Carbon dioxide capture system

Abstract

To provide a carbon dioxide recovery system capable of suppressing effects of water and foreign matters other than water adhering to an electrochemical cell.SOLUTION: A system comprises an electrochemical cell 12a, which adsorbs carbon dioxide by application of an adsorption potential and desorbs the adsorbed carbon dioxide by application of a desorption potential, collection units 11, 13, 14, 16, which collect the carbon dioxide desorbed from the electrochemical cell, and a blower 19, which feeds an atmosphere containing carbon dioxide into a housing when the electrochemical cell adsorbs carbon dioxide contained in atmosphere. A controller 17, when not controlling the electrochemical cell and the collection units to adsorb carbon dioxide, activates the blower to force out air to remove water and / or foreign matters other than water adhering to the electrochemical cell.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a carbon dioxide recovery system that recovers carbon dioxide from the atmosphere containing carbon dioxide.

Background Art

[0002] In Patent Document 1, a gas separation system that separates carbon dioxide from a mixed gas containing carbon dioxide by an electrochemical reaction has been proposed. In this gas separation system, a mixed gas containing carbon dioxide is introduced into a housing in which an electrochemical cell is disposed. In a charging mode in which electrons are directed to the negative electrode of the electrochemical cell, the electroactive material provided at the negative electrode is reduced. For this reason, a bond between the electroactive material at the negative electrode and carbon dioxide occurs, and carbon dioxide is separated from the mixed gas. On the other hand, in a discharging mode in which an electron flow is generated in a direction opposite to the electron flow during the charging mode, the electroactive material at the negative electrode is oxidized. As a result, carbon dioxide is released from the electroactive material at the negative electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the atmosphere contains moisture (water vapor) and foreign substances other than moisture (such as dust and pollen). Therefore, when the electrochemical cell is exposed to the atmosphere to adsorb carbon dioxide from the atmosphere, it is inevitable that moisture and foreign substances other than moisture adhere to the electrochemical cell. When moisture and foreign substances other than moisture adhere to the electrochemical cell, there is a risk that the electrochemical cell may not be able to sufficiently exhibit its performance of adsorbing carbon dioxide, or an unintended short - circuit may occur due to moisture.

[0005] This disclosure is made in view of the above-mentioned points and aims to provide a carbon dioxide recovery system that can suppress the effects of moisture and other foreign substances adhering to the electrochemical cell. [Means for solving the problem]

[0006] To achieve the above objectives, the carbon dioxide capture system described herein is This method recovers carbon dioxide from the atmosphere containing carbon dioxide through an electrochemical reaction. An electrochemical cell (12a) is placed inside the enclosure and adsorbs carbon dioxide when an adsorption potential is applied, and desorbs the adsorbed carbon dioxide when a desorption potential is applied, Recovery units (11, 13, 14, 16) that recover carbon dioxide released from the electrochemical cell, A control unit (17) controls the electrochemical cell and the recovery unit so as to apply an adsorption potential to the electrochemical cell to adsorb carbon dioxide contained in the air introduced into the enclosure onto the electrochemical cell, apply a desorption potential to the electrochemical cell to desorb carbon dioxide from the electrochemical cell, and recover the desorbed carbon dioxide in the recovery unit. The system includes a control unit that controls the air supply unit (19, 13) that sends air containing carbon dioxide into the housing when the electrochemical cell adsorbs carbon dioxide from the atmosphere, The control unit is At least no adsorption potential is applied to the electrochemical cell, and carbon dioxide is being recovered in the recovery unit. When not present, the system is configured to remove moisture and / or other foreign matter adhering to the electrochemical cell by activating the blower unit to forcibly pass air through the housing.

[0007] In this way, the control unit can remove moisture and / or other foreign substances adhering to the electrochemical cell by forced airflow from the blower unit, thereby suppressing the effects of moisture and other foreign substances adhering to the electrochemical cell.

[0008] The reference numbers in parentheses above are merely examples of correspondences with specific configurations in embodiments described later, in order to facilitate understanding of this disclosure, and are not intended to limit the scope of this disclosure in any way.

[0009] Furthermore, technical features described in each claim of the patent claims, other than those described above, will become clear from the description of the embodiments and the accompanying drawings, which will be discussed later. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the configuration of the carbon dioxide capture system 10 according to the embodiment. [Figure 2] This flowchart shows the processes performed in the control unit to execute a series of control sequences for carbon dioxide capture. [Figure 3] (a)-(c) are explanatory diagrams illustrating the adsorption mode, scavenging mode, and desorption / recovery mode included in a series of control sequences. [Figure 4] This flowchart shows the foreign matter removal process, primarily for removing foreign substances other than water that adhere to an electrochemical cell. [Figure 5] This flowchart shows the water removal process, primarily for removing water that adheres to an electrochemical cell. [Figure 6] This flowchart shows a condensation prevention process that detects situations where moisture is likely to adhere to an electrochemical cell and suppresses moisture adhesion. [Modes for carrying out the invention]

[0011] Hereinafter, a carbon dioxide capture system according to an embodiment of this disclosure will be described in detail with reference to the drawings. Parts that are identical or equivalent to each other across multiple drawings are denoted by the same reference numerals. The carbon dioxide capture system according to this embodiment captures carbon dioxide from the atmosphere containing carbon dioxide. The air from which the carbon dioxide has been removed is discharged to the outside. Figure 1 schematically shows the configuration of the carbon dioxide capture system 10 according to this embodiment.

[0012] The carbon dioxide capture system 10 shown in Figure 1 includes a flow control valve 11, a capture unit 12, a pump 13, a flow control valve 14, a CO2 sensor 15, a CO2 capture tank 16, a control device 17, a blower 19, a temperature sensor 20, a humidity sensor 21, and an external server 22.

[0013] The flow control valve 11 is controlled to open or close by the control device 17. When the flow control valve 11 is open, air containing carbon dioxide can be introduced into the recovery unit 12 via the flow control piping that connects the atmosphere and the recovery unit 12. On the other hand, when the flow control valve 11 is closed, the flow control piping that connects the atmosphere and the recovery unit 12 is blocked, and the recovery unit 12 is sealed. As a result, air cannot enter the recovery unit 12 through the flow control piping where the flow control valve 11 is installed.

[0014] Although not shown in the illustration, each blower 19 has a fan that is rotated by a motor. When the flow path valve 11 is open, the fan of the blower 19 is driven to rotate by the control device 17. As a result, air containing carbon dioxide is sent into the recovery unit 12 through the flow path piping that connects the atmosphere and the inside of the recovery unit 12. However, the blower 19 may be omitted. Alternatively, the pump 13 may also perform the role of the blower 19. That is, when the flow path valve 11 is open, the pump 13 may be driven to draw air containing carbon dioxide from the outside into the recovery unit 12 through the flow path piping. Therefore, either the blower 19 or the pump 13 corresponds to the air supply unit.

[0015] The recovery unit 12 includes an electrochemical cell 12a, for example, located inside a metal casing. The electrochemical cell 12a is capable of adsorbing carbon dioxide through an electrochemical reaction, separating it from the atmosphere, and desorbing the adsorbed carbon dioxide, which is then stored in a CO2 recovery tank 16 by a pump 13. The recovery unit 12 has two openings. One opening is an inlet for introducing air containing carbon dioxide from the outside into the casing of the recovery unit 12. The other opening is an outlet for discharging the air from which carbon dioxide has been removed, or the carbon dioxide desorbed from the electrochemical cell 12a. The flow channel piping equipped with the aforementioned flow channel valve 11 is connected to the inlet, and the flow channel piping equipped with the pump 13 is connected to the outlet. Note that "inside the recovery unit 12" is synonymous with "inside the casing."

[0016] Multiple electrochemical cells 12a are stacked inside the housing of the recovery unit 12. The stacking direction of the multiple electrochemical cells 12a is perpendicular to the direction of atmospheric flow. Each electrochemical cell 12a is constructed in a plate shape, and its plate surface is arranged to intersect with the cell stacking direction. A predetermined gap is provided between adjacent electrochemical cells 12a. The gap provided between adjacent electrochemical cells 12a serves as a flow path for the atmosphere.

[0017] Each electrochemical cell 12a is configured by laminating, for example, a working electrode current collector layer, a working electrode, a separator, a counter electrode, and a counter electrode current collector layer in the described order. Note that the working electrode is the negative electrode, and the counter electrode paired with the working electrode is the positive electrode. By changing the potential difference applied between these working electrode and counter electrode, electrons can be given to the working electrode to adsorb carbon dioxide to the carbon dioxide adsorbent of the working electrode, or electrons can be released from the working electrode to desorb the adsorbed carbon dioxide. That is, by applying an adsorption potential between the working electrode and the counter electrode of the electrochemical cell 12a, carbon dioxide can be adsorbed to the electrochemical cell 12a (carbon dioxide adsorbent of the working electrode). Further, by applying a desorption potential different from the adsorption potential between the working electrode and the counter electrode of the electrochemical cell 12a, carbon dioxide can be desorbed from the electrochemical cell 12a.

[0018] The working electrode current collector layer is made of a porous conductive material having pores through which air containing carbon dioxide can pass. The working electrode current collector layer only needs to have gas permeability and conductivity, and for example, a metal material or a carbonaceous material can be used as the material for forming the working electrode current collector layer.

[0019] The working electrode is formed of a material in which a carbon dioxide adsorbent, a conductive substance, a binder, etc. are mixed. The carbon dioxide adsorbent has the property of adsorbing carbon dioxide by receiving electrons and desorbing the adsorbed carbon dioxide by releasing electrons. For example, polyanthraquinone can be used as the carbon dioxide adsorbent. The conductive substance forms a conduction path to the carbon dioxide adsorbent. As the conductive substance, for example, carbon materials such as carbon nanotubes, carbon black, and graphene can be used. The binder is for holding the carbon dioxide adsorbent and the conductive substance. For example, a conductive resin can be used as the binder. As the conductive resin, for example, an epoxy resin containing Ag or the like as a conductive filler, a fluororesin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc. can be used.

[0020] The counter electrode is formed from a mixture of materials including an electroactivating auxiliary, a conductive substance, and a binder. The conductive substance and binder of the counter electrode are the same as those of the working electrode, so their explanation is omitted. The electroactivating auxiliary of the counter electrode is composed of a material having an active substance that acts as an electron donor. The electroactivating auxiliary of the counter electrode is an auxiliary electroactive species that facilitates electron transfer with the carbon dioxide adsorbent of the working electrode. As an electroactivating auxiliary, for example, a metal complex that enables electron transfer by changing the valence of metal ions can be used. Examples of such metal complexes include cyclopentadienyl metal complexes such as ferrocene, nickerosene, and cobaltocene, or porphyrin metal complexes. These metal complexes may be polymers or monomers. The counter electrode current collector layer is formed from a conductive material such as a metal material or a carbonaceous material, similar to the working electrode current collector layer.

[0021] A separator is placed between the working electrode and the counter electrode to separate them. The separator is an insulating ion-permeable membrane that prevents physical contact between the working electrode and the counter electrode, thereby suppressing electrical short circuits, while also allowing ions to pass through. Cellulose membranes, polymers, composite materials of polymers and ceramics, etc., can be used as separators.

[0022] Furthermore, the electrochemical cell 12a is provided with an electrolyte that spans both the working electrode and the counter electrode. For example, an ionic liquid can be used as the electrolyte. An ionic liquid is a salt of a liquid that is non-volatile at room temperature and pressure.

[0023] Pump 13 sucks in residual air from which carbon dioxide has been removed, which remains in the recovery unit 12, and releases it to the outside (i.e., scavenging the residual air in the recovery unit 12), and when the carbon dioxide adsorbent desorbs the carbon dioxide, it sucks in the desorbed carbon dioxide from the recovery unit 12 and discharges it toward the CO2 recovery tank 16. When pump 13 scavenges the residual air in the recovery unit 12, the flow path valve 11 shuts off the flow path piping that connects the outside and the inside of the recovery unit 12. In other words, the flow path valve 11 is open only during the adsorption mode when the control device 17 performs control for carbon dioxide recovery and adsorbs carbon dioxide onto the electrochemical cell 12a (carbon dioxide adsorbent), and is closed during the scavenging mode when residual air is scavenged from inside the recovery unit 12, and during the desorption / recovery mode when the electrochemical cell 12a desorbs the adsorbed carbon dioxide and recovers it in the CO2 recovery tank 16. Therefore, the residual air in the recovery unit 12 is scavenged by vacuuming using the pump 13. Furthermore, the subsequent discharge of carbon dioxide into the CO2 recovery tank 16 is also carried out under conditions closer to a vacuum than atmospheric pressure.

[0024] The flow path switching valve 14 is a three-way valve that switches the flow path of the gas (atmosphere or carbon dioxide) flowing through the piping downstream of the pump 13. The switching of the flow path of the flow path switching valve 14 is controlled by the control device 17. Specifically, when atmospheric air containing carbon dioxide is introduced into the recovery unit 12, and when residual atmospheric air in the recovery unit 12 is scavenged by the pump 13, the control device 17 controls the flow path switching valve 14 to connect the piping downstream of the pump 13 to the outside (atmosphere). As a result, the atmospheric air from which carbon dioxide has been removed, and the residual atmospheric air in the recovery unit 12, are released to the outside. On the other hand, when the electrochemical cell 12a desorbs the carbon dioxide it has adsorbed, and the pump 13 sucks the desorbed carbon dioxide from the recovery unit 12 and discharges it, the control device 17 controls the flow path switching valve 14 to connect the piping downstream of the pump 13 to the CO2 recovery tank 16. As a result, the carbon dioxide recovered by the recovery unit 12 can be stored in the CO2 recovery tank 16.

[0025] The CO2 sensor 15 detects the carbon dioxide concentration and flow rate of the gas flowing through the piping connected to the CO2 recovery tank 16 at predetermined time intervals. The control device 17 can calculate (detect) the amount of carbon dioxide recovered in the CO2 recovery tank 16 from the carbon dioxide concentration and flow rate detected by the CO2 sensor 15. Alternatively, the amount of carbon dioxide recovered may be calculated by the CO2 sensor 15. In this case, the CO2 sensor 15 outputs the calculated amount of carbon dioxide recovered to the control device 17.

[0026] The control device 17 consists of a well-known microcomputer including a CPU, ROM, and RAM, and its peripheral devices. The peripheral devices include a transceiver that communicates with an external server 22, etc.

[0027] The temperature sensor 20 detects the ambient temperature around the carbon dioxide capture system 10. The humidity sensor 21 detects the humidity around the carbon dioxide capture system 10. The temperature and humidity detected by the temperature sensor 20 and humidity sensor 21 are provided to the control device 17. The external server 22 provides the control device 17 with weather information (for example, weather information such as rain and snow, as well as warning information such as low temperature and frost) for the area where the carbon dioxide capture system 10 is installed. The external server 22 can obtain weather information and various warning information from information published by, for example, the Japan Meteorological Agency.

[0028] The control device 17 performs various calculations based on a control program stored in a storage medium such as ROM, and controls the operation of various controlled devices such as the flow path opening / closing valve 11, the recovery unit 12, the pump 13, the flow path switching valve 14, and the blower 19. Furthermore, the control device 17 communicates with the external server 22 via the transmitting / receiving unit. Based on the information detected by the temperature sensor 20 and the humidity sensor 21, and the information obtained through communication with the external server 22, the control device 17 determines whether or not it is necessary to perform foreign matter removal processing and / or moisture removal processing. If it determines that it is necessary, the control device 17 performs foreign matter removal processing and / or moisture removal processing. Foreign matter removal processing and moisture removal processing will be described in detail later.

[0029] In this embodiment, the control device 17 controls the operation of various controlled devices so that, when performing control for carbon dioxide recovery, a series of control sequences including at least an adsorption mode, a scavenging mode, and a desorption / recovery mode are executed in the carbon dioxide recovery system 10. Note that the desorption / recovery mode indicates that the desorption mode and the recovery mode are combined into a single mode.

[0030] The following describes a series of control sequences for carbon dioxide recovery performed in the carbon dioxide recovery system 10, which include at least an adsorption mode, a scavenging mode, and a desorption / recovery mode. Figure 2 is a flowchart showing the processes performed in the control device 17 to execute the series of control sequences. Figures 3(a)-(c) are explanatory diagrams illustrating the adsorption mode, scavenging mode, and desorption / recovery mode included in the series of control sequences.

[0031] As shown in the flowchart of Figure 2, the control device 17 first starts the adsorption mode, which is the first operating mode in a series of control sequences, in step S100. In this adsorption mode, as shown in Figure 3(a), the flow path valve 11 is opened to allow air containing carbon dioxide to be introduced into the recovery device 12. If a blower 19 is provided, the blower 19 is driven at a predetermined constant rotational speed to ensure that a predetermined amount of air is introduced into the recovery device 12. If the pump 13 also serves the role of the blower 19, the pump 13 is driven by a motor (not shown) at a predetermined rotational speed to draw in air and bring air into the recovery device 12 from the outside. In this case, since the pump 13 is driven simply to draw in air from the outside, the energy required for this suction is less than the energy required to drive the pump for vacuuming in the scavenging mode and desorption / recovery mode described later.

[0032] Furthermore, in adsorption mode, an adsorption potential is applied between the working electrode and the counter electrode of the electrochemical cell 12a of the recovery unit 12, such that the carbon dioxide adsorbent at the working electrode can adsorb carbon dioxide. This adsorption potential is a predetermined constant potential. In addition, in adsorption mode, as shown in Figure 3(a), the flow path switching valve 14 is controlled to connect the flow path piping downstream of the pump 13 to the outside.

[0033] Through the control of the flow control valve 11, the electrochemical cells 12a of the recovery unit 12, and the flow control valve 14, in the adsorption mode, as shown by the dotted arrow in Figure 3(a), air containing carbon dioxide passes through the flow control valve 11 and enters the recovery unit 12. The carbon dioxide contained in the air that enters the recovery unit 12 is adsorbed by multiple electrochemical cells 12a. As a result, carbon dioxide is removed from the air. The air from which carbon dioxide has been removed passes through the pump 13 and is guided by the flow control valve 14 to a flow pipe leading to the outside, and is released to the outside through that flow pipe.

[0034] In step S110 of the flowchart in Figure 2, the control device 17 determines whether the suction mode execution time has elapsed. The suction mode execution time is set by the control device 17. In step S110, it is determined whether the set suction mode execution time has elapsed.

[0035] In the determination process of step S110, if it is determined that the set adsorption mode execution time has elapsed, the process proceeds to step S120. On the other hand, if it is determined that the set adsorption mode execution time has not elapsed, the determination process of step S110 is repeatedly executed until the adsorption mode execution time has elapsed.

[0036] In step S120, the adsorption mode termination process is executed. Specifically, the control device 17 closes the flow path valve 11 to block the flow of air into the recovery unit 12 from the outside. If a blower 19 is provided, the control device 17 also stops the operation of the blower 19. The control device 17 also resets the count value of the counter that counts the adsorption mode execution time.

[0037] In step S130, the control device 17 starts the scavenging mode, which is the second operating mode of the series of control sequences. In this scavenging mode, the flow path valve 11 remains closed, as shown in Figure 3(b). The adsorption potential applied between the working electrode and the counter electrode of the electrochemical cell 12a of the recovery unit 12 is maintained. Communication between the flow path piping downstream of the pump 13 and the outside is also maintained by the flow path switching valve 14.

[0038] In scavenging mode, the pump 13 is started. As described above, the flow path valve 11 is closed, so the recovery unit 12 is sealed upstream of the pump 13. When the pump 13 is started in this state, the residual air, which is the air from which carbon dioxide has been removed and remains in the sealed recovery unit 12, is sucked out of the recovery unit 12 and released to the outside. This allows the residual air in the recovery unit 12 to be scavenged. Since the recovery unit 12 upstream of the pump 13 is sealed, the scavenging of the residual air in the recovery unit 12 is performed by vacuuming with the pump 13. For this reason, for example, if the pump 13 also functions as a blower 19, the pump 13 continues to run, but its output is increased compared to the intake mode when the scavenging mode starts.

[0039] Through the control of the flow control valve 11, the electrochemical cell 12a of the recovery unit 12, the pump 13, and the flow control valve 14, in the scavenging mode, as shown by the dotted arrow in Figure 3(b), the residual air from which carbon dioxide has been removed in the recovery unit 12 passes through the pump 13, is guided by the flow control valve 14 to a flow pipe leading to the outside, and is released to the outside through that flow pipe.

[0040] In step S140 of the flowchart in Figure 2, the control device 17 determines whether the scavenging mode execution time has elapsed. This scavenging mode execution time is predetermined to be sufficient time to scavenge the residual air in the recovery unit 12.

[0041] In the determination process of step S140, if it is determined that a predetermined scavenging mode execution time has elapsed, the process proceeds to step S150. On the other hand, if it is determined that the set scavenging mode execution time has not elapsed, the determination process of step S140 is repeatedly executed until the scavenging mode execution time has elapsed. In step S150, the scavenging mode termination process is executed. Specifically, the control device 17 resets the count value of the counter that counts the scavenging mode execution time, etc.

[0042] In step S160, the control device 17 starts the desorption / recovery mode, which is the third operating mode in the series of control sequences. In this desorption / recovery mode, the flow path valve 11 is kept closed, as shown in Figure 3(c). The pump 13 also continues to be driven with the same drive output as in the scavenging mode, as it sucks up the carbon dioxide desorbed from the adsorbent of the electrochemical cell 12a in a state closer to a vacuum than atmospheric pressure.

[0043] Meanwhile, a desorption potential is applied between the working electrode and the counter electrode of the electrochemical cell 12a of the recovery unit 12, causing electrons to be released from the working electrode, thereby enabling the desorption of carbon dioxide adsorbed by the carbon dioxide adsorbent on the working electrode. This desorption potential is a predetermined constant potential. Furthermore, in the desorption / recovery mode, as shown in Figure 3(c), the flow path switching valve 14 is controlled to connect the piping downstream of the pump 13 to the CO2 recovery tank 16.

[0044] Through the control of the flow control valve 11, the electrochemical cell 12a, the pump 13, and the flow control valve 14 of the recovery unit 12, in the desorption / recovery mode, as shown by the dotted arrow in Figure 3(c), carbon dioxide desorbed from the adsorbent of the electrochemical cell 12a passes through the pump 13 and is guided by the flow control valve 14 to a flow control pipe leading to the CO2 recovery tank 16, where it is accumulated in the CO2 recovery tank 16 via that flow control pipe. Therefore, the flow control valve 11, the pump 13, the flow control valve 14, and the CO2 recovery tank 16 correspond to the recovery section that recovers carbon dioxide desorbed from the electrochemical cell 12a.

[0045] In this process, the concentration and flow rate of carbon dioxide flowing through the piping toward the CO2 recovery tank 16 are detected by the CO2 sensor 15. Based on the detection results from the CO2 sensor 15, the control device 17 can calculate the amount of carbon dioxide recovered in the CO2 recovery tank 16 by executing a series of control sequences. The concentration of carbon dioxide flowing through the piping toward the CO2 recovery tank 16 is usually close to 100%. For this reason, the CO2 sensor 15 may be a sensor capable only of detecting the flow rate of carbon dioxide.

[0046] Furthermore, the desorption / recovery mode does not perform carbon dioxide desorption and recovery simultaneously. Instead, carbon dioxide is desorbed from the electrochemical cell 12a first, and the recovery of the desorbed carbon dioxide is started after a predetermined time has elapsed since the desorption. In other words, the desorption mode and the recovery mode can be separated, and the start time of the recovery mode can be delayed compared to the start time of the desorption mode, thereby shortening the execution time of the recovery mode. In this case, the pump 13 is temporarily stopped when the desorption mode starts. With the pump 13 stopped, a desorption potential is applied between the working electrode and the counter electrode of the electrochemical cell 12a to desorb carbon dioxide from the carbon dioxide adsorbent on the working electrode. After a predetermined time has elapsed since the start of the desorption mode and a certain amount of carbon dioxide desorption has progressed, the recovery mode is started and the pump 13 is restarted. As a result, the pump 13 only needs to be driven in the recovery mode, making it possible to drive the pump 13 efficiently. However, even during the recovery mode in which the pump 13 is driven, a desorption potential is applied between the working electrode and the counter electrode of the electrochemical cell 12a, and the desorption of carbon dioxide from the electrochemical cell 12a continues. In other words, when the recovery mode is executed, the desorption mode is also executed, and the recovery mode and the desorption mode are executed simultaneously.

[0047] In step S170 of the flowchart in Figure 2, the control device 17 determines whether the detachment / recovery mode execution time or the recovery mode execution time (hereinafter referred to as the recovery mode execution time) has elapsed. The recovery mode execution time is set by the control device 17. In step S170, it is determined whether the set recovery mode execution time has elapsed.

[0048] In the determination process in step S170, if it is determined that the set recovery mode execution time has elapsed, the process proceeds to step S180. On the other hand, if it is determined that the set recovery mode execution time has not elapsed, the determination process in step S170 is repeatedly executed until the recovery mode execution time has elapsed.

[0049] In step S180, the recovery mode termination process is executed. Specifically, the control device 17 opens the flow path valve 11 to connect the recovery unit 12 to the outside. However, the flow path valve 11 may be opened at the start of the adsorption mode and kept closed at the end of the recovery mode. The control device 17 stops applying the desorption potential to the electrochemical cell 12a. The control device 17 stops driving the pump 13. The control device 17 switches the flow path switching valve 14 to connect the flow path piping downstream of the pump 13 to the outside. This connection of the flow path piping downstream of the pump 13 to the outside may also be performed at the start of the adsorption mode. Furthermore, the control device 17 also resets the count value of the counter that counts the recovery mode execution time.

[0050] In this context, the atmosphere contains moisture (water vapor) and other foreign substances (such as dust and pollen). Therefore, when the electrochemical cell 12a is exposed to the atmosphere to adsorb carbon dioxide, it is unavoidable that moisture and other foreign substances will adhere to the electrochemical cell 12a. If moisture or other foreign substances adhere to the electrochemical cell 12a, the electrochemical cell 12a may not be able to fully perform its carbon dioxide adsorption function, or moisture may cause unintended short circuits.

[0051] Therefore, in the carbon dioxide recovery system 10 according to this disclosure, when the control device 17 is not controlling the recovery unit, such as the electrochemical cell 12a, the flow path on / off valve 11, the pump 13, the flow path switching valve 14, and the CO2 recovery tank 16, to adsorb carbon dioxide, the blower 19 or pump 13 is activated as a blower unit. As a result, air is forcibly passed through the recovery unit 12, so that moisture and other foreign matter attached to the electrochemical cell 12a can be removed. Consequently, the carbon dioxide recovery system 10 according to this disclosure can suppress the effects of moisture and other foreign matter attached to the electrochemical cell 12a.

[0052] First, when foreign matter other than water adheres to the electrochemical cell 12a, the foreign matter removal process for removing such foreign matter will be explained with reference to the flowchart in Figure 4. The foreign matter removal process shown in the flowchart in Figure 4 can be performed, for example, periodically by the control device 17.

[0053] First, in step S200, the control device 17 determines whether the conditions for removing foreign matter other than water have been met. The conditions for executing this foreign matter removal process can be at least one of the following: the amount of carbon dioxide recovered, calculated based on the detection value of the CO2 sensor 15, has decreased by a predetermined percentage or more from the initial amount recovered; the number of repetitions of the carbon dioxide recovery cycle (a series of control sequences) has reached a predetermined number; and the operating time of the carbon dioxide recovery system 10 has reached a predetermined time. If any one of these conditions is met, it can be estimated that foreign matter other than water has adhered to the electrochemical cell 12a. In other words, a positive judgment in the determination process of step S200 corresponds to the estimation unit estimating that foreign matter other than water has adhered to the electrochemical cell 12a. Note that the conditions for executing the foreign matter removal process are not limited to the conditions described above. For example, if the user instructs the electrochemical cell 12a to be cleaned, it may also be determined that the conditions for executing the foreign matter removal process have been met. If the control device 17 determines in step S200 that the conditions for executing the foreign matter removal process have been met, it proceeds to the process of step S210. On the other hand, if the control device 17 determines that the execution conditions are not met, it terminates the foreign matter removal process shown in Figure 4.

[0054] In step S210, the control device 17 initializes a timer that counts the execution time of the foreign matter removal process, and then starts the timer count. In step S220, the control device 17 turns on the blower 19, opens the flow path switching valve 11, and controls the flow path switching valve 14 to connect the piping downstream of the pump 13 to the outside. As a result, the air blown out by the blower 19 flows through the recovery unit 12 and the pump 13, as shown in Figure 3(a), and is discharged to the outside. At this time, foreign matter other than water adhering to the electrochemical cell 12a in the recovery unit 12 is detached from the electrochemical cell 12a by the air and discharged to the outside with the air. Furthermore, even if some water is adhering to the electrochemical cell 12a, the air blown out by the blower 19 will also release the water to the outside along with other foreign matter.

[0055] In step S230, the control device 17 acquires the ambient temperature detected by the temperature sensor 20 and the humidity detected by the humidity sensor 21, as well as weather information from the external server 22. Then, in step S240, based on the various information acquired in step S230, the control device 17 determines whether there is a possibility that some moisture may adhere to the surface of the electrochemical cell 12a, and whether there is a possibility that a short circuit abnormality may occur in the electrochemical cell 12a due to the moisture adhering to the surface when a potential is applied between the working electrode and the counter electrode of the electrochemical cell 12a.

[0056] For example, if the acquired weather information indicates rain or snow, or if the humidity is relatively high (e.g., above the first threshold), and the outside temperature drops, the temperature difference between the electrochemical cell 12a and the outside temperature becomes large (e.g., above the second threshold), condensation may occur on the surface of the electrochemical cell 12a. If condensation occurs on the surface of the electrochemical cell 12a, a short-circuit malfunction may occur in the electrochemical cell 12a via the moisture adhering to the surface.

[0057] If the control device 17 determines in step S240 that there is a possibility of a short-circuit abnormality occurring in the electrochemical cell 12a, it proceeds to the process in step S260. On the other hand, if it determines that there is no possibility of a short-circuit abnormality occurring in the electrochemical cell 12a, the control device 17 proceeds to the process in step S250.

[0058] In step S250, since it is considered that a short circuit will not occur in the electrochemical cell 12a even if a potential is applied between the working electrode and the counter electrode of the electrochemical cell 12a, the control device 17 applies a desorption potential to the electrochemical cell 12a. This allows carbon dioxide adhering to the electrochemical cell 12a to be desorbed, and at the same time, the removal of foreign substances other than water adhering to the electrochemical cell 12a can be promoted. On the other hand, in S260, since a short circuit may occur in the electrochemical cell 12a if a potential is applied between the working electrode and the counter electrode of the electrochemical cell 12a, the control device 17 turns off the application of voltage to the electrochemical cell 12a. However, even in this case, water and foreign substances other than water adhering to the electrochemical cell 12a are removed by the air blown by the blower 19.

[0059] In step S270, the control device 17 determines whether the timer count value has reached or exceeded a predetermined foreign matter removal determination time. If the timer count value is less than the predetermined foreign matter removal determination time, the control device 17 repeats the process in step S270 until it reaches or exceeds the predetermined foreign matter removal determination time. When the timer count value reaches or exceeds the predetermined foreign matter removal determination time, the control device 17 considers that sufficient foreign matter removal has been performed and proceeds to the process in step S280.

[0060] In step S280, the control device 17 determines whether or not to start executing a series of control sequences. For example, if there is a user request to start, or if the execution of a series of control sequences after the foreign matter removal process is reserved, the control device 17 determines to start executing the series of control sequences. In this case, the control device 17 proceeds to the process in step S290 and transitions to the adsorption mode, which is the first operating mode of the series of control sequences.

[0061] On the other hand, if the execution of the series of control sequences is not initiated, the control device 17 proceeds to step S300. In step S300, the control device 17 stops the operation of the carbon dioxide capture system 10 by turning off the blower 19, closing the flow path on / off valve 11, turning off the voltage application to the electrochemical cell 12a, turning off the pump 13, and controlling the flow path switching valve 14 to connect the downstream piping of the pump 13 to the outside.

[0062] Next, a moisture removal process for removing moisture that has adhered to the electrochemical cell 12a will be explained with reference to the flowchart in Figure 5. The moisture removal process shown in the flowchart of Figure 5 can be performed, for example, periodically by the control device 17, similar to the foreign matter removal process in Figure 4.

[0063] First, in step S400, the control device 17 acquires the ambient temperature detected by the temperature sensor 20 and the humidity detected by the humidity sensor 21, and also acquires weather information from the external server 22. Then, in step S410, based on the various information acquired in step S400, the control device 17 determines whether the conditions for performing the moisture removal process have been met. The conditions for performing this moisture removal process can be at least one of the following: for example, the acquired weather information indicates rain or snow, a frost warning has been issued, or the ambient temperature has decreased when the humidity is somewhat high (for example, above the first threshold), resulting in a large temperature difference between the temperature of the electrochemical cell 12a and the ambient temperature (for example, above the second threshold). If any one of these conditions is met, it can be estimated that moisture has adhered to the electrochemical cell 12a. In other words, a positive judgment in the determination process of step S410 corresponds to the estimation unit estimating that moisture has adhered to the electrochemical cell 12a. In this way, it is possible to estimate that moisture has adhered to the electrochemical cell 12a based on the atmospheric temperature (outside temperature) and humidity, and / or based on acquired weather information. Note that the conditions for performing the moisture removal process are not limited to those described above. For example, if the carbon dioxide capture system 10 was stopped at night when the temperature was low, the moisture adhesion may be estimated when it is started up the following morning. If the control device 17 determines in step S410 that the conditions for performing the moisture removal process have been met, it proceeds to the process in step S420. On the other hand, if the control device 17 determines that the conditions for performing the process have not been met, it terminates the moisture removal process shown in Figure 5.

[0064] In step S420, the control device 17 initializes a timer that counts the execution time of the moisture removal process, and then starts the timer count. In step S430, the control device 17 turns on the blower 19, opens the flow path valve 11, turns off the voltage application to the electrochemical cell 12a, turns off the pump 13, and controls the flow path switching valve 14 to connect the piping downstream of the pump 13 to the outside. As a result, the air blown out by the blower 19 flows through the recovery unit 12 and the pump 13, as shown in Figure 3(a), and is discharged to the outside. At this time, moisture adhering to the electrochemical cell 12a in the recovery unit 12 is detached from the electrochemical cell 12a by the air and discharged to the outside with the air. Furthermore, if any foreign matter other than moisture is adhering to the electrochemical cell 12a, the foreign matter other than moisture is also discharged to the outside along with the moisture.

[0065] In step S440, the control device 17 determines whether the timer count value has reached or exceeded a predetermined moisture removal determination time. This moisture removal determination time may be the same as or different from the foreign matter removal determination time. If the timer count value is less than the predetermined moisture removal determination time, the control device 17 repeats the process in step S440 until it reaches or exceeds the predetermined moisture removal determination time. Once the timer count value reaches or exceeds the predetermined moisture removal determination time, the control device 17 proceeds to the process in step S450.

[0066] In step S450, the control device 17 determines whether or not to start executing the series of control sequences. For example, if there is a user request to start, or if the user has reserved the execution of the series of control sequences after the moisture removal process, the control device 17 determines to start executing the series of control sequences. In this case, the control device 17 proceeds to the process in step S460 and transitions to the adsorption mode, which is the first operating mode of the series of control sequences.

[0067] On the other hand, if the execution of the series of control sequences is not initiated, the control device 17 proceeds to step S470. In step S470, the control device 17 stops the operation of the carbon dioxide capture system 10 by turning off the blower 19, closing the flow path on / off valve 11, turning off the voltage application to the electrochemical cell 12a, turning off the pump 13, and controlling the flow path switching valve 14 to connect the downstream piping of the pump 13 to the outside.

[0068] While preferred embodiments of this disclosure have been described above, this disclosure can be implemented in various ways without being limited to the embodiments described above, and without departing from the spirit of this disclosure.

[0069] For example, in the embodiment described above, the control device 17 performed a moisture removal process to remove the moisture when it estimated that moisture had adhered to the electrochemical cell 12a. However, the control device 17 may also proactively detect situations in which there is a high probability of moisture adhering to the electrochemical cell 12a and perform a condensation prevention process to suppress moisture adhesion. An example of a condensation prevention process will be explained with reference to the flowchart in Figure 6.

[0070] First, in step S500, the control device 17 acquires the ambient temperature detected by the temperature sensor 20 and the humidity detected by the humidity sensor 21, and also acquires the time period to which the current time belongs from the external server 22 or the internal clock. Then, in step S510, based on the various information acquired in step S500, the control device 17 determines whether the conditions for performing condensation prevention processing to suppress the adhesion of moisture have been met. The conditions for performing this condensation prevention processing can be, for example, at least one of the following: it is nighttime when the temperature is low, or the humidity is relatively high (e.g., above the third threshold), and it is expected that the ambient temperature will drop, resulting in a large temperature difference between the temperature of the electrochemical cell 12a and the ambient temperature (e.g., above the fourth threshold). This is because if any one of these conditions is met, there is a high possibility that moisture will adhere to (condense) the electrochemical cell 12a. In this way, it is possible to determine whether the conditions for a high probability of moisture adhering to the electrochemical cell 12a have been met, based on the ambient temperature (ambient temperature) and humidity, or the time period.

[0071] If the control device 17 determines in step S510 that the conditions for performing the condensation prevention treatment have been met, it proceeds to the process in step S520. On the other hand, if the control device 17 determines that the conditions for performing the treatment have not been met, it terminates the condensation prevention treatment shown in Figure 6.

[0072] In step S520, the control device 17 stops the operation of the carbon dioxide capture system 10 for carbon dioxide capture, that is, the series of control sequences described above, and also starts blowing air with the blower 19. This blowing by the blower 19 may be temporary, intermittent, or continuous. By performing such condensation prevention control, the control device 17 can suppress the occurrence of condensation on the surface of the electrochemical cell 12a.

[0073] Furthermore, condensation prevention control is not limited to stopping the operation of the carbon dioxide recovery system 10 described above. For example, when the control device 17 determines, based on the temperature and humidity of the atmosphere or the time of day, that there is a high probability that moisture will adhere to the electrochemical cell 12a, it may, as condensation prevention control, shorten the application time of the adsorption potential and / or desorption potential applied to the electrochemical cell 12a for carbon dioxide recovery compared to the application time of the adsorption potential and / or desorption potential applied to the electrochemical cell 12a when there is a low probability that moisture will adhere to the electrochemical cell 12a. By shortening the application time of the adsorption potential and / or desorption potential applied to the electrochemical cell 12a, heat generation in the electrochemical cell 12a can be suppressed. As a result, the temperature difference between the ambient temperature and the temperature of the electrochemical cell 12a can be reduced, and condensation on the surface of the electrochemical cell 12a can be suppressed.

[0074] Furthermore, the above-described embodiment does not specify the number of housings that house the electrochemical cells 12a. There may be only one housing, or there may be multiple housings. If multiple housings are provided, each housing an electrochemical cell 12a, the multiple housings may be connected in parallel to the CO2 recovery tank 16. The control device 17 may be configured to perform an individual recovery mode in which carbon dioxide is recovered individually from each electrochemical cell 12a in the multiple housings, and a simultaneous recovery mode in which carbon dioxide is recovered simultaneously from each electrochemical cell 12a in at least two or more housings. The simultaneous recovery mode may be performed, for example, when the usage time of the carbon dioxide recovery system 10 reaches a predetermined time.

[0075] In the embodiment described above, the control device 17 was configured to perform calculation processing for executing a series of control sequences. However, at least some of the processing of the control device 17 may be performed by a processing device other than the control device 17, such as an external server 22.

[0076] Finally, this specification discloses several technical concepts and several combinations thereof, as listed below.

[0077] (Technical thought 1) A carbon dioxide capture system that recovers carbon dioxide from the atmosphere containing carbon dioxide through an electrochemical reaction, An electrochemical cell (12a) is placed inside the enclosure and adsorbs carbon dioxide when an adsorption potential is applied, and desorbs the adsorbed carbon dioxide when a desorption potential is applied, Recovery units (11, 13, 14, 16) for recovering carbon dioxide released from the electrochemical cell, A control unit (17) controls the electrochemical cell and the recovery unit so as to apply an adsorption potential to the electrochemical cell to adsorb carbon dioxide contained in the air introduced into the housing onto the electrochemical cell, apply a desorption potential to the electrochemical cell to desorb carbon dioxide from the electrochemical cell, and recover the desorbed carbon dioxide in the recovery unit. The enclosure is equipped with a control unit that controls the air supply unit (19, 13) that sends air containing carbon dioxide into the enclosure when the electrochemical cell adsorbs carbon dioxide contained in the atmosphere, A carbon dioxide recovery system configured such that when the control unit is not controlling the electrochemical cell and the recovery unit to recover carbon dioxide, it operates the air blower to forcibly pass air through the housing, thereby removing moisture and / or other foreign matter adhering to the electrochemical cell.

[0078] (Technical thought 2) The electrochemical cell further comprises an estimation unit that estimates whether moisture and / or other foreign substances are attached to it. The carbon dioxide recovery system according to technical concept 1, wherein the control unit operates the air blower unit in response to the estimation unit estimating the presence of moisture and / or other foreign matter, and removes moisture and / or other foreign matter attached to the electrochemical cell by air passing through the housing.

[0079] (Technical Thought 3) The carbon dioxide recovery system according to technical concept 2, wherein the estimation unit estimates that foreign matter other than water has adhered to the electrochemical cell based on at least one of the following: the amount of carbon dioxide recovered by the recovery unit has decreased; the number of carbon dioxide recovery repetitions has reached a predetermined number; and the operating time of the carbon dioxide recovery system has reached a predetermined time.

[0080] (Technical Thought 4) A carbon dioxide recovery system according to technical concept 2 or 3, wherein, when the estimation unit estimates the presence of foreign matter other than moisture, the control unit operates the air blower to allow air to pass through the housing and applies a desorption potential to the electrochemical cell.

[0081] (Technical Thought 5) The carbon dioxide recovery system according to technical concept 4, wherein the control unit stops applying the desorption potential to the electrochemical cell if the external environment, including at least weather conditions, is likely to cause a short circuit abnormality by applying the desorption potential to the electrochemical cell.

[0082] (Technical Thought 6) The carbon dioxide recovery system according to technical idea 2 or 3, wherein the estimation unit estimates that moisture has adhered to the electrochemical cell based on the temperature and humidity of the atmosphere and / or based on acquired meteorological information.

[0083] (Technical Thought 7) The carbon dioxide recovery system according to any one of technical concepts 1 to 6, wherein the control unit, based on the temperature and humidity of the atmosphere or the time of day, determines that there is a high probability that moisture will adhere to the electrochemical cell, and at the same time, stops the operation of the carbon dioxide recovery system and performs air supply by the air supply unit.

[0084] (Technical Thought 8) A carbon dioxide recovery system according to any one of technical ideas 1 to 6, wherein the control unit, when it determines that there is a high probability that moisture will adhere to the electrochemical cell based on the temperature and humidity of the atmosphere or the time of day, shortens the application time of the adsorption potential and / or desorption potential applied to the electrochemical cell for carbon dioxide recovery compared to the application time of the adsorption potential and / or desorption potential applied to the electrochemical cell when there is a low probability that moisture will adhere to the electrochemical cell. [Explanation of Symbols]

[0085] 10: Carbon dioxide capture system, 11: Flow control valve, 12: Recovery unit, 12a: Electrochemical cell, 13: Pump, 14: Flow switching valve, 15: CO2 sensor, 17: Control device, 19: Blower, 20: Temperature sensor, 21: Humidity sensor, 22: External server

Claims

1. A carbon dioxide capture system that recovers carbon dioxide from the atmosphere containing carbon dioxide through an electrochemical reaction, An electrochemical cell (12a) is placed inside the enclosure and adsorbs carbon dioxide when an adsorption potential is applied, and desorbs the adsorbed carbon dioxide when a desorption potential is applied, Recovery units (11, 13, 14, 16) for recovering carbon dioxide desorbed from the electrochemical cell, A control unit (17) controls the electrochemical cell and the recovery unit so as to apply an adsorption potential to the electrochemical cell to adsorb carbon dioxide contained in the air introduced into the housing onto the electrochemical cell, apply a desorption potential to the electrochemical cell to desorb carbon dioxide from the electrochemical cell, and recover the desorbed carbon dioxide in the recovery unit. The enclosure is equipped with a control unit that controls the air supply unit (19, 13) that sends air containing carbon dioxide into the enclosure when the electrochemical cell adsorbs carbon dioxide contained in the atmosphere, A carbon dioxide recovery system configured such that the control unit removes moisture and / or foreign matter other than moisture adhering to the electrochemical cell by operating the blower unit to forcibly pass air through the housing when at least the adsorption potential is not applied to the electrochemical cell and the recovery unit is not recovering the carbon dioxide.

2. The electrochemical cell further comprises an estimation unit that estimates whether moisture and / or other foreign substances are attached to it. The carbon dioxide recovery system according to claim 1, wherein the control unit operates the air blower in response to the estimation unit estimating the presence of moisture and / or other foreign matter, and removes moisture and / or other foreign matter attached to the electrochemical cell by air passing through the housing.

3. The carbon dioxide recovery system according to claim 2, wherein the estimation unit estimates that foreign matter other than water has adhered to the electrochemical cell based on at least one of the following: the amount of carbon dioxide recovered by the recovery unit has decreased; the number of carbon dioxide recovery repetitions has reached a predetermined number; and the operating time of the carbon dioxide recovery system has reached a predetermined time.

4. The carbon dioxide recovery system according to claim 2 or 3, wherein, if the estimation unit estimates the presence of foreign matter other than moisture, the control unit operates the air blower to allow air to pass through the housing and applies a desorption potential to the electrochemical cell.

5. The carbon dioxide recovery system according to claim 4, wherein the control unit discontinues applying a desorption potential to the electrochemical cell if the external environment, including at least weather conditions, is likely to cause a short circuit abnormality by applying a desorption potential to the electrochemical cell.

6. The carbon dioxide recovery system according to claim 2 or 3, wherein the estimation unit estimates that moisture has adhered to the electrochemical cell based on the temperature and humidity of the atmosphere and / or based on acquired meteorological information.

7. The carbon dioxide recovery system according to claim 1 or 2, wherein the control unit determines, based on the temperature and humidity of the atmosphere or the time of day, whether conditions have been met that increase the likelihood of moisture adhering to the electrochemical cell due to condensation, and when it determines that such conditions have been met, it stops the operation of the carbon dioxide recovery system and performs air supply by the air supply unit.

8. The carbon dioxide recovery system according to claim 1 or 2, wherein the control unit determines, based on the temperature and humidity of the atmosphere or the time of day, whether conditions have been met that increase the likelihood of moisture adhering to the electrochemical cell due to condensation, and when it is determined that such conditions have been met, the application time of the adsorption potential and / or desorption potential applied to the electrochemical cell for carbon dioxide recovery is made shorter than the application time of the adsorption potential and / or desorption potential applied to the electrochemical cell when the conditions have not been met and the likelihood of moisture adhering to the electrochemical cell is low, thereby suppressing heat generation in the electrochemical cell.

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