Membrane separation system and method for operating membrane separation system

Abstract

A membrane separation system 100 includes a membrane separation device 10. The membrane separation device 10 has a pervaporation membrane 11 for separating a mixed liquid containing a liquid A and a liquid B different from the liquid A into a permeated fluid and a non-permeated fluid. The membrane separation system 100 adjusts the flow rate of the mixed liquid such that the linear velocity of the mixed liquid supplied to the membrane separation device 10 is 11.0 m / h or more. Provided is a method for operating a membrane separation device having a pervaporation membrane, the method comprising: a supply step of supplying a mixed liquid containing a liquid A and a liquid B different from the liquid A to the membrane separation device 10; and a membrane separation step of separating the mixed liquid into a permeated fluid and a non-permeated fluid by the pervaporation membrane 11. The membrane separation step is performed in a state in which the flow rate of the mixed liquid is adjusted such that the linear velocity of the mixed liquid supplied to the membrane separation device 10 is 11.0 m / h or more.

Description

Membrane separation system and method for operating the membrane separation system

[0001] The present invention relates to a membrane separation system and a method for operating a membrane separation system.

[0002] Mixed liquids containing solvents such as isopropanol (IPA) are used as cleaning liquids, for example, in the manufacturing processes of separation membranes, semiconductors, and the like. It is desirable for the solvents contained in the cleaning liquid to be reused from the viewpoints of reducing environmental impact and suppressing energy consumption. Therefore, various methods for recovering solvents from used cleaning liquids have been proposed. Distillation and adsorption are common methods for recovering solvents from cleaning liquids. In recent years, separation methods using separation membranes such as polymer membranes and zeolite membranes have been proposed as alternatives to conventional recovery methods. For example, Patent Document 1 proposes a purification system that separates a cleaning liquid containing multiple solvents using a pervaporation membrane.

[0003] Japanese Patent Application Laid-Open No. 2021-49518

[0004] Conventional separation systems have room for improvement in terms of recovery costs.

[0005] An object of the present invention is to provide a membrane separation system and an operating method for the membrane separation system that are highly practical in terms of recovery costs.

[0006] In one aspect, the present invention provides a membrane separation system including a membrane separation device, wherein the membrane separation device has a pervaporation membrane that separates a mixed liquid containing liquid A and liquid B different from liquid A into a permeable fluid and a non-permeable fluid, and the membrane separation system adjusts the flow rate of the mixed liquid so that the linear velocity of the mixed liquid supplied to the membrane separation device is 11.0 m / h or more.

[0007] From another aspect, the present invention provides a method for operating a membrane separation apparatus having a pervaporation membrane, the method comprising: a supply step of supplying a mixed liquid containing liquid A and liquid B different from liquid A to the membrane separation apparatus; and a membrane separation step of separating the mixed liquid into a permeated fluid and a non-permeated fluid by the pervaporation membrane, wherein the membrane separation step is performed while adjusting the flow rate of the mixed liquid so that the linear velocity of the mixed liquid supplied to the membrane separation apparatus is 11.0 m / h or more.

[0008] According to the present invention, it is possible to provide a membrane separation system and an operating method for a membrane separation system that are highly practical in terms of recovery costs.

[0009] FIG. 1 is a schematic configuration diagram showing an example of a membrane separation system according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a membrane separation device. FIG. 3 is a schematic cross-sectional view showing an example of a pervaporation membrane provided in a membrane separation device. FIG. 4 is an exploded perspective view schematically showing an example of a spiral membrane element. FIG. 5 is a schematic configuration diagram showing a first modified example of a membrane separation system. FIG. 6 is a schematic configuration diagram showing a second modified example of a membrane separation system. FIG. 7 is a diagram showing the relationship between the linear velocity (m / h) of the mixed liquid and the recovery cost (yen / kg) of liquid A in the supply step of measurement examples 1 to 22.

[0010] A membrane separation system according to a first aspect of the present invention is a membrane separation system equipped with a membrane separation device, wherein the membrane separation device has a pervaporation membrane that separates a mixed liquid containing liquid A and liquid B different from liquid A into a permeable fluid and a non-permeable fluid, and the membrane separation system adjusts the flow rate of the mixed liquid so that the linear velocity of the mixed liquid supplied to the membrane separation device is 11.0 m / h or more.

[0011] In a second aspect of the present invention, for example, in the membrane separation system according to the first aspect, the pervaporation membrane allows the liquid A to permeate preferentially.

[0012] In a third aspect of the present invention, for example, the membrane separation system according to the first or second aspect further includes a tank for storing the mixed liquid to be supplied to the membrane separation device.

[0013] In a fourth aspect of the present invention, for example, the membrane separation system according to the third aspect further includes a non-permeated fluid discharge path connected to the membrane separation device for discharging the non-permeated fluid from the membrane separation device, and the non-permeated fluid discharge path is connected to the tank.

[0014] In a fifth aspect of the present invention, for example, in a membrane separation system according to any one of the first to fourth aspects, the membrane separation system adjusts the temperature of the mixed liquid so that the absolute value of the difference between the temperature T1 (°C) of the mixed liquid supplied to the membrane separation device and the boiling point T2 (°C) of the liquid A is 90°C or less.

[0015] In a sixth aspect of the present invention, for example, in the membrane separation system according to any one of the first to fifth aspects, the membrane separation system adjusts the pressure of the membrane separation device so that the pressure on the permeation side of the membrane separation device is 50 kPa or less.

[0016] In a seventh aspect of the present invention, for example, in the membrane separation system according to any one of the first to sixth aspects, the content of the liquid A in the mixed liquid is 50 wt % or less.

[0017] In an eighth aspect of the present invention, for example, in the membrane separation system according to any one of the first to seventh aspects, the liquid A is an organic solvent.

[0018] In a ninth aspect of the present invention, for example, in the membrane separation system according to any one of the first to eighth aspects, the membrane separation device is a spiral membrane element, and the membrane element includes a central tube having through holes and a laminate having the pervaporation membrane and wound around the central tube.

[0019] In a tenth aspect of the present invention, for example, in the membrane separation system according to the ninth aspect, the outer diameter of the membrane element is 180 mm or more.

[0020] In an eleventh aspect of the present invention, for example, in the membrane separation system according to any one of the first to tenth aspects, the pervaporation membrane contains a silicone-based polymer.

[0021] In a twelfth aspect of the present invention, for example, in the membrane separation system according to any one of the first to eleventh aspects, the pervaporation membrane has a matrix containing a silicone-based polymer and a filler containing silica dispersed in the matrix.

[0022] A method for operating a membrane separation device according to a thirteenth aspect of the present invention is a method for operating a membrane separation device having a pervaporation membrane, the method comprising: a supply step of supplying a mixed liquid containing liquid A and liquid B different from liquid A to the membrane separation device; and a membrane separation step of separating the mixed liquid into a permeated fluid and a non-permeated fluid using the pervaporation membrane, wherein the membrane separation step is carried out while adjusting the flow rate of the mixed liquid so that the linear velocity of the mixed liquid supplied to the membrane separation device is 11.0 m / h or more.

[0023] In a fourteenth aspect of the present invention, for example, in the method of operating a membrane separation apparatus according to the thirteenth aspect, the pervaporation membrane allows the liquid A to permeate preferentially.

[0024] In a fifteenth aspect of the present invention, for example, the method for operating a membrane separation apparatus according to the thirteenth or fourteenth aspect further comprises a circulating step of circulating the non-permeated fluid discharged from the membrane separation apparatus back into the membrane separation apparatus.

[0025] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0026] <Membrane Separation System> Figure 1 is a schematic diagram showing an example of a membrane separation system 100 according to one embodiment of the present invention. As shown in Figure 1, the membrane separation system 100 includes a membrane separation device 10. The membrane separation device 10 has a pervaporation membrane 11 and a supply space and a permeation space separated by the pervaporation membrane 11. The pervaporation membrane 11 can separate a mixed liquid containing liquid A and liquid B different from liquid A into a permeating fluid and a non-permeating fluid.

[0027] In this embodiment, the mixed liquid to be separated contains liquid A and liquid B. Liquid A is, for example, an organic solvent, and liquid B is, for example, water. An example of the mixed liquid is a cleaning liquid used to clean an object to be cleaned, such as a separation membrane (e.g., an RO membrane), in a manufacturing process of the separation membrane. However, the mixed liquid is not particularly limited as long as it contains liquid A and liquid B that is different from liquid A. For example, the mixed liquid may be waste liquid generated in various chemical processes, a fermented liquid obtained by fermenting a carbon source, or the like.

[0028] As described above, the membrane separation device 10 is a device that performs membrane separation of a mixed liquid using a pervaporation membrane 11. The pervaporation membrane 11 is typically a membrane that preferentially allows liquid A contained in the mixed liquid to permeate. Therefore, the permeated fluid separated by the pervaporation membrane 11 has a higher content of liquid A than the mixed liquid. On the other hand, the non-permeated fluid has a lower content of liquid A than the mixed liquid. However, the pervaporation membrane 11 may also be a membrane that preferentially allows liquid B contained in the mixed liquid to permeate.

[0029] Conventionally, when a mixed liquid is supplied to a membrane element, the linear velocity is adjusted to a relatively low value (for example, about 1.2 m / h). In contrast, in the membrane separation system 100 of this embodiment, the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 is operated at 11.0 m / h or higher. By setting the linear velocity LV to 11.0 m / h or higher, the content of liquid A on the surface of the pervaporation membrane 11 is maintained high, allowing liquid A to be efficiently separated from the mixed liquid. This allows the amount of liquid A recovered per power required to operate the membrane separation device 10 to be increased. As such, the membrane separation system 100 of this embodiment is highly practical in terms of recovery costs.

[0030] In this embodiment, the linear velocity LV (m / h) of the mixed liquid supplied to the membrane separation device 10 is the cross-sectional area S (m 2) where the cross-sectional area S of the supply space means the cross-sectional area of ​​the supply space in a plane perpendicular to the direction in which the mixed liquid passes. The linear velocity LV (m / h) of the mixed liquid supplied to the membrane separation device 10 is calculated by multiplying the flow rate Q (m 3 / h) and the cross-sectional area S (m 2 ) and is calculated using the following formula:

[0031] LV(m / h)=Q(m 3 / h) / S(m 2 )

[0032] Therefore, by adjusting the flow rate Q of the mixed liquid supplied to the membrane separation device 10, the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 can be controlled to 11.0 m / h or more.

[0033] The lower limit of the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 may be 11.5 m / h, 12.0 m / h, 12.5 m / h, 13.0 m / h, 13.5 m / h, or even 14.0 m / h.

[0034] The upper limit of the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 is, for example, 100 m / h. The upper limit of the linear velocity LV of the mixed liquid may be 95 m / h, 90 m / h, 85 m / h, 80 m / h, 75 m / h, or even 70 m / h.

[0035] The lower limit of the flow rate Q of the mixed liquid supplied to the membrane separation device 10 is, for example, 400 L / h. The lower limit of the flow rate Q of the mixed liquid may be 600 L / h, 800 L / h, 1000 L / h, 1200 L / h, 1400 L / h, 1600 L / h, 1800 L / h, or even 2000 L / h.

[0036] The upper limit of the flow rate Q of the mixed liquid supplied to the membrane separation device 10 is, for example, 2200 L / h. The upper limit of the flow rate Q of the mixed liquid may be 2000 L / h, 1800 L / h, 1600 L / h, 1400 L / h, 1200 L / h, 1000 L / h, 800 L / h, or even 600 L / h.

[0037] The lower limit of the cross-sectional area S of the supply space of the membrane separation device 10 is, for example, 0.010 m 2The lower limit of the cross-sectional area S of the supply space is 0.0125 m 2 , 0.015m 2 , 0.0175m 2 , 0.020m 2 , 0.0225m 2 , and a further 0.026 m 2 may be.

[0038] The upper limit of the cross-sectional area S of the supply space of the membrane separation device 10 is, for example, 0.050 m 2 The upper limit of the cross-sectional area S of the supply space is 0.0475 m 2 , 0.045 m 2 , 0.0425m 2 , and another 0.040 m 2 may be.

[0039] The membrane separation system 100 further includes a tank 20. The tank 20 stores the mixed liquid to be supplied to the membrane separation apparatus 10. By including the tank 20, the mixed liquid can be continuously supplied to the membrane separation apparatus 10.

[0040] The membrane separation system 100 further includes a mixed liquid supply path 60 , a non-permeate fluid discharge path 61 , and a permeate fluid discharge path 62 .

[0041] The mixed liquid supply path 60 is a path for supplying the mixed liquid from the tank 20 to the membrane separation device 10 during operation, and is connected to the outlet 21 of the tank 20 and the supply space inlet 13a of the membrane separation device 10. The mixed liquid supply path 60 is provided with, for example, a pump 40 for adjusting the flow rate Q of the mixed liquid.

[0042] For example, the flow rate Q of the mixed liquid can be adjusted by the pump 40 so that the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 is 11.0 m / h or more.

[0043] As shown in FIG. 1, a flow meter 51 may be disposed in the mixed liquid supply path 60. The flow meter 51 measures the flow rate Q (m 3 The flow meter 51 is located, for example, between the pump 40 and the membrane separation device 10, and is preferably located near the feed space inlet 13a of the membrane separation device 10.

[0044] The membrane separation system 100 may adjust the temperature of the mixed liquid so that the absolute value |T1-T2| of the difference between the temperature T1 (°C) of the mixed liquid supplied to the membrane separation device 10 and the boiling point T2 (°C) of Liquid A is 90°C or less. Adjusting the temperature of the mixed liquid in this manner promotes membrane separation in the membrane separation device 10. As a result, the cost of recovering Liquid A is further reduced.

[0045] The upper limit of the absolute value |T1-T2| may be 80°C, 70°C, 60°C, or even 50°C.

[0046] The lower limit of the absolute value |T1-T2| is, for example, 10° C. The lower limit of the absolute value |T1-T2| may be 15° C., 20° C., 25° C., 30° C., 35° C., or even 40° C.

[0047] As shown in FIG. 1 , a heating unit 45 for heating the mixed liquid supplied to the membrane separation device 10 may be disposed in the mixed liquid supply path 60. The heating unit 45 may be configured to utilize heat (waste heat) obtained from another heat exchanger included in the membrane separation system 100 (for example, a heat exchanger 46 disposed in the permeate fluid discharge path 62 described later). The heating unit 45 may be a heater such as an electric heater. As shown in FIG. 1 , the heating unit 45 may be located between the pump 40 and the membrane separation device 10 (downstream of the pump 40). The heating unit 45 may be located between the tank 20 and the pump 40 (upstream of the pump 40).

[0048] For example, the heating unit 45 can adjust the absolute value |T1-T2| of the difference between the temperature T1 (°C) of the mixed liquid supplied to the membrane separation device 10 and the boiling point T2 (°C) of liquid A.

[0049] A temperature sensor (not shown) for measuring the temperature T1 (°C) of the mixed liquid supplied to the membrane separation device 10 may be disposed in the mixed liquid supply path 60. The temperature sensor is located, for example, between the pump 40 and the membrane separation device 10, and is preferably located near the supply space inlet 13a of the membrane separation device 10.

[0050] The non-permeated fluid discharge path 61 is a path for discharging the non-permeated fluid from the membrane separation device 10 during operation, and is connected to the supply space outlet 13b of the membrane separation device 10. For example, a pump 41 for controlling the flow rate of the non-permeated fluid is disposed in the non-permeated fluid discharge path 61. The pump 41 does not necessarily have to be disposed in the non-permeated fluid discharge path 61. A temperature sensor (not shown) for measuring the temperature of the non-permeated fluid discharged from the membrane separation device 10 may be disposed in the non-permeated fluid discharge path 61. The temperature sensor is located, for example, between the membrane separation device 10 and the pump 41, and is preferably located near the supply space outlet 13b of the membrane separation device 10.

[0051] The non-permeated fluid discharge path 61 may be connected to the inlet 22 of the tank 20, and may be configured to send the non-permeated fluid to the tank 20 during operation. That is, during operation, the non-permeated fluid may be mixed with the mixed liquid in the tank 20 and circulated through the mixed liquid supply path 60 and the non-permeated fluid discharge path 61. With this configuration, the recovery cost of liquid A can be further reduced. When the non-permeated fluid is sent to the tank 20, the mixed liquid and the non-permeated fluid are mixed in the tank 20, and the content of liquid A in the mixed liquid decreases.

[0052] In the membrane separation system 100, the pressure of the membrane separation device 10 may be adjusted so that the pressure on the permeate side of the membrane separation device 10 is 50 kPa or less. Adjusting the pressure on the permeate side of the membrane separation device 10 in this manner promotes membrane separation in the membrane separation device 10. As a result, the cost of recovering Liquid A is further reduced. In this specification, unless otherwise specified, "pressure" refers to absolute pressure.

[0053] The upper limit of the pressure on the permeate side of the membrane separation device 10 may be 40 kPa, 30 kPa, 20 kPa, 10 kPa, or even 5 kPa.

[0054] The lower limit of the pressure on the permeation side of the membrane separation device 10 is, for example, 0.1 kPa. The lower limit of the pressure on the permeation side of the membrane separation device 10 may be 0.25 kPa, 0.5 kPa, 0.75 kPa, or even 1.0 kPa.

[0055] The permeate discharge path 62 is a path for discharging the permeate fluid from the membrane separation device 10 during operation and is connected to the permeate space outlet 14a of the membrane separation device 10. For example, a pressure reducing device 42 is disposed in the permeate discharge path 62. The pressure reducing device 42 can reduce the pressure inside the permeate space of the membrane separation device 10. The pressure reducing device 42 is preferably a vacuum device such as a vacuum pump. Vacuum pumps are typically gas transport vacuum pumps, and examples of such pumps include reciprocating vacuum pumps and rotary vacuum pumps. Examples of reciprocating vacuum pumps include diaphragm and oscillating piston vacuum pumps. Examples of rotary vacuum pumps include liquid ring pumps; oil rotary pumps (rotary pumps); mechanical booster pumps; and various dry pumps such as roots, claw, screw, turbo, and scroll types. The pump used as the pressure reducing device 42 may be equipped with a variable speed mechanism for changing the rotation speed, etc. An example of such a variable speed mechanism is an inverter that drives the pump motor. By controlling the rotation speed of the pump with the variable speed mechanism, the pressure in the permeate space of the membrane separation device 10 can be adjusted appropriately.

[0056] For example, the pressure on the permeate side of the membrane separation device 10 can be adjusted by a pressure reducing device 42 .

[0057] A heat exchanger 46 for cooling the permeate fluid may be disposed in the permeate discharge path 62. The heat exchanger 46 can cool and condense the gaseous permeate fluid. The heat exchanger 46 is, for example, a gas-liquid heat exchanger that causes heat exchange between a cooling medium such as antifreeze and the gaseous permeate fluid. As shown in FIG. 1, the heat exchanger 46 may be located between the membrane separation apparatus 10 and the pressure reduction device 42 (upstream of the pressure reduction device 42). The heat exchanger 46 may be located between the pressure reduction device 42 and the recovery section 30 (downstream of the pressure reduction device 42), which will be described later.

[0058] The membrane separation system 100 further includes a recovery unit 30. The recovery unit 30 recovers the permeated fluid sent from the membrane separation device 10 and can store the permeated fluid, for example. The recovery unit 30 is, for example, a tank for storing the permeated fluid. A permeated fluid discharge path 62 is connected to an inlet 31 of the recovery unit 30.

[0059] The membrane separation system 100 may further include a controller 50 that controls each component of the membrane separation system 100. The controller 50 is, for example, a DSP (Digital Signal Processor) including an A / D conversion circuit, an input / output circuit, an arithmetic circuit, a storage device, etc. The controller 50 stores a program for appropriately operating the membrane separation system 100. For example, the controller 50 can control the operation of the pump 40 to adjust the flow rate Q of the mixed liquid supplied to the membrane separation device 10.

[0060] Unless otherwise specified, each of the paths of the membrane separation system 100 is made up of, for example, metal or resin piping.

[0061] As described above, the mixed liquid contains liquid A and liquid B, which is different from liquid A. In this specification, "liquid" means a substance that is in a liquid state under an environment of a temperature of 20°C and an atmospheric pressure of 101.325 kPa. Therefore, for convenience, the components contained in the permeate fluid (typically gas) discharged from the membrane separation device 10 may also be referred to as liquid A or liquid B.

[0062] An example of liquid A contained in the mixed liquid is an organic solvent. When liquid A is an organic solvent, liquid B may be water. However, liquid A may also be water. When liquid A is water, liquid B may also be an organic solvent. Liquid A may also be a volatile organic solvent, and liquid B may be an organic solvent with a higher boiling point than liquid A.

[0063] An example of the organic solvent is a volatile organic compound C. The term "volatile organic compound" refers to, for example, an organic compound having a boiling point of 20°C to 260°C under atmospheric pressure (101.325 kPa).

[0064] The volatile organic compound C is not particularly limited as long as it is volatile. For example, when the content of the organic compound C in an aqueous solution is high, the organic compound C generates an aqueous phase containing water as a main component and an organic phase having a higher content of the organic compound C than the aqueous phase.

[0065] The number of carbon atoms in the organic compound C is not particularly limited and may be, for example, 10 or less, 8 or less, 6 or less, or even 4 or less. The lower limit of the number of carbon atoms in the organic compound C may be 1 or 2. The organic compound C has a functional group containing an oxygen atom, such as a hydroxyl group, a carbonyl group, or an ether group. In the organic compound C, the number of functional groups containing an oxygen atom is typically one.

[0066] Examples of the organic compound C include alcohols and ketones, with alcohols being preferred. When the organic compound C is an alcohol, the organic compound C is highly compatible with water and is less likely to cause imbalances in the environment within the system. The alcohol may be an alkyl alcohol composed only of an alkyl group and a hydroxyl group, or an aryl alcohol containing an aryl group and a hydroxyl group. The alkyl alcohol may be linear, branched, or cyclic. Examples of the alkyl alcohol include methanol, ethanol, n-propanol, isopropanol (IPA), n-butanol, 2-butanol, isobutanol, t-butanol, and n-pentanol, with IPA being preferred. Examples of the aryl alcohol include phenol.

[0067] The ketone may be a dialkyl ketone consisting of only an alkyl group and a carbonyl group, such as methyl ethyl ketone (MEK) or acetone.

[0068] The organic compound C is not limited to the above-mentioned compounds, and may be an aromatic hydrocarbon such as benzene, toluene, or xylene.

[0069] The organic compound C may be a fermentation product produced by fermenting a carbon source with a microorganism, or may be alcohol (bioalcohol) produced by a microorganism.

[0070] The content of Liquid A in the mixed liquid is, for example, 50 wt % or less, preferably 40 wt % or less, and more preferably 10 wt % or less. The lower limit of the content of Liquid A in the mixed liquid is not particularly limited, and is, for example, 1 wt %. In this specification, unless otherwise specified, "content" refers to the weight percent concentration when the temperature of the mixed liquid or fluid containing the target component is 20°C.

[0071] The content of Liquid B in the mixed liquid is, for example, higher than 50 wt %, preferably 80 wt % or more, and more preferably 90 wt % or more. The upper limit of the content of Liquid B in the mixed liquid is not particularly limited, and is, for example, 99 wt %.

[0072] The mixed liquid may be a cleaning liquid containing a volatile organic compound C as liquid A. The cleaning liquid may be a cleaning liquid used to clean an object to be cleaned, such as a separation membrane (e.g., an RO membrane), in a manufacturing process of the separation membrane or the like. The mixed liquid may also be waste liquid generated in various chemical processes.

[0073] The cleaning solution may contain impurities in addition to water and the organic compound C. The impurities are derived from the object to be cleaned, for example. Examples of the impurities include organic compounds other than the organic compound C, inorganic compounds, and the like.

[0074] The mixed liquid may be a fermentation broth containing a volatile organic compound C (fermented product) as liquid A. The fermentation broth contains organic compound C as well as microorganisms that produce the organic compound C. The fermentation broth is obtained by fermenting a carbon source such as glucose or synthetic gas in an aqueous solution using microorganisms. Therefore, the fermentation broth contains volatile organic compound C as well as microorganisms that produce the organic compound C. The microorganisms that produce organic compound C are typically bacteria. Generally, during the fermentation of a carbon source in an aqueous solution, gases such as carbon dioxide are generated as by-products. Therefore, gases are present as dissolved gases in the fermentation broth obtained by fermentation. Dissolved gases include carbon dioxide. The fermentation broth contains, for example, water in addition to organic compound C, microorganisms, and dissolved gases. The fermentation broth is typically an aqueous solution containing organic compound C, microorganisms, and dissolved gases.

[0075] In addition to water, organic compound C, microorganisms, and dissolved gases, the fermentation liquid may further contain other components such as a carbon source, a nitrogen source, inorganic ions, etc. Examples of carbon sources include polysaccharides such as starch and monosaccharides such as glucose.

[0076] [Membrane Separation Apparatus] Figure 2 is a schematic cross-sectional view showing an example of a membrane separation apparatus 10. The membrane separation apparatus 10 shown in Figure 2 includes a pervaporation membrane 11 and a container 12. The container 12 has a first chamber 13 and a second chamber 14. The first chamber 13 functions as a supply space to which the mixed liquid F0 is supplied. The second chamber 14 functions as a permeation space to which the permeated fluid F1 is supplied. The permeated fluid F1 is obtained by the permeation of the mixed liquid F0 through the pervaporation membrane 11.

[0077] Pervaporation membrane 11 is disposed inside container 12. Inside container 12, pervaporation membrane 11 separates first chamber 13 from second chamber 14. Pervaporation membrane 11 extends from one of a pair of walls of container 12 to the other.

[0078] The first chamber 13 has a feed space inlet 13a and a feed space outlet 13b. The second chamber 14 has a permeate space outlet 14a. The feed space inlet 13a is an opening for supplying the mixed liquid F0 to the feed space (first chamber 13). The permeate space outlet 14a is an opening for discharging the permeated fluid F1 from the permeate space (second chamber 14). The feed space outlet 13b is an opening for discharging the mixed liquid F0 (non-permeated fluid F2) that has not permeated the pervaporation membrane 11 from the feed space (first chamber 13). The feed space inlet 13a, the feed space outlet 13b, and the permeate space outlet 14a are each formed, for example, on a wall surface of the container 12.

[0079] The membrane separation apparatus 10 is suitable for a one-pass (continuous) membrane separation method, but may also be used for a batch (batch) membrane separation method.

[0080] (Pervaporation Membrane) As described above, the pervaporation membrane 11 is typically a membrane that preferentially allows the liquid A contained in the mixed liquid F0 to permeate. The pervaporation membrane 11 generates a gaseous permeating fluid F1 containing the gaseous liquid A by, for example, pervaporation.

[0081] Figure 3 is a schematic cross-sectional view showing an example of the pervaporation membrane 11 included in the membrane separation device 10 shown in Figure 2. As shown in Figure 3, the pervaporation membrane 11 may include a separation function layer 1, a porous support 3 supporting the separation function layer 1, and an intermediate layer 2 disposed between the separation function layer 1 and the porous support 3. The intermediate layer 2 is, for example, in direct contact with both the separation function layer 1 and the porous support 3. For example, the main surface 11a of the pervaporation membrane 11 on the separation function layer 1 side is exposed to the first chamber 13, and the main surface 11b on the porous support 3 side is exposed to the second chamber 14.

[0082] (Separation Functional Layer) The separation functional layer 1 is typically a layer that allows preferential permeation of liquid A contained in the mixed liquid F0. The separation functional layer 1 includes, for example, a hydrophobic material. In this specification, the term "hydrophobic material" refers to a material that has a static contact angle with water of more than 90° when, for example, a 10 μL water droplet (temperature 25° C.) is dropped onto the surface of a test piece made of the material. The static contact angle with water can be measured using a commercially available contact angle meter.

[0083] Examples of hydrophobic materials include compounds having a siloxane bond (Si—O—Si bond), olefin-based polymers, oils, and fluorine-based compounds. The separation functional layer 1 preferably contains a compound having a siloxane bond as the hydrophobic material. Compounds having a siloxane bond are typically silicone-based polymers. Silicon-based polymers may be solid or liquid at 25°C. Specific examples of silicone-based polymers include polydimethylsiloxane (PDMS). Specific examples of olefin-based polymers include polyethylene and polypropylene. Examples of oils include hydrocarbon oils such as liquid paraffin. Specific examples of fluorine-based compounds include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA). The hydrophobic materials can be used alone or in combination of two or more.

[0084] The separation functional layer 1 may contain a hydrophobic material as a main component, or may be composed essentially of a hydrophobic material. The "main component" refers to the component that is contained in the separation functional layer 1 in the largest amount by weight.

[0085] The separation functional layer 1 may include a matrix containing a hydrophobic material and a filler dispersed in the matrix. The filler is embedded in the matrix. Within the matrix, all of the fillers may be spaced apart from one another or may be partially aggregated.

[0086] The filler includes, for example, inorganic materials such as zeolite, silica, and bentonite. The zeolite contained in the filler is preferably a high-silica zeolite having a high ratio of silica to alumina. High-silica zeolite has excellent hydrolysis resistance and is therefore suitable for applications such as separating fermentation liquid. Examples of high-silica zeolites that can be used include HSZ (registered trademark) manufactured by Tosoh Corporation, HiSiv (registered trademark) manufactured by Union Showa Corporation, USKY (registered trademark) manufactured by Union Showa Corporation, and Zeoal (registered trademark) manufactured by Nakamura Choukou Co., Ltd.

[0087] The filler may include a metal-organic framework (MOF). The metal-organic framework is also called a porous coordination polymer (PCP). The metal-organic framework is preferably hydrophobic. The metal-organic framework includes, for example, a metal ion and an organic ligand. Examples of the metal ion include Zn ions. Examples of the organic ligand include an aromatic ring. Examples of the aromatic ring included in the organic ligand include an imidazole ring. Examples of the organic ligand include 2-methylimidazole. Specific examples of the metal-organic framework include ZIF-8.

[0088] The shape of the filler is, for example, particulate. In this specification, "particulate" includes spherical, ellipsoidal, scaly, and fibrous shapes. The average particle size of the filler is not particularly limited and is, for example, 50 μm or less, preferably 20 μm or less, and more preferably 10 μm or less. The lower limit of the average particle size of the filler is, for example, 0.01 μm. The average particle size of the filler can be determined, for example, by the following method. First, the cross section of the separation functional layer 1 is observed with a transmission electron microscope. In the obtained electron microscope image, the area of ​​a specific filler is calculated by image processing. The diameter of a circle having the same area as the calculated area is considered to be the particle size (particle diameter) of that specific filler. The particle sizes of an arbitrary number (at least 50) of fillers are calculated, and the average of the calculated values ​​is considered to be the average particle size of the filler.

[0089] The filler content in the separation functional layer 1 is, for example, 10 wt % or more, preferably 30 wt % or more, and more preferably 40 wt % or more. The upper limit of the filler content in the separation functional layer 1 is not particularly limited and is, for example, 70 wt %. The matrix content in the separation functional layer 1 is not particularly limited and is, for example, 30 wt % to 90 wt %.

[0090] The thickness of the separation functional layer 1 is, for example, 200 μm or less, preferably 100 μm or less, and more preferably 80 μm or less. The lower limit of the thickness of the separation functional layer 1 is, for example, 0.1 μm. The lower limit of the thickness of the separation functional layer 1 may be 0.5 μm, 1 μm, 5 μm, 10 μm, or even 30 μm.

[0091] The separation functional layer 1 may have a microporous structure with an average pore size of less than 0.01 μm, but may also be a dense layer with no pores on the surface.

[0092] (Intermediate Layer) The intermediate layer 2 may contain, for example, a resin and may further contain nanoparticles dispersed in the resin (matrix). The nanoparticles may be spaced apart within the matrix or may be partially aggregated. The material of the matrix is ​​not particularly limited, and examples thereof include silicone resins such as polydimethylsiloxane; fluororesins such as polytetrafluoroethylene; epoxy resins such as polyethylene oxide; polyimide resins; polysulfone resins; polyacetylene resins such as polytrimethylsilylpropyne and polydiphenylacetylene; and polyolefin resins such as polymethylpentene. The matrix preferably contains a silicone resin.

[0093] The nanoparticles may contain an inorganic material or an organic material. Examples of inorganic materials contained in the nanoparticles include silica, titania, and alumina. The nanoparticles preferably contain silica.

[0094] The thickness of the intermediate layer 2 is not particularly limited and is, for example, less than 50 μm, preferably 40 μm or less, more preferably 30 μm or less, even more preferably 25 μm or less, particularly preferably 10 μm or less, and most preferably 5 μm or less. The lower limit of the thickness of the intermediate layer 2 is not particularly limited and may be 0.01 μm or 1 μm. The intermediate layer 2 is, for example, a layer having a thickness of less than 50 μm.

[0095] (Porous Support) The porous support 3 supports the separation function layer 1 via the intermediate layer 2. Examples of the porous support 3 include nonwoven fabrics, porous polytetrafluoroethylene, aromatic polyamide fibers, porous metals, sintered metals, porous ceramics, porous polyesters, porous nylons, activated carbon fibers, latex, silicone, silicone rubber, polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyether ether ketone, polyacrylonitrile, polyimide, and polyphenylene oxide. Permeable (porous) polymers containing at least one selected from the group consisting of metal foams having open or closed cells, polymer foams having open or closed cells, silica, porous glass, and mesh screens. The porous support 3 may be a combination of two or more of these.

[0096] The porous support 3 has an average pore size of, for example, 0.01 to 0.4 μm. The thickness of the porous support 3 is not particularly limited and is, for example, 10 μm or more, preferably 50 μm or more, and more preferably 100 μm or more. The thickness of the porous support 3 is, for example, 300 μm or less, and preferably 200 μm or less.

[0097] The configuration of the pervaporation membrane 11 is not limited to the example shown in Fig. 3. The pervaporation membrane 11 may be composed of, for example, a separation functional layer 1 and a porous support 3 that is disposed on one side of the separation functional layer 1 and supports the separation functional layer 1. The pervaporation membrane 11 may further include a protective layer that protects the separation functional layer 1. The protective layer is disposed on, for example, one side of the separation functional layer 1. The protective layer may include a material described for the intermediate layer 2.

[0098] (Method for producing pervaporation membrane) The pervaporation membrane 11 can be produced, for example, by forming a separation functional layer 1 on a porous support 3. In detail, first, a coating liquid containing the material of the separation functional layer 1 is prepared. The coating liquid may contain a filler as well as a dispersant for dispersing the filler in the coating liquid. When the coating liquid contains a compound having a siloxane bond, the coating liquid may further contain a catalyst for curing the compound. Next, a coating film is obtained by coating the coating liquid on the porous support 3. The coating film is dried to form the separation functional layer 1.

[0099] [Operation of Membrane Separation System] A method for operating the membrane separation system 100 (and the membrane separation device 10) includes, for example, a supply step of supplying a mixed liquid containing liquid A and liquid B different from liquid A to the membrane separation device 10, and a membrane separation step of separating the mixed liquid into a permeated fluid and a non-permeated fluid using a pervaporation membrane 11. The membrane separation step is performed while adjusting the flow rate Q of the mixed liquid so that the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 is 11.0 m / h or more.

[0100] In this operating method, the membrane separation device 10 is operated at a linear velocity LV of 11.0 m / h or higher for the mixed liquid supplied thereto. By setting the linear velocity LV to 11.0 m / h or higher, the content of Liquid A on the surface of the pervaporation membrane 11 is maintained high, allowing Liquid A to be efficiently separated from the mixed liquid. This allows the amount of Liquid A recovered per unit of power required to operate the membrane separation device 10 to be increased.

[0101] In the supply step, as shown in Fig. 2, the mixed liquid is supplied to the first chamber 13 of the membrane separation device 10 through the supply space inlet 13a. This allows the mixed liquid to come into contact with one surface (e.g., the main surface 11a) of the pervaporation membrane 11.

[0102] In the supply step, the temperature of the mixed liquid may be adjusted so that the absolute value |T1-T2| of the difference between the temperature T1 (°C) of the mixed liquid supplied to the membrane separation device 10 and the boiling point T2 (°C) of liquid A is 90°C or less. For example, the heating unit 45 can adjust the absolute value |T1-T2| of the difference between the temperature T1 (°C) of the mixed liquid supplied to the membrane separation device 10 and the boiling point T2 (°C) of liquid A to 90°C or less.

[0103] The membrane separation process is performed as follows. First, with the mixed liquid in contact with one surface of the pervaporation membrane 11, the space adjacent to the other surface (e.g., the main surface 11b) of the pervaporation membrane 11 is depressurized. Specifically, the pressure in the second chamber 14 is reduced through the permeation space outlet 14a. The pressure in the second chamber 14 can be reduced by, for example, a depressurization device 42. The pressure in the second chamber 14 is preferably 50 kPa or less.

[0104] By reducing the pressure inside the second chamber 14, a permeated fluid with a high content of Liquid A can be obtained on the other side of the pervaporation membrane 11. In other words, the permeated fluid is supplied to the second chamber 14. In the second chamber 14, the permeated fluid is typically a gas. The permeated fluid is discharged to the outside of the membrane separation device 10 through the permeate space outlet 14a.

[0105] On the other hand, the content of liquid A in the mixed liquid gradually decreases from the feed space inlet 13a to the feed space outlet 13b of the first chamber 13. The mixed liquid (non-permeated fluid) treated in the first chamber 13 is discharged to the outside of the membrane separation device 10 through the feed space outlet 13b. The non-permeated fluid is typically a liquid.

[0106] As described above, the pervaporation membrane 11 of the membrane separation apparatus 10 allows liquid A contained in the mixed liquid to preferentially permeate. Therefore, the permeated fluid obtained by operation of the membrane separation apparatus 10 has a higher content of liquid A than the mixed liquid supplied to the membrane separation apparatus 10. The ratio of the content (wt%) of liquid A in the permeated fluid to the content (wt%) of liquid A in the mixed liquid is not particularly limited.

[0107] In this operating method, the membrane separation step is performed while adjusting the flow rate Q of the mixed liquid so that the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 is 11.0 m / h or more. The flow rate Q of the mixed liquid supplied to the membrane separation device 10 can be adjusted by, for example, the pump 40.

[0108] The operating method may further include a circulation step of circulating the non-permeated fluid discharged from the membrane separation device 10 back to the membrane separation device 10. Such a configuration can further reduce the cost of recovering the liquid A. In the circulation step, the non-permeated fluid is mixed with the mixed liquid in the tank 20, and circulated through the mixed liquid supply path 60 and the non-permeated fluid discharge path 61.

[0109] The operating method may further include a recovery step of recovering the permeated fluid discharged from the membrane separation device 10. With such a configuration, it is possible to recover liquid A as the permeated fluid. In the recovery step, the gaseous permeated fluid discharged from the membrane separation device 10 is cooled and condensed in the heat exchanger 46, and the liquid permeated fluid is recovered in the recovery section 30.

[0110] According to the operating method of this embodiment, it is possible to produce, for example, a permeated fluid having a high content of Liquid A. In other words, according to the operating method of this embodiment, Liquid A can be produced as the permeated fluid.

[0111] [Modifications of Membrane Separation Device] The membrane separation device 10 may include a spiral membrane element, a hollow fiber membrane element, a disk-tube membrane element in which multiple pervaporation membranes are stacked, a plate-and-frame membrane element, or the like. Figure 4 is an exploded perspective view schematically showing an example of a spiral membrane element. The spiral membrane element 15 shown in Figure 4 includes a central tube 16 having through holes and a laminate 17 having pervaporation membranes 11 and wound around the central tube 16. The membrane separation device 10 may include the spiral membrane element 15.

[0112] The membrane element 15 may be housed in a casing (not shown in FIG. 4). A plurality of membrane elements 15 may be provided in series inside the casing. The number of membrane elements 15 is not particularly limited and may be, for example, 2 to 5.

[0113] The outer diameter of the membrane element 15 is preferably 180 mm or more.

[0114] There is no particular upper limit to the outer diameter of the membrane element 15. The upper limit to the outer diameter of the membrane element 15 is, for example, 500 mm or less.

[0115] The central tube 16 has a cylindrical shape. One or more through holes or slits are formed on the surface of the central tube 16 to allow the permeation fluid F1 to flow into the interior of the central tube 16. Examples of materials for the central tube 16 include resins such as acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); and metals such as stainless steel and titanium. The inner diameter of the central tube 16 is, for example, in the range of 20 to 100 mm.

[0116] In addition to the pervaporation membrane 11, the laminate 17 further includes a feed-side channel material 18 and a permeate-side channel material 19. The laminate 17 is wound around a central tube 16. The membrane element 15 may further include an exterior material (not shown).

[0117] As the feed-side flow path material 18 and the permeate-side flow path material 19, for example, a resin net, woven fabric, or knitted fabric made of polyethylene, polypropylene, polyethylene terephthalate (PET), polyphenylene sulfide (PPS), or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.

[0118] The membrane element 15 can be operated, for example, by the following method. First, the mixed liquid F0 is supplied to one end of the wound stack 17. The space inside the central tube 16 is depressurized. As a result, the permeated fluid F1 that has permeated the pervaporation membrane 11 of the stack 17 moves into the central tube 16. The permeated fluid F1 is discharged to the outside through the central tube 16. The mixed liquid F0 (non-permeated fluid F2) that has been treated in the membrane element 15 is discharged to the outside from the other end of the wound stack 17.

[0119] [Modification of Membrane Separation System] The membrane separation system 100 may include multiple membrane separation devices 10, and the multiple membrane separation devices 10 may be connected to each other in series or in parallel. In this specification, "multiple membrane separation devices 10 connected to each other in series" means a configuration in which the multiple membrane separation devices 10 are connected to each other so that the mixed liquid discharged from the supply space of the upstream membrane separation device 10 (the non-permeated fluid of the upstream membrane separation device 10 when the membrane separation process is being performed) is supplied to the supply space of the downstream membrane separation device 10. "multiple membrane separation devices 10 connected to each other in parallel" means a configuration in which the multiple membrane separation devices 10 are connected to each other so that the mixed liquid sent from the tank 20 is supplied to each supply space of the multiple membrane separation devices 10. The number of membrane separation devices 10 in the membrane separation system 10 is not particularly limited and may be, for example, 2 to 5.

[0120] (Variation 1) Fig. 5A is a schematic diagram of a membrane separation system 110 including two membrane separation devices 10A and 10B connected in series. The membrane separation system 110 has the same configuration as the membrane separation system 100, except for the inclusion of two membrane separation devices 10A and 10B. Therefore, elements common to the above-described membrane separation system 100 and the membrane separation system 110 of the variation are given the same reference numerals, and their description may be omitted. In other words, the descriptions of each embodiment can be mutually applied unless there is a technical contradiction. Furthermore, each embodiment may be combined with each other unless there is a technical contradiction.

[0121] As described above, in the membrane separation system 110, the membrane separation apparatuses 10A and 10B are connected in series. Specifically, the membrane separation system 110 further includes a connection path 63 that connects the membrane separation apparatuses 10A and 10B to each other. The connection path 63 is connected to the feed space outlet 13b of the membrane separation apparatus 10A and the feed space inlet 13c of the membrane separation apparatus 10B. A mixed liquid feed path 60 is connected to the feed space inlet 13a of the membrane separation apparatus 10A, and a non-permeated fluid discharge path 61 is connected to the feed space outlet 13d of the membrane separation apparatus 10B.

[0122] The permeate fluid discharge path 62 has a first portion 62a and a second portion 62b. The first portion 62a of the permeate fluid discharge path 62 is connected to the permeate space outlet 14a of the membrane separation apparatus 10A, and the second portion 62b is connected to the permeate space outlet 14b of the membrane separation apparatus 10B. The second portion 62b merges with the first portion 62a at a merger position 70.

[0123] For example, two pressure reducing devices 42A and 42B are disposed in the permeate discharge path 62. The pressure reducing device 42A is located between the membrane separation device 10A and the confluence position 70 and can reduce the pressure in the permeate space of the membrane separation device 10A. The pressure reducing device 42B is located between the membrane separation device 10B and the confluence position 70 and can reduce the pressure in the permeate space of the membrane separation device 10B. However, the permeate discharge path 62 may be provided with one pressure reducing device, which may be located between the confluence position 70 and the recovery section 30. In other words, one pressure reducing device may be shared by both the membrane separation devices 10A and 10B.

[0124] The membrane separation system 110 includes a flow meter 51A and a flow meter 51B. The flow meter 51A measures the flow rate Q (m 3 The flow meter 51B measures the flow rate Q (m 3 / h). The flow meter 51A is located, for example, between the pump 40A and the membrane separation apparatus 10A, for example, near the supply space inlet 13a of the membrane separation apparatus 10A. The flow meter 51B is located, for example, between the pump 40B and the membrane separation apparatus 10B, for example, near the supply space inlet 13c of the membrane separation apparatus 10B.

[0125] The membrane separation system 110 includes a pump 40A that adjusts the flow rate of the mixed liquid supplied to the membrane separation apparatus 10A, and a pump 40B that adjusts the flow rate of the mixed liquid (non-permeated fluid of the membrane separation apparatus 10A when the membrane separation process is being performed) supplied to the membrane separation apparatus 10B. The pump 40A is disposed in the mixed liquid supply path 60. The pump 40B is disposed in the connection path 63.

[0126] The membrane separation system 110 includes a heating unit 45A for heating the mixed liquid supplied to the membrane separation apparatus 10A, and a heating unit 45B for heating the mixed liquid supplied to the membrane separation apparatus 10B. The heating unit 45A is located near the membrane separation apparatus 10A, for example, in the mixed liquid supply path 60. The heating unit 45B is located near the membrane separation apparatus 10B, for example, in the connection path 63.

[0127] The membrane separation system 110 includes a heat exchanger 46A and a heat exchanger 46B. The heat exchanger 46A cools and condenses the permeated fluid F1 of the membrane separation apparatus 10A. The heat exchanger 46B cools and condenses the permeated fluid F1 of the membrane separation apparatus 10B. The heat exchanger 46A is disposed, for example, in the first portion 62a of the permeated fluid discharge path 62. The heat exchanger 46B is disposed, for example, in the second portion 62b of the permeated fluid discharge path 62. However, one heat exchanger may be disposed in the permeated fluid discharge path 62, and the heat exchanger may be located between the junction position 70 and the recovery section 30. That is, one heat exchanger may be shared by both the membrane separation apparatuses 10A and 10B.

[0128] In the membrane separation system 110, the pervaporation membrane 11A of the membrane separation device 10A may be the same as or different from the pervaporation membrane 11B of the membrane separation device 10B, except for the membrane area. 2 ) relative to the membrane area (m 2 The ratio of

[0129] The membrane separation system 110 can be operated by the following method. First, in the supply step, the pump 40A is operated to supply the mixed liquid from the tank 20 to the membrane separation device 10A, and then the mixed liquid is supplied from the membrane separation device 10A to the membrane separation device 10B. This allows the mixed liquid to come into contact with the pervaporation membrane 11A of the membrane separation device 10A and the pervaporation membrane 11B of the membrane separation device 10B.

[0130] Next, the permeate space of the membrane separation apparatus 10A is depressurized through the permeate space outlet 14a, and the permeate space of the membrane separation apparatus 10B is depressurized through the permeate space outlet 14b. This allows the membrane separation process to be performed in both the membrane separation apparatuses 10A and 10B, and permeated fluids can be obtained from each of the membrane separation apparatuses 10A and 10B. The mixed liquid (non-permeated fluid) treated in the membrane separation apparatus 10A is sent to the membrane separation apparatus 10B through the connecting path 63 and is further treated therein.

[0131] In the membrane separation process, the membrane separation system 110 adjusts the flow rate Q of the mixed liquid so that the linear velocity LV of the mixed liquid supplied to the membrane separation apparatus 10A is 11.0 m / h or more. Similarly, the membrane separation system 110 adjusts the flow rate Q of the mixed liquid so that the linear velocity LV of the mixed liquid supplied to the membrane separation apparatus 10B is 11.0 m / h or more. By doing so, the content of liquid A on the surfaces of the pervaporation membranes 11A and 11B is maintained high, allowing efficient separation of liquid A from the mixed liquid. This increases the amount of liquid A recovered per power required to operate the membrane separation apparatuses 10A and 10B. The flow rate Q of the membrane separation apparatus 10A and the flow rate Q of the membrane separation apparatus 10B can be adjusted by pumps 40A and 40B, respectively.

[0132] A circulation step may be further performed in which the non-permeated fluid discharged from the membrane separation device 10B is circulated to the membrane separation device 10A. The circulation step can further reduce the cost of recovering the liquid A. In the circulation step, the non-permeated fluid from the membrane separation device 10B is mixed with the mixed liquid in the tank 20, and the mixed liquid is circulated through the mixed liquid supply path 60, the connection path 63, and the non-permeated fluid discharge path 61.

[0133] A recovery step may be further carried out to recover the permeated fluid discharged from the membrane separation devices 10A and 10B. The recovery step allows recovery of liquid A as the permeated fluid. In the recovery step, the gaseous permeated fluid discharged from the membrane separation devices 10A and 10B is cooled and condensed in the heat exchangers 46A and 46B, respectively, and the liquid permeated fluid is recovered in the recovery section 30.

[0134] 5B is a schematic diagram of a membrane separation system 120 including two membrane separation devices 10A and 10B connected in parallel to each other. The membrane separation system 120 has the same configuration as the membrane separation system 100, except that it includes two membrane separation devices 10A and 10B.

[0135] As described above, in the membrane separation system 120, the membrane separation apparatuses 10A and 10B are connected in parallel to each other. Specifically, the mixed liquid supply path 60 has a first portion 60a and a second portion 60b. The first portion 60a of the mixed liquid supply path 60 is connected to the feed space inlet 13a of the membrane separation apparatus 10A, and the second portion 60b is connected to the feed space inlet 13c of the membrane separation apparatus 10B. The second portion 60b branches off from the first portion 60a at a branching position 71. The branching position 71 is located, for example, between the pump 40 and the membrane separation apparatus 10A.

[0136] Furthermore, the non-permeated fluid discharge path 61 has a first portion 61a and a second portion 61b. The first portion 61a of the non-permeated fluid discharge path 61 is connected to the feed space outlet 13b of the membrane separation apparatus 10A, and the second portion 61b is connected to the feed space outlet 13d of the membrane separation apparatus 10B. The second portion 61b merges with the first portion 61a at a merging position 72. The merging position 72 is located, for example, between the pump 41 and the membrane separation apparatus 10A.

[0137] Similar to the above-described membrane separation system 110, the permeate fluid discharge path 62 has a first portion 62a and a second portion 62b. The first portion 62a of the permeate fluid discharge path 62 is connected to the permeate space outlet 14a of the membrane separation apparatus 10A, and the second portion 62b is connected to the permeate space outlet 14b of the membrane separation apparatus 10B. The second portion 62b merges with the first portion 62a at a merging position 70.

[0138] For example, two pressure reducing devices 42A and 42B are disposed in the permeate discharge path 62. The pressure reducing device 42A is located between the membrane separation device 10A and the confluence position 70 and can reduce the pressure in the permeate space of the membrane separation device 10A. The pressure reducing device 42B is located between the membrane separation device 10B and the confluence position 70 and can reduce the pressure in the permeate space of the membrane separation device 10B. However, the permeate discharge path 62 may be provided with one pressure reducing device, which may be located between the confluence position 70 and the recovery section 30. In other words, one pressure reducing device may be shared by both the membrane separation devices 10A and 10B.

[0139] The membrane separation system 110 includes a pump 40 that adjusts the flow rate Q of the mixed liquid supplied to the membrane separation apparatus 10A and the flow rate Q of the mixed liquid supplied to the membrane separation apparatus 10B. The pump 40 is located between the tank 20 and the branch position 71.

[0140] The membrane separation system 120 includes a flow meter 51A and a flow meter 51B. The flow meter 51A measures the flow rate Q (m 3 The flow meter 51B measures the flow rate Q (m 3 / h). The flow meter 51A is located, for example, between the pump 40 and the membrane separation apparatus 10A, for example, near the supply space inlet 13a of the membrane separation apparatus 10A. The flow meter 51B is located, for example, between the pump 40 and the membrane separation apparatus 10B, for example, near the supply space inlet 13c of the membrane separation apparatus 10B.

[0141] The membrane separation system 110 includes a heating unit 45A for heating the mixed liquid supplied to the membrane separation apparatus 10A, and a heating unit 45B for heating the mixed liquid supplied to the membrane separation apparatus 10B. The heating unit 45A is located near the membrane separation apparatus 10A, for example, in the first portion 60a of the mixed liquid supply path 60. The heating unit 45B is located near the membrane separation apparatus 10B, for example, in the second portion 60b of the mixed liquid supply path 60.

[0142] The membrane separation system 110 includes a heat exchanger 46A and a heat exchanger 46B. The heat exchanger 46A cools and condenses the permeated fluid F1 of the membrane separation apparatus 10A. The heat exchanger 46B cools and condenses the permeated fluid F1 of the membrane separation apparatus 10B. The heat exchanger 46A is disposed, for example, in the first portion 62a of the permeated fluid discharge path 62. The heat exchanger 46B is disposed, for example, in the second portion 62b of the permeated fluid discharge path 62. However, one heat exchanger may be disposed in the permeated fluid discharge path 62, and the heat exchanger may be located between the junction position 70 and the recovery section 30. That is, one heat exchanger may be shared by both the membrane separation apparatuses 10A and 10B.

[0143] In the membrane separation system 120, the pervaporation membrane 11A of the membrane separation device 10A may be the same as or different from the pervaporation membrane 11B of the membrane separation device 10B. 2 ) relative to the membrane area (m 2 The ratio of

[0144] The membrane separation system 120 can be operated by the following method. First, in the supply step, the pump 40 is operated to supply the mixed liquid from the tank 20 to each of the membrane separation devices 10A and 10B. This allows the mixed liquid to come into contact with the pervaporation membrane 11A of the membrane separation device 10A and the pervaporation membrane 11B of the membrane separation device 10B.

[0145] Next, the permeate space of the membrane separation device 10A is depressurized through the permeate space outlet 14a, and the permeate space of the membrane separation device 10B is depressurized through the permeate space outlet 14b. This allows the membrane separation process to be performed in both the membrane separation devices 10A and 10B, and permeated fluids can be obtained from each of the membrane separation devices 10A and 10B.

[0146] In the membrane separation process, the membrane separation system 120 adjusts the flow rate Q of the membrane separation device 10A so that the linear velocity LV of the mixed liquid supplied to the membrane separation device 10A is 11.0 m / h or more. Similarly, the membrane separation system 120 adjusts the flow rate Q of the membrane separation device 10B so that the linear velocity LV of the mixed liquid supplied to the membrane separation device 10B is 11.0 m / h or more. By doing so, the content of liquid A on the surfaces of the pervaporation membranes 11A and 11B is maintained high, allowing efficient separation of liquid A from the mixed liquid. This increases the amount of liquid A recovered per unit power required to operate the membrane separation devices 10A and 10B. The flow rate Q of the membrane separation device 10A and the flow rate Q of the membrane separation device 10B can be adjusted by the pump 40.

[0147] A circulation step may be further performed in which the non-permeated fluid discharged from the membrane separation devices 10A and 10B is circulated back to the membrane separation devices 10A and 10B. The circulation step can further reduce the cost of recovering the liquid A. In the circulation step, the non-permeated fluid from the membrane separation devices 10A and 10B is mixed into a mixed liquid in the tank 20, and the mixed liquid is circulated through the mixed liquid supply path 60 and the non-permeated fluid discharge path 61.

[0148] A recovery step may be further carried out to recover the permeated fluid discharged from the membrane separation devices 10A and 10B. The recovery step allows recovery of liquid A as the permeated fluid. In the recovery step, the gaseous permeated fluid discharged from the membrane separation devices 10A and 10B is cooled and condensed in the heat exchangers 46A and 46B, respectively, and the liquid permeated fluid is recovered in the recovery section 30.

[0149] The present invention will be explained in more detail below with reference to measurement examples, but the present invention is not limited thereto.

[0150] [Preparation of Pervaporation Membrane] First, a pervaporation membrane was prepared by the following method. A coating solution was prepared by mixing 1.650 kg (solid content 30 wt%) of silicone resin (YSR3022 manufactured by Momentive Performance Materials Japan), 2.805 kg of toluene, 0.495 kg of high-silica zeolite (HiSiv3000 manufactured by Union Showa Corporation), 0.0495 kg of silicone curing catalyst (YC6831 manufactured by Momentive Performance Materials Japan), and 0.0495 kg of acetylacetone as a curing retarder. The coating solution was then applied to a 150 μm-thick porous support (RS-50 manufactured by Nitto Denko Corporation) to obtain a coating membrane (thickness 500 μm). The coating membrane was heated at 90°C for 4 minutes and dried to prepare a 50 μm-thick separation functional layer. In the separation functional layer, the weight ratio of silicone resin to high-silica zeolite was 50:50. This resulted in a pervaporation membrane.

[0151] [Fabrication of Membrane Separation Apparatus] Using the fabricated pervaporation membrane, a spiral-type membrane element as shown in Figure 4 was fabricated. The outer diameter of the membrane element was 191 mm (8 inches), and the cross-sectional area S of the supply space was 0.0286 m 2 Four membrane elements were arranged in series inside the casing, thereby obtaining a membrane separation device.

[0152] Measurement Example 1 Using the prepared membrane separation device, a supply step, a membrane separation step, a circulation step, and a recovery step were carried out in the membrane separation system 100 shown in FIG.

[0153] In the supply step, the mixed liquid discharged from the tank 20 was supplied to the supply space of the membrane separation device 10 using the pump 40. The mixed liquid contained isopropanol (IPA) as liquid A and water as liquid B. The IPA content in the mixed liquid was 2.5 wt%. The supply step was performed using the heating unit 45 while adjusting the temperature T1 of the mixed liquid to 40.0°C so that the absolute value |T1-T2| of the difference between the temperature T1 (°C) of the mixed liquid supplied to the membrane separation device 10 and the boiling point T2 (°C) of liquid A was 42.3°C.

[0154] Next, the internal space (permeation space) of the central tube of the membrane separation device 10 was reduced in pressure to 1.3 kPa, and the membrane separation process was carried out. This separated the mixed liquid into a permeated fluid and a non-permeated fluid. The membrane separation process was carried out using the pump 40 while adjusting the flow rate Q of the mixed liquid to 127 L / h so that the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 was 4.4 m / h.

[0155] In the circulation step, the non-permeated fluid discharged from the membrane separation device 10 was returned to the tank 20 at a flow rate of 126 L / h using the pump 41 .

[0156] In the recovery step, the gaseous permeated fluid discharged from the membrane separation device 10 was condensed, and then the liquid permeated fluid was recovered. The content of Liquid A (IPA) in the permeated fluid was 18.1 wt %.

[0157] (Measurement Examples 2 to 22) In Measurement Examples 2 to 22, the temperature T1 (°C) of the mixed liquid in the supply step, the flow rate Q (L / h) of the mixed liquid in the membrane separation step, and the degree of reduced pressure (kPa) were changed as shown in Table 1. Other than these, the supply step, membrane separation step, circulation step, and recovery step were performed in the same manner as in Measurement Example 1. The content of Liquid A (IPA) in the permeated fluid in Measurement Examples 2 to 22 is shown in Table 1.

[0158] For each of Measurement Examples 1 to 22, the recovery cost required to recover Liquid A (IPA) was calculated assuming that the cost per kg of steam used for heating was 5.8 yen / kg and the cost per kWh of power of the pump used for decompression was 19.85 yen / kWh. The calculation results are shown in Table 1.

[0159] FIG. 6 shows the relationship between the linear velocity LV (m / h) of the mixed liquid in the supplying step of Measurement Examples 1 to 22 and the recovery cost of Liquid A (yen / kg).

[0160]

[0161] As can be seen from Table 1 and Figure 6, in Measurement Examples 4 to 22, the recovery cost of Liquid A was 300 yen / kg or less, which was lower than that of Measurement Examples 1 to 3. This is presumably because, in the membrane separation process, by setting the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 to 11.0 m / h or more, the concentration of Liquid A on the surface of the pervaporation membrane 11 was maintained high, and Liquid A was efficiently separated from the mixed liquid, thereby increasing the amount of Liquid A recovered per power required to operate the membrane separation device 10. From these results, it was found that, in the membrane separation process, if the flow rate Q of the mixed liquid is adjusted so that the linear velocity LV of the mixed liquid supplied to the membrane separation device 10 is 11.0 m / h or more, a membrane separation system 100 with excellent practicality in terms of recovery costs can be obtained.

[0162] In the membrane separation system of this embodiment, a non-permeate fluid that is sufficiently suitable for reuse can be obtained by processing using a pervaporation membrane.

Claims

1. A membrane separation system equipped with a membrane separation device, the membrane separation device having a pervaporation membrane that separates a mixed liquid containing liquid A and liquid B different from liquid A into a permeable fluid and a non-permeable fluid, and the membrane separation system adjusts the flow rate of the mixed liquid so that the linear velocity of the mixed liquid supplied to the membrane separation device is 11.0 m / h or more.

2. The membrane separation system according to claim 1, wherein the pervaporation membrane preferentially allows the liquid A to permeate.

3. The membrane separation system according to claim 1, further comprising a tank for storing the mixed liquid to be supplied to the membrane separation device.

4. The membrane separation system according to claim 3, further comprising a non-permeate fluid discharge path connected to the membrane separation device for discharging the non-permeate fluid from the membrane separation device, the non-permeate fluid discharge path being connected to the tank.

5. The membrane separation system according to claim 1, wherein the membrane separation system adjusts the temperature of the mixed liquid so that the absolute value of the difference between the temperature T1 (°C) of the mixed liquid supplied to the membrane separation device and the boiling point T2 (°C) of the liquid A is 90°C or less.

6. The membrane separation system according to claim 1, wherein the pressure in the membrane separation device is adjusted so that the pressure on the permeate side of the membrane separation device is 50 kPa or less.

7. The membrane separation system according to claim 1, wherein the content of said liquid A in said mixed liquid is 50 wt % or less.

8. The membrane separation system of claim 1, wherein liquid A is an organic solvent.

9. The membrane separation system according to claim 1, wherein the membrane separation device is a spiral membrane element, and the membrane element includes a central tube having through holes, and a laminate having the pervaporation membrane and wound around the central tube.

10. The membrane separation system according to claim 9, wherein the outer diameter of the membrane element is 180 mm or more.

11. The membrane separation system of claim 1, wherein the pervaporation membrane comprises a silicone-based polymer.

12. The membrane separation system according to claim 1, wherein the pervaporation membrane has a matrix containing a silicone-based polymer and a filler dispersed in the matrix and containing silica.

13. A method for operating a membrane separation device having a pervaporation membrane, the method comprising: a supply step of supplying a mixed liquid containing liquid A and liquid B different from liquid A to the membrane separation device; and a membrane separation step of separating the mixed liquid into a permeating fluid and a non-permeating fluid using the pervaporation membrane, wherein the membrane separation step is performed while adjusting the flow rate of the mixed liquid so that the linear velocity of the mixed liquid supplied to the membrane separation device is 11.0 m / h or more.

14. The method for operating a membrane separation apparatus according to claim 13, wherein the pervaporation membrane preferentially allows the liquid A to permeate.

15. The method for operating a membrane separation apparatus according to claim 13, further comprising a circulating step of circulating the non-permeate fluid discharged from the membrane separation apparatus back to the membrane separation apparatus.

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