JP7728038B2 - Carbon dioxide recovery device and carbon dioxide recovery method - Google Patents

Description

This disclosure relates to a carbon dioxide capture device and a carbon dioxide capture method.

Apparatus for separating carbon dioxide from gases containing carbon dioxide are known (for example, Patent Documents 1 to 3). Patent Document 1 discloses a gas separation apparatus that separates carbon dioxide and water vapor from a mixed gas containing carbon dioxide and water vapor as main component gases. Patent Document 2 discloses a gas recovery apparatus that individually separates carbon dioxide and an inert gas from a mixed gas containing carbon dioxide and an inert gas as main components. Patent Document 3 discloses a gas separation system that includes a carbon dioxide separation membrane that separates carbon dioxide and a water vapor removal means that removes water vapor from the gas from which carbon dioxide has been separated.

International Publication No. 2012/086836 International Publication No. 2017/086293 JP 2017-221864 A

This disclosure provides a carbon dioxide recovery device and a carbon dioxide recovery method that can easily recover gases in which the ratio of carbon dioxide to contaminant gases has increased.

A carbon dioxide recovery apparatus according to one aspect of the present disclosure includes a first processing unit arranged to separate a first supply space from a first processing space, the first processing unit having a first separation unit that separates carbon dioxide contained in a raw material gas supplied to the first supply space from impurity gases containing components of the raw material gas other than carbon dioxide by either adsorption, absorption, or permeation, and extracts at least a portion of the carbon dioxide contained in the raw material gas and releases a first processing gas from the first processing space, the first processing gas having a higher carbon dioxide to impurity gas ratio than the raw material gas; a second processing unit arranged to separate a second supply space to which the first processing gas released by the first processing unit is supplied and the second processing space, the second separation unit having a second separation unit that reduces water vapor contained in the first processing gas by either adsorption, absorption, or permeation, and the second processing unit removing at least a portion of the water vapor contained in the first processing gas and releasing a second processing gas having a higher carbon dioxide purity than the first processing gas. The second processing unit further includes a regeneration gas supply unit that supplies a regeneration gas having a lower water vapor pressure than the first processing gas to the second processing space.

In this carbon dioxide recovery apparatus, a first process gas containing an increased ratio of carbon dioxide to contaminant gases in the raw gas is sent from the first processing unit to the second supply space of the second processing unit. In the second processing unit, a regeneration gas with a lower water vapor pressure than the first process gas is supplied to a second processing space separated from the second supply space by a second separation unit. This reduces the water vapor pressure of the second process gas while removing water vapor from the first process gas by the second separation unit. The load on the device for aspirating the second process gas from which at least some of the water vapor has been removed depends on the amount of water vapor contained in the second process gas. In the above recovery apparatus, the reduced water vapor pressure of the second process gas reduces the performance requirements of the device for aspirating the second process gas. This makes it possible to easily recover a gas containing an increased ratio of carbon dioxide to contaminant gases in the raw gas.

The first processing unit may further include a water vapor supply unit that supplies a water vapor-containing gas containing water vapor to the first processing space. The first separation unit may include a separation membrane that selectively allows carbon dioxide contained in the source gas to permeate. In this case, the water vapor-containing gas promotes permeation of carbon dioxide through the separation membrane of the first separation unit. This makes it possible to efficiently separate carbon dioxide from the source gas.

The first processing unit may further include a water vapor supply unit that supplies a water vapor-containing gas containing water vapor to the first supply space. The first separation unit may include a material that selectively adsorbs or absorbs carbon dioxide contained in the source gas. In this case, the water vapor-containing gas promotes the release of carbon dioxide stored in the material of the first separation unit. This makes it possible to efficiently separate carbon dioxide from the source gas.

The temperature of the regeneration gas may be lower than the temperature of the water vapor-containing gas. In this case, the temperature of the second treatment gas is lowered to the same level as the temperature of the regeneration gas. This reduces the performance requirements of the device for sucking in the second treatment gas, making it easier to recover gas with an increased ratio of carbon dioxide to contaminant gases.

The regeneration gas may be air. In this case, it is easy to supply the regeneration gas to the second treatment space.

The water vapor pressure of the second process gas may be lower than the saturated water vapor pressure of the second process gas. In this case, the performance requirements for the device for sucking the second process gas can be reduced compared to when the second process gas contains water vapor at saturated water vapor pressure.

The recovery device may further include a suction unit that sucks gas from the first processing space. In this configuration, the water vapor pressure of the second processing gas is lowered in the second processing unit, so the performance requirements for the suction unit can be lowered compared to when the water vapor pressure is not lowered. This makes it possible to simplify the suction unit.

The second separation section may include a separation membrane that selectively allows water vapor contained in the first process gas to pass through. In this case, it becomes possible to easily remove water vapor from the first process gas.

A carbon dioxide recovery method according to another aspect of the present disclosure includes a first step of extracting at least a portion of the carbon dioxide contained in the raw material gas using a first separation unit that separates the carbon dioxide contained in the raw material gas from contaminant gases containing components of the raw material gas other than carbon dioxide by either adsorption, absorption, or permeation, thereby producing a first treated gas having a higher ratio of carbon dioxide to contaminant gases than the raw material gas; and a second step of removing at least a portion of the water vapor contained in the first treated gas using a second separation unit that reduces the water vapor contained in the first treated gas by either adsorption, absorption, or permeation, thereby producing a second treated gas having a higher carbon dioxide purity than the first treated gas. In the second step, the second treated gas is produced using a regeneration gas that has a lower water vapor pressure than the first treated gas.

In this carbon dioxide recovery method, a first separation unit is used to generate a first treated gas in which the ratio of carbon dioxide to contaminant gases contained in the raw gas is increased. A second separation unit is then used to reduce the water vapor contained in the first treated gas, and a regeneration gas with a lower water vapor pressure than the first treated gas to generate a second treated gas. By using a regeneration gas with a lower water vapor pressure, the water vapor pressure of the second treated gas can be reduced while the second separation unit removes water vapor from the first treated gas. The load on the device for aspirating the second treated gas from which at least a portion of the water vapor has been removed depends on the amount of water vapor contained in the second treated gas. In the above recovery method, the water vapor pressure of the second treated gas can be reduced, thereby lowering the performance requirements of the device for aspirating the second treated gas. Therefore, it is possible to easily recover a gas in which the ratio of carbon dioxide to contaminant gases contained in the raw gas is increased.

This disclosure provides a carbon dioxide recovery device and a carbon dioxide recovery method that can easily recover gas in which the ratio of carbon dioxide to contaminant gases has increased.

FIG. 1 is a schematic diagram showing an example of a carbon dioxide recovery device. FIG. 2 is a schematic diagram showing another example of a carbon dioxide recovery device. FIG. 3 is a schematic diagram showing another example of a carbon dioxide recovery device. FIG. 4 is a schematic diagram showing another example of a carbon dioxide recovery device. Fig. 5(a) is a diagram showing the flow of the carbon dioxide separation process that is the subject of calculation in the example, and Fig. 5(b) is a table showing the prerequisites for the calculation in the example. 6(a) is a graph showing the pressure and temperature of the gas on the supply side and the process side in the module and the calculation results, and FIG. 6(b) is a table showing the comparison results of the water vapor concentration between the flash method and the membrane separation method.

One embodiment will be described below with reference to the drawings. In the description, identical elements or elements with identical functions will be assigned the same reference numerals, and duplicate explanations will be omitted.

[Carbon dioxide capture device]
FIG. 1 is a schematic diagram showing an example of a carbon dioxide capture device. The carbon dioxide capture device 1 shown in FIG. 1 is a device that captures carbon dioxide from a gas containing carbon dioxide. Specifically, the capture device 1 separates carbon dioxide contained in a supplied gas (hereinafter referred to as "raw material gas G0"), thereby producing a gas having a higher carbon dioxide purity (concentration) than the raw material gas G0. As the raw material gas G0, for example, exhaust gas emitted after burning fuel in a factory, agricultural heater, engine of an automobile or the like, a gas heat pump, a boiler, a combustion-type water heater, a power plant, or the like, indoor or outdoor air, or fossil fuel reformed with steam is used.

Such a source gas contains carbon dioxide and contaminant gases containing components other than carbon dioxide. Contaminant gases include, for example, nitrogen, oxygen, or hydrogen. Alternatively, the source gas may contain the above-mentioned contaminant gases in addition to carbon dioxide and water vapor. Below, we will explain an example in which the source gas contains carbon dioxide, water vapor, and contaminant gases containing components other than carbon dioxide and water vapor, and the components contained in the contaminant gas will be referred to as "contaminant gas components."

When combustion exhaust gas is used as the raw material gas G0, the concentration of carbon dioxide contained in the raw material gas (carbon dioxide in the raw material gas) may be less than 40%. For example, the concentration of carbon dioxide in the combustion exhaust gas may be 3% to 30%, 4% to 25%, or 5% to 20%. The concentration of carbon dioxide contained in the gas obtained by separating carbon dioxide using the recovery device 1 (hereinafter referred to as "separated gas Gc") may be, for example, 40% or more. For example, the concentration of carbon dioxide in the separated gas Gc may be 60% or more, 70% or more, or 80% or more. In this disclosure, the carbon dioxide concentration is the volumetric concentration under standard conditions (0°C, 1 atmosphere). The recovery device 1 includes, for example, a first processing unit 10, a second processing unit 30, and an suction unit 50.

The first processing unit 10 extracts at least a portion of the carbon dioxide in the raw material gas G0 and generates a first processing gas G1 having a higher ratio of carbon dioxide to contaminant gases than the raw material gas G0. That is, the ratio of carbon dioxide to contaminant gases in the first processing gas G1 is higher than the ratio of carbon dioxide to contaminant gases in the raw material gas G0. The first processing unit 10 releases the generated first processing gas G1 toward the second processing unit 30. The first processing unit 10 includes, for example, a first separation module 12 and a raw material gas supply unit 22.

The first separation module 12 separates carbon dioxide contained in the source gas G0 from impurity gases contained in the source gas G0. The first separation module 12 includes, for example, a housing 14 and a first separation unit 16. The housing 14 houses the first separation unit 16 and forms an internal space. The first separation unit 16 is a component that separates the carbon dioxide contained in the source gas G0 from impurity gases by either adsorption, absorption, or permeation. The first separation unit 16 is arranged to divide the internal space within the housing 14 into two spaces. Hereinafter, of the pair of spaces separated by the first separation unit 16, the space to which the source gas G0 is supplied will be referred to as the "supply space Vs1," and the other space will be referred to as the "processing space Vd1." In other words, the first separation unit 16 is arranged to separate the supply space Vs1 (first supply space) and the processing space Vd1 (first processing space).

The first separation section 16 may include a separation membrane 18 that selectively allows carbon dioxide in the source gas G0 to permeate. In the present disclosure, "selectively allowing one component to permeate" means allowing a portion of the gas to permeate so that the amount of permeation of that one component among the various components contained in the supplied gas is greater than the amount of permeation of contaminating gas components. The separation membrane 18 is a membrane that has the property of allowing carbon dioxide, among the various components contained in the source gas G0, to permeate more easily than the contaminating gas components. A membrane that has the property of allowing carbon dioxide and water vapor, among the various components contained in the source gas G0, to permeate more easily than the contaminating gas components (e.g., nitrogen, oxygen, hydrogen, etc.) may be used as the separation membrane 18. The separation membrane 18 may be made of an alkaline material.

The separation membrane 18 includes, for example, a monolayer membrane containing gelling polymer particles having basic functional groups. Gelling polymer particles are polymer particles that swell in water or a polar solvent to form gel-like microparticles. The gelling polymer particles may be, for example, particles of a neutral, alkaline, or acidic polymer compound impregnated with basic molecules. The thickness of the monolayer membrane containing the gelling polymer particles may be less than 50 μm. The functional groups contained in the gelling polymer particles may be one or more functional groups selected from the group consisting of amino groups, ammonium groups, carboxylic acids, and sulfuric acids. The polymer compound constituting the gelling polymer particles may be a polymer of monomer components containing a monomer having a basic functional group or an acidic functional group. The impregnated basic molecules may include an amine-containing compound having a molecular weight of 61 to 10,000, and the pKa of the conjugate acid of the amine-containing compound may be 5 to 10. The impregnated basic molecules may have a hydroxyl group, a carboxylic acid group, or a sulfonic acid group. Alternatively, the basic molecule to be impregnated may have multiple amino groups or multiple hydroxyl groups.

The monomer may include a substituted acrylamide monomer, an N-(aminoalkyl)acrylamide, or a carboxylic acid or sulfonic acid. The proportion of the carboxylic acid or sulfonic acid-containing monomer in the monomer component may be 1 to 95 mol %, or may be 5 to 95 mol %. The monomer component may include a carboxylic acid or sulfonic acid-containing monomer and a hydrophobic group-containing monomer. In this case, the molar ratio of the carboxylic acid or sulfonic acid-containing monomer to the hydrophobic group-containing monomer may be 1:95 to 95:5. The carboxylic acid-containing monomer may be methacrylic acid or acrylic acid, and the hydrophobic group-containing monomer may be an N-alkylacrylamide. Alternatively, the sulfonic acid-containing monomer may be an acrylamido-t-butylsulfonic acid or vinylsulfonic acid, and the hydrophobic group-containing monomer may be an N-alkylacrylamide.

The first separation section 16 may further include a carrier 18a supporting the separation membrane 18. The carrier 18a may be a porous material (e.g., a porous film). The monolayer membrane containing gelling polymer particles may be formed by applying an aqueous solution containing gelling polymer particles to the surface of a porous film and then drying the aqueous solution. The gelling polymer particles may be large enough to block the surface pores of the porous carrier 18a. The particle diameter of the gelling polymer particles may be larger than the surface pores of the porous carrier 18a. The porous carrier 18a may have a first surface and a second surface facing opposite each other. The surface pores on the first surface may be blocked by the polymer particles, while the surface pores on the second surface may not be blocked by the polymer particles. In this case, the separation membrane 18 and carrier 18a may be arranged so that the first surface faces the supply space Vs1 and the second surface faces the treatment space Vd1. The carrier 18a may have a regular uneven structure on its surface that is sufficiently larger than the surface pores.

The raw gas supply unit 22 supplies raw gas G0 to the supply space Vs1 of the first separation module 12. As described above, the raw gas supply unit 22 may supply post-combustion exhaust gas discharged from a factory or the like as raw gas G0 to the supply space Vs1. The pressure of the supply space Vs1, to which the raw gas G0 is supplied from the raw gas supply unit 22, may be approximately 100 kPa (equivalent to 1 atmosphere). On the other hand, the pressure of the processing space Vd1 may be maintained at a pressure lower than the pressure of the supply space Vs1. For example, the pressure of the processing space Vd1 may be 50 kPa or less, or may be 20 kPa or less. The processing space Vd1 may be maintained in a substantially vacuum state. When the diameter of the polymer particles contained in the separation membrane 18 is larger than the pore diameter of the porous carrier 18a, the first separation unit 16 is less likely to be damaged by the pressure difference between the processing space Vd1 and the supply space Vs1.

The first processing unit 10 further includes a water vapor supply unit 24. The water vapor supply unit 24 supplies a gas containing water vapor to the processing space Vd1. The water vapor supply unit 24 supplies the gas containing water vapor (hereinafter referred to as "water vapor-containing gas Gs") to the processing space Vd1, thereby promoting the separation of carbon dioxide by the first separation unit 16 (permeation of carbon dioxide through the separation membrane 18). Specifically, the supply of the water vapor-containing gas Gs dilutes the carbon dioxide in the processing space Vd1, and the partial pressure of carbon dioxide in the processing space Vd1 becomes lower than the partial pressure of carbon dioxide in the supply space Vs1. As a result, a greater amount of carbon dioxide is separated by the first separation unit 16 than when the water vapor-containing gas Gs is not supplied. The water vapor-containing gas used to promote permeation of carbon dioxide through the separation membrane 18 is also referred to as a sweep gas.

The temperature of the water vapor-containing gas Gs supplied from the water vapor supply unit 24 may be 25°C to 80°C. Alternatively, the temperature of the water vapor-containing gas Gs may be 30°C to 70°C, or 35°C to 65°C. The relative humidity of the water vapor-containing gas Gs may be 50% or more, 60% or more, or 70% or more. The water vapor-containing gas Gs supplied from the water vapor supply unit 24 may be generated using exhaust heat generated in a factory, etc.

The first separation module 12 releases the remaining gas Gd1 from the supply space Vs1 after carbon dioxide has been removed from the source gas G0. The first separation module 12 may also release the gas Gd1 from the supply space Vs1 to the outside. The first separation module 12 releases the carbon dioxide-containing gas (first processing gas G1) separated in the processing space Vd1 (permeated from the supply space Vs1 to the processing space Vd1) from the processing space Vd1 toward the second processing unit 30. In addition to carbon dioxide, this first processing gas G1 contains water vapor in the source gas G0 that has permeated the separation membrane 18 of the first separation unit 16 and water vapor in the water vapor-containing gas Gs from the water vapor supply unit 24. The relative humidity of the first processing gas G1 may be, for example, 50% or more, 60% or more, or 70% or more.

The second processing unit 30 removes at least a portion of the water vapor in the first processing gas G1 to produce a gas having a higher carbon dioxide purity than the first processing gas G1. Hereinafter, the gas produced by the second processing unit 30 and having a higher carbon dioxide purity than the first processing gas G1 will be referred to as the "second processing gas G2." The second processing unit 30 has a second separation module 32.

The second separation module 32 separates carbon dioxide contained in the first process gas G1 by removing at least a portion of the water vapor contained in the first process gas G1. The second separation module 32 includes, for example, a housing 34 and a second separation unit 36. The housing 34 houses the second separation unit 36 and forms an internal space. The second separation unit 36 is a member that reduces water vapor contained in the first process gas G1 by either adsorption, absorption, or permeation. The second separation unit 36 is arranged to divide the internal space within the housing 34 into two spaces. Hereinafter, of the pair of spaces separated by the second separation unit 36, the space to which the first process gas G1 is supplied will be referred to as the "supply space Vs2," and the other space will be referred to as the "processing space Vd2." In other words, the second separation unit 36 is arranged to separate the supply space Vs2 (second supply space) and the processing space Vd2 (second processing space).

The second separation section 36 may include a separation membrane 38 that selectively allows water vapor in the first process gas G1 to pass through. The separation membrane 38 is a membrane that has the property of allowing water vapor, one of the various components contained in the first process gas G1, to pass through more easily than other components. The separation membrane 38 may be made of an ionic material.

The separation membrane 38 includes, for example, a monolayer membrane containing gelling polymer particles having acidic functional groups. The thickness of the monolayer membrane containing gelling polymer particles may be less than 500 μm. The acidic functional groups contained in the gelling polymer particles may be one or more functional groups selected from the group consisting of carboxyl groups and sulfate groups, or salts of such functional groups with cations. The polymer compound constituting the gelling polymer particles may be a polymer of monomer components including a monomer having an acidic functional group. Examples of polymer compounds having carboxyl groups include polymer compounds containing acrylic acid, methacrylic acid, acrylamido t-butylsulfonic acid, or vinylsulfonic acid as constituent monomers. Examples of cations include lithium ions, sodium ions, potassium ions, and magnesium ions.

The second separation section 36 may further include a carrier 38a that supports the separation membrane 38. This carrier 38a may be configured similarly to the carrier 18a (porous carrier 18a) that supports the separation membrane 18. The separation membrane 38 and carrier 38a may be arranged so that the surface of the carrier 38a on which the separation membrane 38 is provided faces the space with the lower pressure, either the supply space Vs2 or the processing space Vd2. The arrangement of the separation membrane 38 and carrier 38a and the configuration of each surface of the separation membrane 38 and carrier 38a may be changed based on the pressure difference between the supply space Vs2 and the processing space Vd2. For example, if the pressure in the supply space Vs2 is lower than the pressure in the processing space Vd2, the separation membrane 38 may be arranged closer to the supply space Vs2 than the carrier 38a.

The second processing unit 30 further includes a regeneration gas supply unit 42. The regeneration gas supply unit 42 supplies the processing space Vd2 with a regeneration gas Gr having a lower water vapor pressure than the first processing gas G1. The temperature of the regeneration gas Gr may be lower than the temperature of the water vapor-containing gas Gs supplied by the water vapor supply unit 24 of the first processing unit 10. The relative humidity of the regeneration gas Gr may be, for example, 30% to 80%, 35% to 75%, or 40% to 70%. The temperature of the regeneration gas Gr may be, for example, 0°C to 45°C, 5°C to 40°C, or 10°C to 35°C.

The regeneration gas supply unit 42 may supply air as the regeneration gas Gr to the processing space Vd2. When the regeneration gas supply unit 42 supplies air as the regeneration gas Gr to the processing space Vd2, the temperature and relative humidity of the regeneration gas Gr described above are expressed as average values over a predetermined period (e.g., one day, one week, one month, or one year). The second separation module 32 releases gas Gd2 containing water vapor removed from the first processing gas G1 from the processing space Vd2. The second separation module 32 may release gas Gd2 to the outside. The second separation module 32 releases the gas (second processing gas G2) from which water vapor has been removed in the supply space Vs2 to the suction unit 50.

The suction unit 50 suctions gas within the processing space Vd1 of the first processing unit 10. The suction unit 50 may suction gas within the processing space Vd1 via the supply space Vs2. In this case, the processing space Vd1, supply space Vs2, and suction unit 50 may be connected to each other via a gas flow path. The suction unit 50 may be a compressor or pump (e.g., a vacuum pump) that depressurizes the processing space Vd1. In this case, the pressure in the processing space Vd1 and the supply space Vs2 decreases. The suction unit 50 may maintain the pressure in the processing space Vd1 at a value lower than the pressure in the supply space Vs1 (e.g., 50 kPa or less, as described above).

Gas suction by the suction unit 50 promotes the release of the first process gas G1 from the processing space Vd1 and the release of the second process gas G2 from the supply space Vs1. The suction unit 50 may suction the second process gas G2 and send the suctioned second process gas G2 to the outside of the recovery device 1 as a separation gas Gc. The suction unit 50 may also maintain a low pressure within the water vapor supply unit 24 via the processing space Vd1. This allows water vapor to be efficiently generated in the water vapor supply unit 24. A pressure control valve or a flow rate control valve may be provided between the water vapor supply unit 24 and the processing space Vd1 to adjust the amount of water vapor supplied to the processing space Vd1. Alternatively, the amount of heat input to the water vapor supply unit 24 may be controlled. This control may adjust the amount of water vapor generated in the water vapor supply unit 24 (the amount of water vapor supplied to the processing space Vd1).

[Method for capturing carbon dioxide]
Next, as an example of a carbon dioxide recovery method, a recovery method using the above-mentioned recovery apparatus 1 will be described. The recovery method using the recovery apparatus 1 includes at least a step (first step) of extracting at least a portion of the carbon dioxide from the raw material gas G0 using a first separation section 16 that separates the carbon dioxide contained in the raw material gas G0 from contaminant gases by permeation, thereby generating a first process gas G1 having a higher carbon dioxide to contaminant gas ratio than the raw material gas G0. The recovery method also includes a step (second step) of removing at least a portion of the water vapor from the first process gas G1 using a second separation section 36 that reduces the water vapor contained in the first process gas G1 by permeation, thereby generating a second process gas G2 having a higher carbon dioxide purity than the first process gas G1. In the step of generating the second process gas G2, a regeneration gas Gr having a lower water vapor pressure than the first process gas G1 is further utilized.

Explaining in more detail, first, in the first processing unit 10, raw material gas G0 is supplied from the raw material gas supply unit 22 to the supply space Vs1 of the first separation module 12. In conjunction with the supply of raw material gas G0, the processing space Vd1 of the first separation module 12 is depressurized by the suction unit 50, and water vapor-containing gas Gs is supplied to the processing space Vd1 from the water vapor supply unit 24. As a result, a difference in carbon dioxide partial pressure occurs between the supply space Vs1 and the processing space Vd1, and at least a portion of the carbon dioxide contained in the raw material gas G0 supplied to the supply space Vs1 permeates the first separation unit 16 (separation membrane 18) and is sent to the processing space Vd1.

Since the processing space Vd1 is being suctioned by the suction unit 50, the first processing gas G1, which contains carbon dioxide and water vapor that has permeated the first separation unit 16, flows from the processing space Vd1 toward the second processing unit 30. Because the first processing gas G1 contains carbon dioxide that has been selectively separated by the separation membrane 18 of the first separation unit 16, the ratio of carbon dioxide to impurity gases in the first processing gas G1 is greater than the ratio of carbon dioxide to impurity gases in the source gas G0. The first processing gas G1 that has flowed into the second processing unit 30 is supplied to the supply space Vs2 of the second separation module 32 in the second processing unit 30.

In addition to the supply of the first process gas G1 to the supply space Vs2, the regeneration gas Gr is supplied from the regeneration gas supply unit 42 to the processing space Vd2 of the second separation module 32. This allows the second separation unit 36 (separation membrane 38) of the second separation module 32 to remove water vapor from the first process gas G1 supplied to the supply space Vs2. Specifically, a portion of the water vapor in the first process gas G1 supplied to the supply space Vs2 permeates the second separation unit 36 (separation membrane 38) and is sent to the processing space Vd2. Because the water vapor pressure of the regeneration gas Gr is lower than that of the first process gas G1, the water vapor pressure of the gas in the supply space Vs2 may decrease to the same level as the water vapor pressure in the processing space Vd2. In other words, the relative humidity of the gas in the supply space Vs2 may become less than 100%. Furthermore, because the temperature of the regeneration gas Gr is lower than that of the water vapor-containing gas Gs, it may be lower than the temperature of the first process gas G1. In this case, the gas in the supply space Vs2 is cooled by the regeneration gas Gr, so the temperature of the gas in the supply space Vs2 drops to approximately the same temperature as the regeneration gas Gr.

Since the supply space Vs2 is being suctioned by the suction section 50, the temperature is lowered by the second separation section 36, and the remaining second process gas G2 after the water vapor has been removed is sent from the supply space Vs2 toward the suction section 50. The amount of water vapor in the second process gas G2 is reduced to a value lower than the saturated water vapor amount of the second process gas G2 due to the removal of water vapor by the second separation section 36. Furthermore, the temperature of the second process gas G2 is lowered below the temperature of the first process gas G1 due to the supply of regeneration gas Gr to the process space Vd2. The second process gas G2 sucked in by the suction section 50 is sent outside the recovery device 1 as separated gas Gc. The carbon dioxide concentration (purity) of the second process gas G2 becomes higher than the carbon dioxide concentration (purity) of the first process gas G1 due to the removal of water vapor by the second separation section 36. As a result, the carbon dioxide concentration of the separated gas Gc released from the suction section 50 is higher than the carbon dioxide concentration of the raw material gas G0 supplied to the recovery device 1. In other words, a gas with concentrated carbon dioxide (a gas in which the ratio of carbon dioxide to impurity gases has increased) is recovered by the recovery device 1.

[Modification 1]
In order to increase the ratio of carbon dioxide to contaminant gases in the raw material gas G0, the carbon dioxide recovery apparatus may use a material that absorbs or adsorbs and releases carbon dioxide instead of a separation membrane that selectively allows carbon dioxide to permeate. Figure 2 is a schematic diagram showing another example of a carbon dioxide recovery apparatus. In the carbon dioxide recovery apparatus 1A shown in Figure 2, the first separation section 16 of the first separation module 12 includes a material 18A that selectively adsorbs or absorbs carbon dioxide in the raw material gas G0 instead of a separation membrane 18.

Similar to the first separation unit 16 including the separation membrane 18, the first separation unit 16 including material 18A is disposed to separate the supply space Vs1 (first supply space) from the processing space Vd1 (first processing space). In the present disclosure, selective absorption (adsorption) of one component means absorbing (adsorbing) a portion of the gas so that the amount of absorption (adsorption) of that one component among the various components contained in the supplied gas is greater than the amount of absorption of the other components. Material 18A may be an adsorbent that has the property of more easily adsorbing carbon dioxide than other components among the various components contained in the source gas G0, or may be an absorbent that has the property of more easily adsorbing carbon dioxide than other components. When material 18A is an adsorbent, material 18A may be composed of activated carbon or silica gel.

When material 18A is an absorbent, material 18A may be composed of an alkaline material, similar to separation membrane 18. Material 18A includes, for example, polymer compound particles having amino groups. These polymer compound particles may be hydrogel particles. The polymer compound constituting the polymer compound particles may be a polymer of monomer components including a monomer having an amino group. The monomer may include a substituted acrylamide monomer, an N-(aminoalkyl)acrylamide, or a tertiary amino group. The proportion of the monomer having an amino group in the monomer components may be 5 to 99 mol%.

The monomer components may include a monomer having an amino group and a monomer having a hydrophobic group. In this case, the molar ratio of the monomer having an amino group to the monomer having a hydrophobic group may be 1:99 to 99:1. The monomer having an amino group may be N-(aminoalkyl)acrylamide, and the monomer having a hydrophobic group may be N-alkylacrylamide. The first separation section 16 may include a carrier 19A supporting the material 18A instead of the carrier 18a. In this case, the material 18A may be a membrane provided on the carrier 19A and containing gel particles of a polymer compound having an amino group. Alternatively, the material 18A may be multiple membranes containing gel particles formed in layers on the carrier 19A. The carrier 19A may be a flat plate, sheet, foil, or fiber assembly. The carrier 19A may be a porous body or a honeycomb structure. The carrier 19A may be a powder of polymer compound fine particles or particles granulated from the powder. The powders and particles may contain fillers such as carbon or silica with a primary particle size of 100 nanometers or less.

In the recovery apparatus 1A, the water vapor supply unit 24 supplies a water vapor-containing gas Gs containing water vapor to the supply space Vs1. The gas in the processing space Vd1 is sucked in by the suction unit 50, as in the recovery apparatus 1. Valves (not shown) may be provided in the gas flow path between the supply space Vs1 and the raw material gas supply unit 22 and the gas flow path between the supply space Vs1 and the water vapor supply unit 24. Valves (not shown) may be provided in the gas flow path through which the gas Gd1 is exhausted from the processing space Vd1 to the outside and in the gas flow path between the processing space Vd1 and the supply space Vs2 of the second processing unit 30. The open/closed states of these valves may be switched by a control device (not shown).

To explain the carbon dioxide recovery method using the recovery apparatus 1A illustrated above, first, a raw material gas G0 is supplied from the raw material gas supply unit 22 to the supply space Vs1 of the first separation module 12. At this time, the supply of the water vapor-containing gas Gs from the water vapor supply unit 24 and the suction of the processing space Vd1 by the suction unit 50 are stopped. At least a portion of the carbon dioxide contained in the raw material gas G0 supplied to the supply space Vs1 is absorbed (adsorbed) by the material 18A. The raw material gas G0 is sent to the processing space Vd1 while the carbon dioxide is absorbed by the material 18A, and the remaining gas after the carbon dioxide has been absorbed by the material 18A is discharged from the processing space Vd1 as gas Gd1. By continuing this state for a predetermined period of time, carbon dioxide is stored in the material 18A.

After carbon dioxide has accumulated in the material 18A, the supply of source gas G0 from the source gas supply unit 22 and the discharge of gas Gd1 from the processing space Vd1 to the outside are stopped. Instead, the water vapor supply unit 24 supplies water vapor-containing gas Gs to the supply space Vs1, and the flow path between the processing space Vd1 and the supply space Vs2 of the second processing unit 30 is opened. As a result, the water vapor-containing gas Gs supplied to the supply space Vs1 delivers the carbon dioxide stored in the material 18A to the processing space Vd1. The carbon dioxide-containing gas delivered to the processing space Vd1 is then supplied to the supply space Vs2 as the first processing gas G1. Because the first processing gas G1 contains the carbon dioxide stored in the material 18A, it has a higher carbon dioxide to impurity gas ratio than the source gas G0. In the second processing unit 30 and suction unit 50, the second processing gas G2 and separation gas Gc are generated and delivered, similar to the recovery device 1 described above.

[Modification 2]
The carbon dioxide capture apparatus may include multiple second processing units and multiple suction units to remove at least a portion of the water vapor in the first process gas G1. FIG. 3 is a schematic diagram showing another example of a carbon dioxide capture apparatus. The carbon dioxide capture apparatus 1B shown in FIG. 3 includes second processing units 30a and 30b instead of the second processing unit 30, and includes suction units 50a and 50b instead of the suction unit 50. The second processing units 30a and 30b are configured similarly to the second processing unit 30, and the suction units 50a and 50b have the same function as the suction unit 50. In the capture apparatus 1B, the pressure in the supply space Vs2 decompressed by the suction unit 50b may be higher than the pressure in the supply space Vs2 decompressed by the suction unit 50a.

To explain the carbon dioxide recovery method using this recovery apparatus 1B, similar to the recovery apparatus 1 illustrated in FIG. 1, a first process gas G1 is supplied from the first processing unit 10 (first separation module 12) to the supply space Vs2 of the second processing unit 30a. In the second separation module 32 of the second processing unit 30a, at least a portion of the water vapor in the first process gas G1 is removed by the second separation unit 36, thereby generating a second process gas G21. The carbon dioxide purity of the second process gas G21 is higher than that of the first process gas G1. The gas in the supply space Vs2 of the second processing unit 30a is sucked in and compressed by the suction unit 50a, resulting in a second process gas G21 with increased carbon dioxide partial pressure and water vapor pressure. The second process gas G21 is then supplied to the supply space Vs2 of the second processing unit 30b.

In the second separation module 32 of the second processing unit 30b, the second separation unit 36 removes at least a portion of the water vapor in the second processing gas G21, thereby generating a second processing gas G22. The carbon dioxide purity of the second processing gas G22 is higher than that of the second processing gas G21. The second processing gas G22 is sucked from the supply space Vs2 of the second processing unit 30b by the suction unit 50b, and the gas is sent to the outside of the recovery device 1B as a separated gas Gc.

The recovery apparatus 1B may further include one or more additional second processing units 30 and one or more additional suction units 50. In the recovery apparatus 1A illustrated in FIG. 2, second processing units 30a, 30b and suction units 50a, 50b may be provided instead of the second processing unit 30 and suction unit 50. In the recovery apparatus 1B described above, a greater amount of water vapor can be removed from the first process gas G1 than in the recovery apparatuses 1 and 1A. Alternatively, the performance per suction unit (e.g., compressor) can be reduced compared to the recovery apparatuses 1 and 1A.

[Other Modifications]
In the recovery apparatus 1, 1A described above, the second treatment unit 30 reduces the water vapor contained in the first treatment gas G1 using the separation membrane 38. However, instead of the separation membrane 38, a material (absorbent or adsorbent) that selectively adsorbs or absorbs water vapor contained in the first treatment gas G1 may be included. Even in this case, the regeneration gas supply unit 42 may supply the regeneration gas Gr to one of a pair of spaces (treatment spaces) separated by the absorbent (adsorbent) in the second treatment unit 30. Such an absorbent may include a film, powder, or particles containing gelling polymer particles having acidic functional groups, or may include a film, powder, or particles containing both a salt of gelling polymer particles having acidic functional groups and a salt of gelling polymer microparticles having basic functional groups. The absorbent may be supported on a carrier such as a porous material, or may include a filler such as carbon black or fumed silica.

[Effects of the embodiment]
In the carbon dioxide recovery apparatus 1 described above, the first process gas G1, in which the ratio of impurity gases contained in the raw material gas G0 is reduced and the ratio of carbon dioxide is increased, is sent from the first process unit 10 to the supply space Vs2 of the second process unit 30. Then, a regeneration gas Gr, which has a water vapor pressure lower than that of the first process gas G1, is supplied to the process space Vd2, which is separated from the supply space Vs2 by the second separation unit 36. As a result, the water vapor in the first process gas G1 is removed by the second separation unit 36, and the water vapor pressure of the second process gas G2 is reduced to below the saturated water vapor pressure. The load on the device for aspirating the second process gas G2 depends on the water vapor pressure (amount of water vapor) contained in the second process gas G2. In the recovery apparatus 1 described above, the water vapor pressure of the second process gas G2 is reduced, so the performance requirements of the device for aspirating the second process gas G2 can be reduced. Therefore, it is possible to easily recover a gas in which the ratio of carbon dioxide to impurity gases contained in the raw material gas G0 is increased.

In the above embodiment, the first processing unit 10 of the recovery device 1 further includes a water vapor supply unit 24 that supplies a water vapor-containing gas Gs containing water vapor to the processing space Vd1. The first separation unit 16 includes a separation membrane 18 that selectively allows carbon dioxide contained in the raw material gas G0 to permeate. In this case, the water vapor-containing gas Gs promotes permeation of carbon dioxide through the separation membrane 18 of the first separation unit 16. This makes it possible to efficiently separate carbon dioxide from the raw material gas G0.

In the above embodiment, the first processing unit 10 of the recovery apparatus 1A further includes a water vapor supply unit 24 that supplies a water vapor-containing gas Gs containing water vapor to the supply space Vs1. The first separation unit 16 includes a material 18A that selectively adsorbs or absorbs carbon dioxide contained in the source gas G0. In this case, the water vapor-containing gas Gs promotes the release (desorption) of carbon dioxide stored in the material 18A of the first separation unit 16. This makes it possible to efficiently separate carbon dioxide from the source gas G0.

In the above embodiment, the temperature of the regeneration gas Gr is lower than the temperature of the water vapor-containing gas Gs. In this case, the temperature of the second treatment gas G2 is lowered to approximately the same as the temperature of the regeneration gas Gr. This allows the performance requirements of the device for sucking in the second treatment gas G2 to be further reduced, making it possible to more easily recover gas with an increased ratio of carbon dioxide to contaminant gases.

In the above embodiment, the regeneration gas Gr is air. In this case, it is easy to supply the regeneration gas Gr to the treatment space Vd2.

In the above embodiment, the water vapor pressure of the second process gas G2 is lower than the saturated water vapor pressure of the second process gas G2. In this case, the performance requirements of the device for sucking the second process gas G2 can be reduced compared to when the second process gas G2 contains water vapor at saturated water vapor pressure.

The recovery device 1, 1A according to the above embodiments includes a suction unit 50 that sucks gas from the processing space Vd1. In this configuration, the water vapor pressure of the second processing gas G2 is lowered in the second processing unit 30, so the performance requirements for the suction unit 50 can be lowered compared to when the water vapor pressure is not lowered. This makes it possible to simplify the suction unit 50.

In the above embodiment, the second separation section 36 includes a separation membrane 38 that selectively allows water vapor contained in the first process gas G1 to pass through. In this case, it is possible to easily remove water vapor from the first process gas G1.

In the carbon dioxide recovery method using the recovery apparatuses 1, 1A, and 1B according to the above embodiments, the first separation section 16 is used to increase the ratio of carbon dioxide to contaminant gases contained in the raw gas G0 (by separating or concentrating the carbon dioxide), thereby generating a first process gas G1. The second separation section 36 reduces the water vapor contained in the first process gas G1, and a regeneration gas Gr, which has a lower water vapor pressure than the first process gas G1, is used to generate a second process gas G2. By using the regeneration gas Gr with a lower water vapor pressure, the second separation section 36 can remove water vapor from the first process gas G1 while lowering the water vapor pressure of the second process gas G2. The load on the device for aspirating the second process gas G2 depends on the amount of water vapor contained in the second process gas G2. The above recovery method allows the water vapor pressure of the second process gas G2 to be reduced, thereby reducing the performance requirements of the device for aspirating the second process gas G2. Therefore, it is possible to easily recover a gas in which the ratio of carbon dioxide to contaminant gases contained in the raw gas G0 has increased.

Another possible device or method for recovering carbon dioxide after separating it (e.g., concentrating it) is one in which the treated gas from which carbon dioxide has been separated (e.g., concentrated) in the first processing unit 10 is recovered via a heat exchanger, gas-liquid separator, and compressor. In this device or method, the heat exchanger, gas-liquid separator, and compressor are arranged in this order from upstream, and the treated gas is cooled in the heat exchanger, liquefying some of the water vapor in the treated gas. The gas-liquid separator then separates some of the liquefied water vapor (moisture) from the remaining gas containing carbon dioxide, and the separated gas containing carbon dioxide is sucked in by the compressor.

In this device or method, the treatment gas can be cooled to a temperature similar to that of the cooling gas by the heat exchanger, but the cooled gas contains a saturated amount of water vapor. The performance required of the compressor increases depending on the amount of water vapor in the gas to be sucked in by the compressor, so a compressor that sucks in carbon dioxide-containing gas (gas with a saturated water vapor amount) separated by the gas-liquid separator requires high performance and large power. In contrast, in the recovery device 1 and recovery method of the above embodiment, gas with a low relative humidity (below the saturated water vapor amount) is generated in the second separation section 36 of the second processing unit 30, so the performance required of the compressor can be reduced.

While the above describes embodiments of the present disclosure, the present disclosure is not limited to these embodiments. The heat exchanger and gas-liquid separator used in the other devices or methods described above may be used in combination with one or more second processing units (second separation modules). Figure 4 is a schematic diagram showing another example of a carbon dioxide capture device. The capture device 1C shown in Figure 4 differs from the capture device 1B shown in Figure 3 in that it further includes a heat exchanger 62 and a gas-liquid separator 64 disposed between the first processing unit 10 and the second processing unit 30a. The capture device 1C also differs from the capture device 1B in that the suction unit 50a is disposed between the first processing unit 10 and the second processing unit 30a (downstream of the gas-liquid separator 64) and the suction unit 50b is disposed between the second processing unit 30a and the second processing unit 30b. Note that another suction unit (not shown) may be disposed further downstream of the downstream second separation module 32. The capture device 1C shown in Figure 4 also enables a reduction in the load on each suction unit. In the recovery devices 1 and 1A shown in Figures 1 and 2, the suction section 50 (heat exchanger 62 and gas-liquid separator 64) may also be disposed between the first processing section 10 and the second processing section 30.

In the recovery apparatus 1, 1A described above, the water vapor-containing gas Gs is supplied to the processing space Vd1 or supply space Vs1 of the first processing unit 10 by the water vapor supply unit 24, but the first processing unit 10 does not have to have the water vapor supply unit 24. In this case, the first processing gas G1 sent to the second processing unit 30, which removes water vapor from the gas, contains water vapor that was contained in the source gas G0 and that has passed through the first separation unit 16 (separation membrane 18 or material 18A).

The temperature of the regeneration gas Gr supplied by the regeneration gas supply unit 42 may be approximately the same as the temperature of the water vapor-containing gas Gs supplied from the water vapor supply unit 24 in the first processing unit 10, or may be higher than the temperature of the water vapor-containing gas Gs. The regeneration gas supply unit 42 may supply a gas other than air. For example, the regeneration gas supply unit 42 may include a humidity regulator capable of adjusting humidity, and gas having a humidity adjusted by the humidity regulator may be supplied to the processing space Vd2 as the regeneration gas Gr.

[Evaluation results]
The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to the following examples. In the following examples, removal performance when using a separation membrane module (the above-described second separation module 32) capable of selectively separating water vapor is evaluated by calculation.

(Calculation method)
The target gas for water vapor removal was the permeate gas (gas in the treatment space) under the conditions previously used as the reference case for carbon dioxide separation membrane calculations. Figure 5(a) shows the process flow used for the calculation, and the table in Figure 5(b) shows the assumptions for the calculation, such as the properties of the water vapor separation membrane and the gas flow rate. "Case 1" shown in Figures 5(a) and 5(b) shows the condition in which the permeate gas of the carbon dioxide separation membrane was directly introduced into the water vapor separation membrane. "Case 2" shows the condition in which the permeate gas was flushed at 40°C and the compressed gas was introduced into the water vapor separation membrane. The mass balance within the membrane separation module was calculated using a differential equation that sets the membrane permeation rate, and the energy balance was calculated using a differential equation that takes into account the enthalpy change due to gas permeation within the membrane and heat transfer through the membrane. The amount of water vapor removed was calculated by simultaneously solving these equations using Matlab.

(result)
Figure 6(a) shows an example of calculations of the gas partial pressures and gas temperatures on the feed and permeate sides of the module in Case 2. Water vapor is removed by the partial pressure difference between the permeate and non-permeate sides of the membrane. It was confirmed that the gas temperature dropped from approximately 343 K to 305 K, indicating that a heat exchanger and gas-liquid separator can be omitted. Figure 6(b) shows a comparison of the water vapor removal rate with flash operation. In Case 1, the target gas contained a large amount of water vapor, but the partial pressure difference between the target gas and the regeneration gas was small due to the low total pressure, resulting in insufficient water vapor removal. In contrast, in Case 2, although the total pressure was approximately twice as high, water vapor was removed by membrane separation, resulting in a lower water vapor concentration than in the flash method. Furthermore, by increasing the sweep gas flow rate from 200 mol/s to 300 mol/s, the water vapor concentration decreased from 21% to 14%. This indicates that dehydration using a membrane module is effective for gases pressurized to a certain extent, and that it has the potential to significantly reduce the energy required and costs compared to the flash method.

This disclosure provides a carbon dioxide recovery device and recovery method that can easily recover gas in which the ratio of carbon dioxide to contaminant gases has increased.

1, 1A, 1B, 1C...carbon dioxide recovery apparatus, 10...first processing unit, 16...first separation unit, 18...separation membrane, 18A...material, 24...water vapor supply unit, 30...second processing unit, 36...second separation unit, 38...separation membrane, 42...regeneration gas supply unit, 50...suction unit, Vs1, Vs2...supply space, Vd1, Vd2...processing space, G0...raw material gas, G1...first processing gas, G2...second processing gas, Gs...water vapor-containing gas, Gr...regeneration gas.

Claims (6)

a first processing unit that is disposed so as to divide the inside of the housing into two spaces, and that has a first separation unit that separates carbon dioxide contained in a source gas supplied into the housing from an impurity gas that contains components of the source gas other than carbon dioxide, and that extracts at least a portion of the carbon dioxide contained in the source gas and releases a first processing gas from one of the two spaces, the first processing gas having a higher ratio of carbon dioxide to the impurity gas than the source gas;
a second treatment section that is disposed to separate a supply space to which the first treatment gas released by the first treatment section is supplied from a treatment space, the second treatment section having a second separation section that reduces water vapor contained in the first treatment gas by any of adsorption, absorption, or permeation, and that removes at least a portion of the water vapor contained in the first treatment gas and releases a second treatment gas having a higher carbon dioxide purity than the first treatment gas;
a suction unit that sucks gas from the one space,
the first separation unit includes a material that selectively adsorbs or absorbs carbon dioxide contained in the source gas,
the second processing unit further includes a regeneration gas supply unit that supplies a regeneration gas having a water vapor pressure lower than that of the first processing gas to the processing space,
The carbon dioxide recovery apparatus , wherein the first processing section further includes a water vapor supply section that supplies a water vapor-containing gas containing water vapor to the space of the two spaces to which the raw material gas is supplied. 2. The recovery apparatus of claim 1 , wherein the temperature of the regeneration gas is lower than the temperature of the water vapor-containing gas. 3. The recovery apparatus according to claim 1, wherein the regeneration gas is air. 4. The recovery apparatus according to claim 1 , wherein the water vapor pressure of the second process gas is lower than the saturated water vapor pressure of the second process gas. The recovery apparatus according to claim 1 , wherein the second separation section includes a separation membrane that selectively allows water vapor contained in the first process gas to pass through. a first step of extracting at least a portion of the carbon dioxide contained in the source gas supplied into the housing using a first separation unit that is arranged to partition the inside of the housing into two spaces and that separates the carbon dioxide contained in the source gas from an impurity gas that contains components of the source gas other than carbon dioxide, thereby generating a first process gas in one of the two spaces, the first process gas having a higher ratio of carbon dioxide to the impurity gas than the source gas;
a second step of removing at least a portion of the water vapor contained in the first process gas using a second separation unit that reduces the water vapor contained in the first process gas by adsorption, absorption, or permeation, thereby generating a second process gas having a higher carbon dioxide purity than the first process gas;
a suction step of suctioning the gas in the one space by a suction part,
the first separation unit includes a material that selectively adsorbs or absorbs carbon dioxide contained in the source gas,
In the second step, the second treated gas is generated by further using a regeneration gas having a water vapor pressure lower than that of the first treated gas,
In the first step, a water vapor-containing gas containing water vapor is supplied to the space of the two spaces to which the raw material gas is supplied .