Method and device for collection of carbon dioxide

Abstract

To provide a novel method for collection of carbon dioxide which can be performed at lower cost.SOLUTION: A method for collection of carbon dioxide includes the steps of: bringing carbon dioxide into contact with an adsorbent capable of adsorbing carbon dioxide to cause the carbon dioxide to adsorb onto the adsorbent; immersing the adsorbent in liquid to cause the carbon dioxide to desorb from the adsorbent to collect the carbon dioxide as a gas phase. The adsorbent has an amount of the liquid adsorbed at 25°C under saturated vapor pressure of the liquid of 0.5 mmol / g or more.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present disclosure relates to a method and an apparatus for recovering carbon dioxide.

Background Art

[0002] From the perspective of suppressing global warming, research and development of technologies for recovering carbon dioxide (CO2) and separating carbon dioxide from mixed gases are actively underway. The recovered CO2 can also be used as a raw material for synthetic fuels (e-fuels) by means of carbon recycling technology.

[0003] As a technology for recovering CO2, for example, as described in Non-Patent Document 1, a method of using an adsorbent such as zeolite and desorbing and recovering the adsorbed CO2 by heating and depressurization has attracted attention.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology disclosed in Non-Patent Document 1, in order to desorb CO2, a heat source for heating and a high-cost pump power for depressurization are required, which may increase the cost.

[0006] The present disclosure has been made in view of such a situation, and one of its objects is to provide a new method and apparatus for recovering carbon dioxide that can achieve lower costs.

Means for Solving the Problems

[0007] Aspect 1 of the present invention is An adsorption step of bringing carbon dioxide into contact with an adsorbent capable of adsorbing carbon dioxide to adsorb the carbon dioxide onto the adsorbent; A recovery step of immersing the adsorbent in a liquid to desorb the carbon dioxide adsorbed by the adsorbent in the adsorption step and recovering it as a gas phase, and The method for recovering carbon dioxide, wherein the adsorbent has an adsorption amount of the liquid of 0.5 mmol / g or more at 25°C and under the saturated vapor pressure of the liquid.

[0008] Aspect 2 of the present invention is The method according to aspect 1, further including a step of bringing a second gas mainly composed of nitrogen into contact with the adsorbent after the recovery step.

[0009] Aspect 3 of the present invention is The method according to aspect 1 or 2, wherein the adsorbent has an adsorption amount of carbon dioxide of 0.5 mmol / g or more at 25°C and under a carbon dioxide partial pressure of 100 kPa.

[0010] Aspect 4 of the present invention is The method according to any one of aspects 1 to 3, wherein the Henry constant obtained from the vapor adsorption isotherm of the liquid on the adsorbent at 25°C is 100 mmol / (g·kPa) or more.

[0011] Aspect 5 of the present invention is The method according to any one of aspects 1 to 3, wherein the Henry constant obtained from the vapor adsorption isotherm of the liquid on the adsorbent at 25°C is less than 100 mmol / (g·kPa).

[0012] Aspect 6 of the present invention is The method according to any one of aspects 1 to 3, wherein the ratio of the carbon dioxide adsorption amount at 25°C and under the saturated vapor pressure of the liquid to the carbon dioxide adsorption amount at 25°C in a situation where the liquid does not exist as a vapor with respect to the adsorbent is 0.8 or more.

[0013] Aspect 7 of the present invention is The method according to any one of Aspects 1 to 6, wherein the liquid is any one or more selected from the group consisting of water and an organic solvent.

[0014] Aspect 8 of the present invention is including a region containing an adsorbent capable of adsorbing carbon dioxide, the region includes one or more openings that enable introduction of carbon dioxide and a liquid for immersing the adsorbent, the adsorbent is a device for recovering carbon dioxide, wherein the amount of the liquid adsorbed at 25 °C and under the saturated vapor pressure of the liquid is 0.5 mmol / g or more.

[0015] Aspect 9 of the present invention is the device according to Aspect 8, having two or more of the regions.

Advantages of the Invention

[0016] According to an embodiment of the present invention, it is possible to provide a novel method and device for recovering carbon dioxide that can be made more cost-effective.

Brief Description of the Drawings

[0017]

Figure 1A

Figure 1B

Figure 1C

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 2E

Figure 2F

Figure 2G

Figure 2H

Figure 2I

Figure 3

Figure 4

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present inventors have studied from various angles in order to realize a novel method for recovering carbon dioxide that can be made more cost-effective. As a result, they have found that carbon dioxide can be recovered by adsorbing carbon dioxide onto an adsorbent that satisfies predetermined requirements and then immersing the adsorbent in a liquid. According to this method, it is not always necessary to use a heat source and the high-cost pump power for reducing pressure, and carbon dioxide can be recovered at a lower cost. The details of each requirement defined by the embodiments of the present invention are shown below. In this specification, "recovering carbon dioxide" means recovering carbon dioxide in the gas phase unless otherwise specified, and does not intend to recover carbon dioxide in a state dissolved in a liquid, for example.

[0019] The method for recovering carbon dioxide according to an embodiment of the present invention (hereinafter also referred to as the "carbon dioxide recovery method") is an adsorption step of bringing carbon dioxide into contact with an adsorbent capable of adsorbing carbon dioxide to adsorb the carbon dioxide onto the adsorbent, A recovery step of immersing the adsorbent in a liquid to desorb the carbon dioxide adsorbed by the adsorbent in the adsorption step and recovering it as a gas phase is included. The adsorbent has an adsorption amount of the liquid of 0.5 mmol / g or more at 25°C and under the saturated vapor pressure of the liquid. The above method is a novel method for recovering carbon dioxide that can be made more cost-effective. Also, in the prior art, in order to desorb CO2, pump power for reducing pressure was required, and when reducing pressure by a pump, there was a risk that it was difficult to obtain high-purity CO2 as a gas phase due to air entrainment etc. However, according to the above method, air entrainment etc. by a pump does not occur, and as a result, it is possible to obtain high-purity CO2 as a gas phase.

[0020] FIG. 1A is a schematic diagram of an example of an apparatus enabling a carbon dioxide recovery method according to an embodiment of the present invention. As shown in FIG. 1A, a carbon dioxide recovery apparatus 1 includes a region 10 that houses a predetermined adsorbent 2 capable of adsorbing carbon dioxide. The region 10 includes a first opening 11 that enables introduction of carbon dioxide and a second opening 12 that enables introduction of a liquid. The first opening 11 can be connected by piping to the outside (for example, a carbon dioxide storage unit etc., not shown) via a valve 11a. The second opening 12 can be connected by piping to the outside (for example, a liquid storage unit etc., not shown) via a valve 12a.

[0021] The method for recovering carbon dioxide according to an embodiment of the present invention can be implemented as follows using the above apparatus 1. As shown in FIG. 1B, open the valve 11a and introduce a gas 3 containing, for example, carbon dioxide into the region 10 from the first opening 11, and bring the gas 3 into contact with the adsorbent 2. Thereby, carbon dioxide can be adsorbed by the adsorbent 2. Also, if necessary, by opening the valve 12a, the residual gas 3b from which carbon dioxide has been reduced or removed from the gas 3 can be recovered (discharged) from the second opening 12.

[0022] After introducing the gas 3 containing carbon dioxide, the liquid 4 is introduced into the region 10 from the second opening 12, and the adsorbent 2 is immersed in the liquid 4 as shown in FIG. 1C. At this time, the adsorbent 2 has an adsorption amount of the liquid 4 of 0.5 mmol / g or more at 25°C and under the saturated vapor pressure of the liquid 4. Thereby, in the adsorbent 2, the exchange adsorption between the carbon dioxide 3a and the liquid 4 proceeds, and the carbon dioxide 3a can be desorbed from the adsorbent 2. The desorbed carbon dioxide 3a forms bubbles and is separated from the liquid 4, and can be recovered from the first opening 11. After recovering the carbon dioxide 3a, the liquid 4 can be discharged by opening the valve 12a. According to the above method, for example, it is possible to separate and recover the carbon dioxide 3a (and the residual gas 3b) from the mixed gas containing the carbon dioxide 3a.

[0023] When discharging the liquid 4 by, for example, gravity, the gas 3 containing the carbon dioxide 3a may be introduced into the region 10 to further extrude the liquid 4 from the region 10 and cause the adsorbent 2 to adsorb the carbon dioxide 3a again (at this time, exchange adsorption between the liquid 4 and the carbon dioxide 3a may occur in the adsorbent 2). Alternatively, when discharging the liquid 4, a second gas (purge gas) 5 mainly composed of nitrogen (not shown) may be introduced into the region 10 to extrude the liquid 4 from the region 10 and bring the second gas 5 into contact with the adsorbent 2. Thereby, the liquid 4 adsorbed on the adsorbent 2 can be desorbed and removed, and it becomes easier for the adsorbent 2 to adsorb the carbon dioxide 3a again. Alternatively, when discharging the liquid 4, a third gas (water level adjustment gas) 6 (not shown) for adjusting the water level may be introduced into the region 10 to extrude the liquid 4 from the region 10. The third gas 6 may be less expensive than the second gas 5 and may be used mainly for the purpose of extruding the liquid 4 from the region 10.

[0024] Note that FIGS. 1A to 1C show an example of the configuration and operation of the apparatus 1, and the apparatus 1 may have other configurations and perform other operations so as to implement the carbon dioxide recovery method according to the embodiment of the present invention. For example, the gas 3 and the liquid 4 (as well as the second gas 5 and the third gas 6) may be introduced (and discharged) using separate openings, or may be introduced (and discharged) using the same opening. Hereinafter, each component will be described in further detail.

[0025] <Adsorbent 2> The adsorbent 2 has an adsorption amount of the liquid 4 of 0.5 mmol / g or more at 25°C and under the saturated vapor pressure of the liquid 4. The adsorbent 2 may have a porous structure and may be capable of selectively adsorbing carbon dioxide 3a. Further, the adsorbent 2 can adsorb the liquid 4, and since the adsorption amount of the liquid 4 at 25°C and under the saturated vapor pressure of the liquid 4 is 0.5 mmol / g or more, when the adsorbent 2 adsorbed with carbon dioxide 3a is immersed in the liquid 4, exchange adsorption between carbon dioxide 3a and the liquid 4 becomes possible. The above adsorption amount can be measured by the volumetric method. Note that it is preferable that the adsorbent 2 does not undergo (or undergoes little) change as a material such as reaction and decomposition due to coexistence with the liquid 4. The form of the adsorbent 2 is not particularly limited, but for reducing pressure loss, pellets, beads, or molded bodies (for example, those coated on a honeycomb-shaped support) on the order of several millimeters are preferable.

[0026] The adsorbent 2 preferably has an adsorption amount of carbon dioxide 3a of 0.5 mmol / g or more, more preferably 1.5 mmol / g or more, and still more preferably 3.5 mmol / g or more at 25°C and under a carbon dioxide partial pressure of 100 kPa. Thereby, carbon dioxide 3a can be adsorbed more selectively, and it becomes easier to recover a sufficient amount of carbon dioxide. The adsorption amount can be measured by the volumetric method.

[0027] The adsorbent 2 can be porous and can be somewhat flexible. Therefore, the pores of the adsorbent 2 can change in size by, for example, about 1.1 times due to an external force. When the liquid 4 enters the pores, the liquid 4 can be adsorbed by the adsorbent 2. Therefore, it is preferable that 1.1 times the window diameter of the adsorbent 2 is equal to or greater than the dynamic diameter of the liquid 4. Thereby, in the adsorbent 2 to which the carbon dioxide 3a is adsorbed, the exchange adsorption between the carbon dioxide 3a and the liquid 4 becomes easier. When the adsorbent 2 contains a plurality of types of adsorbents, it is preferable that 1.1 times the window diameter of any one type of adsorbent contained in the adsorbent 2 is equal to or greater than the dynamic diameter of the liquid 4, and it is more preferable that 1.1 times the window diameter of all types of adsorbents contained in the adsorbent 2 is equal to or greater than the dynamic diameter of the liquid 4. When the liquid 4 contains a plurality of liquid compounds, it is preferable that 1.1 times the window diameter of the adsorbent 2 is equal to or greater than the dynamic diameter of any one type of liquid compound contained in the liquid 4, and it is more preferable that 1.1 times the window diameter of the adsorbent 2 is equal to or greater than the dynamic diameters of all the liquid compounds contained in the liquid 4. When the adsorbent 2 contains a plurality of types of adsorbents and the liquid 4 contains a plurality of liquid compounds, it is preferable that 1.1 times the window diameter of any one type of adsorbent contained in the adsorbent 2 is equal to or greater than the dynamic diameter of any one type of liquid compound contained in the liquid 4, and it is more preferable that 1.1 times the window diameter of all types of adsorbents contained in the adsorbent 2 is equal to or greater than the dynamic diameters of all the liquid compounds contained in the liquid 4. The upper limit of the window diameter is not particularly limited and can be, for example, 1.5 nm or less. In this specification, the window diameter of the adsorbent 2 is defined as the maximum spherical diameter that can pass through the narrowest part in the path that the molecule must pass through when being taken into the adsorbent. If the adsorbent 2 is a crystalline material, the window diameter may be geometrically calculated from the crystal structure obtained by X-ray crystal structure analysis, or otherwise, it may be determined by, for example, the molecular probe method as disclosed in T.A. Braymer, et al., Carbon, Vol. 32, 445-452, 1994. In the molecular probe method, in an atmosphere of 25 °C and 1 atm, by measuring the presence or absence of adsorption using several types of probe molecules with different dynamic diameters, the dynamic diameter of the smallest probe molecule adsorbed can be used as the window diameter. In this specification, the dynamic diameter of the liquid 4 is the mean free path l (unit: m) and the number density n (unit: m.-3 ) to (√2πln) (-1 / 2) is defined as

[0028] In one preferred embodiment of the present invention, the Henry constant determined from the adsorption isotherm of the liquid 4 to the adsorbent 2 at 25°C is 100 mmol / (g·kPa) or more. Thereby, the adsorption force of the liquid 4 to the adsorbent 2 can be increased, and the exchange adsorption between the carbon dioxide 3a and the liquid 4 can be more easily performed. In this specification, the above Henry constant can be obtained from the slope obtained by linearly approximating three or more plots in a sufficiently low pressure region where the adsorption amount of the adsorption isotherm is 0.5 mmol / g or less.

[0029] In one preferred embodiment of the present invention described above, since the adsorption force of the liquid 4 to the adsorbent 2 is relatively high, when the second gas 5 is brought into contact with the adsorbent 2 after the introduction and discharge of the liquid 4, the second gas 5 and / or the region 10 (i.e., the adsorbent 2) may be appropriately heated to facilitate the desorption of the liquid 4. The heating temperature is preferably 40°C or higher. On the other hand, from the viewpoint of suppressing the thermal change of the adsorbent 2, the heating temperature is preferably 200°C or lower.

[0030] In another preferred embodiment of the present invention, the Henry constant determined from the adsorption isotherm of the liquid 4 to the adsorbent 2 at 25°C is less than 100 mmol / (g·kPa). Thereby, the adsorption force of the liquid 4 to the adsorbent 2 can be reduced, and after the introduction and discharge of the liquid 4, it becomes easy to desorb the liquid 4 from the adsorbent 2 without heating the second gas 5 and / or the region 10. Regarding the Henry constant, it is more preferably 50 mmol / (g·kPa) or less, and still more preferably 20 mmol / (g·kPa) or less. The lower limit of the Henry constant is not particularly limited, but it can be, for example, 0.01 mmol / (g·kPa) or more.

[0031] In yet another preferred embodiment of the present invention, for the adsorbent 2, the ratio of the adsorption amount of carbon dioxide 3a at 25°C and under the saturated vapor pressure of the liquid 4 to the adsorption amount of carbon dioxide 3a in a situation where the liquid 4 does not exist as vapor at 25°C is 0.8 or more. This indicates the property that the adsorbent 2 particularly easily adsorbs carbon dioxide 3a rather than the liquid 4. Thereby, even if the step of bringing the second gas 5 into contact with the adsorbent 2 after introducing the liquid 4 is not carried out, carbon dioxide 3a can be sufficiently recovered from the gas 3 again. The upper limit of the ratio is not particularly limited, and can be, for example, 1.2 or less.

[0032] As the porous material, the adsorbent 2 may be any one or more selected from the group consisting of, for example, zeolite, MOF (Metal Organic Frameworks), activated carbon, solid absorbent, silica, and activated alumina. Among them, any one or more selected from the group consisting of zeolite, MOF, activated carbon, and solid absorbent are preferably used because they have a large carbon dioxide adsorption amount. For example, regarding the adsorption amount of carbon dioxide under a carbon dioxide partial pressure of 25°C and 100 kPa, it can be about 3 mmol / g for zeolite 4A, about 5 mmol / g for zeolite 13X, about 2.5 mmol / g for, for example, a squaric acid complex as MOF, about 2 mmol / g for, for example, molecular sieve carbon as activated carbon, and about 4 mmol / g for a solid absorbent.

[0033] Zeolite can be represented by the general formula: M 2 / n O·Al2O3·xSiO2·yH2O (where M is a cation, n is the valence of the cation, x≥2, and y≥0). Since it is known that carbon dioxide strongly interacts with cations in zeolite pores, as zeolite, those having a window diameter of 0.33 nm or more, which is the dynamic diameter of carbon dioxide, and a small Si / Al ratio are preferred. In particular, zeolite 4A, zeolite 5A, and zeolite 13X, which have proven results in carbon dioxide removal, are preferred.

[0034] MOF (Metal Organic Frameworks) is a material with a porous coordination network structure formed by the interaction between metals and organic ligands. Examples of MOF suitable for Embodiment 5 of the present invention include any one or more selected from the group consisting of Ca squarate complex, CALF-20, MIL-101, Al-PyrMOF, and Al-PMOF.

[0035] Activated carbon can be a porous substance mainly composed of carbon. As the activated carbon, molecular sieve carbon capable of selectively adsorbing carbon dioxide is preferably used.

[0036] The solid absorbent can be a porous carrier supporting a substance capable of adsorbing (absorbing) carbon dioxide. Examples of the porous carrier include SBA-15, MCM-41, MSU-H, MSU-F, etc., which are mesoporous silica. As the substance capable of adsorbing carbon dioxide, an amine compound is preferably used. Examples of the amine compound include polyethyleneimine, tetraethylenepentamine, 3-aminopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, etc.

[0037] <Gas 3 containing carbon dioxide 3a> Gas 3 contains carbon dioxide 3a. Gas 3 may be only carbon dioxide 3a or a mixture of two or more gases. Gas 3 may be, for example, a mixed gas of nitrogen and carbon dioxide 3a, or exhaust gas from an automobile or the like. The content of carbon dioxide 3a in Gas 3 is not particularly limited, but a higher content is preferable as the effects of the embodiments of the present invention become more significant. For example, 0.1% by volume or more is preferable, and 1% by volume or more is more preferable. The upper limit of the content is not particularly limited, but it may be, for example, 50% by volume or less, or 25% by volume or less.

[0038] <Liquid 4> The liquid 4 is not particularly limited as long as it satisfies the relationship with the adsorbent 2 as described above, and it may be a single liquid compound or two or more liquid compounds. It is preferable that the liquid 4 does not affect (or has a small effect on) the adsorbent 2. It is preferable that the liquid 4 does not dissolve carbon dioxide. For example, the solubility of carbon dioxide under a carbon dioxide partial pressure of 25 °C and 100 kPa is 0.01 g / cm 3 or less. From the viewpoints of cost and safety, the liquid 4 is preferably any one or more selected from the group consisting of water and organic solvents, and more preferably water. Examples of the organic solvent include any one or more selected from the group consisting of acetone, acetonitrile, benzene, chloroform, cyclohexane, dichloromethane, N,N-dimethylformamide, 1,4-dioxane, ethanol, ethyl acetate, isopropyl ether, methanol, 2-propanol, propylene carbonate, pyridine, tetrahydrofuran, toluene, and xylene. Also, the liquid 4 preferably has a high boiling point (for example, 50 °C or higher). This can suppress the volatilization of the liquid 4, which is preferable from the viewpoints of cost and process efficiency. On the other hand, it is preferable that the boiling point is 200 °C or lower because, for example, it becomes easier to remove the liquid 4 by the second gas 5.

[0039] <Second gas 5> The second gas 5 is a gas mainly composed of nitrogen. The second gas 5 can contain, for example, 50% by volume or more of nitrogen, preferably 75% by volume or more, and more preferably 100% by volume (i.e., pure nitrogen). The second gas 5 is preferably less in the content of the vapor of the liquid 4. For example, the content of the vapor of the liquid 4 is preferably 5% by volume or less, 3% by volume or less, 1% by volume or less, 0.1% by volume or less, and 0.01% by volume or less in that order. From the viewpoints of cost and safety, the second gas 5 is preferably air (atmosphere). Further, from the viewpoint of reducing the adsorption component of the adsorbent 2 as much as possible, the second gas 5 is more preferably dry air from which water vapor or the like that can be adsorbed by the adsorbent 2 has been removed. The amount of water vapor in the dry air is preferably 0.1% by volume or less, and more preferably 0.01% by volume or less. Also, the second gas 5 is preferably heated air in which the amount of water vapor is reduced by heating, and the heating temperature is preferably 40°C or higher and 200°C or lower.

[0040] <Third gas 6> The third gas 6 is a gas for discharging the liquid 4 at low cost. The third gas 6 is preferably, for example, air, more preferably air that has not been subjected to drying treatment and heat treatment. For example, the amount of water vapor in the third gas 6 can be more than 0.1% by volume and 5% by volume or less.

[0041] Hereinafter, the apparatus for recovering carbon dioxide according to the embodiment of the present invention and the method using the same will be described in more detail. According to the embodiment of the present invention, it is possible to provide an apparatus for recovering carbon dioxide that can be made more cost-effective, and the apparatus can also separate and recover carbon dioxide 3a (and residual gas 3b) from, for example, a mixed gas containing carbon dioxide 3a.

[0042] As illustrated in FIG. 1A, the apparatus 1 for recovering carbon dioxide 3a according to the embodiment of the present invention includes a region 10 that houses an adsorbent 2 capable of adsorbing carbon dioxide 3a, and the region 10 includes one or more openings (the first opening 11 and the second opening 12 in FIG. 1A) that enable introduction of carbon dioxide 3a and a liquid 4 for immersing the adsorbent 2. The adsorbent 2 has an adsorption amount of the liquid 4 of 0.5 mmol / g or more at 25°C and under the saturated vapor pressure of the liquid 4. The above-described apparatus 1 is an apparatus for recovering carbon dioxide that can be made more cost-effective. The following constituent elements will be described in detail. Constituent elements that have already been described in detail (the adsorbent 2, the gas 3, the liquid 4, the second gas 5, the third gas 6, etc.) will be omitted.

[0043] <Region 10> It includes a region 10 that houses an adsorbent 2 capable of adsorbing carbon dioxide 3a, and the region 10 includes one or more openings (the first opening 11 and the second opening 12 in FIG. 1A) that enable the introduction of carbon dioxide 3a and the liquid 4 for immersing the adsorbent 2. One or more openings (the first opening 11 and the second opening 11 in FIG. 1A) may be provided at any position in the region 10. In one embodiment of the present invention, the first opening 11 is preferably provided above the region 10 in FIG. 1A, and more preferably provided on the upper surface of the region 10. This makes it easier to recover carbon dioxide 3a. Also, in one embodiment of the present invention, the second opening 12 is preferably provided below the region 10 in FIG. 1A, and more preferably provided on the lower surface of the region 10. This makes it easier to introduce and discharge the liquid 4. The material of the region 10 is not particularly limited and may be, for example, stainless steel, acrylic, glass, etc. The region 10 may be provided with a heater (not shown) so that it can be heated as necessary.

[0044] Valves (valve 11a, valve 12a in FIG. 1A) may be provided at or near one or more openings so as to be able to open and close the one or more openings. One or more openings may be connected by piping to other regions (for example, a housing portion of the gas 3 containing carbon dioxide, a housing portion of the carbon dioxide 3a, a housing portion of the residual gas 3b, a housing portion of the liquid 4, a housing portion of the second gas 5, a housing portion of the third gas 6, etc.; not shown), and valves may be provided between each and other regions.

[0045] It is preferable to provide two or more regions 10. By doing so, the steps of bringing carbon dioxide 3a into contact with the adsorbent 2 to adsorb the carbon dioxide 3a onto the adsorbent 2 and immersing the adsorbent 2 in the liquid 4 to desorb and recover the carbon dioxide 3a from the adsorbent 2 can be carried out in parallel, improving the processing efficiency. Hereinafter, an example of an apparatus provided with two or more regions 10 will be described.

[0046] FIG. 2A is a schematic diagram of an example of an apparatus enabling a method for recovering carbon dioxide according to an embodiment of the present invention when two regions 10 are provided. The carbon dioxide recovery apparatus 100 includes a region 10 that houses the adsorbent 2, and the region 10 has one or more openings (the first opening 11 and the second opening 12 in FIG. 2A) that enable the introduction of carbon dioxide 3a and the liquid 4. Further, separately from the region 10, a region 20 having a configuration similar to that of the region 10 is included, and the region 20 has a third opening 21 corresponding to the first opening 11 and a fourth opening 22 corresponding to the second opening 12. Also, the first opening 11, the second opening 12, the third opening 21, and the fourth opening 22 are each connected to the outside (for example, a storage portion for the gas 3 containing carbon dioxide 3a, a storage portion for carbon dioxide 3a, a storage portion for the residual gas 3b, a storage portion for the liquid 4, a storage portion for the second gas 5, a storage portion for the third gas 6, etc. Not shown.) via valves (valves 11a, 11b, 12a, 21a, 21b, 22a). Further, the second opening 12 is connected to the fourth opening 22 via a valve 12b.

[0047] The method for recovering carbon dioxide according to the embodiment of the present invention can be implemented as follows using the above apparatus 100.

[0048] In FIG. 2B, in the region 10, the adsorbent 2 is in a state where it can adsorb carbon dioxide 3a, and in the region 20, the adsorbent 2 is immersed in the liquid 4, and after opening the valve 21b and recovering the carbon dioxide 3a from the third opening 21.

[0049] After the state of Fig. 2B, in Fig. 2C, open valve 11a and valve 12a, introduce gas 3 containing carbon dioxide 3a from the first opening 11 into region 10, and bring gas 3 into contact with adsorbent 2. Thereby, carbon dioxide 3a can be adsorbed by adsorbent 2. Further, if necessary, residual gas 3b other than carbon dioxide 3a can be recovered (discharged) from the second opening 12.

[0050] After the state of Fig. 2C, in Fig. 2D, close valve 11a, valve 12a and valve 21a, open valve 12b, and move liquid 4 from region 20 to region 10.

[0051] After the state of Fig. 2D, in Fig. 2E, open valve 21a and valve 11b, introduce gas 3 from the third opening 21 into region 20, adsorb carbon dioxide 3a onto adsorbent 2 in region 20, and push out liquid 4 from region 20 to region 10. Region 10 is immersed in liquid 4, carbon dioxide 3a is desorbed from adsorbent 2 in region 10, and carbon dioxide 3a is recovered from the first opening 11. At this time, the differential pressure required to raise the water level of liquid 4 in region 10 is about 10 kPa / m, which can be realized with a very low power (i.e., low cost) compared to, for example, the pump power for decompression.

[0052] After the state of Fig. 2E, in Fig. 2F, close valve 12b, open valve 22a, introduce gas 3 further into region 20, adsorb carbon dioxide 3a onto adsorbent 2, and if necessary, recover (discharge) residual gas 3b from the fourth opening 22.

[0053] After the state of Fig. 2F, in Fig. 2G, close valve 21a, valve 22a and valve 11b, open valve 12b, and move liquid 4 from region 10 to region 20.

[0054] After the state of Fig. 2G, in Fig. 2H, valves 11a and 21b are opened to introduce gas 3 from the first opening 11 into region 10, adsorb carbon dioxide 3a onto the adsorbent 2 in region 10, and extrude liquid 4 from region 10 into region 20. Region 20 is immersed in liquid 4, carbon dioxide 3a is desorbed from the adsorbent 2 in region 20, and carbon dioxide 3a is recovered from the third opening 21.

[0055] After the state of Fig. 2H, in Fig. 2I, valve 12b is closed and valve 12a is opened to further introduce gas 3 into region 10 and adsorb carbon dioxide 3a onto the adsorbent 2. Further, if necessary, residual gas 3b is recovered (discharged) from the second opening 12 (i.e., return to the state of Fig. 2C).

[0056] As shown in Figs. 2C to 2H, by using the apparatus 100, the step of desorbing and removing the liquid 4 adsorbed on the adsorbent 2 by introducing and discharging the second gas 5 is not included, and carbon dioxide 3a can be repeatedly recovered from the gas 3. It is preferable to use an adsorbent according to still another preferred embodiment of the present invention (i.e., an adsorbent in which the ratio of the adsorption amount of carbon dioxide 3a under 25°C and the saturated vapor pressure of liquid 4 to the adsorption amount of carbon dioxide 3a in a situation where liquid 4 does not exist as vapor at 25°C is 0.8 or more) in the apparatus 100. Note that Figs. 2A to 2H show an example of the configuration and operation of the apparatus 100, and the apparatus 100 may have other configurations and perform other operations so as to implement the method for recovering carbon dioxide according to the embodiment of the present invention.

[0057] Fig. 3 is a schematic diagram of an example of an apparatus enabling a method for recovering carbon dioxide according to an embodiment of the present invention when four regions 10 are provided. The carbon dioxide recovery device 200 includes a region 10 that houses the adsorbent 2, and the region 10 has one or more openings (the first opening 11 and the second opening 12 in FIG. 3) that allow carbon dioxide and the like to be introduced. Further, separately from the region 10, there are a region 20 (including the third opening 21 and the fourth opening 22) having the same configuration as the region 10, a region 30 (including the fifth opening 31 and the sixth opening 32), and a region 40 (including the seventh opening 41 and the eighth opening 42). Each region is connected via a valve to a pipe for introducing the gas 3, the second gas 5, and the water level adjustment gas 6 respectively, a pipe for recovering (discharging) the carbon dioxide 3a, the residual gas 3b, the second gas 5, and the water level adjustment gas 6 respectively, a liquid storage unit 50. Also, a liquid level sensor 60 is connected to the liquid storage unit 50 and the pipe for recovering the carbon dioxide 3a.

[0058] By using the device 200 in FIG. 3, A. A step of bringing the gas 3 containing carbon dioxide 3a into contact with the adsorbent 2 to adsorb the carbon dioxide 3a onto the adsorbent 2; B. A step of immersing the adsorbent 2 in the liquid 4 to desorb and recover the carbon dioxide 3a from the adsorbent 2; C. A step of introducing the water level adjustment gas 6 into the region to discharge (push out) the liquid 4 from the region containing the adsorbent 2; D. A step of introducing the second gas 5 and bringing the second gas 5 into contact with the adsorbent 2; can be performed simultaneously. For example, in FIG. 3, a state is shown where step A is performed in region 10, step B is performed in region 20, step C is performed in region 30, and step D is performed in region 40. In step B, the liquid level sensor 60 can be used to adjust the water level of the liquid 4 in the region 20. The device 200 can switch the steps in the order of A, B, C, D in each region by appropriately switching the opening and closing of the valves, and can perform the steps A to D simultaneously. Note that FIG. 3 shows an example of the configuration and operation of the device 200, and the device 200 may have other configurations and perform other operations so as to implement the carbon dioxide recovery method according to the embodiment of the present invention.

Example

[0059] Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. The embodiments of the present invention are not limited by the following examples, and can be implemented with appropriate modifications within the scope that can conform to the foregoing and following gists, and all of them are included in the technical scope of the embodiments of the present invention.

[0060] As adsorbents, in Test Examples No. 1 to 4, zeolite 4A (manufactured by Fujifilm Wako Pure Chemical Corporation, spherical, size: 1.4 to 2.3 mm, window diameter: 0.42 nm) was prepared, and in Test Example No. 5, zeolite 13X (manufactured by Fujifilm Wako Pure Chemical Corporation, pellet-shaped, size: 1.4 to 2.0 mm, window diameter: 0.74 nm) was prepared. In Test Example No. 6, activated carbon (molecular sieve carbon SHIRASAGI MSC 3K-172, manufactured by Osaka Gas Chemical Co., Ltd., pellet-shaped, size: 1.4 to 2.0 mm, window diameter: 0.38 nm) was prepared. The window diameters of zeolite 4A and zeolite 13X were geometrically calculated from the crystal structures obtained by X-ray crystal structure analysis, and the window diameter of the molecular sieve carbon was the value obtained by the molecular probe method. As liquids, in Test Examples No. 1 and 6, water (dynamic diameter: 0.35 nm) was prepared, in Test Examples No. 2 and 5, ethanol (dynamic diameter: 0.43 nm) was prepared, in Test Example No. 3, ethyl butyrate (dynamic diameter ≧ 0.52 nm) was prepared, and in Test Example No. 4, N,N-dimethylformamide (DMF) (dynamic diameter: 0.55 nm) was prepared. For the above adsorbents in Test Examples No. 1 to 6, the vapor adsorption isotherms of the above liquids at 25°C were obtained by the volumetric method. From the obtained data, the adsorption amounts and Henry's constants of the above liquids at 25°C and under the saturated vapor pressures of the above liquids were determined. The results are shown in Table 1 below. As an example, for Test Example No. 2, the adsorption isotherm of ethanol on zeolite 4A at 25°C is shown in FIG. 4.

[0061] As the adsorbent, in Test Example No. 7, MOF (Ca squarate complex, window diameter: 0.34 nm) was prepared as follows. First, Solution A was prepared by adding 0.1 mmol of 3,4-Dihydroxy-3-cyclobutene-1,2-dione and 0.2 mmol of NaOH per 1 mL of water, and Solution B was prepared by adding 0.2 mmol of CaCl2, 0.4 mmol of CH3COOH, and 0.8 mmol of CH3COONa per 1 mL of water. Solution A was dropped onto Solution B so as not to disrupt the interface. The solution was allowed to stand for 7 days, and the crystals of the Ca squarate complex obtained were filtered and washed. Pure water was used for washing. The window diameter of the above MOF was geometrically calculated from the crystal structure obtained by X-ray crystal structure analysis. As the liquid, in Test Example No. 7, water (dynamic diameter: 0.35 nm) was prepared. For the above MOF, the adsorption isotherm of water at 25 °C was obtained by the volumetric method. From the obtained data, the adsorption amount and Henry's constant at 25 °C and under the saturated vapor pressure of water were determined. The results are shown in Table 1 below.

[0062] For the above MOF, the ratio of the carbon dioxide adsorption amount at 25 °C and under the saturated vapor pressure of water to the carbon dioxide adsorption amount in the situation where water does not exist as vapor at 25 °C was calculated from the values in a known literature (Tu et al. Energy & Fuels, August 18, 2021, Fig. 8). The results are shown in Table 1 below.

[0063] Using the apparatus 1 as shown in Fig. 1A, the following carbon dioxide recovery test was conducted. The combination of the adsorbent 2 and the liquid 4 was as described in Table 1 below. First, using dry air, the region 10 (and the adsorbent 2) which is a glass tube (about 30 mm φ × about 20 mm) was sufficiently dried. After drying, carbon dioxide 3a was circulated into the region 10 at 10 mL / min for 10 minutes. The liquid 4 was introduced into the region 10, and the adsorbent 2 was immersed in the liquid 4 to observe the state of desorption of carbon dioxide 3a (hereinafter also referred to as "first observation"). After discharging the liquid 4 from the region 10, dry air was circulated at 100 mL / min as the second gas 5 for 1 hour (when the liquid 4 is an organic solvent) or half a day (when the liquid 4 is water). Thereafter, carbon dioxide 3a was circulated into the region 10 at 10 mL / min for 10 minutes. The liquid 4 was introduced into the region 10, and the adsorbent 2 was immersed in the liquid 4, and the state of desorption of carbon dioxide 3a was observed again (hereinafter also referred to as "second observation"). The results are shown in Table 1. In Table 1, the "liquid adsorption amount" is the adsorption amount of the liquid 4 by the adsorbent 2 under 25°C and the saturated vapor pressure of the liquid 4, the "Henry's constant" is the Henry's constant obtained from the adsorption isotherm of the liquid 4 on the adsorbent 2 at 25°C, and the "carbon dioxide adsorption amount ratio" is the ratio of the carbon dioxide adsorption amount of the adsorbent 2 under 25°C and the saturated vapor pressure of water to the carbon dioxide adsorption amount of the adsorbent 2 in the situation where water does not exist as vapor at 25°C. Also, in the "first observation" and "second observation", the determination was made as follows, and AA to C were considered qualified and D was considered unqualified. AA: Carbon dioxide 3a desorbed from the entire adsorbent 2 accommodated in the region 10 to such an extent that the liquid level of the liquid 4 shook violently, and a considerably large amount of carbon dioxide 3a was recovered. A: Carbon dioxide 3a desorbed from the entire adsorbent 2 accommodated in the region 10 to such an extent that the liquid level of the liquid 4 shook slightly, and a large amount of carbon dioxide 3a was recovered. B: The liquid level of the liquid 4 did not shake, carbon dioxide 3a desorbed from the entire adsorbent 2 accommodated in the region 10, and a slightly large amount of carbon dioxide 3a was recovered. C: The liquid level of the liquid 4 did not shake, carbon dioxide 3a desorbed from a plurality of locations of the adsorbent 2 accommodated in the region 10, and a sufficient amount of carbon dioxide 3a was recovered. D: The liquid level of the liquid 4 did not shake, the number of locations where carbon dioxide 3a desorbed from the adsorbent 2 accommodated in the region 10 was less than that in C above, and a sufficient amount of carbon dioxide 3a was not recovered.

[0064]

Table 1

[0065] It can be seen from Table 1 below. Test Examples No. 1, 2, and 5 to 7 satisfy all the requirements according to the embodiments of the present invention, and a sufficient amount of carbon dioxide was recovered in the first observation. Test Example No. 1 satisfies the requirements of one preferred embodiment of the present invention (i.e., the Henry constant at 25°C in the adsorption isotherm of liquid 4 to adsorbent 2 is 100 mmol / (g·kPa) or more), and a considerably large amount of carbon dioxide was recovered in the first observation. This is presumably because the adsorption force of liquid 4 to adsorbent 2 increases due to the Henry constant being 100 mmol / (g·kPa) or more, and the exchange adsorption between carbon dioxide 3a and liquid 4 is more promoted. Test Examples No. 2, 5, and 6 satisfy the requirements of another preferred embodiment of the present invention (i.e., the Henry constant at 25°C in the adsorption isotherm of liquid 4 to adsorbent 2 is less than 100 mmol / (g·kPa)), and even in the second observation, a slightly large to considerably large amount of carbon dioxide was recovered. This is presumably because the adsorption force of liquid 4 to adsorbent 2 decreases due to the Henry constant being less than 100 mmol / (g·kPa), and even when unheated dry air is used as the second gas 5 after introducing and discharging liquid 4, a large amount of liquid 4 can be desorbed from adsorbent 2, and a large amount of carbon dioxide 3a can be adsorbed to adsorbent 2 even in the second adsorption step. Test Example No. 7 satisfies the requirements of yet another preferred embodiment of the present invention (i.e., the ratio of the carbon dioxide adsorption amount at 25°C and under the saturated vapor pressure of water to the carbon dioxide adsorption amount at 25°C in a situation where water does not exist as vapor in adsorbent 2 is 0.8 or more), and a considerably large amount of carbon dioxide was desorbed in both the first and second observations. On the other hand, Test Examples No. 3 and 4 do not satisfy the requirement of the embodiments of the present invention that "the adsorption amount of liquid 4 at 25°C and under the saturated vapor pressure of liquid 4 is 0.5 mmol / g or more", and a sufficient amount of carbon dioxide was not recovered in the first observation. This is presumably because the adsorption force of liquid 4 to adsorbent 2 is low and almost no exchange adsorption occurred.

Explanation of symbols

[0066] 1, 100, 200 Carbon dioxide recovery device 2 Adsorbent 3 Gas containing carbon dioxide 3a Carbon dioxide 3b Residual gas 4 Liquid 5 Second gas 6 Third gas 10, 20, 30, 40 Regions 11 First opening 12 Second opening 21 Third opening 22 Fourth opening 31 Fifth opening 32 Sixth opening 31 Seventh opening 32 Eighth opening 50 Liquid storage section 60 Liquid level sensor 11a, 11b, 12a, 12b, 21a, 21b, 22a Valve

Claims

1. An adsorption step of bringing carbon dioxide into contact with an adsorbent capable of adsorbing carbon dioxide to adsorb the carbon dioxide onto the adsorbent; A recovery step of immersing the adsorbent in a liquid to desorb the carbon dioxide adsorbed by the adsorbent in the adsorption step and recovering it as a gas phase, and The method for recovering carbon dioxide, wherein the adsorbent has an adsorption amount of the liquid of 0.5 mmol / g or more at 25°C and under the saturated vapor pressure of the liquid.

2. The method according to claim 1, further comprising a step of bringing a second gas mainly composed of nitrogen into contact with the adsorbent after the recovery step.

3. The method according to claim 1 or 2, wherein the adsorbent has an adsorption amount of carbon dioxide of 0.5 mmol / g or more at 25°C and under a carbon dioxide partial pressure of 100 kPa.

4. The method according to claim 1 or 2, wherein the Henry's constant obtained from the vapor adsorption isotherm of the liquid on the adsorbent at 25°C is 100 mmol / (g·kPa) or more.

5. The method according to claim 1 or 2, wherein the Henry's constant obtained from the vapor adsorption isotherm of the liquid on the adsorbent at 25°C is less than 100 mmol / (g·kPa).

6. The method according to claim 1 or 2, wherein the ratio of the carbon dioxide adsorption amount at 25°C and under the saturated vapor pressure of the liquid to the carbon dioxide adsorption amount in a situation where the liquid does not exist as a vapor at 25°C with respect to the adsorbent is 0.8 or more.

7. The method according to claim 1 or 2, wherein the liquid is any one or more selected from the group consisting of water and organic solvents.

8. An apparatus for recovering carbon dioxide, comprising a region for accommodating an adsorbent capable of adsorbing carbon dioxide, The region includes one or more openings that enable introduction of carbon dioxide and a liquid for immersing the adsorbent, and The adsorbent has an adsorption amount of the liquid of 0.5 mmol / g or more at 25°C and under the saturated vapor pressure of the liquid.

9. The apparatus according to claim 8, having two or more of the regions.

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