Exhaust gas treatment system, absorption liquid management device, and exhaust gas treatment method

Abstract

This exhaust gas treatment system comprises: a cooling tower in which an exhaust gas containing carbon dioxide is cooled; an absorption tower into which an amine-based absorption liquid capable of absorbing the carbon dioxide in the exhaust gas is introduced and in which the carbon dioxide in the exhaust gas passing through the cooling tower is absorbed by the amine-based absorption liquid; a regeneration tower in which the amine-based absorption liquid having the carbon dioxide absorbed therein is heated to separate the carbon dioxide from the amine-based absorption liquid, thereby regenerating the amine-based absorption liquid; an addition unit in which an additive for adjusting the hydroxide ion concentration in a cooling liquid is added to the cooling liquid; a state detection unit in which the state of the amine-based absorption liquid is detected; and a control device which adjusts the amount of the additive to be added in the addition unit on the basis of the state of the amine-based absorption liquid which has been detected by the state detection unit.

Description

Exhaust gas treatment system, absorption liquid management device, and exhaust gas treatment method

[0001] This application claims priority to U.S. application Ser. No. 18 / 738,242 filed on June 10, 2024, the contents of which are incorporated herein by reference.

[0002] It is desirable to reduce the amount of carbon dioxide emitted from exhaust gases from ships, power plants, and other plants. For this reason, for example, Patent Document 1 discloses a carbon dioxide separation and capture system that captures carbon dioxide contained in exhaust gases by bringing the exhaust gases into contact with an amine-based absorbent. In this system, the amine-based absorbent is replaced based on the electrical conductivity and oxidation-reduction potential of the amine-based absorbent, whose absorption performance deteriorates with use.

[0003] Japanese Patent Application Laid-Open No. 2023-148274

[0004] However, when the amine-based absorbent reacts with oxygen (O2) contained in the exhaust gas in the absorption tower and is oxidized, aldehydes are generated. It is undesirable for the generated aldehydes to be discharged from the absorption tower into the atmosphere. In response to this, when the amine-based absorbent deteriorates due to oxidation, the amine-based absorbent can be replaced using a configuration such as that disclosed in Patent Document 1, but replacing the amine-based absorbent requires time and effort and costs.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an exhaust gas treatment system, an absorption liquid management device, and an exhaust gas treatment method that can effectively suppress oxidative degradation of the absorption liquid while reducing effort and cost.

[0006] In order to solve the above problems, the exhaust gas treatment system according to the present disclosure includes a cooling tower that cools exhaust gas containing carbon dioxide by bringing a cooling liquid into contact with the exhaust gas, an absorption tower into which an amine-based absorbing liquid capable of absorbing carbon dioxide in the exhaust gas is introduced and which causes the amine-based absorbing liquid to absorb the carbon dioxide in the exhaust gas that has passed through the cooling tower, a regeneration tower that heats the amine-based absorbing liquid that has absorbed carbon dioxide, separates the carbon dioxide from the amine-based absorbing liquid, and regenerates the amine-based absorbing liquid, an addition unit that adds an additive to the cooling liquid to adjust the hydroxide ion concentration of the cooling liquid, a state detection unit that detects the state of the amine-based absorbing liquid, and a control device that adjusts the amount of sodium hydroxide added in the addition unit based on the state of the amine-based absorbing liquid detected by the state detection unit.

[0007] The absorbent management device according to the present disclosure is an absorbent management device provided in an exhaust gas treatment system including a cooling tower that cools exhaust gas containing carbon dioxide by bringing a cooling liquid into contact with the exhaust gas, an absorption tower into which an amine-based absorbent capable of absorbing carbon dioxide in the exhaust gas is introduced and which causes the amine-based absorbent to absorb the carbon dioxide in the exhaust gas that has passed through the cooling tower, and a regeneration tower that heats the amine-based absorbent that has absorbed carbon dioxide and separates the carbon dioxide from the amine-based absorbent to regenerate the amine-based absorbent, and is equipped with: an addition unit that adds an additive to the coolant to adjust the hydroxide ion concentration of the coolant; a state detection unit that detects the state of the amine-based absorbent; and a control device that adjusts the amount of sodium hydroxide added in the addition unit based on the state of the amine-based absorbent detected by the state detection unit.

[0008] The method for treating exhaust gas according to the present disclosure includes cooling exhaust gas containing carbon dioxide by bringing a coolant into contact with the exhaust gas, absorbing the carbon dioxide in the exhaust gas with an amine-based absorbing liquid capable of absorbing the carbon dioxide in the exhaust gas, and heating the amine-based absorbing liquid that has absorbed the carbon dioxide to separate the carbon dioxide from the amine-based absorbing liquid and regenerating the amine-based absorbing liquid, and includes the steps of detecting a state of the amine-based absorbing liquid, and adjusting the amount of the additive to be added to the coolant, which adjusts the hydroxide ion concentration of the coolant, based on the detected state of the amine-based absorbing liquid.

[0009] According to the flue gas treatment system, absorbent management device, and flue gas treatment method of the present disclosure, it is possible to effectively suppress oxidation degradation of the absorbent while reducing the effort and cost.

[0010] FIG. 1 is a diagram showing a configuration of an exhaust gas treatment system according to a first embodiment of the present disclosure. FIG. 2 is a diagram showing a hardware configuration of a control device of the exhaust gas treatment system according to an embodiment of the present disclosure. FIG. 3 is a functional block diagram of the control device of the exhaust gas treatment system according to an embodiment of the present disclosure. FIG. 4 is a diagram showing an example of correlation information stored in a control device according to an embodiment of the present disclosure, relating to the correlation between the oxidation-reduction potential of an amine-based absorbing solution and the degree of deterioration due to oxidation of the amine-based absorbing solution. FIG. 5 is a diagram showing an example of correlation information stored in a control device according to an embodiment of the present disclosure, relating to the correlation between the hydrogen ion concentration of a cooling liquid, the sulfur dioxide removal rate in a cooling tower, and the carbon dioxide removal rate in an absorption tower. FIG. 6 is a flowchart showing the flow of a method for treating exhaust gas according to an embodiment of the present disclosure. FIG. 7 is a diagram showing the configuration of an exhaust gas treatment system according to a second embodiment of the present disclosure.

[0011] Hereinafter, embodiments for implementing an exhaust gas treatment system, an absorption liquid management device, and an exhaust gas treatment method according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to these embodiments. <First Embodiment> (Configuration of Exhaust Gas Treatment System) An exhaust gas treatment system 10A shown in FIG. 1 is connected to a gas emission source (not shown) that emits exhaust gas containing carbon dioxide, and is installed in a plant such as a ship or a power plant. Specifically, in the case of a ship, the gas emission source is, for example, an internal combustion engine used as a main engine for propelling the ship, an internal combustion engine used in a power generation facility that supplies electricity to the ship, or a boiler that generates steam. In addition, in the case of a power plant, the gas emission source is a blast furnace. In such gas emission sources, exhaust gas generated by burning fuel contains carbon dioxide and sulfur components such as sulfur dioxide (SO2).

[0012] The flue gas treatment system 10A recovers carbon dioxide contained in flue gas from a gas emission source, and includes a cooling tower 11, an absorption tower 12, a regeneration tower 13, a recovery unit 15, and an absorption liquid management device 20A.

[0013] The cooling tower 11 cools the exhaust gas from the gas emission source with a cooling liquid L1. If the gas emission source is provided on a ship, the water around the ship or fresh water stored in a fresh water tank (not shown) provided on the ship can be used as the cooling liquid L1. If the gas emission source is provided on a plant such as a power plant, for example, seawater, river water, industrial water, etc. can be used as the cooling liquid L1.

[0014] One end of a gas introduction line 101 is connected to the bottom of the cooling tower 11. The gas introduction line 101 is provided at the inlet of the flue gas treatment system 10A, and flue gas is fed into the gas introduction line 101 from a gas emission source (not shown) outside the flue gas treatment system 10A. The other end of the gas introduction line 101 is connected to a desulfurization device (not shown) provided between the gas emission source and the cooling tower 11. The desulfurization device removes sulfur components such as sulfur dioxide (SO2) contained in the flue gas.

[0015] The cooling tower 11 includes a tower body 11a and a nozzle 11b that sprays a cooling liquid L1 from the top of the tower body 11a. A cooling liquid supply line 102 that circulates the cooling liquid L1 is connected to the cooling tower 11. One end of the cooling liquid supply line 102 is connected to the bottom of the tower body 11a. The other end of the cooling liquid supply line 102 is connected to the nozzle 11b at the top of the tower body 11a.

[0016] A coolant supply pump 31 and a first heat exchanger 41 are provided along the coolant supply line 102. The coolant supply pump 31 sucks the coolant L1 accumulated at the bottom of the tower body 11a out of the tower body 11a and supplies it to a nozzle 11b at the top of the tower body 11a. The coolant L1 supplied to the nozzle 11b is sprayed into the tower body 11a from the nozzle 11b and comes into contact (gas-liquid contact) with the flue gas sent into the tower body 11a. This cools the flue gas, and soot and dust contained in the flue gas are captured and washed away by the coolant L1.

[0017] The first heat exchanger 41 exchanges heat between the coolant L1 flowing in the coolant supply line 102 and the cooling water flowing in the refrigerant line 107, thereby cooling the coolant L1.

[0018] One end of an exhaust gas discharge line 103 is connected to the top of the tower body 11a. The exhaust gas discharge line 103 sends the exhaust gas, which has been cooled by washing away soot and dust with a cooling liquid inside the tower body 11a, to the absorption tower 12.

[0019] The absorption tower 12 absorbs carbon dioxide contained in the flue gas into an amine-based absorption solution L2 containing an amine. The absorption tower 12 includes a tower body 12a and nozzles 12b and 12c. The nozzle 12b sprays the absorption solution L2 into the tower body 12a and brings it into gas-liquid contact with the flue gas, thereby removing carbon dioxide from the flue gas. The nozzle 12c sprays wash water into the tower body 12a and brings it into contact with the flue gas from which carbon dioxide has been removed, thereby recovering the absorption solution L2 sprayed from the nozzle 12b and contained in the flue gas. The other end of the flue gas discharge line 103 is connected to the bottom of the tower body 12a. The flue gas that has passed through the cooling tower 11 is sent into the tower body 12a through the flue gas discharge line 103.

[0020] The nozzle 12b is provided in the lower part of the absorption tower 12. The nozzle 12c is provided in the upper part of the absorption tower 12. The amine-based absorbent L2 is supplied to the nozzle 12b from the regeneration tower 13 via a circulation line 106 described later.

[0021] A wash water circulation line 105 for circulating wash water is connected to the absorption tower 12. One end of the wash water circulation line 105 is connected to the middle of the tower body 12a. The other end of the absorption liquid circulation line 105 is connected to a nozzle 12c in the tower body 12a at the upper part of the tower body 12a. A wash water circulation pump 33 and a second heat exchanger 43 are provided midway along the wash water circulation line 105. The wash water circulation pump 33 sucks wash water from above a wash water receiver 12d provided in the middle part of the tower body 12a and supplies it to the nozzle 12c at the upper part of the tower body 12a.

[0022] The amine-based absorbent L2 supplied to the nozzle 12b is sprayed into the tower body 12a and comes into contact with the flue gas sent into the tower body 12a. As a result, carbon dioxide contained in the flue gas is absorbed by the amine-based absorbent L2 in the tower body 12a of the absorption tower 12.

[0023] A cooling water supply pipe 82A is connected to the second heat exchanger 43. Cooling water is supplied to the second heat exchanger 43 from outside the exhaust gas treatment system 10A through this cooling water supply pipe 82A. The second heat exchanger 43 exchanges heat between the cooling water supplied from outside the exhaust gas treatment system 10A and the cleaning water flowing in the cleaning water circulation line 105. In other words, the second heat exchanger 43 cools the cleaning water circulating in the cleaning water circulation line 105 with the cooling water supplied from outside the exhaust gas treatment system 10A. The cleaning water cooled by the second heat exchanger 43 is sprayed into the tower body 12a from nozzles 12c at the top of the tower body 12a.

[0024] One end of an exhaust pipe 12e is connected to the top of the tower body 12a. The exhaust pipe 12e guides the exhaust gas that has left the absorption tower 12, in other words, the exhaust gas from which the amine-based absorbent L2 has been removed by the absorption tower 12, to, for example, an exhaust funnel (not shown) or the like, and releases the exhaust gas into the atmosphere.

[0025] The regeneration tower 13 separates gaseous carbon dioxide from the amine-based absorbing solution L2 that has absorbed carbon dioxide in the absorption tower 12. The regeneration tower 13 includes a tower body 13a, a nozzle 13b that sprays the amine-based absorbing solution L2 into the tower body 13a, and a nozzle 13c that sprays the refluxed condensed water. The nozzle 13b is provided in the lower part of the tower body 13a. The nozzle 13c is provided in the upper part of the tower body 13a.

[0026] A circulation line 106 is provided between the absorption tower 12 and the regeneration tower 13. The circulation line 106 circulates the amine-based absorbent L2 between the absorption tower 12 and the regeneration tower 13. The circulation line 106 includes an absorbent supply line 106A, an absorbent discharge line 106B, and a heat exchanger 45.

[0027] One end of the absorbing liquid supply line 106A is connected to the bottom of the tower body 13a of the regenerator 13. The other end of the absorbing liquid supply line 106A is connected to a nozzle 12b in the tower body 12a of the absorption tower 12. A first circulation pump 32A and a third heat exchanger 46 are provided along the absorbing liquid supply line 106A. The first circulation pump 32A sucks the amine-based absorbing liquid L2 from the bottom of the tower body 13a of the regenerator 13 through the absorbing liquid supply line 106A and supplies it to the nozzle 12b of the tower body 12a of the absorption tower 12.

[0028] A cooling water supply pipe 82B is connected to the third heat exchanger 46. Cooling water is supplied to the third heat exchanger 46 from outside the flue gas treatment system 10A through the cooling water supply pipe 82B. The third heat exchanger 46 exchanges heat between the cooling water supplied from outside the flue gas treatment system 10A and the amine-based absorbing solution L2 flowing through the absorbent supply line 106A. In other words, the third heat exchanger 46 cools the amine-based absorbing solution L2 supplied to the absorber 12 through the absorbent supply line 106A using the cooling water supplied from outside the flue gas treatment system 10A. The amine-based absorbing solution L2 cooled by the third heat exchanger 46 is sprayed into the tower body 12a from the nozzles 12b of the absorber 12.

[0029] One end of the absorbent discharge line 106B is connected to the bottom of the tower body 12a of the absorption tower 12. The other end of the absorbent discharge line 106B is connected to a nozzle 13b provided in the tower body 13a of the regeneration tower 13. A second circulation pump 32B is provided midway along the absorbent discharge line 106B. The second circulation pump 32B sucks the amine-based absorbent L2 from the bottom of the tower body 12a of the absorption tower 12 through the absorbent discharge line 106B and supplies it to the nozzle 13b of the tower body 13a of the regeneration tower 13.

[0030] The heat exchanger 45 exchanges heat between the amine-based absorbing solution L2 flowing in the absorbing solution supply line 106A and the amine-based absorbing solution L2 flowing in the absorbing solution discharge line 106B. In other words, the amine-based absorbing solution L2 that has absorbed carbon dioxide and that has not yet been introduced into the regeneration tower 13 is heated by the heat of the amine-based absorbing solution L2 immediately after the carbon dioxide has been separated by the regeneration tower 13.

[0031] The regeneration tower 13 separates gaseous carbon dioxide from the amine-based absorbing solution L2 that has absorbed carbon dioxide in the absorption tower 12. To this end, the regeneration tower 13 heats, by an absorption solution heating line 108, the amine-based absorbing solution L2 that has been sent from the absorption tower 12 to the regeneration tower 13 via an absorption solution discharge line 106B.

[0032] The absorbent heating line 108 is connected to the regenerator 13. The absorbent heating line 108 circulates the amine-based absorbent L2 between the regenerator 13 and the reboiler 48. That is, the absorbent heating line 108 supplies the amine-based absorbent L2 taken out from the regenerator 13 to the reboiler 48, and returns the amine-based absorbent L2 from the reboiler 48 to the regenerator 13. In other words, the reboiler 48 is provided midway along the absorbent heating line 108.

[0033] A steam supply pipe 81 is connected to the reboiler 48. Steam supplied from a boiler (not shown) or the like provided outside the exhaust gas treatment system 10A is sent to the reboiler 48 through the steam supply pipe 81. The reboiler 48 exchanges heat between the steam sent through the steam supply pipe 81 and the amine-based absorbing solution L2 flowing in the absorption solution heating line 108. In other words, the reboiler 48 heats the amine-based absorbing solution L2 with the heat of the steam.

[0034] The reboiler 48 heats the amine-based absorbing solution L2 to separate gaseous carbon dioxide from the amine-based absorbing solution L2. The amine-based absorbing solution L2 and gaseous carbon dioxide separated by the reboiler 48 are returned to the tower main body 13a through an absorbent heating line 108. The amine-based absorbing solution L2 from which gaseous carbon dioxide has been separated and regenerated in this manner is returned to the absorption tower 12 through an absorbent supply line 106A and reused. On the other hand, the separated gaseous carbon dioxide is sent to the recovery section 15 through a gaseous carbon dioxide discharge line 109.

[0035] A condenser 49 is provided in the gaseous carbon dioxide discharge line 109. A cooling water supply pipe 82C is connected to the condenser 49. Cooling water is supplied to the condenser 49 from outside the exhaust gas treatment system 10A through the cooling water supply pipe 82C. The condenser 49 condenses moisture contained in the gaseous carbon dioxide by heat exchange with the cooling water supplied from outside the exhaust gas treatment system 10A.

[0036] The recovery unit 15 recovers the gaseous carbon dioxide separated in the regeneration tower 13. The recovery unit 15 is a gas-liquid separator, and separates the gaseous carbon dioxide sent through the condenser 49 from the condensed water.

[0037] The condensed water after gas-liquid separation is returned from the bottom of the recovery section 15 to the regeneration tower 13 through a reflux line 110. A reflux pump 112 for returning the condensed water to the regeneration tower 13 is provided in the middle of the reflux line 110. The reflux line 110 is connected to a nozzle 13c provided at the top of the regeneration tower 13. The condensed water returned to the regeneration tower 13 is sprayed into the tower body 13a from the nozzle 13c of the regeneration tower 13 as the amine-based absorption liquid L2.

[0038] On the other hand, the gaseous carbon dioxide from which moisture has been removed in the recovery unit 15 is discharged to the outside of the exhaust gas treatment system 10A through the carbon dioxide discharge pipe 111. The gaseous carbon dioxide discharged through the carbon dioxide discharge pipe 111 is stored, for example, in a carbon dioxide recovery tank (not shown). At this time, the gaseous carbon dioxide may be liquefied by an appropriate carbon dioxide liquefaction device and stored in the carbon dioxide recovery tank.

[0039] In the exhaust gas treatment system 10A as described above, exhaust gas discharged from a gas emission source (not shown) is washed through a cooling tower 11 and then introduced into an absorption tower 12. In the absorption tower 12, carbon dioxide contained in the exhaust gas is absorbed by an amine-based absorbent L2. The exhaust gas from which carbon dioxide has been separated as a result of the carbon dioxide being absorbed by the amine-based absorbent L2 is released into the atmosphere. Furthermore, the amine-based absorbent L2 that has absorbed the carbon dioxide contained in the exhaust gas in the absorption tower 12 is sent to a regeneration tower 13 via a circulation line 106. The amine-based absorbent L2 that has absorbed carbon dioxide is heated by a reboiler 48 to increase its temperature, and gaseous carbon dioxide contained in the amine-based absorbent L2 is separated. The separated gaseous carbon dioxide is recovered via a recovery section 15. Meanwhile, the amine-based absorbent L2 from which carbon dioxide has been separated in the regeneration tower 13 is circulated to the absorption tower 12 via a circulation line 106.

[0040] (Configuration of Absorbing Solution Management Device) The absorbing solution management device 20A manages the amine-based absorbing solution L2 in the absorption tower 12. The absorbing solution management device 20A includes an addition unit 21, a state detection unit 201, a pH detection unit 203, and a control device 60A.

[0041] The addition unit 21 adds an additive to the coolant L1 in the cooling tower 11 to adjust the hydroxide ion concentration of the coolant L1. The addition unit 21 adds, as an additive, an alkaline substance such as sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, or magnesium hydroxide. The additive added to the coolant L1 by the addition unit 21 preferably includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, and magnesium hydroxide. In this embodiment, the addition unit 21 adds, as an additive, sodium hydroxide (NaOH), to the coolant L1 in the cooling tower 11. Note that, among the additives exemplified above, an additive other than sodium hydroxide may also be used. The addition unit 21 includes an addition line 22 and a flow rate adjustment valve 23.

[0042] One end of the addition line 22 is connected to the coolant supply line 102, for example, between the coolant supply pump 31 and the first heat exchanger 41. The other end of the addition line 22 is connected to a sodium hydroxide supply source (not shown), such as a tank for storing sodium hydroxide. The sodium hydroxide is added from the supply source through the addition line 22 to the coolant L1 flowing through the coolant supply line 102.

[0043] The flow rate adjustment valve 23 is provided midway along the addition line 22. The opening degree of the flow rate adjustment valve 23 can be adjusted under the control of the control device 60A. By adjusting the opening degree of the flow rate adjustment valve 23, the amount of sodium hydroxide added to the coolant L1 in the coolant supply line 102 through the addition line 22 can be adjusted.

[0044] The pH detection unit 203 detects the hydrogen ion concentration (pH) of the coolant L1. The pH detection unit 203 detects, for example, the hydrogen ion concentration of the coolant L1 flowing through the coolant supply line 102. In this embodiment, the pH detection unit 203 is disposed between the coolant supply pump 31 and one end of the addition line 22. The pH detection unit 203 repeatedly detects the hydrogen ion concentration of the coolant L1 flowing through the coolant supply line 102 at regular time intervals. The pH detection unit 203 outputs the detected value of the hydrogen ion concentration of the coolant L1 to the control device 60A.

[0045] The state detection unit 201 detects the state of the amine-based absorbent L2 in the absorption tower 12. The state detection unit 201 in this embodiment detects the state of the amine-based absorbent L2 in the tower body 12a of the absorption tower 12. The state detection unit 201 in this embodiment detects the state of the amine-based absorbent L2 at the bottom of the absorption tower 12. The state detection unit 201 detects, for example, the state of the amine-based absorbent L2 that is discharged from the bottom of the absorption tower 12 and flows through the absorbent discharge line 106B.

[0046] In this embodiment, the state detection unit 201 detects the oxidation-reduction potential (ORP) of the amine-based absorbing solution L2 as the state of the amine-based absorbing solution L2. The state detection unit 201 repeatedly detects the oxidation-reduction potential of the amine-based absorbing solution L2 in the absorption tower 12 at regular time intervals. The state detection unit 201 outputs the detected value of the oxidation-reduction potential of the amine-based absorbing solution L2 to the control device 60A.

[0047] (Hardware Configuration Diagram) Fig. 2 is a diagram showing the hardware configuration of a control device of an exhaust gas treatment system according to an embodiment of the present disclosure. As shown in Fig. 2, the control device 60A is a computer including a processor 61 such as a CPU (Central Processing Unit), a ROM 62 (Read Only Memory), a RAM 63 (Random Access Memory), a storage 64, and a signal transmission / reception module 65. The signal transmission / reception module 65 receives signals related to the hydrogen ion concentration of the coolant L1 and the oxidation-reduction potential of the amine-based absorption solution L2 from the pH detection unit 203 and the state detection unit 201, respectively.

[0048] (Functional Block Diagram) Figure 3 is a functional block diagram of a control device of an exhaust gas treatment system according to an embodiment of the present disclosure. As shown in Figure 3, a processor 61 of the control device 60A executes programs pre-stored in a storage device such as a ROM 62 or a storage 64, thereby implementing the components of a signal input unit 70, an information acquisition unit 71, an information storage unit 72, an addition amount adjustment unit 74A, and an output unit 75. The signal input unit 70 receives signals related to the hydrogen ion concentration of the coolant L1 and the oxidation-reduction potential of the amine-based absorption solution L2 from a pH detection unit 203 and a state detection unit 201, respectively, via a signal transmission / reception module 65, which is hardware.

[0049] The information acquisition unit 71 acquires the values ​​of the hydrogen ion concentration of the coolant L1 and the oxidation-reduction potential of the amine-based absorption liquid L2 detected by the pH detection unit 203 and the state detection unit 201, respectively, based on the signal received by the signal input unit 70.

[0050] Fig. 4 is a diagram showing an example of correlation information stored in a control device according to an embodiment of the present disclosure, which relates to the correlation between the oxidation-reduction potential of the amine-based absorbing solution and the degree of deterioration of the amine-based absorbing solution due to oxidation. Fig. 5 is a diagram showing an example of correlation information stored in a control device according to an embodiment of the present disclosure, which relates to the correlation between the hydrogen ion concentration of the cooling solution, the sulfur dioxide removal rate in the cooling tower, and the carbon dioxide removal rate in the absorption tower. The information storage unit 72 stores correlation information, for example, as shown in Fig. 4, relating to the correlation between the oxidation-reduction potential of the amine-based absorbing solution L2 and the degree of deterioration of the amine-based absorbing solution L2 due to oxidation. The information storage unit 72 stores a control range A1 of the oxidation-reduction potential that is preset based on the correlation information. This control range A1 is set as a range of oxidation-reduction potential within which aldehydes are unlikely to be generated in the amine-based absorbing solution L2.

[0051] The information storage unit 72 also stores correlation information, such as that shown in FIG. 5 , relating to the correlation between the hydrogen ion concentration of the cooling liquid L1 and the sulfur dioxide removal rate in the cooling tower 11 and the carbon dioxide removal rate in the absorption tower 12. The information storage unit 72 stores a pH range A2 that is set in advance based on this correlation information. This pH range A2 is set so that the oxidation potential of the amine-based absorbent L2 falls within the control range A1. This correlation information is acquired in advance by performing a test operation of the flue gas treatment system 10A, for example. The information storage unit 72 may store only the control range A1 and the upper and lower thresholds of the pH range A2, without storing the correlation information as shown in FIGS. 4 and 5 .

[0052] The addition amount adjusting unit 74A adjusts the amount of sodium hydroxide added in the addition unit 21 based on the hydrogen ion concentration of the coolant L1 and the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the pH detecting unit 203 and the state detecting unit 201. The addition amount adjusting unit 74A adjusts the amount of sodium hydroxide added in the addition unit 21 based on the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detecting unit 201. The addition amount adjusting unit 74A adjusts the amount of sodium hydroxide added in the addition unit 21 so that the oxidation-reduction potential of the amine-based absorbing solution L2 is equal to or lower than the upper threshold of a preset control range A1.

[0053] The addition amount adjustment unit 74A also manages the hydrogen ion concentration of the coolant L1 in a state in which the addition amount of sodium hydroxide is adjusted based on the oxidation-reduction potential of the amine-based absorption solution L2 as described above. The addition amount adjustment unit 74A adjusts the amount of sodium hydroxide added in the addition unit 21 as needed, based on the hydrogen ion concentration of the coolant L1 detected by the pH detection unit 203. The addition amount adjustment unit 74A adjusts the amount of sodium hydroxide added in the addition unit 21 so that the hydrogen ion concentration of the coolant L1 falls within a preset pH range A2.

[0054] The output unit 75 outputs a control signal for changing the amount of sodium hydroxide added in the adding unit 21 based on the control of the adding amount adjusting unit 74A.

[0055] (Procedure of Exhaust Gas Treatment Method) Figure 6 is a flowchart showing the flow of an exhaust gas treatment method according to an embodiment of the present disclosure. In this embodiment, an exhaust gas treatment method S10 described below is realized by a control device 60A sequentially executing processes based on a pre-stored program. As shown in Figure 6, the exhaust gas treatment method S10 according to this embodiment includes step S11 of detecting the state of the amine-based absorption solution and step S12 of adjusting the amount of sodium hydroxide added.

[0056] In step S11 of detecting the state of the amine-based absorbing liquid, information including the oxidation-reduction potential of the amine-based absorbing liquid L2 and the hydrogen ion concentration of the coolant L1 is acquired. To do this, the signal input unit 70 receives the oxidation-reduction potential of the amine-based absorbing liquid L2 detected by the state detection unit 201 and the hydrogen ion concentration of the coolant L1 detected by the pH detection unit 203 at regular time intervals. The information acquisition unit 71 acquires the oxidation-reduction potential of the amine-based absorbing liquid L2 and the hydrogen ion concentration of the coolant L1 based on the signals received by the signal input unit 70.

[0057] In step S12 of adjusting the amount of sodium hydroxide added, the addition amount adjustment unit 74A adjusts the amount of sodium hydroxide added in the addition unit 21 based on the oxidation-reduction potential of the amine-based absorbing solution L2 and the hydrogen ion concentration of the coolant L1, which are acquired by the information acquisition unit 71. In this embodiment, the addition amount adjustment unit 74A adjusts the amount of sodium hydroxide added in the addition unit 21 so that the oxidation-reduction potential of the amine-based absorbing solution L2 is equal to or lower than the upper threshold of a preset control range A1. For example, when the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 201 exceeds the control range A1, the addition amount adjustment unit 74A reduces the aperture of the flow control valve 23 to reduce the amount of sodium hydroxide added in the addition unit 21. When the amount of sodium hydroxide added to the coolant L1 is reduced, the sulfur dioxide removal rate in the cooling tower 11 decreases. As a result, the amount of sulfur dioxide that was not completely removed in the cooling tower 11 that flows into the absorption tower 12 increases. The sulfur dioxide that has flowed into the absorption tower 12 reacts with water contained in the amine-based absorbent L2 to produce sulfurous acid. The produced sulfurous acid reacts with dissolved oxygen in the amine-based absorbent L2, thereby consuming oxygen in the absorption tower 12. The reaction between this sulfurous acid and dissolved oxygen in the amine-based absorbent L2 occurs more quickly than the reaction between the amines contained in the amine-based absorbent L2 and oxygen contained in the exhaust gas. This suppresses oxidation of the amine-based absorbent L2 in the absorption tower 12, thereby making it possible to suppress the production of aldehydes. That is, the addition amount adjustment unit 74A sets the oxidation-reduction potential of the amine-based absorbent L2 within the control range A1, thereby making it difficult for the production of aldehydes due to oxidative degradation to occur in the absorption tower 12.

[0058] Furthermore, the addition amount adjustment unit 74A controls the hydrogen ion concentration of the coolant L1 in a state in which the addition amount of sodium hydroxide in the addition unit 21 is adjusted, based on the oxidation-reduction potential of the amine-based absorption solution L2. The addition amount adjustment unit 74A adjusts the addition amount of sodium hydroxide in the addition unit 21 so that the hydrogen ion concentration of the coolant L1 falls within a predetermined pH range A2. When the hydrogen ion concentration of the coolant L1 detected by the pH detection unit 203 exceeds the pH range A2, the addition amount adjustment unit 74A reduces the opening of the flow rate adjustment valve 23 to reduce the amount of sodium hydroxide added in the addition unit 21. In other words, the addition amount adjustment unit 74A controls the sulfur dioxide removal rate of the coolant L1 in the cooling tower 11 by keeping the hydrogen ion concentration of the coolant L1 within the pH range A2.

[0059] The control device 60A repeatedly executes steps S11 and S12 described above at regular time intervals while the exhaust gas treatment system 10A is in operation.

[0060] (Effects) In the flue gas treatment system 10A, the absorption solution management device 20A, and the flue gas treatment method S10 configured as described above, the amount of sodium hydroxide added as an additive to the cooling solution L1 in the cooling tower 11 is adjusted based on the state of the amine-based absorption solution L2. In the cooling tower 11, sulfur dioxide contained in the flue gas is removed by contacting the cooling solution L1 with the flue gas. When the amount of sodium hydroxide added to the cooling solution L1 is reduced, the sulfur dioxide removal rate in the cooling tower 11 decreases. As a result, the amount of sulfur dioxide that was not completely removed by the cooling tower 11 that flows into the absorption tower 12 increases. The sulfur dioxide that flows into the absorption tower 12 reacts with water contained in the amine-based absorption solution L2 to produce sulfurous acid. The produced sulfurous acid reacts with dissolved oxygen in the amine-based absorption solution L2. This consumes oxygen in the absorption tower 12. The reaction between the sulfurous acid and the dissolved oxygen in the amine-based absorption solution L2 occurs more quickly than the reaction between the amine contained in the amine-based absorption solution L2 and the oxygen contained in the flue gas. Therefore, oxidation of the amine-based absorbent L2 in the absorber 12 is suppressed, and the generation of aldehydes can be suppressed. Thus, by adjusting the amount of sodium hydroxide added to the coolant L1 according to the state of the amine-based absorbent L2, oxidation of the amine-based absorbent L2 is suppressed, and the labor and cost required for replacing the amine-based absorbent L2 are reduced. As a result, it is possible to effectively suppress oxidation degradation of the absorbent while reducing the labor and cost. Furthermore, since the oxygen concentration in the absorber 12 is reduced, corrosion of the metal material forming the absorber 12 can be suppressed. This suppresses elution of the metal material forming the absorber 12 into the amine-based absorbent L2, and in this respect, degradation of the amine-based absorbent L2 can also be suppressed.

[0061] Furthermore, the control device 60A adjusts the amount of sodium hydroxide added so that the hydrogen ion concentration of the cooling liquid L1 detected by the pH detection unit 203 falls within a predetermined pH range A2. This allows the sulfur dioxide removal rate in the cooling tower 11 to be maintained within an appropriate range. Therefore, oxidation of the amine-based absorbing liquid L2 in the absorption tower 12 can be effectively suppressed.

[0062] Furthermore, the state detection unit 201 detects the state of the amine-based absorbent L2 at the bottom of the absorption tower 12. This makes it possible to sequentially adjust the amount of sodium hydroxide to be added based on the state of the amine-based absorbent L2 after absorbing carbon dioxide and the like contained in the exhaust gas in the absorption tower 12.

[0063] Furthermore, the state detection unit 201 detects the oxidation-reduction potential of the amine-based absorbing solution L2, thereby making it possible to grasp the oxidation state of the amine-based absorbing solution L2 and appropriately adjust the amount of sodium hydroxide to be added.

[0064] Furthermore, when the detected oxidation-reduction potential of the amine-based absorbent L2 is equal to or higher than a preset upper threshold, the control device 60A reduces the amount of sodium hydroxide added. This reduces the hydroxide ion concentration (or pH) of the coolant L1 and reduces the sulfur dioxide removal rate in the cooling tower 11. This increases oxygen consumption in the absorption tower 12 and effectively suppresses oxidation of the amine-based absorbent L2 in the absorption tower 12.

[0065] In addition, by using at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, and magnesium hydroxide as an additive and adjusting the amount added to the coolant L1, oxidation of the amine-based absorption solution L2 can be suppressed.

[0066] Second Embodiment Next, a second embodiment of the flue gas treatment system and flue gas treatment method according to 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 description thereof will be omitted. In the second embodiment, the configuration of the absorption liquid management device 20B is different from that of the first embodiment.

[0067] 7 is a diagram showing the configuration of an air pollution control system according to a second embodiment of the present disclosure. As shown in Fig. 7, the air pollution control system 10B includes a cooling tower 11, an absorption tower 12, a regeneration tower 13, a recovery unit 15, and an absorption liquid management device 20B.

[0068] The absorption liquid management device 20B in this embodiment includes an addition unit 21, state detection units 201 and 202, a pH detection unit 203, and a control device 60B.

[0069] The exhaust gas treatment system 10B in this embodiment includes an absorbent cooling line 151. One end of the absorbent cooling line 151 is connected to a lower side of the nozzle 12b in the tower body 12a. The other end of the absorbent cooling line 151 is connected to the tower body 12a above the one end of the absorbent cooling line 151. A cooler 152 is provided midway along the absorbent cooling line 151. The cooler 152 cools the amine-based absorbent L2 flowing through the absorbent cooling line 151 with cooling water supplied from the outside. The absorbent cooling line 151 cools the amine-based absorbent L2 extracted from a vertically intermediate portion of the absorber 12 above the bottom of the absorber 12, and supplies the cooled amine-based absorbent L2 to the absorber 12. The absorbent cooling line 151 cools the amine-based absorbent L2 whose temperature has increased due to absorption of carbon dioxide in the absorber 12, and returns the cooled amine-based absorbent L2 to the absorber 12.

[0070] The state detection unit 202 is provided in the absorbent cooling line 151. The state detection unit 202 detects the state of the amine-based absorbent L2 flowing through the absorbent cooling line 151. In this embodiment, the state detection unit 202 detects the state of the amine-based absorbent L2 supplied to the absorption tower 12. In this embodiment, the state detection unit 202 detects the oxidation-reduction potential of the amine-based absorbent L2 as the state of the amine-based absorbent L2. The state detection unit 202 repeatedly detects the oxidation-reduction potential of the amine-based absorbent L2 in the absorption tower 12 at regular time intervals. The state detection unit 202 outputs the detected value of the oxidation-reduction potential of the amine-based absorbent L2 to the control device 60A.

[0071] As shown in FIG. 3, the processor 61 of the control device 60B in this embodiment executes a program pre-stored in a storage device such as a ROM 62 or a storage 64, thereby realizing each of the components of the signal input unit 70, the information acquisition unit 71, the information storage unit 72, the addition amount adjustment unit 74B, and the output unit 75.

[0072] The addition amount adjusting unit 74B adjusts the amount of sodium hydroxide added in the addition unit 21 based on the hydrogen ion concentration of the coolant L1 detected by the pH detecting unit 203, the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detecting unit 201, and the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detecting unit 202. The addition amount adjusting unit 74B adjusts the amount of sodium hydroxide added in the addition unit 21 detected by the state detecting unit 202 based on the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detecting unit 202. The addition amount adjusting unit 74B adjusts the amount of sodium hydroxide added in the addition unit 21 so that the oxidation-reduction potential of the amine-based absorbing solution L2 is equal to or lower than the upper threshold of a preset control range.

[0073] Furthermore, the addition amount adjustment unit 74B may adjust the amount of sodium hydroxide added in the addition unit 21 based on the difference between the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 202 and the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 201. When the carbon dioxide absorption reaction in the amine-based absorbing solution L2 is occurring at a certain level or higher, the difference between the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 202 and the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 201 becomes equal to or greater than a predetermined value. In contrast, when the amount of carbon dioxide absorption in the amine-based absorbing solution L2 increases (approaching the absorption amount limit), the degree of the carbon dioxide absorption reaction in the amine-based absorbing solution L2 decreases. As a result, the difference between the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 202 and the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 201 becomes smaller. Therefore, when the difference between the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 202 and the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 201 becomes smaller than a predetermined value set in advance, the addition amount adjustment unit 74B reduces the amount of sodium hydroxide added in the addition unit 21.

[0074] (Procedure of Exhaust Gas Treatment Method) As shown in FIG. 6, the exhaust gas treatment method S20 according to this embodiment includes step S21 of detecting the state of the amine-based absorption solution and step S22 of adjusting the amount of sodium hydroxide added.

[0075] In step S21 of detecting the state of the amine-based absorbing liquid, the hydrogen ion concentration of the coolant L1 detected by the pH detection unit 203, the oxidation-reduction potential of the amine-based absorbing liquid L2 detected by the state detection unit 201, and the oxidation-reduction potential of the amine-based absorbing liquid L2 detected by the state detection unit 202 are acquired.

[0076] In step S22 of adjusting the amount of sodium hydroxide added, the addition amount adjustment unit 74B adjusts the amount of sodium hydroxide added in the addition unit 21 based on the hydrogen ion concentration of the coolant L1 detected by the pH detection unit 203 and the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 201, as in the first embodiment, and also adjusts the amount of sodium hydroxide added in the addition unit 21 based on the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 202. The addition amount adjustment unit 74B adjusts the amount of sodium hydroxide added in the addition unit 21 so that the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 202 is equal to or lower than the upper threshold of a preset management range. Furthermore, the addition amount adjustment unit 74B reduces the amount of sodium hydroxide added in the addition unit 21 when the difference between the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 202 and the oxidation-reduction potential of the amine-based absorbing solution L2 detected by the state detection unit 201 becomes smaller than a preset value.

[0077] The control device 60B repeatedly executes steps S21 and S22 described above at regular time intervals while the exhaust gas treatment system 10B is in operation.

[0078] (Effects) In the flue gas treatment system 10B, the absorbent management device 20B, and the flue gas treatment method S20 configured as described above, as in the first embodiment, the amount of sodium hydroxide added to the cooling medium is adjusted according to the state of the amine-based absorbent L2, thereby suppressing oxidation of the amine-based absorbent L2 and reducing the effort and cost required to replace the amine-based absorbent L2. As a result, it becomes possible to effectively suppress oxidation degradation of the absorbent while reducing the effort and cost.

[0079] Furthermore, the state detection unit 202 detects the state of the amine-based absorbing solution L2 flowing through the absorption solution cooling line 151. Thus, by detecting the state of the amine-based absorbing solution L2 that is extracted from an intermediate portion inside the absorption tower 12 and supplied into the absorption tower 12, the amount of sodium hydroxide added can be successively adjusted.

[0080] Furthermore, the control device 60A adjusts the amount of sodium hydroxide added based on the difference between the state of the amine-based absorbent L2 flowing through the absorbent cooling line 151 and the state of the amine-based absorbent L2 at the bottom of the absorption tower 12. This allows the amount of sodium hydroxide added to be appropriately adjusted based on the state of the amine in the amine-based absorbent L2.

[0081] (Other Embodiments) Although the embodiments of the present disclosure have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment and includes design modifications and the like within the scope of the present disclosure. In the above-described embodiments, the state detection units 201 and 202 detect the oxidation-reduction potential of the amine-based absorbing solution L2, but this is not limited to this. The state detection units 201 and 202 may also detect the dissolved oxygen concentration of the amine-based absorbing solution L2 as the state of the amine-based absorbing solution L2. Furthermore, the additive added by the addition unit 21 is not limited to the substances exemplified in the examples or this specification, and may be any substance that can adjust the coolant L1 to a predetermined pH.

[0082] Alternatively, a program for implementing all or part of the functions of control devices 60A and 60B may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed to perform processing by each functional unit. Here, the term "computer system" includes hardware such as an OS and peripheral devices. Furthermore, if a WWW system is used, the term "computer system" also includes the homepage provision environment (or display environment). Furthermore, the term "computer-readable recording medium" refers to portable media such as CDs, DVDs, and USBs, as well as storage devices such as hard disks built into the computer system. Furthermore, if the program is distributed to control devices 60A and 60B via a communication line, control devices 60A and 60B may load the program into storage 64 and execute the above-described processing. Furthermore, the program may be for implementing part of the above-described functions, or may be capable of implementing the above-described functions in combination with a program already stored in the computer system.

[0083] <Additional Notes> The flue gas treatment systems 10A and 10B, the absorption liquid management devices 20A and 20B, and the flue gas treatment methods S10 and S20 described in the respective embodiments can be understood, for example, as follows.

[0084] (1) Each of the exhaust gas treatment systems 10A and 10B according to a first aspect includes a cooling tower 11 that cools exhaust gas containing carbon dioxide by bringing a cooling liquid L1 into contact with the exhaust gas; an absorption tower 12 into which an amine-based absorbing liquid L2 capable of absorbing carbon dioxide in the exhaust gas is introduced, and in which the amine-based absorbing liquid L2 absorbs the carbon dioxide in the exhaust gas that has passed through the cooling tower 11; a regeneration tower 13 that heats the amine-based absorbing liquid L2 that has absorbed carbon dioxide, separates the carbon dioxide from the amine-based absorbing liquid L2, and regenerates the amine-based absorbing liquid L2; an addition unit 21 that adds an additive to the cooling liquid L1 to adjust the hydroxide ion concentration of the cooling liquid; a state detection unit 201 that detects the state of the amine-based absorbing liquid L2; and control devices 60A and 60B that adjust the amount of the additive added in the addition unit 21, based on the state of the amine-based absorbing liquid L2 detected by the state detection unit 201.

[0085] The exhaust gas treatment systems 10A and 10B adjust the amount of additive added to the cooling liquid L1 in the cooling tower 11 based on the state of the amine-based absorbent L2. In the cooling tower 11, sulfur dioxide (SO2) contained in the exhaust gas is removed by bringing the cooling liquid L1 into contact with the exhaust gas. When the amount of additive added to the cooling liquid L1 is reduced, the sulfur dioxide removal rate in the cooling tower 11 decreases. As a result, the amount of sulfur dioxide that was not completely removed by the cooling tower 11 that flows into the absorption tower 12 increases. The sulfur dioxide that flows into the absorption tower 12 reacts with water contained in the amine-based absorbent L2 to produce sulfurous acid. The produced sulfurous acid reacts with dissolved oxygen in the amine-based absorbent L2. This consumes oxygen in the absorption tower 12. The reaction between the sulfurous acid and the dissolved oxygen in the amine-based absorbent L2 occurs more quickly than the reaction between the amine contained in the amine-based absorbent L2 and the oxygen contained in the exhaust gas. Therefore, oxidation of the amine-based absorbent L2 in the absorption tower 12 is suppressed, and the generation of aldehydes can be suppressed. In this way, by adjusting the amount of additive added to the coolant L1 according to the state of the amine-based absorbent L2, oxidation of the amine-based absorbent L2 is suppressed, and the effort and cost of replacing the amine-based absorbent L2 are reduced. As a result, it is possible to effectively suppress oxidation degradation of the absorbent while reducing effort and cost. Furthermore, since the oxygen concentration in the absorption tower 12 is reduced, corrosion of the metal material forming the absorption tower 12 can be suppressed. This suppresses elution of the metal material into the amine-based absorbent L2, and in this respect, deterioration of the amine-based absorbent L2 can also be suppressed.

[0086] (2) The exhaust gas treatment systems 10A and 10B according to a second aspect are the exhaust gas treatment systems 10A and 10B of (1), further including a pH detection unit 203 that detects the hydrogen ion concentration of the coolant L1, and the control devices 60A and 60B adjust the amount of additive added so that the hydrogen ion concentration of the coolant L1 detected by the pH detection unit 203 falls within a predetermined pH range.

[0087] According to this configuration, the amount of additive added is adjusted based on the hydrogen ion concentration of the coolant L1, and the hydrogen ion concentration of the coolant L1 is set within a predetermined pH range, thereby making it possible to maintain the sulfur dioxide removal rate in the cooling tower 11 within an appropriate range. This makes it possible to effectively suppress oxidation of the amine-based absorbent L2 in the absorption tower 12.

[0088] (3) The exhaust gas treatment systems 10A and 10B according to a third aspect are the exhaust gas treatment systems 10A and 10B according to (1) or (2), in which the state detection unit 201 detects the state of the amine-based absorption solution L2 at the bottom of the absorption tower 12.

[0089] According to this configuration, by detecting the state of the amine-based absorbent L2 at the bottom of the absorption tower 12, the amount of additive added can be successively adjusted based on the state of the amine-based absorbent L2 after absorbing carbon dioxide and the like contained in the exhaust gas in the absorption tower 12.

[0090] (4) An air pollution control system 10B according to a fourth aspect is the air pollution control system 10B according to any one of (1) to (3), wherein the absorption tower 12 further includes an absorption liquid cooling line 151 that cools the amine-based absorption liquid L2 extracted from an intermediate portion of the absorption tower 12 and supplies the cooled amine-based absorption liquid L2 into the absorption tower 12, and the state detection unit 202 detects the state of the amine-based absorption liquid L2 circulating through the absorption liquid cooling line 151.

[0091] According to this configuration, the amount of additive added can be successively adjusted by detecting the state of the amine-based absorbing solution L2 that is extracted from the middle part of the absorption tower 12 and supplied into the absorption tower 12.

[0092] (5) An air pollution control system 10B according to a fifth aspect is the air pollution control system 10B of (4), wherein the state detection unit 201 further detects a state of the amine-based absorbent L2 at the bottom of the absorption tower 12, and the control devices 60A, 60B adjust the amount of additive added based on a difference between the state of the amine-based absorbent L2 circulating through the absorbent cooling line 151 and the state of the amine-based absorbent L2 at the bottom of the absorption tower 12.

[0093] According to this configuration, the amount of additive added is adjusted based on the difference between the state of the amine-based absorbent L2 flowing through the absorbent cooling line 151 and the state of the amine-based absorbent L2 at the bottom of the absorption tower 12, so that the amount of additive added can be appropriately adjusted based on the state of the amine in the amine-based absorbent L2.

[0094] (6) The exhaust gas treatment systems 10A and 10B according to a sixth aspect are any one of the exhaust gas treatment systems 10A and 10B according to (1) to (5), in which the state detection unit 201 detects the oxidation-reduction potential of the amine-based absorption liquid L2.

[0095] According to this configuration, the oxidation state of the amine-based absorbing solution L2 can be grasped by detecting the oxidation-reduction potential of the amine-based absorbing solution L2, thereby making it possible to appropriately adjust the amount of additive added.

[0096] (7) The seventh aspect of the exhaust gas treatment systems 10A and 10B is the exhaust gas treatment systems 10A and 10B of (6), in which the control devices 60A and 60B reduce the amount of additive added when the detected oxidation-reduction potential of the amine-based absorption solution L2 is equal to or greater than a preset upper threshold value.

[0097] According to this configuration, when the oxidation-reduction potential of the amine-based absorbent L2 is equal to or higher than a preset upper threshold, the hydroxide ion concentration of the cooling liquid L1 can be reduced by reducing the amount of additive added, thereby reducing the sulfur dioxide removal rate in the cooling tower 11. This increases oxygen consumption in the absorption tower 12, and effectively suppresses oxidation of the amine-based absorbent L2 in the absorption tower 12.

[0098] (8) The exhaust gas treatment systems 10A and 10B according to an eighth aspect are any one of the exhaust gas treatment systems 10A and 10B according to (1) to (7), in which the state detection unit 201 detects the dissolved oxygen concentration of the amine-based absorption liquid L2.

[0099] According to this configuration, the oxidation state of the amine-based absorbing solution L2 can be grasped by detecting the dissolved oxygen concentration of the amine-based absorbing solution L2, thereby making it possible to appropriately adjust the amount of additive added.

[0100] (9) The exhaust gas treatment systems 10A and 10B according to a ninth aspect are the exhaust gas treatment systems 10A and 10B of any one of (1) to (8), in which the additive includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, and magnesium hydroxide.

[0101] According to this configuration, at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, and magnesium hydroxide is used as the additive, and the amount of the additive added to the coolant L1 is adjusted, thereby suppressing oxidation of the amine-based absorbing solution L2.

[0102] (10) The absorption liquid management devices 20A and 20B according to a tenth aspect include a cooling tower 11 that cools exhaust gas containing carbon dioxide by bringing a cooling liquid L1 into contact with the exhaust gas, an absorption tower 12 that is introduced with an amine-based absorption liquid L2 capable of absorbing carbon dioxide in the exhaust gas and that uses the amine-based absorption liquid L2 to absorb the carbon dioxide in the exhaust gas that has passed through the cooling tower 11, and an absorption tower 12 that heats the amine-based absorption liquid L2 that has absorbed carbon dioxide, separates carbon dioxide from the amine-based absorption liquid L2, and absorbs the carbon dioxide from the amine-based absorption liquid L2. The absorption liquid management devices 20A, 20B are provided in exhaust gas treatment systems 10A, 10B, each including a regeneration tower 13 that regenerates an absorption liquid L2, and each include an addition unit 21 that adds an additive to the cooling liquid L1 to adjust the hydroxide ion concentration of the cooling liquid, a state detection unit 201 that detects the state of the amine-based absorption liquid L2, and a control device 60A, 60B that adjusts the amount of the additive added in the addition unit 21, based on the state of the amine-based absorption liquid L2 detected by the state detection unit 201.

[0103] The absorbent management devices 20A, 20B adjust the amount of additive added based on the state of the amine-based absorbent L2, thereby suppressing oxidation of the amine-based absorbent L2 in the absorption tower 12 and suppressing the generation of aldehydes. As a result, it becomes possible to effectively suppress oxidation degradation of the absorbent while reducing labor and costs.

[0104] (11) Exhaust gas treatment methods S10 and S20 according to an eleventh aspect are methods for treating exhaust gas, which include bringing a cooling liquid L1 into contact with an exhaust gas containing carbon dioxide to cool the exhaust gas, absorbing the carbon dioxide in the exhaust gas with an amine-based absorbing liquid L2 capable of absorbing the carbon dioxide in the exhaust gas, and heating the amine-based absorbing liquid L2 that has absorbed the carbon dioxide to separate the carbon dioxide from the amine-based absorbing liquid to regenerate the amine-based absorbing liquid L2, and include steps S11 and S21 of detecting a state of the amine-based absorbing liquid L2, and steps S12 and S22 of adjusting the amount of the additive to be added to the coolant L1, which adjusts the hydroxide ion concentration of the coolant L1, based on the detected state of the amine-based absorbing liquid L2.

[0105] In the exhaust gas treatment methods S10 and S20, the amount of additive added is adjusted based on the state of the amine-based absorbing solution L2, thereby suppressing oxidation of the amine-based absorbing solution L2 and suppressing the generation of aldehydes. As a result, it is possible to effectively suppress oxidation degradation of the absorbing solution while reducing labor and costs.

[0106] (12) The exhaust gas treatment methods S10 and S20 according to a twelfth aspect are the exhaust gas treatment methods S10 and S20 of (11), in which in steps S11 and S12 of detecting the state of the amine-based absorption liquid L2, the hydrogen ion concentration of the cooling liquid L1 is further detected, and in steps S12 and S22 of adjusting the addition amount, the addition amount of the additive is adjusted so that the detected hydrogen ion concentration of the cooling liquid L1 falls within a predetermined pH range.

[0107] According to this configuration, the amount of additive added is adjusted based on the hydrogen ion concentration of the coolant L1, and the hydrogen ion concentration of the coolant L1 is set within a predetermined pH range, thereby making it possible to maintain the sulfur dioxide removal rate in the cooling tower 11 within an appropriate range. This makes it possible to effectively suppress oxidation of the amine-based absorbent L2 in the absorption tower 12.

[0108] (13) The exhaust gas treatment methods S10 and S20 according to a thirteenth aspect are the exhaust gas treatment methods S10 and S20 according to (11) or (12), in which in steps S11 and S21 for detecting the state of the amine-based absorbing solution L2, an oxidation-reduction potential of the amine-based absorbing solution L2 is detected, and in steps S12 and S22 for adjusting the amount of additive, the amount of additive added is reduced if the detected oxidation-reduction potential of the amine-based absorbing solution L2 is equal to or higher than a preset upper threshold value.

[0109] According to this configuration, when the oxidation-reduction potential of the amine-based absorbent L2 is equal to or higher than a preset upper threshold, the hydroxide ion concentration of the cooling liquid L1 can be reduced by reducing the amount of additive added, thereby reducing the sulfur dioxide removal rate in the cooling tower 11. This increases oxygen consumption in the absorption tower 12, and effectively suppresses oxidation of the amine-based absorbent L2 in the absorption tower 12.

[0110] According to each embodiment of the present disclosure, it is possible to effectively suppress oxidation degradation of the absorption solution while reducing the effort and cost.

[0111] DESCRIPTION OF SYMBOLS 10A, 10B... Exhaust gas treatment system 11... Cooling tower 11a... Tower body 11b... Nozzle 12... Absorption tower 12a... Tower body 12b, 12c... Nozzle 12d... Washing water receiver 12e... Exhaust pipe 13... Regeneration tower 13a... Tower body 13b, 13c... Nozzle 15... Recovery section 16... Regeneration reflux tower 20A, 20B... Absorbent liquid management device 21... Addition section 22... Addition line 23... Flow rate control valve 31... Cooling liquid supply pump 32A... First circulation pump 32B... Second circulation pump 33... Absorbent liquid circulation pump 41... First heat exchanger 43... Second heat exchanger 45... Heat exchanger 46... Third heat exchanger 48... Reboiler 49... Condenser 60A, 60B... Control device 61... Processor 62... ROM 63... RAM 64...Storage 65...Signal transmission / reception module 70...Signal input unit 71...Information acquisition unit 72...Information storage unit 74A, 74B...Addition amount adjustment unit 75...Output unit 81...Steam supply pipe 82A to 82C...Cooling water supply pipe 101...Gas introduction line 102...Cooling liquid supply line 103...Exhaust gas discharge line 105...Cleaning water circulation line 106...Circulation line 106A...Absorption liquid supply line 106B...Absorption liquid discharge line 107...Refrigerant line 108...Absorption liquid heating line 109...Gaseous carbon dioxide discharge line 110...Reflux line 111...Carbon dioxide discharge pipe 112...Reflux pump 151...Absorption liquid cooling line 152...Cooler 201, 202...Status detection unit 203...pH detection unit L1...Cooling liquid L2...Amine-based absorption liquid

Claims

1. An exhaust gas treatment system comprising: a cooling tower that cools exhaust gas containing carbon dioxide by bringing a cooling liquid into contact with the exhaust gas; an absorption tower into which an amine-based absorbing liquid capable of absorbing carbon dioxide in the exhaust gas is introduced, and which causes the amine-based absorbing liquid to absorb the carbon dioxide in the exhaust gas that has passed through the cooling tower; a regeneration tower that heats the amine-based absorbing liquid that has absorbed carbon dioxide, separates the carbon dioxide from the amine-based absorbing liquid, and regenerates the amine-based absorbing liquid; an addition unit that adds an additive to the cooling liquid to adjust the hydroxide ion concentration of the cooling liquid; a state detection unit that detects the state of the amine-based absorbing liquid; and a control device that adjusts the amount of additive added in the addition unit based on the state of the amine-based absorbing liquid detected by the state detection unit.

2. The exhaust gas treatment system according to claim 1, further comprising a pH detection unit that detects the hydrogen ion concentration of the coolant, wherein the control device adjusts the amount of the additive added so that the hydrogen ion concentration of the coolant detected by the pH detection unit falls within a preset pH range.

3. The exhaust gas treatment system according to claim 1 or 2, wherein the state detection unit detects the state of the amine-based absorbing solution at the bottom of the absorption tower.

4. The exhaust gas treatment system according to claim 1 or 2, wherein the absorption tower further comprises an absorption liquid cooling line that cools the amine-based absorption liquid extracted from an intermediate portion within the absorption tower and supplies the cooled amine-based absorption liquid into the absorption tower, and the state detection unit detects the state of the amine-based absorption liquid circulating through the absorption liquid cooling line.

5. The exhaust gas treatment system according to claim 4, wherein the state detection unit further detects the state of the amine-based absorption liquid at the bottom of the absorption tower, and the control device adjusts the amount of additive added based on the difference between the state of the amine-based absorption liquid circulating through the absorption liquid cooling line and the state of the amine-based absorption liquid at the bottom of the absorption tower.

6. The exhaust gas treatment system according to claim 1 or 2, wherein the state detection unit detects the oxidation-reduction potential of the amine-based absorbing solution.

7. The exhaust gas treatment system according to claim 6, wherein the control device reduces the amount of the additive added when the detected oxidation-reduction potential of the amine-based absorbing solution is equal to or higher than a preset upper threshold value.

8. The exhaust gas treatment system according to claim 1 or 2, wherein the state detection unit detects the dissolved oxygen concentration of the amine-based absorbing solution.

9. The exhaust gas treatment system according to claim 1 or 2, wherein the additive contains at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, and magnesium hydroxide.

10. An absorption liquid management device provided in an exhaust gas treatment system including a cooling tower that cools exhaust gas containing carbon dioxide by bringing a cooling liquid into contact with the exhaust gas, an absorption tower into which an amine-based absorption liquid capable of absorbing carbon dioxide in the exhaust gas is introduced and which causes the amine-based absorption liquid to absorb the carbon dioxide in the exhaust gas that has passed through the cooling tower, and a regeneration tower that heats the amine-based absorption liquid that has absorbed carbon dioxide and separates the carbon dioxide from the amine-based absorption liquid to regenerate the amine-based absorption liquid, the absorption liquid management device comprising: an addition unit that adds an additive to the cooling liquid to adjust the hydroxide ion concentration of the cooling liquid; a state detection unit that detects the state of the amine-based absorption liquid; and a control device that adjusts the amount of additive added in the addition unit based on the state of the amine-based absorption liquid detected by the state detection unit.

11. A method for treating exhaust gas, comprising: cooling exhaust gas containing carbon dioxide by bringing the exhaust gas into contact with a cooling liquid; absorbing the carbon dioxide in the exhaust gas with an amine-based absorbing liquid capable of absorbing the carbon dioxide in the exhaust gas; and heating the amine-based absorbing liquid that has absorbed the carbon dioxide to separate the carbon dioxide from the amine-based absorbing liquid and regenerating the amine-based absorbing liquid, the method comprising: detecting a state of the amine-based absorbing liquid; and adjusting the amount of the additive to be added to the coolant, which adjusts the hydroxide ion concentration of the coolant, based on the detected state of the amine-based absorbing liquid.

12. The method for treating exhaust gas according to claim 11, wherein the step of detecting the state of the amine-based absorption liquid further detects the hydrogen ion concentration of the cooling liquid, and the step of adjusting the amount of additive to be added adjusts the amount of additive to be added so that the detected hydrogen ion concentration of the cooling liquid falls within a predetermined pH range.

13. The method for treating exhaust gas according to claim 11 or 12, wherein in the step of detecting the state of the amine-based absorbing solution, an oxidation-reduction potential of the amine-based absorbing solution is detected, and in the step of adjusting the amount of additive, the amount of additive added is reduced if the detected oxidation-reduction potential of the amine-based absorbing solution is equal to or higher than a preset upper threshold value.

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