Carbon dioxide capture system

Abstract

To provide a system of recovering carbon dioxide, whose power source facility can be downsized when grouping a plurality of electrochemical cells.SOLUTION: There are provided a plurality of grouped electrochemical cells 121 to 123 adsorbing CO2 from CO2-containing gas containing CO2 to recover CO2. A power source 170 is provided to each of the grouped electrochemical cells 121 to 123. A controller 180 controls the timing of applying an adsorption voltage in the adsorption process of at least one of the electrochemical cells 121 to 123 among the plurality of electrochemical cells 121 to 123, at a timing different from the timing of applying an adsorption voltage in the adsorption process of the remaining electrochemical cells 121 to 123.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a carbon dioxide recovery system.

Background Art

[0002] Conventionally, a carbon dioxide recovery system has been proposed, for example, in Patent Document 1. The carbon dioxide recovery system supplies CO2 that undergoes a reduction reaction to the working electrode side of an electrolyte, and supplies a substance that undergoes an oxidation reaction to the counter electrode side of the electrolyte.

[0003] Then, the carbon dioxide recovery system adsorbs CO2 to the working electrode by controlling the applied voltage between the working electrode and the counter electrode. Further, the carbon dioxide recovery system desorbs the adsorbed CO2 from the working electrode by controlling the applied voltage.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The carbon dioxide recovery system includes an electrochemical cell including a working electrode and a counter electrode. For example, when grouping a plurality of electrochemical cells, it is conceivable to share a power supply unit for applying a voltage to the plurality of electrochemical cells.

[0006] [[ID=,,]] However, the electrochemical cell operates like a capacitor. Therefore, during the adsorption process of adsorbing CO2 to the electrochemical cell, an instantaneous large current flows through the power supply unit due to the adsorption voltage being applied to each electrochemical cell simultaneously. Therefore, a power supply with a large rated current or wiring for a large current is required as the power supply unit, and consequently, the equipment of the power supply unit constituting the carbon dioxide recovery system becomes large-scale.

[0007] In view of the above, the present invention aims to provide a carbon dioxide recovery system that can reduce the size of the power supply equipment when grouping multiple electrochemical cells. [Means for solving the problem]

[0008] To achieve the above objective, Claim 1 In the described invention, the carbon dioxide recovery system includes an electrochemical cell (121-123), a power supply unit (170), and a control unit (180).

[0009] The electrochemical cell recovers CO2 by adsorbing it from a CO2-containing gas. The power supply unit is connected to the electrochemical cell. The control unit controls the power supply unit to apply an adsorption voltage to the electrochemical cell, thereby performing an adsorption process to adsorb CO2 onto the electrochemical cell.

[0010] electric Multiple gaseous chemical cells are provided, For each of the multiple electrochemical cells grouping This is constructed It is.

[0011] system The system controls the timing of the application of the adsorption voltage in the adsorption process for multiple electrochemical cells included in a single grouping, so that they start sequentially with a time staggeration.

[0012] According to this, the timing of the peak current flowing to the power supply during the adsorption process of at least one of the multiple electrochemical cells will be out of sync with the timing of the peak current flowing to the power supply during the adsorption process of the other electrochemical cells. Therefore, when considering a grouping of electrochemical cells, the peak current flowing to the power supply can be reduced compared to when an adsorption voltage is applied to multiple electrochemical cells simultaneously. Consequently, when grouping multiple electrochemical cells, the power supply equipment can be reduced.

[0013] Note that the reference signs within parentheses for each means described in this column and the claims indicate the correspondence with the specific means described in the embodiments described later.

Brief Description of the Drawings

[0014] [Figure 1] It is a diagram showing a carbon dioxide recovery system according to the first embodiment. [Figure 2] It is a diagram for explaining the adsorption process. [Figure 3] It is a diagram showing the pressure profile inside the housing in each process. [Figure 4] It is a diagram for explaining the scavenging process. [Figure 5] It is a diagram for explaining the desorption process. [Figure 6] It is a diagram for explaining the recovery process. [Figure 7] It is a diagram showing the peak current when the timing of applying the adsorption voltage is shifted in each adsorption process of three electrochemical cells. [Figure 8] It is a diagram showing the peak current when the timing of applying the adsorption voltage is the same in each adsorption process of three electrochemical cells. [Figure 9] It is a diagram showing the control content of the control unit according to the second embodiment.

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described based on the drawings. In the following embodiments, parts that are identical or equivalent to each other are denoted by the same reference signs in the drawings.

[0016] (First Embodiment) The carbon dioxide recovery system according to the present embodiment separates CO2 from a CO2-containing gas containing CO2 by an electrochemical reaction. As shown in FIG. 1, the carbon dioxide recovery system 100 includes a recovery unit 110, a duct unit 130, a scavenging unit 140, a collection unit 150, a pressure sensor 160, a power supply unit 170, and a control unit 180.

[0017] The recovery unit 110 is a device that separates and recovers CO2 from the CO2-containing gas. The CO2-containing gas is, for example, the atmosphere containing CO2. The recovery unit 110 includes a recovery chamber 111, a CO2 sensor 112, a pump 113 for the recovery chamber, a dehumidification filter 114, a deodorization filter 115, and a plurality of recoverers 116 to 118.

[0018] The recovery chamber 111 is a room that houses the plurality of recoverers 116 to 118. The recovery chamber 111 protects the plurality of recoverers 116 to 118 from moisture and the like. The recovery chamber 111 has an introduction pipe 131 for introducing the atmosphere from the outside and an exhaust hole 120 communicating with the outside.

[0019] The CO2 sensor 112 is disposed inside the recovery chamber 111 and detects the CO2 concentration inside the recovery chamber 111. The pump 113 for the recovery chamber, the dehumidification filter 114, and the deodorization filter 115 are disposed in the introduction pipe 131. The pump 113 for the recovery chamber introduces the atmosphere into the recovery chamber 111 through the introduction pipe 131.

[0020] The dehumidification filter 114 is disposed downstream of the pump 113 for the recovery chamber and dehumidifies the atmosphere introduced by the pump 113 for the recovery chamber. The deodorization filter 115 is disposed downstream of the dehumidification filter 114 and deodorizes the atmosphere passing through the dehumidification filter 114.

[0021] The plurality of recoverers 116 to 118 recover CO2 by adsorbing CO2 from the atmosphere introduced into the recovery chamber 111. In addition, each of the recoverers 116 to 118 discharges the CO2-removed gas after CO2 is recovered or the CO2 recovered from the atmosphere.

[0022] In the present embodiment, three recoverers 116 to 118 are disposed in the recovery chamber 111. Each of the recoverers 116 to 118 has each of the electrochemical cells 121 to 123 and each of the casings 124 to 126.

[0023] Each electrochemical cell 121-123 is a device that recovers CO2 by adsorbing it from the atmosphere, while also capturing CO2 by desorbing it. Each electrochemical cell 121-123 performs CO2 adsorption and desorption through electrochemical reactions, enabling the separation and recovery of CO2 from the atmosphere.

[0024] Each electrochemical cell 121-123 is an electric field cell stack in which multiple cell sections, each having a working electrode, a counter electrode, an insulating layer, and an ion-conducting member, are stacked. The working electrode, counter electrode, and insulating layer are each configured in a plate shape. The working electrode is the negative electrode. The counter electrode is the positive electrode.

[0025] The working electrode contains a CO2 adsorbent. The CO2 adsorbent is an electroactive species that possesses redox activity and is capable of reversibly undergoing oxidation-reduction reactions. The CO2 adsorbent can bind to and adsorb CO2 in the reduced state and release CO2 in the oxidized state. The CO2 adsorbent has functional groups that bind to CO2. These functional groups that bind to CO2 become CO2 adsorption sites through electron transfer.

[0026] The working electrode comprises a working electrode substrate, a working electrode conductive additive, and a working electrode binder, in addition to the CO2 adsorbent. The working electrode substrate is a porous conductive material that allows CO2 to pass through. The working electrode conductive additive is a conductive substance that forms a conductive path to the CO2 adsorbent. The working electrode binder is a retaining material for holding the CO2 adsorbent and the working electrode conductive additive to the working electrode substrate. The CO2 adsorbent, the working electrode conductive additive, and the working electrode binder are provided inside the porous working electrode substrate.

[0027] The counter electrode has the same configuration as the working electrode. The counter electrode contains a counter-electrode active material. The counter-electrode active material is an auxiliary electroactive species that has an opposite oxidation-reduction state to the CO2 adsorbent and facilitates the transfer of electrons between it and the CO2 adsorbent. As the counter-electrode active material, for example, a metal complex that enables the transfer of electrons by changing the valence of a metal ion can be used.

[0028] The counter electrode comprises, in addition to the counter electrode-side active material, a counter electrode-side substrate, a counter electrode-side conductive additive, and a counter electrode-side binder. The counter electrode-side substrate, counter electrode-side conductive additive, and counter electrode-side binder may be made of the same materials as those used in the working electrode, or they may be made of different materials.

[0029] The insulating layer is placed between the working electrode and the counter electrode. The insulating layer separates the working electrode and the counter electrode. The insulating layer prevents physical contact between the working electrode and the counter electrode. In addition, the insulating layer suppresses electrical short circuits between the working electrode and the counter electrode. A separator or a gaseous layer such as air can be used as the insulating layer.

[0030] The ion-conducting member is placed between the working electrode and the counter electrode. Specifically, the ion-conducting member is placed between the working electrode-side substrate and the counter electrode-side substrate via an insulating layer.

[0031] The ion-conducting member is in contact with the CO2 adsorbent inside the working electrode substrate. The ion-conducting member has ionic conductivity. This promotes conductivity to the CO2 adsorbent. The ions contained in the ion-conducting member do not directly react with the functional groups that bind to CO2 contained in the CO2 adsorbent. The ion-conducting member may be made of the same material as the working electrode binder, or a different material may be used.

[0032] Enclosure 124 is a container for housing the electrochemical cell 121. Enclosure 125 is a container for housing the electrochemical cell 122. Enclosure 126 is a container for housing the electrochemical cell 123. Each enclosure 124 to 126 is resealable.

[0033] The duct section 130 is a device for supplying air to each of the recovery units 116-118. The duct section 130 includes an introduction pipe 131, an opening / closing section 132 for the first duct, an opening / closing section 133 for the second duct, an exhaust pump 134, an oil filter 135, and a CO2 sensor 136.

[0034] The intake pipe 131 is a pipe for introducing and exhausting air to each of the recovery units 116-118. One end of the intake pipe 131 is located inside the recovery chamber 111. The other end of the intake pipe 131 is located outside the recovery chamber 111.

[0035] The first duct opening / closing unit 132 is located upstream of each recovery unit 116-118 in the introduction piping 131. The first duct opening / closing unit 132 opens and closes the upstream section of the introduction piping 131 according to a command from the control unit 180. The second duct opening / closing unit 133 is located downstream of each recovery unit 116-118 in the introduction piping 131. The second duct opening / closing unit 133 opens and closes the downstream section of the introduction piping 131 according to a command from the control unit 180.

[0036] The first duct opening / closing section 132 and the second duct opening / closing section 133 are located inside the recovery chamber 111. The first duct opening / closing section 132 and the second duct opening / closing section 133 are, for example, valves that open or close the passage of the introduction piping 131. Note that the housings 124 to 126 of each recovery unit 116 to 118 may be configured as part of the introduction piping 131.

[0037] The exhaust pump 134 is located downstream of the second duct opening / closing section 133 in the inlet piping 131. The exhaust pump 134 is located outside the recovery chamber 111. The exhaust pump 134 generates an airflow in the inlet piping 131, thereby passing air through each of the recovery units 116-118. The exhaust pump 134 is, for example, a dry-type pump.

[0038] The oil filter 135 is positioned downstream of the exhaust pump 134 in the intake piping 131. The oil filter 135 blocks the passage of oil leaking from the oil-type exhaust pump 134. A blower fan may be used instead of the exhaust pump 134. In this case, the oil filter 135 is not necessary.

[0039] The CO2 sensor 136 is positioned downstream of the oil filter 135 in the introduction piping 131. The CO2 sensor 136 detects the concentration of CO2 contained in the air discharged from each recovery unit 116 to 118 and outputs the detection result to the control unit 180.

[0040] The scavenging unit 140 is a device for scavenging the inside of each housing 124-126 of each recovery unit 116-118 while the electrochemical cells 121-123 have adsorbed CO2 and the housings 124-126 are sealed. In other words, the scavenging unit 140 creates a vacuum inside each housing 124-126.

[0041] Here, the state in which each housing 124-126 is sealed means that at least the duct section 130 prevents air from being introduced into the interior of each housing 124-126. In order for the scavenging section 140 to scavenge the interior of each housing 124-126, it is necessary that the sealed housings 124-126 and the scavenging section 140 are connected. Similarly, in order for CO2 to be collected from each recovery unit 116-118 into the collection unit 150, it is necessary that the sealed housings 124-126 and the collection unit 150 are connected.

[0042] The scavenging unit 140 includes a scavenging pipe 141, a scavenging switch 142, a first scavenging pump 143, a second scavenging pump 144, and an oil filter 145.

[0043] The scavenging pipe 141 is a pipe that connects the inside and outside of each housing 124-126. One end of the scavenging pipe 141 is connected to each housing 124-126. The other end of the scavenging pipe 141 is located outside the recovery chamber 111. In this way, the inside of each housing 124-126 is connected to the outside of the recovery chamber 111 via the scavenging pipe 141. A portion of the scavenging pipe 141 branches and then rejoins. That is, a portion of the scavenging pipe 141 is divided into two.

[0044] The scavenging switch 142 opens and closes the scavenging pipe 141 according to a command from the control unit 180. The scavenging switch 142 is, for example, a valve that opens or closes the passage of the scavenging pipe 141. The scavenging switch 142 is, for example, a three-way valve. The scavenging switch 142 opens and closes the sides of each housing 124 to 126 of the scavenging pipe 141 according to a command from the control unit 180. The scavenging switch 142 also returns the vacuum state inside the recovery chamber 111 to the atmosphere according to a command from the control unit 180.

[0045] The first scavenging pump 143 and the second scavenging pump 144 are positioned downstream of the scavenging switch 142 in the scavenging piping 141. Each scavenging pump 143 and 144 is located outside the recovery chamber 111. Each scavenging pump 143 and 144 is positioned in each branch of the scavenging piping 141. Each scavenging pump 143 and 144 scavenges the inside of each housing 124 to 126 by generating a gas flow in the scavenging piping 141. Since scavenging is performed by two scavenging pumps 143 and 144, the scavenging capacity can be increased compared to using one pump. Each scavenging pump 143 and 144 is, for example, an oil-type pump.

[0046] The oil filter 145 is located downstream of each of the scavenging pumps 143 and 144 in the scavenging piping 141. The oil filter 145 blocks the passage of oil leaking from each of the oil-type scavenging pumps 143 and 144. Note that if dry-type pumps are used for each of the scavenging pumps 143 and 144, the oil filter 135 is not required.

[0047] The collection unit 150 is a device for collecting CO2 recovered by each recovery unit 116-118. The collection unit 150 includes a tank 151, collection piping 152, collection opening / closing unit 153, vacuum filter 154, and collection pump 155.

[0048] Tank 151 is a device for storing the CO2 recovered by each recovery unit 116-118. Tank 151 collects CO2 from each recovery unit 116-118 via collection piping 152. Note that Tank 151 may be a factory or equipment that utilizes CO2.

[0049] The collection pipe 152 is a pipe that connects the inside of each housing 124-126 to the tank 151. One end of the collection pipe 152 is connected to one end of the scavenging pipe 141. Therefore, one end of the collection pipe 152 is common to one end of the scavenging pipe 141. Of course, one end of the collection pipe 152 and one end of the scavenging pipe 141 may also be independently connected to each housing 124-126. The other end of the collection pipe 152 is connected to the tank 151.

[0050] The collection opening / closing section 153 is provided on the side of each housing 124 to 126 of the collection piping 152. The collection opening / closing section 153 is located inside the recovery chamber 111. The collection opening / closing section 153 opens and closes the side of each housing 124 to 126 of the collection piping 152 according to a command from the control unit 180. The collection opening / closing section 153 is, for example, a valve that opens or closes the passage of the collection piping 152.

[0051] The vacuum filter 154 is a filter for removing moisture, dust, and other contaminants contained in the gas sucked in by the collection pump 155 when the pressure in each recovery unit 116 to 118 is reduced. The vacuum filter 154 is located downstream of the collection opening / closing section 153 in the collection piping 152.

[0052] The collection pump 155 is a dry-type pump used to draw the CO2 collected by each recovery unit 116-118 into the tank 151. The collection pump 155 is located downstream of the vacuum filter 154 in the collection piping 152. The collection pump 155 is located, for example, on the wall of the recovery chamber 111.

[0053] The pressure sensor 160 is a sensor for detecting the internal pressure of each housing 124-126 of each recovery unit 116-118. The pressure sensor 160 is installed, for example, at one end of the scavenging pipe 141. The pressure sensor 160 outputs a detection signal to the control unit 180.

[0054] The power supply unit 170 is the power supply device for the carbon dioxide capture system 100. The power supply unit 170 supplies power to the capture unit 110, the duct unit 130, the scavenging unit 140, the collection unit 150, and the pressure sensor 160 according to the commands of the control unit 180.

[0055] The power supply unit 170 includes a first power unit 171, a second power unit 172, a first driver 173, a second driver 174, a third driver 175, a first current probe 176, and a second current probe 177.

[0056] The first power unit 171 and the second power unit 172 change the potential difference between the working electrode and the counter electrode by applying a predetermined voltage to each electrochemical cell 121 to 123 of each recovery unit 116 to 118 in accordance with the command of the control unit 180.

[0057] The first power unit 171 generates an adsorption voltage for adsorbing CO2 onto each electrochemical cell 121-123. The adsorption voltage is, for example, a positive voltage. The second power unit 172 generates a desorption voltage for desorbing CO2 from each electrochemical cell 121-123. The desorption voltage is, for example, a negative voltage. The desorption voltage generated by the second power unit 172 is a voltage that is in opposite phase to the adsorption voltage generated by the first power unit 171.

[0058] Furthermore, a single power unit is sufficient as long as it can generate an adsorption voltage and a desorption voltage that is in the opposite phase to the adsorption voltage, and can supply each voltage to each electrochemical cell 121-123 at different timings.

[0059] Each driver 173-175 is a switch device that turns ON or OFF the power supply to each power unit 171, 172 and each electrochemical cell 121-123 according to a command from the control unit 180.

[0060] For example, the first driver 173 does not turn on each power unit 171, 172 and the electrochemical cell 121 simultaneously, but rather turns on either one of the power units 171, 172 and the electrochemical cell 121. The same applies to the second driver 174 and the third driver 175.

[0061] The first current probe 176 is a sensor that detects the current flowing between the first power unit 171 and each electrochemical cell 121-123. The second current probe 177 is a sensor that detects the current flowing between the second power unit 172 and each electrochemical cell 121-123. The detection results of each current probe 176 and 177 are output to the control unit 180.

[0062] The control unit 180 consists of a well-known microcomputer including a CPU, ROM, and RAM, and its peripheral circuits. The control unit 180 performs various calculations and processes according to the control program stored in the ROM.

[0063] For example, the control unit 180 controls the power supply unit 170 to apply an adsorption voltage to each electrochemical cell 121 to 123, thereby performing an adsorption process to adsorb CO2 onto each electrochemical cell 121 to 123. The control unit 180 also controls the power supply unit 170 to apply a desorption voltage to each electrochemical cell 121 to 123, thereby performing a desorption process to desorb CO2 from each electrochemical cell 121 to 123.

[0064] In addition, the control unit 180 controls the first duct opening / closing unit 132, the second duct opening / closing unit 133, and the exhaust pump 134 of the duct section 130. The control unit 180 controls the scavenging opening / closing unit 142 and the respective scavenging pumps 143 and 144 of the scavenging section 140. The control unit 180 controls the tank 151, the collection opening / closing unit 153, and the collection pump 155 of the collection section 150. The above is the overall configuration of the carbon dioxide recovery system 100 according to this embodiment.

[0065] Next, the operation of the carbon dioxide capture system 100 will be described. The control unit 180 performs the adsorption process, scavenging process, desorption process, and capture process for each electrochemical cell 121 to 123. The process from the adsorption process to the capture process constitutes one cycle. The control unit 180 controls the repetition of the cycle.

[0066] The following describes each step of the electrochemical cell 121 of the recovery unit 116. The contents of each step are the same for the other electrochemical cells 122 and 123.

[0067] First, the control unit 180 performs an adsorption process to adsorb CO2 onto the electrochemical cell 121. As shown in Figure 2, the control unit 180 controls the collection switch 153 and the scavenging switch 142 to the closed state. The control unit 180 also controls the scavenging pumps 143, 144 and the collection pump 155 to the OFF state.

[0068] Furthermore, the control unit 180 controls the first duct opening / closing section 132 and the second duct opening / closing section 133 to the open state, and controls the recovery chamber pump 113 and the exhaust pump 134 to the ON state. As a result, atmospheric air is supplied to the electrochemical cell 121 of the recovery unit 116. Therefore, as shown in Figure 3, the pressure inside the housing 124 becomes atmospheric pressure P0 at time t1.

[0069] The control unit 180 turns on the power supply between the first power unit 171 and the electrochemical cell 121 at the first driver 173, and turns off the power supply between the second power unit 172 and the electrochemical cell 121. This applies the adsorption voltage of the first power unit 171 between the working electrode and the counter electrode of the electrochemical cell 121. Thus, electron donation by the counter electrode active material and electron withdrawal by the CO2 adsorbent at the working electrode can be achieved simultaneously. Note that the first driver 173 is omitted in Figure 2.

[0070] When an adsorption voltage is applied between the working electrode and the counter electrode, the counter electrode's active material releases electrons and enters an oxidized state, supplying electrons from the counter electrode to the working electrode. The CO2 adsorbent at the working electrode accepts electrons and enters a reduced state.

[0071] When the CO2 adsorbent is in a reduced state, its ability to bind to CO2 increases, and it binds to and adsorbs CO2 contained in the atmosphere. In this way, when an adsorption voltage is applied between the working electrode and the counter electrode of the electrochemical cell 121, electrons are supplied from the counter electrode to the working electrode, and the CO2 adsorbent binds to CO2 in response to the supply of electrons. Therefore, the recovery unit 116 can recover CO2 from the atmosphere.

[0072] After atmospheric CO2 is recovered in the recovery unit 116, CO2-free air is discharged from the recovery unit 116. The control unit 180 terminates the adsorption process, for example, based on the concentration difference between each CO2 sensor 112, 136.

[0073] After the adsorption process, the control unit 180 performs a scavenging process to clean the inside of the housing 124 of the recovery unit 116. As shown in Figure 4, the control unit 180 controls the exhaust pump 134 and the collection pump 155 to the OFF state while CO2 is adsorbed on the electrochemical cell 121, that is, while an adsorption voltage is applied to the electrochemical cell 121.

[0074] Furthermore, the control unit 180 controls the first duct opening / closing unit 132, the second duct opening / closing unit 133, and the collection opening / closing unit 153 to the closed state. The control unit 180 also controls the scavenging opening / closing unit 142 to the open state, and controls the recovery chamber pump 113 and each of the scavenging pumps 143 and 144 to the ON state.

[0075] This causes the inside of the housing 124 of the recovery unit 116 to be scavenged via the scavenging pipe 141. The inside of the housing 124 becomes negative pressure. Therefore, as shown in Figure 3, the pressure inside the housing 124 drops to the removal target pressure P1. The control unit 180 terminates the scavenging process at the timing t2 when the pressure inside the housing 124 reaches the removal target pressure P1.

[0076] After the scavenging process, the control unit 180 performs a desorption process to desorb the CO2 adsorbed on the electrochemical cell 121. As shown in Figure 5, with CO2 adsorbed on the electrochemical cell 121, the control unit 180 controls the exhaust pump 134, the collection pump 155, and the respective scavenging pumps 143, 144 to the OFF state. The control unit 180 controls the recovery chamber pump 113 to the ON state. Alternatively, the control unit 180 may control the recovery chamber pump 113 to the OFF state.

[0077] Furthermore, the control unit 180 controls all of the first duct opening / closing section 132, the second duct opening / closing section 133, the collection opening / closing section 153, and the scavenging opening / closing section 142 to be in the closed state.

[0078] The control unit 180 then turns OFF the power supply between the first power unit 171 and the electrochemical cell 121 at the first driver 173, and turns ON the power supply between the second power unit 172 and the electrochemical cell 121. This applies the desorption voltage of the second power unit 172 between the working electrode and the counter electrode of the electrochemical cell 121. Thus, electron donation by the CO2 adsorbent at the working electrode and electron withdrawal by the counter-electrode-side active material at the counter electrode can be achieved simultaneously.

[0079] The CO2 adsorbent at the working electrode releases electrons and enters an oxidized state. The CO2 adsorbent's binding force to CO2 decreases, causing it to desorb and release. The counter electrode's counter-electrode active material accepts electrons and enters a reduced state.

[0080] In this way, CO2 is desorbed from the electrochemical cell 121. The CO2 is released into the housing 124. Therefore, as shown in Figure 3, at the end of the desorption process t3, the pressure inside the housing 124 rises to the desorption target pressure P2.

[0081] After the desorption process, the control unit 180 performs a recovery process to collect the CO2 desorbed from the electrochemical cell 121. As shown in Figure 6, with CO2 desorbed from the electrochemical cell 121, the control unit 180 controls the first duct opening / closing section 132, the second duct opening / closing section 133, and the scavenging opening / closing section 142 to the closed state. The control unit 180 also controls the exhaust pump 134 and the respective scavenging pumps 143 and 144 to the OFF state.

[0082] The control unit 180 then controls the collection opening / closing unit 153 to the open state and controls the collection pump 155 to the ON state. As a result, the CO2 released from the CO2 adsorbent is discharged from the recovery unit 116 and collected in the tank 151 via the collection piping 152.

[0083] While CO2 is being collected in tank 151, the collection pump 155 is operating. Therefore, as shown in Figure 3, the pressure inside the housing 124 drops to the recovery target pressure P3. After the recovery process, the system moves to the adsorption process, and the pressure inside the housing 124 returns to atmospheric pressure P0 at time t4. Thus, one cycle is completed. The control unit 180 repeatedly executes the above cycle.

[0084] In this embodiment, the three recovery units 116 to 118 are grouped together. That is, the three electrochemical cells 121 to 123 are treated as one set. In other words, the power supply unit 170 is common to the three grouped electrochemical cells 121 to 123.

[0085] The control unit 180 then controls the timing at which the adsorption voltage is applied in the adsorption process of at least one of the three electrochemical cells 121 to 123 to be different from the timing at which the adsorption voltage is applied in the adsorption process of the other electrochemical cells 121 to 123.

[0086] In this embodiment, as shown in Figure 7, the control unit 180 starts the adsorption process for the next electrochemical cells 121 to 123 after the adsorption process for the currently running electrochemical cells 121 to 123 has finished.

[0087] For example, the timing of the start of the adsorption process is defined as the timing of applying the adsorption voltage during the adsorption process. The timing of applying the adsorption voltage can be anytime during the adsorption process, so it is acceptable to apply the adsorption voltage even after the valve control has ended.

[0088] For example, at time T10, the control unit 180 starts the adsorption process of the electrochemical cell 121. As a result, time T11 is the timing of the peak current flowing to the power supply unit 170 during the adsorption process of the electrochemical cell 121. The peak current at time T11 is the current for one electrochemical cell 121. After this, the peak current decreases.

[0089] Then, at time T12, the control unit 180 completes the adsorption process of the electrochemical cell 121 and starts the scavenging process. The control unit 180 also starts the adsorption process of the electrochemical cell 122.

[0090] The control unit 180 controls the first driver 173 to turn off the power supply between the first power unit 171 and the electrochemical cell 121, and controls the second driver 174 to turn on the power supply between the first power unit 171 and the electrochemical cell 122. Since the first power unit 171 continues to generate an adsorption voltage, the adsorption voltage of the first power unit 171 can be used continuously. Similarly, the second power unit 172 continues to generate a detachment voltage.

[0091] Therefore, time point T13 corresponds to the timing of the peak current flowing to the power supply unit 170 during the adsorption process of the electrochemical cell 122. The peak current at time point T13 is the current for one electrochemical cell 122. After this, the peak current decreases. Since each electrochemical cell 121 to 123 has the same configuration, the magnitude of the peak current flowing to each electrochemical cell 121 to 123 is also the same.

[0092] At time T14, the control unit 180 completes the scavenging process of the electrochemical cell 121 and starts the desorption process. That is, the control unit 180 controls the first driver 173 to turn on the power supply between the second power unit 172 and the electrochemical cell 121. As a result, a desorption voltage with the opposite phase to the adsorption voltage is applied to the electrochemical cell 121. In other words, a current flows in the electrochemical cell 121 in the reverse direction compared to the adsorption process.

[0093] When a desorption voltage is applied to the electrochemical cell 121, CO2 is desorbed from the electrochemical cell 121. Time T15 is the timing of the peak current flowing to the power supply unit 170 during the desorption process of the electrochemical cell 121.

[0094] At time T16, the control unit 180 completes the adsorption process of the electrochemical cell 122 and starts the scavenging process. The control unit 180 also starts the adsorption process of the electrochemical cell 123. Therefore, time T17 is the timing of the peak current flowing to the power supply unit 170 during the adsorption process of the electrochemical cell 123. The peak current at time T17 is the current for one electrochemical cell 123. After this, the peak current decreases.

[0095] At time T18, the control unit 180 completes the desorption process of the electrochemical cell 121 and starts the recovery process.

[0096] At time T19, the control unit 180 completes the scavenging process of the electrochemical cell 122 and starts the desorption process. Therefore, time T20 is the timing of the peak current flowing to the power supply unit 170 during the desorption process of the electrochemical cell 122. The peak current at time T20 is the current for one electrochemical cell 122.

[0097] At time T21, the control unit 180 finishes the recovery process for the electrochemical cell 121 and restarts the adsorption process. At time T21, the adsorption process for the electrochemical cell 123 is in progress. Therefore, the peak current at time T22 is the sum of the current flowing through the electrochemical cell 123 and the current flowing through the electrochemical cell 121.

[0098] From time point T21 onward, the control unit 180 repeats the processes of each electrochemical cell 121 to 123 in the same manner as from time point T10 onward. Since the current values ​​during periods when the adsorption process or desorption process overlaps in each process of each electrochemical cell 121 to 123 are summed, the peak current is slightly larger than that of a single electrochemical cell 121 to 123. For example, the period from time point T23 to time point T24 is the period when the desorption process of electrochemical cell 121 and the desorption process of electrochemical cell 123 overlap, and the peak current is the sum of these two values.

[0099] Here, we compare this with the peak current when the timing of applying the adsorption voltage in each of the three electrochemical cells 121 to 123 during their respective adsorption processes is simultaneous. As shown in Figure 8, at time T30, the control unit 180 simultaneously starts the adsorption process for each of the electrochemical cells 121 to 123.

[0100] As a result, time point T31 coincides with the timing of the peak current flowing to the power supply unit 170 during the adsorption process of each electrochemical cell 121-123. Therefore, the peak current value at time point T31 becomes the sum of the peak currents of the three electrochemical cells 121-123, causing a large current to flow through the wiring between the first power unit 171 and each driver 173-175.

[0101] At time T32, the control unit 180 simultaneously starts the scavenging process for each electrochemical cell 121-123. Then, at time T33, the control unit 180 simultaneously starts the desorption process for each electrochemical cell 121-123. Therefore, the control unit 180 simultaneously turns OFF the power supply between the first power unit 171 and each electrochemical cell 121-123. The control unit 180 also turns ON the power supply between the second power unit 172 and each electrochemical cell 121-123.

[0102] As a result, a desorption voltage in the opposite phase to the adsorption voltage is simultaneously applied to each electrochemical cell 121-123, causing a current in the reverse direction to flow between the second power unit 172 and each driver 173-175 during the adsorption process. Time T34 coincides with the timing of the peak current flowing to the power supply unit 170 during the desorption process. Therefore, the value of the peak current at time T34 becomes the sum of the peak currents of the three electrochemical cells 121-123, causing a large current to flow through the wiring between the second power unit 172 and each driver 173-175.

[0103] At time T35, the control unit 180 simultaneously starts the recovery process for each electrochemical cell 121-123. From time T36 onward, the control unit 180 repeats each process for each electrochemical cell 121-123, as it did from time T30 onward. In the above cycle, a large current flows at times T31 and T34.

[0104] In contrast, in this embodiment, the timing of the peak current flowing during the adsorption process of one of the electrochemical cells 121 to 123, electrochemical cell 121, is out of sync with the timing of the peak current flowing during the adsorption processes of the other electrochemical cells 122 and 123. Therefore, when viewed as a grouping of electrochemical cells 121 to 123, the peak current flowing to the power supply unit 170 can be reduced compared to when the adsorption voltage is applied to each electrochemical cell 121 to 123 simultaneously. In other words, the maximum current can be smoothed.

[0105] As a result, the size of the power supply unit 170 can be reduced. In other words, the power supply capacity can be reduced. In addition, the copper wires and connectors that make up the power supply unit 170 can be made smaller.

[0106] Furthermore, because the timing of the adsorption processes of each electrochemical cell 121 to 123 is staggered, the power supplies of each power unit 171 and 172 can be continuously utilized. For example, if the timing of the adsorption processes of each electrochemical cell 121 to 123 is simultaneous, as shown in Figure 8, the power supply of the first power unit 171 is not utilized during the period from time T33 to time T36. However, if the timing of the adsorption processes of the electrochemical cells 121 to 123 is different, as shown in Figure 7, the power supply of the first power unit 171 can be continuously utilized. Therefore, the power supply efficiency can be increased.

[0107] Furthermore, since the operation of the duct section 130, the scavenging section 140, and the collection section 150, which are common to each recovery unit 116-118, is also distributed, the load on each part can be distributed.

[0108] Regarding the correspondence between the description of this embodiment and the description of the claims, the first current probe 176 and the second current probe 177 correspond to the "current probe" in the claims.

[0109] (Second Embodiment) This embodiment will mainly describe the differences from the first embodiment. In this embodiment, the control unit 180 sums the current value of the current flowing through the currently executing adsorption process and the maximum value of the current for the next adsorption process among the multiple electrochemical cells 121 to 123, based on the current values ​​obtained from each current probe 176, 177. Then, if the sum of the currents is less than or equal to a predetermined current value, the control unit 180 starts applying the adsorption voltage to the electrochemical cells 121 to 123 that are scheduled to perform the next adsorption process. In this way, the control unit 180 controls the timing of the adsorption process of each electrochemical cell 121 to 123 based on the current value.

[0110] Specifically, as shown in Figure 9, if the carbon dioxide capture system 100 cycle is started at time T50, a peak current flows between the first power unit 171 and the electrochemical cell 121 at time T50. This is the current value of the current flowing through the adsorption process of the electrochemical cell 121 that is currently in operation.

[0111] The control unit 180 adds up the current value of the current flowing to the power supply unit 170 during the currently running adsorption process and the maximum value of the current that flowed to the power supply unit 170 during the previous adsorption process in the electrochemical cell 122 scheduled for the next adsorption process. The maximum value of the current in each electrochemical cell 121 to 123 is the peak current value at time T50. Then, if the sum of the current value and the maximum value is less than or equal to the current criterion, the control unit 180 starts applying the adsorption voltage to the electrochemical cells 121 to 123 scheduled for the next adsorption process. The current criterion is an arbitrary value with a safety margin added to the power supply output, and is a predetermined current value.

[0112] At time T50, the adsorption process of electrochemical cell 121 begins, and the peak current related to electrochemical cell 121 decreases. Consequently, the sum of the current value currently flowing through electrochemical cell 121 and the maximum current value that flowed through electrochemical cell 122 during the previous adsorption process decreases. At time T51, the sum of the currents falls below the current criterion. In other words, the sum falls below the current criterion. Therefore, the control unit 180 starts the adsorption process of electrochemical cell 122 at time T51.

[0113] Similarly, after time point T51, the sum of the currents decreases, and at time point T52, the sum of the currents falls below the current criteria. Therefore, the control unit 180 starts the adsorption process of the electrochemical cell 123 at time point T52. The same applies from time point T53 onwards.

[0114] As described above, the control unit 180 estimates the sum of currents using the maximum current that flowed through the power supply unit 170 during the previous adsorption process. In other words, the control unit 180 estimates the sum of currents from the previous cycle. In this way, the control unit 180 may control the start timing of the adsorption process for each electrochemical cell 121 to 123 based on the estimated current value.

[0115] In addition, when combined with the first embodiment, the control unit 180 may start the next adsorption process after the completion of the previous adsorption process, and may also perform control to start the next adsorption process if the sum of the currents falls below the current criteria.

[0116] (Other embodiments) The configurations of the carbon dioxide capture system 100 shown in each of the above embodiments are examples, and the present invention can be realized with other configurations without being limited to those shown above. For example, the CO2-containing gas is not limited to the atmosphere, but can be any gas that contains CO2.

[0117] Each grouping of electrochemical cells 121-123 is not limited to three units. It is sufficient for two or more electrochemical cells 121-123 to be grouped together. Furthermore, the number of groupings is not limited to one. For example, the carbon dioxide capture system 100 may have multiple groupings. In this case, the number of electrochemical cells 121-123 included in each grouping may differ. A power supply unit 170 is sufficient for each grouped electrochemical cell 121-123.

[0118] Furthermore, the carbon dioxide capture system 100 does not necessarily have a duct section 130. For example, the housings 124 to 126 of each capturer 116 to 118 only need to have openable doors for taking in air and sealing them. In this case, the capture chamber 111 becomes unnecessary. When the carbon dioxide capture system 100 is installed outdoors, natural wind passes through the inside of the housings 124 to 126. [Explanation of symbols]

[0119] 121-123 Electrochemical Cells 170 Power supply section 171, 172 Power Unit 173~175 Driver 176, 177 Current probe 180 Control Unit

Claims

1. CO ２ Contains CO ２ From the contained gas, the CO ２ By adsorbing the CO ２ Electrochemical cells (121-123) for recovering, A power supply unit (170) connected to the electrochemical cell, By controlling the power supply unit and applying an adsorption voltage to the electrochemical cell, the CO2 is introduced into the electrochemical cell. ２ A control unit (180) that performs an adsorption process to adsorb the material, Includes, Multiple electrochemical cells are provided, and groupings are formed for each of the multiple electrochemical cells. A carbon dioxide recovery system in which the control unit controls the electrochemical cells included in one grouping to sequentially start applying the adsorption voltage in the adsorption process with a time staggered relative to each other.

2. The power supply unit detects the current value flowing between the power supply unit and the plurality of electrochemical cells constituting the grouping, The carbon dioxide recovery system according to claim 1, wherein the control unit, based on the current value, adds the current value of the current flowing through the adsorption process currently in progress and the maximum value of the current for the next adsorption process among the plurality of electrochemical cells included in the grouping, and if the sum of the currents is less than or equal to a predetermined current value, it starts applying the adsorption voltage to the electrochemical cell scheduled to perform the next adsorption process.

3. The carbon dioxide recovery system according to claim 1 or 2, wherein the control unit starts the adsorption process for the next electrochemical cell after the adsorption process for the currently running electrochemical cell in one grouping has been completed.

Images