Carbon dioxide capture system

Abstract

To provide a carbon dioxide recovery system which can easily determine that a system is normally operating and an expected carbon dioxide recovery amount is obtained.SOLUTION: A control device 17 considers a recovery amount of carbon dioxide detected by using a sensor 15 as an actual carbon dioxide adsorption amount actually adsorbed by an adsorbent of an electrochemical cell. The control device 17 determines whether or not a carbon dioxide recovery system is normally operating on the basis of a reduction degree of inclination of a straight line indicating a relation between the actual carbon dioxide adsorption amount and the execution time of an adsorption mode with respect to a threshold of inclination set on the basis of the inclination of the straight line indicating a relation between a maximum carbon dioxide adsorption amount and a maximum adsorption amount time, and / or the control system 17 determines whether or not the carbon dioxide recovery system is normally operating on the basis of a reduction degree of the carbon dioxide recovery amount detected by using the sensor 15 with respect to a threshold of the recovery amount set on the basis of the maximum carbon dioxide adsorption amount.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a carbon dioxide recovery system for recovering carbon dioxide from a mixed gas containing carbon dioxide.

Background Art

[0002] In Patent Document 1, a gas separation system for separating 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. Thereby, carbon dioxide is released from the electroactive material of the negative electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the system described above, if, for example, the electrochemical cell is degraded or the mixed gas introduced into the enclosure is insufficient, the desired amount of carbon dioxide adsorbed by the electrochemical cell may not be achieved. As a result, it becomes difficult to obtain the expected amount of carbon dioxide recovered. However, it is difficult to directly detect the amount of carbon dioxide adsorbed by the electrochemical cell, or the amount of carbon dioxide desorbed from the electrochemical cell. Therefore, there is a need to establish a method that can easily confirm whether the system is operating normally, that is, whether the electrochemical cell is adsorbing and desorbing the desired amount of carbon dioxide, and as a result, whether the expected amount of carbon dioxide recovered is obtained.

[0005] This disclosure is made in view of the above-mentioned points, and aims to provide a carbon dioxide capture system that makes it easy to determine whether the system is operating normally and whether the expected amount of carbon dioxide is being captured. [Means for solving the problem]

[0006] To achieve the above objectives, the carbon dioxide capture system described herein is A carbon dioxide capture system that recovers carbon dioxide from a mixed gas containing carbon dioxide by an electrochemical reaction, A carbon dioxide capture tank (16) for storing the captured carbon dioxide, A recovery device (12) having an electrochemical cell having a working electrode containing an adsorbent material capable of adsorbing carbon dioxide, a counter electrode paired with the working electrode, and a housing for housing the electrochemical cell, When the adsorbent desorbs the carbon dioxide it has adsorbed, a pump (13) sucks the carbon dioxide desorbed from the adsorbent from the recovery unit and discharges it toward the carbon dioxide recovery tank. A sensor (15) for detecting the amount of carbon dioxide recovered from the recovery unit to the carbon dioxide recovery tank, A control device (17) that performs an adsorption mode in which a first potential is applied between the working electrode and the counter electrode to adsorb carbon dioxide onto the adsorbent, and a recovery mode in which a second potential is applied between the working electrode and the counter electrode, and the pump is controlled to suck in and discharge carbon dioxide, thereby recovering the carbon dioxide adsorbed by the adsorbent into a carbon dioxide recovery tank. The system includes a storage unit (18) that stores data showing the change in the amount of carbon dioxide adsorbed by the adsorbent over time when the adsorption mode is being executed, In order to determine if the carbon dioxide capture system is functioning correctly, The control device determines the execution time of the adsorption mode corresponding to the target carbon dioxide adsorption amount based on the adsorption amount change data, and executes the adsorption mode during that execution time. The control device is In the recovery mode after the adsorption mode, The amount of carbon dioxide recovered using the sensor is considered to be the actual amount of carbon dioxide adsorbed by the adsorbent, and the initial maximum carbon dioxide adsorption amount of the electrochemical cell is compared with the amount of carbon dioxide adsorbed. maximum The carbon dioxide capture system is configured to determine whether it is operating normally based on the degree of decrease in the slope of the line representing the relationship between the actual carbon dioxide adsorption amount and the execution time, relative to a threshold of the slope of the line representing the relationship between the execution time, which is the execution time corresponding to the amount of adsorption, and / or based on the degree of decrease in the amount of carbon dioxide captured detected by a sensor, relative to a threshold of the amount of capture, which is set based on the maximum amount of carbon dioxide adsorption.

[0007] As described above, in the carbon dioxide capture system according to this disclosure, adsorption amount change data is stored in the storage unit (18). The adsorption amount change data shows the change in the amount of carbon dioxide adsorbed by the adsorbent over time when the adsorption mode is executed. The control device (17) refers to this adsorption amount change data and determines the execution time of the adsorption mode corresponding to the target carbon dioxide adsorption amount. The control device then executes the adsorption mode for the determined execution time. Therefore, if the system is operating normally, the adsorption mode should result in an amount of carbon dioxide equivalent to the target carbon dioxide adsorption amount being adsorbed onto the adsorbent of the electrochemical cell.

[0008] The control device then considers the amount of carbon dioxide recovered using the sensor (15) as the actual amount of carbon dioxide adsorbed by the adsorbent. Therefore, the control device can determine whether the carbon dioxide recovery system is operating normally based on the degree of decrease in the slope of the line representing the relationship between execution time and the actual amount of carbon dioxide adsorbed, relative to a threshold of the slope set based on the slope of the line representing the relationship between the maximum amount of carbon dioxide adsorbed and the maximum adsorption time. And / or, the control system can determine whether the carbon dioxide recovery system is operating normally based on the degree of decrease in the amount of carbon dioxide recovered using the sensor, relative to a threshold of the recovery amount set based on the maximum amount of carbon dioxide adsorbed.

[0009] 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.

[0010] 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]

[0011] [Figure 1] This is a diagram showing the configuration of a carbon dioxide capture system according to an embodiment. [Figure 2] This is a flowchart showing the processing in a control device for executing a series of control sequences for carbon dioxide capture. [Figure 3] This is a time chart showing the operation of each part when the process shown in the flowchart in Figure 2 is performed. [Figure 4] (a)-(c) are explanatory diagrams illustrating the adsorption mode, scavenging mode, and desorption / recovery mode included in a series of control sequences. [Figure 5] This figure shows an example of adsorption amount change map data. [Figure 6]It is a flowchart showing a map creation process for creating adsorption amount change map data. [Figure 7] (a)-(c) are explanatory diagrams for explaining an example of the procedure of a method for estimating the maximum carbon dioxide adsorption amount and the maximum adsorption amount time of an electrochemical cell. [Figure 8] It is a flowchart showing a process of changing the target carbon dioxide adsorption amount using the adsorption amount change map data and setting the execution time of the adsorption mode corresponding to the changed target carbon dioxide adsorption amount. [Figure 9] It is an enlarged view of the IX part of FIG. 10. [Figure 10] It is a diagram showing an example in which the target carbon dioxide adsorption amount is changed so as to decrease as the number of cycles of a series of control sequences increases. [Figure 11] (a) and (b) are explanatory diagrams for explaining two types of changes in the slope of a straight line showing the relationship between the carbon dioxide adsorption amount and the adsorption time when the carbon dioxide adsorption performance of the electrochemical cell decreases as the number of cycles increases. [Figure 12] It is a flowchart showing a process of self-learning which of the two types of changes shown in FIG. 11 the slope of the straight line showing the relationship between the carbon dioxide adsorption amount and the adsorption time follows when the carbon dioxide adsorption performance of the electrochemical cell decreases as the number of cycles increases. [Figure 13] It is a diagram showing the first and second threshold values for determining control deviation and occurrence of abnormality (sign) set for the slope of the straight line showing the relationship between the carbon dioxide adsorption amount and the adsorption time when the relationship between the carbon dioxide adsorption amount and the adsorption time changes according to the relationship shown in FIG. 11(a) as the number of cycles increases. [Figure 14] It is a diagram showing the first and second threshold values for determining control deviation and occurrence of abnormality (sign) set for the slope of the straight line showing the relationship between the carbon dioxide adsorption amount and the adsorption time when the relationship between the carbon dioxide adsorption amount and the adsorption time changes according to the relationship shown in FIG. 11(b) as the number of cycles increases. [Figure 15]A diagram showing third and fourth threshold values for determining control deviation and occurrence of abnormalities (signs), and a cell replacement determination value, which are set with respect to the amount of carbon dioxide recovered. [Figure 16] A flowchart showing a system state diagnosis process for diagnosing whether a carbon dioxide recovery system is operating normally and taking appropriate measures when control deviation or operation abnormalities occur. [Figure 17] A flowchart showing a part of the control deviation adjustment process. [Figure 18] A flowchart showing the remainder of the control deviation adjustment process following the flowchart of FIG. 17.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a carbon dioxide recovery system according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In the plurality of drawings, the same reference numerals are assigned to parts that are identical or equivalent to each other. The carbon dioxide recovery system according to the present embodiment recovers carbon dioxide from a mixed gas containing carbon dioxide (for example, atmospheric gas). The mixed gas from which carbon dioxide has been removed is discharged to the outside (atmosphere). FIG. 1 shows the configuration of a carbon dioxide recovery system 10 according to the present embodiment.

[0013] The carbon dioxide recovery system 10 shown in FIG. 1 includes a flow path opening / closing valve 11, a recovery device 12, a pump 13, a flow path switching valve 14, a sensor 15, a CO2 recovery tank 16, a control device 17, a blower 19, and an external server 20.

[0014] The opening / closing state of the flow path opening / closing valve 11 is controlled by the control device 17. When the flow path opening / closing valve 11 is opened, a mixed gas containing carbon dioxide can be introduced into the recovery device 12 through a flow path pipe that connects the outside (atmosphere) and the inside of the recovery device 12. On the other hand, when the flow path opening / closing valve 11 is closed, the flow path pipe that connects the outside and the inside of the recovery device 12 is blocked, and the recovery device 12 is sealed from the outside.

[0015] The blower 19 is driven by the control device 17 when the flow path valve 11 is open, and sends a mixed gas containing carbon dioxide into the recovery unit 12 via a flow path piping that connects the outside 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 the mixed gas containing carbon dioxide from the outside into the recovery unit 12 via the aforementioned flow path piping. Therefore, either the blower 19 or the pump 13 corresponds to the blowing means.

[0016] The recovery unit 12 includes an electrochemical cell, for example, located inside a metal casing. The electrochemical cell is capable of adsorbing carbon dioxide through an electrochemical reaction, separating it from the mixed gas, and desorbing the adsorbed carbon dioxide, which is then stored in the CO2 recovery tank 16 by a pump 13. The recovery unit 12 has two openings. One opening is an inlet for introducing a mixed gas containing carbon dioxide from the outside into the casing of the recovery unit 12. The other opening is an outlet for discharging the mixed gas from which carbon dioxide has been removed, or the carbon dioxide desorbed from the electrochemical cell. A flow channel pipe connecting the outside and the inside of the recovery unit 12 is connected to the inlet, and a flow channel pipe equipped with the pump 13 is connected to the outlet. Note that "inside the recovery unit 12" is synonymous with "inside the casing."

[0017] Multiple electrochemical cells are stacked inside the housing of the recovery unit 12. The stacking direction of the multiple electrochemical cells is perpendicular to the flow direction of the mixed gas. Each electrochemical cell is plate-shaped, and its plate surface is arranged to intersect with the cell stacking direction. A predetermined gap is provided between adjacent electrochemical cells. The gap provided between adjacent electrochemical cells serves as a gas channel through which the mixed gas flows.

[0018] Each electrochemical cell is constructed by stacking components such as a working electrode current collector layer, working electrode, separator, counter electrode, and counter electrode current collector layer in the order described. The working electrode is the negative electrode, and the counter electrode, which is paired with the working electrode, is the positive electrode. By changing the potential difference applied between the working electrode and the counter electrode, electrons can be supplied to the working electrode, causing carbon dioxide to be adsorbed onto the carbon dioxide adsorbent on the working electrode, or electrons can be released from the working electrode, causing the adsorbed carbon dioxide to be desorbed.

[0019] The working electrode current collector layer consists of a porous conductive material having pores through which a mixed gas containing carbon dioxide can pass. The working electrode current collector layer only needs to have gas permeability and conductivity, and materials such as metallic materials or carbonaceous materials can be used to form the working electrode current collector layer.

[0020] The working electrode is formed from a mixture of materials including a carbon dioxide adsorbent, a conductive material, and a binder. The carbon dioxide adsorbent has the property of adsorbing carbon dioxide by accepting electrons and desorbing the adsorbed carbon dioxide by releasing electrons. For example, polyanthraquinone can be used as the carbon dioxide adsorbent. The conductive material forms a conductive path to the carbon dioxide adsorbent. For example, carbon materials such as carbon nanotubes, carbon black, and graphene can be used as the conductive material. The binder is for holding the carbon dioxide adsorbent and the conductive material. For example, a conductive resin can be used as the binder. For example, the conductive resin can be an epoxy resin containing Ag as a conductive filler, or a fluororesin such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).

[0021] 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.

[0022] 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.

[0023] Furthermore, the electrochemical cell 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.

[0024] Pump 13 sucks residual mixed gas remaining in the recovery unit 12 and releases it to the outside (i.e., scavenges the residual mixed gas in the recovery unit 12), and when the carbon dioxide adsorbent desorbs the carbon dioxide it has adsorbed, pump 13 sucks the desorbed carbon dioxide from the recovery unit 12 and discharges it toward the CO2 recovery tank 16. When pump 13 scavenges the residual mixed gas in the recovery unit 12, the flow path shut-off valve 11 shuts off the flow path piping that connects the outside and the inside of the recovery unit 12. Therefore, the scavenging of residual mixed gas in the recovery unit 12 is performed by vacuuming with pump 13. Furthermore, the subsequent discharge of carbon dioxide to the CO2 recovery tank 16 is also performed in a state closer to a vacuum than atmospheric pressure.

[0025] The flow path switching valve 14 is a three-way valve that switches the flow path of the gas 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 a mixed gas containing carbon dioxide is introduced into the recovery unit 12, and when residual mixed gas 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 mixed gas from which carbon dioxide has been removed, and the residual mixed gas in the recovery unit 12, are released to the outside. On the other hand, when the carbon dioxide adsorbent desorbs the carbon dioxide, 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.

[0026] 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 sensor 15. This amount of recovered carbon dioxide corresponds to the detection result using sensor 15. Alternatively, the amount of recovered carbon dioxide may be calculated by sensor 15. In this case, sensor 15 outputs the amount of recovered carbon dioxide to the control device 17.

[0027] 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 unit that communicates with an external server 20, a storage unit 18 having a storage medium, and so on. The storage unit 18 stores adsorption amount change map data. The adsorption amount change map data corresponds to adsorption amount change data. As shown in Figure 5, the adsorption amount change map data shows the relationship between the target carbon dioxide adsorption amount and the execution time of the adsorption mode (adsorption time). The adsorption amount change map data will be explained in detail later.

[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 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 an external server 20 via a transceiver. Although not shown in Figure 1, a sensor is provided to detect the gas flow rate or gas flow velocity of the mixed gas introduced into the recovery unit 12 via the flow path valve 11. A sensor is provided to detect the current corresponding to the voltage applied between the working electrode and the counter electrode of the electrochemical cell. A sensor is provided to detect the suction pressure or suction velocity by the pump 13. In addition, sensors are provided to detect the temperature of the atmosphere (mixed gas), the humidity of the atmosphere, and the carbon dioxide concentration of the atmosphere. When a control deviation occurs, the control device 17 performs adjustment operations based on the values ​​detected by these sensors. Control deviations and adjustment operations will be explained in detail later.

[0029] The control device 17 of this embodiment controls the operation of various controlled devices in the carbon dioxide capture system 10 so that a series of control sequences for carbon dioxide capture, including at least an adsorption mode, a scavenging mode, and a desorption / recovery mode, are executed. 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, including 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 control sequence. Figure 3 is a time chart showing the operation of each part when the processes shown in the flowchart of Figure 2 are performed. Figure 4 is an explanatory diagram for describing 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, the flow path valve 11 is opened to allow the introduction of a mixed gas containing carbon dioxide 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 mixed gas 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 the mixed gas and bring it into the recovery device 12 from the outside. In this case, since the pump 13 is driven simply to draw in the mixed gas from the outside, the energy required for this suction is less than that required for driving the pump for vacuuming in the scavenging mode and desorption / recovery mode described later.

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

[0033] Through the control of the flow control valve 11, the electrochemical cells of the recovery unit 12, and the flow control valve 14, in the adsorption mode, as shown by the dotted arrow in Figure 4(a), the mixed gas containing carbon dioxide (atmospheric gas) passes through the flow control valve 11 and enters the recovery unit 12. The carbon dioxide contained in the mixed gas that enters the recovery unit 12 is adsorbed by multiple electrochemical cells. As a result, carbon dioxide is removed from the mixed gas. The mixed gas 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 adsorption mode execution time has elapsed. The adsorption mode execution time is not constant and changes for several reasons, including estimating the maximum carbon dioxide adsorption amount of the electrochemical cell in the map creation process described later, the maximum adsorption time which is the adsorption mode execution time required to obtain that maximum carbon dioxide adsorption amount, and changing (reducing) the target carbon dioxide adsorption amount when the carbon dioxide adsorption performance of the electrochemical cell changes due to aging or other factors. This changing adsorption mode execution time is set by the control device 17. In step S110, it is determined whether the set adsorption 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 mixed gas flowing 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] Here, the adsorption mode execution time can be obtained from the adsorption amount change map data, as shown in Figure 5. For example, the control device 17 can initially set the maximum carbon dioxide adsorption amount of the electrochemical cell as the target carbon dioxide adsorption amount. Then, by referring to the adsorption amount change map data, the control device 17 can obtain the execution time of the adsorption mode corresponding to the target carbon dioxide adsorption amount (maximum carbon dioxide adsorption amount) (adsorption time corresponding to the maximum adsorption time). For example, if the maximum carbon dioxide adsorption amount of the electrochemical cell is estimated to be 100 [g], then in the example shown in Figure 5, the target carbon dioxide adsorption amount is 100 [g], so the corresponding adsorption time can be determined to be 100 [s].

[0038] 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. The adsorption potential applied between the working electrode and the counter electrode of the electrochemical cell of the recoverer 12 is maintained. Communication between the downstream piping of the pump 13 and the outside is also maintained by the flow path switching valve 14.

[0039] In scavenging mode, as shown in Figure 3, 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 mixed gas from which carbon dioxide has been removed, remaining in the sealed recovery unit 12, is sucked out of the recovery unit 12 and released to the outside. This allows the residual mixed gas in the recovery unit 12 to be scavenged.

[0040] Furthermore, since the recovery unit 12 upstream of the pump 13 is sealed, the residual mixed gas in the recovery unit 12 is scavenged by vacuuming with the pump 13. For this reason, 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 is initiated.

[0041] Through the control of the flow path switching valve 11, the electrochemical cell of the recovery unit 12, the pump 13, and the flow path switching valve 14, in the scavenging mode, as shown by the dotted arrow in Figure 4(b), the residual mixed gas from which carbon dioxide has been removed in the recovery unit 12 passes through the pump 13, is guided by the flow path switching valve 14 to a flow path piping leading to the outside, and is released to the outside through that flow path piping.

[0042] 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 mixed gas in the recovery unit 12.

[0043] 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.

[0044] 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.

[0045] 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. 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 in a state closer to a vacuum than atmospheric pressure.

[0046] Meanwhile, between the working electrode and the counter electrode of the electrochemical cell of the recovery unit 12, a desorption potential (corresponding to the second potential) is applied, which causes electrons to be released from the working electrode, enabling the carbon dioxide adsorbent on the working electrode to desorb the carbon dioxide it has adsorbed. This adsorption potential is a predetermined constant potential. Furthermore, in the desorption / recovery mode, as shown in Figure 3, the flow path switching valve 14 is controlled to connect the piping downstream of the pump 13 to the CO2 recovery tank 16.

[0047] Through the control of the flow path switching valve 11, the electrochemical cell of the recovery unit 12, the pump 13, and the flow path switching valve 14, in the desorption / recovery mode, as shown by the dotted arrow in Figure 4(c), carbon dioxide desorbed from the adsorbent of the electrochemical cell passes through the pump 13 and is guided by the flow path switching valve 14 to the flow path piping leading to the CO2 recovery tank 16, where it is accumulated. At this time, the concentration and flow rate of carbon dioxide flowing through the flow path piping toward the CO2 recovery tank 16 are detected by the sensor 15. Based on the detection results of the 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 flow path piping toward the CO2 recovery tank 16 is usually close to 100%. For this reason, a sensor capable only of detecting the flow rate of carbon dioxide may be used as the sensor 15.

[0048] Furthermore, the desorption / recovery mode does not necessarily perform carbon dioxide desorption and recovery simultaneously. Instead, carbon dioxide may be desorbed from the electrochemical cell first, and the recovery of the desorbed carbon dioxide may begin 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 at the start of the desorption mode. With the pump 13 stopped, a desorption potential is applied between the working electrode and the counter electrode of the electrochemical cell to desorb carbon dioxide from the carbon dioxide adsorbent at 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, and the desorption of carbon dioxide from the electrochemical cell 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.

[0049] In step S170 of the flowchart in Figure 2, the control device 17 determines whether the desorption / 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 not constant and changes for reasons such as optimizing the amount of carbon dioxide recovered and the energy consumed when the carbon dioxide adsorption performance of the electrochemical cell changes due to repeated use (aging deterioration) or environmental changes. This changing recovery mode execution time is set by the control device 17. For example, the control device 17 may set the recovery mode execution time in proportion to the length of the adsorption mode execution time. In step S170, it is determined whether the set recovery mode execution time has elapsed.

[0050] 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.

[0051] 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. The control device 17 stops applying the desorption potential to the electrochemical cell. The control device 17 stops driving the pump 13. The control device 17 switches the flow path switching valve 14 to connect the downstream piping of the pump 13 to the outside. Furthermore, the control device 17 also resets the count value of the counter that counts the recovery mode execution time.

[0052] Here, it is thought that the carbon dioxide adsorption performance of the electrochemical cell described above changes due to changes in the external environment such as temperature, humidity, and atmospheric carbon dioxide concentration, as well as deterioration over time. However, it is not possible to directly detect the upper limit of carbon dioxide that the electrochemical cell can adsorb. For this reason, it cannot be ruled out that the adsorption mode may continue even if the carbon dioxide adsorption capacity of the electrochemical cell has reached its upper limit, or that the recovery mode may continue even if the recovery of carbon dioxide released from the electrochemical cell has substantially ended.

[0053] Thus, in an attempt to maximize the amount of carbon dioxide recovered, for example, if the adsorption mode is always run for a sufficient time to adsorb the upper limit of the amount of carbon dioxide that the electrochemical cell can adsorb, and the recovery mode is run for a sufficient time to recover all the carbon dioxide that the electrochemical cell has adsorbed, then the carbon dioxide recovery system 10 may consume an excessive amount of energy relative to the amount of carbon dioxide recovered.

[0054] Therefore, in the carbon dioxide capture system 10 according to this embodiment, the storage unit 18 of the control device 17 is configured to store adsorption amount change map data that shows the change in the amount of carbon dioxide adsorbed by the electrochemical cell over time when the adsorption mode is executed. The adsorption amount change map data will be described in detail below. First, the map creation process for creating the adsorption amount change map data will be described based on the flowchart in Figure 6.

[0055] In step S200, the control device 17 executes multiple adsorption modes with different adsorption mode execution times (adsorption times), and uses the sensor 15 to detect the amount of carbon dioxide recovered in the multiple recovery modes executed in accordance with each adsorption mode. For example, Figure 3 shows an example in which three adsorption modes are executed with different adsorption mode execution times. Note that the number of times the multiple adsorption modes are executed may be as few as two.

[0056] In Figure 3, the execution time of the first adsorption mode is relatively short and set so that the carbon dioxide adsorption capacity of the electrochemical cell does not reach its upper limit (corresponding to the maximum carbon dioxide adsorption capacity). Therefore, the amount of carbon dioxide recovered when the recovery mode corresponding to the first adsorption mode is executed is less than the upper limit of the carbon dioxide adsorption capacity of the electrochemical cell.

[0057] The execution time for the second adsorption mode is relatively long, and it is set so that the amount of carbon dioxide adsorbed by the electrochemical cell reaches approximately its upper limit. Therefore, the amount of carbon dioxide recovered when the recovery mode corresponding to the second adsorption mode is executed is approximately equal to the upper limit of the carbon dioxide adsorption capacity of the electrochemical cell.

[0058] The execution time for the third adsorption mode is the longest, and it is set so that the adsorption mode continues for a certain period even after the carbon dioxide adsorption capacity of the electrochemical cell reaches its upper limit. Therefore, the amount of carbon dioxide recovered when the recovery mode corresponding to the third adsorption mode is executed is equal to the upper limit of the carbon dioxide adsorption capacity of the electrochemical cell.

[0059] In step S210, the control device 17 determines whether the map creation conditions are met based on the amount of carbon dioxide recovered by the three recovery modes described above. For example, the control device 17 determines, as a map creation condition, that it is possible to plot the amount of carbon dioxide recovered by the three recovery modes described above on a single adsorption amount change map. Alternatively, the control device 17 may determine, as a map creation condition, that there is a maximum value of carbon dioxide recovered by the three recovery modes that is not plotted on the same straight line. When determining whether or not the values ​​are plotted on the same straight line, the same straight line may include tolerances. If the control device 17 determines that the map creation conditions are met, it proceeds to step S220; if it determines that they are not met, it proceeds to step S250.

[0060] In step S250, the adsorption mode is executed multiple times again with different adsorption mode execution times (adsorption times), and the amount of carbon dioxide recovered in the multiple recovery modes executed in accordance with each adsorption mode is detected using the sensor 15. At this time, it is desirable for the control device 17 to make the execution time of the third adsorption mode longer than the execution time of the previous third adsorption mode.

[0061] Then, in step S210, the control device 17 determines whether the map creation conditions are met based on the amount of carbon dioxide recovered obtained in step S250. The control device 17 repeatedly executes steps S250 and S210 until it determines YES in step S200.

[0062] Based on the sensor detection results during the execution of the multiple adsorption modes described above, and the multiple recovery modes corresponding to each adsorption mode, the maximum adsorption amount of the electrochemical cell and the maximum adsorption time, which is the execution time of the adsorption mode required to obtain that maximum adsorption amount, are estimated. Referring to Figures 7(a), (b), and (c), which show specific examples of methods for estimating the maximum adsorption amount and maximum adsorption time of the electrochemical cell, the procedure for estimating the maximum adsorption amount and maximum adsorption time is described below.

[0063] In step S220, the slope of the straight line showing the relationship between the maximum adsorption amount and the maximum adsorption time is determined in the adsorption amount change map. Figure 7(a) is a graph showing the amount of carbon dioxide adsorbed by the electrochemical cell and the execution time of the first adsorption mode, based on the amount of carbon dioxide recovered when the recovery mode corresponding to the first adsorption mode is executed. Note that the amount of carbon dioxide adsorbed by the electrochemical cell is assumed to be equal to the amount of carbon dioxide recovered. As mentioned above, the execution time of the first adsorption mode is relatively short and is set so that the amount of carbon dioxide adsorbed by the electrochemical cell does not reach the upper limit. Therefore, as shown in Figure 7(a), based on the amount of carbon dioxide adsorbed by the electrochemical cell due to the execution of the first adsorption mode, an increasing slope line can be determined by assuming that the amount of carbon dioxide adsorbed increases linearly as the execution time of the adsorption mode increases.

[0064] In step S230, the maximum carbon dioxide adsorption amount is calculated. Figure 7(b) is a graph showing the carbon dioxide adsorption amount of each electrochemical cell and the execution time of the second and third adsorption modes, based on the amount of carbon dioxide recovered when the recovery modes corresponding to the second and third adsorption modes are executed. As described above, the execution time of the second adsorption mode is relatively long, set so that the carbon dioxide adsorption amount of the electrochemical cell reaches almost the upper limit, and the execution time of the third adsorption mode is the longest, set so that the adsorption mode is executed for a certain period of time even after the carbon dioxide adsorption amount of the electrochemical cell has reached the upper limit. Therefore, as shown in Figure 7(b), an upper limit line for the carbon dioxide adsorption amount of the electrochemical cell can be determined based on the carbon dioxide adsorption amount of the electrochemical cell due to the execution of the second and third adsorption modes. The carbon dioxide adsorption amount corresponding to the upper limit line corresponds to the maximum adsorption amount that the adsorbent material of the electrochemical cell can adsorb.

[0065] Furthermore, the upper limit of the carbon dioxide adsorption capacity of the electrochemical cell may be determined based on the amount of carbon dioxide adsorbed by the electrochemical cell obtained through the execution of one adsorption mode and the corresponding recovery mode.

[0066] In step S240, as shown in Figure 7(c), the maximum adsorption time, which is the adsorption mode execution time required to obtain the maximum adsorption amount of carbon dioxide, can be determined from the intersection of the increasing gradient line in Figure 7(a) and the upper limit line in Figure 7(b).

[0067] In this way, the control device 17 can estimate the maximum carbon dioxide adsorption amount of the electrochemical cell and the maximum adsorption time, which is the duration of the adsorption mode required to obtain that maximum adsorption amount, based on the sensor detection results during the execution of multiple adsorption modes and multiple recovery modes corresponding to each adsorption mode. Then, from the estimated maximum carbon dioxide adsorption amount and maximum adsorption time, the control device 17 can obtain adsorption amount change map data, as shown in Figure 5, which shows the change in the amount of carbon dioxide adsorbed by the electrochemical cell over time. The obtained adsorption amount change map data is stored in the storage unit 18 in step S240.

[0068] Next, referring to the flowchart in Figure 8, we will explain the process of changing the target carbon dioxide adsorption amount using the adsorption amount change map data, and the process of setting the execution time of the adsorption mode corresponding to the changed target carbon dioxide adsorption amount. The control device 17 determines whether to maintain the current value of the target carbon dioxide adsorption amount or change it by executing the flowchart in Figure 8.

[0069] With repeated use, the carbon dioxide adsorption performance of the electrochemical cell gradually decreases. Despite this aging degradation, even if the adsorption mode is run for the duration corresponding to the initial maximum carbon dioxide adsorption amount of the electrochemical cell, the amount of carbon dioxide recovered detected by the sensor 15 gradually decreases below the amount corresponding to the maximum carbon dioxide adsorption amount, as shown in Figure 9. In other words, the decrease in the amount of carbon dioxide recovered due to repeated use of the electrochemical cell indicates that the electrochemical cell can only adsorb less carbon dioxide than the target carbon dioxide adsorption amount (initially, the maximum carbon dioxide adsorption amount) due to the decrease in adsorption performance. If the adsorption mode is run for the duration corresponding to the target carbon dioxide adsorption amount without changing the target carbon dioxide adsorption amount, despite the decreased adsorption performance of the electrochemical cell, energy will be wasted.

[0070] Therefore, in this embodiment, as shown in Figures 5, 9, and 10, when the amount of carbon dioxide recovered using the sensor 15 falls below an update threshold (corresponding to the fifth threshold) set based on the target carbon dioxide adsorption amount, the control device 17 changes the target carbon dioxide adsorption amount to decrease by, for example, an amount equivalent to the update threshold. In other words, as shown in Figure 9, the range from the target carbon dioxide adsorption amount to the update threshold is the target carbon dioxide adsorption amount retention region, and if the amount of carbon dioxide recovered using the sensor 15 falls within this retention region, the target carbon dioxide adsorption amount is maintained at its current value. However, as shown in Figure 9, when the amount of carbon dioxide recovered using the sensor 15 falls below the update threshold and enters the target carbon dioxide adsorption amount update region, the target carbon dioxide adsorption amount is changed to decrease by, for example, the amount of the update threshold.

[0071] In step S300 of the flowchart in Figure 8, the control device 17 determines whether the amount of carbon dioxide recovered detected by the sensor 15 falls within the retention area for the target carbon dioxide adsorption amount. If the detected amount of carbon dioxide recovered falls within the retention area, the control device 17 proceeds to step S310. If the detected amount of carbon dioxide recovered does not fall within the retention area, i.e., it falls within the update area, the control device 17 proceeds to step S320.

[0072] In step S310, the control device 17 does not change the target carbon dioxide adsorption amount and maintains it at the current value. On the other hand, in step S320, the control device 17 changes the target carbon dioxide adsorption amount to decrease by, for example, the update threshold amount. Then, in step S330, the control device 17 updates the execution time of the adsorption mode (adsorption time) to correspond to the maintained or changed (decreased) target carbon dioxide adsorption amount based on the adsorption amount change map data. As a result, the control device 17 can determine an appropriate execution time of the adsorption mode regardless of the decrease in the carbon dioxide adsorption performance of the electrochemical cell.

[0073] Furthermore, if the carbon dioxide adsorption performance of the electrochemical cell deteriorates and the amount of carbon dioxide recovered detected by the sensor 15 falls below the cell replacement judgment value (corresponding to the sixth threshold) shown in Figure 10, the control device 17 may output a signal indicating that it is time to replace the electrochemical cell. This signal may cause, for example, a lamp (not shown) to light up or a message prompting replacement to be displayed on the monitor. This allows the user to know that it is time to replace the electrochemical cell. The cell replacement judgment value can be set based on the initial maximum carbon dioxide adsorption amount of the electrochemical cell.

[0074] In the example described above, when the carbon dioxide adsorption performance of the electrochemical cell deteriorated, the relationship between the amount of carbon dioxide adsorbed and the adsorption time was assumed to be determined by a straight line (increasing gradient line) defined by the relationship between the initial maximum carbon dioxide adsorption amount and the maximum adsorption time, as shown in Figure 11(a), i.e., it was assumed to move along the increasing gradient line. However, when the carbon dioxide adsorption performance of the electrochemical cell deteriorates over time, as shown in Figure 11(b), it is also possible that the slope of the straight line showing the relationship between the amount of carbon dioxide adsorbed and the adsorption time may decrease more than the slope of the increasing gradient line showing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time.

[0075] Therefore, when the carbon dioxide adsorption performance of the electrochemical cell decreases, it may be possible to determine whether the relationship between the amount of carbon dioxide adsorbed and the adsorption time moves along an increasing gradient line, or whether it is represented by a straight line with a slope lower than the slope of the increasing gradient line. Based on this determination, the adsorption time corresponding to the target amount of carbon dioxide adsorbed may be determined according to the relationship between the amount of carbon dioxide adsorbed and the adsorption time when the carbon dioxide adsorption performance of the electrochemical cell decreases.

[0076] The following describes an example of a method for calculating the adsorption time corresponding to a target carbon dioxide adsorption amount, in accordance with an appropriate relationship between carbon dioxide adsorption amount and adsorption time, by determining whether the relationship between carbon dioxide adsorption amount and adsorption time moves along an increasing gradient line or is represented by a straight line with a slope lower than the slope of the increasing gradient line, when the carbon dioxide adsorption performance of an electrochemical cell deteriorates over time.

[0077] For example, if the detected carbon dioxide recovery amount falls below the update threshold shown in Figure 9, the control device 17 will execute the self-learning process shown in the flowchart of Figure 12 immediately after the target carbon dioxide adsorption amount is changed (for example, when the carbon dioxide recovery amount is detected in the first recovery mode). Furthermore, whether the change in the target carbon dioxide adsorption amount was made according to the relationship shown in Figure 11(a) or the relationship shown in Figure 11(b), the method shown in Figure 12 can be used to determine whether the relationship used was appropriate.

[0078] In step S400, it is determined whether the amount of carbon dioxide recovered is within the range for the target carbon dioxide adsorption amount. This determination may be made based on the detection results of multiple recovery modes. If the control device 17 determines that the amount of carbon dioxide recovered is within the range, it proceeds to step S410; if it determines that it is not within the adsorption amount range, it proceeds to step S420.

[0079] The control device 17 can determine, through the process in step S400 described above, whether the change in the target carbon dioxide adsorption amount was made according to an appropriate relationship between the amount of carbon dioxide adsorbed and the adsorption time when the carbon dioxide adsorption performance of the electrochemical cell deteriorates. If the target carbon dioxide adsorption amount is changed according to an appropriate relationship, the amount of carbon dioxide recovered detected immediately after the change is expected to remain within the retention range determined according to the changed target carbon dioxide adsorption amount. On the other hand, if the target carbon dioxide adsorption amount is changed according to an inappropriate relationship, the amount of carbon dioxide recovered detected is likely to deviate from the retention range, even immediately after the change. Therefore, if it is determined in step S400 that the detected amount of carbon dioxide recovered is within the retention range, the relationship between the amount of carbon dioxide adsorbed and the adsorption time can be considered appropriate. Conversely, if it is determined in step S400 that the detected amount of carbon dioxide recovered is outside the retention range, the relationship between the amount of carbon dioxide adsorbed and the adsorption time can be considered inappropriate.

[0080] In step S410, the relationship between carbon dioxide adsorption amount and adsorption time is deemed appropriate, and therefore the current relationship is maintained. That is, the relationship shown in Figure 11(a) is to be continued and used to determine the adsorption time corresponding to the next target carbon dioxide adsorption amount when the target carbon dioxide adsorption amount is changed. Step S410 also decides to retain the current adsorption time until the next target carbon dioxide adsorption amount is changed. As a result, the adsorption mode will run for the duration of the retained adsorption time.

[0081] On the other hand, in step S420, the relationship between the amount of carbon dioxide adsorbed and the adsorption time is not appropriate, so the relationship between the amount of carbon dioxide adsorbed and the adsorption time is switched from the current relationship. That is, if the adsorption time corresponding to the target amount of carbon dioxide adsorbed is currently determined according to the relationship shown in Figure 11(a), it is switched to the relationship shown in Figure 11(b). Conversely, if the adsorption time corresponding to the target amount of carbon dioxide adsorbed is currently determined according to the relationship shown in Figure 11(b), it is switched to the relationship shown in Figure 11(a).

[0082] Then, in step S440, the adsorption time corresponding to the target carbon dioxide adsorption amount is calculated according to the relationship after the switchover. As a result, the adsorption mode will be executed for the calculated adsorption time.

[0083] For example, when switching from the relationship shown in Figure 11(a) to the relationship shown in Figure 11(b), the calculated adsorption time will be changed to be longer than the previous adsorption time. If the adsorption time corresponding to the reduced target carbon dioxide adsorption amount is calculated according to the relationship shown in Figure 11(a), that adsorption time will be shorter than the maximum adsorption time corresponding to the maximum carbon dioxide adsorption amount. However, if the adsorption time corresponding to the reduced target carbon dioxide adsorption amount is calculated according to the relationship shown in Figure 11(b), the optimal adsorption time will be the same regardless of the change in the target carbon dioxide adsorption amount. That is, the adsorption time according to the relationship in Figure 11(b) is the same as the maximum adsorption time. Therefore, when switching from the relationship shown in Figure 11(a) to the relationship shown in Figure 11(b), the adsorption time will be changed to be longer than the previous adsorption time. Conversely, when switching from the relationship shown in Figure 11(b) to the relationship shown in Figure 11(a), the adsorption time will be changed to be shorter than the previous adsorption time.

[0084] As described above, the carbon dioxide recovery system 10 according to this embodiment separates and recovers carbon dioxide from a mixed gas by executing a series of control sequences that include at least an adsorption mode, a scavenging mode, and a desorption / recovery mode. In each mode included in the series of control sequences, various controlled devices such as the blower 19, electrochemical cell, and pump 13 are driven according to predetermined control target values ​​and signal values ​​for each of the controlled devices. For example, in the adsorption mode, the rotational speed that drives the blower 19 is predetermined to achieve an airflow that is sufficient to introduce a mixed gas containing carbon dioxide into the recovery unit 12, and the blower 19 is driven to the predetermined rotational speed. Furthermore, with respect to the electrochemical cell, in the adsorption mode, the adsorption potential is predetermined so that the electrochemical cell can fully exhibit carbon dioxide adsorption performance, and in the desorption mode, the desorption potential is predetermined so that the adsorbed carbon dioxide can be almost completely desorbed. In addition, with respect to the pump 13, the suction pressure is predetermined so that the residual mixed gas can be almost completely discharged in the scavenging mode, and so that the desorbed carbon dioxide can be recovered without loss in the recovery mode. Then, the motor that operates the pump 13 is driven to achieve the respective suction pressures.

[0085] However, even when driven according to the control target values ​​and signal values ​​for each of the various controlled devices, control deviations may occur due to changes in the external environment such as wind, temperature, humidity, and atmospheric carbon dioxide concentration, which may prevent the carbon dioxide recovery system 10 from securing the desired amount of carbon dioxide and from operating normally. For example, if the wind direction in the external environment is opposite to the direction of airflow from the blower 19, and a sufficient amount of air cannot be supplied to the recovery unit 12, the amount of carbon dioxide adsorbed in the electrochemical cell may not reach the target adsorption amount. Also, if the external environmental temperature decreases or increases, even if a voltage is applied so that the potential difference between the working electrode and the counter electrode of the electrochemical cell becomes the desired adsorption potential or desorption potential, changes in the resistance of various parts of the circuit may cause deviations from the desired adsorption potential or desorption potential. Furthermore, if the humidity of the air increases or the carbon dioxide concentration in the air decreases, and the air quality deteriorates, the execution time of the determined adsorption mode may be insufficient to achieve the target amount of carbon dioxide adsorbed. Thus, in this embodiment, the state in which the desired amount of carbon dioxide recovery cannot be secured due to changes in the external environment is called a control deviation. Furthermore, if there are malfunctions in the operation of various controlled devices, or if malfunctions are indicative of such malfunctions, it may be possible to recover significantly less carbon dioxide than the desired amount.

[0086] Furthermore, the carbon dioxide adsorption performance of the electrochemical cell due to aging, as described above, gradually decreases with the number of times the electrochemical cell is used, and this decrease in carbon dioxide adsorption performance falls within the range of normal operation of the carbon dioxide capture system 10. On the other hand, the decrease in carbon dioxide capture amount due to the control deviations and malfunctions described above appears as a larger change over a shorter period of time.

[0087] Therefore, the carbon dioxide capture system 10 according to this embodiment is configured to use the adsorption amount change map data described above to determine whether it is operating normally to ensure the desired amount of carbon dioxide capture, that is, whether there are any control errors or operational abnormalities. Furthermore, if the carbon dioxide capture system 10 according to this embodiment determines that it is not operating normally, it is configured to determine whether this is due to a control error or an abnormality or a sign of an abnormality, and to take appropriate measures in each case.

[0088] First, we will describe some specific examples of methods for determining whether the carbon dioxide capture system 10 according to this embodiment is operating normally using adsorption amount change map data.

[0089] If the relationship between carbon dioxide adsorption amount and adsorption time moves along an increasing gradient line, as shown in Figure 11(a), then even if the carbon dioxide adsorption performance of the electrochemical cell deteriorates over time, the slope of the line showing the relationship between carbon dioxide adsorption amount and adsorption time will be the same as the slope of the increasing gradient line. Therefore, as long as the carbon dioxide capture system 10 is operating normally, as shown in Figure 13, even if the number of times the electrochemical cell is used (number of times the adsorption mode is executed), i.e., the number of cycles of the series of control sequences in the carbon dioxide capture system 10 increases, the slope of the line showing the relationship between carbon dioxide adsorption amount and adsorption time will not change.

[0090] Conversely, if the relationship between the amount of carbon dioxide adsorbed and the adsorption time moves along an increasing gradient line, as shown in Figure 11(a), and the slope of the line representing the relationship between the amount of carbon dioxide adsorbed and the adsorption time decreases significantly, the carbon dioxide capture system 10 can be considered to have deviated from normal operation and is experiencing control errors or malfunctions. For this reason, as shown in Figure 13, a first threshold and a second threshold are defined as thresholds for the slope based on the slope of the increasing gradient line. The first threshold is set to a value lower than the slope of the increasing gradient line by a first reference value. The second threshold is set to a value lower than the slope of the increasing gradient line by a second reference value. The second reference value is greater than the first reference value.

[0091] The control device 17 then calculates the slope of a straight line showing the relationship between the amount of carbon dioxide adsorbed and the adsorption time, and determines the relationship between the calculated slope (also called the judgment value) and the first threshold and the second threshold. If the calculated slope (judgment value) is smaller than the first threshold and greater than or equal to the second threshold, that is, if it falls within the range from the first threshold to the second threshold, the control device 17 determines that a control error has occurred. If the calculated slope (judgment value) is smaller than the second threshold, the control device 17 determines that there is an operational abnormality or a malfunction due to an indication of an abnormality.

[0092] Furthermore, as shown in Figure 11(b), when the carbon dioxide adsorption performance of the electrochemical cell deteriorates over time, if the slope of the straight line showing the relationship between the amount of carbon dioxide adsorbed and the adsorption time falls below the slope of the increasing gradient line showing the relationship between the maximum amount of carbon dioxide adsorbed and the maximum adsorption time, then, as shown in Figure 14, the slope showing the relationship between the amount of carbon dioxide adsorbed and the adsorption time will gradually decrease as the number of cycles of the series of control sequences in the carbon dioxide capture system 10 increases. However, if the slope of the straight line showing the relationship between the amount of carbon dioxide adsorbed and the adsorption time suddenly drops significantly beyond the range of decrease due to deterioration over time, the carbon dioxide capture system 10 can be considered to have deviated from normal operation and is experiencing control errors or malfunctions.

[0093] In the example shown in Figure 14, as in the example in Figure 13, a first threshold and a second threshold are defined as slope thresholds to determine the occurrence of control deviation or operational abnormality. However, in the example shown in Figure 14, since the slope of the straight line showing the relationship between carbon dioxide adsorption amount and adsorption time gradually decreases due to aging, the first and second thresholds are also set to decrease as the number of cycles of the series of control sequences in the carbon dioxide capture system 10 increases. For example, the first threshold is calculated as a value that is lower than the slope of the increasing gradient line by a first reference value, and further lower by a variable that increases with the increase in the number of cycles (= coefficient A × number of cycles). Similarly, the second threshold is calculated as a value that is lower than the slope of the increasing gradient line by a second reference value, and further lower by a variable that increases with the increase in the number of cycles (= coefficient A × number of cycles). The second reference value is greater than the first reference value. Also, as shown in Figure 14, the variable may be calculated as zero up to a predetermined number of cycles.

[0094] In the example shown in Figure 14, the control device 17 calculates the slope of the straight line representing the relationship between the amount of carbon dioxide adsorbed and the adsorption time, and determines the relationship between the calculated slope (judgment value) and the first threshold and the second threshold. If the calculated slope (judgment value) is smaller than the first threshold and greater than or equal to the second threshold, that is, if it falls within the range from the first threshold to the second threshold, the control device 17 determines that a control error has occurred. If the calculated slope (judgment value) is smaller than the second threshold, the control device 17 determines that there is an operational abnormality or a malfunction due to an indication of an abnormality.

[0095] In Figures 13 and 14, the normal operation of the carbon dioxide capture system 10 was determined based on the degree of decrease in the slope of the straight line showing the relationship between the amount of carbon dioxide adsorbed and the adsorption time. However, it is also possible to determine whether the normal operation of the carbon dioxide capture system 10 is determined based on the degree of decrease in the amount of carbon dioxide captured detected by the sensor 15 relative to a threshold set based on the maximum amount of carbon dioxide adsorbed.

[0096] Figure 15 shows an example of determining whether the carbon dioxide capture system 10 is operating normally based on the degree of decrease in the amount of carbon dioxide captured detected by the sensor 15 relative to a threshold set based on the maximum amount of carbon dioxide adsorbed. In the example shown in Figure 15, as in the examples in Figures 13 and 14, a third threshold and a fourth threshold are defined as thresholds for the amount of carbon dioxide captured in order to determine the occurrence of a control deviation or malfunction. The control device 17 determines that a control deviation has occurred if the detected amount of carbon dioxide captured (determination value) is smaller than the third threshold and greater than or equal to the fourth threshold, that is, if it falls within the range from the third threshold to the fourth threshold. The control device 17 also determines that a malfunction or a malfunction due to an indication of a malfunction has occurred if the detected amount of carbon dioxide captured (determination value) is smaller than the fourth threshold.

[0097] In the example shown in Figure 15, the amount of carbon dioxide adsorbed by the electrochemical cell gradually decreases due to aging. Therefore, similar to the example shown in Figure 14, the third and fourth thresholds are set to decrease as the number of cycles in the series of control sequences in the carbon dioxide capture system 10 increases. For example, the third threshold is calculated as a value lower than the maximum carbon dioxide adsorption amount by the third reference value, and further lower by a variable that increases with the number of cycles (= coefficient B × number of cycles). Similarly, the fourth threshold is calculated as a value lower than the maximum carbon dioxide adsorption amount by the fourth reference value, and further lower by a variable that increases with the number of cycles (= coefficient B × number of cycles). The fourth reference value is greater than the third reference value. Also, as shown in Figure 15, the variable may be calculated as zero up to a predetermined number of cycles.

[0098] Next, a system status diagnostic process is described with reference to the flowchart in Figure 16, which diagnoses whether the carbon dioxide capture system 10 is operating normally and takes appropriate action if control errors or operational abnormalities occur. The system status diagnostic process is performed by the control device 17, for example, each time the capture mode is executed and the amount of carbon dioxide captured is obtained using the sensor 15.

[0099] In step S500, the amount of carbon dioxide recovered detected using the sensor 15 is acquired. And / or, the acquired amount of carbon dioxide recovered is considered to be the actual amount of carbon dioxide adsorbed by the adsorbent of the electrochemical cell, and the slope of the straight line showing the relationship between the actual amount of carbon dioxide adsorbed and the execution time of the adsorption mode is calculated.

[0100] In step S510, the slope of the line representing the relationship between the amount of carbon dioxide recovered and / or the actual amount of carbon dioxide adsorbed obtained in step S500 and the execution time of the adsorption mode is used as a determination value and compared with each of the first to fourth thresholds described above. As a result of this comparison, if the slope of the line as the determination value is smaller than the first threshold and greater than or equal to the second threshold, it is considered that a control error has occurred and the process proceeds to step S530. On the other hand, if the slope of the line as the determination value is greater than or equal to the first threshold or less than the second threshold, the process proceeds to step S540. And / or, if the amount of carbon dioxide recovered as the determination value is smaller than the third threshold and greater than or equal to the fourth threshold, it is also considered that a control error has occurred and the process proceeds to step S530. On the other hand, if the amount of carbon dioxide recovered as the determination value is greater than or equal to the third threshold or less than the fourth threshold, the process proceeds to step S540.

[0101] In step S530, the control device 17 performs a control deviation adjustment process based on the values ​​detected by various sensors. This control deviation adjustment process will be explained in detail later with reference to the flowcharts in Figures 17 and 18.

[0102] In step S540, it is determined whether the slope of the line, which is the judgment value, is less than the second threshold, and / or whether the amount of carbon dioxide captured, which is the judgment value, is less than the fourth threshold. If, in the judgment process of step S540, it is determined that the slope of the line, which is the judgment value, is less than the second threshold, the process proceeds to step S550. On the other hand, if it is determined that the slope of the line, which is the judgment value, is not less than the second threshold, it is considered to be above the first threshold and is functioning normally, so the process proceeds to step S560. And / or, if it is determined that the amount of carbon dioxide captured, which is the judgment value, is less than the fourth threshold, the process proceeds to step S550. On the other hand, if it is determined that the amount of carbon dioxide captured, which is the judgment value, is not less than the fourth threshold, it is considered to be above the third threshold and is functioning normally, so the process proceeds to step S560.

[0103] In step S550, the control device 17 stops the operation of the carbon dioxide capture system 10 and displays a warning, as it is considered that an operational malfunction or a sign of an abnormality has occurred. In step S560, the count values ​​of each control deviation counter, which are incremented in the control deviation adjustment process described later, are initialized, as it is considered that the carbon dioxide capture system 10 is operating normally.

[0104] Next, the adjustment process for control deviations will be explained with reference to the flowcharts in Figures 17 and 18.

[0105] In step S600, the detected values ​​from various sensors are read out. These sensors include a sensor that detects the gas flow rate or gas flow velocity of the mixed gas introduced into the recovery unit 12, a sensor that detects the current corresponding to the voltage applied between the working electrode and the counter electrode of the electrochemical cell, a sensor that detects the suction pressure or suction speed from the pump 13, a sensor that detects the temperature of the atmosphere (mixed gas), a sensor that detects the humidity of the atmosphere, and a sensor that detects the carbon dioxide concentration of the atmosphere.

[0106] In step S610, it is determined whether there is a deviation in the airflow rate. As described above, in the adsorption mode, the rotational speed that drives the blower 19 is predetermined to achieve an airflow rate that is sufficient to introduce a mixed gas containing carbon dioxide into the recovery unit 12, and the blower 19 is driven to the predetermined rotational speed. However, depending on the wind direction in the external environment, the airflow rate from the blower 19 into the recovery unit 12 may be insufficient or excessive compared to the target airflow rate. If such a deviation in the airflow rate occurs, the process proceeds to step S620; if there is no deviation in the airflow rate, the process proceeds to step S630. Note that if the actual airflow rate falls within the target range based on the target airflow rate, it is determined that there is no control deviation; if it falls outside that target range, it is determined that there is a control deviation.

[0107] In step S620, the rotational speed of the blower 19 is set to increase or decrease the airflow in the suction mode, according to the difference between the actual airflow and the target airflow. As a result, in subsequent operations, the blower 19 will be driven at the set rotational speed in suction mode until the rotational speed of the blower 19 is reset. If the wind direction of the external environment matches the direction of airflow from the blower 19, and the airflow is greater than the target airflow, the rotational speed of the blower 19 may be maintained at its current speed without needing to be reset. Furthermore, in step S620, the airflow counter, which is one of the control deviation counters, is counted up. The control deviation counter is used to measure the length of time that the control deviation state persists despite the control deviation adjustment process being performed.

[0108] Step S630 determines whether there is a deviation in the adsorption potential. In adsorption mode, the adsorption potential applied between the working electrode and counter electrode of the electrochemical cell is specified so that the electrochemical cell can fully exhibit carbon dioxide adsorption performance. However, even if a voltage is applied between the working electrode and counter electrode to achieve the specified adsorption potential, the actual adsorption potential may deviate from the desired adsorption potential due to a decrease or increase in temperature in the external environment. Therefore, in step S630, it is determined whether the adsorption potential deviates from the target range based on the desired adsorption potential, based on the magnitude of the applied voltage between the working electrode and counter electrode of the electrochemical cell detected by the sensor or the current supplied by the applied voltage. If there is a deviation in the adsorption potential, the process proceeds to step S640; if there is no deviation in the adsorption potential, the process proceeds to step S650.

[0109] In step S640, the applied voltage for the adsorption potential is set so that, in adsorption mode, the voltage applied between the working electrode and the counter electrode of the electrochemical cell is increased or decreased according to the difference between the actual adsorption potential and the target adsorption potential. As a result, in subsequent operations, until the applied voltage for the adsorption potential is reset, the set applied voltage for the adsorption potential is applied between the working electrode and the counter electrode of the electrochemical cell in adsorption mode. Furthermore, in step S640, the adsorption potential counter, which is one of the control deviation counters, is counted up.

[0110] In step S650, it is determined whether there is a deviation in the desorption potential. In desorption mode, the desorption potential applied between the working electrode and the counter electrode of the electrochemical cell is defined so that the electrochemical cell can desorb the adsorbed carbon dioxide almost completely. However, even if a voltage is applied between the working electrode and the counter electrode to achieve the defined desorption potential, the actual desorption potential may deviate from the desired desorption potential due to a decrease or increase in the temperature of the external environment, similar to the case of adsorption potential. Therefore, in step S650, it is determined whether the desorption potential deviates from the target range based on the desired desorption potential, based on the magnitude of the applied voltage between the working electrode and the counter electrode of the electrochemical cell detected by the sensor or the current supplied by the applied voltage. If there is a deviation in the desorption potential, the process proceeds to step S660; if there is no deviation in the desorption potential, the process proceeds to step S660.

[0111] In step S660, the applied voltage for the desorption potential is set so that the voltage applied between the working electrode and the counter electrode of the electrochemical cell is increased or decreased in desorption mode, depending on the difference between the actual desorption potential and the target desorption potential. As a result, in subsequent operations, until the applied voltage for the desorption potential is reset, the set applied voltage for the desorption potential is applied between the working electrode and the counter electrode of the electrochemical cell in desorption mode. Furthermore, in step S660, the desorption potential counter, which is one of the control deviation counters, is counted up.

[0112] Step S670 determines whether there is a deviation in the suction pressure of pump 13. For pump 13, the suction pressure is defined so that in scavenging mode, the residual mixed gas in the recovery unit 12 is almost completely discharged, and in recovery mode, the carbon dioxide desorbed from the adsorbent of the electrochemical cell is completely recovered. The motor that operates pump 13 is driven to achieve these respective suction pressures. However, if the operation of the moving parts of pump 13 or the motor malfunctions for any reason, a deviation in the suction pressure of pump 13 may occur. Therefore, in step S670, based on the suction pressure or suction speed detected by the sensor, it is determined whether the suction pressure in scavenging mode and / or recovery mode deviates from the target range based on the desired suction pressure. If a deviation in suction pressure occurs, the process proceeds to step S680; if no deviation occurs, the process proceeds to step S690.

[0113] In step S680, the motor speed that operates the pump 13 is set to increase or decrease the suction pressure of the pump 13 in the scavenging mode and / or recovery mode, depending on the difference between the actual suction pressure and the target suction pressure. As a result, from the next time onward, until the motor speed that operates the pump 13 is reset, the motor will be driven at the set speed in the scavenging mode and / or recovery mode, and the pump 13 will be operated by this motor. Furthermore, in step S680, the pump counter, which is one of the control deviation counters, is counted up. Note that since the operation of the pump 13 has a significant impact on carbon dioxide recovery, if the actual suction pressure deviates from the target suction pressure, the operation of the carbon dioxide recovery system 10 may be stopped without performing any adjustment processing, as this may be considered an abnormality.

[0114] In step S690, it is determined whether or not the air quality has deteriorated based on the detection results from sensors such as those that detect atmospheric humidity and atmospheric carbon dioxide concentration. For example, if the humidity rises above a first predetermined value or the carbon dioxide concentration falls below a second predetermined value, it can be determined that the air quality has deteriorated. If the air quality has deteriorated, the process proceeds to step S700; if the air quality has not deteriorated, the process proceeds to step S710.

[0115] When atmospheric humidity increases or the concentration of carbon dioxide in the atmosphere decreases, resulting in a deterioration of air quality, the determined execution time of the adsorption mode may be insufficient to achieve the target amount of carbon dioxide adsorbed. Therefore, in step S700, the adsorption time determined based on the adsorption amount change map data is extended by a predetermined time. As a result, the adsorption mode is executed for the extended adsorption time until the deterioration of air quality improves and the extension of the adsorption time is released. On the other hand, in step S710, since the air quality has not deteriorated, the extension of the adsorption time is released. After executing the process in step S700 or S710, the control device 17 proceeds to the process in step S720 of the flowchart in Figure 18.

[0116] In step S720, it is determined whether the count value of any of the control deviation counters is greater than the abnormality detection value. If the control deviation state is not resolved despite the adjustment process described above, the control deviation counter is not initialized in step S560 of the flowchart in Figure 16, and continues to count the number of repetitions of the control deviation adjustment process. In other words, the control deviation counter measures the length of time that the control deviation state persists. When the count value of the control deviation counter becomes greater than the abnormality detection value, it means that the period during which the control deviation is not resolved will be long. For this reason, if it is determined in step S720 that the count value of any of the control deviation counters is greater than the abnormality detection value, the control device 17 considers this to be an abnormality in the carbon dioxide capture system 10, and in step S730, it stops the operation of the carbon dioxide capture system 10 and displays a warning.

[0117] 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.

[0118] For example, the above-described embodiment does not specify the number of housings that house the electrochemical cells. There may be only one housing, or there may be multiple housings. If there are multiple housings, each housing an electrochemical cell, the multiple housings are 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 in the multiple housings, and a simultaneous recovery mode in which carbon dioxide is recovered simultaneously from each electrochemical cell in at least two or more housings. The simultaneous recovery mode may be performed, for example, when the sum of the maximum carbon dioxide adsorption amounts of the electrochemical cells in the multiple housings falls below a predetermined value, or when the usage time of the carbon dioxide recovery system 10 reaches a predetermined time.

[0119] In the embodiment described above, the adsorption amount change map data showing the change in the amount of carbon dioxide adsorbed by the electrochemical cell over time was created by a map creation process, but it may also be obtained from an external server 20. Furthermore, values ​​of environmental factors that affect the operation of the carbon dioxide capture system 10 (e.g., humidity, temperature, carbon dioxide concentration, wind speed, wind direction, etc.) may be detected and transmitted to the external server 20. Based on the detected values ​​of the environmental factors received, the external server 20 can determine the control target range of the equipment subject to control deviation adjustment processing in the carbon dioxide capture system 10, such as the blower 19, electrochemical cell, and pump 13, and send it back to the carbon dioxide capture system 10. The carbon dioxide capture system 10 controls each piece of equipment based on the received control target range and can use this control range as a target range based on a target value when determining whether a control deviation has occurred.

[0120] In the embodiment described above, the storage unit 18 was located inside the control device 17, but the storage unit 18 may be located outside the control device 17. Alternatively, the storage unit 18 may be located on an external server 20. Furthermore, at least some of the processing performed by the control device 17 may be performed by the external server 20.

[0121] Finally, this specification discloses several technical concepts and several combinations thereof, as listed below.

[0122] (Technical thought 1) A carbon dioxide capture system that recovers carbon dioxide from a mixed gas containing carbon dioxide by an electrochemical reaction, A carbon dioxide capture tank (16) for storing the captured carbon dioxide, A recovery device (12) having an electrochemical cell having a working electrode containing an adsorbent capable of adsorbing carbon dioxide, a counter electrode paired with the working electrode, and a housing for housing the electrochemical cell, When the adsorbent desorbs the carbon dioxide it has adsorbed, a pump (13) sucks the carbon dioxide desorbed from the adsorbent from the recovery device and discharges it toward the carbon dioxide recovery tank. A sensor (15) for detecting the amount of carbon dioxide recovered from the recovery device to the carbon dioxide recovery tank, A control device (17) that performs an adsorption mode in which a first potential is applied between the working electrode and the counter electrode to adsorb carbon dioxide onto the adsorbent, and a recovery mode in which a second potential is applied between the working electrode and the counter electrode, and the pump is controlled to suck and discharge carbon dioxide, thereby recovering the carbon dioxide adsorbed by the adsorbent into the carbon dioxide recovery tank. The system includes a storage unit (18) that stores data showing the change in the amount of carbon dioxide adsorbed by the adsorbent over time when the adsorption mode is being executed, The control device determines the execution time of the adsorption mode corresponding to the target carbon dioxide adsorption amount based on the adsorption amount change data, and executes the adsorption mode during that execution time. A carbon dioxide recovery system configured to determine whether the carbon dioxide recovery system is operating normally, based on the degree of decrease in the slope of the straight line showing the relationship between the actual carbon dioxide adsorbed amount and the execution time, relative to a threshold of slope set based on the slope of the straight line showing the relationship between the initial maximum carbon dioxide adsorbed amount of the electrochemical cell and the execution time which is the execution time corresponding to the carbon dioxide adsorbed amount, and / or based on the degree of decrease in the amount of carbon dioxide recovered detected using the sensor relative to a threshold of recovery amount set based on the maximum carbon dioxide adsorbed amount.

[0123] (Technical thought 2) The slope threshold, which is set based on the slope of the straight line representing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time, includes a first threshold, The carbon dioxide capture system according to technical concept 1, wherein the control device considers a control error to have occurred when the slope of the straight line representing the relationship between the actual carbon dioxide adsorption amount and the execution time falls below the first threshold, and performs an adjustment process to resolve the control error.

[0124] (Technical Thought 3) The carbon dioxide capture system according to technical concept 2, wherein the first threshold is set as a value lower by a first reference value from the slope of the straight line showing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time.

[0125] (Technical Thought 4) The carbon dioxide capture system according to technical concept 2 or 3, wherein the first threshold is calculated as a value lower by a first reference value from the slope of the straight line showing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time, and further lower by a variable that increases with increasing number of executions of the adsorption mode.

[0126] (Technical Thought 5) The carbon dioxide capture system according to any one of technical ideas 2 to 4, wherein the control device considers it abnormal and stops the operation of the carbon dioxide capture system when the slope of the straight line showing the relationship between the actual amount of carbon dioxide adsorbed and the execution time falls below a second threshold that is smaller than the first threshold with respect to the slope of the straight line showing the relationship between the maximum amount of carbon dioxide adsorbed and the maximum adsorption time.

[0127] (Technical Thought 6) The carbon dioxide capture system according to technical concept 5, wherein the second threshold is set as a value lower by a second reference value from the slope of the straight line showing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time.

[0128] (Technical Thought 7) The carbon dioxide capture system according to technical concept 5 or 6, wherein the second threshold is calculated as a value lower by a second reference value from the slope of the straight line showing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time, and further lower by a variable that increases with increasing number of executions of the adsorption mode.

[0129] (Technical Thought 8) The carbon dioxide recovery system according to any one of technical ideas 1 to 7, wherein the control device considers a control error to have occurred when the amount of carbon dioxide recovered detected using the sensor falls below a third threshold included in the recovery amount threshold relative to the maximum carbon dioxide adsorption amount, and performs an adjustment process to resolve the control error.

[0130] (Technical Thought 9) The carbon dioxide capture system according to technical concept 8, wherein the third threshold gradually decreases in response to an increase in the number of times the adsorption mode is executed.

[0131] (Technical Thought 10) The carbon dioxide recovery system according to technical concept 8 or 9, wherein the control device considers it abnormal when the amount of carbon dioxide recovered using the sensor falls below a fourth threshold that is smaller than the third threshold relative to the maximum carbon dioxide adsorption amount, and stops the operation of the carbon dioxide recovery system.

[0132] (Technical Thought 11) The carbon dioxide capture system according to technical idea 10, wherein the fourth threshold gradually decreases in response to an increase in the number of times the adsorption mode is executed.

[0133] (Technical Thought 12) During the execution of the adsorption mode, the recovery device is further provided with a blowing means for blowing a mixed gas containing carbon dioxide into the recovery device. The carbon dioxide capture system according to any one of technical ideas 2 to 11, wherein the adjustment process includes adjusting the amount of air blown or the air blowing speed by the blowing means.

[0134] (Technical Thought 13) The carbon dioxide capture system according to any one of technical ideas 2 to 11, wherein the adjustment process includes adjusting the first potential.

[0135] (Technical Thought 14) The carbon dioxide capture system according to any one of technical ideas 2 to 11, wherein the adjustment process includes adjusting the second potential.

[0136] (Technical Thought 15) The carbon dioxide recovery system according to any one of technical ideas 2 to 11, wherein the adjustment process includes adjusting the suction force or suction speed of the pump.

[0137] (Technical Thought 16) A carbon dioxide recovery system according to any one of technical ideas 2 to 11, wherein the adjustment process includes extending the execution time of the adsorption mode when the quality of the mixed gas deteriorates.

[0138] (Technical Thought 17) It further includes a physical quantity detector that detects a physical quantity related to the physical quantity to be adjusted, The carbon dioxide capture system according to any one of technical concepts 2 to 16, wherein the control device adjusts the physical quantity to be adjusted based on the physical quantity detected by the physical quantity detector so that the physical quantity to be adjusted falls within a target range.

[0139] (Technical Thought 18) An environmental factor detection unit that detects values ​​of environmental factors that affect the operation of the carbon dioxide capture system, A transmission unit that transmits the detected values ​​of the environmental factors detected by the environmental factor detection unit to an external server, A carbon dioxide capture system according to technical concept 17, further comprising: a receiving unit that receives from an external server a target range for the physical quantity to be adjusted based on the detected values ​​of the environmental factors transmitted.

[0140] (Technical Thought 19) The carbon dioxide capture system according to any one of technical ideas 2 to 18, wherein the control device considers the control deviation to be abnormal and stops the operation of the carbon dioxide capture system if the adjustment operation is not resolved even after repeating the adjustment operation a predetermined number of times.

[0141] (Technical Thought 20) The carbon dioxide recovery system according to any one of Technical Ideas 1 to 19, wherein the control device, when the amount of carbon dioxide recovered detected using the sensor gradually decreases with increasing execution counts of the adsorption mode and falls below a fifth threshold based on the target carbon dioxide adsorption amount, reduces the target carbon dioxide adsorption amount and updates the execution time to correspond to the reduced target carbon dioxide adsorption amount based on the adsorption amount change data.

[0142] (Technical Thought 21) The carbon dioxide recovery system according to technical concept 20, wherein the control device outputs a signal indicating that it is time to replace the electrochemical cell when the amount of carbon dioxide recovered detected using the sensor falls below a sixth threshold from the initial maximum carbon dioxide adsorption amount of the electrochemical cell. [Explanation of Symbols]

[0143] 10: Carbon dioxide capture system 10a~10c: Subsystem 11,11a~11c: Flow control valve 12,12a~12c: Recovery unit 13: Pump 14: Flow control valve 15: Sensor 16: CO2 capture tank 17: Control device 18: Memory unit 19: Blower 20a~20c: Switching valve

Claims

1. A carbon dioxide capture system that recovers carbon dioxide from a mixed gas containing carbon dioxide by an electrochemical reaction, A carbon dioxide capture tank (16) for storing the captured carbon dioxide, A recovery device (12) having an electrochemical cell having a working electrode containing an adsorbent material capable of adsorbing carbon dioxide, a counter electrode paired with the working electrode, and a housing for housing the electrochemical cell, When the adsorbent desorbs the carbon dioxide it has adsorbed, a pump (13) sucks the carbon dioxide desorbed from the adsorbent from the recovery device and discharges it toward the carbon dioxide recovery tank. A sensor (15) for detecting the amount of carbon dioxide recovered from the recovery device to the carbon dioxide recovery tank, A control device (17) that performs an adsorption mode in which a first potential is applied between the working electrode and the counter electrode to adsorb carbon dioxide onto the adsorbent, and a recovery mode in which a second potential is applied between the working electrode and the counter electrode, and the pump is controlled to suck and discharge carbon dioxide, thereby recovering the carbon dioxide adsorbed by the adsorbent into the carbon dioxide recovery tank. The system includes a storage unit (18) that stores data showing the change in the amount of carbon dioxide adsorbed by the adsorbent over time when the adsorption mode is being executed, In order to determine the normal operation of the carbon dioxide capture system, the control device determines the execution time of the adsorption mode corresponding to the target carbon dioxide adsorption amount based on the adsorption amount change data, and executes the adsorption mode during that execution time. A carbon dioxide recovery system configured such that, in the recovery mode after the adsorption mode, the control device considers the amount of carbon dioxide recovered using the sensor as the actual amount of carbon dioxide adsorbed by the adsorbent, and determines whether the carbon dioxide recovery system is operating normally based on the degree of decrease in the slope of the line representing the relationship between the actual amount of carbon dioxide adsorbed and the execution time, with respect to a threshold of slope set based on the slope of the line representing the relationship between the initial maximum amount of carbon dioxide adsorbed by the electrochemical cell and the execution time which is the execution time corresponding to the maximum amount of carbon dioxide adsorbed, and / or based on the degree of decrease in the amount of carbon dioxide recovered using the sensor with respect to a threshold of recovery amount set based on the maximum amount of carbon dioxide adsorbed.

2. The threshold of the slope, which is set based on the slope of the straight line showing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time, includes a first threshold, The carbon dioxide recovery system according to claim 1, wherein the control device considers that a control error has occurred when the slope of the straight line representing the relationship between the actual carbon dioxide adsorption amount and the execution time falls below the first threshold, and performs an adjustment process to resolve the control error.

3. The carbon dioxide recovery system according to claim 2, wherein the first threshold is set to a value lower by a first reference value from the slope of the straight line showing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time.

4. The carbon dioxide recovery system according to claim 2, wherein the first threshold is calculated by lowering the slope of the straight line representing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time by a first reference value, and further lowering it by a variable that increases with increasing number of executions of the adsorption mode.

5. The carbon dioxide recovery system according to claim 2, wherein the control device considers it abnormal and stops the operation of the carbon dioxide recovery system when the slope of the straight line showing the relationship between the actual amount of carbon dioxide adsorbed and the execution time falls below a second threshold that is smaller than the first threshold with respect to the slope of the straight line showing the relationship between the maximum amount of carbon dioxide adsorbed and the maximum adsorption time.

6. The carbon dioxide recovery system according to claim 5, wherein the second threshold is set to a value lower by a second reference value from the slope of the straight line showing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time.

7. The carbon dioxide capture system according to claim 5, wherein the second threshold is calculated by lowering the slope of the straight line representing the relationship between the maximum carbon dioxide adsorption amount and the maximum adsorption time by a second reference value, and further lowering it by a variable that increases with increasing number of executions of the adsorption mode.

8. The carbon dioxide recovery system according to claim 1, wherein the control device considers a control error to have occurred when the amount of carbon dioxide recovered detected using the sensor falls below a third threshold included in the recovery amount threshold relative to the maximum carbon dioxide adsorption amount, and performs an adjustment process to resolve the control error.

9. The carbon dioxide recovery system according to claim 8, wherein the third threshold gradually decreases in response to an increase in the number of times the adsorption mode is executed.

10. The carbon dioxide recovery system according to claim 8, wherein the control device considers it abnormal and stops the operation of the carbon dioxide recovery system when the amount of carbon dioxide recovered detected using the sensor falls below a fourth threshold that is smaller than the third threshold relative to the maximum carbon dioxide adsorption amount.

11. The carbon dioxide recovery system according to claim 10, wherein the fourth threshold gradually decreases in response to an increase in the number of times the adsorption mode is executed.

12. During the execution of the adsorption mode, the recovery device is further provided with a blowing means for blowing a mixed gas containing carbon dioxide into the recovery device. The carbon dioxide recovery system according to any one of claims 2 to 11, wherein the adjustment process includes adjusting the amount of air blown or the air blowing speed by the air blowing means.

13. The carbon dioxide recovery system according to any one of claims 2 to 11, wherein the adjustment process includes adjusting the first potential.

14. The carbon dioxide recovery system according to any one of claims 2 to 11, wherein the adjustment process includes adjusting the second potential.

15. The carbon dioxide recovery system according to any one of claims 2 to 11, wherein the adjustment process includes adjusting the suction force or suction speed of the pump.

16. The carbon dioxide recovery system according to any one of claims 2 to 11, wherein the adjustment process includes extending the execution time of the adsorption mode when the quality of the mixed gas deteriorates.

17. It further includes a physical quantity detector that detects a physical quantity related to the physical quantity to be adjusted, The carbon dioxide recovery system according to any one of claims 2 to 11, wherein the control device adjusts the physical quantity to be adjusted based on the physical quantity detected by the physical quantity detector so that the physical quantity to be adjusted falls within a target range, as part of the adjustment process.

18. An environmental factor detection unit for detecting values ​​of environmental factors that affect the operation of a carbon dioxide capture system, A transmission unit that transmits the detected values ​​of the environmental factors detected by the environmental factor detection unit to an external server, The carbon dioxide capture system according to claim 17, further comprising: a receiving unit that receives from an external server a target range for the physical quantity to be adjusted based on the detected values ​​of the environmental factors transmitted.

19. The carbon dioxide capture system according to any one of claims 2 to 11, wherein the control device considers the control deviation to be abnormal and stops the operation of the carbon dioxide capture system if the adjustment process is repeated a predetermined number of times and the control deviation is not resolved.

20. The carbon dioxide recovery system according to claim 1, wherein the control device, when the amount of carbon dioxide recovered using the sensor gradually decreases with increasing execution counts of the adsorption mode and falls below a fifth threshold based on the target carbon dioxide adsorption amount, reduces the target carbon dioxide adsorption amount and updates the execution time to correspond to the reduced target carbon dioxide adsorption amount based on the adsorption amount change data.

21. The carbon dioxide recovery system according to claim 20, wherein the control device outputs a signal indicating that it is time to replace the electrochemical cell when the amount of carbon dioxide recovered detected using the sensor falls below a sixth threshold from the initial maximum carbon dioxide adsorption amount of the electrochemical cell.

22. The carbon dioxide recovery system according to Claim 1, wherein the adsorption amount change data is created by executing the adsorption mode multiple times at different execution times for the adsorption mode, detecting the amount of carbon dioxide recovered in the multiple recovery modes executed in accordance with each of the adsorption modes using the sensor, and determining the maximum adsorption amount of the adsorbent and the maximum adsorption time, which is the execution time of the adsorption mode to obtain the maximum adsorption amount, based on the execution time of the multiple adsorption modes and the amount of carbon dioxide recovered by the sensor in the multiple recovery modes.

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