Method for recovering acidic gas

Abstract

Provided is a method for recovering an acid gas capable of increasing the amount of the acid gas desorbed from an acid gas adsorbent. A method for recovering an acid gas according to an embodiment of the present invention comprises an adsorption step and a desorption step. In the adsorption step, a gas to be treated containing an acid gas is supplied to an acid gas adsorption device containing an acid gas adsorption material, and the acid gas is adsorbed to the acid gas adsorption material. In the desorption step, the acid gas adsorption device is heated to desorb the acid gas from the acid gas adsorption material. The separation process includes a first separation process, and at least includes a second separation process after the first separation process. In the first desorption step, the first desorption gas is supplied to the acid gas adsorption device, and the acid gas desorbed from the acid gas adsorption material is recovered together with the first desorption gas. In the second desorption step, a second desorbed gas having a lower humidity than the first desorbed gas is supplied to the acid gas adsorption device, and the acid gas desorbed from the acid gas adsorption material is recovered together with the second desorbed gas.

Description

Technical Field

[0001] The invention relates to a method for recovering acidic gas. Background Art

[0002] In recent years, efforts have been made to separate and recover acid gases contained in the atmosphere in order to reduce the environmental load. As such acid gases, carbon dioxide (hereinafter sometimes referred to as CO2) which causes global warming can be mainly cited. As a representative example of the above efforts, the carbon dioxide capture, utilization and storage (CCUS) cycle is known. As a carbon dioxide adsorption device used in such separation and recovery of carbon dioxide, a gas separation unit has been proposed, which includes an adsorption material layer filled with a granular carbon dioxide adsorption material (see, for example, Patent Document 1). In such a gas separation unit, the granular carbon dioxide adsorption material adsorbs CO2 from a gas fluid passing through the adsorption material layer at a predetermined adsorption temperature, and when heated to a desorption temperature exceeding the adsorption temperature, the adsorbed CO2 is desorbed. However, in the gas separation unit described in Patent Document 1, one of the CO2 desorption reactions of amines, which are representative CO2 adsorbents, is HCO3 － +NH2 + R 1 R 2 →NHR 1 R 2 +CO2+H2O, therefore, if there is a lot of water in the CO2 adsorbent and its surroundings, the CO2 desorption reaction becomes slow or the desorption temperature becomes high, so the desorption amount of CO2 sometimes decreases.

[0003] In addition, the amine as a CO2 adsorbent reacts with CO2 to produce carbamate (R 1 R 2 NCOO － ) In most cases, it is mixed with water with high polarity. Therefore, during the CO2 desorption reaction, if there is a lot of water in the CO2 adsorbent and its surroundings, the CO2 desorption reaction will be slow or the desorption temperature will be high, so the CO2 desorption amount will sometimes decrease.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2014 / 170184 Summary of the invention

[0007] A main object of the present invention is to provide a method for recovering acid gas that can increase the amount of acid gas desorbed from an acid gas adsorbent.

[0008] [1] The acid gas recovery method involved in the embodiment of the present invention includes an adsorption step and a desorption step in sequence. In the adsorption step, a gas to be treated containing acid gas is supplied to an acid gas adsorption device including an acid gas adsorption material, so that the acid gas is adsorbed on the acid gas adsorption material. In the desorption step, the acid gas adsorption device is heated to desorb the acid gas from the acid gas adsorption material. The desorption step includes a first desorption step and includes a second desorption step at least after the first desorption step. In the first desorption step, a first desorbed gas is supplied to the acid gas adsorption device, so that the acid gas desorbed from the acid gas adsorption material is recovered together with the first desorbed gas. In the second desorption step, a second desorbed gas having a humidity lower than that of the first desorbed gas is supplied to the acid gas adsorption device, so that the acid gas desorbed from the acid gas adsorption material is recovered together with the second desorbed gas.

[0009] [2] In the method for recovering acid gas described in [1] above, the acid gas may be carbon dioxide.

[0010] [3] In the acid gas recovery method described in [1] or [2] above, in the second desorption step, a mixed gas containing the acid gas and the second desorption gas can be discharged from the acid gas adsorption device, the humidity of the mixed gas can be measured, and the humidity of the second desorption gas supplied to the acid gas adsorption device can be adjusted in such a way that the humidity of the mixed gas is within a desired range.

[0011] Effects of the Invention

[0012] According to the embodiment of the present invention, it is possible to realize a method for recovering acid gas that can increase the amount of acid gas desorbed from an acid gas adsorbent. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic configuration diagram of an acid gas adsorption device according to an acid gas recovery method according to one embodiment of the present invention.

[0014] Figure 2 This is a schematic perspective view of an acid gas adsorption device involved in an acid gas recovery method according to another embodiment of the present invention.

[0015] Figure 3 yes Figure 2 A schematic cross-sectional view of an acid gas adsorption device.

[0016] Figure 4 Yes Figure 2 This is a schematic diagram of the acid gas recovery system of the acid gas adsorption device in FIG. DETAILED DESCRIPTION

[0017] A. Overview of acid gas recovery methods

[0018] A method for recovering acid gas according to one embodiment of the present invention includes an adsorption step and a desorption step in sequence. Typically, the method for recovering acid gas repeats the adsorption step and the desorption step in sequence. In the adsorption step, a gas to be treated containing acid gas is supplied to an acid gas adsorption device including an acid gas adsorption material, so that the acid gas is adsorbed on the acid gas adsorption material. In the desorption step, the acid gas adsorption device is heated so that the acid gas is desorbed from the acid gas adsorption material. The desorption step includes a first desorption step and includes a second desorption step at least after the first desorption step. In the first desorption step, a first desorption gas is supplied to the acid gas adsorption device, so that the acid gas desorbed from the acid gas adsorption material is recovered together with the first desorption gas. In the second desorption step, a second desorption gas having a humidity lower than that of the first desorption gas is supplied to the acid gas adsorption device, so that the acid gas desorbed from the acid gas adsorption material is recovered together with the second desorption gas.

[0019] In the desorption process, desorption gas may be supplied to the acid gas adsorbing device, and the acid gas desorbed from the acid gas adsorbing material may be recovered together with the desorption gas. In this case, as the desorption process proceeds, the surface of the acid gas adsorbing material may be excessively humidified, and the desorption rate of the acid gas from the acid gas adsorbing material may decrease, and even the desorption amount of the acid gas may decrease.

[0020] In contrast, in one embodiment of the present invention, after the first desorption step of supplying the first desorption gas to the acid gas adsorbing device is performed, the second desorption step of supplying the second desorption gas having a humidity lower than that of the first desorption gas to the acid gas adsorbing device is performed. Therefore, even if the surface of the acid gas adsorbing material is gradually humidified in the first desorption step, the humidity of the surface of the acid gas adsorbing material and the vicinity can be temporarily reduced in the second desorption step, so that the acid gas that could not be desorbed in the first desorption step can be smoothly desorbed. As a result, as the entire desorption step, the amount of acid gas desorbed from the acid gas adsorbing material can be increased, so that the acid gas can be efficiently recovered.

[0021] Furthermore, by supplying the second desorbed gas having a lower humidity than the first desorbed gas to the acid gas adsorbing device, the amount of moisture adhering to the acid gas adsorbing material and / or substrate (described later) included in the acid gas adsorbing device can be reduced. Thus, the desorbed energy of water can be reduced, thereby reducing the energy required for heating the acid gas adsorbing device (heating energy).

[0022] In the adsorption process, typically, a gas to be treated containing acidic gas is supplied to an acidic gas adsorption device at a predetermined adsorption temperature, and the acidic gas contacts the acidic gas adsorbent, whereby the acidic gas adsorbent adsorbs the acidic gas.

[0023] As the acidic gas contained in the gas to be treated, for example, there can be mentioned: carbon dioxide (CO2), hydrogen sulfide, sulfur dioxide, nitrogen dioxide, dimethyl sulfide (DMS), hydrogen chloride, etc. In one embodiment, the acidic gas is carbon dioxide (CO2), and the gas to be treated is a CO2-containing gas. The CO2-containing gas may contain nitrogen in addition to CO2. The CO2-containing gas is representatively air (atmosphere). The CO2 concentration in the CO2-containing gas is, for example, greater than 100 ppm (volume basis) and less than 2 volume %.

[0024] The temperature of the gas to be treated supplied to the acid gas adsorption device is, for example, 0° C. or higher and 50° C. or lower, and is preferably the same as the outside air temperature.

[0025] The volume absolute humidity of the gas to be treated is, for example, 0.5 g / m 3 Above, preferably 4.5g / m 3 Above, for example 75g / m 3 Below, preferably 30g / m 3 the following.

[0026] The temperature of the acid gas adsorption device in the adsorption process (adsorption temperature) is, for example, 0° C. or more, preferably 10° C. or more, for example, 50° C. or less, preferably 40° C. or less. In one embodiment, the adsorption temperature is the same as the external air temperature. The implementation time of the adsorption process (adsorption time) is, for example, 15 minutes or more, preferably 30 minutes or more, for example, 3 hours or less, preferably 2 hours or less.

[0027] When the adsorption temperature and / or the adsorption time are within the above ranges, the acid gas adsorbent can efficiently adsorb the acid gas.

[0028] The acid gas recovery rate in the adsorption process (=100-(acid gas concentration in the gas to be treated that has passed through the acid gas adsorption device / acid gas concentration in the gas to be treated before being supplied to the acid gas adsorption device×100)) is, for example, 60% or more, preferably 75% or more, more preferably 80% or more, for example 90% or less.

[0029] In the desorption step, the acid gas adsorbent is typically heated to a desorption temperature exceeding the adsorption temperature. Thus, the acid gas adsorbed by the acid gas adsorbent in the adsorption step is desorbed from the acid gas adsorbent. The temperature of the acid gas adsorbent in the desorption step (desorption temperature) is, for example, 70° C. or higher, preferably 80° C. or higher, for example, 200° C. or lower, preferably 110° C. or lower.

[0030] Typically, the detaching step includes a first detaching step and a second detaching step in sequence. If the first detaching step and the second detaching step are in this order, another step may be performed between the first detaching step and the second detaching step.

[0031] In the first desorption process, the first desorption gas is supplied to the acid gas adsorption device heated to the desorption temperature. More specifically, in the first desorption process, the acid gas adsorption device is heated to the desorption temperature and maintained at the desorption temperature for a predetermined first desorption time, and the first desorption gas is supplied to the acid gas adsorption device. Thus, the desorbed acid gas can be recovered together with the first desorption gas. The gas recovered in the first desorption process is sometimes referred to as the first recovered gas. The first recovered gas is a mixed gas containing the acid gas and the first desorption gas.

[0032] As the first desorbing gas, for example, there can be cited: atmosphere, carbon dioxide, water vapor, nitrogen, argon, and the first recycled gas recovered in the first desorbing step. These first desorbing gases can be used alone, or mixed or used in combination one after another. Among the first desorbing gases, it is preferred to cite the first recycled gas that has been previously recovered by the acid gas adsorption device. By using the first recycled gas as the first desorbing gas, the acid gas concentration in the first recycled gas can be increased.

[0033] The volume absolute humidity of the first desorbed gas is, for example, 50 g / m 3 Above, preferably 400g / m 3 Above, for example 3500g / m 3 Below, preferably 900g / m 3 If the humidity of the first desorbed gas is within the above range, the acidic gas can be smoothly desorbed from the acidic gas adsorbent.

[0034] The temperature of the first desorption gas is, for example, 60° C. or higher, preferably 90° C. or higher, and for example, 200° C. or lower, preferably 160° C. or lower.

[0035] The flow rate of the first desorption gas is, for example, 0.001 m / s to 10 m / s, and preferably 0.1 m / s to 2 m / s. For example, the flow rate of the gas can be measured by the method described in JIS B 7556 using an ultrasonic flow meter or the like.

[0036] The implementation time of the first desorption step (the first desorption time during which the acid gas adsorbent is maintained at the desorption temperature) is, for example, 3 minutes or more, preferably 10 minutes or more, for example, 1 hour or less, preferably 30 minutes or less. If the temperature of the first desorption gas and / or the first desorption time are within the above ranges, the acid gas can be more smoothly desorbed from the acid gas adsorbent.

[0037] In addition, in the first desorption step, for example, the first desorption gas and a pressure reduction pump may be used in combination to suck the first recovery gas.

[0038] In the second desorption process performed subsequent to the first desorption process, typically, the first desorption gas supplied to the acid gas adsorption device is switched to a second desorption gas having a lower humidity than the first desorption gas, and is supplied to the acid gas adsorption device maintained at the desorption temperature for a predetermined second desorption time. Thus, the desorbed acid gas is recovered together with the second desorption gas. The gas recovered in the second desorption process is sometimes referred to as the second recovered gas. The second recovered gas is a mixed gas containing the acid gas and the second desorption gas. The oxygen concentration in the second recovered gas is preferably 15% by volume or less.

[0039] Preferred examples of the second desorbing gas include air, carbon dioxide, nitrogen, and argon. As the second desorbing gas, a second recovered gas previously recovered by an acid gas adsorption device may be used.

[0040] The humidity of the second desorbed gas is lower than that of the first desorbed gas. The lower the humidity of the second desorbed gas, the better. When the humidity of the first desorbed gas is 100%, the humidity of the second desorbed gas is, for example, 80% or less, preferably 50% or less. In addition, the volume absolute humidity of the second desorbed gas is, for example, 2800 g / m 3 Below, preferably 450g / m 3 Below, more preferably 380g / m 3 the following.

[0041] If the humidity of the second desorbed gas is below the above upper limit, the humidity of the surface of the acidic gas adsorbent after the first desorbing step can be adjusted to a preferred range, so that the acidic gas that was not desorbed from the acidic gas adsorbent in the first desorbing step can be stably desorbed. It should be noted that, when the humidity of the first desorbed gas is set to 100%, the lower limit of the humidity of the second desorbed gas is typically 10% or more, specifically 5 g / m 3 above.

[0042] The temperature of the second desorption gas is, for example, 60° C. or higher, preferably 90° C. or higher, and for example, 200° C. or lower, preferably 110° C. or lower.

[0043] The flow rate of the second desorption gas is, for example, 0.001 m / s to 10 m / s, and preferably 0.1 m / s to 2 m / s.

[0044] In one embodiment, the implementation time of the second desorption process (second desorption time) is shorter than the implementation time of the first desorption process (first desorption time). The second desorption time is, for example, 45% or less, preferably 40% or less, more preferably 30% or less, further preferably 20% or less, for example 5% or more, preferably 10% or more, relative to the total implementation time of the desorption process (the sum of the first desorption time and the second desorption time). The second desorption time is, for example, 50 minutes or less, preferably 20 minutes or less, for example 2 minutes or more, preferably 5 minutes or more. If the temperature of the second desorption gas and / or the second desorption time are within the above ranges, the acidic gas that was not desorbed in the first desorption process can be desorbed more stably.

[0045] In addition, in the second desorption step, for example, the second desorption gas and a pressure reduction pump may be used in combination to suck the second recovery gas.

[0046] Hereinafter, embodiments of the present invention will be described with reference to the drawings; however, the present invention is not limited to these embodiments.

[0047] B. Acid gas adsorption device (carbon dioxide adsorption device)

[0048] Figure 1 is a schematic diagram of the structure of an acid gas adsorption device involved in an acid gas recovery method according to one embodiment of the present invention. Figure 2 is a schematic perspective view of an acid gas adsorption device involved in an acid gas recovery method according to another embodiment of the present invention. Figure 3 yes Figure 2 A schematic cross-sectional view of an acid gas adsorption device.

[0049] B-1. First Embodiment of Acid Gas Adsorption Device

[0050] In one embodiment, if Figure 1 As shown, the acid gas adsorbing device 7 includes a plurality of adsorbent layers 71. The plurality of adsorbent layers 71 constitute the acid gas adsorbing section 19. When the gas to be treated by the acid gas adsorbing device is a CO2-containing gas, the acid gas adsorbing device 7 is a carbon dioxide adsorbing device 7a.

[0051] The plurality of adsorbent layers 71 are stacked with a gap in the thickness direction thereof. In the example shown in the figure, five adsorbent layers 71 are arranged in parallel, but the number of adsorbent layers 71 is not limited thereto. The number of adsorbent layers 71 is, for example, 5 or more, preferably 10 or more, and more preferably 20 or more. The gap between adjacent adsorbent layers 71 in the plurality of adsorbent layers 71 is, for example, 0.5 cm or more and 1.5 cm or less.

[0052] Each of the plurality of adsorbent layers 71 includes a flexible fiber member 73 and a plurality of granular adsorbents 72 .

[0053] The flexible fiber component 73 allows the passage of gas and restricts the passage of the granular adsorbent material. Typically, the flexible fiber component 73 is formed into a hollow shape (bag shape) capable of accommodating a plurality of granular adsorbent materials 72. The flexible fiber component 73 may be a fabric or a non-woven fabric. Examples of the material of the flexible fiber component 73 include organic fibers and natural fibers, preferably polyethylene terephthalate fibers, polyethylene fibers, and cellulose fibers. The thickness of the flexible fiber component 73 is, for example, not less than 25 μm and not more than 500 μm.

[0054] A plurality of granular adsorbent materials 72 are filled in the interior of a flexible fiber member 73 having a hollow shape (bag shape). The granular adsorbent material 72 functions as an acid gas adsorbent, and typically functions as a carbon dioxide adsorbent. As the material of the granular adsorbent 72, for example, an amine-modified material can be cited, preferably amine-modified cellulose can be cited, and more preferably amine-modified nanofibrillated cellulose can be cited. The average primary particle size of the granular adsorbent material 72 is, for example, not less than 60 μm and not more than 1200 μm. The filling ratio of the granular adsorbent material 72 in the adsorbent layer 71 can adopt any appropriate value.

[0055] The acid gas adsorption device 7 shown in the figure further includes a plurality of spacers 74. The spacers 74 are sandwiched between the adjacent adsorption material layers 71 among the plurality of adsorption material layers 71. The plurality of spacers 74 constitute the acid gas adsorption unit 19. Thus, the intervals between the adjacent adsorption material layers can be stably ensured. In one embodiment, the plurality of adsorption material layers 71 and the plurality of spacers 74 are arranged such that: from a direction orthogonal to the thickness direction of the adsorption material layer 71 ( Figure 1 When viewed in the depth direction of the paper, it becomes a roughly Z shape.

[0056] As such an acid gas adsorption device 7, for example, there can be mentioned a gas separation unit described in International Publication No. 2014 / 170184, the entire contents of which are incorporated herein by reference.

[0057] B-2. Second Embodiment of Acid Gas Adsorption Device

[0058] In another embodiment, if Figure 2 and Figure 3 As shown, the acid gas adsorption device 1 includes a substrate 10 and an acid gas adsorption layer 15. The substrate 10 and the acid gas adsorption layer 15 constitute an acid gas adsorption unit 19. When the gas to be treated by the acid gas adsorption device is a CO2-containing gas, the acid gas adsorption device 1 is a carbon dioxide adsorption device 1a.

[0059] The structure of the substrate 10 is not particularly limited, and examples thereof include a honeycomb structure, a filter structure such as filter cloth, and a particle structure. The acid gas adsorption layer 15 may be disposed on the surface of the substrate 10 and is not particularly limited.

[0060] B-2-1. Base material (honeycomb base material)

[0061] In one embodiment, the substrate 10 is a honeycomb substrate 10 a . The honeycomb substrate 10 a includes partition walls 13 defining a plurality of cells 14 .

[0062] The cells 14 extend from the first end face E1 (inflow end face) to the second end face E2 (outflow end face) of the honeycomb substrate 10a in the longitudinal direction (axial direction) of the honeycomb substrate 10a (see Figure 3 ). The cell 14 has any appropriate shape in the cross section of the honeycomb substrate 10a in a direction perpendicular to the length direction. Examples of the cross-sectional shape of the cell include: a triangle, a quadrilateral, a pentagon, a polygon larger than a hexagon, a circle, and an ellipse. The cross-sectional shape and size of the cell may be all the same or at least partially different. Among the cross-sectional shapes of such cells, preferably a hexagon or a quadrilateral can be mentioned, and more preferably a square, a rectangle or a hexagon can be mentioned.

[0063] The cell density in the cross section of the honeycomb substrate in a direction perpendicular to the longitudinal direction (i.e., the number of cells 14 per unit area) can be appropriately set according to the purpose. For example, the cell density can be 4 cells / cm 2 ~320 compartments / cm 2 When the cell density is within such a range, the strength and effective GSA (geometric surface area) of the honeycomb substrate can be sufficiently ensured.

[0064] The honeycomb substrate 10a has any appropriate shape (overall shape). Examples of the shape of the honeycomb substrate include: a cylindrical shape with a circular bottom surface, an elliptical cylindrical shape with an elliptical bottom surface, a prism shape with a polygonal bottom surface, and a column shape with an irregular bottom surface. The honeycomb substrate 10a shown in the figure has a cylindrical shape. The outer diameter and length of the honeycomb substrate can be appropriately set according to the purpose. Although not shown in the figure, the honeycomb substrate may have a hollow area in the center of the cross section in a direction perpendicular to the longitudinal direction.

[0065] Typically, the honeycomb substrate 10a includes an outer peripheral wall 11 and partition walls 13 located inside the outer peripheral wall 11. In the example shown in the figure, the outer peripheral wall 11 and the partition walls 13 are formed integrally. The outer peripheral wall 11 and the partition walls 13 may be separate bodies.

[0066] The outer peripheral wall 11 has a cylindrical shape. The thickness of the outer peripheral wall 11 can be set arbitrarily and appropriately. The thickness of the outer peripheral wall 11 is, for example, 0.1 mm to 10 mm.

[0067] The partition wall 13 defines a plurality of compartments 14. More specifically, the partition wall 13 includes 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 compartments 14. The cross-sectional shape of the compartment 14 is a quadrilateral except for the portion where the first partition wall 13a and the second partition wall 13b contact the outer peripheral wall 11. It should be noted that the configuration of the partition wall is not limited to the above-mentioned partition wall 13. The partition wall may include: a first partition wall extending in a radial direction, and a second partition wall extending in a circumferential direction, which define a plurality of compartments.

[0068] The thickness of the partition wall 13 can be appropriately set according to the purpose of the honeycomb substrate. Typically, the thickness of the partition wall 13 is thinner than the thickness of the peripheral wall 11. The thickness of the partition wall 13 is, for example, 0.03 mm to 0.6 mm. The thickness of the partition wall is measured by, for example, cross-sectional observation based on SEM (scanning electron microscope). If the thickness of the partition wall is within such a range, the mechanical strength of the honeycomb substrate can be sufficient, and the opening area (the total area of ​​the cells in the cross section) can be sufficient.

[0069] The porosity of the partition walls 13 can be appropriately set according to the purpose. The porosity of the partition walls 13 is, for example, 15% or more, preferably 20% or more, and for example, 70% or less, preferably 45% or less. The porosity can be measured by, for example, mercury penetration.

[0070] The bulk density of the partition walls 13 can be appropriately set according to the purpose. For example, the bulk density is 0.10 g / cm 3 Above, preferably 0.20 g / cm 3 Above, for example, 0.60 g / cm 3Below, preferably 0.50g / cm 3 Hereinafter, the bulk density can be measured by, for example, mercury intrusion porosimetry.

[0071] As the material constituting the partition wall 13, representatively, ceramics can be cited. As ceramics, for example, silicon carbide, silicon-silicon carbide composite materials, cordierite, mullite, alumina, silicon nitride, spinel, silicon carbide-cordierite composite materials, lithium aluminum silicate and aluminum titanate can be cited. The material constituting the partition wall can be used alone or in combination. Among the materials constituting the partition wall, cordierite, alumina, mullite, silicon carbide, silicon-silicon carbide composite materials and silicon nitride can be preferably cited, and silicon carbide and silicon-silicon carbide composite materials can be more preferably cited.

[0072] Typically, such a honeycomb substrate 10a is produced by the following method. First, a binder and water or an organic solvent are added to the material powder containing the above-mentioned ceramic powder as needed, and the obtained mixture is kneaded to form a blank, and the blank is molded (typically extrusion molded) into a desired shape, and then dried and fired as needed to produce the honeycomb substrate 10a. In the case of firing, for example, the firing is performed at 1200°C to 1500°C. The firing time is, for example, 1 hour or more and 20 hours or less.

[0073] B-2-2. Acidic gas adsorption layer (carbon dioxide adsorption layer)

[0074] In one embodiment, the acid gas adsorption layer 15 is formed on the surface of the partition wall 13. In the honeycomb substrate 10a, a gas flow path 16 is formed in a portion (representatively, a central portion) of the cross section of the cell 14 where the acid gas adsorption layer 15 is not formed. The acid gas adsorption layer 15 may be formed on the entire inner surface of the partition wall 13 (i.e., in a manner that surrounds the gas flow path 16) as shown in the example of the figure, or may be formed on a portion of the surface of the partition wall. If the acid gas adsorption layer 15 is formed on the entire inner surface of the partition wall 13, the removal efficiency of the acid gas (representatively, CO2) can be improved.

[0075] The gas flow path 16 extends from the first end face E1 (inflow end face) to the second end face E2 (outflow end face) in the same manner as the compartment 14. The cross-sectional shape of the gas flow path 16 may be the same as that of the compartment 14, preferably a hexagon or a quadrilateral, more preferably a square, a rectangle or a hexagon. The cross-sectional shape and size of the gas flow path 16 may be the same in all or may be at least partially different.

[0076] Typically, in the adsorption process, the above-mentioned gas to be treated flows through the compartment 14 (more specifically, the gas flow path 16). In addition, in one embodiment, in the first desorption process, the above-mentioned first desorption gas flows through the compartment 14 (more specifically, the gas flow path 16), and in the second desorption process, the above-mentioned second desorption gas flows through the compartment 14.

[0077] The acid gas adsorption layer 15 contains an acid gas adsorption material corresponding to the acid gas to be adsorbed. In one embodiment, the acid gas adsorption layer 15 is a carbon dioxide adsorption layer 15a. The carbon dioxide adsorption layer 15a contains a carbon dioxide adsorption material as an example of an acid gas adsorption material.

[0078] As a carbon dioxide adsorbent, any appropriate compound that can adsorb and desorb CO2 can be used. Examples of carbon dioxide adsorbents include: nitrogen-containing compounds described below; alkaline compounds such as sodium hydroxide and potassium hydroxide; carbonates such as calcium carbonate and potassium carbonate; bicarbonates such as calcium hydrogen carbonate and potassium hydrogen carbonate; organometallic structures (MOFs) such as MOF-74, MOF-200, and MOF-210; zeolites; activated carbon; nitrogen-doped carbon; ionic liquids, etc. Carbon dioxide adsorbents can be used alone or in combination.

[0079] Among the carbon dioxide adsorbents, nitrogen-containing compounds and ionic liquids are preferred. More specifically, the nitrogen-containing compounds include: primary amines such as monoethanolamine and polyethyleneamine; 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 monomers having primary to tertiary amino groups such as ethyleneimine and styrene endowed with amino groups; organic polymers having primary to tertiary amino groups such as linear polyethyleneimine and branched polyethyleneimine having primary to tertiary amino groups; piperazine compounds such as 1-(2-hydroxyethyl)piperazine; amide compounds such as polyamideamine; polyethyleneamine; and organic / inorganic compounds endowed with amino groups as substituents.

[0080] Among the nitrogen-containing compounds, preferred examples include methyldiethylamine, monoethanolamine, cyclic amines, diethanolamine, tetraethylenepentamine, ethyleneimine, linear polyethyleneimine, branched polyethyleneimine, and organic / inorganic compounds having an amino group as a substituent.

[0081] Ionic liquids are liquid "salts" composed only of ions (anions and cations), and are in a liquid state at normal temperature and pressure (23°C, 0.1 MPaA (absolute pressure)). Examples of cations of ionic liquids include: ammonium ions such as imidazolium salts and pyridinium salts, phosphonium ions, sulfonium salts, inorganic ions, and the like. Examples of anions of ionic liquids include: halogen ions such as bromide ions and trifluoromethanesulfonates; boron ions such as tetraphenylborate; phosphorus ions such as hexafluorophosphate; sulfur ions such as alkylsulfonates. Among ionic liquids, a combination of imidazolium salts as cations and trifluoromethanesulfonates as anions is preferred.

[0082] The ionic liquid is more preferably used in combination with a carbon dioxide adsorbent material other than the ionic liquid (hereinafter referred to as other carbon dioxide adsorbent material). In this case, the ionic liquid is coated with the other carbon dioxide adsorbent material (eg, a nitrogen-containing compound). Therefore, the performance of the carbon dioxide adsorbent material can be improved and the life can be extended.

[0083] The content ratio of the ionic liquid is, for example, 0.000001 parts by mass or more, preferably 0.00001 parts by mass or more, for example, 0.1 parts by mass or less, preferably 0.05 parts by mass or less, relative to 1 part by mass of other carbon dioxide adsorbents. If the content ratio of the ionic liquid is within the above range, the performance improvement and long life of the carbon dioxide adsorbent can be stably achieved.

[0084] In one embodiment, the carbon dioxide adsorption layer 15a further includes a porous carrier in addition to the above-mentioned carbon dioxide adsorption material. In this case, the carbon dioxide adsorption material is typically supported on the porous carrier and faces the gas flow path. If the carbon dioxide adsorption layer includes a porous carrier, it is possible to suppress the carbon dioxide adsorption material from falling off from the carbon dioxide adsorption layer during the adsorption process and / or the desorption process.

[0085] The porous carrier can form mesopores in the carbon dioxide adsorption layer. As the porous carrier, for example, there can be mentioned: organometallic structures (MOFs) such as MOF-74, MOF-200, and MOF-210; activated carbon; nitrogen-doped carbon; mesoporous silica; mesoporous alumina; zeolite; carbon nanotubes; fluorinated resins such as polyvinylidene fluoride (PVDF), preferably, there can be mentioned: organometallic structures (MOFs), PVDF, activated carbon, zeolite, mesoporous silica, and mesoporous alumina. The porous carrier can be used alone or in combination. The porous carrier preferably uses a material different from the carbon dioxide adsorbent material.

[0086] The BET specific surface area of ​​the porous carrier is, for example, 50 m 2 / g or more, preferably 500m 2If the surface area of ​​the porous carrier is greater than or equal to the above lower limit, the carbon dioxide adsorbent can be stably supported, thereby improving the CO2 recovery rate. The upper limit of the BET specific surface area of ​​the porous carrier is typically 2000 m 2 / g or less.

[0087] When the carbon dioxide adsorption layer contains a carbon dioxide adsorbent and a porous carrier, the total content ratio of the carbon dioxide adsorbent and the porous carrier in the carbon dioxide adsorption layer is, for example, 30 mass % or more, preferably 50 mass % or more, for example, 100 mass % or less, preferably 99 mass % or less.

[0088] The content ratio of the carbon dioxide adsorbent in the carbon dioxide adsorption layer is, for example, 30% by mass or more, preferably 50% by mass or more, for example, 99% by mass or less. The content ratio of the porous carrier is, for example, 0.01% by mass or more, preferably 0.3% by mass or more, for example, 0.7% by mass or less, preferably 0.5% by mass or less, relative to 1% by mass of the carbon dioxide adsorbent. If the content ratio of the porous carrier is within the above range, the carbon dioxide adsorbent can be more stably supported.

[0089] In addition, the carbon dioxide adsorption layer may be composed only of carbon dioxide adsorption material. In this case, the carbon dioxide adsorption material is directly supported on the partition wall 13 and faces the gas flow path. In the case where the carbon dioxide adsorption layer is composed only of carbon dioxide adsorption material, the content of carbon dioxide adsorption material in the carbon dioxide adsorption layer is typically 95.0 mass % or more and 100 mass % or less. If the content of carbon dioxide adsorption material is within the above range, it is possible to stably ensure an excellent CO2 recovery rate.

[0090] Typically, such a carbon dioxide adsorption layer is produced by the following method. The above-mentioned carbon dioxide adsorption material is dissolved in a solvent to prepare a solution of the carbon dioxide adsorption material. In addition, the above-mentioned porous carrier is added to the solvent as needed. There is no particular restriction on the order of adding the carbon dioxide adsorption material and the porous carrier. Afterwards, the solution of the carbon dioxide adsorption material is applied to a substrate (specifically, a partition), and then the coating is dried and sintered as needed to form a carbon dioxide adsorption layer.

[0091] Alternatively, a dispersion containing a carbon dioxide adsorbent other than an ionic liquid and a porous carrier is applied to a substrate, the coating is dried, and if necessary, sintered, and then only the ionic liquid is applied to the substrate to form a carbon dioxide adsorbing layer.

[0092] Although not shown, the acid gas adsorption device 1 may include a heater in addition to the substrate 10 and the acid gas adsorption layer 15. The heater can heat the substrate 10. Typically, the heater is in contact with the substrate 10. If the acid gas adsorption device includes a heater, the temperature of the acid gas adsorption device can be smoothly raised to the desorption temperature in the desorption step.

[0093] Although not shown, the acid gas adsorption device 1 and the acid gas adsorption device 7 may each further include a housing. The housing has a cylindrical shape (hollow shape) through which gas can pass, and accommodates the acid gas adsorption unit 19. Examples of the cylindrical shape include a cylindrical shape and a square cylindrical shape. Typically, the acid gas adsorption unit 19 is supported by the housing in a manner that it cannot move relatively.

[0094] In the second desorption step, the second desorption gas is typically supplied to the entire acid gas adsorption unit 19 supported by the housing in a relatively immovable manner. When the acid gas adsorption unit is supported by the housing in a relatively movable manner, the supply of the second desorption gas becomes uneven due to the boundary portion for dividing the first desorption step and the second desorption step, and the acid gas adsorption unit 19 near the boundary portion cannot be made into a low humidity environment, so the amount of acid gas desorbed from the acid gas adsorption unit 19 may decrease. On the other hand, when the acid gas adsorption unit is supported by the housing in a relatively immovable manner, since there is no boundary portion, the entirety can be made into a uniform low humidity environment, so the amount of acid gas desorbed from the acid gas adsorption material 19 can be increased.

[0095] C. Acid Gas Recovery System

[0096] Next, refer to Figure 4 , an acid gas recovery system capable of implementing the above-mentioned acid gas recovery method is described.

[0097] The acid gas recovery system 100 shown in the figure is provided with an acid gas adsorption device, and further includes: an acid gas supply blower 2, a first desorption gas supply unit 5, a second desorption gas supply unit 3, a recovery unit 4, a hygrometer 8, and a control unit 9. It should be noted that the acid gas recovery system 100 shown in the figure is provided with one each of the acid gas adsorption device 1, the acid gas supply blower 2, the first desorption gas supply unit 5, the second desorption gas supply unit 3, the recovery unit 4, the hygrometer 8, and the control unit 9, but the number of these may be one or more, and there is no particular limitation.

[0098] In one embodiment, the acid gas recovery system 100 is a carbon dioxide recovery system 100a including a carbon dioxide adsorbent 1a as an example of the acid gas adsorbent 1. The acid gas recovery system 100 includes an acid gas adsorbent 7 (carbon dioxide adsorbent 7a) instead of the acid gas adsorbent 1 (carbon dioxide adsorbent 1a).

[0099] C-1. Blower for acid gas supply

[0100] The acid gas supply blower 2 is configured to supply the above-mentioned gas to be treated (representatively, CO2-containing gas) to the acid gas adsorption device 1 (representatively, the acid gas adsorption unit 19) during the adsorption process. The acid gas supply blower 2 shown in the figure can convey the gas to be treated containing the acid gas toward the acid gas adsorption device 1. The acid gas supply blower 2 can adopt any appropriate structure. The connection between the acid gas supply blower 2 and the acid gas adsorption device 1 can be a pipe or a portion on the upstream side of the acid gas adsorption device in the container that accommodates the acid gas adsorption device 1.

[0101] C-2. First desorption gas supply unit

[0102] The first desorption gas supply unit 5 is configured to supply the first desorption gas to the acid gas adsorption device 1 (representatively, the acid gas adsorption unit 19) in the first desorption step. The first desorption gas supply unit 5 shown in the figure includes a first desorption gas supply line 51 and a first opening and closing valve 52. The first desorption gas supply line 51 is typically a pipe capable of supplying the first desorption gas to the acid gas adsorption device 1. The downstream end of the first desorption gas supply line 51 in the supply direction of the desorption gas is connected to a portion between the acid gas supply blower 2 and the acid gas adsorption device 1. When the first desorption gas is the first recovered gas, although not shown in the figure, the upstream end of the first desorption gas supply line 51 in the supply direction of the desorption gas is connected to an intermediate tank for storing the first recovered gas. The first opening and closing valve 52 is provided on the first desorption gas supply line 51 and can open and close the first desorption gas supply line 51. As the first opening and closing valve 52, for example, a ball valve, a gate valve, and a butterfly valve can be cited, and preferably a butterfly valve can be cited.

[0103] C-3. Second desorption gas supply unit

[0104] The second desorption gas supply unit 3 is configured to supply the second desorption gas to the acid gas adsorption device 1 (representatively, the acid gas adsorption unit 19) in the second desorption process. The second desorption gas supply unit 3 shown in the figure includes a dehumidifier 30, a second desorption gas supply line 31, and a second opening and closing valve 32. The dehumidifier 30 can adjust the humidity of the second desorption gas. The second desorption gas supply line 31 is typically a pipe that can supply the second desorption gas from the dehumidifier 30 to the acid gas adsorption device 1. The second opening and closing valve 32 is provided on the second desorption gas supply line 31, and can open and close the second desorption gas supply line 31. As the second opening and closing valve 32, for example, a valve similar to the first opening and closing valve 52 can be cited.

[0105] C-4. Recovery Unit

[0106] The recovery unit 4 is configured to recover the acid gas separated in the separation process. More specifically, the recovery unit 4 can recover the first recovered gas containing the acid gas in the first separation process, and can recover the second recovered gas containing the acid gas in the second separation process. The recovery unit 4 shown in the figure includes a suction pump 40 and a gas discharge part 41. The suction pump 40 can suck the gas in the acid gas adsorption device. As the suction pump 40, for example, a vacuum pump can be cited. In the gas discharge part 41, the gas discharged from the acid gas adsorption device 1 and heading toward the suction pump 40 passes. The gas discharge part 41 can be a pipe, or it can be a part of the container that accommodates the acid gas adsorption device 1 that is on the downstream side of the acid gas adsorption device.

[0107] C-5. Hygrometer and control unit

[0108] The hygrometer 8 can measure the humidity of the mixed gas (first recovered gas or second recovered gas) discharged from the acid gas adsorbing device 1, typically the humidity of the second recovered gas discharged from the acid gas adsorbing device in the second desorption step. The hygrometer 8 can adopt any appropriate configuration.

[0109] As a modified example, although not shown in the figure, the hygrometer 8 can further measure the humidity of the gas supplied to the acid gas adsorbing device 1. By measuring the humidity of the gas (representatively, the second desorbed gas) introduced into the acid gas adsorbing device 1, the humidity in the acid gas adsorbing device 1 can be controlled more accurately.

[0110] The control unit 9 can control the operation of the acid gas recovery system 100. Any appropriate configuration can be adopted for the control unit 9. The control unit 9 includes, for example, a central processing unit (CPU), a ROM, a RAM, and the like.

[0111] D. Operation of the Acid Gas Recovery System

[0112] Next, an embodiment of an acid gas recovery method implemented by the acid gas recovery system 100 is described. In one embodiment, the acid gas recovery method includes the above-mentioned adsorption step, the replacement step, and the above-mentioned desorption step (first desorption step and second desorption step) in sequence.

[0113] In the acid gas recovery system 100, first, an adsorption process is performed. In the adsorption process, the control unit 9 sets the first on-off valve 52 and the second on-off valve 32 to the closed state and drives the acid gas supply blower 2. As a result, the above-mentioned gas to be treated is sent out through the acid gas supply blower 2, supplied to the acid gas adsorption unit 19 of the acid gas adsorption device 1, and flows through the gas flow path 16. It should be noted that the temperature of the acid gas adsorption device in the adsorption process (representatively, the temperature of the acid gas adsorption unit 19) is adjusted in advance to the above-mentioned adsorption temperature.

[0114] In the adsorption process, the temperature range of the gas to be treated supplied to the acid gas adsorption device is the same as the above-mentioned adsorption temperature range. The temperature of the gas to be treated may be the same as or different from the adsorption temperature of the acid gas adsorption device. The pressure of the gas to be treated is, for example, 0.3×10 5 PaA (absolute pressure) or above and 2.0×10 5 The flow rate of the gas to be treated is, for example, 0.5 m / sec to 5 m / sec.

[0115] Thereafter, when the above-mentioned adsorption time has elapsed, the control unit 9 stops driving the acid gas supply blower 2, and the adsorption process is completed.

[0116] Next, the replacement process is performed in the acid gas recovery system 100. In the replacement process, the control unit 9 changes the first on-off valve 52 from the closed state to the open state, and drives the suction pump 40. Then, the first desorbed gas is supplied to the acid gas adsorption unit 19 of the acid gas adsorption device 1 through the desorbed gas supply line 51, and flows through the gas flow path 16. As a result, the gas flow path 16 is replaced from the gas to be treated to the first desorbed gas.

[0117] In the replacement step, the temperature range of the first desorbed gas supplied to the acid gas adsorbing device is the same as the above-mentioned adsorption temperature range. The pressure of the first desorbed gas is, for example, 0.1×10 4 PaA or above and 1.0×10 4 PaA or less, for example, 0.1×10 4 PaA or above and 5.0×10 4The implementation time of the replacement step (hereinafter referred to as replacement time) is, for example, 1 minute or more and 30 minutes or less.

[0118] It should be noted that in the replacement step, a purge gas different from the first degassing gas may be introduced into the acid gas adsorption device, thereby replacing the gas to be treated in the acid gas adsorption device with the purge gas. In this case, the pressure of the purge gas is, for example, 0.1×10 4 PaA or above and 11×10 4 The replacement time is, for example, 1 minute or more and 30 minutes or less. Examples of the purge gas include water vapor, carbon dioxide, nitrogen, and argon.

[0119] After that, the first desorption process is performed immediately after the substitution process in the acid gas recovery system 100. The control unit 9 controls the heating body (not shown) to heat the acid gas adsorption device 1 (representatively, the acid gas adsorption unit 19) while maintaining the driving state of the suction pump 40. It should be noted that the heating of the acid gas adsorption device may be started in the middle of the substitution process.

[0120] When the temperature of the acid gas adsorption device (representatively, the temperature of the acid gas adsorption unit 19) reaches the desorption temperature, the acid gas retained by the acid gas adsorption material is desorbed (released) from the acid gas adsorption material. The desorbed acid gas is discharged from the acid gas adsorption device 1 together with the first desorbed gas, and after passing through the gas discharge unit 41 and the suction pump 40, it is stored in an intermediate tank as needed. Such a first recovered gas can be used for various purposes as described above, and can be supplied to the acid gas adsorption device again as the first desorbed gas as described above, and can also be used as a raw material for various industrial products (for example, a raw material for hydrocarbon fuel).

[0121] Next, when the first desorption time has elapsed, the second desorption process is performed in the acid gas recovery system 100. The controller 9 changes the first on-off valve 52 from open to closed while maintaining the driving of the suction pump 40, and changes the second on-off valve 32 from closed to open.

[0122] Then, the second desorbed gas is supplied to the acid gas adsorption device 1 (representatively, the acid gas adsorption section 19) through the second desorbed gas supply line 31, and circulates in the gas flow path 16. At this time, in the first desorbed process, the surface of the humidified acid gas adsorbent is appropriately dried, and the humidity of the surface of the acid gas adsorbent is appropriately adjusted. Thus, the acid gas that was not desorbed in the first desorbed process is desorbed from the acid gas adsorbent. The desorbed acid gas is discharged from the acid gas adsorbent together with the second desorbed gas, and after passing through the gas discharge section 41 and the suction pump 40, it is stored in a tank as needed. The second recovered gas can be stored in the same intermediate tank as the first recovered gas, or in another tank. Such a second recovered gas can be used for various purposes like the first recovered gas. In addition, the second recovered gas can also be returned to the dehumidification device 30.

[0123] In addition, the control unit 9 can measure (representatively monitor) the humidity of the second recovered gas discharged from the acid gas adsorbing device 1 using the hygrometer 8 in the second desorption process, and adjust the humidity of the second desorption gas supplied to the acid gas adsorbing device 1 so that the humidity of the second recovered gas is within a desired range. For example, when the humidity of the mixed gas exceeds the desired range, the dehumidification device 30 is controlled to reduce the humidity of the second desorption gas supplied to the acid gas adsorbing device 1. In this way, the humidity on the surface and the vicinity of the acid gas adsorbing material can be appropriately reduced.

[0124] The volume absolute humidity of the second recovered gas discharged from the acid gas adsorption device in the second desorption step is, for example, 2800 g / m 3 Below, preferably 450g / m 3 Below, for example, 380g / m 3 above.

[0125] After that, the acid gas recovery system 100 performs the adsorption process again as needed. More specifically, the control unit 9 stops driving the suction pump 40 and then performs the above-mentioned adsorption process again. In this way, the acid gas recovery system 100 can repeatedly perform the adsorption process, the replacement process, the first desorption process, and the second desorption process in sequence.

[0126] Industrial Applicability

[0127] The acid gas recovery method according to the embodiment of the present invention is used for separation and recovery of acid gas, and can be particularly well used in a carbon dioxide recovery, utilization and storage (CCUS) cycle.

[0128] Explanation of symbols

[0129] 1Acid gas adsorption device

[0130] 1a Carbon dioxide adsorption device

[0131] 7Acid gas adsorption device

[0132] 7a Carbon dioxide adsorption device

[0133] 100 Acid Gas Recovery System

[0134] 100a Carbon dioxide recovery system

Claims

1. A method for recovering acidic gas, comprising: an adsorption step in which a gas to be treated containing acid gas is supplied to an acid gas adsorption device including an acid gas adsorbing material, so that the acid gas is adsorbed by the acid gas adsorbing material; as well as a desorption step in which the acid gas adsorption device is heated to desorb the acid gas from the acid gas adsorption material; The separation process comprises: a first desorption step of supplying a first desorption gas to the acid gas adsorbing device to recover the acid gas desorbed from the acid gas adsorbing material together with the first desorption gas; and A second desorption process is a process that, after at least the first desorption process, supplies a second desorption gas having a humidity lower than that of the first desorption gas to the acid gas adsorbing device, thereby recovering the acid gas desorbed from the acid gas adsorbing material together with the second desorption gas.

2. The method for recovering acidic gas according to claim 1, wherein: The acid gas is carbon dioxide.

3. The method for recovering acidic gas according to claim 1 or 2, wherein: In the second desorption step, a mixed gas including the acid gas and the second desorption gas is discharged from the acid gas adsorption device, the humidity of the mixed gas is measured, and the humidity of the second desorption gas supplied to the acid gas adsorption device is adjusted so that the humidity of the mixed gas is within a desired range.

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