Carbon dioxide recovery method

Abstract

This carbon dioxide recovery method comprises: a step for causing an absorbent (4) to absorb carbon dioxide from a carbon dioxide-containing gas; a step in which the absorbing material (4) that has absorbed carbon dioxide is introduced into the wastewater; and a step for recovering carbon dioxide from the absorbent material (4) introduced into the wastewater.

Description

Technical Field

[0001] The present disclosure relates to carbon dioxide recovery methods. Background Art

[0002] Patent Document 1 discloses a DAC (Direct Air Capture) technology for recovering carbon dioxide from the air.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-169079 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the above-mentioned technology, the recovery efficiency of carbon dioxide may be reduced. Therefore, it is necessary to improve the recovery efficiency of carbon dioxide.

[0008] In view of the above situation, the present disclosure aims to provide a carbon dioxide recovery method capable of improving the recovery efficiency of carbon dioxide.

[0009] Solutions to Solve Problems

[0010] One embodiment of the carbon dioxide recovery method involved in the present disclosure includes: a step of allowing an absorbent to absorb carbon dioxide from a carbon dioxide-containing gas; a step of putting the absorbent that has absorbed the carbon dioxide into sewage; and a step of recovering the carbon dioxide from the absorbent put into the sewage.

[0011] Effects of the Invention

[0012] According to the present disclosure, a carbon dioxide recovery method capable of improving the recovery efficiency of carbon dioxide can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of a carbon dioxide collection device used in the carbon dioxide recovery method involved in embodiment 1.

[0014] Figure 2 This is a schematic diagram for explaining the carbon dioxide recovery method involved in Embodiment 1.

[0015] Figure 3 This is a schematic diagram of a carbon dioxide recovery system capable of implementing the carbon dioxide recovery method involved in embodiment 1.

[0016] Figure 4 is a schematic diagram of a first example of a carbon dioxide recovery system.

[0017] Figure 5 is a schematic diagram of a second example of a carbon dioxide recovery system.

[0018] Figure 6 This is a schematic diagram illustrating the carbon dioxide recovery method involved in embodiment 2.

[0019] Figure 7 This is a schematic diagram illustrating the carbon dioxide recovery method involved in embodiment 3.

[0020] Figure 8 This is a schematic diagram illustrating the carbon dioxide recovery method involved in embodiment 4.

[0021] Fig. 9 This is a schematic diagram illustrating the carbon dioxide recovery method involved in embodiment 5.

[0022] Fig.10 This is a schematic diagram illustrating the carbon dioxide recovery method involved in embodiment 6.

[0023] Fig.11 This is a schematic diagram illustrating the carbon dioxide recovery method involved in embodiment 6. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In addition, the scope of the present disclosure is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical concept of the present disclosure.

[0025] Implementation Method 1

[0026] Figure 1 Schematic diagram of a carbon dioxide collection device 10 used in the carbon dioxide recovery method according to Embodiment 1. Figure 1 As shown, the carbon dioxide collection device 10 includes a supply path 1 , a carbon dioxide absorption unit 2 , and a derivation path 3 .

[0027] One end of the supply path 1 is connected to a ventilator 12 for indoor ventilation of a building 11. The other end of the supply path 1 is connected to a carbon dioxide absorption unit 2. The supply path 1 guides exhaust gas (carbon dioxide-containing gas) discharged from the ventilator 12 to the carbon dioxide absorption unit 2. The ventilator 12 has a fan (blower) for conveying air.

[0028] The carbon dioxide absorption unit 2 includes an absorbent 4 and an outer casing 5 .

[0029] The absorbent 4 absorbs carbon dioxide contained in the exhaust gas (carbon dioxide-containing gas). The absorbent 4 may be a liquid absorbent or a solid absorbent. The absorbent 4 can separate carbon dioxide contained in the carbon dioxide-containing gas from other components of the exhaust gas by absorbing carbon dioxide.

[0030] The liquid absorbent 4 can, for example, chemically or physically absorb carbon dioxide. Examples of the liquid absorbent 4 include amines. Examples of the amines include aliphatic amines, polyamines, polyimines, cyclic amines, amidine compounds, and the like. Examples of the liquid absorbent 4 include aqueous solutions of alkali metal hydroxides. Examples of the alkali metal hydroxides include sodium hydroxide and potassium hydroxide. The absorbent 4 can also be used in the form of an aqueous solution.

[0031] The solid absorbent material 4 can, for example, physically adsorb or chemically adsorb carbon dioxide. Examples of the solid absorbent material 4 that physically adsorbs carbon dioxide include zeolite, activated carbon, diatomaceous earth, alumina, silica gel, and the like. The solid absorbent material 4 can be granular, powdery, and the like. Granular forms include beads (spherical), granules (cylindrical), and the like. When a powdered absorbent material 4 is used, the absorbent material 4 can also be supported on the surface of a carrier. Examples of the absorbent material 4 that chemically adsorbs carbon dioxide include absorbent materials in which amines, alkali metal hydroxides, and the like are supported on porous bodies such as activated carbon. Calcium oxide can also be used as the absorbent material 4 that chemically adsorbs carbon dioxide.

[0032] The outer casing 5 accommodates the absorbent material 4 so that the absorbent material 4 can be taken out. The outer casing 5 includes, for example, a main body having an opening and a cover for closing the opening in an openable and closable manner.

[0033] The outlet path 3 outlets the exhaust gas from which at least a part of the carbon dioxide has been removed by the carbon dioxide absorption unit 2 to the outside of the system.

[0034] The building 11 is an example of a supply source of carbon dioxide-containing gas. The building 11 has, for example, a living space where people live. The air in the living space (indoor air) tends to have a high carbon dioxide concentration due to human breathing. The indoor air may also have a high carbon dioxide concentration due to the use of a gas stove, a heating device, etc.

[0035] Next, the carbon dioxide recovery method according to Embodiment 1 will be described. Figure 3 This is a schematic diagram of a carbon dioxide recovery system capable of implementing the carbon dioxide recovery method involved in embodiment 1.

[0036] like Figure 3 As shown, the carbon dioxide recovery system 100 includes a carbon dioxide collection device 10 (see Figure 1), sewage treatment facilities 20 and carbon dioxide recovery device 30.

[0037] The sewage treatment facility 20 treats sewage F1 and purifies it so that it can be discharged into public waters. Examples of sewage include sewage and rainwater. Examples of sewage include feces, domestic sewage, industrial sewage, etc. Examples of rainwater include precipitation, melted snow, etc. Sewage F1 is collected from homes, offices, etc. to the sewage treatment facility 20 through paths 31. A plurality of paths 31 are connected to the sewage treatment facility 20.

[0038] The carbon dioxide recovery device 30 separates at least a portion of the carbon dioxide contained in the treatment fluid F2 of the sewage treatment facility 20 by separation methods such as adsorption separation, membrane separation, liquefaction separation, and electrochemical separation. In the carbon dioxide recovery device 30, one of these separation methods may be used, or two or more may be combined. The treatment fluid F2 is an intermediate treatment fluid, a final treatment fluid, or the like of the sewage treatment facility 20.

[0039] The carbon dioxide recovery device 30 utilizing adsorption separation, for example, separates a specific component (for example, carbon dioxide) by adsorbing it onto an adsorbent. The adsorbent may be a liquid adsorbent or a solid adsorbent. The adsorbent, for example, is capable of chemically adsorbing or physically adsorbing carbon dioxide. Examples of liquid adsorbents include amines. Examples of amines include aliphatic amines, polyamines, polyimines, cyclic amines, amidine compounds, and the like. Examples of liquid adsorbents include aqueous solutions of alkali metal hydroxides, and the like. Examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and the like.

[0040] As solid adsorbents for physical adsorption of carbon dioxide, zeolite, activated carbon, diatomaceous earth, alumina, silica gel, etc. can be cited. The solid adsorbent can be granular, powdery, etc. Granular, for example, is beaded (spherical), granular (cylindrical), etc. In the case of using a powdered adsorbent, the adsorbent can also be supported on the surface of a carrier. As adsorbents for chemical adsorption of carbon dioxide, adsorbents in which amines, alkali metal hydroxides, etc. are supported on porous bodies such as activated carbon can be cited. As adsorbents for chemical adsorption of carbon dioxide, calcium oxide can also be cited.

[0041] The carbon dioxide recovery device 30 using membrane separation uses, for example, a separation membrane that can permeate components with small molecular sizes to separate specific components from other components. Specifically, for example, a separation membrane that selectively allows carbon dioxide to permeate is used. The separation membrane separates carbon dioxide from a mixed fluid containing carbon dioxide and other components. Examples of the separation membrane include organic membranes (dendritic polymer membranes, etc.) and inorganic membranes (zeolite membranes, silica membranes, carbon membranes, etc.).

[0042] The carbon dioxide recovery device 30 using liquefaction separation liquefies a specific component and separates it from other components (gases), for example. Specifically, for example, carbon dioxide is liquefied under high pressure and low temperature conditions and separated from other components (gases).

[0043] The carbon dioxide recovery device 30 using electrochemical separation ionizes a specific component (for example, carbon dioxide) to separate it from other components.

[0044] The exhaust water F3 discharged from the carbon dioxide recovery device 30 is led out of the system. The exhaust water F3 may be further used for purification. The exhaust water F3 may also be discharged to public waters (rivers, lakes, harbors, coastal seas, etc.).

[0045] A first example of the carbon dioxide recovery system 100 will be described.

[0046] Figure 4 1 is a schematic diagram of a first example of the carbon dioxide recovery system 100 (carbon dioxide recovery system 100A). Figure 4 As shown, the sewage treatment facility 20A (sewage treatment facility 20 ) includes a first sedimentation tank 21 , a biological treatment tank 22 , a second sedimentation tank 23 , an advanced treatment unit 24 , and a digestion tank 25 .

[0047] The first sedimentation tank 21 performs sedimentation separation on the solid matter (sludge) contained in the sewage F1. The biological treatment tank 22 performs biological treatment on the intermediate treated water F21 that has passed through the first sedimentation tank 21. The second sedimentation tank 23 performs sedimentation separation on the solid matter (sludge) contained in the intermediate treated water F22 that has passed through the biological treatment tank 22. The advanced treatment unit 24 performs advanced treatment on the intermediate treated water F23 that has passed through the second sedimentation tank 23. Advanced treatment is, for example, treatment to remove nutrients. The treated water that has passed through the advanced treatment unit 24 is discharged to the outside of the system as final treated water F24.

[0048] When the absorbent 4 is solid, the sludge obtained from the first sedimentation tank 21 and the second sedimentation tank 23 contains the absorbent 4 .

[0049] The digestion tank 25 digests the sludge obtained from the first sedimentation tank 21 and the second sedimentation tank 23 by methane fermentation. The digestion gas F25 (process fluid F2) generated by the digestion contains methane and carbon dioxide as fermentation products, and carbon dioxide from the absorbent 4.

[0050] The carbon dioxide recovery device 30 is provided on the downstream side of the digestion tank 25 .

[0051] The carbon dioxide recovery method according to Embodiment 1 includes a first step (collection step), a second step (input step), and a third step (recovery step).

[0052] like Figure 1 As shown, in the first step (collection step), exhaust gas from the ventilator 12, i.e., carbon dioxide-containing gas, is guided to the carbon dioxide absorption unit 2 through the supply path 1. The carbon dioxide-containing gas is, for example, indoor air in a living space of a building 11. The carbon dioxide concentration of indoor air is easily higher than that of outdoor air.

[0053] In the carbon dioxide absorption section 2 , the carbon dioxide contained in the carbon dioxide-containing gas is absorbed by the absorbent 4 . As a result, the carbon dioxide contained in the carbon dioxide-containing gas is taken into the absorbent 4 .

[0054] In the first step, the exhaust pressure of the exhaust gas from the ventilator 12 can be used to make the exhaust gas (gas containing carbon dioxide) contact with the absorbent 4 of the carbon dioxide absorption unit 2. This can improve the contact efficiency between the carbon dioxide-containing gas and the absorbent 4, and thus improve the absorption efficiency of carbon dioxide by the absorbent 4.

[0055] like Figure 2 As shown, in the second step (input step), the absorbent material 4 is taken out from the outer body 5 .

[0056] like Figure 3 As shown, the taken-out absorbent material 4 is put into the sewage F1. Specifically, for example, the absorbent material 4 is poured into the path 31 through which the sewage F1 flows. The sewage F1 containing the absorbent material 4 is transported to the sewage treatment facility 20.

[0057] In the third step (recovery step), the digestion gas F25 (treated fluid F2) containing carbon dioxide from the absorbent 4 is supplied to the carbon dioxide recovery device 30. The carbon dioxide recovery device 30 recovers carbon dioxide contained in the digestion gas F25 (treated fluid F2).

[0058] According to the carbon dioxide recovery method of the first embodiment, since the carbon dioxide collected by the absorbent 4 is put into the sewage, the carbon dioxide from the absorbent 4 containing carbon dioxide collected at home, office, etc. can be recovered in the sewage treatment facility 20. Thus, the recovery efficiency of carbon dioxide can be improved.

[0059] According to this carbon dioxide recovery method, since indoor air, in which the carbon dioxide concentration is likely to increase, is used as the carbon dioxide-containing gas, it is possible to improve the efficiency of recovering carbon dioxide.

[0060] According to this carbon dioxide recovery method, since carbon dioxide is recovered from the digestion gas obtained in the digestion tank 25, the recovery efficiency of carbon dioxide can be improved.

[0061] A second example of the carbon dioxide recovery system 100 will be described.

[0062] Figure 5 is a schematic diagram of a second example of the carbon dioxide recovery system 100 (carbon dioxide recovery system 100B). Figure 5 As shown, the sewage treatment facility 20B (sewage treatment facility 20 ) includes a first sedimentation tank 21 , a biological treatment tank 22 , a second sedimentation tank 23 , an advanced treatment unit 24 , and a digestion tank 25 .

[0063] The carbon dioxide recovery system 100B and the carbon dioxide recovery system 100A (refer to Figure 4 ) is that the carbon dioxide recovery device 30 is not arranged on the downstream side of the digestion tank 25, but is arranged between the second sedimentation tank 23 and the high-level treatment unit 24.

[0064] The intermediate treated water F23 (treated fluid F2) passed through the second sedimentation tank 23 is supplied to the carbon dioxide recovery device 30. In the carbon dioxide recovery device 30, carbon dioxide is recovered from the absorbent 4 contained in the intermediate treated water F23. In the case where the absorbent 4 is solid, for example, after the absorbent 4 is recovered from the intermediate treated water F23, carbon dioxide is recovered from the absorbent 4. The absorbent 4 can be recovered from the intermediate treated water F23 by a solid-liquid separation method such as sedimentation separation and suspension separation.

[0065] The intermediate treated water F26 that has passed through the carbon dioxide recovery device 30 is supplied to the advanced treatment unit 24. The treated water that has passed through the advanced treatment unit 24 is discharged to the outside of the system as final treated water F24.

[0066] According to this carbon dioxide recovery method, since the carbon dioxide collected by the absorbent 4 is introduced into sewage, the carbon dioxide collected at home, office, etc. can be recovered together in the sewage treatment facility 20. Thus, the recovery efficiency of carbon dioxide can be improved.

[0067] According to this carbon dioxide recovery method, since carbon dioxide is recovered from the intermediate treated water F23 that has passed through the second sedimentation tank 23, carbon dioxide can be efficiently recovered even when the absorbent 4 is liquid.

[0068] Implementation Method 2

[0069] Next, a description will be given of a carbon dioxide recovery method according to Embodiment 2. The same components as those in other embodiments are denoted by the same reference numerals and description thereof will be omitted.

[0070] Figure 6 Schematic diagram of the carbon dioxide recovery method according to Embodiment 2. Figure 6As shown, the carbon dioxide collection device 10A includes a supply path 1, a carbon dioxide absorption unit 2, a derivation path 3, and a control unit 6. The carbon dioxide collection device 10A is different from the carbon dioxide collection device 10 (see Figure 1 ) is different from the above in that it has a control unit 6.

[0071] The control unit 6 adds the absorbent material 4 to the bottom water F1 based on the fact that the carbon dioxide absorption amount of the absorbent material 4 has reached a preset value. The carbon dioxide absorption amount can be calculated based on the carbon dioxide concentration and flow rate of the carbon dioxide-containing gas. The carbon dioxide absorption amount is proportional to the carbon dioxide concentration and flow rate, and therefore, for example, can be calculated based on the carbon dioxide concentration and flow rate of the carbon dioxide-containing gas. The flow rate of the carbon dioxide-containing gas can also be calculated based on the rotation speed of the blower (fan) of the ventilation device 12.

[0072] When the carbon dioxide concentration of the carbon dioxide-containing gas changes, the carbon dioxide concentration of the carbon dioxide-containing gas is measured by the carbon dioxide concentration sensor provided in the supply path 1. The control unit 6 can calculate the carbon dioxide absorption amount based on the measurement value of the carbon dioxide concentration sensor. When the flow rate of the carbon dioxide-containing gas changes, the flow rate of the carbon dioxide-containing gas is measured by the flow meter provided in the supply path 1. The control unit 6 can calculate the carbon dioxide absorption amount based on the measurement value of the flow meter.

[0073] When the carbon dioxide absorption amount of the absorbent 4 reaches a set value, the control unit 6 can, for example, open the opening of the outer body 5 and put the absorbent 4 into the path 31 (see Figure 3 ).

[0074] According to the carbon dioxide recovery method of the second embodiment, since the carbon dioxide collected by the absorbent 4 is put into the sewage, the carbon dioxide collected at home, office, etc. can be recovered together in the sewage treatment facility 20. Thus, the recovery efficiency of carbon dioxide can be improved.

[0075] In this carbon dioxide recovery method, the absorbent material 4 is added to the water F1 based on the fact that the carbon dioxide absorption amount of the absorbent material 4 has reached the set value, so it is easy to automate the operation of adding the absorbent material 4 to the water F1. In addition, the absorption capacity of the absorbent material 4 can be used without waste, and the absorption efficiency of the carbon dioxide by the absorbent material 4 can be improved.

[0076] In this carbon dioxide recovery method, since the carbon dioxide absorption amount of the absorbent 4 is calculated, the replenishment timing of the absorbent 4 can be easily grasped.

[0077] Implementation 3

[0078] Next, a description will be given of a carbon dioxide recovery method according to Embodiment 3. The same components as those in other embodiments are denoted by the same reference numerals, and description thereof will be omitted.

[0079] Figure 7 Schematic diagram of the carbon dioxide recovery method according to Embodiment 3. Figure 7 As shown, one end of the supply path 1 is connected to an outdoor unit 14 of an air conditioning device 13. The outdoor unit 14 has a fan (air blower) for conveying air. The air conditioning device 13 is an example of a supply source of carbon dioxide-containing gas.

[0080] In the first step (collecting step), exhaust gas (carbon dioxide-containing gas) exhausted from the outdoor unit 14 is guided to the carbon dioxide absorption unit 2 through the supply path 1. In the carbon dioxide absorption unit 2, the absorbent 4 absorbs carbon dioxide contained in the carbon dioxide-containing gas.

[0081] In this carbon dioxide recovery method, since the exhaust pressure of the outdoor unit 14 is used, power loss in the first step can be suppressed.

[0082] In this carbon dioxide recovery method, the exhaust pressure of the exhaust gas from the outdoor unit 14 can be used to make the exhaust gas (carbon dioxide-containing gas) contact with the absorbent 4 of the carbon dioxide absorption unit 2. This can improve the contact efficiency between the carbon dioxide-containing gas and the absorbent 4, and thus improve the absorption efficiency of carbon dioxide by the absorbent 4.

[0083] Implementation 4

[0084] Next, a description will be given of a carbon dioxide recovery method according to Embodiment 4. The same components as those in other embodiments are denoted by the same reference numerals and description thereof will be omitted.

[0085] Figure 8 Schematic diagram of the carbon dioxide recovery method according to Embodiment 4. Figure 8 As shown, the burner 15 is provided with an air supply device 16. The air supply device 16 supplies air for combustion support in the burner 15. One end of the supply path 1 is connected to the burner 15. As the burner 15, for example, a gas water heater, a gas boiler, an oil heater, etc. can be cited. The burner 15 is an example of a supply source of carbon dioxide-containing gas. The burner 15 is used, for example, in a living space.

[0086] In the first step (collecting step), exhaust gas (carbon dioxide-containing gas) from the burner 15 is guided to the carbon dioxide absorption section 2 through the supply path 1. In the carbon dioxide absorption section 2, the absorbent 4 absorbs carbon dioxide contained in the carbon dioxide-containing gas.

[0087] In this carbon dioxide recovery method, exhaust gas (carbon dioxide-containing gas) having a large exhaust volume and a high carbon dioxide concentration can be used, and therefore, the carbon dioxide absorption efficiency can be improved.

[0088] In this carbon dioxide recovery method, the carbon dioxide-containing gas can be brought into contact with the absorbent 4 of the carbon dioxide absorbing section 2 by utilizing the gas supply pressure from the gas supply device 16. This can improve the contact efficiency between the carbon dioxide-containing gas and the absorbent 4, thereby improving the absorption efficiency of carbon dioxide by the absorbent 4.

[0089] Implementation method 5

[0090] Next, a description will be given of a carbon dioxide recovery method according to Embodiment 5. The same components as those in other embodiments are denoted by the same reference numerals and description thereof will be omitted.

[0091] Fig. 9 Schematic diagram of the carbon dioxide recovery method according to Embodiment 5. Fig. 9 As shown, the fuel cell system 17 includes an air supply device 18. The fuel cell system 17 can generate electricity by reaction between air supplied from the air supply device 18 and reformed gas. One end of the supply path 1 is connected to the fuel cell system 17. The fuel cell system 17 is an example of a supply source of carbon dioxide-containing gas.

[0092] In the first step (collection step), the exhaust gas discharged from the fuel cell system 17, that is, the carbon dioxide-containing gas is introduced to the carbon dioxide absorption section 2 through the supply path 1. In the carbon dioxide absorption section 2, the absorbent 4 absorbs carbon dioxide contained in the carbon dioxide-containing gas.

[0093] In this carbon dioxide recovery method, carbon dioxide can be collected from the high-concentration carbon dioxide-containing gas from the fuel cell system 17, so the amount of carbon dioxide emissions can be reduced.

[0094] In this carbon dioxide recovery method, the carbon dioxide-containing gas can be brought into contact with the absorbent 4 of the carbon dioxide absorbing section 2 by utilizing the gas supply pressure from the gas supply device 18. This can improve the contact efficiency between the carbon dioxide-containing gas and the absorbent 4, thereby improving the absorption efficiency of carbon dioxide by the absorbent 4.

[0095] Implementation 6

[0096] Next, a description will be given of a carbon dioxide recovery method according to Embodiment 6. The same components as those in other embodiments are denoted by the same reference numerals and description thereof will be omitted.

[0097] Fig.10 and Fig.11Schematic diagram of the carbon dioxide recovery method according to Embodiment 6. Fig.10 and Fig.11 As shown in FIG. 1 , in the carbon dioxide recovery method, in the second step (input step), when the absorbent 4 is put into the sewage, the absorbent 4 is taken out from the outer body 5 and then stored in the container 7. That is, the absorbent 4 is stored in the container 7 and then put into the sewage. Specifically, for example, the container 7 storing the absorbent 4 is poured into the path 31 (refer to FIG. 3 ) where the sewage F1 flows. Figure 3 ).

[0098] The container 7 is, for example, a bag or a box. The bag is formed of, for example, a plastic sheet. The box is formed of, for example, a plastic plate. The container 7 is preferably waterproof and can seal the absorbent material 4 in a liquid-tight manner.

[0099] In the third step (collection step), the absorbent material 4 is collected in the container 7. Therefore, safety can be improved regardless of the properties of the absorbent material 4. For example, the absorbent material 4 that may have an effect on the human body can be used without compromising safety.

[0100] In addition, the technical scope of the present disclosure is not limited to the above-mentioned embodiment, and various modifications can be added within the scope not departing from the gist of the present disclosure.

[0101] For example, the treatment fluid F2 (see Figure 3 ) is provided with one or more concentrators in the path leading to the carbon dioxide recovery device. The concentrator increases the concentration of carbon dioxide in the treatment fluid F2 by, for example, adsorption separation, membrane separation, liquefaction separation, electrochemical separation, etc. Therefore, the recovery efficiency of carbon dioxide in the carbon dioxide recovery device can be improved.

[0102] exist Figure 4 and Figure 5 In the embodiment, the carbon dioxide recovery device 30 is arranged on the downstream side of the digestion tank 25 in the sewage treatment facility 20 or between the second sedimentation tank 23 and the high-level treatment section 24, but the location of the carbon dioxide recovery device is not particularly limited. The carbon dioxide recovery device can be arranged at any position in the sewage treatment facility. For example, the carbon dioxide recovery device can also be arranged on the upstream side of the first sedimentation tank. The carbon dioxide recovery device can also be arranged between the first sedimentation tank and the biological treatment tank. The carbon dioxide recovery device can also be arranged between the biological treatment tank and the second sedimentation tank. The carbon dioxide recovery device can also be arranged on the downstream side of the high-level treatment section. The carbon dioxide recovery device can also be arranged between the first sedimentation tank or the second sedimentation tank and the digestion tank.

[0103] Description of Reference Numerals

[0104] 4 Absorbent 7 Container 11 Building 12 Ventilator 13 Air conditioning device 14 Outdoor unit 15 Burner 16 Air supply device 17 Fuel cell system 18 Air supply device

Claims

1. A method for recovering carbon dioxide, wherein: The carbon dioxide recovery method has the following features: A process in which an absorbent material absorbs carbon dioxide from a carbon dioxide-containing gas; a step of putting the absorbent material having absorbed the carbon dioxide into sewage; and A step of recovering the carbon dioxide from the absorbent introduced into the sewage.

2. The carbon dioxide recovery method according to claim 1, wherein: In the step of adding the absorbent material into the sewage, the adding of the absorbent material is performed based on the fact that the amount of carbon dioxide absorbed by the absorbent material has reached a preset value.

3. The carbon dioxide recovery method according to claim 1 or 2, wherein: The carbon dioxide-containing gas is exhaust gas discharged from a ventilation device used for indoor ventilation of a building, In the step of causing the absorbent to absorb the carbon dioxide from the carbon dioxide-containing gas, the carbon dioxide-containing gas is brought into contact with the absorbent using exhaust pressure of the ventilator.

4. The carbon dioxide recovery method according to claim 1 or 2, wherein: The carbon dioxide-containing gas is exhaust gas exhausted from an outdoor unit of an air conditioning device. In the step of causing the absorbent to absorb the carbon dioxide from the carbon dioxide-containing gas, the carbon dioxide-containing gas is brought into contact with the absorbent using exhaust pressure of the outdoor unit.

5. The carbon dioxide recovery method according to claim 1 or 2, wherein: The carbon dioxide-containing gas is exhaust gas discharged from a burner equipped with an air supply device for supplying air for combustion support. In the step of causing the absorbent to absorb the carbon dioxide from the carbon dioxide-containing gas, the carbon dioxide-containing gas is brought into contact with the absorbent using the gas supply pressure of the gas supply device.

6. The carbon dioxide recovery method according to claim 1 or 2, wherein: The carbon dioxide-containing gas is exhaust gas discharged from a fuel cell system having an air supply device for supplying air. In the step of causing the absorbent to absorb the carbon dioxide from the carbon dioxide-containing gas, the carbon dioxide-containing gas is brought into contact with the absorbent using the gas supply pressure of the gas supply device.

7. The carbon dioxide recovery method according to claim 2, wherein: The carbon dioxide absorption amount of the absorption material is calculated based on the carbon dioxide concentration and flow rate of the carbon dioxide-containing gas.

8. The method for recovering carbon dioxide according to any one of claims 1 to 7, wherein: The sewage is collected in sewage treatment facilities, In the step of recovering the carbon dioxide from the absorbent, the absorbent is recovered by the sewage treatment facility, and the carbon dioxide is recovered from the recovered absorbent.

9. The method for recovering carbon dioxide according to any one of claims 1 to 8, wherein: In the step of putting the absorbent into the sewage, the absorbent is placed in a container and put into the sewage. In the step of recovering the carbon dioxide from the absorbent, when recovering the absorbent, the absorbent is recovered in a state of being stored in the container.

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