Gas separation system and gas separation method

Abstract

A gas separation system (1) has an adsorption device (11) and a separation membrane device (12). A mixed gas that includes a target gas is introduced into the adsorption device (11). A displacement gas is also introduced into the adsorption device (11), at least some of the gas discharged from the adsorption device (11) at this time is guided to a space on the non-permeable side of the separation membrane device (12) to acquire a first enriched gas obtained by enriching the target gas using the separation membrane. Alternatively, after the introduction of the displacement gas, a second enriched gas that is an enriched target gas can be obtained by discharging gas from the adsorption device (11) while desorbing or dissipating the target gas from the adsorbent.

Description

[Technical Field]

[0001] The present invention relates to a technique for obtaining a gas enriched in a target gas from a mixed gas. [Reference to Related Application] This application claims the benefit of priority from Japanese Patent Application JP2021-160292, filed on September 30, 2021, the entire disclosure of which is incorporated herein by reference. [Background technology]

[0002] As exemplified by JP 61-230715 A (Reference 1), JP 2008-247632 A (Reference 2), JP 2008-247636 A (Reference 3), JP 2012-236134 A (Reference 4), and JP 2021-49482 A (Reference 5), proposals have been made to combine a pressure swing adsorption (PSA) system with a separation membrane system to obtain desired gases from mixed gases. In Reference 1, converter exhaust gas containing CO, CO₂, HO, N₂, HO, and O₂ is introduced into an adsorption system, where HO, CO₂, and CO are adsorbed and separated onto an adsorbent. Then, CO₂ and HO are separated from the mixed gas by permeating through a separation membrane. The permeated gas is used as a cleaning gas to purge the remaining gas after the adsorption process in the adsorption system is completed.

[0003] In References 2 and 3, components other than H2 in a gas containing H2 and CO2 are adsorbed onto an adsorbent in a PSA unit, and a first hydrogen-rich gas is extracted as product hydrogen. The PSA off-gas is passed through a hydrogen separation membrane and then a CO2 separation membrane, or through a CO2 separation membrane and then a hydrogen separation membrane, and the second hydrogen-rich gas obtained through the hydrogen separation membrane is recycled to the PSA unit.

[0004] In Reference 4, a CO2 separation membrane is used to obtain a permeable gas with a CO2 concentration of 80% or more from a CO2-containing mixed gas, and then a PSA device is used to obtain a CO2-enriched gas with a CO2 concentration of 80% or more from the non-permeable gas.

[0005] In Literature 5, impurities are adsorbed and removed from a feed gas containing at least CO and H in a temperature swing adsorption unit, or a pressure swing adsorption unit and a temperature swing adsorption unit, and a portion of the H is separated in a hydrogen separation unit to obtain a purified gas. The separated H is used as a purge gas in the temperature swing adsorption unit, or a pressure swing adsorption unit and a temperature swing adsorption unit.

[0006] Incidentally, when the target gas to be recovered is a gas that can be adsorbed or absorbed by an adsorbent in a pressure swing adsorption apparatus, it has been conventional to increase recovery efficiency by introducing a high-concentration gas of the same type as the adsorbed gas into the pressure swing adsorption apparatus after adsorption. However, there is a certain amount of gas that cannot be recovered, and there is a demand for technology that can recover gas more efficiently. Summary of the Invention

[0007] The present invention is directed to a gas separation system for obtaining a gas enriched in a target gas from a mixed gas containing the target gas.

[0008] A first aspect of the present invention is a gas separation system for obtaining a gas enriched in a target gas from a mixed gas containing the target gas, the system comprising: an adsorption device having an adsorbent in an internal space that adsorbs or absorbs the target gas; a separation membrane device having a separation membrane that is permeable to the target gas and that guides the target gas from a gas guided to a non-permeate side space of the separation membrane to a permeate side space of the separation membrane; a mixed gas inlet section that introduces a mixed gas containing the target gas into the adsorption device; a replacement gas inlet section that introduces a replacement gas into the adsorption device, the replacement gas having a higher concentration of the target gas than the mixed gas; a gas outlet section that discharges the gas in the adsorption device; a communication path that includes a flow path that guides the gas in the adsorption device to the non-permeate side space of the separation membrane, the communication path having a valve on the flow path; and a control section.

[0009] The control unit controls the mixed gas inlet, the replacement gas inlet, the gas outlet, and the valve, thereby performing the following steps: a) introducing the mixed gas into the adsorption device, causing the adsorbent to adsorb or absorb the target gas, and discharging the gas that was not adsorbed or absorbed by the adsorbent from the adsorption device; b) after step a), introducing the replacement gas into the adsorption device; c) in step b), at least a portion of the gas discharged from the adsorption device is guided to the non-permeation side space of the separation membrane, and a gas in which the target gas is enriched relative to the mixed gas by the separation membrane is obtained from the gas in the non-permeation side space; and d) after step b), discharging the gas from the adsorption device while desorbing or dispersing the target gas from the adsorbent, thereby obtaining a gas enriched relative to the mixed gas.

[0010] According to the gas separation system of the present invention, the target gas can be obtained efficiently.

[0012] Aspects of the present invention 2 is the aspect 1 The gas separation system further comprises a flow path that introduces the gas in the non-permeation side space of the separation membrane to the mixed gas inlet so that the gas can be used as part of the mixed gas.

[0013] Aspects of the present invention 3 is the aspect 1 (Aspect 1 or 2 The gas separation system may further include another adsorption device similar to the adsorption device, and the communication path includes a flow path that guides the gas in the other adsorption device to the non-permeation side space of the separation membrane, and another valve is provided on the flow path.

[0014] The control unit controls the mixed gas inlet, the replacement gas inlet, the gas outlet, the valve, and the other valve to perform the following steps: e) introducing the mixed gas into the other adsorption apparatus; f) introducing the replacement gas into the other adsorption apparatus after step e); g) directing at least a portion of the gas discharged from the other adsorption apparatus in step f) into the non-permeate side space of the separation membrane to obtain a gas enriched in the target gas relative to the mixed gas from the gas in the non-permeate side space by the separation membrane; and h) discharging the gas from the other adsorption apparatus after step f) while desorbing or stripping the target gas from the adsorbent of the other adsorption apparatus, thereby obtaining a gas enriched in the target gas relative to the mixed gas. Here, steps f) to h) are performed while step a) is being performed, and steps b) to d) are performed while step e) is being performed.

[0015] Aspects of the present invention 4 is the aspect 1 (Aspects 1 to 3 In the gas separation system of the above, the target gas is carbon dioxide gas.

[0016] Aspects of the present invention 5 is the aspect Any one of 1 to 4 In the gas separation system, the concentration of the target gas in the replacement gas is 98% or more.

[0017] The present invention is also directed to a gas separation method for obtaining a gas enriched in a target gas from a mixed gas containing the target gas.

[0018] Aspects of the present invention 6is a gas separation method for obtaining a gas enriched in a target gas from a mixed gas containing the target gas, the method comprising the steps of: a) introducing a mixed gas containing the target gas into an adsorption apparatus having an adsorbent in an internal space, allowing the adsorbent to adsorb or absorb the target gas, and discharging from the adsorption apparatus any gas not adsorbed or absorbed by the adsorbent; b) after step a), introducing a replacement gas having a higher concentration of the target gas than the mixed gas into the adsorption apparatus; c) guiding at least a portion of the gas discharged from the adsorption apparatus in step b) into a non-permeate side space of a separation membrane apparatus having a separation membrane that is permeable to the target gas, and obtaining a gas enriched in the target gas relative to the mixed gas from the gas in the non-permeate side space by the separation membrane; and d) after step b), discharging the gas from the adsorption apparatus while desorbing or dispersing the target gas from the adsorbent, thereby obtaining a gas enriched in the target gas relative to the mixed gas.

[0019] According to the gas separation method of the present invention, the target gas can be obtained efficiently.

[0021] Aspects of the present invention 7 is the aspect 6 In the gas separation method of the above, the average concentration of the target gas in the gas introduced into the separation membrane device in the step c) is higher than the concentration of the target gas in the mixed gas.

[0022] Aspects of the present invention 8 is the aspect 6 (Aspect 6 or 7 In the gas separation method of step c), the gas in the non-permeation side space of the separation membrane obtained in step c) is used as part of the mixed gas.

[0023] Aspects of the present invention 9 is the aspect 6 (Aspect 6 Or 8The gas separation method of (1) may further comprise: e) the step of introducing the mixed gas into another adsorption apparatus similar to the adsorption apparatus; f) the step of introducing the replacement gas into the other adsorption apparatus after the step e); g) the step of directing at least a portion of the gas discharged from the other adsorption apparatus in the step f) into the non-permeate side space of the separation membrane apparatus and obtaining a gas enriched in the target gas relative to the mixed gas from the gas in the non-permeate side space by the separation membrane; and h) the step of discharging the gas from the other adsorption apparatus while desorbing or stripping the target gas from the adsorbent of the other adsorption apparatus after the step f), thereby obtaining a gas enriched in the target gas relative to the mixed gas. Here, steps f) to h) are performed while step a) is being performed, and steps b) to d) are performed while step e) is being performed.

[0024] Aspects of the present invention 10 is the aspect 6 (Aspect 6 Or 9 The gas separation method of the above (1), wherein the target gas is carbon dioxide gas.

[0026] Aspects of the present invention 11 is the aspect 6 (Aspect 6 Or 10 The gas separation method of step (c) may further comprise a step of mixing the gas enriched in the target gas obtained in step (c) with the gas enriched in the target gas obtained in step (d).

[0027] Aspects of the present invention 12 is the aspect 6 (Aspect 6 Or 11 In the gas separation method of the above (1), the replacement gas in the step (b) is the gas enriched in the target gas obtained in the step (c), or the gas enriched in the target gas obtained in the step (d). Aspects of the present invention 13 is the aspect Any one of 6 to 12In the gas separation method of claim 1, the concentration of the target gas in the replacement gas is 98% or more.

[0028] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a diagram showing the configuration of a gas separation system. [Figure 2] FIG. 1 is a diagram showing the operation flow of a gas separation system. [Figure 3] FIG. 2 is a diagram for explaining the operation of the gas separation system. [Figure 4] FIG. 2 is a diagram for explaining the operation of the gas separation system. [Figure 5] FIG. 2 is a diagram for explaining the operation of the gas separation system. [Figure 6] FIG. 1 shows a modified example of a gas separation system. [Figure 7] FIG. 10 is a diagram showing another example of a gas separation system. [Figure 8] FIG. 1 is a diagram showing the operation flow of a gas separation system. [Figure 9] FIG. 2 is a diagram for explaining the operation of the gas separation system. [Figure 10] FIG. 2 is a diagram for explaining the operation of the gas separation system. [Figure 11] FIG. 2 is a diagram for explaining the operation of the gas separation system. [Figure 12] FIG. 2 is a diagram for explaining the operation of the gas separation system. [Figure 13] FIG. 1 shows a modified example of a gas separation system. DETAILED DESCRIPTION OF THE INVENTION

[0030] FIG. 1 is a diagram showing the configuration of a gas separation system 1 according to one embodiment of the present invention. The gas separation system 1 obtains a gas enriched in a target gas from a mixed gas containing the target gas. In other words, the target gas is a gas to be recovered from the mixed gas. The term "target gas" refers to a specific type of gas and is one or more of the gas components contained in the mixed gas. The term "mixed gas" refers to a gas in which multiple types of gases are mixed and is a gas supplied to the gas separation system 1. In this embodiment, the target gas is, for example, carbon dioxide gas (hereinafter simply referred to as "CO2"). In this embodiment, the mixed gas is, for example, exhaust gas emitted from a power plant, a waste incineration plant, a steel mill, a cement factory, etc.

[0031] The gas separation system 1 includes an adsorption device 11, a separation membrane device 12, a mixed gas inlet 13, a replacement gas inlet 14, a gas outlet 15, a communication path 161, and a control unit 17. The adsorption device 11 in the present invention is, for example, a pressure swing adsorption (PSA) device, a temperature swing adsorption (TSA (Thermal Swing Adsorption)) device, a pressure and thermal swing adsorption (PTSA (Pressure and Thermal Swing Adsorption)) device, a solid absorption device (a device using a solid absorbent), or the like. The adsorption device 11 has an adsorbent in the internal space of a substantially cylindrical container called an "adsorption tower," for example. The adsorbent in the present invention is a solid that selectively adsorbs or absorbs the target gas. Preferably, an adsorbent that adsorbs or absorbs only the target gas or the largest amount of the target gas is used. The adsorbent may also adsorb or absorb other types of gases besides the target gas. As the adsorbent, various known adsorbents may be used, such as zeolite, molecular sieving carbon, activated carbon, activated alumina, silica gel, silica alumina, metal-organic frameworks (MOFs), and solid amines. Alternatively, a porous material (e.g., porous silica, porous alumina, porous titania, etc.) carrying a substance that absorbs the target gas (so-called "solid absorbent") may be used. The adsorbent may be one or more materials selected from these. When the target gas is CO2, for example, a solid absorbent carrying X-type zeolite, molecular sieving carbon, or amine may be used. Note that the adsorbent is a solid, and liquids such as an aqueous amine solution are not included in the definition. In this embodiment, a case where the adsorption device 11 is a PSA device will be described.

[0032] The separation membrane device 12 has a separation membrane that selectively permeates the target gas. The separation membrane device 12 has a housing (container) that contains the separation membrane, and the housing is divided by the separation membrane into a non-permeate side space into which the gas before separation is introduced and a permeate side space in which the separated gas exists. The separation membrane device 12 may include multiple separation membranes and housings. In the separation membrane device 12, the target gas is introduced into the non-permeate side space of the separation membrane, and then introduced into the permeate side space of the separation membrane. Preferably, a separation membrane that permeates only the target gas or the target gas most is used. The separation membrane may also be permeable to gases other than the target gas. Various known separation membranes may be used, such as zeolite membranes, carbon membranes, silica membranes, polymer membranes, and facilitated transport membranes. A preferred example of the separation membrane is a zeolite membrane formed on a porous support. When the target gas is CO2, for example, a Y-type zeolite membrane, a DDR-type zeolite membrane, a CHA-type zeolite membrane, or the like is used as the separation membrane.

[0033] Gas introduced into the separation membrane device 12 is guided to the non-permeate side space, and gas that can permeate the separation membrane moves to the permeate side space. In the example of FIG. 1, a discharge channel 121 is connected to the non-permeate side space of the separation membrane device 12, and a discharge valve 122 is provided on the discharge channel 121. A communication channel 161 is connected to the non-permeate side space for introducing gas. A recovery channel 123 is connected to the permeate side space, and a recovery valve 124 and a decompression pump 125 are provided on the recovery channel 123. The recovery channel 123 is connected to the recovery tank 18. The discharge valve 122 and the recovery valve 124 are on-off valves.

[0034] In this embodiment, a housing that accommodates a separation membrane is described as the separation membrane device 12, but the discharge channel 121, discharge valve 122, recovery channel 123, recovery valve 124, and pressure reduction pump 125, which are related to gas separation, may also be considered as parts of the separation membrane device 12. Note that other valves (not limited to on-off valves, but may also be pressure adjustment valves (e.g., back pressure valves (same below)) or other types of valves), pressure reduction pumps, compressors, flow paths, etc. may be provided at various locations in relation to the separation membrane device 12. For example, a blower or pressure reduction pump may be provided on the discharge channel 121.

[0035] The mixed gas introduction unit 13 introduces the mixed gas into the adsorption device 11. The mixed gas introduction unit 13 includes a mixed gas supply source 131, a supply path 132, and a supply valve 133 provided on the supply path 132. The supply valve 133 is an on-off valve. The mixed gas supply source 131 is generally a tank that stores the mixed gas, and a blower or pump for delivering the gas may be connected to the tank. The piping that introduces the mixed gas to the supply path 132 may be considered as the mixed gas supply source 131. The mixed gas supply source 131 may also be the source of the mixed gas. The supply path 132 connects the mixed gas supply source 131 and the adsorption device 11. A portion of the supply path 132 near the adsorption device 11 is shared with other flow paths. The mixed gas introduction unit 13 in FIG. 1 is merely an example, and other valves (not limited to on-off valves, but may also be pressure regulating valves or other types of valves), pressure reducing pumps, compressors, flow paths, etc. may be provided in various locations. In addition, between the mixed gas supply source 131 and the adsorption device 11, other devices such as a dehydration device may be installed.

[0036] The concentration of the target gas in the mixed gas is preferably 1% or more and 30% or less, and more preferably 2% or more and 20% or less. When the target gas is CO2, the concentration of the target gas in the mixed gas is preferably 3% or more and 30% or less.

[0037] The replacement gas inlet 14 introduces a replacement gas into the adsorption apparatus 11. The term "replacement gas" refers to a gas supplied to the adsorption apparatus 11 to replace the gas inside the adsorption apparatus 11. The replacement gas is a gas having a higher concentration of the target gas than the mixed gas. The concentration of the target gas in the replacement gas is preferably 95% or more and 100% or less, and more preferably 98% or more and 100% or less.

[0038] The replacement gas introduction unit 14 includes a replacement gas supply source 141, a supply path 142, and a supply valve 143 provided on the supply path 142. The supply valve 143 is an on-off valve. The replacement gas supply source 141 is generally a tank that stores the replacement gas, and a blower or pump for delivering the gas may be connected to the tank. The replacement gas supply source 141 may be a pipe that introduces the replacement gas to the supply path 142. The replacement gas supply source 141 may also be a source of the replacement gas. The supply path 142 connects the replacement gas supply source 141 and the adsorption device 11. A portion of the supply path 142 near the adsorption device 11 is shared with other flow paths. The replacement gas introduction unit 14 in FIG. 1 is merely an example, and other valves (not limited to on-off valves, but may also be pressure regulating valves or other types of valves), pressure reducing pumps, compressors, flow paths, etc. may be provided in various locations.

[0039] The gas discharge unit 15 discharges gas from the adsorption device 11. The gas discharge unit 15 includes a discharge path 151, a discharge valve 152 provided on the discharge path 151, and a pressure reducing pump 153 provided on the discharge path 151. The discharge path 151 connects the adsorption device 11 and the recovery tank 19. The discharge valve 152 is an on-off valve. The gas discharge unit 15 discharges gas from the internal space of the adsorption device 11, thereby causing the gas to be desorbed or diffused from the adsorbent and stored in the recovery tank 19. The gas discharge unit 15 is merely an example, and other valves (not limited to on-off valves, but may also be pressure regulating valves or other types of valves), pressure reducing pumps, compressors, flow paths, etc. may be provided in various locations.

[0040] The communication path 161 connects the adsorption device 11 and the separation membrane device 12. The communication path 161 guides the gas in the adsorption device 11 to the non-permeation side space of the separation membrane. A communication valve 162 is provided on the communication path 161. The communication valve 162 is an on-off valve. A discharge path 163 is connected to the communication path 161 between the adsorption device 11 and the communication valve 162. A discharge valve 164 is provided on the discharge path 163. The discharge valve 164 is an on-off valve.

[0041] The control unit 17 controls each of the above-mentioned components. That is, it controls the valves, pressure reducing pumps, various supply sources, etc. included in each of the above-mentioned components. In particular, the control unit 17 controls the mixed gas inlet unit 13, the replacement gas inlet unit 14, the gas outlet unit 15, and the communication valve 162. Furthermore, it also controls the peripheral components of the adsorption device 11 and the separation membrane device 12 (including those not shown), the outlet valve 164, etc.

[0042] Next, a description will be given of the operation of the gas separation system 1 under the control of the control unit 17. Fig. 2 is a diagram showing the flow of the operation of the gas separation system 1. Figs. 3 to 5 are diagrams for explaining the operation of the gas separation system 1.

[0043] First, as shown in Fig. 3, the mixed gas introduction unit 13 introduces the mixed gas into the adsorption device 11 (step S11). Specifically, the pressure inside the adsorption device 11 is reduced in advance, and the valves 133, 143, 152, 162, and 164 around the adsorption device 11 are closed. Then, the supply valve 133 is opened, and the mixed gas is introduced into the adsorption device 11 from the mixed gas supply source 131 via the supply path 132. Furthermore, when the pressure inside the adsorption device 11 reaches atmospheric pressure or higher, the discharge valve 164 is opened, and further mixed gas is introduced from the mixed gas supply source 131 to the adsorption device 11. As a result, the target gas is adsorbed or absorbed by the adsorbent, and further, the gas that is not adsorbed or absorbed by the adsorbent is discharged from the adsorption device 11 via the discharge path 163. The discharged gas is the adsorbed gas. or absorption It is not necessary that all of the gas that has not been adsorbed is exhausted. The gas that is exhausted from the adsorption device 11 before the adsorbent breaks through, i.e., before the adsorbent can no longer adsorb or absorb the target gas, is depleted gas with a low concentration of the target gas. The exhausted gas may be recovered for use in other applications. Before the adsorbent in the adsorption device 11 breaks through, the supply valve 133 is closed and the supply of the mixed gas to the adsorption device 11 is stopped.

[0044] After step S11, as shown in Fig. 4, replacement gas is introduced into the adsorption device 11 by the replacement gas introduction unit 14 (step S12). Specifically, valves 133 and 164 are closed, supply valve 143 is opened, and communication valve 162 is also opened, thereby introducing replacement gas from replacement gas supply source 141 into the adsorption device 11 via supply path 142. As a result, the gaps in the adsorbent are filled with replacement gas. At this time, the pressure inside the adsorption device 11 is maintained at or above atmospheric pressure in order to suppress desorption or diffusion of the target gas from the adsorbent.

[0045] In step S12, a portion of the mixed gas and replacement gas present in the gaps in the adsorbent is guided to the non-permeate side space of the separation membrane device 12 via the communication path 161. Note that the gas in the initial stage of step S12 is a gas from which the target gas has been removed from the mixed gas, and therefore may be discharged from the discharge path 163 or the discharge path 121. That is, at least a portion of the gas discharged from the adsorption device 11 is guided to the non-permeate side space of the separation membrane. Note that when the pressure inside the separation membrane device 12 is reduced, the discharge valve 122 may remain closed.

[0046] Specifically, the initial portion of the gas discharged from the adsorption device 11 is discharged from the discharge path 163 and is not introduced into the non-permeate side space of the separation membrane. Alternatively, when the initial portion of the gas discharged from the adsorption device 11 is introduced into the non-permeate side space, the recovery valve 124 is closed to prevent gas separation by the separation membrane. This makes it possible to efficiently separate the target gas from the gas discharged from the adsorption device 11 using the separation membrane during gas replacement in the adsorption device 11. Preferably, the average concentration of the target gas in the gas introduced to the separation membrane device 12 is higher than the concentration of the target gas in the mixed gas. This allows the target gas to be efficiently obtained using the separation membrane.

[0047] When gas separation is performed in the separation membrane device 12, valves 164 and 122 are closed, recovery valve 124 is opened, and pressure reduction pump 125 is driven, thereby obtaining a gas (hereinafter referred to as a "first enriched gas") in which the target gas is enriched more than the mixed gas from the gas in the non-permeation side space by the separation membrane (step S13). The first enriched gas is stored in recovery tank 18. The concentration of the target gas in the first enriched gas is preferably 90% or more and 100% or less, and more preferably 98% or more and 100% or less. Gas separation in the separation membrane device 12 may be performed while valves 164 and 122 are open, while the replacement gas is being introduced into the adsorption device 11.

[0048] 5, supply valve 143 and communication valve 162 are closed, exhaust valve 152 is opened, and pressure-reducing pump 153 is driven. This causes gas to be discharged from adsorption device 11 while desorbing or dispersing the target gas from the adsorbent by gas exhaust unit 15. This results in a gas (hereinafter referred to as "second enriched gas") that is more enriched in the target gas than the mixed gas (step S14). The second enriched gas is stored in recovery tank 19 via exhaust path 151. The concentration of the target gas in the second enriched gas is preferably 95% or more and 100% or less, and more preferably 98% or more and 100% or less.

[0049] In the above description, steps S12 and S13 are performed in parallel, but step S13 may be performed in parallel with step S14, or step S13 may be performed between steps S12 and S14. For example, the order of steps S13 and S14 can be changed arbitrarily by providing a buffer tank on communication path 161 and storing the gas discharged from adsorption device 11 in step S12 in the buffer tank. When a buffer tank is provided, steps S13 and S14 are preferably performed in parallel.

[0050] The first enriched gas and the second enriched gas are mixed together as needed (step S15). Of course, the first enriched gas and the second enriched gas do not have to be mixed together.

[0051] The gas remaining in the non-permeate side space of the separation membrane obtained in step S13 is a gas from which the target gas has been removed by the separation membrane, i.e., a depleted gas in which the target gas has been depleted. However, a certain amount of target gas is still contained. Therefore, in order to obtain the target gas more efficiently, it is preferable that the gas remaining in the non-permeate side space be returned to the mixed gas inlet section 13 via the flow path 121a and used as part of the mixed gas. Although not shown in the figure, the gas remaining in the non-permeate side space is appropriately discharged from the discharge path 121 using a decompression pump or the like. The gas discharged from the discharge path 121 may also be collected in a tank.

[0052] The replacement gas in step S12 may be the first enriched gas or the second enriched gas. The enriched gas mixed in step S15 may be used as the replacement gas. The gas discharged from the adsorption device 11 in step S11 may be led to the non-permeation side space of the separation membrane device 12. At this time, the gas discharged from the adsorption device 11 may be subjected to separation of a small amount of target gas in the separation membrane device 12, or may be discharged from the discharge path 121 without separation.

[0053] As described above, in the gas separation system 1, a gas enriched in the target gas (second enriched gas) is obtained from the adsorption device 11, and a gas enriched in the target gas (first enriched gas) is also obtained from the gas discharged during gas replacement in the adsorption device 11 using the separation membrane device 12, thereby enabling the target gas to be obtained efficiently (in the form of enriched gas). Furthermore, not only is the recovery rate of the target gas improved, but an enriched gas with a high concentration of the target gas can also be obtained.

[0054] Next, an example of an experiment conducted assuming specific development of the gas separation system 1 will be described. For the experiment, a gas separation system 1 without the control unit 17 was prepared. In practice, a gas separation system 1 having two or more adsorption devices 11 (see FIG. 7 described later) was prepared, and one of the adsorption devices 11 was used. In addition, X-type zeolite beads were used as the adsorbent for the adsorption device 11. A separation membrane composite consisting of a porous alumina support and a Y-type zeolite membrane was used as the separation membrane for the separation membrane device 12.

[0055] The supply valve 133 of the mixed gas introduction section 13 was opened, and a blower was used to supply a mixed gas with a CO concentration of 10% and an N (nitrogen) concentration of 90% to the adsorption device 11. When the discharge valve 164 was opened, gas with a CO concentration of 5% or less, obtained by adsorption of CO in the mixed gas by the adsorbent, was obtained from the discharge path 163 (step S11).

[0056] Before the adsorbent in the adsorption device 11 broke through, the supply valve 133 was closed to stop the supply of the mixed gas. Thereafter, the supply valve 143 was opened to introduce a replacement gas with a CO2 concentration of 98% or more into the adsorption device 11 at a pressure equal to or higher than atmospheric pressure, thereby replacing the gas in the adsorption device 11 (step S12). At this time, the exhaust valve 164 was closed, the connection valve 162 was opened, and the exhaust valve 122 was closed, and the exhaust gas discharged from the adsorption device 11 was introduced into the separation membrane device 12. The recovery valve 124 was opened, and the permeate side space of the separation membrane device 12 was depressurized to 10 kPa using the decompression pump 125, thereby recovering a gas with a CO2 concentration of 98% or more as a first enriched gas (step S13).

[0057] After gas replacement in the adsorption device 11 was completed, the supply valve 143 was closed to stop the supply of replacement gas, and the communication valve 162 was closed. The exhaust valve 152 was opened, and the pressure inside the adsorption device 11 was reduced to 10 kPa using the vacuum pump 153, thereby recovering a second enriched gas with a CO concentration of 98% or more (step S14). After gas recovery was completed, operation of the vacuum pump 153 was stopped, the exhaust valve 152 was closed, and the adsorption device 11 was sealed. Furthermore, after a certain amount of the first enriched gas was recovered in the separation membrane device 12 and the communication valve 162 was closed in the aforementioned step S13, the exhaust valve 122 of the exhaust path 121 connected to the non-permeation side space was opened, and the pressure was reduced using a vacuum pump (not shown), thereby discharging a gas with a CO concentration of 10% or less. Thereafter, operation of the vacuum pump was stopped, and the exhaust valve 122 was closed, and the separation membrane device 12 was sealed.

[0058] Fig. 6 is a diagram showing a modified example of the gas separation system 1 of Fig. 1. In the gas separation system 1 of Fig. 1, a gas flow is generated by the pressure difference between the reduced pressure by the decompression pumps 125, 153 and a pressure close to normal pressure. On the other hand, in the gas separation system 1 of Fig. 6, the decompression pumps 125, 153 are omitted, and the gas flow is generated by increasing the pressure by the compressors 134, 144. The compressor 134 is provided in the supply channel 132 of the mixed gas inlet 13, and the compressor 144 is provided in the supply channel 142 of the replacement gas inlet 14.

[0059] In the gas separation system 1 of Figure 6, when a mixed gas or replacement gas is introduced into the adsorption device 11, the pressure inside the adsorption device 11 is increased by compressors 134, 144, and the pressure inside the adsorption device 11 is used to discharge gas from the adsorption device 11. Except for this point, the operation of the gas separation system 1 of Figure 6 is similar to the operation of the gas separation system 1 of Figure 1. The gas separation system 1 of Figure 1 is used when the adsorbent adsorbs or absorbs the target gas at atmospheric pressure and desorbs or releases the target gas when the pressure is reduced. On the other hand, the gas separation system 1 of Figure 6 is used when the adsorbent adsorbs or absorbs the target gas at high pressure and desorbs or releases the target gas when the pressure returns to atmospheric pressure.

[0060] Specifically, in order to discharge the gas inside the adsorption apparatus 11 while maintaining a high pressure inside the adsorption apparatus 11 when introducing the mixed gas or replacement gas into the adsorption apparatus 11, a combination of an on-off valve and a pressure regulating valve is used as the discharge valve 164. Furthermore, in order to appropriately discharge the gas from the adsorption apparatus 11, the discharge valve 122 and the valves 152 and 124 also use combinations of on-off valves and a pressure regulating valve. The connection valve 162 may also use a combination of an on-off valve and a pressure regulating valve. Other types of valves and piping elements may be used instead of these valves.

[0061] FIG. 7 is a diagram illustrating another example of a gas separation system 1a. The gas separation system 1a includes two adsorption devices 11a and 11b. The structures of the two adsorption devices 11a and 11b are similar to those of the adsorption device 11 shown in FIG. 1. In the gas separation system 1a, the operation of each adsorption device is similar to that of the gas separation system 1 shown in FIG. 1. That is, the operation of the separation membrane device 12 (and its peripheral components), the mixed gas inlet 13, the replacement gas inlet 14, the gas outlet 15, and other valves is alternately performed for the adsorption device 11a and the adsorption device 11b. Furthermore, by performing operations related to the adsorption device 11a and other operations related to the adsorption device 11b in parallel, an enriched gas in which the target gas concentration is higher than that of the target gas in the mixed gas can be continuously and efficiently obtained. In the following description of the gas separation system 1a, the description of the gas separation system 1 shown in FIG. 1 is referenced, except that two adsorption devices 11a and 11b are provided.

[0062] To achieve the above operation, supply path 132 of mixed gas inlet 13 branches into two, one branched path connected to adsorption apparatus 11a via valve 133a and the other branched path connected to adsorption apparatus 11b via valve 133b. Supply path 142 of replacement gas inlet 14 also branches into two, one branched path connected to adsorption apparatus 11a via valve 143a and the other branched path connected to adsorption apparatus 11b via valve 143b.

[0063] In the discharge path 151 of the gas discharge unit 15, the flow path from the adsorption device 11a is connected to the decompression pump 153 via a valve 152a, and the flow path from the adsorption device 11b is connected to the decompression pump 153 via a valve 152b. To be precise, a partial flow path from the adsorption device 11a and a partial flow path from the adsorption device 11b join together and are connected to the decompression pump 153, and the valve 152a is provided on the partial flow path from the adsorption device 11a, and the valve 152b is provided on the partial flow path from the adsorption device 11b.

[0064] In the communication path 161, the flow path from the adsorption device 11a is connected to the non-permeate side space of the separation membrane device 12 via a communication valve 162a, and the flow path from the adsorption device 11b is connected to the non-permeate side space of the separation membrane device 12 via a communication valve 162b. More precisely, in the communication path 161, a partial flow path from the adsorption device 11a and a partial flow path from the adsorption device 11b join together and are connected to the separation membrane device 12, with a communication valve 162a provided on the partial flow path from the adsorption device 11a and a communication valve 162b provided on the partial flow path from the adsorption device 11b. A discharge path 163a is connected to the flow path from the adsorption device 11a between the adsorption device 11a and the communication valve 162a, and a discharge valve 164a is provided on the discharge path 163a. ​​A discharge path 163b is connected to the flow path from the adsorption device 11b between the adsorption device 11b and the communication valve 162b, and a discharge valve 164b is provided on the discharge path 163b.

[0065] All the valves in the above explanation are on-off valves. 7 1. In FIG. 1, components that are given the same reference numerals as those in FIG. 1 are the same as those in FIG.

[0066] With the above configuration, the mixed gas inlet 13 can introduce the mixed gas into the adsorption devices 11a and 11b individually. The replacement gas inlet 14 can introduce the replacement gas into the adsorption devices 11a and 11b individually. The gas outlet 15 can discharge the gas inside the adsorption devices 11a and 11b individually. The communication path 161 can guide the gas from the adsorption devices 11a and 11b individually to the non-permeation side space of the separation membrane device 12 and can also discharge the gas.

[0067] The control unit 17 controls the above-mentioned components. That is, it controls the valves, pressure reducing pumps, various supply sources, etc. included in the above-mentioned components. In particular, the control unit 17 controls the mixed gas inlet unit 13, the replacement gas inlet unit 14, the gas outlet unit 15, and the communication valves 162a and 162b. Furthermore, it also controls the peripheral components of the adsorption devices 11a and 11b and the separation membrane device 12 (including those not shown), the discharge valves 164a and 164b, etc.

[0068] Figure 8 is a diagram showing the flow of operation of the gas separation system 1a. In normal operation, continuous operation is performed in which the operations shown in Figure 8 are repeated. Figures 9 to 12 are diagrams for explaining the operation of the gas separation system 1a. The operation of the gas separation system 1a under the control of the control unit 17 will be described below.

[0069] First, as shown in FIG. 9, the mixed gas introduction section 13 introduces the mixed gas into the adsorption device 11a (hereinafter also referred to as the "first adsorption device 11a") (step S11a). Specifically, the pressure inside the first adsorption device 11a is reduced in advance, and the valves 133a, 143a, 152a, 162a, and 164a around the first adsorption device 11a are closed. Then, the supply valve 133a is opened, and the mixed gas is introduced from the mixed gas supply source 131 into the first adsorption device 11a via the supply path 132. Furthermore, the discharge valve 164a is opened, and the mixed gas is further introduced from the mixed gas supply source 131 into the first adsorption device 11a. As a result, the target gas is adsorbed or absorbed by the adsorbent in the first adsorption device 11a, and further, the gas that is not adsorbed or absorbed by the adsorbent is discharged from the first adsorption device 11a via the discharge path 163a. ​​Note that the discharged gas is the adsorbed gas. or absorption The discharged gas may be recovered for other uses. Before the adsorbent in the first adsorption device 11a breaks through, the supply of the mixed gas to the adsorption device 11a is stopped.

[0070] Meanwhile, when step S11a is started, the introduction of the mixed gas into adsorption device 11b (hereinafter also referred to as "second adsorption device 11b") is completed, and in parallel with step S11a, replacement gas is introduced into first adsorption device 11b by replacement gas introduction unit 14 (step S12b). Specifically, with valves 133b, 143b, 152b, 162b, and 164b closed, supply valve 143b is opened, and further, communication valve 162b is opened, whereby replacement gas is introduced from replacement gas supply source 141 through supply path 142 into second adsorption device 11b. As a result, the gaps in the adsorbent are filled with replacement gas.

[0071] In step S12b, a portion of the mixed gas and replacement gas present in the gaps in the adsorbent of the second adsorption device 11b is guided to the non-permeation side space of the separation membrane device 12 via the communication path 161. The gas in the initial stage of step S12b may be discharged from the discharge path 163b or the discharge path 121. That is, at least a portion of the gas discharged from the second adsorption device 11b is guided to the non-permeation side space of the separation membrane.

[0072] Specifically, the initial portion of the gas discharged from the second adsorption device 11b is discharged through the discharge path 163b and is therefore not introduced into the non-permeate side space of the separation membrane. Alternatively, when the initial portion of the gas discharged from the second adsorption device 11b is introduced into the non-permeate side space, the recovery valve 124 is closed to prevent gas separation by the separation membrane. This allows the target gas to be efficiently separated from the gas discharged from the second adsorption device 11b by the separation membrane during gas replacement in the second adsorption device 11b. Preferably, the average concentration of the target gas in the gas introduced to the separation membrane device 12 is higher than the concentration of the target gas in the mixed gas. This allows the target gas to be efficiently obtained by the separation membrane.

[0073] When gas separation is performed in the separation membrane device 12, the valves 164b and 122 are closed, the recovery valve 124 is opened, and the decompression pump 125 is driven, thereby obtaining a first enriched gas in which the target gas is enriched more than the mixed gas from the gas in the non-permeation side space by the separation membrane (step S13b). The first enriched gas is stored in the recovery tank 18. The concentration of the target gas in the first enriched gas is preferably 90% or more and 100% or less, and more preferably 98% or more and 100% or less. Gas separation in the separation membrane device 12 may be performed while the valves 164b and 122 are open, while the replacement gas is introduced into the second adsorption device 11b. The explanation of step S13b above also applies to step S13a, which will be described later.

[0074] 10, supply valve 143b and communication valve 162b are closed, exhaust valve 152b is opened, and pressure reduction pump 153 is driven, thereby discharging gas from second adsorption device 11b while desorbing or discharging the target gas from the adsorbent. This results in a second enriched gas in which the target gas is more enriched than in the mixed gas (step S14b). The second enriched gas is stored in recovery tank 19. The concentration of the target gas in the second enriched gas is preferably 95% or more and 100% or less, and more preferably 98% or more and 100% or less.

[0075] In the above description, steps S12b and S13b are performed in parallel, but step S13b may be performed in parallel with step S14b, or step S13b may be performed between steps S12b and S14b. For example, the order of steps S13b and S14b can be changed arbitrarily by providing a buffer tank on communication path 161 and storing the gas discharged from second adsorption device 11b in step S12b in the buffer tank. When a buffer tank is provided, steps S13b and S14b are preferably performed in parallel. The above description of steps S12b through S14b also applies to steps S12a through S14a, which will be described later.

[0076] In order to obtain the target gas more efficiently, it is preferable that the gas remaining in the non-permeation side space obtained in step S13b be returned to the mixed gas inlet part 13 via the flow path 121a and used as part of the mixed gas. Although not shown in the figure, the gas remaining in the non-permeation side space is appropriately discharged from the discharge path 121 using a decompression pump or the like. The gas discharged from the discharge path 121 may also be collected in a tank.

[0077] If steps S12b to S14b are executed while step S11a is being executed, then, as shown in FIG. 11, the mixed gas introduction unit 13 introduces the mixed gas into the second adsorption device 11b (step S11b). Specifically, the second adsorption device 11b is in a reduced pressure state, and valves 133b, 143b, 152b, 162b, and 164b around the second adsorption device 11b are closed. Then, supply valve 133b is opened, and the mixed gas is introduced into the second adsorption device 11b from the mixed gas supply source 131 via supply path 132. Furthermore, exhaust valve 164b is opened, and further mixed gas is introduced from the mixed gas supply source 131 to the second adsorption device 11b. As a result, the target gas is adsorbed or absorbed by the adsorbent in the second adsorption device 11b, and further, the gas that is not adsorbed or absorbed by the adsorbent is discharged from the second adsorption device 11b via exhaust path 163b. Note that the discharged gas is the adsorbed gas. or absorption Not all of the gas that was not adsorbed is discharged. The discharged gas may be recovered for other uses. Before the adsorbent in the second adsorption device 11b breaks through, the supply of the mixed gas to the second adsorption device 11b is stopped.

[0078] Meanwhile, when step S11b is started, the introduction of the mixed gas into the first adsorption device 11a is completed, and in parallel with step S11b, a replacement gas is introduced into the first adsorption device 11a through the replacement gas introduction unit 14 (step S12a). Specifically, with valves 133a, 143a, 152a, 162a, and 164a closed, supply valve 143a is opened, and then communication valve 162a is opened, thereby introducing replacement gas from replacement gas supply source 141 into the first adsorption device 11a via supply path 142. This fills the gaps in the adsorbent with replacement gas. At this time, as in step S12b, at least a portion of the gas discharged from the first adsorption device 11a is introduced into the non-permeation side space of the separation membrane.

[0079] Then, the valves 164a and 122 are closed, the recovery valve 124 is opened, and the decompression pump 125 is driven. This results in a first enriched gas, which is enriched in the target gas relative to the mixed gas, being obtained from the gas in the non-permeation side space by the separation membrane (step S13a). The first enriched gas is stored in the recovery tank 18. Note that separation using the separation membrane may be performed while the valves 164a and 122 are open, while the replacement gas is introduced into the first adsorption device 11a. As shown in FIG. 12, the communication valve 162a is closed, the discharge valve 152a is opened, and the decompression pump 153 is driven. This discharges the gas from the first adsorption device 11a while desorbing or discharging the target gas from the adsorbent. This results in a second enriched gas, which is enriched in the target gas relative to the mixed gas (step S14a). The second enriched gas is stored in the recovery tank 19 via the discharge path 151.

[0080] In order to obtain the target gas more efficiently, it is preferable that the gas remaining in the non-permeation side space obtained in step S13a is returned to the mixed gas inlet part 13 via the flow path 121a and used as part of the mixed gas.

[0081] Thereafter, the process returns to step S11a, and steps S12b to S14b are executed during step S11a. That is, in the gas separation system 1a, steps S12b to S14b are executed while step S11a is being executed, and steps S12a to S14a are executed while step S11b is being executed.

[0082] 1, the first enriched gas and the second enriched gas may be mixed as needed. Furthermore, the first enriched gas or the second enriched gas may be used as the replacement gas in step S12a or step S12b. A mixture of the first enriched gas and the second enriched gas may be used as the replacement gas.

[0083] As described above, in gas separation system 1a, target gas can be efficiently obtained (in the form of enriched gas) by obtaining a gas enriched in target gas (second enriched gas) from adsorption devices 11a and 11b, and also obtaining a gas enriched in target gas (first enriched gas) from the gas discharged during gas replacement in adsorption devices 11a and 11b using separation membrane device 12. Furthermore, by using two adsorption devices 11a and 11b, the first enriched gas and the second enriched gas can be obtained continuously.

[0084] Figure 13 is a diagram showing a modified example of the gas separation system 1a of Figure 7. In the gas separation system 1a of Figure 7, a gas flow is generated by the pressure difference between the reduced pressure by the decompression pumps 125, 153 and a pressure close to normal pressure. In the gas separation system 1a of Figure 13, the decompression pumps 125, 153 are omitted, and the gas flow is generated by increasing the pressure by the compressors 134, 144. The compressor 134 is provided in the supply path 132 of the mixed gas inlet 13, and the compressor 144 is provided in the supply path 142 of the replacement gas inlet 14.

[0085] In the gas separation system 1a of FIG. 13, when a mixed gas or a replacement gas is introduced into the adsorption apparatuses 11a and 11b, the pressure inside the adsorption apparatuses 11a and 11b is increased by the compressors 134 and 144, and the pressure inside the adsorption apparatuses 11a and 11b is used to discharge gas from the adsorption apparatuses 11a and 11b. Except for this point, the operation of the gas separation system 1a of FIG. 13 is similar to the operation of the gas separation system 1a of FIG. 7. The gas separation system 1a of FIG. 7 is used when the adsorbent adsorbs or absorbs the target gas at normal pressure and desorbs or releases the target gas when the pressure is reduced. On the other hand, the gas separation system 1a of FIG. 13 is used when the adsorbent adsorbs or absorbs the target gas at high pressure and desorbs or releases the target gas when the pressure returns to normal.

[0086] In particular, when introducing the mixed gas or replacement gas into the adsorption apparatuses 11a, 11b, in order to discharge the gas inside the adsorption apparatuses 11a, 11b while maintaining high pressure inside the adsorption apparatuses 11a, 11b, the discharge valves 164a, 164b are configured by combining an on-off valve with a pressure regulation valve. Furthermore, in order to appropriately discharge the gas from the adsorption apparatuses 11a, 11b, the discharge valve 122 and the valves 152a, 152b, 124 are also configured by combining an on-off valve with a pressure regulation valve. The connection valves 162a, 162b may also be configured by combining an on-off valve with a pressure regulation valve. Instead of these valves, other types of valves or piping elements may be used.

[0087] The gas separation systems 1, 1a are not limited to those shown in the above embodiments, and various modifications are possible.

[0088] The mixed gas in the above embodiment may be a mixed gas containing two or more types of gases. The target gas may also be a gas containing two or more types of gases (excluding trace amounts of gas). In this case, the number of types of gases contained in the mixed gas is greater than the number of types of gases contained in the target gas. Preferably, the target gas contains two or less types of gases, and more preferably, the target gas is one type of gas. When the target gas contains two or more types of gases, the adsorbent of the adsorption device 11 (including the adsorption devices 11a and 11b; the same applies below) adsorbs or absorbs each of the multiple types of gases that make up the target gas. The separation membrane device 12 also permeates and separates each of the multiple types of gases that make up the target gas. However, the separation membrane of the separation membrane device 12 does not need to selectively permeate all types of gases absorbed or adsorbed by the adsorption device 11; the separation membrane may permeate only some of the types of gases absorbed or adsorbed by the adsorption device 11. That is, the separation membrane device 12 may obtain a gas enriched in all types of gas absorbed or adsorbed by the adsorption device 11, or may obtain a gas enriched in some types, or the separation membrane device 12 may allow only one type of gas to pass through.

[0089] The adsorption device 11 may have an internal space containing an adsorbent that adsorbs or absorbs the target gas depending on the temperature and desorbs or releases the target gas depending on the temperature. The adsorption device 11 may also have an internal space containing an adsorbent that adsorbs or absorbs the target gas depending on the pressure and temperature and desorbs or releases the target gas depending on the pressure and temperature. The adsorbent of the adsorption device 11 may also adsorb or absorb the target gas or desorb or release the target gas using other physical or chemical phenomena. In this case, a device that causes the physical or chemical phenomenon may be installed in or around the adsorption device 11.

[0090] The operation of the gas separation system 1 (including the case of the gas separation system 1a; the same applies below) is preferably automated by the control unit 17, but may also include some operation by an operator. In other words, the gas separation system 1 may operate semi-automatically. Furthermore, the operation of the gas separation system 1 may be entirely performed by an operator.

[0091] The gas separation system 1 may include both a decompression pump and a compressor. That is, the gas flow may be generated by the pressure difference between the decompression by the decompression pump and the pressure increase by the compressor.

[0092] 2, as described above, step S13 (obtaining a first enriched gas) may be performed in parallel with step S12 (introducing a replacement gas), partially in parallel with step S12, or after step S12. Furthermore, step S13 may be performed before step S14 (obtaining a second enriched gas), in parallel with step S12, partially in parallel with step S12, or after step S14. Of course, for efficient operation, step S13 is preferably performed between the start of step S12 and the end of step S14.

[0093] In the operation of Figure 8, the relationship between step S13b and steps S12b and S14b, and the relationship between step S13a and steps S12a and S14a are the same as those of steps S12 to S14. Because steps S11a and S11b typically require time, in order to perform the operation efficiently, in Figure 8, steps S12b to S14b are executed while step S11a is being executed, and steps S12a to S14a are executed while step S11b is being executed. However, if other steps require time, the steps executed in parallel may be changed as appropriate. For example, if steps S14a and S14b require time, steps S11b to S13b may be executed while step S14a is being executed, and steps S11a to S13a may be executed while step S14b is being executed.

[0094] The number of adsorption devices 11 is not limited to one or two. Furthermore, the number of adsorption devices 11 in the above description refers to the unit of equipment containing adsorbents used simultaneously. For example, when multiple adsorption towers are used simultaneously, these multiple adsorption towers correspond to one adsorption device 11 in the above embodiment. The number of adsorption devices 11 may be three or more. Similarly, the number of separation membrane devices 12 is not limited to one but may be two or more. The number of separation membrane devices 12 refers to the unit of equipment containing separation membranes used simultaneously. For example, even when multiple devices containing multiple separation membranes are used simultaneously, they correspond to one separation membrane device 12 (i.e., count as one separation membrane device 12). Preferably, the number of separation membrane devices 12 is less than the number of adsorption devices 11. By providing as many separation membrane devices 12 as there are adsorption devices 11 that discharge gas at the same time, even if the number of adsorption devices 11 is greater than the number of separation membrane devices 12, gas discharged from any of the adsorption devices 11 can be introduced into any of the separation membrane devices 12, thereby efficiently obtaining enriched gas. For example, in another preferred embodiment, the number of adsorption devices 11 is three and the number of separation membrane devices 12 is one.

[0095] The positions at which the mixed gas inlet 13, the replacement gas inlet 14, the gas outlet 15, and the communication path 161 are connected to the adsorption device 11 may be changed as appropriate. For example, the gas outlet 15 may be connected to the communication path 161.

[0096] In order to suppress a decrease in the concentration of the target gas in the second enriched gas, the concentration of the target gas in the replacement gas is preferably equal to or higher than the concentration of the target gas in the second enriched gas.

[0097] In the example of FIG. 1, for example, a mixed gas is introduced into the adsorption device 11 whose internal space is at a pressure lower than atmospheric pressure, and after the internal space reaches atmospheric pressure, the exhaust valve 164 is opened to discharge the gas, and the internal space is filled with the mixed gas. Therefore, the mixed gas is introduced by the mixed gas introduction unit 13 at atmospheric pressure or a pressure slightly higher than atmospheric pressure. The subsequent introduction of the replacement gas is also carried out at atmospheric pressure or a pressure slightly higher than atmospheric pressure. On the other hand, in the example of FIG. 6, the mixed gas and replacement gas are introduced into the adsorption device 11 at a pressure higher than atmospheric pressure by the compressors 134 and 144. Therefore, the mixed gas and replacement gas are introduced into the adsorption device 11 at a pressure equal to or higher than atmospheric pressure.

[0098] On the other hand, in the example of Fig. 1, the replacement gas is discharged from the adsorption device 11 at a pressure lower than atmospheric pressure by the decompression pump 153. Preferably, the internal space of the adsorption device 11 is decompressed to 30 kPa or less by the decompression pump 153. In the example of Fig. 6, the replacement gas is in a compressed state in the internal space of the adsorption device 11, and therefore can be discharged simply by opening the discharge valve 152 of the gas discharge unit 15. Therefore, the gas discharge unit 15 preferably discharges the gas from the adsorption device 11 at a pressure lower than atmospheric pressure.

[0099] As mentioned above, the gas separation system 1 (1a) described in the above embodiment is merely an example, and other components may be arranged in various locations, and the arrangement of each component may also be changed as appropriate.

[0100] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0101] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention. [Explanation of symbols]

[0102] 1,1a Gas Separation System 11,11a,11b Adsorption device 12 Separation membrane device 13 Mixed gas inlet 14 Replacement gas inlet 15 Gas exhaust section 17 Control Unit 121a Channel 161 Access Road 162, 162a, 162b Connecting valve S11~S15, S11a~S14a, S11b~S14b steps

Claims

1. A gas separation system for obtaining a gas enriched in a target gas from a mixed gas containing the target gas, an adsorption device having an adsorbent in an internal space that adsorbs or absorbs the target gas; a separation membrane device having a separation membrane permeable to the target gas, and directing the target gas from a gas directed to a non-permeation side space of the separation membrane to a permeation side space of the separation membrane; a mixed gas inlet that introduces a mixed gas containing the target gas into the adsorption device; a replacement gas inlet that introduces a replacement gas having a higher concentration of the target gas than the mixed gas into the adsorption device; a gas exhaust unit that exhausts gas from the adsorption device; a communication path including a flow path for guiding the gas in the adsorption device to the non-permeation side space of the separation membrane, the communication path having a valve on the flow path; A control unit; Equipped with The control unit controls the mixed gas inlet, the replacement gas inlet, the gas outlet, and the valve, a) introducing the mixed gas into the adsorption device, allowing the adsorbent to adsorb or absorb the target gas, and discharging the gas that has not been adsorbed or absorbed by the adsorbent from the adsorption device; b) introducing the replacement gas into the adsorption apparatus after the step a); c) a step of guiding at least a portion of the gas discharged from the adsorption device in the step b) into the non-permeation side space of the separation membrane, and obtaining a gas in which the target gas is enriched more than the mixed gas by the separation membrane from the gas in the non-permeation side space; d) after the step b), discharging the gas from the adsorption device while desorbing or diffusing the target gas from the adsorbent, thereby obtaining a gas enriched in the target gas relative to the mixed gas; A gas separation system in which

2. 10. The gas separation system of claim 1, The gas separation system further comprises a flow path that introduces the gas in the non-permeation side space of the separation membrane to the mixed gas inlet so that the gas can be used as part of the mixed gas.

3. 10. The gas separation system of claim 1, Further comprising another adsorption device similar to the adsorption device; the communication path includes a flow path that guides the gas in the other adsorption device to the non-permeation side space of the separation membrane, and has another valve on the flow path; The control unit controls the mixed gas inlet, the replacement gas inlet, the gas outlet, the valve, and the other valve, e) introducing the mixed gas into the other adsorption device; f) after the step e), introducing the replacement gas into the other adsorption device; g) a step of guiding at least a portion of the gas discharged from the other adsorption device in the step f) into the non-permeation side space of the separation membrane, and obtaining a gas in which the target gas is enriched more than the mixed gas by the separation membrane from the gas in the non-permeation side space; h) after the step f), a step of obtaining a gas enriched in the target gas compared to the mixed gas by discharging the gas from the other adsorption device while desorbing or diffusing the target gas from the adsorbent of the other adsorption device; is executed, While the step a) is being performed, the steps f) to h) are performed; A gas separation system in which the steps b) to d) are carried out while the step e) is being carried out.

4. 10. The gas separation system of claim 1, A gas separation system in which the target gas is carbon dioxide gas.

5. 5. A gas separation system according to any one of claims 1 to 4, A gas separation system, wherein the concentration of the target gas in the replacement gas is 98% or more.

6. A gas separation method for obtaining a gas enriched in a target gas from a mixed gas containing the target gas, a) introducing a mixed gas containing a target gas into an adsorption device having an adsorbent in an internal space, allowing the adsorbent to adsorb or absorb the target gas, and discharging gas that has not been adsorbed or absorbed by the adsorbent from the adsorption device; b) after the step a), introducing a replacement gas having a higher concentration of the target gas than the mixed gas into the adsorption device; c) guiding at least a portion of the gas discharged from the adsorption device in the b) step into a non-permeation side space of a separation membrane device having a separation membrane permeable to the target gas, and obtaining a gas enriched in the target gas relative to the mixed gas by the separation membrane from the gas in the non-permeation side space; d) after the step b), discharging the gas from the adsorption device while desorbing or diffusing the target gas from the adsorbent, thereby obtaining a gas enriched in the target gas relative to the mixed gas; A gas separation method comprising:

7. 7. The gas separation method according to claim 6, A gas separation method, wherein the average concentration of the target gas in the gas introduced to the separation membrane device in the step c) is higher than the concentration of the target gas in the mixed gas.

8. 7. The gas separation method according to claim 6, A gas separation method, wherein the gas in the non-permeation side space of the separation membrane obtained in the step c) is utilized as part of the mixed gas.

9. 7. The gas separation method according to claim 6, e) introducing the mixed gas into another adsorption apparatus similar to the adsorption apparatus; f) after the step e), introducing the replacement gas into the other adsorption device; g) introducing at least a portion of the gas discharged from the other adsorption device in the f) step into the non-permeation side space of the separation membrane device, and obtaining a gas in which the target gas is enriched more than the mixed gas by the separation membrane from the gas in the non-permeation side space; h) after the step f), a step of obtaining a gas enriched in the target gas compared to the mixed gas by discharging the gas from the other adsorption device while desorbing or diffusing the target gas from the adsorbent of the other adsorption device; Furthermore, While the step a) is being performed, the steps f) to h) are performed; A gas separation method in which the steps b) to d) are carried out while the step e) is being carried out.

10. 7. The gas separation method according to claim 6, A gas separation method wherein the target gas is carbon dioxide gas.

11. 7. The gas separation method according to claim 6, A gas separation method further comprising a step of mixing the gas enriched in the target gas obtained in the step c) and the gas enriched in the target gas obtained in the step d).

12. 7. The gas separation method according to claim 6, A gas separation method, wherein the replacement gas in the step b) is the gas enriched with the target gas obtained in the step c) or the gas enriched with the target gas obtained in the step d).

13. 13. A gas separation method according to any one of claims 6 to 12, comprising: A gas separation method, wherein the concentration of the target gas in the replacement gas is 98% or more.

Images