Spiral membrane element, membrane separation system, and membrane separation method

Abstract

A spiral membrane element 100 is provided with a center tube 21 and a laminate 22 wound around the center tube 21. The laminate 22 includes: a membrane leaf 11 having a separation membrane 12 and a permeable spacer 14; and a supply spacer 13. The thickness of the permeable spacer 14 is 400μm or less, and the ratio of the thickness of the permeable spacer 14 to the thickness of the supply spacer 13 is 0.4 or more. A membrane separation system 200 comprises said spiral membrane element 100. A membrane separation method using said spiral membrane element 100 involves generating a differential pressure between the inside of a supply space and the inside of a permeation space of the spiral membrane element 100.

Description

Spiral membrane element, membrane separation system, and membrane separation method

[0001] The present invention relates to a spiral membrane element, a membrane separation system, and a membrane separation method.

[0002] Membrane separation is a method developed to separate acidic gases, such as carbon dioxide, from gas mixtures. Compared to absorption methods, which separate acidic gases by having an absorbent absorb them, membrane separation can efficiently separate acidic gases while keeping operating costs down.

[0003] For example, spiral membrane elements are used in membrane separation methods. Spiral membrane elements are suitable for increasing the effective membrane area of ​​the separation membrane. Effective membrane area refers to the surface area of ​​the separation membrane that actually contributes to the separation of a supply fluid, such as a gas mixture. A spiral membrane element comprises a central tube and a laminate wound around the central tube. The laminate includes membrane leaves having a separation membrane and permeable spacers, and a supply spacer (see, for example, Patent Document 1).

[0004] Japanese Patent Publication No. 2015-24372

[0005] To improve the performance of the separation membrane in spiral membrane elements, it is necessary to further increase the effective membrane area of ​​the separation membrane. One way to increase the effective membrane area of ​​the separation membrane is to reduce the thickness of the permeation spacer included in the laminate. When the outer diameter of the spiral membrane element is kept constant, reducing the thickness of the permeation spacer increases the number of separation membranes included in the laminate. However, reducing the thickness of the permeation spacer increases the pressure loss of the permeating fluid, which reduces the permeation flow rate. There is a trade-off relationship between the effective membrane area of ​​the separation membrane and the permeation flow rate, and it has been difficult to achieve both by reducing the thickness of the permeation spacer.

[0006] Therefore, the present invention aims to provide a spiral-type membrane element suitable for achieving both an increase in the effective membrane area and an increase in the permeate flow rate of a separation membrane, a membrane separation system equipped with the spiral-type membrane element, and a membrane separation method using the spiral-type membrane element.

[0007] The present invention provides a spiral membrane element comprising a central tube and a laminate wound around the central tube, wherein the laminate includes membrane leaves having a separation membrane and a permeation spacer and a supply spacer, the thickness of the permeation spacer being 400 μm or less, and the ratio of the thickness of the permeation spacer to the thickness of the supply spacer being 0.4 or more.

[0008] In another aspect, the present invention provides a membrane separation system comprising the spiral membrane element of the present invention described above.

[0009] In another aspect, the present invention provides a membrane separation method using the spiral membrane element of the present invention, comprising generating a differential pressure between the supply space and the permeate space of the spiral membrane element.

[0010] According to the present invention, it is possible to provide a spiral-type membrane element suitable for achieving both an increase in the effective membrane area and an increase in the permeate flow rate of a separation membrane, a membrane separation system equipped with the spiral-type membrane element, and a membrane separation method using the spiral-type membrane element.

[0011] This is a schematic exploded perspective view showing a spiral membrane element according to the first embodiment of the present invention. This is a schematic cross-sectional view of the spiral membrane element. This is a schematic cross-sectional view of the separation membrane. This is a diagram illustrating the manufacturing method of the spiral membrane element. This is a diagram illustrating the manufacturing method of the spiral membrane element. This is a diagram illustrating the effective membrane area per separation membrane. This is a schematic cross-sectional view showing an example of a measuring device for measuring pressure loss due to a permeable spacer. This is a schematic configuration diagram showing an example of a membrane separation system according to the second embodiment of the present invention. This is a schematic configuration diagram showing a modified example of the membrane separation system.

[0012] A spiral membrane element according to a first aspect of the present invention comprises a central tube and a laminate wound around the central tube, wherein the laminate includes membrane leaves having a separation membrane and a permeation spacer and a supply spacer, the thickness of the permeation spacer being 400 μm or less, and the ratio of the thickness of the permeation spacer to the thickness of the supply spacer being 0.4 or more.

[0013] In a second aspect of the present invention, for example, in the spiral-type membrane element according to the first aspect, a ratio of a thickness of said permeate spacer to a thickness of said feed spacer is 2.0 or less.

[0014] In a third aspect of the present invention, for example, in the spiral-type membrane element according to the first or second aspect, the thickness of said feed spacer is 1000 μm or less.

[0015] In a fourth aspect of the present invention, for example, in the spiral-type membrane element according to any one of the first to third aspects, a pressure loss generated by passing nitrogen gas through said permeate spacer at a flow rate of 1.0 L / min is 10 kPa / m or less.

[0016] In a fifth aspect of the present invention, for example, in the spiral-type membrane element according to any one of the first to fourth aspects, a pressure loss generated by passing nitrogen gas through said feed spacer at a flow rate of 1.0 L / min is 14 kPa / m or less.

[0017] In a sixth aspect of the present invention, for example, the spiral-type membrane element according to any one of the first to fifth aspects is used for separating acidic gas from a mixed gas containing acidic gas.

[0018] A membrane separation system according to a seventh aspect of the present invention comprises the spiral-type membrane element according to any one of the first to sixth aspects.

[0019] In an eighth aspect of the present invention, for example, the membrane separation system according to the seventh aspect further comprises a pressurizing device that pressurizes the interior of the feed space of said spiral-type membrane element.

[0020] A membrane separation method according to a ninth aspect of the present invention is a membrane separation method using the spiral-type membrane element according to any one of the first to sixth aspects, and comprises generating a differential pressure between the interior of the feed space and the interior of the permeate space of said spiral-type membrane element.

[0021] In the tenth embodiment of the present invention, for example, in the membrane separation method according to the ninth embodiment, generating the differential pressure includes increasing the pressure within the supply space of the spiral membrane element.

[0022] The details of the present invention will be described below, but the following description is not intended to limit the present invention to any particular embodiment.

[0023] (First Embodiment) <Embodiment of Spiral Membrane Element> Figures 1 and 2 are schematic exploded perspective views showing a spiral membrane element according to the first embodiment. The spiral membrane element 100 according to the first embodiment (hereinafter sometimes referred to as membrane element 100) comprises a central tube 21 and a laminate 22. The laminate 22 is wrapped around the central tube 21 and arranged around the central tube 21. A supply fluid channel and a permeable fluid channel are formed inside the laminate 22.

[0024] The supply fluid F0 is supplied into the membrane element 100 from one end face of the laminate 22 and flows through the supply fluid channel parallel to the longitudinal direction of the central pipe 21. In the membrane element 100, the supply fluid F0 is separated to generate a permeable fluid F1 and an impermeable fluid F2. The permeable fluid F1 is guided to the outside through the central pipe 21. The impermeable fluid F2 is discharged to the outside of the membrane element 100 from the other end face of the laminate 22.

[0025] The supply fluid F0 to be processed by the membrane element 100 may be a gas or a liquid. As an example, the supply fluid F0 may be a gas mixture containing acidic gases, particularly a gas mixture containing carbon dioxide and nitrogen.

[0026] As shown in Figure 2, the laminate 22 has a plurality of membrane leaves 11. Each membrane leaf 11 has a separation membrane 12 and a permeable spacer 14. In Figure 2, the permeable spacer 14 is shown by a dashed line. In detail, each membrane leaf 11 has two separation membranes 12. The two separation membranes 12 are overlapped and sealed on three sides to form a bag-like structure. For sealing the two separation membranes 12, for example, an adhesive layer 26 containing an adhesive is used. A permeable spacer 14 is positioned between the two separation membranes 12 so as to be located inside the bag-like structure. The permeable spacer 14 secures a space (permeable space) between the two separation membranes 12 as a permeable fluid channel. In this way, the permeable spacer 14 is used in combination with the separation membranes 12. The number of membrane leaves 11 in the laminate 22 is not particularly limited and can be, for example, 2 to 50.

[0027] The laminate 22 further includes supply spacers 13. In Figure 2, the supply spacers 13 are shown by dashed lines. The supply spacers 13 are located outside the bag-like structure described above and are laminated on the membrane leaves 11. In detail, the laminate 22 has a plurality of supply spacers 13, and in the laminate 22, the plurality of supply spacers 13 and the plurality of membrane leaves 11 are alternately laminated. The supply spacers 13 secure a space (supply space) between the membrane leaves 11 that serves as a supply fluid channel.

[0028] In the membrane element 100 according to this embodiment, the thickness of the permeable spacer 14 is 400 μm or less, and the ratio of the thickness of the permeable spacer 14 to the thickness of the supply spacer 13 is 0.4 or more.

[0029] In the membrane element 100 according to this embodiment, in addition to reducing the thickness of the permeation spacer 14 to the above range, attention is paid to the ratio of the thickness of the permeation spacer 14 to the thickness of the supply spacer 13, and by controlling these to the above range, the decrease in permeation flow rate is suppressed. As a result, the effective membrane area of ​​the separation membrane 12 can be increased while increasing the permeation flow rate. The membrane element 100 is suitable for achieving both an increase in the effective membrane area of ​​the separation membrane 12 and an increase in the permeation flow rate.

[0030] The membrane element 100 can be used in either an operating method that generates a differential pressure by increasing the pressure within the supply space of the membrane element 100 (pressurization method) or an operating method that generates a differential pressure by reducing the pressure within the permeate space of the membrane element 100 (depressurization method). However, the pressurization method tends to increase the permeate flow rate more easily than the depressurization method.

[0031] The ratio of the thickness of the permeation spacer 14 to the thickness of the supply spacer 13 may be 2.0 or less. With a membrane element 100 in which the above thickness ratio is 0.4 or more and 2.0 or less, it is easier to achieve both an increase in the effective membrane area of ​​the separation membrane 12 and an increase in the permeation flow rate.

[0032] The lower limit of the above thickness ratio may be 0.41, 0.42, or even 0.43. The upper limit of the above thickness ratio may be 1.5, 1.0, 0.9, 0.8, or even 0.7.

[0033] The thickness of the permeable spacer 14 may be less than 400 μm. The upper limit of the thickness of the permeable spacer 14 may be 390 μm, 380 μm, or even 370 μm.

[0034] The lower limit of the thickness of the permeable spacer 14 is, for example, 200 μm. The lower limit of the thickness of the permeable spacer 14 may also be 210 μm, 220 μm, or even 230 μm.

[0035] The thickness of the supply spacer 13 may be 1000 μm or less. When the thickness of the supply spacer 13 is 1000 μm or less, it is easier to realize a film element 100 in which the ratio of the above thicknesses is 0.4 or more.

[0036] The upper limit of the thickness of the supply spacer 13 may be 900 μm, 850 μm, 800 μm, 750 μm, 700 μm, 650 μm, 600 μm, or even 550 μm.

[0037] The lower limit of the thickness of the supply spacer 13 is, for example, 200 μm. The lower limit of the thickness of the supply spacer 13 may be 210 μm, 220 μm, or even 230 μm.

[0038] <Method for measuring the thickness of the spacer> The thickness of the supply spacer 13 and the thickness of the permeable spacer 14 can be measured, for example, using a dial gauge (PEACOCK, digital gauge). The thickness of the supply spacer 13 and the thickness of the permeable spacer 14 may be the average of measurements taken at any multiple locations (for example, five locations). If the supply spacer 13 and the permeable spacer 14 have multiple grooves and multiple protrusions on one of their surfaces (for example, see Figure 2 of Patent Document 1), the thickness of the spacer is the distance between the top of the protrusions on the surface of the spacer and the surface.

[0039] As shown in Figures 1 and 2, the shape of the central tube 21 is typically cylindrical, particularly cylindrical. The central tube 21 plays the role of collecting the permeate fluid F1 that has permeated through each separation membrane 12 and guiding it to the outside of the membrane element 100. The surface of the central tube 21 is provided with through holes 21h for allowing the supply fluid F0 to flow into the interior of the central tube 21. The number of through holes 21h is not particularly limited and may be one or two or more. The central tube 21 may have a plurality of through holes 21h provided at predetermined intervals along the direction in which the central tube 21 extends. The number of rows of plurality of through holes 21h provided along the direction in which the central tube 21 extends is not particularly limited and may be one or two or more. The outer diameter of the through holes 21h is, for example, 10 to 100 mm, preferably 12 to 50 mm.

[0040] The membrane element 100 may further include a flow path spacer 15. In Figure 2, the flow path spacer 15 is shown by a dashed line. The flow path spacer 15 is located between the central tube 21 and the laminate 22, and is wrapped around the central tube 21 on the side of the laminate 22 that faces the central tube 21. The flow path spacer 15 secures a space (permeable space) between the laminate 22 and the central tube 21 as a permeable fluid flow path. The flow path spacer 15 is connected to the open end of the membrane leaf 11 described above. As a result, the permeable spacer 14 of the membrane leaf 11 is connected to the flow path spacer 15. The flow path spacer 15 is in contact with the through hole 21h of the central tube 21. As a result, the permeable fluid F1 can flow from the flow path spacer 15 into the interior of the central tube 21 through the through hole 21h.

[0041] The membrane element 100 may further comprise a shell that surrounds the laminate 22. The shell may be made of FRP (fiber-reinforced plastic). End face members may be positioned on both sides of the laminate 22 to protect the end faces of the laminate 22 and to prevent the laminate 22 from stretching telescopically.

[0042] The supply spacer 13, permeation spacer 14, and flow path spacer 15 are not particularly limited. Known spacers such as nets, meshes, wire fabrics, fiber fabrics, nonwoven fabrics, grooved sheets, and corrugated sheets can be used as the supply spacer 13, permeation spacer 14, and flow path spacer 15. Examples of materials for these spacers include resin materials such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyamide, polyphenylene sulfide (PPS), ethylene-chlorotrifluoroethylene copolymer (ECTFE), epoxy resin, and urethane resin; natural polymers; rubber; and metals. Tricot knitted spacers such as single tricot knitted fabric may be used as the supply spacer 13 and permeation spacer 14. Examples of materials for tricot knitted fabrics include resin materials such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyamide, polyphenylene sulfide (PPS), ethylene-chlorotrifluoroethylene copolymer (ECTFE), epoxy resin, and urethane resin; natural polymers; rubber; and metals. The spacers in the tricot knitting may be impregnated with epoxy resin.

[0043] The supply spacer 13, the permeable spacer 14, and the flow path spacer 15 may be the same or different. For example, the supply spacer 13, the permeable spacer 14, and the flow path spacer 15 may all be net spacers. The supply spacer 13 and the permeable spacer 14 may be tricot knit spacers, and the flow path spacer 15 may be a net spacer.

[0044] [Separation Membrane] Figure 3 is a schematic cross-sectional view of the separation membrane 12. As shown in Figure 3, the separation membrane 12 comprises, for example, a separation functional layer 1, a porous support 3 that supports the separation functional layer 1, and an intermediate layer 2 disposed between the separation functional layer 1 and the porous support 3. The intermediate layer 2 is in direct contact with, for example, the separation functional layer 1 and the porous support 3.

[0045] (Separation Functional Layer) The separation functional layer 1 is, for example, a layer that can preferentially permeate acidic gases contained in a gas mixture. The separation functional layer 1 preferably contains a resin. Examples of resins that can be contained in the separation functional layer 1 include polyether block amide resin, polyamide resin, polyether resin, polyimide resin, polyetherimide resin, cellulose acetate resin, silicone resin, and fluororesin. The separation functional layer 1 preferably contains a polyimide resin or a cellulose acetate resin, and more preferably contains a cellulose acetate resin. The separation functional layer 1 preferably consists substantially of a resin. In this specification, "substantially consisting of" means excluding other components that alter the essential characteristics of the material mentioned, for example, that 95 wt% or more, and more precisely 99 wt% or more, is composed of the material.

[0046] The thickness of the separation functional layer 1 is, for example, 50 μm or less, preferably 25 μm or less, and more preferably 15 μm or less. The thickness of the separation functional layer 1 may be 0.05 μm or more, or 0.1 μm or more.

[0047] (Intermediate layer) The intermediate layer 2 may, for example, contain a resin and further contain nanoparticles dispersed in the resin (matrix). The nanoparticles may be spaced apart from each other in the matrix or partially aggregated. The material of the matrix is ​​not particularly limited and includes, for example, silicone resins such as polydimethylsiloxane; fluororesins such as polytetrafluoroethylene; epoxy resins such as polyethylene oxide; polyimide resins; polysulfone resins; polyacetylene resins such as polytrimethylsilylpropyne and polydiphenylacetylene; and polyolefin resins such as polymethylpentene. The matrix preferably contains a silicone resin.

[0048] Nanoparticles may contain inorganic materials or organic materials. Examples of inorganic materials that can be included in nanoparticles include silica, titania, and alumina. It is preferable that the nanoparticles contain silica.

[0049] The thickness of the intermediate layer 2 is not particularly limited, and is, for example, less than 50 μm, preferably 40 μm or less, and more preferably 30 μm or less. The lower limit of the thickness of the intermediate layer 2 is not particularly limited, and is, for example, 1 μm. The intermediate layer 2 is, for example, a layer having a thickness of less than 50 μm.

[0050] (Porous support) The porous support 3 supports the separation functional layer 1 via the intermediate layer 2. Examples of the porous support 3 include nonwoven fabric; porous polytetrafluoroethylene; aromatic polyamide fiber; porous metal; sintered metal; porous ceramic; porous polyester; porous nylon; activated carbon fiber; latex; silicone; silicone rubber; permeable (porous) polymer containing at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyetheretherketone, polyacrylonitrile, polyimide, and polyphenylene oxide; metal foam having open or closed cells; polymer foam having open or closed cells; silica; porous glass; mesh screen, etc. The porous support 3 may be a combination of two or more of these.

[0051] The porous support 3 has an average pore diameter of, for example, 0.01 to 0.4 μm. The thickness of the porous support 3 is not particularly limited, but is, for example, 10 μm or more, preferably 20 μm or more, and more preferably 50 μm or more. The thickness of the porous support 3 is, for example, 300 μm or less, preferably 200 μm or less, and more preferably 150 μm or less.

[0052] [Method for Manufacturing a Spiral-Type Membrane Element] Next, an example of a method for manufacturing the membrane element 100 will be described with reference to Figures 4 and 5. First, as shown in Figure 4, the separation membrane 12 is folded in half so that the separation functional layer 1 of the separation membrane 12 is located on the inside. A supply spacer 13 is placed between the two folded separation membranes 12, and a permeable spacer 14 is placed on top of the separation membrane 12. Next, adhesive 26a is applied to three sides of the outer circumference of the permeable spacer 14. This gives rise to the separation membrane unit 25. At this point, the adhesive 26a is in an uncured state.

[0053] Next, as shown in Figure 5, a central tube 21, a spacer 16, and a plurality of separation membrane units 25 are prepared. The spacer 16 has, for example, a first portion 16a that is directly wrapped around the central tube 21 and a second portion 16b that is stacked with the separation membrane units 25. The first portion 16a of the spacer 16 corresponds to the flow path spacer 15, and the second portion 16b corresponds to the permeation spacer 14. The material, thickness, etc. of the first portion 16a may be the same as or different from that of the second portion 16b. The plurality of separation membrane units 25 are arranged in a stepped manner on the second portion 16b of the spacer 16. The number of the plurality of separation membrane units 25 is not particularly limited, and is, for example, 2 to 30. Note that the uppermost separation membrane unit 25 may not have, for example, a permeation spacer 14.

[0054] Next, the first portion 16a of the spacer 16 is wrapped around the central tube 21. The number of turns of the first portion 16a is not particularly limited, and is, for example, 1 to 15, preferably 2 to 10.

[0055] Next, multiple separation membrane units 25 are wrapped around the central tube 21. At this time, the uppermost separation membrane unit 25 is stacked with the second portion 16b of the spacer 16. After the separation membrane units 25 are wrapped around the central tube 21, the adhesive 26a hardens to form an adhesive layer 26, and a bag-shaped membrane leaf 11 is formed. This gives rise to an assembly including the central tube 21 and the laminate 22.

[0056] As described above, in the membrane element 100, an increase in the effective membrane area of the separation membrane 12 is achieved. The total effective membrane area of the separation membrane 12 in the membrane element 100 is, for example, 21 m 2 or more.

[0057] The lower limit of the total effective membrane area of the separation membrane 12 in the membrane element 100 may be 25 m 2 , 26 m 2 , 27 m 2 , or even 30 m 2 .

[0058] The upper limit of the total effective membrane area of the separation membrane 12 in the membrane element 100 is, for example, 100 m 2 . The upper limit of the total effective membrane area of the separation membrane 12 may be 90 m 2 , 80 m 2 , 70 m 2 , 60 m 2 , 50 m 2 , 45 m 2 , 40 m 2 , or even 35 m 2 .

[0059] <Method for Calculating Effective Membrane Area of Separation Membrane> FIG. 6 is a diagram for explaining the effective membrane area per separation membrane 12 (hereinafter sometimes referred to as effective membrane area A 12 ). As shown in FIG. 6, the length of the separation membrane 12 excluding the adhesive layer 26 is defined as L 12 , and the width of the separation membrane 12 excluding the adhesive layer 26 is defined as W 12 . At this time, the effective membrane area A 12 ) can be obtained by the following formula (1). That is, in the present specification, the effective membrane area A 12 is defined as the surface area of the separation membrane 12 excluding the adhesive layer 26. A 12 (m 2 ) = L 12 × W 12 --- (1)

[0060] In the present embodiment, the value obtained by the following formula (2) is regarded as the total effective membrane area of the separation membrane 12 in the membrane element 100 (hereinafter sometimes referred to as total effective membrane area A). A (m 2 ) = N × A 12... (2) In equation (2), N is the number of membrane leaves 11 included in the laminate 22 such that the outer diameter of the membrane element 100 is within 8 inches (20.32 cm). The number of membrane leaves 11 N is calculated based on the outer diameter of the central tube 21 of the membrane element 100, the thickness of the separation membrane 12, the thickness of the supply spacer 13, and the length of the membrane leaves 11.

[0061] As described above, the membrane element 100 achieves an increase in permeation flow rate. For example, when CO2 is to be separated, the calculated CO2 permeation flow rate F in the membrane element 100 is calculated when the differential pressure Δp between the pressure of the supply fluid F0 and the pressure of the permeation fluid F1 is 800 kPa as a separation condition. 100 For example, 13500 GPU·m 2 That concludes the explanation. In this specification, unless otherwise specified, "pressure" means absolute pressure.

[0062] Calculated value F of CO2 permeation flow rate in the membrane element 100 when the differential pressure Δp is 800 kPa. 100 The lower limit is 13600 GPU·m 2 It's okay to have it.

[0063] Calculated value F of CO2 permeation flow rate in the membrane element 100 when the differential pressure Δp is 800 kPa. 100 The upper limit is, for example, 30,000 GPU·m 2 The calculated value is F. 100 The upper limit is 29,000 GPU·m 2 , 28000GPU・m 2 , 27000GPU・m 2 , 26000GPU・m 2 Furthermore, 25,000 GPU-m 2 That's fine.

[0064] <Method for calculating CO2 permeation flow rate> In this embodiment, the calculated value obtained by the following formula (3) is the CO2 permeation flow rate per membrane leaf 11 (hereinafter referred to as permeation flow rate F). 11 It is sometimes referred to as such. ) It is considered as such. Note that in the following formula, pressure loss due to the supply spacer 13 and the permeable spacer 14 is not considered. F 11(L / min) = R × k × A / N × Δp / 101.33 × t / 273.15 ... (3) In equation (3), R is the CO2 permeation rate (GPU) of the supply fluid F0 passing through the separation membrane 12. Δp is the pressure difference between the pressure of the supply fluid F0 and the pressure of the permeate fluid F1. k is the conversion number for converting the permeation rate R of the supply fluid F0 to SI units, and is 0.045. t is the ambient temperature, which in this embodiment is 35°C. A is the total effective membrane area of ​​the separation membrane 12 in the membrane element 100 determined by equation (2) above, and N is the number of membrane leaves 11 included in the laminate 22 such that the outer diameter of the membrane element 100 is within 8 inches (20.32 cm).

[0065] The calculated CO2 permeation flow rate F in the membrane element 100 as described above. 100 F is the value obtained by the following formula (4). 100 (GPU-m 2 ) = R × (1 - ΔP 14 / Δp) × A ... (4) In equation (4), R is the CO2 permeation rate (GPU) of the supply fluid F0 passing through the separation membrane 12. ΔP 14 Δp is the calculated pressure loss of the permeation spacer 14 in the membrane element 100. Δp is the pressure difference between the pressure of the supply fluid F0 and the pressure of the permeation fluid F1. A is the total effective membrane area of ​​the separation membrane 12 in the membrane element 100, which is determined by the above equation (2).

[0066] Pressure loss ΔP of the permeable spacer 14 in the membrane element 100 14 This is the CO2 permeation flow rate F per membrane leaf 11, which is obtained by the above equation (3). 11 This value was calculated based on the following: Pressure loss ΔP of the permeable spacer 14. 14 This can be calculated based on the parallel plate formula for pressure loss, using the <Method for Measuring Pressure Loss> described later, and by proportional calculation to the measured value considering the effective membrane width ratio and permeation flow rate ratio of the membrane element 100. Here, the pressure loss ΔP of the permeation spacer 14 is 14 This affects the partial pressure difference, i.e., the decrease in the amount of permeation through the separation membrane 12, and therefore the pressure loss ΔP of the permeation spacer 14 relative to the differential pressure Δp. 14 The ratio can be considered as the decrease in the performance of the separation membrane 12.

[0067] The CO2 permeation rate R of the supply fluid F0 passing through the separation membrane 12 can be calculated based on the results of the following separation operation using a test specimen made from the separation membrane 12. First, a test specimen is made from the separation membrane 12. A separation operation is performed by supplying the supply fluid F0 to a space adjacent to one side of the test specimen and creating a pressure difference in the space adjacent to the other side of the test specimen. In the separation operation, for example, the CO2 content in the supply fluid F0 is 100 vol% (pure CO2 gas), the test gas supplied to the space adjacent to one side is at a temperature of 30°C and a pressure of 0.2 MPa, and the space adjacent to the other side is adjusted so that the pressure in that space is atmospheric pressure in the measurement environment.

[0068] As described above, the membrane element 100 suppresses the increase in pressure loss of the permeate fluid F1.

[0069] <Method for measuring pressure loss> In this embodiment, the pressure loss ΔP generated by supplying nitrogen gas to the permeable spacer 14 at a flow rate of 1.0 L / min is measured. m14 This is considered to be the pressure loss of the permeate fluid F1 (hereinafter sometimes referred to as pressure loss ΔP1). Pressure loss ΔP generated by supplying nitrogen gas to the supply spacer 13 at a flow rate of 1.0 L / min m13 This is considered to be the pressure loss of the supply fluid F0 (hereinafter sometimes referred to as pressure loss ΔP0). In the membrane element 100, the increase in the pressure loss ΔP1 of the permeate fluid F1 is suppressed, for example, by the following method using the measuring device 30 shown in Figure 7: m14This can be confirmed from the above. First, a strip-shaped permeable spacer 14 measuring 47 mm in width and 150 mm in length is prepared. The permeable spacer 14 may also be a rounded rectangle. The permeable spacer 14 has the same shape as the permeable spacer 14 before it was wrapped around the central pipe 21, except for its length and width. If the permeable spacer 14 has grooves and protrusions, the grooves and protrusions extend in the longitudinal direction of the permeable spacer 14 (the X direction in Figure 7). The longitudinal direction of the permeable spacer 14 is parallel to the flow direction of the central pipe 21. Next, a polyethylene terephthalate (PET) film 41 is laminated onto the permeable spacer 14 to create a test piece 40. The film 41 and the permeable spacer 14 may be fixed with tape or the like. The film 41 is, for example, Diafoil T100-100 manufactured by Mitsubishi Chemical Corporation.

[0070] Next, the test specimen 40 is set in the measuring device 30. The measuring device 30 includes, for example, a holder 31, a lid member 35, and a sealing member 34. More specifically, the test specimen 40 is set in the holder 31 of the measuring device 30 such that the permeable spacer 14 of the test specimen 40 is located below the film 41. Openings 32 and 33 are formed in the wall surface of the holder 31. Each of the openings 32 and 33 communicates with the permeable spacer 14 of the test specimen 40. The openings 32 and 33 are positioned so that when nitrogen gas is introduced into the holder 31 from one opening 32, the nitrogen gas moves in the longitudinal direction of the permeable spacer 14 (direction X in Figure 7) and is discharged from the other opening 33. The openings 32 and 33 may or may not face each other in cross-sectional view.

[0071] The lid member 35 is fastened to the holder 31 above the holder 31 using fasteners such as screw members (not shown). The lid member 35 has an opening 36 for supplying nitrogen gas to the space 37 adjacent to the film 41 of the test piece 40. Two ports (not shown) for differential pressure measurement are formed on the bottom surface of the holder 31, perpendicular to the permeable spacer 14. The holder 31 and the lid member 35 may be made of stainless steel (SUS) or of a resin such as acrylic.

[0072] The sealing member 34 is located between the holder 31 and the lid member 35 and prevents air from venting inside and outside the measuring device 30 in areas other than the openings 32, 33, and 36. The sealing member 34 is, for example, a circular cross-section sealing ring (O-ring) made of an elastic material. Figure 7 shows the sealing member 34, which is a sealing ring, in a compressed state.

[0073] Next, nitrogen gas is introduced into the space 37 adjacent to the film 41 of the test piece 40 through the opening 36 of the lid member 35 so that the pressure in the space 37 becomes 0.1 MPa, and nitrogen gas is also introduced into the permeation spacer 14 at a flow rate of 1.0 L / min through the opening 32 of the holder 31. The temperature of the nitrogen gas introduced into the measuring device 30 is, for example, 23°C. The nitrogen gas introduced through the opening 32 moves within the permeation spacer 14 in the longitudinal direction of the permeation spacer 14 (the X direction in Figure 7) and is discharged from the opening 33. The differential pressure Δp of nitrogen gas from the two ports m Measure (kPa). Differential pressure Δp is the distance (m) between the two ports. m By dividing by this, the differential pressure gradient Δp g Calculate (kPa / m). Calculate the differential pressure gradient Δp. g pressure loss ΔP m14 It is assumed that the pressure loss ΔP is such. m13 The same method can be used to determine this as well.

[0074] The pressure loss ΔP1 of the permeating fluid F1 is, for example, 10 kPa / m or less. The upper limit of the pressure loss ΔP1 of the permeating fluid F1 may be 9 kPa / m, or even 8 kPa / m.

[0075] The pressure loss ΔP1 of the permeating fluid F1 is, for example, 4 kPa / m or more. The lower limit of the pressure loss ΔP1 of the permeating fluid F1 may be 5 kPa / m, 6 kPa / m, or even 7 kPa / m.

[0076] The pressure loss ΔP0 of the supply fluid F0 is, for example, 14 kPa / m or less. The upper limit of the pressure loss ΔP0 of the supply fluid F0 may be 13 kPa / m, or even 12 kPa / m.

[0077] The pressure loss ΔP0 of the supply fluid F0 is, for example, 1 kPa / m or more. The lower limit of the pressure loss ΔP0 of the supply fluid F0 may be 2 kPa / m.

[0078] [Applications of Spiral-Type Membrane Element] One application of the membrane element 100 according to this embodiment is the separation of acidic gases from a gas mixture containing acidic gases. Examples of acidic gases in the gas mixture include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, nitrogen oxides (NOx), and preferably carbon dioxide. The gas mixture contains other gases besides the acidic gas. Examples of other gases include nonpolar gases such as hydrogen and nitrogen, and inert gases such as helium, and preferably nitrogen. In particular, the membrane element 100 according to this embodiment is suitable for separating carbon dioxide from a gas mixture containing carbon dioxide and nitrogen. However, the applications of the membrane element 100 are not limited to separating acidic gases from the above-mentioned gas mixture.

[0079] [Membrane separation method using spiral-type membrane element] Next, a membrane separation method using the membrane element 100 according to this embodiment will be described. The membrane separation method using the membrane element 100 includes, for example, creating a differential pressure between the supply space and the permeate space of the membrane element 100 (step 1). Step 1 includes increasing the pressure in the supply space of the membrane element 100 and decreasing the pressure in the supply space of the membrane element 100. According to this membrane separation method, it is possible to suppress the increase in pressure loss of the permeate fluid F1 during operation of the membrane element 100.

[0080] Step 1 may involve increasing the pressure within the supply space of the membrane element 100. The above-described effects of the membrane separation method can be more effectively achieved when the membrane element 100 is applied in a pressurized manner.

[0081] (Second Embodiment) <Embodiment of Membrane Separation System> Figure 8 is a schematic diagram showing an example of a membrane separation system according to the second embodiment. The membrane separation system 200 according to the second embodiment includes the membrane element 100 according to the first embodiment. In the membrane separation system 200, the membrane element 100 achieves both an increase in the effective membrane area of ​​the separation membrane 12 and an increase in the permeate flow rate. As a result, excellent separation performance is achieved.

[0082] The membrane separation system 200 may further include a pressurizing device 51. The pressurizing device 51 increases the pressure within the supply space of the membrane element 100. In other words, the pressurizing device 51 can create a differential pressure between the supply space and the permeate space of the membrane element 100.

[0083] A specific example of the pressurizing device 51 is a pump. The pressurizing device 51 may be a pump that pressurizes the supply fluid F0 toward the supply-side space of the membrane element 100. The pump is typically a gas transport type pressurizing pump, and examples include reciprocating pressurizing pumps and rotary pressurizing pumps. Examples of reciprocating pressurizing pumps include diaphragm pumps and oscillating piston pumps. Examples of rotary pumps include liquid-sealed pumps, oil rotary pumps (rotary pumps), mechanical booster pumps, and various dry pumps such as Roots type, claw type, screw type, turbo type, and scroll type. The pump as the pressurizing device 51 may be equipped with a variable speed mechanism for changing the rotation speed, etc. An example of a variable speed mechanism is an inverter that drives the motor of the pump. By controlling the rotation speed of the pump with the variable speed mechanism, the pressure in the supply space of the membrane element 100 can be appropriately adjusted.

[0084] The pressurizing device 51 may be a collection of multiple pumps. That is, the pressurizing device 51 may be configured so that each of the multiple pumps can increase the pressure in the supply space of the membrane element 100. With this configuration, the pressure in the supply space of the membrane element 100 can be appropriately adjusted by adjusting the number of operating pumps.

[0085] Figure 9 is a schematic diagram showing a modified example of the membrane separation system according to the second embodiment. The membrane separation system 201 shown in Figure 9 is equipped with a depressurizing device 52 instead of a pressurizing device 51. The depressurizing device 52 reduces the pressure inside the permeation space of the membrane element 100. In other words, the depressurizing device 52 can create a differential pressure between the supply space and the permeation space of the membrane element 100. A specific example of the depressurizing device 52 is a pump. Preferably, the depressurizing device 52 is a vacuum device such as a vacuum pump. A vacuum pump is typically a gas transport type vacuum pump, and examples include a reciprocating vacuum pump or a rotary vacuum pump. Examples of reciprocating vacuum pumps include diaphragm type or oscillating piston type vacuum pumps. Examples of rotary vacuum pumps include liquid-sealed pumps; oil rotary pumps (rotary pumps); mechanical booster pumps; and various dry pumps such as Roots type, claw type, screw type, turbo type, and scroll type. The pump as the depressurizing device 52 may be equipped with a variable speed mechanism to change the rotational speed, etc. An example of a variable speed mechanism is an inverter that drives the motor of a pump. By controlling the rotational speed of the pump with a variable speed mechanism, the pressure in the permeable space of the membrane element 100 can be appropriately adjusted.

[0086] The pressure reducing device 52 may be a collection of multiple pumps. That is, the pressure reducing device 52 may be configured so that each of the multiple pumps can reduce the pressure inside the permeable space of the membrane element 100. With this configuration, the pressure inside the permeable space of the membrane element 100 can be appropriately adjusted by adjusting the number of operating pumps.

[0087] The above-described embodiments are mutually applicable, insofar as they do not conflict with technical standards. The above embodiments and their variations may be combined with each other, insofar as they do not conflict with technical standards. Furthermore, the components of the spiral membrane element, the components of the membrane separation system, and the steps of the membrane separation method may be substituted, added to, or combined with each other, insofar as they do not conflict with technical standards. For example, the components described with respect to the spiral membrane element and the membrane separation system may be used in embodiments relating to the membrane separation method, and the steps described with respect to the membrane separation method may be performed by the spiral membrane element and the membrane separation system. These combinations are also included within the scope of the present invention.

[0088] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0089] (Examples 1-16 and Comparative Examples 1-3) [Preparation of Separation Membrane] First, a coating solution containing silicone resin and polyurethane resin in a weight ratio of 9:1 was prepared. The coating solution contained water as a solvent. Next, a coating film was obtained by applying the coating solution onto a porous support using the gravure coating method. As the porous support, a UF membrane (ultrafiltration membrane) RS-50 (a laminate of a porous PVDF layer and a PET nonwoven fabric) manufactured by Nitto Denko Corporation was used. An intermediate layer was formed by drying the obtained coating film. This resulted in obtaining a separation membrane.

[0090] [Spacers] Spacers having the configurations shown in Table 1 were used as supply spacers and permeable spacers in Examples 1 to 16 and Comparative Examples 1 to 3.

[0091] <Calculation of the effective membrane area of ​​the separation membrane> Based on the method described above, the total effective membrane area A (m²) of the separation membrane in a spiral-type membrane element with an outer diameter of 8 inches is calculated using equation (2). 2 ) was calculated.

[0092]

[0093] A simulation was performed when the spiral membrane element 100 (outer diameter: 8 inches) shown in Figure 1 was operated. Specifically, it was assumed that the membrane element 100 would use the separation membrane 12 prepared above, along with a supply spacer 13 and a permeation spacer 14 configured as shown in Table 1. The permeation rate R (GPU) of CO2 permeating through the separation membrane 12, the pressure of the supply fluid F0 (kPa), and the pressure of the permeation fluid F1 (kPa) were set as shown in Table 2. Furthermore, the supply conditions for the supply fluid F0 were set as follows. [Supply Fluid Supply Conditions] (Examples 1-15 and Comparative Examples 1-3) Composition (volume ratio): N2 / CO2 = 80 / 20 Pressure: 101.33 kPa Temperature: 35°C Flow rate: 12000 NL / min (Example 16) Composition (volume ratio): N2 / CO2 = 40 / 60 Pressure: 101.33 kPa Temperature: 35°C Flow rate: 12000 NL / min

[0094] <Calculation of CO2 permeation flow rate> Based on the method described above, the CO2 permeation flow rate F in the membrane element is calculated using equation (4) above, under the conditions shown in Table 2. 100 (GPU-m 2 ) was sought.

[0095] <Measurement of pressure loss> For the supply spacer and permeation spacer, the pressure loss ΔP generated by supplying nitrogen gas to the supply spacer at a flow rate of 1.0 L / min, based on the method described above, is measured. m13 This was calculated and considered as the pressure loss ΔP0 (kPa / m) of the supply fluid. The pressure loss ΔP0 was generated by supplying nitrogen gas to the permeable spacer at a flow rate of 1.0 L / min. m14 This was calculated and considered as the pressure loss ΔP1 (kPa / m) of the permeating fluid F1. The results are shown in Table 2.

[0096]

[0097] As shown in Tables 1 and 2, Examples 1 to 16 differ from Comparative Examples 1 to 3 in the total effective membrane area A of the separation membrane and the calculated CO2 permeation flow rate F in the membrane element. 100Both values ​​were large. From these results, it is inferred that when a spiral-type membrane element is fabricated in which the thickness of the permeation spacer is 400 μm or less and the ratio of the thickness of the permeation spacer to the thickness of the supply spacer is 0.4 or more, it is possible to achieve both an increase in the effective membrane area of ​​the separation membrane and an increase in the permeation flow rate.

[0098] In Examples 1-11 and 13-16, a tricot knitted spacer was used as the permeable spacer, while in Example 12, a net spacer was used as the permeable spacer. Furthermore, in Examples 1-2, 4-7, 9-10, 12-14 and 16, a net spacer was used as the supply spacer, while in Examples 3, 8, 11 and 15, a tricot knitted spacer was used as the supply spacer. However, even if the permeable spacer is not tricot knitted or net, and even if the supply spacer is not net or tricot knitted, similar effects can be expected as long as the thickness of the permeable spacer is 400 μm or less and the ratio of the thickness of the permeable spacer to the thickness of the supply spacer is 0.4 or more. This is because the above-mentioned effects are thought to be achieved by the dimensional relationship between the thickness of the permeable spacer and the ratio of the thickness of the permeable spacer to the thickness of the supply spacer.

[0099] The spiral membrane element according to this embodiment is suitable for separating acidic gases from a gas mixture containing acidic gases. In particular, the spiral membrane element according to this embodiment is suitable for separating carbon dioxide from off-gas in chemical plants or thermal power plants.

Claims

1. A spiral membrane element comprising a central tube and a laminate wound around the central tube, wherein the laminate includes membrane leaves having a separation membrane and a permeation spacer and a supply spacer, the thickness of the permeation spacer being 400 μm or less, and the ratio of the thickness of the permeation spacer to the thickness of the supply spacer being 0.4 or more.

2. The spiral membrane element according to claim 1, wherein the ratio of the thickness of the permeable spacer to the thickness of the supply spacer is 2.0 or less.

3. The spiral film element according to claim 1, wherein the thickness of the supply spacer is 1000 μm or less.

4. The spiral membrane element according to claim 1, wherein the pressure loss caused by supplying nitrogen gas to the permeable spacer at a flow rate of 1.0 L / min is 10 kPa / m or less.

5. The spiral membrane element according to claim 1, wherein the pressure loss caused by supplying nitrogen gas to the supply spacer at a flow rate of 1.0 L / min is 14 kPa / m or less.

6. The spiral membrane element according to claim 1, used for separating an acidic gas from a gas mixture containing an acidic gas.

7. A membrane separation system comprising a spiral membrane element according to any one of claims 1 to 6.

8. The membrane separation system according to claim 7, further comprising a pressurizing device for increasing the pressure within the supply space of the spiral membrane element.

9. A membrane separation method using a spiral membrane element according to any one of claims 1 to 6, comprising generating a differential pressure between the supply space and the permeate space of the spiral membrane element.

10. The membrane separation method according to claim 9, wherein generating the differential pressure includes increasing the pressure within the supply space of the spiral membrane element.

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