Gas recovery system

Abstract

Provided is a novel gas recovery system suitable for reducing recovery power. A gas recovery system (100) is provided with: a gas separation device (10) for separating a mixed gas (G) containing a specific gas to obtain a separated gas (Gs) having a higher content of the specific gas than the mixed gas (G); and a recovery unit (20) that has an adsorbent (21) that adsorbs a specific gas contained in the separated gas (Gs). The gas separation device (10) has, for example, a separation membrane (11) for separating a mixed gas (G). The adsorbent 21 contains, for example, a metal-organic structure.

Description

Technical Field

[0001] The present invention relates to a gas recovery system. Background Art

[0002] In recent years, the technology of separating and recovering specific gases such as carbon dioxide from mixed gases has attracted attention. For example, Patent Document 1 proposes a technology of separating CO2 and SO2 from the exhaust gas of a boiler by using a membrane separation unit, and then cooling and condensing them by using a cooling unit.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application No. 2020-501884 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the system configuration of Patent Document 1, a large recovery power is required to recover high-concentration carbon dioxide.

[0008] An object of the present invention is to provide a new gas recovery system suitable for reducing recovery power.

[0009] Means for solving problems

[0010] The present invention provides a gas recovery system, which comprises:

[0011] A gas separation device for separating a mixed gas containing a specific gas to obtain a separated gas having a higher content of the specific gas than that of the mixed gas;

[0012] The recovery unit includes an adsorbent that adsorbs the specific gas included in the separation gas.

[0013] Effects of the Invention

[0014] According to the present invention, a new gas recovery system suitable for reducing recovery power can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] [ Figure 1 ] is a schematic diagram showing an example of a gas recovery system according to the first embodiment.

[0016] [ Figure 2 ] is a schematic cross-sectional view showing an example of a gas separation device provided in a gas recovery system.

[0017] [ Figure 3 ] is a schematic cross-sectional view showing an example of a separation membrane provided in a gas separation device.

[0018] [ Figure 4A ] is a schematic diagram showing a modified example 1 of the gas recovery system of the first embodiment.

[0019] [ Figure 4B ] is a schematic diagram showing a second modification of the gas recovery system of the first embodiment.

[0020] [ Figure 4C ] is a schematic diagram showing a third modification of the gas recovery system of the first embodiment.

[0021] [ Figure 5 ] is a schematic diagram showing an example of a gas recovery system according to the second embodiment.

[0022] [ Fig. 6A ] is a schematic diagram showing a modified example 1 of the gas recovery system of the second embodiment.

[0023] [ Figure 6B ] is a schematic diagram showing a second modification of the gas recovery system of the second embodiment.

[0024] [ Figure 6C ] is a schematic diagram showing a third modification of the gas recovery system of the second embodiment.

[0025] [ Figure 7 ] is an expanded stereoscopic view showing another example of a gas separation device provided in a gas recovery system.

[0026] [ Figure 8 ] is a schematic diagram showing the structure of the gas recovery system used in calculation example 3.

[0027] [ Fig. 9 ] is a schematic diagram showing the structure of the gas separation system used in calculation example 4. DETAILED DESCRIPTION

[0028] A gas recovery system according to a first aspect of the present invention includes:

[0029] A gas separation device for separating a mixed gas containing a specific gas to obtain a separated gas having a higher content of the specific gas than that of the mixed gas;

[0030] The recovery unit includes an adsorbent that adsorbs the specific gas included in the separation gas.

[0031] Regarding a second aspect of the present invention, for example, in the gas recovery system according to the first aspect, the specific gas is carbon dioxide.

[0032] Regarding a third aspect of the present invention, for example, in the gas recovery system according to the first or second aspect, the gas separation device includes a separation membrane for separating the mixed gas.

[0033] In a fourth aspect of the present invention, for example, in the gas recovery system according to any one of the first to third aspects, the adsorbent includes a metal organic structure.

[0034] Regarding a fifth aspect of the present invention, for example, in the gas recovery system according to the fourth aspect, the metal organic structure has a tetradentate organic ligand and a metal ion, a metal cluster, or a metal oxide cluster as a core.

[0035] In a sixth aspect of the present invention, for example, in the gas recovery system according to the fifth aspect, the organic ligand includes a tetracarboxylic acid.

[0036] In a seventh aspect of the present invention, for example, in the gas recovery system according to the sixth aspect, the tetracarboxylic acid contains a nitrogen atom.

[0037] In an eighth aspect of the present invention, for example, in the gas recovery system according to any one of the fourth to sixth aspects, the metal-organic structure has an nbo structure.

[0038] Regarding the 9th embodiment of the present invention, for example, in a gas recovery system involving any one of the 4th to 7th embodiments, the adsorption amount of the metal-organic structure by the specific gas within the pressure range of greater than 0.1MPa and less than 1.1MPa is greater than the adsorption amount of the metal-organic structure by the specific gas within the pressure range of greater than 0MPa and less than 0.1MPa.

[0039] Regarding a tenth aspect of the present invention, for example, in the gas recovery system according to any one of the first to ninth aspects, a content rate of the specific gas in the separation gas is 95 vol% or less.

[0040] Regarding an eleventh aspect of the present invention, for example, in the gas recovery system according to the tenth aspect, a content rate of the specific gas in the separation gas is 70 vol% or more.

[0041] Regarding a twelfth aspect of the present invention, for example, in the gas recovery system according to any one of the first to eleventh aspects, a pressurizing device for pressurizing the separation gas is further provided.

[0042] Regarding the 13th embodiment of the present invention, for example, in a gas recovery system involved in any one of the 1st to 12th embodiments, after an adsorption operation is performed to adsorb the specific gas contained in the separation gas onto the adsorbent and a desorption operation is performed to desorb the adsorbed gas containing the specific gas from the adsorbent, the content of the specific gas in the adsorbed gas is higher than the content of the specific gas in the separation gas.

[0043] Regarding the 14th aspect of the present invention, for example, in the gas recovery system involved in the 13th aspect, the recovery unit further has a container, a gas inlet and a gas outlet, and during the adsorption operation, the non-adsorbed gas is discharged from the gas outlet.

[0044] Regarding a fifteenth aspect of the present invention, for example, in the gas recovery system according to the fourteenth aspect, a non-adsorbed gas circulation path for conveying at least a part of the non-adsorbed gas to the recovery unit or the gas separation device is further provided.

[0045] Regarding the 16th embodiment of the present invention, for example, in the gas recovery system involved in the 14th or 15th embodiment, it includes a plurality of recovery units connected in series with each other, and during the disengagement operation, the adsorbed gas discharged from the gas outlet of the recovery unit on the upstream side is supplied to the gas inlet of the recovery unit on the downstream side.

[0046] According to a seventeenth aspect of the present invention, for example, the gas recovery system according to any one of the first to sixteenth aspects further includes a combustion device to which the oxygen-containing fuel gas is supplied and which discharges the mixed gas.

[0047] Regarding an eighteenth aspect of the present invention, for example, in the gas recovery system according to the seventeenth aspect, the combustion device includes a boiler.

[0048] A gas recovery system according to a nineteenth aspect of the present invention comprises:

[0049] A gas separation device for separating a mixed gas containing carbon dioxide to obtain a separated gas having a higher carbon dioxide content than the mixed gas;

[0050] The recovery unit includes an adsorbent for adsorbing carbon dioxide contained in the separation gas.

[0051] Hereinafter, the present invention will be described in detail, but the following description is not intended to limit the present invention to specific embodiments.

[0052] <Implementation Method of Gas Recovery System>

[0053] The gas recovery system of this embodiment includes a gas separation device and a recovery unit. The gas separation device is a device for separating a mixed gas G containing a specific gas to obtain a separated gas Gs having a higher content of the specific gas than the mixed gas G. The recovery unit includes an adsorbent. The adsorbent adsorbs the specific gas contained in the separated gas Gs.

[0054] The specific gas includes, for example, an acidic gas. Examples of the acidic gas include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, nitrogen oxides (NOx), etc., preferably carbon dioxide. When the specific gas is an acidic gas, the mixed gas includes other gases other than the acidic gas. Examples of other gases include hydrogen, nitrogen, oxygen, methane, helium, argon, propane, propylene, etc., preferably nitrogen, methane, etc. In particular, the gas recovery system of the present embodiment is suitable for use in recovering carbon dioxide from a mixed gas containing carbon dioxide and nitrogen. It should be noted that the specific gas may also be a gas described above as other gases.

[0055] The gas separation device is not particularly limited as long as it can separate the mixed gas G to obtain the separated gas Gs having a higher content of a specific gas than the mixed gas G. For example, the gas separation device can be a device that uses a membrane separation method to separate the mixed gas G using a separation membrane to obtain the separated gas Gs, or a device that uses a physical adsorption method to separate the mixed gas G using an adsorbent to obtain the separated gas Gs. Physical adsorption methods include, for example, PSA (pressure swing adsorption; Pressure Swing Adsorption) method, TSA (temperature swing adsorption; Temperature Swing Adsorption) method, PTSA (pressure swing temperature swing adsorption; Pressure and Temperature Swing Adsorption) method, etc. The PSA method, TSA method, and PTSA method are methods of separating gases using adsorbents that make chemical adsorption components such as potassium carbonate or amines supported on carriers such as activated carbon or porous resins. In the PSA method, the gas is separated by using the difference in adsorption capacity caused by the pressure of the adsorbent. In the TSA method, the gas is separated by using the difference in adsorption capacity caused by the temperature of the adsorbent. In the PTSA method, the difference in adsorption capacity caused by the pressure and temperature of the adsorbent is used to separate gases. When the gas separation device adopts a physical adsorption method, the gas separation device can adopt a PSA method.

[0056] When the gas separation device adopts a membrane separation method, the gas separation device may include a separation membrane for separating the mixed gas G. By separating the mixed gas G using the separation membrane, a separated gas Gs can be obtained.

[0057] The separation membrane of the gas separation device can be called a separation membrane that separates the mixed gas G into the permeated gas S1 and the non-permeated gas S2. The permeated gas S1 may be the separation gas Gs, and the non-permeated gas S2 may be the separation gas Gs.

[0058] In the past, as a system for separating and recovering a specific gas from a mixed gas, for example, a system is known that separates a specific gas such as carbon dioxide from a mixed gas such as an exhaust gas by a chemical absorption method, and recovers the separated specific gas after condensing and liquefying. However, the liquefaction of specific gases such as carbon dioxide requires large-scale equipment. The inventors of the present application have conducted in-depth research on a more compact system for recovering the separated specific gas, and as a result, created a new gas recovery system that combines a gas separation device and a recovery unit with an adsorbent. According to the gas recovery system of this embodiment, the specific gas contained in the separated gas Gs obtained by separation in the gas separation device can be adsorbed on the adsorbent of the recovery unit for recovery, so the recovery power of the specific gas can be reduced. In addition, since an adsorbent is used in the recovery of the specific gas, the recovery unit can be made into a compact structure. In the present invention specification, "the recovery power of the specific gas" is the sum of the power required for recovering the specific gas. The recovery power of the specific gas of the gas recovery system includes the separation power of the gas separation device per unit amount of the specific gas to be recovered.

[0059] The content of the specific gas in the separation gas Gs is preferably 95 vol% or less. If the content of the specific gas in the separation gas Gs is 95 vol% or less, the excessive increase in the separation power of the gas separation device can be suppressed. In the present specification, the content (vol%) of the specific gas in the separation gas Gs is the volume ratio of the specific gas relative to the separation gas Gs under the conditions of standard conditions (0°C, 101.33 kPa).

[0060] The content of the specific gas in the separation gas Gs is preferably 70 vol% or more. If the content of the specific gas in the separation gas Gs is 70 vol% or more, the gas recovery system 100 can recover a higher concentration of the specific gas.

[0061] The lower limit of the content of the specific gas in the separation gas Gs may be 80 vol % or 85 vol %.

[0062] Hereinafter, as a first embodiment, a gas recovery system 100 is described in which the specific gas is carbon dioxide, the gas separation device 10 has a separation membrane 11, and the separated gas Gs is a permeated gas S1. As a second embodiment, a gas recovery system 110 is described in which the specific gas is carbon dioxide, the gas separation device 10 has a separation membrane 11, and the separated gas Gs is a non-permeated gas S2.

[0063] <First Embodiment>

[0064] Figure 1 1 is a schematic diagram showing an example of a gas recovery system 100 according to the first embodiment. The gas recovery system 100 includes a gas separation device 10 and a recovery unit 20. The gas separation device 10 includes a separation membrane 11. The separation membrane 11 separates a mixed gas G containing carbon dioxide into a permeated gas S1 and a non-permeated gas S2. In the first embodiment, the carbon dioxide content of the permeated gas S1 is higher than that of the mixed gas G. That is, in the first embodiment, the permeated gas S1 is the separated gas Gs. The recovery unit 20 includes an adsorbent 21. The adsorbent 21 adsorbs carbon dioxide contained in the separated gas Gs.

[0065] [Gas separation device]

[0066] Figure 2 1 is a schematic cross-sectional view showing an example of a gas separation device 10 included in the gas recovery system 100. Figure 2 In the example of FIG. 1 , the gas separation device 10 includes a separation membrane 11 for separating the supplied mixed gas G. The separated gas Gs (permeated gas S1 ) obtained by the separation membrane 11 has a higher carbon dioxide content than the mixed gas G.

[0067] like Figure 2 As shown, the gas separation device 10 includes a separation membrane 11 and a container 12. The container 12 has a first chamber 13 and a second chamber 14. The first chamber 13 functions as a supply space to which the mixed gas G is supplied. The second chamber 14 functions as a permeation space to which the permeated gas S1 is supplied. The permeated gas S1 is obtained by the mixed gas G permeating through the separation membrane 11.

[0068] The separation membrane 11 is disposed inside the container 12. The separation membrane 11 partitions the container 12 into a first chamber 13 and a second chamber 14. The separation membrane 11 extends from one of a pair of wall surfaces of the container 12 to the other.

[0069] The first chamber 13 has a supply space inlet 13a and a supply space outlet 13b. The second chamber 14 has a permeation space outlet 14b. The supply space inlet 13a is an opening for supplying the mixed gas G to the supply space (the first chamber 13). The permeation space outlet 14b is an opening for discharging the permeated gas S1 from the permeation space (the second chamber 14). The supply space outlet 13b is an opening for discharging the mixed gas G (non-permeated gas S2) that has not permeated the separation membrane 11 from the supply space (the first chamber 13). The supply space inlet 13a, the supply space outlet 13b, and the permeation space outlet 14b are respectively formed on, for example, the wall surface of the container 12.

[0070] The gas separation device 10 may adopt an operation mode (decompression mode) in which a pressure difference is generated by reducing pressure from the permeation space side, or an operation mode (pressurization mode) in which a pressure is increased by controlling the supply pressure from the non-permeation space side. The gas separation device 10 may adopt a scavenging mode in which a pressure difference is generated by supplying an inert gas, dry air, etc. to the permeation space side. When the content of carbon dioxide in the supplied mixed gas G is low (for example, less than 10 vol%), the excessive increase in the separation power of the gas separation device 10 can be suppressed by adopting the decompression mode.

[0071] There is no particular limitation on the content of carbon dioxide in the mixed gas G. The content of carbon dioxide in the mixed gas G is, for example, 1 to 70 vol%.

[0072] The gas separation device 10 is suitable for a flow-through (continuous) membrane separation method. The gas separation device 10 can also be used for a batch membrane separation method.

[0073] The structure of the separation membrane 11 is not particularly limited. Figure 3 To show Figure 2 FIG. 1 is a schematic cross-sectional view of an example of a separation membrane 11 included in the gas separation device 10 shown in FIG. Figure 3 As shown, the separation membrane 11 may include a separation functional layer 1, a porous support 3 supporting 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 the separation functional layer 1 and the porous support 3, for example.

[0074] In the first embodiment, the separation membrane 11 is a membrane (carbon dioxide separation membrane) that allows carbon dioxide contained in the mixed gas G to preferentially permeate. In this case, the content of carbon dioxide in the permeated gas S1 is higher than the content of carbon dioxide in the mixed gas G. On the other hand, the content of carbon dioxide in the non-permeated gas S2 is lower than the content of carbon dioxide in the mixed gas G. That is, when the separation membrane 11 is a carbon dioxide separation membrane, the permeated gas S1 corresponds to the separation gas Gs.

[0075] (Separation Functional Layer)

[0076] In the first embodiment, the separation functional layer 1 is a layer that allows carbon dioxide contained in the mixed gas G to preferentially pass through. The separation functional layer 1 preferably contains a resin. As the resin contained in the separation functional layer 1, for example, polyether block amide resin, polyamide resin, polyether resin, polyimide resin, polyetherimide resin, cellulose acetate resin, silicone resin and fluororesin can be cited. 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 is preferably substantially formed of a resin. In the present specification, "substantially formed of..." means excluding other components that change the essential characteristics of the material, and means, for example, that more than 95wt%, and further more than 99wt% is composed of the material.

[0077] 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.

[0078] (Middle layer)

[0079] The intermediate layer 2 includes, for example, a resin, and may further include nanoparticles dispersed in the resin (matrix). The nanoparticles may be separated from each other in the matrix, or may be partially aggregated. The material of the matrix is ​​not particularly limited, and examples thereof include silicone resins such as polydimethylsiloxane; fluororesins such as polytetrafluoroethylene; epoxy resins such as polyethylene oxide; polyimide resins; polysulfone resins; polyalkyne resins such as polytrimethylsilylpropyne and polydiphenylacetylene; and polyolefin resins such as polymethylpentene. The matrix preferably includes a silicone resin.

[0080] Nanoparticles may contain inorganic materials or organic materials. Examples of inorganic materials contained in nanoparticles include silicon dioxide, titanium dioxide, and aluminum oxide. Nanoparticles preferably contain silicon dioxide.

[0081] 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.

[0082] (Porous Support)

[0083] The porous support 3 supports the separation functional layer 1 via the intermediate layer 2. Examples of the porous support 3 include nonwoven fabrics; porous polytetrafluoroethylene; aromatic polyamide fibers; porous metals; sintered metals; porous ceramics; porous polyesters; porous nylons; activated carbon fibers; latex; silicone resins; silicone rubbers; permeable (porous) polymers containing at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyetheretherketone, polyacrylonitrile, polyimide, and polyphenylene ether; metal foams having open or closed cells; polymer foams having open or closed cells; silicon dioxide; porous glass; meshes, etc. The porous support 3 may be composed of a combination of two or more of these.

[0084] The porous support 3 has an average pore size of, for example, 0.01 to 0.4 μm. The thickness of the porous support 3 is not particularly limited, and is, for example, 10 μm or more, preferably 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.

[0085] The composition of the separation membrane is not limited to Figure 3 The example shown. The separation membrane 11 can be composed of, for example, a separation functional layer 1, and a porous support body 3 arranged on one side of the separation functional layer 1 to support the separation functional layer 1. The separation membrane 11 can be composed of, for example, a separation functional layer 1, a protective layer arranged on one side of the separation functional layer 1 to protect the separation functional layer 1, and a porous support body 3 arranged on the other side of the separation functional layer 1 to support the separation functional layer 1. As the protective layer, a layer containing the material described for the intermediate layer 2 can be used.

[0086] [Recycling Department]

[0087] The recovery unit 20 includes an adsorbent 21 that adsorbs carbon dioxide contained in the supplied separation gas Gs (permeated gas S1 ). The recovery unit 20 includes the adsorbent 21 and a container 22 . The adsorbent 21 is disposed inside the container 22 .

[0088] Hereinafter, the operation of the recovery unit 20 in which the separation gas Gs contacts the adsorbent 21 and carbon dioxide contained in the separation gas Gs is adsorbed on the adsorbent 21 is referred to as adsorption operation. The operation of the recovery unit 20 in which the adsorbed gas Ga containing carbon dioxide is desorbed from the adsorbent 21 adsorbing carbon dioxide is referred to as desorption operation.

[0089] The pressure in the recovery unit 20 during adsorption operation is, for example, less than 1.1MPa, or less than 1.0MPa or less than 0.9MPa. The pressure in the recovery unit 20 during adsorption operation is preferably above atmospheric pressure (for example, 0.1MPa), for example, above 0.1MPa, or above 0.2MPa. The pressure in the recovery unit 20 during adsorption operation can be above 0.1MPa and less than 1.1MPa. The pressure in the recovery unit 20 can also be reduced during the separation operation. In other words, the adsorbed gas Ga can be separated from the adsorbent 21 by reducing the pressure in the recovery unit 20 during the separation operation. The pressure in the recovery unit 20 can be reduced to atmospheric pressure during the separation operation. According to the gas recovery system 100, a specific gas can be adsorbed and separated within a range of above 0.1MPa and less than 1.1MPa. Therefore, not only can the separation operation be implemented without using a vacuum pump, but also it is not necessary to use a high-pressure tank as the container 22 of the recovery unit 20. When a high-pressure tank is not used, it is outside the scope of application of the High-Pressure Gas Safety Act, so it is easy to handle the container 22 and operate the recovery unit 20. It should be noted that in the present specification, "pressure" refers to absolute pressure unless otherwise specified.

[0090] The pressure in the recovery unit 20 when out of operation can be less than 0.1MPa or less than 0.05MPa according to the situation. The pressure in the recovery unit 20 when out of operation can be, for example, more than 0.001MPa. It should be noted that the pressure in the recovery unit 20 can be adjusted by a pressure reducing device such as a pressurizing device 30 or a vacuum pump described later.

[0091] The container 22 has a gas inlet 20a. During adsorption operation, the gas inlet 20a is used as an opening for supplying the separation gas Gs into the container 22. During desorption operation, the gas inlet 20a can be used as an opening for discharging the adsorbed gas Ga from the container 22. That is, the gas inlet 20a can serve as both a gas introduction port (supply port) and a gas discharge port.

[0092] In the present embodiment, the container 22 further has a gas outlet 20b. During the adsorption operation, the gas outlet 20b is used as an opening for discharging the non-adsorbed gas Gn that is not adsorbed by the adsorbent 21 in the separation gas Gs from the container 22. In other words, during the adsorption operation, the non-adsorbed gas Gn is discharged from the gas outlet 20b. During the desorption operation, the gas outlet 20b is used as an opening for discharging the adsorbed gas Ga from the container 22. In other words, during the desorption operation, the adsorbed gas Ga is discharged from the gas outlet 20b.

[0093] On the gas outlet 20b side of the recovery unit 20, a pressure regulating valve 50 for adjusting the pressure of the gas discharged from the recovery unit 20 can be arranged. The gas discharged from the recovery unit 20 is a non-adsorbed gas Gn during adsorption operation and an adsorbed gas Ga during separation operation. During adsorption operation, by adjusting the pressure regulating valve 50, the adsorption amount of carbon dioxide on the adsorbent 21 can be increased. Thus, during separation operation, the content of carbon dioxide in the adsorbed gas Ga can be increased. That is, when separation operation is performed after adsorption operation, the content of carbon dioxide in the adsorbed gas Ga is higher than the content of carbon dioxide in the separation gas Gs. The content of carbon dioxide in the adsorbed gas Ga is, for example, 95 vol% or more.

[0094] The container 22 of the recovery unit 20 can be configured to be detachable and freely movable from the gas recovery system 100. Thus, the gas recovery system 100 can be made more compact. The shape of the container 22 of the recovery unit 20 is not particularly limited. The container 22 can have, for example, a cubic shape, a rectangular parallelepiped shape, a cylindrical shape or a prism shape. For example, in the recovery system based on liquefied carbon dioxide in the past, in order to store liquefied carbon dioxide, it is necessary to use a dedicated high-pressure tank, and in addition, in order to transport liquefied carbon dioxide, it is necessary to use a dedicated high-pressure tank truck. However, according to the gas recovery system 100 of the present embodiment, as described above, carbon dioxide can be adsorbed and separated within a range of more than 0.1MPa and less than 1.1MPa, so as the container 22 of the recovery unit 20, it is not necessary to use a dedicated high-pressure tank for transporting liquefied carbon dioxide. In addition, the container 22 of the recovery unit 20 can be used as a storage and transportation container for carbon dioxide. In addition, multiple containers 22 can also be stacked and stored.

[0095] The material of the container 22 of the recovery unit 20 is not particularly limited. As the material of the container 22, for example, metal, alloy, plastic, and a combination thereof can be cited. The plastic can be a fiber reinforced plastic. The container 22 can be composed of a fiber reinforced plastic. In this case, the weight of the recovery unit 20 can be reduced.

[0096] (Adsorbent)

[0097] The adsorbent 21 is not particularly limited as long as it can adsorb specific gases such as carbon dioxide contained in the separation gas Gs. The adsorbent 21 can be composed of a porous material, for example. As porous materials, for example, activated carbon, zeolite, molecular sieve, mesoporous silica, metal organic structure (MOF), covalently bonded organic structure (COF), metal organic polyhedron (MOP), covalently bonded organic polymer (COP), porous aromatic structure (PAF), hydrogen bonded organic structure (HOF), porous organic polymer (POP), etc. can be cited. The porous material can include one or a combination of more than two selected from the group consisting of the above materials. The adsorbent 21 can also be composed of a polymer having an amino group. Such a polymer is, for example, an amine polymer containing a structural unit derived from an epoxy monomer.

[0098] The adsorbent 21 may include MOF. MOF is a crystalline porous material having a core such as a metal ion or a metal cluster and an organic ligand coordinated to the core. Compared with other adsorbents, MOF has a large adsorption capacity per unit volume. By using MOF as the adsorbent 21, a large amount of specific gases such as carbon dioxide can be adsorbed and released. Using MOF, a large amount of specific gases such as carbon dioxide can be adsorbed and released with a smaller pressure difference. In addition, from the perspective of high repeated adsorption and desorption performance and excellent durability, MOF is also preferably used as the adsorbent 21. Furthermore, MOF also has a MOF with a so-called gate-type adsorption and desorption performance, in which it is observed that there is almost no adsorption before reaching a specific pressure P1, but when exceeding the specific pressure P1, the gas adsorption phenomenon begins sharply, and the gas is almost not released before reaching a specific pressure P2, but if it becomes below a specific pressure P2, the gas release phenomenon begins sharply.

[0099] The MOF used in the adsorbent 21 is not particularly limited, and a MOF with high adsorption and desorption performance for specific gases such as carbon dioxide is preferred. For example, it is known that the adsorption and desorption performance of carbon dioxide on MOF is greatly affected by the presence of metal sites (open metal sites) with strong coordination of oxygen atoms of carbon dioxide, the specific surface area of ​​MOF and the flexibility of MOF. In the low-pressure region (below 0.1 MPa), the adsorption and desorption performance of carbon dioxide on MOF is easily affected by the presence of the above-mentioned metal sites. In the high-pressure region (above 0.1 MPa), the adsorption and desorption performance of carbon dioxide on MOF tends to improve as the specific surface area increases.

[0100] In MOF, the organic ligand includes a functional group for coordination with the core. In the organic ligand, the number of the functional groups is, for example, more than 1, and may be more than 2, more than 3, or more than 4. The upper limit of the number of the functional groups is not particularly limited, for example, less than 10. The organic ligand preferably has 4 functional groups for coordination with the core. That is, MOF preferably has a 4-dentate organic ligand and a metal ion, a metal cluster or a metal oxide cluster as a core. MOF with such a structure has a tendency to have a large specific surface area, and is easy to adsorb and desorb specific gases such as carbon dioxide.

[0101] MOFs can be composed of tetradentate organic ligands and metal ions, metal clusters or metal oxide clusters as cores.

[0102] Examples of the metal contained in the core include Cu, Zn, Pd, Mg, Al, Fe, Cr, Zr, Ni, and Co.

[0103] The metal ion used as the core is preferably Cu 2+ 、Zn 2+ 、Al 3+ 、Co 2+ etc., more preferably Cu 2+ .

[0104] The metal cluster as the core may be a Zn cluster. Examples of MOFs having a Zn cluster include MOF-5.

[0105] The metal oxide cluster as the core may be a Zr oxide cluster. Examples of MOFs having a Zr oxide cluster include UiO-66.

[0106] As described above, the organic ligand includes a functional group for coordination with the core. The functional group may be at least one selected from the group consisting of a carboxyl group and a hydroxyl group. The functional group may be a carboxyl group. The organic ligand may be a tetracarboxylic acid containing four carboxyl groups as a functional group for coordination with the core.

[0107] The organic ligand may contain a nitrogen atom (specifically, a functional group containing a nitrogen atom) in addition to the above functional groups. Examples of the functional group containing a nitrogen atom include an amide group, an azo group, and an amino group. Tetracarboxylic acid as an organic ligand may contain a nitrogen atom.

[0108] The organic ligand may contain a ring structure. The number of ring structures contained in the organic ligand is, for example, more than 1, or more than 2, or more than 3. The upper limit of the number of ring structures is, for example, less than 5. The ring structure is preferably an aromatic ring. The aromatic ring may be composed only of carbon atoms, or a heteroaromatic ring containing heteroatoms. The aromatic ring may be a monocyclic ring or a polycyclic ring. The number of carbon atoms in the aromatic ring is not particularly limited, and is, for example, 4 to 14. Specific examples of aromatic rings include benzene rings, naphthalene rings, and the like. In the organic ligand, the functional group used for coordination with the core may be a substituent of the ring structure.

[0109] The organic ligand can be represented by the following formula (a).

[0110] [Chemical formula 1]

[0111]

[0112] In the above formula (a), R 1 is a single bond or an optional linking group. The optional linking group may contain at least one carbon atom. The optional linking group may contain one selected from the group consisting of unsaturated hydrocarbons and heterocyclic compounds. As a linking group containing unsaturated hydrocarbons, for example, arylene groups such as phenylene can be cited. In addition to the above-mentioned linking groups, the optional linking group may further contain a nitrogen-containing functional group (e.g., an amide group, an azo group, an amino group).

[0113] In the above formula (a), R 2 ~R 7 Each of the above is independently a hydrogen atom or an optional substituent. Examples of the optional substituent include hydrocarbon groups such as an alkyl group, a nitro group, and a nitrogen atom-containing functional group such as an amino group.

[0114] As an MOF having an organic ligand having a structure represented by the above formula (a), for example, a MOF having an nbo (niobium oxide) structure can be cited. MOF can have an nbo structure. MOF having an nbo structure tends to have a large specific surface area and a large adsorption amount of specific gases such as carbon dioxide. It should be noted that MOF can also have other structures besides the nbo structure.

[0115] Preferably, the amount of MOF adsorbed by a specific gas in a pressure range of 0.1 MPa to less than 1.1 MPa is greater than the amount of MOF adsorbed by a specific gas in a pressure range of 0 MPa to less than 0.1 MPa. Such a MOF is suitable for the purpose of the gas recovery system 100 of this embodiment.

[0116] As MOF, for example, MOFs listed in the following Table 1 can be used among the materials cited in the literature. It should be noted that the MOFs listed in Table 1 are non-limiting examples, and MOFs other than these can also be used. In Table 1, based on the data on the adsorption amount per unit weight of carbon dioxide at 0.1 to 1.0 MPa at room temperature (20 to 30° C.) recorded in various documents, the difference between the adsorption amount per unit weight of MOF under 1.0 MPa conditions and the adsorption amount per unit weight of MOF under 0.1 MPa conditions is calculated as the effective adsorption amount.

[0117] [Table 1]

[0118]

[0119] As MOF, for example, the MOF shown in the following Table 2 can also be used. It should be noted that the MOF shown in Table 2 is a non-limiting example, and MOFs other than these can also be used. In No. 23 of Table 2, based on the adsorption data of carbon dioxide per unit weight of 0.1 to 1.0 MPa at room temperature (20 to 30°C) recorded in the literature (Nano Res. 14, 2021, 507-511), the difference between the adsorption per unit weight of MOF under 1.0 MPa conditions and the adsorption per unit weight of MOF under 0.1 MPa conditions is calculated as the effective adsorption amount. In No. 24 to 35 in Table 2, each MOF was subjected to vacuum heating pretreatment at 150°C for 6 hours, and then a high-pressure gas adsorption apparatus (manufactured by Anton Paar GmbH, isorbHP1) was used to determine the adsorption amount per unit weight of the MOF under 1.0 MPa conditions at 25°C and the adsorption amount per unit weight of the MOF under 0.1 MPa conditions, and the difference between the two was calculated as the effective adsorption amount.

[0120] [Table 2]

[0121]

[0122] The pore size of MOF shown in Table 1 is relatively large, and the effective adsorption per unit weight is excellent, which is 8 to 14 mmol / g. Therefore, it is considered to be useful for the transportation of specific gases such as carbon dioxide. No. 1 (NOTT-125), No. 3 (HNUST-3), No. 4 (HNUST-7), No. 9 (PCN-11), and No. 10 (PCN-16) have nbo structures. No. 22 (HKUST-1) has the advantage of being cheap and mass-producible.

[0123] It should be noted that there are also MOFs with slightly lower stability to water, such as No. 2 (Cu-TPBTM), No. 3 (HNUST-3), No. 5 (HNUST-5), and No. 22 (HKUST-1) in Table 1. Therefore, for example, when the exhaust gas containing carbon dioxide is directly adsorbed on the MOF, it may not be possible to obtain a sufficient adsorption effect brought about by the MOF, and there is also the possibility that the durability of the MOF is reduced. According to the gas recovery system 100 of this embodiment, since the separated gas Gs after the mixed gas G containing a specific gas such as carbon dioxide is separated by the gas separation device 10 can be adsorbed on the MOF in the recovery unit 20, it is possible to obtain a sufficient adsorption effect brought about by the MOF, and at the same time, it is possible to suppress the reduction of the durability of the MOF.

[0124] Here, in the embodiment of the above-mentioned gas recovery system, the gas separation device is described as a device that separates a mixed gas G containing carbon dioxide to obtain a separated gas Gs having a higher carbon dioxide content than the mixed gas G, and the recovery section is described as a component having an adsorbent that adsorbs carbon dioxide contained in the separated gas Gs. However, in the present invention, the gas separated by the gas separation device and the gas adsorbed by the adsorbent in the recovery section are not limited to carbon dioxide.

[0125] That is, another aspect of the present invention provides a gas recovery system comprising: a gas separation device for separating a mixed gas containing a specific gas to obtain a separated gas having a higher content of the specific gas than the mixed gas;

[0126] The recovery unit has an adsorbent for adsorbing the specific gas contained in the separation gas.

[0127] The adsorbent comprises a metal organic framework (MOF).

[0128] As the gas separation device, for example, the gas separation device 10 described above can be used. As the MOF contained in the adsorbent, for example, the MOF mentioned as the MOF used in the adsorbent 21 can be used.

[0129] [Pressure device]

[0130] The gas recovery system 100 may further include a pressurizing device 30 for pressurizing the separation gas Gs. When the gas recovery system 100 includes the pressurizing device 30, the pressurizing device 30 may be disposed in the front section of the recovery section 20 and pressurize the inside of the recovery section 20. During the adsorption operation, by pressurizing the separation gas Gs using the pressurizing device 30, the adsorption of carbon dioxide on the adsorbent 21 can be promoted. During the desorption operation, by reducing the pressurization using the pressurizing device 30, the desorption of the adsorbed gas Ga from the adsorbent 21 can be promoted.

[0131] The pressurizing device 30 can be a pump that pressurizes the separated gas Gs to the recovery part 20. Typically, the pump is a gas delivery pump, and a reciprocating pump, a rotary pump, etc. can be cited. As a reciprocating pump, a diaphragm pump and a swing piston pump can be cited. As a rotary pump, a liquid seal pump; an oil rotary pump (rotary pump); a mechanical booster pump; various dry pumps such as Roots type, claw type, screw type, turbine type, and vortex type can be cited. The pump as the pressurizing device 30 can also 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, etc. using a variable speed mechanism, the pressure in the recovery part 20 can be appropriately adjusted.

[0132] [Combustion device]

[0133] The gas recovery system 100 may further include a combustion device 40 to which the oxygen-containing fuel gas Gf is supplied and to which the mixed gas G is discharged.

[0134] In the present specification, "combustion device" refers to a device that uses fuel gas to burn fuel and discharge exhaust gas. Examples of the combustion device 40 include boilers, incinerators, internal combustion engines such as engines, etc. Typically, the combustion device 40 is a boiler.

[0135] In the gas recovery system 100 of the present embodiment, the content of carbon dioxide in the separated gas Gs can be increased by separating the mixed gas G discharged from the combustion device 40 using the gas separation device 10. As described above, according to the gas recovery system 100 of the present embodiment, even in a low carbon dioxide concentration range (for example, the content of carbon dioxide in the exhaust gas is 10 vol% or less), the content of carbon dioxide in the separated gas Gs can be increased using the gas separation device 10. The content of carbon dioxide in the separated gas Gs is, for example, 70 vol% or more and 95 vol% or less.

[0136] The combustion device 40 can burn fuel using the fuel gas Gf containing oxygen, and discharge a mixed gas G containing carbon dioxide as exhaust gas.

[0137] The fuel used in the combustion device 40 is not particularly limited. Examples of the fuel include liquid fuels such as petroleum, gaseous fuels such as natural gas, solid fuels such as coal and wood, and special fuels such as waste. The combustion device 40 may also be connected to a fuel supply device (not shown) for supplying fuel.

[0138] The combustion device 40 may include a burner for burning fuel, a fuel supply pipe for supplying fuel to the burner, and a fuel gas supply pipe for supplying the burner with a mixed gas G. In this case, in the combustion device 40, the fuel is burned using the fuel gas Gf supplied to the burner, thereby generating a mixed gas G containing carbon dioxide.

[0139] The oxygen content in the fuel gas Gf supplied to the combustion device 40 is not particularly limited. The oxygen content in the fuel gas Gf is, for example, 20 vol% or more. If the oxygen content in the fuel gas Gf is 20 vol% or more, the carbon dioxide content in the mixed gas G discharged from the combustion device 40 can be increased. Therefore, the separation power of the gas separation device 10 can be reduced. In the present specification, the oxygen content (vol%) in the fuel gas Gf is the volume ratio of oxygen to the fuel gas Gf under standard conditions.

[0140] The upper limit of the oxygen content in the fuel gas Gf supplied to the combustion device 40 is not particularly limited. The upper limit of the oxygen content in the fuel gas Gf is, for example, 100 vol%. The oxygen content in the fuel gas Gf may be 90 vol% or less, 80 vol% or less, or 70 vol% or less.

[0141] The combustion device 40 may also be connected to a gas supply unit (not shown) that supplies the fuel gas Gf to the combustion device 40. The gas supply unit may be a tank or a gas cylinder that stores the fuel gas Gf. The gas supply unit may include a gas generating device that generates the fuel gas Gf from the air. The fuel gas Gf generated by the gas generating device may be configured to be stored in the above-mentioned gas tank or gas cylinder.

[0142] [Gas Path]

[0143] The gas recovery system 100 may further include a gas supply path 61 , a permeated gas exhaust path 62 , and a non-permeated gas exhaust path 63 as gas paths.

[0144] The gas supply path 61 is a path for supplying the mixed gas G from the combustion device 40 to the gas separation device 10 during the adsorption operation, and is connected to the gas outlet 40 b of the combustion device 40 and the supply space inlet 13 a of the gas separation device 10 .

[0145] The permeated gas discharge path 62 is a path for discharging the permeated gas S1 from the gas separation device 10 during operation, and is connected to the permeation space outlet 14b of the gas separation device 10 and the gas inlet 20a of the recovery unit 20. For example, a pump for controlling the flow rate of the permeated gas S1 may be disposed in the permeated gas discharge path 62. The non-permeated gas discharge path 63 is a path for discharging the non-permeated gas S2 from the gas separation device 10 during operation, and is connected to the supply space outlet 13b of the gas separation device 10. For example, a pump for controlling the flow rate of the non-permeated gas S2 may be disposed in the non-permeated gas discharge path 63.

[0146] exist Figure 1 In the example of FIG. 6 , a pressurizing device 30 is disposed in the transmitted gas exhaust path 62 . The pressurizing device 30 can pressurize the inside of the recovery unit 20 .

[0147] The gas recovery system 100 may further include a gas discharge path 71 as a gas path. The gas discharge path 71 is connected to the gas outlet 20b of the recovery unit 20. The gas discharge path 71 is used as a path for discharging the non-adsorbed gas Gn from the recovery unit 20 during adsorption operation. The gas discharge path 71 is used as a path for discharging the adsorbed gas Ga containing carbon dioxide from the recovery unit 20 during desorption operation. Figure 1 In the example of FIG. 5 , a pressure regulating valve 50 is arranged in the gas exhaust path 71 .

[0148] Unless otherwise specified, each gas path of the gas recovery system 100 is formed of, for example, a pipe made of metal or resin.

[0149] When the gas separation device 10 adopts a decompression method, the gas recovery system 100 may further include a decompression device (not shown) for decompressing the permeation space side of the gas separation device 10. When the gas separation device 10 adopts a pressurization method, the gas recovery system 100 may further include a pressurizing device (not shown) for pressurizing the non-permeation space side of the gas separation device 10. As the decompression device or the pressurizing device, the device described above as the pump used in the pressurizing device 30 can be used. When the gas separation device 10 adopts a scavenging method, the gas recovery system 100 may further include a supply device (not shown) for supplying inert gas, dry air, etc. to the permeation space side of the gas separation device 10.

[0150] The gas recovery system 100 may further include a control device 60 for controlling the various components of the gas recovery system 100. The control device 60 is, for example, a DSP (digital signal processor) including an A / D conversion circuit, an input / output circuit, an operation circuit, a storage device, etc. A program for properly operating the gas recovery system 100 is stored in the control device 60. For example, the control device 60 can adjust the pressure in the recovery unit 20 by controlling the operation of the pressurizing device 30, thereby pressurizing the separation gas Gs.

[0151] The gas recovery system 100 may further include a heating device (not shown) for heating the adsorbent 21 of the recovery unit 20. The heating device may be configured without particular limitation as long as it can heat the adsorbent 21 of the recovery unit 20. Typically, the heating device is a heater. During the separation operation, by heating the adsorbent 21 using the heating device, the separation of the adsorbed gas Ga from the adsorbent 21 can be further promoted.

[0152] In the first embodiment, the content of carbon dioxide in the adsorbed gas Ga obtained by the gas recovery system 100 is, for example, 95 vol% or more. Thus, by using the gas recovery system 100, high-purity carbon dioxide can be recovered.

[0153] The use of the carbon dioxide recovered by the gas recovery system 100 of the first embodiment is not particularly limited. For example, the recovered carbon dioxide can be directly used as dry ice after a solidification process. The recovered carbon dioxide can also be reused as a carbon resource (carbon compound).

[0154] [Operation method of gas recovery system]

[0155] The operating method of the gas recovery system 100 of the first embodiment includes: using the gas separation device 10 to separate the mixed gas G to obtain a separated gas Gs having a higher carbon dioxide content than the mixed gas G (step ST1); using the adsorbent 21 of the recovery unit 20 to adsorb the carbon dioxide contained in the separated gas Gs (permeated gas S1) (step ST2).

[0156] In step ST1, the mixed gas G is separated by the gas separation device 10 to obtain the separated gas Gs. When the gas separation device 10 has a separation membrane 11, the mixed gas G is separated by the separation membrane 11 to obtain the separated gas Gs. For the specific implementation method of step ST1, refer to Figure 2 and Figure 3In step ST1 , first, the mixed gas G is supplied from the supply space inlet 13 a to the supply space 13 of the gas separation device 10 . This allows the mixed gas G to contact one surface (eg, the main surface 11 a ) of the separation membrane 11 .

[0157] Next, in a state where the mixed gas G is in contact with one side surface of the separation membrane 11, the space adjacent to the other side surface (e.g., the main surface 11b) of the separation membrane 11 is depressurized. Specifically, the gas passes through the permeation space outlet 14b and depressurizes the permeation space 14. The depressurization in the permeation space 14 can be performed, for example, using a decompression device such as a vacuum pump. The pressure of the permeation space 14 is, for example, 50 kPa or less, and may also be 20 kPa or less, 10 kPa or less, 5 kPa or less, 3 kPa or less, or even 2 kPa or less.

[0158] By reducing the pressure in the permeation space 14, the separation gas Gs, that is, the permeation gas S1 with a high carbon dioxide content can be obtained on the other side surface (e.g., the main surface 11b) of the separation membrane 11. In other words, the permeation gas S1 is supplied to the permeation space 14. The permeation gas S1 passes through the permeation space outlet 14b and is discharged to the outside of the gas separation device 10.

[0159] On the other hand, the carbon dioxide content in the mixed gas G gradually decreases from the supply space inlet 13a to the supply space outlet 13b of the supply space 13. The treated mixed gas G in the supply space 13, i.e., the non-permeated gas S2, passes through the supply space outlet 13b and is discharged to the outside of the gas separation device 10.

[0160] In step ST1, the separation membrane 11 of the gas separation device 10 allows the carbon dioxide contained in the mixed gas G to be preferentially permeated. Therefore, the carbon dioxide content in the permeated gas S1 obtained by the operation of the gas separation device 10 is higher than that in the mixed gas G supplied to the gas separation device 10. The ratio of the carbon dioxide content (wt%) in the permeated gas S1 to the carbon dioxide content (wt%) in the mixed gas G supplied to the gas separation device 10 is not particularly limited.

[0161] In step ST2, carbon dioxide contained in the separation gas Gs (permeated gas S1) is adsorbed by the adsorbent 21 of the recovery unit 20. The adsorption of carbon dioxide by the adsorbent 21 is performed during the adsorption operation. That is, step ST2 is a step corresponding to the adsorption operation.

[0162] In step ST2 , the pressure of the recovery unit 20 during the adsorption operation may be 0.1 MPa or more and less than 1.1 MPa.

[0163] Step ST2 may include pressurizing the separation gas Gs in the recovery unit 20 by the pressurizing device 30. This can promote the adsorption of carbon dioxide to the adsorbent 21 during the adsorption operation.

[0164] The operation method of the gas recovery system 100 may further include desorbing the adsorbed gas Ga containing carbon dioxide from the adsorbent 21 of the recovery unit 20 (step ST3). The desorption of the adsorbed gas Ga from the adsorbent 21 is performed during the desorption operation. That is, step ST3 is a step corresponding to the desorption operation.

[0165] Step ST3 may further include reducing the pressurization of the separation gas Gs in the recovery unit 20 by the pressurizing device 30. In step ST3, the pressure in the recovery unit 20 may be reduced. This can promote the desorption of the adsorbed gas Ga from the adsorbent 21 during the desorption operation.

[0166] Step ST3 may include heating the inside of the recovery unit 20 by using a heating device. Thus, during the desorption operation, desorption of the adsorbed gas Ga from the adsorbent 21 can be further promoted.

[0167] According to step ST3, it is possible to produce the adsorbed gas Ga having a high content of carbon dioxide. In other words, according to step ST3, it is possible to obtain carbon dioxide as the adsorbed gas Ga.

[0168] The method for operating the gas recovery system 100 of the first embodiment may further include supplying the fuel gas Gf containing oxygen to the combustion device 40 and discharging the mixed gas G containing carbon dioxide from the combustion device 40 (step ST4). Step ST4 is performed before step ST1.

[0169] According to the method of operating the gas recovery system 100 of the first embodiment, it is possible to reduce the power required to recover carbon dioxide.

[0170] [Modification 1]

[0171] Figure 4A 1 is a schematic diagram showing a modification 1 of the gas recovery system 100 of the first embodiment. The gas recovery system 101 of the modification 1 further includes a non-adsorbed gas circulation path 73 for conveying at least a part of the non-adsorbed gas Gn to the recovery unit 20 .

[0172] exist Figure 4A In the example, the permeate gas discharge path 62 has a first portion 62A and a second portion 62B. The first portion 62A is a portion connecting the permeate space outlet 14b of the gas separation device 10 and the confluence position 62C, and the second portion 62B is a portion connecting the confluence position 62C and the gas inlet 20a of the recovery unit 20. The pressurizing device 30 is disposed in the second portion 62B. Figure 4A In the example, the gas exhaust path 71 has a first portion 71A and a second portion 71B. The first portion 71A is a portion connecting the gas outlet 20b of the recovery unit 20 and the branch position 71C, and the second portion 71B is a portion extending from the branch position 71C to the outside. Figure 4A In the example of , the non-adsorbed gas circulation path 73 branches from the gas exhaust path 71 at the branch position 71C and merges with the permeated gas exhaust path 62 at the confluence position 62C. With such a configuration, during the adsorption operation, at least a portion of the non-adsorbed gas Gn is mixed with the separation gas Gs and circulates in the second portion 62B, the first portion 71A, and the non-adsorbed gas circulation path 73. By circulating at least a portion of the non-adsorbed gas Gn in the recovery unit 20, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery unit 20 can be increased. In other words, when the separation operation is performed after the adsorption operation, the content of carbon dioxide in the adsorbed gas Ga can be higher than the content of carbon dioxide in the separation gas Gs (permeated gas S1). The content of carbon dioxide in the adsorbed gas Ga is, for example, 95 vol% or more.

[0173] exist Figure 4A In the example of FIG. 7 , the non-adsorbed gas circulation path 73 branches from the gas exhaust path 71 at the branch position 71C and merges with the permeated gas exhaust path 62 at the merging position 62C. However, the connection position of the non-adsorbed gas circulation path 73 is not limited to Figure 4A For example, the non-adsorbed gas circulation path 73 may branch from the gas outlet 20b of the recovery unit 20 and merge with the permeated gas exhaust path 62 at the merging position 62C.

[0174] The operating method of the gas recovery system 101, in addition to the steps of the operating method of the gas recovery system 100 described above, further includes circulating at least a portion of the non-adsorbed gas Gn to the recovery unit 20 during adsorption operation. According to the operating method of the gas recovery system 101, the content of carbon dioxide in the adsorbed gas Ga released from the recovery unit 20 can be increased.

[0175] [Modification 2]

[0176] Figure 4B This is a schematic diagram showing a second modification of the gas recovery system 100 of the first embodiment. The gas recovery system 102 of the second modification further includes a non-adsorbed gas circulation path 75 for conveying at least a portion of the non-adsorbed gas Gn to the gas separation device 10. Hereinafter, the same reference numerals are used for the elements common to the first modification, and the description thereof is sometimes omitted.

[0177] exist Figure 4BIn the example of , the non-adsorbed gas circulation path 75 branches from the gas discharge path 71 at the branch position 71C and merges with the gas supply path 61 at the merging position 61C. With such a configuration, at least a portion of the non-adsorbed gas Gn is mixed with the mixed gas G during the adsorption operation and circulates in the second portion 61B, the permeated gas discharge path 62, the first portion 71A, and the non-adsorbed gas circulation path 75. By circulating at least a portion of the non-adsorbed gas Gn in the gas separation device 10, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery unit 20 can be increased. In other words, when the separation operation is performed after the adsorption operation, the content of carbon dioxide in the adsorbed gas Ga can be higher than the content of carbon dioxide in the separated gas Gs (permeated gas S1). The content of carbon dioxide in the adsorbed gas Ga is, for example, 95 vol% or more.

[0178] exist Figure 4B In the example of FIG. 7 , the non-adsorbed gas circulation path 75 branches from the gas discharge path 71 at the branch position 71C and merges with the gas supply path 61 at the merging position 61C. However, the connection position of the non-adsorbed gas circulation path 75 is not limited to Figure 4B For example, the non-adsorbed gas circulation path 75 may branch from the gas outlet 20b of the recovery unit 20 and merge with the gas supply path 61 at the merging position 61C.

[0179] The operating method of the gas recovery system 102 includes, in addition to the steps of the operating method of the gas recovery system 100, further circulating at least a portion of the non-adsorbed gas Gn to the gas separation device 10 during adsorption operation. According to the operating method of the gas recovery system 102, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery unit 20 can be increased.

[0180] [Variation 3]

[0181] Figure 4C FIG. 2 is a schematic diagram showing a third modification of the gas recovery system 100 of the first embodiment. Figure 4C The gas separation device 10 is omitted. The gas recovery system 103 of the modification 3 includes a plurality of recovery units 20 connected in series, and is configured so that the adsorbed gas Ga discharged from the gas outlet 20b of the recovery unit 20 on the upstream side during the deactivated operation is supplied to the gas inlet 20a of the recovery unit 20 on the downstream side.

[0182] Figure 4CThis is an example in which the first recovery unit 201 and the second recovery unit 202 are connected in series. The adsorbed gas Ga discharged from the gas outlet 201b of the first recovery unit 201 on the upstream side during the separation operation is supplied to the gas inlet 202a of the second recovery unit 202 on the downstream side. With such a structure, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery unit 20 (second recovery unit 202) on the most downstream side can be increased. In other words, when the separation operation is performed after the adsorption operation, the content of carbon dioxide in the adsorbed gas Ga can be higher than the content of carbon dioxide in the separation gas Gs (permeated gas S1). The content of carbon dioxide in the adsorbed gas Ga is, for example, 95 vol% or more.

[0183] In the gas recovery system 103, the gas discharge path 71 connects the gas discharge port 201b of the first recovery unit 201 and the gas inlet 202a of the second recovery unit 202. A pressurizing device 302 for pressurizing the second recovery unit 202 is arranged in the gas discharge path 71. A pressure regulating valve 501 for regulating the pressure of the gas (non-adsorbed gas Gn, adsorbed gas Ga) discharged from the first recovery unit 201 may also be arranged in the gas discharge path 71.

[0184] The gas recovery system 103 further includes a gas discharge path 77 as a gas path. The gas discharge path 77 is connected to the gas discharge port 202b of the second recovery unit 202. In the gas discharge path 77, a pressure regulating valve 502 for regulating the pressure of the gas (non-adsorbed gas Gn, adsorbed gas Ga) discharged from the second recovery unit 202 may also be arranged.

[0185] The operating method of the gas recovery system 103, in addition to the steps of the operating method of the gas recovery system 100, further includes supplying the adsorbed gas Ga discharged from the gas outlet 20b of the recovery unit 20 on the upstream side to the gas inlet 20a of the recovery unit 20 on the downstream side during the decoupling operation. According to the operating method of the gas recovery system 102, the content of carbon dioxide in the adsorbed gas Ga desorbed from the recovery unit 20 on the most downstream side can be increased.

[0186] <Second Embodiment>

[0187] Figure 5This is a schematic diagram showing an example of a gas recovery system 110 according to the second embodiment. The gas recovery system 110 includes a gas separation device 10 and a recovery unit 20. The gas separation device 10 includes a separation membrane 11. The separation membrane 11 separates a mixed gas G containing carbon dioxide into a permeable gas S1 and a non-permeable gas S2. In the second embodiment, the carbon dioxide content of the non-permeable gas S2 is higher than that of the mixed gas G. That is, in the second embodiment, the non-permeable gas S2 is a separated gas Gs. Hereinafter, the same reference numerals are used for elements common to the first embodiment, and descriptions thereof are sometimes omitted.

[0188] [Gas separation device]

[0189] In the second embodiment, the separation membrane 11 is a membrane (nitrogen separation membrane) that allows nitrogen contained in the mixed gas G to preferentially permeate. In this case, the content of carbon dioxide in the permeated gas S1 is lower than the content of carbon dioxide in the mixed gas G. On the other hand, the content of carbon dioxide in the non-permeated gas S2 is higher than the content of carbon dioxide in the mixed gas G. That is, when the separation membrane 11 is a nitrogen separation membrane, the non-permeated gas S2 corresponds to the separation gas Gs.

[0190] (Separation Functional Layer)

[0191] In the second embodiment, the separation functional layer 1 is a layer that allows nitrogen contained in the mixed gas G to preferentially permeate.

[0192] (Middle layer)

[0193] As the intermediate layer 2 , the intermediate layers mentioned as the intermediate layer 2 in the first embodiment can be used.

[0194] (Porous Support)

[0195] As the porous support 3 , the porous support exemplified as the porous support 3 in the first embodiment can be used.

[0196] [Recycling Department]

[0197] The recovery unit 20 includes an adsorbent 21 that adsorbs carbon dioxide contained in the supplied separation gas Gs (non-permeated gas S2). As the adsorbent 21, the adsorbents mentioned as the adsorbent 21 in the first embodiment can be used.

[0198] [Gas Path]

[0199] In the second embodiment, the permeated gas discharge path 62 is connected to the permeation space outlet 14b of the gas separation device 10. The non-permeated gas discharge path 63 is connected to the supply space outlet 13b of the gas separation device 10 and the gas inlet 20a of the recovery unit 20. The pressurizing device 30 is arranged on the non-permeated gas discharge path 63.

[0200] The gas recovery system 110 may further include a gas discharge path 72 as a gas path. The gas discharge path 72 is connected to the gas outlet 20b of the recovery unit 20. The gas discharge path 72 is used as a path for discharging the non-adsorbed gas Gn from the recovery unit 20 during adsorption operation. The gas discharge path 72 is used as a path for discharging the adsorbed gas Ga containing carbon dioxide from the recovery unit 20 during de-operation. In the second embodiment, a pressure regulating valve 50 is arranged on the gas discharge path 72.

[0201] In the second embodiment, the content of carbon dioxide in the adsorbed gas Ga obtained by the gas recovery system 110 is, for example, 95 vol% or more. Thus, by using the gas recovery system 110, high-purity carbon dioxide can be recovered.

[0202] The use of the carbon dioxide recovered by the gas recovery system 110 of the second embodiment is not particularly limited. For example, the recovered carbon dioxide can be directly used as dry ice after a solidification process. The recovered carbon dioxide can also be reused as a carbon resource (carbon compound).

[0203] [Operation method of gas recovery system]

[0204] The operating method of the gas recovery system 110 of the second embodiment includes: separating the mixed gas G by the gas separation device 10 to obtain the separated gas Gs having a higher carbon dioxide content than the mixed gas G (step ST1); and adsorbing the carbon dioxide contained in the separated gas Gs (non-permeable gas S2) by the adsorbent 21 of the recovery unit 20 (step ST2). The operating method of the second embodiment is basically the same as the operating method of the first embodiment, except that the separated gas Gs is the non-permeable gas S2. In the following, only the steps different from the operating method of the first embodiment are described, and the description of other steps is omitted.

[0205] In step ST1, the space adjacent to the other side surface (e.g., the main surface 11b) of the separation membrane 11 is depressurized while the mixed gas G is in contact with one side surface of the separation membrane 11. By depressurizing the inside of the permeation space 14, a permeation gas S1 having a high nitrogen content and a low carbon dioxide content can be obtained on the other side surface (e.g., the main surface 11b) of the separation membrane 11. In other words, the permeation gas S1 is supplied to the permeation space 14. The permeation gas S1 passes through the permeation space outlet 14b and is discharged to the outside of the gas separation device 10.

[0206] On the other hand, the carbon dioxide content in the mixed gas G gradually increases from the supply space inlet 13a to the supply space outlet 13b of the supply space 13. The treated separation gas Gs in the supply space 13, i.e., the non-permeated gas S2, passes through the supply space outlet 13b and is discharged to the outside of the gas separation device 10.

[0207] In step ST1, nitrogen contained in the mixed gas G can be preferentially permeated by the separation membrane 11 of the gas separation device 10. Therefore, the non-permeated gas S2 obtained by the operation of the gas separation device 10 has a higher carbon dioxide content than the mixed gas G supplied to the gas separation device 10. The ratio of the carbon dioxide content (wt%) in the non-permeated gas S2 to the carbon dioxide content (wt%) in the mixed gas G supplied to the gas separation device 10 is not particularly limited.

[0208] In step ST2 , carbon dioxide contained in the separation gas Gs (non-permeated gas S2 ) is adsorbed by the adsorbent 21 of the recovery unit 20 .

[0209] According to the operating method of the gas recovery system 110 of the second embodiment, the power for recovering carbon dioxide can be reduced.

[0210] [Modification 1]

[0211] Fig. 6A 1 is a schematic diagram showing a modification 1 of the gas recovery system 110 of the second embodiment. The gas recovery system 111 of the modification 1 further includes a non-adsorbed gas circulation path 74 for conveying at least a portion of the non-adsorbed gas Gn to the recovery unit 20. The gas recovery system 111 is a modification corresponding to the modification 1 of the first embodiment.

[0212] exist Fig. 6AIn the example of FIG. 1 , the non-permeable gas discharge path 63 includes a first portion 63A and a second portion 63B. The first portion 63A is a portion connecting the permeable space outlet 14b of the gas separation device 10 and the confluence position 63C, and the second portion 63B is a portion connecting the confluence position 63C and the gas inlet 20a of the recovery unit 20. The pressurizing device 30 is disposed in the second portion 63B. In the gas recovery system 111, Fig. 6A In the example, the gas exhaust path 72 has a first portion 72A and a second portion 72B. The first portion 72A is a portion connecting the gas outlet 20b of the recovery unit 20 and the branch position 72C, and the second portion 72B is a portion extending from the branch position 72C to the outside. Fig. 6A In the example of , the non-adsorbed gas circulation path 74 branches from the gas exhaust path 72 at the branch position 72C and merges with the non-permeated gas exhaust path 63 at the confluence position 63C. With such a configuration, at least a portion of the non-adsorbed gas Gn is mixed with the separation gas Gs during the adsorption operation and circulates in the second portion 63B, the first portion 72A, and the non-adsorbed gas circulation path 74. By circulating at least a portion of the non-adsorbed gas Gn in the recovery section 20, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery section 20 can be increased. In other words, when the separation operation is performed after the adsorption operation, the content of carbon dioxide in the adsorbed gas Ga can be higher than the content of carbon dioxide in the separation gas Gs (non-permeated gas S2). The content of carbon dioxide in the adsorbed gas Ga is, for example, 95 vol% or more.

[0213] exist Fig. 6A In the example of FIG. 7 , the non-adsorbed gas circulation path 74 branches from the gas exhaust path 72 at the branch position 72C and merges with the non-permeated gas exhaust path 63 at the merging position 63C. However, the connection position of the non-adsorbed gas circulation path 74 is not limited to Fig. 6A For example, the non-adsorbed gas circulation path 74 may branch from the gas outlet 20b of the recovery unit 20 and merge with the non-permeated gas exhaust path 63 at the merging position 63C.

[0214] The operating method of the gas recovery system 111 further includes, in addition to the steps of the operating method of the gas recovery system 110, circulating at least a portion of the non-adsorbed gas Gn to the recovery unit 20 during adsorption operation. According to the operating method of the gas recovery system 111, the content of carbon dioxide in the adsorbed gas Ga released from the recovery unit 20 can be increased.

[0215] [Modification 2]

[0216] Figure 6BThis is a schematic diagram showing a modified example 2 of the gas recovery system 110 of the second embodiment. The gas recovery system 112 of the modified example 2 further includes a non-adsorbed gas circulation path 76 for conveying at least a portion of the non-adsorbed gas Gn to the gas separation device 10. The gas recovery system 112 is a modified example corresponding to the modified example 2 of the first embodiment. Hereinafter, the same reference numerals are used for the elements common to the gas recovery system 111 of the modified example 1, and the description is sometimes omitted.

[0217] exist Figure 6B In the example of FIG. 1 , the gas supply path 61 includes a first portion 61A and a second portion 61B. The first portion 61A is a portion connected to the merging position 61C, and the second portion 61B is a portion connecting the merging position 61C and the supply space inlet 13a of the gas separation device 10. Figure 6B In the example of , the non-adsorbed gas circulation path 76 branches from the gas discharge path 72 at the branch position 72C and merges with the gas supply path 61 at the merging position 61C. With such a configuration, at least a portion of the non-adsorbed gas Gn is mixed with the mixed gas G during the adsorption operation and circulates in the second portion 61B, the non-permeable gas discharge path 63, the first portion 72A, and the non-adsorbed gas circulation path 76. By circulating at least a portion of the non-adsorbed gas Gn in the gas separation device 10, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery unit 20 can be increased. In other words, when the separation operation is performed after the adsorption operation, the content of carbon dioxide in the adsorbed gas Ga can be higher than the content of carbon dioxide in the separated gas Gs (permeated gas S1). The content of carbon dioxide in the adsorbed gas Ga is, for example, 95 vol% or more.

[0218] exist Figure 6B In the example of FIG. 7 , the non-adsorbed gas circulation path 76 branches from the gas discharge path 72 at the branch position 72C and merges with the gas supply path 61 at the merging position 61C. However, the connection position of the non-adsorbed gas circulation path 76 is not limited to Figure 6B For example, the non-adsorbed gas circulation path 76 may branch from the gas outlet 20b of the recovery unit 20 and merge with the gas supply path 61 at the merging position 61C.

[0219] The operating method of the gas recovery system 112 includes, in addition to the steps of the operating method of the gas recovery system 110, further circulating at least a portion of the non-adsorbed gas Gn to the gas separation device 10 during adsorption operation. According to the operating method of the gas recovery system 112, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery unit 20 can be increased.

[0220] [Variation 3]

[0221] Figure 6C FIG. 2 is a schematic diagram showing a third modification of the gas recovery system 110 of the second embodiment. Figure 6C , the gas separation device 10 is omitted. The gas recovery system 113 of the modification 3 includes a plurality of recovery units 20 connected in series, and is configured in such a way that the adsorbed gas Ga discharged from the gas outlet 20b of the recovery unit 20 on the upstream side during the deactivation operation is supplied to the gas inlet 20a of the recovery unit 20 on the downstream side. The gas recovery system 113 is a modification corresponding to the modification 3 of the first embodiment.

[0222] Figure 6C This is an example in which the first recovery unit 201 and the second recovery unit 202 are connected in series. The adsorbed gas Ga discharged from the gas outlet 201b of the first recovery unit 201 on the upstream side during the separation operation is supplied to the gas inlet 202a of the second recovery unit 202 on the downstream side. With such a structure, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery unit 20 (second recovery unit 202) on the most downstream side can be increased. In other words, when the separation operation is performed after the adsorption operation, the content of carbon dioxide in the adsorbed gas Ga can be higher than the content of carbon dioxide in the separation gas Gs (non-permeable gas S2). The content of carbon dioxide in the adsorbed gas Ga is, for example, 95 vol% or more.

[0223] In the gas recovery system 113, the gas discharge path 72 connects the gas discharge port 201b of the first recovery unit 201 and the gas inlet 202a of the second recovery unit 202. A pressurizing device 302 for pressurizing the inside of the second recovery unit 202 is arranged in the gas discharge path 72. A pressure regulating valve 501 for regulating the pressure of the gas (non-adsorbed gas Gn, adsorbed gas Ga) discharged from the first recovery unit 201 may also be arranged in the gas discharge path 72.

[0224] The gas recovery system 113 further includes a gas discharge path 78 as a gas path. The gas discharge path 78 is connected to the gas discharge port 202b of the second recovery unit 202. In the gas discharge path 78, a pressure regulating valve 502 for regulating the pressure of the gas (non-adsorbed gas Gn, adsorbed gas Ga) discharged from the second recovery unit 202 may also be arranged.

[0225] The operating method of the gas recovery system 113, in addition to the steps of the operating method of the gas recovery system 110, further includes supplying the adsorbed gas Ga discharged from the gas outlet 20b of the upstream recovery unit 20 to the gas inlet 20a of the downstream recovery unit 20 during adsorption operation. According to the operating method of the gas recovery system 113, the content of carbon dioxide in the adsorbed gas Ga separated from the recovery unit 20 on the most downstream side can be increased.

[0226] [Other examples of gas separation devices]

[0227] When the gas separation device 10 has the separation membrane 11 , the gas separation device 10 may be a spiral membrane element, a hollow fiber membrane element, a coil-type membrane element in which a plurality of pervaporation membranes are stacked, a plate-and-frame membrane element, or the like. Figure 7 FIG. 1 is a schematic diagram showing an expanded stereogram of a spiral membrane element. The gas separation device 10 can be Figure 7 The spiral membrane element shown. Figure 7 The gas separation device 10 (membrane element) includes a central tube 16 and a stacked body 17 having a separation membrane 11 and wound around the central tube 16 .

[0228] The center tube 16 has a cylindrical shape. A through hole 16h is formed on the surface of the center tube 16 for allowing the permeating gas S1 to flow into the center tube 16. The number of through holes 16h is not particularly limited, and may be one or more than two. Examples of the material of the center tube 16 include resins such as acrylonitrile / butadiene / styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); and metals such as stainless steel and titanium. The inner diameter of the center tube 16 is, for example, in the range of 20 to 100 mm.

[0229] The gas separation device 10 has a plurality of stacks 17. Each stack 17 includes a separation membrane 11 and a supply side flow path material 18. For example, in the stack 17, a supply side flow path material 18 is arranged between the separation membrane 11 folded into two layers in such a manner that the separation functional layer 1 of the separation membrane 11 is located on the inner side. The supply side flow path material 18 ensures a space (supply space) as a flow path for the mixed gas G between the separation membrane 11 folded into two layers. In this way, the supply side flow path material 18 is used in combination with the separation membrane 11. The number of stacks 17 is not particularly limited, and is, for example, 2 to 30.

[0230] The gas separation device 10 further includes a permeate side flow path material 19. The permeate side flow path material 19 is arranged outside the separation membrane 11 folded into two layers. Specifically, a plurality of permeate side flow path materials 19 and a plurality of stacks 17 are alternately stacked. The permeate side flow path material 19 ensures a space (permeate space) between the stacks 17 as a flow path for the permeated gas S1.

[0231] As the supply side flow path material 18 and the permeation side flow path material 19, for example, a net, woven fabric or knitted fabric made of a resin obtained from polyethylene, polypropylene, polyethylene terephthalate (PET), polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.

[0232] The outer peripheral surface of the membrane element is formed by a shell (not shown) made of a material that does not allow gas to pass through. The shell can be made of FRP (fiber reinforced plastic). The membrane element can be accommodated in a housing (not shown).

[0233] Figure 7 The gas separation device 10 (membrane element) can be operated, for example, by the following method. First, a mixed gas G is supplied to one end of the wound stack 17. The center tube 16 is depressurized. As a result, the permeated gas S1 that permeates the separation membrane 11 moves to the inside of the center tube 16. The permeated gas S1 passes through the center tube 16 and is discharged to the outside. The non-permeated gas S2 treated by the gas separation device 10 is discharged to the outside from the other end of the wound stack 17.

[0234] The descriptions of the above-mentioned embodiments can be applied to each other as long as there is no technical contradiction. Furthermore, the above-mentioned embodiments and modifications can be combined with each other as long as there is no technical contradiction.

[0235] Example

[0236] Hereinafter, the present invention will be described in more detail using calculation examples, but the present invention is not limited thereto.

[0237] (Calculation Example 1)

[0238] A carbon dioxide separation membrane with a CO2 permeation rate of 800 GPU, a N2 permeation rate of 26.6 GPU, and a separation coefficient α of 30 was used to separate the Figure 1 The gas recovery system 100 shown in the figure is simulated during operation. The gas recovery system 100 includes a gas separation device 10, a recovery unit 20, a pressurizing device 30, etc. Specifically, in the gas recovery system 100, it is assumed that the above-mentioned carbon dioxide separation membrane is used as the separation membrane of the gas separation device 10. Figure 7The spiral membrane element shown is used as the gas separation device 10. In the operation of the gas separation device 10, it is assumed that a decompression method is adopted. It is assumed that the MOF No. 22 (HKUST-1) in Table 1 is used as the adsorbent possessed by the recovery unit 20. It should be noted that for HKUST-1, the adsorption selectivity of carbon dioxide is 3.2, and the various adsorption amounts when the adsorption conditions of the gas containing carbon dioxide are assumed to depend on the partial pressure. It is assumed that the pressure in the recovery unit 20 during the adsorption operation is adjusted to 1.0 MPa by the pressurizing device 30. It is assumed that the pressure in the recovery unit 20 during the separation operation after the adsorption operation is adjusted to 0.1 MPa by the pressurizing device 30.

[0239] In Calculation Example 1, the power (MWh / t-CO2) of carbon dioxide recovery was calculated under the following assumptions. Symmetry, a process simulation software manufactured by Schlumberger, was used for the calculation.

[0240] <Assumptions>

[0241] During the adsorption operation, the content of carbon dioxide in the separation gas Gs (permeated gas S1 ) supplied to the recovery unit 20 was 95 vol %.

[0242] During the deactivation operation, the carbon dioxide content in the adsorbed gas Ga recovered from the recovery unit 20 is 95 vol% to 98.4 vol%. The carbon dioxide content in the adsorbed gas Ga is a value given a range in consideration of the variability of the filling amount of MOF contained in the recovery unit 20.

[0243] (Calculation Example 2)

[0244] The same carbon dioxide separation membrane as in Calculation Example 1 was used to perform Figure 4C The gas recovery system 103 shown in FIG. 1 is a simulation of the operation of the gas recovery system 103. The gas recovery system 103 includes a gas separation device 10, a first recovery unit 201, a second recovery unit 202, and a pressurizing device 30. Specifically, in the gas recovery system 103, it is assumed that the above-mentioned carbon dioxide separation membrane is used as the separation membrane of the gas separation device 10. Figure 7 The spiral membrane element shown is used as the gas separation device 10. In the operation of the gas separation device 10, it is assumed that a decompression method is adopted. As the adsorbent provided in the first recovery unit 201 and the second recovery unit 202, it is assumed that MOF (HKUST-1) No. 22 in Table 1 is used, as in Calculation Example 1. It is assumed that the pressure in the recovery unit 20 during adsorption operation is adjusted to 1.0 MPa by the pressurizing device 30. It is assumed that the pressure in the recovery unit 20 during the separation operation after the adsorption operation is adjusted to 0.1 MPa by the pressurizing device 30.

[0245] In Calculation Example 2, the power of carbon dioxide recovery (MWh / t-CO2) was calculated under the following assumptions. Symmetry, a process simulation software manufactured by Schlumberger, was used for the calculation.

[0246] <Assumptions>

[0247] During the adsorption operation, the content of carbon dioxide in the separation gas Gs (permeated gas S1 ) supplied to the recovery unit 20 was 95 vol %.

[0248] During the deactivation operation, the carbon dioxide content in the adsorbed gas Ga recovered from the recovery unit 20 is 95 vol% or more and 99.5 vol% or less. It should be noted that the carbon dioxide content in the adsorbed gas Ga is a value given a range in consideration of the variability of the filling amount of MOF contained in the first recovery unit 201 and the second recovery unit 202.

[0249] (Calculation Example 3)

[0250] The same carbon dioxide separation membrane as in Calculation Example 1 was used to perform Figure 8 The gas recovery system 200 shown in FIG. 1 is a simulation of the operation of the gas recovery system 200. The gas recovery system 200 includes a combustion device 81, a gas separation device 82, a heat exchanger 83, a pressurizing device 84, etc. The gas recovery system 200 is similar to the gas recovery system 200 in that the heat exchanger 83 is provided instead of the recovery unit 20. Figure 1 The gas recovery system 100 shown is different. Specifically, in the gas recovery system 200, it is assumed that the above-mentioned carbon dioxide separation membrane is used as the separation membrane provided in the gas separation device 82. Figure 7 The spiral membrane element shown is used as the gas separation device 82. It is assumed that a decompression method is adopted in the operation of the gas separation device 82. It is assumed that the separation gas Gs (permeated gas S1) is pressurized by the pressurizing device 84 and cooled by the heat exchanger 83 to be liquefied.

[0251] In Calculation Example 3, the power of carbon dioxide recovery (MWh / t-CO2) was calculated under the following assumptions. Symmetry, a process simulation software manufactured by Schlumberger, was used for the calculation.

[0252] <Assumptions>

[0253] The content of carbon dioxide in the separated gas Gs (permeated gas S1) supplied during the liquefaction process was 95 vol%.

[0254] The content of carbon dioxide in the recovered liquid recovered from the heat exchanger 83 after the liquefaction process is 99 vol% or more.

[0255] (Calculation Example 4)

[0256] The same carbon dioxide separation membrane as in Calculation Example 1 was used to perform Fig. 9 The gas separation system 300 shown in FIG. 1 is a simulation of the operation of the gas separation system 300. The gas separation system 300 includes a combustion device 81 and a gas separation device 82. The gas separation system 300 is different from the gas separation system 300 in that it does not include a heat exchanger 83 and a pressurizing device 84. Figure 8 The gas recovery system 200 shown is different. Specifically, in the gas separation system 300, it is assumed that the above-mentioned carbon dioxide separation membrane is used as the separation membrane provided in the gas separation device 82. Figure 7 The spiral membrane element shown is used as the gas separation device 82. In the operation of the gas separation device 82, it is assumed that a decompression method is adopted.

[0257] In Calculation Example 4, the recovery power of carbon dioxide was calculated when the following assumptions were satisfied. In the calculation, the process simulation software Symmetry manufactured by Schlumberger was used.

[0258] <Assumptions>

[0259] The content of carbon dioxide in the separated gas Gs (permeated gas S1) discharged from the gas separation device 82 was 98 vol%.

[0260] It should be noted that, for calculation examples 1 to 2, the sum of the separation power of the gas separation device 10 and the compression power of the pressurizing device 30 is regarded as the recovery power of carbon dioxide. Regarding the separation power of the gas separation device 10, the calculation is assumed to be cooling power, a vacuum pump (efficiency 40%) and a pressurizing pump (efficiency 70%). For calculation example 3, the separation power of the gas separation device 82 and the liquefaction power of the heat exchanger 83 (the sum of the compression power and the cooling power) are regarded as the recovery power of carbon dioxide. For calculation example 4, the separation power of the gas separation device 80 is regarded as the recovery power of carbon dioxide. Use an estimated value (>0.25MWh / t-CO2) as the liquefaction power of the heat exchanger 83.

[0261] Table 3 shows the simulation results of Calculation Examples 1 to 4 together with the dimensions of the installation area required for each system.

[0262] [Table 3]

[0263]

[0264] From the comparison of the simulation results of Calculation Examples 1 to 2 and Calculation Examples 3 to 4 in Table 3, it can be seen that when the gas recovery system of the above-mentioned embodiment is operated, the recovery power of carbon dioxide can be reduced. From the comparison of the simulation results of Calculation Examples 1 to 3 and Calculation Example 4, it can be seen that by making the content of carbon dioxide in the separation gas supplied to the gas separation device 95 vol% or less, the separation power of the gas separation device can be reduced.

[0265] It should be noted that, compared with the systems of Calculation Examples 1 to 2, the system of Calculation Example 3 has a much larger installation area required for the system due to the equipment (pressurizing device and heat exchanger) used for the liquefaction process. Although the records in Table 3 are omitted, it can be seen that when a mixed gas containing carbon dioxide is separated by a system using a chemical absorption method (a method of chemically absorbing carbon dioxide into an absorption liquid using solvents such as amines for separation) rather than a membrane separation method, the installation area required for the system is much larger than that of the systems of Calculation Examples 1 to 2. From these results, it can be seen that the systems of Calculation Examples 1 to 2 are also suitable for compactness of the system.

[0266] Industrial Applicability

[0267] The gas recovery system of this embodiment is suitable for efficiently recovering specific gases such as carbon dioxide from mixed gases. The gas recovery system of this embodiment is particularly suitable for efficiently recovering carbon dioxide from exhaust gas discharged from a combustion device and having a carbon dioxide content of 10 vol% or less.

Claims

1. A gas recovery system having: a gas separation device for separating a mixed gas containing a specific gas to obtain a separated gas having a higher content of the specific gas than that of the mixed gas; and The recovery unit includes an adsorbent that adsorbs the specific gas included in the separation gas.

2. The gas recovery system according to claim 1, wherein: The specific gas is carbon dioxide.

3. The gas recovery system according to claim 1, wherein: The gas separation device includes a separation membrane for separating the mixed gas.

4. The gas recovery system according to claim 1, wherein: The adsorbent comprises a metal-organic structure.

5. The gas recovery system according to claim 4, wherein: The metal organic structure has a tetradentate organic ligand and a metal ion, a metal cluster or a metal oxide cluster as a core.

6. The gas recovery system according to claim 5, wherein: The organic ligand comprises a tetracarboxylic acid.

7. The gas recovery system according to claim 6, wherein: The tetracarboxylic acid contains a nitrogen atom.

8. The gas recovery system according to claim 4, wherein: The metal organic structure has an nbo structure.

9. The gas recovery system according to claim 4, wherein: The amount of the specific gas adsorbed to the metal-organic structure within the pressure range of 0.1 MPa to less than 1.1 MPa is greater than the amount of the specific gas adsorbed to the metal-organic structure within the pressure range of 0 MPa to less than 0.1 MPa.

10. The gas recovery system of claim 1, wherein: The content of the specific gas in the separation gas is 95 vol% or less.

11. The gas recovery system of claim 10, wherein: The content of the specific gas in the separation gas is 70 vol% or more.

12. The gas recovery system according to claim 1, further comprising a pressurizing device for pressurizing the separated gas.

13. The gas recovery system of claim 1, wherein: When a desorption operation is performed to desorb the adsorbed gas containing the specific gas from the adsorbent after an adsorption operation is performed to adsorb the specific gas contained in the separation gas onto the adsorbent, the content of the specific gas in the adsorbed gas is higher than the content of the specific gas in the separation gas.

14. The gas recovery system of claim 13, wherein: The recovery unit further comprises a container, a gas inlet and a gas outlet, During the adsorption operation, the non-adsorbed gas is discharged from the gas discharge port. 15 . The gas recovery system according to claim 14 , further comprising a non-adsorbed gas circulation path for conveying at least a portion of the non-adsorbed gas to the recovery unit or the gas separation device.

16. The gas recovery system according to claim 14, comprising a plurality of said recovery units connected in series with each other, During the desorption operation, the adsorbed gas exhausted from the gas exhaust port of the recovery unit on the upstream side is supplied to the gas introduction port of the recovery unit on the downstream side.

17. The gas recovery system according to claim 1, further comprising a combustion device to which the oxygen-containing fuel gas is supplied and to discharge the mixed gas.

18. The gas recovery system of claim 17, wherein: The combustion device comprises a boiler.

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