Carbon dioxide recovery device and carbon dioxide recovery method

Abstract

To provide a carbon dioxide recovery device capable of dehumidifying gas to be separated with saved energy.SOLUTION: A carbon dioxide recovery device 1 comprises a separation device 2 that separates carbon dioxide from ambient air, and a first supply line L11 that supplies the ambient air to the separation device 2. The device further comprises a dehumidifying device 3 that dehumidifies the ambient air using a dehumidifying agent on the first supply line L11, and a second supply line L12 that supplies the separated gas after carbon dioxide has been separated from the ambient air from the separation device 2 to the dehumidifying device 3. The dehumidifying device 3 regenerates the dehumidifying agent using the separated gas supplied from the second supply line L12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide recovery device comprising a separation device that separates carbon dioxide from a gas to be separated and a first supply line for supplying the gas to be separated to the separation device, and a carbon dioxide recovery method that recovers carbon dioxide by separating carbon dioxide from the gas to be separated. [Background technology]

[0002] In recent years, carbon dioxide has become a problem as a greenhouse gas that has a large impact on global warming. Demand for carbon dioxide is also increasing, for example, for dry ice used in logistics. Against this backdrop, there is a demand for technology to separate and capture carbon dioxide from gases containing carbon dioxide, such as combustion exhaust gas, and the atmosphere (hereinafter referred to as "gas to be separated").

[0003] Known examples of separation devices that separate carbon dioxide from a gas to be separated include a separation device disclosed in Patent Document 1. This separation device includes an absorption tower that absorbs carbon dioxide into an absorbing liquid by bringing the gas to be separated into gas-liquid contact with the absorbing liquid, and a regeneration tower that regenerates the absorbing liquid that has absorbed carbon dioxide and releases the carbon dioxide. The release of carbon dioxide in the regeneration tower is achieved by heating or depressurizing, or heating and depressurizing, the absorbing liquid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-270814 [Patent Document 2] Japanese Patent Application Publication No. 2023-145852 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional techniques have the following problems. For example, when carbon dioxide is separated from a moisture-containing gas (such as atmospheric air or combustion exhaust gas) in an absorption tower, when the gas comes into gas-liquid contact with a hydrophilic absorbing liquid in an absorption tower, not only the carbon dioxide in the gas but also the moisture in the gas is absorbed by the absorbing liquid. Therefore, when the absorbing liquid that has absorbed the gas and still contains moisture is heated or depressurized in a regeneration tower, not only the absorbed carbon dioxide is released from the absorbing liquid but also the moisture evaporates. This moisture evaporation removes heat from the absorbing liquid in the regeneration tower, which may cause the temperature to drop below the release temperature required for carbon dioxide release. To prevent this, heat equivalent to the latent heat of water evaporation must be added, which increases the energy load. Therefore, the present inventors have considered the dehumidification of the gas before separating carbon dioxide from it in a separation device.

[0006] However, when the carbon dioxide concentration of the gas to be separated is low (especially when the gas to be separated is atmospheric air), a large amount of gas to be separated is required per unit amount of carbon dioxide recovered. Therefore, a large amount of energy is required to dehumidify a large amount of gas to be separated, raising concerns about increased electricity costs and the generation of new carbon dioxide for power generation. Note that dehumidification of the gas to be separated is effective not only for chemical absorption carbon dioxide capture devices such as those in Patent Document 1, but also for adsorption, membrane separation, and cryogenic separation carbon dioxide capture devices. For example, Patent Document 2 discloses a pretreatment device in the upstream stage of an adsorption carbon dioxide separation device to remove moisture. Furthermore, these carbon dioxide capture devices also have the same problem of requiring a large amount of dehumidification energy when the carbon dioxide concentration of the gas to be separated is low.

[0007] The present invention has been made to solve the above problems, and has an object to provide a carbon dioxide recovery apparatus and a carbon dioxide recovery method that can dehumidify a gas to be separated with more energy savings. [Means for solving the problem]

[0008] In order to solve the above problems, the carbon dioxide recovery device of the present invention has the following configuration.

[0009] (1) A carbon dioxide recovery device comprising a separation device that separates carbon dioxide from a gas to be separated and a first supply line for supplying the gas to be separated to the separation device, characterized in that a dehumidifier that dehumidifies the gas to be separated using a dehumidifying agent is provided on the first supply line, a second supply line that supplies the separated gas after carbon dioxide has been separated from the gas to the dehumidifier from the separation device, and the dehumidifier regenerates the dehumidifier using the separated gas supplied from the second supply line.

[0010] (2) In the carbon dioxide recovery device described in (1), it is preferable that the relative humidity of the separated gas in the second supply line is lower than the relative humidity of the separated gas in the first supply line downstream of the dehumidifier.

[0011] (3) In the carbon dioxide recovery device described in (1) or (2), the dehumidifying agent is preferably an adsorption type dehumidifying agent that adsorbs moisture from the gas to be separated.

[0012] (4) In the carbon dioxide recovery device described in (3), it is preferable that the dehumidifier comprises a first air duct on the first supply line through which the gas to be separated passes, a second air duct connected to the second supply line through which the separated gas passes, and a desiccant rotor as the dehumidifier, arranged across the first air duct and the second air duct.

[0013] (5) In the carbon dioxide recovery device described in (3), it is preferable that the dehumidifier has a first dehumidification unit and a second dehumidification unit arranged in parallel for performing the dehumidification, and is switchable between a first state in which the dehumidification is performed by the first dehumidification unit and the regeneration is performed by the second dehumidification unit, and a second state in which the regeneration is performed by the first dehumidification unit and the dehumidification is performed by the second dehumidification unit.

[0014] (6) In the carbon dioxide recovery device described in (1) or (2), the dehumidifying agent is preferably an absorbing liquid that absorbs moisture from the gas to be separated.

[0015] (7) In the carbon dioxide recovery system described in (6), it is preferable that the dehumidifier includes an absorption tower that brings the gas to be separated, supplied from the first supply line, into gas-liquid contact with the dehumidifying agent to cause the dehumidifying agent to absorb moisture, and a regeneration tower that performs the regeneration using the separated gas, supplied from the second supply line.

[0016] (8) In the carbon dioxide recovery system described in any one of (1) to (7), it is preferable that the separation device comprises a carbon dioxide absorption tower that brings the gas to be separated into gas-liquid contact with a carbon dioxide absorbing liquid that absorbs carbon dioxide, thereby causing the carbon dioxide to be absorbed by the carbon dioxide absorbing liquid, and an absorption liquid regeneration tower that regenerates the carbon dioxide absorbing liquid that has absorbed carbon dioxide, and releases carbon dioxide.

[0017] (9) In the carbon dioxide recovery device described in (8), it is preferable that the water content of the carbon dioxide absorbing solution is higher after absorbing carbon dioxide than before absorbing carbon dioxide.

[0018] (10) In the carbon dioxide recovery device described in (8) or (9), it is preferable that the carbon dioxide absorbing liquid is a non-aqueous absorbing liquid. Note that the non-aqueous absorbing liquid is one in which a substance other than water is used as a main solvent, and the main solvent is one that dissolves amines and the like and has the largest mass fraction in the absorbing liquid.

[0019] (11) In the carbon dioxide recovery system according to any one of (1) to (7), the separation device preferably contains a physical or chemical adsorbent for performing the separation.

[0020] (12) In the carbon dioxide recovery device described in any one of (1) to (7), it is preferable that the separation device is provided with a permeable membrane that selectively permeates carbon dioxide, and that the separation is performed by allowing the carbon dioxide contained in the gas to be separated that is supplied to the separation device to permeate through the permeable membrane.

[0021] (13) In the carbon dioxide recovery system according to any one of (1) to (7), it is preferable that the separation device performs the separation by cryogenic separation.

[0022] The carbon dioxide capture device described above is provided with a dehumidifier that dehumidifies the gas to be separated with a dehumidifying agent on the first supply line for supplying the gas to the separation device, so the gas to be separated is dehumidified with the dehumidifying agent before being supplied to the separation device. This makes it possible to reduce the amount of water vapor generated when separating carbon dioxide in the separation device, enabling efficient carbon dioxide capture.

[0023] Here, the gas to be separated is dehumidified by a dehumidifier before being supplied to a separation device, where it is further dehumidified. Therefore, the post-separation gas after carbon dioxide has been separated from the gas to be separated is a dehumidified, dry gas. Therefore, the above-mentioned carbon dioxide capture device is equipped with a second supply line that supplies the post-separation gas from the separation device to the dehumidifier, and the dehumidifier can regenerate the dehumidifying agent using the post-separation gas supplied from the second supply line. Since the gas to be separated is dehumidified using a dehumidifier and the dehumidifying agent is regenerated using the post-separation gas, it is possible to reduce the energy consumption required for dehumidification.

[0024] In order to solve the above problems, the carbon dioxide recovery method of the present invention has the following configuration.

[0025] (14) A carbon dioxide recovery method for recovering carbon dioxide by separating carbon dioxide from a gas to be separated, characterized in that the separation uses the gas to be separated that has been dehumidified with a dehumidifying agent, and the dehumidifying agent is regenerated using the gas after separation of carbon dioxide from the gas to be separated.

[0026] (15) In the carbon dioxide recovery method described in (14), the relative humidity of the separated gas before the regeneration is lower than the relative humidity of the separated gas after the dehumidification.

[0027] (16) In the carbon dioxide recovery method described in (14) or (15), the dehumidifying agent is preferably an adsorption type dehumidifying agent that adsorbs moisture from the gas to be separated.

[0028] (17) In the carbon dioxide recovery method described in (16), it is preferable to use a desiccant rotor as the dehumidifying agent.

[0029] (18) In the carbon dioxide recovery method described in (16), it is preferable that a first dehumidification unit and a second dehumidification unit for performing the dehumidification using the dehumidifying agent are provided in parallel, and when the dehumidification is performed in one of the first dehumidification unit and the second dehumidification unit, the regeneration is performed in the other.

[0030] (19) In the carbon dioxide recovery method described in (14) or (15), the dehumidifying agent is preferably an absorbing liquid that absorbs moisture from the gas to be separated.

[0031] (20) In the carbon dioxide recovery method described in (19), it is preferable that the dehumidification is performed by gas-liquid contact between the gas to be separated and the dehumidifying agent, and the regeneration is performed by gas-liquid contact between the separated gas and the dehumidifying agent that has absorbed moisture.

[0032] (21) In the carbon dioxide recovery method according to any one of (14) to (20), the separation is preferably carried out by bringing the gas to be separated into gas-liquid contact with a carbon dioxide absorbing liquid that absorbs carbon dioxide, causing the carbon dioxide to be absorbed into the carbon dioxide absorbing liquid, and regenerating the carbon dioxide absorbing liquid that has absorbed the carbon dioxide.

[0033] (22) In the carbon dioxide recovery method described in (21), it is preferable that the water content of the carbon dioxide absorbing solution is higher after absorbing carbon dioxide than before absorbing carbon dioxide.

[0034] (23) In the carbon dioxide recovery method according to (21) or (22), the carbon dioxide absorbing liquid is preferably a non-aqueous absorbing liquid. Note that the non-aqueous absorbing liquid is one in which a substance other than water is used as a main solvent, and the main solvent is one that dissolves amines and the like and has the largest mass fraction in the absorbing liquid.

[0035] (24) In the carbon dioxide recovery method according to any one of (14) to (20), the separation is preferably carried out using a physical adsorbent or a chemical adsorbent.

[0036] (25) In the carbon dioxide recovery method according to any one of (14) to (20), the separation is preferably carried out using a permeable membrane that selectively allows carbon dioxide to permeate.

[0037] (26) In the carbon dioxide recovery method according to any one of (14) to (20), the separation is preferably carried out by cryogenic separation.

[0038] According to the carbon dioxide capture method described above, carbon dioxide is separated using a gas to be separated that has been dehumidified with a dehumidifying agent. This makes it possible to suppress the amount of water vapor generated during carbon dioxide separation, enabling carbon dioxide to be captured efficiently.

[0039] Furthermore, since the gas to be separated has been dehumidified by a dehumidifying agent and is further dehumidified in the separation device, the separated gas after carbon dioxide is separated from the gas to be separated is a dehumidified, dry gas. Therefore, the above-described carbon dioxide recovery method can regenerate the dehumidifying agent using the separated gas. Since the gas to be separated is dehumidified using a dehumidifying agent and the regeneration of the dehumidifying agent is performed using the separated gas, it is possible to reduce the energy consumption required for dehumidification. [Effects of the Invention]

[0040] According to the carbon dioxide recovery device or carbon dioxide recovery method of the present invention, it is possible to dehumidify the gas to be separated with more energy savings. [Brief explanation of the drawings]

[0041] [Figure 1] 1 is a diagram schematically illustrating a configuration of a carbon dioxide capture device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating a schematic configuration of a carbon dioxide recovery device using a desiccant dehumidifier. [Figure 3] FIG. 1 is a diagram showing a schematic configuration of a carbon dioxide capture device using a chemical absorption separation device. [Figure 4] FIG. 1 is a diagram showing a schematic configuration of a carbon dioxide recovery device using a two-tower dehumidifier. [Figure 5] FIG. 1 is a diagram schematically illustrating the configuration of a carbon dioxide recovery device using a chemical absorption dehumidifier. [Figure 6] FIG. 1 is a diagram showing a schematic configuration of a carbon dioxide capture device using an adsorptive separation device. [Figure 7] FIG. 1 is a diagram showing a schematic configuration of a carbon dioxide capture device using a membrane separation type separation device. [Figure 8] FIG. 1 is a diagram showing a schematic configuration of a carbon dioxide capture device using a cryogenic separation type separation device. [Figure 9] FIG. 1 is a diagram showing the configuration of a desiccant dehumidifying device that regenerates a dehumidifying agent using atmospheric air. [Figure 10]FIG. 2 is a psychrometric chart showing the state of the gas to be separated and the gas after separation. DETAILED DESCRIPTION OF THE INVENTION

[0042] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a carbon dioxide capture device according to the present invention will be described in detail with reference to the drawings.

[0043] (Overview of carbon dioxide capture equipment) First, the schematic configuration of a carbon dioxide capture device 1 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram that schematically shows the configuration of the carbon dioxide capture device 1 according to this embodiment.

[0044] As shown in FIG. 1, the carbon dioxide capture device 1 includes a separation device 2, a dehumidification device 3, and a blower 4 as main components.

[0045] The separation device 2 is a device for separating carbon dioxide from a gas to be separated (details will be described later). In this embodiment, the gas to be separated is the atmosphere. A first supply line L11 is connected to the separation device 2. This first supply line L11 is a pipeline for supplying the gas to be separated to the separation device 2. This gas to be separated is supplied by a blower 4 disposed upstream of the first supply line L11. The blower 4 sends the atmosphere into the separation device 2 via the first supply line L11 by rotating a fan (not shown).

[0046] A dehumidifier 3 is disposed on the first supply line L11. The dehumidifier 3 is provided with a dehumidifying agent therein. The dehumidifying agent adsorbs or absorbs moisture from the gas to be separated passing through the first supply line L11. In this way, the dehumidifier 3 dehumidifies the gas to be separated (details will be described later). Therefore, the gas to be separated is dehumidified by the dehumidifier 3 before being supplied to the separation device 2. Note that the upstream side of the first supply line L11 from the dehumidifier 3 is referred to as the first supply line L111, and the downstream side of the dehumidifier 3 is referred to as the first supply line L116.

[0047] The separator 2 is further connected to a transfer pipe L14 and a second supply line L12.

[0048] The transfer pipe L14 is a pipeline for transferring the carbon dioxide separated from the gas to be separated in the separation device 2 to the outside of the separation device 2. The carbon dioxide transferred through the transfer pipe L14 may be used, for example, as carbon dioxide gas or may be sublimated (solidified) and used as dry ice. A device for sublimating (solidifying) carbon dioxide may be provided at the end of the transfer pipe L14.

[0049] The second supply line L12 is a pipeline for supplying the gas remaining after carbon dioxide is separated from the gas to be separated in the separator 2 (hereinafter referred to as post-separation gas) to the dehumidifier 3. This post-separation gas is a dehumidified, dry gas. This is because the gas to be separated, which has been dehumidified in the dehumidifier 3, is further dehumidified in the separator 2. By supplying this dry post-separation gas to the dehumidifier 3, the moisture adsorbed or absorbed from the gas to be separated by the dehumidifying agent in the dehumidifier 3 is contained in the post-separation gas. This makes it possible to regenerate the dehumidifying agent. The post-separation gas after being used to regenerate the dehumidifying agent is then discharged from the discharge path L13 connected to the dehumidifier 3.

[0050] (About dehumidifiers) The dehumidifier 3 will be described in more detail with reference to Fig. 2. Fig. 2 is a diagram showing a schematic configuration of a carbon dioxide recovery device 1 using a desiccant type dehumidifier 3A.

[0051] The dehumidifying agent used in the dehumidifying device 3 may be an adsorption type dehumidifying agent (adsorption type dehumidifying agent) that adsorbs moisture from the gas to be separated (air). As the dehumidifying device 3 that uses an adsorption type dehumidifying agent, for example, a desiccant type dehumidifying device 3A shown in Fig. 2 may be used. In the following description, the desiccant type dehumidifying device 3A will be simply referred to as the dehumidifying device 3A.

[0052] 2, the dehumidifier 3A mainly comprises a housing 41, a desiccant rotor 42, and a sensible heat exchange rotor 43. Note that the sensible heat exchange rotor 43 is not necessarily required in the dehumidifier 3A.

[0053] The interior of the housing 41 is divided by a partition wall 44 into a first air passage 411 and a second air passage 412. The first air passage 411 constitutes a part of the first supply line L11. Therefore, the gas to be separated flows through the first air passage 411 from the blower 4 side toward the separator 2 side. The second air passage 412 is connected to the second supply line L12 on the separator 2 side and is connected to the discharge passage L13 on the opposite side. Therefore, the separated gas flows through the second air passage 412 from the separator 2 side toward the opposite side.

[0054] The desiccant rotor 42 is formed into a cylindrical shape using, for example, a honeycomb-shaped adsorption element impregnated with an adsorption-type desiccant. Examples of the adsorption-type desiccant include silica gel, alumina gel, molecular sieve, zeolite, and activated carbon. The desiccant rotor 42 is disposed within the housing 41, straddling the first air passage 411 and the second air passage 412.

[0055] The desiccant rotor 42 is rotated continuously or intermittently around its axis in a predetermined direction (for example, the direction of arrow A11 in the figure) by a motor (not shown). When this rotation causes the portion of the desiccant rotor 42 that has adsorbed moisture from the gas to be separated in the first air passage 411 to enter the second air passage 412, it is regenerated by the separated gas passing through the second air passage 412.

[0056] The sensible heat exchange rotor 43 is formed into a cylindrical shape using a honeycomb-shaped heat storage element made of, for example, an aluminum alloy. The sensible heat exchange rotor 43 is disposed within the housing 41, straddling the first air passage 411 and the second air passage 412. In terms of its position relative to the desiccant rotor 42, the sensible heat exchange rotor 43 is disposed downstream of the desiccant rotor 42 in the first air passage 411 (i.e., upstream of the second air passage 412). The sensible heat exchange rotor 43 is rotated continuously or intermittently about its axis in a predetermined direction (e.g., the direction of arrow A12 in the figure) by a motor (not shown). This rotation allows the sensible heat exchange rotor 43 to exchange sensible heat between the gas to be separated flowing through the first air passage 411 and the separated gas flowing through the second air passage 412.

[0057] (About the separation device) The separation device 2 will be described in more detail with reference to Fig. 3. Fig. 3 is a diagram showing a schematic configuration of a carbon dioxide recovery device 1 using a chemical absorption separation device 2A.

[0058] A chemical absorption type separation device 2A can be used as the separation device 2. In the following description, the chemical absorption type separation device 2A will be simply referred to as the separation device 2A.

[0059] As shown in FIG. 3, the separation device 2A mainly comprises a carbon dioxide absorption tower 71 (hereinafter simply referred to as the absorption tower 71) and an absorbent regeneration tower 72 (hereinafter simply referred to as the regeneration tower 72).

[0060] The absorption tower 71 is, for example, a countercurrent gas-liquid contactor, and is filled therein with packing material 711. As the packing material 711, for example, random packing material such as Raschig rings or structured packing material such as wire gauze packing is used.

[0061] The absorption tower 71 also has a gas inlet 712 below the packing material 711, and a first supply line L116 is connected to the gas inlet 712. As a result, the gas to be separated is supplied to the absorption tower 71 via the first supply line L116. This gas to be separated is the gas dehumidified by the dehumidifier 3.

[0062] The absorption tower 71 is also provided with an absorption liquid inlet 713 above the filler 711 for introducing a carbon dioxide absorbing liquid (lean liquid) into the absorption tower 71. The carbon dioxide absorbing liquid introduced from the absorption liquid inlet 713 is the carbon dioxide absorbing liquid (hereinafter referred to as lean liquid) after carbon dioxide has been stripped in the regeneration tower 72. The carbon dioxide absorbing liquid is preferably, for example, a non-aqueous absorption liquid, such as a non-aqueous amine-based absorption liquid. The non-aqueous absorption liquid here refers to a liquid having a substance other than water (an organic solvent) as its main solvent, and the main solvent refers to a substance that dissolves amines and the like and has the largest mass fraction in the absorption liquid. This is because if an absorption liquid having water as its main solvent is used, the gas after separation will contain moisture, which may prevent efficient regeneration of the desiccant in the dehumidification device 3. Examples of amines include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diethylethanolamine (DEEA), diisopropylamine (DIPA), aminoethoxyethanol (AEE), methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol, monopropanolamine, monoisopropanolamine, DL-1-amino-2-propanol, and 3-amino-1,2-propanediol. The carbon dioxide absorbing liquid is not limited to amine-based absorbing liquids, and alkaline absorbing liquids (potassium-based, calcium-based, or sodium-based) may also be used.

[0063] The gas to be separated, supplied to the absorption tower 71 from the gas inlet 712, rises within the absorption tower 71 toward the packing material 711. In addition, the lean liquid introduced into the absorption tower 71 from the absorbing liquid inlet 713 falls toward the packing material 711. Therefore, the lean liquid comes into gas-liquid contact with the gas to be separated while falling along the surface of the packing material 711, and selectively absorbs carbon dioxide in the gas to be separated. At this time, the carbon dioxide absorbing liquid also absorbs moisture from the gas to be separated, so that the moisture content of the carbon dioxide absorbing liquid becomes higher than before the absorption of carbon dioxide. Then, the gas to be separated from which carbon dioxide has been removed (i.e., the separated gas) is supplied to the dehumidifier 3 via a second supply line L12 connected to the top of the absorption tower 71. Then, the separated gas is used to regenerate the dehumidifying agent in the dehumidifier 3. Furthermore, the carbon dioxide absorbing liquid that has absorbed carbon dioxide (hereinafter referred to as the rich liquid) is discharged from an outlet 714 at the bottom of the absorption tower 71.

[0064] One end of an extraction pipe L17 is connected to the discharge port 714 of the absorption tower 71, and the other end of the extraction pipe L17 is connected to the regeneration tower 72. As a result, the rich liquid discharged from the absorption tower 71 to the extraction pipe L17 is transferred to the regeneration tower 72.

[0065] The regeneration tower 72 is, for example, a countercurrent gas-liquid contactor, and is filled therein with packing material 721. As the packing material 721, for example, random packing material such as Raschig rings or structured packing material such as wire gauze packing is used.

[0066] The regeneration tower 72 is provided with an absorbent liquid inlet 722 connected to an outlet pipe L17 above the packing material 721. Thus, the rich liquid is supplied into the regeneration tower 72 through the outlet pipe L17 and the absorbent liquid inlet 722. The rich liquid supplied into the regeneration tower 72 falls toward the packing material 721.

[0067] Then, while falling, the rich liquid is heated or depressurized, or heated and depressurized, in the regeneration tower 72 so that it reaches the dissipation temperature, and dissipates carbon dioxide. The rich liquid is heated, for example, by a heat pump (not shown) that uses waste heat or environmental heat, or a heat pump (not shown) that uses heat generated when the lean liquid absorbs carbon dioxide in the absorption tower 71. The rich liquid is depressurized by a vacuum pump (not shown) or a device (not shown) that sublimates carbon dioxide. As a device for sublimating carbon dioxide, for example, a carbon dioxide sublimator described in International Publication No. 2021 / 221007 is used.

[0068] The lean liquid after diffusing carbon dioxide is discharged from an outlet 723 at the bottom of the regeneration tower 72. The lean liquid discharged from the regeneration tower 72 to the outlet pipe L18 is returned to the absorption tower 71. Because the outlet pipe L18 is connected to the absorption liquid inlet 713 of the absorption tower 71, the lean liquid returned to the absorption tower 71 falls toward the filler 711 and is reused to absorb carbon dioxide.

[0069] In addition, the carbon dioxide released in the regeneration tower 72 is transferred from the top of the regeneration tower 72 through the transfer pipe L14 to the outside of the separation device 2A, where it is used, for example, as carbon dioxide gas or is sublimated (solidified) and used as dry ice.

[0070] (Dehumidification process and dehumidifying agent regeneration process) The dehumidification process of the gas to be separated and the regeneration process of the adsorption-type desiccant using the separated gas in the carbon dioxide recovery device 1 having the above configuration will be described with reference to Fig. 10. Fig. 10 is a psychrometric chart showing the states of the gas to be separated and the gas after separation. Note that the states of the gas to be separated flowing through range AF in Fig. 2 correspond to points AF in Fig. 10, and the states of the gas to be separated flowing through ranges AC and GI in Fig. 9 correspond to points AC and GI in Fig. 10, respectively.

[0071] The gas to be separated is atmospheric air, and its temperature is 25°C and its relative humidity is 60% (see point A in Figure 10). When the gas to be separated is introduced from the first supply line L111 into the first air duct 411, the gas is first dehumidified by passing through the desiccant rotor 42. If the gas to be separated is dehumidified with an isoenthalpy change (arrow Y11 in Figure 10), the temperature of the gas to be separated rises to 50°C and a relative humidity of 2.8% (see point B in Figure 10). Furthermore, as the desiccant rotor 42 rotates, the portion of the desiccant rotor 42 from which the gas to be separated has been dehumidified enters the second air duct 412 and is regenerated by the separated gas.

[0072] Next, the gas to be separated passes through sensible heat exchange rotor 43, whereby sensible heat is exchanged with post-separation gas (temperature 25°C, relative humidity 3.5%: see point D in FIG. 10) flowing through second air passage 412 (range D). This lowers the temperature of the gas to be separated (arrow Y12 in FIG. 10) to a temperature of 25°C and a relative humidity of 10% (see point C in FIG. 10). Thereafter, the gas to be separated is discharged from first air passage 411 and supplied to separation device 2 via first supply line L116. Then, carbon dioxide is separated from the gas to be separated in separation device 2, and the gas to be separated is supplied to separation device 2 via second supply line L12 as post-separation gas.

[0073] The post-separation gas has a temperature of 25°C and a relative humidity of 3.5% (see point D in Figure 10).At this time, the relative humidity of the post-separation gas is lower than the relative humidity of the gas to be separated supplied to the separation device 2 (10%: see point C in Figure 10) because it is dehumidified in the separation device 2.

[0074] When the separated gas is introduced into second air passage 412 from second supply line L12, it first passes through sensible heat exchange rotor 43 and undergoes sensible heat exchange with the gas to be separated (temperature 50°C, relative humidity 2.8%: see point B in Figure 10) flowing through first air passage 411. As a result, the temperature of the separated gas is raised to a temperature required for regenerating the adsorption-type desiccant (arrow Y13 in Figure 10), and the temperature becomes 50°C and the relative humidity becomes 0.97% (see point E in Figure 10).

[0075] Next, the separated gas passes through the desiccant rotor 42. This regenerates the adsorption-type desiccant in the desiccant rotor 42. Assuming that the separated gas undergoes an isenthalpy change (arrow Y14 in FIG. 10) by regenerating the adsorption-type desiccant, the temperature becomes 25°C and the relative humidity becomes 53.9% (see point F in FIG. 10). Furthermore, the regenerated part of the desiccant rotor 42 enters the first air passage 411 as the desiccant rotor 42 rotates, and again dehumidifies the gas to be separated.

[0076] Here, a case where the adsorption-type dehumidifying agent is regenerated using atmospheric air will be described as a comparison with the carbon dioxide recovery apparatus 1. In this case, a desiccant-type dehumidifying apparatus 30 shown in Fig. 9 is used. In the following description, the atmospheric air used to regenerate the adsorption-type dehumidifying agent will be referred to as "atmosphere for regeneration."

[0077] In desiccant dehumidifier 30, the air for regeneration flows from left to right in the figure through second air passage 412. Furthermore, heater 301 is provided in second air passage 412 between desiccant rotor 42 and sensible heat exchange rotor 43. The rest of the configuration is the same as that of desiccant dehumidifier 3A.

[0078] The temperature and humidity of the regenerating air are set to 25°C and 60% relative humidity, similar to those of the gas to be separated (see point G in FIG. 10). When this regenerating air is introduced into second air passage 412, it first passes through sensible heat exchange rotor 43 and undergoes sensible heat exchange with the gas to be separated (temperature 50°C, relative humidity 2.8%: see point B in FIG. 10) flowing through first air passage 411. This heat exchange reduces the temperature of the gas to be separated (arrow Y12 in FIG. 10) to 25°C and 10% relative humidity (see point C in FIG. 10). Meanwhile, the temperature of the regenerating air is increased (arrow Y15 in FIG. 10) to 50°C and 16.7% relative humidity (see point H in FIG. 10).

[0079] The regenerating air must be heated because it is not possible to sufficiently regenerate the adsorption-type desiccant in the state shown by point H in Figure 10 (temperature 50°C, relative humidity 16.7%). Therefore, after passing through sensible heat exchange rotor 43, the regenerating air is heated by heater 301 (arrow Y16 in Figure 10) to a temperature of 95°C and a relative humidity of 2.8% (see point I in Figure 10).

[0080] The regenerating air heated by the heater 301 passes through the desiccant rotor 42. This regenerates the adsorption-type desiccant in the desiccant rotor 42. As the adsorption-type desiccant is regenerated, the regenerating air undergoes an isenthalpy change (arrow Y17 in FIG. 10) and reaches a temperature of 43°C and a relative humidity of 60% (not shown in FIG. 10 because it is outside the graph). The regenerated portion of the desiccant rotor 42 enters the first air duct 411 as the desiccant rotor 42 rotates, and again dehumidifies the gas to be separated.

[0081] To summarize the above, in the carbon dioxide recovery device 1 according to this embodiment, in the desiccant rotor 42, the gas to be separated changes from point A to point B in Fig. 10 (arrow Y11), while the separated gas changes from point E to point F in Fig. 10 (arrow Y14), and in the sensible heat exchange rotor 43, the gas to be separated changes from point B to point C in Fig. 10 (arrow Y12), while the separated gas changes from point D to point E in Fig. 10 (arrow Y13). This shows that the relative humidity of the separated gas is lower than that of the gas to be separated, and therefore moisture and heat are efficiently exchanged between the separated gas and the separated gas.

[0082] On the other hand, in a dehumidification device 30 that uses atmospheric air to regenerate an adsorption-type desiccant, the atmospheric air for regeneration must be heated (the change from point H to point I in FIG. 10 (arrow Y16)). The energy required for this heating (energy per ton of recovered carbon dioxide) is 69 GJ / t-CO2 when the carbon dioxide recovery rate is assumed to be 60%, whereas in the carbon dioxide recovery device 1 according to this embodiment, the post-separation gas can be used directly to regenerate the desiccant (i.e., the post-separation gas does not need to be heated), thereby reducing the above energy consumption.

[0083] (Other types of dehumidifiers) Other embodiments of the dehumidifier 3 will be described with reference to Figs. 4 and 5. Fig. 4 is a diagram schematically showing the configuration of a carbon dioxide recovery apparatus 1 using a two-tower dehumidifier 3B. Fig. 5 is a diagram schematically showing the configuration of a carbon dioxide recovery apparatus 1 using a chemical absorption dehumidifier 3C.

[0084] When an adsorption type dehumidifying agent is used as the dehumidifying agent, the dehumidifying device 3 may be the desiccant type dehumidifying device 3A described above, or a two-tower type dehumidifying device 3B shown in FIG.

[0085] In addition to the adsorption-type dehumidifying agent, an absorption liquid that absorbs moisture from the gas to be separated can also be used as the dehumidifying agent. As the dehumidifier 3 that uses an absorption liquid, a chemical absorption-type dehumidifier 3C shown in FIG. 5 can be used. In the following description, the two-tower dehumidifier 3B will be simply referred to as the dehumidifier 3B, and the chemical absorption-type dehumidifier 3C will be simply referred to as the dehumidifier 3C. The term dehumidifier 3 will be used to collectively refer to the dehumidifiers 3A, 3B, and 3C.

[0086] (About the two-tower dehumidifier) First, the dehumidifier 3B will be described. As shown in Fig. 4, the dehumidifier 3B has a first dehumidifying section 51 and a second dehumidifying section 52 as main components.

[0087] The first dehumidifying section 51 and the second dehumidifying section 52 are the same device, and for example, a pellet or honeycomb made by mixing a dehumidifying agent with a binder or the like is held inside. Examples of adsorption-type dehumidifying agents that can be used include silica gel, alumina gel, molecular sieve, zeolite, and activated carbon.

[0088] The first dehumidifying section 51 and the second dehumidifying section 52 are arranged in parallel with each other by branching the first supply line L11 by the switching valves 53 and 54. Specifically, the first dehumidifying section 51 and the second dehumidifying section 52 are arranged in parallel with each other as follows.

[0089] Upstream of the first dehumidifying section 51 and the second dehumidifying section 52, the first supply line L111 is branched into branch pipes L112 and L113 by a switching valve 53. The branch pipe L112 is connected to the first dehumidifying section 51, and the branch pipe L113 is connected to the second dehumidifying section 52. Downstream of the first dehumidifying section 51 and the second dehumidifying section 52, the first supply line L116 is branched into branch pipes L114 and L115 by a switching valve 54. The branch pipe L114 is connected to the first dehumidifying section 51, and the branch pipe L115 is connected to the second dehumidifying section 52.

[0090] Furthermore, the second supply line L12 is branched into branch pipes L121 and L122 by a switching valve 55, with the branch pipe L121 connected to the first dehumidifying section 51 and the branch pipe L122 connected to the second dehumidifying section 52. Furthermore, the discharge path L13 is branched into branch pipes L131 and L132 by a switching valve 56, with the branch pipe L131 connected to the first dehumidifying section 51 and the branch pipe L132 connected to the second dehumidifying section 52.

[0091] According to the dehumidification device 3B, it is possible to efficiently dehumidify the gas to be separated by switching between a first state in which the first dehumidification section 51 dehumidifies the gas to be separated and the second dehumidification section 52 regenerates the dehumidifying agent, and a second state in which the first dehumidification section 51 regenerates the dehumidifying agent and the gas to be separated is dehumidified by the second dehumidification section 52. Specifically, this is as follows.

[0092] In the first state, the switching valve 53 connects the first supply line L111 to the branch pipe L112, the switching valve 54 connects the branch pipe L114 to the first supply line L116, the switching valve 55 connects the second supply line L12 to the branch pipe L122, and the switching valve 56 connects the branch pipe L132 to the discharge path L13. As a result, the gas to be separated is supplied to the first dehumidification unit 51 via the first supply line L111 and the branch pipe L112, dehumidified, and supplied to the separation device 2 via the branch pipe L114 and the first supply line L116. Carbon dioxide is then separated from the gas to be separated in the separation device 2, and the separated gas is supplied to the second dehumidification unit 52 via the second supply line L12 and the branch pipe L122. The separated gas supplied to the second dehumidifying section 52 regenerates the dehumidifying section of the second dehumidifying section 52, and is then discharged via the branch pipe L132 and the discharge path L13.

[0093] In the second state, the switching valve 53 connects the first supply line L111 to the branch pipe L113, the switching valve 54 connects the branch pipe L115 to the first supply line L116, the switching valve 55 connects the second supply line L12 to the branch pipe L121, and the switching valve 56 connects the branch pipe L131 to the discharge path L13. As a result, the gas to be separated is supplied to the second dehumidification unit 52 via the first supply line L111 and the branch pipe L113, dehumidified, and then supplied to the separation device 2 via the branch pipe L115 and the first supply line L116. Carbon dioxide is then separated from the gas to be separated in the separation device 2, and the separated gas is supplied to the first dehumidification unit 51 via the second supply line L12 and the branch pipe L121. The separated gas supplied to the first dehumidifying section 51 regenerates the dehumidifying section of the first dehumidifying section 51, and is then discharged via the branch pipe L131 and the discharge path L13.

[0094] As described above, in the first state, while the first dehumidifier 51 is dehumidifying the gas to be separated, the second dehumidifier 52 is regenerating the dehumidifying agent, and the second dehumidifier 52 can be placed on standby in a state where it can dehumidify. On the other hand, in the second state, while the second dehumidifier 52 is dehumidifying the gas to be separated, the first dehumidifier 51 is regenerating the dehumidifying agent, and the first dehumidifier 51 can be placed on standby in a state where it can dehumidify.

[0095] Since the amount of moisture that a dehumidifying agent can absorb is fixed, for example, if the first dehumidifying unit 51 can no longer dehumidify the gas to be separated in the first state (or just before dehumidification can no longer be performed) and the state is switched to the second state, the second dehumidifying unit 52 can continue to dehumidify the gas to be separated. The same applies when switching from the second state to the first state. Therefore, the gas to be separated can be dehumidified efficiently.

[0096] (Chemical absorption dehumidifier) Next, the dehumidifier 3C will be described. As shown in FIG.

[0097] The absorption tower 61 is, for example, a countercurrent gas-liquid contactor, and is filled with packing material 611. As the packing material 611, for example, random packing material such as Raschig rings or structured packing material such as wire gauze packing is used.

[0098] The absorption tower 61 also has a gas inlet 612 below the packing material 611, and a first supply line L111 is connected to the gas inlet 612. As a result, the gas to be separated is supplied to the absorption tower 61 via the first supply line L111.

[0099] The absorption tower 61 is also provided with a dehumidifying agent inlet 613 above the packing material 611 for introducing a dehumidifying agent (absorption liquid) into the absorption tower 61. Examples of the dehumidifying agent that can be used include ethylene glycol, triethylene glycol, lithium chloride, and lithium bromide.

[0100] The gas to be separated, which is supplied to the absorption tower 61 from the gas inlet 612, rises within the absorption tower 61 toward the packing material 611. In addition, the dehumidifying agent introduced into the absorption tower 61 from the dehumidifying agent inlet 613 falls toward the packing material 611. Therefore, the dehumidifying agent comes into gas-liquid contact with the gas to be separated while falling along the surface of the packing material 611, and absorbs moisture in the gas to be separated. The dehumidified gas to be separated is then supplied to the separation device 2 via a first supply line L116 connected to the top of the absorption tower 61. The dehumidifying agent that has absorbed moisture is discharged from an outlet 614 at the bottom of the absorption tower 61.

[0101] One end of an outlet pipe L15 is connected to the outlet 614 of the absorption tower 61, and the other end of the outlet pipe L15 is connected to the regeneration tower 62. Therefore, the dehumidifying agent (dehumidifying agent that has absorbed moisture) discharged from the absorption tower 61 to the outlet pipe L15 is transferred to the regeneration tower 62.

[0102] The regeneration tower 62 is, for example, a countercurrent gas-liquid contactor, and is filled with packing material 621. As the packing material 621, for example, random packing material such as Raschig rings or structured packing material such as wire gauze packing is used.

[0103] The regeneration tower 62 also includes a dehumidifying agent inlet 622 connected to an outlet pipe L15 above the packing material 621. Thus, the dehumidifying agent (dehumidifying agent that has absorbed moisture) is supplied into the regeneration tower 62 through the outlet pipe L15 and the dehumidifying agent inlet 622.

[0104] The regeneration tower 62 also has a gas inlet 623 below the packing material 621, and a second supply line L12 is connected to the gas inlet 623. As a result, the separated gas is supplied to the regeneration tower 62 via the second supply line L12.

[0105] The separated gas supplied to the regenerator 62 from the gas inlet 623 rises inside the regenerator 62 toward the packing material 621. The dehumidifying agent (dehumidifying agent that has absorbed moisture) introduced into the regenerator 62 from the dehumidifying agent inlet 622 falls toward the packing material 621. Therefore, the dehumidifying agent (dehumidifying agent that has absorbed moisture) comes into gas-liquid contact with the separated gas while falling over the surface of the packing material 621. Because the separated gas is a dehumidified, dry gas, the dehumidifying agent can be regenerated by coming into contact with the dehumidifying agent.

[0106] The separated gas after the regeneration of the desiccant is discharged from a discharge line L13 connected to the top of the regeneration tower 62. The regenerated desiccant is also discharged from an outlet 624 at the bottom of the regeneration tower 62 to an outlet pipe L16. The desiccant discharged to the outlet pipe L16 is returned to the absorption tower 61. Because the outlet pipe L16 is connected to the desiccant inlet 23 of the absorption tower 61, the desiccant returned to the absorption tower 61 falls toward the packing material 611 and is reused to dehumidify the gas to be separated.

[0107] (Process simulation results) Generally, to regenerate a desiccant such as ethylene glycol, triethylene glycol, lithium chloride, or lithium bromide, it is necessary to provide, for example, a reboiler in the regeneration tower 62, which heats the desiccant and dissipates the absorbed moisture. However, when the inventors of the present application performed a process simulation (using the process simulator Aspen Plus), they found that the carbon dioxide recovery device 1, which combines the separation device 2A and the dehumidification device 3C, uses dry post-separation gas and therefore can regenerate the desiccant without the need for heating.

[0108] The simulation conditions were as follows: the gas to be separated was atmospheric air, its temperature was 25°C, and its relative humidity was 60%. Furthermore, the dehumidifying agent between the absorption tower 61 and the regeneration tower 62 was used so that the liquid-to-gas ratio in the absorption tower 61 was 1.1 L / m 3 The circulation amount was set as follows.

[0109] As a result of the simulation, the gas to be separated dehumidified in the absorption tower 61 had a temperature of 25°C and a relative humidity of 39%, and the post-separation gas obtained by using such a gas to be separated had a temperature of 30°C and a relative humidity of 14%. The reason why the post-separation gas has a higher temperature and a lower relative humidity than the gas to be separated is that, in addition to the heat generated when the carbon dioxide absorbing liquid absorbs the carbon dioxide in the gas to be separated in the carbon dioxide absorption tower 71, the carbon dioxide absorbing liquid also absorbs water along with the carbon dioxide. The simulation results showed that by using post-separation gas with a temperature of 30°C and a relative humidity of 14%, it is possible to regenerate the desiccant without requiring heat input to the regeneration tower 62.

[0110] On the other hand, when the desiccant is regenerated without using the gas after separation, that is, when the desiccant is regenerated by heating the reboiler, a process simulation performed under the same conditions showed that the energy required to heat the reboiler (energy per ton of carbon dioxide recovered) was 954 GJ / t-CO2. In carbon dioxide recovery system 1, which combines separation unit 2A and dehumidification unit 3C, it is possible to reduce the energy consumption required for the above heating.

[0111] (Other forms of separation device) Other embodiments of the separation device 2 will be described with reference to Figs. 6 to 8. Fig. 6 is a diagram schematically showing the configuration of a carbon dioxide capture device 1 using an adsorption-type separation device 2B. Fig. 7 is a diagram schematically showing the configuration of a carbon dioxide capture device 1 using a membrane separation-type separation device 2C. Fig. 8 is a diagram schematically showing the configuration of a carbon dioxide capture device 1 using a cryogenic separation-type separation device 2D.

[0112] As the separation device 2, in addition to the above-mentioned chemical absorption separation device 2A, an adsorption separation device 2B, a membrane separation separation device 2C, or a cryogenic separation separation device 2D can be used. In the following description, the adsorption separation device 2B will be simply referred to as separation device 2B, the membrane separation separation device 2C will be simply referred to as separation device 2C, and the cryogenic separation separation device 2D will be simply referred to as separation device 2D. Separation device 2 will be used to collectively refer to the above separation devices 2A, 2B, 2C, and 2D.

[0113] (About adsorption type separator) First, the separating device 2 B will be described. As shown in FIG. 6, the separating device 2 B has a first separating section 81 and a second separating section 82 as main components.

[0114] The first separation section 81 and the second separation section 82 are the same device, and each contains a physical adsorbent 811, 821. As the physical adsorbent 811, 821, for example, zeolite, activated carbon, metal organic framework, or the like is used.

[0115] The separation sections 81 and 82 are provided with gas inlets 812 and 822, respectively, and a first supply line L116 is connected to the gas inlets 812 and 822 to supply the gas to be separated to the separation sections 81 and 82. More specifically, the downstream side of the first supply line L116 is branched into a branch pipe L117 and a branch pipe L118 by a switching valve 83, and the branch pipe L117 is connected to the gas inlet 812 of the first separation section 81, and the branch pipe L118 is connected to the gas inlet 822 of the second separation section 82.

[0116] The gas to be separated supplied to the separation units 81, 82 from the gas inlets 812, 822 comes into contact with the physical adsorbents 811, 821 housed in the separation units 81, 82. The physical adsorbents 811, 821 then selectively adsorb carbon dioxide contained in the gas to be separated. This adsorption separates the carbon dioxide from the gas to be separated.

[0117] The gas to be separated after carbon dioxide has been separated (i.e., post-separation gas) is discharged from outlets 813, 823 provided in the separation sections 81, 82. A second supply line L12 is connected to the outlets 813, 823. More specifically, the upstream side of the second supply line L12 is branched into a branch pipe L119 and a branch pipe L120 by a switching valve 84, and the branch pipe L119 is connected to the outlet 813 of the first separation section 81, and the branch pipe L120 is connected to the outlet 823 of the second separation section 82. Thus, the post-separation gas of the first separation section 81 is supplied to the dehumidifier 3 via the branch pipe L119 and the second supply line L12, and the post-separation gas of the second separation section 82 is supplied to the dehumidifier 3 via the branch pipe L120 and the second supply line L12.

[0118] The carbon dioxide adsorbed by the physical adsorbents 811 and 821 is recovered by desorbing the carbon dioxide from the physical adsorbents 811 and 821. Specifically, the process is as follows.

[0119] Because the physical adsorbents 811, 821 have a fixed capacity to adsorb carbon dioxide, once they have adsorbed a certain amount of carbon dioxide, they can no longer adsorb any more carbon dioxide. Therefore, in order to adsorb more carbon dioxide, it is necessary to desorb the physical adsorbents 811, 821. This desorption is performed by heating or reducing the pressure inside the separation units 81, 82, or by heating and reducing the pressure inside the separation units 81, 82. After desorbing carbon dioxide, the physical adsorbents 811, 821 become able to adsorb carbon dioxide again.

[0120] Furthermore, carbon dioxide desorbed from the physical adsorbents 811, 821 is discharged to the transfer pipe L14 via the diffusion ports 814, 824 provided in the separation sections 81, 82. More specifically, the upstream side of the transfer pipe L14 is branched into the branch pipes L121 and L122 by the switching valve 85. The branch pipe L121 is connected to the diffusion port 814 of the first separation section 81, and the branch pipe L122 is connected to the diffusion port 824 of the second separation section 82. Thus, the carbon dioxide desorbed in the first separation section 81 is transferred to the outside of the separation device 2B via the branch pipe L121 and the transfer pipe L14, and the carbon dioxide desorbed in the second separation section 82 is transferred to the outside of the separation device 2B via the branch pipe L122 and the transfer pipe L14. The branch pipes L121, L122 are equipped with on-off valves 86, 87, respectively.

[0121] In the separation device 2B configured as above, when carbon dioxide is adsorbed in one of the separation sections 81, 82, desorption is performed in the other, thereby enabling efficient recovery of carbon dioxide.

[0122] For example, when carbon dioxide is adsorbed in the first separation section 81, desorption of the physical adsorbent 821 is carried out in the second separation section 82. Specifically, this is as follows.

[0123] The switching valve 83 connects the first supply line L116 to the branch pipe L117, and supplies the gas to be separated to the first separation section 81. This causes carbon dioxide in the gas to be separated to be adsorbed in the first separation section 81. At the same time, the switching valve 84 connects the branch pipe L119 connected to the discharge port 813 of the first separation section 81 to the second supply line L12. This causes the separated gas to be supplied from the first separation section 81 to the dehumidifier 3. At this time, the opening / closing valve 86 of the branch pipe L121 connected to the diffusion port 814 of the first separation section 81 is closed, so that the separated gas does not flow into the transfer pipe L14.

[0124] When the gas to be separated is being supplied to the first separation section 81, the branch pipe L118 is not in communication with the first supply line L116, and the branch pipe L120 is not in communication with the second supply line L12. Meanwhile, the on-off valve 87 on the branch pipe L122 is kept open, and the branch pipe L122 is connected to the transfer pipe L14 by the switching valve 85. If desorption of the physical adsorbent 821 is performed in the second separation section 82 in this state, the desorbed carbon dioxide is recovered via the branch pipe L122 and the transfer pipe L14 without flowing into the first supply line L116 or the second supply line L12.

[0125] On the other hand, when desorption of the physical adsorbent 821 is carried out in the first separation section 81, adsorption of carbon dioxide is carried out in the second separation section 82. Specifically, this is as follows.

[0126] The switching valve 83 connects the first supply line L116 to the branch pipe L118, and the gas to be separated is supplied to the second separation section 82. As a result, carbon dioxide in the gas to be separated is adsorbed in the second separation section 82. At the same time, the switching valve 84 connects the branch pipe L120 connected to the discharge port 823 of the second separation section 82 with the second supply line L12. As a result, the separated gas is supplied from the second separation section 82 to the dehumidifier 3. At this time, the opening / closing valve 87 of the branch pipe L122 connected to the diffusion port 824 of the second separation section 82 is closed, so that the separated gas does not flow into the transfer pipe L14.

[0127] When the gas to be separated is being supplied to the second separation section 82, the branch pipe L117 is not in communication with the first supply line L116, and the branch pipe L119 is not in communication with the second supply line L12. Meanwhile, the on-off valve 86 on the branch pipe L121 is kept open, and the branch pipe L121 and the transfer pipe L14 are connected by the switching valve 85. If desorption of the physical adsorbent 811 is performed in the first separation section 81 in this state, the desorbed carbon dioxide is recovered via the branch pipe L121 and the transfer pipe L14 without flowing into the first supply line L116 or the second supply line L12.

[0128] In the separation device 2B described above, the separation sections 81 and 82 accommodate the physical adsorbents 811 and 821, but a chemical adsorbent may be used instead of the physical adsorbents 811 and 821. Examples of the chemical adsorbent that can be used include an amine-supported porous material, an alkali metal salt, and an ion exchange resin.

[0129] (Membrane separation equipment) Next, the separation device 2C will be described. As shown in FIG.

[0130] A permeable membrane 731 that selectively allows carbon dioxide to permeate is held inside the separation tank 73. Examples of the permeable membrane 731 that can be used include inorganic membranes such as zeolite membranes (e.g., high-silica CHA-type zeolite membranes or DDR-type zeolite membranes) and organic membranes such as molecular gate membranes. The permeable membrane 731 divides the interior of the separation tank 73 into a non-permeable side 732 and a permeable side 733.

[0131] A gas inlet 734 is provided on the non-permeation side 732, and a first supply line L116 is connected to the gas inlet 734. This allows the gas to be separated to be supplied to the separation tank 73 (non-permeation side 732).

[0132] Since the permeable membrane 731 selectively allows carbon dioxide to permeate, of the components contained in the gas to be separated supplied to the separation tank 73 (non-permeation side 732), only carbon dioxide can move to the permeation side 733. Components other than carbon dioxide, such as nitrogen and oxygen (i.e., the gas after separation), do not permeate the permeable membrane 731 and remain on the non-permeation side 732. If the gas to be separated contains water vapor, some of the water vapor also moves to the permeation side 733.

[0133] Furthermore, an outlet 735 is provided on the non-permeation side 732 of the separation tank 73, and a second supply line L12 is connected to this outlet 735. As a result, the separated gas remaining on the non-permeation side 732 is supplied to the dehumidifier 3 via the second supply line L12. The separated gas is then used to regenerate the desiccant in the dehumidifier 3.

[0134] An outlet 736 is provided on the permeation side 733 of the separation tank 73, and a transfer pipe L14 is connected to the outlet 736. Therefore, the carbon dioxide that has permeated the permeable membrane 731 is transferred to the outside of the separation device 2C via the outlet 736 and the transfer pipe L14, and is used as carbon dioxide gas, or is sublimated (solidified) and used as dry ice, for example.

[0135] (About cryogenic separation equipment) Next, the separation device 2D will be described. As shown in Fig. 8, the separation device 2D includes a compressor 75, a cooling device 76, and a distillation column 77 connected in series.

[0136] The compressor 75 is, for example, a compressor, and is connected to the first supply line 116. The gas to be separated is pressurized to a predetermined pressure. Then, the pressurized gas to be separated flows into the cooling device 76. Note that the predetermined pressure is, for example, 1 MPa when the gas to be separated is atmospheric pressure.

[0137] The cooling device 76 is, for example, a compression refrigerator. The pressurized gas to be separated is cooled to a predetermined temperature by the cooling device 76. The predetermined temperature is a temperature at which the components of the gas to be separated can be liquefied, and is -180°C at which nitrogen, oxygen, carbon dioxide, etc. can be liquefied when the gas to be separated is air pressurized to 1 MPa.

[0138] The gas to be separated, which has been adjusted to a predetermined pressure and a predetermined temperature, flows into the distillation column 77. In the distillation column 77, the liquefied gas to be separated is heated to a predetermined temperature. This predetermined temperature is, for example, -50°C. As a result, the nitrogen and oxygen change phase from liquid to gas, and the separated gas is discharged from the top of the distillation column 77 to the second supply line L12. As a result, the separated gas is supplied to the dehumidification device 3. Meanwhile, carbon dioxide and moisture, which have higher boiling points than nitrogen and oxygen, accumulate in liquid form at the bottom of the distillation column 77. They are then recovered from the transfer pipe L14 connected to the bottom of the distillation column 77. The cooling device 76 and the distillation column 77 may be integrated into one device.

[0139] As described above, the carbon dioxide recovery device 1 according to this embodiment has the following features: (1) A carbon dioxide recovery system 1 includes a separation device 2 (e.g., a chemical absorption separation device 2A, an adsorption separation device 2B, a membrane separation separation device 2C, or a cryogenic separation separation device 2D) that separates carbon dioxide from a gas to be separated (atmosphere), and a first supply line L11 for supplying the gas to be separated (atmosphere) to the separation device 2. The system is characterized in that a dehumidifier 3 (e.g., a desiccant dehumidifier 3A, a two-tower dehumidifier 3B, or a chemical absorption dehumidifier 3C) that dehumidifies the gas to be separated (atmosphere) using a dehumidifying agent is provided on the first supply line L11, a second supply line L12 is provided to supply the separated gas from the gas to be separated (atmosphere) from the separation device 2 to the dehumidifier 3, and the dehumidifier 3 regenerates the dehumidifying agent using the separated gas supplied from the second supply line L12.

[0140] (2) In the carbon dioxide recovery device 1 described in (1), it is preferable that the relative humidity of the separated gas in the second supply line L12 is lower than the relative humidity of the gas to be separated in the first supply line L11 (L116) downstream of the dehumidifier 3.

[0141] (3) In the carbon dioxide recovery device 1 described in (1) or (2), it is preferable that the dehumidifying agent is an adsorption-type dehumidifying agent (e.g., silica gel, alumina gel, molecular sieve, zeolite, activated carbon, etc.) that adsorbs moisture from the gas to be separated (air).

[0142] (4) In the carbon dioxide recovery device 1 described in (3), it is preferable that the dehumidifier 3 (desiccant type dehumidifier 3A) comprises a first air duct 411 on the first supply line L11 through which the gas to be separated (atmosphere) passes, a second air duct 412 connected to the second supply line L12 through which the separated gas passes, and a desiccant rotor 42 as a dehumidifier arranged across the first air duct 411 and the second air duct 412.

[0143] (5) In the carbon dioxide recovery device 1 described in (3), it is preferable that the dehumidifier 3 (two-tower dehumidifier 3B) has a first dehumidification section 51 and a second dehumidification section 52 arranged in parallel for dehumidification, and be switchable between a first state in which the first dehumidification section 51 dehumidifies the gas to be separated (atmosphere) and the second dehumidification section 52 regenerates the dehumidifying agent, and a second state in which the first dehumidification section 51 regenerates the dehumidifying agent and the second dehumidification section 52 dehumidifies the gas to be separated (atmosphere).

[0144] (6) In the carbon dioxide recovery device 1 described in (1) or (2), the dehumidifying agent is preferably an absorbing liquid (e.g., ethylene glycol, triethylene glycol, lithium chloride, lithium bromide, etc.) that absorbs moisture from the gas to be separated (air).

[0145] (7) In the carbon dioxide recovery device 1 described in (6), the dehumidifier 3 (chemical absorption dehumidifier 3C) preferably includes an absorption tower 61 that brings the gas to be separated (air) supplied from the first supply line L11 (L111) into gas-liquid contact with the dehumidifying agent to cause the dehumidifying agent to absorb moisture, and a regeneration tower 62 that regenerates the dehumidifying agent using the separated gas supplied from the second supply line L12.

[0146] (8) In the carbon dioxide recovery device 1 described in any one of (1) to (7), the separation device 2 (chemical absorption separation device 2A) preferably includes a carbon dioxide absorption tower 71 that brings the gas to be separated (air) into gas-liquid contact with a carbon dioxide absorbing liquid that absorbs carbon dioxide, causing the carbon dioxide to be absorbed by the carbon dioxide absorbing liquid (lean liquid), and an absorption liquid regeneration tower 72 that regenerates the carbon dioxide absorbing liquid (rich liquid) that has absorbed the carbon dioxide, and releases the carbon dioxide.

[0147] (9) In the carbon dioxide recovery device 1 described in (8), it is preferable that the water content of the carbon dioxide absorbing solution is higher after absorbing carbon dioxide than before absorbing carbon dioxide.

[0148] (10) In the carbon dioxide recovery device 1 described in (8) or (9), the carbon dioxide absorbing liquid is preferably a non-aqueous absorbing liquid (for example, a non-aqueous amine absorbing liquid). Note that the non-aqueous absorbing liquid is one in which a substance other than water is used as a main solvent, and the main solvent is one that dissolves amines and the like and has the largest mass fraction in the absorbing liquid.

[0149] (11) In the carbon dioxide recovery device 1 described in any one of (1) to (7), it is preferable that the separation device 2 (adsorption-type separation device 2B) contains a physical adsorbent or a chemical adsorbent for separation.

[0150] (12) In the carbon dioxide recovery device 1 described in any one of (1) to (7), it is preferable that the separation device 2 (membrane separation type separation device 2C) is provided with a permeable membrane 731 that selectively allows carbon dioxide to permeate, and that separation is performed by allowing the permeable membrane 731 to permeate the carbon dioxide contained in the gas to be separated (atmosphere) supplied to the separation device 2.

[0151] (13) In the carbon dioxide recovery device 1 described in any one of (1) to (7), the separator 2 (cryogenic separation type separator 2D) preferably performs separation by cryogenic separation.

[0152] The carbon dioxide recovery system 1 described above is provided with dehumidifiers 3 (desiccant dehumidifier 3A, two-tower dehumidifier 3B, chemical absorption dehumidifier 3C) that dehumidify the gas to be separated with a dehumidifying agent on a first supply line L11 for supplying the gas to be separated (air) to separation systems 2 (chemical absorption separation system 2A, adsorption separation system 2B, membrane separation separation system 2C, cryogenic separation separation system 2D), so that the gas to be separated is dehumidified with the dehumidifying agent before being supplied to separation system 2. Therefore, the amount of water vapor generated when carbon dioxide is separated in separation system 2 can be reduced, enabling efficient carbon dioxide recovery.

[0153] Here, the gas to be separated is dehumidified by the dehumidifier 3 before being supplied to the separator 2, where it is further dehumidified. Therefore, the separated gas after carbon dioxide has been separated from the gas to be separated is a dehumidified, dry gas. Therefore, the carbon dioxide capture device 1 described above is equipped with a second supply line L12 that supplies the separated gas from the separator 2 to the dehumidifier 3, and the dehumidifier 3 can regenerate the dehumidifying agent using the separated gas supplied from the second supply line L12. The gas to be separated is dehumidified using a dehumidifier, and the regeneration of the dehumidifying agent is performed using the separated gas, so it is possible to reduce the energy consumption required for dehumidification.

[0154] In addition, the carbon dioxide recovery method according to this embodiment includes: (14) A carbon dioxide recovery method for recovering carbon dioxide by separating carbon dioxide from a gas to be separated (atmosphere), characterized in that the separation of carbon dioxide uses a gas to be separated that has been dehumidified with a dehumidifying agent (for example, an adsorption-type dehumidifying agent (silica gel, alumina gel, molecular sieve, zeolite, activated carbon, etc.) or an absorption liquid (for example, ethylene glycol, triethylene glycol, lithium chloride, lithium bromide, etc.)), and the dehumidifying agent is regenerated using the gas after separation of carbon dioxide from the gas to be separated.

[0155] (15) The carbon dioxide recovery method described in (14) is characterized in that the relative humidity of the separated gas before regeneration (3.5%: see point D in Figure 10) is lower than the relative humidity of the separated gas after dehumidification (10%: see point C in Figure 10).

[0156] (16) In the carbon dioxide recovery method described in (14) or (15), the dehumidifying agent is preferably an adsorption type dehumidifying agent that adsorbs moisture from the gas to be separated.

[0157] (17) In the carbon dioxide recovery method described in (16), it is preferable to use a desiccant rotor 42 as a dehumidifying agent.

[0158] (18) In the carbon dioxide recovery method described in (16), it is preferable to provide a first dehumidification unit 51 and a second dehumidification unit 52 in parallel for dehumidifying using a dehumidifying agent, and when dehumidifying is performed in one of the first dehumidification unit 51 and the second dehumidification unit 52, regeneration is performed in the other.

[0159] (19) In the carbon dioxide recovery method described in (14) or (15), the dehumidifying agent is preferably an absorbing liquid (e.g., ethylene glycol, triethylene glycol, lithium chloride, lithium bromide, etc.) that absorbs moisture from the gas to be separated.

[0160] (20) In the carbon dioxide recovery method described in (19), it is preferable that the dehumidification is carried out by gas-liquid contact between the gas to be separated and a dehumidifying agent, and the regeneration is carried out by gas-liquid contact between the separated gas and a dehumidifying agent that has absorbed moisture.

[0161] (21) In the carbon dioxide recovery method according to any one of (14) to (20), the separation is preferably carried out by bringing the gas to be separated into gas-liquid contact with a carbon dioxide absorbing liquid (lean liquid) that absorbs carbon dioxide, causing the carbon dioxide absorbing liquid to absorb the carbon dioxide, and regenerating the carbon dioxide absorbing liquid (rich liquid) that has absorbed the carbon dioxide.

[0162] (22) In the carbon dioxide recovery method described in (21), it is preferable that the water content of the carbon dioxide absorbing solution is higher after absorbing carbon dioxide than before absorbing carbon dioxide.

[0163] (23) In the carbon dioxide recovery method according to (21) or (22), the carbon dioxide absorbing liquid is preferably a non-aqueous absorbing liquid (for example, a non-aqueous amine absorbing liquid). Note that the non-aqueous absorbing liquid is one in which a substance other than water serves as a main solvent, and the main solvent is one that dissolves amines and the like and has the largest mass fraction in the absorbing liquid.

[0164] (24) In the carbon dioxide recovery method according to any one of (14) to (20), the separation is preferably carried out using a physical adsorbent or a chemical adsorbent.

[0165] (25) In the carbon dioxide recovery method according to any one of (14) to (20), the separation is preferably carried out by a permeable membrane 731 that selectively allows carbon dioxide to permeate.

[0166] (26) In the carbon dioxide recovery method according to any one of (14) to (20), the separation is preferably carried out by cryogenic separation.

[0167] According to the carbon dioxide capture method described above, carbon dioxide is separated using a gas to be separated that has been dehumidified with a dehumidifying agent. This makes it possible to suppress the amount of water vapor generated during carbon dioxide separation, enabling carbon dioxide to be captured efficiently.

[0168] The above-described embodiment is merely illustrative and does not limit the present invention in any way. Therefore, various improvements and modifications of the present invention are possible without departing from the spirit and scope of the present invention. For example, although air is cited as the gas to be separated, combustion exhaust gas or the like can also be used as the gas to be separated. When the gas to be separated is combustion exhaust gas, it is conceivable that the combustion exhaust gas contains sulfur oxides. Therefore, a desulfurization device may be provided on the first supply line L11, and the combustion exhaust gas from which sulfur oxides have been removed may be supplied to the dehumidification device 3 and the separation device 2. [Explanation of symbols]

[0169] 1. Carbon dioxide capture device 2 Separation device 2A Chemical absorption separator (an example of a separator) 2B Adsorption type separator (example of separator) 2C Membrane separation device (example of separation device) 2D cryogenic separation type separation equipment (an example of separation equipment) 3 Dehumidifier 3A Desiccant dehumidifier 3A (an example of a dehumidifier) 3B Two-tower dehumidifier (an example of a dehumidifier) 3C Chemical absorption dehumidifier 3C (an example of a dehumidifier) L11 First supply line L12 Second supply line

Claims

1. A carbon dioxide recovery apparatus including a separation device that separates carbon dioxide from a gas to be separated, and a first supply line for supplying the gas to be separated to the separation device, a dehumidification device that dehumidifies the gas to be separated using a dehumidifying agent, provided on the first supply line; a second supply line for supplying a separated gas obtained after separating carbon dioxide from the gas to be separated from the separation device to the dehumidification device; the dehumidifying device regenerates the dehumidifying agent by the separated gas supplied from the second supply line; A carbon dioxide capture device characterized by:

2. The carbon dioxide recovery system according to claim 1, the relative humidity of the separated gas in the second supply line is lower than the relative humidity of the separated gas in the first supply line downstream of the dehumidifier; A carbon dioxide capture device characterized by:

3. The carbon dioxide recovery apparatus according to claim 1 or 2, the dehumidifying agent is an adsorption type dehumidifying agent that adsorbs moisture in the gas to be separated; A carbon dioxide capture device characterized by:

4. The carbon dioxide recovery system according to claim 3, The dehumidifying device is a first air passage on the first supply line through which the gas to be separated passes; a second air passage connected to the second supply line and through which the separated gas passes; a desiccant rotor as the dehumidifying agent, the desiccant rotor being disposed across the first air passage and the second air passage; To have A carbon dioxide capture device characterized by:

5. The carbon dioxide recovery system according to claim 3, The dehumidifying device is a first dehumidifying unit and a second dehumidifying unit for performing the dehumidification are provided in parallel, a first state in which the dehumidification is performed by the first dehumidification unit and the regeneration is performed by the second dehumidification unit, and a second state in which the regeneration is performed by the first dehumidification unit and the dehumidification is performed by the second dehumidification unit; A carbon dioxide capture device characterized by:

6. The carbon dioxide recovery apparatus according to claim 1 or 2, the dehumidifying agent is an absorbing liquid that absorbs moisture from the gas to be separated; A carbon dioxide capture device characterized by:

7. The carbon dioxide recovery system according to claim 6, The dehumidifying device is an absorption tower that brings the gas to be separated, which is supplied from the first supply line, into gas-liquid contact with the dehumidifying agent, thereby causing the dehumidifying agent to absorb moisture; a regeneration tower that performs the regeneration using the separated gas supplied from the second supply line; To have A carbon dioxide capture device characterized by:

8. The carbon dioxide recovery apparatus according to claim 1 or 2, The separation device comprises: a carbon dioxide absorption tower that brings the gas to be separated into gas-liquid contact with a carbon dioxide absorbing liquid that absorbs carbon dioxide, thereby causing the carbon dioxide to be absorbed by the carbon dioxide absorbing liquid; an absorption liquid regeneration tower that regenerates the carbon dioxide absorbing liquid that has absorbed carbon dioxide and releases carbon dioxide; To have A carbon dioxide capture device characterized by:

9. The carbon dioxide recovery system according to claim 8, the water content of the carbon dioxide absorbing solution is higher after carbon dioxide absorption than before carbon dioxide absorption; A carbon dioxide capture device characterized by:

10. The carbon dioxide recovery apparatus according to claim 8 or 9, The carbon dioxide absorbing liquid is a non-aqueous absorbing liquid; A carbon dioxide capture device characterized by:

11. The carbon dioxide recovery apparatus according to claim 1 or 2, the separation device contains a physical or chemical adsorbent material for performing the separation; A carbon dioxide capture device characterized by:

12. The carbon dioxide recovery apparatus according to claim 1 or 2, the separation device is provided with a permeable membrane that selectively permeates carbon dioxide, and the separation is performed by allowing the carbon dioxide contained in the gas to be separated that is supplied to the separation device to permeate through the permeable membrane; A carbon dioxide capture device characterized by:

13. The carbon dioxide recovery apparatus according to claim 1 or 2, the separation device performs the separation by cryogenic separation; A carbon dioxide capture device characterized by:

14. A carbon dioxide recovery method for recovering carbon dioxide by separating carbon dioxide from a gas to be separated, The separation is performed using the gas to be separated that has been dehumidified with a dehumidifying agent; The dehumidifying agent is regenerated using a separated gas obtained after separating carbon dioxide from the gas to be separated. A carbon dioxide recovery method characterized by:

15. The carbon dioxide recovery method according to claim 14, the relative humidity of the separated gas before the regeneration is lower than the relative humidity of the to-be-separated gas after the dehumidification is performed; A carbon dioxide recovery method characterized by:

16. 16. The carbon dioxide recovery method according to claim 14 or 15, the dehumidifying agent is an adsorption type dehumidifying agent that adsorbs moisture in the gas to be separated; A carbon dioxide recovery method characterized by:

17. 17. The carbon dioxide recovery method according to claim 16, using a desiccant rotor as the dehumidifying agent; A carbon dioxide recovery method characterized by:

18. 17. The carbon dioxide recovery method according to claim 16, a first dehumidifying unit and a second dehumidifying unit for performing the dehumidification by the dehumidifying agent are provided in parallel; When one of the first dehumidifying unit and the second dehumidifying unit performs the dehumidification, the other performs the regeneration. A carbon dioxide recovery method characterized by:

19. 16. The carbon dioxide recovery method according to claim 14 or 15, the dehumidifying agent is an absorbing liquid that absorbs moisture from the gas to be separated; A carbon dioxide recovery method characterized by:

20. 20. The carbon dioxide recovery method according to claim 19, The dehumidification is performed by gas-liquid contact between the gas to be separated and the dehumidifying agent; The regeneration is carried out by gas-liquid contact between the separated gas and the dehumidifying agent that has absorbed moisture; A carbon dioxide recovery method characterized by:

21. 16. The carbon dioxide recovery method according to claim 14 or 15, The separation may include: bringing the gas to be separated into gas-liquid contact with a carbon dioxide absorbing liquid that absorbs carbon dioxide, thereby allowing the carbon dioxide to be absorbed into the carbon dioxide absorbing liquid; By regenerating the carbon dioxide absorbing solution that has absorbed carbon dioxide, A carbon dioxide recovery method characterized by:

22. 22. The carbon dioxide recovery method according to claim 21, the water content of the carbon dioxide absorbing solution is higher after carbon dioxide absorption than before carbon dioxide absorption; A carbon dioxide recovery method characterized by:

23. 23. The carbon dioxide recovery method according to claim 21 or 22, The carbon dioxide absorbing liquid is a non-aqueous absorbing liquid; A carbon dioxide recovery method characterized by:

24. 16. The carbon dioxide recovery method according to claim 14 or 15, The separation is carried out by a physical or chemical adsorbent; A carbon dioxide recovery method characterized by:

25. 16. The carbon dioxide recovery method according to claim 14 or 15, The separation is carried out using a permeable membrane that selectively allows carbon dioxide to pass through; A carbon dioxide recovery method characterized by:

26. 16. The carbon dioxide recovery method according to claim 14 or 15, The separation is carried out by cryogenic separation; A carbon dioxide recovery method characterized by:

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