chemical resistance can be obtained. Can maintain sex.

  The vinylidene fluoride resin is not particularly limited as long as it is a vinylidene fluoride resin that can form a hollow fiber membrane. Specific examples of the vinylidene fluoride resin include a homopolymer of vinylidene fluoride, a vinylidene fluoride copolymer, and the like. The vinylidene fluoride copolymer is not particularly limited as long as it is a copolymer having a repeating unit based on vinylidene fluoride. Specific examples of the vinylidene fluoride copolymer include a copolymer of vinylidene fluoride and at least one selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, and trifluorochloroethylene. Examples include coalescence. As the vinylidene fluoride-based resin, among the above examples, polyvinylidene fluoride which is a homopolymer of vinylidene fluoride is preferable. Further, as the vinylidene fluoride resin, the above-exemplified resins may be used alone or in combination of two or more.

  The molecular weight of the resin contained in the hollow fiber membrane, for example, vinylidene fluoride-based resin, varies depending on the use of the hollow fiber membrane, but is, for example, 50,000 to 1,000,000 in weight average molecular weight. It is preferable. When the molecular weight is too small, the strength of the hollow fiber membrane tends to decrease. Moreover, when molecular weight is too large, there exists a tendency for the film forming property of a hollow fiber membrane to fall. In addition, when a hollow fiber membrane is used for water treatment that is exposed to chemical cleaning, the hollow fiber membrane is required to have higher performance, so that it has excellent strength, and in order to obtain a suitable hollow fiber membrane, It is required to have excellent film forming properties. For this reason, it is preferable that the weight average molecular weight of resin contained in a hollow fiber membrane, for example, a vinylidene fluoride resin, is 100,000-900,000, and it is more preferable that it is 150,000-800,000. .

  The shape of the hollow fiber membrane is not particularly limited. The hollow fiber membrane has a hollow fiber shape, and one side in the longitudinal direction may be open, and the other side may be open or closed. Examples of the shape of the hollow fiber membrane include a hollow fiber shape in which one side in the longitudinal direction is left open and the other side is closed. Moreover, as a shape of the open side of a hollow fiber membrane, the case where it is a shape as shown in FIG. 4, etc. are mentioned, for example. FIG. 4 is a partial perspective view of the hollow fiber membrane provided in the hollow fiber membrane module according to the embodiment of the present invention.

  The outer diameter R1 of the hollow fiber membrane is preferably 800 to 5000 μm (0.8 to 5 mm), more preferably 1000 to 2000 μm (1 to 2 mm), and 1000 to 1800 μm. More preferably, it is 1000-1600 micrometers. When the outer diameter of the hollow fiber membrane is too large, the number of hollow fiber membranes accommodated in the housing is not small, so the membrane area of the hollow fiber membrane is reduced, and a practically sufficient flow rate is secured as a hollow fiber membrane module. There is a tendency to not be able to. Moreover, when the outer diameter of the hollow fiber membrane is too small, the practical operation tends to be difficult, for example, the strength of the hollow fiber membrane is insufficient and the hollow fiber membrane is broken. If the outer diameter of the hollow fiber membrane is as described above, it is a suitable size as a hollow fiber membrane provided in an apparatus for realizing a separation technique using the hollow fiber membrane.

  Further, the inner diameter R2 of the hollow fiber membrane is preferably 500 to 3000 μm (0.5 to 3 mm), more preferably 600 to 1500 μm (0.6 to 1.5 mm), and 600 to 1100 μm. More preferably, it is particularly preferably 600 to 1000 μm. When the inner diameter of the hollow fiber membrane is too small, the permeate resistance (pressure loss in the tube) increases and the flow tends to be poor. That is, when realizing a high permeation flux, the pressure loss when passing through the hollow portion of the hollow fiber membrane is increased, which can be a factor of reducing the module permeability coefficient. Further, if the inner diameter of the hollow fiber membrane is too large, the shape of the hollow fiber membrane cannot be maintained, and the membrane tends to be crushed or distorted. That is, the hollow fiber membrane tends to be crushed by the filtration pressure, and problems such as breakage of the hollow fiber membrane tend to occur.

  The thickness T of the hollow fiber membrane is preferably 1000 to 150 μm, more preferably 400 to 150 μm, still more preferably 400 to 200 μm, and particularly preferably 350 to 200 μm. . When the hollow fiber membrane is too thin, deformation such as distortion tends to occur due to insufficient strength. On the other hand, if the film thickness is too thick, it is difficult to obtain a suitable film structure, for example, it is difficult to suppress the generation of macrovoids. In some cases, the strength may decrease.

  If the outer diameter R1, inner diameter R2, and film thickness T of the hollow fiber membrane are within the above ranges, respectively, the hollow fiber membrane has a suitable size as a hollow fiber membrane provided in a device that realizes a separation technique using a hollow fiber membrane. In addition, the apparatus can be miniaturized.

  The hollow fiber membrane provided in the hollow fiber membrane module preferably has an effective length of 0.3 to 2 m, more preferably 0.3 to 1.5 m, and more preferably 0.5 to 1 m. Further preferred. When the effective length of the hollow fiber membrane is too long, the resistance of the permeate (in-pipe pressure loss) increases and the flow tends to be poor. That is, when realizing a high permeation flux, the pressure loss when passing through the hollow portion of the hollow fiber membrane is increased, which can be a factor of reducing the module permeability coefficient. Moreover, when the effective length of the hollow fiber membrane is too short, even if the module permeability coefficient can be increased, there is a tendency that a practically sufficient flow rate cannot be secured as the hollow fiber membrane module.

  Moreover, the manufacturing method of the said hollow fiber membrane will not be specifically limited if the said hollow fiber membrane can be manufactured. Examples of the method for producing the hollow fiber membrane include a method for producing a porous hollow fiber membrane. As a method for producing such a porous hollow fiber membrane, a method utilizing phase separation is known. Examples of a method for producing a hollow fiber membrane utilizing this phase separation include a non-solvent induced phase separation method (NIPS method) and a thermally induced phase separation method (TIPS method). Can be mentioned.

  The NIPS method refers to a polymer stock solution solvent in which a uniform polymer stock solution in which a polymer is dissolved in a solvent is brought into contact with a non-solvent that does not dissolve the polymer, and the concentration difference between the polymer stock solution and the non-solvent is a driving force. This is a method of causing a phase separation phenomenon by substitution with a non-solvent. In the NIPS method, the pore diameter of the formed pores generally changes depending on the solvent exchange rate. Specifically, the slower the solvent exchange rate, the larger the pore size. In addition, in the production of the hollow fiber membrane, the solvent exchange rate is the fastest at the contact surface with the non-solvent, and becomes slower as it goes into the membrane. For this reason, the hollow fiber membrane produced by the NIPS method is dense in the vicinity of the contact surface with the non-solvent and has an asymmetric structure in which pores are gradually coarsened toward the inside of the membrane.

  In addition, the TIPS method means that a polymer can be dissolved at a high temperature but dissolved at a high temperature in a poor solvent that cannot be dissolved when the temperature is lowered, and the solution is cooled to cause a phase separation phenomenon. It is a method to make it. Since the heat exchange rate is generally faster than the solvent exchange rate in the NIPS method and it is difficult to control the rate, the TIPS method tends to form uniform pores in the film thickness direction.

  From the above, the method for producing the hollow fiber membrane is not particularly limited as long as the hollow fiber membrane can be produced, but a non-solvent induced phase separation method is preferable. Specifically, this manufacturing method includes the following manufacturing methods. As this production method, an extrusion step of extruding a membrane forming stock solution containing the resin constituting the hollow fiber membrane and a solvent into a hollow fiber shape, and contacting the extruded hollow fiber membrane forming stock solution with an external coagulation solution And a method of forming a hollow fiber membrane.

  Moreover, the film-forming stock solution used in the extrusion step in the production method according to this embodiment is not particularly limited as long as it is a film-forming stock solution that contains the resin and the solvent and can produce a hollow fiber membrane.

  The resin is a resin contained in the hollow fiber membrane. Moreover, the said solvent will not be specifically limited if it is a solvent which can dissolve the said resin at the time of preparation of a film-forming stock solution, or an extrusion process.

  Moreover, the said extrusion process will not be specifically limited if it is the process of extruding the said film forming undiluted | stock solution to hollow fiber shape. Examples of the extrusion step include a step of extruding the film-forming stock solution from a hollow fiber molding nozzle shown in FIG. FIG. 5 is a schematic view showing an example of a hollow fiber membrane molding nozzle used when manufacturing a hollow fiber membrane included in the hollow fiber membrane module according to the embodiment of the present invention. FIG. 5 (a) shows a cross-sectional view thereof, and FIG. 5 (b) is a plan view showing a discharge port side of a hollow fiber molding nozzle for discharging a film-forming stock solution. Specifically, the hollow fiber molding nozzle 21 here includes an annular outer discharge port 26 and a circular or annular inner discharge port 27 arranged inside the outer discharge port 26. The hollow fiber molding nozzle 21 is provided at the end of the flow pipe 24 through which the film-forming stock solution is circulated, and the film-forming stock solution flowing in the flow pipe 24 is discharged outside through the flow path 22 in the nozzle. Discharge from the outlet 26. In addition, the hollow fiber molding nozzle 21 causes the internal coagulating liquid to flow through the flow pipe 25 at the same time as the film-forming stock solution is discharged from the outer discharge port 26, and passes through the flow path 23 in the nozzle. Discharge from the outlet 27. By doing so, the hollow fiber-shaped film-forming stock solution extruded from the hollow fiber molding nozzle 21 is brought into contact with the internal coagulation liquid.

  Moreover, the formation process in the manufacturing method which concerns on this embodiment will not be specifically limited if it is the process of making the extruded hollow fiber-shaped membrane forming undiluted solution contact an external coagulation liquid, and forming a hollow fiber membrane. Specific examples of the forming step include a step of immersing the hollow fiber-shaped film-forming stock solution extruded in the extrusion step in an external coagulation solution stored in an external coagulation bath.

  Moreover, the hollow fiber membrane module which concerns on this embodiment can perform a liquid process, specifically, a filtration process, by using for a membrane filtration method. Specifically, the liquid treatment method using the hollow fiber membrane module includes a filtration step of filtering a liquid to be treated using the hollow fiber membrane provided in the hollow fiber membrane module, and the hollow fiber membrane module. And a backwashing process for backwashing the hollow fiber membrane to be obtained, and the filtration process and the backwashing process are alternately performed. And as this method, for example, the backwashing step supplies a gas such as compressed air or a liquid such as a filtrate to the secondary side in the filtration step, so that the gas permeated through the hollow fiber membrane or The hollow fiber membrane is washed with a liquid. Further, during or after the cleaning, air may be introduced from the introduction port 35 in FIG. 1 to generate bubbles on the hollow fiber membrane or the like, and scrubbing cleaning with the bubbles may be performed.

  The filtration step is not particularly limited as long as it is a filtration using the hollow fiber membrane. In this filtration step, the liquid to be treated to be filtered is not particularly limited. Examples of the liquid to be treated include raw water such as river surface water and industrial water. The raw water preferably has a turbidity of 1.0 NTU or more. In addition, the liquid to be treated may contain an aggregating agent such as polyaluminum chloride, sulfuric acid band (aluminum sulfate), and iron chloride. When the raw water with high turbidity as described above is filtered as the liquid to be treated, the occurrence of fouling tends to become more prominent. Even if raw water having such a tendency is used, if it is treated using the hollow fiber membrane module according to the present embodiment, excellent permeation performance can be maintained over a long period of time.

  The permeation flux in the filtration step is preferably 5 to 40 m / day, more preferably 5 to 30 m / day, and even more preferably 5 to 20 m / day. When the permeation flux is too low, the hollow fiber membrane module tends not to have a sufficient cost-saving effect such as space saving by improving the permeation flux. On the other hand, when the permeation flux is too high, the transmembrane pressure difference is increased, and the fouling suppression effect tends not to be sufficiently obtained.

  Moreover, it is preferable that the transmembrane differential pressure in the said filtration process is 10-80 kPa, It is more preferable that it is 10-60 kPa, It is further more preferable that it is 10-50 kPa. When the transmembrane pressure difference is too low, there is a tendency that a practically sufficient flow rate cannot be secured as a hollow fiber membrane module. Moreover, when the transmembrane pressure difference is too high, there is a tendency that a fouling suppressing effect cannot be obtained sufficiently.

  The backwashing step is not particularly limited, but backwashing using the following gas is preferable. Specifically, in the hollow fiber membrane module as shown in FIG. 1, compressed air is supplied from the outlet port 36, and air is supplied to each hollow fiber membrane 32 constituting the hollow fiber membrane module 30. After the turbid components are peeled off, air is supplied from the inlet 35 to perform scrubbing cleaning. By doing so, each hollow fiber membrane 32 which comprises the hollow fiber membrane module 30 is backwashed.

  If it is such a liquid processing method, the liquid processing by the filtration process using a hollow fiber membrane can be performed suitably over a long period of time. Specifically, first, an excellent washing efficiency can be exhibited in a backwashing step performed between the filtration step and the filtration step. For this reason, the fall of the filtration efficiency in the filtration process using a hollow fiber membrane can fully be suppressed by performing such a backwashing process regularly between a filtration process and a filtration process. Therefore, the liquid process by the filtration process using a hollow fiber membrane can be suitably performed over a long period of time.

  The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is not limited to these examples.

[Example 1]
First, as a resin constituting the hollow fiber membrane, polyvinylidene fluoride (hereinafter, may be abbreviated as PVDF) which is a vinylidene fluoride resin (Kynar 741 manufactured by Arkema Co., Ltd.) and γ-butyrolactone (Mitsubishi) as a solvent. GBL manufactured by Kagaku Co., Ltd., and polyvinyl pyrrolidone, which is a polyvinyl pyrrolidone-based resin (Socaran K-90P manufactured by BASF Japan Ltd.), as a phase separation accelerator, are mixed so as to have a mass ratio of 25:62:13. Was prepared.

  A film-forming stock solution obtained by dissolving the above mixture in a dissolution tank at a constant temperature of 95 ° C. is a nozzle having a double ring structure having an outer diameter of 1.6 mm and an inner diameter of 0.8 mm as shown in FIG. Extruded from a hollow fiber membrane forming nozzle). At this time, as an internal coagulating liquid, a mixture of γ-butyrolactone (GBL manufactured by Mitsubishi Chemical Corporation) and glycerin (purified glycerin manufactured by Kao Corporation) so as to have a mass ratio of 15:85 Were discharged at the same time.

  The film-forming stock solution extruded together with the internal coagulation liquid was immersed in an external coagulation liquid composed of an aqueous solution containing 18% by mass of sodium sulfate through an idle running distance of 30 mm. By doing so, the membrane-forming stock solution was solidified, and a hollow fiber membrane was obtained.

  Next, the obtained hollow fiber membrane was washed after being stretched and contracted. By doing so, the solvent (γ-butyrolactone) and the phase separation accelerator (polyvinylpyrrolidone) are extracted and removed from the hollow fiber membrane. Thereafter, the obtained hollow fiber membrane was subjected to a hydrophilic treatment. Specifically, the obtained hollow fiber membrane was immersed in a 0.5 mass% aqueous solution of polyvinyl alcohol (PVA-505 manufactured by Kuraray Co., Ltd.). Thereafter, the hollow fiber membrane immersed in the aqueous polyvinyl alcohol solution was immersed in an aqueous solution containing 1% by mass of glutaraldehyde and 4% by mass of sulfuric acid. The water permeability in a wet state and the water permeability in a dry state of the hollow fiber membrane subjected to the hydrophilization treatment as described above were measured by the above methods. As a result, the ratio of the water permeability (dry water permeability) in the dry state (dry water permeability / wet water permeability) to the water permeability (wet water permeability) in the wet state was 85%. From this, it was found that the obtained hollow fiber membrane has hydrophilicity. The dry water permeability is the water permeability of the hollow fiber membrane in a dry state at a transmembrane differential pressure of 100 kPa, and the wet water permeability is the water permeability of the hollow fiber membrane in a wet state at a transmembrane differential pressure of 100 kPa. is there.

The hollow fiber membrane thus obtained had an outer diameter of 1 mm, an inner diameter of 0.6 mm, and a film thickness of 0.2 mm. The hollow fiber membrane has a pure water permeation amount (measured using a hollow fiber membrane having a length of 20 cm) at 5000 LMH (5000 L / m ² / hour) at a transmembrane differential pressure of 0.1 MPa. there were.

  Moreover, the fraction particle diameter of the obtained hollow fiber membrane was measured by the following method.

  At least two kinds of particles having different particle diameters (cataloid SI-550, cataloid SI-45P, cataloid SI-80P, manufactured by JGC Catalysts & Chemicals, Inc., particle diameters 0.1 μm, 0.2 μm, manufactured by Dow Chemical Co., Ltd. , 0.5 μm polystyrene latex, etc.) was measured, and based on the measured value, the value of S at which R was 90 was determined in the following approximate formula, and this was taken as the fractional particle size.

R = 100 / (1−m × exp (−a × log (S)))
“A” and “m” in the above formula are constants determined by the hollow fiber membrane, and are calculated based on measured values of two or more types of rejection.

  The fractional particle size obtained by this measurement method was 0.1 μm.

  Moreover, the membrane structure of the hollow fiber membrane which concerns on Example 1 was confirmed using the scanning electron microscope (S-3000N by Hitachi, Ltd.). The results are shown in FIGS.

  First, FIG. 6 is a view showing a scanning electron micrograph of a cross section of the hollow fiber membrane according to Example 1. FIG. Moreover, FIG. 7 is a figure which shows the scanning electron micrograph of the outer peripheral surface of the hollow fiber membrane which concerns on Example 1. FIG. Moreover, FIG. 8 is a figure which shows the scanning electron micrograph of the internal peripheral surface of the hollow fiber membrane which concerns on Example 1. FIG.

  From FIG. 6, it was found that a dense layered portion was formed in the vicinity of the outer peripheral surface, and a sparser portion was formed in the other portions. That is, it was found that this hollow fiber membrane has an inclined structure that gradually decreases from the inner surface toward the outer surface so that the holes existing on the outer surface are smaller than the holes existing on the inner surface. .

  Further, a hollow fiber membrane module as shown in FIG. 1 was produced using this hollow fiber membrane. The hollow fiber membrane provided in the hollow fiber membrane module had a lower end sealed with an epoxy resin and an upper end opened in the hollow portion. The hollow fiber membrane had an effective length of 1 m. The casing of the hollow fiber membrane module had an inner diameter of 20 cm. And this hollow fiber membrane was accommodated in the housing | casing of the hollow fiber membrane module so that a filling rate might be 40%, and the concrete number was about 16000.

  When pure water was filtered using the hollow fiber membrane module thus obtained, the transmembrane pressure difference was 20 kPa and the permeation flux was 6.5 m / day. The module permeability coefficient was 0.325 m / day / kPa. Table 1 shows values such as the module permeability coefficient and the fractional particle size.

(Evaluation)
The obtained hollow fiber membrane module was evaluated as follows. The results are shown in Table 1.

Hollow obtained by using, as a liquid to be treated, a liquid obtained by adding polyaluminum chloride as a flocculant to a river water having a turbidity of 2.0 NTU (manufactured by HACH: 2100Q) at a concentration of 1 mg / L in terms of aluminum The liquid to be treated was filtered with a thread membrane module. That is, a filtrate was obtained from the outlet of the hollow fiber membrane module. After filtration for 10 minutes at a set flow rate of 8 m / day (the set flow rate (m / day) is a value obtained by dividing the filtration flow rate (m ³ / day) by the hollow fiber membrane area (m ² )), the flow rate is reduced to 0. Air was supplied to the hollow fiber membrane with compressed air of 2 MPa for 10 seconds to separate turbid components. Thereafter, air scrubbing was performed with compressed air of 0.1 MPa from the inlet at the bottom of the module for 60 seconds to clean the membrane dirt (the inlet air outlet was secured by opening the air outlet). The washed dirt was extracted from the inlet and filtration was started again.

  The rate of increase in the transmembrane pressure difference when such a cycle was continued for 10 days was 0.3 kPa or less per 24 hours of operation time. That is, the rate of increase in the transmembrane pressure difference was 0.3 kPa / day or less. From this, it was found that the fouling suppressing effect is excellent.

In such filtration, the initial permeate flow rate (initial permeate flow rate) at a transmembrane pressure difference of 20 kPa was 13.6 m ³ / hour per hollow fiber module. Moreover, the transmembrane differential pressure (transmembrane differential pressure at the time of a to-be-processed liquid filtration) at the time of filtering a to-be-processed liquid with the permeation | transmission flow rate of 20 m < ³ > / hr was 29 kPa.

  Moreover, the disinfection performance of the obtained hollow fiber membrane was measured by the following method.

First, Brevundimonas diminuta (NBRC14213) was cultured so that the number of bacteria was 1 × 10 ³ to 2 × 10 ⁴ . The bacterial solution thus obtained was filtered as an object to be treated with a module as described above in which one end of the hollow fiber membrane was sealed so that the flow rate was 1 L / min or less. And the number of bacteria of the obtained filtrate was investigated.

  When the hollow fiber membrane according to Example 1 is used. It was found that the number of bacteria in the obtained filtrate was 0, indicating excellent sterilization performance.

[Examples 2-6, Comparative Examples 1-7]
The hollow fiber membrane modules according to Examples 2 to 6 and Comparative Examples 1 to 7 were manufactured at the time of producing the hollow fiber membranes so that the numerical values such as the module permeability coefficient and the fractional particle diameter were as shown in Table 1. The same as Example 1, except that the conditions and the filling rate in the hollow fiber membrane module were changed.

  Moreover, the hollow fiber membrane module which concerns on each Example and a comparative example evaluated similarly to Example 1. FIG. The results are shown in Table 1. If the hollow fiber membrane can confirm the inclined structure as described above, the column of the inclined structure indicates “Yes” and the inclined structure as described above cannot be confirmed. For example, the pore diameter is the thickness of the hollow fiber membrane. In the case of almost the same homogeneous structure regardless of the position in the direction, “None” is indicated. In addition, if the increase rate of the transmembrane pressure difference when the above cycle is continued for 10 days is 0.3 kPa / day or less, “◯” is indicated, and this increase rate exceeds 0.3 kPa / day. If there is, “x” is shown.

From Table 1, it is a hollow fiber membrane module provided with the hollow fiber membrane whose fraction particle diameter is 0.001-0.5 micrometer, Comprising: Module permeability coefficient is 0.2-1.5 m / day / kPa. When a certain hollow fiber membrane module is used (Examples 1 to 6), even when the liquid to be treated is continuously filtered for 10 days under the above conditions, an obvious increase in transmembrane pressure difference is confirmed. There wasn't. That is, when the hollow fiber membrane module according to Examples 1 to 6 is used, the increase in the transmembrane pressure difference is sufficiently suppressed as compared with the case where the hollow fiber membrane module according to Comparative Examples 1 to 6 is used. I found out. From this, it was found that the fouling suppressing effect is excellent.

  Moreover, it turns out that the hollow fiber membrane with which the hollow fiber membrane module which concerns on Examples 1-6 was equipped was excellent also in the fractionation characteristic from the fraction particle diameter being small as mentioned above. On the other hand, since the hollow fiber membrane provided in the hollow fiber membrane module according to Comparative Example 7 has a large fractional particle diameter of 1 μm, the fractionation characteristics are not sufficiently excellent.

  From the above, it was found that the hollow fiber membrane modules according to Examples 1 to 6 are not only excellent in fractionation characteristics but also a hollow fiber membrane module that can maintain excellent permeation performance over a long period of time.

21 hollow fiber molding nozzle 22, 23 flow path 24, 25 flow pipe 26 outer discharge port 27 inner discharge port 30, 40 hollow fiber membrane module 31, 41 housing 32, 42 hollow fiber membrane 33, 43 upper end portion 34, 44 Lower end 35,45 Inlet 36,46 Outlet 37 Air vent

Claims (3)

A hollow fiber membrane module in which a plurality of hollow fiber membranes are housed in a housing,
The hollow fiber membrane is a fractionation particle diameter 0.02 - 0.2 [mu] m, an effective length 0.3～2M, permeation amount of pure water at the transmembrane pressure 0.1MPa is 4000 to 13000 L / m ² / hour,
The casing has an inner diameter of 10 to 200 cm and a height of 0.3 to 3 m.
The ratio of the total cross-sectional area of the plurality of hollow fiber membranes to the area of the cross section perpendicular to the longitudinal direction of the hollow fiber membranes in the housing is 10 to 65%,
A hollow fiber membrane module characterized in that a value obtained by dividing a permeation flux when pure water permeates through the hollow fiber membrane module by a transmembrane differential pressure is 0.2 to 1.5 m / day / kPa. . The outer diameter of the hollow fiber membrane is 0.8 to 5 mm,
The hollow fiber membrane module according to claim 1, wherein an inner diameter of the hollow fiber membrane is 0.5 to 3 mm.   The hollow fiber membrane module according to claim 1 or 2, wherein the hollow fiber membrane contains a vinylidene fluoride resin, is hydrophilic, and has pores present on the outer surface smaller than pores present on the inner surface.