JP2023182366A - Operational method of volatile solute removal device - Google Patents

Abstract

To provide an operational method of a volatile solute removal device, in which both of precipitation of a scale into a surface of a hollow yarn membrane and pressure loss are suppressed in the volatile solute removal device that uses the hollow yarn membrane as a membrane for a membrane contactor.SOLUTION: In an operation method of a volatile solute removal device 1000 for removing volatile solutes from treated water containing both of the volatile solutes and nonvolatile solutes using a membrane contactor 100, a membrane that is used for the membrane contactor 100 is a hollow yarn membrane, and the volatile solutes are removed by distributing treated water to the inside of the hollow yarn membrane, where Reynolds number of the treated water being distributed through the hollow yarn membrane is set to be 1,100 or more and a linear velocity of the treated water being distributed through the hollow yarn membrane is set to be 3.5 m/s or lower.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method of operating a volatile solute removal device using a hollow fiber membrane contactor. Specifically, in a volatile solute removal device that uses a hollow fiber membrane as a membrane contactor, it is possible to suppress the precipitation of scale on the membrane surface of the membrane contactor caused by nonvolatile solutes contained in the water to be treated, and to suppress pressure loss. The present invention relates to an operating method that is compatible with both the above and is capable of efficiently removing volatile solutes.

The volatile solute removal method using a membrane contactor (hereinafter referred to as the membrane contactor method) involves bringing treated water containing volatile solutes into contact with a membrane, and using the vapor pressure difference on both sides of the volatile solute membrane as a driving force, the volatile solutes in the water to be treated are removed. This is a method in which sexual solutes are selectively permeated through a membrane and removed. Methods of obtaining a vapor pressure difference on both sides of a volatile solute membrane include, for example, placing an absorbing liquid on the permeate side to create a temperature or concentration difference between the water to be treated and the absorbing liquid, and reducing the pressure on the permeate side. Examples include methods for making the state. Furthermore, when the volatile solute is a reactive solute or an acidic or basic solute, a method is also known in which the vapor pressure of the volatile solute is lowered by using an absorption liquid that reacts with the volatile solute.
Compared to stripping methods, vacuum degassing methods, etc., the membrane contactor method uses a membrane to increase the area of the gas-liquid interface, making it possible to improve processing speed and make the equipment more compact. This is an advantage.

A problem when handling highly concentrated water to be treated using the membrane contactor method is the precipitation of scale on the membrane surface. When scale precipitates and covers the membrane surface, it causes clogging of the membrane pores, impeding the movement of volatile solutes, and significantly reducing removal performance. Furthermore, when the membrane surface becomes hydrophilic due to scale, the water to be treated tends to enter the permeate side, resulting in a decrease in the stability of the separation performance of the membrane contactor.

In recent years, fluid-dynamic considerations regarding membrane-based technologies have been actively pursued.
For example, in Non-Patent Document 1, a model experiment using a membrane distillation system using a DCMD (Direct Contact Membrane Distillation) method using a flat membrane made of PVDF (polyvinylidene fluoride) was conducted to investigate scale precipitation on the membrane and Reynolds reduction of the liquid to be treated. A report was made on the relationship with numbers.
Furthermore, in Non-Patent Document 2, consideration is made based on Leveque theory using a model membrane of a membrane oxygenator.

Journal of Membrane Science 346 (2010) 263-269 Journal of chemical engineering of Japan, 18, (1985) 550-555

The teaching of Non-Patent Document 1 above is a discussion on membrane distillation using a flat membrane-like membrane for membrane distillation, and the discussion of Non-Patent Document 2 is regarding a model membrane having a symmetrical wavy wall. It is not directly applicable to a volatile solute removal device using a thread membrane.
An object of the present invention is to provide an operating method for a volatile solute removal device that uses a hollow fiber membrane as a membrane for a membrane contactor, in which both scale precipitation on the membrane surface and pressure loss are suppressed. It is to provide.

The present invention is as follows.
<Aspect 1> A method of operating a volatile solute removal device for removing volatile solutes from treated water containing both volatile and non-volatile solutes using a membrane contactor, the method comprising:
The membrane used in the membrane contactor is a hollow fiber membrane, and the water to be treated is passed inside the hollow fiber membrane to remove volatile solutes,
The Reynolds number of the water to be treated flowing inside the hollow fiber membrane is 1,100 or more, and
The linear velocity of the water to be treated flowing inside the hollow fiber membrane is 3.5 m/s or less,
how to drive.
<Aspect 2> The operating method according to aspect 1, wherein the Reynolds number of the water to be treated flowing inside the hollow fiber membrane is 7,000 or less.
<Aspect 3> The operating method according to aspect 2, wherein the Reynolds number of the water to be treated flowing inside the hollow fiber membrane is 2,300 or less.
<Aspect 4> The operating method according to any one of aspects 1 to 3, wherein the linear velocity of the water to be treated flowing inside the hollow fiber membrane is 0.4 m/s or more and 2.0 m/s or less.
<<Aspect 5>> The absorption liquid of the volatile solute is passed through the outside of the hollow fiber membrane, and the water to be treated and the absorption liquid are brought into contact with each other through the hollow fiber membrane, and the The operating method according to any one of aspects 1 to 4, wherein the volatile solute is removed from the water to be treated by moving the volatile solute.
<Aspect 6> The operating method according to any one of aspects 1 to 4, wherein the outside of the hollow fiber membrane is reduced in pressure.
<Aspect 7> The operating method according to any one of aspects 1 to 6, wherein the hollow fiber membrane is hydrophobic.
<Aspect 8> The volatile solute according to any one of aspects 1 to 7, wherein the volatile solute contains one or more selected from ammonia, hydrochloric acid, carbonic acid, acetic acid, alcohols, and acetonitrile. how to drive.
<Aspect 9> The volatile solute contains one or more selected from ammonia, hydrochloric acid, carbonic acid, acetic acid, alcohols, and acetonitrile, and
When the volatile solute contains ammonia, the absorption liquid is an aqueous acid solution,
When the volatile solute contains one or more selected from hydrochloric acid, carbonic acid, and acetic acid, the absorption liquid is an aqueous solution of a base,
When the volatile solute contains one or more selected from alcohols and acetonitrile, the absorption liquid is water.
The operating method according to aspect 5.
<Aspect 10> The nonvolatile solute is selected from amino acids, peptides, proteins, protein preparations, sugars, vaccines, nucleic acids, antibiotics, vitamins, surfactants, antibody drug conjugates (ADCs), and inorganic salts. The operating method according to any one of aspects 1 to 9, comprising one or more species.
<Aspect 11> The operating method according to any one of aspects 1 to 10, wherein the hollow fiber membrane is a hollow fiber in a membrane module having a hollow fiber bundle constituted by a plurality of hollow fiber membranes.

According to the operating method of a volatile solute removal device of the present invention, when volatile solutes are removed from treated water containing a large amount of scale-causing substances in a volatile solute removal device using a membrane contactor method using a hollow fiber membrane, Even in this case, both scale precipitation on the membrane surface and pressure loss are suppressed. Therefore, according to the operating method of the present invention, it is possible to operate the volatile solute removal device stably with high efficiency over a long period of time.

FIG. 1 is a schematic cross-sectional view for explaining an example of the structure of a membrane module for a membrane contactor applied to the method of the present invention. FIG. 2 is a schematic cross-sectional view for explaining another example of the structure of a membrane module for a membrane contactor applied to the method of the present invention. FIG. 3 is a schematic diagram for explaining an example of the structure of a volatile solute removal device to which the method of the present invention is preferably applied. FIG. 4 is a schematic diagram for explaining another example of the structure of a volatile solute removal device to which the method of the present invention is preferably applied. FIG. 5 is a schematic diagram for explaining the configuration of an apparatus used in Examples to measure the pressure drop of a membrane module for a membrane contactor. FIG. 6 is a graph showing the relationship between the linear velocity of the water to be treated and the pressure drop, and a graph showing the relationship between the Reynolds number and the pressure drop in Example 1. FIG. 7 is a schematic diagram showing the structure of a cleaning device used in Examples for washing out scale deposited on the surface of the hollow fiber membrane. FIG. 8 is a graph showing the relationship between the linear velocity of the water to be treated and the pressure drop, and a graph showing the relationship between the Reynolds number and the pressure drop in Example 2.

Hereinafter, preferred embodiments of the present invention will be specifically described as non-limiting examples.
The present invention
A method of operating a volatile solute removal device for removing volatile solutes from treated water containing both non-volatile solutes and volatile solutes using a membrane contactor, wherein the membrane used in the membrane contactor is a hollow fiber. a membrane, in which volatile solutes are removed by circulating the water to be treated inside the hollow fiber membrane;
The Reynolds number of the water to be treated flowing inside the hollow fiber membrane is 1,100 or more, and
The linear velocity of the water to be treated flowing inside the hollow fiber membrane is 3.5 m/s or less,
Regarding driving methods.

《Mechanism of action of the present invention》
In the operating method of the volatile solute removal device of the present invention, a hollow fiber membrane is used as the membrane for the membrane contactor, and when the volatile solute is removed by circulating the water to be treated inside the hollow fiber membrane, the hollow fiber membrane is By setting the Reynolds number and linear velocity of the water to be treated flowing inside the membrane within the above ranges, scale precipitation on the membrane surface is suppressed, and at the same time, pressure loss is also suppressed.
The reason why this effect appears is presumed as follows.
However, the present invention is not bound to any particular theory.

<Suppression of scale precipitation>
The water to be treated of the present invention often contains a large amount of scale components. In that case, when the concentration of scale components in the water to be treated exceeds the saturated solubility, the scale components will precipitate on the surface of the hollow fiber membrane.
The ease with which the scale component is precipitated is determined by the concentration polarization coefficient (CPC) of the scale component, which is expressed by the following formula (1).

{In formula (1), C _{m, f} is the nonvolatile solute concentration (wt%) on the membrane surface, C _{b, f} is the nonvolatile solute concentration (wt%) in the entire water to be treated, and J _w is is the water vapor flux (kg/m ² h) in the membrane, ρ is the solution density (kg/m ³ ) of the water to be treated, and k is the mass transfer coefficient when nonvolatile solutes diffuse through the membrane ( m/s). }

Equation (1) shows that the larger the water vapor flux _Jw of the membrane, the larger the CPC, and the easier it is for scale to precipitate. Further, the mass transfer coefficient k is expressed by the following formula (2).
k=D/δ (2)
{In formula (2), D is the diffusion coefficient of the nonvolatile solute (m ² /s), and δ is the thickness of the boundary film (m). }
By substituting equation (2) into equation (1), it is understood that as the thickness δ of the film becomes thinner, the CPC becomes smaller and it becomes difficult for scale to precipitate.
Furthermore, the membrane thickness δ can be calculated from the following formulas (3) to (5).

{In the above formulas (3) to (5), D is the diffusion coefficient of the nonvolatile solute (m ² /s), and k is the mass transfer coefficient (m/s) when the nonvolatile solute diffuses in the boundary film. ), d _h is the hydraulic diameter (m), d is the inner diameter of the hollow fiber membrane (m), Sh is the Sherwood number (dimensionless number), Re is the Reynolds number, and Sc is the Schmidt number. l is the flow path length (m), a ₁ , a ₂ , a ₃ , and a ₄ are constants determined by experiments, and μ is the viscosity of the water to be treated (Pa・s ). }
In the present invention, the hydraulic diameter d _h (m) is equal to the inner diameter d (m) of the hollow fiber membrane.

From equations (3) to (5), it is understood that the film thickness δ is inversely proportional to the Reynolds number Re. Therefore, it is understood that the larger the Reynolds number Re, the thinner the film thickness δ, the smaller the CPC, and the more difficult it is for scale to precipitate.
In the present invention, by setting the Reynolds number Re to 1,100 or more, even when the water vapor pressure difference is large and the water vapor flux _Jw of the membrane is large, the CPC is sufficiently small, so that volatile solute removal is possible. Scale precipitation is suppressed to the extent that it can be carried out stably.
It should be noted that the above formula takes into account the contributions of the hydraulic diameter d _h , which is equal to the inner diameter of the hollow fiber membrane, and the membrane thickness δ, so the Reynolds number Re in the present invention is determined based on the hollow fiber used. This is valid regardless of the size of the membrane.

From the above-mentioned viewpoint, the Reynolds number Re in the present invention is 1,100 or more, preferably 1,500 or more, and may be 2,000 or more or 2,300 or more. On the other hand, the advantage of excessively increasing the Reynolds number Re is small, and if the Reynolds number is set too high, there are concerns about the efficiency or stability of volatile solute removal. From this point of view, the Reynolds number Re in the present invention is preferably 7,000 or less, more preferably 6,000 or less, still more preferably 5,000 or less, particularly 4,000 or less, It may be 3,000 or less, 2,300 or less, or 2,000 or less.

<Suppression of pressure loss>
On the other hand, the pressure loss ΔP (Pa) of the water to be treated is determined by the following equation (6).
{In formula (6), f is the friction coefficient, ρ is the solution density (kg/m ³ ) of the water to be treated, ν is the linear velocity (m/s) of the water to be treated, and L is the hollow fiber It is the length (m) of the membrane, and d is the inner diameter (m) of the hollow fiber membrane. }
When the hollow fiber membrane is in the form of a membrane contactor module and a part of the hollow fiber membrane is embedded in the adhesive resin layer, the length of the hollow fiber membrane L in the above formula (6) is as follows: It also includes a portion embedded in the adhesive resin layer.
The friction coefficient f differs between the friction coefficient F _l when the flow is laminar and the friction coefficient F _t when the flow is turbulent. The pressure loss ΔP _l (Pa) of the water to be treated and the pressure loss ΔP _t (Pa) of the water to be treated in the case of turbulence are expressed by the following equations (7) and (8), respectively.
{The symbols in formulas (7) and (8) have the same meanings as the same symbols in the previous formulas. }

From equations (7) and (8), it is understood that the smaller the linear velocity ν of the water to be treated, the smaller the pressure loss of the water to be treated, regardless of whether the flow is laminar or turbulent. Ru.
In the present invention, by setting the linear velocity ν of the water to be treated to 3.5 m/s or less, pressure loss can be reduced to the extent that volatile solute removal can be performed with high efficiency.
According to general fluid mechanics theory, if the Reynolds number Re is approximately 2,300 or less, the flow will be laminar, and if the Reynolds number Re exceeds approximately 2,300, the flow will be turbulent. Theory has been constructed as a model that differentiates laminar flow and turbulent flow.
However, in the present invention, regardless of whether the flow is laminar or turbulent, the pressure loss of the water to be treated can be reduced by setting the linear velocity ν of the water to be treated within the range specified by the present invention. It can be controlled.

From the above point of view, the linear velocity ν of the water to be treated in the present invention is 3.5 m/s or less, preferably 3.0 m/s or less, more preferably 2.5 m/s or less, and It is preferably 2.0 m/s or less, and may particularly be 1.6 m/s or less, 1.0 m/s or less, or 0.8 m/s or less.
On the other hand, from the viewpoint of increasing the efficiency of volatile solute removal, the linear velocity ν of the water to be treated is preferably 0.4 m/s or more, more preferably 0.5 m/s or more, and still more preferably 0.4 m/s or more. It is preferably 7 m/s or more, particularly preferably 1.0 m/s or more.

《Transmembrane pressure differential》
According to the method of the present invention, pressure loss is suppressed. As a result, the transmembrane pressure difference between the inside and outside of the hollow fiber membrane can be lowered, and the water to be treated is prevented from directly passing through the membrane wall of the hollow fiber membrane.
According to the method of the present invention, the transmembrane pressure difference at the inlet of the water to be treated in the hollow fiber membrane can be set to 450 kPa or less, and can also be set to 390 kPa or less or 150 kPa or less.

《Water vapor flux》
When removing volatile solutes by the method of the present invention, from the viewpoint of suppressing scale precipitation, etc., it is preferable that the water vapor flux moving from the liquid to be treated via the hollow fiber membrane is 10 kg/m ² ·h or less. , more preferably 8 kg/m ² ·h or less, still more preferably 4 kg/m ² ·h or less.
The water vapor flux J _w is expressed by the following formula (9).
{In formula (9), Wp is the mass (kg) of water that evaporated from the water to be treated and moved through the hollow fiber membrane, A is the effective area (m ² ) of the hollow fiber membrane, and T is the operating time (h). }

《Volatile solute removal device》
In the volatile solute removal performed by the volatile solute removal apparatus of the present invention, a membrane contactor whose membrane is a hollow fiber membrane is used, and the water to be treated is made to flow inside the hollow fiber membrane. Preferably, the volatile solute in the liquid to be treated is removed by creating a vapor pressure difference between the volatile solute inside and outside the hollow fiber membrane using one of the following methods.
A method in which a volatile solute absorption liquid is passed around the outside of a hollow fiber membrane. As a result, the water to be treated and the absorption liquid come into contact with each other through the hollow fiber membrane, creating a vapor pressure difference between the volatile solutes inside and outside the hollow fiber membrane, and moving the volatile solutes into the absorption liquid. Volatile solutes are removed from the treated water.
A method of reducing pressure on the outside of a hollow fiber membrane. This creates a vapor pressure difference between the volatile solutes inside and outside the hollow fiber membrane, and moves the volatile solutes to the outer space of the hollow fiber membranes, thereby removing the volatile solutes from the water to be treated.

<Membrane for membrane contactor>
The hollow fiber membrane in the present invention is preferably composed of a hydrophobic porous membrane.
The membrane for a membrane contactor used in the present invention may be a hollow fiber membrane made of a highly hydrophobic and porous material. Although this hollow fiber membrane is porous, liquid water does not penetrate into the membrane wall, and only one or both of volatile solutes and water vapor can pass through the membrane wall. It is preferable.

In order to meet these requirements, the water contact angle on the hollow fiber membrane surface is preferably 90° or more, more preferably more than 90°, and more preferably 100° or more, from the viewpoint of avoiding membrane wetting. More preferably, the angle may be 110° or more or 120° or more. Although there is no upper limit to the water contact angle of the hollow fiber membrane in relation to the effects of the present invention, it may actually be 150° or less. The hollow fiber membrane preferably exhibits such a water contact angle on at least one surface, preferably both surfaces.
The water contact angle in this specification is a value measured by a droplet method according to JIS R 3257. Specifically, 2 μL of pure water is dropped onto the surface of the object to be measured, and the angle formed by the object to be measured and the droplet is quantified by analyzing the projected image.
The membrane for a membrane contactor used in the present invention preferably exhibits a water contact angle within the above range in substantially all regions of at least one surface.

The hydrophobicity of a hollow fiber membrane can also be estimated by measuring the liquid entry pressure of water into the membrane wall of the hollow fiber membrane. The liquid intrusion pressure with respect to the water to be treated is preferably 0.1 MPa or more and 2.0 MPa or less, more preferably 0.2 MPa or more and 1.5 MPa or less.

The membrane wall of the hollow fiber membrane is porous and has pores (communicating pores) that communicate in the thickness direction from one surface of the membrane to the other surface. The pores may be voids in the network of the membrane material (eg, polymer) and may be branched or straight pores. The pores may be permeable to vapor but impermeable to liquid.
The average pore diameter of the pores of the hollow fiber membrane is preferably 0.02 μm or more and 0.5 μm or less, more preferably 0.03 μm or more and 0.4 μm or less, and 0.1 μm or more and 0.3 μm or less. More preferably. When the average pore diameter is 0.02 μm or more, the water vapor permeation resistance does not become too large, and the water vapor generated from the water to be treated permeates quickly. When the average pore diameter is 0.5 μm or less, the effect of suppressing wetting of the membrane is good. The average pore diameter of the hollow fiber membrane is a value measured by a half-dry method in accordance with ASTM: F316-86.
Further, from the viewpoint of achieving both vapor permeability and wetting suppression, it is preferable that the pore size distribution of the hollow fiber membrane is narrow. Specifically, the pore size distribution, which is the ratio of the maximum pore size to the average pore size, is preferably within the range of 1.2 to 2.5, more preferably within the range of 1.2 to 2.0. The maximum pore diameter is a value measured using the bubble point method.

The porosity of the hollow fiber membrane is preferably in the range of 60% or more and 90% or less from the viewpoint of achieving both high vapor permeability and long-term durability. In order to obtain high vapor permeability, the porosity of the porous hollow fiber membrane is preferably 60% or more, more preferably 70% or more. From the viewpoint of maintaining the strength of the membrane itself well and making it difficult to cause problems such as breakage during long-term use, the porosity of the porous hollow fiber membrane is preferably 90% or less, more preferably It is 85% or less, more preferably 70% or less.
The above porosity is a value calculated from the true specific gravity and apparent specific gravity of the material constituting the hollow fiber membrane.

From the viewpoint of efficient volatile solute removal, the surface aperture ratio of the hollow fiber membrane is preferably 15% or more, more preferably 18% or more, and still more preferably 20% or more on both surfaces of the hollow fiber membrane. % or more, and from the viewpoint of maintaining the strength of the membrane itself well and making it difficult to cause problems such as breakage during long-term use, it is preferably 60% or less, more preferably 55% or less, and even more preferably 50%. It is as follows.
The above-mentioned surface aperture ratio is a value obtained by detecting pores using image analysis software in an image of the membrane surface observed by a scanning electron microscope (SEM).

Examples of materials constituting the hollow fiber membrane in the present invention include polysulfone, polyethersulfone, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, ethylene/tetrafluoroethylene copolymer, polychlorotrifluoroethylene, etc. One type of Maya selected from these is a material containing two or more types of resin. Among these, polyvinylidene fluoride, ethylene/tetrafluoroethylene copolymer, or Polychlorotrifluoroethylene is preferred.

In order to improve the hydrophobicity of the hollow fiber membrane, a hydrophobic polymer may be attached to at least a portion of the hollow fiber membrane before application to the present invention.
Specific examples of hydrophobic polymers include the following:
(a) Polymers with siloxane bonds: dimethyl silicone gel, methylphenyl silicone gel, reactive modified silicone gels with organic functional groups (amino groups, fluoroalkyl groups, etc.), which form crosslinked structures by reacting with silane coupling agents. (a) Fluorine atom-containing polymer: Polymer with a fluorine atom-containing group in the side chain (Fluorine atom-containing groups include (per)fluoroalkyl group, (per)fluoropolyether group, alkylsilyl group, fluorine atom-containing group, etc.) silyl group, etc.)

The thickness of the hollow fiber membrane in the present invention is preferably 10 μm or more and 1,000 μm or less, and more preferably 20 μm or more and 500 μm or less, from the viewpoint of achieving both vapor permeability and mechanical strength of the membrane. If the film thickness is 1,000 μm or less, high vapor permeability can be obtained, and on the other hand, if the film thickness is 10 μm or more, the film can be used without being deformed.
The outer diameter of the hollow fiber membrane is preferably 300 μm or more and 5,000 μm or less, more preferably 350 μm or more and 4,000 μm or less. The inner diameter of the hollow fiber membrane is preferably 200 μm or more and 4,000 μm or less, more preferably 250 μm or more and 3,000 μm or less.

The length (effective length) of the hollow fiber membrane is preferably 500 mm or more, more preferably 1,000 mm or more, from the viewpoint of increasing the efficiency of volatile solute removal. On the other hand, from the viewpoint of suppressing pressure loss, the length of the hollow fiber membrane is preferably 4,000 times or less, more preferably 3,500 times or less, the inner diameter of the hollow fiber membrane.
Note that in the above formulas (6) to (8), the length L (m) of the hollow fiber membrane when evaluating the pressure loss ΔP (Pa) is not the effective length but the total length of the hollow fiber membrane. That is, when the hollow fiber membrane is used in the form of a membrane module for a membrane contactor, the length L (m) of the hollow fiber membrane in formulas (6) to (8) is calculated by adding two points to the effective length of the hollow fiber membrane. Adopt the length including the thickness of the adhesive resin layer.

<Membrane module for membrane contactor>
In the present invention, a membrane bundle obtained by bundling a plurality of hollow fiber membranes may be used in the form of a membrane module for a membrane contactor filled in a suitable housing.
A membrane module for a membrane contactor stores a hollow fiber membrane bundle in a cylindrical or polygonal cylinder housing such that the longitudinal direction of the hollow fiber membranes coincides with the axial direction of the housing. Both ends may be fixed within the housing with a suitable adhesive resin. In this case, it is preferable to fix the hollow fiber bundle with the adhesive resin in a liquid-tight manner so that the channels inside and outside the hollow fiber membrane are not mixed.

The housing is selected from the viewpoints of chemical resistance, pressure resistance, heat resistance, impact resistance, weather resistance, and the like. The material constituting the housing is selected from, for example, synthetic resins such as polypropylene, polysulfone, polyethersulfone, polyvinylidene fluoride, ABS resin, fiber-reinforced plastic, and vinyl chloride resin, and metals such as stainless steel, brass, and titanium. It is preferable that
The adhesive resin is desired to have strong mechanical strength and heat resistance at 100°C. Examples of the adhesive resin include thermosetting epoxy resins and thermosetting urethane resins. Epoxy resin is preferred from the viewpoint of heat resistance. Urethane resin is preferred from the viewpoint of handling properties.

FIG. 1 shows a schematic cross-sectional view for explaining an example of the structure of a membrane module for a membrane contactor to which the method of the present invention is preferably applied.
In the membrane module (100) for a membrane contactor shown in FIG. 1, a hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes (20) is housed in a cylindrical housing (10), and both ends of the hollow fiber membranes (20) are It is fixed to the housing (10) by an adhesive resin layer (30). Here, both ends of the hollow fiber membrane (20) are open without being closed.
The inside of the membrane module for membrane contactor (100) is divided by the hollow fiber membrane into a space on the hollow side of the hollow fiber membrane and a space on the outside space side of the hollow fiber membrane. These two spaces are fluidly isolated, except that volatile solutes and/or water vapor can pass back and forth through the membrane wall of the hollow fiber membrane.

The housing (10) has a treated water inlet (11) and a treated water outlet (12) at both ends of the cylindrical shape, and the treated water is supplied from the treated water inlet (11) to the membrane contactor. It is configured to enter the inside of the membrane module (100), pass through the hollow part of the hollow fiber membrane (20), and be discharged to the outside of the membrane module for membrane contactor (100) from the treated water outlet (12). ing.
Further, the housing (10) has an absorption liquid inlet (13) and an absorption liquid outlet (14) on the side surface of the cylindrical shape, and the absorption liquid is supplied from the absorption liquid inlet (13) to the membrane module for membrane contactor (100). ), passes through the outside of the hollow fiber membrane (20), and is configured to be discharged to the outside of the membrane contactor module (100) from the absorption liquid outlet (14).

Using this membrane module for a membrane contactor (100), volatile solute removal can be performed, for example, as follows.
For example, the water to be treated enters the membrane module (100) for a membrane contactor from the water inlet (11), passes through the hollow part of the hollow fiber membrane (20), and exits the water outlet (12). At the same time, the absorption liquid is passed through the absorption liquid inlet (13) into the membrane module for membrane contactor (100), passes through the outside of the hollow fiber membrane (20), and flows through the absorption liquid outlet (14). be distributed so that it is discharged from the Then, the steam generated from the water to be treated, which has a high vapor pressure, passes through the membrane wall of the hollow fiber membrane (20), moves to the absorption liquid with a low vapor pressure, and is released together with the absorption liquid from the absorption liquid outlet (14). The volatile solutes are removed from the water to be treated. At this time, a temperature difference may be created between the water to be treated and the absorption liquid to increase the vapor pressure difference.

Note that the membrane module for membrane contactor (100) shown in FIG. 1 is configured so that the water to be treated and the absorption liquid flow in opposite directions inside and outside the hollow fiber membrane. However, the water to be treated and the absorption liquid may be configured to flow in parallel flow inside and outside the hollow fiber membrane.

FIG. 2 shows a schematic cross-sectional view for explaining another example of the structure of a membrane module for a membrane contactor to which the method of the present invention is preferably applied.
The membrane module (101) for a membrane contactor in FIG.
A hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes (20) is housed in a cylindrical housing (10);
both ends of the hollow fiber membrane (20) are fixed to the housing (10) by an adhesive resin layer (30);
The interior of the membrane module for membrane contactor (100) is divided by the hollow fiber membrane into a space on the hollow side of the hollow fiber membrane and a space on the outside space side of the hollow fiber membrane;
The membrane module (100) for a membrane contactor shown in FIG. It is similar to

However, the membrane contactor module (101) of FIG. 2 has a volatile solute vapor outlet (15) on the side surface of the cylindrical shape instead of the absorption liquid inlet and absorption liquid outlet. It is different from the membrane module for membrane contactor (100).

In the membrane module for membrane contactor (101) of FIG. 2, this volatile solute vapor outlet (15) is connected to, for example, a vacuum pump via a condenser as necessary. As a result, the outer region of the hollow fiber membrane becomes under reduced pressure, and volatile solutes that have evaporated from the liquid to be treated and have passed through the hollow fiber membrane and moved to the outside of the hollow fiber membrane are removed from the water to be treated. volatile solute removal is performed.

In the present invention, volatile solutes are removed from the water to be treated using the membrane module for a membrane contactor, for example, as described above.

<Configuration of volatile solute removal device>
The configuration of the volatile solute removal device according to the present invention will be described below with reference to the drawings.
FIGS. 3 and 4 each show a schematic diagram for explaining an example of the structure of a volatile solute removal device to which the method of the present invention is preferably applied.

The volatile solute removal device (1000) in FIG. 3 is an example of a device for removing volatile solutes from treated water containing non-volatile solutes and volatile solutes.
The volatile solute removal device (1000) in FIG. 3 incorporates the membrane module for membrane contactor (100) shown in FIG. 1.
In the volatile solute removal device (1000), the water to be treated stored in the water to be treated tank (500) is sent to the membrane module for membrane contactor (100) by the water to be treated pump (P1). After the water to be treated passes through the hollow part of the hollow fiber membrane in the membrane module for membrane contactor (100), it is returned to the water to be treated tank (500) and circulated. Before the water to be treated is introduced into the membrane module (100) for a membrane contactor, it is heated by a heat exchanger (HE) (for example, a heater) to increase its vapor pressure, thereby facilitating the removal of volatile solutes. Ru. The piping before and after the membrane module for membrane contactor (100) may be equipped with a thermometer (TM).

The volatile solute removal device (1000) of FIG. 3 is further equipped with an absorption liquid tank (200). The absorption liquid stored in the absorption liquid tank (200) is sent to the membrane contactor module (100) by an absorption liquid supply pump (P2). After passing through the outside of the hollow fiber membrane in the membrane contactor membrane module (100), the absorption liquid is returned to the absorption liquid tank (200) and circulated. The absorption liquid may be heated or cooled by a heat exchanger (HE) before being introduced into the membrane contactor module (100). This adjusts the vapor pressure of the volatile solute and facilitates removal of the volatile solute.
The piping before and after the membrane module for membrane contactor (100) may be equipped with a thermometer (TM).

The volatile solute removal device (1001) in FIG. 4 is another example of a device for removing volatile solutes from treated water containing non-volatile solutes and volatile solutes.
The volatile solute removal device (1001) in FIG. 4 incorporates the membrane module for membrane contactor (101) shown in FIG. 2. The space outside the hollow fiber membrane of the membrane module for membrane contactor (101) is connected to a vacuum pump (V) via a volatile solute vapor outlet and a condenser (600).
With such a configuration, a vapor pressure difference of volatile solutes is created between the water to be treated flowing inside the hollow fibers and the outside of the hollow fibers, so that the volatile solutes are evaporated from the liquid to be treated, pass through the hollow fiber membranes, and are released into the hollow fibers. Volatile solutes that have migrated to the outside of the membrane can be removed. Thereby, volatile solutes can be removed from the liquid to be treated.

The volatile solute removal devices (1000, 1001) in FIGS. 3 and 4 may further include a flow rate regulator, a pressure regulator, a heat retention structure, etc., as necessary.

《Water to be treated》
The method of the present invention is a method for removing volatile solutes from water to be treated.
The water to be treated is a liquid mixture containing a volatile solute, a non-volatile solute, and a solvent. The water to be treated is typically a solution, but may be an emulsion, suspension, etc. as long as it is in a liquid state.

<Nonvolatile solute>
The nonvolatile solute contained in the water to be treated refers to a substance that has substantially no vapor pressure and does not decompose at the operating temperature of the volatile solute removal device.
Typical examples of non-volatile solutes are pharmaceutical raw materials, chemicals, etc., and inorganic salts.
Examples of pharmaceutical raw materials, chemicals, etc. include amino acids, peptides, proteins, sugars, vaccines, nucleic acids, antibiotics, antibody-drug conjugates (ADCs), surfactants, vitamins, and the like.

An amino acid is a compound having one amino acid skeleton consisting of a carboxyl group, an amino group, and a part connecting these groups. The term "amino acid" as used herein is a concept that includes essential amino acids, non-essential amino acids, and unnatural amino acids.
Examples of essential amino acids include tryptophan, lysine, methionine, phenylalanine, threonine, valine, leucine, isoleucine, and the like. Examples of non-essential amino acids include arginine, glycine, alanine, serine, tyrosine, cysteine, asparagine, glutamine, proline, aspartic acid, and glutamic acid.

An unnatural amino acid refers to any artificial compound that has an amino acid skeleton in its molecule and does not exist in nature. However, examples of unnatural amino acids used as pharmaceutical raw materials include those obtained by bonding a desired labeling compound to an amino acid skeleton. Examples of labeling compounds include dyes, fluorescent substances, luminescent substances, enzyme substrates, coenzymes, antigenic substances, protein-binding substances, and the like.
Examples of unnatural amino acids preferable as pharmaceutical raw materials include labeled amino acids, functionalized amino acids, and the like. A labeled amino acid is an unnatural amino acid in which an amino acid skeleton and a labeling compound are bonded, and specific examples include amino acids in which a labeling compound is bonded to an amino acid skeleton containing an aromatic ring in the side chain. Examples of functionalized amino acids include photoresponsive amino acids, photoswitch amino acids, fluorescent probe amino acids, fluorescently labeled amino acids, and the like.

A peptide refers to a compound in which 2 or more and less than 70 amino acid residues are bonded, and may be chain-like or cyclic. Examples of the peptide include L-alanyl-L-glutamine, β-alanyl-L-histidine cyclosporine, and glutathione.
A protein generally refers to a compound having amino acid residues bonded thereto that has a longer chain than a peptide. The protein used herein is preferably one that can be applied as a protein preparation, for example.
Examples of protein preparations include interferon α, interferon β, interleukins 1 to 12, growth hormone, erythropoietin, insulin, granular colony stimulating factor (G-CSF), tissue plasminogen activator (TPA), and natriuresis. Examples include peptides, blood coagulation factor VIII, somatomedin, glucagon, growth hormone releasing factor, serum albumin, calcitonin, and the like.

Examples of the sugar include monosaccharides, disaccharides, sugar chains (excluding disaccharides), sugar chain derivatives, and the like.
Examples of monosaccharides include glucose, fructose, galactose, mannose, ribose, deoxyribose, and the like. Examples of disaccharides include maltose, sucrose, and lactose.
The term "sugar chain" as used herein refers to a concept excluding disaccharides, and includes, for example, glucose, galactose, mannose, fucose, xylose, glucuronic acid, iduronic acid, and the like. Examples of sugar chain derivatives include sugar derivatives such as N-acetylglucosamine, N-acetylgalactosamine, and N-acetylneuraminic acid.

Examples of vaccines include hepatitis A vaccine, hepatitis B vaccine, hepatitis C vaccine, new coronavirus vaccine, etc.;
Examples of nucleic acids include oligonucleotides, RNA, aptamers, decoys, etc.;
Examples of antibiotics include streptomycin, vancomycin, etc.;
Each can be mentioned.
Examples of vitamins include vitamin A, vitamin B, and vitamin C, and the concept also includes derivatives and salts of these. The B vitamins include, for example, vitamin B6, vitamin B12, and the like.
Examples of surfactants include polysaccharides, phospholipids, peptides, anionic surfactants such as sodium lauryl sulfate, cationic surfactants such as benzalkonium chloride; amphoteric surfactants; Examples include ionic surfactants.
Examples of inorganic salts include sodium chloride, magnesium chloride, and the like.

The number average molecular weight of the non-volatile solute may be 75,000 or less, preferably 50,000 or less, more preferably 10,000 or less, and 6,000 or less is particularly preferred. If the molecular weight of the nonvolatile solute is excessively large, the viscosity of the water to be treated becomes excessively high, increasing the pressure loss in the flow path of the water to be treated, and causing solute precipitation due to overconcentration on the surface of the hollow fiber membrane. There is.

<Volatile solute>
The volatile solute contained in the water to be treated refers to a substance that exhibits a significant vapor pressure and does not decompose at the operating temperature of the volatile solute removal device.
Examples of volatile solutes include volatile acids, volatile bases, volatile polar compounds (excluding acids and bases), and the like.
Examples of volatile acids include hydrochloric acid, carbonic acid, and acetic acid.
Examples of volatile bases include ammonia and the like.
Examples of volatile polar compounds (excluding acids and bases) include alcohols, acetonitrile, and the like. Examples of alcohols include methanol, ethanol, n-propanol, i-propanol, and the like.

<solvent>
The solvent for the water to be treated may contain water. Water preferably has a large surface energy with respect to the surface of the hydrophobic hollow fiber membrane, and therefore the liquid on the membrane surface is efficiently separated from the vapor of the volatile solute. It is preferable that
The solvent for the water to be treated may be water or a mixed solvent consisting of water and a water-soluble organic solvent, and is typically water.

<Aspects of treated water>
The water to be treated to which the present invention is applied includes, for example, solutions containing pharmaceutical ingredients, chemicals, etc.; chemical processes; wastewater from denitrification equipment; food; seawater; produced water discharged from gas fields, oil fields, etc. can be mentioned.
When the method of the present invention is applied to remove volatile solutes from water to be treated, it is possible to stably obtain treated water in which the composition of nonvolatile solutes in the original water to be treated is maintained almost unchanged. Therefore, the method of the present invention can be applied to wastewater treatment, etc., and is also useful in the purification process of raw materials in intermediate stages of manufacturing pharmaceuticals and chemicals.
Moreover, when water is produced by applying the method of the present invention, purified water from which substantially all nonvolatile solutes contained in the water to be treated are removed can be stably obtained. Therefore, the method of the present invention is also useful for producing drinking water, domestic water, etc. in dry areas.

In the present invention, the temperature of the water to be treated when volatile solutes are removed from the water to be treated may be, for example, 0° C. or more and 100° C. or less.
When volatile solutes are removed by flowing the absorption liquid through the outer space of the hollow fiber membrane of the membrane contactor, it is not necessary to raise the temperature of the water to be treated very high. The temperature of the water to be treated in this case may be, for example, 0°C or higher, 10°C or higher, 20°C or higher, or 30°C or higher, and, for example, 60°C or lower, 50°C or lower, or 40°C or lower. good.
On the other hand, when volatile solutes are removed by reducing the pressure in the outer space of the hollow fiber membrane of the membrane contactor, the temperature of the water to be treated may be high. However, increasing the temperature of the water to be treated is not an essential requirement in this embodiment. The temperature of the water to be treated in this case may be, for example, 0°C or higher, 10°C or higher, 20°C or higher, 30°C or higher, or 40°C or higher, and for example, 100°C or lower, 90°C or lower, or 80°C or lower. , 70°C or less, or 60°C or less.

《Absorption liquid》
In the volatile solute removal device of the present invention, the absorption liquid is distributed to the outside of the hollow fiber membrane so as to be in contact with the liquid to be treated through the hollow fiber membrane. This liquid has the property of capturing volatile solutes that have passed through the hollow fiber membrane and moved to the outside of the hollow fiber membrane.
Such an absorption liquid may be, for example, a good solvent for a volatile solute, a solution containing a substance that can react with a volatile solute, or the like.
Specifically, for example, when the volatile solute contains a volatile base (eg, ammonia), the absorption liquid may be an aqueous solution of an acid. Further, when the volatile solute contains a volatile acid (eg, hydrochloric acid, carbonic acid, acetic acid, etc.), the absorption liquid may be an aqueous solution of a base. Furthermore, when the volatile solute contains a volatile polar compound (eg, alcohols, acetonitrile, etc.), the absorption liquid may be water.

The linear velocity at which the absorption liquid flows outside the hollow fiber membrane is arbitrary. The linear velocity of this absorption liquid can be, for example, 0.1 m/s or more and 5.0 m/s or less.
The absorption liquid may be a parallel flow that flows in the same direction as the flow direction of the liquid to be treated, or a counter flow that flows in a direction opposite to the flow direction of the liquid to be treated.
The temperature of the absorption liquid when volatile solute removal is performed is arbitrary. The temperature of the absorption liquid may be, for example, 0°C or more and 100°C or less, preferably 15°C or more and 60°C or less, and more preferably 20°C or more and 50°C or less.

《Decompression》
When the volatile solute removal device is operated with the outside of the hollow fiber membrane in a reduced pressure state, the pressure outside the hollow fiber membrane is equal to It only needs to be lower than the vapor pressure of the solute. The pressure outside the hollow fiber membrane may be, for example, 90% or less, preferably 80% or less, 70% or less, 60% or less, or 50% or less of the vapor pressure of the volatile solute.
Specifically, for example, when the pressure inside the hollow fiber membrane is 1 atm, the pressure outside the hollow fiber membrane may be 0.9 atm or less, 0.8 atm or less, 0.7 atm or less, 0. It is preferably 6 atm or less, or 0.5 atm or less.

Hereinafter, the configuration and effects of the present invention will be specifically explained in the form of examples. However, the present invention is not limited in any way by the following examples.
In the following examples, various physical properties of hollow fiber membranes were measured by the following methods.

(1) Outer diameter, inner diameter, and thickness of the hollow fiber membrane The outer diameter, inner diameter, and thickness of the hollow fiber membrane were determined by microscopic observation.
Specifically, we used the following method.
The hollow fiber membrane was cut thinly with a razor in a direction perpendicular to the longitudinal direction, and a microscopic image of the cross section was taken to obtain a microscopic image. By measuring the obtained microscopic image, the outer diameter and inner diameter of the hollow fiber membrane were determined. The thickness of the hollow fiber membrane was determined by calculation from the obtained outer diameter and inner diameter.

(2) Average pore diameter of hollow fiber membrane The average pore diameter of the hollow fiber membrane was measured by the average pore diameter measuring method (half-dry method) described in ASTM: F316-86.
A hollow fiber membrane cut into a length of 10 cm was used as a sample, and ethanol was used as the liquid, and the measurement was carried out under standard measurement conditions of a temperature of 25° C. and a pressure increase rate of 0.01 atm/sec.
The average pore diameter was determined using the following formula (10):
Average pore diameter [μm] = 2,860 x (s/p) (10)
{In formula (10), s is the surface tension of the liquid used (unit: dyne/cm), and p is the half-dry air pressure (unit: Pa). }
Here, the value of the surface tension s of ethanol at 25° C. was 21.97 dyne/cm.

(3) Maximum pore diameter of hollow fiber membrane The maximum pore diameter of the hollow fiber membrane was measured by the bubble point method using ethanol as an immersion liquid.
The hollow fiber membrane was cut into a length of 8 cm, one end was closed, and a nitrogen gas supply line was connected to the other end via a pressure gauge. In this state, nitrogen gas was supplied to replace the inside of the hollow fiber membrane with nitrogen, and then the hollow fiber membrane was immersed in ethanol while the inside of the line was extremely slightly pressurized with nitrogen. This nitrogen pressurization is a measure to prevent ethanol from flowing back into the line.
Next, with the hollow fiber membrane immersed in ethanol, the pressure of nitrogen gas was slowly increased until the pressure P (kg/cm ² ) at which nitrogen gas bubbles began to stably emerge from the hollow fiber membrane was reached. Recorded. This P is expressed by the following formula (11):
d=C1γ/P (11)
{In formula (11), d is the maximum pore diameter of the hollow fiber, C1 is a constant, γ is the surface tension of the immersion liquid, and P is the pressure. } to calculate the maximum pore diameter d of the hollow fiber membrane. At this time, the value of C1γ when ethanol was used as the immersion liquid was 0.632 (kg/cm).

(4) Porosity of hollow fiber membrane The porosity of the hollow fiber membrane contactor membrane (average porosity of the entire membrane) is calculated from the mass of the hollow fiber membrane and the density (true density) of the material that makes up the hollow fiber membrane. Calculated.
That is, the hollow fiber membrane is cut to a certain length, its mass is measured, and the following formula (12):
{In the above formula (12), d is the true density of the raw material polymer of the hollow fiber membrane, and π is the circumference. }, the porosity of the hollow fiber was determined.

(5) [Water contact angle of hollow fiber membrane]
The water contact angle of the hollow fiber membrane was measured by a droplet method according to JIS R 3257.
In an environment with a temperature of 23°C and a relative humidity of 50%, droplets of 2 μL of pure water were dropped on the outer surface of the hollow fiber membrane sample, and the angle formed between the droplet and the outer surface of the hollow fiber membrane was determined by image analysis. The contact angle was calculated. The measurement was performed five times, and the number average value was adopted as the water contact angle.

《Example 1》
(1) Preparation of hollow fiber membrane for membrane contactor 23 parts by mass of hydrophobic silica (AEROSIL-R972, manufactured by Nippon Aerosil Co., Ltd.) with an average primary particle size of 0.016 μm and a specific surface area of 110 m ² /g, and DOP (phthalic acid). 31 parts by mass of dioctyl di-2-ethylhexyl phthalate) and 6 parts by mass of DBP (dibutyl phthalate) were mixed in a Henschel mixer, and polyvinylidene fluoride having a weight average molecular weight of 310,000 (manufactured by SOLVAY Co., Ltd., 40 parts by mass of Solef (registered trademark) 6010) were added and mixed again using the Henschel mixer. This mixture was mixed using a twin-screw kneading extruder and then pelletized.
The obtained pellets were melt-kneaded at 240° C. in a twin-screw kneading extruder equipped with a spinneret for forming hollow fibers at the extrusion port to obtain a melt-kneaded product. The obtained melt-kneaded product was extruded from the outer annular hole of the spinneret for forming hollow fibers, and nitrogen gas was discharged from the inner circular hole of the spinneret to extrude a hollow fiber-shaped extrudate from the spinneret. . This hollow fiber extrudate was introduced into a water bath (40° C.) at a free running distance of 20 cm and wound up at a speed of 20 m/min.

The wound hollow fiber extrudate was immersed in methylene chloride to extract and remove DOP and DBP in the hollow fiber extrudate, and then dried. Next, the hollow fiber extrudate was immersed in a 50% by mass aqueous ethyl alcohol solution, and then immersed in a 5% by mass aqueous sodium hydroxide solution at 40° C. for 1 hour to extract and remove the silica in the hollow fiber extrudate.
Thereafter, the hollow fiber membrane made of polyvinylidene fluoride (PVDF) was obtained by washing with water and drying. The various physical properties of this hollow fiber membrane measured by the method described above were as follows.
Inner diameter: 0.68mm
Outer diameter: 1.25mm
Film thickness: 0.28mm
Average pore size: 0.21μm
Maximum pore diameter: 0.29μm
Porosity: 72%
Water contact angle: 103° (hollow fiber membrane outer surface)

(2) Production of hollow fiber membrane module A hollow fiber membrane module having the structure shown in FIG. 1 was produced using the PVDF hollow fiber membrane obtained above.
Thirty-five hollow fiber membranes cut to a length of 15 cm were bundled to form a fiber bundle, which was housed in a housing. A thermosetting epoxy resin was used as the adhesive resin, an adhesive resin layer was formed by centrifugal adhesion, and the membrane bundle was adhesively fixed in the housing.
Through the above operations, a hollow fiber membrane module with a pore length of the hollow fiber membrane (the length of the portion not buried in the adhesive resin layer) of 8 cm and a total area of the inner surface of the hollow fiber membrane of 60 cm ² was produced.

(3) Attachment of hydrophobized polymer to hollow fiber membrane (fabrication of membrane module for membrane contactor)
Using a syringe, a fluororesin water repellent "FS1610" (polymer concentration 1.0% by mass) manufactured by Fluorotechnology was injected into the hollow portion of the hollow fiber from the water inlet to be treated of the hollow fiber membrane module. This injection operation was continued until the entire inner surface of the hollow fiber membrane was wetted with the water repellent and the water repellent oozed out to the outside of the hollow fiber membrane. Next, after removing excess water repellent from the hollow fiber membrane module, dry air at 25°C is flowed through the hollow part of the hollow fiber membrane to dry it, resulting in a membrane in which the entire hollow fiber membrane has been made hydrophobic. A membrane module for contactor was fabricated.
Three membrane modules for the membrane contactor were manufactured, and one was used for measuring pressure drop, one was used for removing volatile solutes, and one was used for evaluating module life.

(4) Measurement of pressure drop of membrane module for membrane contactor Using the membrane module for membrane contactor obtained above, the apparatus shown in FIG. 5 was constructed, and the pressure drop of the membrane module for membrane contactor was measured.
The apparatus shown in FIG. 5 uses a membrane module (100) for a membrane contactor with the absorption liquid inlet and absorption liquid outlet closed, and the water in the water tank (300) is introduced from the water to be treated inlet using a pump (P). The water can be passed through the hollow part of the hollow fiber membrane of the membrane contactor module (100), taken out from the water outlet, and returned to the water tank (300) for circulation. Here, pressure gauges (PM) are installed on the inlet side and the outlet side of the membrane module for membrane contactor (100), respectively, so that the liquid pressure at each location can be measured.

Measurements were performed at 25°C.
Using the apparatus shown in Fig. 5, water is caused to flow through the hollow fibers of the membrane module for membrane contactors at varying linear velocities, and the liquid pressures on the inlet and outlet sides are checked, and the difference is taken as the pressure loss. The value of pressure drop at each Reynolds number was determined. Here, the Reynolds number was calculated using a density of 997 kg/m ² and a viscosity of 0.00089 Pa·s of pure water at 25°C.
The results are shown in FIG. FIG. 6 also shows theoretical pressure drop curves when the flow is laminar and turbulent.
As seen in Figure 6, the pressure drop of the membrane module for the membrane contactor of Example 1 closely matches the theoretical curve for laminar flow at Reynolds numbers of 1,000 or less, and matches the theoretical curve for turbulent flow at Reynolds numbers of 1,500 or higher. It matched well. This result is different from the conventional theory that the flow becomes laminar when the Reynolds number is approximately 2,300 or less.

(5) Implementation of volatile solute removal The membrane module for membrane contactor obtained above was incorporated into the volatile solute removal apparatus shown in FIG. 3, and volatile solute removal was performed.
Solutions having the following configurations were used as the water to be treated and the absorption liquid containing volatile solutes.
Water to be treated: Seawater containing 300 ppm of ammonia as a volatile solute (liquid amount: 1,000 g)
Absorption liquid: 10% by mass sulfuric acid aqueous solution (liquid amount: 1,000g)
Seawater was collected from a depth of 1 m at a point 2 km offshore from Suruga Bay. Further, ammonia was adjusted to a concentration of 300 ppm by adding 999 g of seawater to 1 g of commercially available ammonia water with a concentration of 30% by mass. Calculations were performed by focusing on CaCO ₃ , which is a major scale component when seawater is concentrated, as a scale model compound.
After the water to be treated was filled into the water to be treated tank (500), a sodium hydroxide aqueous solution having a concentration of 10 mol/L was added dropwise to adjust the pH to 10 or more.
The water to be treated was circulated through the inside of the hollow fiber membrane of the membrane module for membrane contactor (100) at a flow rate of 750 ml/min using the water to be treated pump (P1). At this time, the temperature of the raw material liquid was adjusted using a temperature controller so as to be maintained at 50° C. on the inlet side of the membrane module for membrane contactor (100). At this time, the average linear velocity of the water to be treated flowing inside the hollow fiber membrane was 0.98 m/s, and the Reynolds number was 1,142.

On the other hand, the absorption liquid tank (200) is filled with 1,000 g of absorption liquid, and the hollow fiber membrane of the membrane module for membrane contactor (100) is pumped at a flow rate of 300 mL/min using the absorption liquid supply pump (P2). flowed outside. At this time, the temperature of the absorption liquid was adjusted using a temperature controller so as to be maintained at 50°C. As shown in FIG. 5, the absorption liquid was flowed into the module in a direction facing the water to be treated.
The volatile solute removal run continued for approximately 8 hours. Table 1 shows the water vapor flux and volatile solute flux at this time.

The water vapor flux J _W (kg/m ² h) and volatile solute flux J _VS (g/m ² h) of the membrane contactor were determined using the following formulas (9) and (13) to (15). .
In formula (9), W _P is the weight (kg) of the permeated steam, which is calculated by subtracting the raw material liquid weight W _f ( ^kg ) before and after a certain period of time from the initial weight of the water to be treated W _{f 0} (kg). (Equation (13). A is the membrane area (m ² ) of the membrane for membrane contactor, T is the operating time (h). In addition, W _VS in Equation (14) is the permeated volatile The weight of the solute (kg) is the value obtained by multiplying the initial weight of the water to be treated W _f ⁰ (kg) by the initial volatile solute concentration C _f ⁰ (wt%), plus the weight of the water to be treated before and after a certain period of time. It is equal to _{the value obtained by subtracting the value obtained by multiplying the weight of water to be treated W f (} kg) before and after a certain period of time by the initial volatile solute concentration C _f (wt%) from the weight of water W f (kg) (Formula (15) ).
In Example 1, the water vapor flux during the 8-hour operation was 1.50 kg/m ² ·h, and the volatile solute (ammonia) flux was 3.58 g/m ² ·h.

After 8 hours of operation, the membrane module for the membrane contactor was taken out and installed in the apparatus shown in FIG.
The hydrochloric acid tank (400) is filled with 50 mL of 0.1M hydrochloric acid as a cleaning liquid, and the hollow part of the hollow fiber membrane of the membrane module (100) for membrane contactor is filled with the pump (P) at a flow rate of 100 mL/min. was allowed to flow for 1 minute. After flowing for 1 minute, the washing solution was replaced with fresh hydrochloric acid, and circulation was carried out again for 1 minute. The same operation was repeated a total of 5 times.
The five washed wash liquids after distribution were combined into one, and the concentration of calcium ions in the liquid was measured using an ICP-OES analyzer (manufactured by Hitachi High-Tech Science Co., Ltd., "SPS6100").

Then, using the obtained values, the amount of scale (CaCO ₃ ) precipitation N _s (mg/m ² ·h) was calculated using the following formulas (16) and (17).
{In formulas (16) and (17), m _s is the precipitation amount (g) of scale (CaCO ₃ ), W _a is the total mass (g) of the cleaning solution, and C _i is the amount of cation (CaCO 3 ) in the cleaning solution. ²⁺ ) is the mass percent concentration (wt%), M _s is the molecular weight (g/mol) of the scale (CaCO ₃ ), M _i is the formula weight (g/mol) of the cation (Ca ²⁺ ), A is the membrane area (m ² ) inside the hollow fiber membrane, and T is the operating time. }
In addition, the numerical values obtained above, the linear velocity of the water to be treated passing through the hollow part of the hollow fiber membrane of the membrane contactor module during operation of the volatile solute removal device, and the density of seawater at 50°C 1014 kg/m ² The Reynolds number was calculated from the viscosity of 0.000594 Pa·s.

Table 1 shows the average values of the linear velocity and Reynolds number of the water to be treated, the water vapor flux, the volatile solute flux, and the amount of precipitated CaCO ₃ in the above volatile solute removal operation.
When a volatile solute removal operation was performed using the membrane module for a membrane contactor of Example 1 under the conditions of a Reynolds number of 1,142 and a linear velocity of the water to be treated of 0.983 m/s, the amount of precipitated CaCO ₃ was 0. .78 mg/m ² ·h, and it was verified that almost no scale was precipitated.

(6) Measurement of life span Using the remaining membrane module for membrane contactors, the life span of the membrane module for membrane contactors was evaluated.
First, using the evaluation results obtained in the volatile solute removal operation described above, we calculated the pressure drop when using a hollow fiber membrane in which the length L of the hollow fiber was 2,000 times the inner diameter. It was .0kPa. For this calculation, the above equation (8) regarding pressure drop during turbulent flow was used. Note that this calculation is based on the assumption that the module will be scaled up.
Then, volatile solute removal operation was performed for 24 hours under the same conditions as above, except that the liquid pressure at the inlet of the treated water was adjusted to the same value as the calculated pressure drop value, and the initial value of volatile solute flux was determined. It was measured. After 24 hours of operation, the raw material liquid was replaced, and membrane distillation operation was performed for 24 hours under the same conditions without washing the hollow fiber membrane. This operation was repeated to continue the volatile solute removal operation until the total operating time reached 1,000 hours.

The volatile solute flux after 1,000 hours of operation was measured, compared with the initial value, and evaluated based on the following criteria.
A: When the volatile solute flux after 1,000 hours of operation was 70% or more of the initial value B: When the volatile solute flux after 1,000 hours of operation was 50% or more and less than 70% of the initial value Time C: When the volatile solute flux after 1,000 hours of operation is less than 50% of the initial value.

In Example 1, the volatile solute flux after 1,000 hours of operation was 88% of the initial value, which was an extremely good result.

《Examples 5 to 7 and Comparative Examples 1, 4, and 5》
A membrane module for a membrane contactor was produced in the same manner as in Example 1, except that the flow rate of the water to be treated was as shown in Table 1, and various evaluations were performed.
The results are shown in Table 1.
In addition, when evaluating the lifespan in Comparative Example 5, wetting of the hollow fiber membrane occurred when the cumulative operating time reached 250 hours, and the water to be treated began to mix into the permeated water side, so the operation was stopped at that point. did.

《Example 2 and Comparative Example 2》
A membrane module for a membrane contactor was produced in the same manner as in Example 1, except that the inner diameter of the hollow fiber membrane was adjusted to 1.02 mm and the outer diameter to 1.83 mm, and 20 hollow fiber membranes were bundled into a module.

The pressure drop of the obtained membrane module for membrane contactor was measured in the same manner as in "(4) Measurement of pressure drop of membrane module for membrane contactor" of Example 1.
The results are shown in FIG. FIG. 8 also shows theoretical pressure drop curves when the flow is laminar and turbulent.
As seen in Figure 8, the pressure drop of the membrane module for the membrane contactor of Example 2 closely matches the theoretical curve for laminar flow at Reynolds numbers of 1,000 or less, and matches the theoretical curve for turbulent flow at Reynolds numbers of 1,500 or higher. It matched well.

Using the obtained membrane module for a membrane contactor, a volatile solute removal operation was carried out in the same manner as in Example 1, except that the flow rate of the water to be treated was as shown in Table 1. We conducted an evaluation.
The results are shown in Table 1.

《Example 3》
The membrane module for a membrane contactor obtained in the same manner as in Example 1 was incorporated into the volatile solute removal apparatus shown in FIG. 3 to perform volatile solute removal.
Solutions having the following configurations were used as the water to be treated and the absorption liquid containing volatile solutes, respectively.
Water to be treated: Seawater containing 300 ppm of acetic acid as a volatile solute (liquid amount: 1,000 g)
Absorption liquid: 10 mass percent sodium hydroxide aqueous solution (liquid amount: 1,000 g)

Seawater was collected from a depth of 1 m at a point 2 km offshore from Suruga Bay. Further, acetic acid was adjusted to a concentration of 300 ppm by adding 999.7 g of seawater to 0.3 g of commercially available 100 mass percent acetic acid. Calculations were performed focusing on CaCO ₃ , which is a major scale component when seawater is concentrated, as a scale model compound.
After filling the above treated water into the treated water tank (500), hydrochloric acid with a concentration of 5 mol/L was added dropwise to adjust the pH to 2 or less.
The volatile solute removal operation was carried out in the same manner as in Example 1, except that the above treated water and absorption liquid were used, and various evaluations were performed.
The results are shown in Table 1.

《Example 4》
The membrane module for a membrane contactor obtained in the same manner as in Example 1 was incorporated into the volatile solute removal apparatus shown in FIG. 3 to remove volatile solutes.
Solutions having the following configurations were used as the water to be treated and the absorption liquid containing volatile solutes, respectively.
Water to be treated: Seawater containing 3,000 ppm of ethanol as a volatile solute (liquid amount: 1,000 g)
Absorption liquid: Pure water (Liquid amount: 1,000g)

Seawater was collected from a depth of 1 m at a point 2 km offshore from Suruga Bay. Further, the concentration of ethanol was adjusted to 3,000 ppm by adding 997.0 g of seawater to 3.0 g of commercially available ethanol. Calculations were performed focusing on CaCO ₃ , which is a major scale component when seawater is concentrated, as a scale model compound.
The volatile solute removal operation was carried out in the same manner as in Example 1, except that the above treated water and absorption liquid were used, and various evaluations were performed.
The results are shown in Table 1.

《Comparative example 3》
The volatile solute removal operation was carried out in the same manner as in Example 3, except that the flow rate of the water to be treated was changed as shown in Table 1, and various evaluations were performed.
The results are shown in Table 1.

10 Housing 11 Inlet of water to be treated 12 Outlet of water to be treated 13 Absorption liquid inlet 15 Volatile solute vapor outlet 20 Hollow fiber membrane 30 Adhesive resin layer 100, 101 Membrane module for membrane contactor 200 Absorption liquid tank 300 Water tank 400 Hydrochloric acid tank 500 Treated water tank 600 Condenser 1000, 1001 Volatile solute removal device HE Heat exchanger P Pump P1 Treated water supply pump P2 Absorption liquid supply pump PM Pressure gauge TM Thermometer V Pressure reduction pump

Claims (11)

A method of operating a volatile solute removal device for removing volatile solutes from treated water containing both volatile and non-volatile solutes using a membrane contactor, the method comprising:
The membrane used in the membrane contactor is a hollow fiber membrane, and the water to be treated is passed inside the hollow fiber membrane to remove volatile solutes,
The Reynolds number of the water to be treated flowing inside the hollow fiber membrane is 1,100 or more, and
The linear velocity of the water to be treated flowing inside the hollow fiber membrane is 3.5 m/s or less,
how to drive. The operating method according to claim 1, wherein the Reynolds number of the water to be treated flowing inside the hollow fiber membrane is 7,000 or less. The operating method according to claim 2, wherein the Reynolds number of the water to be treated flowing inside the hollow fiber membrane is 2,300 or less. The operating method according to claim 1, wherein the linear velocity of the water to be treated flowing inside the hollow fiber membrane is 0.4 m/s or more and 2.0 m/s or less. The volatile solute absorption liquid is passed through the outside of the hollow fiber membrane to bring the water to be treated and the absorption liquid into contact through the hollow fiber membrane, and the volatile solute is contained in the absorption liquid. The operating method according to any one of claims 1 to 4, wherein the volatile solute is removed from the water to be treated by moving the water. The operating method according to any one of claims 1 to 4, wherein the outside of the hollow fiber membrane is reduced in pressure. The operating method according to any one of claims 1 to 4, wherein the hollow fiber membrane is hydrophobic. The operating method according to any one of claims 1 to 4, wherein the volatile solute contains one or more selected from ammonia, hydrochloric acid, carbonic acid, acetic acid, alcohols, and acetonitrile. The volatile solute contains one or more selected from ammonia, hydrochloric acid, carbonic acid, acetic acid, alcohols, and acetonitrile, and
When the volatile solute contains ammonia, the absorption liquid is an aqueous acid solution,
When the volatile solute contains one or more selected from hydrochloric acid, carbonic acid, and acetic acid, the absorption liquid is an aqueous solution of a base,
When the volatile solute contains one or more selected from alcohols and acetonitrile, the absorption liquid is water.
The operating method according to claim 5. The nonvolatile solute is one or two selected from amino acids, peptides, proteins, protein preparations, sugars, vaccines, nucleic acids, antibiotics, vitamins, surfactants, antibody drug conjugates (ADCs), and inorganic salts. The operating method according to any one of claims 1 to 4, comprising the above. The operating method according to any one of claims 1 to 4, wherein the hollow fiber membrane is a hollow fiber in a membrane module having a hollow fiber bundle constituted by a plurality of hollow fiber membranes.

Images