Acidic gas recovering method

Abstract

Provided is a method for recovering an acidic gas, whereby the temperature of an acidic gas adsorbent can be efficiently raised, and the acidic gas can be recovered with excellent recovery efficiency. The method for recovering an acidic gas according to an embodiment of the present invention includes an adsorbing step and a temperature raising step, in this order. In the adsorbing step, a gas to be treated that contains an acidic gas is supplied to an acidic gas adsorbent, and the acidic gas is adsorbed by the acidic gas adsorbent. In the temperature raising step, the temperature of the acidic gas adsorbent is raised to a predetermined desorption temperature. In the temperature raising step, a non-condensable gas that can be adsorbed by the acidic gas adsorbent is supplied to the acidic gas adsorbent.

Description

Methods for recovering acidic gases

[0001] This invention relates to a method for recovering acidic gases.

[0002] In recent years, in order to reduce the environmental burden, carbon dioxide (hereinafter referred to as CO2) has been used. ２ Efforts are being made to separate and recover acidic gases (sometimes referred to as CO2) from mixed gases. As an example of a method for separating and recovering acidic gases, a method for separating carbon dioxide has been proposed (see, for example, Patent Document 1). In such a carbon dioxide separation method, the mixed gas is brought into contact with an adsorbent to adsorb carbon dioxide gas onto the adsorbent, and then saturated or superheated steam is supplied to the adsorbent to raise the temperature of the adsorbent and release CO2. ２ The detachment process begins, and then CO2 is released from the steam due to condensation. ２ Separate them.

[0003] International Publication No. 2021 / 259760

[0004] As described in Patent Document 1, when a condensable gas such as steam is supplied to an acidic gas adsorbent to raise its temperature, the acidic gas adsorbent can be efficiently heated by condensing a portion of the condensable gas and releasing latent heat. However, when the condensable gas condenses and forms a liquid, the acidic gas detached from the acidic gas adsorbent may dissolve in the liquid, potentially reducing the acidic gas recovery efficiency. Therefore, it is difficult to achieve both high heating efficiency for the acidic gas adsorbent and high acidic gas recovery efficiency. The main objective of the present invention is to provide an acidic gas recovery method that can efficiently heat an acidic gas adsorbent and recover the acidic gas with excellent recovery efficiency.

[0005] [1] An acid gas recovery method according to an embodiment of the present invention includes an adsorption step and a heating step in this order. In the adsorption step, a gas to be treated containing an acid gas is supplied to an acid gas adsorbent to adsorb the acid gas onto the acid gas adsorbent. In the heating step, the acid gas adsorbent is heated to a predetermined desorption temperature. In the heating step, a non-condensable gas that can be adsorbed by the acid gas adsorbent is supplied to the acid gas adsorbent. [2] The acid gas recovery method described in [1] above may further include a desorption step. The desorption step is performed after the heating step. In the desorption step, the acid gas adsorbent is maintained at the desorption temperature to desorb the acid gas from the acid gas adsorbent. [3] In the acid gas recovery method described in [1] or [2] above, the molar ratio of the amount of non-condensable gas adsorbed per unit mass of the acid gas adsorbent in the heating step to the amount of acid gas adsorbed per unit mass of the acid gas adsorbent in the adsorption step may be 0.6 times or more and 3.3 times or less. [4] In the acid gas recovery method described in any of [1] to [3] above, the amount of non-condensable gas adsorbed per unit mass of the acid gas adsorbent in the heating step may be 0.10 mmol / g or more and 0.80 mmol / g or less. [5] In the acid gas recovery method described in any of [1] to [4] above, the desorption temperature may be within ±10% of the set temperature. [6] In the acid gas recovery method described in any of [1] to [4] above, the non-condensable gas may be selected from carbon dioxide, sulfur dioxide, nitrogen dioxide, or a mixture thereof. [7] In the method for recovering acidic gas described in [6] above, the non-condensable gas and the acidic gas may each be carbon dioxide.

[0006] According to embodiments of the present invention, the temperature of the acidic gas adsorbent can be efficiently raised, and the acidic gas can be recovered with excellent recovery efficiency.

[0007] Figure 1 is a schematic diagram of an acid gas recovery system capable of implementing one embodiment of the present invention. Figure 2 is a schematic diagram of the acid gas adsorption section of the acid gas recovery system of Figure 1. Figure 3 is a schematic perspective view of the acid gas adsorption section of an acid gas recovery system according to another embodiment of the present invention. Figure 4 is a central cross-sectional view of the acid gas adsorption section of Figure 3.

[0008] Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Furthermore, in order to clarify the explanation, the drawings may schematically represent the width, thickness, shape, etc., of each part compared to the embodiments; however, these are merely examples and do not limit the interpretation of the present invention.

[0009] A. Overview of the Acid Gas Recovery Method One embodiment of the present invention provides a method for recovering acid gases, which includes an adsorption step and a heating step in that order. In the adsorption step, a gas to be treated containing acid gas is supplied to an acid gas adsorbent, causing the acid gas to be adsorbed onto the acid gas adsorbent. In the heating step, the acid gas adsorbent is heated to a predetermined desorption temperature. In the heating step, a non-condensable gas that can be adsorbed onto the acid gas adsorbent is supplied to the acid gas adsorbent. With this method, since a non-condensable gas is supplied to the acid gas adsorbent as the heating gas in the heating step, it is possible to suppress the condensation of the heating gas and the formation of a condensate. Therefore, it is possible to suppress the dissolution of acid gas in the condensate, and as a result, the recovery efficiency of acid gases can be improved. In addition, since the non-condensable gas is adsorbed onto the acid gas adsorbent in the heating step, heat of adsorption is generated and used to heat the acid gas adsorbent. Therefore, even if a non-condensable gas is used as the heating gas, the acid gas adsorbent can be heated efficiently. As a result, it is possible to achieve both high efficiency in recovering acidic gases and high heating efficiency in the acidic gas adsorbent.

[0010] A-1. Adsorption Process In the adsorption process, typically, the gas to be treated is supplied to an acidic gas adsorbent that has been adjusted to the adsorption temperature.

[0011] The gas to be treated contains acidic gases. Examples of acidic gases include carbon dioxide (CO2). ２), hydrogen sulfide, sulfur dioxide, nitrogen dioxide, dimethyl sulfide (DMS), hydrogen chloride. In one embodiment, the acid gas is CO ２ and the gas to be treated is CO ２ -containing gas. The CO ２ -containing gas may contain nitrogen in addition to CO ２ . The CO ２ concentration in the CO ２ -containing gas is, for example, 100 ppm (volume basis) or more and 2% by volume or less. The CO ２ -containing gas is typically air (atmosphere).

[0012] The acid gas adsorbent can be optionally and appropriately selected according to the acid gas. When the acid gas is carbon dioxide, the acid gas adsorbent is a CO ２ adsorbent. The CO ２ adsorbent may be composed only of a CO ２ adsorption compound capable of adsorbing and desorbing CO ２ , or may include a CO ２ adsorption compound and a carrier for supporting the adsorption compound.

[0013] As the CO ２ adsorption compound, for example, nitrogen-containing compounds; alkali compounds such as sodium hydroxide and potassium hydroxide; carbonates such as calcium carbonate and potassium carbonate; bicarbonates such as calcium bicarbonate and potassium bicarbonate; metal-organic frameworks (MOFs) such as MOF-74, MOF-200, and MOF-210; ionic liquids; deep eutectic solvents; oxides such as cerium oxide and iron oxide; zeolites; activated carbon; nitrogen-doped carbon; can be mentioned. The CO ２ adsorption compound can be used alone or in combination.

[0014] The CO ２Among the adsorbent compounds, nitrogen-containing compounds are preferred. Specific examples of nitrogen-containing compounds include primary amines such as monoethanolamine and polyvinylamine; secondary amines such as diethanolamine, cyclic amines, and N-(3-aminopropyl)diethanolamine; tertiary amines such as methyldiethylamine and triethanolamine; ethyleneamine compounds such as tetraethylenepentamine; aminosilane coupling agents such as aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, and polyethyleneimine-trimethoxysilane; organic polymers having primary to tertiary amino groups; organic monomers having primary to tertiary amino groups; piperazine compounds such as 1-(2-hydroxyethyl)piperazine; and organic / inorganic compounds to which amino groups are added as substituents. Nitrogen-containing compounds can be used alone or in combination. Among the nitrogen-containing compounds, organic monomers having primary to tertiary amino groups and organic polymers having primary to tertiary amino groups are preferred. Examples of organic monomers having primary to tertiary amino groups include ethyleneimine and styrene to which amino groups have been added. Examples of organic polymers having primary to tertiary amino groups include linear polyethyleneimine, branched polyethyleneimine, polyamidoamine, and polystyrene to which amino groups have been added. The weight-average molecular weight Mw (in polystyrene equivalent) of the organic polymer is, for example, 1,000 to 1,000,000, and preferably 50,000 to 300,000.

[0015] The carrier is CO ２The carrier may have any suitable configuration capable of supporting the adsorbed compound. The carrier is preferably a porous carrier. If the carrier is porous, mesopores can be formed on the surface that can come into contact with acidic gases. Examples of porous carriers include organometallic structures (MOFs) such as MOF-74, MOF-200, MOF-210; activated carbon; nitrogen-doped carbon; porous silica; porous alumina; zeolite; carbon nanotubes; polymers. The porous carriers may be used alone or in combination. The porous carrier is preferably CO ２ A material different from the adsorbent compound is used. Among porous carriers, porous silica is more preferable.

[0016] The BET specific surface area of ​​a porous carrier is, for example, 50 m². ２ / g or more, preferably 500m ２ It is 1 / g or more. If the surface area of ​​the porous carrier is greater than or equal to the lower limit above, CO ２ It can stably support adsorbed compounds, CO ２ This can improve recovery efficiency. The upper limit of the BET specific surface area of ​​porous carriers is typically 2000 m². ２ It is less than or equal to / g.

[0017] In one embodiment, CO ２ The adsorbent is the CO2 mentioned above. ２ It is constructed by arbitrarily and appropriately combining the adsorbent compound and the above-mentioned carrier. ２ Examples of adsorbents include amine-supported polymers, amine-supported MOFs, and amine-supported nitrogen-doped carbons. ２ Adsorbent CO ２ When an adsorbent compound and a support are included, CO2 is released to the support. ２ Mass ratio of adsorbed compounds (CO ２ The adsorbent compound / carrier is, for example, 0.1 to 5, preferably 1 to 3.

[0018] The adsorption temperature is, for example, from 0°C to 50°C, preferably from 10°C to 40°C. In one embodiment, the adsorption temperature is the same as the outside air temperature. The implementation time (adsorption time) of the adsorption process is, for example, from 15 minutes to 10 hours, preferably from 30 minutes to 6 hours. When the adsorption temperature and / or the adsorption time are within the above ranges, the acidic gas adsorbent can stably adsorb the acidic gas.

[0019] Thereby, in the adsorption process, the acidic gas adsorbent adsorbs and recovers the acidic gas from the gas to be treated. The amount of acidic gas adsorbed per unit mass of the acidic gas adsorbent in the adsorption process (hereinafter referred to as the amount of acidic gas adsorbed in the adsorption process) is, for example, from 0.01 mmol / g to 1.0 mmol / g, preferably from 0.1 mmol / g to 0.5 mmol / g. By desorbing all the acidic gas from the acidic gas adsorbent adsorbed with the acidic gas by heating and analyzing the desorbed acidic gas by gas chromatography or infrared spectroscopy, the acidic gas species can be identified and the amount of acidic gas adsorbed can be measured. Also, the amount of acidic gas adsorbed can be specified by adsorption isotherm measurement in which, after identifying the acidic gas species, while changing the partial pressure of the acidic gas in a state where the acidic gas adsorbent is kept at a constant temperature, the amount of acidic gas adsorbed on the acidic gas adsorbent is measured.

[0020] The acidic gas adsorption rate in the adsorption process (=100 - (acidic gas concentration in the treated gas treated with the acidic gas adsorbent / acidic gas concentration in the gas to be treated before being supplied to the acidic gas adsorbent × 100)) is, for example, 60% or more, preferably 75% or more, more preferably 80% or more, and particularly preferably 90% or more. On the other hand, the upper limit of the acidic gas adsorption rate in the adsorption process is typically 100%.

[0021] A-2. Heating process Next, in the heating process, typically, a non-condensable gas is supplied as a heating gas to the acidic gas adsorbent, and the acidic gas adsorbent is heated to a temperature higher than the adsorption temperature. The condensation point (boiling point) of the non-condensable gas is, for example, 20°C or lower under normal pressure (0.1 MPa).

[0022] As the non-condensable gas, for example, carbon dioxide (CO ２Examples include sulfur dioxide and nitrogen dioxide. The non-condensable gas can be used alone or in combination. Among the non-condensable gases, preferably, carbon dioxide, sulfur dioxide, nitrogen dioxide, and mixed gases thereof are included. When the non-condensable gas contains these gases, the non-condensable gas can be sufficiently adsorbed by the acid gas adsorbent, and the temperature increase efficiency of the acid gas adsorbent can be further improved. The non-condensable gas may be the same as or different from the acid gas.

[0023] The temperature of the non-condensable gas supplied to the acid gas adsorbent typically exceeds the adsorption temperature described above. The temperature of the non-condensable gas is, for example, 60°C or higher, preferably 80°C or higher, more preferably 140°C or higher. On the other hand, the temperature of the non-condensable gas is, for example, 300°C or lower, preferably 250°C or lower. When the non-condensable gas having such a temperature is supplied to the acid gas adsorbent, the acid gas adsorbent can be stably heated.

[0024] The non-condensable gas is supplied to the acid gas adsorbent at any appropriate pressure. The pressure of the non-condensable gas is, for example, 0.01 MPa (absolute pressure) to 1 MPa (absolute pressure), preferably 0.05 MPa (absolute pressure) to 0.2 MPa (absolute pressure). When the pressure of the non-condensable gas is within such a range, the non-condensable gas can be appropriately adsorbed by the acid gas adsorbent in the temperature increase process. As a result, the gas adsorption amount of the non-condensable gas to the acid gas adsorbent can be stably adjusted within the range described below.

[0025] In such a heating process, non-condensable gases are further adsorbed onto the acidic gas adsorbent, which has already adsorbed acidic gases. This generates heat of adsorption. Therefore, the acidic gas adsorbent is heated by at least the heat of adsorption of the non-condensable gases. The amount of non-condensable gas adsorbed per unit mass of the acidic gas adsorbent in the heating process (hereinafter referred to as the amount of non-condensable gas adsorbed in the heating process) is, for example, 0.05 mmol / g or more, preferably 0.10 mmol / g or more, more preferably 0.30 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 0.60 mmol / g or more. If the amount of non-condensable gas adsorbed in the heating process is above this lower limit, the acidic gas adsorbent can be heated more efficiently in the heating process. On the other hand, the amount of non-condensable gas adsorbed in the heating process is, for example, 1.00 mmol / g or less, preferably 0.80 mmol / g or less. If the amount of non-condensable gas adsorbed during the heating process is below this upper limit, the rapid temperature rise of the acidic gas adsorbent can be suppressed during the heating process, and the acidic gas adsorbent can be stably controlled. Therefore, the deterioration of the acidic gas adsorbent can be suppressed, and the lifespan of the acidic gas adsorbent can be extended. The amount of non-condensable gas adsorbed during the heating process is measured, for example, in the same way as the amount of acidic gas adsorbed during the adsorption process described above.

[0026] The molar ratio of the amount of non-condensable gas adsorbed in the heating step to the amount of acidic gas adsorbed in the adsorption step (amount of non-condensable gas adsorbed / amount of acidic gas adsorbed) is, for example, 0.5 times or more, preferably 0.6 times or more, more preferably 1.0 times or more, even more preferably 2.0 times or more, and particularly preferably 2.5 times or more. When the amount of non-condensable gas adsorbed / the amount of acidic gas adsorbed is adjusted to be above this lower limit, the acidic gas adsorbent can be heated more efficiently in the heating step. On the other hand, the amount of non-condensable gas adsorbed / the amount of acidic gas adsorbed is, for example, 4.0 times or less, preferably 3.3 times or less. When the amount of non-condensable gas adsorbed / the amount of acidic gas adsorbed is adjusted to be below this upper limit, the rapid heating of the acidic gas adsorbent can be stably suppressed, and the deterioration of the acidic gas adsorbent can be sufficiently suppressed.

[0027] In one embodiment, during the heating step, the acidic gas adsorbent is heated not only by the heat of adsorption but also by heat exchange with a non-condensable gas. In addition to heating with a non-condensable gas during the heating step, the acidic gas adsorbent may also be heated by any appropriate method.

[0028] Such a heating process is completed when the temperature of the non-condensable gas after contact with the acidic gas adsorbent stabilizes within ±10% of the set temperature, more specifically, when it is maintained for 30 seconds or more. This raises the temperature of the acidic gas adsorbent from the adsorption temperature to the desorption temperature. The desorption temperature is, for example, 60°C or higher, preferably 80°C or higher, and more preferably 140°C or higher. On the other hand, the desorption temperature is, for example, 300°C or lower, preferably 250°C or lower. In one embodiment, the desorption temperature is within ±10% of the set temperature. When the desorption temperature is within this range, the acidic gas can be stably desorbed while suppressing the deterioration of the acidic gas adsorbent. The duration of the heating process (heating time) is appropriately changed according to the desorption temperature. The heating time is, for example, less than 30 minutes, preferably 25 minutes or less, and more preferably 20 minutes or less. On the other hand, the heating time is, for example, 10 minutes or more, or for example, 15 minutes or more.

[0029] A-3. Desorption Step In one embodiment, the method for recovering acidic gas further includes a desorption step after the heating step. In the desorption step, the acidic gas adsorbent is maintained at the above-mentioned desorption temperature to desorb the acidic gas from the acidic gas adsorbent. Typically, in the desorption step, the acidic gas is recovered by any appropriate recovery mechanism. In other words, the desorption step begins when the acidic gas adsorbent has reached the desorption temperature and the recovery mechanism has started to recover the acidic gas.

[0030] Any suitable method can be employed to maintain the acidic gas adsorbent at its desorption temperature. Examples of such methods include supplying the acidic gas adsorbent with a heating medium heated to its desorption temperature, or directly heating the acidic gas adsorption with a heating element. These methods can be applied individually or in combination.

[0031] As a heating medium, for example, carbon dioxide (CO2)２ Examples of heating media include sulfur dioxide and nitrogen dioxide. The heating media can be used alone or in combination. Examples of heating elements include electric heaters, steam heat exchangers (STMs), and heat exchangers using heat transfer media. Examples of recovery mechanisms include vacuum pumps.

[0032] The duration of the desorption process (desorption time) is, for example, 1 minute to 1 hour, preferably 5 minutes to 30 minutes. A desorption time within this range can suppress oxidative degradation and volatilization of the acidic gas adsorbent.

[0033] In one embodiment, the desorption step yields a recovered gas containing the acidic gas desorbed from the acidic gas adsorbent.

[0034] In such a desorption process, the non-condensable gas may or may not be desorbed from the acidic gas adsorbent. If the non-condensable gas is desorbed from the acidic gas adsorbent in the desorption process, the recovered gas will contain the non-condensable gas in addition to the acidic gas. Therefore, if the acidic gas and the non-condensable gas are different from each other, the acidic gas may be separated from the recovered gas by any appropriate separation and purification method as needed.

[0035] On the other hand, when the acidic gas and the non-condensable gas are the same, the cost of separation and purification can be reduced compared to when the acidic gas and the non-condensable gas are different. Therefore, the acidic gas and the non-condensable gas are preferably the same gas species, and more preferably carbon dioxide (CO2). ２ ) Acidic gases and non-condensable gases are carbon dioxide (CO2). ２ ) If the CO in the recovered gas ２ The content ratio is, for example, 50% to 100% by volume, preferably 80% to 100% by volume.

[0036] The method for recovering acidic gas may include a cooling step in addition to the adsorption step, heating step, and desorption step. The cooling step is performed after the desorption step and before the adsorption step, and cools the acidic gas adsorption section to the adsorption temperature described above. Preferably, the adsorption step, heating step, desorption step, and cooling step are performed in sequence and repeated.

[0037] B. Acid Gas Recovery System Next, an acid gas recovery system 100 capable of implementing an acid gas recovery method according to one embodiment of the present invention will be described with reference to Figures 1 to 4.

[0038] As shown in Figure 1, the acid gas recovery system 100 comprises an acid gas adsorption unit 1, a containment unit 2, a non-condensable gas supply unit 6, and a recovery mechanism 7.

[0039] B-1. Acid Gas Adsorption Section The acid gas adsorption section 1 contains the acid gas adsorbent described above. As shown in Figure 2, in one embodiment, the acid gas adsorption section 1 includes a plurality of adsorbent housing sections 17.

[0040] Each of the multiple adsorbent storage sections 17 has a substantially plate shape with thickness in a predetermined direction. The multiple adsorbent storage sections 17 are stacked with spacing between them in the thickness direction. A flow path is formed between adjacent adsorbent storage sections 17. In the illustrated example, five adsorbent storage sections 17 are arranged in parallel, but the number of adsorbent storage sections 17 is not limited to this. The number of adsorbent storage sections 17 is, for example, five or more, preferably ten or more, and more preferably twenty or more. The spacing between adjacent adsorbent storage sections 17 is, for example, 0.5 cm or more and 1.5 cm or less.

[0041] Each of the multiple adsorbent housing sections 17 comprises multiple pellet-shaped adsorbent materials 17a and a flexible fiber member 17b.

[0042] The pelletized adsorbent 17a functions as the acidic gas adsorbent described above, and is typically CO ２ It functions as an adsorbent. Examples of materials for the pellet-shaped adsorbent 17a include materials modified with the above-mentioned acidic gas adsorbent, preferably cellulose modified with the above-mentioned acidic gas adsorbent, and more preferably nanofiberized cellulose modified with the above-mentioned acidic gas adsorbent. The average primary particle diameter of the pellet-shaped adsorbent 17a is, for example, 60 μm or more and 1200 μm or less. The filling ratio of the pellet-shaped adsorbent 17a in the adsorbent containment section 17 can be any appropriate value.

[0043] The flexible fiber member 17b is typically formed in a hollow shape (bag shape) capable of accommodating a plurality of pellet-shaped adsorbents 17a. The flexible fiber member 17b allows the passage of gas and restricts the passage of pellet-shaped adsorbents. The flexible fiber member 17b may be a woven fabric or a nonwoven fabric. Examples of materials for the flexible fiber member 17b include organic fibers and natural fibers, and preferably polyethylene terephthalate fibers, polyethylene fibers, and cellulose fibers. The thickness of the flexible fiber member 17b is, for example, 25 μm to 500 μm.

[0044] The acid gas adsorption section 1 in the illustrated example further includes a plurality of spacers 18. The spacers 18 are sandwiched between adjacent adsorbent storage sections 17. This ensures a stable spacing between adjacent adsorbent layers. In one embodiment, the plurality of adsorbent storage sections 17 and the plurality of spacers 18 are arranged in a roughly zigzag shape when viewed from a direction perpendicular to the thickness direction of the adsorbent storage section 17 (the depth direction of the paper in Figure 2).

[0045] Examples of such acidic gas adsorption units 1 include the gas separation unit described in International Publication No. 2014 / 170184. The entire description of this publication is incorporated herein by reference.

[0046] As shown in Figures 3 and 4, in another embodiment, the acid gas adsorption unit 1 comprises a substrate 11 and an acid gas adsorption layer 16. The structure of the substrate 11 is not particularly limited and includes, for example, a honeycomb structure, a filter structure such as a filter cloth, or a pellet structure. The acid gas adsorption layer 16 is not particularly limited as long as it is disposed on the surface of the substrate 11.

[0047] In the illustrated example, the base material 11 is a honeycomb-shaped base material 11a. The honeycomb-shaped base material 11a has partition walls 13 that define a plurality of cells 14.

[0048] Cell 14 extends along the length (axial direction) of the honeycomb substrate 11a from the first end face E1 (inlet end face) to the second end face E2 (outlet end face) (see Figure 4). Cell 14 has any suitable shape in a cross-section perpendicular to the length direction of the honeycomb substrate 11a. Examples of cell cross-sectional shapes include triangles, quadrilaterals, pentagons, polygons with hexagons or more, circles, and ellipses. The cross-sectional shapes and sizes of the cells may all be the same, or at least some may differ. Among such cell cross-sectional shapes, hexagons and quadrilaterals are preferred, and squares, rectangles, or hexagons are more preferred.

[0049] The cell density (i.e., the number of cells 14 per unit area) in a cross-section perpendicular to the longitudinal direction of the honeycomb substrate can be appropriately set depending on the purpose. For example, the cell density could be 4 cells / cm². ２ ~320 cells / cm ２ This is possible. If the cell density is within this range, sufficient strength and effective GSA (geometric surface area) of the honeycomb substrate can be ensured.

[0050] The honeycomb substrate 11a has any suitable shape (overall shape). Examples of honeycomb substrate shapes include a cylindrical shape with a circular base, an elliptical columnar shape with an elliptical base, a prismatic columnar shape with a polygonal base, and a columnar shape with an irregular base. The honeycomb substrate 11a in the illustrated example has a prismatic shape. The outer diameter and length of the honeycomb substrate can be appropriately set depending on the purpose.

[0051] The honeycomb-shaped substrate 11a typically comprises an outer wall 12 and a partition wall 13 located inside the outer wall 12. In the illustrated example, the outer wall 12 and the partition wall 13 are formed integrally. The outer wall 12 and the partition wall 13 may be separate components.

[0052] In the illustrated example, the outer wall 12 has a rectangular tubular shape. The thickness of the outer wall 12 can be set arbitrarily and appropriately. The thickness of the outer wall 12 is, for example, 0.1 mm to 10 mm.

[0053] The partition wall 13 defines a plurality of cells 14. More specifically, the partition wall 13 has a first partition wall 13a and a second partition wall 13b that are orthogonal to each other, and the first partition wall 13a and the second partition wall 13b define a plurality of cells 14. The cross-sectional shape of the cells 14 is approximately rectangular. Note that the configuration of the partition wall is not limited to the partition wall 13 described above. The partition wall may have a first partition wall extending in the radial direction and a second partition wall extending in the circumferential direction, and these may define a plurality of cells.

[0054] The thickness of the partition wall 13 can be appropriately set depending on the application of the acidic gas adsorption section. Typically, the thickness of the partition wall 13 is thinner than the thickness of the outer wall 12. For example, the thickness of the partition wall 13 is 0.03 mm to 0.6 mm. The thickness of the partition wall is measured, for example, by cross-sectional observation using an SEM (scanning electron microscope). If the thickness of the partition wall is within this range, the mechanical strength of the honeycomb substrate can be made sufficient, and the opening area (total area of ​​cells in the cross-section) can be made sufficient.

[0055] The porosity of the partition wall 13 can be appropriately set depending on the purpose. The porosity of the partition wall 13 is, for example, 15% to 70%, preferably 20% to 45%. The porosity can be measured, for example, by the mercury intrusion method. The bulk density of the partition wall 13 can be appropriately set depending on the purpose. Their bulk density is, for example, 0.10 g / cm³. ３ ~0.60 g / cm ３ The concentration is preferably 0.20 g / cm³. ３ ~0.50 g / cm ３ The bulk density can be measured, for example, by the mercury intrusion method.

[0056] Typical materials for the partition wall 13 include ceramics. Examples of ceramics include silicon carbide, silicon-silicon carbide composite materials, cordierite, mullite, alumina, silicon nitride, spinel, silicon carbide-cordierite composite materials, lithium aluminum silicate, and aluminum titanate. The materials constituting the partition wall can be used individually or in combination. Among the materials constituting the partition wall, cordierite, alumina, mullite, silicon carbide, silicon-silicon carbide composite materials, and silicon nitride are preferred, and silicon carbide and silicon-silicon carbide composite materials are preferred.

[0057] In one embodiment, the acidic gas adsorption layer 16 is formed on the surface of the partition wall 13 within the cell 14. In the honeycomb substrate 11a, the flow path 15 is formed in the portion of the cross-section of the cell 14 where the acidic gas adsorption layer 16 is not formed (typically the central portion). The acidic gas adsorption layer 16 may be formed over the entire inner surface of the partition wall 13 (i.e., surrounding the flow path 15) as shown in the illustrated example, or it may be formed on a part of the surface of the partition wall. When the acidic gas adsorption layer 16 is formed over the entire inner surface of the partition wall 13, acidic gases (typically CO) are absorbed. ２ This may improve the adsorption efficiency of )

[0058] The flow path 15 extends from the first end face E1 (inlet end face) to the second end face E2 (outlet end face), similar to the cell 14. The cross-sectional shape of the flow path 15 can be the same as that of the cell 14 described above, preferably a hexagon or quadrilateral, and more preferably a square, rectangle or hexagon. The cross-sectional shape and size of the flow path 15 may all be the same, or at least some may differ. Typically, the cell 14 (more specifically the flow path 15) is supplied with a gas to be treated, including an acidic gas, in the adsorption step, a non-condensable gas flows through it in the heating step, and a heating medium flows through it in the desorption step.

[0059] The acid gas adsorption layer 16 contains the above-mentioned acid gas adsorbent. ２ In this case, the acidic gas adsorption layer 16 contains the carbon dioxide adsorbent described above.

[0060] The acidic gas adsorption layer may consist solely of an acidic gas adsorbent, or it may contain other components in addition to the acidic gas adsorbent. Examples of other components include organic binders. The content of the acidic gas adsorbent in the acidic gas adsorption layer is, for example, 30% to 100% by mass, and preferably 50% to 80% by mass.

[0061] B-2. Containment Section As shown in Figure 1, the containment section 2 houses the acidic gas adsorption section 1. In the illustrated example, the containment section 2 has a cylindrical shape extending in a predetermined direction. During the adsorption process, the gas to be treated as described above is supplied to the containment section 2.

[0062] In one embodiment, the containment unit 2 has a first inlet 22, a first outlet 23, a second inlet 24, and a second outlet 25. The first inlet 22 is located at the upstream end of the containment unit 2 in the direction of supply of the gas to be treated. The gas to be treated passes through the first inlet 22 during the adsorption process. The first outlet 23 is located at the downstream end of the containment unit 2 in the direction of supply of the gas to be treated. The treated gas, whose acid gas concentration has been reduced after passing through the acid gas adsorption unit 1 during the adsorption process, passes through the first outlet 23. The second inlet 24 is located between the first inlet 22 and the first outlet 23 in the direction of supply of the gas to be treated. The second inlet 24 is typically provided on the side wall of the containment unit 2. Non-condensable gas passes through the second inlet 24 during the heating process. The second outlet 25 is located between the first inlet 22 and the first outlet 23 in the direction of supply of the gas to be treated. In the illustrated example, the second outlet 25 is located between the second inlet 24 and the first outlet 23. Typically, the second outlet 25 is provided on the side wall of the containment section 2. During the desorption process, the recovered gas containing the acidic gas desorbed from the acidic gas adsorbent passes through the second outlet 25. With this configuration, the opening areas of the first inlet, first outlet, second inlet, and second outlet can be appropriately designed according to the flow rate of the corresponding process. As a result, the adsorption process, heating process, and desorption process can be carried out efficiently.

[0063] In one embodiment, the acid gas recovery system 100 further comprises a first valve 51 and a second valve 52. Each of the first valve 51 and the second valve 52 can open and close the internal space of the containment section 2. The first valve 51 is located upstream of the acid gas adsorption section 1 in the direction of supply of the gas to be treated. The second valve 52 is located on the opposite side of the acid gas adsorption section 1 from the first valve 51. When the first valve 51 and the second valve 52 are closed, they partition the internal space of the containment section 2, defining the containment space S in which the acid gas adsorption section 1 is located. The second inlet 24 and the second outlet 25 are located between the first valve 51 and the second valve 52. With this configuration, when the heating process is carried out with the first and second valves closed, the pressure and temperature inside the containment space in which the acid gas adsorption section is housed can be appropriately adjusted. Therefore, the amount of non-condensable gas adsorbed during the heating process can be stably adjusted to the above range.

[0064] Examples of the first valve 51 include a ball valve, a gate valve, and a butterfly valve. The first valve 51 is preferably a butterfly valve. The second valve 52 is described in the same manner as the first valve 51.

[0065] The acid gas recovery system 100 may further include a heating element 9. The heating element 9 can heat the acid gas adsorption section 1. In the illustrated example, the heating element 9 is in contact with the acid gas adsorption section 1. If the acid gas recovery system includes a heating element, the acid gas adsorption section can be directly heated, so the temperature of the acid gas adsorption section can be appropriately adjusted in the heating step and the desorption step.

[0066] Examples of the heating element 9 include an electric heater, a steam heat exchanger (STM), and a heat exchanger using a heat transfer medium. The acid gas recovery system 100 may be equipped with multiple heating elements 9. The multiple heating elements 9 may all be identical, or at least some of them may be different. The heating element 9 can adopt any suitable shape. Examples of the shape of the heating element 9 include a flat plate shape, a spiral shape, and a film shape. In the illustrated example, the heating element 9 has a flat plate shape and is positioned between the acid gas adsorption section 1 and the side wall of the containment section 2.

[0067] B-3. ​​Non-condensable gas supply section The non-condensable gas supply section 6 is configured to supply the above-mentioned non-condensable gas to the acid gas adsorption section 1 during the heating process. In the illustrated example, the non-condensable gas supply section 6 is capable of supplying non-condensable gas to the second inlet 24 of the containment section 2.

[0068] In one embodiment, the non-condensable gas supply unit 6 includes a supply line 61, a pressurizing device 62, a heating device 63, and an on-off valve 64. The supply line 61 is typically a pipe through which non-condensable gas can pass. The upstream end of the supply line 61 in the direction of non-condensable gas passage may be connected to a non-condensable gas supply source (not shown). The downstream end of the supply line 61 in the direction of non-condensable gas passage is connected to the side wall of the containment unit 2 so as to be connected to the second inlet 24.

[0069] The pressurizing device 62 is typically capable of pumping non-condensable gases. The pressurizing device 62 can have any suitable configuration. Examples of the pressurizing device 62 include a fan, a blower, and a compressor.

[0070] The heating device 63 is typically capable of heating non-condensable gas passing through the supply line 61. In the illustrated example, the heating device 63 is supplied with non-condensable gas pressurized by the pressurizer 62. The heating device 63 has any suitable configuration. Examples of the heating device 63 include a heater and a heat exchanger.

[0071] The on-off valve 64 is provided in the supply line 61 and can open and close the supply line 61. In the illustrated example, the on-off valve 64 is provided in the supply line 61 on the side opposite the pressurizing device 62 to the heating device 63. Examples of the on-off valve 64 include a ball valve, a gate valve, and a butterfly valve.

[0072] B-4. Recovery Mechanism The recovery mechanism 7 is configured to recover the recovered gas discharged from the acid gas adsorption section 1 during the desorption process. In the illustrated example, the recovery mechanism 7 can recover the recovered gas from the second outlet 25 of the containment section 2.

[0073] In one embodiment, the recovery mechanism 7 includes a recovery line 71, a pressure reducing device 73, and an on / off valve 72.

[0074] The discharge line 71 is typically a pipe through which the recovered gas discharged from the second outlet 25 can pass. The upstream end of the discharge line 71 in the direction of the recovered gas's passage is connected to the side wall of the containment section 2 so as to connect to the second outlet 25. The downstream end of the discharge line 71 in the direction of the recovered gas's passage may be connected to a tank (not shown) capable of storing the recovered gas.

[0075] The pressure reducing device 73 is typically installed in the recovery line 71. In the illustrated example, the pressure reducing device 73 can reduce the internal space of the containment section 2 via the second outlet 25. Examples of the pressure reducing device 73 include a pressure reducing pump and a blower.

[0076] The on-off valve 72 is provided in the outflow line 71 and can open and close the outflow line 71. In the illustrated example, the on-off valve 72 is provided in the recovery line 71, downstream of the pressure reducing device 73. Examples of the on-off valve 72 include those similar to the on-off valve 64.

[0077] B-5. Temperature Detection Unit In one embodiment, the acid gas recovery system 100 further includes a temperature detection unit 8. The temperature detection unit 8 is configured to detect the temperature of the non-condensable gas supplied to the acid gas adsorption unit 1 and / or the temperature of the non-condensable gas discharged from the acid gas adsorption unit 1 during the heating process. When the acid gas recovery system includes a temperature detection unit, the temperature of the acid gas adsorption unit can be appropriately controlled during the heating process according to the detection result of the temperature detection unit.

[0078] The temperature detection unit 8 may have any suitable configuration. In the illustrated example, the temperature detection unit 8 includes a first thermocouple 81 and a second thermocouple 82. The first thermocouple 81 is capable of detecting the temperature of the non-condensable gas before it is supplied to the acid gas adsorption unit 1. At least a portion of the first thermocouple 81 is typically located in the internal space of the housing unit 2. In one embodiment, at least a portion of the first thermocouple 81 is located between the first inlet 22 of the housing unit 2 and the acid gas adsorption unit 1. In the illustrated example, at least a portion of the first thermocouple 81 is located between the first valve 51 and the acid gas adsorption unit 1.

[0079] The second thermocouple 82 is capable of detecting the temperature of the non-condensable gas discharged from the acid gas adsorption section 1. At least a portion of the second thermocouple 82 is typically located in the internal space of the housing section 2. In one embodiment, at least a portion of the second thermocouple 82 is located between the acid gas adsorption section 1 and the first outlet 23 of the housing section 2. In the illustrated example, at least a portion of the second thermocouple 82 is located between the acid gas adsorption section 1 and the second valve 52.

[0080] C. Details of the Acid Gas Recovery Method Next, the method for recovering acid gas using the acid gas recovery system 100 will be described. In the acid gas recovery system 100, first, the gas to be treated is supplied to the acid gas adsorption unit 1 housed in the containment unit 2, and the acid gas is adsorbed onto the acid gas adsorbent (adsorption step). In the illustrated example, the first valve 51 and the second valve 52 are opened, and the gas to be treated containing acid gas is supplied to the acid gas adsorption unit 1 via the first inlet 22. At this time, the gas to be treated containing acid gas passes through the acid gas adsorption unit 1. As a result, the above-described adsorption step is performed, and the acid gas adsorbent contained in the acid gas adsorption unit 1 absorbs the acid gas (typically CO ２ It adsorbs ) and separates acidic gases from the gas to be treated.

[0081] Next, once the adsorption process is complete, non-condensable gas is supplied from the non-condensable gas supply unit 6 to the acid gas adsorption unit 1, raising the temperature of the acid gas adsorption unit 1 from the adsorption temperature to the desorption temperature (heating process). In the illustrated example, the first valve 51, the second valve 52, and the on-off valve 72 are closed, and the on-off valve 64 is opened, after which the pressurizing device 62 and the heating device 63 are driven. As a result, non-condensable gas, whose temperature and pressure have been adjusted to the above range, passes through the second inlet 24 and is supplied to the containment space S of the containment unit 2. Then, the pressure in the containment space S is adjusted to, for example, 0.01 MPa (absolute pressure) to 1 MPa (absolute pressure), preferably 0.5 MPa (absolute pressure) to 0.2 MPa (absolute pressure). As a result, the heating process described above is carried out, and the acid gas adsorbent is heated using the heat of adsorption generated by the adsorption of at least the non-condensable gas.

[0082] In one embodiment, during the heating step, the temperature of the non-condensable gas supplied to the acid gas adsorption unit 1 is monitored by a first thermocouple 81, and the temperature of the non-condensable gas discharged from the acid gas adsorption unit 1 is monitored by a second thermocouple 82. Based on these monitoring results, the temperature of the non-condensable gas supplied to the acid gas adsorption unit 1 is adjusted to appropriately heat the acid gas adsorbent. Subsequently, when the temperature of the non-condensable gas discharged from the acid gas adsorption unit 1 is maintained within ±10% of the set temperature of the heating step for, for example, 30 seconds or more, it is determined that the acid gas adsorbent has reached the desired desorption temperature.

[0083] Next, when the acidic gas adsorbent reaches the desorption temperature, the on-off valve 64 is closed and the on-off valve 72 is opened (start of the desorption process). In one embodiment, the start of the desorption process means the timing when the on-off valve 72 of the recovery mechanism 7 is opened. After that, with the acidic gas adsorption section maintained at the desorption temperature, the depressurization device 73 is driven. Then, the recovered gas containing the acidic gas passes through the second outlet 25 and is discharged from the containment space S of the containment section 2. At this time, if necessary, a heating medium is supplied to the acidic gas adsorption section 1 and / or the acidic gas adsorption section 1 is heated by the heating element 9. As a result, the above-described desorption process is carried out, and the recovery mechanism 7 can smoothly recover the recovered gas.

[0084] After the desorption process is completed, in one embodiment, the first valve 51 and the second valve 52 are opened, and the on-off valves 64 and 72 are closed, and the acidic gas adsorption unit 1 is cooled to the adsorption temperature (cooling process), after which the adsorption process is restarted.

[0085] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0086] <Preparation Example 1> A clay mixture containing alumina, silica, and magnesia (i.e., cordierite) was extruded and then dried to prepare the honeycomb substrate shown in Figure 3. The honeycomb substrate had a prismatic shape. The axial dimension of the honeycomb substrate was 100 mm, and the side length of the honeycomb substrate was 120 mm. The honeycomb substrate had partition walls defining multiple cells and an outer wall surrounding the partition walls. The cross-sectional shape of the cells was square. The cell density in the honeycomb substrate was 62 cells / cm². ２ The septum thickness was 0.10 mm, and the porosity of the septum was 30%.

[0087] An amine-supported polymer (average primary particle size 20 μm) mainly composed of polyethyleneimine was dispersed in an organic solvent by adding isopropyl alcohol (IPA, organic solvent) and stirring in a circular or circular motion. This yielded a dispersion of the amine-supported polymer. The content of the amine-supported polymer in the dispersion was 50% by mass.

[0088] Next, a dispersion of amine-supported polymer was passed through the cells of the honeycomb substrate at room temperature and atmospheric pressure (23°C, 0.1 MPa). This coated the surface of the partitions of the honeycomb substrate, forming a coating containing the amine-supported polymer. The honeycomb substrate with the coating was then dried at 50°C for 120 minutes. This removed the organic solvent from the coating, forming an acidic gas adsorption layer containing the amine-supported polymer. The thickness of the acidic gas adsorption layer was 300 μm. Thus, an acidic gas adsorption device (carbon dioxide adsorption device) comprising a honeycomb substrate and an acidic gas adsorption layer was manufactured.

[0089] <Example 1> The acid gas adsorption apparatus obtained in Preparation Example 1 was placed in a quartz tube reactor so that the direction in which the cells extend was parallel to the vertical direction. Next, the gas flow path was degassed in nitrogen at 100°C, and then the acid gas adsorption apparatus was cooled to room temperature (25°C). A mixed gas of carbon dioxide and nitrogen (the gas to be treated) was supplied to the gas flow path of this acid gas adsorption apparatus at 25°C and a flow rate of 2.2 m / s for 120 minutes (adsorption step). The carbon dioxide content in the mixed gas was 0.04 volume%. This caused the acid gas to be adsorbed onto the acid gas adsorbent. Table 1 shows the amount of carbon dioxide adsorbed per unit mass of the amine-supported polymer in the adsorption step (amount of acid gas adsorbed).

[0090] Next, carbon dioxide heated to 100°C was supplied as a heating gas to the gas flow path of the acid gas adsorption apparatus at a flow rate of 0.1 m / s and a partial pressure of 0.10 MPa to raise the temperature of the acid gas adsorption layer to the set temperature shown in Table 1 (heating process). Table 1 shows the heating time from the start of heating gas supply until the acid gas adsorption layer reached the set temperature, the maximum temperature in the heating process, and the amount of heating gas adsorbed per unit mass of amine-supported polymer in the heating process (heating gas adsorption amount).

[0091] <Example 2> The acid gas adsorption layer was heated in the same manner as in Example 1, except that the partial pressure of carbon dioxide introduced into the gas flow path of the acid gas adsorption apparatus as the heating gas was set to 0.14 MPa, and the amount of heating gas adsorbed was changed to 0.75 mmol / g.

[0092] <Example 3> The acid gas adsorption layer was heated in the same manner as in Example 2, except that the set temperature was changed to 120°C.

[0093] <Example 4> The acid gas adsorption layer was heated in the same manner as in Example 2, except that the set temperature was changed to 150°C.

[0094] <Example 5> The acid gas adsorption layer was heated in the same manner as in Example 2, except that the set temperature was changed to 200°C.

[0095] <Example 6> The acid gas adsorption layer was heated in the same manner as in Example 1, except that the partial pressure of carbon dioxide introduced into the gas flow path of the acid gas adsorption apparatus as the heating gas was set to 0.17 MPa, and the amount of heating gas adsorbed was changed to 0.89 mmol / g.

[0096] <Example 7> The acid gas adsorption layer was heated in the same manner as in Example 1, except that the partial pressure of carbon dioxide introduced into the gas flow path of the acid gas adsorption apparatus as the heating gas was set to 0.01 MPa, and the amount of heating gas adsorbed was changed to 0.07 mmol / g.

[0097] <Example 8> The acid gas adsorption layer was heated in the same manner as in Example 1, except that the carbon dioxide content in the mixed gas of carbon dioxide and nitrogen introduced into the gas flow path of the acid gas adsorption device was set to 90% by volume, thereby changing the acid gas adsorption rate to 0.41 mmol / g, and the partial pressure of carbon dioxide introduced into the gas flow path of the acid gas adsorption device as the heating gas was set to 0.05 MPa, thereby changing the heating gas adsorption rate to 0.25 mmol / g.

[0098] <Example 9> The acid gas adsorption layer was heated in the same manner as in Example 8, except that the partial pressure of carbon dioxide introduced into the gas flow path of the acid gas adsorption apparatus as the heating gas was set to 0.01 MPa and the amount of heating gas adsorbed was changed to 0.07 mmol / g.

[0099] <Example 10> The heating gas is sulfur dioxide (SO ２ The acid gas adsorption layer was heated in the same manner as in Example 1, except that it was changed to ).

[0100] <Example 11> The heating gas is nitrogen dioxide (NO ２ The acid gas adsorption layer was heated in the same manner as in Example 1, except that it was changed to ).

[0101] <Comparative Example 1> The acid gas adsorption layer was heated in the same manner as in Example 1, except that the heating gas was changed to water vapor.

[0102] <Comparative Example 2> The acidic gas adsorption layer was heated in the same manner as in Example 1, except that the heating gas was changed to oxygen.

[0103]

[0104] <Evaluation> In Comparative Example 1, some of the water vapor condensed to produce liquid water (condensate). As a result, acidic gas (CO2) was released into the liquid water. ２ ) dissolved. Therefore, the recovery efficiency of the acidic gas calculated by the following formula (1) was 73.3%. Acidic gas recovery efficiency = ((Amount of acidic gas adsorbed - Amount of acidic gas dissolved) / Amount of acidic gas adsorbed) × 100 ... (1) (In formula (1), the amount of acidic gas adsorbed represents the amount of acidic gas adsorbed per unit mass of the acidic gas adsorbent in the adsorption process [unit: mmol / g]. The amount of acidic gas dissolved represents the amount of acidic gas dissolved per unit mass of the condensate produced in the heating process [unit: mmol / g].) In contrast, in Examples 1 to 11 and Comparative Example 2, the heating gas was a non-condensable gas, so the non-condensable gas did not condense in the heating process. Therefore, the recovery efficiency of the acidic gas was 100%.

[0105] Furthermore, in Examples 1 to 11, the amount of adsorbed gas during the heating process exceeded 0 mmol / g, indicating that the heating gas was adsorbed onto the acidic gas adsorbent. As a result, in Examples 1 to 11, heat of adsorption was generated, and the acidic gas adsorbent was efficiently heated. Consequently, in Examples 1 to 11, the heating time to reach the set temperature was significantly shortened compared to Comparative Example 2, in which the heating gas was not adsorbed onto the acidic gas adsorbent. Therefore, it can be seen that supplying a non-condensable gas that can be adsorbed onto the acidic gas adsorbent during the heating process allows for efficient heating of the acidic gas adsorbent and excellent recovery efficiency of the acidic gas.

[0106] The method for recovering acidic gases according to embodiments of the present invention can be used for the separation and recovery of acidic gases, and is particularly suitable for use in the carbon dioxide capture, utilization, and storage (CCUS) cycle.

[0107] 1 Acid gas adsorption section 2 Storage section 22 First inlet 23 First outlet 25 Second outlet 51 First valve 52 Second valve 100 Acid gas recovery system

Claims

1. A method for recovering acidic gas, comprising: an adsorption step of supplying a gas to be treated containing an acidic gas to an acidic gas adsorbent to adsorb the acidic gas onto the acidic gas adsorbent; and a heating step of raising the temperature of the acidic gas adsorbent to a predetermined desorption temperature, wherein in the heating step, a non-condensable gas that can be adsorbed by the acidic gas adsorbent is supplied to the acidic gas adsorbent.

2. The method for recovering an acidic gas according to claim 1, further comprising a desorption step after the heating step, in which the acidic gas adsorbent is maintained at the desorption temperature to desorb the acidic gas from the acidic gas adsorbent.

3. The method for recovering acidic gas according to claim 1 or 2, wherein the molar ratio of the amount of non-condensable gas adsorbed per unit mass of the acidic gas adsorbent in the heating step to the amount of acidic gas adsorbed per unit mass of the acidic gas adsorbent in the adsorption step is 0.6 times or more and 3.3 times or less.

4. The method for recovering acidic gas according to claim 1 or 2, wherein the amount of non-condensable gas adsorbed per unit mass of the acidic gas adsorbent in the heating step is 0.10 mmol / g or more and 0.80 mmol / g or less.

5. The method for recovering acidic gas according to claim 1 or 2, wherein the desorption temperature is within ±10% of the set temperature.

6. The method for recovering an acidic gas according to claim 1 or 2, wherein the non-condensable gas is selected from carbon dioxide, sulfur dioxide, nitrogen dioxide, or a mixture thereof.

7. The method for recovering an acidic gas according to claim 6, wherein each of the non-condensable gas and the acidic gas is carbon dioxide.

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