Absorption tower configuration for carbon dioxide recovery system, carbon dioxide absorption method

Abstract

An absorption tower according to the present invention comprises: a carbon dioxide absorption part that brings a gas to be processed that includes carbon dioxide into contact with an absorption liquid; and a washing part that brings a decarbonated gas that has contacted the absorption liquid at the carbon dioxide absorption part into contact with washing water. The carbon dioxide absorption part has an absorption unit and absorbs the carbon dioxide from the gas to be processed. The washing part has a recovery unit and recovers an absorption liquid component entrained in the decarbonated gas. At least one of the absorption unit and the recovery unit includes a storage part that stores a liquid and an aeration part that sprays a gas into the liquid stored at the storage part.

Description

Absorption tower configuration of carbon dioxide capture system and carbon dioxide absorption method

[0001] This disclosure relates to an absorption tower configuration of a carbon dioxide capture system and a carbon dioxide absorption method. This application claims priority to Japanese Patent Application No. 2023-202557, filed on November 30, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, from the perspective of carbon neutrality, carbon dioxide (CO ２ ) concentration has been attracting attention. From the perspective of reducing the concentration of carbon dioxide in the atmosphere, carbon dioxide capture systems that capture carbon dioxide from flue gas are known. For example, in carbon dioxide capture systems using the chemical absorption method, an absorption liquid is circulated between a regenerator and an absorber to capture carbon dioxide from flue gas.

[0003] For example, Patent Document 1 describes a decarbonation process in which carbon dioxide is removed from combustion flue gas, which is a gas containing carbon dioxide, using an amine compound-containing absorption liquid. In this decarbonation process, carbon dioxide is removed from the combustion flue gas by contacting the combustion flue gas with the absorption liquid in an absorption tower. The absorption tower has a carbon dioxide absorption section and a water washing section. In the carbon dioxide absorption section, the absorption liquid is brought into contact with the combustion flue gas. As a result, the carbon dioxide in the combustion flue gas is absorbed and removed by the absorption liquid. The loaded absorption liquid that has absorbed the carbon dioxide is sent to a regeneration tower, regenerated, and returned to the absorption tower. In addition, the combustion flue gas (decarbonated flue gas) decarbonated in the carbon dioxide absorption section is sent to a water washing section. In the water washing section, wash water is discharged from a nozzle into a space through which the decarbonated flue gas flows, causing countercurrent contact and lowering the temperature of the decarbonated flue gas. As a result, water vapor entrained in the decarbonated flue gas condenses, and the amine compound, which is the absorption liquid entrained in the decarbonated flue gas, is recovered. In particular, the water washing section has a two-stage structure consisting of a first-stage water washing section and a second-stage water washing section, which makes it possible to efficiently recover amine compounds entrained in the decarbonated flue gas.

[0004] Japanese Patent Application Laid-Open No. 2002-126439

[0005] Incidentally, in a carbon dioxide capture system such as the decarbonation process described above, in the water washing section, wash water is supplied to the gas from above via a nozzle. This configuration tends to increase the height of the absorption tower. Particularly when multiple water washing sections are used as in Patent Document 1, the height of the absorption tower complicates assembly work at the installation site and makes it difficult to secure a work space. Therefore, there is a demand for a structure that can reduce the height of the absorption tower while maintaining the efficiency of recovering carbon dioxide from the gas and the efficiency of recovering the absorption solution contained in the gas after carbon dioxide recovery.

[0006] The present disclosure describes an absorption tower, a carbon dioxide recovery system, and a carbon dioxide absorption method that enable the height to be reduced while maintaining the efficiency of recovering carbon dioxide from gas and the efficiency of recovering absorbent components contained in the gas after carbon dioxide has been recovered.

[0007] The absorption tower according to the present disclosure comprises a carbon dioxide absorption section that brings a gas to be treated containing carbon dioxide into contact with an absorption liquid and causes the absorption liquid to absorb the carbon dioxide, and a water washing section that brings decarbonated gas that has come into contact with the absorption liquid in the carbon dioxide absorption section into contact with wash water and recovers absorption liquid components entrained in the decarbonated gas, the carbon dioxide absorption section having an absorption unit that absorbs the carbon dioxide from the gas to be treated, the water washing section having a recovery unit that recovers the absorption liquid components entrained in the decarbonated gas, and at least a part of the absorption unit and the recovery unit have a storage section that stores liquid, and an aeration section that sprays gas into the liquid stored in the storage section.

[0008] In addition, 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 a decarbonated gas from which the carbon dioxide has been removed, and a regeneration tower that strips the carbon dioxide from the absorption liquid discharged from the absorption tower and discharges the absorption liquid from which the carbon dioxide has stripped and a regeneration tower exhaust gas containing the carbon dioxide.

[0009] In addition, the carbon dioxide absorption method according to the present disclosure includes a carbon dioxide absorption step in which a gas to be treated containing carbon dioxide is brought into contact with an absorption liquid and the carbon dioxide is absorbed into the absorption liquid, and a water washing step in which the decarbonated gas after contact with the absorption liquid in the carbon dioxide absorption step is brought into contact with wash water and the absorption liquid components entrained in the decarbonated gas are recovered, and at least a part of the carbon dioxide absorption step and the water washing step include a step of injecting gas into the stored liquid to generate a froth flow, a step of sending a part of the stored liquid downward in the vertical direction and extracting the gas contained in the liquid and sending it upward in the vertical direction, and a step of sending the gas that has escaped from the liquid upward in the vertical direction.

[0010] According to the present disclosure, it is possible to reduce the height of the absorption tower while maintaining the efficiency of recovering carbon dioxide from the gas and the efficiency of recovering the absorbing solution contained in the gas after recovering the carbon dioxide.

[0011] Fig. 5 is a schematic diagram showing a carbon dioxide capture system according to the present embodiment. Fig. 6 is a schematic diagram showing an absorption tower according to the first embodiment. Fig. 7 is a schematic diagram showing an absorption unit (capture unit) according to the first embodiment. Fig. 8 is a cross-sectional view taken along line IV-IV in Fig. 3, showing a gas to be treated diffusing section (decarbonated gas diffusing section). Fig. 9 is a schematic diagram showing an absorption tower according to a second embodiment. Fig. 10 is a cross-sectional view taken along line VI-VI in Fig. 5, showing a partition plate.

[0012] Hereinafter, an embodiment for carrying out an absorption tower and a carbon dioxide recovery system according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to only this embodiment.

[0013] First Embodiment (Carbon Dioxide Capture System) A carbon dioxide capture system 1 captures carbon dioxide (CO ２) can be recovered. Examples of exhaust gas sources include boilers, incinerators, gas turbines, and plants for producing sustainable aviation fuels (SAF) and ethanol. That is, examples of gas to be treated include exhaust gas containing carbon dioxide that is finally emitted and process gas containing carbon dioxide that is used midway through 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.

[0014] The carbon dioxide recovery system 1 of this embodiment includes an absorption tower 2, a gas line 11 to be treated, a regeneration tower 3, a rich line 13, a lean line 14, an absorbent heat exchanger 4, and a regeneration tower discharge line 15.

[0015] A gas to be treated containing 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 solution. Examples of the absorbing solution include amine solutions. Specifically, alkanolamines such as monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), diisopropanolamine (DIPA), and diglycolamine (DGA) can be used as the absorbing solution. Hindered amines can also be used. Aqueous solutions of these amines alone or a mixture of two or more of these amines can also be used. The absorption tower 2 separately discharges the absorbing solution that has absorbed carbon dioxide and the absorber exhaust gas containing the gas to be treated from which carbon dioxide has been removed. The detailed configuration of the absorption tower 2 will be described later.

[0016] 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 cooled gas to the absorption tower 2. The gas to be treated line 11 is connected to the absorption tower 2.

[0017] The absorber discharge line 12 is connected to the top of the absorber 2 and discharges the absorber exhaust gas discharged from the absorber 2 to the outside.

[0018] The regenerator 3 strips carbon dioxide from the absorption liquid discharged from the absorption tower 2. The regenerator 3 heats the absorption liquid using a reboiler 31. As a result, in the regenerator 3, most of the carbon dioxide is stripped from the absorption liquid together with steam, and the carbon dioxide is separated from the absorption liquid. High-temperature steam is supplied to the reboiler 31. The reboiler 31 heats the absorption liquid by performing heat exchange between the steam and the absorption liquid. The regenerator 3 separately discharges the absorption liquid from which carbon dioxide has been stripped and the regenerator exhaust gas mainly composed of carbon dioxide.

[0019] The rich line 13 supplies the absorption liquid that has absorbed carbon dioxide from the absorption tower 2 to the regeneration tower 3. Here, the absorption liquid that is discharged from the absorption tower 2 and flows through the rich line 13 is referred to as the rich liquid. The rich liquid is the absorption 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 with 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.

[0020] The lean line 14 supplies the absorption liquid from which carbon dioxide has been stripped from the regenerator 3 to the absorber 2. Here, the absorption liquid discharged from the regenerator 3 and flowing through the lean line 14 is referred to as the lean liquid. The lean liquid is the absorption 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 with the top of the absorber 2. A lean pump 37 is arranged in the lean line 14. The lean pump 37 pressurizes the lean liquid and sends it to the absorber 2 via the absorber heat exchanger 4.

[0021] The absorbent 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, the absorbent heat exchanger 4 heats the absorbent 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 absorber 2 to the regenerator 3. The absorbent heat exchanger 4 also cools the absorbent 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 regenerator 3 to the absorber 2.

[0022] 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 transfers the regenerator exhaust gas to an external destination depending on the intended use. The regenerator exhaust gas, which is mainly composed of carbon dioxide and discharged from the regenerator discharge line 15, is compressed or liquefied depending on the intended use, and is stored in a tank or transferred via a pipeline to be stored inside an oil field or in an aquifer, etc.

[0023] (Absorption Tower) As shown in FIG. 2 , the absorption tower 2 of the first embodiment includes an absorption tower body 40 , a carbon dioxide absorption section 50 , a water washing section 60 , a liquid level adjusting section 70 , and a demister 80 .

[0024] The absorber main body 40 is a cylindrical container extending in the vertical direction Dv. The gas to be treated can flow inside the absorber main body 40 from a lower position Dvd in the vertical direction Dv to an upper position Dvu. A gas line 11 to be treated is connected near the bottom of the absorber main body 40. An absorber discharge line 12 is connected near the top of the absorber main body 40. A rich line 13 is connected to the absorber main body 40 at a position Dvd below the connection position with the gas line 11 to be treated in the vertical direction Dv. A lean line 14 is connected to the absorber main body 40 at a position Dvu above the connection position with the gas line 11 to be treated in the vertical direction Dv and at a position Dvd below the connection position with the absorber discharge line 12 in the vertical direction Dv. A wash water supply line 69 is connected to the absorber body 40 at a position Dvu above the connection position with the lean line 14 in the vertical direction Dv and at a position Dvd below the connection position with the absorber discharge line 12 in the vertical direction Dv.

[0025] The carbon dioxide absorption unit 50 brings the gas to be treated containing carbon dioxide into contact with the absorbing liquid. As a result, the carbon dioxide absorption unit 50 causes the absorbing liquid to absorb carbon dioxide. The carbon dioxide absorption unit 50 of the first embodiment causes the absorbing liquid to sequentially absorb carbon dioxide from the gas to be treated over multiple stages. The carbon dioxide absorption unit 50 of the present embodiment has a lower reservoir 51 and multiple absorption units 52.

[0026] The lower reservoir 51 stores the absorption liquid. The lower reservoir 51 stores the absorption liquid having the highest carbon dioxide concentration in the carbon dioxide absorption section 50. The lower reservoir 51 is arranged at a position Dvd below the plurality of absorption units 52 in the vertical direction Dv. The lower reservoir 51 is arranged near the bottom of the absorption tower main body 40. The absorption liquid is stored in the lower reservoir 51 such that the liquid level of the stored absorption liquid is located at a position Dvd below in the vertical direction Dv with respect to the connection position between the absorption tower main body 40 and the gas line 11 to be treated. The absorption liquid is stored in the lower reservoir 51 such that the connection position between the absorption tower main body 40 and the rich line 13 is located within the stored absorption liquid.

[0027] The absorption units 52 are arranged side by side in the vertical direction Dv. The absorption units 52 arranged side by side in the vertical direction Dv sequentially absorb carbon dioxide from the gas to be treated. The number of absorption units 52 is preferably two to eight, and more preferably three to five.

[0028] The absorption unit 52 injects the target gas into the stored absorption liquid. That is, the absorption unit 52 sends the target gas into the absorption liquid to generate bubbles (bubbling), thereby bringing the target gas into contact with the absorption liquid. At this time, the absorption unit 52 sends the target gas into the absorption liquid so as to form a froth flow.

[0029] Here, there are multiple flow states in a gas-liquid two-phase flow in which gas flows through a liquid. Specifically, when the gas flow rate is low relative to the liquid flow rate, the gas disperses as small bubbles through the liquid. As a result, the gas-liquid two-phase flow becomes a bubble flow, which is not agitated. Bubble flow is a state in which the gas disperses as small bubbles through the liquid when the gas flow rate is low relative to the liquid flow rate. In other words, in a bubble flow, the liquid surface is barely disturbed. On the other hand, as the gas flow rate increases relative to the liquid flow rate from the bubble flow state, the bubbles gradually grow larger and violently disrupt the flow. Then, when the gas flow rate exceeds a certain level relative to the liquid flow rate, the gas violently agitates the liquid. As a result, the gas-liquid two-phase flow becomes a froth flow, which is a state in which violent agitation occurs. In other words, in a froth flow, the gas-liquid interface is violently turbulent, causing the gas and liquid to mix, accelerating the transfer of carbon dioxide from the gas to the absorption liquid.

[0030] Furthermore, the liquid level of the liquid stored in the storage sections (the absorption liquid storage section 55 and the wash water storage section 65) described below is the liquid level in a state before gas is sprayed from the aeration sections (the treatment target gas aeration section 57 and the decarbonated gas aeration section 67) described below. In other words, it is the liquid level of the liquid when operation of the absorption tower 2 is stopped. In this state, the stored liquid is hardly rippling, and the position of the liquid level in the vertical direction Dv is maintained at a predetermined position.

[0031] As shown in FIG. 3 , the absorption unit 52 of this embodiment has an absorbent liquid storage section (storage section) 55 and a target gas diffusion section (diffusion section) 57 .

[0032] The absorbent liquid reservoir 55 stores a liquid at a flow rate that results in a predetermined depth. The absorbent liquid reservoir 55 forms a space capable of storing the liquid by a flat bottom plate 551 and the side wall of the absorber body 40. The absorbent liquid reservoir 55 of this embodiment stores the absorbent liquid as the liquid.

[0033] The target gas diffuser 57 injects gas into the absorbent stored in the absorbent storage unit 55. The target gas diffuser 57 of this embodiment injects the target gas as a gas. The target gas diffuser 57 injects the target gas into the absorbent in a direction including a component directed downward Dvd in the vertical direction Dv or in a horizontal direction. The target gas diffuser 57 of this embodiment injects the target gas directly below in the vertical direction Dv. Note that a direction including a component directed downward Dvd in the vertical direction Dv is a direction other than a horizontal direction perpendicular to the vertical direction Dv or a direction directed upward Dvu in the vertical direction Dv relative to the horizontal position. Therefore, a direction including a component directed downward Dvd in the vertical direction Dv also includes a direction directed directly below the vertical direction Dv and a direction directed diagonally downward Dvd in the vertical direction Dv. The target gas diffusion unit 57 has a flow rate ratio, which is the ratio of the amount of stored liquid to the flow rate of the target gas to be sprayed, of 1 to 5 L / Nm ３ As shown in Fig. 4, a plurality of (four in this embodiment) target gas diffusion units 57 are arranged at positions spaced apart from one another.

[0034] 2, the carbon dioxide absorption section 50 of this embodiment has a plurality of absorption units 52, including a first absorption unit 521, a second absorption unit 522, and a third absorption unit 523. The first absorption unit 521, the second absorption unit 522, and the third absorption unit 523 have the same structure. The first absorption unit 521 is disposed at the lowest position Dvd of the three absorption units 52 in the vertical direction Dv. The third absorption unit 523 is disposed at the highest position Dvu of the three absorption units 52 in the vertical direction Dv.

[0035] The first absorption unit 521 is disposed at a position Dvu above the lower reservoir 51 in the vertical direction Dv. That is, in the first absorption unit 521, the gas to be treated from which carbon dioxide has not yet been absorbed is ejected as a gas from the gas to be treated diffuser 57. In the first absorption unit 521, the absorption liquid reservoir 55 stores an absorption liquid having the highest carbon dioxide concentration among the plurality of absorption units 52, and having a lower carbon dioxide concentration than the absorption liquid stored in the lower reservoir 51.

[0036] The second absorption unit 522 is disposed at a position Dvu above the first absorption unit 521 in the vertical direction Dv. That is, in the second absorption unit 522, the gas to be treated, from which carbon dioxide has been absorbed by the absorption liquid in the first absorption unit 521, is ejected as a gas from the gas to be treated diffuser 57. In addition, in the second absorption unit 522, an absorption liquid having a lower carbon dioxide concentration than the absorption liquid stored in the first absorption unit 521 is stored in the absorption liquid storage section 55.

[0037] The third absorption unit 523 is disposed at a position Dvu above the second absorption unit 522 in the vertical direction Dv. That is, in the third absorption unit 523, the gas to be treated from which carbon dioxide has been absorbed by the absorption liquid in the second absorption unit 522 is ejected as a gas from the gas to be treated diffuser 57. In addition, in the third absorption unit 523, an absorption liquid having a lower carbon dioxide concentration than the absorption liquid stored in the second absorption unit 522 is stored in the absorption liquid storage section 55. In the third absorption unit 523, the absorption liquid is stored such that the connection position between the absorber main body 40 and the lean line 14 is located within the stored absorption liquid.

[0038] The water washing section 60 brings the gas to be treated, which has been in contact with the absorbing solution in the carbon dioxide absorption section 50, into contact with wash water. As a result, the water washing section 60 recovers components of the absorbing solution entrained in the gas to be treated. Here, the gas to be treated, which has been in contact with the absorbing solution in the carbon dioxide absorption section 50, is referred to as decarbonated gas. The decarbonated gas is the gas to be treated that has passed through the carbon dioxide absorption section 50 and from which carbon dioxide has been removed. The decarbonated gas contains almost no carbon dioxide, but is entrained with a large amount of steam and mist containing components of the absorbing solution. The water washing section 60 of the first embodiment brings the decarbonated gas into contact with wash water in two stages, and sequentially recovers the absorbing solution from the decarbonated gas. The water washing section 60 of this embodiment has multiple recovery units 61. Here, the wash water refers to steam condensate generated in the regeneration tower and condensate generated during cooling in the water washing section, in which components of the absorbing solution are dissolved.

[0039] The plurality of recovery units 61 are arranged above Dvu in the vertical direction Dv relative to the plurality of absorption units 52. The plurality of recovery units 61 are arranged side by side in the vertical direction Dv. The plurality of recovery units 61 arranged side by side in the vertical direction Dv sequentially recover the absorption liquid from the decarbonated gas. The number of recovery units 61 is preferably one to five, and more preferably two to three.

[0040] The recovery unit 61 sprays decarbonated gas into the stored cleaning water. That is, the recovery unit 61 sends the decarbonated gas into the cleaning water to generate bubbles (bubbling), bringing the cleaning water into contact with the decarbonated gas. At this time, the recovery unit 61 sends the decarbonated gas into the cleaning water so as to form a froth flow.

[0041] The recovery unit 61 of this embodiment has the same structure as the absorption unit 52. As shown in FIG. 3 , the recovery unit 61 has a cleaning water storage section (storage section) 65 and a decarbonated gas diffusing section (diffusing section) 67. That is, the cleaning water storage section 65 has the same structure as the absorption liquid storage section 55. The cleaning water storage section 65 of this embodiment stores cleaning water as a liquid rather than absorption liquid. Note that, hereinafter, the absorption liquid storage section 55 and the cleaning water storage section 65 may be collectively referred to as a storage section. Furthermore, the decarbonated gas diffusing section 67 has the same structure as the target gas diffusing section 57. The decarbonated gas diffusing section 67 of this embodiment sprays decarbonated gas as a gas rather than target gas. Note that, hereinafter, the target gas diffusing section 57 and the decarbonated gas diffusing section 67 may be collectively referred to as a diffusing section.

[0042] Specifically, the treatment target gas diffusing section 57 and the decarbonated gas diffusing section 67 of this embodiment are box-shaped and have a discharge hole 571 , a direction changing section 572 , and an ejection hole 573 .

[0043] The discharge hole 571 discharges gas toward an upper Dvu in the vertical direction Dv. The discharge hole 571 is formed to penetrate the bottom plate portion 551 in the vertical direction Dv. The discharge hole 571 protrudes from the bottom plate portion 551 toward an upper Dvu in the vertical direction Dv to form a cylindrical shape. The discharge hole 571 opens at a position higher than the liquid level of the liquid stored in the storage portion. As a result, the discharge hole 571 supplies gas present in a space Dvd below one absorption unit 52 (or recovery unit 61) in the vertical direction Dv to an upper Dvu in the vertical direction Dv, which is higher than the liquid level of the liquid stored in the storage portion.

[0044] The direction changer 572 covers the discharge hole 571 from above Dvu in the vertical direction Dv, directing the flow direction of the gas toward below Dvd in the vertical direction Dv. The direction changer 572 ejects gas into the liquid. The direction changer 572 curves the flow direction of the gas discharged from the discharge hole 571 so that it flows from above Dvu toward below Dvd in the vertical direction Dv. The direction changer 572 of this embodiment is formed in a box shape with an opening toward below Dvd in the vertical direction Dv, so as to cover the opening of the discharge hole 571 from above Dvu in the vertical direction Dv. More specifically, the direction changer 572 has a collision plate 581 and a flow path forming plate 582.

[0045] The collision plate 581 is configured so that gas discharged from the discharge hole 571 and traveling upward Dvu in the vertical direction Dv can collide with it. The collision plate 581 is disposed above Dvu in the vertical direction Dv with respect to the opening of the discharge hole 571. The collision plate 581 is formed in a flat plate shape that extends horizontally at a position facing the opening of the discharge hole 571.

[0046] The flow path forming plate 582 forms a flow path that guides the gas that has collided with the collision plate 581 to the ejection holes 573. The flow path forming plate 582 extends in a plate shape from the end of the collision plate 581 downward in the vertical direction Dv toward Dvd. The flow path forming portion forms a flow path that extends in the vertical direction Dv between itself and the outer surface of the discharge holes 571.

[0047] The ejection hole 573 is connected to the lower end of the flow path forming portion in the vertical direction Dv. The ejection hole 573 ejects, into the liquid, the gas that has flowed through the flow path formed by the flow path forming plate 582 toward the downward direction Dvd in the vertical direction Dv. The ejection hole 573 opens toward the downward direction Dvd in the vertical direction Dv. The ejection hole 573 is, for example, a perforated plate with multiple openings formed therein.

[0048] 2, the water washing section 60 of this embodiment has a first recovery unit 611 and a second recovery unit 612 as the plurality of recovery units 61. The first recovery unit 611 and the second recovery unit 612 have the same structure.

[0049] The first recovery unit 611 is disposed at a position Dvu above the carbon dioxide absorption section 50 in the vertical direction Dv. That is, in the first recovery unit 611, decarbonated gas, which is the gas to be treated in which carbon dioxide has been absorbed by the absorption liquid in the third absorption unit 523, is ejected as a gas from the decarbonated gas diffuser 67. At this time, the decarbonated gas from the third absorption unit 523 is supplied to the first recovery unit 611 after passing through a demister 80, which will be described later. Also, in the first recovery unit 611, the wash water storage section 65 stores wash water that has the highest concentration of the components of the absorption liquid among the multiple recovery units 61 and has a significantly lower concentration of the components of the absorption liquid than the absorption liquid stored in the third absorption unit 523.

[0050] The second recovery unit 612 is disposed at a position Dvu above the first recovery unit 611 in the vertical direction Dv. That is, in the second recovery unit 612, decarbonated gas in which components of the absorption solution have been recovered in the wash water in the first recovery unit 611 is ejected from a decarbonated gas diffuser 67. In the second recovery unit 612, wash water is supplied from a wash water supply line 69 connected to the regeneration tower 3, for example. In the second recovery unit 612, wash water having a lower concentration of components of the absorption solution than the wash water stored in the first recovery unit 611 is stored in a wash water storage section 65. In the second recovery unit 612, the wash water is stored so that the connection position between the absorption tower main body 40 and the wash water supply line 69 is located within the stored wash water.

[0051] The liquid level adjusting unit 70 adjusts the liquid level of the liquid stored in the absorption unit 52 or the recovery unit 61 to maintain it at a constant position. The liquid level adjusting unit 70 separates gas supplied from the ejection holes 573 contained in the liquid stored in the absorption unit 52 or the recovery unit 61, and supplies the gas from the upper part of the gas-liquid separation line 71 to the gas phase part of the absorption unit 52 or the recovery unit 61, and supplies the liquid from the overflow line 72 to join with the liquid stored in another absorption unit 52 or recovery unit 61 located Dvd below in the vertical direction Dv. The liquid level adjusting unit 70 of this embodiment includes the gas-liquid separation line 71 and the overflow line 72.

[0052] The gas-liquid separation line 71 is a pipe that connects the liquid phase stored in the storage section to a space Dvu above the liquid in the storage section in the vertical direction Dv. During operation of the device, the gas-liquid separation line 71 is connected to a space Dvu above the liquid surface in the vertical direction Dv when gas coexists in the liquid as gas is ejected from the gas diffuser. The gas-liquid separation line 71 supplies only the gas, of the liquid and gas flowing inside, to the space Dvu above the liquid surface in the vertical direction Dv.

[0053] The overflow line 72 circulates the liquid obtained after gas separation in the gas-liquid separation line 71 downward in the vertical direction Dv toward Dvd. The overflow line 72 is connected to the gas-liquid separation line 71 at a position in the vertical direction Dv that is the same as the liquid level of the liquid stored in the storage section when the device is stopped. The connection position between the overflow line 72 and the gas-liquid separation line 71 is lower in the vertical direction Dv than the opening position of the discharge hole 571. The connection position between the overflow line 72 and the gas-liquid separation line 71 is higher in the vertical direction Dv than the position at which gas is ejected by the ejection hole 573. The overflow line 72 is also connected to a storage section of another absorption unit 52 or recovery unit 61 that is located below Dvd in the vertical direction Dv with respect to the storage section to which the gas-liquid separation line 71 is connected.

[0054] The absorber 2 of this embodiment has a plurality of liquid level adjusting units 70. Specifically, the absorber 2 has a first absorbent liquid adjusting unit 74, a second absorbent liquid adjusting unit 75, a third absorbent liquid adjusting unit 76, a first wash water adjusting unit 78, and a second wash water adjusting unit 79 as the plurality of liquid level adjusting units 70.

[0055] The first absorbent liquid adjuster 74 separates the gas to be treated that is mixed in the absorbent stored in the first absorption unit 521. The first absorbent liquid adjuster 74 supplies the separated gas to be treated to a space Dvu above the absorbent liquid reservoir 55 of the first absorption unit 521 in the vertical direction Dv. That is, the first absorbent liquid adjuster 74 supplies the separated gas to be treated to a space between the absorbent liquid reservoir 55 of the first absorption unit 521 and the absorbent liquid reservoir 55 of the second absorption unit 522 in the vertical direction Dv. The first absorbent liquid adjuster 74 supplies the separated absorbent so that it merges with the absorbent stored in the lower reservoir 51.

[0056] The second absorbent liquid adjuster 75 separates the gas to be treated that is mixed in the absorbent stored in the second absorption unit 522. The second absorbent liquid adjuster 75 supplies the separated gas to be treated to a space Dvu above the absorbent liquid reservoir 55 of the second absorption unit 522 in the vertical direction Dv. That is, the second absorbent liquid adjuster 75 supplies the separated gas to be treated to a space between the absorbent liquid reservoir 55 of the second absorption unit 522 and the absorbent liquid reservoir 55 of the third absorption unit 523 in the vertical direction Dv. The second absorbent liquid adjuster 75 supplies the separated absorbent so that it merges with the absorbent stored in the absorbent liquid reservoir 55 of the first absorption unit 521.

[0057] The third absorbent liquid adjuster 76 separates the gas to be treated that is mixed in the absorbent stored in the third absorption unit 523. The third absorbent liquid adjuster 76 supplies the separated gas to be treated to a space Dvu above the absorbent liquid reservoir 55 of the third absorption unit 523 in the vertical direction Dv. In other words, the third absorbent liquid adjuster 76 supplies the separated gas to be treated to a space between the absorbent liquid reservoir 55 of the third absorption unit 523 and the first demister 81 in the vertical direction Dv. The third absorbent liquid adjuster 76 supplies the separated absorbent so that it merges with the absorbent stored in the absorbent liquid reservoir 55 of the second absorption unit 522.

[0058] The first wash water adjustment section 78 separates decarbonated gas mixed in the wash water stored in the first recovery unit 611. The first wash water adjustment section 78 supplies the separated decarbonated gas to a space Dvu above the wash water storage section 65 of the first recovery unit 611 in the vertical direction Dv. In other words, the first wash water adjustment section 78 supplies the separated decarbonated gas to the space between the wash water storage section 65 of the first recovery unit 611 and the wash water storage section 65 of the second recovery unit 612 in the vertical direction Dv. The first wash water adjustment section 78 supplies the separated wash water so that it flows together with the absorption liquid stored in the absorption liquid storage section 55 of the third absorption unit 523.

[0059] The second flush water adjustment section 79 separates the decarbonated gas mixed in the flush water stored in the second recovery unit 612. The second flush water adjustment section 79 supplies the separated decarbonated gas in the vertical direction Dv to the space between the flush water storage section 65 of the second recovery unit 612 and the second demister 82. The second flush water adjustment section 79 supplies the separated flush water so that it merges with the flush water stored in the flush water storage section 65 of the first recovery unit 611.

[0060] The demister 80 is installed to remove mist (small droplets) contained in the gas as the gas flows through it. Gas flows through the demister 80 from the lower Dvd to the upper Dvu in the vertical direction Dv. The demister 80 is formed, for example, by stacking multiple layers of mesh woven with thin wires. A plurality of demisters 80 are arranged inside the absorption tower main body 40. In this embodiment, a first demister 81 and a second demister 82 are arranged.

[0061] The first demister 81 is installed inside the absorber main body 40 to remove mist from the gas to be treated after contact with the absorption liquid. The first demister 81 is disposed between the carbon dioxide absorption section 50 and the water washing section 60. Specifically, the first demister 81 is disposed between the third absorption unit 523 and the first recovery unit 611 in the vertical direction Dv. The first demister 81 is disposed at a position Dvu above, in the vertical direction Dv, the connection position between the gas-liquid separation line 71 of the third absorption unit 523 and the absorber main body 40.

[0062] The second demister 82 is installed inside the absorber main body 40 to remove mist in the decarbonated gas after contact with the wash water. The second demister 82 is disposed between the water washing section 60 and the absorber discharge line 12. Specifically, the second demister 82 is disposed between the second recovery unit 612 and the top surface of the absorber 2 in the vertical direction Dv. The second demister 82 is disposed Dvu above, in the vertical direction Dv, the connection position between the gas-liquid separation line 71 of the second recovery unit 612 and the absorber main body 40. The second demister 82 is disposed Dvd below, in the vertical direction Dv, the connection position between the absorber discharge line 12 and the absorber main body 40.

[0063] The cooling section 90 cools the liquid in the absorber main body 40. At least one cooling section 90 is provided for each absorber main body 40. In this embodiment, only one cooling section 90 is provided. The cooling section 90 is installed to suppress an increase in the amount of water vapor in the decarbonated gas discharged from the absorber discharge line 12 and an increase in the absorption liquid component vapor because the temperature of the liquid and gas increases due to heat generated by the carbon dioxide absorption reaction in the carbon dioxide absorption section 50. By cooling the liquid, the cooling section 90 can lower the temperature of the liquid and gas. The cooling section 90 cools the wash water flowing through the cooling water withdrawal line 94 and supplies it to the space Dvu above the wash water reservoir 65 of the second recovery unit 612. Specifically, the cooling section 90 has a cooling line 91, a cooling pump 92, a wash water cooler 93, and a cooling withdrawal line 94.

[0064] The cooling pump 92 is installed between the cooling water withdrawal line 94 and the cooling line 91, and pumps the circulating wash water. The wash water cooler 93 is placed midway along the cooling line 91, and cools the wash water pumped by the cooling pump 92. Specifically, the wash water cooler 93 exchanges heat between the cooling water supplied from the outside and the wash water circulating through the cooling line 91, thereby cooling the wash water.

[0065] As conditions for operating the absorption tower 2 as described above, it is preferable that the superficial velocity Ug when the gas is sprayed from the treatment gas diffusing section 57 and the decarbonated gas diffusing section 67 is in the range of 0.5 m / s to 2.5 m / s. Furthermore, it is preferable that the flow rate ratio L / G of the gas to the liquid when the gas is sprayed from the treatment gas diffusing section 57 and the decarbonated gas diffusing section 67 is 0.5 L / Nm ３ ~5.0L / Nm ３ In addition, when the nozzle holes 573 are formed as a perforated plate, the aperture ratio is preferably between 25% and 70%. In this case, the size of the nozzle holes 573 is preferably within the range of 1 to 10 mm.

[0066] As shown in FIG. 3 , the height at which the gas is ejected from the bottom plate 551, where the ejection holes 573 are located, is referred to as the ejection height H1. The height at which the overflow line 72 and the gas-liquid separation line 71 connect with the bottom plate 551 in the vertical direction Dv is referred to as the overflow height H2. The height at which the discharge holes 571 open with respect to the bottom plate 551 in the vertical direction Dv is referred to as the gas return height H3. The height of the liquid surface of the stored liquid with respect to the bottom plate 551 in the vertical direction Dv while the device is stopped is referred to as the liquid surface height H4. The height of the highest liquid surface in a large wavy state after gas is ejected from the gas diffuser with respect to the bottom plate 551 in the vertical direction Dv while the device is operating is referred to as the maximum liquid surface height H5.

[0067] The overflow height H2 is equal to the liquid level height H4. The blowout height H1 is preferably lower than the overflow height H2. The gas return height H3 is preferably higher than the overflow height H2. The gas return height H3 is preferably lower than the maximum liquid level height H5. The height of the absorption unit 52 and the recovery unit 61 in the vertical direction Dv is referred to as the stage height H. The stage height H is higher than the maximum liquid level height H5.

[0068] In the carbon dioxide capture system 1 having the above configuration, as shown in FIG. 1 , the gas to be treated flowing through the gas to be treated line 11 is sent to the absorption tower 2. The gas to be treated supplied to the absorption tower 2 comes into contact with an absorbing liquid in the absorption tower 2, thereby removing carbon dioxide. As a result, the absorber exhaust gas from which carbon dioxide has been removed is discharged to the outside from the absorption tower 2 via the absorption tower discharge line 12. Furthermore, in the absorption tower 2, a rich liquid, which is an absorbing liquid that has absorbed carbon dioxide, is produced. The rich liquid is pressurized by a rich pump 35 via a 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 sent to the regeneration tower 3. In the regeneration tower 3, the rich liquid is heated by a reboiler 31, thereby stripping carbon dioxide from the rich liquid. As a result, in the regeneration tower 3, a lean liquid, which is an absorbing liquid from which carbon dioxide has been stripped, is produced. The lean liquid is pressurized by a lean pump 37 via the lean line 14 and sent to the absorbing liquid heat exchanger 4. The lean liquid is cooled by heat exchange with the rich liquid in the absorption liquid heat exchanger 4. The cooled lean liquid is returned to the absorption tower 2. In this manner, the absorption liquid circulates between the absorption tower 2 and the regeneration tower 3. In addition, in the regeneration tower 3, a regeneration tower exhaust gas containing carbon dioxide as a main component is generated by dissipating carbon dioxide from the rich liquid, and the generated gas is sent to the regeneration tower discharge line 15.

[0069] 2 , in the absorption tower 2, the gas to be treated supplied from the gas to be treated line 11 is first supplied to the upper Dvu of the lower reservoir 51. The lower reservoir 51 stores absorption liquid (rich liquid) that has absorbed carbon dioxide in a plurality of absorption units 52, and is sent to the rich line 13. The supplied gas to be treated moves to the upper Dvu in the vertical direction Dv and is sent to the plurality of absorption units 52.

[0070] Specifically, the target gas is sent to the first absorption unit 521. In the first absorption unit 521, the target gas is injected from the target gas diffuser 57 so as to generate a froth flow in the absorption liquid stored in the absorption liquid storage section 55. More specifically, the target gas flowing upward Dvu in the vertical direction Dv from the lower storage section 51 passes through the discharge holes 571 toward the upward Dvu in the vertical direction Dv, as shown in FIG. 3 . The target gas passing through the discharge holes 571 collides with the collision plate 581 and changes its flow direction to flow downward Dvd in the vertical direction Dv. The target gas flowing downward Dvd in the vertical direction Dv passes through a flow path formed by the flow path forming plate 582 and reaches the ejection holes 573. The target gas is then ejected from the multiple ejection holes 573 into the absorption liquid so as to flow downward Dvd in the vertical direction Dv. The gas to be treated sprayed into the absorption liquid flows upward Dvu through the absorption liquid in the vertical direction Dv to form a froth flow. As a result, the gas to be treated and the absorption liquid come into contact with each other and are mixed vigorously, and some of the carbon dioxide contained in the gas to be treated is absorbed by the absorption liquid. The absorption liquid that has absorbed the carbon dioxide is sent to the lower storage section 51 via the first absorption liquid adjustment section 74. The gas to be treated that has escaped from the stored absorption liquid moves upward Dvu in the vertical direction Dv through the space above the absorption liquid Dvu and is sent to the second absorption unit 522.

[0071] The gas to be treated also flows through the second absorption unit 522, as in the first absorption unit 521. As a result, the gas to be treated and the absorbing liquid also come into contact in the second absorption unit 522, and some of the carbon dioxide contained in the gas to be treated is absorbed by the absorbing liquid. The absorbing liquid that has absorbed the carbon dioxide is sent to the absorbing liquid storage section 55 of the first absorption unit 521 via the second absorbing liquid adjustment section 75. In addition, the gas to be treated that has escaped from the absorbing liquid moves in the space Dvu above the absorbing liquid in the vertical direction Dv toward Dvu above the absorbing liquid, and is sent to the third absorption unit 523.

[0072] The gas to be treated also flows through the third absorption unit 523, as in the first absorption unit 521. At this time, in the absorption liquid storage section 55 of the third absorption unit 523, the lean liquid supplied via the lean line 14 merges with the stored absorption liquid. Then, in the third absorption unit 523, the gas to be treated and the absorption liquid come into contact with each other, and some of the carbon dioxide contained in the gas to be treated is absorbed by the absorption liquid. The absorption liquid that has absorbed the carbon dioxide is sent to the absorption liquid storage section 55 of the second absorption unit 522 via the third absorption liquid adjustment section 76. In addition, the gas to be treated that has escaped from the stored absorption liquid moves in the space Dvu above the absorption liquid in the vertical direction Dv toward Dvu above the absorption liquid and is sent to the first demister 81.

[0073] As described above, in the carbon dioxide absorption section 50 of this embodiment, the carbon dioxide in the gas to be treated is absorbed by the absorption liquid over three stages: the first absorption unit 521, the second absorption unit 522, and the third absorption unit 523. As a result, most of the carbon dioxide contained in the gas to be treated is removed, resulting in decarbonated gas. The decarbonated gas flows upward Dvu in the vertical direction Dv and passes through the first demister 81, thereby removing the mist contained in the decarbonated gas. The decarbonated gas from which the mist has been removed is sent to the water washing section 60.

[0074] Specifically, the decarbonated gas is sent to the first recovery unit 611. In the first recovery unit 611, the decarbonated gas flows in the same manner as the gas to be treated flowing through the first absorption unit 521. As a result, the decarbonated gas comes into contact with the cleaning water in the first recovery unit 611. The cleaning water from which the absorption liquid components have been recovered from the decarbonated gas is sent to the absorption liquid storage section 55 of the third absorption unit 523 via the first cleaning water adjustment section 78. In addition, the decarbonated gas that has escaped from the cleaning water moves in the space Dvu above the cleaning water in the vertical direction Dv toward Dvu above the cleaning water, and is sent to the second recovery unit 612.

[0075] The decarbonated gas also flows through the second recovery unit 612, as in the first recovery unit 611. At this time, new wash water is supplied to the wash water storage section 65 of the second recovery unit 612 via a wash water supply line 69 and merges with the stored wash water. Then, in the second recovery unit 612, the decarbonated gas and the wash water also come into contact. The wash water from which the absorption liquid components have been recovered from the decarbonated gas is sent to the wash water storage section 65 of the first recovery unit 611 via a second wash water adjustment section 79. Furthermore, a portion of the wash water sent to the first recovery unit 611 is cooled via a cooling section 90 and returned to the wash water storage section 65 of the second recovery unit 612. Furthermore, the decarbonated gas that has escaped from the stored wash water moves in the space Dvu above the wash water in the vertical direction Dv toward the upper Dvu and is sent to the second demister 82.

[0076] As described above, in the water washing section 60 of this embodiment, the absorption solution components entrained in the decarbonated gas are recovered over two stages, in the first recovery unit 611 and the second recovery unit 612. As a result, most of the vapor and mist of the absorption solution entrained in the decarbonated gas is removed from the decarbonated gas, and the decarbonated gas becomes absorber exhaust gas. The absorber exhaust gas flows upward Dvu in the vertical direction Dv and passes through the second demister 82, whereby the mist contained in the absorber exhaust gas is further removed. The absorber exhaust gas from which the mist has been removed is discharged to the outside of the absorber main body 40 through the absorber discharge line 12.

[0077] (Effects) In this type of absorption tower 2, the gas to be treated is sprayed into the absorbing liquid stored in the absorption unit 52. This allows the stored absorbing liquid to come into contact with the gas to be treated efficiently. As a result, the carbon dioxide absorption reaction by the absorbing liquid is promoted. In particular, in this embodiment, the gas to be treated is sprayed into the absorbing liquid so as to form a froth flow. The generation of a froth flow in the absorbing liquid causes the absorbing liquid to be vigorously agitated by the gas to be treated, resulting in more efficient contact between the absorbing liquid and the gas to be treated, and further promoting the carbon dioxide absorption reaction by the absorbing liquid. As a result, even if the height of the absorption unit 52 is reduced, the efficiency of recovering carbon dioxide from the gas to be treated can be improved.

[0078] Furthermore, the decarbonated gas, which is the gas to be treated after passing through the carbon dioxide absorption section 50, is injected into the cleaning water stored in the recovery unit 61. This allows the stored cleaning water and the decarbonated gas to come into contact with each other efficiently. As a result, recovery of the absorbent components by the cleaning water is promoted. In particular, in this embodiment, the decarbonated gas is injected into the cleaning water so as to form a froth flow. The generation of a froth flow in the cleaning water causes the cleaning water to be vigorously agitated by the decarbonated gas, so that the cleaning water and the decarbonated gas come into contact with each other more efficiently, further promoting recovery of the absorbent components by the cleaning water. This allows the recovery efficiency of the absorbent components from the decarbonated gas to be improved even if the height of the recovery unit 61 is reduced.

[0079] As a result, the height of the absorption tower 2 can be reduced while maintaining the efficiency of recovering carbon dioxide from the gas and the efficiency of recovering the absorption liquid components contained in the decarbonated gas after recovering the carbon dioxide at the same level as absorption towers of conventional heights.

[0080] In this embodiment, the carbon dioxide absorption section 50 has a plurality of absorption units 52 arranged in the vertical direction Dv. By arranging a plurality of absorption units 52 with high carbon dioxide absorption efficiency in this manner, the efficiency of recovering carbon dioxide from the gas to be treated can be improved while reducing the overall height of the carbon dioxide absorption section 50 compared to when configured with other devices. Similarly, the water washing section 60 has a plurality of recovery units 61 arranged in the vertical direction Dv. By arranging a plurality of recovery units 61 with high absorption solution component recovery efficiency in this manner, the efficiency of recovering the absorption solution component from the decarbonated gas can be improved while reducing the height of the water washing section 60 compared to when configured with other devices. Furthermore, the plurality of recovery units 61 are stacked in the absorber main body 40 at a position Dvu above the plurality of absorption units 52 in the vertical direction Dv. Even when a plurality of absorption units 52 and a plurality of recovery units 61 are arranged in one absorber main body 40 in this manner, the efficiency of recovering carbon dioxide from the gas to be treated and the efficiency of recovering the absorption solution component contained in the decarbonated gas can be improved while reducing the overall height of the absorber 2.

[0081] Furthermore, the target gas diffuser 57 injects the target gas into the absorption liquid toward the downward direction Dvd in the vertical direction Dv. Similarly, the decarbonated gas diffuser 67 injects the decarbonated gas into the cleaning water toward the downward direction Dvd in the extension direction. In this way, by injecting the gas into the liquid toward the downward direction Dvd in the vertical direction Dv, the contact time between the liquid and the gas can be increased compared to when the gas is injected toward the upward direction Dvu in the vertical direction Dv. In other words, the contact time between the injected gas and the liquid is increased without raising the liquid level of the stored liquid. This further improves the efficiency of recovering carbon dioxide from the target gas and the efficiency of recovering the absorption liquid components contained in the decarbonated gas. Therefore, the height of the absorption tower 2 can be further reduced.

[0082] The target gas diffuser 57 and the decarbonated gas diffuser 67 each have a discharge hole 571, a direction changer 572, and an ejection hole 573. The discharge hole 571 discharges the target gas or decarbonated gas toward the upper Dvu in the vertical direction Dv. Therefore, when the absorption units 52 and the recovery units 61 are stacked in the vertical direction Dv, the target gas or decarbonated gas can be easily supplied from an absorption unit 52 or recovery unit 61 located at the lower Dvd in the vertical direction Dv to another absorption unit 52 or recovery unit 61 located at the upper Dvu in the vertical direction Dv via the discharge hole 571. The direction changer 572 changes the flow direction of the target gas or decarbonated gas supplied from the discharge hole 571 before ejecting it from the ejection hole 573. Therefore, a configuration can be easily achieved in which the target gas or decarbonated gas is ejected toward the lower Dvd in the vertical direction Dv inside the stored absorption liquid or cleaning water. Therefore, the gas supplied from the absorption unit 52 or the recovery unit 61 in the lower Dvd can be ejected downward Dvd in the vertical direction Dv within the stored liquid with a simple configuration.

[0083] Furthermore, a liquid level adjusting section 70 is provided to adjust the liquid level of the liquid stored in the absorption unit 52 or the recovery unit 61 so that it remains constant. Therefore, even if the flow rates of the gases supplied from the gas to be treated and the decarbonated gas diffusing section 67 change, the liquid level of the stored liquid can be maintained constant. This allows stable contact between the gas to be treated and the absorption liquid, or the decarbonated gas and cleaning water, regardless of fluctuations in the flow rates of the gas to be treated and the decarbonated gas supplied.

[0084] Furthermore, in the liquid level adjusting section 70, the gas-liquid separation line 71 and the overflow line 72 are connected at the same position as the liquid levels of the liquid stored in the absorbent liquid storage section 55 and the wash water storage section 65. Therefore, when the liquid is about to be stored beyond the connection position of the gas-liquid separation line 71 and the overflow line 72, the stored liquid is sent from the overflow line 72 to the absorbent liquid storage section 55 of another absorption unit 52 or the wash water storage section 65 of the recovery unit 61 located below Dv in the vertical direction Dv. Therefore, the liquid level of the liquid stored in the absorbent liquid storage section 55 and the wash water storage section 65 can be maintained without using a complex device.

[0085] Furthermore, the gas return height H3 is higher than the overflow height H2, and the blowout height H1 is lower than the overflow height H2. That is, in the vertical direction Dv, the opening position of the discharge hole 571 is higher than the connection position of the gas-liquid separation line 71 and the overflow line 72, and the position at which gas is blown out by the jet hole 573 is lower. Since the opening position of the discharge hole 571 is higher than the connection position of the liquid separation line and the overflow line 72, the liquid level height H4, which is the liquid level during operation shutdown of the absorber 2, is always lower than the gas return height H3 associated with the opening position of the discharge hole 571 and always higher than the blowout height H1 associated with the installation position of the jet hole 573. Therefore, it is possible to prevent an event in which gas is not blown out within the liquid when the absorber 2, 2A, starts operating. Furthermore, if the opening position of the discharge hole 571 were lower than the connection position of the liquid separation line and the overflow line 72, the liquid level H4 would drop to the gas turnback height H3 during shutdown of the absorber 2, making it impossible to maintain the liquid level at the overflow height H2. However, in this embodiment, the liquid level H4, which is the liquid level during shutdown of the absorber 2, is always maintained at the overflow height H2 and can always be higher than the blowout height H1 associated with the installation position of the ejection hole 573. Therefore, stable contact between the gas and the liquid can be achieved immediately after the start of operation.

[0086] Furthermore, within the absorber main body 40, the temperatures of the absorbing solution and the gas rise due to heat generated during the carbon dioxide absorption reaction by the absorbing solution. In particular, when carbon dioxide is absorbed into the absorbing solution in multiple absorption units 52 as in this embodiment, the temperatures of the first absorption unit 521 to the third absorption unit 523 rise in stages. An excessive temperature rise in the absorption unit 52 could result in an increase in the amount of water vapor in the decarbonated gas and an increase in the vapor of the absorbing solution components. However, the cooling section 90 cools the wash water present in the second recovery unit 612. That is, the cooling section 90 cools the space near the connection position with the absorber discharge line 12, condensing the water vapor and absorbing solution components in the decarbonated gas at the outlet of the recovery unit 61 and recovering them together with the water wash water from the water wash section, thereby suppressing the discharge of the absorbing solution components in the decarbonated gas.

[0087] Furthermore, by providing the absorption tower 2 as described above, the carbon dioxide treatment system can be installed even in cases where there is a limit to the height of the installation location.

[0088] 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 description thereof will be omitted. In the second embodiment, the configuration of an absorption tower 2A is different from that of the first embodiment.

[0089] As shown in FIG. 5 , the absorption tower 2A of the second embodiment includes a first absorption tower body 41, a second absorption tower body 42, a body connecting line 43, a carbon dioxide absorption section 50A, a water washing section 60A, a liquid level adjusting section 70A, and a demister 80.

[0090] The first absorption tower body 41 is a cylindrical container extending in the vertical direction Dv. The gas to be treated can flow inside the first absorption tower body 41 from a lower position Dvd to an upper position Dvu in the vertical direction Dv. A gas line 11 to be treated is connected near the bottom of the first absorption tower body 41. A main body connection line 43 is connected near the top of the first absorption tower body 41. A lean line 14 is connected to the first absorption tower body 41 at a position Dvu above the connection position with the gas line 11 in the vertical direction Dv and at a position Dvd below the connection position with the main body connection line 43 in the vertical direction Dv.

[0091] The second absorption tower body 42 is a cylindrical container extending in the vertical direction Dv. The second absorption tower body 42 is formed with a lower height in the vertical direction Dv than the absorption tower body 40 and the first absorption tower body 41 of the first embodiment. The second absorption tower body 42 is disposed horizontally apart from the first absorption tower body 41. The top of the second absorption tower body 42 is positioned so as not to protrude upward Dvu in the vertical direction Dv relative to the top of the first absorption tower body 41. Decarbonated gas can flow inside the second absorption tower body 42 from a lower Dvd in the vertical direction Dv to an upper Dvu. An absorber discharge line 12 is connected near the top of the second absorption tower body 42. A wash water supply line 69 is connected to the second absorption tower body 42 at a position Dvd below the connection position with the absorber discharge line 12 in the vertical direction Dv. A body connection line 43 is connected near the bottom of the second absorption tower body 42. A wash water discharge line 14′ is connected to the second absorption tower main body 42 at a position Dvd below in the vertical direction Dv with respect to the connection position with the main body connection line 43. The wash water discharge line merges with the lean line 14 via a pump (not shown).

[0092] The main body connecting line 43 connects the first absorption tower main body 41 and the second absorption tower main body 42. The main body connecting line 43 sends the decarbonated gas discharged from the first absorption tower main body 41 to the second absorption tower main body 42. The main body connecting line 43 is connected near the top of the first absorption tower main body 41 and near the bottom of the second absorption tower main body 42.

[0093] The carbon dioxide absorption section 50A of the second embodiment has a downward air diffuser 53 and a plurality of absorption units 52A.

[0094] The lower aeration section 53 stores the absorption liquid and injects the gas to be treated into the absorption liquid. The lower aeration section 53 is disposed below the plurality of absorption units 52A in the vertical direction Dv, at a position Dvd. The lower aeration section 53 is disposed near the bottom of the first absorption tower body 41. The lower aeration section 53 includes a first bottom storage section 531, an aeration pipe 532, a lower gas-liquid separation line 533, and a lower liquid level adjustment tank 534.

[0095] The first bottom reservoir 531 stores the absorption liquid. The absorption liquid having the highest carbon dioxide concentration in the carbon dioxide absorption unit 50A is stored in the first bottom reservoir 531. In the first bottom reservoir 531, the absorption liquid is stored so that the liquid level of the stored absorption liquid is located Dvu above the connection position between the first absorption tower body 41 and the gas line 11 to be treated in the vertical direction Dv.

[0096] The air diffuser pipe 532 extends into the stored absorption liquid from the connection position between the first absorption tower body 41 and the gas to be treated line 11. The air diffuser pipe 532 is arranged horizontally and has a plurality of holes formed therein that face downward toward Dvd in the vertical direction Dv. The air diffuser pipe 532 sprays the gas to be treated into the stored absorption liquid. The air diffuser pipe 532 sprays the gas to be treated toward Dvd downward in the vertical direction Dv so as to form a froth flow in the absorption liquid.

[0097] The downward gas-liquid separation line 533 is a pipe connecting the inside of the absorption liquid stored in the first bottom storage section 531 with a space Dvu above the absorption liquid in the first bottom storage section 531 in the vertical direction Dv. The downward gas-liquid separation line 533 is capable of supplying the absorption liquid stored in the first bottom storage section 531 and the gas to be treated contained in the absorption liquid toward the upward Dvu in the vertical direction Dv. The lower gas-liquid separation line 533 is connected to the space Dvu above the vertical direction Dv with respect to the liquid surface in a greatly wavy state after the gas to be treated is sprayed from the aeration pipe 532. The lower gas-liquid separation line 533 supplies only the gas to be treated among the absorption liquid and the gas to be treated flowing inside to the space Dvu above the liquid surface in the vertical direction Dv.

[0098] The lower liquid level adjustment tank 534 stores the absorption liquid so as to be located at a position Dvd below in the vertical direction Dv with respect to the liquid level of the absorption liquid stored in the first bottom storage section 531. The lower liquid level adjustment tank 534 is connected to the lower gas-liquid separation line 533 at a position in the vertical direction Dv that is the same as the liquid level of the absorption liquid stored in the first bottom storage section 531 during operation shutdown. The rich line 13 is connected to the lower liquid level adjustment tank 534 at a position Dvd below in the vertical direction Dv with respect to the connection position with the lower gas-liquid separation line 533.

[0099] The plurality of absorption units 52A are disposed within the first absorption tower body 41. The carbon dioxide absorption section 50A of the second embodiment includes a first absorption unit 521A, a second absorption unit 522A, a third absorption unit 523A, and a fourth absorption unit 524A as the plurality of absorption units 52A. The first absorption unit 521A, the second absorption unit 522A, the third absorption unit 523A, and the fourth absorption unit 524A have the same structure. In the second embodiment, the first absorption unit 521A, the second absorption unit 522A, the third absorption unit 523A, and the fourth absorption unit 524A are disposed in this order, facing upward Dvu in the vertical direction Dv relative to the downward aeration section 53. That is, the first absorption unit 521A is disposed furthest downward Dvd of the four absorption units 52A in the vertical direction Dv. The fourth absorption unit 524A is disposed furthest upward Dvu of the four absorption units 52A in the vertical direction Dv.

[0100] In addition, in the plurality of absorption units 52A, the absorption liquid arranged at the upper Dvu in the vertical direction Dv has a lower concentration of carbon dioxide. Furthermore, in the fourth absorption unit 524A, the absorption liquid is stored so that the connection position between the first absorption tower body 41 and the lean line 14 is located within the stored absorption liquid.

[0101] The water washing section 60A of the second embodiment has a second bottom reservoir 63 and a plurality of recovery units 61A. The second bottom reservoir 63 stores wash water. The second bottom reservoir 63 stores wash water having the highest concentration of absorption liquid components in the water washing section 60A. In the second bottom reservoir 63, wash water is stored so that the liquid level of the stored wash water is located at Dvd in the vertical direction Dv below the connection position between the second absorption tower body 42 and the body connection line 43. In the second bottom reservoir 63, wash water is stored so that the connection position between the second absorption tower body 42 and the wash water discharge line 14′ is located within the stored wash water.

[0102] The plurality of recovery units 61A are disposed within the second absorption tower body 42. That is, the plurality of recovery units 61A are arranged at positions separated horizontally from the plurality of absorption units 52A. The plurality of recovery units 61A are also arranged side by side in the vertical direction Dv. The water washing section 60A of the second embodiment includes a first recovery unit 611A and a second recovery unit 612A as the plurality of recovery units 61A. The first recovery unit 611A and the second recovery unit 612A have the same structure.

[0103] The first recovery unit 611A is disposed above Dvu in the vertical direction Dv relative to the second bottom storage section 63. In the second embodiment, the first recovery unit 611A and the second recovery unit 612A are disposed side by side in this order toward Dvu above the second bottom storage section 63 in the vertical direction Dv.

[0104] In the second recovery unit 612A, for example, wash water is supplied from a wash water supply line 69 connected to the regeneration tower 3. In the second recovery unit 612A, the wash liquid is stored so that the connection position between the second absorption tower body 42 and the wash water supply line 69 is located within the stored wash water.

[0105] Moreover, the absorption unit 52A and the recovery unit 61A of the second embodiment further include a partition plate 59. The partition plate 59 is disposed in at least a portion of the absorption unit 52A and the recovery unit 61A. In the second embodiment, the partition plate 59 is disposed in all of the absorption units 52A and the recovery units 61A.

[0106] The partition plate 59 divides the storage portion into a plurality of regions arranged horizontally. The partition plate 59 extends above Dvu in the vertical direction Dv above the liquid level of the absorption liquid stored in the storage portion. The partition plate 59 is a plate-shaped member extending straight from the bottom plate portion 551 in the vertical direction Dv above Dvu. In this embodiment, the partition plate 59 divides the storage portion into two regions arranged horizontally. As shown in FIG. 6 , the partition plate 59 has a communication hole 591 that opens into the liquid stored in the storage portion. A plurality of communication holes 591 (for example, two in this embodiment) are formed. Liquid can move between the plurality of regions through the communication holes 591.

[0107] As shown in FIG. 5 , the absorption tower 2A of the second embodiment has a plurality of liquid level adjusting units 70A, including a first absorbent liquid adjusting unit 74A, a second absorbent liquid adjusting unit 75A, a third absorbent liquid adjusting unit 76A, a fourth absorbent liquid adjusting unit 77A, a first wash water adjusting unit 78A, and a second wash water adjusting unit 79A.

[0108] The first absorbent liquid adjusting section 74A is connected to the first absorption tower main body 41. The first absorbent liquid adjusting section 74A separates the gas to be treated from the absorbent stored in the first absorption unit 521A. The first absorbent liquid adjusting section 74A supplies the separated gas to be treated to a space Dvu above the absorbent liquid storage section 55 of the first absorption unit 521A in the vertical direction Dv. The first absorbent liquid adjusting section 74A supplies the separated absorbent to join the absorbent stored in the first bottom storage section 531.

[0109] The second absorbent liquid adjusting section 75A is connected to the first absorption tower main body 41. The second absorbent liquid adjusting section 75A separates the gas to be treated from the absorbent stored in the second absorption unit 522A. The second absorbent liquid adjusting section 75A supplies the separated gas to be treated to a space Dvu above the absorbent liquid storage section 55 of the second absorption unit 522A in the vertical direction Dv. The second absorbent liquid adjusting section 75A supplies the separated absorbent so that it merges with the absorbent stored in the absorbent liquid storage section 55 of the first absorption unit 521A.

[0110] The third absorbent liquid adjuster 76A is connected to the first absorption tower main body 41. The third absorbent liquid adjuster 76A separates the gas to be treated from the absorbent stored in the third absorption unit 523A. The third absorbent liquid adjuster 76A supplies the separated gas to a space Dvu above the absorbent liquid reservoir 55 of the third absorption unit 523A in the vertical direction Dv. The third absorbent liquid adjuster 76A supplies the separated absorbent so that it merges with the absorbent stored in the absorbent reservoir 55 of the second absorption unit 522A.

[0111] The fourth absorbent liquid adjuster 77A is connected to the first absorption tower main body 41. The fourth absorbent liquid adjuster 77A separates the gas to be treated from the absorbent stored in the fourth absorption unit 524A. The fourth absorbent liquid adjuster 77A supplies the separated gas to a space Dvu above the absorbent liquid reservoir 55 of the fourth absorption unit 524A in the vertical direction Dv. The fourth absorbent liquid adjuster 77A supplies the separated absorbent so that it merges with the absorbent stored in the absorbent reservoir 55 of the third absorption unit 523A.

[0112] The first wash water adjustment section 78A is connected to the second absorption tower main body 42. The first wash water adjustment section 78A separates decarbonated gas from the wash water stored in the first recovery unit 611A. The first wash water adjustment section 78A supplies the separated decarbonated gas to a space Dvu above the wash water storage section 65 of the first recovery unit 611A in the vertical direction Dv. The first wash water adjustment section 78A supplies the separated wash water so that it merges with the wash water stored in the second bottom storage section 63.

[0113] The second wash water adjustment section 79A is connected to the second absorption tower main body 42. The second wash water adjustment section 79A separates decarbonated gas from the wash water stored in the second recovery unit 612A. The second wash water adjustment section 79A supplies the separated decarbonated gas to a space Dvu above the wash water storage section 65 of the second recovery unit 612A in the vertical direction Dv. The second wash water adjustment section 79A supplies the separated wash water so that it merges with the wash water stored in the wash water storage section 65 of the first recovery unit 611A.

[0114] The first demister 81A of the second embodiment allows the gas to be treated after contacting the absorption liquid to flow inside the first absorption tower body 41. The first demister 81A is disposed above the fourth absorption unit 524A in the vertical direction Dv. The first demister 81A is disposed below the connection position Dvd of the first absorption tower body 41 and the body connection line 43 in the vertical direction Dv.

[0115] The second demister 82A of the second embodiment allows the decarbonated gas that has come into contact with the wash water to flow inside the second absorption tower body 42. The second demister 82A is disposed at a position Dvu above the second recovery unit 612A in the vertical direction Dv. The second demister 82A is disposed at a position Dvd below the position where the absorber discharge line 12 and the second absorption tower body 42 are connected in the vertical direction Dv.

[0116] The cooling section 90 of the second embodiment is disposed in each of the first absorption tower body 41 and the second absorption tower body 42. That is, the absorption tower 2A of the second embodiment has two cooling sections 90. Specifically, the absorption tower 2A of the second embodiment has a first cooling section 90A and a second cooling section 90B.

[0117] The first cooling section 90A is disposed in the first absorption tower body 41. The first cooling section 90A has a first cooling line 91A, a first cooling pump 92A, and a first cooler 93A. The first cooling line 91A is connected to the overflow line 72 of the fourth absorbent adjusting section 77A. The first cooling line 91A supplies a portion of the absorption liquid flowing through the overflow line 72 to a space Dvu above the absorbent storage section 55 of the fourth absorption unit 524A in the vertical direction Dv.

[0118] The first cooling pump 92A is installed in the first cooling line 91A and pumps the absorbing liquid flowing through it. The first cooler 93A is placed midway through the first cooling line 91A and cools the absorbing liquid pumped by the first cooling pump 92A. Specifically, the first cooler 93A cools the absorbing liquid by exchanging heat between cooling water supplied from the outside and the absorbing liquid flowing through the first cooling line 91A.

[0119] The second cooling section 90B is disposed in the second absorption tower main body 42. The second cooling section 90B has a second cooling line 91B, a second cooling pump 92B, and a second cooler 93B. The second cooling line 91B is connected to the overflow line 72 of the second wash water adjustment section 79A. The second cooling line 91B supplies a portion of the wash water circulating through the overflow line 72 to a space Dvu above the wash water storage section 65 of the second recovery unit 612A in the vertical direction Dv.

[0120] The second cooling pump 92B is installed in the second cooling line 91B and pumps the circulating wash water. The second cooler 93B is placed midway along the second cooling line 91B and cools the wash water pumped by the second cooling pump 92B. Specifically, the second cooler 93B cools the wash water by exchanging heat between cooling water supplied from the outside and the wash water circulating through the second cooling line 91B.

[0121] In the absorption tower 2A of the second embodiment, the target gas supplied from the target gas line 11 is first supplied to the downward diffuser 53 within the first absorption tower body 41. In the downward diffuser 53, the target gas is sprayed by the diffuser into the absorbing liquid stored in the first bottom reservoir 531. As a result, the target gas sprayed into the absorbing liquid flows downward Dvd in the vertical direction Dv, forming a froth flow through the absorbing liquid. As a result, the target gas and the absorbing liquid come into contact with each other so as to be vigorously mixed, and the carbon dioxide contained in the target gas is supplied to the absorbing liquid. The absorbing liquid that has absorbed the carbon dioxide is sent to the lower liquid level adjustment tank 534 through the lower gas-liquid separation line 533. The absorbing liquid sent to the lower liquid level adjustment tank 534 is a rich liquid and is temporarily stored there before being sent to the rich line 13. The supplied target gas moves upward Dvu in the vertical direction Dv and is sent to the multiple absorption units 52A.

[0122] Thereafter, the gas to be treated flows through the first absorption unit 521A, the second absorption unit 522A, the third absorption unit 523A, and the fourth absorption unit 524A in this order, as in the first embodiment.

[0123] The gas to be treated supplied to the first absorption unit 521A is sprayed into the absorption liquid and comes into contact with the absorption liquid. The absorption liquid that has absorbed carbon dioxide is sent to the first bottom reservoir 531 via the first absorption liquid adjustment section 74A. The gas to be treated that has escaped from the absorption liquid moves in the space Dvu above the absorption liquid toward the upper Dvu in the vertical direction Dv, and is sent to the second absorption unit 522A.

[0124] The gas to be treated supplied to the second absorption unit 522A is sprayed into the absorbing liquid and comes into contact with the absorbing liquid. The absorbing liquid that has absorbed carbon dioxide is sent to the absorbing liquid storage section 55 of the first absorption unit 521A via the second absorbing liquid adjustment section 75A. The gas to be treated that has escaped from the absorbing liquid moves in the space Dvu above the absorbing liquid in the vertical direction Dvu and is sent to the third absorption unit 523A.

[0125] The gas to be treated supplied to the third absorption unit 523A is sprayed into the absorbing liquid and comes into contact with the absorbing liquid. The absorbing liquid that has absorbed carbon dioxide is sent to the absorbing liquid reservoir 55 of the second absorption unit 522A via the third absorbing liquid adjustment section 76A. The gas to be treated that has escaped from the absorbing liquid moves in the space Dvu above the absorbing liquid in the vertical direction Dvu and is sent to the fourth absorption unit 524A.

[0126] The gas to be treated flows through the fourth absorption unit 524A in the same manner as the other absorption units 52A. In the absorption liquid storage section 55 of the fourth absorption unit 524A, the lean liquid supplied via the lean line 14 merges with the stored absorption liquid. The gas to be treated and the absorption liquid then come into contact with each other in the fourth absorption unit 524A. The absorption liquid that has absorbed carbon dioxide is sent to the absorption liquid storage section 55 of the third absorption unit 523A via the fourth absorption liquid adjustment section 77A. The gas to be treated that has been released from the absorption liquid becomes decarbonated gas and moves upward in the vertical direction Dv through the space Dvu above the absorption liquid and is sent to the first demister 81A. By passing through the first demister 81A, mist contained in the decarbonated gas is removed. The decarbonated gas from which the mist has been removed is sent to the main body connection line 43. The decarbonated gas passes through the first absorption tower body 41 and flows into the second absorption tower body 42 via the body connection line 43 .

[0127] As described above, in the carbon dioxide absorption section 50A of this embodiment, the carbon dioxide in the gas to be treated is absorbed by the absorption liquid over five stages: the downward aeration section 53, the first absorption unit 521A, the second absorption unit 522A, the third absorption unit 523A, and the fourth absorption unit 524A. As a result, most of the carbon dioxide contained in the gas to be treated is removed, resulting in decarbonated gas. The decarbonated gas flows upward Dvu in the vertical direction Dv and passes through the first demister 81A, thereby removing the mist contained in the decarbonated gas. The decarbonated gas from which the mist has been removed is sent to the water washing section 60A.

[0128] In the second absorption tower body 42 , the decarbonated gas is sent above the second bottom reservoir 63 .

[0129] The second bottom reservoir 63 stores wash water. The second bottom reservoir 63 stores wash water having the highest concentration of absorption liquid in the second absorption tower body 42. In the second bottom reservoir 63, the wash water is stored so that the liquid level of the stored wash water is located at Dvd below in the vertical direction Dv with respect to the connection position between the second absorption tower body 42 and the wash water discharge line 14′.

[0130] The cleaning water from which the mist of the absorption liquid has been collected is sent to a cleaning water discharge line 14'. Thereafter, the cleaning water discharge line 14' merges with lean liquid (not shown) supplied from the regeneration tower 3, and is sent to the absorption liquid storage section 55 of the fourth absorption unit 524A via the lean line 14. The supplied decarbonated gas moves upward Dvu in the vertical direction Dv, and is sent to the multiple recovery units 61A.

[0131] Thereafter, the decarbonated gas flows through the first recovery unit 611A and the second recovery unit 612A in this order, as in the first embodiment. The decarbonated gas that has escaped from the cleaning water after passing through the second recovery unit 612A moves through the space Dvu above the cleaning water toward the upper Dvu in the vertical direction Dv and is sent to the second demister 82A. As a result, the absorbent liquid that was entrained in the decarbonated gas is removed, and the decarbonated gas becomes absorber exhaust gas. The absorber exhaust gas flows toward the upper Dvu in the vertical direction Dv and passes through the second demister 82A, whereby mist contained in the absorber exhaust gas is further removed. The absorber exhaust gas from which the mist has been removed is discharged to the outside of the second absorption tower body 42 through the absorber discharge line 12.

[0132] (Operation and Effect) In this absorption tower 2A, the carbon dioxide absorption section 50A has a plurality of absorption units 52A lined up in the vertical direction Dv within the first absorption tower body 41. The water washing section 60A has a plurality of recovery units 61A lined up in the vertical direction Dv within the second absorption tower body 42, which is disposed horizontally apart from the first absorption tower body 41. That is, the carbon dioxide absorption section 50A and the water washing section 60A are disposed side by side in the horizontal direction, not in the vertical direction Dv. In addition, the second absorption tower body 42 is disposed so that the position of its top does not protrude upward Dvu in the vertical direction Dv relative to the position of the top of the first absorption tower body 41. Therefore, the height of the absorption tower 2A as a whole can be reduced significantly compared to the absorption tower 2 of the first embodiment, while maintaining the efficiency of recovery of carbon dioxide from the gas and the efficiency of recovery of the absorption solution contained in the decarbonated gas after carbon dioxide recovery at levels equivalent to those of absorption towers of conventional heights.

[0133] Furthermore, the carbon dioxide absorption section 50A has a downward diffuser 53 located upstream of the multiple absorption units 52A (at an upstream position in the flow direction of the gas to be treated). The downward diffuser 53 ejects the gas to be treated into the stored absorption liquid. In particular, in this embodiment, the gas to be treated is ejected into the absorption liquid so as to form a froth flow. This allows the absorption liquid and the gas to be treated to come into contact more efficiently, further promoting the carbon dioxide absorption reaction by the absorption liquid. Therefore, a large amount of carbon dioxide can be recovered from the gas to be treated before it is supplied to the multiple absorption units 52A. This further improves the efficiency of carbon dioxide recovery from the gas to be treated.

[0134] Furthermore, partition plates 59 are disposed in the absorbent liquid storage section 55 and the cleaning water storage section 65. The partition plates 59 divide the absorbent liquid storage section 55 and the cleaning water storage section 65 into multiple regions aligned horizontally. Therefore, the regions storing liquid in the absorbent liquid storage section 55 and the cleaning water storage section 65 are separated. As a result, even if unstable flow (swaying of the stored liquid) occurs in the storage section, which is expected when the flow rate distribution in the air diffuser pipe 532 is not uniform, causing the liquid surface to ripple, the amount of displacement of the liquid surface in the vertical direction Dv can be suppressed. Furthermore, the formation of communication holes 591 in the partition plates 59 allows the liquid stored in each region to move freely between the regions. This suppresses differences in the amount of liquid stored in the regions and the resulting differences in liquid level. As a result, the liquid level of the liquid stored in the absorbent liquid storage section 55 and the cleaning water storage section 65 can be maintained at a constant position while suppressing displacement of the liquid surface in the vertical direction Dv.

[0135] In addition, not only a second cooling section 90B for cooling the wash water present in the second recovery unit 612A but also a first cooling section 90A for cooling the absorption liquid present in the fourth absorption unit 524A are provided. The absorption liquid can be effectively cooled by being cooled by the fourth absorption unit 524A, which is located at the uppermost position Dvu in the vertical direction Dv among the multiple absorption units 52A. The first cooling section 90A is provided in the first absorption tower body 41, and the second cooling section 90B is provided in the second absorption tower body 42. A rise in the temperature of the absorption liquid increases the vapor pressure of the amine in the absorption liquid, resulting in an increase in the absorption liquid components in the decarbonated gas. Cooling in the fourth absorption unit 524A suppresses the temperature rise of the absorption liquid in the first absorption tower body 41 and improves absorption efficiency. Cooling in the second recovery unit 612A suppresses the absorption liquid components from the second absorption tower body 42. Cooling each tower body individually in this manner improves the absorption efficiency in the first absorption tower body 41 and suppresses the absorption liquid components in the second absorption tower body 42.

[0136] (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 within the scope that does not deviate from the gist of the present disclosure are also included.

[0137] The number of absorption units 52, 52A and recovery units 61, 61A to be arranged is not limited to the number described in the embodiments. For example, the number of absorption units 52, 52A may be two, four, or more, instead of three. Similarly, the number of recovery units 61, 61A may be three or more. That is, the absorption tower 2 of the first embodiment may have two or fewer absorption units 52, or four or more absorption units 52A, and the absorption tower 2A of the second embodiment may have three or fewer absorption units 52A, or five or more absorption units 52A. Furthermore, the absorption towers 2, 2A of the first and second embodiments may have one or three or more recovery units 61, 61A. Furthermore, the multiple absorption units 52, 52A and recovery units 61, 61A are not necessarily all of the same structure. The multiple absorption units 52, 52A and recovery units 61, 61A may have different structures as long as they can eject gas into the liquid.

[0138] Furthermore, the configurations of the target gas diffusion section 57 and the decarbonated gas diffusion section 67 are not limited to those of the above embodiment. That is, the target gas diffusion section 57 and the decarbonated gas diffusion section 67 are not limited to those having a structure including an exhaust hole 571, a direction change section 572, and an ejection hole 573. Furthermore, the target gas diffusion section 57 and the decarbonated gas diffusion section 67 are not limited to all having the same structure. The target gas diffusion section 57 and the decarbonated gas diffusion section 67 may have different structures and arrangements depending on the stage in which they are arranged. Furthermore, the structures of the exhaust hole 571, the direction change section 572, and the ejection hole 573 are not limited to those of the above embodiment.

[0139] Furthermore, the liquid level adjusting units 70, 70A are not limited to the arrangements shown in the first and second embodiments. The liquid level adjusting units 70, 70A may have different structures and arrangements depending on the stages on which they are arranged.

[0140] Furthermore, the cooling unit 90 is not limited to being disposed in the same manner as in the first and second embodiments. The cooling unit 90 may be disposed in another stage. Furthermore, the cooling unit 90 may be disposed for each of the plurality of liquid level adjusting units 70, 70A. Note that the first cooling unit 90A that cools the absorbing liquid disclosed in the second embodiment may be applied to the first embodiment.

[0141] The lower air diffuser 53 of the second embodiment may be arranged in place of the lower storage section 51 of the first embodiment. The lower storage section 51 of the first embodiment may be arranged in place of the lower air diffuser 53 of the second embodiment.

[0142] Furthermore, the partition plate 59 is not limited to a structure that divides the storage section into two regions as in this embodiment. The partition plate 59 may divide the storage section into two or more regions. In other words, a plurality of partition plates 59 may be arranged for one storage section. The partition plate 59 may be arranged in only some of the multiple stages of absorption units or recovery units. The partition plate 59 of the second embodiment may be arranged in the same manner as in the first embodiment.

[0143] <Additional Notes> The absorption towers 2, 2A and carbon dioxide recovery systems 1, 1A described in the respective embodiments can be understood, for example, as follows.

[0144] (1) The absorption tower 2, 2A according to the first aspect includes a carbon dioxide absorption section 50, 50A that brings a gas to be treated containing carbon dioxide into contact with an absorption liquid and causes the absorption liquid to absorb the carbon dioxide, and a water washing section 60, 60A that brings the decarbonated gas that has come into contact with the absorption liquid in the carbon dioxide absorption section 50, 50A into contact with wash water and recovers the absorption liquid components entrained in the decarbonated gas, and the carbon dioxide absorption section 50, 50A has an absorption unit 52, 52A, The absorption units 52, 52A absorb the carbon dioxide from the gas to be treated, the water washing sections 60, 60A have recovery units 61, 61A, and the recovery units 61, 61A recover the absorption liquid components entrained in the decarbonated gas, and at least a portion of the absorption units 52, 52A and the recovery units 61, 61A have a storage section that stores liquid, and an aeration section that sprays gas into the liquid stored in the storage section.

[0145] With this configuration, the gas to be treated is sprayed into the absorption liquid stored in the absorption units 52 and 52A. This allows the stored absorption liquid to come into contact with the gas to be treated efficiently. As a result, the carbon dioxide absorption reaction by the absorption liquid is promoted. This allows the efficiency of recovering carbon dioxide from the gas to be treated to be improved even if the height of the storage section in which the absorption liquid is stored and the height of the space Dvu above the absorption liquid are reduced in the absorption units 52 and 52A.

[0146] Furthermore, the decarbonated gas that has passed through the carbon dioxide absorption section 50, 50A is sprayed into the wash water stored in the recovery unit 61, 61A. This allows the stored wash water to come into efficient contact with the decarbonated gas. As a result, recovery of the absorbent component by the wash water is promoted. This makes it possible to improve the recovery efficiency of the absorbent component from the gas to be treated in the recovery unit 61, 61A, even if the height of the storage section in which the wash water is stored and the height of the space Dvu above the wash water are reduced.

[0147] As a result, the height of the absorption towers 2, 2A can be reduced while maintaining the efficiency of recovering carbon dioxide from the gas and the efficiency of recovering the absorbent components contained in the decarbonated gas after recovering the carbon dioxide.

[0148] (2) The absorption towers 2, 2A according to the second aspect are the absorption towers 2, 2A of (1), in which in the absorption units 52, 52A, the liquid is the absorption liquid and the gas is the gas to be treated, and in the recovery units 61, 61A, the liquid is the wash water and the gas is the decarbonated gas that has passed through the carbon dioxide absorption sections 50, 50A.

[0149] (3) The absorption tower 2, 2A according to a third aspect is the absorption tower 2, 2A of (1) or (2), wherein the carbon dioxide absorption section 50, 50A has a plurality of absorption units 52, 52A arranged side by side in the vertical direction Dv, and the plurality of absorption units 52, 52A sequentially absorb the carbon dioxide from the gas to be treated, and the water washing section 60, 60A has a plurality of recovery units 61, 61A arranged side by side in the vertical direction Dv, and the plurality of recovery units 61, 61A sequentially recover the absorption solution components entrained in the decarbonated gas.

[0150] (4) The absorption tower 2, 2A according to the fourth aspect is any one of the absorption towers 2, 2A of (1) to (3), in which the gas diffuser ejects the gas within the liquid in a direction including a component directed downward in the vertical direction Dv toward Dvd or in a horizontal direction.

[0151] According to this configuration, by ejecting the gas in the liquid in a direction including a component directed downward in the vertical direction Dvd or in the horizontal direction, the contact time between the liquid and the gas can be increased compared to when the gas is ejected upward in the vertical direction Dvu. In other words, the contact time between the ejected gas and the liquid is increased without raising the liquid level of the stored liquid. This further improves the efficiency of recovering carbon dioxide from the gas to be treated and the efficiency of recovering the absorbent components contained in the decarbonated gas. Therefore, the height of the absorption towers 2 and 2A can be further reduced.

[0152] (5) The absorption tower 2, 2A according to the fifth aspect is any one of the absorption towers 2, 2A of (1) to (4), and the aeration section has an exhaust hole 571 that exhausts the gas toward the upward direction Dvu in the vertical direction Dv, a direction change section 572 that covers the exhaust hole 571 from the upward direction Dvu in the vertical direction Dv and directs the flow direction of the gas toward the downward direction Dvd in the vertical direction Dv, and an ejection hole 573 that ejects the gas that has flowed through the direction change section 572 into the liquid.

[0153] With this configuration, gas is discharged through the discharge holes 571 toward the upper Dvu in the vertical direction Dv. Therefore, when the absorption units 52, 52A and the recovery units 61, 61A are stacked in the vertical direction Dv, gas can be easily supplied from an absorption unit 52, 52A or recovery unit 61, 61A located at the lower Dvd in the vertical direction Dv to another absorption unit 52, 52A or recovery unit 61, 61A located at the upper Dvu in the vertical direction Dv via the discharge holes 571. The direction changer 572 changes the flow direction of the gas supplied from the discharge holes 571 and then ejects it from the ejection holes 573. Therefore, a simple configuration allows gas supplied from the absorption unit 52, 52A or recovery unit 61, 61A at the lower Dvd to be ejected downward Dvd in the vertical direction Dv within the stored liquid.

[0154] (6) The absorption tower 2, 2A relating to the sixth aspect is an absorption tower 2, 2A of any one of (1) to (5), and further includes a gas-liquid separation line 71 that connects the liquid stored in the storage section with the space Dvu above the liquid in the storage section in the vertical direction Dv, and an overflow line 72 that is connected to the gas-liquid separation line 71 at the same position in the vertical direction Dv as the liquid level of the liquid stored in the storage section when the device is stopped, and that causes the liquid flowing through the gas-liquid separation line 71 to flow downward Dvd in the vertical direction Dv.

[0155] With this configuration, when the liquid is about to accumulate beyond the connection point between the gas-liquid separation line 71 and the overflow line 72, the accumulated liquid is sent from the overflow line 72 to the storage section of another absorption unit 52, 52A or recovery unit 61, 61A located Dvd below in the vertical direction Dv. Therefore, the liquid level of the liquid stored in the water storage section can be maintained without using a complex device.

[0156] (7) The absorption tower 2, 2A according to the seventh aspect is the absorption tower 2, 2A of (6), in which, in the vertical direction Dv, the opening position of the discharge hole 571 is higher than the connection position of the gas-liquid separation line 71 and the overflow line 72, and in the vertical direction Dv, the position at which the gas is ejected by the ejection hole 573 is lower than the connection position of the gas-liquid separation line 71 and the overflow line 72.

[0157] According to this configuration, in the vertical direction Dv, the opening position of the discharge hole 571 is higher than the connection position of the gas-liquid separation line 71 and the overflow line 72, and the position at which gas is ejected by the ejection hole 573 is lower. Since the opening position of the discharge hole 571 is higher than the connection position of the liquid separation line and the overflow line 72, the liquid level, which is the liquid surface level of the liquid when the absorber 2, 2A is not operating, is always higher than the opening position of the discharge hole 571. Therefore, it is possible to prevent an event from occurring in which gas is not ejected into the liquid when the absorber 2, 2A starts operating.

[0158] (8) The absorption tower 2, 2A relating to the eighth aspect is an absorption tower 2, 2A of any one of (1) to (7), wherein at least a portion of the absorption unit 52, 52A and the recovery unit 61, 61A further includes a partition plate 59 extending Dvu above the liquid level of the liquid stored in the storage section in the vertical direction Dv and dividing the storage section into a plurality of horizontally arranged regions, and the partition plate 59 has a communication hole 591 that opens into the liquid stored in the storage section.

[0159] With this configuration, the liquid storage area is divided into separate areas. As a result, even if the stored liquid sways (unstable flow) and the liquid surface ripples, the amount of displacement of the liquid surface in the vertical direction Dv can be suppressed. Furthermore, the formation of communication holes 591 in the partition plate 59 allows the liquid stored in each area to move freely between the areas. If there is a difference in the amount of liquid stored in the areas, a difference in reaction time between the absorption liquid and the gas to be treated will occur, resulting in an imbalance in carbon dioxide absorption performance, but this can be suppressed. As a result, the position of the liquid surface of the liquid stored in the storage area can be maintained at a constant position while also suppressing displacement of the liquid surface in the vertical direction Dv.

[0160] (9) The absorption tower 2, 2A according to a ninth aspect is the absorption tower 2, 2A according to any one of (1) to (8), further comprising a cooling unit 90 that cools the liquid.

[0161] According to this configuration, it is possible to suppress a rise in temperature by cooling the liquid using the cooling unit 90. This makes it possible to suppress a decrease in absorption efficiency and an increase in absorbent components in the absorption towers 2 and 2A, which are caused by a rise in the temperature of the absorbent.

[0162] (10) The absorption tower 2, 2A according to the tenth aspect is any one of the absorption towers 2, 2A of (1) to (9), in which the carbon dioxide absorption section 50, 50A is arranged below the absorption unit 52, 52A in the vertical direction Dv, stores the absorption liquid, and has a downward aeration section 53 that sprays the gas to be treated into the absorption liquid.

[0163] According to this configuration, carbon dioxide can be absorbed more efficiently by being sprayed into the absorption liquid stored in the first bottom storage section 531.

[0164] (11) The absorption tower 2, 2A according to the eleventh aspect is the absorption tower 2, 2A of any one of (1) to (10), in which the carbon dioxide absorption section 50, 50A and the water washing section 60, 60A are arranged side by side in the horizontal direction.

[0165] With this configuration, the overall height of the absorption towers 2, 2A can be significantly reduced while maintaining the efficiency of recovering carbon dioxide from the gas and the efficiency of recovering the absorption liquid contained in the decarbonated gas after recovering the carbon dioxide.

[0166] (12) A carbon dioxide capture system 1, 1A according to a twelfth aspect includes an absorption tower 2, 2A selected from any one of (1) to (11) 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 that contains the gas to be treated from which the carbon dioxide has been removed; and a regeneration tower 3 that strips the carbon dioxide from the absorption liquid discharged from the absorption tower 2, 2A and discharges the absorption liquid from which the carbon dioxide has stripped and a regeneration tower exhaust gas that contains the carbon dioxide.

[0167] (13) A method for absorbing carbon dioxide according to a thirteenth aspect includes a carbon dioxide absorption step of contacting a gas to be treated containing carbon dioxide with an absorption liquid and causing the absorption liquid to absorb the carbon dioxide, and a water washing step of contacting the decarbonated gas after contact with the absorption liquid in the carbon dioxide absorption step with wash water and recovering absorption liquid components entrained in the decarbonated gas, wherein at least a part of the carbon dioxide absorption step and the water washing step includes a step of injecting gas into the stored liquid to generate a froth flow, a step of sending a part of the stored liquid vertically downward and extracting the gas contained in the liquid and sending it vertically upward, and a step of sending the gas that has escaped from the liquid vertically upward.

[0168] According to this step, the froth flow causes intense turbulence at the gas-liquid interface, resulting in a state in which the gas and liquid are mixed together, and this can promote the transfer of carbon dioxide from the target gas to the absorbent, or the recovery of absorbent components from the decarbonated gas into the wash water. This makes it possible to efficiently recover carbon dioxide from the target gas and recover absorbent components contained in the decarbonated gas after carbon dioxide recovery, and can reduce the height of the absorption tower.

[0169] According to the present disclosure, it is possible to reduce the height of the absorption tower while maintaining the efficiency of recovering carbon dioxide from the gas and the efficiency of recovering the absorbing solution contained in the gas after recovering the carbon dioxide.

[0170] 1, 1A Carbon dioxide recovery system 2, 2A Absorption tower 11 Gas line to be treated 12 Absorption tower discharge line 3 Regeneration tower 31 Reboiler 13 Rich line 35 Rich pump 14 Lean line 14' Wash water discharge line 37 Lean pump 4 Absorbent heat exchanger 15 Regeneration tower discharge line 40 Absorption tower main body 50, 50A Carbon dioxide absorption section 51 Lower storage section 52, 52A Absorption unit 521, 521A First absorption unit 522, 522A Second absorption unit 523, 523A Third absorption unit 55 Absorption liquid storage section 551 Bottom plate section 57 Gas diffuser to be treated 571 Discharge hole 572 Direction change section 573 Jet hole 581 Collision plate 582 Flow path forming plate 60, 60A Water washing section 61, 61A Recovery unit 611, 611A First recovery unit 612, 612A Second recovery unit 65 Wash water storage section 67 Decarbonated gas diffuser section 69 Wash water supply line 70, 70A Liquid level adjustment section 71 Gas-liquid separation line 72 Overflow line 74, 74A First absorbent adjustment section 75, 75A Second absorbent adjustment section 76, 76A Third absorbent adjustment section 77A Fourth absorbent adjustment section 78, 78A First wash water adjustment section 79, 79A Second wash water adjustment section 80 Demister 81, 81A First demister 82, 82A Second demister 90 Cooling section 91 Cooling line 92 Cooling pump 93 Wash water cooler 94, 94A, 94B Cooling section withdrawal line 41 First absorption tower body 42 Second absorption tower main body 43 Main body connecting line 524A Fourth absorption unit 53 Lower aeration section 531 First bottom storage section 532 Aeration pipe 533 Lower gas-liquid separation line 534 Lower liquid level adjustment tank 59 Partition plate 591 Communication hole 63 Second bottom storage section 90A First cooling section 91A First cooling line 92A First cooling pump 93A First cooler 90B Second cooling section 91B Second cooling line 92B Second cooling pump 93B Second cooler Dv Vertical direction Dvu Upward Dvd Downward

Claims

1. An absorption tower comprising: a carbon dioxide absorption section that brings a gas to be treated containing carbon dioxide into an absorbing liquid and causes the absorbing liquid to absorb the carbon dioxide; and a water washing section that brings a decarbonated gas after contact with the absorbing liquid in the carbon dioxide absorption section into contact with wash water and recovers absorbing liquid components entrained in the decarbonated gas, wherein the carbon dioxide absorption section has an absorption unit that absorbs the carbon dioxide from the gas to be treated; the water washing section has a recovery unit that recovers the absorbing liquid components entrained in the decarbonated gas; and at least a portion of the absorption unit and the recovery unit have a storage section that stores liquid, and an aeration section that sprays gas into the liquid stored in the storage section.

2. An absorption tower as described in claim 1, wherein in the absorption unit, the liquid is the absorption liquid and the gas is the gas to be treated, and in the recovery unit, the liquid is the wash water and the gas is the decarbonated gas that has passed through the carbon dioxide absorption section.

3. An absorption tower as described in claim 1 or 2, wherein the carbon dioxide absorption section has a plurality of absorption units arranged in a vertical direction, and the plurality of absorption units sequentially absorb the carbon dioxide from the gas to be treated, and the water washing section has a plurality of recovery units arranged in a vertical direction, and the plurality of recovery units sequentially recover the absorption liquid components entrained in the decarbonated gas.

4. An absorption tower as described in claim 1 or 2, wherein the gas diffuser section ejects the gas within the liquid in a direction including a vertically downward component or in a horizontal direction.

5. An absorption tower as described in claim 1 or 2, wherein the aeration section has an exhaust hole that exhausts the gas vertically upward, a direction change section that covers the exhaust hole from above in the vertical direction and directs the flow direction of the gas vertically downward, and an ejection hole that ejects the gas that has flowed through the direction change section into the liquid.

6. An absorption tower as described in claim 5, further comprising a gas-liquid separation line connecting the liquid stored in the storage section with a space vertically above the liquid in the storage section, and an overflow line connected to the gas-liquid separation line at a position in the vertical direction that is the same as the liquid level of the liquid stored in the storage section when the device is stopped, and which causes the liquid flowing through the gas-liquid separation line to flow downward in the vertical direction.

7. An absorption tower as described in claim 6, wherein, in the vertical direction, the opening position of the discharge hole is higher than the connection position of the gas-liquid separation line and the overflow line, and, in the vertical direction, the position at which the gas is ejected by the ejection hole is lower than the connection position of the gas-liquid separation line and the overflow line.

8. An absorption tower as described in claim 1 or 2, wherein at least a portion of the absorption unit and the recovery unit further include a partition plate extending vertically above the liquid level of the liquid stored in the storage section and dividing the storage section into a plurality of horizontally aligned regions, and the partition plate has a communicating hole that opens into the liquid stored in the storage section.

9. The absorption tower according to claim 1 or 2, further comprising a cooling section for cooling the liquid.

10. An absorption tower as described in claim 1 or 2, wherein the carbon dioxide absorption section is arranged vertically below the absorption unit, stores the absorption liquid, and has a downward aeration section that sprays the gas to be treated into the absorption liquid.

11. An absorption tower according to claim 1 or 2, wherein the carbon dioxide absorption section and the water washing section are arranged side by side in the horizontal direction.

12. A carbon dioxide recovery system comprising: an absorption tower as described in claim 1 or 2, which 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; and 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.

13. A method for absorbing carbon dioxide, comprising: a carbon dioxide absorption step of contacting a gas to be treated containing carbon dioxide with an absorbing liquid and causing the absorbing liquid to absorb the carbon dioxide; and a water washing step of contacting the decarbonated gas after contact with the absorbing liquid in the carbon dioxide absorption step with wash water and recovering absorption liquid components entrained in the decarbonated gas, wherein at least a part of the carbon dioxide absorption step and the water washing step include: a step of ejecting gas into the stored liquid so as to generate a froth flow; a step of sending a part of the stored liquid vertically downward, while extracting the gas contained in the liquid and sending it vertically upward; and a step of sending the gas that has escaped from the liquid vertically upward.

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