Carbon dioxide recovery system

Abstract

To suppress an amount of gas containing carbon dioxide to be discharged to outside.SOLUTION: A carbon dioxide recovery system includes a recycling part capable of adjusting a supply amount of regeneration tower discharge gas on a recycle line for connecting a regeneration tower discharge line to discharge regeneration tower discharge gas to outside, and a treatment object gas line to introduce treatment object gas into an absorption tower. The recycling part has a first recycling line capable of supplying the regeneration tower discharge gas before compressed by a discharge compressor, and a second recycling line capable of supplying the regeneration tower discharge gas compressed by the discharge compressor. A control part of the recycling part opens a first recycling valve, when a value of a pressure acquired by a first pressure acquisition part exceeds a pressure reference, and blocks the first recycling valve when the value is lower than the pressure reference. The control part opens a second recycling valve when a value of a pressure acquired by a second pressure acquisition part exceeds the pressure reference, and blocks the second recycling valve when the value is lower than the pressure reference.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to carbon dioxide capture systems. [Background technology]

[0002] In recent years, from the perspective of carbon neutrality, the amount of carbon dioxide (CO 2 ) is attracting attention. From the perspective of lowering the concentration of carbon dioxide in the atmosphere, carbon dioxide capture systems that capture carbon dioxide from flue gas are known. In carbon dioxide capture systems, an absorbing liquid is circulated between a regenerator and an absorber to capture carbon dioxide from flue gas.

[0003] For example, Patent Document 1 describes a carbon dioxide capture system capable of responding to abrupt changes in the carbon dioxide concentration and gas flow rate of a gas to be treated that contains carbon dioxide. This carbon dioxide capture system includes an absorption tower that absorbs carbon dioxide with an absorption liquid, and a regeneration tower that removes carbon dioxide from the absorption liquid and returns it to the absorption tower. The absorption tower brings the gas to be treated into contact with the absorption liquid. As a result, the absorption tower discharges the absorption liquid that has absorbed carbon dioxide and the absorption tower exhaust gas that contains the gas to be treated from which carbon dioxide has been removed. In addition, the regeneration tower dissipates carbon dioxide from the absorption liquid discharged from the absorption tower. As a result, the regeneration tower discharges the absorption liquid from which carbon dioxide has been dissipated and the regeneration tower exhaust gas that contains carbon dioxide. Furthermore, the carbon dioxide capture system of Patent Document 1 further includes a first introduction mechanism that introduces a first gas having a higher carbon dioxide concentration than the gas to be treated into a gas line to be treated for introducing the gas to be treated into the absorption tower, and a second introduction mechanism that introduces a second gas having a lower carbon dioxide concentration than the gas to be treated into the gas line to be treated. By supplying gases with different carbon dioxide concentrations in this way, the carbon dioxide capture system of Patent Document 1 can handle sudden changes in the carbon dioxide concentration and gas flow rate of the gas to be treated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6148522 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned carbon dioxide capture system, it is necessary to control the concentration of carbon dioxide supplied to the absorption tower. Therefore, in order to maintain the concentration of carbon dioxide, the system is operated to constantly recycle carbon dioxide from the outlet of the regeneration tower, which consumes unnecessary energy.

[0006] The present disclosure has been made to address the above-mentioned needs, and aims to provide a carbon dioxide capture system that can adjust the amount of carbon dioxide returned from the regeneration tower to the absorption tower, thereby reducing emissions to the outside. [Means for solving the problem]

[0007] In order to solve the above problems, the carbon dioxide capture system according to the present disclosure includes an absorption tower that brings a gas to be treated containing carbon dioxide into contact with an absorption liquid and discharges the absorption liquid that has absorbed the carbon dioxide and an absorption tower exhaust gas containing the gas to be treated from which the carbon dioxide has been removed, a regeneration tower that dissipates the carbon dioxide from the absorption liquid discharged from the absorption tower and discharges the absorption liquid from which the carbon dioxide has been dissipated and a regeneration tower exhaust gas containing the carbon dioxide, a gas to be treated line that introduces the gas to be treated into the absorption tower, and a regeneration tower exhaust gas containing the gas to be treated. a regenerator discharge line that discharges gas to the outside, a discharge compressor that is disposed on the regenerator discharge line and that compresses the regenerator discharge gas, a recycle line that connects the regenerator discharge line and the target gas line, and a recycle unit that is capable of adjusting a supply amount of the regenerator discharge gas that is supplied from the regenerator discharge line through the recycle line to the target gas line, wherein the recycle unit is connected to the regenerator discharge line between the regenerator and the discharge compressor, and compresses at least a portion of the regenerator discharge gas before being compressed by the discharge compressor into the regenerator discharge line. a first recycle line capable of supplying the regenerator discharge gas to a gas line to be treated, and a second recycle line capable of supplying at least a portion of the regenerator discharge gas compressed by the discharge compressor to the gas line to be treated, the recycle unit having a first recycle valve disposed on the first recycle line and capable of adjusting the amount of the regenerator discharge gas supplied from the regenerator discharge line to the gas line to be treated, a first pressure acquisition unit acquiring information on the pressure of the regenerator discharge gas flowing through the regenerator discharge line between the regenerator and the discharge compressor, a second recycle valve disposed on the second recycle line and capable of adjusting the amount of the regenerator discharge gas supplied from the regenerator discharge line to the gas line to be treated, a second pressure acquisition unit acquiring information on the pressure of the regenerator discharge gas compressed by the discharge compressor and flowing through the regenerator discharge line, and a control unit controlling the opening degree of the first recycle valve and the second recycle valve, the control unit opening the first recycle valve when the pressure value acquired by the first pressure acquisition unit exceeds a predetermined pressure standard, and closing the first recycle valve when the pressure value falls below the pressure standard,When the value of the pressure acquired by the second pressure acquisition unit exceeds the pressure standard, the second recycle valve is opened, and when the value of the pressure acquired by the second pressure acquisition unit falls below the pressure standard, the second recycle valve is closed. Effect of the Invention

[0008] According to the carbon dioxide capture system of the present disclosure, the amount of carbon dioxide returned from the regeneration tower to the absorption tower can be adjusted, thereby reducing the amount of carbon dioxide emitted to the outside. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a carbon dioxide capture system according to a first embodiment. [Diagram 2] FIG. 1 is a schematic diagram showing a carbon dioxide capture system according to a second embodiment. [Diagram 3] FIG. 11 is a schematic diagram showing a carbon dioxide capture system according to a third embodiment. [Figure 4] FIG. 13 is a schematic diagram showing a carbon dioxide capture system according to a fourth embodiment. [Diagram 5] FIG. 13 is a schematic diagram showing a carbon dioxide capture system according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the carbon dioxide capture system according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiment.

[0011] First Embodiment (Carbon dioxide capture system) The carbon dioxide recovery system 1 recovers carbon dioxide (CO 2) can be recovered. Examples of exhaust gas sources include boilers, incinerators, gas turbines, and SAF and ethanol manufacturing plants. In other words, examples of gas to be treated include exhaust gas containing carbon dioxide that is finally discharged, and process gas containing carbon dioxide that is used in the course of various plants. As shown in FIG. 1, the gas to be treated supplied from the exhaust gas source is sent to a carbon dioxide recovery system 1.

[0012] The carbon dioxide capture system 1 of this embodiment includes an absorption tower 2, a gas line 11 to be treated, a compression section 21, a regeneration tower 3, a rich line 13, a lean line 14, an absorption liquid heat exchanger 4, a regeneration tower discharge line 15, a discharge compressor 5, a recycle line 60, and a recycle section 70.

[0013] A gas to be treated that contains carbon dioxide is introduced into the absorption tower 2. The absorption tower 2 removes carbon dioxide from the gas to be treated by contacting the gas to be treated with an absorbing liquid. An example of the absorbing liquid is an amine-based solution. The absorption tower 2 separately discharges the absorbing liquid that has absorbed the carbon dioxide and the absorption tower exhaust gas that contains the gas to be treated from which the carbon dioxide has been removed.

[0014] The gas to be treated line 11 introduces the gas to be treated into the absorption tower 2. The gas to be treated line 11 cools the gas to be treated sent from the exhaust gas source in a cooling device (not shown) and then sends the gas to be treated to the absorption tower 2. The gas to be treated line 11 is connected to the absorption tower 2.

[0015] The pressure-feeding unit 21 is disposed in the target gas line 11. The pressure-feeding unit 21 is a blower that pressure-feeds the target gas to be introduced into the absorption tower 2. The pressure-feeding unit 21 increases the pressure of the target gas after cooling to an arbitrary pressure required for treatment in the absorption tower 2.

[0016] The absorber discharge line 12 discharges the absorber exhaust gas discharged from the absorber 2 to the outside. The absorber discharge line 12 is connected to the top of the absorber 2.

[0017] The regenerator 3 strips carbon dioxide from the absorption liquid discharged from the absorption tower 2. The regenerator 3 heats the absorption liquid using the reboiler 31. As a result, in the regenerator 3, most of the carbon dioxide is stripped from the absorption liquid together with the steam, and the carbon dioxide is separated from the absorption liquid. High-temperature steam is supplied to the reboiler 31. In the reboiler 31, the absorption liquid is heated by heat exchange between the steam and the absorption liquid. The regenerator 3 separately discharges the absorption liquid from which the carbon dioxide has been stripped and the regenerator exhaust gas containing carbon dioxide.

[0018] The rich line 13 supplies the absorbing liquid that has absorbed carbon dioxide from the absorption tower 2 to the regeneration tower 3. Here, the absorbing liquid discharged from the absorption tower 2 and flowing through the rich line 13 is called the rich liquid. The rich liquid is an absorbing liquid with a high concentration of carbon dioxide after absorbing carbon dioxide in the absorption tower 2. The rich line 13 connects the bottom of the absorption tower 2 and the top of the regeneration tower 3. A rich pump 35 is arranged in the rich line 13. The rich pump 35 pressurizes the rich liquid and sends it to the regeneration tower 3 via the absorption liquid heat exchanger 4.

[0019] The lean line 14 supplies the absorbing liquid from which carbon dioxide has been stripped to the absorbing tower 2 from the regenerator 3. Here, the absorbing liquid discharged from the regenerator 3 and flowing through the lean line 14 is called the lean liquid. The lean liquid is an absorbing liquid with a low concentration of carbon dioxide after carbon dioxide has been stripped in the regenerator 3. In other words, the lean liquid has a lower concentration of carbon dioxide than the rich liquid. The lean line 14 connects the bottom of the regenerator 3 to the top of the absorbing tower 2. A lean pump 37 and a cooler 38 are arranged in the lean line 14. The lean pump 37 pressurizes the lean liquid and sends it to the absorbing tower 2 via the absorbing liquid heat exchanger 4. The cooler 38 further cools the absorbing liquid cooled in the absorbing liquid heat exchanger 4 and sends it to the absorbing tower 2.

[0020] The absorbing liquid heat exchanger 4 exchanges heat between the rich liquid flowing through the rich line 13 and the lean liquid flowing through the lean line 14. As a result, in the absorbing liquid heat exchanger 4, the absorbing liquid flowing through the rich line 13 in a state where the pressure has been increased by the rich pump 35 so as to travel from the absorption tower 2 to the regeneration tower 3 is heated. Also, in the absorbing liquid heat exchanger 4, the absorbing liquid flowing through the lean line 14 in a state where the pressure has been increased by the lean pump 37 so as to travel from the regeneration tower 3 to the absorption tower 2 is cooled.

[0021] The regenerator discharge line 15 discharges the regenerator exhaust gas discharged from the regenerator 3 to the outside (outside the system) of the carbon dioxide capture system 1. The regenerator discharge line 15 is connected to the top of the regenerator 3. The regenerator discharge line 15 transports the regenerator exhaust gas to an external destination according to the intended use. The regenerator exhaust gas discharged from the regenerator discharge line 15 is transferred to a state according to the intended use, for example, and is stored in a tank, a lorry, a pipeline, inside an oil field, an aquifer, or the like.

[0022] The discharge compressor 5 is disposed in the regenerator discharge line 15. The discharge compressor 5 compresses the regenerator discharge gas. More specifically, the discharge compressor 5 compresses the regenerator discharge gas flowing through the regenerator discharge line 15 until it reaches a state according to the intended use, such as a supercritical state or a liquid state.

[0023] The recycle line 60 is capable of supplying the regenerator exhaust gas to the absorption tower 2. The recycle line 60 connects the regenerator exhaust line 15 and the target gas line 11. The recycle line 60 in this embodiment has a first recycle line 61 and a second recycle line 62.

[0024] The first recycle line 61 is capable of supplying at least a portion of the regeneration tower exhaust gas before being compressed by the discharge compressor 5 to the target gas line 11. The first recycle line 61 is connected to the regeneration tower exhaust line 15 between the regeneration tower 3 and the discharge compressor 5. The first recycle line 61 in this embodiment is connected to the target gas line 11 so as to merge at least a portion of the regeneration tower exhaust gas with the target gas before being supplied to the compression section 21. Therefore, the first recycle line 61 is connected to the target gas line 11 upstream of the compression section 21. In other words, the first recycle line 61 supplies the regeneration tower exhaust gas discharged from the regeneration tower 3 and before being compressed by the discharge compressor 5 to the target gas line 11 before being sent to the compression section 21.

[0025] In this embodiment, the terms "upstream" and "downstream" refer to the upstream and downstream in the flow direction of various gases flowing through the carbon dioxide capture system 1.

[0026] The second recycle line 62 is capable of supplying at least a portion of the regeneration tower discharge gas compressed by the discharge compressor 5 to the target gas line 11. The second recycle line 62 is connected to the regeneration tower discharge line 15 beyond the discharge compressor 5 (downstream of the discharge compressor 5). The second recycle line 62 in this embodiment is connected to the target gas line 11 upstream of the pressure-feeding section 21. More specifically, the second recycle line 62 merges with the first recycle line 61 and is connected to the target gas line 11. As a result, the second recycle line 62 is indirectly connected to the target gas line 11 via the first recycle line 61 so as to merge at least a portion of the regeneration tower discharge gas with the target gas before being supplied to the pressure-feeding section 21. In other words, the second recycle line 62 supplies the regeneration tower discharge gas discharged from the regeneration tower 3 and compressed by the discharge compressor 5 to the target gas line 11 before being sent to the pressure-feeding section 21.

[0027] The recycle unit 70 is capable of adjusting the supply amount of the regenerator exhaust gas supplied from the regenerator discharge line 15 through the recycle line 60 to the gas line 11 to be treated. The recycle unit 70 is capable of adjusting the supply amount of the regenerator exhaust gas returned to the absorption tower 2 from the first recycle line 61 and the second recycle line 62 through the gas line 11 to be treated. The recycle unit 70 of this embodiment has a first recycle valve 71, a first pressure acquisition unit 72, a second recycle valve 73, a second pressure acquisition unit 74, an emission concentration acquisition unit 75, and a control unit 100.

[0028] The first recycle valve 71 is capable of adjusting the amount of regenerator exhaust gas before compression supplied from the regenerator discharge line 15 to the gas to be treated line 11. The first recycle valve 71 is disposed in the first recycle line 61. That is, the first recycle valve 71 adjusts the amount of regenerator exhaust gas before compression by the discharge compressor 5 supplied to the gas to be treated line 11. The first recycle valve 71 in this embodiment is a control valve whose opening and closing is controlled by the control unit 100.

[0029] The first pressure acquisition unit 72 acquires information on the pressure of the regenerator exhaust gas flowing through the regenerator exhaust line 15 between the regenerator 3 and the discharge compressor 5. The first pressure acquisition unit 72 is a pressure gauge arranged in the regenerator exhaust line 15 between the regenerator 3 and the discharge compressor 5. In this way, the first pressure acquisition unit 72 acquires information on the pressure of the regenerator exhaust gas before it is supplied to the discharge compressor 5. The first pressure acquisition unit 72 outputs the acquired information on the pressure of the regenerator exhaust gas to the control unit 100 as a first pressure value.

[0030] The second recycle valve 73 is capable of adjusting the amount of compressed regenerator exhaust gas supplied from the regenerator discharge line 15 to the target gas line 11. The second recycle valve 73 is disposed in the second recycle line 62. That is, the second recycle valve 73 adjusts the amount of compressed regenerator exhaust gas supplied to the target gas line 11. The second recycle valve 73 in this embodiment is a control valve whose opening and closing is controlled by the control unit 100.

[0031] The second pressure acquisition unit 74 acquires information on the pressure of the regenerator discharge gas compressed by the discharge compressor 5 and flowing through the regenerator discharge line 15. The second pressure acquisition unit 74 is a pressure gauge arranged in the regenerator discharge line 15 downstream of the discharge compressor 5. In this way, the second pressure acquisition unit 74 acquires information on the pressure of the regenerator discharge gas after it is supplied to the discharge compressor 5. The second pressure acquisition unit 74 outputs the acquired information on the pressure of the regenerator discharge gas to the control unit 100 as a second pressure value.

[0032] The discharge concentration acquisition unit 75 acquires information on the concentration of carbon dioxide in the regenerator exhaust gas flowing through the regenerator exhaust line 15. The discharge concentration acquisition unit 75 in this embodiment is a concentration meter arranged in the regenerator exhaust line 15 between the regenerator 3 and the discharge compressor 5. In this way, the discharge concentration acquisition unit 75 acquires information on the carbon dioxide concentration of the regenerator exhaust gas before it is supplied to the discharge compressor 5. The discharge concentration acquisition unit 75 outputs the acquired information on the carbon dioxide concentration of the regenerator exhaust gas to the control unit 100 as a concentration value.

[0033] The control unit 100 controls the opening degree of the first recycle valve 71 and the second recycle valve 73. The control unit 100 adjusts the opening degree of the first recycle valve 71 and the second recycle valve 73 based on the information on the pressure of the regeneration tower exhaust gas acquired from the first pressure acquisition unit 72 and the second pressure acquisition unit 74. The control unit 100 of this embodiment opens the first recycle valve 71 when the pressure value acquired by the first pressure acquisition unit 72 exceeds a predetermined pressure standard, and closes the first recycle valve 71 when it falls below the pressure standard. In addition, the control unit 100 opens the second recycle valve 73 when the pressure value acquired by the second pressure acquisition unit 74 exceeds the pressure standard, and closes the second recycle valve 73 when it falls below the pressure standard. In addition, the control unit 100 closes at least one of the first recycle valve 71 and the second recycle valve 73 when the concentration value acquired by the discharge concentration acquisition unit 75 exceeds a predetermined concentration standard. Furthermore, when the concentration falls below the concentration standard, the control unit 100 controls to open at least one of the first recycle valve 71 and the second recycle valve 73. The control unit 100 of this embodiment has an input unit 101, a determination unit 102, a first valve control unit 103, and a second valve control unit 104.

[0034] The input unit 101 acquires signals from various components of the recycle unit 70. The input unit 101 of this embodiment acquires information from the first pressure acquisition unit 72, the second pressure acquisition unit 74, and the emission concentration acquisition unit 75. The input unit 101 outputs the acquired information from the first pressure acquisition unit 72, the second pressure acquisition unit 74, and the emission concentration acquisition unit 75 to the determination unit 102.

[0035] The judgment unit 102 judges the information input from the input unit 101. The judgment unit 102 in this embodiment judges whether the first pressure value input from the first pressure acquisition unit 72 exceeds a predetermined pressure standard. Here, the pressure standard is a value that is predetermined and is a pressure value set as an upper limit value of the operation management range in the regenerator 3. In other words, when the pressure standard is exceeded, the regenerator exhaust gas immediately after being discharged from the regenerator 3 can be supplied to the treatment target gas line 11 as it is. When the first pressure value exceeds the pressure standard, the judgment unit 102 sends a signal to the first valve control unit 103 to open the first recycle valve 71. In addition, when the first pressure value exceeds the pressure standard, the judgment unit 102 sends a signal to the second valve control unit 104 to close the second recycle valve 73. Moreover, when the first pressure value falls below the pressure standard, the judgment unit 102 sends a signal to the first valve control unit 103 to close the first recycle valve 71.

[0036] Moreover, the judgment unit 102 judges whether the second pressure value input from the second pressure acquisition unit 74 exceeds the pressure standard. Furthermore, the judgment unit 102 judges whether the second pressure value exceeds the storage pressure standard, which is a value smaller than the pressure standard. The storage pressure standard is a predetermined value, and is a pressure value when the regenerator exhaust gas is at a pressure that allows storage. In other words, when the pressure value falls below the storage pressure standard, the regenerator exhaust gas is not suitable for storage and cannot be discharged directly to the destination from the regenerator discharge line 15. When the second pressure value exceeds the pressure standard and the storage pressure standard, the judgment unit 102 sends a signal to the second valve control unit 104 to open the second recycle valve 73. When the second pressure value falls below the pressure standard and exceeds the storage pressure standard, the judgment unit 102 sends a signal to the second valve control unit 104 to close the second recycle valve 73. When the second pressure value falls below the pressure standard and exceeds the storage pressure standard, the judgment unit 102 sends a signal to the second valve control unit 104 to close the second recycle valve 73. When the second pressure value falls below the pressure standard and the storage pressure standard, the judgment unit 102 sends a signal to the second valve control unit 104 to close the second recycle valve 73.

[0037] In addition, the determination unit 102 determines whether the concentration value input from the discharge concentration acquisition unit 75 exceeds a predetermined concentration standard. The concentration standard is a predetermined value, which is a concentration value when the regenerator discharge gas has a concentration that can be stored. In other words, when the concentration value falls below the concentration standard, the regenerator discharge gas is not suitable for storage and cannot be discharged directly from the regenerator discharge line 15. When the concentration value exceeds the concentration standard, the determination unit 102 sends a signal to the first valve control unit 103 and the second valve control unit 104 to control the opening degree of the first recycle valve 71 and the second recycle valve 73 according to the judgment results of the pressure standard and the storage pressure standard. Furthermore, when the concentration value falls below the concentration standard, the determination unit 102 sends a signal to the first valve control unit 103 to open the first recycle valve 71 regardless of the judgment results of the pressure standard and the storage pressure standard.

[0038] The first valve control unit 103 controls the opening degree of the first recycle valve 71 based on a signal from the determination unit 102. When the first valve control unit 103 receives a determination result from the determination unit 102 that the concentration value is below the concentration standard, the first valve control unit 103 opens the first recycle valve 71 regardless of the determination results of the pressure standard and the storage pressure standard. When the first valve control unit 103 receives a determination result from the determination unit 102 that the concentration value exceeds the concentration standard and the first pressure value also exceeds the pressure standard, the first valve control unit 103 opens the first recycle valve 71 regardless of the determination result of the storage pressure standard. When the first valve control unit 103 receives a determination result from the determination unit 102 that the concentration value exceeds the concentration standard and the first pressure value is below the pressure standard, the first valve control unit 103 closes the first recycle valve 71 regardless of the determination result of the storage pressure standard.

[0039] The second valve control unit 104 controls the opening degree of the second recycle valve 73 based on a signal from the determination unit 102. When the second valve control unit 104 receives a determination result from the determination unit 102 that the concentration value is below the concentration standard, the second valve control unit 104 closes the second recycle valve 73 regardless of the determination results of the pressure standard and the storage pressure standard. When the second valve control unit 104 receives a determination result from the determination unit 102 that the concentration value exceeds the concentration standard and the second pressure value also exceeds the pressure standard, the second valve control unit 104 opens the second recycle valve 73 regardless of the determination result of the storage pressure standard. When the second valve control unit 104 receives a determination result from the determination unit 102 that the concentration value exceeds the concentration standard and the second pressure value is below the pressure standard and the storage pressure standard, the second valve control unit 104 closes the second recycle valve 73. When the second valve control unit 104 receives a determination result from the determination unit 102 that the concentration value exceeds the concentration standard, the second pressure value exceeds the pressure standard, and the second pressure value is below the storage pressure standard, the second valve control unit 104 closes the second recycle valve 73.

[0040] (Action and effect) In the carbon dioxide capture system 1 having the above configuration, the gas to be treated flowing through the gas to be treated line 11 is pressurized by the pumping unit 21 and sent to the absorption tower 2. The gas to be treated, which has been pressurized and has an increased flow rate, comes into contact with the absorbing liquid in the absorption tower 2, whereby carbon dioxide is removed. As a result, the absorption tower exhaust gas from which carbon dioxide has been removed is discharged to the outside from the absorption tower 2 through the absorption tower discharge line 12. In addition, in the absorption tower 2, a rich liquid, which is an absorbing liquid that has absorbed carbon dioxide, is generated. The rich liquid is pressurized by the rich pump 35 through the rich line 13 and sent to the absorbing liquid heat exchanger 4. The rich liquid is heated in the absorbing liquid heat exchanger 4, and further flows through the rich line 13 and is sent to the regeneration tower 3. In the regeneration tower 3, the rich liquid is heated by the reboiler 31 to dissipate carbon dioxide from the rich liquid. As a result, in the regeneration tower 3, a lean liquid, which is an absorbing liquid that has dissipated carbon dioxide, is generated. The lean liquid is pressurized by the lean pump 37 through the lean line 14 and sent to the absorbing liquid heat exchanger 4. The lean liquid is cooled by exchanging heat with the rich liquid in the absorbing liquid heat exchanger 4. The cooled lean liquid is further cooled in a cooler 38 and returned to the absorption tower 2. In this manner, the absorbing liquid circulates between the absorption tower 2 and the regenerator 3. In the regenerator 3, carbon dioxide-containing regenerator exhaust gas is generated by dissipating carbon dioxide from the rich liquid, and is sent to the regenerator exhaust line 15.

[0041] Before the regenerator exhaust gas flowing through the regenerator discharge line 15 is sent to the discharge compressor 5, a first pressure value, which is pressure information, is acquired by a first pressure acquisition unit 72. When the first pressure value exceeds a pressure standard, a first recycle valve 71 is opened by a control unit 100. As a result, when the first pressure value exceeds the pressure standard, the regenerator exhaust gas before being compressed by the discharge compressor 5 is sent to the gas to be treated line 11 through a first recycle line 61. The regenerator exhaust gas sent to the gas to be treated line 11 is pressurized by a compression unit 21 and sent to the absorption tower 2.

[0042] In addition, when the first pressure value falls below the pressure standard, the first recycle valve 71 is closed. Therefore, the regenerator exhaust gas cannot flow through the first recycle line 61, and is sent to the discharge compressor 5 without being sent to the gas line 11 to be treated. The regenerator exhaust gas sent to the discharge compressor 5 is compressed and the pressure increases. After that, the second pressure acquisition unit 74 acquires a second pressure value, which is pressure information, from the regenerator exhaust gas compressed by the discharge compressor 5. When the second pressure value exceeds the pressure standard, the control unit 100 opens the second recycle valve 73. As a result, when the second pressure value exceeds the pressure standard, the compressed regenerator exhaust gas is sent to the gas line 11 to be treated through the second recycle line 62. The regenerator exhaust gas sent to the gas line 11 to be treated is pressurized by the pressure sending unit 21 and sent to the absorption tower 2.

[0043] In addition, when the second pressure value falls below the pressure standard, the second recycle valve 73 is closed. Therefore, the compressed regenerator exhaust gas cannot flow through the second recycle line 62, and is not sent to the gas to be treated line 11, but is sent to an external destination.

[0044] In this way, the pressures of the regenerator exhaust gas flowing through the regenerator exhaust line 15 are acquired by the first pressure acquisition unit 72 and the second pressure acquisition unit 74 at the upstream and downstream positions with respect to the discharge compressor 5. Then, based on the results of the first pressure acquisition unit 72 and the second pressure acquisition unit 74, the first recycle valve 71 and the second recycle valve 73 are opened and closed. Therefore, if the pressure of the regenerator exhaust gas immediately after being discharged from the regenerator 3 is high, the regenerator exhaust gas can be sent from the first recycle line 61 to the gas line 11 to be treated. Also, if the pressure of the regenerator exhaust gas immediately after being discharged from the regenerator 3 is low, the regenerator exhaust gas can be compressed by the discharge compressor 5 and then sent from the second recycle line 62 to the gas line 11 to be treated. In this way, regardless of the pressure of the regenerator exhaust gas immediately after being discharged from the regenerator 3, the regenerator exhaust gas at a pressure that can be used in the absorption tower 2 can be sent to the gas line 11 to be treated. Therefore, most of the regenerator exhaust gas discharged from the regenerator 3 can be sent to the absorption tower 2 for recycling. This makes it possible to adjust the amount of carbon dioxide returned from the regenerator 3 to the absorber 2, thereby reducing the amount of carbon dioxide emitted to the outside.

[0045] In addition, the determination unit 102 of the control unit 100 determines whether the second pressure value exceeds not only the pressure standard but also the storage pressure standard. In this way, by determining the second pressure value not only by the pressure standard but also by the storage pressure standard smaller than the pressure standard, it is possible to grasp whether the regenerator exhaust gas has reached a pressure suitable for supply to the transfer destination. Then, the control unit 100 opens the second recycle valve 73 when the second pressure value exceeds the pressure standard and the storage pressure standard. Also, the control unit 100 closes the second recycle valve 73 when the second pressure value falls below the pressure standard and exceeds the storage pressure standard. Furthermore, the control unit 100 also closes the second recycle valve 73 when the second pressure value falls below the pressure standard and the storage pressure standard. When the second pressure value exceeds the storage pressure standard, the regenerator exhaust gas is generally in a state where it can be supplied to the transfer destination. However, when the supply is stopped at the transfer destination for some reason, the second recycle valve 73 is closed and the gas cannot be supplied to the transfer destination, so the pressure rises. After that, the second pressure value finally becomes a value that exceeds the pressure standard. As a result, the control unit 100 determines that the second pressure value exceeds the pressure standard and the storage pressure standard, and opens the second recycle valve 73. This makes it possible to prevent the pressure of the regenerator exhaust gas from increasing excessively even when the regenerator exhaust gas cannot be supplied to the destination.

[0046] In addition, the regenerator exhaust gas flowing through the regenerator discharge line 15 has a concentration value, which is information on the concentration of carbon dioxide in the regenerator exhaust gas, acquired by the discharge concentration acquisition unit 75. When the concentration value acquired by the discharge concentration acquisition unit 75 exceeds the concentration standard, the control unit 100 adjusts the opening degree of the first recycle valve 71 and the second recycle valve 73 according to the judgment result of the pressure standard and the storage pressure standard. On the other hand, when the concentration value falls below the concentration standard, the first recycle valve 71 is opened regardless of the judgment result of the pressure standard and the storage pressure standard. Therefore, when the concentration of carbon dioxide in the regenerator exhaust gas discharged from the regenerator 3 is too low and is not suitable for supply to the transfer destination, the regenerator exhaust gas is sent to the gas line 11 to be treated through the first recycle line 61. Therefore, even if the regenerator exhaust gas has a carbon dioxide concentration that is not suitable for recycling, it is sent to the gas line 11 to be treated. In this way, it is also possible to suppress the regenerator exhaust gas with a carbon dioxide concentration that is not suitable for supply to the transfer destination from being discharged to the outside. Therefore, it is possible to suppress the discharge amount of the regenerator exhaust gas to the outside regardless of the carbon dioxide concentration.

[0047] In addition, the first recycle line 61 after merging with the second recycle line 62 is connected to the target gas line 11 at a position upstream of the pressure delivery section 21. Therefore, the regeneration tower exhaust gas can be merged with the target gas to be treated, which has a low pressure before being supplied to the pressure delivery section 21. Here, the pressure of the regeneration tower exhaust gas flowing through the regeneration tower discharge line 15 is higher than the target gas to be treated, which has a low pressure before being supplied to the pressure delivery section 21. Therefore, in the first recycle line 61 and the second recycle line 62, a gas flow is generated from the regeneration tower discharge line 15 to the target gas to be treated line 11 due to the pressure difference between the regeneration tower discharge gas and the target gas to be treated. As a result, the regeneration tower exhaust gas can be stably flowed from the regeneration tower discharge line 15 to the target gas to be treated line 11 by the first recycle line 61 and the second recycle line 62 without providing another device such as a pump in the recycle line 60.

[0048] Second Embodiment Next, a carbon dioxide capture system 1A according to a second embodiment of the present disclosure will be described. In the second embodiment described below, components common to the first embodiment will be denoted by the same reference numerals in the drawings and will not be described. In the second embodiment, the configuration of the recycling section 70A in the carbon dioxide capture system 1A is different from that of the first embodiment.

[0049] The carbon dioxide capture system 1A of the second embodiment adjusts the amount of carbon dioxide supplied to the absorption tower 2 according to the amount of carbon dioxide contained in the regeneration tower exhaust gas supplied from the recycle line 60. As shown in Fig. 2, the carbon dioxide capture system 1A of the second embodiment further includes a treatment target gas information acquisition unit 81, a regeneration tower exhaust gas information acquisition unit 82, a capture line valve 83, and a steam supply valve 84.

[0050] The treated gas information acquisition unit 81 acquires information on the treated gas flowing through the treated gas line 11. The treated gas information acquisition unit 81 is disposed in the treated gas line 11 at a position upstream of the connection position between the first recycle line 61 and the treated gas line 11. The treated gas information acquisition unit 81 measures the flow rate of the treated gas flowing through the treated gas line 11 and the carbon dioxide concentration of the treated gas flowing through the treated gas line 11. The treated gas information acquisition unit 81 outputs information on the measured amount of treated gas and the carbon dioxide concentration to the control unit 100A.

[0051] The regenerator exhaust gas information acquisition unit 82 acquires information on the regenerator exhaust gas flowing through the recycle line 60. The regenerator exhaust gas information acquisition unit 82 is disposed on the first recycle line 61 at a downstream position relative to the connection position of the first recycle line 61 and the second recycle line 62. The regenerator exhaust gas information acquisition unit 82 measures the flow rate of the regenerator exhaust gas flowing through the first recycle line 61 after merging with the second recycle line 62, and the carbon dioxide concentration of the regenerator exhaust gas flowing through the first recycle line 61 after merging with the second recycle line 62. The regenerator exhaust gas information acquisition unit 82 outputs information on the measured amount of regenerator exhaust gas and the carbon dioxide concentration to the control unit 100A.

[0052] The recovery line valve 83 is capable of adjusting the amount of absorption liquid supplied from the regenerator 3 to the absorber 2. The recovery line valve 83 is disposed in the lean line 14. The recovery line valve 83 is disposed in the lean line 14 between the cooler 38 and the absorber 2. That is, the recovery line valve 83 adjusts the amount of absorption liquid supplied to the absorber 2 after being cooled by the absorption liquid heat exchanger 4 and the cooler 38. The recovery line valve 83 in this embodiment is a control valve whose opening is controlled by the control unit 100A.

[0053] The steam supply valve 84 is capable of adjusting the amount of steam supplied to the reboiler 31. That is, the steam supply valve 84 is capable of adjusting the amount of heating of the absorption liquid by changing the amount of high-temperature steam supplied to the reboiler 31. The steam supply valve 84 in this embodiment is a control valve whose opening degree is controlled by the control unit 100A.

[0054] Furthermore, in the recycle unit 70A of the second embodiment, the configuration of the control unit 100A is also different from that of the first embodiment. The control unit 100A of the second embodiment further includes a recovery amount acquisition unit 106 and a carbon dioxide amount adjustment unit 110.

[0055] The recovery amount acquisition unit 106 acquires information on the amount of carbon dioxide contained in the gas flowing through the treatment gas line 11. Here, the gas flowing through the treatment gas line 11 refers to all gases that flow through the treatment gas line 11, including not only the treatment gas but also the regenerator exhaust gas that is joined at the treatment gas line 11 and is supplied to the absorption tower 2. The recovery amount acquisition unit 106 of this embodiment acquires information on the amount of carbon dioxide contained in the gas flowing through the treatment gas line 11 from the information acquired by the treatment gas information acquisition unit 81 and the information acquired by the regenerator exhaust gas information acquisition unit 82. Specifically, the recovery amount acquisition unit 106 receives information on the flow rate of the treatment gas and information on the carbon dioxide concentration of the treatment gas from the treatment gas information acquisition unit 81 via the input unit 101. The recovery amount acquisition unit 106 acquires information on the amount of carbon dioxide contained in the treatment gas based on the product of the acquired flow rate of the treatment gas and the carbon dioxide concentration of the treatment gas. Further, the recovery amount acquisition unit 106 receives information on the flow rate of the regeneration tower exhaust gas and information on the carbon dioxide concentration of the regeneration tower exhaust gas from the regeneration tower exhaust gas information acquisition unit 82 via the input unit 101. The recovery amount acquisition unit 106 acquires information on the amount of carbon dioxide contained in the regeneration tower exhaust gas based on the product of the acquired flow rate of the regeneration tower exhaust gas and the carbon dioxide concentration of the regeneration tower exhaust gas. Then, the recovery amount acquisition unit 106 acquires information on the total amount of carbon dioxide contained in the gas flowing through the gas to be treated (total amount information) based on the sum of the amount of carbon dioxide contained in the gas to be treated and the amount of carbon dioxide contained in the regeneration tower exhaust gas. The recovery amount acquisition unit 106 outputs the acquired information on the total amount of carbon dioxide contained in the gas to be treated (total amount information) to the carbon dioxide amount adjustment unit 110.

[0056] The carbon dioxide amount adjustment unit 110 adjusts the amount of carbon dioxide to be treated in the absorption tower 2 when the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds a predetermined amount standard. Here, the amount standard is a predetermined value, which is the amount of carbon dioxide that can be absorbed in the absorption tower 2. The amount standard is, for example, a value determined from the device design conditions or a value determined from the operating state amount of the carbon dioxide capture system 1. In other words, when the amount standard is exceeded, even if gas is supplied to the absorption tower 2, the carbon dioxide in the gas cannot be sufficiently absorbed, which may cause the absorption tower 2 to break down or a large amount of carbon dioxide to remain in the absorption tower exhaust gas.

[0057] The carbon dioxide amount adjustment unit 110 of the second embodiment adjusts the amount of carbon dioxide flowing through the gas line 11 to be treated by controlling the opening of the recovery line valve 83 and the steam supply valve 84. When the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds the amount standard, the carbon dioxide amount adjustment unit 110 controls the recovery line valve 83 and the steam supply valve 84 to increase the opening. In addition, when the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 falls below the amount standard, the carbon dioxide amount adjustment unit 110 controls the recovery line valve 83 and the steam supply valve 84 to decrease the opening. The carbon dioxide amount adjustment unit 110 of this embodiment has an amount determination unit 111, a recovery control unit 112, and a steam control unit 113.

[0058] The amount determination unit 111 determines the information input from the recovery amount acquisition unit 106. The amount determination unit 111 of this embodiment determines whether the value of the total amount information exceeds the amount standard. When the value of the total amount information exceeds the amount standard, the amount determination unit 111 sends a signal to the recovery control unit 112 to increase the opening degree of the recovery line valve 83. In addition, when the value of the total amount information exceeds the amount standard, the amount determination unit 111 sends a signal to the steam control unit 113 to increase the opening degree of the steam supply valve 84. Also, when the value of the total amount information falls below the amount standard, the amount determination unit 111 sends a signal to the recovery control unit 112 to decrease the opening degree of the recovery line valve 83. When the value of the total amount information falls below the amount standard, the amount determination unit 111 sends a signal to the steam control unit 113 to decrease the opening degree of the steam supply valve 84.

[0059] The recovery control unit 112 controls the opening degree of the recovery line valve 83 based on a signal from the amount determination unit 111. When the recovery control unit 112 receives a determination result from the amount determination unit 111 that the value of the total amount information exceeds the amount standard, the recovery control unit 112 increases the opening degree of the recovery line valve 83. When the recovery control unit 112 receives a determination result from the amount determination unit 111 that the value of the total amount information falls below the amount standard, the recovery control unit 112 decreases the opening degree of the recovery line valve 83.

[0060] The steam control unit 113 controls the opening degree of the steam supply valve 84 based on a signal from the amount determination unit 111. When the steam control unit 113 receives a determination result from the amount determination unit 111 that the value of the total amount information exceeds the amount standard, the steam control unit 113 increases the opening degree of the steam supply valve 84. When the steam control unit 113 receives a determination result from the amount determination unit 111 that the value of the total amount information falls below the amount standard, the steam control unit 113 decreases the opening degree of the steam supply valve 84.

[0061] (Action and effect) In the carbon dioxide capture system 1A having the above configuration, information on the amount of carbon dioxide contained in the gas flowing through the gas line 11 to be treated is acquired by the capture amount acquisition unit 106. Therefore, the amount of carbon dioxide contained in the gas to be treated and the regeneration tower exhaust gas are mixed through the first recycle line 61 and the second recycle line 62, and the gas flowing through the gas line 11 to be treated can be grasped. Furthermore, when the amount of carbon dioxide contained in these gases exceeds a quantity standard, the carbon dioxide amount adjustment unit 110 adjusts the amount of carbon dioxide to be treated in the absorption tower 2. Therefore, it is possible to prevent the absorption tower 2 from treating too little carbon dioxide relative to the amount of carbon dioxide in the gas flowing through the gas line 11 to be treated. Therefore, it is possible to prevent the absorption tower 2 from being unable to sufficiently treat the amount of carbon dioxide, resulting in a state in which a large amount of carbon dioxide is contained in the absorption tower exhaust gas. In other words, it is possible to prevent a decrease in the carbon dioxide capture rate in the absorption tower 2. This makes it possible to suppress the amount of gas containing carbon dioxide discharged from the absorption tower 2 to be discharged to the outside.

[0062] Further, the treatment target gas information acquisition unit 81 acquires information on the flow rate of the treatment target gas flowing through the treatment target gas line 11 and information on the carbon dioxide concentration of the treatment target gas. This makes it possible to acquire information on the amount and carbon dioxide concentration of only the treatment target gas that has flowed through the treatment target gas line 11 without passing through the recycle line 60. By being able to grasp the amount of the treatment target gas and the carbon dioxide concentration, the amount of carbon dioxide contained in the treatment target gas can be grasped with high accuracy. Furthermore, the regeneration tower exhaust gas information acquisition unit 82 acquires information on the flow rate of the regeneration tower exhaust gas flowing through the recycle line 60 and information on the carbon dioxide concentration of the regeneration tower exhaust gas. This makes it possible to acquire information on the amount and carbon dioxide concentration of only the regeneration tower exhaust gas that has flowed through the recycle line 60 before merging with the treatment target gas line 11. By being able to grasp the amount and carbon dioxide concentration of the regeneration tower exhaust gas, the amount of carbon dioxide contained in the regeneration tower exhaust gas can be grasped with high accuracy. Then, from the information obtained by the treatment gas information obtaining unit 81 and the information obtained by the regeneration tower exhaust gas information obtaining unit 82, the recovery amount obtaining unit 106 can obtain information on the total amount of carbon dioxide contained in the gas flowing through the treatment gas line 11. In this way, by obtaining information on the amount of carbon dioxide contained in the gas separately for the treatment gas line 11 and the recycle line 60, the amount of carbon dioxide supplied to the absorption tower 2 can be grasped with high accuracy. Therefore, a decrease in the carbon dioxide recovery rate in the absorption tower 2 can be effectively suppressed. This makes it possible to further suppress the amount of carbon dioxide-containing gas discharged from the absorption tower 2 to the outside.

[0063] Furthermore, the opening degree of the recovery line valve 83, which adjusts the supply amount of the lean liquid to the absorption tower 2 via the lean line 14, is adjusted by the carbon dioxide amount adjustment unit 110 in accordance with the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106. Furthermore, the opening degree of the steam supply valve 84, which can adjust the supply amount of steam to the reboiler 31, is also adjusted by the carbon dioxide amount adjustment unit 110 in accordance with the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106. Specifically, when the total amount of carbon dioxide exceeds the amount standard, the opening degrees of the recovery line valve 83 and the steam supply valve 84 are increased. By increasing the opening degree of the steam supply valve 84, the amount of heating in the reboiler 31 increases, and the amount of lean liquid generated in the regeneration tower 3 increases. As a result, the supply amount of the lean liquid supplied from the regeneration tower 3 to the lean line 14 increases. Furthermore, by increasing the opening degree of the recovery line valve 83, the supply amount of the lean liquid supplied to the absorption tower 2 via the lean line 14 also increases. In addition, when the total amount of carbon dioxide falls below the amount standard, the opening of the recovery line valve 83 and the steam supply valve 84 is reduced. By narrowing the opening of the steam supply valve 84, the amount of heating in the reboiler 31 is reduced, and the amount of lean liquid generated in the regenerator 3 is reduced. As a result, the supply amount of lean liquid supplied from the regenerator 3 to the lean line 14 is reduced. Furthermore, by narrowing the opening of the recovery line valve 83, the supply amount of lean liquid supplied to the absorption tower 2 via the lean line 14 is reduced. In this way, the amount of lean liquid generated in the regenerator 3 and the supply amount of the generated lean liquid to the absorption tower 2 are adjusted according to the total amount of carbon dioxide flowing through the treatment target gas line 11. Therefore, the decrease in the recovery rate of carbon dioxide in the absorption tower 2 can be suppressed by adjusting the supply amount of the absorption liquid. As a result, the amount of gas containing carbon dioxide discharged from the absorption tower 2 to the outside can be further suppressed.

[0064] <Third embodiment> Next, a carbon dioxide capture system 1B according to a third embodiment of the present disclosure will be described. In the third embodiment described below, components common to the first and second embodiments are denoted by the same reference numerals in the drawings and will not be described. In the third embodiment, the carbon dioxide capture system 1B has a different configuration from the first and second embodiments in terms of the recycle section 70B.

[0065] The recycle section 70B of the carbon dioxide capture system 1B of the third embodiment is capable of suppressing the amount of carbon dioxide-rich regenerator exhaust gas supplied to the absorption tower 2. As shown in FIG. 3, the recycle section 70B of the third embodiment further includes a bypass line 85, a first bypass valve 86, and a second bypass valve 87.

[0066] The bypass line 85 is capable of supplying the regeneration tower exhaust gas flowing through the recycle line 60 to the absorber discharge line 12 without supplying it to the absorber 2. The bypass line 85 connects the recycle line 60 and the absorber discharge line 12. In this embodiment, the bypass line 85 is connected to the recycle line 60 at a position upstream of the first recycle valve 71 and the second recycle valve 73. Specifically, the bypass line 85 is connected to the first recycle line 61 at a position upstream of the first recycle valve 71. The bypass line 85 is also connected to the second recycle line 62 at a position upstream of the second recycle valve 73. The pipe connected to the first recycle line 61 and the pipe connected to the second recycle line 62 are joined together and extend to the absorber discharge line 12.

[0067] The first bypass valve 86 is capable of adjusting the amount of regenerator exhaust gas supplied from the recycle line 60 to the absorber discharge line 12. The first bypass valve 86 is disposed in the bypass line 85. That is, the first bypass valve 86 adjusts the amount of regenerator exhaust gas supplied from the first recycle line 61 and the second recycle line 62 to the absorber discharge line 12 without passing through the gas to be treated line 11 and the absorber 2. The first bypass valve 86 in this embodiment is a control valve whose opening and closing is controlled by the control unit 100B.

[0068] The second bypass valve 87 is capable of adjusting the supply amount of the regeneration tower exhaust gas from the recycle line 60 to the target gas line 11. The second bypass valve 87 is disposed between the arrangement position of the first recycle valve 71 and the second recycle valve 73 and the connection position of the target gas line 11 and the recycle line 60. Specifically, the second bypass valve 87 is disposed in the first recycle line 61 between the connection position of the first recycle line 61 and the second recycle line 62 and the connection position of the target gas line 11 and the first recycle line 61. That is, the second bypass valve 87 adjusts the supply amount of the regeneration tower exhaust gas to the target gas line 11 at a position downstream of the first recycle valve 71 and the second recycle valve 73 in the recycle line 60. The second bypass valve 87 in this embodiment is a control valve whose opening and closing is controlled by the control unit 100B.

[0069] Furthermore, the carbon dioxide amount adjustment unit 110B of the control unit 100B of the third embodiment adjusts the amount of carbon dioxide flowing through the treatment target gas line 11 by controlling the opening and closing of the first bypass valve 86 and the second bypass valve 87. When the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds the amount standard, the carbon dioxide amount adjustment unit 110B opens the first bypass valve 86 and closes the second bypass valve 87. When the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 falls below the amount standard, the carbon dioxide amount adjustment unit 110B closes the first bypass valve 86 and opens the second bypass valve 87. The carbon dioxide amount adjustment unit 110B of the third embodiment has an amount determination unit 111B, a first bypass control unit 115, and a second bypass control unit 116.

[0070] The amount determination unit 111B of the third embodiment sends a signal to the first bypass control unit 115 to open the first bypass valve 86 when the value of the total amount information exceeds the amount standard. In addition, the amount determination unit 111B sends a signal to the second bypass control unit 116 to close the second bypass valve 87 when the value of the total amount information exceeds the amount standard. Also, the amount determination unit 111B sends a signal to the first bypass control unit 115 to close the first bypass valve 86 when the value of the total amount information falls below the amount standard. The amount determination unit 111B sends a signal to the second bypass control unit 116 to open the second bypass valve 87 when the value of the total amount information falls below the amount standard.

[0071] The first bypass control unit 115 controls the opening degree of the first bypass valve 86 based on a signal from the amount determination unit 111B. When the first bypass control unit 115 receives a determination result from the amount determination unit 111B that the value of the total amount information exceeds the amount standard, the first bypass control unit 115 opens the first bypass valve 86. When the first bypass control unit 115 receives a determination result from the amount determination unit 111B that the value of the total amount information falls below the amount standard, the first bypass control unit 115 closes the first bypass valve 86.

[0072] The second bypass control unit 116 controls the opening degree of the second bypass valve 87 based on a signal from the amount determination unit 111B. When the second bypass control unit 116 receives a determination result from the amount determination unit 111B that the value of the total amount information exceeds the amount standard, the second bypass control unit 116 closes the second bypass valve 87. When the second bypass control unit 116 receives a determination result from the amount determination unit 111B that the value of the total amount information falls below the amount standard, the second bypass control unit 116 opens the second bypass supply valve.

[0073] (Action and effect) In the carbon dioxide recovery system 1B having the above configuration, a first bypass valve 86 is disposed in the bypass line 85 connecting the recycle line 60 and the absorber discharge line 12. The first bypass valve 86 is opened and closed by the carbon dioxide amount adjustment unit 110B according to the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106. Specifically, when the total amount of carbon dioxide exceeds the amount standard, the first bypass valve 86 is opened. By opening the first bypass valve 86, the regeneration tower exhaust gas flowing through the first recycle line 61 and the second recycle line 62 is sent from the bypass line 85 to the absorber discharge line 12, and the amount sent to the gas to be treated line 11 is reduced. In other words, the regeneration tower exhaust gas flowing through the first recycle line 61 and the second recycle line 62 is discharged to the outside without being sent to the absorber 2. In addition, when the total amount of carbon dioxide falls below the amount standard, the first bypass valve 86 is closed. By closing the first bypass valve 86, the bypass line 85 becomes unable to flow, and the regenerator exhaust gas is sent to the treated gas line 11. In other words, all of the regenerator exhaust gas flowing through the first recycle line 61 is sent to the absorption tower 2. In this way, when the total amount of carbon dioxide flowing through the treated gas line 11 exceeds the amount of carbon dioxide that can be absorbed by the absorption tower 2 and treatment in the absorption tower 2 is impossible, it is possible to prevent excess carbon dioxide from being supplied to the absorption tower 2. Therefore, it is possible to prevent instability in treatment due to a breakdown of the absorption tower 2 caused by excess carbon dioxide being supplied to the absorption tower 2. This makes it possible to stably prevent the amount of gas containing carbon dioxide discharged from the absorption tower 2 to the outside.

[0074] In addition to the first bypass valve 86, a second bypass valve 87 capable of adjusting the supply amount of the regenerator exhaust gas from the recycle line 60 to the target gas line 11 is also disposed. The second bypass valve 87 is also opened and closed by the carbon dioxide amount adjustment unit 110B according to the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106. Specifically, when the total amount of carbon dioxide exceeds the amount standard, the first bypass valve 86 is opened and the second bypass valve 87 is closed. By opening the first bypass valve 86 and closing the second bypass valve 87, the flow of the regenerator exhaust gas from the first recycle line 61 to the target gas line 11 is completely blocked. The regenerator exhaust gas flowing through the first recycle line 61 is discharged to the outside without being sent to the absorber 2 at all. In this way, when the regenerator exhaust gas is supplied to the absorber exhaust line 12 via the first bypass valve 86, the flow of the regenerator exhaust gas to the target gas line 11 is completely blocked, thereby reliably suppressing the instability of the treatment caused by the supply of excess carbon dioxide to the absorber 2. In addition, the first bypass valve 86 and the second bypass valve 87 are not limited to being fully open or fully closed, but can be used at an intermediate opening to adjust the flow rate ratio through the first recycle line 61 and the bypass line 85. This makes it possible to more stably suppress the amount of gas containing carbon dioxide discharged to the outside from the absorption tower 2.

[0075] In addition, the bypass line 85 is connected to the absorber discharge line 12 that is connected to the top of the absorber 2. Therefore, when the regenerator exhaust gas flowing through the first recycle line 61 is discharged to the outside, it can be mixed with the absorber exhaust gas discharged from the absorber 2 and then discharged to the outside. In other words, even if the regenerator exhaust gas contains a large amount of carbon dioxide, it can be diluted with the absorber exhaust gas and discharged to the outside. Therefore, it is possible to prevent concentrated carbon dioxide from being directly discharged to the outside.

[0076] In the third embodiment, as described above, the second bypass valve 87 is disposed in the first recycle line 61, but the present invention is not limited to such a structure. For example, the third embodiment may have a structure that does not include the second bypass valve 87 and only includes the first bypass valve 86.

[0077] <Fourth embodiment> Next, a carbon dioxide capture system 1C according to a fourth embodiment of the present disclosure will be described. In the fourth embodiment described below, the configurations common to the first to third embodiments are denoted by the same reference numerals in the drawings and the description thereof will be omitted. In the fourth embodiment, the carbon dioxide capture system 1C differs from the first to third embodiments in the configuration for circulating the absorption liquid and the recycle section 70C.

[0078] As shown in FIG. 4, the carbon dioxide capture system 1C of the fourth embodiment further includes a lean tank 91, a lean valve 92, a rich tank 93, and a rich valve 94.

[0079] The lean tank 91 is capable of storing the lean liquid, which is the absorbing liquid from which carbon dioxide has been released. The lean tank 91 stores the lean liquid flowing through the lean line 14.

[0080] The lean valve 92 is capable of adjusting the amount of absorbent liquid supplied between the lean tank 91 and the lean line 14. The lean valve 92 is capable of adjusting both the supply of lean liquid from the lean tank 91 to the lean line 14 and the supply of lean liquid from the lean line 14 to the lean tank 91. The lean valve 92 is connected to the lean line 14 between the absorption tower 2 and the cooler 38. That is, the lean valve 92 is capable of transferring the lean liquid cooled by the absorption liquid heat exchanger 4 and the cooler 38 from the lean line 14 to the lean tank 91. In addition, the lean valve 92 is capable of supplying the lean liquid stored in the lean tank 91 so as to merge with the lean liquid flowing through the lean line 14. The lean valve 92 in this embodiment is a control valve whose opening is controlled by the control unit 100C.

[0081] The rich tank 93 is capable of storing a rich liquid that is an absorbing liquid that has absorbed carbon dioxide. The rich tank 93 stores the rich liquid that flows through the rich line 13.

[0082] The rich valve 94 is capable of adjusting the amount of absorbent liquid supplied between the rich tank 93 and the rich line 13. The rich valve 94 is capable of adjusting both the supply of rich liquid from the rich tank 93 to the rich line 13 and the supply of rich liquid from the rich line 13 to the rich tank 93. The rich valve 94 is connected to the rich line 13 between the rich pump 35 and the absorbent heat exchanger 4. That is, the rich valve 94 is capable of transferring the rich liquid before being heated by the absorbent heat exchanger 4 from the rich line 13 to the rich tank 93. In addition, the rich valve 94 is capable of supplying the rich liquid stored in the rich tank 93 so as to join the rich liquid flowing through the rich line 13. The rich valve 94 in this embodiment is a control valve whose opening is controlled by the control unit 100C.

[0083] Furthermore, the carbon dioxide amount adjustment unit 110C of the control unit 100C of the fourth embodiment adjusts the amount of lean liquid supplied to the absorption tower 2 by controlling the opening degree of the lean valve 92 and the rich valve 94. As a result, the carbon dioxide amount adjustment unit 110C of the fourth embodiment increases the amount of lean liquid supplied to the absorption tower 2 to increase the amount of carbon dioxide treated in the absorption tower 2. At that time, the carbon dioxide amount adjustment unit 110C changes the amount of lean liquid and rich liquid so that the total amount of the absorbing liquid flowing through the lean line 14 and the rich line 13 between the absorption tower 2 and the regeneration tower 3 is kept constant. When the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds the amount standard, the carbon dioxide amount adjustment unit 110C increases the amount of absorbing liquid supplied from the lean tank 91 to the lean line 14 by the lean valve 92, and increases the amount of absorbing liquid supplied from the rich line 13 to the rich tank 93 by the rich valve 94. Furthermore, when the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 falls below a quantity reference, the carbon dioxide amount adjustment unit 110C increases the amount of absorbent supplied from the rich tank 93 to the rich line 13 by the rich valve 94, and increases the amount of absorbent supplied from the lean line 14 to the lean tank 91 by the lean valve 92. The carbon dioxide amount adjustment unit 110C of the third embodiment has an amount determination unit 111C, a lean control unit 118, and a rich control unit 119.

[0084] The amount determination unit 111C of the third embodiment sends a signal to the lean control unit 118 to adjust the lean valve 92 so as to release the absorbing liquid from the lean tank 91 to the lean line 14 when the value of the total amount information exceeds the amount standard. In addition, the amount determination unit 111C sends a signal to the rich control unit 119 to adjust the rich valve 94 so as to store the absorbing liquid from the rich line 13 to the rich tank 93 when the value of the total amount information exceeds the amount standard. At that time, the amount determination unit 111C sends a signal to adjust the lean valve 92 and the rich valve 94 so that the amount of the lean liquid released from the lean tank 91 to the lean line 14 is the same as the amount of the rich liquid stored from the rich line 13 to the rich tank 93. In addition, the amount determination unit 111C sends a signal to the lean control unit 118 to adjust the lean valve 92 so as to store the absorbing liquid from the lean line 14 to the lean tank 91 when the value of the total amount information falls below the amount standard. When the value of the total amount information falls below the amount standard, the amount determination unit 111C sends a signal to the rich control unit 119 to adjust the rich valve 94 so as to release the absorbing liquid from the rich tank 93 to the rich line 13. At that time, the amount determination unit 111C sends a signal to adjust the lean valve 92 and the rich valve 94 so that the amount of lean liquid stored from the lean line 14 to the lean tank 91 and the amount of rich liquid released from the rich tank to the rich line 13 are the same.

[0085] The lean control unit 118 controls the supply state of the lean liquid by the lean valve 92 based on a signal from the amount determination unit 111C. When the lean control unit 118 receives a determination result from the amount determination unit 111C that the value of the total amount information exceeds the amount standard, the lean control unit 118 adjusts the lean valve 92 so as to supply the absorbing liquid from the lean tank 91 to the lean line 14. When the lean control unit 118 receives a determination result from the amount determination unit 111C that the value of the total amount information falls below the amount standard, the lean control unit 118 adjusts the lean valve 92 so as to supply the absorbing liquid from the lean line 14 to the lean tank 91.

[0086] The rich control unit 119 controls the supply state of the rich liquid by the rich valve 94 based on a signal from the amount determination unit 111C. When the rich control unit 119 receives a determination result from the amount determination unit 111C that the value of the total amount information exceeds the amount standard, the rich control unit 119 adjusts the rich valve 94 so as to supply the absorbing liquid from the rich line 13 to the rich tank 93. When the rich control unit 119 receives a determination result from the amount determination unit 111C that the value of the total amount information falls below the amount standard, the rich control unit 119 adjusts the rich valve 94 so as to supply the absorbing liquid from the rich tank 93 to the rich line 13.

[0087] (Action and effect) In the carbon dioxide capture system 1C having the above configuration, a lean tank 91 capable of storing lean liquid and a lean valve 92 capable of adjusting the supply amount of lean liquid between the lean tank 91 and the lean line 14 are arranged. Therefore, the lean liquid flowing through the lean line 14 can be stored in the lean tank 91, and the lean liquid stored in the lean tank 91 can be supplied to the lean line 14. In addition, a rich tank 93 capable of storing rich liquid and a rich valve 94 capable of adjusting the supply amount of rich liquid between the rich tank 93 and the rich line 13 are arranged. Therefore, the rich liquid flowing through the rich line 13 can be stored in the rich tank 93, and the rich liquid stored in the rich tank 93 can be supplied to the rich line 13. The total amount of the absorbing liquid flowing through the lean line 14 and the rich line 13 is kept constant by such a lean tank 91 and rich tank 93.

[0088] In addition, the carbon dioxide amount adjustment unit 110C adjusts the supply state of the absorbing liquid by the lean valve 92 and the rich valve 94 according to the total amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106. Specifically, when the total amount of carbon dioxide exceeds the amount standard, the lean valve 92 increases the amount of the absorbing liquid supplied from the lean tank 91 to the lean line 14, and the rich valve 94 increases the amount of the absorbing liquid supplied from the rich line 13 to the rich tank 93. That is, the ratio of the lean liquid in the absorbing liquid circulating between the lean line 14 and the rich line 13 can be increased. As a result, the amount of the lean liquid supplied to the absorption tower 2 can be increased, and the amount of carbon dioxide treated in the absorption tower 2 can be increased. In addition, when the total amount of carbon dioxide falls below the amount standard, the rich valve 94 increases the amount of the absorbing liquid supplied from the rich tank 93 to the rich line 13, and the lean valve 92 increases the amount of the absorbing liquid supplied from the lean line 14 to the lean tank 91. In other words, the ratio of rich liquid in the absorption liquid circulating between the lean line 14 and the rich line 13 can be increased. As a result, the amount of lean liquid supplied to the absorption tower 2 can be reduced, and the amount of carbon dioxide treated in the absorption tower 2 can be reduced. In this manner, the amount of lean liquid supplied to the absorption tower 2 is adjusted according to the total amount of carbon dioxide supplied to the absorption tower 2. Therefore, the decrease in the carbon dioxide recovery rate in the absorption tower 2 can be suppressed by adjusting the amount of absorption liquid supplied. This makes it possible to further suppress the amount of gas containing carbon dioxide discharged to the outside from the absorption tower 2.

[0089] <Fifth embodiment> Next, a carbon dioxide capture system 1D according to a fifth embodiment of the present disclosure will be described. In the fifth embodiment described below, components common to the first to fourth embodiments are denoted by the same reference numerals in the drawings and will not be described. In the fifth embodiment, the control of the first recycle valve 71 and the second recycle valve 73 by the control unit 100D is different from the first to fourth embodiments.

[0090] The control unit 100D of the carbon dioxide capture system 1D of the fourth embodiment estimates the flow state of the regenerator exhaust gas flowing through the regenerator discharge line 15, and controls the first recycle valve 71 and the second recycle valve 73. The control unit 100D opens the first recycle valve 71 and the second recycle valve 73 when it is estimated that a predetermined condition that can be regarded as a sudden change in the flow state of the regenerator exhaust gas flowing through the regenerator discharge line 15 is satisfied. In addition, the control unit 100D closes the first recycle valve 71 and the second recycle valve 73 when it is estimated that the condition is not satisfied. In the fifth embodiment, the flow state of the regenerator exhaust gas flowing through the regenerator discharge line 15 is estimated by acquiring information on the operating state of the discharge compressor 5.

[0091] In the fifth embodiment, as shown in FIG. 5, in the control unit 100D, when the discharge compressor 5 stops operating, a stop signal for the discharge compressor 5 is input to the input unit 101D. The input unit 101D outputs information that the stop signal for the discharge compressor 5 has been acquired to the determination unit 102D. When the information that the stop signal has been acquired is input, the determination unit 102D determines that the flow state of the regenerator discharge gas flowing through the regenerator discharge line 15 satisfies a predetermined condition. In addition, when a predetermined time has elapsed since the information that the stop signal has been acquired was input, the determination unit 102D determines that the flow state of the regenerator discharge gas flowing through the regenerator discharge line 15 does not satisfy the predetermined condition.

[0092] Here, the predetermined condition is a condition that can be considered to be a sudden change in the flow rate, pressure, or concentration of the regenerator exhaust gas discharged from the regenerator 3 or the discharge compressor 5, so that it becomes impossible to recover or discharge at the transfer destination connected to the regenerator discharge line 15. For example, when this condition is satisfied, the flow rate, pressure, or concentration of the regenerator exhaust gas circulating in the regenerator discharge line 15 is suddenly increased.

[0093] The predetermined time is the time when the flow condition of the regenerator exhaust gas, which has changed abruptly, can be considered to return to an acceptable range. In other words, after the predetermined time has elapsed, the flow rate, pressure, and concentration of the regenerator exhaust gas flowing through the regenerator exhaust line 15 are in a state that can be handled by normal operation.

[0094] When the judgment unit 102D judges that the conditions are satisfied, it sends a signal to the first valve control unit 103 to rapidly open the first recycle valve 71, and sends a signal to the second valve control unit 104 to rapidly open the second recycle valve 73. In other words, the judgment unit 102D sends a signal to immediately fully open the first recycle valve 71 and the second recycle valve 73. When the judgment unit 102D judges that the conditions are not satisfied, it sends a signal to the first valve control unit 103 to close the first recycle valve 71, and sends a signal to the second valve control unit 104 to close the second recycle valve 73.

[0095] (Action and effect) In the carbon dioxide capture system 1D having the above configuration, by inputting a stop signal of the discharge compressor 5, it is possible to grasp that the flow state of the regenerator exhaust gas flowing through the regenerator discharge line 15 satisfies the conditions. In other words, in an emergency such as an emergency stop due to a failure of the discharge compressor 5, it is possible to appropriately grasp the case where the flow rate, pressure, and concentration of the regenerator exhaust gas flowing through the regenerator discharge line 15 suddenly change. Furthermore, when the flow state of the regenerator exhaust gas satisfies the conditions, the first recycle valve 71 and the second recycle valve 73 are immediately fully opened. Therefore, when the flow state of the regenerator exhaust gas in the regenerator discharge line 15 suddenly changes, the regenerator exhaust gas discharged from the regenerator 3 can be sent to the absorption tower 2 and recycled without being discharged to the outside. Therefore, it is possible to respond to a sudden change in the flow state of the regenerator exhaust gas discharged from the regenerator 3 and suppress the emission of gas containing carbon dioxide to the outside.

[0096] In the control unit 100D of the fifth embodiment, the determination that the flow state of the regenerator exhaust gas satisfies the condition is not limited to only the stop signal when the discharge compressor 5 stops operating. The control unit 100D may receive other signals that can estimate that the flow state of the regenerator exhaust gas changes suddenly. For example, a signal notifying a poor supply of steam to the reboiler 31 or a signal notifying a stop of the supply source of the gas to be treated may be input to the control unit 100D.

[0097] In addition, in the control unit 100D of the fifth embodiment, when the flow state of the regenerator exhaust gas satisfies the condition, only the first recycle valve 71 and the second recycle valve 73 are controlled, but the present invention is not limited to such a configuration. For example, when the flow state of the regenerator exhaust gas satisfies the condition, the control unit 100D may further control the supply state of the absorbing liquid by the lean valve 92 and the rich valve 94 in addition to the control of the first recycle valve 71 and the second recycle valve 73. In this way, when the flow state of the regenerator exhaust gas satisfies the condition, by also controlling the lean valve 92 and the rich valve 94, even if the regenerator exhaust gas that has been rapidly sent through the recycle line 60 is sent to the absorption tower 2, the decrease in the carbon dioxide recovery rate in the absorption tower 2 can be suppressed by adjusting the supply amount of the absorbing liquid. This makes it possible to further suppress the emission of gas containing carbon dioxide from the absorption tower 2 to the outside.

[0098] (Other embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not depart from the gist of the present disclosure are also included.

[0099] The configurations of the first to fifth embodiments may be combined in various ways. Thus, for example, the configuration of the second embodiment may be further combined with the configuration of the third embodiment. Also, the configuration of the fourth embodiment may be combined with the second and third embodiments. Furthermore, the configuration of the fifth embodiment may be further combined with the configurations of the second to fourth embodiments.

[0100] In addition, the first recycle line 61 and the second recycle line 62 are not limited to a configuration in which they are connected to the target gas line 11 upstream of the pressure delivery section 21 as in this embodiment. For example, the first recycle line 61 and the second recycle line 62 may be connected to the target gas line 11 downstream of the pressure delivery section 21. In other words, the first recycle line 61 and the second recycle line 62 may merge the regeneration tower exhaust gas with the target gas after pressure increase in the pressure delivery section 21. In addition, the second recycle line 62 is not limited to a configuration in which it is connected to the first recycle line 61. The second recycle line 62 may be configured to be directly connected to the target gas line 11 separately from the first recycle line 61.

[0101] Furthermore, the discharge concentration acquisition unit 75 is not limited to a configuration in which it is a concentration meter arranged in the regenerator discharge line 15 between the regenerator 3 and the discharge compressor 5. The discharge concentration acquisition unit 75 may be arranged in the regenerator discharge line 15. Therefore, the discharge concentration acquisition unit 75 may be arranged in the regenerator discharge line 15 downstream of the discharge compressor 5. Furthermore, the discharge concentration acquisition unit 75 is not limited to a single concentration meter. The discharge concentration acquisition unit 75 may be able to acquire information on the concentration of carbon dioxide in the regenerator exhaust gas. Therefore, the discharge concentration acquisition unit 75 may be a sensor integrated with the first pressure acquisition unit 72 or the second pressure acquisition unit 74.

[0102] In the present embodiment, the control units 100, 100A, 100B, 100C, and 100D open the first recycle valve 71 when the concentration value acquired by the discharge concentration acquisition unit 75 falls below the concentration standard, but the present invention is not limited to such a configuration. The control units 100, 100A, 100B, 100C, and 100D may open at least one of the first recycle valve 71 and the second recycle valve 73 when the concentration value falls below the concentration standard. Therefore, the control units 100, 100A, 100B, 100C, and 100D may open the second recycle valve 73 or may open both the first recycle valve 71 and the second recycle valve 73 when the concentration value falls below the concentration standard.

[0103] Furthermore, in the second to fifth embodiments, instead of the treatment target gas information acquisition unit 81 and the regeneration tower exhaust gas information acquisition unit 82, a gas information acquisition unit that collectively acquires information on the gas flowing through the treatment target gas line 11 may be provided. Such a gas information acquisition unit may be disposed in the treatment target gas line 11, for example, between the compression unit 21 and the absorption tower 2. This enables the gas information acquisition unit to measure information on the flow rate of the gas flowing through the treatment target gas line 11 and the carbon dioxide concentration of the gas.

[0104] In the second to fifth embodiments, the recovery amount acquisition unit 106 is not limited to acquiring information on the amount of carbon dioxide contained in the gas flowing through the treatment gas line 11 from the information acquired by the treatment gas information acquisition unit 81 and the information acquired by the regeneration tower exhaust gas information acquisition unit 82. The recovery amount acquisition unit 106 may have any configuration as long as it can acquire information on the amount of carbon dioxide contained in the gas flowing through the treatment gas line 11. For example, the recovery amount acquisition unit 106 may estimate and acquire information on the amount of carbon dioxide contained in the gas flowing through the treatment gas line 11 based on information such as the operating state of the carbon dioxide capture systems 1, 1A, 1B, 1C, and 1D and the surrounding devices, the opening degree of various valves, the gas pressure, and the gas temperature, without directly measuring the flow rate and concentration of the gas. By estimating information on the amount of carbon dioxide flowing through the treatment gas line 11 by such means, the cost of installing a sensor or the like can be reduced.

[0105] Further, the configuration is not limited to the one in which only the recycle line 60 is connected to the gas line 11 to be treated. For example, in addition to the recycle line 60, a line capable of supplying a gas with a low concentration of carbon dioxide may be connected to the gas line 11 to be treated.

[0106] <Additional Notes> The carbon dioxide capture systems 1, 1A, 1B, 1C, and 1D described in the respective embodiments can be understood, for example, as follows.

[0107] (1) The carbon dioxide capture systems 1, 1A, 1B, 1C, and 1D according to a first aspect include an absorption tower 2 that brings a gas to be treated containing carbon dioxide into contact with an absorption liquid and discharges the absorption liquid having absorbed the carbon dioxide and an absorption tower exhaust gas containing the gas to be treated from which the carbon dioxide has been removed, a regeneration tower 3 that dissipates the carbon dioxide from the absorption liquid discharged from the absorption tower 2 and discharges the absorption liquid from which the carbon dioxide has been dissipated and a regeneration tower exhaust gas containing the carbon dioxide, a gas to be treated line 11 that introduces the gas to be treated into the absorption tower 2, and a regeneration tower exhaust gas containing the gas to be treated. The regeneration tower exhaust gas supply system includes a regeneration tower discharge line 15 for discharging the regeneration tower exhaust gas discharged from the tower 3 to the outside, a discharge compressor 5 disposed on the regeneration tower discharge line 15 for compressing the regeneration tower exhaust gas, a recycle line 60 connecting the regeneration tower discharge line 15 and the target gas line 11, and recycle units 70, 70A, 70B, 70C capable of adjusting the supply amount of the regeneration tower exhaust gas supplied from the regeneration tower discharge line 15 through the recycle line 60 to the target gas line 11. The recycle units 70, 70A, 70B, 70C are a first recycle line 61 that is connected to the regenerator discharge line 15 between the regenerator 3 and the discharge compressor 5 and that is capable of supplying at least a portion of the regenerator discharge gas before being compressed by the discharge compressor 5 to the gas line 11 to be treated; and a second recycle line 62 that is capable of supplying at least a portion of the regenerator discharge gas compressed by the discharge compressor 5 to the gas line 11 to be treated. The recycle units 70, 70A, 70B, and 70C are disposed on the first recycle line 61 and are connected to the regenerator discharge line 15 from the gas line 11 to be treated. a first recycle valve 71 capable of adjusting the supply amount of the regenerator exhaust gas to the regenerator 3; a first pressure acquisition unit 72 acquiring information on the pressure of the regenerator exhaust gas flowing through the regenerator exhaust line 15 between the regenerator 3 and the discharge compressor 5; a second recycle valve 73 arranged on the second recycle line 62 and capable of adjusting the supply amount of the regenerator exhaust gas from the regenerator exhaust line 15 to the gas line 11 to be treated; and a second pressure acquisition unit 74 acquiring information on the pressure of the regenerator exhaust gas compressed by the discharge compressor 5 and flowing through the regenerator exhaust line 15.The control unit 100, 100A, 100B, 100C, 100D controls the opening degree of the first recycle valve 71 and the second recycle valve 73. The control units 100, 100A, 100B, 100C, 100D open the first recycle valve 71 when the pressure value acquired by the first pressure acquisition unit 72 exceeds a predetermined pressure standard, close the first recycle valve 71 when the pressure value falls below the pressure standard, open the second recycle valve 73 when the pressure value acquired by the second pressure acquisition unit 74 exceeds the pressure standard, and close the second recycle valve 73 when the pressure value falls below the pressure standard.

[0108] According to this configuration, the pressure of the regenerator exhaust gas flowing through the regenerator exhaust line 15 is acquired by the first pressure acquisition unit 72 and the second pressure acquisition unit 74 at the upstream and downstream positions with respect to the discharge compressor 5. Then, based on the results of the first pressure acquisition unit 72 and the second pressure acquisition unit 74, the first recycle valve 71 and the second recycle valve 73 are opened and closed. Therefore, if the pressure of the regenerator exhaust gas immediately after being discharged from the regenerator 3 is high, the regenerator exhaust gas can be sent from the first recycle line 61 to the gas line 11 to be treated. Also, if the pressure of the regenerator exhaust gas immediately after being discharged from the regenerator 3 is low, the regenerator exhaust gas can be compressed by the discharge compressor 5 and then sent from the second recycle line 62 to the gas line 11 to be treated. In this way, regardless of the pressure of the regenerator exhaust gas immediately after being discharged from the regenerator 3, the regenerator exhaust gas at a pressure usable in the absorption tower 2 can be sent to the gas line 11 to be treated. Therefore, most of the regenerator exhaust gas discharged from the regenerator 3 can be sent to the absorption tower 2 for recycling. This adjusts the amount of carbon dioxide returned from the regeneration tower 3 to the absorption tower 2, reducing the amount emitted to the outside.

[0109] (2) The carbon dioxide recovery systems 1, 1A, 1B, 1C, and 1D of the second aspect are the carbon dioxide recovery systems 1, 1A, 1B, 1C, and 1D of (1), wherein the recycle units 70, 70A, 70B, and 70C further have an emission concentration acquisition unit 75 that acquires information on the concentration of carbon dioxide in the regeneration tower exhaust gas circulating through the regeneration tower discharge line 15, and the control units 100, 100A, 100B, 100C, and 100D control at least one of the first recycle valve 71 and the second recycle valve 73 to be opened when the concentration value acquired by the emission concentration acquisition unit 75 falls below a predetermined concentration standard.

[0110] According to this configuration, when the concentration of carbon dioxide in the regenerator exhaust gas discharged from the regenerator 3 is too low to be suitable for supply to the destination, the regenerator exhaust gas is sent to the gas line 11 to be treated through at least one of the first recycle line 61 and the second recycle valve 73. Therefore, even if the regenerator exhaust gas has a carbon dioxide concentration that is not suitable for recycling, it is sent to the gas line 11 to be treated. In this way, it is also possible to prevent the regenerator exhaust gas with a carbon dioxide concentration that is not suitable for supply to the destination from being discharged to the outside. Therefore, it is possible to prevent the amount of regenerator exhaust gas discharged to the outside regardless of the carbon dioxide concentration.

[0111] (3) The carbon dioxide recovery system 1, 1A, 1B, 1C, 1D according to a third aspect is the carbon dioxide recovery system 1, 1A, 1B, 1C, 1D of (1) or (2), further comprising a compression section 21 arranged in the gas to be treated line 11 for compressing the gas to be introduced into the absorption tower 2, and the recycle line 60 is connected to the gas to be treated line 11 so as to merge at least a portion of the regeneration tower exhaust gas with the gas to be treated before being supplied to the compression section 21.

[0112] According to this configuration, the recycle line 60 is connected to the target gas line 11 at a position upstream of the pressure delivery section 21. Therefore, at least a part of the regeneration tower exhaust gas can be merged with the target gas to be treated, which has a low pressure before being supplied to the pressure delivery section 21. Here, the pressure of the regeneration tower exhaust gas flowing through the regeneration tower discharge line 15 is higher than the target gas to be treated, which has a low pressure before being supplied to the pressure delivery section 21. Therefore, in the recycle line 60, a gas flow is generated from the regeneration tower discharge line 15 toward the target gas to be treated line 11 due to the pressure difference between the regeneration tower discharge gas and the target gas to be treated. As a result, the recycle line 60 can stably flow the regeneration tower exhaust gas from the regeneration tower discharge line 15 to the target gas to be treated line 11 without providing a separate device such as a pump in the recycle line 60.

[0113] (4) A carbon dioxide capture system 1A, 1B, 1C, 1D according to a fourth aspect is any one of the carbon dioxide capture systems 1, 1A, 1B, 1C, 1D according to (1) to (3), and further includes a capture amount acquisition unit 106 that acquires information on the amount of carbon dioxide contained in the gas circulating through the gas line 11 to be treated, and a carbon dioxide amount adjustment unit 110, 110B, 110C that adjusts the amount of carbon dioxide to be treated in the absorption tower 2 when the amount of carbon dioxide contained in the gas acquired by the capture amount acquisition unit 106 exceeds a predetermined amount standard.

[0114] According to this configuration, the recovery amount acquisition unit 106 acquires information on the amount of carbon dioxide contained in the gas flowing through the gas line 11 to be treated. Therefore, the amount of carbon dioxide contained in the gas to be treated and the regeneration tower exhaust gas that are mixed and finally flow through the gas line 11 to be treated can be grasped. Furthermore, when the amount of carbon dioxide contained in these gases exceeds a quantity standard, the carbon dioxide amount adjustment units 110, 110B, and 110C adjust the amount of carbon dioxide to be treated in the absorption tower 2. Therefore, it is possible to prevent the absorption tower 2 from treating too little carbon dioxide compared to the amount of carbon dioxide in the gas flowing through the gas line 11 to be treated. Therefore, it is possible to prevent the absorption tower 2 from being unable to sufficiently treat the amount of carbon dioxide, resulting in a state in which a large amount of carbon dioxide is contained in the absorption tower exhaust gas. In other words, it is possible to suppress a decrease in the recovery rate of carbon dioxide in the absorption tower 2. This makes it possible to suppress the amount of gas containing carbon dioxide discharged from the absorption tower 2 to be discharged to the outside.

[0115] (5) The carbon dioxide recovery systems 1A, 1B, 1C, and 1D according to a fifth aspect are the carbon dioxide recovery systems 1A, 1B, 1C, and 1D of (4), and further include a treatment target gas information acquisition unit 81 that acquires information on the flow rate of the treatment target gas flowing through the treatment target gas line 11 and information on the carbon dioxide concentration of the treatment target gas, and a regeneration tower exhaust gas information acquisition unit 82 that acquires information on the flow rate of the treatment target gas flowing through the recycle line 60 and information on the carbon dioxide concentration of the regeneration tower exhaust gas, and the recovery amount acquisition unit 106 acquires information on the amount of carbon dioxide contained in the gas flowing through the treatment target gas line 11 from the information on the flow rate of the treatment target gas and the information on the carbon dioxide concentration of the treatment target gas acquired by the treatment target gas information acquisition unit 81, and the information on the flow rate of the regeneration tower exhaust gas and the information on the carbon dioxide concentration of the regeneration tower exhaust gas acquired by the regeneration tower exhaust gas information acquisition unit 82.

[0116] According to this configuration, the target gas information acquisition unit 81 acquires information on the flow rate of the target gas flowing through the target gas line 11 and information on the carbon dioxide concentration of the target gas. This makes it possible to acquire information on the amount and carbon dioxide concentration of only the target gas that has flowed through the target gas line 11 without passing through the recycle line 60. By being able to grasp the amount and carbon dioxide concentration of the target gas, the amount of carbon dioxide contained in the target gas can be grasped with high accuracy. Furthermore, the regenerator exhaust gas information acquisition unit 82 acquires information on the flow rate of the regenerator exhaust gas flowing through the recycle line 60 and information on the carbon dioxide concentration of the regenerator exhaust gas. This makes it possible to acquire information on the amount and carbon dioxide concentration of only the regenerator exhaust gas that has flowed through the recycle line 60 before merging with the target gas line 11. By being able to grasp the amount and carbon dioxide concentration of the regenerator exhaust gas, the amount of carbon dioxide contained in the regenerator exhaust gas can be grasped with high accuracy. Then, from the information obtained by the treatment gas information obtaining unit 81 and the information obtained by the regeneration tower exhaust gas information obtaining unit 82, the recovery amount obtaining unit 106 can obtain information on the total amount of carbon dioxide contained in the gas flowing through the treatment gas line 11. In this way, by obtaining information on the amount of carbon dioxide contained in the gas separately for the treatment gas line 11 and the recycle line 60, the amount of carbon dioxide supplied to the absorption tower 2 can be grasped with high accuracy. Therefore, a decrease in the carbon dioxide recovery rate in the absorption tower 2 can be effectively suppressed. This makes it possible to further suppress the amount of carbon dioxide-containing gas discharged from the absorption tower 2 to the outside.

[0117] (6) The carbon dioxide recovery system 1A according to a sixth aspect is the carbon dioxide recovery system 1A, 1B, 1C, or 1D of (4) or (5), and further includes a lean line 14 that supplies the absorption liquid discharged from the regenerator 3 and from which the carbon dioxide has been released to the absorption tower 2, a reboiler 31 that heats the absorption liquid discharged from the regenerator 3 by heat exchange with steam, and a recovery line valve 83 that is disposed in the lean line 14 and is capable of adjusting the amount of the absorption liquid supplied from the regenerator 3 to the absorption tower 2, and a steam supply valve 84 that is capable of adjusting the amount of steam supplied to the reboiler 31. When the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds the amount standard, the carbon dioxide amount adjustment units 110, 110B, and 110C control the recovery line valve 83 and the steam supply valve 84 to be larger in opening and smaller in opening when the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds the amount standard, and control the recovery line valve 83 and the steam supply valve 84 to be smaller in opening.

[0118] According to this configuration, when the amount of carbon dioxide exceeds the amount standard, the opening of the recovery line valve 83 and the steam supply valve 84 is increased. By increasing the opening of the steam supply valve 84, the amount of heating in the reboiler 31 increases, and the amount of lean liquid generated in the regenerator 3 increases. As a result, the supply amount of lean liquid supplied from the regenerator 3 to the lean line 14 increases. Furthermore, by increasing the opening of the recovery line valve 83, the supply amount of lean liquid supplied to the absorption tower 2 via the lean line 14 also increases. Furthermore, when the amount of carbon dioxide falls below the amount standard, the opening of the recovery line valve 83 and the steam supply valve 84 is reduced. By narrowing the opening of the steam supply valve 84, the amount of heating in the reboiler 31 decreases, and the amount of lean liquid generated in the regenerator 3 decreases. As a result, the supply amount of lean liquid supplied from the regenerator 3 to the lean line 14 decreases. Furthermore, by narrowing the aperture of the recovery line valve 83, the amount of lean liquid supplied to the absorption tower 2 via the lean line 14 is reduced. In this manner, the amount of lean liquid generated in the regeneration tower 3 and the amount of the generated lean liquid supplied to the absorption tower 2 are adjusted according to the amount of carbon dioxide supplied to the absorption tower 2. Therefore, a decrease in the carbon dioxide recovery rate in the absorption tower 2 can be suppressed by adjusting the amount of absorption liquid supplied. This makes it possible to further suppress the amount of gas containing carbon dioxide discharged to the outside from the absorption tower 2.

[0119] (7) A carbon dioxide capture system 1B according to a seventh aspect is any one of the carbon dioxide capture systems 1A, 1B, 1C, 1D of (5) to (6), further comprising an absorption tower discharge line 12 that discharges the absorption tower exhaust gas discharged from the absorption tower 2 to the outside, and the recycle unit 70, 70A, 70B, 70C further comprises a bypass line 85 that connects the recycle line 60 and the absorption tower discharge line 12, and a first bypass valve 86 that is arranged on the bypass line 85 and can adjust the supply amount of the regeneration tower exhaust gas from the recycle line 60 to the absorption tower discharge line 12, and the carbon dioxide amount adjustment unit 110, 110B, 110C opens the first bypass valve 86 when the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds the amount standard, and closes the first bypass valve 86 when the amount falls below the amount standard.

[0120] According to this configuration, when the amount of carbon dioxide exceeds the amount standard, the first bypass valve 86 is opened. By opening the first bypass valve 86, the regenerator exhaust gas flowing through the recycle line 60 is sent from the bypass line 85 to the absorber discharge line 12, and the amount sent to the gas line 11 to be treated is reduced. In other words, most of the regenerator exhaust gas flowing through the recycle line 60 is discharged to the outside without being sent to the absorber 2. Also, when the amount of carbon dioxide falls below the amount standard, the first bypass valve 86 is closed. By closing the first bypass valve 86, the bypass line 85 becomes inoperable, and the regenerator exhaust gas is sent to the gas line 11 to be treated. In other words, the regenerator exhaust gas flowing through the first recycle line 61 is sent to the absorber 2. In this way, when the amount of carbon dioxide supplied to the absorber 2 exceeds the amount of carbon dioxide that can be absorbed by the absorber 2 and the absorber 2 cannot treat the carbon dioxide, it is possible to prevent excess carbon dioxide from being supplied to the absorber 2. This makes it possible to prevent instability in the process due to a breakdown in the absorption tower 2 caused by an excess supply of carbon dioxide to the absorption tower 2. This makes it possible to stably suppress the amount of gas containing carbon dioxide discharged from the absorption tower 2 to the outside.

[0121] (8) The carbon dioxide capture system 1C according to an eighth aspect is the carbon dioxide capture system 1A, 1B, 1C, 1D of (7), wherein the recycle section 70, 70A, 70B, 70C further includes a second bypass valve 87 that is arranged between the arrangement positions of the first recycle valve 71 and the second recycle valve 73 and the connection position of the gas line to be treated 11 and the recycle line 60 and is capable of adjusting the supply amount of the regeneration tower exhaust gas from the recycle line 60 to the gas line to be treated 11, and the carbon dioxide amount adjustment section 110, 110B, 110C opens the first bypass valve 86 and closes the second bypass valve 87 when the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition section 106 exceeds the amount standard, and closes the first bypass valve 86 and opens the second bypass valve 87 when the amount falls below the amount standard.

[0122] According to this configuration, when the amount of carbon dioxide exceeds the amount standard, the first bypass valve 86 is opened and the second bypass valve 87 is closed. By opening the first bypass valve 86 and closing the second bypass valve 87, the flow of the regenerator exhaust gas from the first recycle line 61 to the target gas line 11 is completely blocked. The regenerator exhaust gas flowing through the first recycle line 61 is discharged to the outside without being sent to the absorber 2 at all. In this way, when the regenerator exhaust gas is supplied to the absorber exhaust line 12 via the first bypass valve 86, the flow of the regenerator exhaust gas to the target gas line 11 is completely blocked, so that it is possible to reliably suppress instability of the treatment caused by excessive carbon dioxide being supplied to the absorber 2. This makes it possible to more stably suppress the discharge of gas containing carbon dioxide from the absorber 2 to the outside.

[0123] (9) A carbon dioxide capture system 1D according to a ninth aspect is any one of the carbon dioxide capture systems 1A, 1B, 1C, and 1D according to (4) to (8), and further includes a lean line 14 that supplies the absorbing liquid discharged from the regenerator 3 and having released the carbon dioxide to the absorption tower 2, a lean tank 91 that stores the absorbing liquid that has released the carbon dioxide and is circulating through the lean line 14, a lean valve 92 that can adjust the amount of the absorbing liquid supplied between the lean tank 91 and the lean line 14, a rich line 13 that supplies the absorbing liquid discharged from the absorption tower 2 and having absorbed the carbon dioxide to the regenerator 3, a rich tank 93 that stores the absorbing liquid that has absorbed the carbon dioxide and is circulating through the rich line 13, and a valve between the rich tank 93 and the rich line 13. and a rich valve 94 capable of adjusting the amount of the absorption liquid supplied. In the carbon dioxide amount adjustment units 110, 110B, 110C, when the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds the amount standard, the lean valve 92 increases the amount of the absorption liquid supplied from the lean tank 91 to the lean line 14, and the rich valve 94 increases the amount of the absorption liquid supplied from the rich line 13 to the rich tank 93. When the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit 106 exceeds the amount standard, the rich valve 94 increases the amount of the absorption liquid supplied from the rich tank 93 to the rich line 13, and the lean valve 92 increases the amount of the absorption liquid supplied from the lean line 14 to the lean tank 91.

[0124] According to this configuration, when the total amount of carbon dioxide exceeds the amount standard, the lean valve 92 increases the amount of absorbent supplied from the lean tank 91 to the lean line 14, and the rich valve 94 increases the amount of absorbent supplied from the rich line 13 to the rich tank 93. That is, the ratio of the lean liquid in the absorbent circulating between the lean line 14 and the rich line 13 can be increased. As a result, the amount of lean liquid supplied to the absorption tower 2 can be increased, and the amount of carbon dioxide treated in the absorption tower 2 can be increased. In addition, when the total amount of carbon dioxide falls below the amount standard, the rich valve 94 increases the amount of absorbent supplied from the rich tank 93 to the rich line 13, and the lean valve 92 increases the amount of absorbent supplied from the lean line 14 to the lean tank 91. That is, the ratio of the rich liquid in the absorbent circulating between the lean line 14 and the rich line 13 can be increased. As a result, the amount of lean liquid supplied to the absorption tower 2 can be reduced, and the amount of carbon dioxide treated in the absorption tower 2 can be reduced. In this way, the amount of lean liquid supplied to the absorption tower 2 is adjusted according to the total amount of carbon dioxide supplied to the absorption tower 2. Therefore, it is possible to suppress a decrease in the carbon dioxide recovery rate in the absorption tower 2 by adjusting the amount of absorption liquid supplied. This makes it possible to further suppress the amount of gas containing carbon dioxide discharged from the absorption tower 2 to the outside.

[0125] (10) A carbon dioxide recovery system 1D according to a tenth aspect is any one of the carbon dioxide recovery systems 1, 1A, 1B, 1C, 1D of (1) to (9), and the control unit 100, 100A, 100B, 100C, 100D opens the first recycle valve 71 and the second recycle valve 73 when it is estimated that a predetermined condition is satisfied that indicates a sudden change in the flow state of the regeneration tower exhaust gas flowing through the regeneration tower discharge line 15.

[0126] According to this configuration, when the flow state of the regenerator exhaust gas satisfies the conditions, the first recycle valve 71 and the second recycle valve 73 are opened. Therefore, when the flow state of the regenerator exhaust gas in the regenerator discharge line 15 changes suddenly, the regenerator exhaust gas discharged from the regenerator 3 can be sent to the absorption tower 2 and recycled without being discharged to the outside. Therefore, it is possible to respond to the sudden change in the flow state of the regenerator exhaust gas discharged from the regenerator 3 and suppress the amount of gas containing carbon dioxide discharged to the outside. [Explanation of symbols]

[0127] 1, 1A, 1B, 1C, 1D...Carbon dioxide capture system 2. Absorption tower 11…Gas line to be treated 21…Pumping section 12…Absorption tower discharge line 3…Regeneration Tower 31…Reboiler 13…Rich Line 35…Rich Pump 14…Lean Line 37…Lean pump 38...Cooler 4…Absorption liquid heat exchanger 15…Regeneration tower discharge line 5…Discharge compressor 60…Recycling line 61…First recycling line 62…Second recycling line 70, 70A, 70B, 70C...Recycling Department 71...First recycle valve 72…First pressure acquisition unit 73...Second recycle valve 74…Second pressure acquisition unit 75...Emission concentration acquisition section 100, 100A, 100B, 100C, 100D...Control section 101, 101D...Input section 102, 102D...judgment section 103...First valve control section 104...Second valve control section 81... Processing target gas information acquisition unit 82…Regeneration tower exhaust gas information acquisition section 83...Recovery line valve 84...Steam supply valve 106…Collection amount acquisition section 110, 110B, 110C... Carbon dioxide amount adjustment section 111, 111B, 111C...Quantity judgment section 112... Collection control unit 113...Steam control unit 85…Detour line 86…First bypass valve 87...Second bypass valve 115...First bypass control section 116...Second bypass control unit 91…Lean tank 92...Lean valve 93…Rich Tank 94…Rich valve 118...Lean control unit 119…Rich control section

Claims

1. an absorption tower that contacts a gas to be treated containing carbon dioxide with an absorption liquid and discharges the absorption liquid having absorbed the carbon dioxide and an absorption tower exhaust gas containing the gas to be treated from which the carbon dioxide has been removed; A regeneration tower that dissipates the carbon dioxide from the absorption liquid discharged from the absorption tower and discharges the absorption liquid from which the carbon dioxide has been dissipated and a regeneration tower exhaust gas containing the carbon dioxide; a gas to be treated line for introducing the gas to be treated into the absorption tower; a regeneration tower discharge line for discharging the regeneration tower exhaust gas discharged from the regeneration tower to the outside; a discharge compressor disposed in the regeneration tower discharge line and compressing the regeneration tower discharge gas; a recycle line connecting the regeneration tower discharge line and the target gas line; a recycle unit capable of adjusting a supply amount of the regeneration tower exhaust gas supplied from the regeneration tower discharge line through the recycle line to the gas line to be treated, The recycling section includes: A first recycle line is connected to the regeneration tower discharge line between the regeneration tower and the discharge compressor, and is capable of supplying at least a portion of the regeneration tower discharge gas before being compressed by the discharge compressor to the gas line to be treated; A second recycle line capable of supplying at least a portion of the regeneration tower exhaust gas compressed by the exhaust compressor to the treatment target gas line, The recycling section includes: a first recycle valve arranged in the first recycle line and capable of adjusting a supply amount of the regeneration tower exhaust gas from the regeneration tower exhaust line to the gas line to be treated; a first pressure acquisition unit that acquires information on the pressure of the regeneration tower exhaust gas flowing through the regeneration tower exhaust line between the regeneration tower and the discharge compressor; a second recycle valve arranged in the second recycle line and capable of adjusting the amount of the regeneration tower exhaust gas supplied from the regeneration tower exhaust line to the gas line to be treated; A second pressure acquisition unit that acquires information on the pressure of the regeneration tower exhaust gas compressed by the exhaust compressor and flowing through the regeneration tower exhaust line; a control unit for controlling the opening degree of the first recycle valve and the second recycle valve, The control unit is When the value of the pressure acquired by the first pressure acquisition unit exceeds a predetermined pressure standard, the first recycle valve is opened, and when the value of the pressure acquired by the first pressure acquisition unit falls below the pressure standard, the first recycle valve is closed, A carbon dioxide capture system that opens the second recycle valve when the pressure value acquired by the second pressure acquisition unit exceeds the pressure standard, and closes the second recycle valve when the pressure value falls below the pressure standard.

2. The recycle unit further includes an emission concentration acquisition unit that acquires information on the concentration of carbon dioxide in the regeneration tower exhaust gas flowing through the regeneration tower exhaust line, The carbon dioxide capture system according to claim 1, wherein the control unit controls at least one of the first recycle valve and the second recycle valve to be opened when the concentration value acquired by the emission concentration acquisition unit falls below a predetermined concentration standard.

3. a pressure delivery unit arranged in the treatment target gas line and pressure delivery of the treatment target gas to be introduced into the absorption tower; 3. The carbon dioxide recovery system according to claim 1, wherein the recycle line is connected to the gas to be treated line so as to merge at least a portion of the regeneration tower exhaust gas with the gas to be treated before it is supplied to the pressure delivery section.

4. a recovery amount acquiring unit that acquires information on the amount of carbon dioxide contained in the gas flowing through the treatment target gas line; The carbon dioxide recovery system according to claim 1 or 2, further comprising a carbon dioxide amount adjustment unit that adjusts the amount of carbon dioxide to be treated in the absorption tower when the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit exceeds a predetermined amount standard.

5. a target gas information acquisition unit that acquires information on a flow rate of the target gas flowing through the target gas line and information on a concentration of the carbon dioxide in the target gas; A regeneration tower exhaust gas information acquisition unit that acquires information on the flow rate of the regeneration tower exhaust gas circulating through the recycle line and information on the carbon dioxide concentration of the regeneration tower exhaust gas, The carbon dioxide recovery system of claim 4, wherein the recovery amount acquisition unit acquires information on the amount of carbon dioxide contained in the gas supplied to the absorption tower from information on the flow rate of the gas to be treated and information on the carbon dioxide concentration of the gas to be treated acquired by the gas to be treated information acquisition unit, and information on the flow rate of the regeneration tower exhaust gas and information on the carbon dioxide concentration of the regeneration tower exhaust gas acquired by the regeneration tower exhaust gas information acquisition unit.

6. a lean line that supplies the absorption liquid discharged from the regeneration tower and from which the carbon dioxide has been released to the absorption tower; a reboiler that heats the absorption liquid discharged from the regeneration tower by heat exchange with steam; a recovery line valve disposed in the lean line and capable of adjusting the amount of the absorbing liquid supplied from the regeneration tower to the absorption tower; A steam supply valve capable of adjusting the amount of steam supplied to the reboiler, The carbon dioxide capture system of claim 4, wherein the carbon dioxide amount adjustment unit increases the opening of the capture line valve and the steam supply valve when the amount of carbon dioxide contained in the gas acquired by the capture amount acquisition unit exceeds the amount standard, and controls the opening of the capture line valve and the steam supply valve to be smaller when the amount of carbon dioxide contained in the gas acquired by the capture amount acquisition unit falls below the amount standard.

7. An absorber exhaust line is further provided for exhausting the absorber exhaust gas discharged from the absorber to the outside. The recycling section includes: a bypass line connecting the recycle line and the absorber discharge line; A first bypass valve is disposed in the bypass line and is capable of adjusting the supply amount of the regeneration tower exhaust gas from the recycle line to the absorption tower exhaust line, 5. The carbon dioxide capture system of claim 4, wherein the carbon dioxide amount adjustment unit opens the first bypass valve when the amount of carbon dioxide contained in the gas acquired by the capture amount acquisition unit exceeds the amount standard, and closes the first bypass valve when the amount of carbon dioxide falls below the amount standard.

8. The recycling section includes: A second bypass valve is disposed between the positions of the first recycle valve and the second recycle valve and the connection position of the gas line to be treated and the recycle line, and is capable of adjusting the supply amount of the regeneration tower exhaust gas from the recycle line to the gas line to be treated, 8. The carbon dioxide capture system of claim 7, wherein the carbon dioxide amount adjustment unit opens the first bypass valve and closes the second bypass valve when the amount of carbon dioxide contained in the gas acquired by the capture amount acquisition unit exceeds the amount standard, and closes the first bypass valve and opens the second bypass valve when the amount of carbon dioxide falls below the amount standard.

9. a lean line that supplies the absorption liquid discharged from the regeneration tower and from which the carbon dioxide has been released to the absorption tower; a lean tank that stores the absorbing liquid from which the carbon dioxide flowing through the lean line has been stripped; a lean valve capable of adjusting the amount of the absorption liquid supplied between the lean tank and the lean line; A rich line that supplies the absorption liquid discharged from the absorption tower and absorbing the carbon dioxide to the regeneration tower; A rich tank that stores the absorption liquid that absorbs the carbon dioxide flowing through the rich line; A rich valve capable of adjusting the amount of the absorption liquid supplied between the rich tank and the rich line, In the carbon dioxide amount adjustment unit, the amount of carbon dioxide contained in the gas acquired by the recovery amount acquisition unit is When the amount of the absorbent exceeds the amount standard, the lean valve increases the amount of the absorbent supplied from the lean tank to the lean line, and the rich valve increases the amount of the absorbent supplied from the rich line to the rich tank; 5. The carbon dioxide capture system according to claim 4, wherein, when the amount falls below the quantity reference, the rich valve increases the amount of the absorption liquid supplied from the rich tank to the rich line, and the lean valve increases the amount of the absorption liquid supplied from the lean line to the lean tank.

10. The carbon dioxide recovery system according to claim 1 or 2, wherein the control unit opens the first recycle valve and the second recycle valve when it is estimated that a predetermined condition is satisfied that indicates that the flow state of the regeneration tower exhaust gas flowing through the regeneration tower discharge line has changed suddenly.

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