Carbon dioxide recovery device

Abstract

To provide a carbon dioxide recovery device which can enhance absorption efficiency of carbon dioxide at start of operation.SOLUTION: A carbon dioxide recovery device 10a includes a control device 22 which is configured to execute carbon dioxide absorption operation of controlling a second solution pump and an intermediate solution pump, thereby supplying object gas to carbon dioxide absorption chambers at each stage, thereby absorbing carbon dioxide contained in the object gas supplied from an object gas source to carbon dioxide absorption solution, wherein the control device 22 executes solution penetration operation of immersing gas-liquid contact parts at each of the stages in carbon dioxide absorption solution, before the start of the carbon dioxide absorption operation, and thereby penetrating the carbon dioxide absorption solution into the gas-liquid contact parts at each of the stages.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] The carbon dioxide recovery device disclosed in Patent Document 1 includes a substantially cylindrical gas-liquid contact part (described as a rotating drum in Patent Document 1) configured to allow fluid to pass therethrough in the radial direction, and a nozzle configured to be able to eject a carbon dioxide absorption solution toward the inner peripheral surface of the gas-liquid contact part. And this carbon dioxide recovery device is configured such that the carbon dioxide absorption solution jetted from the nozzle toward the inner peripheral surface of the gas-liquid contact part moves from the inner peripheral side to the outer peripheral side of the gas-liquid contact part by the centrifugal force of the rotation of the gas-liquid contact part. For this reason, when gas (exhaust gas of an engine in Patent Document 1) flows from the outer side to the inner side in the radial direction of the gas-liquid contact part, the gas and the carbon dioxide absorption solution countercurrently contact in the gas-liquid contact part, and the carbon dioxide contained in the gas is absorbed by the carbon dioxide absorption solution.

[0003] By the way, in such a carbon dioxide recovery device, the carbon dioxide absorption efficiency (the ratio indicating the amount of carbon dioxide absorbed by the carbon dioxide absorption solution with respect to the amount of carbon dioxide contained in the inflowing gas) is affected by the gas-liquid contact area between the gas and carbon dioxide in the gas-liquid contact part. For this reason, in order to increase the carbon dioxide absorption efficiency, it is required to be maintained in a state where the carbon dioxide absorption solution is held in the gas-liquid contact part (specifically, a state where a film of the carbon dioxide absorption solution is formed over a wide range of the surface of the gas-liquid contact part). However, at the start of operation of the carbon dioxide recovery device, the supply of the carbon dioxide absorption solution to the gas-liquid contact part is started, and until a film of the carbon dioxide absorption solution is formed over a wide range of the surface of the gas-liquid contact part, the carbon dioxide absorption efficiency becomes low. Note that Patent Document 1 does not disclose a configuration for holding the carbon dioxide absorption solution in the gas-liquid contact part (rotating drum) (in other words, a configuration for forming a film of the carbon dioxide absorption solution on the surface of the gas-liquid contact part).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] (Problems to be Solved by the Invention) In view of the above circumstances, one of the objects of the present invention is to provide a carbon dioxide recovery apparatus capable of starting an operation of absorbing carbon dioxide from a gas in a state where a carbon dioxide absorption solution is held in a gas-liquid contact part (specifically, a state where a film of the carbon dioxide absorption solution is formed over a wide range of the surface of the gas-liquid contact part).

[0006] (Means for Solving the Problems) To achieve the above object, a carbon dioxide recovery apparatus according to the present invention is a carbon dioxide recovery apparatus configured to recover carbon dioxide from a gas by absorbing carbon dioxide contained in the gas generated from a gas source into a carbon dioxide absorption solution, a carbon dioxide absorption tower provided with a carbon dioxide absorption chamber therein, a rotating body rotatably disposed inside the carbon dioxide absorption chamber and provided with a gas-liquid contact part configured to allow the gas to pass therethrough and the carbon dioxide absorption solution to penetrate therethrough, a carbon dioxide absorption solution supply unit configured to supply the carbon dioxide absorption solution to the carbon dioxide absorption chamber, a control device configured to execute a carbon dioxide absorption operation of absorbing carbon dioxide contained in the gas supplied from the gas source into the carbon dioxide absorption solution by controlling the carbon dioxide absorption solution supply unit to supply the solution to the carbon dioxide absorption chamber, and includes before starting the carbon dioxide absorption operation, the control device executes a solution penetration operation of causing the carbon dioxide absorption solution to penetrate into the gas-liquid contact part by immersing the gas-liquid contact part in the carbon dioxide absorption solution.

[0007] Before starting the carbon dioxide absorption operation of absorbing carbon dioxide from the target gas, the carbon dioxide recovery device according to the present invention preliminarily permeates a carbon dioxide absorption solution into the gas-liquid contact part. According to such a configuration, it is possible to prevent or suppress a decrease in the absorption efficiency of carbon dioxide immediately after the start of the carbon dioxide absorption operation.

Brief Description of the Drawings

[0008]

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DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described. In the following description, the carbon dioxide recovery apparatus is abbreviated as "recovery apparatus", the carbon dioxide absorption tower is abbreviated as "absorption tower", the carbon dioxide dissipation tower (sometimes referred to as "carbon dioxide regeneration tower") is abbreviated as "dissipation tower", and the carbon dioxide absorption solution may be abbreviated as "solution". Further, the gas that is the target of carbon dioxide recovery by the recovery apparatus (that is, the gas containing carbon dioxide) may be referred to as "target gas". Further, in the following description, the "flow rate" of the target gas, carbon dioxide, and solution means the flow rate per unit time unless otherwise specified.

[0010] The target gas source 90 is applied to a device or facility that generates a gas containing carbon dioxide. For example, as the target gas source 90, a metal melting furnace and a carburizing furnace that utilize the combustion heat of fossil fuels (i.e., use fossil fuels as fuel) can be applied. In this case, the combustion exhaust gas of fossil fuels is the target gas. Also, as the solution, various conventionally known carbon dioxide absorption solutions such as an aqueous amine solution are applied.

[0011] <First Embodiment> (Configuration of the Recovery Device) FIG. 1 is a diagram showing a schematic configuration of a recovery device 10a according to the first embodiment. The recovery device 10a includes an absorption tower 11a, a stripping tower 12, a target gas introduction path 13, a target gas pump 14, a target gas inlet valve 15, a target gas discharge path 16, a first solution path 17, a solution outlet valve 18, a first solution pump 19, a second solution path 20, a second solution pump 21, and a control device 22. Further, the recovery device 10a includes a drain tank 23, a first drain path 24, a second drain path 25, a drain outlet valve 26, a solution heat exchanger 27, a solution cooler 28, a reboiler 29, and a carbon dioxide recovery path 30.

[0012] The absorption tower 11a is configured such that the solution absorbs carbon dioxide (in other words, carbon dioxide is removed from the target gas) by bringing the solution into gas-liquid contact with the target gas. Inside the absorption tower 11a, an upper target gas chamber 41, an upper absorption chamber 42, an intermediate solution chamber 43, an intermediate target gas chamber 44, and a lower absorption chamber 45 are provided in order from the top. Also, inside the absorption tower 11a, a rotating body 46a that rotates by the driving force of a rotating body driving force source 50 is accommodated. Each stage of the absorption chambers 42, 45 is an example of the carbon dioxide absorption chamber of the present invention.

[0013] The upper absorption chamber 42 is configured such that the solution flows in from the second solution path 20 through the rotating body 46a. The upper absorption chamber 42 and the intermediate solution chamber 43 are communicatively connected through the intermediate solution path 48 so that the solution can flow through. An intermediate solution pump 49 is provided on the intermediate solution path 48. The intermediate solution pump 49 is configured to feed the solution accumulated in the upper absorption chamber 42 to the intermediate solution chamber 43 when it operates. The intermediate solution chamber 43 and the lower absorption chamber 45 are communicatively connected through the rotating body 46a so that the solution can flow through. Therefore, the solution fed to the absorption tower 11a through the second solution path 20, which will be described later, passes through the upper absorption chamber 42, the intermediate solution path 48, the intermediate solution chamber 43, and the lower absorption chamber 45 in this order.

[0014] The lower absorption chamber 45 and the intermediate target gas chamber 44 are communicatively connected through the rotating body 46a so that the target gas can flow through. The intermediate target gas chamber 44 and the upper absorption chamber 42 are communicatively connected through the intermediate target gas path 47 so that the target gas can flow through. The upper absorption chamber 42 and the upper target gas chamber 41 are communicatively connected through the rotating body 46a so that the target gas can flow through. Therefore, the target gas supplied through the target gas introduction path 13 passes through the lower absorption chamber 45, the intermediate target gas chamber 44, the intermediate target gas path 47, the upper absorption chamber 42, and the upper target gas chamber 41 in this order.

[0015] The rotating body 46a includes an upper gas-liquid contact part 63 and an upper gas-liquid separation part 62 accommodated in the upper absorption chamber 42, and a lower gas-liquid contact part 66 and a lower gas-liquid separation part 65 accommodated in the lower absorption chamber 45. The gas-liquid contact parts 63, 66 of each stage are parts for promoting the gas-liquid contact between the solution and the target gas. When the solution and the target gas come into gas-liquid contact in the gas-liquid contact parts 63, 66 of each stage, the carbon dioxide contained in the target gas is absorbed by the solution. The detailed configuration of the rotating body 46a will be described later.

[0016] In the upper absorption chamber 42, an upper limit liquid level sensor 421 and a lower limit liquid level sensor 422 for detecting the liquid level height of the solution in the upper absorption chamber 42 are provided. In the lower absorption chamber 45, a lower limit liquid level sensor 451 and a lower limit liquid level sensor 452 for detecting the liquid level height of the solution in the lower absorption chamber 45 are provided. In the present embodiment, the upper limit liquid level sensor 421 and the lower limit liquid level sensor 451 of the lower stage are configured to be in the ON state when the liquid level height is equal to or higher than a preset upper limit height, and to be in the OFF state when it is less than the upper limit height. The upper limit liquid level sensor 422 and the lower limit liquid level sensor 452 of the upper stage are configured to be in the ON state when the liquid level height is equal to or higher than a preset lower limit height, and to be in the OFF state when it is less than the lower limit height. The upper limit height of the liquid level in each absorption chamber 42, 45 of each stage is the height at which the entire gas-liquid contact portions 63, 66 of each stage are immersed in the solution. The lower limit height of the liquid level in the upper absorption chamber 42 is the height at which the gas-liquid contact portion 63 of the upper stage is not immersed in the solution and the target gas does not flow into the intermediate solution path 48 (the intermediate solution path 48 can be liquid-sealed). The lower limit height of the liquid level in the lower absorption chamber 45 is the height at which the gas-liquid contact portion 66 of the lower stage is not immersed in the solution and the target gas does not flow into the first solution path 17 (the first solution path 17 can be liquid-sealed).

[0017] The stripping tower 12 is configured to dissipate carbon dioxide from the solution by heating the inflowing solution. Inside the stripping tower 12, an upper packing material 121 and a lower packing material 122 are arranged. Both the upper packing material 121 and the lower packing material 122 are members through which the solution can penetrate and gases (vapor and carbon dioxide) can pass. For example, porous metals or mesh-like members with a large specific surface area are applicable. The lower packing material 122 is a member for promoting gas-liquid contact between the solution and the vapor generated by heating the solution. The upper packing material 121 is arranged near the top of the stripping tower 12, and the lower packing material 122 is arranged below it. At the upper part of the stripping tower 12, between the upper packing material 121 and the lower packing material 122, the other end of the first solution path 17 is connected. At the bottom (or near it) of the stripping tower 12, below the lower packing material 122, the other end of the second solution path 20 is connected. Note that the configuration of the stripping tower 12 is not particularly limited, and a conventionally known configuration can be applied.

[0018] The reboiler 29 is configured to generate vapor at a predetermined temperature (specifically, a temperature at which the solution fed to the stripping tower 12 can be heated to a temperature at which a reaction for dissipating carbon dioxide occurs) by heating the solution accumulated inside (at the bottom) of the stripping tower 12. The reboiler 29 is connected to the bottom of the stripping tower 12 via a first reboiler path 291 and a second reboiler path 292. Then, the reboiler 29 heats the solution flowing in through the first reboiler path 291 to generate vapor. The vapor generated in the reboiler 29 flows into the inside of the stripping tower 12 via the second reboiler path 292.

[0019] The target gas introduction path 13 is a path for feeding the target gas generated in the target gas source 90 to the absorption tower 11a. One end of the target gas introduction path 13 is connected to the absorption tower 11a, and the other end is connected to the target gas source 90. The target gas pump 14 is provided on the target gas introduction path 13. The target gas pump 14 is configured to feed (pressure-feed) the target gas on the other end side of the target gas introduction path 13 (the target gas generated in the target gas source 90) to one end side (the absorption tower 11a) of the target gas introduction path 13 when it operates. A known electric air supply pump can be applied to the target gas pump 14.

[0020] The target gas inlet valve 15 is provided between the target gas pump 14 and the absorption tower 11a on the target gas introduction path 13. The target gas inlet valve 15 is configured to prevent the backflow of the solution from the lower absorption chamber 45 to the side of the target gas pump 14 when it is closed. For example, an electromagnetic valve can be applied to the target gas inlet valve 15. Note that a torii piping portion 131 is provided between the target gas pump 14 and the target gas inlet valve 15 of the target gas introduction path 13. The torii piping portion 131 includes a portion arranged at least higher than the upper limit height of the solution in the upper absorption chamber 42.

[0021] The target gas discharge path 16 is a path for discharging the target gas (sometimes referred to as off-gas) after carbon dioxide is absorbed in the absorption tower 11a to the outside of the absorption tower 11a. One end of the target gas discharge path 16 is connected to the upper end portion of the absorption tower 11a, and the other end is, for example, released to the atmosphere.

[0022] The first solution path 17 is a path for feeding the solution from the absorption tower 11a to the stripping tower 12. One end of the first solution path 17 is connected to the absorption tower 11a, and the other end is connected to the stripping tower 12. The solution outlet valve 18, the first solution pump 19, and the solution heat exchanger 27 are arranged on the first solution path 17. The solution outlet valve 18 is configured to be switchable between a closed state and an open state of the first solution path 17. For the solution outlet valve 18, for example, a known solenoid valve is applied. The first solution pump 19 is provided on the side closer to the stripping tower 12 than the solution outlet valve 18. The first solution pump 19 is configured to feed the solution from the absorption tower 11a toward the stripping tower 12 by operating. The configuration of the first solution pump 19 is not particularly limited, and various conventionally known electric liquid feeding pumps can be applied.

[0023] In addition, a solution heat exchanger 27 is provided on the first solution path 17. The solution heat exchanger 27 is configured to perform heat exchange between the solution flowing through the first solution path 17 and the solution flowing through the second solution path 20. By performing heat exchange between the solution flowing through the first solution path 17 and the solution flowing through the second solution path 20 in the solution heat exchanger 27, the solution flowing through the first solution path 17 is heated, and the solution flowing through the second solution path 20 is cooled. Note that the configuration of the solution heat exchanger 27 is not limited, and various conventionally known heat exchangers can be applied.

[0024] The drain tank 23 is configured to be able to store a solution. The drain tank 23 is connected between the torii pipe portion 131 of the target gas introduction path 13 and the target gas inlet valve 15 via the first drain path 24, and is also connected between the solution outlet valve 18 of the first solution path 17 and the first solution pump 19 via the second drain path 25. A drain outlet valve 26 is provided in the second drain path 25. When a solution is accumulated between the target gas inlet valve 15 of the target gas introduction path 13 and the absorption tower 11a, if the target gas inlet valve 15 is opened, the accumulated solution flows into the drain tank 23 through the first drain path 24. Further, when the first solution pump 19 operates with the drain outlet valve 26 open, the solution accumulated in the drain tank 23 is discharged from the drain tank 23 through the second drain path 25. Further, a drain tank liquid level sensor 231 is provided in the drain tank 23. The drain tank liquid level sensor 231 is configured to be able to detect whether the liquid level height of the solution accumulated in the drain tank 23 is equal to or greater than a predetermined value or less than the predetermined value. This predetermined value is not particularly limited, but for example, a liquid level height that can be regarded as having substantially no solution accumulated in the drain tank 23 is applied.

[0025] At the top (or in the vicinity thereof) of the vent tower 12 and above the upper packing material 121, one end of the carbon dioxide recovery path 30 is connected. On the carbon dioxide recovery path 30, a demister 301, a mixed gas cooler 302, and a gas-liquid separator 303 are arranged in order from the side closer to the vent tower 12. The demister 301 is configured to remove the mist of the solution vapor from the mixed gas of the solution vapor and carbon dioxide and return the condensed water generated by the removed mist to the vent tower 12. The mixed gas cooler 302 is configured to liquefy the solution vapor by cooling the mixed gas of the solution vapor and carbon dioxide. The gas-liquid separator 303 is configured to separate the solution and carbon dioxide generated by the liquefaction of the vapor. According to such a configuration, gaseous carbon dioxide can be separated from the mixed gas of the solution vapor and carbon dioxide flowing into the carbon dioxide recovery path 30. The separated carbon dioxide is discharged (recovered) outside the recovery device 10a. The gas-liquid separator 303 and the vent tower 12 are connected by a solution reflux path 304. This solution reflux path 304 is configured such that the solution separated from carbon dioxide in the gas-liquid separator 303 returns to the vent tower 12.

[0026] The second solution path 20 is a path for feeding the solution from the vent tower 12 to the absorption tower 11a. One end of the second solution path 20 is connected to the absorption tower 11a, and the other end of the second solution path 20 is connected to the bottom of the vent tower 12. The second solution pump 21, the solution heat exchanger 27 described above, and the solution cooler 28 are provided on the second solution path 20. The second solution pump 21 is an example of the carbon dioxide absorption solution supply section of the present invention. By operating, the second solution pump 21 is configured to feed the solution accumulated inside the vent tower 12 to the absorption tower 11a through the second solution path 20. A known electric liquid delivery pump can be applied to the second solution pump 21. The solution cooler 28 is configured to adjust the temperature (cool) of the solution fed to the absorption tower 11a to the temperature at which the reaction of absorbing carbon dioxide occurs. Various known coolers can be applied to the solution cooler 28.

[0027] The control device 22 is connected to the target gas pump 14, the first solution pump 19, the second solution pump 21, the reboiler 29, the intermediate solution pump 49 (described later), the rotating body drive source 50, the target gas inlet valve 15, the solution outlet valve 18, and the drain outlet valve 26, and can control these. Further, the control device 22 is connected to the upper upper liquid level sensor 421, the upper lower liquid level sensor 422, the lower upper liquid level sensor 451, the lower lower liquid level sensor 452, and the drain tank liquid level sensor 231, and can acquire the states (ON state or OFF state) of these sensors. The control device 22 is a device including a computer equipped with a CPU, a RAM, a ROM, and an I / F. A computer program for controlling the recovery device 10a including the above devices is stored in advance in the ROM. Then, the CPU reads out the computer program stored in the ROM, expands it in the RAM (using the RAM as a work area), and executes it. Thereby, each part of the recovery device 10a is controlled.

[0028] (Configuration of the absorption tower and the rotating body) Next, the configuration and operation of the absorption tower 11a will be described. FIG. 2 is a cross-sectional view showing the configuration of the absorption tower 11a. In FIG. 2, the upper side of the absorption tower 11a is indicated by an arrow Up, and the lower side is indicated by an arrow Dw. As shown in FIG. 2, inside the absorption tower 11a, an upper target gas chamber 41, an upper absorption chamber 42, an intermediate solution chamber 43, an intermediate target gas chamber 44, and a lower absorption chamber 45 are provided in order from the upper side. Further, a rotating body 46a is rotatably disposed inside the absorption tower 11a. The rotating body 46a rotates by the driving force of a rotating body drive source 50 disposed outside the absorption tower 11a (the lower side in FIG. 2). The rotating body drive source 50 is controlled by the control device 22. The rotating body drive source 50 only needs to be able to output rotational power, and the specific configuration is not particularly limited. Various known motors can be applied to the rotating body drive source 50.

[0029] Each absorption chamber 42, 45 of each stage is a space through which the target gas and the solution can pass and in which the solution can be stored. One end of the target gas introduction path 13 is connected to the lower absorption chamber 45, and it is configured such that the target gas fed from the target gas source 90 through the target gas introduction path 13 flows in. Also, one end of the first solution path 17 is connected to the lower absorption chamber 45, and the solution accumulated at the bottom of the lower absorption chamber 45 is configured to be fed to the stripping tower 12 through the first solution path 17. And inside each absorption chamber 42, 45 of each stage, the gas-liquid contact parts 63, 66 of each stage provided on the rotating body 46a and the gas-liquid separation parts 62, 65 of each stage are rotatably arranged.

[0030] The intermediate solution chamber 43 is a space provided adjacent to the lower side of the upper absorption chamber 42 and is configured to be able to store the solution. The upper absorption chamber 42 and the intermediate solution chamber 43 are connected by an intermediate solution path 48. An intermediate solution pump 49 is provided on the intermediate solution path 48. The intermediate solution pump 49 is an example of the carbon dioxide absorption solution supply part of the present invention. The solution accumulated at the lower part of the upper absorption chamber 42 is fed to the intermediate solution chamber 43 through the intermediate solution path 48 by the operation of the intermediate solution pump 49. The intermediate solution pump 49 is controlled by the control device 22. Note that the configuration of the intermediate solution pump 49 is not particularly limited, and various known electric liquid transfer pumps are applicable.

[0031] The intermediate target gas chamber 44 is provided so as to be adjacent to the upper side of the lower absorption chamber 45 (in other words, between the lower absorption chamber 45 and the intermediate solution chamber 43). The lower absorption chamber 45 and the intermediate target gas chamber 44 communicate with each other such that the target gas can flow through the intermediate shaft part 64 (described later) of the rotating body 46a. Also, the intermediate target gas chamber 44 and the upper absorption chamber 42 communicate with each other such that the target gas can flow through the intermediate target gas path 47. For this reason, the target gas that has flowed into the intermediate target gas chamber 44 from the lower absorption chamber 45 through the intermediate shaft part 64 of the rotating body 46a passes through the intermediate target gas chamber 44 and flows into the upper absorption chamber 42 through the intermediate target gas path 47.

[0032] The upper target gas chamber 41 is provided so as to be adjacent to the upper side of the upper absorption chamber 42. One end of the target gas discharge path 16 is connected to the upper target gas chamber 41. Further, the upper target gas chamber 41 communicates with the upper absorption chamber 42 in the upper stage so that the target gas can flow through an upper shaft portion 61 (described later) provided on the rotating body 46a (described later). For this reason, the target gas flowing from the upper absorption chamber 42 in the upper stage into the upper target gas chamber 41 through the upper shaft portion 61 of the rotating body 46a passes through the inside of the upper target gas chamber 41 and flows out from the upper target gas chamber 41 (that is, from the absorption tower 11a) through the target gas discharge path 16.

[0033] In this way, the upper absorption chamber 42 in the upper stage and the lower absorption chamber 45 in the lower stage are connected in series via the intermediate target gas chamber 44 and the intermediate target gas path 47 so that the target gas fed from the outside passes in a predetermined one direction (specifically, the direction from the lower absorption chamber 45 in the lower stage toward the upper absorption chamber 42 in the upper stage). Further, the upper absorption chamber 42 in the upper stage and the lower absorption chamber 45 in the lower stage are connected in series via the intermediate solution chamber 43 and the intermediate solution path 48 so that the solution fed from the outside passes in the direction opposite to the predetermined one direction (specifically, the direction from the upper absorption chamber 42 in the upper stage toward the lower absorption chamber 45 in the lower stage).

[0034] The rotating body 46a includes, in order from the upper side, an upper shaft portion 61, an upper gas-liquid separation portion 62, an upper gas-liquid contact portion 63, an intermediate shaft portion 64, a lower gas-liquid separation portion 65, a lower gas-liquid contact portion 66, and a lower shaft portion 67. The respective portions of the rotating body 46a are coaxially arranged and rotate integrally.

[0035] The gas-liquid contact parts 63 and 66 of each stage are parts for promoting the absorption of carbon dioxide by the solution. It can also be said that the gas-liquid contact parts 63 and 66 of each stage are parts for increasing the contact area between the solution and the target gas. The gas-liquid contact parts 63 and 66 of each stage are configured such that the solution can penetrate and diffuse inside, and the target gas can flow through the inside. Specifically, the gas-liquid contact parts 63 and 66 of each stage include a container substantially cylindrical in the vertical view and a packing material filled inside the container. The container is formed of a member through which the solution and the target gas can flow. For example, the container is formed of a perforated metal (a metal plate with a large number of through holes). As the packing material, a member having a predetermined shape and a large specific surface area is applied. For example, as the packing material, a molded body formed by shaping a metal mesh into a predetermined shape (e.g., a round bar shape) is applied. And a plurality (a large number) of molded bodies (packing materials) are filled inside the container.

[0036] Note that the gas-liquid contact parts 63 and 66 of each stage are configured such that the solution can penetrate into the inside from the central part of the upper surface (the upper end part of the approximate rotation center), and the penetrated solution can flow down (can fall) from the outer peripheral surface (the outer surface in the radial direction of rotation) and the lower surface. Also, the gas-liquid contact parts 63 and 66 of each stage are configured such that the target gas can flow into the inside from the outer peripheral surface and the lower surface, and the flowed-in target gas can flow out upward from substantially the entire upper surface.

[0037] The gas-liquid separation parts 62 and 65 of each stage are parts configured to separate the solution from the target gas that has passed through the gas-liquid contact parts 63 and 66 of each stage (in other words, the target gas that is about to flow out from the absorption chambers 42 and 45 of each stage). The gas-liquid separation parts 62 and 65 of each stage are parts provided with a space through which the target gas can pass inside. The gas-liquid separation parts 62 and 65 of each stage are arranged above the gas-liquid contact parts 63 and 66 of each stage respectively.

[0038] The upper shaft portion 61 is a portion located at the upper end of the rotating body 46a. The upper shaft portion 61 has a double-tube structure. Specifically, the upper shaft portion 61 includes a substantially cylindrical outer shaft portion 611 and an inner shaft portion 612, and the inner shaft portion 612 is disposed substantially coaxially with the outer shaft portion 611 inside the outer shaft portion 611. The outer shaft portion 611 (more specifically, the space between the inner peripheral surface of the outer shaft portion 611 and the outer peripheral surface of the inner shaft portion 612) forms a path for the target gas (off-gas).

[0039] The upper end of the outer shaft portion 611 of the upper shaft portion 61 is located inside the upper target gas chamber 41, and the internal space of the outer shaft portion 611 (the space between the inner peripheral surface of the outer shaft portion 611 and the outer peripheral surface of the inner shaft portion 612) communicates with the internal space of the upper target gas chamber 41. The inner shaft portion 612 is a portion configured in a cylindrical shape with both the upper end and the lower end open, and forms a path for the solution. The upper end of the inner shaft portion 612 of the upper shaft portion 61 protrudes upward from the upper end of the outer shaft portion 611 of the upper shaft portion 61 and is located outside the upper target gas chamber 41. And one end of the second solution path 20 is connected to the upper end of the inner shaft portion 612 of the upper shaft portion 61.

[0040] The lower end portion of the upper shaft portion 61 and its vicinity are located inside the upper absorption chamber 42. And an upper gas-liquid contact portion 63 is disposed below the upper shaft portion 61. Further, an upper gas-liquid separation portion 62 is disposed above the upper gas-liquid contact portion 63 so as to surround the vicinity of the lower end portion of the upper shaft portion 61. Also, the upper shaft portion 61 is rotatably supported with respect to the absorption tower 11a via a bearing.

[0041] The upper gas-liquid contact part 63 is accommodated in the upper absorption chamber 42. Further, the upper gas-liquid contact part 63 is located below the lower end part of the upper shaft part 61. Therefore, the solution flowing out from the lower end part of the inner shaft part 612 of the upper shaft part 61 flows into the inside of the upper gas-liquid contact part 63 from the substantially center of rotation on the upper surface of the upper gas-liquid contact part 63 (the upper end part of the rotation center of the upper gas-liquid contact part 63). Then, the solution flowing into (penetrating) the upper gas-liquid contact part 63 diffuses and penetrates radially outward and downward from the substantially center of rotation of the upper surface due to the centrifugal force and gravity of the rotation of the upper gas-liquid contact part 63. For this reason, the solution diffuses over substantially the entire upper gas-liquid contact part 63. And a film (liquid film) of the solution is formed on the surface of the upper gas-liquid contact part 63 (specifically, the surface of the molded body (packing material) accommodated in the container).

[0042] The upper gas-liquid separation part 62 is arranged above the upper gas-liquid contact part 63. The lower end part of the upper shaft part 61 and the vicinity thereof enter into the inside of the upper gas-liquid separation part 62. And target gas passage holes 613 are provided in the part of the outer shaft part 611 of the upper shaft part 61 that enters into the internal space of the upper gas-liquid separation part 62. The target gas passage holes 613 are through holes (openings) that allow gas to pass through and communicate the inside of the outer shaft part 611 (that is, the space between the inner peripheral surface of the outer shaft part 611 and the outer peripheral surface of the inner shaft part 612) and the outside (that is, the internal space of the upper gas-liquid separation part 62).

[0043] The intermediate shaft part 64 is provided between the upper gas-liquid contact part 63 and the lower gas-liquid contact part 66. The intermediate shaft part 64 is a hollow shaft-shaped part. The upper part of the intermediate shaft part 64 is located inside the upper absorption chamber 42. And the upper end part of the intermediate shaft part 64 is joined to the lower part of the upper gas-liquid contact part 63. The lower end part of the intermediate shaft part 64 and the vicinity thereof are located inside the lower absorption chamber 45. And the lower gas-liquid contact part 66 is arranged below the intermediate shaft part 64, and the lower gas-liquid separation part 65 is arranged so as to surround the lower end part of the intermediate shaft part 64 and the vicinity thereof. The vertical intermediate part of the intermediate shaft part 64 is located inside the intermediate solution chamber 43 and the intermediate target gas chamber 44.

[0044] The intermediate shaft portion 64 has a cylindrical configuration with a space provided inside. The intermediate shaft portion 64 is rotatably supported with respect to the absorption tower 11a via a bearing. The lower portion of the intermediate shaft portion 64 (the portion located inside the intermediate target gas chamber 44 and inside the lower absorption chamber 45) has a double-tube structure. Specifically, the intermediate shaft portion 64 includes a substantially cylindrical outer shaft portion 641 and an inner shaft portion 642, and the inner shaft portion 642 is disposed substantially coaxially with the outer shaft portion 641 at the lower part inside the outer shaft portion 641. In the upper portion of the intermediate shaft portion 64 (the portion located inside the intermediate solution chamber 43), the outer shaft portion 641 forms a path for the solution. In the lower portion of the intermediate shaft portion 64 (the portion located inside the intermediate target gas chamber 44 and the lower absorption chamber 45), the outer shaft portion 641 (specifically, the space between the inner peripheral surface of the outer shaft portion 641 and the outer peripheral surface of the inner shaft portion 642) forms a path for the target gas, and the inner shaft portion 642 (specifically, the internal space of the inner shaft portion 642) forms a path for the solution. Note that the upper and lower ends of the inner shaft portion 642 are open, and the internal space of the outer shaft portion 641 in the upper portion of the intermediate shaft portion 64 communicates with the internal space of the inner shaft portion 642 in the lower portion. On the other hand, the upper and lower ends of the space between the outer shaft portion 641 and the inner shaft portion 642 are closed.

[0045] A lower gas-liquid contact portion 66 is disposed below the intermediate shaft portion 64, and a lower gas-liquid separation portion 65 is disposed so as to surround the vicinity of the lower end portion of the intermediate shaft portion 64. For this reason, the solution flowing out from the lower end portion of the inner shaft portion 642 of the intermediate shaft portion 64 is supplied to the lower gas-liquid contact portion 66 from substantially the rotation center of the upper surface of the lower gas-liquid contact portion 66 (the upper end portion of the substantially rotation center of the lower gas-liquid contact portion 66). The solution supplied to the lower gas-liquid contact portion 66 diffuses and penetrates radially outward and downward from the substantially rotation center of the upper surface by the centrifugal force and gravity of the rotation of the lower gas-liquid contact portion 66. For this reason, similar to the upper gas-liquid contact portion 63, the solution diffuses over substantially the entire lower gas-liquid contact portion 66. Then, a film (liquid film) of the solution is formed on the surface of the lower gas-liquid contact portion 66 (specifically, the surface of the molded body (packing material) accommodated in the container). The solution that has diffused and penetrated inside the lower gas-liquid contact portion 66 flows down (falls) from the outer peripheral surface and the lower surface of the lower gas-liquid contact portion 66. The solution that has flowed down from the outer peripheral surface and the lower surface of the lower gas-liquid contact portion 66 accumulates at the bottom of the lower absorption chamber 45.

[0046] A portion located inside the intermediate solution chamber 43 of the intermediate shaft portion 64 and above the upper end of the inner shaft portion 642 is provided with a solution passage hole 643. The solution passage hole 643 is a through hole that allows the solution to pass through and communicate between the outside and the inside of the outer shaft portion 641 of the intermediate shaft portion 64. Therefore, the solution accumulated in the intermediate solution chamber 43 flows into the inside thereof from the solution passage hole 643 provided in the intermediate shaft portion 64, further flows down through the inside of the inner shaft portion 642, and flows out from the lower end thereof. Also, an upstream-side target gas passage hole 644 is provided in a portion of the intermediate shaft portion 64 located inside the lower absorption chamber 45, and a downstream-side target gas passage hole 645 is provided in a portion of the intermediate shaft portion 64 located inside the intermediate target gas chamber 44. Both the upstream-side target gas passage hole 644 and the downstream-side target gas passage hole 645 are through holes that allow the target gas to pass through and communicate between the outside and the inside (the space between the outer shaft portion 641 and the inner shaft portion 642) of the outer shaft portion 641.

[0047] The lower shaft portion 67 is a substantially cylindrical or round bar-shaped portion. The lower end portion of the lower shaft portion 67 protrudes outside the absorption tower 11a and is connected to the rotating body driving force source 50 so that the rotational driving force is transmitted from the rotating body driving force source 50. Also, the lower shaft portion 67 is rotatably supported with respect to the absorption tower 11a via a bearing.

[0048] The flow of the target gas in the absorption tower 11a provided with the rotating body 46a having such a configuration is as follows. The target gas that has flowed into the inside of the lower absorption chamber 45 through the target gas introduction path 13 flows into the inside of the lower gas-liquid contact portion 66 from the outer peripheral surface and the lower surface of the lower gas-liquid contact portion 66 and passes through the inside of the lower gas-liquid contact portion 66. Then, the target gas flows out (upward) from the upper surface of the lower gas-liquid contact portion 66 to the outside (upper side) of the lower gas-liquid contact portion 66. When the target gas passes through the inside of the lower gas-liquid contact portion 66, carbon dioxide contained in the target gas is absorbed by the solution by contacting the solution that diffuses and penetrates inside the lower gas-liquid contact portion 66.

[0049] The target gas that has flowed out to the outside of the lower gas-liquid contact part 66 flows into the internal space of the lower gas-liquid separation part 65. The target gas that has flowed into the internal space of the lower gas-liquid separation part 65 passes through the internal space of the lower gas-liquid separation part 65 and flows into the inside of the outer shaft part 641 through the upstream-side target gas path hole 644 provided at the lower end part of the outer shaft part 641 of the intermediate shaft part 64. And while the target gas is passing through the internal space of the lower gas-liquid separation part 65, the solution contained in the target gas is removed.

[0050] The target gas that has flowed into the inside of the outer shaft part 641 of the intermediate shaft part 64 flows into the intermediate target gas chamber 44 through the downstream-side target gas path hole 645 of the outer shaft part 641 of the intermediate shaft part 64, and further flows into the upper absorption chamber 42 through the intermediate target gas path 47. And the target gas that has flowed into the inside of the upper absorption chamber 42 flows into the inside of the upper gas-liquid contact part 63 from the outer peripheral surface and the lower surface of the upper gas-liquid contact part 63, passes through the inside of the upper gas-liquid contact part 63, and flows into the inside of the upper gas-liquid separation part 62 from the upper surface of the upper gas-liquid contact part 63.

[0051] The target gas that has flowed into the inside of the upper gas-liquid separation part 62 passes through the inside of the upper gas-liquid separation part 62 and flows into the inside of the outer shaft part 611 through the target gas path hole 613 provided in the outer shaft part 611 of the upper shaft part 61. And while the target gas is passing through the internal space of the upper gas-liquid separation part 62, the solution contained in the target gas is removed. The target gas that has flowed into the inside of the outer shaft part 611 flows into the inside of the upper target gas chamber 41 from the upper end of the outer shaft part 611, and further flows out of the absorption tower 11a to the outside through the target gas discharge path 16 from the upper target gas chamber 41.

[0052] The solution that has flowed into the upper absorption chamber 42 passes through the upper gas-liquid contact part 63 and temporarily accumulates at the bottom of the upper absorption chamber 42, and then is fed to the intermediate solution chamber 43 by the operation of the intermediate solution pump 49, and further flows into the lower absorption chamber 45. The absorption liquid that has flowed into the lower absorption chamber 45 accumulates at the bottom of the lower absorption chamber 45.

[0053] Then, in the gas-liquid contact parts 63 and 66 of each stage disposed in the absorption chambers 42 and 45 of each stage, the solution and the target gas are in gas-liquid contact, whereby carbon dioxide contained in the target gas is absorbed by the solution. For this reason, the concentration of carbon dioxide contained in the target gas gradually decreases each time it passes through the lower absorption chamber 45 and the upper absorption chamber 42. On the other hand, while the solution flows through the upper absorption chamber 42 and the lower absorption chamber 45, the absorption rate of carbon dioxide in the solution gradually increases (the carbon dioxide loading value increases). That is, the solution changes from a carbon dioxide-lean state to a carbon dioxide-rich state. The target gas from which carbon dioxide has been removed is discharged to the outside of the absorption tower 11a from the upper absorption chamber 42 through the upper target gas chamber 41 and the target gas discharge path 16. The solution accumulated at the bottom of the lower absorption chamber 45 is fed toward the stripping tower 12 by the operation of the first solution pump 19 as described above.

[0054] Thus, the absorption tower 11a is configured such that the solution fed from the stripping tower 12 via the second solution path 20 passes in one direction through the upper absorption chamber 42, the intermediate target gas chamber 44, and the lower absorption chamber 45 in this order, and is discharged from the lower absorption chamber 45 to the outside of the absorption tower 11a (specifically, fed to the stripping tower 12). Further, the absorption tower 11a is configured such that the target gas fed from the target gas source 90 through the target gas introduction path 13 passes in the direction opposite to the one direction through the lower absorption chamber 45, the intermediate target gas chamber 44, the upper absorption chamber 42, and the upper target gas chamber 41 in this order, and is discharged from the upper target gas chamber 41 to the outside of the absorption tower 11a.

[0055] (Normal operation of the recovery device) Next, the normal operation of the recovery device 10a will be described. The normal operation is an operation of absorbing carbon dioxide contained in the target gas in the absorption tower 11a and stripping carbon dioxide from the solution that has absorbed carbon dioxide in the stripping tower 12. The control device 22 executes the normal operation while the target gas source 90 is operating. The operation of the absorption tower 11a in the normal operation is an example of the carbon dioxide absorption operation of the present invention.

[0056] During normal operation, the control device 22 opens the target gas inlet valve 15 and activates the target gas pump 14. The target gas generated at the target gas source 90 is fed (pumped) into the inside of the absorption chamber 45 at the lower stage of the absorption tower 11a by the operation of the target gas pump 14. The target gas flowing into the inside of the lower absorption chamber 45 sequentially passes through the lower absorption chamber 45 and the upper absorption chamber 42, and is discharged to the outside of the absorption tower 11a through the target gas discharge path 16.

[0057] Also during normal operation, the control device 22 opens the solution outlet valve 18 and activates the first solution pump 19, the second solution pump 21, and the intermediate solution pump 49. The solution temperature-controlled (cooled) to a temperature suitable for carbon dioxide absorption in the solution heat exchanger 27 and the solution cooler 28 is supplied to the upper absorption chamber 42 of the absorption tower 11a through the second solution path 20 by the operation of the second solution pump 21. The solution flowing into the inside of the upper absorption chamber 42 flows into the lower absorption chamber 45 by the operation of the intermediate solution pump 49 after passing through the upper absorption chamber 42, and accumulates at the bottom of the lower absorption chamber 45. Then, in the gas-liquid contact parts 63, 66 of each stage arranged in each absorption chamber 42, 45 of each stage, the target gas and the solution are in gas-liquid contact, and the carbon dioxide contained in the target gas is absorbed by the solution.

[0058] The solution accumulated at the bottom of the lower absorption chamber 45 is fed from the absorption tower 11a toward the stripping tower 12 by the operation of the first solution pump 19. Then, the solution flowing through the first solution path 17 is heated by exchanging heat with the solution flowing through the second solution path 20 in the solution heat exchanger 27, and then flows into the inside of the stripping tower 12. Note that the control device 22 closes the drain outlet valve 26 during normal operation. For this reason, the solution discharged from the absorption tower 11a does not flow into the drain tank 23.

[0059] The solution that has flowed into the interior of the stripping tower 12 passes through the lower packing material 122 and accumulates at the bottom of the stripping tower 12. A part of the solution that has accumulated at the bottom of the stripping tower 12 flows into the reboiler 29 through the first reboiler path 291 and is heated by the reboiler 29. The vapor generated in the reboiler 29 flows into the interior of the stripping tower 12 through the second reboiler path 292, and then passes through the lower packing material 122 while rising from the bottom of the stripping tower 12. Then, the vapor makes gas-liquid contact (countercurrent contact) with the solution flowing down from the top in the lower packing material 122. As a result, the solution flowing down through the lower packing material 122 is heated, and carbon dioxide is dissipated from the solution.

[0060] The mixture of carbon dioxide dissipated from the solution and the vapor that has not liquefied passes through the upper packing material 121 and flows into the carbon dioxide recovery path 30 from the top of the stripping tower 12. The upper packing material 121 is a porous or mesh-like member. Therefore, when the mixture passes through the upper packing material 121, the mist contained in the mixture is removed to some extent.

[0061] In the demister 301 provided in the carbon dioxide recovery path 30, the vapor mist is removed from the mixture that has flowed into the carbon dioxide recovery path 30. Further, the mixture is cooled in the mixture cooler 302, whereby the vapor condenses (liquefies). Then, in the gas-liquid separator 303, it is separated into carbon dioxide as a gas and a solution as a liquid. The carbon dioxide separated in the gas-liquid separator 303 is discharged to the outside through the carbon dioxide recovery path 30. That is, carbon dioxide is recovered through the carbon dioxide recovery path 30. On the other hand, the solution separated in the gas-liquid separator 303 returns to the stripping tower 12 through the solution reflux path 304 and flows down through the upper packing material 121. As a result, the upper packing material 121 is cooled, so that the condensation of the vapor contained in the mixture passing through the upper packing material 121 is promoted.

[0062] The solution accumulated at the bottom of the stripping tower 12 is fed from the stripping tower 12 to the absorption tower 11a through the second solution path 20 by the operation of the second solution pump 21. Then, the solution flowing through the second solution path 20 is cooled by exchanging heat with the solution flowing through the first solution path 17 in the solution heat exchanger 27, and is further cooled by releasing heat in the solution cooler 28. As a result, the solution reaches a temperature suitable for the absorption of carbon dioxide. Then, the solution flows into the absorption tower 11a through the rotating body 46a.

[0063] In this way, by the operations of the first solution pump 19, the second solution pump 21, and the intermediate solution pump 49, the solution circulates in the order of the absorption tower 11a, the first solution path 17, the stripping tower 12, and the second solution path 20. And while circulating, the solution repeatedly undergoes the reaction of absorbing carbon dioxide contained in the target gas in the absorption tower 11a and releasing the absorbed carbon dioxide in the stripping tower 12. The carbon dioxide released from the solution in the stripping tower 12 is discharged (recovered) from the recovery device 10a through the carbon dioxide recovery path 30.

[0064] Note that the amount of carbon dioxide absorbed by the solution is determined according to the type (characteristics) of the solute, the flow rate of the target gas, the flow rate of the solution, the rotation speed of the rotating body 46a, and the like. For this reason, the control device 22 controls the target gas pump 14, the first solution pump 19, the second solution pump 21, the intermediate solution pump 49, and the rotating body drive power source 50 (that is, the flow rate of the target gas, the flow rate of the solution, and the rotation speed of the rotating body 46a) so that the carbon dioxide absorption efficiency in the absorption tower 11a becomes equal to or higher than a preset target value. The carbon dioxide absorption efficiency is a ratio indicated by the amount of carbon dioxide absorbed by the solution with respect to the amount of carbon dioxide contained in the target gas.

[0065] (Solution penetration operation) Next, the solution penetration operation will be described. The solution penetration operation is an operation of causing the solution to penetrate over substantially the entire area of each of the gas-liquid contact portions 63 and 66 of each stage during the stop of the normal operation, particularly before the start of the normal operation (each time the normal operation is started). The time before the start of the normal operation may be, for example, immediately before the first start of the normal operation of the recovery device 10a, or immediately before the start of the normal operation after a long-term stop of the normal operation (although it varies depending on the size of the gas-liquid contact portions 63 and 66, when the stop time of the recovery device 10a has elapsed for several hours or more), or immediately before the start of the normal operation after a person who has determined that the solution penetration operation is necessary issues an execution command for the solution penetration operation, or immediately before the start of the normal operation after the control device 22 that has determined that the solution penetration operation is necessary issues an execution command for the solution penetration operation. Note that the solution penetration operation can also be said to be an operation of forming a solution film over the entire surface of each of the gas-liquid contact portions 63 and 66 of each stage (the entire surface of the filler of each of the gas-liquid contact portions 63 and 66 of each stage). Further, the solution penetration operation can also be said to be an operation of holding (supplementing) the solution in the entire area of each of the gas-liquid contact portions 63 and 66 of each stage.

[0066] When the normal operation stops, the solution existing inside the gas-liquid contact parts 63 and 66 of each stage (the solution held in the gas-liquid contact parts 63 and 66 of each stage) decreases by falling or vaporizing due to gravity. In other words, when the normal operation stops, the film of the solution existing on the surfaces of the gas-liquid contact parts 63 and 66 of each stage decreases. Then, when the normal operation is started (restarted) with the solution held in the gas-liquid contact parts 63 and 66 of each stage being less than that during the normal operation, the carbon dioxide absorption efficiency may be lower than the target value until the solution penetrates the entire gas-liquid contact parts 63 and 66 of each stage. Therefore, the control device 22 executes a solution penetration operation before the start of the normal operation of the recovery device 10a to make the solution penetrate the entire gas-liquid contact parts 63 and 66 of each stage. The solution penetration operation of the first embodiment is an operation of supplying the solution to the absorption chambers 42 and 45 of each stage so that the liquid level height becomes equal to or higher than the upper limit height, and immersing the entire gas-liquid contact parts 63 and 66 of each stage in the solution, thereby making the solution penetrate the entire inside of the gas-liquid contact parts 63 and 66 of each stage. Thereby, it is possible to prevent or suppress the carbon dioxide absorption efficiency from becoming less than the target value immediately after the start of the normal operation of the recovery device 10a.

[0067] In the solution penetration operation of the first embodiment, first, the lower gas-liquid contact portion 66 is immersed in the solution, and then the upper gas-liquid contact portion 63 is immersed in the solution. The reason for this order is to shorten the time required for supplying the solution to the lower absorption chamber 45. Specifically, when supplying the solution to the lower absorption chamber 45, the gas (the remainder of the target gas) present inside the lower absorption chamber 45 must be discharged. On the other hand, the absorption tower 11a is configured such that the gas present inside the lower absorption chamber 45 is discharged to the outside of the absorption tower 11a via the upper absorption chamber 42. For this reason, if the inside of the upper absorption chamber 42 is filled with the solution when supplying the solution to the lower absorption chamber 45, the passage of the gas through the upper absorption chamber 42 is inhibited by this solution. Therefore, it takes time to discharge the gas present inside the lower absorption chamber 45. In contrast, if the supply of the solution to the lower absorption chamber 45 is performed first (when the supply of the solution to the lower absorption chamber 45 is carried out with no solution accumulated inside the upper absorption chamber 42), the discharge of the gas accumulated inside the lower absorption chamber 45 is not inhibited by the solution, so the time required for supplying the solution to the lower absorption chamber 45 can be shortened.

[0068] However, the absorption tower 11a according to the present embodiment is configured such that the solution is supplied to the lower absorption chamber 45 via the upper absorption chamber 42. For this reason, when there is no solution accumulated in the upper absorption chamber 42 or when the amount of the solution is too small, there is a risk that the intermediate solution path 48 is not liquid-sealed and the intermediate solution pump 49 runs idly. Therefore, the control device 22 supplies the solution to the lower absorption chamber 45 while maintaining the liquid level height of the upper absorption chamber 42 at or near the lower limit height.

[0069] During the execution of the solution penetration operation, the control device 22 continuously and in real time acquires the states of the upper upper liquid level sensor 421, the upper lower liquid level sensor 422, the lower upper liquid level sensor 451, and the lower lower liquid level sensor 452. Thereby, the control device 22 can determine in real time whether the liquid level height of each of the absorption chambers 42, 45 is equal to or higher than the upper limit height, less than the upper limit height, equal to or higher than the lower limit height, or less than the lower limit height.

[0070] First, the control device 22 closes the target gas inlet valve 15 so that the solution does not flow backward upstream of the target gas introduction path 13 from the target gas inlet valve 15. However, since the torii pipe portion 131 is provided in the target gas introduction path 13, even when the solution flows backward, it is prevented or suppressed that the backward-flowing solution reaches the target gas pump 14. Further, the control device 22 opens the drain outlet valve 26 and the solution outlet valve 18. As a result, the lower absorption chamber 45 is in a state where the solution can be stored, and the solution cannot flow into the drain tank 23.

[0071] In that state, the control device 22 supplies the solution to the lower absorption chamber 45 while maintaining the liquid level height of the upper absorption chamber 42 near the lower limit height. Specifically, the control device 22 operates the second solution pump 21. Thereby, the solution is supplied to the upper absorption chamber 42. Then, when the liquid level height of the upper absorption chamber 42 becomes equal to or higher than the lower limit height, the control device 22 operates the intermediate solution pump 49 and starts supplying the solution to the lower absorption tower 11a. At this time, the flow rate of the solution by the intermediate solution pump 49 is set to be equal to or higher than the flow rate of the solution by the second solution pump 21. Thereby, the liquid level height of the upper absorption chamber 42 is maintained near the lower limit height or gradually decreases. When the liquid level height of the upper absorption chamber 42 becomes lower than the lower limit height, the control device 22 stops the operation of the intermediate solution pump 49 while continuing the operation of the second solution pump 21, and when the liquid level height of the upper absorption chamber 42 becomes equal to or higher than the lower limit height, the control device 22 starts (restarts) the operation of the intermediate solution pump 49 and continues such control. According to such control, since the operation of the intermediate solution pump 49 stops when the liquid level height of the upper absorption chamber 42 is lower than the lower limit height, the idling operation of the intermediate solution pump 49 is prevented.

[0072] When the liquid level height of the lower absorption chamber 45 reaches the upper limit height, the control device 22 stops the operation of the intermediate solution pump 49 while continuing the operation of the second solution pump 21. When the liquid level height of the lower absorption chamber 45 reaches the upper limit height, the entire lower gas-liquid contact part 66 is in a state of being immersed in the solution. Then, when the operation of the intermediate solution pump 49 stops while the operation of the second solution pump 21 continues, the liquid level height of the upper absorption chamber 42 gradually increases. When the liquid level height of the upper absorption chamber 42 reaches the upper limit height, the entire upper gas-liquid contact part 63 is in a state of being immersed in the solution. Therefore, when the liquid level height of the upper absorption chamber 42 reaches the upper limit height, the control device 22 stops the operation of the second solution pump 21.

[0073] (Discharge operation) Thereafter, the control device 22 executes a discharge operation which is an operation to return the recovery device 10a to a state where normal operation can be started. Specifically, the control device 22 discharges the solution accumulated inside the upper absorption chamber 42, the lower absorption chamber 45, and the target gas discharge path 16. The content of the discharge operation is as follows.

[0074] The control device 22 first opens the solution outlet valve 18. Thereby, the solution can be discharged from the lower absorption chamber 45. In that state, the control device 22 operates the second solution pump 21, the intermediate solution pump 49, and the first solution pump 19. Thereby, the discharge of the solution from the upper absorption chamber 42 starts. At this time, by operating the second solution pump 21 to continue the supply of the solution to the upper gas-liquid contact part 63, it is possible to prevent or suppress the decrease of the solution held by the upper gas-liquid contact part 63. However, the control device 22 makes the flow rate of the second solution pump 21 less than the flow rates of the intermediate solution pump 49 and the first solution pump 19 so that the solution stored in the upper absorption chamber 42 decreases. The control device 22 makes the flow rate of the intermediate solution pump 49 substantially the same as the flow rate of the first solution pump 19. Thereby, the liquid level height of the upper absorption chamber 42 gradually decreases. On the other hand, since the flow rate of the solution supplied to the lower absorption chamber 45 is substantially the same as the flow rate of the solution discharged from the lower absorption chamber 45, the liquid level height of the lower absorption chamber 45 hardly fluctuates.

[0075] The control device 22 continues the operations of the second solution pump 21, the intermediate solution pump 49, and the first solution pump 19 until the liquid level height of the upper absorption chamber 42 becomes less than the lower limit height. Thereby, the discharge of the solution from the upper absorption chamber 42 continues, and the liquid level height of the upper absorption chamber 42 gradually decreases. When the liquid level height of the upper absorption chamber 42 becomes less than the lower limit height, the discharge of the solution in the upper absorption chamber 42 is completed. Then, while maintaining the liquid level height of the upper absorption chamber 42 near the lower limit height, the control device 22 discharges the solution accumulated in the lower absorption chamber 45. Specifically, the control device 22 operates the intermediate solution pump 49 when the liquid level height of the upper absorption chamber 42 becomes equal to or higher than the lower limit height while continuing the operation of the first solution pump 19, and stops the intermediate solution pump 49 when the liquid level height of the upper absorption chamber 42 becomes less than the lower limit height, and executes such control.

[0076] When the liquid level height of the lower absorption chamber 45 becomes less than the lower limit height, the control device 22 stops the operations of the first solution pump 19, the second solution pump 21, and the intermediate solution pump 49. Thereby, the liquid level heights of the upper absorption chamber 42 and the lower absorption chamber 45 are in a state near the lower limit height.

[0077] After that, the control device 22 discharges the solution accumulated in the target gas introduction path 13. Specifically, the control device 22 closes the solution outlet valve 18 and opens the target gas inlet valve 15. When the target gas inlet valve 15 is opened, the solution accumulated in the portion between the target gas inlet valve 15 of the target gas introduction path 13 and the absorption tower 11a flows into the drain tank 23. Then, the control device 22 opens the drain outlet valve 26, and then operates the first solution pump 19. Thereby, the solution accumulated in the drain tank 23 is discharged from the drain tank 23 and fed toward the dissipation tower 12 through the first solution path 17. At this time, since the solution outlet valve 18 is closed, the solution accumulated inside the lower absorption chamber 45 is not discharged.

[0078] When the discharge of the solution accumulated inside the drain tank 23 is completed, the control device 22 stops the first solution pump 19, closes the drain outlet valve 26, and opens the solution outlet valve 18. As a result, the recovery device 10a can start the normal operation.

[0079] According to the present embodiment, before starting the normal operation (each time the normal operation is started), the control device 22 executes the solution penetration operation and the discharge operation, so that at the start of the normal operation, the gas-liquid contact parts 63 and 66 of each stage hold the solution (a state in which a solution film is formed on substantially the entire surface of the gas-liquid contact parts 63 and 66 of each stage). Therefore, it is possible to prevent or suppress the absorption efficiency of carbon dioxide from becoming less than the target value immediately after the start of the normal operation.

[0080] (Processing executed by the control device) Next, the specific operation of the control device 22 will be described. FIGS. 3, 4A, and 4B are flowcharts showing the processing executed by the computer of the control device 22. Note that FIG. 3 is a flowchart showing the processing for executing the solution penetration operation, and FIGS. 4A and 4B are flowcharts showing the processing for executing the discharge operation. The computer programs for executing these processes are stored in advance in the ROM of the computer of the control device 22. Then, the CPU of the computer of the control device 22 reads out these computer programs from the ROM, expands them in the RAM, and executes them.

[0081] In step S101, the CPU closes the target gas inlet valve 15, the solution outlet valve 18, and the drain outlet valve 26. As a result, the lower absorption chamber 45 becomes a state in which the solution can be stored. Also, the solution in the lower absorption chamber 45 does not flow back into the target gas introduction path 13. Then, the CPU advances the process to step S102.

[0082] In step S102, the CPU starts the operation of the second solution pump 21. As a result, the supply of the solution to the upper absorption chamber 42 is started. Then, the CPU advances the process to step S103.

[0083] In step S103, the CPU determines whether the upper-stage lower liquid level sensor 422 is in the ON state or the OFF state. If it is in the OFF state, the CPU waits in this step. If it is in the ON state, the CPU advances the process to step S104.

[0084] In step S104, the CPU starts the operation of the intermediate solution pump 49. As a result, the solution accumulated in the upper absorption chamber 42 is fed to the lower absorption chamber 45 by the operation of the intermediate solution pump 49. Note that the CPU continues the operation of the second solution pump 21 started in step S102. Then, the CPU advances the process to step S105.

[0085] In step S105, the CPU determines whether the upper-stage lower liquid level sensor 422 is in the ON state or the OFF state. If it is in the OFF state, the amount of the solution accumulated in the upper absorption chamber 42 is too small. In this case, the CPU advances the process to step S106. On the other hand, if the upper-stage lower liquid level sensor 422 is in the ON state, the CPU advances the process to step S107.

[0086] In step S106, the CPU stops the operation of the intermediate solution pump 49. As a result, the discharge of the solution from the upper absorption chamber 42 stops. Then, the CPU returns the process to step S103.

[0087] In step S107, the CPU determines whether the lower-stage upper liquid level sensor 451 is in the ON state or the OFF state. If the lower-stage upper liquid level sensor 451 is in the OFF state, the lower gas-liquid contact part 66 is not immersed in the solution. In this case, the CPU returns the process to step S105. For this reason, the supply of the solution to the lower absorption chamber 45 continues. On the other hand, if the lower-stage upper liquid level sensor 451 is in the ON state, the entire lower gas-liquid contact part 66 is immersed in the solution. In this case, the CPU advances the process to step S108.

[0088] In step S108, the CPU stops the operation of the intermediate solution pump 49. As a result, the supply of the solution to the lower absorption chamber 45 stops. However, the CPU continues the operation of the second solution pump 21 started in step S102. Therefore, the liquid level height of the upper absorption chamber 42 rises. Then, the CPU proceeds with the process to step S109.

[0089] In step S109, the CPU determines whether the upper limit liquid level sensor 421 is in the ON state or the OFF state. When the upper limit liquid level sensor 421 is in the OFF state, the gas-liquid contact part 63 in the upper stage is not immersed in the solution. In this case, the CPU waits in this step S109. On the other hand, when the upper limit liquid level sensor 421 is in the ON state, the entire gas-liquid contact part 63 in the upper stage is immersed in the solution. In this case, the CPU proceeds with the process to step S110.

[0090] In step S110, the CPU stops the operation of the second solution pump 21. Then, the series of processes ends.

[0091] Next, the solution discharge operation will be described. At the time when the above series of processes ends, the liquid level heights of the upper absorption chamber 42 and the lower absorption chamber 45 are equal to or higher than the upper limit height, and the gas-liquid contact parts 63, 66 in each stage are immersed in the solution. Then, the upper limit liquid level sensor 421, the upper lower limit liquid level sensor 422, the lower upper limit liquid level sensor 451, and the lower lower limit liquid level sensor 452 are all in the ON state.

[0092] In step S201, the CPU opens the solution outlet valve 18. As a result, the solution can be discharged from the lower absorption chamber 45. Then, the CPU proceeds with the process to step S202.

[0093] In step S202, the CPU starts the operations of the second solution pump 21, the intermediate solution pump 49, and the first solution pump 19. Note that the flow rate of the second solution pump 21 is made less than the flow rates of the intermediate solution pump 49 and the first solution pump 19. Thereby, while the supply of the solution to the upper gas-liquid contact part 63 continues, the liquid level height of the upper absorption chamber 42 gradually decreases. On the other hand, since the flow rate of the solution supplied to the lower absorption chamber 45 and the flow rate discharged from the lower absorption chamber 45 are substantially the same, the liquid level height of the lower absorption chamber 45 hardly fluctuates. Then, the CPU proceeds with the process to step S203.

[0094] In step S203, the CPU determines whether the upper lower liquid level sensor 422 is in the ON state or the OFF state. The CPU waits in this step while the upper lower liquid level sensor 422 is in the ON state. For this reason, the discharge of the solution from the upper absorption chamber 42 continues. Then, when the upper lower liquid level sensor 422 becomes OFF, the CPU proceeds with the process to step S204.

[0095] In step S204, the CPU stops the operation of the intermediate solution pump 49. Thereby, the discharge of the solution from the upper absorption chamber 42 stops. However, the CPU continues the operation of the first solution pump 19 started in step S202. For this reason, the discharge of the solution from the lower absorption chamber 45 continues. Then, the CPU proceeds with the process to step S205.

[0096] In step S205, the CPU determines whether the upper lower liquid level sensor 422 is in the ON state or the OFF state. If the upper lower liquid level sensor 422 is in the ON state, the CPU proceeds with the process to step S206. If the upper lower liquid level sensor 422 is in the OFF state, the CPU proceeds with the process to step S207.

[0097] In step S206, the CPU starts the operation of the intermediate solution pump 49. Then, the CPU returns the process to step S203. And the CPU repeats steps S203 to S206. As a result, the discharge of the solution from the lower absorption chamber 45 continues while the liquid level height of the upper absorption chamber 42 is maintained near the lower limit height.

[0098] In step S207, the CPU determines whether the lower limit liquid level sensor 452 is in the ON state or the OFF state. If it is in the ON state, the CPU returns the process to step S205. In this case, since the intermediate solution pump 49 is stopped, the discharge of the accumulated solution in the lower absorption chamber 45 continues by the operation of the first solution pump 19. When the lower limit liquid level sensor 452 is in the OFF state, that is, when the liquid level height of the lower absorption chamber 45 becomes less than the lower limit height, the CPU proceeds with the process to step S208.

[0099] In step S208, the CPU stops the operations of the first solution pump 19 and the second solution pump 21. At this point, the liquid level heights of both the upper absorption chamber 42 and the lower absorption chamber 45 are near (immediately below) the lower limit height. Then, the CPU proceeds with the process to step S209.

[0100] In step S209, the CPU closes the solution outlet valve 18 and opens the target gas inlet valve 15. As a result, the solution accumulated in the target gas discharge path 16 flows into the drain tank 23. Then, the CPU proceeds with the process to step S210.

[0101] In step S210, the CPU determines whether the drain tank liquid level sensor 231 is in the ON state or the OFF state. When the drain tank liquid level sensor 231 is in the OFF state, the liquid level height of the drain tank 23 is less than a predetermined value (the state where no solution is accumulated). In this case, the CPU ends this series of processes. On the other hand, when the drain tank liquid level sensor 231 is in the ON state, the solution is accumulated in the drain tank 23. In this case, the CPU proceeds with the process to step S211.

[0102] In step S211, the CPU opens the drain outlet valve 26 and starts the operation of the first solution pump 19. Thereby, the discharge of the solution from the drain tank 23 is started. Then, the CPU proceeds with the process to step S212.

[0103] In step S212, the CPU determines whether the drain tank liquid level sensor 231 is in the ON state or the OFF state. When the drain tank liquid level sensor 231 is in the ON state, it means that the solution is accumulating in the drain tank 23. In this case, the CPU waits for processing in this step. On the other hand, when the drain tank liquid level sensor 231 is in the OFF state, it means that no solution is accumulating in the drain tank 23. In this case, the CPU proceeds with the process to step S213.

[0104] In step S213, the CPU closes the drain outlet valve 26 and stops the operation of the first solution pump 19. Then, the CPU ends this series of processes.

[0105] Through the above processes, the solution penetration operation and the discharge operation are realized. After that, the CPU executes the normal operation.

[0106] <Second Embodiment> (Configuration of the Recovery Device) Next, the second embodiment will be described. Note that the same reference numerals as those in the first embodiment are given to the configurations common to the first embodiment, and the description may be omitted. FIG. 5 is a diagram showing the configuration of the recovery device 10b according to the second embodiment. As shown in FIG. 5, the recovery device 10b according to the second embodiment includes an upper immersion container 51, a lower immersion container 52, an upper immersion container lifting mechanism 71, and a lower immersion container lifting mechanism 72. The configuration of the recovery device 10b according to the second embodiment, which includes the upper immersion container 51, the lower immersion container 52, the upper immersion container lifting mechanism 71, and the lower immersion container lifting mechanism 72, is different from that of the first embodiment, and the configurations common to the first embodiment are applied to the rest.

[0107] (Configuration of the Absorption Tower and the Rotating Body) Figures 6A and 6B are cross-sectional views showing the configuration and operation of the upper immersion container 51 and the upper immersion container lifting mechanism 71 of the absorption tower 11b. Note that since the lower immersion container 52 and the lower immersion container lifting mechanism 72 have the same configuration as the upper immersion container 51 and the upper immersion container lifting mechanism 71, the illustration thereof is omitted. With reference to these figures, the configuration of the immersion containers 51, 52 of each stage and the immersion container lifting mechanisms 71, 72 of each stage will be described.

[0108] The immersion containers 51, 52 of each stage are configured to be able to insert and remove the gas-liquid contact portions 63, 66 of each stage from above. Specifically, the immersion containers 51, 52 of each stage have a bottomed cylindrical configuration with an open upper side and are arranged substantially coaxially with the rotating body 46b. And the immersion containers 51, 52 of each stage are configured to be able to accommodate the entire gas-liquid contact portions 63, 66 of each stage. Specifically, in a state where the gas-liquid contact portions 63, 66 of each stage are accommodated in the immersion containers 51, 52 of each stage, the upper ends (upper edges) of the immersion containers 51, 52 of each stage are configured to be located above the upper ends (upper surfaces) of the gas-liquid contact portions 63, 66 of each stage. At the center of the bottom of each of the immersion containers 51, 52 of each stage, a solution discharge port 511, which is an opening penetrating in the vertical direction, is provided. The solution discharge port 511 is an example of the opening of the present invention. The intermediate shaft portion 64 or the lower shaft portion 67 is inserted into this solution discharge port 511. However, there is a gap through which the solution can flow between the inner peripheral surface of the solution discharge port 511 and the intermediate shaft portion 64 or the lower shaft portion 67. A seal 631 is provided on the lower surface of the gas-liquid contact portions 63, 66 of each stage so as to surround the intermediate shaft portion 64 or the lower shaft portion 67. And in a state where the gas-liquid contact portions 63, 66 of each stage are accommodated in the immersion containers 51, 52 of each stage, the seal 631 of the gas-liquid contact portions 63, 66 of each stage contacts the upper surface of the bottom of the immersion containers 51, 52 of each stage so as to surround the solution discharge port 511 (that is, to block the solution discharge port 511).

[0109] Therefore, as shown in FIG. 6A, when the seals 631 of the gas-liquid contact parts 63 and 66 of each stage do not contact the upper surfaces of the bottoms of the immersion containers 51 and 52 of each stage, the solution supplied to the immersion containers 51 and 52 of each stage flows down from the solution discharge ports 511. Therefore, when the seals 631 of the gas-liquid contact parts 63 and 66 of each stage do not contact the upper surfaces of the bottoms of the immersion containers 51 and 52 of each stage (in other words, when the gas-liquid contact parts 63 and 66 of each stage are not accommodated in the immersion containers 51 and 52 of each stage), the solution does not accumulate in the immersion containers 51 and 52 of each stage. On the other hand, as shown in FIG. 6B, when the seals 631 of the gas-liquid contact parts 63 and 66 of each stage are in contact with the upper surfaces of the bottoms of the immersion containers 51 and 52 of each stage, the solution discharge ports 511 of the immersion containers 51 and 52 of each stage are blocked by these seals 631. Therefore, in this state, the solution can be stored in the immersion containers 51 and 52 of each stage.

[0110] The immersion containers 51 and 52 of each stage can be moved vertically inside the absorption chambers 42 and 45 of each stage by the immersion container elevating mechanisms 71 and 72 of each stage. A ball screw mechanism 711 is applied to the immersion container elevating mechanisms 71 and 72 of each stage. Specifically, the immersion container elevating mechanisms 71 and 72 of each stage include a screw shaft 712 of the ball screw mechanism 711 that is rotatably disposed inside the absorption chambers 42 and 45 of each stage with its axis in a direction substantially parallel to the vertical direction (a direction substantially parallel to the axis of the rotating body 46b), a ball nut 713 of the ball screw mechanism 711 attached to the immersion containers 51 and 52 of each stage, and an immersion container driving power source 714 for rotating the screw shaft 712 of the ball screw mechanism 711. The immersion container driving power source 714 of each stage is controlled by the control device 22. Note that the configuration of the immersion container driving power source 714 of each stage is not particularly limited, and various known electric motors can be applied.

[0111] The immersion container elevating mechanisms 71 and 72 of each stage with such a configuration can move the immersion containers 51 and 52 of each stage vertically inside the absorption chambers 42 and 45 of each stage. And, as shown in FIG. 6B, when the immersion containers 51 and 52 of each stage are located at the upper ends of the vertical movable ranges, the entire respective gas-liquid contact portions 63 and 66 of each stage are accommodated in the immersion containers 51 and 52 of each stage. In this state, the seals 631 of the gas-liquid contact portions 63 and 66 of each stage contact the upper surfaces of the bottoms of the immersion containers 51 and 52 of each stage (the solution discharge ports 511 of the immersion containers 51 and 52 of each stage are blocked by the seals 631). Therefore, when the immersion containers 51 and 52 of each stage are located at the upper ends of the movable ranges, the immersion containers 51 and 52 of each stage can store the solution, and the entire respective gas-liquid contact portions 63 and 66 of each stage can be immersed in the solution.

[0112] On the other hand, as shown in FIG. 6A, when the immersion containers 51 and 52 of each stage are located at the lower ends (or in the vicinity thereof) of the movable ranges, the entire respective gas-liquid contact portions 63 and 66 of each stage are located outside the immersion containers 51 and 52 of each stage, and the seals 631 of the gas-liquid contact portions 63 and 66 of each stage do not contact the upper surfaces of the bottoms of the immersion containers 51 and 52 of each stage (the solution discharge ports 511 of the immersion containers 51 and 52 of each stage are not blocked by the seals 631). Therefore, when the immersion containers 51 and 52 of each stage are located at the lower ends (or in the vicinity thereof) of the movable ranges, the immersion containers 51 and 52 of each stage cannot store the solution. Note that the position of the upper end of the movable range of the immersion containers 51 and 52 of each stage is an example of the first position of the present invention, and the position of the lower end or in the vicinity thereof of the movable range of the immersion containers 51 and 52 of each stage is an example of the second position of the present invention.

[0113] The upper lower liquid level sensor 422 of the upper absorption chamber 42 is configured to be in an ON state when the liquid level height of the upper absorption chamber 42 is equal to or higher than the lower limit height, and in an OFF state when it is lower than the lower limit height. The lower limit height in this case is the "height at which the upper gas-liquid contact part 63 is not immersed in the solution and the target gas does not flow into the intermediate solution path 48 (the intermediate solution path 48 can be liquid-sealed)". The upper upper liquid level sensor 421 of the upper absorption chamber 42 is configured to be in an ON state when the liquid level height of the upper absorption chamber 42 is equal to or higher than the upper limit height, and in an OFF state when it is lower than the upper limit height. The upper limit height in this case is a height that is higher than a predetermined value or more than the "height at which the upper lower liquid level sensor 422 switches from the OFF state to the ON state". The lower lower liquid level sensor 452 of the lower absorption chamber 45 is configured to be in an ON state when the liquid level height of the lower absorption chamber 45 is equal to or higher than the lower limit height, and in an OFF state when it is lower than the lower limit height. The lower limit height in this case is the "height at which the lower gas-liquid contact part 66 is not immersed in the solution and the target gas does not flow into the first solution path 17 (the first solution path 17 can be liquid-sealed)". The lower upper liquid level sensor 451 of the lower absorption chamber 45 is configured to be in an ON state when the liquid level height of the lower absorption chamber 45 is equal to or higher than the upper limit height, and in an OFF state when it is lower than the upper limit height. The upper limit height in this case is a height that is higher than a predetermined value or more than the "height at which the lower lower liquid level sensor 452 switches from the OFF state to the ON state". Note that these "predetermined values" are not particularly limited, but are values greater than 0 and can be distinguished from the liquid level heights at which the upper lower liquid level sensor 422 and the lower lower liquid level sensor 452 switch from the OFF state to the ON state.

[0114] (Normal operation) During normal operation, the recovery device 10b according to the second embodiment positions the immersion containers 51, 52 at each stage at the lower end of the movable range or in the vicinity thereof. In this state, the solution that has flowed into the immersion containers 51, 52 at each stage flows down from the solution discharge port 511. Otherwise, it is the same as the normal operation of the first embodiment.

[0115] (Solution penetration operation) Next, the solution penetration operation will be described. First, the control device 22 controls the immersion container elevating mechanisms 71 and 72 of each stage to position the immersion containers 51 and 52 of each stage at the upper end of the movable range. Then, the control device 22 operates the second solution pump 21. As a result, the solution accumulates inside the upper immersion container 51. When the supplied solution exceeds the capacity of the upper immersion container 51, the solution overflows from the upper immersion container 51 and accumulates at the bottom of the upper absorption chamber 42. When the liquid level height of the upper absorption chamber 42 becomes equal to or higher than the lower limit height, the control device 22 starts supplying the solution to the inside of the lower immersion container 52 by operating the intermediate solution pump 49.

[0116] Then, while maintaining the liquid level height of the upper absorption chamber 42 near the lower limit height, the control device 22 continues to supply the solution to the inside of the lower immersion container 52 until the entire lower gas-liquid contact part 66 is immersed in the solution. Specifically, the control device 22 operates the intermediate solution pump 49 when the liquid level height of the upper absorption chamber 42 is equal to or higher than the lower limit height (when the upper lower liquid level sensor 422 is in the ON state), and stops the operation of the intermediate solution pump 49 when the liquid level height of the upper absorption chamber 42 is lower than the lower limit height (when the upper lower liquid level sensor 422 is in the OFF state).

[0117] In this embodiment, when the liquid level height of the lower absorption chamber 45 becomes equal to or higher than the upper limit height (that is, when the lower upper liquid level sensor 451 is in the ON state), it is considered that the entire lower gas-liquid contact part 66 is immersed in the solution. When the liquid level height of the lower absorption chamber 45 becomes equal to or higher than the upper limit height, the control device 22 stops supplying the solution to the lower immersion container 52 by stopping the operation of the intermediate solution pump 49. However, the control device 22 continues to operate the second solution pump 21. Then, thereafter, if the entire upper gas-liquid contact part 63 is immersed in the solution, the control device 22 stops supplying the solution to the upper immersion container 51 by stopping the operation of the second solution pump 21. In this embodiment, if the liquid level height of the upper absorption chamber 42 is equal to or higher than the upper limit height, it is considered that the entire upper gas-liquid contact part 63 is immersed in the solution.

[0118] (Discharge operation) First, the control device 22 controls the upper immersion container lifting mechanism 71 and the lower immersion container lifting mechanism 72 to move the upper immersion container 51 and the lower immersion container 52 to the positions at the lower ends of their respective movable ranges. As a result, the solutions accumulated in the upper immersion container 51 and the lower immersion container 52 flow down from the solution discharge ports 511 and accumulate at the bottoms of the upper absorption chamber 42 and the lower absorption chamber 45, respectively. The subsequent operations are the same as the discharge operation of the first embodiment.

[0119] (Processing executed by the control device) Next, the specific operation of the control device 22 will be described. FIGS. 7, 8A, and 8B are flowcharts showing the processing executed by the computer of the control device 22. Note that FIG. 7 is a flowchart showing the processing for executing the solution penetration operation, and FIGS. 8A and 8B are flowcharts showing the processing for executing the discharge operation.

[0120] The processing for the solution penetration operation is as follows. In step S301, the CPU operates the immersion container lifting mechanisms 71 and 72 of each stage to move the immersion containers 51 and 52 of each stage to the positions at the upper ends of their respective movable ranges. Then, the CPU proceeds to step S302. Steps S302 to S311 are the same as steps S101 to S110 of the processing of the first embodiment, respectively (see FIG. 3). Therefore, the description is omitted.

[0121] The processing for the discharge operation is as follows. In step S401, the control device 22 operates the immersion container lifting mechanisms 71 and 72 of each stage to move the immersion containers 51 and 52 of each stage to the positions at the lower ends or near the lower ends of their respective movable ranges. Then, the CPU proceeds to step S402. Steps S402 to S414 are the same as steps S201 to S213 of the first embodiment (see FIGS. 4A and 4B). Therefore, the description is omitted.

[0122] According to the above processing, the solution penetration operation and the discharge operation are realized.

[0123] Note that by performing the solution penetration operation as follows, first the lower gas-liquid contact part 66 may be immersed in the solution, and then the upper gas-liquid contact part 63 may be immersed in the solution.

[0124] The control device 22 first controls the lower immersion container lifting mechanism 72 to position the lower immersion container 52 at the upper end of the movable range. However, the upper immersion container 51 is positioned at the lower end of the movable range. After that, the control device 22 operates the second solution pump 21. As a result, the solution supplied to the upper absorption chamber 42 does not accumulate inside the upper immersion container 51 but accumulates at the bottom of the upper absorption chamber 42. Then, when the liquid level height of the upper absorption chamber 42 becomes equal to or higher than the lower limit height, the control device 22 starts supplying the solution to the inside of the lower immersion container 52 by operating the intermediate solution pump 49. At this time, the control device 22 continues to supply the solution to the inside of the lower immersion container 52 while maintaining the liquid level height of the upper absorption chamber 42 near the lower limit height in the same manner as the above operation until the entire lower gas-liquid contact part 66 is immersed in the solution.

[0125] When the liquid level height of the lower absorption chamber 45 becomes equal to or higher than the upper limit height (that is, when the lower upper liquid level sensor 451 is in the ON state), the control device 22 stops the supply of the solution to the lower immersion container 52 by stopping the operation of the intermediate solution pump 49, and operates the upper immersion container lifting mechanism 71 to position the upper immersion container 51 at the upper end of the movable range. Note that the control device 22 continues to operate the second solution pump 21. As a result, the supply of the solution to the upper immersion container 51 starts.

[0126] After that, if the entire upper gas-liquid contact part 63 is in a state of being immersed in the solution, the control device 22 stops the supply of the solution to the upper immersion container 51 by stopping the operation of the second solution pump 21. In this embodiment, if the liquid level height of the upper absorption chamber 42 is equal to or higher than the upper limit height, it is considered that the entire upper gas-liquid contact part 63 is in a state of being immersed in the solution.

[0127] The process for performing the solution penetration operation of penetrating the solution in the order of the lower gas-liquid contact part 66 and the upper gas-liquid contact part 63 is as follows. FIG. 9 is a flowchart showing the process for performing the solution penetration operation of penetrating the solution in the order of the lower gas-liquid contact part 66 and the upper gas-liquid contact part 63. As shown in FIG. 9, the CPU operates the lower immersion container lifting mechanism 72 in step S501 to position the lower immersion container 52 at the upper end of the movable range. Then the CPU advances the process to step S502. Steps S502 to S509 are the same as steps S101 to S108 of the first embodiment. When the process of step S509 is completed, the lower gas-liquid contact part 66 is immersed in the solution, the supply of the solution to the lower absorption chamber 45 is stopped, and the supply of the solution to the upper absorption chamber 42 continues. The CPU controls the upper immersion container lifting mechanism 71 in step S510 to position the upper immersion container 51 at the upper end of the movable range. Thereby, the solution accumulates in the upper immersion container 51. Then the CPU advances the process to step S511. Steps S511 and S512 are the same as steps S109 and S110 of the first embodiment.

[0128] Note that the CPU may temporarily stop the operation of the intermediate solution pump 49 in step S509 and resume the operation of the intermediate solution pump 49 after the upper immersion container 51 is positioned at the upper end of the movable range in step S510.

[0129] <Third Embodiment> (Configuration of the Recovery Device) Next, a third embodiment will be described. Note that components common to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description thereof may be omitted. FIG. 10 is a diagram showing the configuration of a recovery device 10c according to the third embodiment. As shown in FIG. 10, the recovery device 10c according to the third embodiment includes an upper gas-liquid contact part lifting mechanism 73 and a lower gas-liquid contact part lifting mechanism 74. FIGS. 11A and 11B are cross-sectional views showing the configuration and operation of the upper gas-liquid contact part lifting mechanism 73. Note that since the lower gas-liquid contact part lifting mechanism 74 has the same configuration as that of the upper gas-liquid contact part lifting mechanism 73, illustration thereof is omitted.

[0130] (Configuration of Absorption Tower and Rotating Body) The rotating body 46c according to the third embodiment includes a rotating shaft 60 in which the outer shaft part 611 of the upper shaft part 61, the outer shaft part 641 of the intermediate shaft part 64, and the lower shaft part 67 are integrally connected in the axial direction. A solution chamber 614 is provided at the lower end of the upper shaft part 61, and the lower end of the inner shaft part 612 of the upper shaft part 61 is located inside this solution chamber 614. Further, a solution passage hole 615 that communicates the inside of the solution chamber 614 with the outside of the outer shaft part 611 is provided in the outer shaft part 611 of the upper shaft part 61. In this way, the rotating shaft 60 is configured such that the solution fed through the inner shaft part 612 of the upper shaft part 61 flows into the solution chamber 614 and further flows out to the outside through the solution passage hole 615. Further, a target gas passage hole 613 that communicates the outside of the outer shaft part 611 with the internal space is provided above the solution chamber 614 in the outer shaft part 611 of the upper shaft part 61. Although not shown, a solution passage hole 643 that communicates the solution chamber 614 with the inside of this solution chamber 614 and the outside of the outer shaft part 641 is also provided at the lower end of the outer shaft part 641 of the intermediate shaft part 64, and an upstream target gas passage hole 644 (see FIG. 2) that communicates with the outside of the outer shaft part 641 above the solution chamber 614 is provided.

[0131] Further, the gas-liquid contact portions 63, 66 of each stage and the gas-liquid separation portions 62, 65 of each stage are attached to the rotating shaft 60 via cylindrical members of each stage (hereinafter referred to as the sleeve members 68 of each stage). Solution passage holes 681 are provided in the sleeve members 68 of each stage to communicate the gas-liquid contact portions 63, 66 of each stage with the inner peripheral side of the sleeve members 68 in the vicinity of the upper end portions of the gas-liquid contact portions 63, 66 of each stage. Further, target gas passage holes 682 are provided in the sleeve members 68 of each stage above the solution passage holes 681 to communicate the gas-liquid separation portions 62, 65 of each stage with the inner peripheral side of the sleeve members 68.

[0132] The gas-liquid contact portions 63, 66 of each stage and the gas-liquid separation portions 62, 65 of each stage rotate integrally with the rotating shaft 60 together with the sleeve members 68 of each stage and are movable integrally in the vertical direction with respect to the rotating shaft 60 together with the sleeve members 68 of each stage. Then, as shown in FIG. 11A, when the upper sleeve member 68 is located at the upper end of the vertical movement range, the target gas passage hole 682 provided in the sleeve member 68 communicates with the target gas passage hole 613 provided in the upper shaft portion 61, and the solution passage hole 681 provided in the upper sleeve member 68 communicates with the solution passage hole 615 provided in the upper shaft portion 61. Similarly, when the lower sleeve member 68 is located at the upper end of the vertical movement range, the target gas passage hole 682 provided in the lower sleeve member 68 communicates with the upstream target gas passage hole 644 provided in the intermediate shaft portion 64, and the solution passage hole 681 provided in the lower sleeve member 68 communicates with the solution passage hole 615 provided in the intermediate shaft portion 64.

[0133] Further, as shown in FIG. 11B, when the upper sleeve member 68 is located at the lower end of the vertical movement range, the target gas passage hole 682 provided in the upper sleeve member 68 and the target gas passage hole 613 provided in the upper shaft portion 61 do not communicate, and the solution passage hole 681 provided in the lower sleeve member 68 and the solution passage hole 615 provided in the upper shaft portion 61 are configured not to communicate. Similarly, when the lower sleeve member 68 is located at the lower end of the vertical movement range, the target gas passage hole 682 provided in the lower sleeve member 68 and the upstream target gas passage hole 644 provided in the intermediate shaft portion 64 do not communicate, and the solution passage hole 681 provided in the lower sleeve member 68 and the solution passage hole 615 provided in the intermediate shaft portion 64 are configured not to communicate.

[0134] According to such a configuration, when the upper gas-liquid contact portion 63, the upper gas-liquid separation portion 62, and the upper sleeve member 68 are located at the upper end of the movement range, the solution supplied through the inner shaft portion 612 of the upper shaft portion 61 flows into the upper gas-liquid contact portion 63 through the solution chamber 614 of the upper shaft portion 61, the solution passage hole 615 of the upper shaft portion 61, and the solution passage hole 681 of the upper sleeve member 68. Similarly, when the lower gas-liquid contact portion 66, the lower gas-liquid separation portion 65, and the lower sleeve member 68 are located at the upper end of the movement range, the solution supplied through the inner shaft portion 642 of the intermediate shaft portion 64 flows into the lower gas-liquid contact portion 66 through the solution chamber 614 of the intermediate shaft portion 64, the solution passage hole 643 of the intermediate shaft portion 64, and the solution passage hole 681 of the lower sleeve member 68.

[0135] On the other hand, when the upper gas-liquid contact portion 63, the upper gas-liquid separation portion 62, and the upper sleeve member 68 are located at the lower end of the movement range, the solution supplied through the inner shaft portion 612 of the upper shaft portion 61 flows into the interior of the upper absorption chamber 42 through the solution chamber 614 and the solution passage hole 615 of the upper shaft portion 61. Similarly, when the lower gas-liquid contact portion 66, the lower gas-liquid separation portion 65, and the lower sleeve member 68 are located at the lower end of the movement range, the solution supplied through the inner shaft portion 642 of the intermediate shaft portion 64 flows into the interior of the lower absorption chamber 45 through the solution chamber 614 and the solution passage hole 615 of the intermediate shaft portion 64.

[0136] The gas-liquid contact parts 63, 66 of each stage, the gas-liquid separation parts 62, 65 of each stage, and the sleeve members 68 of each stage can move vertically inside the absorption chambers 42, 45 of each stage by the gas-liquid contact part lifting mechanisms 73, 74 of each stage. A ball screw mechanism 731 is applied to the gas-liquid contact part lifting mechanisms 73, 74 of each stage. Specifically, the gas-liquid contact part lifting mechanisms 73, 74 of each stage include a screw shaft 732 of the ball screw mechanism 731 that is rotatably arranged inside the absorption chambers 42, 45 of each stage with its axis in a direction substantially parallel to the vertical direction (a direction substantially parallel to the axis of the rotating body 46c), a ball nut 733 of the ball screw mechanism 731 attached to the sleeve member 68 of each stage, and a gas-liquid contact part driving power source 734 of each stage that rotates the screw shaft 732 of the ball screw mechanism 731. The gas-liquid contact part driving power source 734 of each stage is controlled by the control device 22. Note that the configuration of the gas-liquid contact part driving power source 734 of each stage is not particularly limited, and various known electric motors can be applied.

[0137] The upper-stage upper liquid level sensor 421 is configured to be able to detect whether the liquid level height of the solution stored in the upper-stage absorption chamber 42 is equal to or higher than a predetermined height. Similarly, the lower-stage upper liquid level sensor 451 is configured to be able to detect whether the liquid level height of the solution stored in the lower-stage absorption chamber 45 is equal to or higher than a predetermined height. These predetermined heights in the third embodiment are "the height at which the entire gas-liquid contact parts 63, 66 of each stage can be immersed when the gas-liquid contact parts 63, 66 of each stage, the gas-liquid separation parts 62, 65 of each stage, and the sleeve members 68 of each stage are located at the lower end of the movable range". The upper-stage upper liquid level sensor 421 and the lower-stage upper liquid level sensor 451 are configured to be in the ON state when the liquid level height is equal to or higher than the predetermined height and in the OFF state when the liquid level height is less than the predetermined height. And the control device 22 can continuously acquire the states of the upper-stage upper liquid level sensor 421 and the lower-stage upper liquid level sensor 451 in real time.

[0138] (Normal operation) During normal operation, the recovery device 10c according to the third embodiment positions the gas-liquid contact parts 63, 66 of each stage, the gas-liquid separation parts 62, 65 of each stage, and the sleeve members 68 of each stage at the upper end of the movable range. Otherwise, it is the same as the normal operation of the first embodiment.

[0139] (Solution infiltration operation) In the solution infiltration operation, the control device 22 first controls the gas-liquid contact part lifting mechanisms 73, 74 of each stage to move the gas-liquid contact parts 63, 66 of each stage, the gas-liquid separation parts 62, 65 of each stage, and the sleeve members 68 of each stage to the lower end. The subsequent operations are the same as the solution infiltration operation of the first embodiment.

[0140] (Discharge operation) In the discharge operation, the control device 22 first moves the gas-liquid contact parts 63, 66 of each stage, the gas-liquid separation parts 62, 65 of each stage, and the sleeve members 68 of each stage to the upper end. The subsequent operations are the same as the discharge operation of the first embodiment.

[0141] (Processing executed by the control device) FIG. 12, FIGS. 13A and 13B are flowcharts showing the processing executed by the computer of the control device 22. Note that FIG. 12 is a flowchart showing the processing for executing the solution infiltration operation, and FIGS. 13A and 13B are flowcharts showing the processing for executing the discharge operation.

[0142] The processing for executing the solution infiltration operation is as follows. In step S601, the CPU of the computer of the control device 22 moves the gas-liquid contact parts 63, 66 of each stage, the gas-liquid separation parts 62, 65 of each stage, and the sleeve members 68 of each stage to the lower end of the movable range. Then, the CPU proceeds with the processing to step S602. Steps S602 to S611 are the same as steps S101 to S110 of the first embodiment (see FIG. 3).

[0143] The process for performing the discharge operation is as follows. In step S701, the CPU of the computer of the control device 22 moves the gas-liquid contact parts 63, 66 of each stage, the gas-liquid separation parts 62, 65 of each stage, and the sleeve members 68 of each stage to the upper end of the movable range. Then, the CPU proceeds with the process to step S702. Steps S702 to S714 are the same as steps S201 to S213 of the first embodiment (see FIGS. 4A and 4B).

[0144] According to these processes, the solution penetration operation and the discharge operation of the recovery device 10c according to the third embodiment are realized.

[0145] <Modification Example> Next, the absorption tower 11d according to the modification example will be described. FIG. 14 is a cross-sectional view showing the configuration of the absorption tower 11d according to the modification example. In each of the above embodiments, the gas-liquid contact parts 63, 66 of each stage are immersed in the solution as the solution penetration operation, but the solution penetration operation is not limited to such an operation. The absorption tower 11d according to the modification example is configured to allow the solution to penetrate without immersing the gas-liquid contact parts 63, 66 of each stage in the solution as the solution penetration operation.

[0146] As shown in FIG. 14, the inner shaft part 612 of the upper shaft part 61 of the rotating body 46d is housed in the outer shaft part 611 of the upper shaft part 61 and inside the upper-stage gas-liquid contact part 63 so as to be reciprocally movable in the vertical direction. The absorption tower 11d is provided with an upper-stage inner shaft part elevating mechanism 75 capable of reciprocally moving the inner shaft part 612 of the upper shaft part 61 in the vertical direction. Note that the specific configuration of the upper-stage inner shaft part elevating mechanism 75 is not particularly limited, and a combination of an electric motor that outputs rotational power and a mechanism that converts the rotational power output by the motor into linear reciprocating motion, or various linear actuators can be applied.

[0147] The lower end of the inner shaft portion 612 of the upper shaft portion 61 is closed, and a solution ejection hole 616 that communicates the inside and outside of the inner shaft portion 612 is provided on the side surface of the lower end portion of the inner shaft portion 612. For this reason, the solution supplied to the inner shaft portion 612 of the upper shaft portion 61 by the operation of the second solution pump 21 ejects from the solution ejection hole 616 toward the outside in the radial direction of the inner shaft portion 612. When the inner shaft portion 612 is located at the upper end of the movable range, the solution ejection hole 616 is located near the upper end portion of the upper gas-liquid contact portion 63, and when the inner shaft portion 612 is located at the lower end of the movable range, the solution ejection hole 616 is configured to be located near the lower end portion of the upper gas-liquid contact portion 63.

[0148] In normal operation, the control device 22 holds the inner shaft portion 612 in a state where it is located at the upper end of the movable range. For this reason, the solution ejected from the solution ejection hole 616 of the inner shaft portion 612 flows into the upper gas-liquid contact portion 63 from near the upper end of the rotation center of the upper gas-liquid contact portion 63. Then, the solution that has flowed into the upper gas-liquid contact portion 63 diffuses and penetrates toward the outside in the radial direction and downward of the upper gas-liquid contact portion 63 due to the centrifugal force and gravity of the rotation of the rotating body 46d.

[0149] On the other hand, in the solution penetration operation, the control device 22 operates the first solution pump 19, the second solution pump 21, and the intermediate solution pump 49. In addition, the control device 22 operates the upper inner shaft lifting mechanism 75 to reciprocate the inner shaft portion 612 of the upper shaft portion 61 in the vertical direction a predetermined number of times. Thereby, the solution can be penetrated and diffused over substantially the entire upper gas-liquid contact portion 63.

[0150] Although illustration and description are omitted, the inner shaft portion 642 of the intermediate shaft portion 64 also has the same configuration as described above. The absorption tower 11d includes a lower inner shaft lifting mechanism that can reciprocate the inner shaft portion 642 of the intermediate shaft portion 64 in the vertical direction. The control device 22 controls the lower inner shaft lifting mechanism in the same manner as the upper inner shaft lifting mechanism 75 described above.

[0151] <Regarding the execution timing of the solution penetration operation and the discharge operation> As described above, before the start (resumption) of the normal operation, the control device 22 executes the solution penetration operation and the discharge operation, thereby preventing or suppressing a decrease in the carbon dioxide absorption efficiency at the start of the normal operation. Note that after the execution of the solution penetration operation and the discharge operation, the solution infiltrated into the gas-liquid contact portions 63 and 66 of each stage may decrease over time. For this reason, it is preferable that the control device 22 promptly starts the normal operation after the execution of the solution penetration operation and the discharge operation. In other words, the execution timing of the solution penetration operation and the discharge operation (or the completion timing of the discharge operation) is preferably within a predetermined time before the start timing of the normal operation.

[0152] For example, this predetermined time can be set to be shorter than the time when the amount of the solution infiltrated into the gas-liquid contact portions 63 and 66 of each stage in the solution penetration operation (the solution held by the gas-liquid contact portions 63 and 66 of each stage) becomes less than a predetermined amount. Alternatively, this predetermined time can be set to be shorter than the time when the ratio of "the amount of the solution held by the gas-liquid contact portions 63 and 66 of each stage (the amount of the solution remaining in the gas-liquid contact portions 63 and 66 of each stage without flowing down, etc.)" to "the amount of the solution infiltrated into the gas-liquid contact portions 63 and 66 of each stage in the solution penetration operation" becomes less than a predetermined value. In this case, this predetermined time can be defined by experiments, simulations, or the like.

[0153] In addition, the carbon dioxide absorption efficiency during normal operation varies according to "the amount of the solution held by the gas-liquid contact portions 63, 66 of each stage" or "the ratio indicating the amount actually held with respect to the maximum amount that can be held". Therefore, in advance, the relationship between the amount of the solution or the ratio and the carbon dioxide absorption efficiency, and the change over time of the amount of the solution or the ratio after the execution of the solution penetration operation and the discharge operation are obtained by experiments or the like. Further, from these relationships, the change over time of the carbon dioxide absorption efficiency after the execution of the solution penetration operation and the discharge operation is clarified. And a configuration can be applied in which the predetermined time is set to be shorter than "the time when the carbon dioxide absorption efficiency becomes less than a predetermined threshold value". In this case, the predetermined threshold value can be the target value of the carbon dioxide absorption efficiency during normal operation. However, the predetermined threshold value is not particularly limited and can be set as appropriate.

[0154] <Summary of Embodiments> The carbon dioxide recovery apparatuses 10a, 10b, 10c according to each embodiment are carbon dioxide recovery apparatuses 10a, 10b, 10c configured to recover carbon dioxide from the gas (target gas) by absorbing the carbon dioxide contained in the gas (target gas) generated in the gas source (target gas source 90) into a carbon dioxide absorption solution, carbon dioxide absorption towers 11a, 11b, 11c provided with carbon dioxide absorption chambers (absorption chambers 42, 45 of each stage) inside, rotating bodies 46a, 46b, 46c rotatably arranged inside the carbon dioxide absorption chambers (absorption chambers 42, 45 of each stage) and provided with gas-liquid contact portions (gas-liquid contact portions 63, 66 of each stage) configured such that the gas (target gas) can pass through and the carbon dioxide absorption solution can penetrate, carbon dioxide absorption solution supply portions (second solution pump 21, intermediate solution pump 49) configured to supply the carbon dioxide absorption solution to the carbon dioxide absorption chambers (absorption chambers 42, 45 of each stage), By controlling the carbon dioxide absorption solution supply unit (second solution pump 21, intermediate solution pump 49) and supplying it to the carbon dioxide absorption chamber (absorption chambers 42, 45 of each stage), a control device 22 is configured to execute a carbon dioxide absorption operation (normal operation) in which carbon dioxide contained in the gas (target gas) supplied from the gas source (target gas source 90) is absorbed by the carbon dioxide absorption solution. and includes Before the start of the carbon dioxide absorption operation (normal operation), the control device 22 executes a solution penetration operation of permeating the carbon dioxide absorption solution into the gas-liquid contact part (gas-liquid contact parts 63, 66 of each stage) by immersing the gas-liquid contact part (gas-liquid contact parts 63, 66 of each stage) in the carbon dioxide absorption solution.

[0155] By the control device 22 of the carbon dioxide recovery apparatuses 10a, 10b, 10c according to each embodiment executing the solution penetration operation of immersing the gas-liquid contact parts 63, 66 of each stage in the carbon dioxide absorption solution, the carbon dioxide absorption solution can be permeated (diffused) throughout the inside of the gas-liquid contact parts 63, 66 of each stage. And the control device 22 can prevent or suppress a decrease in the carbon dioxide absorption efficiency at the start point of the carbon dioxide absorption operation (normal operation) by executing the solution penetration operation before the start of the carbon dioxide absorption operation (normal operation: an operation of recovering carbon dioxide from the target gas).

[0156] The solution penetration operation includes an operation of supplying the carbon dioxide absorption solution to the carbon dioxide absorption chamber (absorption chambers 42, 45 of each stage) so that the entire gas-liquid contact part (gas-liquid contact parts 63, 66 of each stage) is immersed to a liquid level height.

[0157] The recovery apparatus 10b according to the second embodiment configured to be insertable into the gas-liquid contact part (gas-liquid contact parts 63, 66 of each stage) from above, and arranged to be movable in the carbon dioxide absorption chamber (absorption chambers 42, 45 of each stage) in the vertical direction between a first position (the upper end position of the movable range) and a second position (the lower end of the movable range or a position near it) below the first position. When located at the first position (the upper end position of the movable range), it can accommodate the gas-liquid contact part (gas-liquid contact parts 63, 66 of each stage) inside and store the carbon dioxide absorption solution. When located at the second position (the lower end of the movable range or near it), it is located below the gas-liquid contact part (gas-liquid contact parts 63, 66 of each stage) and is configured so that the carbon dioxide absorption solution does not accumulate, and an immersion container (immersion containers 51, 52 of each stage); a container lifting mechanism (immersion container lifting mechanisms 71, 72 of each stage) configured to move the immersion container (immersion containers 51, 52 of each stage) between the first position (the upper end of the movable range) and the second position (the lower end of the movable range or a position near it) under the control of the control device 22; The solution penetration operation includes an operation of storing the carbon dioxide absorption solution in the container (immersion containers 51, 52 of each stage) in a state where the container (immersion containers 51, 52 of each stage) is located at the first position (the upper end position of the movable range).

[0158] An opening (solution discharge port 511) through which the carbon dioxide absorption solution can flow is provided at the bottom of the container (immersion containers 51, 52 of each stage); When the container (immersion containers 51, 52 of each stage) is located at the first position, the opening (solution discharge port 511) is blocked by the gas-liquid contact part (gas-liquid contact parts 63, 66 of each stage), enabling the storage of the carbon dioxide absorption solution. When located at the second position, the gas-liquid contact part (gas-liquid contact parts 63, 66 of each stage) is separated from the bottom, and the carbon dioxide absorption solution present inside the container (immersion containers 51, 52 of each stage) is configured to flow down through the opening (solution discharge port 511).

[0159] The carbon dioxide recovery device 10c according to the third embodiment is It is provided with a gas-liquid contact part lifting mechanism (gas-liquid contact part lifting mechanisms 73 and 74 for each stage) capable of moving the gas-liquid contact parts (gas-liquid contact parts 63 and 66 for each stage) in the vertical direction. The solution penetration operation includes an operation of supplying the carbon dioxide absorption solution to the carbon dioxide absorption chambers (absorption chambers 42 and 45 for each stage) to store the carbon dioxide absorption solution in the lower part of the carbon dioxide absorption chambers (absorption chambers 42 and 45 for each stage), and an operation of lowering the gas-liquid contact parts (gas-liquid contact parts 63 and 66 for each stage) to immerse the entire gas-liquid contact parts (absorption chambers 42 and 45 for each stage) in the carbon dioxide absorption solution stored in the lower part of the carbon dioxide absorption chambers (absorption chambers 42 and 45 for each stage).

[0160] According to these configurations, since the entire gas-liquid contact parts 63 and 66 for each stage can be immersed in the solution, the solution can penetrate the entire gas-liquid contact parts 63 and 66 for each stage. In other words, a solution film can be formed on the entire gas-liquid contact parts 63 and 66 for each stage. Therefore, the effect of preventing or suppressing the decrease in the carbon dioxide absorption efficiency at the start of the carbon dioxide absorption operation (normal operation) can be enhanced.

[0161] The carbon dioxide absorption towers 11a, 11b, and 11c of the carbon dioxide recovery apparatuses 10a, 10b, and 10c according to the embodiments include a plurality of the carbon dioxide absorption chambers (absorption chambers 42 and 45 for each stage), and the gas (target gas) fed from the gas source (target gas source 90) passes through the plurality of the carbon dioxide absorption chambers (absorption chambers 42 and 45 for each stage) in one direction, and the carbon dioxide absorption solution passes through the plurality of the carbon dioxide absorption chambers (absorption chambers 42 and 45 for each stage) in a direction opposite to the one direction and contacts the gas in each of the plurality of the carbon dioxide absorption chambers (absorption chambers 42 and 45 for each stage) to absorb the carbon dioxide contained in the gas. The plurality of the carbon dioxide absorption chambers (absorption chambers 42 and 45 for each stage) are connected in series with each other in a multi-stage manner. In the solution penetration operation, the control device 22 stores the carbon dioxide absorption solution in order from the carbon dioxide absorption chamber (the lower absorption chamber 45) located on the most downstream side in the one direction toward the carbon dioxide absorption chamber (the upper absorption chamber 42) on the upstream side in the one direction.

[0162] According to such a configuration, compared with the configuration in which the carbon dioxide absorption solution is stored in order from the carbon dioxide absorption chamber (the upper absorption chamber 42) located on the most upstream side in the one direction toward the carbon dioxide absorption chamber (the lower absorption chamber 45) on the downstream side in the one direction, the time required for supplying the carbon dioxide absorption solution can be shortened. That is, when supplying the carbon dioxide absorption solution to a certain absorption chamber (the lower absorption chamber 45), the gas (the remaining target gas) existing inside the certain absorption chamber (the lower absorption chamber 45) must be discharged. On the other hand, the carbon dioxide absorption towers (absorption towers 11a, 11b, 11c) are configured such that the gas (the remaining target gas) existing inside a certain absorption chamber (the lower absorption chamber 45) is discharged to the outside of the carbon dioxide absorption towers (absorption towers 11a, 11b, 11c) via the absorption chamber (the upper absorption chamber 42) located on the upstream side of the flow of the carbon dioxide absorption solution. For this reason, when supplying the solution to the certain absorption chamber (the lower absorption chamber 45), if the inside of the absorption chamber (the upper absorption chamber 42) on its upstream side is already filled with the solution, the passage of the gas (the remaining target gas) through the upper absorption chamber 42 of the solution is inhibited. Therefore, it takes time to discharge the gas (the remaining target gas) existing inside the certain absorption chamber (the lower absorption chamber 45). In contrast, if the supply of the solution to the certain absorption chamber (the lower absorption chamber 45) is prioritized (when the supply of the solution to the certain absorption chamber (the lower absorption chamber 45) is carried out in a state where the solution is not accumulated inside the absorption chamber (the upper absorption chamber 42) on the upstream side of the certain absorption chamber), the discharge of the gas accumulated inside the certain absorption chamber (the lower absorption chamber 45) is not inhibited by the solution in the absorption chamber (the upper absorption chamber 42) on the upstream side, so the time required for supplying the solution can be shortened.

[0163] As described above, the embodiments of the present invention and their modifications have been explained. However, the technical scope of the present invention is not limited to the above embodiments and modifications. The present invention can be variously modified without departing from its gist, and these are also included in the technical scope of the present invention.

[0164] For example, in the above embodiment, an example in which the absorption tower is a two-stage type has been shown. However, the number of stages of the absorption tower (the number of absorption chambers) is not limited to two stages. For example, the absorption tower may be a single-stage type, or may be a three-stage type or more.

Explanation of Reference Numerals

[0165] 10a, 10b, 10c... Carbon dioxide recovery device, 11a, 11b, 11c, 11d... Carbon dioxide absorption tower, 13... Target gas introduction path, 14... Target gas pump, 15... Target gas inlet valve, 16... Target gas discharge path, 17... First solution path, 19... First solution pump, 20... Second solution path, 21... Second solution pump, 22... Control device, 42... Upper absorption chamber, 45... Lower absorption chamber, 46a, 46b, 46c, 46d... Rotating body, 51... Upper immersion container, 52... Lower immersion container, 63... Upper gas-liquid contact part, 66... Lower gas-liquid contact part, 71... Upper immersion container lifting mechanism, 72... Lower immersion container lifting mechanism, 73... Upper gas-liquid contact part lifting mechanism, 74... Lower gas-liquid contact part lifting mechanism, 90... Target gas source

Claims

1. A carbon dioxide recovery device configured to recover carbon dioxide from a gas by absorbing carbon dioxide contained in the gas generated at a gas source into a carbon dioxide absorption solution, a carbon dioxide absorption tower provided with a carbon dioxide absorption chamber inside, a rotating body rotatably arranged inside the carbon dioxide absorption chamber, provided with a gas-liquid contact part configured such that the gas can pass through and the carbon dioxide absorption solution can penetrate, a carbon dioxide absorption solution supply part configured to supply the carbon dioxide absorption solution to the carbon dioxide absorption chamber, a control device configured to execute a carbon dioxide absorption operation of absorbing carbon dioxide contained in the gas supplied from the gas source to the carbon dioxide absorption chamber into the carbon dioxide absorption solution by controlling the carbon dioxide absorption solution supply part to supply the carbon dioxide absorption solution to the carbon dioxide absorption chamber, comprising: The control device executes a solution penetration operation of causing the carbon dioxide absorption solution to penetrate into the gas-liquid contact part by immersing the gas-liquid contact part in the carbon dioxide absorption solution before the start of the carbon dioxide absorption operation. A carbon dioxide recovery device.

2. The carbon dioxide recovery device according to claim 1, wherein the solution penetration operation includes an operation of supplying the carbon dioxide absorption solution to the carbon dioxide absorption chamber so that the entire gas-liquid contact part is immersed. A carbon dioxide recovery device.

3. The carbon dioxide recovery device according to claim 1, a container configured to be insertable and removable from above the gas-liquid contact part, and movable between a first position and a second position below the first position by moving the carbon dioxide absorption chamber in the vertical direction. When located at the first position, the gas-liquid contact part is accommodated inside and the carbon dioxide absorption solution can be stored. When located at the second position, it is located below the gas-liquid contact part and is configured such that the carbon dioxide absorption solution is not stored, A container lifting mechanism configured to move the container between the first position and the second position under the control of the control device. The solution penetration operation includes an operation of storing the carbon dioxide absorption solution in the container while the container is in the first position. A carbon dioxide recovery device.

4. The carbon dioxide recovery device according to claim 3, An opening through which the carbon dioxide absorption solution can flow is provided at the bottom of the container. The container is capable of storing the carbon dioxide absorption solution when the opening is blocked by the gas-liquid contact part while the container is in the first position, and when the container is in the second position, the gas-liquid contact part is separated from the bottom so that the carbon dioxide absorption solution existing inside the container flows down through the opening. A carbon dioxide recovery device.

5. The carbon dioxide recovery device according to claim 1, It is provided with a gas-liquid contact part lifting mechanism capable of moving the gas-liquid contact part in the vertical direction. The solution penetration operation includes an operation of supplying the carbon dioxide absorption solution to the carbon dioxide absorption chamber to store the carbon dioxide absorption solution at the lower part of the carbon dioxide absorption chamber, and an operation of lowering the gas-liquid contact part to immerse the entire gas-liquid contact part in the carbon dioxide absorption solution stored at the lower part of the carbon dioxide absorption chamber. A carbon dioxide recovery device.

6. The carbon dioxide recovery device according to any one of claims 1 to 5, The carbon dioxide absorption tower includes a plurality of the carbon dioxide absorption chambers, the gas supplied from the gas source passes through the plurality of carbon dioxide absorption chambers in one direction, and the carbon dioxide absorption solution passes through the plurality of carbon dioxide absorption chambers in a direction opposite to the one direction and contacts the gas in each of the plurality of carbon dioxide absorption chambers to absorb carbon dioxide contained in the gas. The plurality of carbon dioxide absorption chambers are connected in series in a multi-stage manner. The control device is a carbon dioxide recovery device that stores the carbon dioxide absorption solution in order from the carbon dioxide absorption chamber located on the most downstream side in the one direction toward the carbon dioxide absorption chamber on the upstream side in the one direction during the solution penetration operation.

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