Acidic gas collection method

Abstract

This acidic gas collection method includes bringing an adsorbent into contact with a raw material gas containing an acidic gas to cause the adsorbent to adsorb the acidic gas contained in the raw material gas. When defining the weight of the adsorbent in a dry state as W1 and the weight of the adsorbent at the start of adsorption as W2, the moisture content C1 of the adsorbent at the start of adsorption calculated by the following formula is 10 wt% or more.　C1 = (W2 - W1) / W1 × 100. In this collection method, the adsorbent contains a polymer having an amino group, for example.

Description

Acid gas recovery method

[0001] The present invention relates to a method for recovering acid gases.

[0002] In recent years, attention has been focused on a technology (DAC: Direct Air Capture) for directly separating and capturing carbon dioxide contained in the atmosphere, exhaust gas, etc. For example, Patent Document 1 describes a method for separating gaseous carbon dioxide from a gas mixture containing gaseous carbon dioxide and a gas other than carbon dioxide, such as the atmosphere, by adsorption / desorption using an adsorbent. In Patent Document 1, the gaseous carbon dioxide is desorbed by bringing water vapor into contact with the adsorbent that has adsorbed the gaseous carbon dioxide.

[0003] Special table 2017-528318 publication

[0004] In Patent Document 1, after the desorption step of gaseous carbon dioxide, the adsorbent from which gaseous carbon dioxide has been desorbed is cooled to a low temperature (for example, below 60°C) to remove moisture from the adsorbent, thereby suppressing deterioration of the adsorbent. As described in Patent Document 1, in DACs that employ desorption using water vapor, it has been considered necessary to remove moisture from the adsorbent after the desorption step. Conventional methods have room for improvement in terms of efficiency and economy.

[0005] An object of the present invention is to provide a new gas recovery method that can recover acidic gases such as carbon dioxide using a simpler process.

[0006] The present invention provides a method for recovering acidic gases, which comprises contacting an adsorbent with a raw gas containing an acidic gas to adsorb the acidic gas contained in the raw gas onto the adsorbent, wherein, when the weight of the adsorbent in a dry state is defined as W1 and the weight of the adsorbent at the start of adsorption is defined as W2, a water content C1 of the adsorbent at the start of adsorption calculated by the following formula is 10% by weight or more: C1 = (W2 - W1) / W1 x 100

[0007] According to the present invention, a new gas recovery method can be provided that can recover acidic gases such as carbon dioxide using a simpler process.

[0008] 1A is a schematic configuration diagram of an adsorption device provided in a recovery system that can be used in the method for recovering acidic gases of the present invention. FIG. 1B is a perspective view schematically showing an example of the adsorption device of FIG. 1A. FIG. 1C is a perspective view schematically showing another example of the adsorption device.

[0009] A method for recovering an acidic gas according to a first aspect of the present invention includes contacting an adsorbent with a raw gas containing an acidic gas, and adsorbing the acidic gas contained in the raw gas onto the adsorbent, wherein, when the weight of the adsorbent in a dry state is defined as W1 and the weight of the adsorbent at the start of adsorption is defined as W2, a water content C1 of the adsorbent at the start of adsorption calculated by the following formula is 10 wt % or more: C1 = (W2 - W1) / W1 × 100

[0010] In a second aspect of the present invention, for example, in the method for recovering an acidic gas according to the first aspect, the water content C1 of the adsorbent at the start of the adsorption is 20% by weight or more.

[0011] In a third aspect of the present invention, for example, the method for recovering an acidic gas according to the first or second aspect further includes contacting the adsorbent that has adsorbed the acidic gas with water vapor to desorb the acidic gas from the adsorbent, and cooling the adsorbent from which the acidic gas has been desorbed, wherein when the weight of the adsorbent at the start of the cooling is defined as W4, a water content C3 of the adsorbent at the start of the cooling calculated by the following formula is 30% by weight or more: C3 = (W4 - W1) / W1 × 100

[0012] In a fourth aspect of the present invention, for example, in the method for recovering an acidic gas according to the third aspect, the cooling comprises cooling the adsorbent from which the acidic gas has been desorbed to a temperature of 20°C or higher and 80°C or lower.

[0013] In a fifth aspect of the present invention, for example, in the method for recovering an acidic gas according to the third or fourth aspect, the adsorption, desorption, and cooling are repeatedly carried out in this order.

[0014] In a sixth aspect of the present invention, for example, in the method for recovering an acidic gas according to any one of the first to fifth aspects, the adsorbent contains a polymer having an amino group.

[0015] In a seventh aspect of the present invention, for example, in the method for recovering an acidic gas according to the sixth aspect, the polymer includes an amine polymer having a constitutional unit derived from an epoxy monomer.

[0016] In an eighth aspect of the present invention, for example, in the method for recovering an acidic gas according to the seventh aspect, the residual rate of the polymer when the adsorbent is immersed in water at 25° C. for 15 hours is 90% or more.

[0017] In a ninth aspect of the present invention, for example, in the method for recovering an acidic gas according to any one of the first to eighth aspects, the adsorbent has a porous structure.

[0018] In a tenth aspect of the present invention, for example, in the method for recovering an acidic gas according to the ninth aspect, the adsorbent has an average pore size of 0.1 μm or more and 50 μm or less.

[0019] In an eleventh aspect of the present invention, for example, in the method for recovering an acidic gas according to the ninth or tenth aspect, the adsorbent has a thickness of 0.5 m 2 / g or more 100m 2 / g or less.

[0020] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0021] 1A is a schematic diagram of an adsorption device 10 included in a recovery system that can be used in the method for recovering acidic gas of this embodiment. The method for recovering acidic gas of this embodiment will be described below with reference to the adsorption device 10 shown in FIG. 1A.

[0022] [Recovery System] A recovery system that can be used in the acidic gas recovery method of this embodiment includes an adsorption device 10 having an adsorbent 11. In the adsorption device 10, the adsorbent 11, while adsorbing the acidic gas, comes into contact with water vapor to desorb the acidic gas. The adsorbent 11 is regenerated by desorbing the acidic gas. The adsorption device 10 releases a desorbed gas (second gas) containing water vapor and the acidic gas desorbed from the adsorbent 11. In FIG. 1A , dashed arrows indicate the flow directions of the water vapor, the second gas, etc. This is also true in other drawings.

[0023] The adsorption device 10 has a case 12 that houses an adsorbent 11. A second gas containing water vapor and an acidic gas can be discharged from a first outlet of the case 12. A third gas having a lower acidic gas content than the second gas can be discharged from a second outlet of the case 12.

[0024] The recovery system includes, for example, a raw material gas supply path. The raw material gas supply path is connected to a raw material gas inlet of the adsorption device 10 and is a path for supplying the raw material gas to the adsorption device 10. The raw material gas supply path is connected to, for example, a tank or the like that stores the raw material gas. The raw material gas is preferably atmospheric air. Therefore, the raw material gas supply path may have an intake port that is open to the atmosphere, and may be configured to continuously supply atmospheric air to the raw material gas supply path from the intake port.

[0025] The raw material gas preferably contains, for example, an acidic gas and further contains other gases besides the acidic gas. The raw material gas is preferably the atmosphere, but may be a combustion gas or the like. By sending the raw material gas to the raw material gas supply path, the amount of acidic gas supplied to the adsorption device 10 increases. This allows the adsorbent 11 to adsorb a sufficient amount of acidic gas.

[0026] The content of acidic gas in the raw material gas is not particularly limited, and is, for example, 0.01% by volume (100 ppm by volume) or more, preferably 0.04% by volume (400 ppm by volume) or more, and may be 0.1% by volume (1000 ppm by volume) or more. The upper limit of the content of acidic gas in the raw material gas is not particularly limited, and is, for example, 20% by volume. The pressure of the raw material gas is typically equal to atmospheric pressure in the environment in which the recovery system is used. The temperature of the raw material gas is, for example, about room temperature (25°C).

[0027] The recovery system includes, for example, a second gas discharge path. The second gas discharge path is connected to the first outlet of the adsorption device 10 and is a path for discharging the second gas (desorbed gas) from the adsorption device 10. The second gas discharge path may have an opening (discharge port) formed therein for discharging the second gas from the second gas discharge path. This discharge port may be connected to, for example, a storage unit. The second gas is supplied to the storage unit through this discharge port, for example.

[0028] The recovery system includes, for example, a third gas discharge path. The third gas discharge path is connected to the second outlet of the adsorption device 10 and is a path for discharging the third gas from the adsorption device 10. The third gas discharge path may be formed with an opening (discharge port) for discharging the third gas from the third gas discharge path. The third gas is released into the atmosphere through this discharge port, for example.

[0029] FIG. 1B is a perspective view schematically illustrating an example of the adsorption device 10 of FIG. 1A. For ease of explanation, the case 12 is omitted from FIG. 1B. The adsorption device 10 may have a configuration in which a structure 15A including an adsorbent 11 and having ventilation paths 14 is housed in the case 12. As shown in FIG. 1B, the ventilation paths 14 extend in the longitudinal direction of the case 12 and function as paths through which the raw material gas, water vapor, and the like pass. The structure 15A is typically a honeycomb structure having a plurality of ventilation paths 14 extending in the same direction.

[0030] The adsorbent 11 included in the structure 15A typically has a sheet shape. The structure 15A may include a support for supporting the adsorbent 11 together with the adsorbent 11, or may not include a support.

[0031] 1B , the structure 15A may include an adsorbent unit U in which, for example, a corrugated adsorbent 11A and a flat adsorbent 11B are stacked. The adsorbent 11A may have a plurality of peaks 13a and a plurality of valleys 13b arranged alternately. In this case, an air passage 14 is formed between the peaks 13a or valleys 13b of the adsorbent 11A and the adsorbent 11B. Thus, the air passage 14 is surrounded by the adsorbents 11A and 11B.

[0032] The configuration of the adsorption device 10 is not limited to the example shown in FIGS. 1A and 1B.

[0033] FIG. 2 is a perspective view schematically illustrating another example of the adsorption device 10. In the example illustrated in FIG. 2, the case 12 is tubular (particularly cylindrical). The ventilation path 14 extends in the direction in which the case 12 extends (the axial direction of the case 12). A structure 15B is housed in the case 12. As illustrated in FIG. 2, the structure 15B has a shape in which one adsorbent unit U is wound around a central tube (not shown). Except for this, the configuration of the structure 15B illustrated in FIG. 2 is the same as the configuration of the structure 15A illustrated in FIG. 1B. The central tube extends in the direction in which the case 12 extends (the axial direction of the case 12). Because the adsorbent unit U is wound around the central tube, in the adsorbent 11A, the multiple peaks 13a and the multiple valleys 13b are, specifically, arranged alternately in the circumferential direction of the central tube.

[0034] The structure 15 included in the adsorption device 10 is not limited to the honeycomb structure such as the structures 15A and 15B described above.

[0035] [Acidic Gas Recovery Method] The acidic gas recovery method of this embodiment includes the steps of bringing the adsorbent 11 into contact with a raw gas containing an acidic gas, thereby adsorbing the acidic gas contained in the raw gas onto the adsorbent 11 (adsorption step), and bringing the adsorbent 11 that has adsorbed the acidic gas into contact with water vapor, thereby desorbing the acidic gas from the adsorbent 11 (desorption step). The adsorption step and the desorption step may be repeatedly performed in this order.

[0036] After the desorption step, the method may include cooling the adsorbent 11 from which the acidic gas has been desorbed (a cooling step). The adsorption step, the desorption step, and the cooling step may be repeatedly performed in this order.

[0037] The adsorption step is carried out, for example, in the above-described recovery system as follows: First, the raw material gas is supplied to the adsorption device 10 through the raw material gas supply path. The adsorbent 11 from which the acidic gas has been desorbed in the desorption step is located inside the case 12 of the adsorption device 10. The temperature of the raw material gas supplied to the adsorption device 10 is, for example, 50°C or less, preferably 40°C or less, or even 30°C or less.

[0038] In the recovery method of this embodiment, when the weight of the adsorbent 11 in a dry state is defined as W1 and the weight of the adsorbent 11 at the start of adsorption in the adsorption process is defined as W2, the moisture content C1 of the adsorbent 11 at the start of adsorption calculated by the following formula (1) is 10% by weight or more. In this embodiment, the "adsorbent in a dry state" refers to an adsorbent that has been dried for 120 minutes under conditions of 100°C in a vacuum atmosphere. The above drying process removes moisture and CO2 contained in the adsorbent. C1 = (W2 - W1) / W1 × 100 ... (1)

[0039] As described above, in DACs employing desorption using steam, it has been considered necessary to remove moisture from the adsorbent after the desorption step. On the other hand, in the recovery method of this embodiment, the moisture content C1 of the adsorbent 11 at the start of adsorption is 10 wt % or more, thereby improving the rate of adsorption of acidic gases. One possible reason for this is that the internal diffusivity of the adsorbent 11 improves as the moisture content of the adsorbent 11 increases. Furthermore, since the moisture content C1 of the adsorbent 11 at the start of adsorption is 10 wt % or more, the water in the adsorbent 11 volatilizes upon contact with the feed gas, allowing the temperature of the adsorbent 11 to be lowered by the heat of vaporization. Therefore, in the recovery method of this embodiment, the step of removing moisture from the adsorbent after the desorption step can be shortened. Therefore, acidic gases can be recovered through a simpler process.

[0040] The moisture content C1 of the adsorbent 11 at the start of adsorption may be 15% by weight or more, and may further be 20% by weight or more.

[0041] The moisture content C1 of the adsorbent 11 at the start of adsorption may be 25% by weight or more, 30% by weight or more, or even 35% by weight or more. The upper limit of the moisture content C1 of the adsorbent 11 at the start of adsorption is, for example, 300% by weight. The upper limit of the moisture content C1 of the adsorbent 11 at the start of adsorption may be 250% by weight, 200% by weight, 170% by weight, or even 150% by weight.

[0042] The raw material gas supplied to the adsorption device 10 comes into contact with the adsorbents 11 (11A and 11B) while traveling through the ventilation path 14. The adsorbent 11 that comes into contact with the raw material gas adsorbs acidic gases contained in the raw material gas. The raw material gas (third gas) treated in the adsorption device 10 is discharged, for example, from a second outlet of the adsorption device 10 and passes through a third gas discharge path, and is then discharged, for example, to the outside.

[0043] The third gas has a lower acidic gas content than the second gas (desorbed gas). The acidic gas content in the third gas is, for example, 0.1% by volume or more, preferably 1% by volume or more, lower than the second gas. The acidic gas content in the third gas is, for example, 0.1 to 5% by volume.

[0044] The desorption step is carried out, for example, in the above-described recovery system as follows. First, water vapor is supplied to the adsorption device 10 through a water vapor supply path. Inside the case 12 of the adsorption device 10, an adsorbent 11 is located, which adsorbs acidic gases in the adsorption step. Examples of acidic gases adsorbed by the adsorbent 11 include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, and nitrogen oxides (NOx), with carbon dioxide being preferred.

[0045] In the desorption step, the adsorbent 11 having adsorbed acidic gases and at a temperature of less than 35° C. may be brought into contact with water vapor to desorb the acidic gases from the adsorbent 11 .

[0046] In DACs employing desorption using steam, a step of heating the adsorbent to a high temperature prior to the desorption step was considered necessary to prevent condensed water from forming on the surface of the adsorbent when steam is brought into contact with the adsorbent during the desorption step. On the other hand, in the recovery method of the present embodiment, when the adsorbent 11, which adsorbs acidic gases, is brought into contact with steam at a temperature below 35°C during the desorption step, condensed water may form on the surface of the adsorbent 11. However, in the recovery method of the present embodiment, even if condensed water forms on the surface of the adsorbent 11, the adsorbent 11 does not deteriorate and the desorption step is not hindered. That is, condensed water may form on the surface of the adsorbent 11 by contacting the adsorbent 11 with steam. The condensed water increases the moisture content of the adsorbent 11, thereby improving the rate at which the adsorbent 11 adsorbs acidic gases.

[0047] The water vapor supplied to the adsorption device 10 travels through the ventilation path 14 and comes into contact with the adsorbents 11 (11A and 11B). The adsorbent 11 in contact with the water vapor receives thermal energy from the water vapor and desorbs the acidic gas. As a result, the water vapor and the acidic gas desorbed from the adsorbent 11 are mixed to form a desorbed gas (second gas). The desorbed gas is discharged, for example, from the first outlet, passes through the second gas discharge path, and is stored, for example, in a storage unit.

[0048] The desorbed gas (second gas) has a lower temperature and a higher acidic gas content than water vapor. The temperature of the desorbed gas is, for example, 10°C or more, preferably 30°C or more lower than water vapor. The temperature of the second gas is, for example, 10°C to 60°C. The acidic gas content in the second gas is, for example, 0.1% by volume or more, preferably 1% by volume or more higher than water vapor. The acidic gas content in the second gas is, for example, 0.1% by volume to 50% by volume.

[0049] In the desorption step, the temperature of the water vapor when the adsorbent 11 that has adsorbed acidic gases is brought into contact with the water vapor is preferably higher than 35°C. The lower limit of the temperature of the water vapor when the adsorbent 11 that has adsorbed acidic gases is brought into contact with the water vapor may be 50°C, 60°C, 70°C, or even 80°C. The upper limit of the water vapor temperature may be, for example, 150°C or 100°C from the viewpoint of suppressing deterioration of the adsorbent 11. In the desorption step, the flow rate of the water vapor introduced into the adsorption device 10 is not particularly limited and may be 0.1 to 1000 m 3 The pressure of the water vapor is typically equal to atmospheric pressure in the environment in which the recovery system is used.

[0050] The temperature of the water vapor when the adsorbent 11 that has adsorbed acidic gases is brought into contact with the water vapor may be higher than 50° C., higher than 60° C., higher than 70° C., higher than 80° C., or even higher than 90° C. The temperature of the water vapor when the adsorbent 11 is brought into contact with the water vapor may be higher than 100° C. In other words, the water vapor may be superheated steam.

[0051] In the recovery method of this embodiment, when the weight of the adsorbent 11 at the start of contact with water vapor in the desorption step is defined as W3, the water content C2 of the adsorbent 11 at the start of contact with water vapor, calculated by the following formula (2), may be 2 wt % or more and 60 wt % or less: C2 = (W3 - W1) / W1 × 100 (2)

[0052] The recovery method of this embodiment may satisfy the following (i) or (ii): (i) before contacting the adsorbent 11 with water vapor, the adsorbent 11 is heated to a temperature of 30° C. or higher and lower than 35° C. (ii) the temperature of the adsorbent 11 when contacting it with water vapor is lower than 30° C.

[0053] When the above condition (i) is satisfied, i.e., when the recovery method of this embodiment includes heating the adsorbent 11 that has adsorbed acidic gases to a temperature of 30°C or higher but lower than 35°C (preheating step) between the adsorption step and the desorption step, it is not necessary to heat the adsorbent 11 to a high temperature in the preheating step, and therefore the power required for the preheating step can be reduced.When the above condition (ii) is satisfied, i.e., when the recovery method of this embodiment does not include a preheating step between the adsorption step and the desorption step, it is not necessary to heat the adsorbent 11 that has adsorbed acidic gases, and therefore the power required for the preheating step can be reduced and acidic gases can be recovered by a simpler process.

[0054] The recovery method of this embodiment may include depressurizing the adsorbent 11 that adsorbs the acidic gas between the adsorption step and the desorption step (depressurization step). The depressurization step can reduce the oxygen contained in the adsorbent 11. This makes it possible to suppress deterioration of the adsorbent 11 due to oxidation even when the adsorbent 11 has low oxidation resistance.

[0055] When a preheating step and a depressurizing step are included between the adsorption step and the desorption step, it is preferable to carry out the preheating step after the depressurizing step.

[0056] In the recovery method of this embodiment, when the weight of the adsorbent 11 at the start of cooling in the cooling step is defined as W4, the moisture content C3 of the adsorbent 11 at the start of cooling calculated by the following formula (3) may be 30% by weight or more. In this case, it is easy to achieve a moisture content C1 of the adsorbent 11 at the start of adsorption of 10% by weight or more. C3 = (W4 - W1) / W1 × 100 (3)

[0057] The upper limit of the moisture content C3 of the adsorbent 11 at the start of cooling is, for example, 350 wt %.

[0058] In the cooling step, the adsorbent 11 from which the acidic gas has been desorbed may be cooled to a temperature of 20° C. or higher and 80° C. or lower. In this case, it is easy to achieve a water content C1 of 10 wt % or higher in the adsorbent 11 at the start of adsorption.

[0059] The adsorbent 11 is not particularly limited as long as it can desorb acidic gases when it comes into contact with water vapor and can adsorb acidic gases contained in a raw material gas when it comes into contact with the raw material gas. The adsorbent 11 is preferably suitable for a temperature swing adsorption method. For example, the adsorbent 11 can adsorb acidic gases at about room temperature (25°C) and can desorb acidic gases by receiving thermal energy from water vapor.

[0060] The material of the adsorbent 11 is not particularly limited, and examples thereof include inorganic and organic materials. Examples of inorganic materials include metal oxides such as cerium oxide, zeolite, silica gel, and activated carbon. Examples of organic materials include polymer P having an amino group and amine compounds other than polymer P. In the recovery method of this embodiment, the adsorbent 11 preferably contains polymer P having an amino group.

[0061] In DACs employing desorption using water vapor, nanoparticles such as silica supported with amines can be used as adsorbents. However, in recent years, it has been known that such amine-based solid adsorbents have a problem of amine elution in water. Therefore, in DACs employing desorption using water vapor, a step of heating the adsorbent to a high temperature has been carried out before the desorption step to prevent amine elution from the adsorbent due to condensed water generated on the surface of the adsorbent.

[0062] However, although the adsorbent 11 containing the polymer P having amino groups swells in water, the elution of amines is suppressed to a low level compared to conventional amine-based solid adsorbents. For example, when the adsorbent 11 is immersed in water at 25°C for 15 hours, the residual rate of the polymer P can be 90% or more. Therefore, the adsorbent 11 containing the polymer P having amino groups is particularly suitable for the recovery method of this embodiment.

[0063] The residual rate of polymer P can be measured, for example, by the following method. A sample of 20 mm x 30 mm is punched out of the adsorbent 11 (250 μm thick) under an environment of 25°C temperature and 50% RH humidity. The weight of the dry sample after vacuum drying at 100°C for 120 minutes is measured, and this is the dry polymer P content R1. If the adsorbent 11 contains a carrier, the weight of the carrier contained in the 20 mm x 30 mm x 250 μm thickness is subtracted to obtain the dry polymer P content R1 (wt%). Next, the sample is immersed in water at 25°C for 15 hours. The sample after immersion is vacuum dried at 100°C for 120 minutes, and the weight of the dry sample after immersion is measured, and this is the polymer P content R2 (wt%). When the adsorbent 11 includes a carrier, the weight of the carrier contained in a 20 mm × 30 mm × 250 μm thickness area is subtracted to obtain the content R2 of polymer P after immersion. The residual rate D of polymer P when the adsorbent 11 is immersed in water at 25° C. for 15 hours can be calculated by the following formula (4): D=1−{(R1−R2) / R1}×100 (4)

[0064] The polymer P is preferably an amine polymer containing a structural unit U1 derived from an epoxy monomer. The amine polymer contains, for example, a reactant P1 of a compound group containing an amine monomer and an epoxy monomer.

[0065] As described above, the group of compounds for forming the reactant P1 includes an amine monomer and an epoxy monomer. The reactant P1 may be, for example, a polymer of a group of monomers including an amine monomer and an epoxy monomer (particularly, a polymer of an amine monomer and an epoxy monomer). The reactant P1 may be a crosslinked product of an amine monomer with an epoxy monomer (a crosslinked product).

[0066] Examples of the amine monomers include ethylamine, ethylenediamine, 1,4-butylenediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, iminobispropylamine, bis(hexamethylene)triamine, 1,3,6-trisaminomethylhexane, tris(2-aminoethyl)amine, N,N'-bis(3-aminopropyl)ethylenediamine, polymethylenediamine, trimethylhexamethylenediamine, poly Examples of suitable amine monomers include aliphatic amines such as etherdiamine, isophoronediamine, menthanediamine, piperazine, N-aminoethylpiperazine, 3,9-bis(3-aminopropyl)2,4,8,10-tetraoxaspiro(5,5)undecane adduct, bis(4-amino-3-methylcyclohexyl)methane, bis(4-aminocyclohexyl)methane, and modified products thereof; aliphatic polyamines such as polyethyleneimine and polyalkylenepolyamine; (meth)acrylic polymers having amino groups such as aminoethylated acrylic polymer; and aliphatic polyamidoamines formed by the reaction of polyamines with dimer acids. These amine monomers can be used alone or in combination of two or more.

[0067] Examples of epoxy monomers include monofunctional epoxy compounds such as n-butyl glycidyl ether, higher alcohol glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, p-sec-butylphenyl glycidyl ether, and t-butylphenyl glycidyl ether; diepoxy alkanes such as 1,5-hexadiene diepoxide, 1,7-octadiene diepoxide, and 1,9-decadiene diepoxide; (poly)ethylene glycol diglycidyl ether; polyfunctional epoxy compounds having an ether group such as N,N,N',N'-tetraglycidylmetaxylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane; and polyfunctional epoxy compounds having an amino group such as N,N,N',N'-tetraglycidylmetaxylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0068] The epoxy monomer may be an aromatic epoxy resin, a non-aromatic epoxy resin, or the like, depending on the circumstances. Examples of aromatic epoxy resins include polyphenyl-based epoxy resins, epoxy resins containing a fluorene ring, epoxy resins containing triglycidyl isocyanurate, and epoxy resins containing a heteroaromatic ring (e.g., a triazine ring). Examples of polyphenyl-based epoxy resins include bisphenol A-type epoxy resins, brominated bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AD-type epoxy resins, stilbene-type epoxy resins, biphenyl-type epoxy resins, bisphenol A novolac-type epoxy resins, cresol novolac-type epoxy resins, diaminodiphenylmethane-type epoxy resins, and tetrakis(hydroxyphenyl)ethane-based epoxy resins. Examples of non-aromatic epoxy resins include aliphatic glycidyl ether-type epoxy resins, aliphatic glycidyl ester-type epoxy resins, alicyclic glycidyl ether-type epoxy resins, alicyclic glycidyl amine-type epoxy resins, and alicyclic glycidyl ester-type epoxy resins.

[0069] The epoxy monomers can be used alone or in combination of two or more. When a monofunctional epoxy compound is used, it is preferable to use it in combination with another epoxy monomer containing two or more epoxy groups. The monofunctional epoxy compound can also be used as a reactive diluent to adjust the viscosity of the monomers used to form the reactant P1.

[0070] As described above, polymer P as an amine polymer contains a structural unit U1 derived from an epoxy monomer. When polymer P is reactant P1, polymer P further contains a structural unit U2 derived from an amine monomer. The content of structural unit U1 in polymer P, particularly reactant P1, is, for example, 20% to 70% by weight. The content of structural unit U2 in polymer P, particularly reactant P1, is, for example, 30% by weight or more, preferably 50% by weight or more. The upper limit of the content of structural unit U2 is not particularly limited, and is, for example, 80% by weight.

[0071] The glass transition temperature Tg of the polymer P is not particularly limited, and is, for example, 40°C or lower, preferably 30°C or lower, more preferably 20°C or lower, and even more preferably 15°C or lower, and may be 10°C or lower, 5°C or lower, or 0°C or lower. When the glass transition temperature Tg of the polymer P is low to this extent, the rate at which the adsorbent 11 adsorbs acidic gases tends to be high. The lower limit of the glass transition temperature Tg of the polymer P is, for example, -100°C, preferably -50°C, and more preferably -10°C, from the viewpoint of ensuring sufficient adsorption of acidic gases in the adsorbent 11 and from the viewpoint of heat resistance. In this specification, the glass transition temperature Tg is the midpoint glass transition temperature (T mg ) The polymer P generally corresponds to a thermosetting resin. The polymer P is solid at, for example, 25°C, preferably in the range of 25°C to 80°C.

[0072] The weight average molecular weight of the polymer P is not particularly limited and is, for example, 500 or more, preferably 1000 or more, more preferably 10000 or more, and even more preferably 100000 or more. The upper limit of the weight average molecular weight of the polymer P is, for example, 10,000,000.

[0073] The adsorbent 11 contains, for example, polymer P as a main component. In this specification, "main component" means the component contained in the adsorbent 11 in the largest amount by weight. The content of polymer P in the adsorbent 11 is, for example, 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, and may be 90% by weight or more, or may be 95% by weight or more. The adsorbent 11 may be composed substantially of polymer P only. The higher the content of polymer P, the more the adsorption ability of the adsorbent 11 tends to improve.

[0074] The adsorbent 11 may be substantially composed of only the polymer P, or may further contain other components in addition to the polymer P. Examples of other components include a carrier, a reaction accelerator, a plasticizer, a pigment, a dye, an antioxidant, a conductive material, an antistatic agent, an ultraviolet absorber, a flame retardant, and an antioxidant.

[0075] Examples of the support include fibers and fiber structures containing fibers. Examples of fibers include glass fibers; natural fibers such as wood pulp, cotton, and hemp (e.g., Manila hemp); and chemical fibers (synthetic fibers) such as polyester fibers, rayon, vinylon, acetate fibers, polyvinyl alcohol (PVA) fibers, polyamide fibers, polyolefin fibers, and polyurethane fibers. Examples of the fiber structure include woven fabrics, nonwoven fabrics, and paper. A specific example of a fiber structure is glass paper.

[0076] The shape of the adsorbent 11 is not particularly limited and may be, for example, a block, a sheet, a particle, etc. In this specification, the particle shape includes a spherical shape, an ellipsoidal shape, a scale shape, a fiber shape, etc.

[0077] The adsorbent 11 may have a porous structure. As an example, the adsorbent 11 may include a porous body S containing a polymer P and a liquid L. The shape of the porous body S may be, for example, a block, a sheet, or a particle. The adsorbent 11 may or may not include a porous resin sheet as the porous body S. The adsorbent 11 may or may not include a member other than the porous body S, such as a carrier for supporting the polymer P. When the adsorbent 11 does not include a carrier, the shape of the adsorbent 11 tends to be easily adjustable by cutting or machining.

[0078] The porous body S preferably has a three-dimensional network skeleton containing the polymer P and the liquid L. The three-dimensional network skeleton may further contain components other than the polymer P and the liquid L. As an example, in the porous body S, the above-mentioned three-dimensional network skeleton extends continuously. The pores contained in the porous body S are preferably continuous pores formed continuously in a three-dimensional manner. The porous body S may have closed pores or may have through pores that penetrate the porous body S.

[0079] The adsorbent 11 (porous body S) preferably has an average pore diameter of 0.1 μm or more and 50 μm or less. The larger the average pore diameter of the adsorbent 11, the more the adsorbent 11 can maintain the diffusion of acidic gases without clogging the pores even when it absorbs water. The lower limit of the average pore diameter of the adsorbent 11 may be 0.2 μm, 0.3 μm, or even 0.5 μm. In this specification, the average pore diameter of the adsorbent 11 refers to the median diameter measured by mercury intrusion porosimetry. The mercury intrusion porosimetry is performed using a commercially available pore distribution analyzer (e.g., Autopore V9620 manufactured by Micromeritics) under an initial pressure of 21 kPa.

[0080] The adsorbent 11 (porous body S) is 0.5 m 2 / g or more 100m 2 The larger the specific surface area of ​​the adsorbent 11, the greater the contact area with the acidic gas, and therefore the faster the rate at which the acidic gas is adsorbed. The lower limit of the specific surface area of ​​the adsorbent 11 is 0.5 m 2 / g, 1.0 m 2 / g, 2.0 m2 / g, 3.0 m 2 / g, 4.0 m 2 / g, 5.0 m 2 / g, 6.0 m 2 / g, 7.0 m 2 / g, and even 8.0m 2 / g. The specific surface area of ​​the adsorbent 11 refers to the Brunauer-Emmett-Teller (BET) specific surface area determined by nitrogen gas adsorption. The specific surface area of ​​the adsorbent 11 can be measured by a method conforming to the provisions of JIS Z8830:2013.

[0081] The adsorbent 11 (porous body S) has a thickness of 0.1 cm 3 / g or more 5.0cm 3 The larger the pore volume of the adsorbent 11, the more the diffusion of the acidic gas in the pores improves, and therefore the rate at which the acidic gas is adsorbed can be increased. The lower limit of the pore volume of the adsorbent 11 is 0.2 cm 3 / g, 0.3 cm 3 / g, 0.5 cm 3 / g, 1.0 cm 3 / g, and even 2.0 cm 3 The upper limit of the pore volume of the adsorbent 11 may be 4.0 cm 3 / g, and 3.0 cm 3 The pore volume of the adsorbent 11 can be measured by mercury intrusion porosimetry. Mercury intrusion porosimetry is performed using a commercially available pore size distribution analyzer (e.g., Autopore V9620 manufactured by Micromeritics) under an initial pressure of 21 kPa.

[0082] When the adsorbent 11 is particulate, the average particle size of the adsorbent 11 is not particularly limited and is, for example, 0.5 μm or more, preferably 1 μm or more, and may be 10 μm or more, 20 μm or more, or 30 μm or more. The average particle size of the adsorbent 11 may be 200 μm or less, 100 μm or less, or less than 75 μm. In this specification, the average particle size of the adsorbent 11 refers to the particle size (d50) corresponding to 50% cumulative volume in a particle size distribution measured by a laser diffraction particle sizer or the like.

[0083] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0084] Example 1 First, 1.50 g of poly(1,2-butanediol)-6 propylene glycol (NOF Corporation, Uniol (registered trademark) PB-500) and 0.64 g of a butylene glycol and propylene glycol copolymer (NOF Corporation, Uniol (registered trademark) PB-700) were added to a 6 mL screw tube bottle (manufactured by AS ONE Corporation). 1.28 g of ethylene glycol diglycidyl ether (Nagase ChemteX Corporation, EX-810) was dissolved in the resulting mixture to prepare a mixture of epoxy monomer and porogen.

[0085] Next, 1.70 g of polyethyleneimine (Epomin SP-012, manufactured by Nippon Shokubai Co., Ltd.) was added to this mixture to prepare a mixture of epoxy monomer, amine monomer, and porogen. In this mixture, the ratio E / A of the equivalent weight E of the epoxy group contained in the epoxy monomer to the equivalent weight A of the active hydrogen of the primary amino group contained in the amine monomer was 0.5.

[0086] Next, the mixture was shaken for 2 minutes using a benchtop shaker (Angel Vibrator Digital 60 Hz) set to intensity 5. Next, using an applicator with a 500 μm gap, the mixture was applied to a 250 μm-thick glass paper (OHJI F-TEX Co., Ltd., PHN-50GC). At this time, the mixture penetrated into the glass paper. The glass paper soaked with the mixture was left in a dryer at 120°C for 30 minutes to harden the mixture. This resulted in a sheet-like cured product containing a polymer P having amino groups and glass paper as a support. This cured product was immersed in ethyl acetate at 60°C for 30 minutes, and this operation was repeated twice with liquid changes. This removed the porogen from the cured product, forming a porous sheet. Next, the product was dried in a dryer at 60°C for 30 minutes to obtain a free-standing porous sheet film containing glass paper as a support.

[0087] Next, the obtained porous sheet was molded into a honeycomb structure as shown in FIG. 1B by the following method. First, one porous sheet was molded into a wave shape using a heated corrugated roll. A vinyl acetate adhesive was applied to the wave peaks, and the sheet was then laminated to another flat porous sheet to obtain a corrugated sheet (a sheet in which a waved sheet and a flat sheet were laminated). Adhesive was again applied to the wave peaks of the corrugated sheet, and the flat surfaces of the corrugated sheets were overlapped to stack the corrugated sheets until the desired size was achieved. After stacking, the sheet was cut to obtain a honeycomb structure measuring 50 mm square and 200 mm long. The obtained honeycomb structure was used as the adsorbent of Example 1.

[0088] [Adsorption Test] For the adsorbent of Example 1, the adsorption amount (mmol / g) was measured after 20 minutes of the following adsorption test for the case where the moisture content C1 of the adsorbent at the start of adsorption was 0 wt% (adsorbent A1) and the case where the moisture content C1 was 30 wt% (adsorbent A2). Adsorption test: Air (composed of carbon dioxide, oxygen, nitrogen, and water vapor) was continuously fed into a column containing the adsorbent. Here, the air had a CO2 concentration of approximately 450 vol ppm, a temperature of 25°C, and a humidity of 70% RH.

[0089] The adsorption test was carried out using an adsorption capacity evaluation device. After setting the adsorbent of Example 1 in the column of the device, a predetermined amount of room air was taken in by adjusting the frequency of the blower with an inverter, and the air was supplied to the column through SUS piping. A CO2 concentration meter was connected to the inlet and outlet of the column, and a portion of the supply gas was sampled to measure the CO2 concentration in real time. The CO2 adsorption capacity of the adsorbent can be calculated from the measured CO2 concentration and the supply air volume.

[0090] The humidity of the supplied air was controlled by using a humidifier to maintain a specified humidity environment in a container placed in front of the blower intake. The condition of the supplied air was measured with a wet and dry bulb thermometer at the outlet of the device, and once the condition was stable, the column containing the adsorbent was connected and the evaluation began.

[0091] (Adsorbent A1) As a pretreatment, a drying treatment was performed on the adsorbent of Example 1. The drying treatment was performed by treating the adsorbent for 120 minutes under conditions of 100°C in a vacuum atmosphere. The adsorbent in the dry state was regarded as adsorbent A1, in which the moisture content C1 at the start of adsorption was 0 wt%. Next, the adsorbent in the dry state was packed into a column in a dry room with a dew point of approximately -60°C. The weight of the adsorbent packed into the column was 78 g.

[0092] (Adsorbent A2) As a pretreatment, first, a drying treatment was performed using the same procedure as the pretreatment for adsorbent A1, and then the weight w1 of the dry adsorbent was measured. Next, the dry adsorbent was packed into a column in a dry room with a dew point of approximately -60°C. Next, nitrogen gas conditioned to 25°C and 70% RH was passed through the column, and pre-humidification was performed until the outlet humidity stabilized to the same as the supply humidity, and then the weight w2 of the humidified adsorbent was measured. The moisture content c1 of the adsorbent after pre-humidification was calculated using the following formula: c1 = (w2 - w1) / w1 × 100. An adsorbent with a moisture content c1 of 30 wt% calculated using the above formula was considered to be adsorbent A2 with a moisture content C1 at the start of adsorption of 30 wt%.

[0093] Next, the supply air condition of the device was adjusted to 25°C and 70% RH. The supply air was stopped, and adsorbent A1 was connected to SUS piping. Next, the start of adsorption was determined when the supply air was restarted, and the CO2 adsorption amount after 20 minutes of adsorption testing was evaluated. The CO2 adsorption amount after 20 minutes of adsorption testing was also evaluated for adsorbent A2 using the same procedure as for adsorbent A1. The supply CO2 concentration of the air was approximately 450 vol ppm. The volumetric flow rate of the supplied air was 225 L / min, and the linear velocity across a 50 mm x 50 mm cross section was 1.5 m / s.

[0094] Table 1 shows the CO2 adsorption amounts (mmol / g) of the adsorbents A1 and A2.

[0095]

[0096] As shown in Table 1, when the water content C1 of the adsorbent of Example 1 at the start of adsorption was 10 wt % or more (adsorbent A2), the CO2 adsorption performance actually increased.

[0097] Example 2 The adsorbent of Example 2 was a free-standing porous sheet film containing glass paper as a support prepared in Example 1.

[0098] [Adsorption Test] For the adsorbent of Example 2, the adsorbent's moisture content C1 at the start of adsorption was 0 wt% (adsorbent B1), 13.5 wt% (adsorbent B2), 21.4 wt% (adsorbent B3), 31.8 wt% (adsorbent B4), and 40.4 wt% (adsorbent B5). The following adsorption test was performed for 20 minutes, and the adsorption amount (mmol / g) was measured for each. Adsorption test: Gas (composed of carbon dioxide, nitrogen, and water vapor) was continuously fed into a sample tube containing the adsorbent. The gas had a CO2 concentration of approximately 400 vol ppm, a temperature of 20°C, and a humidity of 50% RH.

[0099] The adsorption test was carried out using a CO2 flow test device. After the adsorbent of Example 2 was set in the sample tube of the device, nitrogen gas and carbon dioxide gas were supplied and mixed using a mass flow controller, and a portion of the nitrogen gas was bubbled to adjust the temperature to 20°C and 50% RH, and the resulting gas was supplied to the sample tube. A CO2 concentration meter was connected to the inlet and outlet of the sample tube, allowing real-time measurement of the CO2 concentration of the supplied gas. The amount of CO2 adsorption by the adsorbent can be calculated from the measured CO2 concentration and the supplied air volume.

[0100] (Adsorbent B1) As a pretreatment, a drying treatment was performed on the adsorbent of Example 2. The drying treatment was performed by treating the adsorbent for 120 minutes under conditions of 100°C in a vacuum atmosphere. The adsorbent in the dry state was regarded as adsorbent B1, which had a moisture content C1 of 0 wt% at the start of adsorption. Next, the adsorbent in the dry state was packed into a sample tube in a dry room with a dew point of approximately -60°C. The weight of the adsorbent packed into the sample tube was 220 mg.

[0101] (Adsorbent B2) As a pretreatment, first, a drying treatment was performed using the same procedure as the pretreatment for adsorbent B1, and then the weight w1 of the dry adsorbent was measured. Next, the dry adsorbent was packed into a sample tube in a dry room with a dew point of approximately -60°C. Next, nitrogen gas conditioned to 20°C and 50% RH was passed through the sample tube, and pre-humidification was performed until the outlet humidity stabilized to the same as the supply humidity, and then the weight w2 of the humidified adsorbent was measured. The moisture content c1 of the adsorbent after pre-humidification was calculated using the following formula: c1 = (w2 - w1) / w1 × 100. An adsorbent with a moisture content c1 of 13.5 wt% calculated using the above formula was considered to be adsorbent B2 with a moisture content C1 at the start of adsorption of 13.5 wt%.

[0102] (Adsorbent B3) Using the same procedure as for adsorbent B2, nitrogen gas conditioned to 20°C and 65% RH was passed through the sample tube, and an adsorbent with a moisture content c1 of 21.4 wt% was regarded as adsorbent B3 with a moisture content C1 at the start of adsorption of 21.4 wt%.

[0103] (Adsorbent B4) Using the same procedure as for adsorbent B2, nitrogen gas conditioned to 20°C and 80% RH was passed through the sample tube, and an adsorbent with a moisture content c1 of 31.8 wt% was regarded as adsorbent B4 with a moisture content C1 of 31.8 wt% at the start of adsorption.

[0104] (Adsorbent B5) Using the same procedure as for adsorbent B2, nitrogen gas conditioned to 20°C and 90% RH was passed through the sample tube, and an adsorbent with a moisture content c1 of 40.4 wt% was regarded as adsorbent B5 with a moisture content C1 of 40.4 wt% at the start of adsorption.

[0105] Next, the supply air condition of the device was adjusted to 20°C and 50% RH. The supply air was stopped, and adsorbent B1 was connected to the sample tube. Next, the start of adsorption was determined when the supply air was restarted, and the CO2 adsorption amount after 20 minutes of adsorption testing was evaluated. The CO2 adsorption amount after 20 minutes of adsorption testing was also evaluated for adsorbents B2 to B5 using the same procedure as for adsorbent B1. The CO2 concentration of the supplied air was approximately 400 vol ppm. The volumetric flow rate of the supplied air was 0.5 L / min, and the linear velocity relative to the φ7.52 mm cross section was 0.19 m / s.

[0106] Table 2 shows the CO2 adsorption amounts (mmol / g) of the adsorbent B1 and the adsorbents B2 to B5.

[0107]

[0108] As shown in Table 2, the adsorbent of Example 2 exhibited increased CO2 adsorption performance when the water content C1 of the adsorbent at the start of adsorption was 10% by weight or more (adsorbents B2 to B5).

[0109] From the above results, it is inferred that when the moisture content C1 of the adsorbent at the start of adsorption is 10% by weight or more, even if the step for removing moisture from the adsorbent after the desorption step is shortened, the adsorbent will not be deteriorated by moisture and the adsorption step will not be hindered.

[0110] The recovery system of this embodiment is suitable for recovering acid gases, particularly carbon dioxide.

Claims

1. A method for recovering acidic gases, comprising contacting an adsorbent with a raw gas containing an acidic gas to adsorb the acidic gas contained in the raw gas onto the adsorbent, wherein the weight of the adsorbent in a dry state is defined as W1 and the weight of the adsorbent at the start of adsorption is defined as W2, and the water content C1 of the adsorbent at the start of adsorption calculated by the following formula is 10% by weight or more: C1 = (W2 - W1) / W1 x 100 2. The method for recovering acidic gases according to claim 1, wherein the moisture content C1 of the adsorbent at the start of the adsorption is 20% by weight or more.

3. The method for recovering acidic gases according to claim 1, further comprising: bringing the adsorbent that has adsorbed the acidic gases into contact with water vapor to desorb the acidic gases from the adsorbent; and cooling the adsorbent from which the acidic gases have been desorbed, wherein, when the weight of the adsorbent at the start of the cooling is defined as W4, the water content C3 of the adsorbent at the start of the cooling calculated by the following formula is 30% by weight or more: C3 = (W4 - W1) / W1 x 100 4. A method for recovering acidic gases according to claim 3, wherein the cooling step involves cooling the adsorbent from which the acidic gases have been desorbed to a temperature of 20°C or higher and 80°C or lower.

5. The method for recovering acidic gases according to claim 3, wherein the adsorption, desorption, and cooling are repeated in this order.

6. The method for recovering acid gases according to claim 1, wherein the adsorbent comprises a polymer having an amino group.

7. The method for recovering acid gases according to claim 6, wherein the polymer comprises an amine polymer having constitutional units derived from epoxy monomers.

8. The method for recovering acidic gases according to claim 7, wherein the residual rate of the polymer when the adsorbent is immersed in water at 25°C for 15 hours is 90% or more.

9. The method for recovering acid gases according to claim 1, wherein the adsorbent has a porous structure.

10. The method for recovering acid gases according to claim 9, wherein the adsorbent has an average pore size of 0.1 μm or more and 50 μm or less.

11. The adsorbent is 0.5 m 2 / g or more 100m 2 10. The method for recovering acidic gases according to claim 9, wherein the carbon black has a specific surface area of ​​0.15 / g or less.

Images