JP2023161224A - System of recovering carbon dioxide - Google Patents

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

The present invention relates to a carbon dioxide recovery system.

Conventionally, a carbon dioxide recovery system has been proposed, for example, in Patent Document 1. The carbon dioxide recovery system supplies CO ₂ that undergoes a reduction reaction to the working electrode side of the electrolyte, and supplies a substance that undergoes an oxidation reaction to the counter electrode side of the electrolyte.

The carbon dioxide recovery system adsorbs CO ₂ on the working electrode by controlling the applied voltage between the working electrode and the counter electrode. Furthermore, the carbon dioxide recovery system desorbs CO ₂ adsorbed on the working electrode by controlling the applied voltage.

JP 2019-203193 Publication

The carbon dioxide capture system includes an electrochemical cell that includes 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 voltage to the plurality of electrochemical cells.

However, electrochemical cells operate like capacitors. Therefore, during the adsorption step of adsorbing _CO2 into the electrochemical cells, an adsorption voltage is simultaneously applied to each electrochemical cell, causing a large current to instantaneously flow through the power supply section. Therefore, a power source with a large rated current and wiring for large current are required as a power source, and as a result, the equipment for the power source that constitutes the carbon dioxide recovery system becomes large-scale.

In view of the above points, an object of the present invention is to provide a carbon dioxide recovery system that can reduce the size of power supply equipment when a plurality of electrochemical cells are grouped.

In order to achieve the above object, in the invention according to claim 1, the carbon dioxide recovery system includes an electrochemical cell (121 to 123), a power supply section (170), and a control section (180).

Electrochemical cells recover _CO2 by adsorbing _CO2 from a _CO2 -containing gas containing _CO2 . The power supply section 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 step of adsorbing CO ₂ to the electrochemical cell.

A plurality of electrochemical cells are provided and are grouped.

The control unit controls the timing of applying the adsorption voltage in the adsorption process of at least one electrochemical cell of the plurality of electrochemical cells to be different from the timing of applying the adsorption voltage in the adsorption process of other electrochemical cells. do.

According to this, the timing of the peak current flowing to the power supply part during the adsorption process of at least one electrochemical cell among the plurality of electrochemical cells, and the timing of the peak current flowing to the power supply part during the adsorption process of other electrochemical cells. , will slip. Therefore, when looking at the grouping unit of electrochemical cells, the peak current flowing through the power supply section can be made smaller than when applying the adsorption voltage to a plurality of electrochemical cells at the same time. Therefore, when a plurality of electrochemical cells are grouped, the power supply equipment can be made smaller.

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

1 is a diagram showing a carbon dioxide recovery system according to a first embodiment. It is a figure for explaining an adsorption process. It is a figure showing the pressure profile inside a case in each process. It is a figure for explaining a scavenging process. FIG. 3 is a diagram for explaining a desorption step. It is a figure for explaining a collection process. It is a figure which showed the peak current when the timing of applying adsorption voltage was shifted in each adsorption process of three electrochemical cells. It is a figure which showed the peak current when the timing of applying an adsorption voltage in each adsorption process of three electrochemical cells was set at the same time. FIG. 7 is a diagram showing control details of a control unit according to a second embodiment.

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

(First embodiment)
The carbon dioxide recovery system _according to this embodiment separates CO ₂ from a CO ₂ -containing gas by an electrochemical reaction. As shown in FIG. 1, the carbon dioxide recovery system 100 includes a recovery section 110, a duct section 130, a scavenging section 140, a collection section 150, a pressure sensor 160, a power supply section 170, and a control section 180.

The recovery unit 110 is a device that separates and recovers CO ₂ from CO ₂ -containing gas. The CO ₂ -containing gas is, for example, atmospheric air containing CO ₂ . The recovery unit 110 includes a recovery chamber 111, a CO ₂ sensor 112, a recovery chamber pump 113, a dehumidification filter 114, an odorless filter 115, and a plurality of recovery vessels 116 to 118.

The recovery chamber 111 is a room that accommodates a plurality of recovery vessels 116 to 118. The recovery chamber 111 protects the plurality of recovery vessels 116 to 118 from moisture and the like. The recovery chamber 111 has an introduction pipe 131 for introducing atmospheric air from the outside, and an exhaust hole 120 that communicates with the outside.

The CO ₂ sensor 112 is arranged inside the recovery chamber 111 and detects the CO ₂ concentration inside the recovery chamber 111 . The recovery chamber pump 113, dehumidification filter 114, and odorless filter 115 are arranged in the introduction pipe 131. The recovery chamber pump 113 introduces atmospheric air into the recovery chamber 111 via the introduction pipe 131.

The dehumidification filter 114 is disposed downstream of the recovery chamber pump 113 and dehumidifies the atmosphere introduced by the recovery chamber pump 113. The odorless filter 115 is disposed downstream of the dehumidification filter 114 and deodorizes the air passing through the dehumidification filter 114.

The plurality of recovery units 116 to 118 recover CO ₂ by adsorbing CO ₂ from the atmosphere introduced into the recovery chamber 111 . Further, each of the recovery units 116 to 118 discharges CO ₂ removal gas after CO ₂ has been recovered, or CO ₂ recovered from the atmosphere.

In this embodiment, three collectors 116 to 118 are arranged in the collection chamber 111. Each collector 116-118 has a respective electrochemical cell 121-123 and a respective housing 124-126.

Each of the electrochemical cells 121 to 123 is a device capable of recovering CO ₂ by adsorbing CO ₂ from the atmosphere, and capturing CO ₂ by desorbing CO ₂ . Each of the electrochemical cells 121 to 123 adsorbs and desorbs CO ₂ through an electrochemical reaction, thereby making it possible to separate and recover CO ₂ from the atmosphere.

Each of the electrochemical cells 121 to 123 is an electric field cell stack in which a plurality of cell parts each having a working electrode, a counter electrode, an insulating layer, and an ion conductive member are stacked. The working electrode, counter electrode, and insulating layer are each formed into a plate shape. The working electrode is the negative electrode. The opposite electrode is the positive electrode.

The working electrode includes a _CO2 adsorbent. The CO ₂ adsorbent is an electroactive species that has redox activity and can reversibly cause a redox reaction. _CO2 adsorbents can bind and adsorb _CO2 in a reduced state and release _CO2 in an oxidized state. A CO ₂ adsorbent has a functional group that binds CO ₂ . The functional group that binds to CO ₂ exchanges electrons and becomes a CO ₂ adsorption site.

Note that the working electrode includes, in addition to the CO ₂ adsorbent, a working electrode side base material, a working electrode side conductive agent, and a working electrode side binder. The working electrode side base material is a porous conductive material through which CO ₂ can pass. The working electrode side conductive agent is a conductive material that forms a conductive path to the CO ₂ adsorbent. The working electrode side binder is a holding material for holding the CO ₂ adsorbent and the working electrode side conductive agent on the working electrode side base material. The CO ₂ adsorbent, the working electrode side conductive agent, and the working electrode side binder are provided inside the porous working electrode side base material.

The counter electrode has a similar configuration to the working electrode. The counter electrode includes a counter electrode side active material. The counter electrode side active material is an auxiliary electroactive species whose redox state is opposite to that of the CO ₂ adsorbent, and which exchanges electrons with the CO ₂ adsorbent. As the counter electrode side active material, for example, a metal complex that enables transfer of electrons by changing the valence of metal ions can be used.

Note that the counter electrode includes a counter electrode side base material, a counter electrode side conductive agent, and a counter electrode side binder in addition to the counter electrode side active material. For the counter electrode side base material, the counter electrode side conductive agent, and the counter electrode side binder, the same material as that used for the working electrode may be used, or different materials may be used.

An insulating layer is placed between the working electrode and the counter electrode. An insulating layer separates the working and counter electrodes. The insulating layer prevents physical contact between the working and counter electrodes. Further, the insulating layer suppresses electrical short circuit between the working electrode and the counter electrode. A separator or a gas layer such as air can be used as the insulating layer.

The ion conductive member is provided between the working electrode and the counter electrode. Specifically, the ion conductive member is provided between the working electrode side base material and the counter electrode side base material with an insulating layer interposed therebetween.

The ion conductive member is in contact with the CO ₂ adsorbent inside the base material on the working electrode side. The ion conductive member has ion conductivity. Thereby, the ion conductive member promotes electrical conduction to the CO ₂ adsorbent. The ions contained in the ion conductive member do not directly react with the functional groups that bind to CO ₂ contained in the CO ₂ adsorbent. As the ion conductive member, the same material as the working electrode side binder may be used, or a different material from the working electrode side binder may be used.

The housing 124 is a container that houses the electrochemical cell 121. The housing 125 is a container that houses the electrochemical cell 122. The housing 126 is a container that houses the electrochemical cell 123. Each of the casings 124 to 126 can be hermetically sealed.

The duct section 130 is a device for flowing the atmosphere to each of the recovery vessels 116 to 118. The duct section 130 includes an introduction pipe 131, a first duct opening/closing section 132, a second duct opening/closing section 133, an exhaust pump 134, an oil filter 135, and a _CO2 sensor 136.

The introduction pipe 131 is a pipe for introducing and exhausting the atmosphere into each of the recovery vessels 116 to 118. One end of the introduction pipe 131 is arranged inside the recovery chamber 111. The other end of the introduction pipe 131 is arranged outside the recovery chamber 111.

The first duct opening/closing section 132 is arranged upstream of each of the recovery vessels 116 to 118 in the introduction piping 131. The first duct opening/closing section 132 opens/closes the upstream side of the introduction pipe 131 according to commands from the control section 180 . The second duct opening/closing section 133 is arranged downstream of each of the recovery vessels 116 to 118 in the introduction piping 131. The second duct opening/closing section 133 opens and closes the downstream side of the introduction pipe 131 according to commands from the control section 180 .

The first duct opening/closing part 132 and the second duct opening/closing part 133 are arranged inside the collection chamber 111 . The first duct opening/closing part 132 and the second duct opening/closing part 133 are, for example, valves that open or block the passage of the introduction pipe 131. Note that each of the casings 124 to 126 of each recovery device 116 to 118 may be configured as a part of the introduction pipe 131.

The exhaust pump 134 is arranged downstream of the second duct opening/closing section 133 in the introduction piping 131 . The exhaust pump 134 is arranged outside the recovery chamber 111. The exhaust pump 134 generates a flow of air in the introduction pipe 131, thereby causing the air to pass through each of the recovery vessels 116 to 118. The exhaust pump 134 is, for example, a dry pump.

The oil filter 135 is arranged downstream of the exhaust pump 134 in the introduction pipe 131. The oil filter 135 blocks passage of oil leaking from the oil-type exhaust pump 134. Note that a blower fan may be used instead of the exhaust pump 134. In this case, the oil filter 135 is not necessary.

The CO ₂ sensor 136 is arranged downstream of the oil filter 135 in the introduction pipe 131 . The CO ₂ sensor 136 detects the concentration of CO ₂ contained in the atmosphere discharged from each recovery device 116 to 118, and outputs the detection result to the control unit 180.

The scavenging unit 140 scavenges the inside of each of the casings 124 to 126 of each recovery device 116 to 118 in a state in which the electrochemical cells 121 to 123 have adsorbed CO ₂ and in a state in which the casings 124 to 126 are sealed. It is a device for In other words, the scavenging section 140 evacuates the inside of each of the casings 124 to 126.

Here, the state in which each of the casings 124 to 126 is sealed is a state in which atmospheric air is not introduced into each of the casings 124 to 126 through at least the duct portion 130. In order for the scavenging unit 140 to scavenge the inside of each of the casings 124 to 126, it is necessary that each of the sealed casings 124 to 126 and the scavenging unit 140 are connected. Similarly, in order to collect CO ₂ from each of the collectors 116 to 118 to the collection unit 150, each of the sealed casings 124 to 126 and the collection unit 150 must be connected. be.

The scavenging section 140 includes a scavenging pipe 141, a scavenging opening/closing section 142, a first scavenging pump 143, a second scavenging pump 144, and an oil filter 145.

The scavenging pipe 141 is a pipe that connects the inside and outside of each of the casings 124 to 126. One end of the scavenging pipe 141 is connected to each of the casings 124 to 126. The other end of the scavenging pipe 141 is arranged outside the recovery chamber 111. As a result, the inside of each of the casings 124 to 126 is connected to the outside of the recovery chamber 111 via the scavenging pipe 141. A part of the scavenging pipe 141 branches and joins again. That is, part of the scavenging pipe 141 has two pipes.

The scavenging opening/closing section 142 opens and closes the scavenging piping 141 according to commands from the control section 180. The scavenging opening/closing section 142 is, for example, a valve that opens or blocks the passage of the scavenging pipe 141. The scavenging opening/closing section 142 is, for example, a three-way valve. The scavenging opening/closing section 142 opens and closes the scavenging piping 141 on the side of each of the casings 124 to 126 in accordance with commands from the control section 180. Further, the scavenging opening/closing unit 142 returns the vacuum state inside the collection chamber 111 to the atmosphere according to a command from the control unit 180.

The first scavenging pump 143 and the second scavenging pump 144 are arranged downstream of the scavenging opening/closing section 142 in the scavenging piping 141 . Each scavenging pump 143, 144 is arranged outside the recovery chamber 111. The scavenging pumps 143 and 144 are respectively arranged in the branched pipes of the scavenging pipe 141. Each of the scavenging pumps 143 and 144 scavenges the inside of each of the casings 124 to 126 by generating a gas flow in the scavenging pipe 141. Since the two scavenging pumps 143 and 144 perform scavenging, the scavenging capacity can be increased compared to the case with one scavenging pump. Each of the scavenging pumps 143 and 144 is, for example, an oil pump.

The oil filter 145 is arranged downstream of each of the scavenging pumps 143 and 144 in the scavenging piping 141 . The oil filter 145 blocks passage of oil leaking from each of the oil-type scavenging pumps 143 and 144. Note that if dry pumps are employed as the scavenging pumps 143 and 144, the oil filter 135 is not necessary.

The collection unit 150 is a device for collecting CO ₂ collected in each of the collection vessels 116 to 118. The collection section 150 includes a tank 151, a collection pipe 152, a collection opening/closing section 153, a vacuum filter 154, and a collection pump 155.

The tank 151 is a device for storing the CO ₂ recovered in each of the recovery vessels 116 to 118. The tank 151 collects CO ₂ from each of the collectors 116 to 118 via collection piping 152. Note that the tank 151 may be a factory or device that uses CO ₂ .

The collection pipe 152 is a pipe that connects the tank 151 with the inside of each of the casings 124 to 126. 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 be independently connected to each of the casings 124 to 126. The other end of the collection pipe 152 is connected to the tank 151.

The collection opening/closing section 153 is provided on the side of each of the casings 124 to 126 of the collection piping 152. The collection opening/closing section 153 is arranged inside the collection chamber 111. The collection opening/closing section 153 opens and closes the collection piping 152 on the side of each of the casings 124 to 126 in accordance with commands from the control section 180. The collection opening/closing part 153 is, for example, a valve that opens or blocks the passage of the collection pipe 152.

The vacuum filter 154 is a filter for removing moisture, dust, etc. contained in the gas sucked by the collection pump 155 when the pressure in each of the recovery vessels 116 to 118 is reduced. The vacuum filter 154 is arranged downstream of the collection opening/closing section 153 in the collection piping 152 .

The collection pump 155 is a dry pump for drawing CO ₂ collected in each of the collection vessels 116 to 118 into the tank 151. The collection pump 155 is arranged downstream of the vacuum filter 154 in the collection piping 152. The collection pump 155 is arranged, for example, on the wall of the collection chamber 111.

Pressure sensor 160 is a sensor for detecting the internal pressure of each housing 124-126 of each recovery device 116-118. The pressure sensor 160 is provided, for example, at one end of the scavenging pipe 141. Pressure sensor 160 outputs a detection signal to control section 180.

The power supply section 170 is a power supply device of the carbon dioxide recovery system 100. The power supply unit 170 supplies power to the recovery unit 110, the duct unit 130, the scavenging unit 140, the collection unit 150, and the pressure sensor 160 according to instructions from the control unit 180.

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 .

The first power unit 171 and the second power unit 172 reduce 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 device 116 to 118 according to a command from the control unit 180. change.

The first power unit 171 generates an adsorption voltage for adsorbing CO ₂ in each electrochemical cell 121 to 123. The attraction voltage is, for example, a positive voltage. The second power unit 172 is a desorption voltage for desorbing CO ₂ from each electrochemical cell 121-123. The desorption voltage is, for example, a negative voltage. The detachment voltage generated by the second power unit 172 is a voltage in opposite phase to the attraction voltage generated by the first power unit 171.

Note that if it is possible to generate an adsorption voltage and a desorption voltage with a phase opposite to the adsorption voltage, and also to supply each voltage to each electrochemical cell 121 to 123 at different timings, the power unit can A stand is fine.

Each of the drivers 173 to 175 is a switch device for turning ON or OFF energization of each of the power units 171 and 172 and each of the electrochemical cells 121 to 123 according to a command from the control unit 180.

For example, the first driver 173 does not turn on each of the power units 171 and 172 and the electrochemical cell 121 at the same time, but turns on one of the power units 171 and 172 and the electrochemical cell 121. The same applies to the second driver 174 and the third driver 175.

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

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

For example, the control unit 180 controls the power supply unit 170 to apply an adsorption voltage to each of the electrochemical cells 121 to 123, thereby performing an adsorption step in which CO ₂ is adsorbed to each of the electrochemical cells 121 to 123. Further, the control unit 180 controls the power supply unit 170 to apply a desorption voltage to each of the electrochemical cells 121 to 123, thereby performing a desorption step of desorbing CO ₂ from each of the electrochemical cells 121 to 123. .

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

Next, the operation of the carbon dioxide recovery system 100 will be explained. The control unit 180 executes an adsorption process, a scavenging process, a desorption process, and a recovery process for each electrochemical cell 121 to 123. The process from the adsorption process to the recovery process is one cycle. The control unit 180 performs control to repeat the cycle.

Each process of the electrochemical cell 121 of the recovery device 116 will be explained below. The contents of each step are the same for the other electrochemical cells 122 and 123.

First, the control unit 180 performs an adsorption process in which the electrochemical cell 121 adsorbs CO ₂ . As shown in FIG. 2, the control section 180 controls the collection opening/closing section 153 and the scavenging opening/closing section 142 to the closed state. The control unit 180 controls each of the scavenging pumps 143 and 144 and the collecting pump 155 to be in an OFF state.

Further, the control unit 180 controls the first duct opening/closing part 132 and the second duct opening/closing part 133 to be open, and controls the recovery chamber pump 113 and the exhaust pump 134 to be in the ON state. As a result, the atmosphere is supplied to the electrochemical cell 121 of the recovery device 116. Therefore, as shown in FIG. 3, the pressure inside the housing 124 becomes atmospheric pressure P0 at time t1.

The control unit 180 turns on the power between the first power unit 171 and the electrochemical cell 121 and turns off the power between the second power unit 172 and the electrochemical cell 121 in the first driver 173 . Thereby, the adsorption voltage of the first power unit 171 is applied between the working electrode and the counter electrode of the electrochemical cell 121. Therefore, electron donation by the counter electrode side active material of the counter electrode and electron withdrawal by the CO ₂ adsorbent of the working electrode can be simultaneously realized. Note that the first driver 173 is omitted in FIG. 2.

When an adsorption voltage is applied between the working electrode and the counter electrode, the active material on the opposite electrode side of the counter electrode emits electrons and becomes an oxidized state, and the electrons are supplied from the counter electrode to the working electrode. The CO ₂ adsorbent at the working electrode receives electrons and becomes reduced.

The CO ₂ adsorbent in the reduced state has a high CO ₂ binding strength, and binds and adsorbs CO ₂ contained in the atmosphere. In this way, in the electrochemical cell 121, when an adsorption voltage is applied between the working electrode and the counter electrode, electrons are supplied from the counter electrode to the working electrode, and the CO ₂ adsorbent is supplied with electrons. and combines with _CO2 . Therefore, the collector 116 can recover CO ₂ from the atmosphere.

After the atmospheric CO ₂ is collected in the collector 116 , the CO ₂ -free atmosphere is exhausted from the collector 116 . The control unit 180 ends the adsorption process based on the concentration difference between the CO ₂ sensors 112 and 136, for example.

After the adsorption process, the control unit 180 performs a scavenging process to scavenge the inside of the casing 124 of the recovery device 116. As shown in FIG. 4, the control unit 180 controls the exhaust pump 134 and the collection pump 155 in a state in which CO ₂ is adsorbed in the electrochemical cell 121, that is, in a state in which an adsorption voltage is applied to the electrochemical cell 121. Control to OFF state.

Further, the control unit 180 controls the first duct opening/closing part 132, the second duct opening/closing part 133, and the collection opening/closing part 153 to close each state. Then, the control unit 180 controls the scavenging opening/closing unit 142 to be open, and controls the recovery chamber pump 113 and each of the scavenging pumps 143 and 144 to be in the ON state.

Thereby, the inside of the casing 124 of the recovery device 116 is scavenged via the scavenging pipe 141. The inside of the housing 124 becomes negative pressure. Therefore, as shown in FIG. 3, the pressure inside the housing 124 decreases to the ultimate removal pressure P1. The control unit 180 ends the scavenging process at a time point t2 when the internal pressure of the housing 124 reaches the ultimate removal pressure P1.

After the scavenging process, the control unit 180 performs a desorption process to desorb the CO ₂ adsorbed by the electrochemical cell 121. As shown in FIG. 5, the control unit 180 turns off the exhaust pump 134, the collection pump 155, and the scavenging pumps 143 and 144 while the electrochemical cell 121 is adsorbing _CO2 . to control. The control unit 180 controls the recovery chamber pump 113 to be in an ON state. Note that the control unit 180 may control the recovery chamber pump 113 to be in an OFF state.

Further, 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 a closed state.

Then, the control unit 180 turns off the energization between the first power unit 171 and the electrochemical cell 121 in the first driver 173, and turns on the energization between the second power unit 172 and the electrochemical cell 121. Thereby, the desorption voltage of the second power unit 172 is applied between the working electrode and the counter electrode of the electrochemical cell 121. Therefore, electron donation by the CO ₂ adsorbent of the working electrode and electron withdrawal by the counter electrode side active material can be simultaneously realized.

The CO ₂ adsorbent at the working electrode emits electrons and becomes oxidized. The CO ₂ adsorbent has a reduced binding force for CO ₂ and desorbs and releases CO ₂ . The active material on the opposite electrode side receives electrons and becomes a reduced state.

In this way, CO ₂ is desorbed from the electrochemical cell 121. CO ₂ is released into the interior of the housing 124 . Therefore, as shown in FIG. 3, at the end time t3 of the desorption process, the pressure inside the casing 124 rises to the ultimate desorption pressure P2.

After the desorption step, the control unit 180 performs a recovery step of collecting the CO ₂ desorbed from the electrochemical cell 121. As shown in FIG. 6, the control unit 180 controls the first duct opening/closing unit 132, the second duct opening/closing unit 133, and the scavenging opening/closing unit 142 in a state in which CO ₂ is desorbed from the electrochemical cell 121. are controlled to their respective closed states. Further, the control unit 180 controls the exhaust pump 134 and each scavenging pump 143, 144 to be in an OFF state.

Then, the control unit 180 controls the collection opening/closing unit 153 to be in an open state, and controls the collection pump 155 to be in an ON state. As a result, CO ₂ released from the CO ₂ adsorbent is discharged from the recovery device 116 and collected in the tank 151 via the collection pipe 152 .

While CO ₂ is being collected in the tank 151, the collection pump 155 is operating. Therefore, as shown in FIG. 3, the pressure inside the casing 124 decreases to the ultimate recovery pressure P3. After the recovery process, the adsorption process begins, and the pressure inside the housing 124 returns to atmospheric pressure P0 at time t4. In this way, one cycle ends. The control unit 180 repeatedly executes the above cycle.

In this embodiment, three collectors 116 to 118 are grouped. In other words, the three electrochemical cells 121 to 123 are treated as one set. That is, the power supply unit 170 is shared by the three electrochemical cells 121 to 123 that are grouped together.

Then, the control unit 180 controls the timing of applying the adsorption voltage in the adsorption process of at least one of the three electrochemical cells 121 to 123 to the adsorption process of the other electrochemical cells 121 to 123. The timing is controlled to be different from the timing at which the adsorption voltage is applied in the process.

In this embodiment, as shown in FIG. 7, the control unit 180 starts the next adsorption process for the electrochemical cells 121-123 after the current adsorption process for the electrochemical cells 121-123 is completed. .

Note that, for example, the timing of starting the adsorption process is the timing of applying the adsorption voltage in the adsorption process. Since the timing for applying the attraction voltage may be within the attraction process, the timing for applying the attraction voltage may be after the control of the valve is completed.

For example, at time T10, the control unit 180 starts the adsorption process of the electrochemical cell 121. As a result, time T11 becomes the timing of the peak current flowing through 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.

Then, at time T12, the control unit 180 ends the adsorption process of the electrochemical cell 121 and starts the scavenging process. Further, the control unit 180 starts the adsorption process of the electrochemical cell 122.

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 off the power supply between the first power unit 171 and the electrochemical cell 122. Turn on. Since the first power unit 171 continues to generate the attraction voltage, the attraction voltage of the first power unit 171 can be used continuously. Similarly, the second power unit 172 continues to generate a desorption voltage.

Therefore, time T13 is the timing of the peak current flowing through the power supply unit 170 during the adsorption process of the electrochemical cell 122. The peak current at time T13 is the current for one electrochemical cell 122. After this, the peak current decreases. Note that since each of the electrochemical cells 121 to 123 has the same configuration, the magnitude of the peak current flowing through each of the electrochemical cells 121 to 123 is also the same.

At time T14, the control unit 180 ends 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 between the second power unit 172 and the electrochemical cell 121. As a result, a desorption voltage having a phase opposite to the adsorption voltage is applied to the electrochemical cell 121. That is, a current flows in the electrochemical cell 121 in the opposite direction to that during the adsorption process.

By applying a desorption voltage to the electrochemical cell 121, CO ₂ is desorbed from the electrochemical cell 121. Then, time T15 is the timing of the peak current flowing through the power supply unit 170 during the desorption process of the electrochemical cell 121.

At time T16, the control unit 180 ends the adsorption process of the electrochemical cell 122 and starts the scavenging process. Further, the control unit 180 starts the adsorption process of the electrochemical cell 123. Therefore, time T17 is the timing of the peak current flowing through 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.

At time T18, the control unit 180 ends the desorption process of the electrochemical cell 121 and starts the recovery process.

At time T19, the control unit 180 ends the scavenging process of the electrochemical cell 122 and starts the desorption process. Therefore, time T20 is the timing of the peak current flowing through 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.

At time T21, the control unit 180 ends the recovery process of the electrochemical cell 121 and starts the adsorption process again. At time T21, the adsorption step of the electrochemical cell 123 is being performed. 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.

After time T21, the control unit 180 repeats each process for each electrochemical cell 121 to 123 in the same way as after time T10. In each process of each electrochemical cell 121 to 123, the current value during the period when the adsorption process overlaps or the period when the desorption process overlaps is the sum value, so the peak current is slightly less than that for one electrochemical cell 121 to 123. growing. For example, the period from time T23 to time T24 is a period in which the desorption process of the electrochemical cell 121 and the desorption process of the electrochemical cell 123 overlap, and the peak current is the summed value.

Here, a comparison will be made with the peak current when the adsorption voltages are applied at the same time in each adsorption step of the three electrochemical cells 121 to 123. As shown in FIG. 8, at time T30, the control unit 180 simultaneously starts the adsorption process for each of the electrochemical cells 121 to 123.

As a result, time T31 becomes the timing of the peak current flowing through the power supply unit 170 during the adsorption process of each electrochemical cell 121 to 123. Therefore, the value of the peak current at time T31 becomes the total value of the peak currents for the three electrochemical cells 121 to 123, and the wiring between the first power unit 171 and each driver 173 to 175 A large current will flow.

At time T32, the control unit 180 simultaneously starts the scavenging process for each of the electrochemical cells 121 to 123. Then, at time T33, the control unit 180 simultaneously starts the desorption process for each of the electrochemical cells 121 to 123. Therefore, the control unit 180 simultaneously turns off the power supply to the first power unit 171 and each of the electrochemical cells 121 to 123. In addition, the control unit 180 turns on electricity between the second power unit 172 and each of the electrochemical cells 121 to 123.

As a result, a desorption voltage having an opposite phase to the adsorption voltage is simultaneously applied to each electrochemical cell 121 to 123, so that a current in the opposite direction to the adsorption process is applied to the second power unit 172 and each driver 173 to 175. flowing between. Then, time T34 is the timing of the peak current flowing through the power supply section 170 during the desorption process. Therefore, the value of the peak current at time T34 becomes the total value of the peak current for three electrochemical cells 121 to 123, and the wiring between the second power unit 172 and each driver 173 to 175 A large current will flow.

At time T35, the control unit 180 simultaneously starts the recovery process for each of the electrochemical cells 121-123. Further, after time T36, the control unit 180 repeats each process for each electrochemical cell 121 to 123 in the same manner as after time T30. In the above cycle, a large current flows at time T31 and time T34.

On the other hand, in the present embodiment, the timing of the peak current flowing during the adsorption process of one electrochemical cell 121 among the electrochemical cells 121 to 123 and the peak current flowing during the adsorption process of the other electrochemical cells 122 and 123 are determined. The timing of the current is out of sync. Therefore, when viewed in terms of the grouping of electrochemical cells 121 to 123, the peak current flowing through power supply section 170 can be made smaller than when the adsorption voltage is applied to each electrochemical cell 121 to 123 at the same time. That is, the maximum current can be smoothed.

As described above, the scale of the equipment of the power supply section 170 can be reduced. In other words, the power supply capacity can be reduced in size. Furthermore, the copper wires and connectors that constitute the power supply section 170 can be downsized.

Furthermore, since the timings of the adsorption steps in each of the electrochemical cells 121 to 123 are staggered, the power source of each power unit 171 and 172 can always be used. For example, when the adsorption steps of the electrochemical cells 121 to 123 are performed at the same time, the power source of the first power unit 171 is not used during the period from time T33 to time T36, as shown in FIG. However, if the adsorption steps of the electrochemical cells 121 to 123 have different timings, the power source of the first power unit 171 can be used continuously, as shown in FIG. Therefore, power supply efficiency can be increased.

Furthermore, since the operations of the duct section 130, scavenging section 140, and collection section 150 common to each of the recovery units 116 to 118 are distributed, the load on each section can be distributed.

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" of the claims.

(Second embodiment)
In this embodiment, mainly differences from the first embodiment will be explained. In this embodiment, the control unit 180 determines the current value of the current flowing in the adsorption step currently being executed and the current value of the current flowing in the adsorption process among the plurality of electrochemical cells 121 to 123, based on the current value acquired from each current probe 176, 177. The maximum value of the current in the next adsorption step is added up. Then, when the total value of the currents is equal to or less than a predetermined current value, the control unit 180 starts applying the adsorption voltage to the electrochemical cells 121 to 123 scheduled for the next adsorption step. 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.

Specifically, as shown in FIG. 9, when the cycle of the carbon dioxide recovery system 100 is started from time T50, a peak current flows between the first power unit 171 and the electrochemical cell 121 at the timing of time T50. . This becomes the current value of the current flowing in the adsorption step of the electrochemical cell 121 that is currently being executed.

The control unit 180 determines the current value of the current flowing through the power supply unit 170 in the currently executed adsorption process and the current value that flowed through the power supply unit 170 during the previous adsorption process in the electrochemical cell 122 scheduled for the next adsorption process. Add up the maximum value and. The maximum value of the current in each electrochemical cell 121 to 123 is the peak current value at time T50. Then, when the sum of the current value and the maximum value of the current is equal to or less than the current criterion, the control unit 180 starts applying the adsorption voltage to the electrochemical cells 121 to 123 scheduled for the next adsorption step. . The current criterion is an arbitrary value that takes a safety margin for the power output, and is a predetermined current value.

At time T50, the adsorption process of the electrochemical cell 121 begins, and the peak current related to the electrochemical cell 121 decreases. Along with this, the sum of the current value of the current currently flowing through the electrochemical cell 121 and the maximum value of the current flowing during the previous adsorption process in the electrochemical cell 122 scheduled for the next adsorption process is calculated. It's getting smaller. Then, at time T51, the total value of the currents becomes less than or equal to the current criterion. That is, the total value is less than the current criterion. Therefore, the control unit 180 starts the adsorption process of the electrochemical cell 122 at time T51.

Similarly, after time T51, the total current value decreases, and at time T52, the total current value becomes less than or equal to the current criterion. Therefore, the control unit 180 starts the adsorption process of the electrochemical cell 123 at time T52. The same holds true after time T53.

As described above, the control unit 180 estimates the total value of the currents using the maximum value of the currents that flowed through the power supply unit 170 during the previous adsorption process. In other words, the control unit 180 estimates the total current value from the previous cycle. In this manner, the control unit 180 may control the start timing of the adsorption process in each of the electrochemical cells 121 to 123 based on the estimated value of the current value.

In addition, in combination with the first embodiment, the control unit 180 starts the next adsorption process after the previous adsorption process ends, and also starts the next adsorption process when the total value of the current is equal to or less than the current criterion. It may also be controlled.

(Other embodiments)
The configuration of the carbon dioxide recovery system 100 shown in each of the embodiments described above is an example, and the configuration is not limited to the configuration shown above, and other configurations that can realize the present invention may be used. For example, the CO ₂ -containing gas is not limited to the atmosphere, and any gas containing CO ₂ may be used.

The grouping of each electrochemical cell 121 to 123 is not limited to three. It is sufficient that two or more electrochemical cells 121 to 123 are grouped together. Furthermore, the number of groupings is not limited to one. For example, the carbon dioxide recovery system 100 may include multiple groupings. At this time, the number of electrochemical cells 121 to 123 included in each grouping may be different. The power supply section 170 may be provided for each of the plurality of grouped electrochemical cells 121 to 123.

Further, the carbon dioxide recovery system 100 does not need to include the duct part 130. For example, the casings 124 to 126 of each of the collectors 116 to 118 may be provided with an openable/closable door for taking in the atmosphere and for sealing. In this case, the collection chamber 111 becomes unnecessary. When carbon dioxide capture system 100 is installed outdoors, natural wind passes through the interior of enclosures 124-126.

121-123 Electrochemical cell 170 Power supply section 171, 172 Power unit 173-175 Driver 176, 177 Current probe 180 Control section

Claims (3)

an electrochemical cell (121 to 123) that recovers the CO ₂ by adsorbing _the CO ₂ from a CO 2 -containing gas containing CO ₂ ;
a power supply unit (170) connected to the electrochemical cell;
a control unit (180) that performs an adsorption step of adsorbing the CO ₂ to the electrochemical cell by controlling the power supply unit and applying an adsorption voltage to the electrochemical cell;
including;
A plurality of the electrochemical cells are provided and are grouped,
The control unit may set the timing of applying the adsorption voltage in the adsorption process of at least one electrochemical cell of the plurality of electrochemical cells to the timing of applying the adsorption voltage in the adsorption process of another electrochemical cell. Carbon dioxide recovery system controlled at different timings. The power supply section detects a current value flowing between the power supply section and the plurality of electrochemical cells,
Based on the current value, the control unit adds up the current value of the current flowing in the currently executed adsorption process and the maximum value of the current in the next adsorption process among the plurality of electrochemical cells, and also controls the current value. The carbon dioxide recovery system according to claim 1, wherein when the total value of the adsorption voltage is equal to or less than a predetermined current value, application of the adsorption voltage to the electrochemical cell scheduled for the next adsorption step is started. The carbon dioxide recovery system according to claim 1 or 2, wherein the control unit starts the adsorption process of the next electrochemical cell after the adsorption process of the current electrochemical cell is completed.

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