Gas recovery system and gas recovery method

Abstract

To provide a gas recovery system that can suppress performance degradation.SOLUTION: A gas recovery system 100 comprises: a raw material gas supply part 10 which supplies a raw material gas; a separation tank 20 which separates carbon dioxide from the raw material gas; a first discharge part 30 which discharges a first gas from the separation tank 20; a second discharge part which discharges a second gas having a carbon dioxide concentration higher than the first gas from the separation tank 20; and a purge gas supply part 50 which supplies a purge gas. The system executes purge processing for supplying the purge gas into the separation tank 20 after a normal operation for separating carbon dioxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas recovery system and a gas recovery method. [Background technology]

[0002] For example, a carbon dioxide recovery device is known that includes a first processing unit that separates carbon dioxide contained in a raw gas by either adsorption, absorption, or permeation, and a second processing unit that removes at least a portion of the water vapor from a treated gas containing carbon dioxide separated by the first processing unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-133354 Summary of the Invention [Problem to be solved by the invention]

[0004] In a system that separates and captures carbon dioxide, when operation is stopped, water vapor contained in the raw gas cools and condenses, resulting in moisture remaining in a container that contains a separation medium, such as a separation membrane, absorbent, or adsorbent. The water droplets remaining in the container that contains the separation medium mix with and agglomerate with dust contained in the separation medium, and may become an obstacle to gas passing through the container, inhibiting adsorption, absorption, or permeation and causing a decrease in performance.

[0005] An object of the present invention is to provide a gas processing system capable of suppressing performance degradation. [Means for solving the problem]

[0006] The gas recovery system of the present invention includes a raw material gas supply unit that supplies raw material gas, a separation tank that separates carbon dioxide from the raw material gas, a first discharge unit that discharges a first gas from the separation tank, a second discharge unit that discharges a second gas having a higher carbon dioxide concentration than the first gas from the separation tank, and a purge gas supply unit that supplies purge gas, and after normal operation to separate carbon dioxide, a purge process is performed in which the purge gas is supplied to the separation tank. [Effects of the Invention]

[0007] The present invention can provide a gas recovery system capable of suppressing performance degradation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating a gas recovery system according to a first embodiment. [Figure 2] 1 is a block diagram illustrating a hardware configuration of a gas recovery system according to a first embodiment. [Figure 3] 10 is a flowchart illustrating a procedure for a purge process at the end of normal operation of the gas recovery system. [Figure 4] 10 is a flowchart illustrating a procedure for a purge process at the start of normal operation of the gas recovery system. [Figure 5] FIG. 2 is a schematic perspective view illustrating a separation tank according to an embodiment. [Figure 6] FIG. 10 is a schematic diagram illustrating a gas recovery system according to a second embodiment. [Figure 7] FIG. 10 is a schematic diagram illustrating a gas recovery system according to a third embodiment. [Figure 8] FIG. 10 is a schematic diagram illustrating a gas recovery system according to a fourth embodiment. [Figure 9] FIG. 10 is a block diagram illustrating a hardware configuration of a gas recovery system according to a fourth embodiment. [Figure 10] 10 is a flowchart illustrating a procedure of a purge process in a gas recovery system according to a fourth embodiment. [Figure 11]FIG. 10 is a block diagram illustrating a hardware configuration of a gas recovery system according to a fifth embodiment. [Figure 12] FIG. 10 is a block diagram illustrating a hardware configuration of a gas recovery system according to a sixth embodiment. [Figure 13] FIG. 13 is a schematic diagram illustrating a gas recovery system according to a seventh embodiment. [Figure 14] FIG. 13 is a block diagram illustrating a hardware configuration of a gas recovery system according to a seventh embodiment. [Figure 15] FIG. 13 is a schematic diagram illustrating a gas recovery system according to an eighth embodiment. [Figure 16] FIG. 13 is a schematic diagram illustrating a gas recovery system according to a ninth embodiment. [Figure 17] FIG. 19 is a schematic diagram illustrating a gas recovery system according to a tenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a gas recovery system according to an embodiment will be described with reference to the accompanying drawings. In this specification and the drawings, substantially identical components are designated by the same reference numerals, and redundant description may be omitted.

[0010] [Gas recovery system 100 according to the first embodiment] FIG. 1 is a schematic diagram illustrating a gas recovery system 100 according to a first embodiment. The gas recovery system 100 shown in FIG. 1 is a system that separates carbon dioxide contained in a raw material gas and recovers the carbon dioxide. The gas recovery system 100 may be, for example, a system that separates and recovers carbon dioxide from a raw material gas, which is a combustion exhaust gas discharged from a combustor. The raw material gas is not limited to the combustion exhaust gas discharged from a combustor, but may be a gas discharged from other equipment. The gas recovery system 100 is installed, for example, in a factory, a power plant, a ship, or the like. The installation location of the gas recovery system 100 is not particularly limited. The gas recovery system 100 is an example of a gas processing system.

[0011] The gas recovery system 100 includes a raw material gas supply unit 10, a separation tank 20, a first discharge unit 30, a second discharge unit 40, and a purge gas supply unit 50.

[0012] [Source gas supply unit 10] The raw material gas supply unit 10 supplies the raw material gas to the separation tank 20. The raw material gas supply unit 10 is connected to a source of raw material gas, such as a combustor. The raw material gas supply unit 10 includes a raw material gas supply pipe L11 for transporting the raw material gas. The raw material gas supply pipe L11 is connected to the separation tank 20.

[0013] The raw material gas supply unit 10 includes a blower 11 that blows the raw material gas. The blower 11 is connected to a raw material gas supply pipe L11. The raw material gas is blown by the blower 11, flows through the raw material gas supply pipe L11, and is supplied to the separation tank 20.

[0014] An on-off valve V11 is provided in the raw material gas supply pipe L11. The on-off valve V11 is provided between the blower 11 and the separation tank 20. By closing the on-off valve V11, the flow of raw material gas from the blower 11 to the separation tank 20 can be stopped. By opening the on-off valve V11, the blower 11 and the separation tank 20 can be communicated with each other.

[0015] [Separation tank 20] The separation tank 20 separates carbon dioxide from the raw gas. The raw gas contains carbon dioxide. The separation tank 20 has, for example, a separation membrane and a container. The separation membrane is housed in the container. The separation tank 20 may have a separation membrane module. The separation membrane is a membrane that selectively permeates carbon dioxide relative to other components. The separation membrane includes a hollow fiber membrane. The separation membrane may have multiple spiral membranes or may have stacked flat membranes.

[0016] The raw material gas supplied to the separation tank 20 is separated into a permeated gas that has permeated the separation membrane and a retentate gas that has not permeated the separation membrane. The permeated gas has a higher carbon dioxide concentration than the retentate gas. The retentate gas has a lower carbon dioxide concentration than the permeated gas. The retentate gas is an example of a first gas, and the permeated gas is an example of a second gas.

[0017] The separation tank 20 may separate carbon dioxide from the raw material gas by, for example, adsorption. The separation tank 20 may be equipped with a physical adsorbent, a solid adsorbent, or a PCP (Porous Coordination Polymer) instead of a separation membrane. The separation tank 20 may separate the raw material gas into a first gas and a second gas having a higher carbon dioxide concentration than the first gas. The separation tank 20 may separate at least a portion of the carbon dioxide contained in the raw material gas from the raw material gas.

[0018] [First discharge section 30] The first discharge section 30 includes a pipe L31 that discharges the retentate gas from the separation tank 20. The pipe L31 is connected to the separation tank 20. The retentate gas in the separation tank 20 flows through the pipe L31 and is discharged to the outside of the separation tank 20. The retentate gas is released into the atmosphere. The pipe L31 is an example of a first discharge pipe.

[0019] The pipe L31 is provided with a dew point meter 221. The dew point meter 221 may be disposed in the pipe L31 at a position close to the separation tank 20. The dew point meter 221 can detect the concentration of water vapor inside the pipe L31. Instead of the dew point meter 221, a hygrometer or a water vapor concentration detector may be provided.

[0020] [Second discharge section 40] The second discharge section 40 includes a pipe L41 that discharges the permeable gas from the separation tank 20. The pipe L41 is connected to the separation tank 20. The permeable gas in the separation tank 20 flows through the pipe L41 and is discharged to the outside of the separation tank 20. The permeable gas is stored in, for example, a container and shipped as a product (carbon dioxide gas). The pipe L41 is an example of a second discharge pipe.

[0021] [Differential pressure drive mechanism 41] The second discharge section 40 includes a differential pressure driving mechanism 41 connected to the pipe L41. The differential pressure driving mechanism 41 may be, for example, a vacuum pump. The differential pressure driving mechanism 41 generates a pressure difference between the upstream and downstream sides of the separation membrane. The pressure of the permeated gas downstream of the separation membrane is lower than the pressure of the raw material gas upstream of the separation membrane. The differential pressure driving mechanism 41 is not limited to a vacuum pump, and may be a blower, an ejector, or other device.

[0022] [Three-way valve V41] A purge gas discharge pipe L42 is connected to the pipe L41 via a three-way valve V41. The pipe L41 connects the separation tank 20 and the product tank, and the purge gas discharge pipe L42 is a pipe that discharges a purge gas, which will be described later. The three-way valve V41 is a flow path switching valve that switches between a flow path that transfers carbon dioxide to the product tank and a flow path that discharges the purge gas.

[0023] The carbon dioxide that has permeated the separation membrane flows through pipe L41 and is stored in the product tank. The purge gas discharged from separation tank 20 flows through pipe L41 and into purge gas discharge pipe L42, and then is released into the atmosphere.

[0024] A dew point meter 222 is provided in the pipe L41. The dew point meter 222 is provided, for example, in the pipe L41 between the differential pressure drive mechanism 41 and the three-way valve V41. The dew point meter 222 can detect the concentration of water vapor inside the pipe L41. The dew point meter 222 may be provided between the separation tank 20 and the differential pressure drive mechanism 41, or may be provided in the purge gas discharge pipe L42. A hygrometer or a water vapor concentration detector may be provided instead of the dew point meter 222.

[0025] [Purge gas supply unit 50] The gas recovery system 100 includes a purge gas supply unit 50 that supplies a purge gas. The purge gas supply unit 50 includes a purge gas supply pipe L51 and an on-off valve V51. The purge gas supply pipe L51 is connected to the raw material gas supply pipe L11 between the on-off valve V11 and the separation tank 20.

[0026] The purge gas supply pipe L51 is provided with an on-off valve V51. The purge gas supply pipe L51 is connected to a purge gas supply source. When supplying purge gas to the separation tank 20, the on-off valve V11 is closed and the on-off valve V51 is opened, thereby supplying the purge gas to the separation tank 20. During normal operation, when supplying raw material gas to the separation tank 20, the on-off valve V11 is opened and the on-off valve V51 is closed, thereby supplying the raw material gas to the separation tank 20. The supply of purge gas to the separation tank 20 can be stopped by closing the on-off valve V51.

[0027] [Purge gas] The purge gas may be, for example, an inert gas or dry air. For example, a blower for transferring the purge gas may be connected to the purge gas supply pipe L51. In addition, in the gas recovery system 100, for example, moisture in the purge gas may be removed using a dehydration separation membrane for removing moisture from the purge gas.

[0028] [Normal operation] Next, normal operation of the gas recovery system 100 will be described. Normal operation refers to operation in which carbon dioxide is separated and recovered from the raw material gas. During normal operation, the on-off valve V11 is open, and the on-off valve V51 is closed. In normal operation, the three-way valve V41 closes the flow path to the purge gas supply pipe L51, and the separation tank 20 and the flow path on the product side are in communication.

[0029] The blower 11 blows the raw material gas and supplies it to the separation tank 20. The differential pressure drive mechanism 41 generates a pressure difference across the separation membrane. The raw material gas flows through the raw material gas supply pipe L11 and is supplied to the separation tank 20. Carbon dioxide contained in the raw material gas supplied to the separation tank 20 permeates the separation membrane. The permeated gas that has permeated the separation membrane flows from the separation tank 20 into the pipe L41. The permeated gas that has flowed through the pipe L41 is shipped as a product.

[0030] Of the raw material gas supplied to the separation tank 20, the retentate gas that has not permeated the separation membrane flows from the separation tank 20 into the pipe L31. The retentate gas that has flowed through the pipe L31 is released to the atmosphere. The retentate gas may contain carbon dioxide.

[0031] [Purge process: after normal operation] In the gas recovery system 100, a purge process can be performed after normal operation. The purge process is an operation in which a purge gas is supplied to the separation tank 20. By supplying the purge gas to the separation tank 20, the concentration of water vapor inside the separation tank 20 can be reduced. In the gas recovery system 100, by performing a purge process, water droplets adhering to the separation membrane can be removed. The water vapor inside the separation tank 20 is discharged to the outside of the separation tank 20 together with the purge gas. Dust inside the separation tank 20 is also discharged to the outside of the separation tank 20 together with the purge gas. In addition, dust adhering to the separation membrane is also discharged to the outside of the separation tank 20 together with the purge gas.

[0032] During the purging process, the on-off valve V11 is closed and the on-off valve V51 is open. During the purging process, the three-way valve V41 connects the separation tank 20 to the purge gas supply pipe L51, and closes the flow path to the product side.

[0033] The purge gas is supplied from the purge gas supply pipe L51 to the separation tank 20. A portion of the purge gas supplied to the separation tank 20 permeates the separation membrane and is discharged from the separation tank 20. The purge gas on the permeate side that has permeated the separation membrane flows through the pipe L41 and the purge gas discharge pipe L42 and is released to the atmosphere.

[0034] Of the purge gas supplied to separation tank 20, the retentate purge gas that has not permeated the separation membrane flows from separation tank 20 into pipe L31. The retentate purge gas that has flowed through pipe L31 is released to the atmosphere.

[0035] [Purge process: before normal operation] In the gas recovery system 100, a purging process can be performed before normal operation. Here, "before normal operation" means after normal operation ends and before the next normal operation starts. The purging process before normal operation can be performed in the same manner as the purging process after normal operation.

[0036] [Control unit 210] Next, the control unit 210 of the gas recovery system 100 will be described with reference to Fig. 2. Fig. 2 is a block diagram illustrating an example of the hardware configuration of the gas recovery system 100. As shown in Fig. 2, the control unit 210 is electrically connected to the dew point meters 221, 222, the blower 11, the on-off valve V11, the on-off valve V51, the differential pressure drive mechanism 41, and the three-way valve V41.

[0037] The control unit 210 includes a CPU 211 and a storage unit 212. The CPU (Center Processing Unit) 211 is responsible for overall control of the gas recovery system 100. The CPU 211 can control the operation of the blower 11. The CPU 211 can control the operation of the differential pressure drive mechanism 41. The CPU 211 can control the opening and closing operations of the on-off valves V11 and V51. The CPU 211 can control the switching operation of the three-way valve V41.

[0038] The storage unit 212 includes a ROM (Read Only Memory) 213 and a RAM (Random Access Memory) 214. The ROM 213 stores various programs for causing the CPU 211 to execute control processes, as well as various data necessary for operation of the gas recovery system 100. The RAM 214 temporarily stores data acquired from various sensors (dew point meters 221, 222).

[0039] [Ending condition] The memory unit 212 stores data relating to, for example, the number of separation membranes. The memory unit 212 also stores data relating to termination conditions that serve as criteria for terminating the purging process. The termination conditions may be, for example, data relating to the water vapor concentration or dew point temperature inside the separation tank 20. The termination conditions may be data relating to the water vapor concentration or dew point temperature inside the pipe L31. The termination conditions may be data relating to the water vapor concentration or dew point temperature inside the pipe L41. The termination conditions may include different data depending on the number of separation membranes. The termination condition may be the length of time for which the purging process is performed. The length of time for which the purging process is performed may be referred to as the "purge time."

[0040] The termination condition may include, for example, an arithmetic expression derived based on experimental results or operational data of the gas recovery system 100.

[0041] [Purge time calculation formula] The calculation formula for the purge time TP1 may be the following formula (1).

[0042] TP1=(V1 / Q1)+(V2 / Q2)×2...(1)

[0043] "V1" in the above formula (1) is the flow path volume [m 3 ]. The supply port of the separation membrane is the nozzle N11 shown in Figure 5. The discharge port on the unexplored side is the nozzle N31. "Q1" is the purge flow rate [m 3 / min]. "V2" is the flow channel volume on the permeation side of the separation membrane [m 3 The flow channel volume on the permeation side of the separation membrane is the volume inside the piping from the permeation side spatial volume, which is the secondary side of the permeation functional membrane in the separation membrane, through the permeation side outlet nozzle of the separation membrane to the inlet piping of the vacuum pump. "Q2" is the pumping speed [m 3 / min].

[0044] The purge time TP1 is determined by the flow path volume V1 [m 3 ] is the purge flow rate Q1 [m 3 / min], the time required for 5-fold purging is T2 + the flow channel volume on the permeation side of the separation membrane V2 [m 3 ] vacuum pump (differential pressure drive mechanism 41) pumping speed Q2 [m 3 / min] may be three times the time T3 required for pulling.

[0045] The meaning of the first term (V1 / Q1) on the right side of equation (1) will be explained. In the gas recovery system 100, purge gas is flowed at a purge flow rate Q1 that is five times the flow path volume q from the supply port of the separation membrane (separation tank 20) ​​used to the non-permeated side discharge port. This not only discharges water vapor inside the separation tank 20 to the outside of the separation tank 20, but also promotes the volatilization of water droplets remaining inside the separation tank 20. The flow path volume q is the same as the above-mentioned flow path volume V1. In the gas recovery system 100, purge gas may be flowed at a purge flow rate Q1 that is multiple times the flow path volume q; for example, purge gas may be flowed at a purge flow rate Q1 that is three times the flow path volume q.

[0046] The purge time TP may be a time required to thoroughly disperse toxic gas components (e.g., CO, SO2, NO2, etc.) remaining inside the separation membrane and water droplets adhering to the fine parts of the porous support layer of the separation membrane. The purge time TP may be a time required to discharge toxic gas components and water droplets remaining inside the separation tank 20 to the outside of the separation tank 20.

[0047] The meaning of the second term (V2 / Q2) on the right side of equation (1) will be explained. A portion of the purge gas supplied to separation tank 20 permeates the separation membrane. The purge gas that permeates the separation membrane dissipates water vapor within the separation membrane and volatilizes water droplets within the separation membrane. The purge gas dehydrates the separation membrane. The time T4 defined by the second term on the right side is determined by the specific pumping speed of the vacuum pump, which is differential pressure drive mechanism 41.

[0048] In the gas recovery system 100, after the inside of the separation tank 20 reaches the ultimate vacuum, the margin until the environment inside the separation tank 20 stabilizes is set to three times. "Until the environment inside the separation tank 20 stabilizes" may be, for example, until the inside of the separation tank 20 reaches a predetermined dew point temperature (a state where the water vapor concentration is low, such as the dew point).

[0049] [Calculation formula required for removing deposits within the membrane] Next, the calculation formula required for removing the deposits inside the membrane will be described. The "calculation formula required for removing the deposits inside the membrane" may be the purge time TP2 required to discharge the deposits accumulated inside the separation membrane to the outside of separation tank 20.

[0050] The purge time TP2 may be calculated using the following equation (2).

[0051] TP2=TP1+t3 (2)

[0052] In formula (2), t3 is the time required to remove dry dust after dehydration. "After dehydration" may refer to the time after the purging time TP1 according to formula (1) above has elapsed.

[0053] [Procedure for purging at the end of normal operation of the gas recovery system 100] Next, a procedure for purging at the end of normal operation of the gas recovery system 100 will be described with reference to Fig. 3. Fig. 3 is a flowchart illustrating a procedure for purging at the end of normal operation of the gas recovery system 100.

[0054] The gas recovery system 100 performs normal operation to separate and recover carbon dioxide from the raw material gas (step S11).

[0055] Next, the control unit 210 starts supplying purge gas (step S12). In step S12, the control unit 210 opens and closes the on-off valves V11 and V51 and the three-way valve V41. The control unit 210 closes the on-off valve V11 and opens the on-off valve V51. The control unit 210 controls the three-way valve V41 to connect the separation tank 20 and the purge gas discharge pipe L42. The control unit 210 starts driving the differential pressure drive mechanism 41.

[0056] As a result, the purge gas flows through the purge gas supply pipe L51 and is supplied to the separation tank 20. The water vapor inside the separation tank 20 is discharged to the outside of the separation tank 20 together with the purge gas. This promotes the evaporation of water droplets inside the separation tank 20. The dust inside the separation tank 20 is discharged to the outside of the separation tank 20 together with the purge gas.

[0057] Next, the control unit 210 determines whether or not the termination condition is met. If the termination condition is met (step S13; YES), the control unit 210 executes the process of step S14. If the termination condition is not met (step S13; NO), the control unit 210 repeats the process of step S13.

[0058] The control unit 210 determines whether the elapsed time from the start of the supply of the purge gas is equal to or greater than the purge time TP1. If the control unit 210 determines that the elapsed time is equal to or greater than the purge time TP1, the control unit 210 may determine that the termination condition is met.

[0059] The control unit 210 may determine whether or not the termination condition is met based on the detection results from the dew point meters 221, 222. The control unit 210 may determine whether or not the dew point temperature from the measurement result is equal to or lower than a predetermined dew point temperature (determination threshold). The control unit 210 may determine that the termination condition is met when the dew point temperature from the measurement result is equal to or lower than the determination threshold. The dew point temperature may be, for example, the dew point temperature inside the separation tank 20.

[0060] The control unit 210 may determine whether the water vapor concentration obtained from the measurement result is equal to or less than a predetermined water vapor concentration (determination threshold). The control unit 210 may determine that the termination condition is met when the water vapor concentration obtained from the measurement result is equal to or less than the determination threshold. The water vapor concentration may be, for example, the water vapor concentration inside the separation tank 20.

[0061] The control unit 210 may determine whether the time elapsed since the start of the supply of the purge gas is equal to or longer than the purge time TP2. If the control unit 210 determines that the elapsed time is equal to or longer than the purge time TP2, it may determine that the termination condition is met.

[0062] The control unit 210 may determine whether the time elapsed since the start of the supply of purge gas is equal to or greater than a set time (determination threshold) required to remove dust. If the control unit 210 determines that the elapsed time is equal to or greater than the set time, it may determine that the termination condition is met.

[0063] The control unit 210 may determine whether the time elapsed since the start of the supply of the purge gas is equal to or greater than a set time (determination threshold) required to remove the water-soluble gas. The control unit 210 may also set other conditions as the termination conditions. The termination conditions are conditions that can be used to determine whether to terminate the supply of the purge gas.

[0064] In step S14, the control unit 210 stops the supply of purge gas. The control unit 210 stops driving the differential pressure driving mechanism 41. The control unit 210 may open and close the on-off valves V11, V51 and the three-way valve V41.

[0065] Next, the control unit 210 completely stops the gas collection system 100 (step S15). The process shown in Fig. 3 may be executed when the gas collection system 100 is stopped in a planned manner, or may be executed when the gas collection system 100 is stopped in an emergency, for example.

[0066] [Procedure for purging at the start of normal operation of the gas recovery system 100] Next, a procedure for purging at the start of normal operation of the gas recovery system 100 will be described with reference to Fig. 4. Fig. 4 is a flowchart illustrating a procedure for purging at the start of normal operation of the gas recovery system 100.

[0067] The gas recovery system 100 starts operation (step S21). The operation here refers to the start of operation of the gas recovery system 100, for example, the start of control by the control unit 210, and does not include the start of normal operation.

[0068] Next, the control unit 210 executes the processes of steps S22 to S24. The processes of steps S22 to S24 are the same as the processes of steps S12 to S14 described above.

[0069] Next, the gas recovery system 100 starts normal operation (step S25). In step S25, the control unit 210 opens and closes the on-off valves V11 and V51 and the three-way valve V41. The control unit 210 opens the on-off valve V11 and closes the on-off valve V51. The control unit 210 controls the three-way valve V41 to close the flow path to the purge gas discharge pipe L42. The pipe L41 is connected to, for example, a product tank that stores carbon dioxide. The control unit 210 drives the blower 11 and the differential pressure drive mechanism 41. The raw material gas is blown by the blower 11 and supplied to the separation tank 20. The carbon dioxide contained in the raw material gas supplied to the inside of the separation tank 20 permeates the separation membrane, passes through the pipe L41, and is recovered in the product tank. The retentate gas that does not permeate the separation membrane passes through the pipe L31 and is released to the atmosphere.

[0070] [background] The background to the gas recovery system is explained below. In response to the social issue of curbing global warming, developed countries are aiming to achieve carbon neutrality by 2050. Japan has set a goal of reducing greenhouse gas emissions by 46% by 2030 compared to 2013 levels, and achieving carbon neutrality by 2050.

[0071] One of the technologies to reduce greenhouse gas emissions is a system for capturing CO2 from flue gases produced by combustion of fossil fuels. Conventional chemical absorption systems, which are beginning to be put into practical use as CO2 capture systems, are large in size and require thermal energy, so there is a demand for compact, low-power CO2 capture systems.

[0072] On the other hand, the membrane separation method is relatively small due to its simple structure, and since CO2 is separated by the pressure difference between the gas before and after the separation membrane, it is expected that power consumption will decrease if the permeability of the separation membrane is improved.

[0073] [Problems with the prior art] For example, in a system that separates and captures CO2 from combustion exhaust gas, when the separation and capture operation is stopped, the water vapor in the exhaust gas cools and condenses, resulting in moisture remaining in the container containing the separation medium, either the separation membrane, absorbent, or adsorbent. The water droplets mix with dust contained in the separation medium and aggregate, creating an obstacle to gas passage, potentially impairing gas adsorption, absorption, and permeability, resulting in a decrease in performance. Furthermore, in winter, the freezing of water droplets can lead to damage to the separation medium, potentially resulting in a decrease in performance or internal leakage. Internal leakage refers to, for example, the passage of part of the raw gas directly through a damaged part of the separation medium.

[0074] For example, one solution is to heat the entire storage container with a heater after the separation and recovery operation has been stopped, but this requires a continuous power supply during the operation shutdown period, resulting in energy loss.

[0075] [Actions and Effects of the Gas Recovery System 100 According to the First Embodiment] The gas recovery system 100 according to the first embodiment includes a raw gas supply unit 10 for supplying raw gas, a separation tank 20 for separating carbon dioxide from the raw gas, a first discharge unit 30 for discharging an unpermeated gas (first gas) from the separation tank 20, a second discharge unit 40 for discharging a permeated gas (second gas) having a higher carbon dioxide concentration than the unpermeated gas from the separation tank 20, and a purge gas supply unit 50 for supplying a purge gas. After normal operation for separating carbon dioxide, a purge process is performed in which the purge gas is supplied to the separation tank 20.

[0076] According to the gas recovery system 100, by supplying a purge gas to the separation tank 20, water vapor and water droplets inside the separation tank 20 can be discharged to the outside of the separation tank 20. The gas recovery system 100 can promote evaporation of water droplets inside the separation tank 20. Furthermore, the gas recovery system 100 can discharge dust inside the separation tank 20 to the outside of the separation tank 20. This reduces the amount of water vapor and water droplets remaining in the separation tank 20 during periods when the gas recovery system 100 is not in operation. Therefore, the gas recovery system 100 reduces the risk of a decrease in the gas adsorption, absorption, and permeability performance of the separation tank 20 at the next operation. Furthermore, by reducing the amount of water vapor and water droplets remaining in the separation tank 20 during periods when the gas recovery system 100 is not in operation, it is possible to prevent damage to the separation medium (e.g., separation membrane) due to frozen water droplets, for example, in winter. As a result, performance degradation or internal leakage in the separation tank 20 can be suppressed.

[0077] Furthermore, in the gas recovery system 100, a purging process is performed to remove water vapor and water droplets before the gas recovery system 100 is shut down, so that the separation tank 20 does not need to be heated by a heater during the shutdown period. This eliminates the need for a continuous power supply during the shutdown period of the gas recovery system 100. As a result, energy loss during the shutdown period of the gas recovery system 100 can be reduced.

[0078] Furthermore, in the gas recovery system 100, the raw material gas supply unit 10 includes a blower 11 that blows the raw material gas, a raw material gas supply pipe L11 connected to the blower 11 and that supplies the raw material gas to the separation tank 20, and an on-off valve (first on-off valve) V11 provided in the raw material gas supply pipe L11. The purge gas supply unit 50 includes a purge gas supply pipe L51 connected to the raw material gas supply pipe L11 and that supplies the purge gas to the separation tank 20, and an on-off valve (second on-off valve) V51 provided in the purge gas supply pipe L51. When performing a purge process, the on-off valve V11 is closed and the on-off valve V51 is open to supply the purge gas to the separation tank 20.

[0079] In the gas recovery system 100, the flow path for supplying the raw material gas and the flow path for supplying the purge gas can be switched by opening and closing the on-off valves V11 and V51. By connecting the purge gas supply pipe L51 to the raw material gas supply pipe L11, the purge gas can be supplied from the purge gas supply pipe L51 to the separation tank 20 via the raw material gas supply pipe L11.

[0080] Furthermore, in the gas recovery system 100, the first discharge section 30 has a pipe (first discharge pipe) L31 connected to the separation tank 20 and discharging the retentate gas from the separation tank 20, and the second discharge section 40 has a pipe (second discharge pipe) L41 connected to the separation tank 20 and discharging the permeate gas from the separation tank 20, a differential pressure drive mechanism 41 connected to the pipe L41, a three-way valve (third on-off valve) V41 provided on the pipe L41, and a purge gas discharge pipe L42 branching from the pipe L41 and discharging the purge gas; when performing a purge process, the flow path is switched by the three-way valve V41, and the purge gas is discharged through the purge gas discharge pipe L42.

[0081] In the gas recovery system 100 having this configuration, a differential pressure can be generated by driving the differential pressure drive mechanism 41, and the gas in the separation tank 20 can be discharged to the pipe L41. In the gas recovery system 100, by switching the flow path using the three-way valve V41, the purge gas can be released to the atmosphere using the purge gas discharge pipe L42, which is different from the flow path leading to the product tank that recovers carbon dioxide.

[0082] The gas recovery system 100 also includes a control unit 210 that controls the operation of the purging process. The control unit 210 determines whether a preset termination condition is met based on the water vapor concentration and dew point temperature inside the separation tank 20, and terminates the purging process if the termination condition is met. The control unit 210 determines the termination of the purging process using a termination condition that varies depending on the processing capacity of the separation tank 20. The "termination condition that varies depending on the processing capacity of the separation tank 20" may be a termination condition that varies depending on the internal volume of the separation tank 20 or a termination condition that varies depending on the exhaust speed of the vacuum pump.

[0083] According to this gas recovery system 100, it is possible to stop the supply of purge gas after a preset termination condition is met. In the gas recovery system 100, the period of the purge treatment can be appropriately set. Furthermore, in the gas recovery system 100, it is possible to determine the termination of the purge treatment using different termination conditions depending on the treatment capacity of the separation tank 20, and it is possible to set an appropriate period of the purge treatment depending on the treatment capacity of the separation tank 20. As a result, it is possible to reduce energy loss.

[0084] The gas recovery system 100 may also include dew point meters 221, 222 capable of detecting the dew point temperature inside the separation tank 20. The dew point meters 221, 222 may detect the dew point temperature inside the separation tank 20 by detecting the dew point temperature inside the pipes L31, L41 that communicate with the separation tank 20. The control unit 210 can determine whether the termination condition is met using the dew point temperatures detected by the dew point meters 221, 222.

[0085] According to such gas recovery system 100, the dew point temperature inside separation tank 20 can be grasped using dew point meters 221, 222, and the end of the purge process can be appropriately determined based on the dew point temperature.

[0086] The gas recovery system 100 according to this embodiment includes a raw material gas supply unit 10 that supplies a raw material gas, a separation tank 20 that separates carbon dioxide from the raw material gas, a first discharge unit 30 that discharges a non-permeated gas (first gas) from the separation tank 20, a second discharge unit 40 that discharges a permeated gas (second gas) having a higher carbon dioxide concentration than the non-permeated gas from the separation tank 20, and a purge gas supply unit 50 that supplies a purge gas. Before the start of the next operation, the gas recovery system 100 performs a purge process in which the purge gas is supplied to the separation tank 20, and after the purge process, the system transitions to normal operation in which carbon dioxide is separated.

[0087] In such a gas recovery system 100, a purging process is performed before normal operation to separate and recover carbon dioxide, thereby making it possible to discharge water vapor and water droplets present inside the separation tank 20 to the outside of the separation tank 20. In the gas recovery system 100, it is possible to suppress performance degradation caused by water vapor and water droplets present inside the separation tank 20 during normal operation. In the gas recovery system 100, it is possible to maintain stable normal operation. For example, it is possible to reduce the occurrence of emergency shutdowns due to malfunctions.

[0088] The gas recovery system 100 also includes a memory unit 212 that stores an arithmetic formula for calculating the length of the execution time of the purge process, the arithmetic formula including a first arithmetic formula for calculating the length of a first execution time required to discharge water vapor in the separation tank 20 to the outside of the separation tank 20, and a second arithmetic formula for calculating the length of a second execution time required to discharge dust accumulated in the separation tank 20 to the outside, and the control unit 210 calculates the length of the execution time based on the arithmetic formula, and the termination condition includes exceeding the execution time.

[0089] According to such gas recovery system 100, the length of the overall purge time can be set by taking into consideration the purge time (first execution time) required to discharge water vapor from separation tank 20, as well as the purge time (second execution time) required to discharge dust inside separation tank 20 to the outside of separation tank 20. In gas recovery system 100, by performing the purge process, it is possible to reduce the water vapor and water droplets remaining in separation tank 20 and also to discharge dust to the outside of separation tank 20. As a result, it is possible to suppress performance degradation caused by dust present inside separation tank 20.

[0090] Furthermore, in the gas recovery system 100, the gas components remaining inside the separation tank 20 can be discharged to the outside by purging, thereby removing the water-soluble gas components remaining inside the separation tank 20. This suppresses the reaction between the water-soluble gas components and moisture inside the separation membrane. As a result, the gas recovery system 100 can prevent the progression of acid dew and alkalization in the separation membrane.

[0091] In the gas recovery system 100, the separation tank 20 may be provided with a plurality of types of separation membranes.

[0092] [Separation tank 20 according to the embodiment] Next, a separation tank 20 according to an embodiment will be described with reference to Fig. 5. Fig. 5 is a schematic perspective view illustrating a separation tank 20 according to an embodiment. The separation tank 20 shown in Fig. 5 may include a separation membrane module 21.

[0093] The separation membrane module 21 includes, for example, a cylindrical container, and multiple separation membranes are housed inside the container. The separation membranes may be, for example, straw-shaped. The multiple separation membranes are bundled together to form a bundle. The axial direction of the straw-shaped separation membranes is, for example, arranged vertically.

[0094] The separation membrane module 21 has a nozzle N11, a nozzle N31, and a nozzle N41. The nozzle N1 is disposed at the bottom of the separation membrane module 21. The nozzle N31 is disposed at the top of the separation membrane module 21. The nozzle N41 is disposed on a side surface of the separation membrane module 21. The nozzle N11 and the nozzle N31 face each other in the longitudinal direction of the separation membrane module 21.

[0095] The nozzle N11 is connected to the raw material gas supply pipe L11 and is a gas supply port that supplies the raw material gas into the separation membrane module 21. The nozzle N31 is connected to the pipe L31 and is a gas outlet that discharges the retentate gas. The nozzle N41 is connected to the pipe L41 and is a gas outlet that discharges the permeate gas.

[0096] During normal operation, when a raw material gas is supplied to the separation membrane module 21, the raw material gas is supplied to the separation membrane module 21 from the nozzle N11. Permeated gas that has permeated the separation membrane is discharged from the nozzle N41. Non-permeated gas that has not permeated the separation membrane is discharged from the nozzle N31. Inside the separation membrane module 21, permeated gas that has permeated the separation membrane is discharged from the nozzle N41. Inside the separation membrane module 21, an upward flow is generated from the nozzle N11 to the nozzle N31. In FIG. 5, upward arrows are indicated by solid lines.

[0097] During the purging process, when purge gas is supplied to the inside of the separation membrane module 21, the purge gas may be supplied to the inside of the separation membrane module 21 from the nozzle N31. Of the purge gas, the purge gas that has permeated the separation membrane is discharged from the nozzle N41. Of the purge gas, the purge gas that has permeated the separation membrane is discharged from the nozzle N11. Inside the separation membrane module 21, a downward flow is generated from the nozzle N21 toward the nozzle N11. In FIG. 5, the downward arrow is indicated by a dashed line.

[0098] In the gas recovery system 100 including such a separation membrane module 21, a flow of purge gas in the opposite direction to that in normal operation can be formed inside the separation membrane module 21 during the purge process. Water vapor, water droplets, and dust present on the primary side (closer to the nozzle N11) of the separation membrane module 21 can be discharged from the nozzle N11 to the outside of the separation membrane module 21. Since condensed water droplets and dust often remain at the bottom of the separation membrane module 21, these water droplets and dust can be discharged to the outside of the separation membrane module 21 from the nozzle N11 provided at the bottom of the separation membrane module 21.

[0099] In the gas recovery system 100 including the separation membrane module 21, water droplets and dust can be discharged from the nozzle N11 by utilizing gravity together with the flow of purge gas from top to bottom.

[0100] [Gas recovery system 100B according to the second embodiment] Next, a gas recovery system 100B according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a schematic diagram illustrating the gas recovery system 100B according to the second embodiment. The gas recovery system 100B according to the second embodiment shown in Fig. 6 differs from the gas recovery system 100 according to the first embodiment shown in Fig. 1 in that the gas recovery system 100B according to the second embodiment shown in Fig. 6 includes a purge gas supply unit 50B instead of the purge gas supply unit 50, and that the gas recovery system 100B according to the second embodiment includes a purge gas discharge unit 60. Note that in the description of the second embodiment, descriptions similar to those of the first embodiment may be omitted.

[0101] The gas recovery system 100B includes a raw material gas supply unit 10, a separation tank 20, a first discharge unit 30, a second discharge unit 40, a purge gas supply unit 50B, and a purge gas discharge unit 60.

[0102] [Purge gas supply unit 50B] The purge gas supply unit 50B includes a purge gas supply pipe L51B and an on-off valve V51. The purge gas supply pipe L51B is connected to the pipe L31 of the first discharge unit 30. The on-off valve V51 is provided on the purge gas supply pipe L51B. The purge gas is supplied from the purge gas supply pipe L51B through the pipe L31 and the nozzle N31 into the separation tank 20.

[0103] The pipe L31 is also provided with an on-off valve V31. The on-off valve V31 is located downstream of the connection between the purge gas supply pipe L51B and the pipe L31. In other words, the purge gas supply pipe L51B is connected to the pipe L31 between the separation tank 20 and the on-off valve V31. During normal operation, the on-off valve V31 is open, and during the purging process, the on-off valve V31 is closed.

[0104] [Purge gas discharge section 60] The purge gas discharge unit 60 includes a purge gas discharge pipe L61 and an on-off valve V61. The purge gas discharge pipe L61 is connected to the raw material gas supply pipe L11 of the raw material gas supply unit 10. The on-off valve V61 is provided in the purge gas discharge pipe L61. The unpermeated purge gas that has not permeated through the separation membrane of the separation tank 20 is discharged from the nozzle N11, passes through a part of the raw material gas supply pipe L11, flows into the purge gas discharge pipe L61, and is released into the atmosphere.

[0105] The purge gas on the permeate side that has permeated the separation membrane of the separation tank 20 is discharged from the nozzle N41, flows into the pipe L41 of the second discharge part 40 and the purge gas discharge pipe L42, and is released into the atmosphere.

[0106] The gas recovery system 100B according to the second embodiment also provides the same effects as the gas recovery system 100 according to the first embodiment.

[0107] Furthermore, the nozzle N41 may be provided at a position opposite to the flow direction of the raw material gas during normal operation. The nozzle N31 and the nozzle N41 may be disposed opposite to each other in the flow direction of the raw material gas in the separation tank 20.

[0108] Nozzle N41, which is the permeate-side outlet, may be positioned so as to generate a counterflow to the flow from nozzle N11, which is the feed gas inlet, to nozzle N31, which is the retentate-side outlet. During normal operation, the counterflow of the retentate-side gas flow and the permeate-side gas flow can suppress the occurrence of carbon dioxide concentration polarization and concentration unevenness inside separation tank 20. As a result, the performance of gas recovery system 100B during normal operation can be improved.

[0109] [Gas recovery system 100C according to the third embodiment] Next, a gas recovery system 100C according to a third embodiment will be described with reference to Fig. 7. Fig. 7 is a schematic diagram illustrating the gas recovery system 100C according to the third embodiment. The gas recovery system 100C according to the third embodiment shown in Fig. 7 differs from the gas recovery system 100 according to the first embodiment shown in Fig. 1 in that it includes a plurality of separation tanks 20, 20B, and 20C. Note that in the description of the third embodiment, descriptions similar to those of the above embodiments may be omitted.

[0110] The gas recovery system 100B includes a raw material gas supply unit 10, a separation tank 20, a first discharge unit 30, a second discharge unit 40, and a purge gas supply unit 50. The first discharge unit 30 includes a separation tank 20B, and the second discharge unit 40 includes a separation tank 20C.

[0111] [Separation tank 20B] The retentate gas discharged from separation tank 20 is supplied to separation tank 20B. Separation tank 20B separates carbon dioxide contained in the retentate gas. The permeate gas in separation tank 20B has a higher carbon dioxide concentration than the retentate gas in separation tank 20B. Separation tank 20B may have the same structure as separation tank 20, or may have a different structure.

[0112] Also downstream of the separation tank 20B, a first discharge pipe, a second discharge pipe, a differential pressure driving mechanism 41, a three-way valve V41, and a purge gas discharge pipe L42 are provided.

[0113] [Separation tank 20C] The permeate gas discharged from separation tank 20 is supplied to separation tank 20C. Separation tank 20C separates carbon dioxide contained in the retentate gas. The permeate gas in separation tank 20B has a higher carbon dioxide concentration than the retentate gas in separation tank 20B. Separation tank 20C may have the same structure as separation tanks 20 and 20B, or may have a different structure.

[0114] Also downstream of the separation tank 20C, a first discharge pipe, a second discharge pipe, a differential pressure driving mechanism 41, a three-way valve V41, and a purge gas discharge pipe L42 are provided.

[0115] The gas recovery system 100C according to the third embodiment also achieves the same effects as the gas recovery system 100 according to the first embodiment. The gas recovery system 100C may include a plurality of separation tanks 20, 20B, and 20C. The retentate gas and the permeate gas may be supplied to the separation tanks 20B and 20C.

[0116] Separation tanks 20, 20B, and 20C may be provided with separate purge gas supply units 50, or a common purge gas supply unit 50 may be provided. Furthermore, purge gas may be supplied to separation tanks 20, 20B, and 20C from either the upstream or downstream sides. Furthermore, gas recovery system 100C may include multiple separation tanks 20 arranged in parallel. Similarly, gas recovery system 100C may include multiple separation tanks 20B and 20C arranged in parallel. Furthermore, gas recovery system 100C may include four or more separation tanks 20, 20B, and 20C. Furthermore, gas recovery system 100C may include separation tank 20B but not separation tank 20C. Furthermore, gas recovery system 100C may include separation tank 20C but not separation tank 20B.

[0117] [Gas recovery system 100D according to the fourth embodiment] Next, a gas recovery system 100D according to a fourth embodiment will be described with reference to Fig. 8. Fig. 8 is a schematic diagram illustrating a gas recovery system 100D according to the fourth embodiment. Note that in the description of the fourth embodiment, descriptions similar to those of the above embodiments may be omitted.

[0118] The gas recovery system 100D includes a raw material gas supply unit 10, a separation tank 20, a first discharge unit 30, a second discharge unit 40, and a purge gas supply unit 50.

[0119] [Source gas supply unit 10] The raw material gas supply unit 10 includes a raw material gas supply pipe L11 and a pipe L12. The pipe L12 branches off from the raw material gas supply pipe L12. A switching valve V11A is provided in the raw material gas supply pipe L11, and a switching valve V11B is provided in the pipe L12. The pipe L12 is connected to the raw material gas supply pipe L11 between the raw material gas supply source and the switching valve V11A. The "switching valve" may be a "three-way valve."

[0120] The switching valves V11A and V11B are electrically connected to the control unit 210. The switching valves V11A and V11B are driven in accordance with command signals output from the control unit 210. In the raw material gas supply unit 10, the transfer destination of the raw material gas can be changed by opening and closing the switching valves V11A and V11B. In the raw material gas supply unit 10, during normal operation, the switching valve V11A is opened and the switching valve V11B is closed, thereby supplying the raw material gas to the separation tank 20. The raw material gas flows through the raw material gas supply pipe L11 and is supplied to the separation tank 20.

[0121] After normal operation of the raw material gas supply unit 10, the switching valve V11A is closed and the switching valve V11B is opened, thereby discharging the raw material gas from the raw material gas supply unit 10. The raw material gas is not supplied to the separation tank 20, but flows through the pipe L12 and is discharged from the raw material gas supply unit 10. The raw material gas that has flowed through the pipe L12 may be released to the atmosphere, for example. Alternatively, the raw material gas that has flowed through the pipe L12 may be stored in a tank, for example.

[0122] [Separation tank 20] The separation tank 20 separates carbon dioxide from the raw gas. The raw gas contains carbon dioxide. The separation tank 20 has, for example, a separation membrane and a container. The separation membrane is housed in the container. The separation tank 20 may have a separation membrane module. The separation membrane is a membrane that selectively permeates carbon dioxide relative to other components. The separation membrane includes a hollow fiber membrane. The separation membrane may have multiple spiral membranes or may have stacked flat membranes.

[0123] The separation tank 20 has a first space 20a and a second space 20b. The separation membrane is disposed between the first space 20a and the second space 20b. The first space 20a is a space formed inside the separation tank 20, into which the raw material gas is supplied. The second space 20b is a space formed inside the separation tank 20, into which the gas that has permeated the separation membrane flows. The first space 20a is a space on the non-permeated side, and the second space 20b is a space on the permeated side.

[0124] The raw material gas supplied to the first space 20a of the separation vessel 20 is separated into a permeated gas that has permeated the separation membrane and a retentate gas that has not permeated the separation membrane.

[0125] [First discharge section 30] The first discharge section 30 includes a first discharge pipe L31 that discharges the retentate gas from the separation tank 20. The first discharge pipe L31 communicates with the first space 20a of the separation tank 20. The retentate gas in the first space 20a of the separation tank 20 flows through the first discharge pipe L31 and is discharged to the outside of the separation tank 20. The retentate gas is released into the atmosphere.

[0126] A pressure control valve V31 is connected to the first discharge pipe L31. The pressure control valve V31 controls the pressure inside the first space 20a of the separation tank 20 and the first discharge pipe L31. The pressure control valve V31 is electrically connected to the control unit 210. The pressure control valve V31 is driven in accordance with a command signal output from the control unit 210. The control unit 210 can control the valve opening degree of the pressure control valve V31.

[0127] The first discharge pipe L31 is provided with a water vapor concentration meter (water vapor concentration sensor) 221r. The water vapor concentration meter 221r ​​may be disposed in the pipe L31 at a position close to the separation tank 20. The water vapor concentration meter 221r ​​can detect the concentration of water vapor inside the pipe L31. The water vapor concentration meter 221r ​​may be a dew point meter, a hygrometer, a capacitance sensor, or any other sensor.

[0128] [Second discharge section 40] The second discharge section 40 includes a second discharge pipe L41 that discharges the permeable gas from the separation tank 20. The second discharge pipe L41 communicates with the second space 20b of the separation tank 20. The permeable gas in the separation tank 20 flows through the second discharge pipe L41 and is discharged to the outside of the separation tank 20. The permeable gas is stored in, for example, a container and shipped as a product (carbon dioxide gas).

[0129] [Differential pressure drive mechanism 41] The second discharge section 40 includes a differential pressure driving mechanism 41 connected to the pipe L41. The differential pressure driving mechanism 41 may be, for example, a vacuum pump. The differential pressure driving mechanism 41 generates a pressure difference between the upstream and downstream sides of the separation membrane. The pressure of the permeated gas downstream of the separation membrane is lower than the pressure of the raw material gas upstream of the separation membrane. The differential pressure driving mechanism 41 is not limited to a vacuum pump, and may be a blower, an ejector, or other device.

[0130] [Purge gas exhaust piping L42] The second exhaust unit 40 includes a purge gas exhaust pipe L42 branching off from the second exhaust pipe L41. The purge gas exhaust pipe L42 is connected to the second exhaust pipe L41. The purge gas exhaust pipe L42 is connected downstream of the differential pressure drive mechanism 41 with respect to the second exhaust pipe L41.

[0131] [Switching valve V41A, V41B] The second discharge unit 40 includes a switching valve V41A and a switching valve V41B. The switching valve V41A is provided in the second discharge pipe L41, and the switching valve V41B is provided in the purge gas discharge pipe L42. The switching valve V41A is disposed in the second discharge pipe L41 downstream of the differential pressure driving mechanism 41. The purge gas discharge pipe L42 is connected in the second discharge pipe L41 between the differential pressure driving mechanism 41 and the switching valve V41A.

[0132] The switching valves V41A and V41B are electrically connected to the control unit 210. The switching valves V41A and V41B are driven in accordance with command signals output from the control unit 210. The control unit 210 can switch the flow path in the second discharge unit 40 by operating the switching valves V41A and V41B.

[0133] In the second discharge section 40, the switching valves V41A and V41B are opened and closed to switch the flow path in the second discharge section 40 depending on the operating state of the gas recovery system 100. In the second discharge section 40, during normal operation, the switching valve V41A is opened and the switching valve V41B is closed, allowing the permeated gas to be stored or used.

[0134] After normal operation, the second discharge unit 40 can discharge the purge gas by closing the switching valve V41A and opening the switching valve V41B. The purge gas in the second space 20b of the separation tank 20 flows through the second discharge pipe L41 and the flow path in the differential pressure drive mechanism 41, and then flows into the purge gas discharge pipe L42. The purge gas flows through the purge gas discharge pipe L42 and is discharged from the second discharge unit 40. The purge gas that has flowed through the purge gas discharge pipe L42 may be released into the atmosphere, for example.

[0135] The pipe L31 is provided with a water vapor concentration meter (water vapor concentration sensor) 221r. The water vapor concentration meter 221r ​​may be disposed in the pipe L31 at a position close to the separation tank 20. The water vapor concentration meter 221r ​​can detect the concentration of water vapor inside the pipe L31. The water vapor concentration meter 221r ​​may be a dew point meter, a hygrometer, a capacitance sensor, or any other sensor. Data related to the water vapor concentration detected by the water vapor concentration meter 221r ​​is input to the control unit 210.

[0136] The second discharge pipe L41 is provided with a water vapor concentration meter (water vapor concentration sensor) 222p. The water vapor concentration meter 222p is disposed downstream of the differential pressure drive mechanism 41 in the second discharge pipe L41. The water vapor concentration meter 222p can detect the concentration of water vapor in the second discharge pipe L41. The water vapor concentration meter 222p may be a dew point meter, a hygrometer, a capacitance sensor, or other sensors. The water vapor concentration meter 222p can detect the concentration of water vapor in the second space 20b of the separation tank 20, which communicates with the second discharge pipe L41, the differential pressure drive mechanism 41, and the flow path of the purge gas discharge pipe L42. The water vapor concentration meter 222p may be provided in, for example, the purge gas discharge pipe L42. Data related to the water vapor concentration detected by the water vapor concentration meter 222p is input to the control unit 210.

[0137] [Purge gas supply unit 50] The gas recovery system 100D includes a purge gas supply unit 50 that supplies purge gas. The purge gas supply unit 50 includes purge gas supply pipes L51 to L53, an on-off valve V51, a control valve V1r, a control valve V1p, and a control valve V1r.

[0138] The purge gas supply pipe L51 is connected to a purge gas supply source. The purge gas supply pipe L51 branches into a purge gas supply pipe L52 and a purge gas supply pipe L53. The purge gas supply pipe L52 is connected to the source gas supply pipe L11 between the switching valve V11A and the first space 20a of the separation tank 20. The purge gas supply pipe L53 is connected to the second space 20b of the separation tank 20. The purge gas supply pipe L52 is an example of a first purge gas supply unit, and the purge gas supply pipe L53 is an example of a second purge gas supply unit. The purge gas supply unit 50 may include a first purge gas supply unit that supplies purge gas to the first space 20a and a second purge gas supply unit that supplies purge gas to the second space 20b. The purge gas supply unit 50 may include a piping system (a common purge gas piping L51 and an on-off valve V51) common to the first purge gas supply unit and the second purge gas supply unit.

[0139] The on-off valve V51 is provided in the purge gas supply pipe L51, the control valve V1r is provided in the purge gas supply pipe L52, and the control valve V1p is provided in the purge gas supply pipe L53. The on-off valve V51, the control valve V1r, and the control valve V1p are electrically connected to the control unit 210. The on-off valve V51, the control valve V1r, and the control valve V1p are driven in accordance with command signals output from the control unit 210.

[0140] During normal operation, the on-off valve V51, the control valve V1r, and the control valve V1p are closed.

[0141] After normal operation, the purge gas supply unit 50 opens the on-off valve V51, the control valve V1r, and the control valve V1p to supply purge gas to the first space 20a and the second space 20b of the separation tank 20. A portion of the purge gas passes through the purge gas supply pipe L51, the purge gas supply pipe L52, and the raw gas supply pipe L11 and is supplied to the first space 20a of the separation tank 20. A portion of the purge gas passes through the purge gas supply pipe L51 and the purge gas supply pipe L53 and is supplied to the second space 20b of the separation tank 20.

[0142] The control unit 210 controls the valve opening of the control valve V1r to control the flow rate of the purge gas supplied to the first space 20a of the separation tank 20. The control unit 210 controls the valve opening of the control valve V1p to control the flow rate of the purge gas supplied to the second space 20b of the separation tank 20.

[0143] The purge gas supply pipe L52 is provided with a flow meter 223r. The flow meter 223r detects the flow rate of the purge gas flowing through the purge gas supply pipe L52. Data related to the flow rate of the purge gas detected by the flow meter 223r is transmitted to the control unit 210.

[0144] The purge gas supply pipe L53 is provided with a flow meter 223p. The flow meter 223p detects the flow rate of the purge gas flowing through the purge gas supply pipe L53. Data relating to the flow rate of the purge gas detected by the flow meter 223p is transmitted to the control unit 210.

[0145] [Purge gas supply source] The supply source of the purge gas is not particularly limited. The supply source of the purge gas may be a high-pressure cylinder. The high-pressure cylinder ensures the supply pressure (filling pressure) of the purge gas. This eliminates the need for a separate pumping unit to pump the purge gas in the gas recovery system 100D.

[0146] The purge gas supply unit 50 may supply outside air (air) as the purge gas. The gas recovery system 100D may include a pressure-transfer unit (blower, pump) that pressure-transfers the purge gas. The purge gas supply unit 50 may also include a drying unit that dries the purge gas. The purge gas supply unit 50 may also supply, as the purge gas, nitrogen gas generated by a nitrogen gas generator that generates nitrogen gas from outside air.

[0147] [Control unit 210] Next, the control unit 210 of the gas recovery system 100D will be described with reference to Fig. 9. Fig. 9 is a block diagram illustrating the hardware configuration of the gas recovery system 100D according to the fourth embodiment. As shown in Fig. 9, the control unit 210 is electrically connected to the water vapor concentration meters 221r ​​and 222p and the flow meters 223r and 223p. The control unit 210 is electrically connected to the switching valves V11A and V11B, the pressure control valve V31, the differential pressure drive mechanism 41, the switching valves V41A and V41B, the on-off valve V51, and the control valves V1r and V1p.

[0148] The control unit 210 includes a CPU 211 and a memory unit 212. The CPU (Center Processing Unit) 211 may execute overall control of the gas recovery system 100. The CPU 211 can control the switching operation of the switching valves V11A and V11B. The CPU 211 can control the operation of the pressure control valve V31. The CPU 211 can control the operation of the differential pressure drive mechanism 41. The CPU 211 can control the operation of the switching valves V41A and V41B. The CPU 211 can control the opening and closing operation of the on-off valve V51. The CPU 211 can control the valve opening degrees of the control valves V1r and V1p.

[0149] [Purge Procedure in Gas Recovery System 100D] Next, the procedure of the purging process in the gas recovery system 100 will be described with reference to Fig. 10. Fig. 10 is a flow chart illustrating the procedure of the purging process in the gas recovery system according to the fourth embodiment.

[0150] In normal operation, the gas recovery system 100 supplies raw gas to the first space 20a of the separation tank 20 and separates carbon dioxide from the raw gas. The retentate gas that did not permeate the separation membrane is discharged from the first space 20a. The permeate gas that permeated the separation membrane is discharged from the second space 20b of the separation tank 20.

[0151] In the gas recovery system 100, a purging process can be executed after normal operation. First, the control unit 210 operates the on-off valve V51, the switching valves V11A and V11B, and the switching valves V41A and V41B to switch the flow path (step S31). Specifically, the control unit 210 closes the switching valves V11A and V41A and opens the switching valves V11B and V41B.

[0152] Furthermore, after the control unit 210 stops the differential pressure driving mechanism 41 that is in operation, the control unit 210 opens the on-off valve V51.

[0153] Next, the control unit 210 opens the control valves V1r and V1p (step S32), thereby supplying the purge gas to the first space 20a and the second space 20b of the separation tank 20.

[0154] Next, the control unit 210 calculates a purge time T1r for the first space 20a and a purge time T1p for the second space 20b. The purge time T1r for the first space 20a may be the purge time for the first space 20a and a piping system communicating with the first space 20a. The purge time T1p for the second space 20b may be the purge time for the second space 20b and a piping system communicating with the second space 20b.

[0155] The purge time T1r of the first space 20a can be calculated using, for example, the following equation (3).

[0156] T1r=(V1r / F1r)×σ1 (3)

[0157] Here, "V1r" is the sum of the volume of the first space 20a and the volume of the retentate-side flow path communicating with this first space 20a. "F1r" is the flow rate of the purge gas supplied to the first space 20a (retentate-side purge flow rate). "σ1" may be any purge time tolerance in the gas recovery system 100.

[0158] The purge time T1p of the second space 20b can be calculated using, for example, the following equation (4).

[0159] T1p=(V1p / F1p)×σ1 (4)

[0160] Here, "V1p" is the sum of the volume of the second space 20b and the volume of the permeate-side flow path communicating with this second space 20p. "F1p" is the flow rate of the purge gas supplied to the second space 20p (permeate-side purge flow rate).

[0161] The control unit 210 determines whether the purge time T1r of the first space 20a is equal to or greater than the purge time T1p of the second space 20b (step S33). If the purge time T1r is equal to or greater than the purge time T1p (step S33; YES), the control unit 210 executes the process of step S34. If the purge time T1 is less than the purge time T1p (step S33; NO), the control unit 210 executes the process of step S38.

[0162] In step S34, it is determined whether the water vapor concentration C1p is less than or equal to the first determination threshold value CG1. The water vapor concentration C1p is the water vapor concentration detected by the water vapor concentration meter 222p. The water vapor concentration C1p is the water vapor concentration in the permeation side flow path. The "first determination threshold value CG1" is an arbitrary determination threshold value for determining the end of purging. The "first determination threshold value CG1" may be a water vapor concentration value at which no problem occurs even if water vapor remains in the flow path.

[0163] If the water vapor concentration C1p≦the first determinator threshold value CG1 (step S34; YES), the control unit 210 executes the process of step S35. If the water vapor concentration C1p>the first determinator threshold value CG1 (step S34; NO), the control unit 210 waits until the water vapor concentration C1p≦the first determinator threshold value CG1, and then executes the process of step S35.

[0164] In step S35, the control unit 210 closes the control valve V1p. As a result, the control unit 210 ends the supply of the purge gas to the second space 20b. After the supply of the purge gas to the second space 20b is ended, the control unit 210 may execute control to increase the flow rate of the purge gas supplied to the first space 20a.

[0165] In step S36, it is determined whether the water vapor concentration C1r is less than or equal to the first determination threshold CG1. The water vapor concentration C1r is the water vapor concentration detected by the water vapor concentration meter 221r. The water vapor concentration C1r is the water vapor concentration in the non-permeated flow path.

[0166] If the water vapor concentration C1r≦the first determinator threshold value CG1 (step S36; YES), the control unit 210 executes the process of step S37. If the water vapor concentration C1r>the first determinator threshold value CG1 (step S36; NO), the control unit 210 waits until the water vapor concentration C1r≦the first determinator threshold value CG1, and then executes the process of step S37.

[0167] In step S37, the control unit 210 closes the control valve V1r. This causes the control unit 210 to stop supplying the purge gas to the first space 20a. The control unit 210 then ends the processing here.

[0168] In step S38, it is determined whether the water vapor concentration C1r is equal to or smaller than the first determination device threshold value CG1.

[0169] If the water vapor concentration C1r≦the first determinator threshold value CG1 (step S38; YES), the control unit 210 executes the process of step S39. If the water vapor concentration C1r>the first determinator threshold value CG1 (step S38; NO), the control unit 210 waits until the water vapor concentration C1r≦the first determinator threshold value CG1, and then executes the process of step S39.

[0170] In step S39, the control unit 210 closes the control valve V1r. As a result, the control unit 210 ends the supply of purge gas to the first space 20a. After the supply of purge gas to the first space 20a is ended, the control unit 210 may execute control to increase the flow rate of the purge gas supplied to the second space 20b.

[0171] In step S40, it is determined whether the water vapor concentration C1p≦the first determiner threshold value CG1.

[0172] If the water vapor concentration C1p≦the first determinator threshold value CG1 (step S40; YES), the control unit 210 executes the process of step S41. If the water vapor concentration C1p>the first determinator threshold value CG1 (step S40; NO), the control unit 210 waits until the water vapor concentration C1p≦the first determinator threshold value CG1, and then executes the process of step S41.

[0173] In step S41, the control unit 210 closes the control valve V1p. As a result, the control unit 210 stops supplying the purge gas to the second space 20b. The control unit 210 then ends the process here.

[0174] For example, if the purging process is performed during an emergency shutdown, the gas recovery system 100 may resume normal operation after the purging process. An emergency shutdown may also be during a power outage, for example.

[0175] In the state after the purging process and before the start of operation, the on-off valve V51 and the control valves V1r and V1p are closed. The control unit 210 opens the switching valves V11A and V41A and closes the switching valves V11B and V41B.

[0176] The control unit 210 can drive the differential pressure driving mechanism 41 to start (restart) normal operation.

[0177] [Actions and Effects of the Gas Recovery System 100D According to the Fourth Embodiment] A gas recovery system 100D according to the fourth embodiment includes a raw material gas supply unit 10 that supplies a raw material gas, a separation tank 20 having a first space 20a to which the raw material gas is supplied and a second space 20b into which carbon dioxide (separated gas) separated from the raw material gas flows, a first discharge unit 30 that communicates with the first space 20a and discharges an unpermeated gas (first gas) obtained by separating carbon dioxide from the raw material gas, a second discharge unit 40 that communicates with the second space 20b and discharges a permeated gas (second gas) containing carbon dioxide, a purge gas supply pipe (first purge gas supply unit) L52 that supplies a purge gas (first purge gas) to the first space 20a, and a purge gas supply pipe (second purge gas supply unit) L53 that supplies a purge gas (second purge gas) to the second space 20b. After normal operation of separating carbon dioxide in the separation tank 20 is stopped, a purge process is performed to supply purge gases (first purge gas and second purge gas). The "first purge gas" is a purge gas that flows through the purge gas supply pipe L52 and is supplied to the first space 20a, and the "second purge gas" is a purge gas that flows through the purge gas supply pipe L53 and is supplied to the second space 20b.

[0178] According to the gas recovery system 100D, by supplying a purge gas to the first space 20a of the separation tank 20, the water vapor and water droplets in the first space 20a can be discharged to the outside of the first space 20a. According to the gas recovery system 100, by supplying a purge gas to the second space 20b of the separation tank 20, the water vapor and water droplets in the second space 20b can be discharged to the outside of the second space 20b.

[0179] In the gas recovery system 100D, evaporation of water droplets inside the separation tank 20 can be promoted. Furthermore, in the gas recovery system 100D, dust inside the separation tank 20 can be discharged to the outside of the separation tank 20. This reduces the amount of water vapor and water droplets remaining in the separation tank 20 during periods when the gas recovery system 100 is out of operation. Therefore, in the gas recovery system 100, the risk of a decrease in the gas adsorption, absorption, and permeability performance of the separation tank 20 occurring the next time the system is operated (when operation is resumed) is reduced. Furthermore, by reducing the amount of water vapor and water droplets remaining in the separation tank 20 during outages, damage to the separation medium (e.g., separation membrane) due to frozen water droplets can be prevented, for example, in winter. As a result, performance degradation or internal leakage in the separation tank 20 can be suppressed.

[0180] In the gas recovery system 100D, the separation tank 20 has a separation membrane disposed between the first space 20a and the second space 20b, and the second discharge unit 40 has a differential pressure driving mechanism 41 that generates a differential pressure between the first space 20a and the second space 20b. According to the gas recovery system 100D having this configuration, by supplying purge gas to the differential pressure driving mechanism 41 during the purging process, water droplets, water vapor, dust, etc. in the flow path of the differential pressure driving mechanism 41 can be discharged to the outside of the differential pressure driving mechanism 41. The occurrence of malfunctions in the differential pressure driving mechanism 41 can be suppressed during the next operation. The reliability of the gas recovery system 100D can be improved.

[0181] The gas recovery system 100D of this embodiment includes a control unit 210 that controls operation during the purging process, and the raw gas supply unit 10 includes a raw gas supply pipe L11 that communicates with the first space 20a and supplies raw gas to the first space 20a, a pipe (first branch pipe) L12 that branches off from the raw gas supply pipe L11, and switching valves (first switching valves) V11A, V11B that switch the inflow destination of the raw gas flowing through the raw gas supply pipe L11 to the pipe L12.

[0182] The first discharge section 30 includes a first discharge pipe (first gas discharge pipe) L31 that is connected to the first space 20a and discharges non-permeated gas (first gas) from the first space 20a, a pressure control valve (first control valve) V31 that is provided in the first discharge pipe L31 and can control the pressure in the first space 20a, and a water vapor concentration meter (first water vapor concentration sensor) 221r ​​that is connected to the first discharge pipe L31 and detects the water vapor concentration in the first discharge pipe L31.

[0183] The second exhaust section 40 has a second exhaust pipe (second gas exhaust pipe) L41 that communicates with the second space 20b, is connected to a differential pressure drive mechanism 41, and exhausts the permeable gas (second gas) from the second space 20b, a purge gas exhaust pipe (second branch pipe) L42 that branches off from the second exhaust pipe L41, and switching valves (second switching valves) V41A, V41B that switch the inflow destination of the purge gas (second purge gas) flowing through the purge gas exhaust pipe L42 to the purge gas exhaust pipe L42.

[0184] The first purge gas supply unit includes a purge gas supply pipe (first purge gas supply pipe) L52 connected to the raw material gas supply pipe L11 downstream of the switching valve (first switching valve) V11A, a control valve (second control valve) V1r provided in the purge gas supply pipe L52 to control the flow rate of the first purge gas flowing through the purge gas supply pipe L52, and a flow meter (first flow sensor) 223r connected to the purge gas supply pipe L52 to detect the flow rate of the gas flowing through the purge gas supply pipe L52.

[0185] The second purge gas supply unit includes a purge gas supply pipe (second purge gas supply pipe) L53 that is connected to the second space 20b and supplies a second purge gas to the second space 20b, a control valve (third control valve) V1p that is provided in the purge gas supply pipe L53 and controls the flow rate of the gas flowing through the purge gas supply pipe L53, and a flow meter (second flow sensor) 223p that is connected to the purge gas supply pipe L53 and detects the flow rate of the gas flowing through the purge gas supply pipe L53.

[0186] The control unit 210 can control the supply amount of the first purge gas supplied to the first space 20a based on the detection result by the water vapor concentration meter 221r, and can control the supply amount of the second purge gas supplied to the second space 20b based on the detection result by the water vapor concentration meter 222p.

[0187] The gas recovery system 100D having this configuration can control the flow rate of the purge gas supplied to the first space 20a according to the water vapor concentration in the non-permeated side flow path, and the gas recovery system 100D can control the flow rate of the purge gas supplied to the second space 20b according to the water vapor concentration in the permeated side flow path.

[0188] In addition, in the gas recovery system 100D, the control unit 210 has a first purge time calculation unit that calculates a first purge time required for the water vapor concentration in the first space 20a to become equal to or lower than the judgment threshold based on the detection results from the water vapor concentration meter 221r ​​and the detection results from the flow meter 223r, and a second purge time calculation unit that calculates a second purge time required for the water vapor concentration in the second space 20b to become equal to or lower than the judgment threshold based on the detection results from the water vapor concentration meter 222p and the detection results from the flow meter 223p, and the control unit 210 can compare the first purge time with the second purge time and change at least one of the supply amount of the first purge gas and the supply amount of the second purge gas.

[0189] According to the gas recovery system 100D having this configuration, it is possible to determine which of the first space 20a and the second space 20b will finish first by comparing the first purge time and the second purge time. The gas recovery system 100D can execute control to change the supply amount of purge gas according to the first purge time and the second purge time.

[0190] In addition, in the gas recovery system 100D, the control unit 210 may perform control to increase the supply amount of the first purge gas when the first purge time is longer than the second purge time, and to increase the supply amount of the second purge gas when the second purge time is longer than the first purge time.

[0191] In addition, in the gas recovery system 100D, the control unit 210 may compare the detection results from the water vapor concentration meter 221r ​​with the detection results from the water vapor concentration meter 222p, and perform control to increase the supply amount of the first purge gas when the water vapor concentration in the first space 20a is higher than the water vapor concentration in the second space 20b, and to increase the supply amount of the second purge gas when the water vapor concentration in the second space 20b is higher than the water vapor concentration in the first space 20a.

[0192] [Gas recovery system 100E according to the fifth embodiment] Next, a gas recovery system 100E according to a fifth embodiment will be described with reference to Fig. 11. Fig. 11 is a block diagram illustrating the hardware configuration of the gas recovery system 100E according to the fifth embodiment. The gas recovery system 100E according to the fifth embodiment shown in Fig. 11 differs from the gas recovery system 100D according to the fourth embodiment shown in Fig. 9 in that it includes a power supply switching unit 250 that can switch the power supply connection destination. Note that in the description of the fifth embodiment, descriptions similar to those of the first to fourth embodiments may be omitted.

[0193] The gas recovery system 100E may include a purge control unit 210A and a process control unit 210B. The purge control unit 210A controls the purge process. The process control unit 210B controls the normal operation. The purge control unit 210A and the process control unit 210B each include a CPU 211 and a storage unit 212.

[0194] During normal operation, the purge control unit 210A and the process control unit 210B are supplied with power from a normal power supply 241. During a power outage, power is supplied from an uninterruptible power supply 242 to the purge control unit 210A.

[0195] The gas recovery system 100E includes a power supply switching unit 250 that can switch the power supply source in the event of a power outage. A terminal 251 of the power supply switching unit 250 is connected to a normal power supply 241, a terminal 252 is connected to an uninterruptible power supply 242, and a terminal 253 is connected to the purge control unit 210A.

[0196] During normal operation, the power supply switching unit 250 connects terminal 251 and terminal 253. During a power outage, the power supply switching unit 250 connects terminal 252 and terminal 253. The power supply switching unit 250 performs a switching operation, thereby connecting the uninterruptible power supply 242 and the purge control unit 210A during a power outage. As a result, power is supplied from the uninterruptible power supply 242 to the purge control unit 210A during a power outage. During a power outage, the purge control unit 210A operates in the same manner as the control unit 210 according to the above embodiment, switching the flow paths to supply purge gas to the first space 20a and the second space 20b of the separation tank 20.

[0197] [Actions and Effects of the Gas Recovery System 100E According to the Fifth Embodiment] The gas recovery system 100E has a power supply switching unit 250 that switches the power supply source from a normal power supply (first power supply) 241 that supplies power during normal operation to an uninterruptible power supply (second power supply) 242 that supplies power during a power outage when the normal power supply 241 cannot be used.

[0198] According to such a gas recovery system 100E, when power cannot be supplied from the normal power supply 241, the purging process can be performed by supplying power from the uninterruptible power supply 242. Therefore, the water vapor concentration in the flow path can be reduced, and the performance degradation of the gas recovery system 100E after the operation is resumed can be suppressed.

[0199] In the gas recovery system 100E, the first switching valve includes a switching valve (first on-off valve) V11A provided in the raw material gas supply pipe L11 and a switching valve (second on-off valve) V11B provided in the pipe (first branch pipe) L12, and the second switching valve includes a switching valve (third on-off valve) V41A provided in the second exhaust pipe L41 and a switching valve (fourth on-off valve) V41B provided in the purge gas exhaust pipe (second branch pipe) L42, wherein the switching valve V11A is in an open state during normal operation and is switched to a closed state during a power outage, the switching valve V11B is in a closed state during normal operation and is switched to an open state during a power outage, the switching valve V41A is in an open state during normal operation and is switched to a closed state during a power outage, and the switching valve V41B is in an open state during normal operation and is switched to an open state during a power outage.

[0200] In the event of a power outage, by performing the switching operation in this manner, purge gas can be supplied to both the first space 20a and the second space 20b.

[0201] [Gas recovery system 100F according to the sixth embodiment] Next, a gas recovery system 100F according to a sixth embodiment will be described with reference to FIG. 12. FIG. 12 is a block diagram illustrating the hardware configuration of the gas recovery system 100F according to the sixth embodiment. The gas recovery system 100F according to the sixth embodiment shown in FIG. 12 differs from the gas recovery system 100D according to the fourth embodiment shown in FIG. 9 in that it includes a control unit 210C and a control unit 210D. The control unit 210C is an example of a purge control unit, and the control unit 210D is an example of a process control unit. In the description of the sixth embodiment, explanations similar to those of the first to fifth embodiments may be omitted.

[0202] The control unit 210C is electrically connected to the water vapor concentration meters 221r ​​and 222p, the flow meters 223r and 223p, the pressure control valve V31, and the control valves V1r and V1p.

[0203] The control unit 210D is electrically connected to the switching valves V11A and V11B, the on-off valve V51, and the switching valves V41A and V41B.

[0204] The switching valves V11A, V41A and the on-off valve V51 are normally closed valves. The switching valves V11B, V41B are normally open valves. In the event of an emergency stop, the normally closed valves are automatically shut off and the normally open valves are automatically opened. This reduces the power supply required for the opening and closing of the valves during purge operation.

[0205] [Gas recovery system 100G according to the seventh embodiment] Next, a gas recovery system 100G according to a seventh embodiment will be described with reference to FIG. 13. FIG. 13 is a schematic diagram illustrating the gas recovery system 100G according to the seventh embodiment. FIG. 14 is a block diagram illustrating the hardware configuration of the gas recovery system 100G according to the seventh embodiment. The gas recovery system 100G according to the seventh embodiment shown in FIG. 13 differs from the gas recovery system 100D according to the fourth embodiment shown in FIG. 8 in that it includes a separation tank 20B, a purge gas supply pipe L54 that supplies purge gas to the first space 20a of the separation tank 20B, a purge gas supply pipe L55 that supplies purge gas to the second space 20b of the separation tank 20B, and switching valves V41C and V41D. Note that in the description of the seventh embodiment, descriptions similar to those of the first to sixth embodiments may be omitted.

[0206] In this way, the gas recovery system 100G may include multiple separation tanks 20, 20B. The switching valve V41C is driven in the same manner as the switching valve V41A. The switching valve V41D is driven in the same manner as the switching valve V41B. The control valve V2r is driven in the same manner as the control valve V1r. The control valve V2p is driven in the same manner as the control valve V1p.

[0207] A portion of the purge gas flows through purge gas supply pipes L51 and L54 and is supplied to the first space 20a of the separation tank 20B. A portion of the purge gas flows through purge gas supply pipes L51 and L55 and is supplied to the second space 20b of the separation tank 20B.

[0208] [Gas recovery system 100H according to the eighth embodiment] Next, a gas recovery system 100H according to an eighth embodiment will be described with reference to Fig. 15. Fig. 15 is a schematic diagram illustrating a gas recovery system 100H according to the eighth embodiment. The gas recovery system 100H according to the eighth embodiment shown in Fig. 15 differs from the gas recovery system 100G according to the seventh embodiment shown in Fig. 13 in that it includes a recycle section 70 that returns the retentate gas in the separation tank 20B to the upstream side of the separation tank 20, and that it includes a gas mixing header 12. Note that in the description of the seventh embodiment, descriptions similar to those of the first to sixth embodiments may be omitted.

[0209] [Gas Mixing Header 12] The gas recovery system 100H includes a gas mixing header 12 provided upstream of the first-stage separation tank 20. The gas mixing header 12 is a mixing vessel that mixes the retentate gas discharged from the separation tank 20B with the raw material gas. The gas mixing header 12 is connected to a raw material gas supply pipe L11. The gas mixing header 12 is connected to a recycle pipe L71 that is connected to the separation tank 20B. The retentate gas discharged from the separation tank 20B flows through the recycle pipe L71 and is supplied to the gas mixing header 12. The retentate gas discharged from the separation tank 20B and the raw material gas are mixed in the gas mixing header 12 and supplied to the separation tank 20.

[0210] [Recycling Department 70] The gas recovery system 100H includes a recycle section 70 that returns the retentate gas discharged from the separation tank 20B to the supply side of the separation tank 20. The recycle section 70 includes a recycle pipe L71 and a blower 71.

[0211] The recycle pipe L71 connects the first space 20a of the separation tank 20B to the gas mixing header 12. The blower 71 is connected to the recycle pipe L71. The blower 71 blows the retentate gas discharged from the separation tank 20B and transfers it to the gas mixing header 12. The recycle unit 70 may include another transfer unit such as a pump instead of the blower 71. The recycle unit 70 may also include a flow control valve, a pressure control valve, a branch flow path, a pressure gauge, a flow meter, a container, and the like, connected to the recycle pipe L71.

[0212] The recycle pipe L71 is provided with a water vapor concentration meter 225. The water vapor concentration meter 225 may be disposed in the recycle pipe L71 at a position close to the gas mixing header 12. The water vapor concentration meter 225 can detect the concentration of water vapor inside the recycle pipe L71. Data related to the water vapor concentration detected by the water vapor concentration meter 225 is input to the control unit 210.

[0213] In this way, the gas recovery system 100H may include a recycle section 70 that returns the gas on the retentate side of the second-stage separation tank 20B to the first space 20a of the first-stage separation tank 20.

[0214] During the purging process, the purge gas supplied to the first space 20a of the separation tank 20B flows through the recycle pipe L71 and the flow path in the blower 71, and is returned to the raw material gas supply pipe L11.

[0215] In the gas recovery system 100H including such a recycle section 70, a purge process can be performed.

[0216] [Gas recovery system 100I according to the ninth embodiment] Next, a gas recovery system 100I according to a ninth embodiment will be described with reference to Fig. 16. Fig. 16 is a schematic diagram illustrating a gas recovery system 100I according to the ninth embodiment. The gas recovery system 100I according to the ninth embodiment shown in Fig. 16 differs from the gas recovery system D according to the fourth embodiment shown in Fig. 9 in that it includes a heat exchanger 80 that heats the purge gas. Note that in the description of the ninth embodiment, explanations similar to those of the first to eighth embodiments may be omitted.

[0217] The gas recovery system 100I includes a heat exchanger 80, a pipe L81, and a pipe L82. The pipe L81 connects the gas supply pipe L11 to the inlet side of the heat exchanger 80. The pipe L82 connects the outlet side of the heat exchanger 80 to the gas supply pipe L11. The raw material gas flows through the pipe L81 and is supplied to the heat exchanger 80. After heat exchange in the heat exchanger 80, the raw material gas flows through the pipe L81 and is supplied to the gas supply pipe L11, passes through the pipe L12, and is discharged to the outside of the raw material gas supply unit 10.

[0218] The purge gas supply unit 50 of the gas recovery system 100I includes a pipe L56, a pipe L57, a control valve V1a, a control valve V1b, a flow meter 223a, and a thermometer 224b. The pipe L56 connects the purge gas supply pipe L51 to the inlet side of the heat exchanger 80. The pipe 57 connects the outlet side of the heat exchanger 80 to the purge gas supply pipe L51. The purge gas flows through the pipe L56 and is supplied to the heat exchanger 80. The purge gas supplied to the heat exchanger 80 is heated by heat exchange with the raw material gas. After being heated in the heat exchanger 80, the purge gas flows through the pipe L57 and is supplied to the purge gas supply pipe L51. The heated purge gas is supplied to the first space 20a or the second space 20b.

[0219] The control valve V1a is a flow rate control valve provided in the pipe L56. The control valve V1a is controlled by the control unit 210, and can adjust the flow rate of the purge gas supplied to the heat exchanger 80.

[0220] The purge gas supply pipe L51 includes a pipe L51a. The pipe L51a is a part of the purge gas supply pipe L51 and is a pipe between the connection position with the pipe L56 and the connection position with the pipe L57. The purge gas that is not supplied to the heat exchanger 80 flows through the pipe L51a.

[0221] The control valve V1b is a flow rate control valve provided in the pipe L51a. The control valve V1b is controlled by the control unit 210 and can adjust the flow rate of the purge gas flowing through the pipe L51a.

[0222] The flow meter 223a detects the flow rate of the purge gas flowing through the pipe L56. Data relating to the flow rate detected by the flow meter 223a is output to the control unit 210.

[0223] Thermometer 224b detects the temperature of the purge gas flowing through pipe L51. Thermometer 224b is arranged downstream of the connection position with pipe L57. Thermometer 224b can detect the temperature of the purge gas supplied to separation tank 20. Data related to the temperature detected by thermometer 224b is output to control unit 210.

[0224] The control unit 210 can control the flow rate of the purge gas supplied to the heat exchanger 80 by controlling the control valves V1a and V1b based on the temperature detected by the thermometer 224b.

[0225] The gas recovery system 100I may include a heat exchanger 80 that exchanges heat between the raw material gas and the purge gas. During the purge process, the raw material gas can be used as a heat source to raise the temperature of the purge gas. This promotes drying in the separation tank 20 to which the purge gas is supplied and in the flow paths within the differential pressure driving mechanism 41, thereby preventing moisture from accumulating. The temperature of the purge gas is equal to or lower than the heat-resistant temperatures of the separation tank 20 and the differential pressure driving mechanism 41. The heat source for raising the temperature of the purge gas is not limited to the raw material gas.

[0226] [Gas recovery system 100J according to the tenth embodiment] Next, a gas recovery system 100J according to a tenth embodiment will be described with reference to FIG. 17. FIG. 17 is a schematic diagram illustrating the gas recovery system 100J according to the tenth embodiment. The gas recovery system 100J according to the tenth embodiment shown in FIG. 17 differs from the gas recovery system 100D according to the fourth embodiment shown in FIG. 8 in that the purge gas is supplied from a second exhaust pipe L41. The gas recovery system 100J includes a purge gas supply pipe L53B instead of the purge gas supply pipe L53. Note that in the description of the tenth embodiment, explanations similar to those of the first to ninth embodiments may be omitted.

[0227] The purge gas supply unit 50 of the gas recovery system 100J includes a purge gas supply pipe L53B. The purge gas supply pipe L51 branches into a purge gas supply pipe L52 and a purge gas supply pipe L53B. The purge gas supply pipe L53B is connected to the second exhaust pipe L41. The purge gas supply pipe L53B is connected to the second exhaust pipe L41 between the differential pressure drive mechanism 41 and the switching valve V41A.

[0228] The purge gas supply pipe L53B is provided with a flow meter 223p, a control valve V1p, and a switching valve V41B.

[0229] A purge gas discharge pipe L43 is connected to the second space 20b of the separation tank 20. A flow meter 223p is provided in the purge gas discharge pipe L42. A switching valve may be provided in the purge gas discharge pipe L43. The purge gas flows through the purge gas supply pipe L51, the purge gas supply pipe L53B, and the second discharge pipe L41, and is supplied to the second space 20b. The purge gas supplied to the second space 20b flows through the purge gas discharge pipe L42 and is released.

[0230] In the gas recovery system 100J, the flow direction of the purge gas may be opposite to that in the gas recovery system 100D. In the gas recovery system 100J having this configuration, the purge gas that has flowed through the purge gas supply pipe L53B is supplied to the differential pressure driving mechanism 41 before it reaches the second space 20b. After flowing through the second space 20b, the purge gas is not supplied to the differential pressure driving mechanism 41 but is released to the atmosphere.

[0231] It should be noted that the present invention is not limited to the configurations shown here, and other embodiments may be possible in which other components are combined with the configurations described in the above embodiments. In this regard, the present invention can be modified within the scope of the present invention, and can be appropriately determined depending on the application form. [Explanation of symbols]

[0232] 100, 100B, 100C, 100D, 100E, 100F: gas recovery system, 10: raw material gas supply unit, 11: blower, 20, 20B, 20C: separation tank, 21: separation membrane module, 30: first discharge unit, 40: second discharge unit, 41: differential pressure drive mechanism, 50, 50B: purge gas supply unit, 210, 210A, 210B, 210C, 210D: control unit, 22 1,222: dew point meter, L11... raw gas piping, V11: on-off valve (first on-off valve), V31: on-off valve (fourth on-off valve), V41: on-off valve (third on-off valve), V51: second on-off valve, L11: raw gas supply piping, L31: piping (first exhaust piping), L41: piping (second exhaust piping), L42: piping (purge gas exhaust piping), L51, L51B: purge gas supply piping.

Claims

1. a raw material gas supply unit that supplies a raw material gas; a separation tank for separating carbon dioxide from the raw material gas; a first discharge section that discharges a first gas from the separation tank; a second discharge section that discharges a second gas having a higher carbon dioxide concentration than the first gas from the separation tank; a purge gas supply unit that supplies a purge gas, A gas recovery system that performs a purge process of supplying the purge gas to the separation tank after a normal operation of separating carbon dioxide.

2. The raw material gas supply unit a blower that blows the raw material gas; a raw material gas supply pipe connected to the blower and configured to supply the raw material gas to the separation tank; a first on-off valve provided in the raw material gas supply pipe, The purge gas supply unit is a purge gas supply pipe connected to the raw material gas supply pipe and configured to supply the purge gas to the separation tank; a second on-off valve provided in the purge gas supply pipe, 2. The gas recovery system according to claim 1, wherein when the purging process is performed, the first on-off valve is closed and the second on-off valve is opened to supply the purge gas to the separation tank.

3. The first discharge section is a first discharge pipe connected to the separation tank and discharging the first gas from the separation tank; The second discharge section is a second discharge pipe connected to the separation tank and configured to discharge the second gas from the separation tank; a differential pressure drive mechanism connected to the second discharge pipe; a third on-off valve provided in the second discharge pipe; a purge gas discharge pipe branching from the second discharge pipe and discharging the purge gas, 3. The gas recovery system according to claim 1, wherein when the purging process is performed, the flow path is switched by the third on-off valve to discharge the purge gas through the purge gas discharge pipe.

4. a control unit for controlling an operation in the purging process, The control unit determining whether a preset termination condition is met based on the water vapor concentration and dew point temperature inside the separation tank, and terminating the purging process if the termination condition is met; The gas recovery system according to claim 3 , wherein the control unit determines the end of the purge gas using different end conditions depending on the processing capacity of the separation tank.

5. a dew point meter capable of detecting a dew point temperature inside the separation tank; The gas recovery system according to claim 4 , wherein the control unit determines whether the termination condition is met using the dew point temperature detected by the dew point meter.

6. a raw material gas supply unit that supplies a raw material gas; a separation tank for separating carbon dioxide from the raw material gas; a first discharge section that discharges a first gas from the separation tank; a second discharge section that discharges a second gas having a higher carbon dioxide concentration than the first gas from the separation tank; a purge gas supply unit that supplies a purge gas, A gas recovery system that performs a purge process of supplying the purge gas to the separation tank before the start of the next operation, and transitions to normal operation of separating carbon dioxide after the purge process.

7. 2. The gas recovery system according to claim 1, wherein a plurality of types of separation membranes are provided inside the separation tank.

8. a storage unit that stores an arithmetic expression for calculating the execution time of the purge process; The calculation formula is: a first arithmetic expression for calculating a length of a first execution time required to discharge water vapor in the separation tank to the outside of the separation tank; a second calculation formula for calculating the length of a second execution time required to discharge the dust accumulated in the separation tank to the outside, the control unit calculates the length of the execution time based on the arithmetic expression; The gas recovery system of claim 4 , wherein the termination condition includes exceeding the execution time.

9. The separation tank includes a separation membrane, The raw material gas flows from below upward and is supplied to the separation membrane, 2. The gas recovery system according to claim 1, wherein the first gas, which is a non-permeated gas that does not permeate the separation membrane, is discharged upward from above.

10. the purge gas supply unit is connected to the first exhaust unit; 2. The gas recovery system according to claim 1, wherein the purge gas is supplied to the separation tank via a first discharge pipe connected to the separation tank and discharging the first gas from the separation tank.

11. The first discharge section is a first discharge pipe connected to the separation tank and configured to discharge the first gas from the separation tank; a fourth on-off valve provided in the first discharge pipe, The purge gas supply unit is a purge gas supply pipe connected to the first discharge pipe and configured to supply the purge gas to the separation tank; a second on-off valve provided in the purge gas supply pipe, The gas recovery system according to claim 10 , wherein when the purging process is performed, the fourth on-off valve is closed and the second on-off valve is opened to supply the purge gas to the separation tank.

12. a normal operation step of supplying a raw material gas to a separation tank and separating carbon dioxide from the raw material gas; a purging step of supplying a purge gas to the separation tank after the normal operation step is completed.

13. a normal operation step of supplying a raw material gas to a separation tank and separating carbon dioxide from the raw material gas; a purging step of supplying a purge gas to the separation tank after the normal operation step is completed and before the next normal operation step; a next normal operation step of supplying a raw material gas to the separation tank after the purge treatment step is completed, and separating carbon dioxide from the raw material gas. A gas recovery method comprising:

14. a raw material gas supply unit that supplies a raw material gas; a separation tank having a first space to which the raw material gas is supplied and a second space to which a separated gas separated from the raw material gas flows; a first exhaust section communicating with the first space and configured to exhaust a first gas obtained by separating the separated gas from the raw material gas; a second exhaust section communicating with the second space and configured to exhaust a second gas containing the separation gas; a first purge gas supply unit that supplies a first purge gas to the first space; a second purge gas supply unit that supplies a second purge gas to the second space, a gas recovery system that performs a purge process of supplying the first purge gas and the second purge gas after a normal operation of separating the separated gas in the separation tank is stopped;

15. the separation tank has a separation membrane disposed between the first space and the second space, The gas recovery system according to claim 14 , wherein the second discharge unit has a differential pressure generating mechanism that generates a differential pressure between the first space and the second space.

16. a control unit for controlling an operation in the purging process, The raw material gas supply unit a source gas supply pipe that is in communication with the first space and that supplies the source gas to the first space; a first branch pipe branching from the source gas supply pipe; a first switching valve that switches the inflow destination of the raw material gas flowing through the raw material gas supply pipe to the first branch pipe, The first discharge section is a first gas exhaust pipe communicating with the first space and configured to exhaust the first gas from the first space; a first control valve provided in the first gas exhaust pipe and capable of controlling the pressure in the first space; a first water vapor concentration sensor connected to the first gas exhaust pipe and configured to detect a water vapor concentration in the first gas exhaust pipe; The second discharge section is a second gas exhaust pipe that communicates with the second space, that is connected to the differential pressure generating mechanism, and that exhausts the second gas from the second space; a second branch pipe branching from the second gas exhaust pipe; a second switching valve that switches the destination of the second purge gas flowing through the second gas exhaust pipe to the second branch pipe; a second water vapor concentration sensor connected to the second gas exhaust pipe and configured to detect a water vapor concentration in the second gas exhaust pipe; The first purge gas supply unit includes: a first purge gas supply pipe connected to the source gas supply pipe downstream of the first switching valve; a second control valve provided in the first purge gas supply pipe and configured to control a flow rate of the first purge gas flowing through the first purge gas supply pipe; a first flow rate sensor connected to the first purge gas supply pipe and configured to detect a flow rate of gas flowing through the first purge gas supply pipe; The second purge gas supply unit includes: a second purge gas supply pipe communicating with the second space and supplying the second purge gas to the second space; a third control valve provided in the second purge gas supply pipe to control the flow rate of gas flowing through the second purge gas supply pipe; a second flow rate sensor connected to the second purge gas supply pipe and configured to detect a flow rate of gas flowing through the second purge gas supply pipe; The control unit controlling a supply amount of a first purge gas supplied to the first space based on a detection result by the first water vapor concentration sensor; 16. The gas recovery system according to claim 15, wherein the supply amount of the second purge gas supplied to the second space is controlled based on the detection result of the second water vapor concentration sensor.

17. 17. The gas recovery system according to claim 16, further comprising a power supply switching unit that switches the power supply source from a first power source that supplies power during normal operation to a second power source that supplies power during a power outage when the first power source cannot be used.

18. The first switching valve is a first on-off valve provided in the raw material gas supply pipe; a second on-off valve provided in the first branch pipe, The second switching valve is a third on-off valve provided in the second gas exhaust pipe; a fourth on-off valve provided in the second branch pipe, the first on-off valve is in an open state during normal operation and is switched to a closed state during a power outage; the second on-off valve is in a closed state during normal operation and is switched to an open state during a power outage; the third on-off valve is in an open state during normal operation and is switched to a closed state during a power outage; 18. The gas recovery system according to claim 17, wherein the fourth on-off valve is in an open state during normal operation and is switched to an open state during a power outage.

19. The control unit a first purge time calculation unit that calculates a first purge time required for the water vapor concentration in the first space to become equal to or less than a determination threshold value based on a detection result by the first water vapor concentration sensor and a detection result by the first flow rate sensor; a second purge time calculation unit that calculates a second purge time required for the water vapor concentration in the second space to become equal to or less than a determination threshold value based on a detection result by the second water vapor concentration sensor and a detection result by the second flow rate sensor, 17. The gas recovery system according to claim 16, wherein at least one of the supply amount of the first purge gas and the supply amount of the second purge gas is changed by comparing the first purge time and the second purge time.

20. The control unit increasing a supply amount of the first purge gas when the first purge time is longer than the second purge time; 20. The gas recovery system according to claim 19, wherein the supply amount of the second purge gas is increased when the second purge time is longer than the first purge time.

21. The control unit comparing the detection result of the first water vapor concentration sensor with the detection result of the second water vapor concentration sensor; increasing a supply amount of the first purge gas when the water vapor concentration in the first space is higher than the water vapor concentration in the second space; 17. The gas recovery system according to claim 16, wherein the supply amount of the second purge gas is increased when the water vapor concentration in the second space is higher than the water vapor concentration in the first space.

22. a first separation tank which is the separation tank; a second separation tank connected downstream of the first separation tank and having a first space to which the second gas is supplied and a second space into which a separated gas separated from the second gas flows; a third discharge section that communicates with the first space of the second separation tank and discharges a third gas obtained by separating the separated gas from the second gas; a fourth discharge section that communicates with the second space of the second separation tank and discharges a fourth gas containing the separated gas; a third purge gas supply unit that supplies a third purge gas to the first space of the second separation tank; a fourth purge gas supply unit that supplies a fourth purge gas to the second space of the second separation tank, The gas recovery system according to claim 16, wherein a purge process is performed to supply the third purge gas and the fourth purge gas after the normal operation is stopped.

23. The third discharge section is a recycle pipe that returns the third gas discharged from the first space of the second separation tank to the first space of the first separation tank; a recycled gas transfer unit connected to the recycled pipe and transferring the gas in the recycled pipe; a water vapor concentration sensor connected to the recycle pipe and detecting the water vapor concentration in the recycle pipe, In the purging process, the third purge gas discharged from the first space of the second separation tank flows through the recycle pipe, 23. The gas recovery system according to claim 22, wherein the control unit controls the supply amount of the third purge gas based on the water vapor concentration in the recycle pipe.

24. a separation step of supplying a source gas to a first space of a separation tank having a first space and a second space, separating the source gas into a first gas and a second gas, and discharging the first gas from the first space and the second gas from the second space; a first purge gas supplying step of supplying a first purge gas to the first space after the normal operation is stopped due to the separation step; a second purge gas supplying step of supplying a second purge gas to the second space after normal operation is stopped by the separation step.

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