Co2 separation membrane, co2 separation element, and method for producing co2 separation membrane

Abstract

A nonwoven fabric base material 100 is gas permeable. A protective film 102 is provided on the nonwoven fabric base material 100, and includes first pores that are gas permeable and suppress the penetration of a CO2 separation solution. A CO2 separation gel layer 104 is provided on the protective film 102, and is formed by drying the CO2 separation solution. A porous cover material 106 is provided on the CO2 separation gel layer 104, and is gas permeable and suppresses the passage of the CO2 separation gel layer. The pore diameter of second pores is larger than the pore diameter of the first pores.

Description

CO2 separation membrane, CO2 separation element, and method for manufacturing CO2 separation membrane

[0001] The present disclosure provides a method for converting CO ２ CO ２ Separation membrane, CO ２ Separation element, CO ２ The present invention relates to a method for producing a separation membrane.

[0002] CO ２ By applying a separation material to the substrate, ２ The separation element is constructed. ２ A porous substrate having permeability is used (see, for example, Patent Document 1).

[0003] Special Publication No. 11-509251

[0004] Using nonwoven fabric as a porous substrate, ２ When separation material is applied, CO ２ The separation material penetrates into the nonwoven fabric, making it impossible to form a layer with a uniform thickness, resulting in the desired CO ２ Permeability and selectivity cannot be obtained.

[0005] The present disclosure has been made to solve the above problems, and provides a CO ２ In the separation membrane, CO ２ The object is to provide a technology for suppressing the penetration of separation materials and forming a separation membrane layer with a uniform thickness.

[0006] In order to solve the above problems, a CO ２ The separation membrane is made of a nonwoven fabric substrate having gas permeability and a CO ２ a protective film including first pores having permeation suppression properties of a separation solution; ２ CO formed by drying the separation solution ２ A separation gel layer and CO ２ It is installed on the separation gel layer and has gas permeability and CO ２ and a porous cover material including second pores having a property of inhibiting passage of the separation gel layer, the pore diameter of the second pores being larger than the pore diameter of the first pores.

[0007] Another aspect of the present disclosure is a CO２ This method involves forming a gas-permeable, CO 2 -containing membrane on at least one surface of a gas-permeable nonwoven fabric substrate. ２ a step of placing a protective membrane including first pores having a permeation suppressing property of a separation solution; ２ A coating step of coating a separation solution, and ２ The separated solution is dried to obtain the CO ２ The method includes a drying step of forming a gel body of the separation solution, and a cover material bonding step of bonding a porous cover material on the gel body, the second pores having second pores that are permeable to gas and inhibit the passage of the gel body, and have a pore diameter larger than that of the first pores.

[0008] According to the present disclosure, a CO ２ In the separation membrane, CO ２ This suppresses the penetration of the separation material and allows the formation of a separation membrane layer with a uniform thickness.

[0009] FIG. 1 shows a CO ２ 2(a)-(b) are schematic diagrams showing an example of the installation of a separation system. ２ 3 is a diagram showing an outline of a separation element. ２ 4 is a perspective view showing a laminated structure used as a separation element. ２ 5 is a cross-sectional view showing a schematic structure of a separation membrane. ２ 1 is a flowchart showing the procedure for producing a separation membrane. ２ Separation material retention and membrane performance (CO ２ Permeance, CO ２ / N ２ 7(a)-(b) are tables showing the evaluation results of the selectivity of different CO ２ FIG. 2 is a cross-sectional view schematically showing the structure of a separation membrane.

[0010] Hereinafter, embodiments will be described with reference to the drawings. Note that the following embodiments are examples that embody the present disclosure and do not limit the technical scope of the present disclosure. Furthermore, each drawing described in the embodiments is a schematic drawing, and the ratios of the sizes and thicknesses of the components in each drawing do not necessarily reflect the actual dimensional ratios.

[0011] Embodiments of the present disclosure will be described with reference to the accompanying drawings. ２ 1 is a schematic diagram showing an example of installation of a separation system 1. In a building 2 such as a house, CO ２ Separation system 1 is installed. ２ The separation system 1 separates a target gas (e.g., CO ２ It is a device that removes CO ２ The separation system 1 includes a housing 10, a CO ２ It includes a separation element 20, an inside air fan 31, an inside air filter 37, an outside air fan 41, an outside air filter 47, a first temperature control unit 4a, a second temperature control unit 4b collectively referred to as the temperature control unit 4, a control unit 5, an outside air temperature detection unit 7, and an inside air temperature detection unit 8.

[0012] The housing 10 is ２ The housing 10 is an outer frame of the separation system 1. An internal air port 33, an air intake port 35, an external air port 43, and an exhaust port 45 are arranged on the outer periphery of the housing 10. The internal air port 33 is used to introduce air 39a into the CO ２ The indoor air inlet 33 is an intake port that draws air into the separation system 1. The indoor air inlet 33 is connected to an indoor air inlet 51 provided in the building 2 by an indoor air introduction duct 52. The indoor air inlet 51 is an opening provided in the target space of the building 2, and is used to collect air 39a (indoor air) in the target space as RA and CO ２ The inside air intake duct 52 is an opening through which air is introduced into the separation system 1. The inside air intake duct 52 is a duct that introduces inside air into the housing 10. One end of the inside air intake duct 52 is connected to the indoor air inlet 51, and RA from indoors flows into the inside air intake duct 52. The other end of the inside air intake duct 52 is connected to the inside air port 33, and RA is circulated inside the housing 10. In other words, air from a target space indoors is introduced into the inside air intake duct 52 as inside air and circulates therethrough.

[0013] The air inlet 35 is used to supply air 39b to CO２ The air supply port 35 is an outlet for discharging air from the separation system 1. The air supply port 35 is connected to an indoor air outlet 53 provided in the building 2 by an indoor air outlet duct 54. The indoor air outlet 53 is an opening provided in the building 2, and ２ The separation element 20 ２ The inside air outlet duct 54 is an opening that supplies the air 39b with reduced concentration to the target space as SA. The inside air outlet duct 54 is a duct that supplies the inside air from the housing 10 to the target space. One end of the inside air outlet duct 54 is connected to the air intake port 35, and the CO ２ The separation element 20 ２ The air 39b with reduced concentration flows into the duct. The other end of the inside air outlet duct 54 is connected to the indoor outlet 53, and the air 39b in the duct is supplied to the target space as SA. In other words, the inside air outlet duct 54 returns the air 39b to the target space.

[0014] The outside air port 43 is for introducing air 49a into the CO ２ The outdoor air inlet 43 is an intake port that draws in the air into the separation system 1. The outdoor air inlet 43 is connected to an outdoor air inlet 55 provided in the building 2 by an outdoor air introduction duct 56. The outdoor air inlet 55 is an opening provided in the building 2, and is used to introduce outdoor air 49a (outside air) as OA and CO ２ The outside air intake duct 56 is an opening through which outside air is introduced into the separation system 1. The outside air intake duct 56 is a duct that introduces outside air into the housing 10. One end of the outside air intake duct 56 is connected to the outdoor air inlet 55, and OA from outside flows into the outside air intake duct 56. The other end of the outside air intake duct 56 is connected to the outdoor air port 43, and OA is circulated inside the housing 10. In other words, outdoor air is introduced into the outside air intake duct 56 as outside air and circulates therethrough.

[0015] The exhaust port 45 exhausts the air 49b to the CO ２ The exhaust port 45 is an outlet that discharges CO 2 from the separation system 1 to the outdoors. The exhaust port 45 is connected to an outdoor outlet 57 provided in the building 2 by an outdoor air outlet duct 58. The outdoor outlet 57 is an opening provided in the building 2, and ２ The separation element 20 ２The outside air outlet duct 58 is an opening for discharging the air 49b with increased concentration to the outside as EA. The outside air outlet duct 58 is a duct for supplying outside air from the housing 10 to the outside. One end of the outside air outlet duct 58 is connected to the exhaust port 45, and the CO ２ The separation element 20 ２ The air 49b with increased concentration flows into the duct. The other end of the outside air outlet duct 58 is connected to the outdoor outlet 57, and the air 49b in the duct is discharged to the outdoors as EA. In other words, the outside air outlet duct 58 releases the air 49b to the outdoors.

[0016] Hereinafter, air 39a and air 39b may be collectively referred to as "indoor air," and air 49a and air 49b may be collectively referred to as "outdoor air." Furthermore, indoor air introduction duct 52 and indoor air outlet duct 54 may be collectively referred to as an "indoor air duct," and outdoor air introduction duct 56 and outdoor air outlet duct 58 may be collectively referred to as an "outdoor air duct."

[0017] Here, the diameter of each duct will be described. In this embodiment, the duct diameter of the outside air introduction duct 56 and the outside air outlet duct 58 through which the outside air is ventilated is smaller than the duct diameter of the inside air introduction duct 52 and the inside air outlet duct 54 through which the inside air is ventilated. This is because ２ This is because the flow rate of outside air circulating through the separation system 1 is made smaller than the flow rate of inside air, thereby suppressing pressure loss on the outside air side. Also, although heat exchange generally occurs due to the temperature difference between the outside air and the inside air, suppressing the flow rate of outside air makes it possible to suppress heat loss due to heat exchange.

[0018] Inside the housing 10, ２ A separation element 20, an inside air fan 31 (circulation fan), an inside air filter 37, an outside air fan 41, and an outside air filter 47 are attached. ２ The separation element 20 separates CO from the inside air that has flowed through the inside air inlet duct 52. ２ and CO ２ This is to introduce CO from the inside air to the outside air. ２ It can be said that the material is a member that selectively transmits CO ２ The separation element 20 will be described in detail later.

[0019] The inside air fan 31 is a blower that draws inside air from the target space through the inside air port 33 and discharges it into the target space through the air supply port 35. The inside air drawn from the target space through the inside air port 33 by driving the inside air fan 31 passes through the inside air filter 37, the CO ２ The air passes through the separation element 20 and the internal air fan 31 and is discharged into the target space through the air intake port 9. The volume of air sent out by the internal air fan 31 is preferably greater than the volume of air sent out by the external air fan 41. The internal air filter 37 removes dirt, dust, etc. from the internal air that has flowed into the housing 10 and filters the purified air to remove CO ２ This is a filter that supplies air to the separation element 20, and is, for example, a HEPA (High Efficiency Particulate Air) filter.

[0020] The outdoor air fan 41 is a blower that draws in outdoor air from the outside through the outdoor air port 43 and discharges it to the outside through the exhaust port 45. The outdoor air drawn in through the outdoor air port 43 by driving the outdoor air fan 41 passes through the outdoor air filter 47, the CO ２ The air passes through the separation element 20 and the outside air fan 41, and is then discharged to the outdoors via the exhaust port 45. The volume of air sent out by the outside air fan 41 is preferably smaller than the volume of air sent out by the inside air fan 31. The outside air fan 41 is located downstream of the outside air filter 47 and is also located downstream of the CO ２ The outside air fan 41 is provided upstream of the separation element 20. By arranging the outside air fan 41 in this manner, the outside air can be heated by the heat generated by the operation of the outside air fan 41, and when the outside air is at a lower temperature than the inside air, heat loss due to heat exchange between the outside air and the inside air is reduced. ２ The outside air filter 47 may be provided downstream of the separation element 20. The outside air filter 47 removes dirt, dust, and the like from the outside air that has flowed into the housing 10, and passes the purified air through the CO ２ This is a filter supplied to the separation element 20, such as a HEPA filter.

[0021] where CO ２ CO by the separation element 20 ２ Figure 2(a)-(b) shows the outline of the separation of CO ２ 2(a) shows an outline of the separation element 20. ２1 is a cross-sectional view showing a simplified configuration of a separation element 20. A gas to be treated air passage 16 through which inside air (gas to be treated) flows from left to right and a sweep gas passage 17 through which outside air (sweep gas) flows from left to right are arranged one above the other in the vertical direction. In addition, a CO ２ The separation membrane 22 is disposed. The gas to be treated introduced into the gas to be treated air passage 16 contains CO ２ 18 and N ２ 19 is mixed in. In reality, the air contains O ２ etc. are also included, but for the sake of clarity, ２ The gas to be treated flows through the gas passage 16. ２ When flowing along the separation membrane 22, CO ２ The separation membrane 22 separates CO ２ 18 is selectively permeated, and CO ２ 18 is discharged into the sweep gas in the sweep gas duct 17. As a result, the CO ２ The concentration of 18 decreases, and the CO ２ The concentration of 18 increases.

[0022] Figure 2(b) shows a CO ２ CO for efficient separation of 18 ２ The structure of the separation element 20 is shown. ２ The separation element 20 includes a first treatment target gas passage 16a to a third treatment target gas passage 16c, which are collectively referred to as the treatment target gas passage 16; a first sweep gas passage 17a to a third sweep gas passage 17c, which are collectively referred to as the sweep gas passage 17; ２ The first CO separation membrane 22 ２ The fifth CO ２The number of the treatment target gas passages 16 and the sweep gas passages 17 is not limited to three. From top to bottom, the first sweep gas passage 17a, the first treatment target gas passage 16a, the second sweep gas passage 17b, the second treatment target gas passage 16b, the third sweep gas passage 17c, and the third treatment target gas passage 16c are arranged in this order. In addition, a first CO ２ A separation membrane 22a is disposed between the first treatment target gas passage 16a and the second sweep gas passage 17b. ２ A separation membrane 22b is disposed between the second sweep gas passage 17b and the second treatment target gas passage 16b. ２ A fourth CO 2 separation membrane 22c is disposed between the second treatment target gas passage 16b and the third sweep gas passage 17c. ２ A separation membrane 22d is disposed between the third sweep gas passage 17c and the third treatment target gas passage 16c. ２ 2(a), the CO 2 of the gas to be treated flowing through the gas to be treated air passage 16 is ２ 18 is CO ２ The gas is selectively permeated through the separation membrane 22 and discharged into the sweep gas in the sweep gas passage 17 .

[0023] FIG. 3 shows the CO ２ 1 is a perspective view showing a laminated structure 6 used as a separation element 20. In the following description, the laminated structure 6 is described as having a vertical stacking direction, but this does not necessarily indicate the direction in an actual use state. The laminated structure 6 is made up of a rectangular frame 14 and a CO ２ A rectangular CO ２ The stacked structure 6 is a structure in which the separation element pieces 21 are alternately stacked in the up-down direction, and the target gas passages 16 and the sweep gas passages 17 intersecting the target gas passages 16 are alternately formed one layer at a time. ２ While fitting the separation element piece 21 at the end of the frame 14 from both the top and bottom sides, ２ It is constructed by repeatedly stacking separation element pieces 21 and frames 14. ２When the separation element pieces 21 are fitted into the frames 14 from both the top and bottom, the frames 14 are stacked in a staggered manner, with the frames 14 orthogonal to one another. With this configuration, as shown in Fig. 2(b), gas to be treated air passages 16 through which the gas to be treated flows and sweep gas air passages 17 through which the sweep gas flows are alternately formed. By circulating the gas to be treated taken in from the target space through the gas to be treated air passages 16 and circulating the sweep gas through the sweep gas air passages 17, the gas to be treated and the sweep gas flow alternately and orthogonally through the respective air passages. In this way, the laminated structure 6 is configured such that the gas to be treated and the sweep gas flow in a staggered manner, with the CO ２ The CO flows alternately and perpendicularly in the stacking direction of the separation element pieces 21. ２ The separation element 20 is ２ CO of the separation element piece 21 ２ CO is transferred from the gas to be treated to the sweep gas side through the separation membrane 22. ２ is selectively transparent.

[0024] CO ２ The separation element piece 21 is ２ When the target gas and the sweep gas flow across the separation element piece 21, CO is introduced from the target gas to the sweep gas. ２ CO for permeating ２ It is a sheet-like member made of a separation membrane 22. ２ The separation element piece 21 is bent by being fitted by the frame 14, so it is preferable to use a material that has the flexibility and strength to withstand this bending. ２ The separation membrane 22 ２ The partial pressure difference is CO ２ The driving force for permeation is high concentration CO ２ Low concentration CO from gas ２ Gas and CO ２ In order to allow permeation of CO in the gas to be treated and the sweep gas, ２ The concentration relationship is as follows: target gas > sweep gas. Return to Figure 1.

[0025] The first temperature adjustment unit 4a ２The first temperature adjustment unit 4a is a device that adjusts the temperature of the outside air by heating or cooling the outside air that flows into the separation element 20. The first temperature adjustment unit 4a is also called an outside air temperature adjustment unit. The first temperature adjustment unit 4a is, for example, a heater / Peltier element attached to the outside air introduction duct 56. The first temperature adjustment unit 4a also adjusts the temperature of the outside air by heating or cooling the outside air that flows into the separation element 20. ２ Alternatively, an outside air fan 41 may be provided between the separation element 20 and the outside air duct. In this case, the outside air is heated using the exhaust heat of the outside air fan 41, so that the exhaust heat of the outside air fan 41 is effectively utilized. ２ The second temperature adjustment unit 4b is a device that adjusts the temperature of the inside air by heating or cooling the inside air that flows into the separation element 20. The second temperature adjustment unit 4b is also called an inside air temperature adjustment unit. The second temperature adjustment unit 4b is, for example, a heater / Peltier element attached to the inside air introduction duct 52.

[0026] The outside air temperature detection unit 7 is attached to the outside air introduction duct 56 and detects the temperature of the outside air flowing through the outside air introduction duct 56. Known technology may be used for temperature detection, and therefore a description thereof will be omitted here. Information relating to the outside air temperature detected by the outside air temperature detection unit 7 is transmitted to the control unit 5. The inside air temperature detection unit 8 detects the temperature of the inside air flowing through the inside air introduction duct 52. Information relating to the inside air temperature detected by the inside air temperature detection unit 8 is transmitted to the control unit 5.

[0027] The control unit 5 receives the temperature of the outside air detected by the outside air temperature detection unit 7 and the temperature of the inside air detected by the inside air temperature detection unit 8. The control unit 5 controls the temperature adjustment unit 4 based on the temperature of the outside air and the temperature of the inside air. Specifically, the control unit 5 ２ The temperature of the internal air introduced into the separation element 20 and the CO ２ The first temperature adjusting unit 4a is controlled so that the temperature difference between the temperature of the outside air introduced into the separation element 20 is smaller than the temperature difference between the temperature of the air in the target space and the temperature of the outdoor air. ２Heat loss due to heat exchange in the separation element 20 is reduced. For example, if the outside air temperature is 5°C and the inside air temperature is 25°C, and the temperature is not controlled, the air supplied to the target space by the inside air fan 31 will drop to about 15°C through heat exchange, requiring extra air conditioning energy to maintain the inside air at 25°C. On the other hand, if the temperature is controlled to keep the outside air at 25°C, no heat exchange occurs, and therefore no extra air conditioning energy is required. Furthermore, if temperature control is performed using the exhaust heat of the outside air fan 41, the energy required for temperature control will also be zero. The control unit 5 may control the second temperature adjustment unit 4b.

[0028] The subject of the device, system, or method disclosed herein includes a computer. The computer executes a program to realize the functions of the subject of the device, system, or method disclosed herein. The computer includes, as its main hardware configuration, a processor that operates according to the program. The type of processor is not important as long as it can realize the functions by executing the program. The processor is composed of one or more electronic circuits, including a semiconductor integrated circuit (IC) or an LSI (Large Scale Integration). The multiple electronic circuits may be integrated into a single chip or may be provided on multiple chips. The multiple chips may be integrated into a single device or may be provided on multiple devices. The program is recorded on a non-transitory recording medium, such as a computer-readable ROM, optical disk, or hard disk drive. The program may be pre-stored on the recording medium or may be supplied to the recording medium via a wide area communication network, including the Internet.

[0029] (CO ２ Separation membrane 22) Hereinafter, CO ２ The separation membrane 22 will now be described in more detail. ２ 1 is a cross-sectional view showing a schematic structure of a separation membrane 22. ２ The separation membrane 22 is made up of a nonwoven fabric substrate 100, a protective film 102 provided on the nonwoven fabric substrate 100, and a CO ２ Separation gel layer 104, CO ２The separator includes a porous cover material 106 disposed on the separation gel layer 104. ２ The protective film 102 and the porous cover material 106 provided on the nonwoven fabric substrate 100 used in the separation membrane 22 were ２ Focusing on the viscosity of the separation gel material when it is applied and after drying, the pore diameter and thickness of the protective film 102 and the porous cover material 106 are designed and selected based on the following logic according to the viscosity, thereby achieving a CO ２ The separation membrane 22 can be formed, and the desired CO ２ Permeability and CO ２ / N ２ It has been found that it is possible to obtain high selectivity.

[0030] The Lucas-Washburn equation (1) is commonly used to describe the penetration of liquids. Here, l represents the penetration depth, r represents the capillary radius, γ represents the surface tension of the liquid, θ represents the contact angle, η represents the viscosity, and t represents the time.

[0031] In this embodiment, formula (1) is transformed into formula (2), and the coating liquid, i.e., the CO ２ A suitable substrate capable of supporting a separation solution or gel is defined as one that satisfies formula (2). Here, l represents the thickness (m) of the substrate, r represents the pore radius (m) of the substrate, γ represents the surface tension (N / m) of the coating liquid or gel, θ represents the contact angle (rad) between the coating liquid or gel and the substrate, η represents the viscosity (mPa s) of the coating liquid or gel, and t represents the time (s) until the liquid loses its fluidity. In this embodiment, the time t is set to 30 seconds, which is the time it is generally considered that the applied liquid loses its fluidity.

[0032] The nonwoven fabric substrate 100 is gas permeable. Preferably, the nonwoven fabric substrate 100 has sufficient mechanical strength. Examples of usable fiber materials include polyester (PET: Polyethylene Terephthalate), polyethylene (PE: Polyethylene), polypropylene (PP: Polypropylene), polyphenylene sulfide (PPS: Polyphenylenesulfide), vinylon, rayon, nylon, and fluorine-based fibers.

[0033] The protective film 102 has gas permeability and CO ２ The protective film 102 includes pores (hereinafter also referred to as "first pores") that have the ability to suppress the permeation of the separation solution. The protective film 102 includes a polymer having a porous structure. The porous cover material 106 has gas permeability and CO ２ The protective film 102 and the porous cover material 106 have a common feature of being gas permeable. The protective film 102 and the porous cover material 106 use substrates with pore diameters and thicknesses that satisfy formula (2). Here, the CO ２ Separation solution or CO after drying ２ The required pore diameter and thickness of the first pore and the second pore differ depending on the viscosity of the separation gel.

[0034] Surface tension is CO ２ Depending on the composition of the separation material, the contact angle varies depending on the substrate material and CO ２ The composition of the separation material is determined by two factors: ２In the case of a separation material composition, the contact angle is larger when the substrate is hydrophobic than when it is hydrophilic, which can suppress the penetration of the coating liquid or gel into the substrate. For example, when a coating liquid with a viscosity η = 20,000 mPa·s and a surface tension γ = 0.072 N / m is applied to a polyester protective film, the contact angle θ = 81°, and if the pore radius is 0.5 μm, the substrate thickness l must be greater than 65 μm. When the same coating liquid is applied to a polyacrylonitrile protective film, the contact angle θ = 21°, and if the pore radius is 0.5 μm, the substrate thickness l must be greater than 159 μm, indicating that a thicker film is required. Similarly, when using a protective film of the same thickness, the upper limit of the pore radius of a hydrophilic film is smaller than that of a hydrophobic film. Porous cover materials also show a similar tendency depending on the material.

[0035] Coating CO ２ The smaller the viscosity η of the separation solution, the thicker the protective film must be, or the smaller the pore size, or both. For example, when a coating liquid with a viscosity η = 300,000 mPa s and a surface tension γ = 0.072 N / m is applied to a polyacrylonitrile protective film, if the contact angle θ = 21 ° and the pore radius is 0.5 μm, the substrate thickness l must be greater than 41 μm. On the other hand, when a lower viscosity coating liquid with a viscosity η = 20,000 mPa s and a surface tension γ = 0.072 N / m is similarly applied to a polyacrylonitrile protective film, if the contact angle θ = 21 ° and the pore radius is 0.5 μm, the substrate thickness l must be greater than 159 μm, indicating that a thicker film is required. Similarly, when a protective film of the same thickness is used, the upper limit of the pore radius of the film is smaller when a coating liquid with a lower viscosity is used than when a coating liquid with a higher viscosity is used. The porous covering material also exhibits a similar tendency depending on the viscosity of the gel.

[0036] The protective film 102 can be made of resin materials such as PET, PE, PP, PPS, polyacrylonitrile (PAN), polyethersulfone, etc. Note that melt-blown nonwoven fabrics or nonwoven fabrics using nanofibers, which have a finer fiber diameter than typical nonwoven fabrics, have a small pore radius and are denser, and can therefore be used as a protective film if formula (2) is satisfied. The nonwoven fabric used as the protective film 102 can be made of, for example, PET, PE, PP, cellulose, etc.

[0037] The porous cover material 106 can be made of, for example, nonwoven fabrics such as PET, PE, PP, PPS, vinylon, rayon, nylon, or fluorine-based fibers, or resin materials such as PET, PE, PP, PPS, PAN, polyethersulfone, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, or polyimide. Generally, nonwoven fabrics have higher breathability than resin materials and are less likely to resist gas permeation, while resin materials can suppress gel penetration because the pore size is easier to control than nonwoven fabrics.

[0038] CO after coating ２ By drying and gelling the separation solution, the viscosity of the gel state increases significantly compared to the solution state. Therefore, the restrictions on the pore size and film thickness of the porous cover material 106 are relaxed compared to the protective film 102, and a material with higher breathability can be used. In other words, the pore size of the second pores is made larger than the pore size of the first pores. This allows CO ２ CO separation membrane performance degradation is suppressed while the gel surface is protected ２ The separation membrane is ２ It can be used in separation elements.

[0039] CO ２ The separation gel layer 104 is ２ The separation solution is dried and CO is trapped in a gel film of a hydrophilic polymer containing water. ２The hydrophilic polymer may include, for example, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinyl alcohol-polyacrylate copolymer (PVA / PAA copolymer), chitosan, polyvinylamine, polyallylamine, and polyvinylpyrrolidone.

[0040] CO ２ As the carrier, for example, an alkali metal carbonate, an alkali metal bicarbonate, an alkali metal hydroxide, or an amino acid can be used. ２ When dissolved in water, the amino group (NH ２ ) is protonated to NH ３ ＋ As shown in the following (chemical formula 1), carbon dioxide dissociates into a protonated amino group (NH ３ ＋ ) and does not react with the free amino group (NH ２ ) reacts with CO ２ When an amino acid is used as a carrier, a deprotonating agent is added to a solution in which the amino acid is dissolved, and NH ３ ＋ NH ２ The deprotonating agent is a protonated NH ３ ＋ It steals a proton from ２ Any alkali metal hydroxide or carbonate can be used as long as it has strong basicity enough to convert CO (Chemical Formula 1). ２ +RNH ２ +H ２ O → HCO ３ － +RNH ３ ＋

[0041] (Manufacturing method) CO according to this embodiment ２ The method for manufacturing the separation membrane 22 will be described with reference to FIG. ２ 1 is a flowchart showing the manufacturing procedure of the separation membrane 22. First, a hydrophilic polymer and CO ２A coating solution containing a carrier is prepared (S10). ２ The carrier is added and stirred until dissolved, and the hydrophilic polymer is further added to the resulting solution, which is then stirred at room temperature for, for example, 3 days or more to obtain a coating liquid. ２ When an amino acid is used as the carrier, a deprotonating agent is added in the same manner as the amino acid.

[0042] In addition, a protective film 102 is placed on at least one surface of the nonwoven fabric substrate 100 (S12). Step 12 may be performed before step 10. Next, the coating solution (CO ２ The separation solution is applied with an applicator to the surface of the layered porous membrane on which the protective membrane 102 is bonded to the nonwoven fabric substrate 100, facing the protective membrane 102, and spread evenly (S14). The coating thickness of the sample in the example described below is 500 μm. Here, although the coating liquid may penetrate into the pores in the protective membrane 102, by selecting a protective membrane 102 that satisfies formula (2), not all of the coating liquid passes through, and the coating liquid is carried in the pores of the protective membrane 102, on the surface thereof, or both.

[0043] After coating, the nonwoven fabric substrate 100 with the protective film 102 is dried, for example, at 60° C. for about 30 minutes to gel the coating liquid. ２ A separation gel layer 104 is generated (S16). ２ The separated solution is dried and CO ２ A gel body of the separation solution is formed.

[0044] Next, the CO 2 on the surface of the protective film 102 of the nonwoven fabric substrate 100 with the protective film 102 obtained in step 16 was ２ A porous cover material 106 is adhered to the separation gel layer 104 side. As a result, as shown in FIG. 4, a nonwoven fabric substrate 100 / protective film 102 / CO ２ A four-layer structure including a separation gel layer 104 and a porous cover material 106 ２ The separation membrane 22 is fabricated (S18).

[0045] (Experimental Method) The experimental method for evaluating the membrane performance of each sample in the examples and comparative examples described below will be described. ２The separation membrane 22 was placed in a gas permeation cell (membrane area: 9.62 cm ２ The feed gas supply side chamber and the permeation side chamber of the reactor were fixed using two rubber gaskets as sealing materials. ２ 400 ppm CO in gas ２ The mixed feed gas is humidified by bubbling it through deionized water to a relative humidity of 70%. This feed gas is supplied to the feed side chamber at a flow rate of 2000 cc / min, and a sweep gas (He gas) is supplied to the permeation side chamber at a flow rate of 10 cc / min.

[0046] The composition of the gas recovered from the permeate side chamber was quantified by gas chromatography, and the CO ２ and N ２ Permeance (= permeability, one of the performance indicators of permeability) [mol / (m ２ s kPa)] and from the ratio, CO ２ / N ２ The selectivity is calculated. ２ The separation membrane ２ Permeance and CO ２ / N ２ The higher the selectivity, the higher the performance. ２ To carry out the separation, for example, CO ２ Permeance is 2 x 10 －５ mol / (m ２ .s.kPa) or more, CO ２ / N ２ A selectivity of 5,000 or more is preferred.

[0047] Example 1 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution (for example, viscosity 22,620 mPa·s) is obtained (S10 in FIG. 5). ２The separation solution is applied to a thickness of 500 μm by an applicator onto the surface of the PE porous membrane side of a layered porous membrane in which a PET nonwoven fabric (for example, a film thickness of 120 μm and a pore size of 130 μm) as the nonwoven fabric substrate 100 and a polyethylene (PE) porous membrane (for example, a film thickness of 30 μm and a pore size of 3 μm) as the protective membrane 102 are bonded (S14 in FIG. 5).

[0048] The layered porous film after coating was dried at 60°C for about 30 minutes and then CO ２ The separation solution is gelled and CO ２ A gel layer is formed (S16 in FIG. 5). ２ A PET nonwoven fabric (for example, a film thickness of 100 μm and a pore size of 20 μm) is adhered to the separation gel layer 104 side as a porous cover material 106. As a result, a membrane with a four-layer structure of PET nonwoven fabric / PE porous membrane / gel layer / PET nonwoven fabric is produced (S18 in FIG. 5), as shown schematically in FIG.

[0049] Example 2: 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution (for example, viscosity 22,620 mPa·s) is obtained (S10 in FIG. 5). ２ The separation solution is applied to a thickness of 500 μm by an applicator onto the surface of a layered porous membrane on the side of the PAN porous membrane, which is formed by bonding a PET nonwoven fabric (for example, a film thickness of 160 μm and a pore size of 100 μm) as the nonwoven fabric substrate 100 and a polyacrylonitrile (PAN) porous membrane (for example, a film thickness of 40 μm and a pore size of 50 nm) as the protective membrane 102 (S14 in FIG. 5).

[0050] The layered porous film after coating was dried at 60°C for about 30 minutes and then CO ２ The separation solution is gelled to form a gel layer (S16 in FIG. 5). A PET nonwoven fabric (e.g., 100 μm thick, 20 μm pore size) is attached as a porous cover material 106 to the gel layer side of the surface of the layered porous membrane obtained in step 16. As a result, a membrane with a four-layer structure of PET nonwoven fabric / PAN porous membrane / gel layer / PET nonwoven fabric is produced (S18 in FIG. 5), as schematically shown in FIG.

[0051] (Example 3) 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate were added to 43.3 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution (for example, viscosity 320,000 mPa·s) is obtained (S10 in FIG. 5). ２ The separation solution is applied to a thickness of 250 μm by an applicator onto the surface of a layered porous membrane on the side of the PAN porous membrane, which is formed by bonding a PET nonwoven fabric (for example, a film thickness of 70 μm and a pore size of 110 μm) as the nonwoven fabric substrate 100 and a polyacrylonitrile (PAN) porous membrane (for example, a film thickness of 20 μm and a pore size of 50 nm) as the protective membrane 102 (S14 in FIG. 5).

[0052] The layered porous film after coating was dried at 60°C for about 30 minutes and then CO ２ The separation solution is gelled to form a gel layer (S16 in FIG. 5). A PET nonwoven fabric (e.g., 100 μm thick, 20 μm pore size) is attached as a porous cover material 106 to the gel layer side of the surface of the layered porous membrane obtained in step 16. As a result, a membrane with a four-layer structure of PET nonwoven fabric / PAN porous membrane / gel layer / PET nonwoven fabric is produced (S18 in FIG. 5), as shown schematically in FIG. 1.

[0053] (Example 4) 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate were added to 43.3 g of water, and the mixture was stirred at room temperature for 3 days or more, and then CO ２ A separation solution (for example, viscosity 320,000 mPa·s) is obtained (S10 in FIG. 5). ２ The separation solution is applied to a thickness of 500 μm by an applicator onto the surface of the upper PET nonwoven fabric of a layered nonwoven fabric in which a melt-blown PET nonwoven fabric (for example, a film thickness of 50 μm and a pore size of 2 μm) as the protective film 102 and a PET nonwoven fabric (for example, a film thickness of 70 μm and a pore size of 80 μm) as the nonwoven fabric substrate 100 are bonded to the upper and lower surfaces of the melt-blown PET nonwoven fabric (S14 in FIG. 5). ２ Since the penetration of the separation solution is not hindered, CO ２ The separation solution is impregnated into the PET nonwoven fabric up to the interface with the melt-blown PET nonwoven fabric, and penetration is suppressed on the surface of the melt-blown PET nonwoven fabric.

[0054] After coating, the layered nonwoven fabric was dried at 60°C for about 30 minutes and then CO ２ The separation solution is gelled to produce a gel layer (S16 in FIG. 5). A PET nonwoven fabric (e.g., 100 μm thick, 20 μm pore size) is adhered as a porous cover material 106 to the gel layer side of the surface of the layered nonwoven fabric obtained in step 16. As a result, as shown schematically in FIG. 7( a) described below, a membrane with a four-layer structure of PET nonwoven fabric (nonwoven fabric substrate 100) / melt-blown PET nonwoven fabric (gel-impregnated nonwoven fabric 112) / gel layer partially impregnated in the PET nonwoven fabric (gel layer 110 partially impregnated in the nonwoven fabric) / PET nonwoven fabric (porous cover material 106) is produced (S18 in FIG. 5).

[0055] Comparative Example 1: 2.316 g of polyacrylic acid, 3.47 g of glycine, and 3.194 g of potassium carbonate were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution (for example, viscosity 22,620 mPa·s) is obtained (Step 1). ２ The separation solution is applied to one side of a PET nonwoven fabric (for example, a film thickness of 100 μm and a pore size of 50 μm) as a nonwoven fabric substrate with an applicator to a thickness of 500 μm (Step 2). The layered porous membrane after application is dried at 60° C. for about 30 minutes and then cooled with CO ２ The separation solution is gelled to form a gel layer (step 3).

[0056] (Performance Evaluation Results) FIG. 6 shows the CO ２ Separation material retention and membrane performance (CO ２ Permeance, CO ２ / N ２ 1 is a table showing the evaluation results of CO ２ Permeance is 9.0 x 10 －５ mol / (m ２ ・s・kPa), CO ２ / N ２ The selectivity was 17,000. ２ Permeance is 1.0 x 10 －４ mol / (m ２ ・s・kPa), CO ２ / N ２ The selectivity was 19,500. ２Permeance is 1.0 x 10 －４ mol / (m ２ ・s・kPa), CO ２ / N ２ The selectivity was 21,000. ２ Permeance is 9.3 x 10 －５ mol / (m ２ ・s・kPa), CO ２ / N ２ The selectivity was 16,000. In Examples 1 to 4, the CO ２ Permeance and CO ２ / N ２ This selectivity is achieved because a uniform, defect-free membrane can be formed by using an appropriate substrate that satisfies formula (2).

[0057] On the other hand, in Comparative Example 1, CO ２ / N ２ The selectivity was 250, which was significantly reduced compared to Examples 1 to 4. This is because the CO ２ This is because the protective substrate does not satisfy formula (2) with respect to the separation solution, so the membrane is not formed uniformly, and the raw material gas passes through defective parts of the membrane.

[0058] Previous CO ２ The separation membrane 22 is made up of a nonwoven fabric substrate 100, a protective membrane 102, and a CO ２ Although the structure is a four-layer structure including a separation gel layer 104 and a porous cover material 106, the structure is not necessarily limited to this four-layer structure. ２ 1 is a cross-sectional view showing a schematic structure of the separation membrane 22. For example, nonwoven fabrics may be placed on both the upper and lower surfaces of the protective membrane 102. In this case, CO ２ The separation liquid is applied to the nonwoven fabric. ２ Since the penetration of the separation solution is not hindered, CO ２ The separation solution penetrates into the nonwoven fabric up to the interface with the protective film 102, and penetration is suppressed on the surface of the protective film 102. When a porous cover material 106 is adhered to the gel layer side of the surface of this nonwoven fabric, a four-layer structure is formed, including the nonwoven fabric substrate 100, the protective film 102, the gel layer 110 partially impregnated in the nonwoven fabric, and the porous cover material 106, as schematically shown in Figure 7(a).

[0059] The nonwoven fabric is coated with CO ２ If the thickness is sufficiently thicker than the film thickness of the separation solution, the gel layer after drying will not be exposed to the surface, and therefore the porous cover material 106 is not necessary, resulting in a three-layer structure comprising the nonwoven fabric substrate 100, the protective film 102, and the nonwoven fabric 120 fully impregnated with gel, as shown schematically in Figure 7(b). In this case, in order to maintain the gel layer after drying, the nonwoven fabric 120 fully impregnated with gel must satisfy formula (2).

[0060] Furthermore, if the protective film 102 is a nonwoven fabric with a smaller fiber diameter than general nonwoven fabrics, such as a melt-blown nonwoven fabric or a nonwoven fabric using nanofibers, and has a small, dense pore radius, the nonwoven fabric below the protective film 102 is not necessarily required, and a three-layer structure consisting of a nonwoven fabric protective film / gel layer / porous cover material may also be used.

[0061] According to this embodiment, CO ２ a protective film 102 having permeation suppression properties of a separation solution; ２ Between the separation gel layer 104 and the porous cover material 106 having the property of inhibiting the passage of CO ２ CO formed by drying the separation solution ２ Since the separation gel layer 104 is disposed, a layer with a uniform thickness can be formed. ２ The separation gel layer 104 is formed, so that the desired CO ２ The permeability and selectivity can be obtained. ２ a protective film 102 having permeation suppression properties of a separation solution; ２ Between the separation gel layer 104 and the porous cover material 106 having the property of inhibiting the passage of CO ２ CO formed by drying the separation solution ２ Since the separation gel layer 104 is arranged, the CO ２ In the separation membrane, CO ２ The porous cover material 106 contains a nonwoven fabric, which prevents the permeation of the separation material and allows the formation of a separation membrane layer with a uniform thickness. ２ The manufacturing cost of the separation membrane 22 can be reduced.

[0062] The outline of one aspect of the present disclosure is as follows: (Item 1) A nonwoven fabric substrate (100) having gas permeability, and a gas permeable and CO2-permeable membrane provided on the nonwoven fabric substrate (100). ２ a protective film (102) including first pores having permeation suppression properties of a separation solution; ２ CO formed by drying the separation solution ２ a separation gel layer (104); and ２ The separation gel layer (104) is provided on the separation gel layer (104), and the separation gel layer (104) is permeable to gases and the CO ２ and a porous cover material (106) including second pores having a property of inhibiting passage of CO 2 through the separation gel layer (104), wherein the pore diameter of the second pores is larger than the pore diameter of the first pores. ２ Separation membrane (22).

[0063] (Item 2) The CO 2 according to item 1, wherein the protective film (102) contains a polymer having a porous structure. ２ Separation membrane (22).

[0064] (Item 3) The CO2 filter according to item 1 or 2, wherein the porous covering material (106) comprises a nonwoven fabric. ２ Separation membrane (22).

[0065] (Item 4) The CO according to any one of items 1 to 3. ２ CO separation membrane (22) ２ A separation element (20).

[0066] (Item 5) A nonwoven fabric substrate (100) having gas permeability and CO ２ a step of placing a protective film (102) including first pores having permeation suppression properties of a separation solution; ２ a coating step of coating a separation solution; ２ The separated solution is dried to obtain the CO ２A CO2 filtration method comprising: a drying step of forming a gel body of a separation solution; and a cover material bonding step of bonding, on the gel body, a porous cover material (106) including second pores that are permeable to gas and inhibit passage of the gel body, and have a pore diameter larger than that of the first pores. ２ A method for producing a separation membrane (22).

[0067] The present disclosure has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component or each treatment process, and that such modifications are also within the scope of the present disclosure.

[0068] According to the present disclosure, in a CO2 separation membrane using a nonwoven fabric substrate, it is possible to suppress the permeation of CO2 separation material and form a separation membrane layer with a uniform thickness.

[0069] 1 CO ２ Separation system, 2 Building, 4 Temperature control unit, 5 Control unit, 6 Laminated structure, 7 Outdoor air temperature detection unit, 8 Indoor air temperature detection unit, 10 Housing, 14 Frame, 16 Gas to be treated air passage, 17 Sweep gas air passage, 18 CO ２ , 19 N ２ , 20 CO ２ Separation element, 21 CO ２ Separation element piece, 22 CO ２ Separation membrane, 31 indoor air fan, 33 indoor air outlet, 35 air intake port, 37 indoor air filter, 41 outdoor air fan, 43 outdoor air outlet, 45 exhaust port, 47 outdoor air filter, 51 indoor air intake port, 52 indoor air introduction duct, 53 indoor air outlet, 54 indoor air outlet duct, 55 outdoor air intake port, 56 outdoor air introduction duct, 57 outdoor air outlet, 58 outdoor air outlet duct, 100 nonwoven fabric substrate, 102 protective film, 104 CO ２ Separating gel layer, 106 porous cover material, 110 gel layer partially impregnated in nonwoven fabric, 112 gel-impregnated nonwoven fabric, 120 nonwoven fabric completely impregnated with gel, 122 gel layer impregnated in nonwoven fabric.

Claims

1. A nonwoven fabric substrate having gas permeability; and a gas permeability and CO ２ a protective film including first pores that suppress the permeation of a separation solution; ２ CO formed by drying the separation solution ２ a separation gel layer; and ２ The separation gel layer is provided on the separation gel layer, and the gas permeability and the CO ２ and a porous cover material including second pores having a property of inhibiting passage of a separation gel layer, wherein the pore diameter of the second pores is larger than the pore diameter of the first pores. ２ Separation membrane.

2. The CO according to claim 1, wherein the protective film contains a polymer having a porous structure. ２ Separation membrane.

3. The CO according to claim 1 or 2, wherein the porous cover material comprises a nonwoven fabric. ２ Separation membrane.

4. CO according to any one of claims 1 to 3 ２ CO separation membranes ２ Separation element.

5. A gas-permeable, CO 2 -resistant film is provided on at least one surface of the gas-permeable nonwoven fabric substrate. ２ a step of placing a protective film including first pores having a property of suppressing permeation of a separation solution; ２ a coating step of coating a separation solution; ２ The separated solution is dried to obtain the CO ２ A CO2 filtration method comprising: a drying step of forming a gel body of a separation solution; and a cover material bonding step of bonding a porous cover material on the gel body, the second pores having gas permeability and a property of inhibiting passage of the gel body, the second pores having a pore diameter larger than that of the first pores. ２ A method for manufacturing a separation membrane.

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