Membrane separation system and method for operating membrane separation system

Abstract

This membrane separation system comprises: at least one membrane separation unit including a pervaporation membrane that separates a supply fluid containing a volatile organic compound into a permeated fluid and a non-permeated fluid, a container inside which the pervaporation membrane is disposed, and a supply space and a permeated space separated by the pervaporation membrane inside the container; and a permeated fluid pipe connected to a permeated fluid outlet of the container. Leakage of the membrane separation unit is detected if the temperature of the permeated fluid pipe drops below the temperature of the container by a predetermined value or more.

Description

Membrane separation system and operating method for membrane separation system

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

[0002] As an example of a method for separating volatile organic compounds from an aqueous solution containing the volatile organic compounds, a pervaporation method using a pervaporation membrane is known. The pervaporation method is suitable for separating volatile organic compounds from aqueous solutions containing various substances.

[0003] In a membrane separation system using a pervaporation membrane, in order to maintain the separation performance of the pervaporation membrane, it is required that the pervaporation membrane has no defects such as holes or tears. Further, for example, in a spiral-type membrane element using a pervaporation membrane, it is required that the sealed portion has no defects such as peeling or holes. When leakage occurs due to these defects, problems such as decreased separation performance and decreased energy efficiency arise. Therefore, it is important to appropriately detect leakage caused by defects in the pervaporation membrane and the sealed portion, and to suppress the influence of leakage occurrence as much as possible. For example, Patent Document 1 discloses a method for leak inspection of a selectively permeable membrane module, in which a fluorescent dye solution having a molecular weight of 300 to 3000 is used to detect the dye leaking from defects of the membrane module by fluorescence, thereby specifying the leak location.

[0004] Japanese Patent No. 4058657

[0005] In the leak inspection method described in Patent Document 1, a fluorescent dye solution having a specific molecular weight is introduced into the membrane module, and the dye leaking from the defective portion is detected by fluorescence, thereby specifying the defective portion of the membrane. Therefore, in order to specify the leak location, it is necessary to perform an inspection operation separately from the steady operation. When performing steady operation after the inspection operation, it is also necessary to wash the fluorescent dye adhering to the membrane module. The method described in Patent Document 1 cannot detect leakage during steady operation.

[0006] Accordingly, an object of the present invention is to provide a membrane separation system capable of detecting leakage during operation.

[0007] The present invention provides a membrane separation system comprising: a permeable vaporization membrane for separating a supply fluid containing a volatile organic compound into a permeable fluid and an impermeable fluid; a container in which the permeable vaporization membrane is disposed; at least one membrane separation unit having a supply space and a permeable space separated by the permeable vaporization membrane inside the container; and a permeable fluid pipe connected to the permeable fluid outlet of the container, wherein a leak in the membrane separation unit is detected when the temperature of the permeable fluid pipe drops below a predetermined value or more below the temperature of the container.

[0008] In another aspect, the present invention provides a method for operating a membrane separation system comprising: a permeable vaporization membrane for separating a supply fluid containing a volatile organic compound into a permeable fluid and an impermeable fluid; a container in which the permeable vaporization membrane is disposed; at least one membrane separation unit having a supply space and a permeable space separated by the permeable vaporization membrane inside the container; and a permeable fluid pipe connected to the permeable fluid outlet of the container, the method for operating a membrane separation system comprising detecting a leak in the membrane separation unit when the temperature of the permeable fluid pipe drops below a predetermined value or more below the temperature of the container.

[0009] According to the present invention, a membrane separation system capable of detecting leaks during operation can be provided.

[0010] This is a schematic diagram showing an example of the membrane separation system of this embodiment. This is a schematic cross-sectional view of part II in Figure 1. This is a schematic cross-sectional view showing an example of the permeation vaporization membrane provided in the membrane separation section. This is a schematic cross-sectional view showing another example of the membrane separation section. This is a schematic unfolded perspective view showing a spiral-shaped membrane element. This is a schematic diagram showing a modified example 1 of the membrane separation system. This is a schematic diagram showing a modified example 2 of the membrane separation system. This is a schematic diagram showing a modified example 3 of the membrane separation system.

[0011] A membrane separation system according to a first aspect of the present invention comprises: a permeable vaporization membrane that separates a supply fluid containing a volatile organic compound into a permeable fluid and an impermeable fluid; a container in which the permeable vaporization membrane is disposed; at least one membrane separation unit having a supply space and a permeable space separated by the permeable vaporization membrane inside the container; and a permeable fluid pipe connected to the permeable fluid outlet of the container, wherein a leak in the membrane separation unit is detected when the temperature of the permeable fluid pipe drops below a predetermined value or more below the temperature of the container.

[0012] In a second embodiment of the present invention, for example, in the membrane separation system according to the first embodiment, the predetermined value is 5°C.

[0013] In a third embodiment of the present invention, for example, in the membrane separation system according to the first or second embodiment, the temperature of the permeable fluid piping is the temperature of the surface of the permeable fluid piping.

[0014] In a fourth embodiment of the present invention, for example, in a membrane separation system according to any one of the first to third embodiments, the temperature of the permeate fluid piping is the temperature of the permeate fluid piping near the permeate fluid outlet.

[0015] In a fifth embodiment of the present invention, for example, in a membrane separation system according to any one of the first to fourth embodiments, the temperature of the permeate fluid piping is the temperature of the permeate fluid in the permeate fluid piping.

[0016] In a sixth aspect of the present invention, for example, in a membrane separation system according to any one of the first to fifth aspects, the temperature of the container is the temperature of the surface of the container.

[0017] In a seventh embodiment of the present invention, for example, in a membrane separation system according to any one of the first to sixth embodiments, the temperature of the container is the temperature of the container near the non-permeable fluid outlet of the container.

[0018] In the eighth aspect of the present invention, for example, in a membrane separation system according to any one of the first to seventh aspects, the temperature of the container is the temperature of the impermeable fluid inside the container.

[0019] In a ninth aspect of the present invention, for example, a membrane separation system according to any one of the first to eighth aspects further comprises a first temperature sensor for measuring the temperature of the permeable fluid piping and a second temperature sensor for measuring the temperature of the container.

[0020] In a tenth embodiment of the present invention, for example, in the membrane separation system according to the ninth embodiment, it is determined whether the temperature of the permeable fluid piping has fallen below the temperature of the container by a predetermined value or more, based on the monitoring results from the first temperature sensor and the second temperature sensor.

[0021] In the eleventh embodiment of the present invention, for example, in a membrane separation system according to any one of the first to tenth embodiments, when the leak is detected, control is performed to stop the operation of the membrane separation system.

[0022] In a twelfth aspect of the present invention, for example, the membrane separation system according to the eleventh aspect further comprises a depressurization unit for reducing the pressure of the permeate space of the at least one membrane separation unit, and a pressurization unit for increasing the pressure of the supply space of the at least one membrane separation unit, wherein the control for stopping the operation includes at least one selected from the group consisting of a control for stopping the operation of the depressurization unit and a control for stopping the operation of the pressurization unit.

[0023] In a thirteenth embodiment of the present invention, for example, in a membrane separation system according to any one of the first to twelfth embodiments, the membrane separation unit is disposed inside the container and includes a spiral-shaped membrane element having the permeable vaporization membrane, the container has a cylindrical container body, a first end plate attached to the supply fluid inlet end of the container, and a second end plate attached to the permeable fluid outlet end of the container, and the temperature of the container includes the temperature of the container body and the temperature of the second end plate.

[0024] In a fourteenth embodiment of the present invention, for example, in a membrane separation system according to any one of the first to thirteenth embodiments, the at least one membrane separation unit includes a plurality of membrane separation units, and the plurality of membrane separation units are connected in series such that the impermeable fluid discharged from the membrane separation unit located upstream is supplied as the supply fluid to the membrane separation unit located downstream.

[0025] A method for operating a membrane separation system according to a 15th aspect of the present invention is a method for operating a membrane separation system comprising: a permeable vaporization membrane that separates a supply fluid containing a volatile organic compound into a permeable fluid and an impermeable fluid; a container in which the permeable vaporization membrane is disposed; at least one membrane separation unit having a supply space and a permeable space separated by the permeable vaporization membrane inside the container; and a permeable fluid pipe connected to the permeable fluid outlet of the container, wherein a leak in the membrane separation unit is detected when the temperature of the permeable fluid pipe drops below a predetermined value or more below the temperature of the container.

[0026] In a sixteenth embodiment of the present invention, for example, the operating method of a membrane separation system according to the fifteenth embodiment includes, after detecting the leak, executing control to stop the operation of the membrane separation system.

[0027] The details of the present invention will be described below, but the following description is not intended to limit the present invention to any particular embodiment.

[0028] <Embodiment of the Membrane Separation System> The membrane separation system of this embodiment comprises a permeable vaporization membrane that separates a supply fluid containing volatile organic compounds into a permeable fluid and an impermeable fluid; a container in which the permeable vaporization membrane is disposed; at least one membrane separation unit having a supply space and a permeable space separated by the permeable vaporization membrane inside the container; and a permeable fluid pipe connected to the permeable fluid outlet of the container. In this membrane separation system, a leak in the membrane separation unit is detected when the temperature of the permeable fluid pipe drops below a predetermined value or more below the temperature of the container. In other words, a leak in the membrane separation unit is detected when the temperature of the permeable fluid pipe falls below the temperature of the container and the difference exceeds a predetermined value.

[0029] According to the membrane separation system of this embodiment, leaks can be detected during operation.

[0030] The following describes a specific example of the membrane separation system of this embodiment with reference to the drawings.

[0031] Figure 1 is a schematic diagram showing an example of a membrane separation system according to this embodiment. The membrane separation system 100A in Figure 1 includes a first membrane separation unit 10 as at least one membrane separation unit. The first membrane separation unit 10 includes a first permeation vaporization membrane 11 that separates a raw fluid F0 as a supply fluid into a first permeation fluid F1 and a first impermeable fluid F2, a first container 12 in which the first permeation vaporization membrane 11 is disposed, and a supply space 13 and a permeation space 14 separated by the first permeation vaporization membrane 11 inside the first container 12. The raw fluid F0 contains a volatile organic compound C. The membrane separation system 100A includes a first permeation fluid pipe 92 connected to a first permeation fluid outlet 10b of the first container 12. In the membrane separation system 100A, a leak in the first membrane separation unit 10 is detected when the temperature T1 of the first permeation fluid pipe 92 drops below a predetermined value or more compared to the temperature T2 of the first container 12.

[0032] The inventors of the present invention have observed that when a leak occurs in the membrane separation section of a membrane separation system due to defects in the permeation vaporization membrane and sealing portion during operation, the temperature of the permeable fluid piping decreases. This is thought to be because when a leak occurs in the permeation vaporization membrane and sealing portion, the amount of permeable fluid flowing into the permeable space increases, and consequently, heat absorption due to vaporization in the permeable space increases. In the membrane separation system 100A, when the temperature T1 of the first permeable fluid piping 92 drops below a predetermined value or more than the temperature T2 of the first container 12, it is determined that a leak has occurred and the leak is detected. With the membrane separation system 100A, since leaks can be detected during operation, the effects of leaks, such as a decrease in energy efficiency, can be suppressed.

[0033] In this embodiment, "operation" of the membrane separation system is a concept that includes not only steady-state operation but also startup operation. Steady-state operation means the operating state in which the membrane separation system is running continuously. Steady-state operation includes rated operation. Rated operation means the operating state at the maximum output that the membrane separation system can operate continuously. Startup operation is the startup operation until the membrane separation system is ready for normal operation. With the membrane separation system 100A, leaks can be detected regardless of whether it is during startup operation or steady-state operation, so the effects of leaks can be suppressed.

[0034] When the membrane separation system 100A starts its startup operation, the first container 12 is heated by a temperature control device, such as a hot water jacket, installed around the first container 12. The set temperature of the temperature control device is, for example, 40°C. As a result of the heating, the temperature T1 of the first permeate fluid piping 92 and the temperature T2 of the first container 12 begin to rise. During startup operation, the temperature T1 of the first permeate fluid piping 92 and the temperature T2 of the first container 12 are, for example, 10°C. If a leak occurs during startup operation, the temperature T1 drops to, for example, 0°C, while the temperature T2 is maintained at 10°C. That is, the temperature T1 drops below the temperature T2 by a predetermined value or more. During steady-state operation, the temperature T1 of the first permeate fluid piping 92 and the temperature T2 of the first container 12 are, for example, 30°C. If a leak occurs during steady-state operation, the temperature T1 drops to, for example, 20°C, while the temperature T2 is maintained at 30°C. In other words, temperature T1 decreases by a predetermined value or more compared to temperature T2.

[0035] The above predetermined value may be 5°C. That is, when the temperature T1 of the first permeable fluid piping 92 drops by 5°C or more compared to the temperature T2 of the first container 12, a leak in the first membrane separation unit 10 may be detected.

[0036] The above predetermined value may be 10°C. That is, when the temperature T1 of the first permeable fluid piping 92 drops by 10°C or more compared to the temperature T2 of the first container 12, a leak in the first membrane separation unit 10 may be detected.

[0037] In the membrane separation system 100A, the temperature T1 of the first permeate pipe 92 includes at least one selected from the group consisting of the surface temperature of the first permeate pipe 92, the temperature of the first permeate pipe 92 near the first permeate outlet 10b, and the temperature of the first permeate F1 inside the first permeate pipe 92.

[0038] The temperature T1 of the first permeable fluid piping 92 may be the surface temperature of the first permeable fluid piping 92.

[0039] The temperature T1 of the first permeable fluid piping 92 may be the temperature of the first permeable fluid piping 92 near the first permeable fluid outlet 10b.

[0040] The temperature T1 of the first permeate fluid pipe 92 may be the temperature of the first permeate fluid F1 within the first permeate fluid pipe 92.

[0041] In the membrane separation system 100A, the temperature T2 of the first container 12 includes at least one selected from the group consisting of the surface temperature of the first container 12, the temperature of the first container 12 near the first non-permeate fluid outlet 10c, and the temperature of the first non-permeate fluid F2 within the first container 12.

[0042] The temperature T2 of the first container 12 may be the surface temperature of the first container 12.

[0043] The temperature T2 of the first container 12 may be the temperature of the first container 12 near the first non-permeate fluid outlet 10c.

[0044] The temperature T2 of the first container 12 may be the temperature of the first non-permeate fluid F2 within the first container 12.

[0045] The membrane separation system 100A may comprise a first temperature sensor 71 that measures the temperature T1 of the first permeate fluid pipe 92, and a second temperature sensor 72 that measures the temperature T2 of the first container 12.

[0046] In the membrane separation system 100A, based on the monitoring results from the first temperature sensor 71 and the second temperature sensor 72, it may be determined whether the temperature T1 of the first permeate fluid pipe 92 has decreased by a predetermined value or more relative to the temperature T2 of the first container 12. According to such a configuration, leakage can be easily detected.

[0047] In the example of Figure 1, the first temperature sensor 71 is provided on the surface of the first permeate fluid pipe 92 near the first permeate fluid outlet 10b. As shown in Figure 1, the first temperature sensor 71 may be provided on the lower portion of the surface of the first permeate fluid pipe 92 near the first permeate fluid outlet 10b. The lower portion of the first permeate fluid pipe 92 near the first permeate fluid outlet 10b tends to be more likely to come into contact with the first permeate fluid F1 than the upper portion thereof. Therefore, when the first temperature sensor 71 is provided on the lower portion of the surface of the first permeate fluid pipe 92 near the first permeate fluid outlet 10b, the measured value is easily stabilized.

[0048] The shortest horizontal distance between the first temperature sensor 71 and the first permeated fluid outlet 10b of the first container 12 is, for example, 5 cm or more and 30 cm or less. The shortest horizontal distance between the first temperature sensor 71 and the first permeated fluid outlet 10b of the first container 12 may be 5 cm or more and 20 cm or less, and may further be 5 cm or more and 10 cm or less.

[0049] In the example of Figure 1, the second temperature sensor 72 is provided on the surface of the first container 12 near the first non-permeated fluid outlet 10c. The first container 12 near the first non-permeated fluid outlet 10c is less susceptible to the influence of the first permeated fluid pipe 92 than the first container 12 near the first permeated fluid outlet 10b. Therefore, when the second temperature sensor 72 is provided on the surface of the first container 12 near the first non-permeated fluid outlet 10c, the measured value is likely to be stable. As shown in Figure 1, the second temperature sensor 72 may be provided on the surface of the first container 12 near the first non-permeated fluid outlet 10c.

[0050] The shortest horizontal distance between the second temperature sensor 72 and the first non-permeated fluid outlet 10c of the first container 12 is, for example, 30 cm or less. The shortest horizontal distance between the second temperature sensor 72 and the first non-permeated fluid outlet 10c of the first container 12 may be 20 cm or less, 10 cm or less, and further may be 5 cm or less.

[0051] The membrane separation system 100A may further include a first pressure reducing unit 51. The first pressure reducing unit 51 reduces the pressure of the permeation space 14 of the first membrane separation unit 10. In other words, the first pressure reducing unit 51 generates a differential pressure between the supply space 13 and the permeation space 14 of the first membrane separation unit 10.

[0052] The first pressure reduction section 51 includes a vacuum device such as a vacuum pump. The first pressure reduction section 51 may be a vacuum pump. The vacuum pump is typically a gas transport type vacuum pump, and examples include reciprocating vacuum pumps and rotary vacuum pumps. Examples of reciprocating vacuum pumps include diaphragm type and oscillating piston type vacuum pumps. Examples of rotary vacuum pumps include liquid-sealed pumps, oil rotary pumps (rotary pumps), mechanical booster pumps, and various dry pumps such as Roots type, claw type, screw type, turbo type, and scroll type. The pump as the first pressure reduction section 51 may be equipped with a variable speed mechanism for changing the rotation speed, etc. An example of a variable speed mechanism is an inverter that drives the motor of the pump. By controlling the rotation speed of the pump with the variable speed mechanism, the pressure in the permeable space 14 of the first membrane separation section 10 can be appropriately adjusted.

[0053] In the membrane separation system 100A, the first depressurization unit 51 may be a multi-stage Roots type vacuum pump or a diaphragm type vacuum pump. A multi-stage Roots type vacuum pump can, for example, raise the pressure in the space to a predetermined value in a short time and provide excellent durability. A diaphragm type vacuum pump can, for example, perform depressurization operations efficiently and at low cost.

[0054] The first pressure reduction unit 51 may be an assembly of multiple pumps. That is, the first pressure reduction unit 51 may be configured so that each of the multiple pumps can reduce the pressure in the permeate space 14 of the first membrane separation unit 10. With such a configuration, the pressure in the permeate space 14 of the first membrane separation unit 10 can be appropriately adjusted by adjusting the number of operating pumps.

[0055] The membrane separation system 100A may further include a pressurizing unit 40 that pressurizes the supply space of at least one membrane separation unit. The pressurizing unit 40 pressurizes the supply space 13 of the first membrane separation unit 10. In other words, the pressurizing unit 40 creates a differential pressure between the supply space 13 and the permeate space 14 of the first membrane separation unit 10.

[0056] The pressurizing unit 40 includes a pump that pressurizes the raw fluid F0 as a supply fluid toward the supply space 13 of the first membrane separation unit 10. The pressurizing unit 40 may also be a pump. Specific examples of the pump include centrifugal pumps, gear pumps, diaphragm pumps, plunger pumps, etc., when the raw fluid F0 is a liquid. Examples include blowers, compressors, etc., when the raw fluid F0 is a gas. The pump as the pressurizing unit 40 may be equipped with a variable speed mechanism for changing the rotation speed, etc. An example of a variable speed mechanism is an inverter that drives the motor of the pump. By controlling the rotation speed of the pump with the variable speed mechanism, the pressure in the supply space 13 of the first membrane separation unit 10 can be appropriately adjusted.

[0057] The pressurizing section 40 may be an assembly of multiple pumps. That is, the pressurizing section 40 may be configured so that each of the multiple pumps can increase the pressure in the supply space 13 of the first membrane separation section 10. With such a configuration, the pressure in the supply space 13 of the first membrane separation section 10 can be appropriately adjusted by adjusting the number of operating pumps.

[0058] The membrane separation system 100A may further include a first condensation unit 61. The first condensation unit 61 condenses volatile organic compounds C contained in the first permeate fluid F1 discharged from the permeate space 14 of the first membrane separation unit 10. The first condensation unit 61 is, for example, a heat exchanger for cooling the first permeate fluid F1. The heat exchanger cools the gaseous first permeate fluid F1 to obtain a liquid first permeate fluid F1. The heat exchanger is, for example, a gas-liquid heat exchanger that generates heat exchange between a cooling medium such as antifreeze and the gaseous first permeate fluid F1.

[0059] As shown in Figure 1, the first condensation section 61 may be provided upstream of the first pressure reduction section 51 in the first permeate fluid piping 92. When the raw fluid F0 contains a volatile organic compound C, the first permeate fluid F1 may contain alcohol. If the first permeate fluid F1 containing alcohol gas flows directly into the first pressure reduction section 51, the gas may condense within the first pressure reduction section 51, generating liquid. The liquid generated within the first pressure reduction section 51 may impair the function of the first pressure reduction section 51. By providing the first condensation section 61 upstream of the first pressure reduction section 51, such problems can be avoided.

[0060] Although not shown in the diagram, the first condensation unit 61 may be connected to a recovery unit for recovering the first permeate fluid F1 obtained by condensation. The recovery unit is, for example, a tank for storing the first permeate fluid F1.

[0061] The membrane separation system 100A may further include a supply unit 81. The supply unit 81 stores the raw fluid F0 to be supplied to the first membrane separation unit 10. The supply unit 81 is, for example, a tank for storing the raw fluid F0. The supply unit 81 may also be a culture tank for producing organic compounds C by fermentation of a carbon source by microorganisms.

[0062] In this embodiment, the first permeate pipe 92 connects the first permeate outlet 10b of the first container 12 of the first membrane separation unit 10 to the first permeate inlet of the first condensation unit 61, and is a path for guiding the first permeate F1 from the first membrane separation unit 10 to the first condensation unit 61. A concentration sensor for measuring the content of organic compound C in the first permeate pipe 92 may be placed in the first permeate pipe 92.

[0063] In the example shown in Figure 1, the first condensing section 61 and the first pressure reduction section 51 are located in the first permeable fluid piping 92.

[0064] The membrane separation system 100A further includes a raw fluid pipe 91 and a first impermeable fluid pipe 93 as fluid pathways.

[0065] The raw fluid piping 91 connects the raw fluid outlet of the supply unit 81 to the raw fluid inlet 10a of the first container 12 of the first membrane separation unit 10, and serves as a path for guiding the raw fluid F0 from the supply unit 81 to the first membrane separation unit 10. A concentration sensor for measuring the content of organic compound C in the raw fluid F0 may be placed in the raw fluid piping 91.

[0066] In the example shown in Figure 1, the pressurizing section 40 is located in the raw fluid piping 91.

[0067] The first impermeable fluid piping 93 is connected to the first impermeable fluid outlet 10c of the first container 12 of the first membrane separation unit 10, and is a path for discharging the first impermeable fluid F2 from the first membrane separation unit 10. A concentration sensor for measuring the content of organic compound C in the first impermeable fluid F2 may be placed in the first impermeable fluid piping 93. The first impermeable fluid piping 93 may also be connected to another membrane separation unit having a permeation vaporization membrane for further separating the first impermeable fluid F2, a recovery unit for recovering the first impermeable fluid F2, a filtration separation unit having a filtration membrane for filtering and separating the first impermeable fluid F2, and so on. As the filtration membrane, for example, a reverse osmosis membrane, an ultrafiltration membrane, etc., can be used.

[0068] In the membrane separation system 100A, if a leak is detected, control may be executed to stop the operation of the membrane separation system 100A. With such a configuration, the impact of leaks can be further suppressed.

[0069] In the membrane separation system 100A, an alarm may be issued when a leak is detected. For example, when the temperature T1 of the first permeate fluid piping 92 drops below a predetermined value or more below the temperature T2 of the first container 12, an alarm may be issued and control may be executed to stop the operation of the membrane separation system 100A.

[0070] The control for stopping the operation of the membrane separation system 100A may include at least one selected from the group consisting of a control for stopping the operation of the first pressure reducing unit 51 and a control for stopping the operation of the pressurizing unit 40. With such a configuration, for example, when the temperature T1 of the first permeable fluid piping 92 drops below a predetermined value or more below the temperature T2 of the first container 12, the control for stopping the operation of the first pressure reducing unit 51 and / or the control for stopping the operation of the pressurizing unit 40 are executed, thereby suppressing the effects of leaks.

[0071] The membrane separation system of this embodiment may further include a control unit for controlling each component of the membrane separation system. The control unit may implement PID control such as feedback control, feedforward control, or a combination thereof. The control unit may be a DSP (Digital Signal Processor) including an A / D conversion circuit, input / output circuits, arithmetic circuits, and a memory device. The control unit may store a program for properly operating the membrane separation system.

[0072] The membrane separation system 100A includes a control unit 80 as a control unit that controls each component of the membrane separation system 100A. For example, the control unit 80 controls the operation of the first depressurization unit 51, the pressurization unit 40, and so on. This makes it possible to suppress the effects of a leak when the temperature T1 of the first permeate fluid piping 92 drops below a predetermined value or more below the temperature T2 of the first container 12 during operation, that is, when a leak is detected.

[0073] Each of the pipes serving as pathways in the membrane separation system of this embodiment is, unless otherwise specified, made of, for example, metal or resin.

[0074] [Raw Fluid] The raw fluid F0 contains a volatile organic compound C, such as an alcohol. The raw fluid F0 is typically a fermentation liquid. Fermentation liquids are obtained by fermenting a carbon source such as glucose or synthesis gas in an aqueous solution using microorganisms. Therefore, when the raw fluid F0 is a fermentation liquid, it contains the volatile organic compound C along with microorganisms that produce the organic compound C. The microorganisms that produce the organic compound C are typically fungi. The raw fluid F0 includes, for example, the organic compound C, water, and microorganisms. The raw fluid F0 is typically an aqueous solution containing the organic compound C, water, and microorganisms.

[0075] Organic compound C is not particularly limited as long as it is volatile. In this specification, "volatile organic compound" means, for example, an organic compound whose boiling point at atmospheric pressure (101.325 kPa) is between 20°C and 260°C.

[0076] The number of carbon atoms in 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 organic compound C may be 1 or 2. Organic compound C has functional groups containing oxygen atoms, such as hydroxyl groups, carbonyl groups, ether groups, and ester groups. In organic compound C, the number of functional groups containing oxygen atoms is typically one.

[0077] Examples of organic compound C include alcohols, ketones, and esters, and are typically alcohols. 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 alkyl alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, isobutanol, t-butanol, and n-pentanol. Examples of aryl alcohols include phenol.

[0078] The ketone may be a dialkylketone composed only of an alkyl group and a carbonyl group. Examples of dialkylketones include methyl ethyl ketone (MEK) and acetone.

[0079] The ester may be a fatty acid alkyl ester composed solely of an alkyl group and an ester group. Examples of fatty acid alkyl esters include ethyl acetate.

[0080] Note that organic compound C is not limited to those described above. Organic compound C may also be an aromatic hydrocarbon such as benzene, toluene, or xylene.

[0081] The raw fluid F0 may contain one type of organic compound C, or it may contain two or more types of organic compound C. The content of organic compound C in the raw fluid F0 is, for example, 0.5 wt% or more, and may be 1 wt% or more, 2 wt% or more, or even 5 wt% or more. The upper limit of the content of organic compound C is not particularly limited, but is, for example, 50 wt%.

[0082] Organic compound C may be a fermented product produced by microorganisms fermenting a carbon source, or it may be alcohol produced by microorganisms (bio-alcohol). In other words, the raw fluid F0 may be a fermentation liquid containing organic compound C as a fermentation product. However, the raw fluid F0 is not limited to a fermentation liquid, but may also be waste liquid or wastewater discharged from a chemical plant or the like.

[0083] The raw fluid F0 may further contain other components besides water and organic compound C, such as microorganisms that produce fermentation products, a carbon source, a nitrogen source, and inorganic ions. The microorganisms that produce fermentation products are typically bacteria. Examples of carbon sources include polysaccharides such as starch and monosaccharides such as glucose.

[0084] [Membrane Separation Section] Figure 2 is a schematic cross-sectional view of section II of Figure 1. As described above, the first membrane separation section 10 comprises a first permeation vaporization membrane 11 and a first container 12. The first container 12 has a first chamber 13 and a second chamber 14. The first chamber 13 functions as a supply space to which the raw fluid F0 is supplied. The second chamber 14 functions as a permeation space to which the first permeate fluid F1 is supplied. The first permeate fluid F1 is obtained by the raw fluid F0 permeating through the first permeation vaporization membrane 11.

[0085] The first permeation vaporization membrane 11 is located inside the first container 12. Inside the first container 12, the first permeation vaporization membrane 11 separates the first chamber 13 and the second chamber 14. The first permeation vaporization membrane 11 extends from one of a pair of walls of the first container 12 to the other.

[0086] The first chamber 13 has a raw fluid inlet 10a and a first impermeable fluid outlet 10c. The second chamber 14 has a first permeable fluid outlet 10b. The raw fluid inlet 10a is an opening for supplying the raw fluid F0 to the supply space (first chamber 13). The first permeable fluid outlet 10b is an opening for discharging the first permeable fluid F1 from the permeation space (second chamber 14). The first impermeable fluid outlet 10c is an opening for discharging the raw fluid F0 (first impermeable fluid F2) that did not permeate the first permeation vaporization membrane 11 from the supply space (first chamber 13). The raw fluid inlet 10a, the first permeable fluid outlet 10b, and the first impermeable fluid outlet 10c are each formed, for example, on the wall surface of the first container 12.

[0087] The first membrane separation unit 10 is suitable for a continuous flow membrane separation method. However, the first membrane separation unit 10 may also be used in a batch membrane separation method.

[0088] [Permeation Vaporization Membrane] As described above, the first permeation vaporization membrane 11 separates the raw fluid F0, which is the supply fluid, into a first permeable fluid F1 and a first impermeable fluid F2. Figure 3 is a schematic cross-sectional view showing an example of the first permeation vaporization membrane 11 of the first membrane separation unit 10. The first permeation vaporization membrane 11 comprises, for example, a separation functional layer 1 and a porous support 2 that supports the separation functional layer 1. The separation functional layer 1 is in direct contact with, for example, the porous support 2. The first permeation vaporization membrane 11 has, for example, a main surface 11a on the separation functional layer 1 side exposed to the supply space 13, and a main surface 11b on the porous support 2 side exposed to the permeable space 14.

[0089] The first permeation vaporization membrane 11 may further include a protective layer (not shown) that protects the separation functional layer 1.

[0090] (Separation Functional Layer) The separation functional layer 1 is a layer that can preferentially permeate specific components contained in the supply fluid. For example, the separation functional layer 1 is a layer that can preferentially permeate organic compound C contained in the supply fluid.

[0091] If the separation functional layer 1 is a layer that can preferentially allow organic compound C contained in the supply fluid to pass through, it is preferable that the separation functional layer 1 includes a hydrophobic material. In this specification, "hydrophobic material" means, for example, a material in which, when a 10 μL drop of water (at a temperature of 25°C) is dropped onto the surface of a test piece made of the material, the static contact angle of water exceeds 90°. The static contact angle of water can be measured using a commercially available contact angle meter.

[0092] Examples of hydrophobic materials include compounds having siloxane bonds (Si-O-Si bonds), olefin polymers, oils, and fluorinated compounds. The separation functional layer 1 preferably contains a compound having siloxane bonds as a hydrophobic material. Compounds having siloxane bonds are typically silicone polymers. Silicone polymers may be solid or liquid at 25°C. Specific examples of silicone polymers include polydimethylsiloxane (PDMS). Specific examples of olefin polymers include polyethylene and polypropylene. Examples of oils include hydrocarbon oils such as liquid paraffin. Examples of fluorinated compounds include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Hydrophobic materials can be used individually or in combination of two or more.

[0093] The separation functional layer 1 may contain a hydrophobic material as its main component, or may be composed substantially only of a hydrophobic material. "Main component" means the component that is present in the largest amount by weight in the separation functional layer 1.

[0094] The separation functional layer 1 may include a matrix containing a hydrophobic material and fillers dispersed in the matrix. The fillers are embedded within the matrix. Within the matrix, all fillers may be spaced apart from each other or partially aggregated.

[0095] The filler includes, for example, inorganic materials such as zeolite, silica, and bentonite. The zeolite included in the filler is preferably high-silica zeolite, which has a high silica-to-alumina ratio. High-silica zeolite is suitable for separating solutions containing organic compound C due to its excellent hydrolysis resistance. Examples of high-silica zeolite include HSZ (registered trademark) from Tosoh Corporation, HiSiv (registered trademark) from Union Showa Co., Ltd., USKY from Union Showa Co., Ltd., and Zeoal (registered trademark) from Nakamura Choko Co., Ltd.

[0096] The filler may contain 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 contains, for example, a metal ion and an organic ligand. Examples of metal ions include Zn ions. Examples of organic ligands include aromatic rings. Examples of aromatic rings included in the organic ligand include imidazole rings. Examples of organic ligands include 2-methylimidazole. A specific example of a metal-organic framework is ZIF-8.

[0097] The shape of the filler is, for example, particulate. In this specification, "particulate" includes spherical, ellipsoidal, flaky, and fibrous. The average particle size of the filler is not particularly limited, but 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, a 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 (diameter of the particle) of that specific filler. The particle sizes of any 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.

[0098] The filler content in the separation functional layer 1 is, for example, 5 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, but is, for example, 70 wt%. The matrix content in the separation functional layer 1 is not particularly limited, but is, for example, 30 wt% to 90 wt%.

[0099] If the separation functional layer 1 is a layer that can preferentially permeate organic compound C contained in the supply fluid, 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 thickness of the separation functional layer 1 may be 0.1 μm or more, 1.0 μm or more, 10 μm or more, or 30 μm or more.

[0100] If the separation functional layer 1 is a layer that can preferentially permeate organic compound C contained in the supply fluid, the separation functional layer 1 may have a microporous structure with an average pore diameter of less than 0.01 μm, but it may also be a dense layer without pores on its surface.

[0101] (Porous support) Examples of porous support 2 include nonwoven fabrics; porous polytetrafluoroethylenes; aromatic polyamide fibers; porous metals; sintered metals; porous ceramics; porous polyesters; porous nylons; activated carbon fibers; latex; silicones; silicone rubbers; permeable (porous) polymers containing at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyetheretherketone, polyacrylonitrile, polyimide, and polyphenylene oxide; metal foams having open or closed cells; polymer foams having open or closed cells; silica; porous glass; mesh screens, etc. The porous support 2 may be a combination of two or more of these.

[0102] The porous support 2 has an average pore diameter of, for example, 0.01 to 0.4 μm. The thickness of the porous support 2 is not particularly limited, but 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 2 is, for example, 300 μm or less, and preferably 200 μm or less.

[0103] (Protective layer) The protective layer covers the surface of the separation functional layer 1, for example. The material of the protective layer is not particularly limited, and examples include silicone resin. The material of the protective layer may be the same as or different from the material of the matrix of the separation functional layer 1.

[0104] The thickness of the protective layer is not particularly limited, but is, for example, 0.5 μm or more, preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The thickness of the protective layer is, for example, 100 μm or less, preferably 50 μm or less, and more preferably 30 μm or less.

[0105] (Method for producing a permeable vaporization membrane) The first permeable vaporization membrane 11 can be produced, for example, by forming a separation functional layer 1 on a porous support 2. Specifically, first, a coating solution containing the material for the separation functional layer 1 is prepared. The coating solution may contain a filler along with a dispersant for dispersing the filler in the coating solution. If the coating solution contains a compound having a siloxane bond, the coating solution may further contain a catalyst for curing the compound. Next, a coating film is obtained by coating the coating solution onto the porous support 2. The separation functional layer 1 is formed by drying the coating film. This gives rise to the first permeable vaporization membrane 11.

[0106] <Embodiment of Operating Method for Membrane Separation System> The operating method for the membrane separation system 100A described above includes, for example, detecting a leak in the first membrane separation unit 10 when the temperature T1 of the first permeable fluid piping 92 drops below a predetermined value or more compared to the temperature T2 of the first container 12. According to the operating method for the membrane separation system 100A, since leaks can be detected during operation, the effects of leaks, such as a decrease in energy efficiency, can be suppressed.

[0107] The operation method of the membrane separation system 100A may include executing control to stop operation of the membrane separation system 100A after detecting a leak. With such a configuration, the effects of leaks can be further suppressed.

[0108] In the operation method of the membrane separation system 100A, detecting a leak may include issuing an alarm. For example, when the temperature T1 of the first permeable fluid piping 92 drops below a predetermined value or more below the temperature T2 of the first container 12, control may be performed to stop the operation of the membrane separation system 100A after issuing an alarm.

[0109] In the operation method of the membrane separation system 100A, the control for stopping the operation of the membrane separation system 100A may include at least one selected from the group consisting of a control for stopping the operation of the first pressure reducing unit 51 and a control for stopping the operation of the pressurizing unit 40. With such a configuration, for example, when the temperature T1 of the first permeable fluid piping 92 drops below a predetermined value or more below the temperature T2 of the first container 12, the effects of leakage can be suppressed by executing a control for stopping the operation of the first pressure reducing unit 51 and / or a control for stopping the operation of the pressurizing unit 40.

[0110] [Modifications of the Membrane Separation Section] The membrane separation section of the membrane separation system of this embodiment may include a spiral-type membrane element, a hollow fiber membrane element, a disc-tube type membrane element in which multiple permeation vaporization membranes are stacked, a plate-and-frame type membrane element, and the like. Figure 4 is a schematic cross-sectional view of the membrane separation section including a spiral-type membrane element. Figure 5 is a schematic unfolded perspective view showing a spiral-type membrane element. The membrane separation section may include a spiral-type membrane element as shown in Figure 4.

[0111] In the following section, the case in which the first membrane separation unit 10 of the membrane separation system 100A described above includes a spiral-shaped membrane element will be further explained with reference to Figures 4 and 5.

[0112] The first membrane separation unit 10 shown in Figure 4 includes a spiral-shaped membrane element 15 located inside the first container 12. The spiral-shaped membrane element 15 has a first permeation vaporization membrane 11.

[0113] As shown in Figure 4, the first container 12 has a cylindrical container body 121, a first end plate 122a, and a second end plate 122b. The container body 121 is cylindrical and made of a material with sufficient pressure resistance. The first container 12 may be a high-pressure vessel used in reverse osmosis membranes. The first end plate 122a is attached to the end 12a of the first container 12 on the raw fluid inlet 10a side. The end 12a of the first container 12 is closed by the first end plate 122a. The second end plate 122b is attached to the end 12b of the first container 12 on the first permeate outlet 10b side. The end 12b of the first container 12 is closed by the second end plate 122b.

[0114] The first container 12 has ports 125a, 125b, and 125c. These ports are for communicating the inside and outside of the first container 12. Port 125a is provided at the end 12a of the first container 12 on the side of the raw fluid inlet 10a. Ports 125b and 125c are provided at the end 12b of the first container 12 on the side of the first permeable fluid outlet 10b.

[0115] As shown in Figure 4, a port 125a may be provided on the first end plate 122a. Ports 125b and 125c may be provided on the second end plate 122b.

[0116] As shown in Figure 4, the raw fluid inlet 10a and port 125a are in communication, and port 125a is used as the inlet for the raw fluid F0. The central pipe 16, which will be described later, is connected to port 125b at the first permeable fluid outlet 10b. That is, port 125b is used as the outlet for the first permeable fluid F1. The first impermeable fluid outlet 10c and port 125c are in communication, and port 125c is used as the outlet for the first impermeable fluid F2. Each port may be a simple opening, or it may be a nozzle-shaped opening as shown in Figure 4.

[0117] In the first membrane separation unit 10 shown in Figure 4, the temperature T2 of the first container 12 includes the temperature of the container body 121 and the temperature of the second end plate 122b. With this configuration, leaks can be detected during operation, so the effects of leaks can be suppressed.

[0118] In the first membrane separation section 10 shown in Figure 4, the temperature T2 of the first container 12 includes the temperature of the container body 121 near the first impermeable fluid outlet 10c and the temperature of the second end plate 122b.

[0119] In the first membrane separation section 10 shown in Figure 4, the temperature T2 of the first container 12 may be the temperature of the container body 121, or the temperature of the second end plate 122b. The temperature of the container body 121 may be the surface temperature of the container body 121, the temperature of the container body 121 near the first impermeable fluid outlet 10c, or the temperature of the first impermeable fluid F2 inside the container body 121.

[0120] In the first membrane separation unit 10 shown in Figure 4, the second temperature sensor 72 may be provided on the surface of the container body 121 near the first impermeable fluid outlet 10c, or on the surface of the second end plate 122b near the first impermeable fluid outlet 10c.

[0121] As shown in Figure 5, the spiral-shaped membrane element 15 comprises a central tube 16 and membrane leaves 19 that have a first permeation vaporization membrane 11 and are wound around the central tube 16.

[0122] The central tube 16 has a cylindrical shape. Through holes 16h are formed on the surface of the central tube 16 to allow the first permeable fluid F1 to flow into the interior of the central tube 16. The number of through holes 16h is not particularly limited and may be one or two or more. 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.

[0123] The membrane element 15 has a plurality of membrane leaves 19. Each membrane leaf 19 includes a first permeation vaporization membrane 11 and a permeation-side flow channel material 17. For example, a membrane leaf 19 has two first permeation vaporization membranes 11. The two first permeation vaporization membranes 11 are overlapped and sealed on three sides to form a bag-like structure. The permeation-side flow channel material 17 is positioned between the two first permeation vaporization membranes 11 so as to be located inside the bag-like structure. The permeation-side flow channel material 17 secures a space (permeation space) between the two first permeation vaporization membranes 11 as a flow channel for the first permeating fluid F1. In this way, the permeation-side flow channel material 17 is used in combination with the first permeation vaporization membranes 11. The number of membrane leaves 19 is not particularly limited and can be, for example, 2 to 50.

[0124] The membrane element 15 further includes a supply-side flow channel material 18. The supply-side flow channel material 18 is located outside the bag-like structure described above and is stacked on the membrane leaf 19. More specifically, multiple supply-side flow channel materials 18 and multiple membrane leaf 19 are stacked alternately. The supply-side flow channel material 18 secures a space (supply space) between the membrane leaf 19 that serves as a flow channel for the raw fluid F0.

[0125] For the supply-side channel material 18 and the permeate-side channel material 17, for example, a net, woven fabric, or knitted fabric made of a resin such as polyethylene, polypropylene, polyethylene terephthalate (PET), polyphenylene sulfide (PPS), or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.

[0126] The outer surface of the membrane element 15 is composed of a shell (not shown) made of a material that prevents fluid from passing through. The shell may be made of FRP (fiber-reinforced plastic).

[0127] The first membrane separation unit 10, which includes the spiral-shaped membrane element 15 shown in Figure 4, can be operated, for example, in the following way. First, the pressurizing unit 40 supplies the raw fluid F0 to one end of the wound membrane leaf 19. The space inside the central tube 16 is depressurized. Depressurization can be performed by the first depressurization unit 51. As a result, the first permeate fluid F1 that has permeated through the first permeation vaporization membrane 11 of the membrane leaf 19 moves into the central tube 16. The first permeate fluid F1 is discharged to the outside through the central tube 16. The raw fluid F0 (first non-permeable fluid F2) processed in the first membrane separation unit 10 is discharged to the outside from the other end of the wound membrane leaf 19.

[0128] <Modifications of the Membrane Separation System> The membrane separation system of this embodiment is not limited to the membrane separation system 100A shown in Figure 1. Hereinafter, modifications 1 and 2 of the membrane separation system of this embodiment will be described with reference to Figures 6 and 7. In the following, elements common to the membrane separation system 100A described above will be given the same reference numerals, and detailed explanations will be omitted.

[0129] [Modified Membrane Separation System 1] Modified Membrane Separation System 1 of this embodiment includes multiple membrane separation units as at least one membrane separation unit. The multiple membrane separation units are connected in series so that the impermeable fluid discharged from the membrane separation unit located upstream is supplied as a supply fluid to the membrane separation unit located downstream.

[0130] Figure 6 is a schematic diagram showing a modified example 1 of the membrane separation system of this embodiment. The membrane separation system 100B of modified example 1 shown in Figure 6 includes a second membrane separation unit 20 and a third membrane separation unit 30 in addition to the first membrane separation unit 10. In the membrane separation system 100B, the first membrane separation unit 10, the second membrane separation unit 20, and the third membrane separation unit 30 are connected in series so that the impermeable fluid discharged from the membrane separation unit located on the upstream side is supplied as a supply fluid to the membrane separation unit located on the downstream side. Except for these, the membrane separation system 100B has basically the same configuration as the membrane separation system 100A (Figure 1) described above.

[0131] The second membrane separation unit 20 includes a second permeation vaporization membrane 21 that separates the first impermeable fluid F2, which is the supply fluid, into a second permeable fluid F3 and a second impermeable fluid F4, and a second container 22 in which the second permeation vaporization membrane 21 is located. The third membrane separation unit 30 includes a third permeation vaporization membrane 31 that separates the second impermeable fluid F4, which is the supply fluid, into a third permeable fluid F5 and a third impermeable fluid F6, and a third container 32 in which the third permeation vaporization membrane 31 is located. The configurations of the second membrane separation unit 20 and the third membrane separation unit 30 are basically the same as those of the first membrane separation unit 10, so their explanation is omitted.

[0132] The membrane separation system 100B includes a second permeable fluid pipe 94 connected to the second permeable fluid outlet 20b of the second container 22, and a third permeable fluid pipe 96 connected to the third permeable fluid outlet 30b of the third container 32.

[0133] In the membrane separation system 100B, a leak in the membrane separation section may be detected when any of the following conditions are met: the temperature T1 of the first permeate pipe 92 drops below a predetermined value or more than the temperature T2 of the first container 12; the temperature T3 of the second permeate pipe 94 drops below a predetermined value or more than the temperature T4 of the second container 22; or the temperature T5 of the third permeate pipe 96 drops below a predetermined value or more than the temperature T6 of the third container 32. When a leak is detected, control may be executed to stop the operation of the membrane separation system 100B.

[0134] In the membrane separation system 100B, a leak in the first membrane separation unit 10 may be detected when the temperature T1 of the first permeate fluid piping 92 drops below a predetermined value or more than the temperature T2 of the first container 12. A leak in the second membrane separation unit 20 may be detected when the temperature T3 of the second permeate fluid piping 94 drops below a predetermined value or more than the temperature T4 of the second container 22. A leak in the third membrane separation unit 30 may be detected when the temperature T5 of the third permeate fluid piping 96 drops below a predetermined value or more than the temperature T6 of the third container 32. With this configuration, leaks can be detected in each of the multiple membrane separation units during operation.

[0135] The membrane separation system 100B may further include a third temperature sensor 73 for measuring the temperature T3 of the second permeable fluid piping 94, and a fourth temperature sensor 74 for measuring the temperature T4 of the second container 22.

[0136] In the membrane separation system 100B, if it is determined that the temperature T3 of the second permeable fluid piping 94 has dropped by a predetermined value or more compared to the temperature T4 of the second container 22, based on the monitoring results from the third temperature sensor 73 and the fourth temperature sensor 74, a leak in the second membrane separation unit 20 may be detected. With this configuration, leaks can be easily detected.

[0137] The membrane separation system 100B may further include a fifth temperature sensor 75 for measuring the temperature T5 of the third permeable fluid piping 96, and a sixth temperature sensor 76 for measuring the temperature T6 of the third container 32.

[0138] In the membrane separation system 100B, if it is determined that the temperature T5 of the third permeable fluid piping 96 has dropped by a predetermined value or more compared to the temperature T6 of the third container 32, based on the monitoring results from the fifth temperature sensor 75 and the sixth temperature sensor 76, a leak in the third membrane separation unit 30 may be detected. With this configuration, leaks can be easily detected.

[0139] The positions where the third temperature sensor 73 and the fifth temperature sensor 75 are installed, and the shortest horizontal distance between each temperature sensor, can be determined by applying the positions and shortest horizontal distance described for the first temperature sensor 71. The positions where the fourth temperature sensor 74 and the sixth temperature sensor 76 are installed, and the shortest horizontal distance between each temperature sensor, can be determined by applying the positions and shortest horizontal distance described for the second temperature sensor 72.

[0140] The membrane separation system 100B includes a first depressurization section 51, a second depressurization section 52, and a third depressurization section 53. The second depressurization section 52 reduces the pressure in the permeate space of the second membrane separation section 20. The third depressurization section 53 reduces the pressure in the permeate space of the third membrane separation section 30.

[0141] The second pressure reduction section 52 and the third pressure reduction section 53 can be the same as those described for the first pressure reduction section 51.

[0142] The membrane separation system 100B includes a second condensation section 62 and a third condensation section 63 in addition to the first condensation section 61. The second condensation section 62 condenses the volatile organic compound C contained in the second permeate fluid F3 discharged from the permeate space of the second membrane separation section 20. The third condensation section 63 condenses the volatile organic compound C contained in the third permeate fluid F5 discharged from the permeate space of the third membrane separation section 30. The second condensation section 62 and the third condensation section can be the same as those described for the first condensation section 61.

[0143] As shown in Figure 6, the second condensation section 62 may be provided upstream of the second pressure reduction section 52 in the second permeable fluid piping 94. The third condensation section 63 may be provided upstream of the third pressure reduction section 53 in the third permeable fluid piping 96.

[0144] Although not shown in the diagram, the second condensation section 62 may be connected to a recovery section for recovering the second permeate fluid F3 obtained by condensation. The third condensation section 63 may be connected to a recovery section for recovering the third permeate fluid F5 obtained by condensation.

[0145] In the membrane separation system 100B, the first impermeable fluid piping 93 connects the first impermeable fluid outlet 10c of the first container 12 to the first impermeable fluid inlet 20a of the second container 22, and is a path for guiding the first impermeable fluid F2 from the first membrane separation section 10 to the second membrane separation section 20.

[0146] The membrane separation system 100B further includes a second permeable fluid piping 94, a second non-permeable fluid piping 95, a third permeable fluid piping 96, and a third non-permeable fluid piping 97 as fluid pathways.

[0147] The second permeable fluid piping 94 is connected to the second permeable fluid outlet 20b of the second container 22 and is a path for discharging the second permeable fluid F3 from the second membrane separation section 20. A concentration sensor for measuring the content of organic compound C in the second permeable fluid F3 may be placed in the second permeable fluid piping 94.

[0148] In the example shown in Figure 6, the second condensation section 62 and the second pressure reduction section 52 are located in the second permeable fluid piping 94.

[0149] The second impermeable fluid piping 95 connects the second impermeable fluid outlet 20c of the second container 22 to the second impermeable fluid inlet 30a of the third membrane separation unit 30, and serves as a path for guiding the second impermeable fluid F4 from the second membrane separation unit 20 to the third membrane separation unit 30. A concentration sensor for measuring the content of organic compound C in the second impermeable fluid F4 may be placed in the second impermeable fluid piping 95.

[0150] The third permeate pipe 96 is connected to the third permeate outlet 30b of the third container 32 and is a path for discharging the third permeate F5 from the third membrane separation section 30. A concentration sensor for measuring the content of organic compound C in the third permeate pipe 96 may be placed in the third permeate pipe 96.

[0151] In the example shown in Figure 6, the third condensing section 63 and the third pressure reduction section 53 are located in the third permeable fluid piping 96.

[0152] The third impermeable fluid piping 97 is connected to the third impermeable fluid outlet 30c of the third container 32 and is a path for discharging the third impermeable fluid F6 from the third membrane separation section 30. A concentration sensor for measuring the content of organic compound C in the third impermeable fluid F6 may be placed in the third impermeable fluid piping 97.

[0153] The control for stopping the operation of the membrane separation system 100B may include at least one selected from the group consisting of a control for stopping the operation of the first depressurization unit 51, a control for stopping the operation of the second depressurization unit 52, a control for stopping the operation of the third depressurization unit 53, and a control for stopping the operation of the pressurization unit 40. With such a configuration, it is possible to stop the operation of only the membrane separation unit where a leak has occurred.

[0154] In the membrane separation system 100B, for example, the control unit 80 controls the operation of the first depressurization unit 51, the second depressurization unit 52, the third depressurization unit 53, the pressurization unit 40, and so on.

[0155] The operation method of the membrane separation system 100B described above may include detecting a leak in the membrane separation section when any of the following conditions are met: the temperature T1 of the first permeate fluid piping 92 falls below a predetermined value or more than the temperature T2 of the first container 12; the temperature T3 of the second permeate fluid piping 94 falls below a predetermined value or more than the temperature T4 of the second container 22; or the temperature T5 of the third permeate fluid piping 96 falls below a predetermined value or more than the temperature T6 of the third container 32.

[0156] The operating method of the membrane separation system 100B may include detecting a leak in the first membrane separation unit 10 when the temperature T1 of the first permeation fluid piping 92 drops below a predetermined value or more than the temperature T2 of the first container 12; detecting a leak in the second membrane separation unit 20 when the temperature T3 of the second permeation fluid piping 94 drops below a predetermined value or more than the temperature T4 of the second container 22; and detecting a leak in the third membrane separation unit 30 when the temperature T5 of the third permeation fluid piping 96 drops below a predetermined value or more than the temperature T6 of the third container 32. With such a configuration, leaks can be detected in each of the multiple membrane separation units during operation.

[0157] The operation method of the membrane separation system 100B may include executing control to stop operation of the membrane separation system 100B after detecting a leak. With such a configuration, the effects of leaks can be further suppressed.

[0158] In the operation method of the membrane separation system 100B, the control for stopping the operation of the membrane separation system 100B may include at least one selected from the group consisting of a control for stopping the operation of the first depressurization unit 51, a control for stopping the operation of the second depressurization unit 52, a control for stopping the operation of the third depressurization unit 53, and a control for stopping the operation of the pressurization unit 40.

[0159] [Modified Membrane Separation System 2] Figure 7 is a schematic diagram showing modified membrane separation system 2 of this embodiment. In the modified membrane separation system 100C shown in Figure 7, the second permeable fluid piping 94 and the third permeable fluid piping 96 merge with the first permeable fluid piping 92. Except for this, the membrane separation system 100C has basically the same configuration as the membrane separation system 100B (Figure 6) described above.

[0160] As shown in Figure 7, the second permeable fluid piping 94 may merge with the first permeable fluid piping 92 at a junction 92p located upstream of the first condensing section 61 and the first pressure reducing section 51. The third permeable fluid piping 96 may merge with the second permeable fluid piping 94 at a junction 94p. With this configuration, a common first pressure reducing section 51 can reduce the pressure in the permeable spaces of the first membrane separation section 10, the second membrane separation section 20, and the third membrane separation section 30. A common first condensing section 61 can condense the permeable fluid discharged from the permeable spaces of the first membrane separation section 10, the second membrane separation section 20, and the third membrane separation section 30.

[0161] In the operation method of the membrane separation system 100C, the control for stopping the operation of the membrane separation system 100C may include at least one selected from the group consisting of a control for stopping the operation of the first depressurization unit 51 and a control for stopping the operation of the pressurization unit 40.

[0162] [Modification 3 of the Membrane Separation System] Figure 8 is a schematic diagram showing modification 3 of the membrane separation system of this embodiment. The membrane separation system 100D of modification 3 shown in Figure 8 is equipped with a seventh temperature sensor 77 located in the first permeable fluid piping 92 downstream of the confluence point 92p, instead of the first temperature sensor 71, the third temperature sensor 73, and the fifth temperature sensor 75. Except for this, the membrane separation system 100D has basically the same configuration as the membrane separation system 100C (Figure 7) described above. According to the membrane separation system 100D, the occurrence of at least one leak can be detected based on the temperature T7 of the first permeable fluid piping 92 after the confluence, as measured by the seventh temperature sensor 77.

[0163] The seventh temperature sensor 77 is preferably located in the first permeable fluid piping 92 downstream of the confluence position 92p and upstream of the first condensation section 61.

[0164] In the membrane separation system 100D, it may be determined whether the temperature T7 has dropped by a predetermined value or more from the temperature T2, based on the temperature T7 of the first permeable fluid piping 92 after merging, measured by the seventh temperature sensor 77, and the temperature T2 of the first container 12, measured by the second temperature sensor 72. For example, it may be determined that a leak has occurred if the temperature T7 has dropped by 3°C or more from the temperature T2. Alternatively, it may be determined whether the temperature T7 has dropped by a predetermined value or more from the temperature T4, based on the temperature T7 measured by the seventh temperature sensor 77 and the temperature T4 of the second container 22, measured by the fourth temperature sensor 74. For example, it may be determined that a leak has occurred if the temperature T7 has dropped by 3°C or more from the temperature T4. Furthermore, it may be determined whether the temperature T7 has dropped by a predetermined value or more from the temperature T6, based on the temperature T7 measured by the seventh temperature sensor 77 and the temperature T6 of the third container 32, measured by the sixth temperature sensor 76. For example, a leak may be determined to have occurred if the temperature T7 drops by 3°C or more compared to the temperature T6. In the membrane separation system 100D, if the temperature corresponding to at least one of the permeate fluids drops due to a leak, the temperature T7 may also drop as a result. Therefore, the occurrence of at least one leak can be detected.

[0165] In the operation method of the membrane separation system 100D, the control for stopping the operation of the membrane separation system 100D may include at least one selected from the group consisting of a control for stopping the operation of the first depressurization unit 51 and a control for stopping the operation of the pressurization unit 40.

[0166] The above-described embodiments are mutually applicable, insofar as they do not conflict with technical standards. Each of the above embodiments and each of its modifications may be combined with each other, insofar as they do not conflict with technical standards.

[0167] The membrane separation system of this embodiment is suitable, for example, for efficiently recovering organic compounds from a supply fluid containing volatile organic compounds.

Claims

1. A membrane separation system comprising: a permeable vaporization membrane for separating a supply fluid containing volatile organic compounds into a permeable fluid and an impermeable fluid; a container in which the permeable vaporization membrane is disposed; at least one membrane separation unit having a supply space and a permeable space separated by the permeable vaporization membrane inside the container; and a permeable fluid pipe connected to the permeable fluid outlet of the container, wherein a leak in the membrane separation unit is detected when the temperature of the permeable fluid pipe drops below a predetermined value or more below the temperature of the container.

2. The membrane separation system according to claim 1, wherein the predetermined value is 5°C.

3. The membrane separation system according to claim 1, wherein the temperature of the permeable fluid piping is the temperature of the surface of the permeable fluid piping.

4. The membrane separation system according to claim 1, wherein the temperature of the permeable fluid piping is the temperature of the permeable fluid piping near the permeable fluid outlet.

5. The membrane separation system according to claim 1, wherein the temperature of the permeable fluid piping is the temperature of the permeable fluid in the permeable fluid piping.

6. The membrane separation system according to claim 1, wherein the temperature of the container is the temperature of the surface of the container.

7. The membrane separation system according to claim 1, wherein the temperature of the container is the temperature of the container near the non-permeable fluid outlet of the container.

8. The membrane separation system according to claim 1, wherein the temperature of the container is the temperature of the impermeable fluid inside the container.

9. The membrane separation system according to claim 1, further comprising: a first temperature sensor for measuring the temperature of the permeable fluid piping; and a second temperature sensor for measuring the temperature of the container.

10. The membrane separation system according to claim 9, wherein, based on the monitoring results from the first temperature sensor and the second temperature sensor, it is determined whether or not the temperature of the permeable fluid piping has fallen below the temperature of the container by a predetermined value or more.

11. The membrane separation system according to claim 1, wherein when the leak is detected, control is performed to stop the operation of the membrane separation system.

12. The membrane separation system according to claim 11, further comprising: a depressurization unit for reducing the pressure of the permeation space of the at least one membrane separation unit; and a pressurization unit for increasing the pressure of the supply space of the at least one membrane separation unit, wherein the control for stopping the operation includes at least one selected from the group consisting of a control for stopping the operation of the depressurization unit and a control for stopping the operation of the pressurization unit.

13. The membrane separation unit is disposed inside the container and includes a spiral-shaped membrane element having the permeable vaporization membrane, the container has a cylindrical container body, a first end plate attached to the supply fluid inlet end of the container, and a second end plate attached to the permeable fluid outlet end of the container, and the temperature of the container includes the temperature of the container body and the temperature of the second end plate, according to claim 1.

14. The membrane separation system according to claim 1, wherein the at least one membrane separation unit includes a plurality of membrane separation units, and the plurality of membrane separation units are connected in series such that the impermeable fluid discharged from the membrane separation unit located upstream is supplied as the supply fluid to the membrane separation unit located downstream.

15. A method for operating a membrane separation system comprising: a permeable vaporization membrane for separating a supply fluid containing volatile organic compounds into a permeable fluid and an impermeable fluid; a container in which the permeable vaporization membrane is disposed; at least one membrane separation unit having a supply space and a permeable space separated by the permeable vaporization membrane inside the container; and a permeable fluid pipe connected to the permeable fluid outlet of the container, the method comprising detecting a leak in the membrane separation unit when the temperature of the permeable fluid pipe drops below a predetermined value or more below the temperature of the container.

16. A method for operating a membrane separation system according to claim 15, comprising executing control to stop the operation of the membrane separation system after detecting the leak.

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