Membrane separation system and method for operating membrane separation system

Abstract

Provided is a membrane separation system suitable for efficient recovery of organic compounds. A membrane separation system (100) is provided with a membrane separation unit (10), a condensation unit (20), and a decompression unit (30). The condensing unit (20) is disposed between the membrane separation unit (10) and the decompression unit (30). The membrane separation unit (10) has a pervaporation membrane, and a supply space and a permeation space separated by the pervaporation membrane. The pervaporation membrane separates a feed liquid S containing a volatile organic compound C and a gas G into a permeated fluid S1 and a non-permeated fluid S2. The condensing unit (20) condenses an organic compound (C) contained in the permeate fluid (S1). The decompression unit 30 decompresses the inside of the permeation space of the membrane separation unit 10. During operation, the operating conditions of the pressure reduction unit 30 are controlled so that the pressure P10 in the permeation space of the membrane separation unit 10 becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation unit 10 during rated operation of the pressure reduction unit 30.

Description

Technical Field

[0001] The present invention relates to a membrane separation system and an operation method of the membrane separation system. Background Art

[0002] As an example of a method for separating volatile organic compounds from an aqueous solution containing the organic compounds, a pervaporation method (pervaporation method) using a pervaporation membrane is known. The pervaporation method is suitable for separating volatile organic compounds from aqueous solutions containing various substances. Compared with the distillation method, the pervaporation method also tends to be able to suppress energy consumption and the emission of gases such as carbon dioxide. A technology for continuously producing volatile organic compounds by combining a membrane separation device for performing the pervaporation method with a reaction tank for producing volatile organic compounds has been proposed. For example, Patent Document 1 discloses a membrane separation system that combines a membrane separation device and a reaction tank.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 4048279 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The pervaporation method can be performed using a membrane separation section having a pervaporation membrane and a supply space and a permeation space separated by the pervaporation membrane. The supply liquid permeating the pervaporation membrane is vaporized by depressurizing the permeation space while the supply liquid is in contact with the pervaporation membrane. Thus, a gaseous permeation fluid is obtained. Conventionally, in a membrane separation system using the pervaporation method, the decompression in the permeation space is performed by a decompression section provided at the rear section of the membrane separation section. The obtained gaseous permeation fluid is liquefied in a condensation section provided at the rear section of the decompression section to obtain a liquid permeation fluid.

[0008] The inventors of the present application have obtained the following knowledge, that is, since the pervaporation membrane also permeates the gas contained in the supply liquid, the gas such as carbon dioxide remains in the permeated fluid of the gas separated by the pervaporation membrane. In the conventional membrane separation system using the pervaporation method, the permeated fluid of the gas is supplied to the condensation section as the exhaust gas of the decompression section in a state containing the gas. The gas such as carbon dioxide contained in the permeated fluid of the gas reduces the condensation efficiency in the condensation section, and as a result, the recovery efficiency of the organic compound is reduced.

[0009] Therefore, an object of the present invention is to provide a membrane separation system suitable for efficiently recovering organic compounds.

[0010] Means for solving problems

[0011] The present invention provides a membrane separation system, which comprises a membrane separation section, a condensation section and a pressure reduction section.

[0012] The condensation section is arranged between the membrane separation section and the pressure reducing section.

[0013] The membrane separation section includes a pervaporation membrane, and a supply space and a permeation space separated by the pervaporation membrane, wherein the pervaporation membrane separates a supply liquid containing a volatile organic compound and a gas into a permeated fluid and a non-permeated fluid.

[0014] The condensation unit condenses the organic compound contained in the permeated fluid.

[0015] The decompression unit decompresses the permeation space of the membrane separation unit.

[0016] During operation, the operating conditions of the decompression section are controlled so that the pressure in the permeation space of the membrane separation section becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section during rated operation of the decompression section.

[0017] In another aspect, the present invention provides an operation method of a membrane separation system, wherein the membrane separation system comprises a membrane separation section, a condensation section and a decompression section, wherein the condensation section is arranged between the membrane separation section and the decompression section, wherein:

[0018] The membrane separation section includes a pervaporation membrane, and a supply space and a permeation space separated by the pervaporation membrane.

[0019] The operation method comprises:

[0020] separating a feed liquid containing a volatile organic compound and a gas into a permeated fluid and a non-permeated fluid by the pervaporation membrane of the membrane separation section; and

[0021] condensing the organic compound contained in the permeated fluid by the condensation unit,

[0022] The separation includes controlling the operating conditions of the decompression section so that the pressure in the permeation space of the membrane separation section becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section during rated operation of the decompression section.

[0023] Effects of the Invention

[0024] According to the present invention, a membrane separation system suitable for efficiently recovering organic compounds can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] [ Figure 1] is a schematic configuration diagram showing an example of a membrane separation system according to the present embodiment.

[0026] [ Figure 2 ] is a schematic cross-sectional view showing an example of a membrane separation section included in a membrane separation system.

[0027] [ Figure 3 ] is a schematic cross-sectional view of the pervaporation membrane provided in the membrane separation section.

[0028] [ Figure 4 ] is a flow chart showing the control of the intermittent operation of the pressure reducing section of the membrane separation system.

[0029] [ Figure 5 ] is a timing diagram showing an example of intermittent operation.

[0030] [ Figure 6 ] is a flow chart showing the control of low-speed operation of the pressure reducing section of the membrane separation system.

[0031] [ Figure 7 ] is an expanded stereoscopic view schematically showing another example of a membrane separation section.

[0032] [ Figure 8 ] is a schematic diagram showing the structure of a conventional membrane separation system.

[0033] [ Fig. 9 ] is a graph showing the relationship between the liquid level in the recovery section and the pressure in the permeation space of the membrane separation section and time during the operation of Reference Example 1.

[0034] [ Fig.10 ] is a graph showing the relationship between the liquid level in the recovery section and the pressure in the permeation space of the membrane separation section and time during the operation of Example 1.

[0035] [ Fig.11 ] is a graph showing the relationship between the pressure in the permeation space of the membrane separation section and the liquid level in the recovery section and time during the operation of Example 3.

[0036] [ Fig.12 ] is a graph showing the relationship between the pressure in the permeation space of the membrane separation section and the power consumption of the pressure reducing section (vacuum pump) and time during the operation of Example 2.

[0037] [ Fig.13 ] is a graph showing the relationship between the pressure in the permeation space of the membrane separation section and the cumulative power consumption of the pressure reducing section (vacuum pump) and time during the operation of Example 2. DETAILED DESCRIPTION

[0038] A membrane separation system according to a first aspect of the present invention comprises a membrane separation section, a condensation section, and a pressure reduction section.

[0039] The condensation section is arranged between the membrane separation section and the pressure reducing section.

[0040] The membrane separation section includes a pervaporation membrane, and a supply space and a permeation space separated by the pervaporation membrane, wherein the pervaporation membrane separates a supply liquid containing a volatile organic compound and a gas into a permeated fluid and a non-permeated fluid.

[0041] The condensation unit condenses the organic compound contained in the permeated fluid.

[0042] The decompression unit decompresses the permeation space of the membrane separation unit.

[0043] During operation, the operating conditions of the decompression section are controlled so that the pressure in the permeation space of the membrane separation section becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section during rated operation of the decompression section.

[0044] In the second aspect of the present invention, for example, in the membrane separation system of the first aspect, during operation, the operating conditions of the decompression section are controlled so that the pressure in the permeation space of the membrane separation section is within the range of 0.2 to 20.0 kPa.

[0045] In a third aspect of the present invention, for example, in the membrane separation system of the first or second aspect, in the condensation section, the partial pressure of the organic compound in the permeated fluid is reduced by condensation of the organic compound.

[0046] In the fourth embodiment of the present invention, for example, in a membrane separation system of any one of the first to third embodiments, the pressure reducing section performs intermittent operation in which the operation stop and operation start of the pressure reducing section are repeated alternately, or performs low-speed operation in which the pressure reducing section is operated with an output less than the maximum output.

[0047] In a fifth aspect of the present invention, for example, in the membrane separation system of the fourth aspect, the pressure in the permeation space of the membrane separation section is adjusted to a range of 0.2 to 20.0 kPa by causing the decompression section to perform the intermittent operation or the low-speed operation.

[0048] In a sixth aspect of the present invention, for example, in the membrane separation system of the fourth aspect, the intermittent operation includes: stopping the rated operation of the decompression section when the pressure in the permeation space of the membrane separation section is lower than 0.2 kPa; and starting the rated operation of the decompression section when the pressure in the permeation space of the membrane separation section is higher than 20.0 kPa,

[0049] The low-speed operation includes: operating the decompression section at an output less than a maximum output when the pressure in the permeation space of the membrane separation section is lower than 0.2 kPa; and operating the decompression section at a maximum output when the pressure in the permeation space of the membrane separation section is higher than 20.0 kPa.

[0050] In a seventh aspect of the present invention, for example, the membrane separation system according to any one of the first to sixth aspects further includes a pressure regulating valve for regulating the pressure in the permeation space between the condensation section and the pressure reducing section.

[0051] In the operating method of the membrane separation system according to the eighth aspect of the present invention, the membrane separation system comprises a membrane separation section, a condensation section and a pressure reduction section, wherein the condensation section is arranged between the membrane separation section and the pressure reduction section,

[0052] The membrane separation section includes a pervaporation membrane, and a supply space and a permeation space separated by the pervaporation membrane.

[0053] The operation method comprises:

[0054] separating a feed liquid containing a volatile organic compound and a gas into a permeated fluid and a non-permeated fluid by the pervaporation membrane of the membrane separation section; and

[0055] condensing the organic compound contained in the permeated fluid by the condensation unit,

[0056] The separation includes controlling the operating conditions of the decompression section so that the pressure in the permeation space of the membrane separation section becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section during rated operation of the decompression section.

[0057] Hereinafter, the present invention will be described in detail, but the following description is not intended to limit the present invention to specific embodiments.

[0058] <Embodiment of membrane separation system>

[0059] like Figure 1 As shown, the membrane separation system 100 of the present embodiment includes a membrane separation section 10 having a pervaporation membrane, a condensation section 20, and a decompression section 30. The condensation section 20 is disposed between the membrane separation section 10 and the decompression section 30.

[0060] The membrane separation unit 10 has a pervaporation membrane and a supply space and a permeation space separated by the pervaporation membrane. The pervaporation membrane separates the supply liquid S containing the volatile organic compound C into a permeation fluid S1 and a non-permeation fluid S2. The condensation unit 20 condenses the organic compound C contained in the permeation fluid S1. The decompression unit 30 decompresses the permeation space of the membrane separation unit 10.

[0061] The supply liquid S contains a volatile organic compound C such as alcohol. The supply liquid S is typically a fermentation liquid. The fermentation liquid is obtained by fermenting a carbon source such as glucose or synthesis gas in an aqueous solution using a microorganism. Therefore, when the supply liquid S is a fermentation liquid, the supply liquid S contains a volatile organic compound C and contains a microorganism that produces the organic compound C. The microorganism that produces the organic compound C is typically a bacterium. Usually, during the fermentation process of a carbon source in an aqueous solution, gases such as carbon dioxide are produced as by-products. Therefore, in the supply liquid S obtained by fermentation, the gas exists as a dissolved gas G. The gas G contains carbon dioxide. The supply liquid S, for example, contains water in addition to the organic compound C, the microorganism and the gas G. The supply liquid S is typically an aqueous solution containing an organic compound C, a microorganism and a gas G.

[0062] In the membrane separation system 100, a condensation section 20 is disposed between the membrane separation section 10 and the decompression section 30. The decompression section 30 decompresses the permeation space of the membrane separation section 10 and the condensation section 20. During operation, the pressure P in the permeation space of the membrane separation section 10 is 10 The operating conditions of the decompression section 30 are controlled in such a manner that the pressure becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section 10 during the rated operation of the decompression section 30. As a result, while the organic compound C is condensed in the condensation section 20, the amount of the permeated fluid S1 discharged from the condensation section 20 can be reduced, thereby suppressing the reduction in the condensation efficiency in the condensation section 20. As a result, the recovery efficiency of the organic compound C is improved. The membrane separation system 100 of this embodiment is particularly effective when the supply liquid S is a fermentation liquid. It should be noted that rated operation refers to operating the decompression section 30 at maximum output.

[0063] Figure 81 is a schematic diagram showing a conventional membrane separation system 1000 using a pervaporation method. The membrane separation system 1000 includes a membrane separation section 101 having a pervaporation membrane, a decompression section 102, and a condensation section 103. The decompression section 102 is provided between the membrane separation section 101 and the condensation section 103. It should be noted that reference numeral 104 indicates a tank for storing a supply liquid L to be supplied to the membrane separation section 101. As described above, the pervaporation membrane also allows the gas contained in the supply liquid to pass through. Therefore, if the supply liquid L is separated into a permeation fluid L1 and a non-permeation fluid L2 by the pervaporation membrane of the membrane separation section 101, a gas such as carbon dioxide remains in the separated permeation fluid L1. In the membrane separation system 1000, the permeation fluid L1 discharged from the membrane separation section 101 is supplied to the condensation section 103 as exhaust gas of the decompression section 102 in a state containing gas. The condensation efficiency in the condensation section 103 depends on the partial pressure of the gas to be condensed. Therefore, the gas contained in the permeated fluid L1 reduces the condensation efficiency in the condensation unit 103, resulting in a reduction in the recovery efficiency of the organic compound. The permeated fluid L1 that has not been condensed due to the presence of the gas is discharged to the outside of the system.

[0064] In the conventional membrane separation system 1000, the pressure reducing section 102 is operated at a rated value. The inventors of the present application have obtained the following insight: since the condensation based on the condensation section occurs in the form of a closed system, the pressure in the condensation section decreases due to the volume change during the condensation of the organic compound, and therefore, there is no need to continuously operate the pressure reducing section at a rated value. Furthermore, the inventors of the present application have obtained the following insight: if the amount of permeated fluid discharged to the outside of the system can be reduced, the condensation efficiency in the condensation section can be improved. Based on these insights, the inventors of the present application have found that by configuring the condensation section 20 between the membrane separation section 10 and the pressure reducing section 30, it is possible to reduce the pressure P in the permeation space of the membrane separation section 10 during operation. 10 The operating conditions of the decompression section 30 are controlled so that the pressure P in the permeation space of the membrane separation section 10 becomes greater than the minimum value that can be reached in the rated operation of the decompression section 30. 10 By controlling the operating conditions of the decompression section 30 in a manner that makes the pressure greater than the minimum value that can be reached in the permeation space of the membrane separation section 10 during rated operation of the decompression section 30, the exhaust volume of the decompression section 30 can be reduced, and condensation of the organic compound C in the condensation section 20 can be achieved.

[0065] During operation, if the partial pressure of the organic compound C in the permeated fluid S1 is reduced due to the condensation of the organic compound C in the condenser 20, the volume occupied by the organic compound C in the total volume in the condenser 20 is reduced. As a result, the amount of gas G discharged from the condenser 20 is reduced. That is, the discharge of the gas G from the condenser 20 is suppressed by condensing the organic compound C in the permeated fluid S1 in the condenser 20. As a result, the amount of the permeated fluid S1 discharged to the outside of the system can be reduced.

[0066] It should be noted that the term “to make the pressure P in the permeation space of the membrane separation section 10 during operation” means 10 The operating conditions of the decompression section 30 are controlled in such a way that the pressure P in the permeation space of the membrane separation section 10 becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section 10 during the rated operation of the decompression section 30. The pressure P in the permeation space of the membrane separation section 10 is not limited to 10 The pressure P in the permeation space of the membrane separation section 10 must always be greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section 10 when the decompression section 30 is in rated operation. For example, when the decompression section 30 described later is in intermittent operation or low-speed operation, the pressure P in the permeation space of the membrane separation section 10 is 10 The pressure in the permeation space of the membrane separation section 10 may temporarily become the minimum value that can be achieved during the rated operation of the pressure reducing section 30 .

[0067] During operation, the pressure P in the permeation space of the membrane separation section 10 may be 10 The operating conditions of the pressure reducing section 30 are controlled so as to be greater than the saturated vapor pressure of the permeated fluid S1 at the cooling temperature of the condensing section 20 and less than the saturated vapor pressure of the feed liquid S at the operating temperature of the membrane separation section 10 .

[0068] During operation, the pressure P in the permeation space of the membrane separation section 10 may be 10 The operating conditions of the pressure reducing section 30 are controlled in a manner so as to be within the range of 0.2 to 20.0 kPa. At this time, the operating temperature of the membrane separation section 10 can be within the range of 20 to 40°C, and the cooling temperature of the condensation section 20 can be within the range of -10 to -20°C. The operating temperature of the membrane separation section 10 can also be 30°C, and the cooling temperature of the condensation section 20 can also be -15°C. When a conventional vacuum device such as a vacuum pump is used, the degree of pressure reduction during operation is about several Pa to 100 Pa. In contrast, in the present embodiment, the pressure P in the permeation space of the membrane separation section 10 is 10 Since it is suppressed to a low level, energy saving effect can also be expected.

[0069] During operation, the pressure P in the permeation space of the membrane separation section 10 may be 10 The operating conditions of the pressure reducing unit 30 are controlled so as to be within the range of 0.5 to 10.0 kPa. 10The operating conditions of the pressure reducing unit 30 are controlled so as to be within the range of 1.0 to 5.0 kPa.

[0070] During operation, the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 may be set to 10 The operating conditions of the decompression unit 30 are controlled so as to be within a predetermined range. Specifically, during operation, the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 may be controlled so as to be within a predetermined range. 10 is the saturated vapor pressure Ec of the organic compound C contained in the permeated fluid S1 at the cooling temperature of the condensation unit 20 20 The saturated vapor pressure Ec of the organic compound C contained in the feed liquid S at the operating temperature of the membrane separation unit 10 is 10 The operating conditions of the pressure reducing unit 30 are controlled in the following manner. That is, during operation, Ec 20 ≤Pc 10 ≤Ec 10 The operating conditions of the pressure reducing unit 30 are controlled by satisfying Ec 20 ≤Pc 10 , thereby preventing the following situation: the partial pressure of the organic compound C contained in the permeated fluid S1 in the condensation section 20 is too low, resulting in the inability to properly condense, and the permeated fluid S1 is discharged from the decompression section 30 in a completely vaporized state. 10 ≤Ec 10 , thereby preventing the following situation: due to the excessively high partial pressure of the organic compound C contained in the feed liquid S in the membrane separation section 10, permeation vaporization does not occur and the permeated fluid S1 cannot be obtained.

[0071] The pressure P in the permeation space of the membrane separation unit 10 10 The pressure P in the permeation space of the membrane separation section 10 can be adjusted by controlling the operation of the pressure reducing section 30. 10 Adjust within the range of 0.2~20.0kPa.

[0072] It is also possible to control the operation of the pressure reducing unit 30 so as to adjust the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 during operation. 10 Adjust to meet the above range (Ec 20 ≤Pc 10 ≤Ec 10 ).

[0073] The pressure reducing section 30 may also be a vacuum device such as a vacuum pump. The vacuum pump is typically a gas transport type vacuum pump, and examples include a reciprocating vacuum pump, a rotary vacuum pump, and the like. Examples of reciprocating vacuum pumps include diaphragm type and swing piston type vacuum pumps. Examples of rotary vacuum pumps include liquid seal pumps; oil rotary pumps (rotary pumps); mechanical booster pumps; various dry pumps such as Roots type, claw type, screw type, turbine type, and vortex type. The pump serving as the pressure reducing section 30 may also include a variable speed mechanism for changing the rotation speed, etc. An example of a variable speed mechanism is an inverter for driving a motor of the pump. By controlling the rotation speed of the pump, etc. using a variable speed mechanism, the pressure P in the permeation space of the membrane separation section 10 can be appropriately adjusted. 10 .

[0074] The pressure reducing unit 30 may also perform intermittent operation in which the operation is stopped and started alternately, or perform low-speed operation in which the operation is performed at an output lower than the maximum output. The pressure P in the permeation space of the membrane separation unit 10 may also be reduced by performing intermittent operation or low-speed operation. 10 Adjust within the range of 0.2~20.0kPa.

[0075] The partial pressure Pc of the organic compound C in the permeation space of the membrane separation section 10 may be lowered by performing intermittent operation or low-speed operation. 10 Adjust to meet the above range (Ec 20 ≤Pc 10 ≤Ec 10 ).

[0076] Intermittent operation refers to the alternating and repeated stopping and starting of the operation of the decompression section 30. In the present embodiment, the "operation" in the stopping and starting of the operation refers to the rated operation at the maximum output. Therefore, the intermittent operation can also be said to be the alternating repetition of the stopping of the rated operation and the operation of the rated operation. For example, the intermittent operation can be composed of 5 minutes of stopping of the rated operation and 1 minute of the rated operation. The cycle (repetitive cycle) of the intermittent operation in the decompression section 30 is not particularly limited.

[0077] The intermittent operation may also include: the pressure P in the permeation space of the membrane separation section 10 10 When the pressure drops below 0.2 kPa, the rated operation of the pressure reducing unit 30 is stopped; and the pressure P in the permeation space of the membrane separation unit 10 10 When the pressure exceeds 20.0 kPa, the rated operation of the pressure reducing unit 30 is started.

[0078] More specifically, the intermittent operation may include: the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 is 10 The saturated vapor pressure Ec of the organic compound C contained in the permeated fluid S1 at a temperature lower than the cooling temperature of the condensation unit 20 20When (Pc 10 <Ec 20 ), stop the rated operation of the decompression section 30; and the partial pressure Pc of the organic compound C in the permeation space of the membrane separation section 10 10 Higher than the saturated vapor pressure Ec of the organic compound C contained in the feed liquid S at the operating temperature of the membrane separation unit 10 10 When (Pc 10 >Ec 10 ), and the rated operation of the pressure reducing unit 30 is started.

[0079] Low-speed operation refers to operating the decompression unit 30 at an output less than the maximum output. Compared to rated operation (full-load operation) at the maximum output, low-speed operation can also be said to be partial-load operation at an output less than the maximum output. The operating speed of the decompression unit 30 during low-speed operation can also change over time. For example, the operating speed of the decompression unit 30 can also be gradually reduced. Low-speed operation can be performed, for example, by controlling the inverter provided in the decompression unit 30 to make the operating speed of the decompression unit 30 variable. There is no particular limitation on the duration of the low-speed operation in the decompression unit 30.

[0080] The low speed operation may also include: the pressure P in the permeation space of the membrane separation section 10 10 When the pressure is lower than 0.2 kPa, the pressure reducing unit 30 is operated at an output lower than the maximum output; and the pressure P in the permeation space of the membrane separation unit 10 10 When the pressure is higher than 20.0 kPa, the pressure reducing unit 30 is operated at the maximum output.

[0081] More specifically, the low speed operation may include: the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 is 10 The saturated vapor pressure Ec of the organic compound C contained in the permeated fluid S1 at a temperature lower than the cooling temperature of the condensation unit 20 20 When (Pc 10 <Ec 20 ), the pressure reducing unit 30 is operated with an output less than the maximum output; and the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 10 Higher than the saturated vapor pressure Ec of the organic compound C contained in the feed liquid S at the operating temperature of the membrane separation unit 10 10 When (Pc 10 >Ec 10 ), the pressure reducing unit 30 is operated at maximum output.

[0082] The condensation section 20 condenses the organic compound C by cooling the gas permeate fluid S1 delivered from the membrane separation section 10. In other words, the gas permeate fluid S1 is liquefied according to the condensation section 20 to obtain the condensed fluid S3. The condensed fluid S3 is a liquid fluid containing the organic compound C. The condensation section 20 is, for example, a gas-liquid heat exchanger that generates heat exchange between a cooling medium such as an antifreeze solution and the gas permeate fluid S1.

[0083] The membrane separation system 100 may further include a pressure regulating device for adjusting the pressure P in the permeation space of the membrane separation unit 10 between the condensation unit 20 and the pressure reducing unit 30. 10 The pressure regulating valve 35 is used to adjust the pressure P in the permeation space of the membrane separation section 10. 10 The method of reducing the pressure of the decompression section 30 includes, for example, a method of introducing external gas into the decompression section 30 and a method of adjusting the flow rate by a pressure regulating valve provided in the front section of the decompression section 30. By adopting the pressure regulating valve 35, it is possible to avoid an increase in the exhaust volume due to the introduction of external gas into the decompression section 30.

[0084] The membrane separation system 100 may further include a device for measuring the pressure P in the permeation space of the membrane separation unit 10. 10 or the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 10 The pressure P in the permeation space of the membrane separation section 10 can also be controlled by controlling the operation of the pressure reducing section 30 based on the measurement result of the pressure sensor. 10 The partial pressure Pc of the organic compound C in the permeation space of the membrane separation section 10 can also be adjusted by controlling the operation of the pressure reducing section 30 based on the measurement result of the pressure sensor. 10 Adjust to meet the above range (Ec 20 ≤Pc 10 ≤Ec 10 ).

[0085] In the membrane separation system 100, during operation, the content C of the gas G in the gas permeated fluid S1 may be set to G The operating conditions of the decompression unit 30 are controlled so as to be within a predetermined range. During operation, the content C of the gas G in the permeated fluid S1 in the condensation unit 20 may be set to G As described above, in the condensation section 20, the organic compound C is condensed, thereby reducing the partial pressure of the organic compound C in the permeated fluid S1. Therefore, by adjusting the content C of the gas G in the permeated fluid S1 in the condensation section 20, the pressure of the organic compound C in the permeated fluid S1 is reduced. G , and the amount of the permeated fluid S1 discharged from the condensation unit 20 can also be reduced.

[0086] The pressure P in the permeation space of the membrane separation unit 10 10 or the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 10 Similarly, the content C of the gas G in the gas permeating fluid S1 is G The content C of the gas G in the gas permeating fluid S1 can be adjusted by controlling the operation of the decompression unit 30. That is, the content C of the gas G in the gas permeating fluid S1 can be adjusted by controlling the operation of the decompression unit 30. G Adjust to the specified range.

[0087] In the membrane separation system 100, the pressure P in the permeation space of the membrane separation section 10 may be replaced by 10 or the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 10 or the pressure P in the permeation space of the membrane separation section 10. 10 or the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 10 The content C of the gas G in the gas permeating fluid S1 is controlled together with G of adjustment.

[0088] The membrane separation system 100 may further include a method for measuring the content C of the gas G in the permeated fluid S1. G The gas sensor can also measure the content C of the gas G in the permeating fluid S1 in the condensation section 20. G The content C of the gas G in the gas permeating fluid S1 may be adjusted by controlling the operation of the decompression unit 30 based on the measurement result of the gas sensor. G Adjust to the specified range.

[0089] The membrane separation system 100 includes a membrane separation unit 10, a condensation unit 20, a decompression unit 30, and a tank 40. The tank 40 stores a feed liquid S to be supplied to the membrane separation unit 10. The tank 40 may be a fermentation tank for producing an organic compound C by fermentation of a carbon source by microorganisms.

[0090] The membrane separation system 100 further includes a fermentation liquid supply path 91 , a non-permeated fluid discharge path 92 , a permeated fluid discharge path 93 , and a condensed fluid discharge path 94 as fluid paths.

[0091] The fermentation liquid supply path 91 is a path for supplying the supply liquid S from the tank 40 to the membrane separation section 10 during operation, and is connected to the outlet 40 b of the tank 40 and the fermentation liquid inlet 13 a of the membrane separation section 10 .

[0092] The non-permeated fluid discharge path 92 is a path for discharging the non-permeated fluid S2 from the membrane separation section 10 during operation, and is connected to the supply space outlet 13b of the membrane separation section 10. For example, a pump for controlling the flow rate of the non-permeated fluid S2 may be arranged in the non-permeated fluid discharge path 92. A pump may not be arranged in the non-permeated fluid discharge path 92.

[0093] The non-permeated fluid discharge path 92 may be configured to be connected to the inlet 40a of the tank 40, and to deliver the non-permeated fluid S2 to the tank 40 during operation. That is, during operation, the non-permeated fluid S2 may be mixed with the supply liquid S in the tank 40 and circulate in the fermentation liquid supply path 91 and the non-permeated fluid discharge path 92. When the non-permeated fluid S2 is delivered to the tank 40, the supply liquid S and the non-permeated fluid S2 are mixed in the tank 40, and the content of the organic compound C in the supply liquid S is reduced. When the tank 40 is a fermentation tank, by reducing the content of the organic compound C in the supply liquid S, it is possible to suppress the stop of fermentation by microorganisms, thereby enabling continuous production of fermented products.

[0094] The permeated fluid discharge path 93 is a path for discharging the permeated fluid S1 from the membrane separation section 10 during operation, and is connected to the permeated space outlet 14b of the membrane separation section 10 and the permeated fluid inlet 20a of the condensation section 20. The condensed fluid discharge path 94 is a path for discharging the condensed fluid S3 from the condensation section 20 during operation, and is connected to the condensed fluid outlet 20b of the condensation section 20.

[0095] The membrane separation system 100 may further include a recovery unit 50. The recovery unit 50 recovers the condensed fluid S3 delivered from the condensation unit 20, and may, for example, store the condensed fluid S3. The recovery unit 50 is, for example, a tank for storing the condensed fluid S3. In this case, a condensed fluid discharge path 94 is connected to the inlet 50a of the recovery unit 50.

[0096] The membrane separation system 100 further includes a discharge path 95 as a path for the fluid.

[0097] The exhaust path 95 is connected to the exhaust outlet 20c of the condensing unit 20. The decompression unit 30 is disposed on the exhaust path 95. A pressure regulating valve 35 may be disposed between the condensing unit 20 and the decompression unit 30.

[0098] The membrane separation system 100 may further include a control unit 60 for controlling the various components of the membrane separation system 100. The control unit 60 is, for example, a DSP (Digital Signal Processor) including an A / D conversion circuit, an input / output circuit, an operation circuit, a storage device, etc. A program for properly operating the membrane separation system 100 is stored in the control unit 60. For example, the control unit 60 controls the operation of the decompression unit 30, thereby being able to adjust the pressure P in the permeation space of the membrane separation unit 10 to a certain value. 10 For example, the control unit 60 can adjust the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 by controlling the operation of the pressure reducing unit 30. 10 Adjust to meet the above range (Ec 20 ≤Pc 10 ≤Ec 10 ).

[0099] Unless otherwise specified, each path of the membrane separation system 100 is constituted by, for example, a pipe made of metal or resin.

[0100] Next, the membrane separation unit 10 included in the membrane separation system 100 of the present embodiment will be described in further detail.

[0101] [Membrane separation section]

[0102] Figure 2 1 is a schematic cross-sectional view showing an example of the membrane separation unit 10. Figure 2 As shown, the membrane separation unit 10 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 a supply liquid S is supplied. The second chamber 14 functions as a permeation space to which a permeated fluid S1 is supplied. The permeated fluid S1 is obtained by the supply liquid S permeating through the pervaporation membrane 11.

[0103] The pervaporation membrane 11 is disposed inside the container 12. The pervaporation membrane 11 partitions the inside of the container 12 into a first chamber 13 and a second chamber 14. The pervaporation membrane 11 extends from one of a pair of wall surfaces of the container 12 to the other.

[0104] The first chamber 13 has a supply space inlet 13a and a supply space outlet 13b. The second chamber 14 has a permeation space outlet 14b. The supply space inlet 13a is an opening for supplying the supply liquid S to the supply space (the first chamber 13). The permeation space outlet 14b is an opening for discharging the permeated fluid S1 from the permeation space (the second chamber 14). The supply space outlet 13b is an opening for discharging the supply liquid S (non-permeated fluid S2) that has not permeated the permeation vaporization membrane 11 from the supply space (the first chamber 13). The supply space inlet 13a, the supply space outlet 13b, and the permeation space outlet 14b are each formed, for example, on the wall surface of the container 12.

[0105] The membrane separation section 10 is suitable for a flow-through (continuous) membrane separation method. However, the membrane separation section 10 can also be used for a batch-type membrane separation method.

[0106] (Pervaporation membrane)

[0107] As described above, pervaporation membrane 11 is typically a membrane (separation membrane) that preferentially permeates organic compound C contained in feed liquid S. Pervaporation membrane 11 generates permeated fluid S1 of gas containing organic compound C by, for example, pervaporation.

[0108] like Figure 3 As shown, the pervaporation membrane 11 includes, for example, a separation functional layer 1 and a porous support 2 supporting the separation functional layer 1. The pervaporation membrane 11 may further include a protective layer (not shown) for protecting the separation functional layer 1. The separation functional layer 1 is, for example, directly in contact with the porous support 2. For example, the main surface 11a of the pervaporation membrane 11 on the separation functional layer side is exposed to the first chamber 13, and the main surface 11b of the porous support side is exposed to the second chamber 14.

[0109] (Separation Functional Layer)

[0110] Typically, the separation functional layer 1 is a layer that allows the organic compound C contained in the supply liquid S to preferentially pass through. The separation functional layer 1, for example, includes a hydrophobic material. In this specification, "hydrophobic material" refers to, for example, a material whose static contact angle of water exceeds 90° when a 10 μL drop of water (temperature 25° C.) is dropped on the surface of a test piece composed of the material. It should be noted that the static contact angle of water can be measured using a commercially available contact angle meter.

[0111] As a hydrophobic material, for example, compounds having a siloxane bond (Si-O-Si bond), olefin polymers, oils, fluorine compounds, etc. can be cited. The separation functional layer 1 preferably contains a compound having a siloxane bond as a hydrophobic material. The compound having a siloxane bond is typically an organosilicon polymer. The organosilicon polymer can be solid or liquid at 25°C. As a specific example of an organosilicon polymer, polydimethylsiloxane (PDMS) and the like can be cited. As a specific example of an olefin polymer, polyethylene, polypropylene, etc. can be cited. As an oil, for example, hydrocarbon oils such as liquid paraffin can be cited. As a fluorine compound, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), etc. can be cited. The hydrophobic material can be used alone or in combination of two or more.

[0112] The separation functional layer 1 may contain a hydrophobic material as a main component, or may be substantially composed of only a hydrophobic material. The "main component" refers to the component that is contained in the largest amount by weight in the separation functional layer 1 .

[0113] The separation function layer 1 may include: a matrix including a hydrophobic material, and fillers dispersed in the matrix. The fillers are embedded in the matrix. In the matrix, all fillers may be separated from each other or partially aggregated.

[0114] The filler includes, for example, inorganic materials such as zeolite, silica, and bentonite. The zeolite contained in the filler is preferably a high-silicon zeolite having a high ratio of silica to alumina. High-silicon zeolite is suitable for separating the supply liquid S due to its excellent hydrolysis resistance. As high-silicon zeolite, HSZ (registered trademark) manufactured by Tosoh Corporation, HiSiv (registered trademark) manufactured by United Showa Corporation, USKY manufactured by United Showa Corporation, and Zeoal (registered trademark) manufactured by Nakamura Superhard Co., Ltd. can be used.

[0115] 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, metal ions and organic ligands. Examples of metal ions include Zn ions. Organic ligands include, for example, aromatic rings. Examples of aromatic rings contained in organic ligands include imidazole rings. Examples of organic ligands include 2-methylimidazole. Specific examples of metal-organic frameworks include ZIF-8.

[0116] The shape of the filler is, for example, particulate. In this specification, "particulate" includes spherical, ellipsoidal, scaly and fibrous. The average particle size of the filler is not particularly limited, for example, it is less than 50 μm, preferably less than 20 μm, and more preferably less than 10 μm. 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, observe the cross section of the separation functional layer 1 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 regarded as the particle size (diameter of the particle) of the specific filler. The particle sizes of any number (at least 50) of fillers are calculated separately, and the average value of the calculated values ​​is regarded as the average particle size of the filler.

[0117] The content of the filler 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 content of the filler in the separation functional layer 1 is not particularly limited, and is, for example, 70 wt%. The content of the matrix in the separation functional layer 1 is not particularly limited, and is, for example, 30 wt% to 90 wt%.

[0118] 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 1.0 μm or more, 10 μm or more, or 30 μm or more.

[0119] The separation functional layer 1 may have a microporous structure with an average pore diameter of less than 0.01 μm, or may be a dense layer with no pores on the surface.

[0120] (Porous Support)

[0121] Examples of the porous support 2 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; a permeable (porous) polymer comprising at least one selected from polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyetheretherketone, polyacrylonitrile, polyimide, and polyphenylene ether; a metal foam having open or closed cells; a polymer foam having open or closed cells; silicon dioxide; porous glass; a mesh, and the like. The porous support 2 may be a combination of two or more of these.

[0122] The porous support 2 has an average pore size of, for example, 0.01 to 0.4 μm. The thickness of the porous support 2 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 2 is, for example, 300 μm or less, and preferably 200 μm or less.

[0123] (Protective layer)

[0124] The protective layer, for example, covers the surface of the separation functional layer 1. The material of the protective layer is not particularly limited, and for example, a silicone resin can be cited. The material of the protective layer can also be the same as the material of the matrix of the separation functional layer 1. The thickness of the protective layer is not particularly limited, and for example, it is 0.5 μm or more, preferably 1 μm or more, more preferably 5 μm or more, and further 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.

[0125] (Method for manufacturing pervaporation membrane)

[0126] The permeation vaporization membrane 11 can be made, for example, by forming a separation functional layer 1 on a porous support 2. In detail, first, a coating liquid containing a material for the separation functional layer 1 is prepared. The coating liquid may contain a filler and a dispersant for dispersing the filler in the coating liquid. In the case where 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 applying the coating liquid on the porous support 2. The separation functional layer 1 is formed by drying the coating film.

[0127] <Embodiment of the method for operating the membrane separation system>

[0128] The operating method of the membrane separation system 100 includes: a step of separating a feed liquid S containing a volatile organic compound C and a gas G into a permeated fluid S1 and a non-permeated fluid S2 by a permeation vaporization membrane of a membrane separation unit 10 (step 1); and a step of condensing the organic compound C contained in the permeated fluid S1 by a condensation unit 20 (step 2). Step 1 includes: lowering the pressure P in the permeation space of the membrane separation unit 10 to 10 The operating conditions of the decompression section 30 are controlled so as to be greater than the minimum value of the pressure that can be achieved in the permeation space of the membrane separation section 10 during the rated operation of the decompression section 30 .

[0129] As described above, when the supply liquid S is a fermentation liquid, the supply liquid S contains a volatile organic compound C and a microorganism that produces the organic compound C. The supply liquid S contains water in addition to the organic compound C, the microorganism, and the gas G. The supply liquid S is typically an aqueous solution containing the organic compound C, the microorganism, and the gas G.

[0130] The organic compound C contained in the supply liquid S is not particularly limited as long as it is volatile. In this specification, "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). It should be noted that the organic compound C is a substance that, when the concentration in the aqueous solution is high, produces an aqueous phase containing water as the main component and an organic phase having a higher content of the organic compound C than the aqueous phase.

[0131] 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 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 may have a functional group containing an oxygen atom, such as a hydroxyl group, a carbonyl group, an ether group, or an ester group. In the organic compound C, the number of functional groups containing an oxygen atom is typically 1.

[0132] As the organic compound C, for example, alcohol, ketone, ester, etc. can be cited, preferably alcohol. In the case where the organic compound C is an alcohol, the organic compound C is easily miscible with water, and the environment in the system is not easy to deviate. The alcohol can be an alkyl alcohol consisting only of an alkyl group and a hydroxyl group, or an aromatic alcohol containing an aromatic group and a hydroxyl group. The alkyl alcohol can be any of a straight chain, a branched chain, and a ring. As the alkyl alcohol, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, isobutanol, tert-butanol, n-pentanol, etc. can be cited, preferably n-butanol. n-Butanol is a compound that generates two phases (aqueous phase and organic phase) in an aqueous solution when the content rate in the aqueous solution is about 8wt% or more. Therefore, in the case where the organic compound C is n-butanol, for example, by adjusting the content rate of the organic compound C in the permeable fluid S1 to about 8wt% or more, an aqueous phase and an organic phase can be generated in the condensed fluid S3. In this case, by separating the aqueous phase and the organic phase, the condensed fluid S3 can be easily purified. As an aromatic alcohol, for example, phenol can be cited.

[0133] The ketone may be a dialkyl ketone consisting only of an alkyl group and a carbonyl group. Examples of the dialkyl ketone include methyl ethyl ketone (MEK) and acetone.

[0134] The ester may be a fatty acid alkyl ester consisting only of an alkyl group and an ester group. Examples of the fatty acid alkyl ester include ethyl acetate and the like.

[0135] It should be noted that the organic compound C is not limited to the above compounds and may be an aromatic hydrocarbon such as benzene, toluene, or xylene.

[0136] The supply liquid S may contain one organic compound C, or may contain two or more organic compounds C. The content of the organic compound C in the supply liquid S may be, for example, 50 wt% or less, or 30 wt% or less, 10 wt% or less, 5 wt% or less, 2 wt% or less, or even 1 wt% or less. The lower limit of the content of the organic compound C is not particularly limited, and may be, for example, 0.01 wt%.

[0137] The organic compound C may be a fermentation product produced by fermenting a carbon source by a microorganism. The organic compound C is preferably an alcohol (bioalcohol) produced by a microorganism.

[0138] The supply liquid S may contain other components such as a carbon source, a nitrogen source, and inorganic ions in addition to water, an organic compound C, microorganisms, and a gas G. Examples of the carbon source include polysaccharides such as starch and monosaccharides such as glucose.

[0139] Regarding the specific implementation method of step 1, Figure 2 In step 1, first, supply liquid S is supplied to first chamber 13 of membrane separation section 10 through supply space inlet 13a. Thus, one surface (for example, main surface 11a) of pervaporation membrane 11 can be brought into contact with supply liquid S.

[0140] Next, in a state where one surface of the pervaporation membrane 11 contacts the supply liquid S, the space adjacent to the other surface of the pervaporation membrane 11 (for example, the main surface 11b) is depressurized. Specifically, the pressure in the second chamber 14 is depressurized through the permeation space outlet 14b. The pressure in the second chamber 14 can be depressurized by the depressurizing unit 30. The pressure in the second chamber 14 is, for example, 50 kPa or less, and may be 20 kPa or less, 10 kPa or less, 5 kPa or less, 3 kPa or less, or further may be 2 kPa or less.

[0141] By reducing the pressure in the second chamber 14, a permeate fluid S1 having a high content of organic compound C can be obtained on the other side of the permeation vaporization membrane 11. In other words, the permeate fluid S1 is supplied to the second chamber 14. In the second chamber 14, the permeate fluid S1 is typically a gas. The permeate fluid S1 is discharged to the outside of the membrane separation unit 10 through the permeation space outlet 14b. The permeate fluid S1 passes through the permeate fluid discharge path 93 and the permeate fluid inlet 20a and is supplied to the condensation unit 20.

[0142] On the other hand, the content of the organic compound C in the supply liquid S gradually decreases from the supply space inlet 13a of the first chamber 13 toward the supply space outlet 13b. The supply liquid S (non-permeable fluid S2) treated by the first chamber 13 is discharged to the outside of the membrane separation unit 10 through the supply space outlet 13b. The non-permeable fluid S2 is typically a liquid. The non-permeable fluid S2 passes through the non-permeable fluid discharge path 92 and passes through the inlet 40a to be supplied to the tank 40.

[0143] In step 1, the organic compound C contained in the feed liquid S can be preferentially permeated through the pervaporation membrane 11 of the membrane separation section 10. Therefore, the permeated fluid S1 obtained by the operation of the membrane separation section 10 has a higher content of the organic compound C than the feed liquid S supplied to the membrane separation section 10. The ratio of the content (wt%) of the organic compound C in the permeated fluid S1 to the content (wt%) of the organic compound C in the feed liquid S is not particularly limited.

[0144] According to step 1, for example, it is possible to produce the permeated fluid S1 having a high content of the organic compound C. In other words, according to step 1, the organic compound C can be obtained as the permeated fluid S1.

[0145] Step 1 includes: setting the pressure P in the permeation space of the membrane separation unit 10 to 10 The operating conditions of the decompression section 30 are controlled so as to be greater than the minimum value of the pressure that can be achieved in the permeation space of the membrane separation section 10 during the rated operation of the decompression section 30. As a result, since the organic compound C can be condensed in the condensation section 20 while reducing the exhaust volume of the decompression section 30, the reduction in the condensation efficiency in the condensation section 20 can be suppressed. As a result, the recovery efficiency of the organic compound C is improved.

[0146] In step 1, the pressure P in the permeation space of the membrane separation section 10 may be lowered by performing intermittent operation or low-speed operation of the pressure reducing section 30. 10 Controlled within the range of 0.2~20.0kPa.

[0147] In step 1, the partial pressure Pc of the organic compound C in the permeation space of the membrane separation section 10 may be lowered by performing intermittent operation or low-speed operation of the pressure reducing section 30. 10 Adjust to meet the above range (Ec 20 ≤Pc 10 ≤Ec 10 ). Below, refer to Figures 4 to 7 An example of controlling the intermittent operation and the low-speed operation of the pressure reducing section 30 according to the partial pressure Pc1 of the organic compound C in the permeation space of the membrane separation section 10 will be described.

[0148] (Intermittent operation control)

[0149] Figure 4 1 is a flowchart showing control of the intermittent operation of the pressure reducing unit 30 .

[0150] First, the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 is determined. 10 Is it lower than the saturated vapor pressure Ec of the organic compound C contained in the permeated fluid S1 at the cooling temperature of the condensation unit 20? 20 (Step ST1). In one specific example, the saturated vapor pressure Ec 20 is 0.2 kPa. However, the saturated vapor pressure Ec 20 For example, when the rated operation of the pressure reducing unit 30 is continuously performed, the partial pressure Pc 10 Decreases, below the saturated vapor pressure Ec 20 .

[0151] Repeat the process of step ST1 until the partial pressure Pc 10 Lower than saturated vapor pressure Ec 20 When the partial pressure Pc 10 Lower than saturated vapor pressure Ec 20 When the pressure reducing unit 30 is stopped, the pressure Pc is reduced. 10 rise.

[0152] Next, the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 is determined. 10 Whether the saturated vapor pressure Ec of the organic compound C contained in the feed liquid S at the operating temperature of the membrane separation unit 10 is exceeded 10 (Step ST3). In one specific example, the saturated vapor pressure Ec 10 is 20.0 kPa. However, the saturated vapor pressure Ec 10 For example, if time passes while the operation of the decompression unit 30 is stopped, the partial pressure Pc 10 Rising, exceeding the saturated vapor pressure Ec 10 .

[0153] Repeat the process of step ST3 until the partial pressure Pc 10 Exceeding the saturated vapor pressure Ec 10 When the partial pressure Pc 10 Exceeding the saturated vapor pressure Ec 10 When the pressure reducing unit 30 is started, the partial pressure Pc is increased. 10 reduce.

[0154] The intermittent operation of the decompression unit 30 may also be controlled by the control unit 60. In this case, the control unit 60 executes the intermittent operation at a predetermined cycle (repetition cycle). Figure 4The steps of the flowchart.

[0155] Figure 5 is a timing chart showing an example of intermittent operation. Figure 5 In the figure, the vertical axis represents the partial pressure Pc 10 , the horizontal axis represents time. Figure 5 As shown in the figure, intermittent operation can also be composed of a 5-minute stop of rated operation and a 1-minute rated operation. 20 ≤Pc 10 ≤Ec 10 , there is no particular limitation on the cycle (repetitive cycle) of the intermittent operation in the decompression section 30.

[0156] (Low speed operation control)

[0157] Reference Figure 6 The control of the low-speed operation of the pressure reducing unit 30 will be described in detail. Figure 6 1 is a flowchart showing control of the low-speed operation of the pressure reducing unit 30 .

[0158] First, the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 is determined. 10 Is it lower than the saturated vapor pressure Ec of the organic compound C contained in the permeated fluid S1 at the cooling temperature of the condensation unit 20? 20 (Step STP1). In one specific example, the saturated vapor pressure Ec 20 is 0.2 kPa. However, the saturated vapor pressure Ec 20 For example, when the rated operation of the pressure reducing unit 30 is continuously performed, the partial pressure Pc 10 Decreases, below the saturated vapor pressure Ec 20 .

[0159] Repeat the process of step STP1 until the partial pressure Pc 10 Lower than saturated vapor pressure Ec 20 When the partial pressure Pc 10 Lower than saturated vapor pressure Ec 20 When the pressure reducing unit 30 is operated at an output lower than the maximum output (STP2), the pressure reducing unit 30 is operated at a low speed. By operating the pressure reducing unit 30 at an output lower than the maximum output, the partial pressure Pc 10 rise.

[0160] Next, the partial pressure Pc of the organic compound C in the permeation space of the membrane separation unit 10 is determined. 10 Whether the saturated vapor pressure Ec of the organic compound C contained in the feed liquid S at the operating temperature of the membrane separation unit 10 is exceeded 10 (STP3). In one specific example, the saturated vapor pressure Ec 10is 20.0 kPa. However, the saturated vapor pressure Ec 10 For example, if the pressure reducing unit 30 is continuously operated at an output lower than the maximum output, the partial pressure Pc 10 Rising, exceeding the saturated vapor pressure Ec 10 .

[0161] Repeat the process of step STP3 until the partial pressure Pc 10 Exceeding the saturated vapor pressure Ec 10 At pressure P 10 Exceeding the saturated vapor pressure Ec 10 In the case of , the pressure reducing unit 30 is operated at the maximum output (STP4). That is, the rated operation of the pressure reducing unit 30 is performed. By operating the pressure reducing unit 30 at the maximum output, the partial pressure Pc 10 reduce.

[0162] The control of the low speed operation of the pressure reducing unit 30 may also be performed by the control unit 60. In this case, the control unit 60 executes the low speed operation at a predetermined cycle (repetition cycle). Figure 6 The steps of the flowchart.

[0163] The control unit 60 may control the inverter provided in the decompression unit 30 to make the operating speed of the decompression unit 30 variable, thereby performing low-speed operation. By performing the low-speed operation, the exhaust volume of the decompression unit 30 can be reduced.

[0164] The operation method of the membrane separation system 100 further includes condensing the organic compound C contained in the gaseous permeated fluid S1 by the condensation unit 20 (step 3). According to step 3, the gaseous permeated fluid S1 is liquefied to obtain the condensed fluid S3. The condensed fluid S3 is a liquid fluid containing the organic compound C.

[0165] <Embodiment of the method for producing an organic compound>

[0166] The method for producing an organic compound of the present embodiment is a method for producing an organic compound using a membrane separation section 10, a condensation section 20, and a decompression section 30. The condensation section 20 is disposed between the membrane separation section 10 and the decompression section 30. The method for producing an organic compound of the present embodiment includes: a step of separating a supply liquid S containing a volatile organic compound C and a gas G into a permeable fluid S1 and a non-permeable fluid S2 by a permeation vaporization membrane of the membrane separation section 10; a step of condensing the organic compound C contained in the permeable fluid S1 by the condensation section 20; and a step of recovering the organic compound C. The above separation includes: lowering the pressure P in the permeation space of the membrane separation section 10 to 10 The operating conditions of the decompression section 30 are controlled so as to be greater than the minimum value of the pressure that can be achieved in the permeation space of the membrane separation section 10 during the rated operation of the decompression section 30 .

[0167] In the method for producing an organic compound of the present embodiment, the organic compound C may be an alcohol. According to the method for producing an organic compound of the present embodiment, the alcohol can be efficiently separated from the supply liquid S containing the volatile alcohol.

[0168] [Modification of membrane separation section]

[0169] The membrane separation unit 10 may be a spiral membrane element, a hollow fiber membrane element, a coil-type membrane element in which a plurality of pervaporation membranes are stacked, a plate-and-frame membrane element, or the like. Figure 7 FIG. 1 is a schematic diagram showing an expanded stereogram of a spiral membrane element. The membrane separation unit 10 may also be as follows: Figure 7 The spiral membrane element shown. Figure 7 The membrane separation section 10 (membrane element) includes a central tube 16 and a membrane leaf 17 having a pervaporation membrane 11 and wound around the central tube 16 .

[0170] The center tube 16 has a cylindrical shape. A through hole 16h is formed on the surface of the center tube 16 for allowing the permeable fluid S1 to flow into the center tube 16. The number of through holes 16h is not particularly limited, and may be one or more than two. Examples of the material of the center 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 center tube 16 is, for example, in the range of 20 to 100 mm.

[0171] The membrane separation section 10 has a plurality of membrane leaves 17. Each membrane leaf 17 includes a pervaporation membrane 11 and a permeation side flow path material 19. For example, the membrane leaf 17 has two pervaporation membranes 11. The two pervaporation membranes 11 overlap each other and are sealed on three sides in a bag-like structure. The permeation side flow path material 19 is arranged between the two pervaporation membranes 11 so as to be located inside the bag-like structure. The permeation side flow path material 19 ensures a space (permeation space) as a flow path for the permeating fluid S1 between the two pervaporation membranes 11. In this way, the permeation side flow path material 19 is used in combination with the pervaporation membrane 11. The number of membrane leaves 17 is not particularly limited, and is, for example, 2 to 30.

[0172] The membrane separation section 10 further includes a supply side flow path material 18. The supply side flow path material 18 is located outside the bag-like structure and is stacked on the membrane leaf 17. Specifically, a plurality of supply side flow path materials 18 and a plurality of membrane leaves 17 are alternately stacked. The supply side flow path material 18 ensures a space (supply space) as a flow path for the supply liquid S between the membrane leaves 17.

[0173] As the supply side flow path material 18 and the permeate side flow path material 19, for example, a net, woven fabric or knitted fabric made of a resin obtained from polyethylene, polypropylene, polyethylene terephthalate (PET), polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.

[0174] The outer circumference of the membrane element is formed by a shell (not shown), which is made of a material that is impermeable to fluid. The shell can be made of FRP (fiber reinforced plastic). The membrane element can be accommodated in a shell (not shown).

[0175] Figure 7 The membrane separation section 10 (membrane element) can be operated, for example, by the following method. First, a supply liquid S is supplied to one end of the wound membrane leaf 17. The internal space of the central tube 16 is depressurized. The depressurization can be performed by the depressurization section 30. As a result, the permeated fluid S1 of the permeation vaporization membrane 11 that has permeated the membrane leaf 17 moves to the inside of the central tube 16. The permeated fluid S1 is discharged to the outside through the central tube 16. The supply liquid S (non-permeated fluid S2) processed by the membrane separation section 10 is discharged to the outside from the other end of the wound membrane leaf 17.

[0176] <Modification of membrane separation system>

[0177] The membrane separation system 100 of the present embodiment may include a plurality of membrane separation sections 10, and the plurality of membrane separation sections 10 may be connected in series or in parallel. In the present specification, "a plurality of membrane separation sections 10 are connected in series" means that a plurality of membrane separation sections 10 are connected in series in such a manner that the supply liquid S (non-permeable fluid S2 when the membrane separation system is in operation) discharged from the supply space of the membrane separation section 10 of the front section is supplied to the supply space of the membrane separation section 10 of the rear section. "A plurality of membrane separation sections 10 are connected in parallel" means that a plurality of membrane separation sections 10 are connected in parallel in such a manner that the supply liquid S transported from the tank 40 is supplied to the supply space of each of the plurality of membrane separation sections 10. The number of membrane separation sections 10 in the membrane separation system 100 is not particularly limited, and is, for example, 2 to 5. The membrane separation system 100 of the present embodiment may also be a structure in which a plurality of units having a plurality of membrane separation sections 10 directly connected are provided, and each unit is connected in parallel. For example, the membrane separation system 100 may also include two units having three membrane separation sections 10 directly connected, and the two units are connected in parallel.

[0178] The descriptions of the above-mentioned embodiments are applicable to each other as long as they are not technically contradictory. The above-mentioned embodiments and modifications are combined with each other as long as they are not technically contradictory.

[0179] Example

[0180] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0181] [Fabrication of Pervaporation Membrane]

[0182] First, a permeation vaporization membrane is prepared by the following method. 1.650 kg (solid content concentration 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 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 are mixed to prepare a coating liquid. Next, a coating film (thickness 500 μm) is obtained by coating the coating liquid on a porous support body (RS-50 manufactured by Nitto Denko Corporation) with a thickness of 150 μm. The coating film is heated at 90°C for 4 minutes to dry it, thereby preparing a separation functional layer with a thickness of 50 μm. In the separation functional layer, the weight ratio of silicone resin to high silica zeolite is 50:50. Thus, a permeation vaporization membrane is obtained.

[0183] (Reference Example 1)

[0184] Using the manufactured pervaporation membrane, Figure 1 The membrane separation system 100 shown in FIG. 1 is a membrane separation system 100. Specifically, the membrane separation system 100 uses the above-mentioned pervaporation membrane as the pervaporation membrane 11 provided in the membrane separation section 10. As the membrane separation section 10, two Figure 7 The spiral membrane elements shown are connected in series and used. The membrane area of ​​the membrane element is 25m 2 / pcs. A vacuum pump was used as the decompression unit 30. 2.7 wt% isopropyl alcohol (IPA) was used as the model supply liquid S. The flow rate of the fermentation liquid supply path 91 was set to 1000 kg / h. In Reference Example 1, the pressure P in the permeation space of the membrane separation unit 10 was set to 10 The operating conditions of the pressure reducing unit 30 are controlled so as to be maintained at 1.1 kPa. The liquid level H of the condensed fluid S3 stored in the recovery unit 50 is 50 The permeation rate calculated by the change of the liquid level H is 1.87 kg / h. 50 is the liquid level height of the recovery part 50. The IPA concentration in the condensed fluid S3 stored in the recovery part 50 is 29.8 wt / %. Fig. 9 The liquid level H of the recovery unit 50 in Reference Example 1 is shown in FIG. 50 (mm) and the pressure P in the permeation space of the membrane separation section 10 10(kPa) vs. time.

[0185] (Example 1)

[0186] In Example 1, the pressure P in the permeation space of the membrane separation section 10 is lowered by performing intermittent operation in which the operation of the pressure reducing section 30 is stopped and started alternately. 10 Adjust within the range of 1.1 to 3 kPa. 10 When the pressure drops below 1.1 kPa, the rated operation of the pressure reducing unit 30 is stopped. 10 When the pressure is higher than 3 kPa, the rated operation of the pressure reducing unit 30 is started. Figure 1 The membrane separation system 100 shown in FIG. 1 is a membrane separation system 100 shown in FIG. 1 . The liquid level H of the condensed fluid S3 stored in the recovery section 50 is 50 The permeation flow rate calculated from the change in (mm) was 1.89 kg / h. The IPA concentration in the condensate fluid S3 stored in the recovery unit 50 was 28.7 wt / %. Fig.10 The liquid level H of the recovery unit 50 during operation of the first embodiment is shown. 50 (mm) and the pressure P in the permeation space of the membrane separation section 10 10 (kPa) and time. It should be noted that Fig.10 Only one cycle of intermittent operation is shown. In Example 1, the Fig.10 The cycle shown.

[0187] The power consumption (kWh) required for the operation of Reference Example 1 and Example 1 was measured. The results are shown in Table 1. The saturated vapor pressure (kPa) of the model supply liquid S of Reference Example 1 and Example 1 shown in Table 1 was calculated using the process modeling software Symmetry manufactured by Schlumberger.

[0188] [Table 1]

[0189]

[0190] (Reference Example 2)

[0191] 1.9 wt % IPA was used as the model supply liquid S. Except for this, the operation was carried out under the same conditions as in Reference Example 1. Figure 1 The membrane separation system 100 shown in FIG. 1 is a membrane separation system 100 shown in FIG. 1 . The liquid level H of the condensed fluid S3 stored in the recovery section 50 is 50 The permeation flow rate calculated from the change in (mm) was 1.95 kg / h. The IPA concentration in the condensate fluid S3 stored in the recovery unit 50 was 23.5 wt / %.

[0192] (Example 2)

[0193] In Example 2, by performing intermittent operation in which the operation of the pressure reducing unit 30 is alternately stopped and started, the pressure P in the permeation space of the membrane separation unit 10 is 10 The pressure is adjusted within the range of 1.1 kPa to 5 kPa. 10 When the pressure drops below 1.1 kPa, the rated operation of the pressure reducing unit 30 is stopped. 10 When the pressure is higher than 5 kPa, the rated operation of the pressure reducing unit 30 is started. Figure 1 The membrane separation system 100 shown in FIG. 50 The permeation flow rate calculated from the change in (mm) was 1.75 kg / h. The IPA concentration in the condensate fluid S3 stored in the recovery unit 50 was 24 wt / %.

[0194] (Example 3)

[0195] In Example 3, by performing intermittent operation in which the operation of the pressure reducing unit 30 is alternately stopped and started, the pressure P in the permeation space of the membrane separation unit 10 is 10 The pressure is adjusted within the range of 1.1 kPa to 8 kPa. 10 When the pressure drops below 1.1 kPa, the rated operation of the pressure reducing unit 30 is stopped. 10 When the pressure is higher than 8 kPa, the rated operation of the pressure reducing unit 30 is started. Figure 1 The membrane separation system 100 shown in FIG. 1 is a membrane separation system 100 shown in FIG. 1 . The liquid level H of the condensed fluid S3 stored in the recovery section 50 is 50 The permeation flow rate calculated from the change in (mm) was 1.09 kg / h. The IPA concentration in the condensate fluid S3 stored in the recovery unit 50 was 23 wt / %.

[0196] The power consumption (kWh) required for the operation of Reference Example 2, Examples 2 and 3 was measured. The results are shown in Table 2. It should be noted that the saturated vapor pressure (kPa) of the model supply liquid S of Reference Example 2, Examples 2 and 3 shown in Table 2 was calculated using the process modeling software Symmetry manufactured by Schlumberger.

[0197] [Table 2]

[0198]

[0199] Fig.11 The pressure P in the permeation space of the membrane separation section 10 during operation of Example 3 is shown. 10 (kPa) and the liquid level H of the recovery unit 50 50 (mm) and time.

[0200] Fig.12 The pressure P in the permeation space of the membrane separation section 10 during operation of Example 2 is shown in FIG. 10 (kPa) and the power consumption W of the decompression unit 30 (vacuum pump) 30 (kW) vs. time.

[0201] Fig.13 The pressure P in the permeation space of the membrane separation section 10 during operation of Example 2 is shown in FIG. 10 (kPa) and the cumulative power consumption of the pressure reducing unit 30 (vacuum pump) Wh 30 (kWh) vs. time.

[0202] Comparison of the results of Reference Example 1 and Example 1 shown in Table 1 and comparison of the results of Reference Example 2 and Examples 2 and 3 shown in Table 2 show that intermittent operation of the decompression unit 30 can reduce power consumption.

[0203] As shown in Table 2, when the pressure P in the permeation space during intermittent operation is 10 In Example 3, in which the range of the vapor pressure is expanded to 8.3 kPa, which is the saturated vapor pressure, the permeation flow rate decreases. Fig.11 As shown, although permeation occurs before the saturated vapor pressure is reached, the permeation amount gradually decreases thereafter.

[0204] like Fig.12 As shown in FIG. 1 , the decompression unit 30 (vacuum pump) consumes a large amount of power instantaneously when starting. Fig.12 As shown in FIG. 1 , the rated operation time of the decompression unit 30 (vacuum pump) in the intermittent operation of Example 2 is about 1 minute. Fig.13 As shown, the cumulative power consumption Wh of the decompression unit 30 (vacuum pump) is 30 (kWh) has almost no impact.

[0205] As can be seen from the above, from the viewpoint of power consumption, it is advantageous for the decompression unit 30 to perform intermittent operation in which the operation is stopped and started alternately and repeatedly.

[0206] Industrial Applicability

[0207] The membrane separation system of the present embodiment is suitable for efficiently recovering organic compounds.

Claims

1. A membrane separation system comprising a membrane separation section, a condensation section and a pressure reduction section, The condensation section is arranged between the membrane separation section and the pressure reducing section. The membrane separation section includes a pervaporation membrane, and a supply space and a permeation space separated by the pervaporation membrane, wherein the pervaporation membrane separates a supply liquid containing a volatile organic compound and a gas into a permeated fluid and a non-permeated fluid. The condensation unit condenses the organic compound contained in the permeated fluid. The decompression unit decompresses the permeation space of the membrane separation unit. During operation, the operating conditions of the decompression section are controlled so that the pressure in the permeation space of the membrane separation section becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section during rated operation of the decompression section.

2. The membrane separation system according to claim 1, wherein: During operation, the operating conditions of the pressure reducing section are controlled so that the pressure in the permeation space of the membrane separation section is within a range of 0.2 to 20.0 kPa.

3. The membrane separation system according to claim 1, wherein: In the condensation section, the organic compound is condensed, thereby reducing the partial pressure of the organic compound in the permeated fluid.

4. The membrane separation system according to claim 1, wherein: The decompression unit performs an intermittent operation in which the operation stop and the operation start of the decompression unit are alternately repeated, or performs a low-speed operation in which the decompression unit is operated at an output lower than a maximum output.

5. The membrane separation system according to claim 4, wherein: By causing the decompression section to perform the intermittent operation or the low-speed operation, the pressure in the permeation space of the membrane separation section is adjusted to a range of 0.2 to 20.0 kPa.

6. The membrane separation system according to claim 5, wherein: The intermittent operation includes: stopping the rated operation of the decompression section when the pressure in the permeation space of the membrane separation section is lower than 0.2 kPa; and starting the rated operation of the decompression section when the pressure in the permeation space of the membrane separation section is higher than 20.0 kPa. The low-speed operation includes: operating the decompression section at an output less than a maximum output when the pressure in the permeation space of the membrane separation section is lower than 0.2 kPa; and operating the decompression section at a maximum output when the pressure in the permeation space of the membrane separation section is higher than 20.0 kPa.

7. The membrane separation system according to claim 1, wherein: A pressure regulating valve for regulating the pressure in the permeation space is further provided between the condensation section and the decompression section.

8. A method for operating a membrane separation system, the membrane separation system comprising a membrane separation section, a condensation section and a decompression section, the condensation section being arranged between the membrane separation section and the decompression section, wherein: The membrane separation section includes a pervaporation membrane, and a supply space and a permeation space separated by the pervaporation membrane. The operation method comprises: separating a feed liquid containing a volatile organic compound and a gas into a permeated fluid and a non-permeated fluid by the pervaporation membrane of the membrane separation section; and condensing the organic compound contained in the permeated fluid by the condensation unit, The separation includes controlling the operating conditions of the decompression section so that the pressure in the permeation space of the membrane separation section becomes greater than the minimum value of the pressure that can be reached in the permeation space of the membrane separation section during rated operation of the decompression section.

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