Carbon dioxide capture system
The carbon dioxide recovery system optimizes transition timing using electrochemical cells and capacitance detection to address inefficiencies in conventional systems, reducing energy consumption and capture time.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- DENSO CORP
- Filing Date
- 2022-04-25
- Publication Date
- 2026-05-19
AI Technical Summary
Conventional carbon dioxide capture systems face challenges in determining the optimal transition timing for adsorption and desorption processes due to variations in gas flow rate, humidity, and electrochemical cell deterioration, leading to increased energy consumption and extended capture times.
A carbon dioxide recovery system that includes an adsorption section with electrochemical cells, a process switching unit, and an adsorption state detection unit to determine the transition timing based on the carbon dioxide adsorption state, using capacitance detection to optimize the adsorption and desorption processes.
This approach reduces energy consumption and shortens the time required for carbon dioxide capture by ensuring timely transitions between adsorption and desorption processes, thereby enhancing efficiency.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a carbon dioxide recovery system for recovering carbon dioxide from a carbon dioxide-containing gas containing carbon dioxide.
Background Art
[0002] Conventionally, Patent Document 1 discloses a gas separation system having a carbon dioxide adsorber that adsorbs carbon dioxide from a carbon dioxide-containing gas (e.g., air) by an electrochemical reaction. Such a gas separation system is configured to be able to switch between a plurality of steps, such as an adsorption step in which the carbon dioxide adsorber adsorbs carbon dioxide and a desorption step in which the carbon dioxide adsorber desorbs carbon dioxide. In the carbon dioxide adsorber, the timing of shifting from the adsorption step of adsorbing carbon dioxide to the next step (e.g., the desorption step) is determined by time.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] However, in the above conventional technology, due to the flow rate, humidity, etc. of the carbon dioxide-containing gas supplied to the carbon dioxide adsorber, the carbon dioxide concentration of the supply gas (i.e., the amount of carbon dioxide supplied to the carbon dioxide adsorber) changes. Also, the amount of carbon dioxide adsorbed changes due to deterioration of the electrochemical cell and variations in the control potential.
[0005] Therefore, it is difficult to determine the appropriate transition timing based on time, and carbon dioxide adsorption may end when the adsorption rate is low. Alternatively, carbon dioxide adsorption may continue even when the adsorption rate has reached saturation. As a result, the energy required for carbon dioxide adsorption increases, and the time required for carbon dioxide adsorption also increases.
[0006] In view of the above points, the present invention aims to provide a carbon dioxide capture system that can reduce the energy required for carbon dioxide capture and shorten the time required for carbon dioxide capture. [Means for solving the problem]
[0007] To achieve the above objective, the carbon dioxide recovery system described in claim 1 is a carbon dioxide recovery system that separates and recovers carbon dioxide from a supply gas containing carbon dioxide, Adsorption section (100) for adsorbing and desorbing carbon dioxide, A process switching unit (202) that switches between multiple processes, including an adsorption process in which the adsorption unit adsorbs carbon dioxide contained in the supplied gas, It comprises an adsorption state detection unit (201) for detecting 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 status. death, The adsorption unit has an electrochemical cell (101) comprising a working electrode (102) and a counter electrode (103), wherein when a voltage is applied between the working electrode and the counter electrode, electrons are supplied from the counter electrode to the working electrode, and the working electrode combines with carbon dioxide as electrons are supplied. The adsorption state detection unit detects the carbon dioxide adsorption state based on the capacitance of the electrochemical cell. .
[0008] According to this method, the timing of transitioning from the adsorption process to the next process is determined based on the state of carbon dioxide adsorption on the adsorption unit (100). Therefore, the transition from the adsorption process to the next process can be made at the timing when the state of carbon dioxide adsorption on the adsorption unit (100) reaches a desired state. As a result, it is possible to reduce the energy required for carbon dioxide recovery and shorten the time required for carbon dioxide recovery.
[0009] The reference numerals in parentheses next to each means described in this section and in the claims indicate the correspondence with the specific means described in the embodiments described later. [Brief explanation of the drawing]
[0010] [Figure 1] This is a conceptual diagram showing the overall configuration of the carbon dioxide capture system according to the first embodiment. [Figure 2] This is a perspective view showing a carbon dioxide recovery device in the first embodiment. [Figure 3] This is a perspective view showing a stacked configuration of multiple electrochemical cells according to the first embodiment. [Figure 4] This is a perspective view showing an electrochemical cell in the first embodiment. [Figure 5] This is a block diagram showing the electrical control unit of the carbon dioxide capture system according to the first embodiment. [Figure 6] This is a flowchart showing the process switching control process of the first embodiment. [Figure 7] This is a time chart showing changes in carbon dioxide concentration and other parameters in the carbon dioxide capture system of the first embodiment. [Figure 8] This is a time chart showing the changes in carbon dioxide concentration and other parameters when the electrochemical cell in the carbon dioxide capture system of the first embodiment deteriorates. [Figure 9] This flowchart shows the process switching control process of the second embodiment. [Figure 10] This is a flowchart showing the process switching control process of the third embodiment. [Figure 11] This is a flowchart showing the process switching control process of the fourth embodiment. [Figure 12] This is an explanatory diagram showing the relationship between the amount of charge input and the amount of CO2 adsorbed. [Figure 13] This is a time chart showing changes in carbon dioxide concentration and other parameters in the carbon dioxide capture system of the fourth embodiment. [Figure 14] This is an explanatory diagram showing the relationship between capacitance and the upper limit of CO2 adsorption.
Mode for Carrying Out the Invention
[0011] Hereinafter, embodiments of the present invention will be described based on the drawings. In each of the following embodiments, parts that are identical or equivalent to each other are denoted by the same reference numerals in the drawings.
[0012] (First Embodiment) Hereinafter, the first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the carbon dioxide recovery system 1 of the present embodiment includes a carbon dioxide recovery device 10, a pump 11, a flow path switching valve 12, and a carbon dioxide utilization device 13.
[0013] The carbon dioxide recovery device 10 is a device that separates and recovers carbon dioxide from the supplied gas. The carbon dioxide recovery device 10 has an adsorption unit 100 that adsorbs and desorbs carbon dioxide.
[0014] The supplied gas is a carbon dioxide-containing gas containing carbon dioxide. The supplied gas also contains gases other than carbon dioxide. As the supplied gas, for example, air or exhaust gas of an internal combustion engine can be used. In the present embodiment, air is used as the supplied gas.
[0015] The carbon dioxide recovery device 10 discharges the exhaust gas (hereinafter also referred to as carbon dioxide-removed gas) after the supplied gas is supplied and carbon dioxide is recovered from the supplied gas, or the carbon dioxide recovered from the supplied gas. The configurations of the carbon dioxide recovery device 10 and the adsorption unit 100 will be described in detail later.
[0016] The pump 11 supplies the supplied gas to the carbon dioxide recovery device 10 and discharges carbon dioxide or the exhaust gas from the carbon dioxide recovery device 10. In the example shown in FIG. 1, the pump 11 is provided on the downstream side in the gas flow direction of the carbon dioxide recovery device 10, but the pump 11 may be provided on the upstream side in the gas flow of the carbon dioxide recovery device 10.
[0017] The flow path switching valve 12 is a three-way valve that switches the flow path of the exhaust gas discharged from the carbon dioxide recovery device 10. When exhaust gas (i.e., carbon dioxide-removed gas) is discharged from the carbon dioxide recovery device 10, the flow path of the exhaust gas is switched to the atmosphere side, and when carbon dioxide is discharged from the carbon dioxide recovery device 10, the flow path of the exhaust gas is switched to the carbon dioxide utilization device 13 side.
[0018] The carbon dioxide utilization device 13 is a device that utilizes carbon dioxide. The carbon dioxide utilization device 13 can include, for example, a storage tank for storing carbon dioxide or a conversion device for converting carbon dioxide into fuel. The conversion device can be one that converts carbon dioxide into a hydrocarbon fuel such as methane. The hydrocarbon fuel may be a gaseous fuel at room temperature and pressure, or a liquid fuel at room temperature and pressure.
[0019] Next, the carbon dioxide recovery device 10 of this embodiment will be described using Figures 2 to 4. In Figures 2 to 4, the direction from the front of the page to the back of the page is the gas flow direction, and the vertical direction of the page is the cell stacking direction.
[0020] As shown in Figure 2, the carbon dioxide capture device 10 comprises an adsorption section 100 and a containment section 110. The containment section 110 is formed in a box shape and can be constructed using, for example, a metal material.
[0021] The adsorption unit 100 has an electrochemical cell 101. The electrochemical cell 101 is housed in the containment unit 110. The carbon dioxide recovery device 10 performs adsorption and desorption of carbon dioxide by the electrochemical reaction of the electrochemical cell 101, and separates and recovers carbon dioxide from the supply gas.
[0022] The containment section 110 has two openings. These two openings are an inlet 110a for introducing the supply gas into the interior and an outlet (not shown) for releasing exhaust gas and carbon dioxide from the interior. The gas flow direction is the flow direction of the supply gas as it passes through the containment section 110, and is the direction from the inlet 110a to the outlet of the containment section 110.
[0023] In Figure 2, the supply gas flows from the front of the page towards the back of the page. Therefore, the intake section 110 has an inlet section 110a at the front of the figure and a discharge section at the back of the figure. The intake section 110a and discharge section of the intake section 110 are provided with opening and closing members (not shown) to open and close them, respectively.
[0024] Multiple electrochemical cells 101 are arranged in a stacked manner inside the housing section 110. The direction in which the multiple electrochemical cells 101 are stacked is perpendicular to the direction of gas flow. Each individual electrochemical cell 101 is constructed in a plate shape, and is arranged so that its plate surface intersects with the cell stacking direction.
[0025] Figure 3 shows a stacked configuration of multiple electrochemical cells 101. Figure 4 shows a single electrochemical cell 101. In Figure 4, the components of the electrochemical cell 101, such as the working electrode current collector layer 103, are shown with spacing between them, but in reality, these components are stacked and arranged in contact with each other.
[0026] As shown in Figure 3, a predetermined gap is provided between adjacent electrochemical cells 101. This gap between adjacent electrochemical cells 101 constitutes a gas channel 102 through which the supply gas flows.
[0027] As shown in Figures 3 and 4, the electrochemical cell 101 comprises a working electrode current collector 103, a working electrode 104, a counter electrode current collector 105, a counter electrode 106, and a separator 107. In adjacent electrochemical cells 101, one working electrode current collector 103 and the other counter electrode current collector 105 face each other across a gas flow path 102.
[0028] As shown in Figure 4, an electrolyte solution 108, which is an electrolytic substance, is provided between the working electrode 104 and the counter electrode 106. In this embodiment, the working electrode 104, the counter electrode 106, and the separator 107 are saturated with the electrolyte solution 108.
[0029] The working electrode current collector layer 103, working electrode 104, counter electrode current collector layer 105, counter electrode 106, and separator 107 are each configured in a plate shape. The electrochemical cell 101 is configured as a laminate in which the working electrode current collector layer 103, working electrode 104, counter electrode current collector layer 105, counter electrode 106, and separator 107 are stacked. The direction in which the working electrode current collector layer 103, etc., of each individual electrochemical cell 101 are stacked is the same as the cell stacking direction in which multiple electrochemical cells 101 are stacked.
[0030] The working electrode current collector layer 103 is a porous conductive material having pores through which a supply gas containing carbon dioxide can pass. The working electrode current collector layer 103 only needs to have gas permeability and conductivity; for example, a metallic material or a carbonaceous material can be used. In this embodiment, a porous metallic body is used as the working electrode current collector layer 103.
[0031] The working electrode 104 contains a carbon dioxide adsorbent, a conductive material, and a binder. The carbon dioxide adsorbent, conductive material, and binder are used in a mixture.
[0032] Carbon dioxide adsorbents adsorb carbon dioxide by accepting electrons and release the adsorbed carbon dioxide by releasing electrons. For example, polyanthraquinone can be used as a carbon dioxide adsorbent.
[0033] The conductive material forms a conductive path to the carbon dioxide adsorbent. Examples of conductive materials that can be used include carbon materials such as carbon nanotubes, carbon black, and graphene.
[0034] A binder is provided to hold carbon dioxide adsorbent and conductive material. For example, a conductive resin can be used as the binder. As the conductive resin, epoxy resins containing Ag or the like as conductive fillers, or fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) can be used.
[0035] The counter electrode current collector layer 105 is made of a conductive material. For example, a metallic material or a carbonaceous material can be used as the counter electrode current collector layer 105. In this embodiment, a metal plate is used as the counter electrode current collector layer 105.
[0036] The counter electrode 106 includes an electroactivating auxiliary material, a conductive substance, and a binder. The conductive substance and binder of the counter electrode 106 have the same configuration as those of the working electrode 104, so their description is omitted. In this embodiment, the counter electrode 106 is made of a material having an active substance that acts as an electron donor.
[0037] The electroactivating auxiliary of the counter electrode 106 is an auxiliary electroactive species that facilitates electron transfer between it and the carbon dioxide adsorbent of the working electrode 104. As the electroactivating auxiliary, for example, a metal complex that enables electron transfer by changing the valence of a metal ion 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.
[0038] The separator 107 is positioned between the working electrode 104 and the counter electrode 106, separating them. The separator 107 is an insulating ion-permeable membrane that prevents physical contact between the working electrode 104 and the counter electrode 106, thereby suppressing electrical short circuits, while also allowing ions to pass through. As the separator 107, a cellulose membrane, a polymer, a composite material of polymer and ceramic, etc., can be used.
[0039] The electrochemical cell 101 is equipped with a power supply 109 connected to the working electrode current collector layer 103 and the counter electrode current collector layer 105. The power supply 109 can apply a predetermined voltage to the working electrode 104 and the counter electrode 106, thereby changing the potential difference between the working electrode 104 and the counter electrode 106. The working electrode 104 is the negative electrode, and the counter electrode 106 is the positive electrode.
[0040] The electrochemical cell 101 can operate by changing the potential difference between the working electrode 104 and the counter electrode 106, thereby switching 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. The adsorption process is a charging process that charges the electrochemical cell 101, and the desorption process is a discharge process that discharges the electrochemical cell 101.
[0041] In the adsorption process, 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, the working electrode potential is less than the counter electrode potential. The first voltage V1 can be, for example, in the range of 0.5 to 2.0 V.
[0042] In the desorption process, a second voltage V2 is applied between the working electrode 104 and the counter electrode 106, supplying electrons from the working electrode 104 to the counter electrode 106. The second voltage V2 is different from the first voltage V1. The second voltage V2 only needs to be lower than the first voltage V1, and the relative magnitudes of the working electrode potential and the counter electrode potential are not limited. In other words, in the desorption process, 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.
[0043] Next, the electrolyte 108 of this embodiment will be described. In the carbon dioxide recovery system 1 of this embodiment, the electrolyte 108 employs a substance that has resistance to addition reactivity and resistance to substitution reactivity with respect to at least one of the supply gas, working electrode 104, and counter electrode 106. For example, the electrolyte 108 can be a substance that does not undergo addition reactions and substitution reactions with respect to at least one of the supply gas, working electrode 104, and counter electrode 106.
[0044] Specifically, the electrolyte 108 can be a substance that has oxidation-reduction resistance 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. For example, the electrolyte 108 can be a substance that does not exhibit oxidation-reduction reactions to at least one of the supply gas, the working electrode, and the counter electrode when a voltage is applied between the working electrode 104 and the counter electrode 106.
[0045] More specifically, the electrolyte 108 can use a substance that is resistant to oxidation-reduction reactivity with respect to at least one of the supply gas, the working electrode 104, and the counter electrode 106 when a voltage within the 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. For example, the electrolyte 108 can use a substance that does not exhibit oxidation-reduction reactions with respect to at least one of the supply gas, the working electrode 104, and the counter electrode 106 when a voltage within the 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.
[0046] Furthermore, the electrolyte 108 can be a substance that exhibits resistance to decomposition at normal 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 a substance that does not exhibit a decomposition reaction at normal temperature and pressure when a voltage is applied between the working electrode 104 and the counter electrode 106.
[0047] More specifically, the electrolyte 108 can use a substance that is resistant to decomposition when a voltage within the 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. For example, the electrolyte 108 can use a substance that does not exhibit a decomposition reaction when a voltage within the 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.
[0048] Furthermore, the electrolyte 108 can be a substance that is stable with respect to the constituent materials of the electrochemical cell 101. That is, the electrolyte 108 can be a substance that is resistant to reactivity with respect to the constituent materials of the electrochemical cell 101.
[0049] Furthermore, the electrolyte 108 can be a substance that does not easily produce volatile products through electrochemical reactions. For example, compared to the case where 1-ethyl-3-methylimidazolium dicyanamide [Emin][N(CN)2] is used as the electrolyte, a substance that does not easily produce volatile products through electrochemical reactions can be used as the electrolyte 108. In addition, a substance that does not produce volatile products through electrochemical reactions can be used as the electrolyte 108.
[0050] Furthermore, an ionic liquid can be used as the electrolyte 108. An ionic liquid is a salt of a liquid that is non-volatile at room temperature and pressure.
[0051] Next, the operation of the carbon dioxide recovery system 1 of this embodiment will be described. The carbon dioxide recovery system 1 is configured to perform an adsorption step, a scavenging step, and a desorption step. The carbon dioxide recovery system 1 operates by switching between the adsorption step, scavenging step, desorption step, adsorption step, scavenging step, desorption step, ... The operation of the carbon dioxide recovery system 1 is controlled by a control device 20, which will be described later.
[0052] The adsorption process is an adsorption process in which the adsorption unit 100 adsorbs carbon dioxide contained in the supplied gas. During the adsorption process, the pump 11 operates to supply the supplied gas to the adsorption unit 100. During the adsorption process, the voltage applied between the working electrode 104 and the counter electrode 106 is defined as the first voltage V1. This allows for simultaneous electron donation by the electroactivating auxiliary material of the counter electrode 106 and electron withdrawal by the carbon dioxide adsorbent of the working electrode 104.
[0053] The electroactivating auxiliary material of the counter electrode 106 releases electrons and enters an oxidized state, supplying electrons from the counter electrode 106 to the working electrode 104. The carbon dioxide adsorbent of the working electrode 104 accepts electrons and enters a reduced state.
[0054] When the carbon dioxide adsorbent is in a reduced state, its ability to bind to carbon dioxide increases, and it binds to and adsorbs the carbon dioxide contained in the supply gas. As a result, the carbon dioxide recovery device 10 can recover carbon dioxide from the supply gas.
[0055] In the scavenging process, the pump 11 is operated with the opening / closing member of the inlet 110a in the containment section 110 closed. In the scavenging process, the flow path switching valve 12 is switched so that the flow path of the discharged gas is toward the atmosphere. As a result, the gas present in the containment section 110 is discharged into the atmosphere. At this time, the carbon dioxide in the adsorption section 100 remains adsorbed on the carbon dioxide adsorbent of the working electrode 104.
[0056] In the desorption process, the flow path switching valve 12 is switched so that the flow path of the discharged gas is on the carbon dioxide utilization device 13 side. In the desorption process, the voltage applied between the working electrode 104 and the counter electrode 106 is set to the second voltage V2. This makes it possible to simultaneously achieve electron donation by the carbon dioxide adsorbent of the working electrode 104 and electron withdrawal by the electroactivating auxiliary material of the counter electrode 106.
[0057] The carbon dioxide adsorbent at the working electrode 104 releases electrons and enters an oxidized state. The carbon dioxide adsorbent's binding force to carbon dioxide decreases, and it releases carbon dioxide. The electroactivating auxiliary at the counter electrode 106 accepts electrons and enters a reduced state.
[0058] The carbon dioxide released from the carbon dioxide adsorbent is discharged from the adsorption unit 100 and supplied to the carbon dioxide utilization device 13.
[0059] Next, an overview of the electrical control unit in the carbon dioxide capture system 1 of this embodiment will be described. As shown in Figure 5, the control device 20 is composed of a well-known microcomputer including a CPU, ROM, and RAM, and its peripheral circuits. The control device 20 performs various calculations and processes based on the control program stored in its ROM, and controls the operation of various controlled devices connected to its output side. The controlled devices include the carbon dioxide capture device 10, the pump 11, and the flow path switching valve 12.
[0060] A CO2 concentration sensor 30 is connected to the input side of the control device 20. The control device 20 receives the detection signal from the CO2 concentration sensor 30. The CO2 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 CO2 concentration).
[0061] The control device 20 includes an adsorption state detection unit 201 and a process switching unit 202.
[0062] 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 on the adsorption unit 100 (hereinafter referred to as the adsorbed CO2 amount) is used as the carbon dioxide adsorption state. The adsorption state detection unit 201 detects the adsorbed CO2 amount based on the exhaust gas CO2 concentration detected by the CO2 concentration sensor 30.
[0063] The process switching unit 202 is a switching control unit that switches between multiple operating processes of the carbon dioxide recovery system 1. That is, the process switching unit 202 switches between multiple processes, including the adsorption process. The process switching unit 202 determines the timing to transition 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 transition from the adsorption process to the scavenging process based on the amount of adsorbed CO2 calculated by the adsorption state detection unit 201.
[0064] Next, the switching control from the adsorption process to the scavenging process by the carbon dioxide recovery system 1 according to this first embodiment will be explained with reference to the flowchart shown in Figure 6.
[0065] As shown in Figure 6, first, in step S100, the CO2 concentration of the exhaust gas is periodically detected by the CO2 concentration sensor 30. That is, in step S100, the CO2 concentration of the exhaust gas is detected at a predetermined sampling time, and monitoring of the exhaust gas CO2 concentration is started.
[0066] Next, in step S110, the adsorption process is started. Specifically, the control device 20 controls the operation of the pump 11 to exert a predetermined pumping capacity, and sets the voltage applied between the working electrode 104 and the counter electrode 106 as the first voltage V1.
[0067] Next, in step S120, the amount of adsorbed CO2 is calculated. Specifically, first, the concentration of carbon dioxide adsorbed on the adsorption unit 100 (hereinafter referred to as the adsorbed CO2 concentration) is calculated from the difference between the CO2 concentration in the atmosphere and the exhaust gas CO2 concentration detected by the CO2 concentration sensor 30. Then, the amount of adsorbed CO2 is calculated from the product of the adsorbed CO2 concentration and the flow velocity of carbon dioxide flowing through the adsorption unit 100.
[0068] As shown in Figure 7, once the adsorption process begins, carbon dioxide contained in the supply gas supplied to the adsorption unit 100 is adsorbed by the adsorption unit 100, causing the exhaust gas CO2 concentration to gradually decrease. Consequently, the adsorbed CO2 concentration increases. Subsequently, as the amount of carbon dioxide adsorbed by the adsorption unit 100 increases, the exhaust gas CO2 concentration begins to rise, while the adsorbed CO2 concentration begins to decrease. Ultimately, the exhaust gas CO2 concentration matches the concentration of carbon dioxide in the atmosphere, and the adsorbed CO2 concentration becomes 0.
[0069] Returning to Figure 6, after calculating the amount of adsorbed CO2 in step S120, the process proceeds to step S130. In step S130, it is determined whether the adsorbed CO2 concentration is decreasing and whether the adsorbed CO2 concentration is below a predetermined standard adsorbed CO2 concentration. The standard adsorbed CO2 concentration is determined based on a predetermined upper limit of the amount of adsorbed CO2 (hereinafter referred to as the standard adsorption upper limit).
[0070] As shown in Figure 7, the amount of carbon dioxide adsorbed by the adsorption unit 100 increases over time. However, when the carbon dioxide adsorption rate to the adsorption unit 100 exceeds a predetermined percentage (80% in this example), the carbon dioxide adsorption efficiency deteriorates. Therefore, in the carbon dioxide recovery system 1 of this embodiment, the amount of adsorbed CO2 when the carbon dioxide adsorption rate to the adsorption unit 100 reaches the predetermined percentage is set as the upper limit of the standard adsorption amount, and the standard adsorbed CO2 concentration is determined based on this upper limit of the standard adsorption amount. Then, by determining whether the adsorbed CO2 concentration is less than or equal to the standard adsorbed CO2 concentration, it is determined whether the amount of adsorbed CO2 is greater than or equal to the upper limit of the standard adsorption amount.
[0071] Returning to Figure 6, if in step S130 it is determined that the adsorbed CO2 concentration is not decreasing and / or that the adsorbed CO2 concentration is not below a predetermined standard adsorbed CO2 concentration, it is determined that the amount of adsorbed CO2 is not above the standard adsorption upper limit, and step S130 is repeated.
[0072] On the other hand, if in step S130 it is determined that the adsorbed CO2 concentration is decreasing and that the adsorbed CO2 concentration is below a predetermined standard adsorbed CO2 concentration, it is determined that the amount of adsorbed CO2 is above the standard adsorption upper limit, and the process proceeds to step S140.
[0073] In step S140, the adsorption process is terminated. Specifically, the control device 20 controls the operation of the pump 11 to stop. In the next step, S150, the process transitions to the scavenging process, which is the next step after the adsorption process.
[0074] In this embodiment, as described in steps S130 to S150, when the adsorbed CO2 concentration is decreasing and the adsorbed CO2 concentration is below the standard adsorbed CO2 concentration, the control device 20 determines that the amount of adsorbed CO2 is above the standard adsorption limit and terminates the adsorption process to proceed to the scavenging process. This allows the process to transition from the adsorption process to the next process when the carbon dioxide adsorption state of the adsorption unit 100 reaches a saturated state. As a result, it is possible to reduce the energy required for carbon dioxide recovery and shorten the time required for carbon dioxide recovery.
[0075] Incidentally, the electrochemical cell 101 of the adsorption unit 100 may deteriorate over time. When the electrochemical cell 101 deteriorates, the amount of carbon dioxide that can be adsorbed by the adsorption unit 100 decreases, as shown by the dashed line in Figure 8. Therefore, when the electrochemical cell 101 deteriorates, the CO2 concentration of the exhaust gas increases and the adsorbed CO2 concentration decreases compared to before the deterioration.
[0076] In this embodiment, the carbon dioxide recovery system 1 uses a CO2 concentration sensor 30 to detect the current exhaust gas CO2 concentration and determines the timing for transitioning from the adsorption process to the scavenging process based on the amount of adsorbed CO2 calculated from the exhaust gas CO2 concentration. Therefore, even if the electrochemical cell 101 deteriorates, 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.
[0077] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. Only the parts that differ from the first embodiment described above will be explained below.
[0078] The switching control from the adsorption process to the scavenging process by the carbon dioxide recovery system 1 of this second embodiment will be explained using the flowchart in Figure 9. Steps S200 to S230, S240, and S250 shown in Figure 9 are the same processes as steps S100 to S130, S140, and S150 shown in Figure 6 of the first embodiment, respectively, so their explanation will be omitted.
[0079] As shown in Figure 9, in the carbon dioxide capture system 1 of this second embodiment, step S230 determines whether the exhaust gas CO2 concentration is increasing and whether the exhaust gas CO2 concentration is equal to or greater than a predetermined standard exhaust gas CO2 concentration. The standard exhaust gas CO2 concentration is determined based on a predetermined standard adsorption upper limit. In this embodiment, by determining whether the exhaust gas CO2 concentration is equal to or greater than the standard exhaust gas CO2 concentration, it is determined whether the amount of adsorbed CO2 is equal to or greater than the standard adsorption upper limit.
[0080] If, in step S230, it is determined that the exhaust gas CO2 concentration is not increasing and / or that the exhaust gas CO2 concentration is not equal to or greater than the standard exhaust gas CO2 concentration, then it is determined that the amount of adsorbed CO2 is not equal to or greater than the standard adsorption limit, and step S230 is repeated.
[0081] On the other hand, if in step S230 it is determined that the exhaust gas CO2 concentration is increasing and that the exhaust gas CO2 concentration is equal to or greater than the standard exhaust gas CO2 concentration, it is determined that the amount of adsorbed CO2 is equal to or greater than the standard upper limit of adsorption, and the process proceeds to step S240, ending the adsorption process.
[0082] In the second embodiment described above, the control device 20 determines that the amount of adsorbed CO2 is above the upper limit of the standard adsorption amount when the exhaust gas CO2 concentration is increasing and the exhaust gas CO2 concentration is above the standard exhaust gas CO2 concentration, and terminates the adsorption process and moves to the scavenging process. This allows the same effects as in the first embodiment to be obtained. In other words, the carbon dioxide recovery system 1 of the second embodiment makes it possible to reduce the energy required for carbon dioxide recovery and shorten the time required for carbon dioxide recovery.
[0083] (Third embodiment) Next, a third embodiment of the present invention will be described based on the drawings. Hereinafter, only the parts that differ from the first embodiment will be described.
[0084] The switching control from the adsorption process to the scavenging process by the carbon dioxide recovery system 1 of this third embodiment will be explained using the flowchart in Figure 10. Steps S300 to S330, S340, and S350 shown in Figure 10 are the same processes as steps S100 to S130, S140, and S150 shown in Figure 6 of the first embodiment, respectively, so their explanation will be omitted.
[0085] As shown in Figure 10, in the carbon dioxide capture system 1 of this third embodiment, step S30 determines whether the amount of adsorbed CO2 is equal to or greater than the standard adsorption limit. If it is determined in step S230 that the amount of adsorbed CO2 is not equal to or greater than the standard adsorption limit, step S330 is repeated.
[0086] On the other hand, if it is determined in step S330 that the amount of adsorbed CO2 is equal to or greater than the upper limit of the standard adsorption amount, the process proceeds to step S340 and the adsorption process is terminated.
[0087] In the third embodiment described above, the control device 20 terminates the adsorption process and proceeds to the scavenging process when the amount of adsorbed CO2 exceeds the upper limit of the standard adsorption amount. This allows for the same effects as in the first embodiment. In other words, the carbon dioxide recovery system 1 of this third embodiment makes it possible to reduce the energy required for carbon dioxide recovery and shorten the time required for carbon dioxide recovery.
[0088] (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to the drawings. Only the parts that differ from the first embodiment described above will be explained below.
[0089] The switching control from the adsorption process to the scavenging process by the carbon dioxide recovery system 1 of this fourth embodiment will be explained using the flowchart in Figure 11. Steps S410, S440, and S450 shown in Figure 11 are the same processes as steps S110, S140, and S150 shown in Figure 6 of the first embodiment, respectively, so their explanation will be omitted.
[0090] As shown in Figure 11, in the carbon dioxide recovery system 1 of this fourth embodiment, in step S400, periodic detection of the current value flowing through the electrochemical cell 101 is initiated. That is, in step S400, the current flowing through the electrochemical cell 101 is detected at a predetermined sampling time, and monitoring of the said current is initiated.
[0091] In step S420, the amount of charge input to the electrochemical cell 101 is calculated. Specifically, the amount of charge input to the electrochemical cell 101 is calculated from the time integral of the current flowing through the electrochemical cell 101.
[0092] 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 standard upper limit charge amount.
[0093] The control device 20 stores a predefined map, as shown in Figure 12, which shows the relationship between the amount of adsorbed CO2 and the amount of charge input to the electrochemical cell 101. Based on the reference upper limit of adsorption, the control device 20 refers to this map and calculates the reference upper limit of charge.
[0094] Returning to Figure 11, if it is determined in step S430 that the amount of charge input to the electrochemical cell 101 is not equal to or greater than the standard upper limit of charge, it is determined that the amount of adsorbed CO2 is not equal to or greater than the standard upper limit of adsorption, and step S430 is repeated.
[0095] On the other hand, if it is determined in step S430 that the amount of charge input to the electrochemical cell 101 is equal to or greater than the standard upper limit of charge, it is determined that the amount of adsorbed CO2 is equal to or greater than the standard upper limit of adsorption, and the process proceeds to step S440, ending the adsorption process.
[0096] In this embodiment, as described in steps S430 to S450, the control device 20 determines that the amount of adsorbed CO2 is equal to or greater than the standard upper limit of adsorption when the amount of charge input to the electrochemical cell 101 is equal to or greater than the standard upper limit of adsorption, and terminates the adsorption process and proceeds 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.
[0097] Furthermore, according to the carbon dioxide recovery system 1 of this fourth embodiment, when the carbon dioxide adsorption state of the adsorption unit 100 reaches a saturated state, the system can transition from the adsorption process to the next process. As a result, the same effects as those of the first embodiment can be obtained. In other words, according to the carbon dioxide recovery system 1 of this fourth embodiment, it is possible to reduce the energy required for carbon dioxide recovery and shorten the time required for carbon dioxide recovery.
[0098] Incidentally, as the electrochemical cell 101 deteriorates over time, the current flowing through the electrochemical cell 101 increases and the amount of charge input also increases, as shown by the dashed line in Figure 13. Consequently, as shown by the dashed line in Figure 12, the amount of CO2 adsorbed relative to the amount of charge input decreases compared to before the deterioration.
[0099] Therefore, in step S440, the control device 20 may adjust the upper limit of the reference adsorption amount according to the degree of deterioration of the electrochemical cell 101 estimated by the operating time. This allows the system to transition from the adsorption process to the next process even if the electrochemical cell deteriorates, 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 becomes possible to reduce the energy required for carbon dioxide recovery and shorten the time required for carbon dioxide recovery.
[0100] Incidentally, the upper limit of the standard adsorption amount 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 upper limit of the standard adsorption amount of the adsorption unit 100, which is in a carbon dioxide adsorption state, based on the capacitance of the electrochemical cell 101.
[0101] 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 and capacitance of the electrochemical cell 101 are calculated from the peak current value and the current value at a predetermined time constant (63.2% response in this embodiment) in the current profile.
[0102] The control device 20 stores a predefined map, as shown in Figure 14, which shows the 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 of CO2 adsorption). Based on the capacitance of the electrochemical cell 101, the control device 20 refers to this map and calculates the upper limit of CO2 adsorption. Then, based on the calculated upper limit of CO2 adsorption, it calculates the upper limit of the standard adsorption amount for the adsorption unit 100.
[0103] Here, as the electrochemical cell 101 deteriorates over time, as shown in Figure 14, the capacitance of the electrochemical cell 101 decreases, and the upper limit of CO2 adsorption decreases. Therefore, by determining the upper limit of the standard adsorption amount of the adsorption unit 100 based on the upper limit of CO2 adsorption calculated from the capacitance of the electrochemical cell 101, even if the electrochemical cell deteriorates, the process can be moved from the adsorption process to the next process 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 shorten the time required for carbon dioxide recovery.
[0104] (Other embodiments) The present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of the invention. Furthermore, the means disclosed in each of the above embodiments may be combined as appropriate to the extent that they are feasible.
[0105] (1) For example, in the embodiment described above, an example was given in which the amount of carbon dioxide adsorbed on the adsorption unit 100, which is the amount of adsorbed CO2, was used as the carbon dioxide adsorption state, but the embodiment is not limited to this. For example, the carbon dioxide adsorption rate of the adsorption unit 100 may be used as the carbon dioxide adsorption state.
[0106] (2) In the embodiments described above, an example was described in which the adsorption state detection unit 201 of the control device 20 is configured to detect the carbon dioxide adsorption state of the adsorption unit 100 based on the exhaust gas CO2 concentration, the amount of charge input to the electrochemical cell 101, or the capacitance of the electrochemical cell 101. However, the method for detecting the carbon dioxide adsorption state is not limited to this embodiment.
[0107] For example, the adsorption state detection unit 201 may detect the carbon dioxide adsorption state of the adsorption unit 100 based on the exhaust gas CO2 concentration and at least one of the amount of charge input to the electrochemical cell 101 and the capacitance of the electrochemical cell 101.
[0108] More specifically, the adsorption state detection unit 201 may normally detect the carbon dioxide adsorption state based on the exhaust gas CO2 concentration. On the other hand, if a malfunction occurs in the CO2 concentration sensor 30, the adsorption state detection unit 201 may detect the carbon dioxide adsorption state of the adsorption unit 100 based on at least one of the amount of charge input to the electrochemical cell 101 and the capacitance of the electrochemical cell 101.
[0109] According to this, even if a malfunction occurs in the CO2 concentration sensor 30, the process can be moved from the adsorption process to the next process when the carbon dioxide adsorption state of the adsorption unit 100 reaches a saturated state. Therefore, even if a malfunction occurs in the CO2 concentration sensor 30, it is possible to reduce the energy required for carbon dioxide recovery and shorten the time required for carbon dioxide recovery.
[0110] (3) In the embodiments described above, an example was given in which the exhaust gas CO2 concentration detected by the CO2 concentration sensor 30 was used to detect the carbon dioxide adsorption state, but the embodiment is not limited to this. For example, the deterioration state of the electrochemical cell 101 may be diagnosed based on the exhaust gas CO2 concentration. If it is diagnosed that the electrochemical cell 101 is deteriorated, the user may be notified that the electrochemical cell 101 is deteriorated.
[0111] Furthermore, for example, the relationship between the amount of adsorbed CO2 calculated based on the exhaust gas CO2 concentration and the amount of charge input to the electrochemical cell 101 may be compared with the relationship between the amount of adsorbed CO2 and the amount of charge input shown in a map predefined in the control device 20. If the discrepancy between the two is greater than or equal to a threshold, it may be diagnosed that there is an abnormality in the electrical system of the carbon dioxide capture system 1.
[0112] Incidentally, normally, when air is discharged from the carbon dioxide recovery device 10 during processes other than the adsorption process, the sensor value of the CO2 concentration sensor 30 falls within the range of carbon dioxide concentration in the atmosphere (500 to 700 ppm). Therefore, if the sensor value of the CO2 concentration sensor 30 falls outside the range of carbon dioxide concentration in the atmosphere during processes other than the adsorption process, it may be diagnosed that there is a problem with the CO2 concentration sensor 30.
[0113] (4) In the embodiments described above, an example was given in which a scavenging step was adopted as the step following the adsorption step, but the system is not limited to this embodiment. For example, if the carbon dioxide recovery system 1 operates by switching between the adsorption step, desorption step, adsorption step, desorption step, ... steps in that order, the desorption step may be adopted as the step following the adsorption step.
[0114] (5) In the embodiments described above, an example in which a liquid electrolyte 108 was used as the electrolytic material was explained, but the invention is not limited to this embodiment. For example, an ionic liquid gel obtained by gelling an ionic liquid may be used as the electrolytic material, or a solid electrolyte may be used. [Explanation of symbols]
[0115] 100 Adsorption part 201 Adsorption state detection unit 202 Process switching section
Claims
[Claim 1] A carbon dioxide capture system that separates and recovers carbon dioxide from a supply gas containing carbon dioxide, Adsorption unit (100) for adsorbing and desorbing carbon dioxide, The adsorption unit includes a process switching unit (202) that switches between multiple processes, including an adsorption process in which the adsorption unit adsorbs carbon dioxide contained in the supply gas, The system includes an adsorption state detection unit (201) for detecting 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. The adsorption unit has an electrochemical cell (101) comprising a working electrode (102) and a counter electrode (103), wherein when a voltage is applied between the working electrode and the counter electrode, electrons are supplied from the counter electrode to the working electrode, and the working electrode combines with carbon dioxide as electrons are supplied. The adsorption state detection unit is a carbon dioxide recovery system that detects the carbon dioxide adsorption state based on the capacitance of the electrochemical cell.