JP2023161226A - Carbon dioxide recovery system - Google Patents

Abstract

To provide a carbon dioxide recovery system capable of reducing energy required for carbon dioxide recovery and also shortening a time required for the carbon dioxide recovery.SOLUTION: A carbon dioxide recovery system that separates and recovers carbon dioxide from a supply gas containing the carbon dioxide comprises: an adsorption part 100 which adsorbs and desorbs the carbon dioxide; a process changeover part 202 which changes over a plurality of processes including an adsorption process in which the adsorption part 100 adsorbs the carbon dioxide included in the supply gas; and an adsorption state detection part 201 which detects a carbon dioxide adsorption state of the adsorption part 100, wherein the process changeover part 202 determines the timing of transition from the adsorption process to a next process based upon the carbon dioxide adsorption state.SELECTED DRAWING: Figure 1

Description

The present invention relates to a carbon dioxide recovery system that recovers carbon dioxide from a carbon dioxide-containing gas.

Conventionally, Patent Document 1 discloses a gas separation system having a carbon dioxide adsorber that adsorbs carbon dioxide from a carbon dioxide-containing gas (for example, air) by an electrochemical reaction. Such a gas separation system is configured to be able to switch between a plurality of processes, such as an adsorption process in which a carbon dioxide adsorber adsorbs carbon dioxide, and a desorption process in which a carbon dioxide adsorption device desorbs carbon dioxide. In the carbon dioxide adsorber, the timing of transition from the adsorption step of adsorbing carbon dioxide to the next step (for example, desorption step) is determined by time.

JP 2019-203193 Publication

However, in the above conventional technology, the carbon dioxide concentration of the supplied gas (i.e., the amount of carbon dioxide supplied to the carbon dioxide adsorption device) changes depending on the flow rate, humidity, etc. of the carbon dioxide-containing gas supplied to the carbon dioxide adsorption device. . Furthermore, the amount of carbon dioxide adsorbed changes due to deterioration of the electrochemical cell and variations in control potential.

For this reason, it is difficult to determine an appropriate transition timing based on time, and carbon dioxide adsorption may end in a state where the carbon dioxide adsorption rate is low. Alternatively, carbon dioxide adsorption may continue even if the carbon dioxide adsorption rate becomes high and reaches a saturated state. As a result, the energy required to adsorb carbon dioxide increases, and the time required to adsorb carbon dioxide also increases.

In view of the above points, an object of the present invention is to provide a carbon dioxide recovery system that can reduce the energy required for carbon dioxide recovery and shorten the time required for carbon dioxide recovery.

In order to achieve the above object, the carbon dioxide recovery system according to claim 1 is a carbon dioxide recovery system that separates and recovers carbon dioxide from a supply gas containing carbon dioxide.
an adsorption unit (100) that adsorbs and desorbs carbon dioxide;
a process switching unit (202) that switches between a plurality of processes including an adsorption process in which the adsorption unit adsorbs carbon dioxide contained in the supplied gas;
an adsorption state detection unit (201) that detects the carbon dioxide adsorption state of the adsorption unit;
The process switching unit determines the timing for transitioning from the adsorption process to the next process based on the carbon dioxide adsorption state.

According to this, the timing of moving from the adsorption step to the next step is determined based on the adsorption state of carbon dioxide in the adsorption part (100), so that the adsorption state of carbon dioxide in the adsorption part (100) is adjusted to a desired level. It is possible to move from the adsorption step to the next step at the timing when the state is reached. Therefore, it is possible to reduce the energy required for carbon dioxide recovery and the time required for carbon dioxide recovery.

Note that the reference numerals in parentheses of each means described in this column and the claims indicate correspondence with specific means described in the embodiment described later.

1 is a conceptual diagram showing the overall configuration of a carbon dioxide recovery system according to a first embodiment. It is a perspective view showing a carbon dioxide recovery device in a 1st embodiment. It is a perspective view showing a state where a plurality of electrochemical cells in a 1st embodiment were laminated. It is a perspective view showing an electrochemical cell in a 1st embodiment. FIG. 2 is a block diagram showing an electrical control unit of the carbon dioxide recovery system according to the first embodiment. It is a flowchart which shows the process of process switching control of 1st Embodiment. 5 is a time chart showing changes in carbon dioxide concentration, etc. in the carbon dioxide recovery system of the first embodiment. 5 is a time chart showing changes in the concentration of carbon dioxide, etc. when the electrochemical cell in the carbon dioxide recovery system of the first embodiment deteriorates. It is a flowchart which shows the process of process switching control of 2nd Embodiment. It is a flowchart which shows the process of process switching control of 3rd Embodiment. It is a flowchart which shows the process of process switching control of 4th Embodiment. FIG. 2 is an explanatory diagram showing the relationship between the amount of charged charge and the amount of adsorbed CO ₂ . It is a time chart showing changes in the concentration of carbon dioxide, etc. in the carbon dioxide recovery system of the fourth embodiment. FIG. 2 is an explanatory diagram showing the relationship between capacitance and CO ₂ upper limit adsorption amount.

Embodiments of the present invention will be described below based on the drawings. Note that in each of the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described using the drawings. As shown in FIG. 1, the carbon dioxide recovery system 1 of this embodiment includes a carbon dioxide recovery device 10, a pump 11, a flow path switching valve 12, and a carbon dioxide utilization device 13.

The carbon dioxide recovery device 10 is a device that separates and recovers carbon dioxide from a supplied gas. The carbon dioxide recovery device 10 has an adsorption unit 100 that adsorbs and desorbs carbon dioxide.

The feed gas is a carbon dioxide-containing gas containing carbon dioxide. The feed gas also contains gases other than carbon dioxide. As the supply gas, for example, the atmosphere or exhaust gas from an internal combustion engine can be used. In this embodiment, the atmosphere is used as the supply gas.

The carbon dioxide recovery device 10 is supplied with a supply gas and discharges exhaust gas after carbon dioxide has been recovered from the supply gas (hereinafter also referred to as carbon dioxide removed gas) or carbon dioxide recovered from the supply gas. The configurations of the carbon dioxide recovery device 10 and the adsorption unit 100 will be described in detail later.

Pump 11 supplies feed gas to carbon dioxide recovery device 10 and discharges carbon dioxide or exhaust gas from carbon dioxide recovery device 10 . In the example shown in FIG. 1, the pump 11 is provided on the downstream side of the carbon dioxide recovery device 10 in the gas flow direction, but the pump 11 may be provided on the upstream side of the carbon dioxide recovery device 10 in the gas flow direction.

The flow path switching valve 12 is a three-way valve that switches the flow path of the gas discharged from the carbon dioxide recovery device 10. When the exhaust gas (i.e., carbon dioxide removed gas) is discharged from the carbon dioxide recovery device 10, the flow path switching valve 12 switches the flow path of the exit gas to the atmosphere side, so that the carbon dioxide is removed from the carbon dioxide recovery device 10. If the gas is to be discharged, the flow path for the discharged gas is switched to the carbon dioxide utilization device 13 side.

The carbon dioxide utilization device 13 is a device that utilizes carbon dioxide. As the carbon dioxide utilization device 13, for example, a storage tank that stores carbon dioxide or a conversion device that converts carbon dioxide into fuel can be used. As the conversion device, a device that converts carbon dioxide into hydrocarbon fuel such as methane can be used. The hydrocarbon fuel may be a gaseous fuel at normal temperature and normal pressure, or may be a liquid fuel at normal temperature and normal pressure.

Next, the carbon dioxide recovery device 10 of this embodiment will be explained using FIGS. 2 to 4. In FIGS. 2 to 4, the gas flow direction is from the front to the back of the paper, and the cell stacking direction is the vertical direction of the paper.

As shown in FIG. 2, the carbon dioxide recovery device 10 includes an adsorption section 100 and a storage section 110. The accommodating portion 110 is formed in a box shape and can be made of, for example, a metal material.

The adsorption section 100 has an electrochemical cell 101. Electrochemical cell 101 is housed in housing section 110 . The carbon dioxide recovery device 10 adsorbs and desorbs carbon dioxide through the electrochemical reaction of the electrochemical cell 101, and separates and recovers carbon dioxide from the supplied gas.

The housing section 110 has two openings. These two openings are an introduction part 110a that introduces supply gas into the interior, and an exhaust part (not shown) that discharges exhaust gas and carbon dioxide from the inside. The gas flow direction is the flow direction when the supplied gas passes through the storage section 110, and is the direction from the introduction section 110a of the storage section 110 toward the discharge section.

In FIG. 2, the supplied gas flows from the front side of the page toward the back side of the page. Therefore, the accommodating part 110 has an introduction part 110a on the near side in the figure, and an ejection part on the back side in the figure. Note that the introduction section 110a and the discharge section of the storage section 110 are provided with opening/closing members (not shown) for opening and closing each.

Inside the housing section 110, a plurality of electrochemical cells 101 are arranged in a stacked manner. The cell stacking direction in which the plurality of electrochemical cells 101 are stacked is a direction perpendicular to the gas flow direction. Each electrochemical cell 101 is configured in a plate shape, and arranged so that the plate surface intersects with the cell stacking direction.

FIG. 3 shows a state in which a plurality of electrochemical cells 101 are stacked. FIG. 4 shows one electrochemical cell 101. In FIG. 4, the components of the electrochemical cell 101, such as the working electrode current collecting layer 103, are shown spaced apart from each other, but in reality, these components are stacked and arranged so as to be in contact with each other.

As shown in FIG. 3, a predetermined gap is provided between adjacent electrochemical cells 101. A gap provided between adjacent electrochemical cells 101 constitutes a gas flow path 102 through which supply gas flows.

As shown in FIGS. 3 and 4, the electrochemical cell 101 includes a working electrode current collecting layer 103, a working electrode 104, a counter electrode current collecting layer 105, a counter electrode 106, and a separator 107. In adjacent electrochemical cells 101, one working electrode current collecting layer 103 and the other counter electrode current collecting layer 105 face each other with the gas flow path 102 in between.

As shown in FIG. 4, an electrolytic solution 108, which is an electrolytic substance, is provided between the working electrode 104 and the counter electrode 106. In this embodiment, working electrode 104, counter electrode 106, and separator 107 are saturated with electrolyte 108.

The working electrode current collecting layer 103, the working electrode 104, the counter electrode current collecting layer 105, the counter electrode 106, and the separator 107 are each formed into a plate shape. The electrochemical cell 101 is configured as a laminate in which a working electrode current collecting layer 103, a working electrode 104, a counter electrode current collecting layer 105, a counter electrode 106, and a separator 107 are stacked. The direction in which the working electrode current collecting layer 103 and the like of each electrochemical cell 101 are stacked is the same direction as the cell stacking direction in which a plurality of electrochemical cells 101 are stacked.

The working electrode current collecting layer 103 is a porous conductive material having pores through which a supply gas containing carbon dioxide can pass. The working electrode current collecting layer 103 only needs to have gas permeability and conductivity, and for example, a metal material or a carbonaceous material can be used. In this embodiment, a metal porous body is used as the working electrode current collecting layer 103.

The working electrode 104 contains a carbon dioxide adsorbent, a conductive material, and a binder. The carbon dioxide adsorbent, the conductive material and the binder are used in a mixture.

A carbon dioxide adsorbent adsorbs carbon dioxide by receiving electrons, and desorbs the adsorbed carbon dioxide by releasing electrons. As the carbon dioxide adsorbent, for example, polyanthraquinone can be used.

The electrically conductive material forms a conductive path to the carbon dioxide adsorbent. As the conductive substance, for example, carbon materials such as carbon nanotubes, carbon black, and graphene can be used.

The binder is provided to hold the carbon dioxide adsorbent and the conductive substance. As the binder, for example, a conductive resin can be used. As the conductive resin, an epoxy resin containing Ag or the like as a conductive filler, a fluororesin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc. can be used.

Counter electrode current collecting layer 105 is a conductive material. As the counter electrode current collecting layer 105, for example, a metal material or a carbonaceous material can be used. In this embodiment, a metal plate is used as the counter electrode current collecting layer 105.

Counter electrode 106 includes an electroactive supplement, a conductive material, and a binder. The conductive material and binder of the counter electrode 106 have the same structure as the working electrode 104, so a description thereof will be omitted. In this embodiment, the counter electrode 106 is made of a material containing an active material that serves as an electron donor.

The electroactive auxiliary material of the counter electrode 106 is an auxiliary electroactive species that exchanges electrons with the carbon dioxide adsorbent of the working electrode 104 . As the electroactive auxiliary material, for example, a metal complex that enables transfer of electrons by changing the valence of metal ions can be used. Examples of such metal complexes include cyclopentadienyl metal complexes such as ferrocene, nickelocene, and cobaltocene, and porphyrin metal complexes. These metal complexes may be polymers or monomers.

The separator 107 is disposed between the working electrode 104 and the counter electrode 106, and separates the working electrode 104 and the counter electrode 106. The separator 107 is an insulating ion-permeable membrane that prevents physical contact between the working electrode 104 and the counter electrode 106 to suppress electrical short circuits, and also allows ions to pass therethrough. As the separator 107, a cellulose membrane, a polymer, a composite material of polymer and ceramic, or the like can be used.

The electrochemical cell 101 is provided with a power source 109 connected to a working electrode current collecting layer 103 and a counter electrode current collecting layer 105. The power supply 109 can apply a predetermined voltage to the working electrode 104 and the counter electrode 106 to change the potential difference between the working electrode 104 and the counter electrode 106. Working electrode 104 is a negative electrode, and counter electrode 106 is a positive electrode.

The electrochemical cell 101 operates by changing the potential difference between the working electrode 104 and the counter electrode 106 to switch between an adsorption process in which carbon dioxide is adsorbed onto the working electrode 104 and a desorption process in which carbon dioxide is desorbed from the working electrode 104. can do. The adsorption process is a charging process that charges the electrochemical cell 101, and the desorption process is a discharging process that discharges the electrochemical cell 101.

In the adsorption step, a first voltage V1 is applied between the working electrode 104 and the counter electrode 106, and electrons are supplied from the counter electrode 106 to the working electrode 104. At the first voltage V1, working electrode potential<counter electrode potential. The first voltage V1 can be within a range of 0.5 to 2.0V, for example.

In the desorption step, a second voltage V2 is applied between the working electrode 104 and the counter electrode 106, and electrons are supplied from the working electrode 104 to the counter electrode 106. The second voltage V2 is a voltage different from the first voltage V1. The second voltage V2 only needs to be a voltage lower than the first voltage V1, and the magnitude relationship between the working electrode potential and the counter electrode potential is not limited. That is, in the desorption step, the working electrode potential may be less than the counter electrode potential, the working electrode potential may be equal to the counter electrode potential, or the working electrode potential may be greater than the counter electrode potential.

Next, the electrolytic solution 108 of this embodiment will be explained. In the carbon dioxide recovery system 1 of this embodiment, the electrolytic solution 108 employs a substance that has at least one of addition reaction resistance and displacement reaction resistance with respect to at least one of the supply gas, the working electrode 104, and the counter electrode 106. There is. For example, the electrolytic solution 108 can be made of a substance that does not cause at least one of an addition reaction and a substitution reaction with respect to at least one of the supplied gas, the working electrode 104, and the counter electrode 106.

Specifically, the electrolyte 108 exhibits redox reactivity with respect to at least one of the supply gas, the working electrode 104, and the counter electrode 106 when a voltage is applied between the working electrode 104 and the counter electrode 106. It is possible to use a substance that has For example, the electrolyte 108 may be made of a substance that does not exhibit a redox reaction with at least one of the supplied gas, the working electrode, and the counter electrode when a voltage is applied between the working electrode 104 and the counter electrode 106. can.

More specifically, the electrolytic solution 108 absorbs the supplied gas, the working electrode 104 and A substance having redox reactivity resistance can be used for at least one of the counter electrodes 106. For example, the electrolytic solution 108 is activated when a voltage within a range of a first voltage V1 or more and a second voltage V2 or less is applied between the working electrode 104 and the counter electrode 106. It is possible to use a substance that does not exhibit a redox reaction with one.

Further, the electrolytic solution 108 can be made of a substance that is resistant to decomposition and reactivity at room temperature and pressure when a voltage is applied between the working electrode 104 and the counter electrode 106. For example, the electrolyte 108 can be made of a substance that does not exhibit a decomposition reaction at room temperature and pressure when a voltage is applied between the working electrode 104 and the counter electrode 106.

More specifically, the electrolytic solution 108 is a substance that has decomposition-resistant reactivity when a voltage within a range of a first voltage V1 or more and a second voltage V2 or less is applied between the working electrode 104 and the counter electrode 106. can be used. For example, the electrolyte 108 may be made of a substance that does not exhibit a decomposition reaction when a voltage within a range of the first voltage V1 or more and the second voltage V2 or less is applied between the working electrode 104 and the counter electrode 106. can.

Further, as the electrolyte 108, a substance that is stable with respect to the constituent materials of the electrochemical cell 101 can be used. That is, the electrolytic solution 108 can be made of a substance that is resistant to reactions with the constituent materials of the electrochemical cell 101.

Further, as the electrolytic solution 108, a substance that does not easily generate volatile products due to electrochemical reactions can be used. For example, compared to the case where 1-ethyl-3-methylimidazolium dicyanamide [Emin][N(CN) ₂ ] is used as an electrolyte, a substance that is less likely to generate volatile products through electrochemical reaction, It can be used as the electrolyte 108. Further, as the electrolyte 108, a substance that does not generate volatile products through electrochemical reactions can be used.

Moreover, an ionic liquid can be used as the electrolytic solution 108. Ionic liquids are liquid salts that are nonvolatile at room temperature and pressure.

Next, the operation of the carbon dioxide recovery system 1 of this embodiment will be explained. The carbon dioxide recovery system 1 is configured to be able to perform an adsorption process, a scavenging process, and a desorption process. The carbon dioxide recovery system 1 operates by switching in the order of adsorption process, scavenging process, desorption process, adsorption process, scavenging process, desorption process, and so on. The operation of the carbon dioxide recovery system 1 is controlled by a control device 20, which will be described later.

The adsorption process is an adsorption process in which the adsorption unit 100 adsorbs carbon dioxide contained in the supplied gas. In the adsorption step, the pump 11 is operated to supply supply gas to the adsorption section 100. In the adsorption step, the voltage applied between the working electrode 104 and the counter electrode 106 is set as the first voltage V1. Thereby, electron donation by the electroactive auxiliary material of the counter electrode 106 and electron withdrawal by the carbon dioxide adsorbent of the working electrode 104 can be simultaneously realized.

The electroactive auxiliary material of the counter electrode 106 emits electrons and becomes oxidized, and electrons are supplied from the counter electrode 106 to the working electrode 104 . The carbon dioxide adsorbent of the working electrode 104 receives electrons and enters a reduced state.

The carbon dioxide adsorbent in the reduced state has a high binding force for carbon dioxide, and binds and adsorbs carbon dioxide contained in the supplied gas. Thereby, the carbon dioxide recovery device 10 can recover carbon dioxide from the supplied gas.

In the scavenging step, the pump 11 is operated with the opening/closing member of the introduction section 110a in the housing section 110 closed. In the scavenging step, the flow path switching valve 12 is switched so that the flow path for the exit gas is on the atmosphere side. As a result, the gas present in the housing section 110 is discharged to the atmosphere. At this time, the carbon dioxide in the adsorption unit 100 remains adsorbed by the carbon dioxide adsorbent of the working electrode 104.

In the desorption step, the flow path switching valve 12 is switched so that the flow path of the exit gas is on the carbon dioxide utilization device 13 side. In the desorption step, the voltage applied between the working electrode 104 and the counter electrode 106 is set as the second voltage V2. Thereby, electron donation by the carbon dioxide adsorbent of the working electrode 104 and electron withdrawal by the electroactive auxiliary material of the counter electrode 106 can be simultaneously realized.

The carbon dioxide adsorbent of the working electrode 104 emits electrons and becomes oxidized. The carbon dioxide adsorbent has a reduced bonding force with carbon dioxide and desorbs and releases carbon dioxide. The electroactive auxiliary material of the counter electrode 106 receives electrons and becomes reduced.

Carbon dioxide released from the carbon dioxide adsorbent is discharged from the adsorption unit 100 and supplied to the carbon dioxide utilization device 13.

Next, an overview of the electric control section in the carbon dioxide recovery system 1 of this embodiment will be explained. As shown in FIG. 5, the control device 20 is composed of a well-known microcomputer including a CPU, ROM, RAM, etc., and its peripheral circuits. The control device 20 performs various calculations and processes based on a control program stored in its ROM, and controls the operations of various controlled devices connected to its output side. The devices to be controlled are the carbon dioxide recovery device 10, the pump 11, the flow path switching valve 12, and the like.

A CO ₂ concentration sensor 30 is connected to the input side of the control device 20 . A detection signal from the CO ₂ concentration sensor 30 is input to the control device 20 . The CO ₂ concentration sensor 30 is a carbon dioxide concentration detection unit that detects the concentration of carbon dioxide contained in the exhaust gas after carbon dioxide has been adsorbed by the adsorption unit 100 (hereinafter referred to as exhaust gas CO ₂ concentration).

The control device 20 includes an adsorption state detection section 201 and a process switching section 202.

The adsorption state detection unit 201 detects the carbon dioxide adsorption state of the adsorption unit 100. In this embodiment, the amount of carbon dioxide adsorbed by the adsorption unit 100 (hereinafter referred to as adsorbed CO ₂ amount) is used as the carbon dioxide adsorption state. The adsorption state detection unit 201 detects the adsorbed CO ₂ amount based on the exhaust gas CO ₂ concentration detected by the CO ₂ concentration sensor 30.

The process switching unit 202 is a switching control unit that switches between a plurality of operating processes of the carbon dioxide recovery system 1. That is, the process switching unit 202 switches between a plurality of processes including the adsorption process. The process switching unit 202 determines the timing for transitioning from the adsorption process to the next process based on the carbon dioxide adsorption state of the adsorption unit 100. In this embodiment, the process switching unit 202 determines the timing to shift from the adsorption process to the scavenging process based on the adsorbed CO ₂ amount calculated by the adsorption state detection unit 201.

Next, switching control from the adsorption process to the scavenging process by the carbon dioxide recovery system 1 according to the first embodiment will be described with reference to the flowchart shown in FIG. 6.

As shown in FIG. 6, first, in step S100, the CO ₂ concentration sensor 30 starts periodically detecting the exhaust gas CO ₂ concentration. That is, in step S100, the exhaust gas CO ₂ concentration is detected at a predetermined sampling time, and monitoring of the exhaust gas CO ₂ concentration is started.

Next, in step S110, an adsorption process is started. Specifically, the control device 20 controls the operation of the pump 11 so as to exhibit a predetermined pumping capacity, and sets the voltage applied between the working electrode 104 and the counter electrode 106 to the first voltage V1.

Next, in step S120, the amount of adsorbed CO ₂ is calculated. Specifically, first, the concentration of _{carbon dioxide} adsorbed in the adsorption unit 100 (hereinafter referred _to as adsorbed CO ₂ concentration) is calculated. Then, the adsorbed CO ₂ amount is calculated from the product of the adsorbed CO ₂ concentration and the flow rate of carbon dioxide flowing through the adsorption unit 100.

As shown in FIG. 7, when the adsorption process is started, carbon dioxide contained in the supply gas supplied to the adsorption unit 100 is adsorbed by the adsorption unit 100, so that the exhaust gas CO ₂ concentration gradually decreases. Along with this, the adsorbed CO ₂ concentration increases. Thereafter, as the amount of carbon dioxide adsorbed by the adsorption unit 100 increases, the exhaust gas CO ₂ concentration turns to an increasing trend, and the adsorbed CO ₂ concentration turns to a decreasing trend. Ultimately, the exhaust gas CO ₂ concentration matches the concentration of carbon dioxide contained in the atmosphere, and the adsorbed CO ₂ concentration becomes 0.

Returning to FIG. 6, after calculating the adsorbed CO ₂ amount in step S120, the process proceeds to step S130. In step S130, it is determined whether the adsorbed CO ₂ concentration is on a decreasing trend and whether the adsorbed CO ₂ concentration is equal to or lower than a predetermined reference adsorbed CO ₂ concentration. The reference adsorbed CO ₂ concentration is determined based on a predetermined upper limit of the amount of adsorbed CO ₂ (hereinafter referred to as the reference adsorption amount upper limit).

As shown in FIG. 7, the amount of carbon dioxide adsorbed by the adsorption unit 100 increases as time passes. However, when the carbon dioxide adsorption rate to the adsorption unit 100 exceeds a predetermined ratio (80% in this example), the carbon dioxide adsorption efficiency deteriorates. Therefore, in the carbon dioxide recovery system 1 of the present embodiment, the amount of adsorbed CO ₂ when the carbon dioxide adsorption rate to the adsorption unit 100 reaches the predetermined ratio is set as the reference adsorption amount upper limit value, and the reference adsorption amount is set as the reference adsorption amount upper limit value. A reference adsorbed CO ₂ concentration is determined based on the upper limit value. Then, by determining whether or not the adsorbed CO ₂ concentration is equal to or lower than the reference adsorbed CO ₂ concentration, it is determined whether or not the amount of adsorbed CO ₂ is equal to or greater than the reference adsorption amount upper limit value.

Returning to FIG. 6, if it is determined in step S130 that the adsorbed CO ₂ concentration is not on a decreasing trend and/or that the adsorbed CO ₂ concentration has not become below the predetermined standard adsorbed CO ₂ concentration, the adsorbed It is determined that the amount of CO ₂ is not greater than the reference adsorption amount upper limit value, and step S130 is repeated.

On the other hand, if it is determined in step S130 that the adsorbed CO ₂ concentration is on a decreasing trend and that the adsorbed CO ₂ concentration is below the predetermined standard adsorbed CO ₂ concentration, the adsorbed CO ₂ amount is the standard. It is determined that the adsorption amount is greater than or equal to the upper limit value, and the process proceeds to step S140.

In step S140, the adsorption process ends. Specifically, the control device 20 controls the pump 11 to stop operating. In the next step S150, the process moves to a scavenging process which is the next process after the adsorption process.

In this embodiment, as described in steps S130 to S150, the control device 20 controls the adsorption when the adsorbed CO ₂ concentration is on a decreasing trend and the adsorbed CO ₂ concentration is below the reference adsorbed CO ₂ concentration. It is determined that the amount of CO ₂ is equal to or higher than the reference adsorption amount upper limit value, and the adsorption step is ended and the process proceeds to the scavenging step. According to this, when the carbon dioxide adsorption state of the adsorption unit 100 becomes saturated, it is possible to move from the adsorption step to the next step. As a result, it becomes possible to reduce the energy required for carbon dioxide recovery and to shorten the time required for carbon dioxide recovery.

By the way, the electrochemical cell 101 of the adsorption unit 100 may deteriorate over time or the like. When the electrochemical cell 101 deteriorates, the amount of carbon dioxide that can be adsorbed by the adsorption section 100 decreases, as shown by the dashed line in FIG. Therefore, when the electrochemical cell 101 deteriorates, the exhaust gas CO ₂ concentration increases and the adsorbed CO ₂ concentration decreases compared to before deterioration.

At this time, in the carbon dioxide recovery system 1 of the present embodiment, the CO ₂ concentration sensor 30 detects the current exhaust gas CO ₂ concentration, and based on the adsorbed CO ₂ amount calculated from the exhaust gas CO ₂ concentration, Determine the timing to shift from the adsorption process to the scavenging process. Therefore, even if the electrochemical cell 101 has deteriorated, the timing for transitioning from the adsorption process to the scavenging process can be determined in accordance with the deterioration state of the electrochemical cell 101.

(Second embodiment)
Next, a second embodiment of the present invention will be described based on the drawings. Hereinafter, only the parts that are different from the first embodiment will be described.

Switching control from the adsorption process to the scavenging process by the carbon dioxide recovery system 1 of the second embodiment will be explained using the flowchart of FIG. 9. Note that steps S200 to S230, S240, and S250 shown in FIG. 9 are the same processes as steps S100 to S130, S140, and S150 shown in FIG. 6 of the first embodiment, so the explanation will be omitted.

As shown in FIG. 9, in the carbon dioxide recovery system 1 of the second embodiment, in step S230, the exhaust gas CO ₂ concentration is on an increasing trend, and the exhaust gas CO ₂ concentration is set to a predetermined standard exhaust gas CO. It is determined whether the concentration is ₂ or more. The reference exhaust gas CO ₂ concentration is determined based on a predetermined reference adsorption amount upper limit value. In this embodiment, by determining whether the exhaust gas CO ₂ concentration is equal to or higher than the reference exhaust gas CO ₂ concentration, it is determined whether the adsorbed CO ₂ amount is equal to or higher than the reference adsorption amount upper limit value. .

If it is determined in step S230 that the exhaust gas CO ₂ concentration is not increasing and/or that the exhaust gas CO ₂ concentration is not higher than the standard exhaust gas CO ₂ concentration, the adsorbed CO ₂ amount is the standard. It is determined that the adsorption amount has not exceeded the upper limit value, and step S230 is repeated.

On the other hand, if it is determined in step S230 that the exhaust gas CO ₂ concentration is on an increasing trend and that the exhaust gas CO ₂ concentration is equal to or higher than the standard exhaust gas CO ₂ concentration, the amount of adsorbed CO ₂ is lower than the standard adsorption amount. It is determined that the amount is equal to or greater than the upper limit value, and the process proceeds to step S240, where the adsorption process is ended.

In the second embodiment described above, the control device 20 controls the adsorption of CO 2 when the exhaust gas CO ₂ concentration tends to increase and the exhaust gas CO ₂ concentration is equal to or higher than the reference exhaust gas _{CO 2 concentration} . It is determined that the amount is equal to or greater than the reference adsorption amount upper limit value, the adsorption step is ended, and the process proceeds to the scavenging step. According to this, effects similar to those of the first embodiment can be obtained. That is, according to the carbon dioxide recovery system 1 of the second embodiment, it is possible to reduce the energy required for carbon dioxide recovery and to shorten the time required for carbon dioxide recovery.

(Third embodiment)
Next, a third embodiment of the present invention will be described based on the drawings. Hereinafter, only the parts that are different from the first embodiment will be described.

Switching control from the adsorption process to the scavenging process by the carbon dioxide recovery system 1 of the third embodiment will be explained using the flowchart of FIG. 10. Note that steps S300 to S330, S340, and S350 shown in FIG. 10 are the same processes as steps S100 to S130, S140, and S150 shown in FIG. 6 of the first embodiment, so the explanation will be omitted.

As shown in FIG. 10, in the carbon dioxide recovery system 1 of the third embodiment, it is determined in step S30 whether the amount of adsorbed CO ₂ is equal to or greater than the reference adsorption amount upper limit value. If it is determined in step S230 that the amount of adsorbed CO ₂ is not equal to or greater than the reference adsorption amount upper limit value, step S330 is repeated.

On the other hand, if it is determined in step S330 that the amount of adsorbed CO ₂ is equal to or greater than the reference adsorption amount upper limit value, the process proceeds to step S340 and the adsorption process is ended.

In the third embodiment described above, the control device 20 ends the adsorption process and shifts to the scavenging process when the amount of adsorbed CO ₂ is equal to or greater than the reference adsorption amount upper limit value. According to this, effects similar to those of the first embodiment can be obtained. That is, according to the carbon dioxide recovery system 1 of the third embodiment, it is possible to reduce the energy required for carbon dioxide recovery and to shorten the time required for carbon dioxide recovery.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described based on the drawings. Hereinafter, only the parts that are different from the first embodiment will be described.

Switching control from the adsorption process to the scavenging process by the carbon dioxide recovery system 1 of the fourth embodiment will be explained using the flowchart of FIG. 11. Note that steps S410, S440, and S450 shown in FIG. 11 are the same processes as steps S110, S140, and S150 shown in FIG. 6 of the first embodiment, so a description thereof will be omitted.

As shown in FIG. 11, in the carbon dioxide recovery system 1 of the fourth embodiment, regular detection of the value of the current flowing through the electrochemical cell 101 is started in step S400. That is, in step S400, the current flowing through the electrochemical cell 101 is detected at a predetermined sampling time, and monitoring of the current is started.

Furthermore, in step S420, the amount of charge input to the electrochemical cell 101 is calculated. Specifically, the amount of charge applied to the electrochemical cell 101 is calculated from the time integral of the current flowing through the electrochemical cell 101.

In the next step S430, it is determined whether the amount of charge input to the electrochemical cell 101 is equal to or greater than a predetermined reference upper limit amount of charge.

The control device 20 stores a map in which the relationship between the amount of adsorbed CO ₂ and the amount of charge applied to the electrochemical cell 101 is defined in advance, as shown in FIG. 12 . The control device 20 refers to the map and calculates the reference upper limit charge amount based on the reference adsorption amount upper limit value.

Returning to FIG. 11, if it is determined in step S430 that the amount of charge input to the electrochemical cell 101 is not greater than the reference upper limit charge amount, the amount of adsorbed CO ₂ is greater than or equal to the reference upper limit value of adsorption amount. It is determined that there is not, and step S430 is repeated.

On the other hand, if it is determined in step S430 that the amount of charge input to the electrochemical cell 101 is greater than or equal to the reference upper limit charge amount, it is determined that the amount of adsorbed CO ₂ is greater than or equal to the reference upper limit value of adsorption amount. Then, the process advances to step S440, and the adsorption process ends.

In this embodiment, as described in steps S430 to S450, when the amount of charge input to the electrochemical cell 101 is equal to or greater than the reference upper limit charge amount, the control device 20 determines that the adsorbed CO ₂ amount is the reference adsorption amount. It is determined that the upper limit value is exceeded, the adsorption process is ended, and the process moves to the scavenging process. Therefore, in this embodiment, the adsorption state detection unit 201 of the control device 20 detects the amount of adsorbed _CO2 , which is the carbon dioxide adsorption state, based on the amount of charge input to the electrochemical cell 101.

According to the carbon dioxide recovery system 1 of the fourth embodiment, when the carbon dioxide adsorption state of the adsorption unit 100 becomes saturated, it is possible to move from the adsorption step to the next step. As a result, effects similar to those of the first embodiment can be obtained. That is, according to the carbon dioxide recovery system 1 of the fourth embodiment, it is possible to reduce the energy required for carbon dioxide recovery and to shorten the time required for carbon dioxide recovery.

By the way, when the electrochemical cell 101 deteriorates over time or the like, as shown by the dashed line in FIG. 13, the current flowing through the electrochemical cell 101 becomes larger than before deterioration, and the amount of charged charge also increases. Therefore, as shown by the dashed line in FIG. 12, the amount of CO ₂ adsorption relative to the amount of charged charge becomes smaller compared to before deterioration.

Therefore, in step S440, the control device 20 may adjust the reference adsorption amount upper limit value according to the degree of deterioration of the electrochemical cell 101 estimated based on the operating time. Thereby, even if the electrochemical cell has deteriorated, it is possible to move from the adsorption step to the next step when the carbon dioxide adsorption state of the adsorption unit 100 reaches a saturated state. As a result, even if the electrochemical cell deteriorates, it is possible to reduce the energy required for carbon dioxide recovery and the time required for carbon dioxide recovery.

Incidentally, the reference adsorption amount upper limit value of the adsorption unit 100 may be calculated from the capacitance of the electrochemical cell 101. In this case, the adsorption state detection unit 201 of the control device 20 detects the reference adsorption amount upper limit value of the adsorption unit 100 in the carbon dioxide adsorption state based on the capacitance of the electrochemical cell 101.

The capacitance of the electrochemical cell 101 is calculated from the current profile of the electrochemical cell 101 detected in step S400. Specifically, the resistance value and capacitance of the electrochemical cell 101 are calculated from the peak current value in the current profile and the current value at a predetermined time constant (63.2% response in this embodiment).

The control device 20 has a predetermined relationship between the capacitance of the electrochemical cell 101 and the upper limit of the amount of carbon dioxide adsorbed by the adsorption unit 100 (hereinafter referred to as the upper limit adsorption amount of CO ₂ ), as shown in FIG. Defined maps are stored. The control device 20 calculates the upper limit adsorption amount of CO ₂ based on the capacitance of the electrochemical cell 101 and with reference to the map. Then, the reference adsorption amount upper limit value of the adsorption unit 100 is calculated based on the calculated CO ₂ upper limit adsorption amount.

Here, when the electrochemical cell 101 deteriorates over time or the like, as shown in FIG. 14, the capacitance of the electrochemical cell 101 decreases and the upper limit adsorption amount of CO ₂ decreases. Therefore, by determining the reference adsorption amount upper limit value of the adsorption unit 100 based on the CO ₂ upper limit adsorption amount calculated from the capacitance of the electrochemical cell 101, even if the electrochemical cell deteriorates, the adsorption unit When the carbon dioxide adsorption state of 100 reaches the saturated state, the adsorption step can be shifted to the next step. As a result, even if the electrochemical cell deteriorates, it is possible to reduce the energy required for carbon dioxide recovery and the time required for carbon dioxide recovery.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be modified in various ways as described below without departing from the spirit of the present invention. Further, the means disclosed in each of the embodiments described above may be combined as appropriate within a practicable range.

(1) For example, in the embodiment described above, an example was described in which the amount of adsorbed _CO2 , which is the amount of carbon dioxide adsorbed by the adsorption unit 100, was used as the carbon dioxide adsorption state, but the present invention is not limited to this aspect. For example, the carbon dioxide adsorption rate of the adsorption unit 100 may be used as the carbon dioxide adsorption state.

(2) In the embodiment described above, the adsorption state detection unit 201 of the control device 20 detects the adsorption state based on the exhaust gas CO ₂ concentration, the amount of charge input to the electrochemical cell 101, or the capacitance of the electrochemical cell 101. An example configured to detect 100 carbon dioxide adsorption states has been described. However, the method for detecting the carbon dioxide adsorption state is not limited to this embodiment.

For example, the adsorption state detection unit 201 determines the carbon dioxide adsorption state of the adsorption unit 100 based on the exhaust gas CO ₂ concentration and at least one of the amount of charge input to the electrochemical cell 101 and the capacitance of the electrochemical cell 101. may be detected.

More specifically, the adsorption state detection unit 201 may detect the carbon dioxide adsorption state based on the exhaust gas CO ₂ concentration during normal times. On the other hand, when a malfunction occurs in the CO ₂ concentration sensor 30, the adsorption state detection unit 201 detects the adsorption state based on at least one of the amount of charge input to the electrochemical cell 101 and the capacitance of the electrochemical cell 101. 100 carbon dioxide adsorption states may be detected.

According to this, even if a malfunction occurs in the CO ₂ concentration sensor 30, it is possible to move from the adsorption step to the next step when the carbon dioxide adsorption state of the adsorption unit 100 becomes saturated. Therefore, even if a malfunction occurs in the CO ₂ concentration sensor 30, it is possible to reduce the energy required for carbon dioxide recovery and to shorten the time required for carbon dioxide recovery.

(3) In the embodiment described above, an example has been described in which the exhaust gas CO ₂ concentration detected by the CO ₂ concentration sensor 30 is used to detect the carbon dioxide adsorption state, but the present invention is not limited to this embodiment. For example, the deterioration state of the electrochemical cell 101 may be diagnosed based on the exhaust gas CO ₂ concentration. Then, when it is diagnosed that the electrochemical cell 101 has deteriorated, the user may be notified that the electrochemical cell 101 has deteriorated.

Further, for example, the relationship between the amount of adsorbed CO ₂ calculated based on the exhaust gas CO ₂ concentration and the amount of charge input to the electrochemical cell 101 and the amount of adsorbed CO ₂ shown in a map predefined in the control device 20 may be determined. The relationship between the amount of charge and the amount of input charge may be compared, and if the amount of deviation between the two is greater than or equal to a threshold value, it may be diagnosed that there is an abnormality in the electrical system of the carbon dioxide recovery system 1.

By the way, normally, when the atmosphere is discharged from the carbon dioxide recovery device 10 in a process other than the adsorption process, the sensor value of the CO ₂ concentration sensor 30 is within the concentration range of carbon dioxide contained in the atmosphere (500 to 700 ppm). becomes. Therefore, in a process other than the adsorption process, if the sensor value of the CO ₂ concentration sensor 30 is outside the concentration range of carbon dioxide contained in the atmosphere, it may be diagnosed that the CO ₂ concentration sensor 30 is abnormal.

(4) In the embodiment described above, an example was described in which the scavenging process was adopted as the next process of the adsorption process, but the present invention is not limited to this aspect. For example, when the carbon dioxide recovery system 1 operates by switching in the order of adsorption step, desorption step, adsorption step, desorption step, etc., the desorption step may be adopted as the next step of the adsorption step.

(5) In the embodiment described above, an example was described in which the liquid electrolyte 108 was used as the electrolyte, but the present invention is not limited to this embodiment. For example, as the electrolyte, an ionic liquid gel obtained by gelling an ionic liquid may be used, or a solid electrolyte may be used.

100 Adsorption unit 201 Adsorption state detection unit 202 Process switching unit

Claims (5)

A carbon dioxide recovery system that separates and recovers carbon dioxide from a feed gas containing carbon dioxide, the system comprising:
an adsorption unit (100) that adsorbs and desorbs carbon dioxide;
a process switching unit (202) that switches between a plurality of processes including an adsorption process in which the adsorption unit adsorbs carbon dioxide contained in the supplied gas;
an adsorption state detection unit (201) that detects the carbon dioxide adsorption state of the adsorption unit,
The process switching unit is a carbon dioxide recovery system that determines the timing of transitioning from the adsorption process to the next process based on the carbon dioxide adsorption state. Furthermore, it includes a carbon dioxide concentration detection unit (30) that detects the exhaust gas carbon dioxide concentration, which is the concentration of carbon dioxide contained in the exhaust gas after carbon dioxide has been adsorbed by the adsorption unit,
The carbon dioxide recovery system according to claim 1, wherein the adsorption state detection section detects the carbon dioxide adsorption state based on the exhaust gas carbon dioxide concentration detected by the carbon dioxide concentration detection section. The adsorption part has a working electrode (102) and a counter electrode (103), and when a voltage is applied between the working electrode and the counter electrode, electrons are supplied from the counter electrode to the working electrode, The working electrode has an electrochemical cell (101) that combines with carbon dioxide as electrons are supplied,
The carbon dioxide recovery system according to claim 1, wherein the adsorption state detection unit detects the carbon dioxide adsorption state based on the amount of charge input to the electrochemical cell. The adsorption part has a working electrode (102) and a counter electrode (103), and when a voltage is applied between the working electrode and the counter electrode, electrons are supplied from the counter electrode to the working electrode, The working electrode has an electrochemical cell (101) that combines with carbon dioxide as electrons are supplied,
The carbon dioxide recovery system according to claim 1, wherein the adsorption state detection section detects the carbon dioxide adsorption state based on the capacitance of the electrochemical cell. Furthermore, it includes a carbon dioxide concentration detection unit (30) that detects the exhaust gas carbon dioxide concentration, which is the concentration of carbon dioxide contained in the exhaust gas after carbon dioxide has been adsorbed by the adsorption unit,
The adsorption part has a working electrode (102) and a counter electrode (103), and when a voltage is applied between the working electrode and the counter electrode, electrons are supplied from the counter electrode to the working electrode, The working electrode has an electrochemical cell (101) that combines with carbon dioxide as electrons are supplied,
The adsorption state detection unit detects the carbon dioxide adsorption state based on the concentration of carbon dioxide contained in the exhaust gas and at least one of the amount of charge input to the electrochemical cell and the capacitance of the electrochemical cell. The carbon dioxide recovery system according to claim 1, wherein the carbon dioxide recovery system detects.

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