Carbon dioxide recovery method and carbon dioxide recovery device

Abstract

Provided is, for example, a carbon dioxide recovery method comprising: a step for, in an environment having a relative humidity of 10-50%, bringing a gas including carbon dioxide into contact with an adsorbent, and adsorbing the carbon dioxide with the adsorbent; and a step for, after the adsorbent which has adsorbed the carbon dioxide has been immersed in water, desorbing the carbon dioxide from the adsorbent at a pressure of greater than 0 kPa and not more than 4.5 kPa.

Description

Carbon dioxide capture method and carbon dioxide capture device

[0001] The present disclosure relates to a carbon dioxide capture method and a carbon dioxide capture apparatus.

[0002] Methods for capturing carbon dioxide from the atmosphere have been attracting attention from the perspective of solving the problem of global warming. However, conventional methods require a huge amount of thermal energy to adsorb carbon dioxide onto an adsorbent and then desorb it.

[0003] For example, Japanese Patent Application Laid-Open No. 2019-217430 describes a carbon dioxide absorption method that uses a carbon dioxide absorbent that absorbs carbon dioxide contained in a gas containing moisture and carbon dioxide, the carbon dioxide absorbent containing lithium sodium silicate, and the carbon dioxide absorption method includes a supply step of supplying a gas having a carbon dioxide concentration of 0.1% or more and a relative humidity of 35% or more to the carbon dioxide absorbent.

[0004] JP 2010-505613 A describes a method for adsorbing carbon dioxide using a carbon dioxide adsorbent having an amine compound supported on a carbon-based adsorbent, the carbon-based adsorbent having a hydrophobic surface.

[0005] Japanese Patent Application Laid-Open No. 2017-170359 describes a gas separation apparatus equipped with an adsorption tower in which an adsorption step in which one or more gas components in a mixed gas are adsorbed onto a gas adsorbent and a regeneration step in which the gas adsorbent is regenerated by heating with water vapor to desorb the gas components, characterized in that the gas adsorbent contains an adsorbent that adsorbs the gas components and a hygroscopic exothermic agent.

[0006] JP 2010-505613 A describes a process for removing carbon dioxide from ambient air, which includes the steps of blowing the ambient air into contact with an absorbent to absorb carbon dioxide from the air, and delivering the extracted air to the interior of a greenhouse.

[0007] Japanese Patent Laid-Open Publication No. 63-252528 describes an air purification method that alternately repeats an air purification step in which air is introduced into an adsorption tank to adsorb and separate carbon dioxide, followed by a step in which water vapor is directly introduced to regenerate the adsorbent. The method stops the introduction of water vapor when the outlet temperature of the adsorption tank exceeds a set value, determines the water content in the adsorption tank corresponding to the amount of water vapor supplied during this period, and adjusts the temperature and humidity of the air to be treated so that the water content in the adsorption tank in the latter half of the next adsorption step is maintained at a predetermined value.

[0008] The problem to be solved by one embodiment of the present invention is to provide a carbon dioxide capture method and a carbon dioxide capture device that capture carbon dioxide efficiently with low energy consumption.

[0009] The present disclosure includes the following aspects. <1> A carbon dioxide recovery method comprising the steps of bringing a gas containing carbon dioxide into contact with an adsorbent in an environment of 10% to 50% relative humidity, thereby allowing the adsorbent to adsorb the carbon dioxide, and immersing the adsorbent having adsorbed carbon dioxide in water, and then desorbing the carbon dioxide from the adsorbent under a pressure of more than 0 kPa and not more than 4.5 kPa. <2> The carbon dioxide recovery method according to <1>, in which the adsorbent is an anion exchange resin having a quaternary ammonium group. <3> The carbon dioxide recovery method according to <2>, in which the anion exchange resin having a quaternary ammonium group includes a structural unit derived from styrene having a quaternary ammonium group and a structural unit derived from divinylbenzene. <4> A carbon dioxide capture device comprising: an adsorbent; an adsorbent supply means for supplying a gas containing carbon dioxide to the adsorbent; carbon dioxide adsorption means for accommodating the adsorbent and bringing the gas containing carbon dioxide into contact with the adsorbent in an environment of 10% to 50% relative humidity, thereby causing the adsorbent to adsorb carbon dioxide; water supply means for supplying water to the adsorbent that has adsorbed carbon dioxide; and carbon dioxide desorption means for holding the adsorbent immersed in water under a pressure greater than 0 kPa and not greater than 4.5 kPa, thereby desorbing carbon dioxide from the adsorbent. <5> The carbon dioxide capture device according to <4>, wherein the carbon dioxide adsorption means is connected to a flow path for supplying a gas containing carbon dioxide to the adsorbent, a flow path for supplying water vapor to the adsorbent, and a flow path for supplying water to the adsorbent. <6> The carbon dioxide capture device according to <4> or <5>, further comprising a vaporizer that vaporizes water, wherein the water supply means is connected to a flow path for supplying water to the vaporizer and a flow path for supplying water to the adsorbent, and the vaporizer is connected to a flow path for supplying water vapor to the adsorbent. <7> The carbon dioxide capture device according to any one of <4> to <6>, wherein the carbon dioxide adsorption means has a water-permeable membrane therein and an adsorbent material disposed on the water-permeable membrane. <8> The carbon dioxide capture device according to any one of <4> to <7>, further comprising concentration detection means for detecting the carbon dioxide concentration in the carbon dioxide-containing gas supplied to the carbon dioxide adsorption means and the carbon dioxide concentration in the gas discharged from the carbon dioxide adsorption means.<9> The carbon dioxide recovery device according to <8>, further comprising: a means for determining whether the adsorbent has reached its carbon dioxide adsorption limit based on carbon dioxide concentration data obtained by the concentration detection means; and a means for stopping the supply of carbon dioxide to the carbon dioxide adsorption means when it is determined that the adsorbent has reached its adsorption limit.

[0010] According to one embodiment of the present invention, there are provided a carbon dioxide capture method and a carbon dioxide capture device that capture carbon dioxide efficiently with low energy consumption.

[0011] Fig. 1 is a schematic diagram showing a carbon dioxide capture apparatus according to an embodiment of the present disclosure. Fig. 2 is a diagram showing the amount of carbon dioxide adsorption when the relative humidity during contact of the mixed gas with the adsorbent is adjusted to 0%, 10%, 20%, 50%, and 80% in an example. Fig. 3 is a diagram showing the amount of carbon dioxide adsorption when the adsorption step and the desorption step are repeatedly performed. Fig. 4 is a diagram showing the amount of carbon dioxide adsorption when the pressure inside the adsorbent tank during the desorption step is adjusted to 3 kPa, 4.5 kPa, 6.5 kPa, 10 kPa, and 50 kPa.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] Fig. 1 is a schematic diagram showing a carbon dioxide capture apparatus according to an embodiment of the present disclosure. As shown in Fig. 1, the carbon dioxide capture apparatus 100 includes a carbon dioxide tank 11 and a nitrogen tank 12, which are examples of means for supplying a gas containing carbon dioxide to an adsorbent, an adsorbent tank 20, which is an example of means for adsorbing carbon dioxide by being filled with an adsorbent 21, a water supply device 30, which is an example of means for supplying water, a desorption unit 50, which is an example of means for holding the adsorbent in a reduced pressure environment and desorbing carbon dioxide from the adsorbent, and a detector 60, which is an example of means for detecting the concentration of carbon dioxide.

[0014] The carbon dioxide tank 11 is a tank that stores carbon dioxide. A flow path P11 is connected to the carbon dioxide tank 11.

[0015] The nitrogen tank 12 is a tank for storing nitrogen. A flow path P12 is connected to the nitrogen tank 12.

[0016] A flow path P13 is connected to each of the flow paths P11 and P12.

[0017] The flow path P11 is a flow path for supplying carbon dioxide to the flow path P13. A valve V1 is provided on the flow path P11. When the valve V1 is open, carbon dioxide is supplied to the flow path P13 via P11. On the other hand, when the valve V1 is closed, the supply of carbon dioxide is stopped.

[0018] A mass flow controller (not shown) is provided on the flow path P11 closer to the carbon dioxide tank 11 than the valve V1. The mass flow controller adjusts the flow rate of carbon dioxide.

[0019] The flow path P12 is a flow path for supplying nitrogen to the flow path P13. A valve V2 is provided on the flow path P12. When the valve V2 is open, nitrogen is supplied to the flow path P13 via the flow path P12. On the other hand, when the valve V2 is closed, the supply of nitrogen is stopped.

[0020] Furthermore, a mass flow controller (not shown) is provided on P12 closer to the nitrogen tank 12 than the valve V2. The flow rate of nitrogen is adjusted by the mass flow controller.

[0021] In the flow path P13, the carbon dioxide supplied from the flow path P11 and the nitrogen supplied from the flow path P12 are mixed to generate a mixed gas containing carbon dioxide and nitrogen. Note that when the valve V1 is closed and the valve V2 is open, only nitrogen is sent to the flow path P13.

[0022] In the step of adsorbing carbon dioxide into the adsorbent described below, the carbon dioxide concentration in the carbon dioxide-containing gas is not particularly limited, but is preferably about 400 ppm, similar to the carbon dioxide concentration in the atmosphere.

[0023] In the carbon dioxide recovery device 100, a mixed gas containing carbon dioxide is supplied to the flow path P13 using a carbon dioxide tank 11 and a nitrogen tank 12, but atmospheric air may be supplied directly to the flow path P13 without using the carbon dioxide tank 11 and the nitrogen tank 12.

[0024] The flow path P13 branches into a flow path P14 and a flow path P15. A valve V3 is provided on the flow path P14. A valve V4 is provided on the flow path P15.

[0025] When valve V3 is open and valve V4 is closed, gas is sent from flow path P13 to flow path P14. On the other hand, when valve V4 is open and valve V3 is closed, gas is sent from flow path P13 to flow path P15.

[0026] The flow path P14 is connected to the detector 60 via a flow path P17. A valve V6 is provided on the flow path P14.

[0027] When the valve V3 is open, the valve V4 is closed, the valve V6 is open, and the valve V7 (described later) is closed, gas is sent from the flow path P13 to the detector 60.

[0028] The detector 60 is a device for analyzing gas (for example, analyzing carbon dioxide concentration). The detector 60 is, for example, an FT-IR (Fourier transform infrared spectrophotometer). Alternatively, for example, a carbon dioxide sensor may be provided as the detector 60, and the detected value of the carbon dioxide sensor may be input into a computer and compared with a predetermined threshold value to analyze the carbon dioxide concentration.

[0029] Flow path P15 is connected to the upper end (inlet) of the adsorbent tank 20. The lower end (outlet) of the adsorbent tank 20 is connected to flow path P16, and is connected to the detector 60 via flow path P17. A valve V4 is provided on flow path P15. Details of the adsorbent tank 20 will be described later.

[0030] When valve V4 is opened, valve V3 is closed, valve V7 is opened, and valve V6 is closed, the gas discharged from the lower end (outlet) of the adsorbent tank 20 flows through flow path P16 and is discharged to the detector 60.

[0031] In addition, the water supply device 30 is connected to a flow path P18a and a flow path P18b.

[0032] Flow path P18a is a flow path for supplying water from the water supply device 30 to the adsorbent tank 20. A valve V5a is provided on flow path P18a. When the valve V5a is open, water flows through flow path P18a and is supplied to the adsorbent tank 20. On the other hand, when the valve V5a is closed, the supply of water to the adsorbent tank 20 is stopped.

[0033] Flow path P18b is a flow path for supplying water vapor from the water supply device 30 to the adsorbent tank 20. A valve V5b and a vaporizer 80 are provided on flow path P18b, in this order, from the water supply device 30 toward the adsorbent tank 20. When the valve V5b is open, water is vaporized in the vaporizer 80 to become water vapor, which flows through flow path P18b and is supplied to the adsorbent tank 20. On the other hand, when the valve V5b is closed, the supply of water vapor to the adsorbent tank 20 is stopped.

[0034] The detector 60 is also connected to the desorption unit 50, which is equipped with a vacuum pump (not shown), via a flow path P19. The flow path P19 branches, and the flow path separate from the flow path connected to the desorption unit 50 is a flow path for discharging gas to the outside, and ends in a gas outlet.

[0035] A valve V8 is provided on the flow path that branches off from flow path P19 and leads to desorption section 50. A valve V9 is provided on the flow path that leads to the gas outlet. When valve V6 is closed, valve V7 is open, valve V8 is open, and valve V9 is closed, the inside of adsorbent tank 20 is depressurized. When valve V8 is closed and valve V9 is open, the gas that has passed through detector 60 is discharged to the outside.

[0036] The adsorbent tank 20 has a water-permeable membrane 22 inside, and the adsorbent 21 is arranged in the antigravity direction of the water-permeable membrane 22. The relative humidity inside the adsorbent tank 20 can be adjusted to a range of 10% to 50% by sending a predetermined amount of water vapor from the water supply device 30 to the adsorbent tank 20 via the flow path P18b.

[0037] From the viewpoint of efficiently adsorbing carbon dioxide, the adsorbent 21 is preferably an anion exchange resin having a quaternary ammonium group. Specifically, the anion exchange resin having a quaternary ammonium group preferably contains a structural unit derived from styrene having a quaternary ammonium group.

[0038] Examples of styrenes having a quaternary ammonium group include vinylbenzyltrialkylammonium salts such as vinylbenzyltrimethylammonium salts. Examples of counter ions in the ammonium salts include halide ions, hydroxide ions, phosphate ions, and carboxylate ions.

[0039] From the viewpoint of efficiently adsorbing carbon dioxide, the anion exchange resin having a quaternary ammonium group preferably contains a structural unit derived from styrene having a quaternary ammonium group and a structural unit derived from divinylbenzene, more preferably a structural unit derived from vinylbenzyltrimethylammonium salt and a structural unit derived from divinylbenzene, and even more preferably a structural unit derived from vinylbenzyltrimethylammonium chloride and a structural unit derived from divinylbenzene.

[0040] The water-permeable membrane 22 is not particularly limited as long as it is a membrane that allows water to pass through. By disposing the permeable membrane, the adsorbent is held in a predetermined position within the adsorbent tank. The permeable membrane is preferably a porous material, more preferably porous polytetrafluoroethylene.

[0041] Hereinafter, an example of a carbon dioxide capture method using a carbon dioxide capture device according to an embodiment of the present disclosure will be described.

[0042] The carbon dioxide capture method disclosed herein includes a step of bringing a gas containing carbon dioxide into contact with an adsorbent in an environment of 10% to 50% relative humidity to allow the adsorbent to adsorb the carbon dioxide (hereinafter also referred to as the "adsorption step"), and a step of immersing the adsorbent that has adsorbed the carbon dioxide in water and then desorbing the carbon dioxide from the adsorbent under a pressure of more than 0 kPa and not more than 4.5 kPa (hereinafter also referred to as the "desorption step").

[0043] First, valves V1 to V9 are closed. Carbon dioxide is stored in the carbon dioxide tank 11. Nitrogen is stored in the nitrogen tank 12.

[0044] (Pretreatment Step) In the carbon dioxide recovery method of the present disclosure, it is preferable to carry out the following pretreatment step before carrying out the adsorption step and the desorption step.

[0045] When the adsorbent is an anion exchange resin, ion exchange is performed in advance using an alkaline aqueous solution (e.g., sodium hydroxide aqueous solution). After ion exchange, the adsorbent is washed with water (preferably ultrapure water). After washing with water, the adsorbent is dried in a vacuum dryer. The drying temperature and drying time are not particularly limited and can be appropriately adjusted so that the absorbance of water is 0.1 or less. The adsorbent is dried using nitrogen until the absorbance of water is 0.1 or less. The adsorbent is filled into the adsorbent tank.

[0046] Valves V2, V3, V4, V6, and V7 are opened, whereby flow paths P12, P13, P14, P15, P16, P17, the adsorbent tank 20, and the detector 60 are purged with nitrogen.

[0047] At the detector 60, background data is generated.

[0048] (Adsorption Step) The valves V4 and V7 are closed, whereby nitrogen is supplied to the flow paths P12, P13, P14, and P17.

[0049] Next, valve V1 is opened. As a result, carbon dioxide is supplied to flow path P11, and the carbon dioxide and nitrogen are mixed in flow path P13. A mixed gas containing carbon dioxide and nitrogen is supplied to flow paths P14 and P17. At this time, the flow rates of carbon dioxide and nitrogen are adjusted so that the carbon dioxide concentration in the mixed gas becomes a predetermined value (preferably in the range of 390 ppm to 410 ppm). Below, an example where the carbon dioxide concentration is 400 ppm will be described.

[0050] Valve V5b is opened, and the relative humidity inside the adsorbent tank 20 is adjusted to 10% to 50%. The relative humidity is preferably 15% to 45%, and more preferably 15% to 30%. The temperature inside the adsorbent tank 20 is preferably 20°C to 35°C. The pressure inside the adsorbent tank 20 is preferably normal pressure. The relative humidity can be adjusted by the amount of water supplied from the water supply device 30 to the vaporizer 80.

[0051] Detector 60 detects the carbon dioxide concentration in the carbon dioxide-containing mixed gas before supplying the carbon dioxide-containing mixed gas to adsorbent tank 20. When detector 60 confirms that the carbon dioxide concentration in the carbon dioxide-containing mixed gas is 400 ppm and a hygrometer (not shown) confirms that the relative humidity inside adsorbent tank 20 is a predetermined relative humidity, valves V3, V5b, and V6 are closed, and valves V4 and V7 are opened. As a result, the mixed gas (carbon dioxide concentration 400 ppm) is supplied to adsorbent tank 20 via flow path P15.

[0052] Carbon dioxide is adsorbed into the adsorbent 21 filled in the adsorbent tank 20. When the carbon dioxide is adsorbed into the adsorbent 21, the mixed gas with a reduced carbon dioxide concentration is discharged from the lower end (outlet) of the adsorbent tank 20 to the flow path P16.

[0053] The detector 60 detects the carbon dioxide concentration in the gas discharged from the adsorbent tank 20. The detected carbon dioxide concentration data is sent to the detector 60, which is electrically connected to a computer (controller) (not shown) that stores and processes the data. The detector 60 confirms that the carbon dioxide concentration is decreasing below 400 ppm. As the adsorption of carbon dioxide in the adsorbent 21 progresses, the detector 60 detects that the carbon dioxide concentration, which had once decreased, increases again and finally reaches 400 ppm. When the carbon dioxide concentration decreases from 400 ppm and then returns to 400 ppm, it is determined that the adsorbent 21 has reached its carbon dioxide adsorption limit. The detector 60, for example, collects carbon dioxide concentration data (concentration data), and the obtained concentration data is sent to the computer. Based on the sent concentration data, a determination unit (not shown) of the computer determines whether the adsorbent 21 has reached its carbon dioxide adsorption limit by, for example, determining whether the concentration data is less than a threshold concentration (400 ppm).

[0054] If the determination unit determines that the adsorbent 21 has reached its carbon dioxide adsorption limit, valve V1 is closed and valves V3 and V6 are opened. This causes nitrogen to be purged from flow paths P14, P15, P16, P17, the adsorbent tank 20, and the detector 60. On the other hand, if the determination unit determines that the adsorbent 21 has not reached its carbon dioxide adsorption limit, valve V1 is maintained in the open state until the concentration data returns to 400 ppm.

[0055] Here, all the valves are closed. All the valves can be controlled by a control unit (not shown). The determination result by the determination unit is sent to the control unit, which then opens and closes the valves.

[0056] (Desorption Step) First, the vacuum pump of the desorption unit 50 is operated, and the valves V7 and V8 are opened, thereby placing the inside of the adsorbent tank 20, the flow paths P16, and the flow paths P17 in a reduced pressure state (for example, greater than 0 kPa and equal to or less than 4.5 kPa).

[0057] Next, the valve V7 is closed and the valve V6 is opened, whereby the flow paths P14 and P17 are brought into a reduced pressure state (for example, greater than 0 kPa and equal to or less than 4.5 kPa).

[0058] The vacuum pump is stopped and valves V6 and V8 are closed. At detector 60, background data is generated.

[0059] Valve V5a is opened to supply water (e.g., ultrapure water) from the water supply device 30 to the adsorbent tank 20. As a result, the adsorbent 21 filled in the adsorbent tank 20 is immersed in water. The time for immersing the adsorbent 21 in water is, for example, 30 minutes to 3 hours. The water temperature when immersing the adsorbent 21 in water is preferably higher than 0°C and equal to or lower than 35°C.

[0060] Valve V5a is closed to stop the supply of water from the water supply device 30 to the adsorbent tank 20. The vacuum pump is operated, and valves V7 and V8 are opened. This places the interior of the adsorbent tank 20, flow path P16, and flow path P17 in a reduced pressure state (for example, 3 kPa). The pressure is preferably adjusted to more than 0 kPa and not more than 4.5 kPa, and more preferably adjusted to 3 kPa to 4.5 kPa.

[0061] From the viewpoint of efficiently desorbing carbon dioxide, the time for maintaining the reduced pressure state is preferably 1 hour to 5 hours.

[0062] By maintaining the pressure reduced, the carbon dioxide adsorbed in the adsorbent 21 is desorbed and sent to the flow paths P16 and P17. By measuring the concentration of carbon dioxide with the detector 60, the mass of the desorbed carbon dioxide can be calculated.

[0063] After maintaining the reduced pressure, the vacuum pump is stopped, valve V8 is closed, and valve V9 is opened, thereby discharging the desorbed carbon dioxide to the outside.

[0064] Next, valves V2, V3, V4, and V6 are opened, whereby flow paths P14, P15, P16, and P17, the adsorbent tank 20, and the detector 60 are purged with nitrogen.

[0065] Close valves V2, V3, V4, V6, and V7.

[0066] At the detector 60, background data is generated.

[0067] Valves V2, V3, and V6 are opened, thereby supplying nitrogen to flow paths P12, P13, P14, and P17.

[0068] Valves V3 and V6 are closed, and valves V4 and V7 are opened. Nitrogen is thereby supplied to flow paths P12, P13, P15, and P16. Nitrogen is supplied until it is confirmed that the absorbance of water is 0.1 or less.

[0069] When carbon dioxide recovery is to be completed, all valves are closed. When carbon dioxide recovery is to be continued, valves V3 and V6 are opened and the adsorption step and desorption step are carried out.

[0070] In the carbon dioxide recovery method of the present disclosure, the adsorption efficiency is maintained even when the adsorption step and the desorption step are repeatedly performed.

[0071] In particular, in the desorption process, the adsorbent that has adsorbed carbon dioxide is immersed in water and then the pressure is reduced, allowing the carbon dioxide to be desorbed, and carbon dioxide can be recovered with less energy than conventional methods.

[0072] The following examples further illustrate the embodiments of the present invention, but the scope of the embodiments of the present invention is not limited to the specific examples shown below.

[0073] <Preparation of Adsorbent> A polymerization reaction was carried out using vinylbenzyltrimethylammonium chloride and divinylbenzene as polymerizable monomers, 2,2'-azobis(2-methylpropionamidine) dihydrochloride as a polymerization initiator, and ethanol as a solvent. After the polymerization reaction was completed, the mixture was dried and pulverized in a pulverizer to obtain an adsorbent with a particle size of 100 μm or less.

[0074] The sample was subjected to ion exchange with sodium hydroxide for 16 hours and washed twice with ultrapure water. After washing, the sample was dried in a vacuum dryer at 30°C for 24 hours. The sample was then dried at 30°C using nitrogen until the absorbance of water reached 0.1 or less.

[0075] <Method of capturing carbon dioxide> 0.1 g of the produced adsorbent was filled into the adsorbent tank of the carbon dioxide capture device shown in FIG. 1, and the adsorption step and desorption step were carried out.

[0076] (Adsorption step) A mixed gas with a carbon dioxide concentration of 400 ppm was supplied to the adsorbent tank. The relative humidity when the mixed gas was brought into contact with the adsorbent was adjusted to 0%, 10%, 20%, 50%, and 80%. The mixed gas was supplied until the carbon dioxide concentration discharged from the outlet of the adsorbent tank decreased from 400 ppm and returned to 400 ppm.

[0077] (Desorption step) Approximately 3 mL of ultrapure water was supplied to the adsorbent, and the adsorbent was immersed for 1 hour. The pressure inside the adsorbent tank was increased to 3 kPa using a vacuum pump, and the adsorbent was maintained under reduced pressure for 2 hours to desorb carbon dioxide.

[0078] FIG. 2 shows the results of the amount of carbon dioxide adsorption when the relative humidity during contact of the mixed gas with the adsorbent was adjusted to 0%, 10%, 20%, 50%, and 80%.

[0079] As shown in FIG. 2, when the relative humidity was set to 10%, 20%, and 50%, the amount of adsorption was large, and it was found that the amount of adsorption was particularly large when the relative humidity was set to 20%.

[0080] It has been found that the carbon dioxide recovery method of the present disclosure can efficiently adsorb carbon dioxide and desorb it without adding excessive energy.

[0081] The results of the amount of carbon dioxide adsorbed when the adsorption step and desorption step were repeatedly performed are shown in Figure 3. As shown in Figure 3, it was found that the amount of carbon dioxide adsorbed was maintained even when the adsorption step and desorption step were repeatedly performed.

[0082] Furthermore, the results of the amount of carbon dioxide adsorption when the internal pressure of the adsorbent tank in the desorption step was adjusted to 3 kPa, 4.5 kPa, 6.5 kPa, 10 kPa, and 50 kPa are shown in Figure 4. As shown in Figure 4, it was found that the amount of adsorption was large when the internal pressure of the adsorbent tank in the desorption step was set to more than 0 kPa and not more than 4.5 kPa.

[0083] The disclosure of Japanese Patent Application No. 2023-010434, filed on January 26, 2023, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. a step of contacting a gas containing carbon dioxide with an adsorbent in an environment of 10% to 50% relative humidity to allow the adsorbent to adsorb the carbon dioxide; a step of immersing the adsorbent that has adsorbed the carbon dioxide in water, and then desorbing the carbon dioxide from the adsorbent under a pressure of 3 kPa or more and 4.5 kPa or less.

2. 2. The carbon dioxide recovery method according to claim 1, wherein the adsorbent is an anion exchange resin having a quaternary ammonium group.

3. 3. The carbon dioxide recovery method according to claim 2, wherein the anion exchange resin having a quaternary ammonium group contains a structural unit derived from styrene having a quaternary ammonium group and a structural unit derived from divinylbenzene.

4. an adsorbent; an adsorbent supply means for supplying a gas containing carbon dioxide to the adsorbent; a carbon dioxide adsorption means that accommodates the adsorbent and brings the carbon dioxide-containing gas into contact with the adsorbent in an environment of a relative humidity of 10% to 50% to adsorb the carbon dioxide onto the adsorbent; a water supply means for supplying water to the adsorbent that has adsorbed carbon dioxide; a carbon dioxide desorption means for holding the adsorbent immersed in water under a pressure of 3 kPa or more and 4.5 kPa or less, and desorbing the carbon dioxide from the adsorbent; A carbon dioxide capture device comprising:

5. 5. The carbon dioxide recovery device according to claim 4, wherein a flow path for supplying the gas containing carbon dioxide to the adsorbent, a flow path for supplying water vapor to the adsorbent, and a flow path for supplying water to the adsorbent are connected to the carbon dioxide adsorption means.

6. Further comprising a vaporizer for vaporizing water; a flow path for supplying water to the vaporizer and a flow path for supplying water to the adsorbent are connected to the water supply means; The carbon dioxide recovery device according to claim 4 or 5, wherein a flow path for supplying water vapor to the adsorbent is connected to the vaporizer.

7. 6. The carbon dioxide recovery device according to claim 4, wherein the carbon dioxide adsorption means has a water-permeable membrane therein, and the adsorbent is disposed on the water-permeable membrane.

8. 6. The carbon dioxide recovery device according to claim 4, further comprising concentration detection means for detecting a carbon dioxide concentration in the gas containing carbon dioxide supplied to the carbon dioxide adsorption means and a carbon dioxide concentration in the gas discharged from the carbon dioxide adsorption means.

9. a means for determining whether the adsorbent has reached its carbon dioxide adsorption limit based on data on the carbon dioxide concentration obtained by the concentration detection means; 9. The carbon dioxide capture device according to claim 8, further comprising: means for stopping the supply of carbon dioxide to said carbon dioxide adsorption means when it is determined that said adsorbent has reached its adsorption limit.