Acidic gas recovery system

Abstract

Provided is an acidic gas recovery system with which it is possible to facilitate increase in the amount of acidic gas adsorption and also to suppress deterioration of an acidic gas adsorbing material. An acidic gas recovery system according to an embodiment of the present invention is provided with: a plurality of acidic gas adsorption devices that include an acidic gas adsorbing material; and a fluid supply line. Through the fluid supply line, a fluid is distributed and supplied to each of the plurality of acidic gas absorption devices. The fluid supply line is provided with a branch part and a plurality of flow divisional parts. Each of the plurality of flow dividing parts connects between the branch part and the corresponding acidic gas adsorption device. The plurality of flow dividing parts each have a resistor disposed therein.

Description

Acid Gas Recovery System

[0001] The present invention relates to an acid gas recovery system.

[0002] In recent years, efforts have been made to separate and recover acidic gases contained in the atmosphere in order to reduce the environmental impact. Such acidic gases include carbon dioxide (CO ), which is a cause of global warming. ２ A typical example of such an approach is the carbon dioxide capture, utilization and storage (CCUS) cycle. As a carbon dioxide adsorption device used for separating and capturing carbon dioxide, a gas separation unit including an adsorbent layer filled with pellet-shaped carbon dioxide adsorbent has been proposed (see, for example, Patent Document 1). In the gas separation unit, the pellet-shaped carbon dioxide adsorbent adsorbs CO from a gas fluid passing through the adsorbent layer at a predetermined adsorption temperature. ２ When heated to a desorption temperature exceeding the adsorption temperature, the adsorbed CO ２ Desorbs CO at low cost ２ To provide a recovery system ２ Reduce the number of supply fans and separate the desorbed gas into multiple CO ２ It is conceivable to distribute and supply the CO to each adsorption device. ２ The adsorption devices may have different flow path resistances (pressure losses). In this case, the CO ２ The flow rate of the desorbed gas to the adsorption device is relatively high, and the flow resistance is relatively high. ２ The flow rate of the desorbed gas to the adsorption device becomes relatively small. Then, a plurality of CO ２ Temperature unevenness occurs between the adsorption devices, and the flow resistance is relatively small. ２ The temperature of the adsorption unit may rise excessively. ２ If the temperature of the adsorber rises too much, CO ２ The adsorbent deteriorates due to volatilization and thermal decomposition, etc., and CO ２ In addition, the adsorption capacity of CO２ The temperature is low in the adsorption unit, ２ The temperature required for desorption is not reached and CO ２ However, there is a problem in that the adsorption capacity of the catalyst decreases.

[0003] International Publication No. 2014 / 170184

[0004] A primary object of the present invention is to provide an acid gas recovery system that can improve the amount of acid gas adsorption and suppress deterioration of the acid gas adsorbent.

[0005] [1] An acidic gas recovery system according to an embodiment of the present invention includes a plurality of acidic gas adsorption devices and a fluid supply line. Each of the plurality of acidic gas adsorption devices includes an acidic gas adsorbent. The fluid supply line distributes and supplies a fluid to each of the plurality of acidic gas adsorption devices. The fluid supply line includes a branching section and a plurality of diverting sections. Each of the plurality of diverting sections connects the branching section to each of the plurality of acidic gas adsorption devices. Each of the plurality of diverting sections is provided with a resistor. [2] In the acidic gas recovery system described in [1] above, the acidic gas may be carbon dioxide. [3] The acidic gas recovery system described in [1] or [2] above may be capable of performing an adsorption step of supplying a gas to be treated containing acidic gas to the plurality of acidic gas adsorption devices and allowing the acidic gas to be adsorbed by the acidic gas adsorbent; and a desorption step of heating the plurality of acidic gas adsorption devices to desorb the acidic gas from the acidic gas adsorbent and supplying the desorbed gas to the plurality of acidic gas adsorption devices. In the desorption step, the flow resistance of the resistor may be greater than the flow resistance of each of the plurality of acidic gas adsorption devices. [4] In the acidic gas recovery system described in [3] above, the resistor may be capable of varying its flow resistance. In the adsorption step, the flow resistance of the resistor may be smaller than the flow resistance of each of the plurality of acidic gas adsorption devices. [5] The acidic gas recovery system described in [4] above may further include a control unit. The control unit is capable of controlling the flow resistance of the resistor. [6] The acidic gas recovery system described in any of [3] to [5] above may further include a bypass line capable of bypassing the resistor.

[0006] According to an embodiment of the present invention, it is possible to realize an acidic gas recovery system that can improve the amount of acidic gas adsorption and suppress deterioration of the acidic gas adsorbent.

[0007] Fig. 1 is a schematic configuration diagram of an acid gas recovery system according to one embodiment of the present invention. Fig. 2 is a schematic configuration diagram of one embodiment of an acid gas adsorption device provided in the acid gas recovery system of Fig. 1. Fig. 3 is a schematic perspective view of another embodiment of an acid gas adsorption device provided in the acid gas recovery system of Fig. 1. Fig. 4 is a schematic cross-sectional view of the acid gas adsorption device of Fig. 3. Fig. 5 is a schematic configuration diagram of an acid gas recovery system according to another embodiment of the present invention.

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In addition, in order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part more schematically than in the embodiment, but these are merely examples and do not limit the interpretation of the present invention.

[0009] A. Overview of the Acid Gas Recovery System FIG. 1 is a schematic diagram of an acid gas recovery system according to one embodiment of the present invention. The illustrated acid gas recovery system 100 includes multiple acid gas adsorption devices 1 and a fluid supply line 3. Each of the multiple acid gas adsorption devices 1 contains an acid gas adsorbent. The fluid supply line 3 distributes and supplies the fluid to each of the multiple acid gas adsorption devices 1. The fluid supply line 3 includes a branch section 32 and multiple diverging sections 33. Each of the multiple diverging sections 33 connects the branch section 32 to each of the multiple acid gas adsorption devices 1. Each of the multiple diverging sections 33 is provided with a resistor 5. The acid gas recovery system 100 is typically capable of performing an adsorption process and a desorption process. As will be described in detail later, in the adsorption process, a gas to be treated containing acid gas is supplied to the multiple acid gas adsorption devices 1, and the acid gas is adsorbed by the acid gas adsorbent. In the desorption process, the plurality of acidic gas adsorption devices 1 are heated to desorb the acidic gas from the acidic gas adsorbent, and the desorbed gas is supplied to the plurality of acidic gas adsorption devices 1. According to one embodiment of the present invention, the plurality of acidic gas adsorption devices 1 are connected to a fluid supply line 3 so as to be arranged in parallel. The fluid supply line 3 can distribute and supply the gas to be treated to each of the plurality of acidic gas adsorption devices 1 in the adsorption process. As a result, the acidic gas can be adsorbed simultaneously by the acidic gas adsorbents of the plurality of acidic gas adsorption devices 1, and the number of acidic gas supply blowers can be reduced, thereby providing an inexpensive acidic gas recovery system. Furthermore, in the desorption process, the plurality of acidic gas adsorption devices 1 are heated, and the fluid supply line 3 distributes and supplies the desorbed gas to each of the plurality of acidic gas adsorption devices 1. However, the plurality of acidic gas adsorption devices may have different flow path resistances (pressure losses). In this case, in the desorption process, the flow rate of the desorbed gas to the acid gas adsorption device with a relatively small flow path resistance becomes relatively high, and the flow rate of the desorbed gas to the acid gas adsorption device with a relatively large flow path resistance becomes relatively low, which may cause temperature unevenness among the multiple acid gas adsorption devices depending on the flow rate of the desorbed gas, and may cause the temperature of the acid gas adsorption device with a relatively small flow path resistance to rise excessively.If the temperature of the acidic gas adsorption device rises excessively, the acidic gas adsorbent will deteriorate due to volatilization and thermal decomposition, resulting in a decrease in the acidic gas adsorption capacity. Furthermore, in an acidic gas adsorption device with a relatively large flow resistance, the temperature will be low and will not reach the temperature required for acidic gas desorption, resulting in a decrease in the acidic gas adsorption capacity. In this regard, in one embodiment of the present invention, a resistor 5 is provided in the dividing section 33 connecting the branch section 32 and each acidic gas adsorption device 1. Therefore, the flow rate of the desorbed gas flowing through each acidic gas adsorption device 1 depends more on the flow resistance of the resistor 5 than on the flow resistance (pressure loss) of the multiple acidic gas adsorption devices 1. As a result, the flow rate of the desorbed gas flowing through each acidic gas adsorption device 1 can be made uniform during the desorption process, preventing an excessive rise in the temperature of the acidic gas adsorption device 1 and, ultimately, preventing the deterioration of the acidic gas adsorbent.

[0010] In one embodiment, the flow resistance of the resistor 5 in the desorption process is greater than the flow resistance of each of the multiple acid gas adsorption devices 1. The flow resistance of the resistor 5 in the desorption process is, for example, 0.001 kPaG (gauge pressure) or more, preferably 0.1 kPaG or more, and for example, 5 kPaG or less, preferably 1 kPaG or less. The flow resistance is a pressure drop resistance and can be measured, for example, by differential pressure meters installed before and after the resistor and before and after the acid gas adsorption device. The difference between the flow resistance of the resistor 5 and the flow resistance of the acid gas adsorption device 1 is, for example, 0.01 kPaG (gauge pressure) or more, preferably 0.1 kPaG or more, and for example, 4.5 kPaG or less, preferably 0.9 kPaG or less. If the difference between the flow resistance of the resistor and / or the flow resistance between the resistor and the acid gas adsorption device in the desorption process is equal to or greater than the above-mentioned lower limit, the flow resistance of the acid gas adsorption device can be stably suppressed from affecting the flow rate of the desorbed gas. If the flow resistance of the resistor in the desorption process and / or the difference between the flow resistance of the resistor and the flow resistance of the acidic gas adsorption device is not more than the above upper limit, the desorbed gas can be supplied to the acidic gas adsorption device in the desorption process within an energetically practical range.

[0011] In the desorption step, the friction loss coefficient of the resistor 5 through which the desorbed gas passes is, for example, 0.020 to 2.000, and preferably 0.023 to 1.500. The friction loss coefficient is typically determined from the Colebrook equation or the Moody diagram.

[0012] In the desorption step, the friction loss coefficient of the acidic gas adsorption device 1 through which the desorbed gas passes is, for example, 0.010 to 0.500, and preferably 0.015 to 0.350.

[0013] In one embodiment, the resistor 5 has a variable flow resistance. The lower the flow resistance of the resistor 5 in the adsorption process, the more preferable, and is typically smaller than the flow resistance of the resistor 5 in the desorption process. The flow resistance of the resistor 5 in the adsorption process is, for example, 20 kPaG (gauge pressure) or less, preferably 1 kPaG or less, more preferably 0.1 kPaG or less, even more preferably 0.08 kPaG or less, and particularly preferably 0.0008 kPaG or less. If the flow resistance of the resistor in the adsorption process is equal to or less than the above-mentioned upper limit, the gas to be treated can be efficiently supplied to each acid gas adsorption device in the adsorption process. Note that the lower limit of the flow resistance of the resistor in the adsorption process is, for example, 0.0001 kPaG or more, or, for example, 0.01 kPaG or more. In one embodiment, the flow resistance of the resistor 5 in the adsorption process is smaller than the flow resistance of each of the multiple acid gas adsorption devices 1. This allows the gas to be more efficiently supplied to the acid gas adsorption device.

[0014] In the adsorption step, the friction loss coefficient of the resistor 5 through which the gas to be treated passes is, for example, 0.010 to 0.050, and preferably 0.015 to 0.045.

[0015] In the adsorption step, the friction loss coefficient of the acid gas adsorption device 1 through which the gas to be treated passes is, for example, 0.010 to 0.050, and preferably 0.013 to 0.045.

[0016] 5, the acid gas recovery system 100 may further include a bypass line 34 that bypasses the resistor 5. This allows the resistor 5 to be bypassed by switching the flow path. Therefore, in the adsorption process, the gas to be treated can be efficiently supplied to each acid gas adsorption device via the bypass line. In this case, the flow path resistance (pressure loss) of the resistor 5 may be constant in the adsorption process and the desorption process. When the flow path resistance of the resistor 5 is constant, the range is, for example, the same as the range of the flow path resistance of the resistor 5 in the desorption process described above.

[0017] The acid gas contained in the gas to be treated includes, for example, carbon dioxide (CO ２ ), hydrogen sulfide, sulfur dioxide, nitrogen dioxide, dimethyl sulfide (DMS), hydrogen chloride, etc. In one embodiment, the acid gas is carbon dioxide (CO ２ ) and the gas to be treated is CO ２ It is a contained gas. ２ The contained gas is CO ２ In addition to the above, nitrogen may be contained. ２ The contained gas is typically air (atmospheric air). ２ CO in the containing gas ２ The concentration is, for example, 100 ppm (volume basis) or more and 2% by volume or less. In the following, the acid gas is carbon dioxide (CO ２ ) will be described in detail below.

[0018] B. Details of the Acidic Gas Recovery System Next, details of the acidic gas recovery system 100 will be described with reference to Figure 1. The acidic gas recovery system 100 shown in the figure includes the above-mentioned multiple acidic gas adsorption devices 1, the fluid supply line 3, and the multiple resistors 5, as well as an acidic gas supply blower 2, a desorbed gas supply unit 6, and a recovery unit 4. The gas to be treated by the acidic gas adsorption device is CO ２ In the case of a carbon dioxide-containing gas, the acidic gas adsorption device 1 is a carbon dioxide adsorption device 1a. The illustrated acidic gas recovery system 100 includes four acidic gas adsorption devices 1, but the number of acidic gas adsorption devices 1 is not limited to this. The number of acidic gas adsorption devices 1 is, for example, two or more, preferably four or more, and is, for example, ten or less.

[0019] B-1. First Embodiment of Acidic Gas Adsorption Apparatus As shown in FIG. 2, in one embodiment, the acidic gas adsorption apparatus 1 includes a plurality of adsorbent layers 71.

[0020] The multiple adsorbent layers 71 are stacked at intervals in the thickness direction. In the illustrated example, five adsorbent layers 71 are arranged in parallel, but the number of adsorbent layers 71 is not limited to this. The number of adsorbent layers 71 is, for example, 5 or more, preferably 10 or more, and more preferably 20 or more. The interval between adjacent adsorbent layers 71 among the multiple adsorbent layers 71 is, for example, 0.5 cm or more and 1.5 cm or less.

[0021] Each of the plurality of adsorbent layers 71 includes a flexible fiber member 73 and a plurality of pellet-shaped adsorbent materials 72 .

[0022] The flexible fiber member 73 allows gas to pass through while restricting the passage of the pellet-shaped adsorbent material. The flexible fiber member 73 is typically formed in a hollow (bag-like) shape capable of accommodating a plurality of pellet-shaped adsorbent materials 72. The flexible fiber member 73 may be a woven fabric or a nonwoven fabric. Examples of materials for the flexible fiber member 73 include organic fibers and natural fibers, and preferred examples include polyethylene terephthalate fibers, polyethylene fibers, and cellulose-based fibers. The thickness of the flexible fiber member 73 is, for example, 25 μm or more and 500 μm or less.

[0023] A plurality of pellet-shaped adsorbents 72 are packed inside a flexible fiber member 73 having a hollow (bag-like) shape. The pellet-shaped adsorbents 72 function as acidic gas adsorbents, typically as carbon dioxide adsorbents. Examples of materials for the pellet-shaped adsorbents 72 include amine-modified materials, preferably amine-modified cellulose, and more preferably amine-modified nanofibered cellulose. The average primary particle diameter of the pellet-shaped adsorbents 72 is, for example, 60 μm or more and 1200 μm or less. Any appropriate value can be adopted as the packing ratio of the pellet-shaped adsorbents 72 in the adsorbent layer 71.

[0024] The illustrated acid gas adsorption device 1 further includes a plurality of spacers 74. The spacers 74 are sandwiched between adjacent adsorbent layers 71 among the plurality of adsorbent layers 71. This ensures a stable spacing between adjacent adsorbent layers. In one embodiment, the plurality of adsorbent layers 71 and the plurality of spacers 74 are arranged in a generally zigzag shape when viewed from a direction perpendicular to the thickness direction of the adsorbent layer 71 (the depth direction of the paper in FIG. 1 ).

[0025] An example of such an acid gas adsorption device 1 is the gas separation unit described in WO 2014 / 170184, the entire disclosure of which is incorporated herein by reference.

[0026] B-2. Second Embodiment of Acidic Gas Adsorption Device As shown in Figures 3 and 4, in another embodiment, the acidic gas adsorption device 1 includes a substrate 10 and an acidic gas adsorption layer 15.

[0027] The structure of the substrate 10 is not particularly limited, and examples thereof include a filter structure such as a honeycomb structure or a filter cloth; a pellet structure; etc. The acidic gas adsorption layer 15 is not particularly limited as long as it is disposed on the surface of the substrate 10.

[0028] B-2-1. Substrate (Honeycomb Substrate) In one embodiment, the substrate 10 is a honeycomb substrate 10a. The honeycomb substrate 10a has partition walls 13 that define a plurality of cells 14. The cells 14 extend in the longitudinal direction (axial direction) of the honeycomb substrate 10a from the first end face E1 (inlet end face) to the second end face E2 (outlet end face) of the honeycomb substrate 10a (see FIG. 4). The cells 14 have any appropriate shape in a cross section perpendicular to the longitudinal direction of the honeycomb substrate 10a. Examples of the cross-sectional shape of the cells include a triangle, a rectangle, a pentagon, a polygon with hexagons or more, a circle, and an ellipse. The cross-sectional shapes and sizes of the cells may all be the same, or at least some may differ. Among such cross-sectional shapes of the cells, a hexagon or a quadrangle is preferred, and a square, a rectangle, or a hexagon is more preferred.

[0029] The cell density (i.e., the number of cells 14 per unit area) in the cross section perpendicular to the longitudinal direction of the honeycomb substrate can be appropriately set depending on the purpose. For example, the cell density is 4 cells / cm ２ ~320 cells / cm ２ If the cell density is in this range, the strength and effective GSA (geometric surface area) of the honeycomb substrate can be sufficiently ensured.

[0030] The honeycomb substrate 10a may have any suitable shape (overall shape). Examples of the shape of the honeycomb substrate include a cylindrical shape with a circular bottom, an elliptical cylindrical shape with an elliptical bottom, a rectangular prism with a polygonal bottom, and a cylindrical shape with an irregular bottom. The honeycomb substrate 10a in the illustrated example has a cylindrical shape. The outer diameter and length of the honeycomb substrate can be appropriately set depending on the purpose. Although not shown, the honeycomb substrate may have a hollow region at the center in a cross section perpendicular to the longitudinal direction.

[0031] The honeycomb substrate 10a typically includes an outer peripheral wall 11 and partition walls 13 located inside the outer peripheral wall 11. In the illustrated example, the outer peripheral wall 11 and the partition walls 13 are integrally formed. However, the outer peripheral wall 11 and the partition walls 13 may be separate bodies.

[0032] 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.

[0033] The partition walls 13 define a plurality of cells 14. More specifically, the partition walls 13 include first partition walls 13a and second partition walls 13b that are perpendicular to each other, and the first partition walls 13a and the second partition walls 13b define the plurality of cells 14. The cross-sectional shape of the cells 14 is quadrangular except for the portions where the first partition walls 13a and the second partition walls 13b contact the outer peripheral wall 11. Note that the configuration of the partition walls is not limited to the above-described partition walls 13. The partition walls may include first partition walls extending in the radial direction and second partition walls extending in the circumferential direction, which define a plurality of cells.

[0034] The thickness of the partition walls 13 can be appropriately set depending on the application of the honeycomb substrate. The thickness of the partition walls 13 is typically thinner than the thickness of the outer peripheral wall 11. The thickness of the partition walls 13 is, for example, 0.03 mm to 0.6 mm. The thickness of the partition walls is measured by cross-sectional observation using, for example, a scanning electron microscope (SEM). When the thickness of the partition walls is within this range, the honeycomb substrate can have sufficient mechanical strength and can also have a sufficient opening area (total area of ​​cells in a cross section).

[0035] The porosity of the partition walls 13 can be appropriately set depending on 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 intrusion porosimetry. The bulk density of the partition walls 13 can be appropriately set depending on the purpose. The bulk density is, for example, 0.10 g / cm ３ or more, preferably 0.20 g / cm ３ or more, for example, 0.60 g / cm ３ or less, preferably 0.50 g / cm ３ The bulk density can be measured by, for example, mercury intrusion porosimetry.

[0036] A representative example of a material for forming the partition walls 13 is ceramics. Examples of ceramics include silicon carbide, silicon-silicon carbide composite materials, cordierite, mullite, alumina, silicon nitride, spinel, silicon carbide-cordierite composite materials, lithium aluminum silicate, and aluminum titanate. The materials for forming the partition walls can be used alone or in combination. Among the materials for forming the partition walls, preferred examples include cordierite, alumina, mullite, silicon carbide, silicon-silicon carbide composite materials, and silicon nitride, and more preferred examples include silicon carbide and silicon-silicon carbide composite materials.

[0037] Such a honeycomb substrate 10a is typically produced by the following method. First, a binder and water or an organic solvent are added, if necessary, to a material powder containing the above-mentioned ceramic powder, and the resulting mixture is kneaded to form a clay. The clay is then molded into a desired shape (typically by extrusion molding), dried, and fired as necessary to produce the honeycomb substrate 10a. When firing, the firing is performed at, for example, 1200°C to 1500°C. The firing time is, for example, 1 hour or more and 20 hours or less.

[0038] B-2-2. Acidic Gas Adsorption Layer (Carbon Dioxide Adsorption Layer) In one embodiment, the acidic gas adsorption layer 15 is formed on the surface of the partition wall 13. In the honeycomb substrate 10a, the gas flow path 16 is formed in a portion (typically the center portion) in the cross section of the cell 14 where the acidic gas adsorption layer 15 is not formed. The acidic gas adsorption layer 15 may be formed on the entire inner surface of the partition wall 13 (i.e., so as to surround the gas flow path 16) as in the illustrated example, or may be formed on a part of the surface of the partition wall. When the acidic gas adsorption layer 15 is formed on the entire inner surface of the partition wall 13, the acidic gas (typically CO ２ ) can be removed more efficiently.

[0039] The gas flow passage 16 extends from a first end face E1 (inlet end face) to a second end face E2 (outlet end face), similar to the cells 14. The cross-sectional shape of the gas flow passage 16 may be the same as that of the cells 14, preferably a hexagon or a quadrangle, and more preferably a square, a rectangle, or a hexagon. The cross-sectional shapes and sizes of the gas flow passages 16 may all be the same, or at least some may be different. The gas to be treated described above typically flows through the cells 14 (more specifically, the gas flow passages 16) in the adsorption step. In one embodiment, the desorbed gas flows through the cells 14 (more specifically, the gas flow passages 16) in the desorption step.

[0040] The acidic gas adsorption layer 15 includes an acidic gas adsorbent suitable for the acidic gas to be adsorbed. In one embodiment, the acidic gas adsorption layer 15 is a carbon dioxide adsorption layer 15a. The carbon dioxide adsorption layer 15a includes a carbon dioxide adsorbent as an example of an acidic gas adsorbent.

[0041] The carbon dioxide adsorbent is ２ Any appropriate compound capable of adsorbing and desorbing carbon dioxide may be employed. Examples of carbon dioxide adsorbents include nitrogen-containing compounds described below; alkali compounds such as sodium hydroxide and potassium hydroxide; carbonates such as calcium carbonate and potassium carbonate; bicarbonates such as calcium bicarbonate and potassium bicarbonate; metal-organic frameworks (MOFs) such as MOF-74, MOF-200, and MOF-210; zeolites; activated carbon; nitrogen-doped carbon; ionic liquids, and the like. Carbon dioxide adsorbents can be used alone or in combination.

[0042] Among the carbon dioxide adsorbents, preferred are nitrogen-containing compounds and ionic liquids. More specifically, nitrogen-containing compounds include primary amines such as monoethanolamine and polyvinylamine; secondary amines such as diethanolamine, cyclic amines, and N-(3-aminopropyl)diethanolamine; tertiary amines such as methyldiethylamine and triethanolamine; ethyleneamine compounds such as tetraethylenepentamine; aminosilane coupling agents such as aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, and polyethyleneimine-trimethoxysilane; organic monomers having primary to tertiary amino groups, such as ethyleneimine and styrene to which an amino group is added; 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 polyamidoamine; polyvinylamine; and organic / inorganic compounds to which an amino group is added as a substituent. Among the nitrogen-containing compounds, preferred are methyldiethylamine, monoethanolamine, cyclic amine, diethanolamine, tetraethylenepentamine, ethyleneimine, linear polyethyleneimine, branched polyethyleneimine, and organic / inorganic compounds having amino as a substituent.

[0043] Ionic liquids are liquid "salts" composed only of ions (anions and cations), and are in a liquid state at room temperature and normal pressure (23°C, 0.1 MPa (absolute pressure)). Examples of cations of ionic liquids include ammonium-based ions such as imidazolium salts and pyridinium salts, phosphonium-based ions, sulfonium salts, and inorganic ions. Examples of anions of ionic liquids include halogen-based ions such as bromide ions and triflates; boron-based ions such as tetraphenylborate; phosphorus-based ions such as hexafluorophosphate; and sulfur-based ions such as alkylsulfonates. Among ionic liquids, a combination of an imidazolium salt as the cation and triflate as the anion is preferred.

[0044] More preferably, the ionic liquid is used in combination with a carbon dioxide adsorbent other than the ionic liquid (hereinafter referred to as "other carbon dioxide adsorbent"). In this case, the ionic liquid coats the other carbon dioxide adsorbent (for example, a nitrogen-containing compound). This can improve the performance and extend the life of the carbon dioxide adsorbent. The content of the ionic liquid is, for example, 0.000001 parts by mass or more, preferably 0.00001 parts by mass or more, and for example, 0.1 parts by mass or less, preferably 0.05 parts by mass or less, relative to 1 part by mass of the other carbon dioxide adsorbent. When the content of the ionic liquid is within the above range, the performance of the carbon dioxide adsorbent can be improved and the life can be stably extended.

[0045] In one embodiment, the carbon dioxide adsorption layer 15a further includes a porous carrier in addition to the carbon dioxide adsorbent described above. In this case, the carbon dioxide adsorbent is typically supported on the porous carrier and faces the gas flow path. When the carbon dioxide adsorption layer includes a porous carrier, it is possible to prevent the carbon dioxide adsorbent from falling off from the carbon dioxide adsorption layer during the adsorption step and / or desorption step.

[0046] The porous support can form mesopores in the carbon dioxide adsorption layer. Examples of the porous support include metal-organic frameworks (MOFs) such as MOF-74, MOF-200, and MOF-210; activated carbon; nitrogen-doped carbon; mesoporous silica; mesoporous alumina; zeolites; carbon nanotubes; and fluorinated resins such as polyvinylidene fluoride (PVDF). Preferred examples include metal-organic frameworks (MOFs), PVDF, activated carbon, zeolites, mesoporous silica, and mesoporous alumina. The porous support can be used alone or in combination. Preferably, the porous support is made of a material different from that of the carbon dioxide adsorbent.

[0047] The BET specific surface area of ​​the porous carrier is, for example, 50 m ２ / g or more, preferably 500m ２ When the surface area of ​​the porous carrier is equal to or greater than the lower limit, the carbon dioxide adsorbent can be stably supported, and the CO ２ The recovery rate can be improved. The upper limit of the BET specific surface area of ​​the porous carrier is typically 2000 m ２ / g or less.

[0048] When the carbon dioxide adsorption layer contains a carbon dioxide adsorbent and a porous carrier, the total content of the carbon dioxide adsorbent and the porous carrier in the carbon dioxide adsorption layer is, for example, 30% by mass or more, preferably 50% by mass or more, and for example, 100% by mass or less, preferably 99% by mass or less. The content 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, and for example, 99% by mass or less. The content of the porous carrier is, for example, 0.01 parts by mass or more, preferably 0.3 parts by mass or more, and for example, 0.7 parts by mass or less, preferably 0.5 parts by mass or less, relative to 1 part by mass of the carbon dioxide adsorbent. When the content of the porous carrier is within the above range, the carbon dioxide adsorbent can be supported more stably.

[0049] Alternatively, the carbon dioxide adsorption layer may be composed of only the carbon dioxide adsorbent. In this case, the carbon dioxide adsorbent is directly supported on the partition wall 13 and faces the gas flow path. When the carbon dioxide adsorption layer is composed of only the carbon dioxide adsorbent, the content of the carbon dioxide adsorbent in the carbon dioxide adsorption layer is typically 95.0 mass % or more and 100 mass % or less. When the content of the carbon dioxide adsorbent is within the above range, excellent CO ２ A stable recovery rate can be ensured.

[0050] Such a carbon dioxide adsorption layer is typically produced by the following method. The above-mentioned carbon dioxide adsorbent is dissolved in a solvent to prepare a carbon dioxide adsorbent solution. Furthermore, if necessary, the above-mentioned porous carrier is added to the solvent. The order of adding the carbon dioxide adsorbent and the porous carrier is not particularly limited. The carbon dioxide adsorbent solution is then applied to a substrate (specifically, a partition wall), and the coating film is dried and sintered as necessary to form a carbon dioxide adsorption layer. Alternatively, a dispersion liquid containing a carbon dioxide adsorbent other than the ionic liquid and a porous carrier is applied to the substrate, and the coating film is dried and sintered as necessary, and then only the ionic liquid is applied to the substrate to form a carbon dioxide adsorption layer.

[0051] Although not shown, the acidic gas adsorption device 1 may include a heater in addition to the substrate 10 and the acidic gas adsorption layer 15. The heater is capable of heating the substrate 10. The heater is typically in contact with the substrate 10. When the acidic gas adsorption device includes a heater, the temperature of the acidic gas adsorption device can be smoothly raised to the desorption temperature in the desorption step.

[0052] Although not shown, the acidic gas adsorption device 1 may also include a case. The case has a tubular (hollow) shape extending in the direction in which the target gas passes. Examples of the tubular shape include a cylindrical shape and a rectangular tubular shape. One end of the case is configured as an inlet, and the other end of the case is configured as an outlet. In one embodiment, the case houses a plurality of adsorbent layers 71 and a plurality of spacers 74 (see FIG. 2), and in another embodiment, the case houses a substrate 10 and an acidic gas adsorption layer 15 (see FIGS. 3 and 4).

[0053] B-3. ​​Acidic Gas Supply Fan As shown in FIG. 1, the acidic gas supply fan 2 supplies the target gas (typically CO ) to the multiple acidic gas adsorption devices 1 in the adsorption process. ２ The illustrated acid gas supply blower 2 is capable of blowing gas to be treated, including acid gas, toward the plurality of acid gas adsorption devices 1. The acid gas supply blower 2 may have any appropriate configuration.

[0054] B-4. Fluid Supply Line The fluid supply line 3 typically includes a connection section 31, a branch section 32, and multiple diverging sections 33. The connection section 31 is typically a pipe connecting the acidic gas supply blower 2 and the branching section 32. The branching section 32 is typically a manifold. Although not shown, the branching section 32 has an inlet and multiple outlets. The connection section 31 is connected to the inlet. The number of outlets is the same as the number of acidic gas adsorption devices 1 included in the acidic gas recovery system 100. Each of the multiple diverging sections 33 is typically a pipe connecting the branching section 32 to each acidic gas adsorption device 1. In one embodiment, the diverging section 33 connects the outlet of the branching section 32 to the inlet of a case included in the acidic gas adsorption device 1.

[0055] B-5. Resistor As described above, the resistor 5 is provided in the diverter section 33. The resistor 5 appropriately regulates the flow of desorbed gas in the diverter section 33 during the desorption process. The resistor 5 may have any appropriate configuration as long as it has the above-described flow path resistance. Examples of the resistor 5 include an orifice plate, a nonwoven fabric, a control valve, and a heat exchanger. The multiple resistors 5 included in the acid gas recovery system 100 typically have substantially the same flow path resistance (specifically, within ±30% of a predetermined value or ±5 kPaG (gauge pressure)) in each process. As described above, when the resistor 5 is configured to have a variable flow path resistance, the acid gas recovery system 100 may further include a controller 9. The controller 9 can appropriately control the flow path resistance of the resistor 5. The controller 9 is typically connected to each of the multiple resistors 5 so as to be able to communicate with each other. The controller 9 can send a signal to the resistor 5 instructing it to change the flow path resistance. The control unit 9 includes, for example, a central processing unit (CPU), a ROM, and a RAM.

[0056] B-6. Desorption Gas Supply Unit The desorption gas supply unit 6 is configured to supply the desorption gas to the acidic gas adsorption apparatus 1 in the desorption step. The desorption gas supply unit 6 in the illustrated example includes a desorption gas supply line 62 and an on-off valve 61. The desorption gas supply line 62 is typically a pipe capable of supplying the desorption gas to the fluid supply line 3. The downstream end of the desorption gas supply line 62 in the supply direction of the desorption gas is connected to the connection part 31. When the desorption gas is a recovery gas (described later), the upstream end of the desorption gas supply line 62 in the supply direction of the desorption gas is connected to an intermediate tank (not shown) that stores the desorption gas (typically the recovery gas). The on-off valve 61 is provided in the desorption gas supply line 62 and is capable of opening and closing the desorption gas supply line 62. Examples of the on-off valve 61 include a ball valve, a gate valve, and a butterfly valve, and a butterfly valve is preferred.

[0057] B-7. Recovery Unit The recovery unit 4 is configured to recover the acidic gas desorbed in the desorption step. The recovery unit 4 in the illustrated example includes a suction pump 41 and a discharge line 42. The suction pump 41 is capable of suctioning gas inside the acidic gas adsorption device. An example of the suction pump 41 is a vacuum pump. The discharge line 42 is typically a pipe through which gas discharged from the multiple acidic gas adsorption devices 1 and directed toward the suction pump 41 passes. The upstream end of the discharge line 42 in the gas passage direction branches into the same number of branches as the multiple acidic gas adsorption devices 1, and is connected to each acidic gas adsorption device 1. In one embodiment, the upstream end (branch) of the discharge line 42 is connected to the outlet of the case provided in each acidic gas adsorption device 1. The downstream end of the discharge line 42 in the gas passage direction is connected to the suction pump 41 after the above-mentioned branches join.

[0058] B-8. Bypass Line As shown in FIG. 5 , the acid gas recovery system 100 may further include a bypass line 34. The bypass line 34 is configured so that the gas to be treated bypasses the resistor 5 during the adsorption step and is supplied to the acid gas adsorption device 1. The bypass line 34 is typically a pipe through which gas can pass. In one embodiment, the acid gas recovery system 100 includes a plurality of bypass lines 34. Each of the plurality of bypass lines 34 is connected to a respective one of the plurality of diverging sections 33. The upstream end of the bypass line 34 in the gas passage direction is connected to a portion of the diverging section 33 between the branch section 32 and the resistor 5. The downstream end of the bypass line 34 in the gas passage direction is connected to a portion of the diverging section 33 between the resistor 5 and the acid gas adsorption device 1. In the illustrated example, the bypass line 34 is provided with an on-off valve 35. The on-off valve 35 is capable of opening and closing the bypass line 34. Examples of the on-off valve 35 include a ball valve, a gate valve, and a butterfly valve, and preferably a butterfly valve. Such on-off valve 35 may be electrically connected to the control unit 9. In this case, the control unit 9 can control the opening and closing of the on-off valve 35 instead of controlling the fluctuation of the flow path resistance of the resistor 5.

[0059] C. Operation of the Acid Gas Recovery System Next, one embodiment of a method for recovering acid gases performed by the acid gas recovery system 100 will be described with reference to Figure 1. In one embodiment, the method for recovering acid gases includes, in order, the above-described adsorption step, substitution step, and desorption step.

[0060] In the acidic gas recovery system 100, the adsorption process is first carried out. In the adsorption process, the on-off valve 61 is closed and the acidic gas supply blower 2 is driven. As a result, the gas to be treated is sent out by the acidic gas supply blower 2 and distributed and supplied to each of the multiple acidic gas adsorption devices 1 via the fluid supply line 3. The temperature of each acidic gas adsorption device in the adsorption process is pre-adjusted to the adsorption temperature. The flow path resistance of the resistor in the adsorption process is preferably pre-set to be equal to or lower than the upper limit of the flow path resistance of the resistor in the adsorption process described above. In the illustrated example, the flow path resistance of the resistor 5 is pre-set as described above by a signal from the control unit 9.

[0061] The temperature of the gas to be treated supplied to the plurality of acidic gas adsorption devices is, for example, 0°C or higher and 50°C or lower, and is preferably the same as the ambient temperature. The temperature of the gas to be treated may be the same as or different from the adsorption temperature of the acidic gas adsorption devices. The pressure of the gas to be treated is, for example, 0.3 x 10 ５ PaA (absolute pressure) or more 2.0 x 10 ５ The flow velocity of the gas to be treated sent out by the acidic gas supply blower is, for example, 1.0 m / sec or more and 30 m / sec or less, and the flow velocity of the gas to be treated supplied to each acidic gas adsorption device is, for example, 0.5 m / sec or more and 5 m / sec or less.

[0062] The temperature (adsorption temperature) of each acidic gas adsorption device in the adsorption step is, for example, 0°C or higher, preferably 10°C or higher, and for example, 50°C or lower, preferably 40°C or lower. In one embodiment, the adsorption temperature is the same as the ambient temperature. The duration of the adsorption step (adsorption time) is, for example, 15 minutes or higher, preferably 30 minutes or higher, and for example, 3 hours or lower, preferably 2 hours or lower. When the adsorption temperature and / or adsorption time are within the above ranges, the acidic gas adsorbent can efficiently adsorb acidic gases.

[0063] After that, when the above-mentioned adsorption time has elapsed, the operation of the acidic gas supply blower 2 is stopped, and the adsorption process is completed.

[0064] The acidic gas recovery rate in the adsorption step (= 100 - (acidic gas concentration in the gas to be treated that has passed through the multiple acidic gas adsorption devices / acidic gas concentration in the gas to be treated before being supplied to the multiple acidic gas adsorption devices × 100)) is, for example, 60% or more, preferably 75% or more, more preferably 80% or more, and for example, 90% or less.

[0065] Next, a substitution process is carried out in the acidic gas recovery system 100. In the substitution process, the on-off valve 61 is switched from a closed state to an open state, and the suction pump 41 is driven. The desorbed gas then passes through the desorbed gas supply line 62 and is supplied to the fluid supply line 3, from which it is distributed and supplied to each of the multiple acidic gas adsorption devices 1. As a result, the gas inside the acidic gas adsorption device 1 (typically the gas flow path 16) is replaced with the desorbed gas from the gas to be treated.

[0066] In the substitution step, the temperature range of the desorbed gas supplied to each acidic gas adsorption device is the same as the above-mentioned adsorption temperature range. ４ PaA (absolute pressure) or more 1.0 x 10 ４ PaA or less, and for example, 0.1 × 10 ４ PaA or more 5.0 x 10 ４ The time for which the replacement step is carried out (hereinafter referred to as replacement time) is, for example, 1 minute or more and 30 minutes or less.

[0067] In the substitution step, a purge gas different from the desorbed gas may be introduced into the acidic gas adsorption apparatus to substitute the gas to be treated with the purge gas. In this case, the pressure of the purge gas may be, for example, 0.1×10 ４ PaA or higher 11 x 10 ４ The pressure is not more than PaA. The replacement time is, for example, 1 minute to 30 minutes. Examples of the purge gas include water vapor, carbon dioxide, nitrogen, and argon.

[0068] Subsequently, in the acidic gas recovery system 100, a desorption process is performed following the substitution process. In the desorption process, typically, the multiple acidic gas adsorption devices 1 are heated to a desorption temperature exceeding the adsorption temperature. Heating of the acidic gas adsorption devices may be started midway through the substitution process. The flow resistance of the multiple resistors is preferably set to a value equal to or greater than the lower limit of the flow resistance of the resistors in the desorption process. In the illustrated example, a signal is sent from the control unit 9 to each resistor 5, and the flow resistance of each resistor 5 is changed as described above based on the signal. Next, the desorbed gas is supplied to the multiple acidic gas adsorption devices 1 heated to the desorption temperature. More specifically, in the desorption process, the multiple acidic gas adsorption devices 1 are heated to the desorption temperature and maintained at the desorption temperature for a predetermined desorption time, while the desorbed gas is supplied to each acidic gas adsorption device. In the illustrated example, the suction pump 41 is kept running, and the desorbed gas is uniformly distributed and supplied to each of the multiple acidic gas adsorption devices 1 via the fluid supply line 3 and the resistors 5. As a result, the desorbed acid gas is recovered together with the desorbed gas. The gas recovered in the desorption step is sometimes referred to as recovered gas.

[0069] The desorbed gas is preferably a recovered gas previously recovered by an acidic gas recovery system. By using the recovered gas as the desorbed gas, the acidic gas concentration in the recovered gas can be improved. The oxygen concentration in the recovered gas is preferably 15% by volume or less.

[0070] The temperature of the desorption gas supplied to the acidic gas adsorption device is, for example, 60°C or higher, preferably 90°C or higher, and for example, 200°C or lower, preferably 160°C or lower. The temperature of the acidic gas adsorption device in the desorption step (desorption temperature) is, for example, 70°C or higher, preferably 80°C or higher, and for example, 200°C or lower, preferably 110°C or lower. The duration of the desorption step (desorption time during which the acidic gas adsorption device is maintained at the desorption temperature) is, for example, 1 minute or higher, preferably 5 minutes or higher, and for example, 1 hour or lower, preferably 30 minutes or lower. When the desorption temperature and / or desorption time are within the above ranges, acidic gases can be desorbed more smoothly from the acidic gas adsorbent.

[0071] As described above, when the temperature of each acidic gas adsorption device reaches the desorption temperature, the acidic gas held in the acidic gas adsorbent is desorbed (released) from the acidic gas adsorbent. The desorbed acidic gas is discharged from the acidic gas adsorption device 1 together with the desorbed gas, passes through the discharge line 42 and the suction pump 41, and is stored in an intermediate tank as needed. Such recovered gas can be used for various purposes, and may be resupplied to the acidic gas adsorption device as the desorbed gas as described above, or may be used as a raw material for various industrial products (e.g., a raw material for hydrocarbon fuels).

[0072] Thereafter, the adsorption process is carried out again as necessary in the acidic gas recovery system 100. More specifically, the above-described adsorption process is carried out again after the driving of the suction pump 41 is stopped. In this way, the acidic gas recovery system 100 can repeat the adsorption process, the substitution process, and the desorption process in sequence.

[0073] Furthermore, as shown in FIG. 5 , when the acidic gas recovery system 100 includes a bypass line 34, the on-off valve 61 is closed and the on-off valve 35 is open during the adsorption process, and the acidic gas supply blower 2 is driven. Then, due to the flow resistance of the resistor 5, the flow rate of the target gas passing through the bypass line 34 becomes greater than the flow rate of the target gas passing through the diverter 33. Therefore, the target gas passes through the bypass line 34 and is smoothly supplied to the acidic gas adsorption device 1. After the adsorption time has elapsed, the operation of the acidic gas supply blower 2 is stopped. Next, the substitution process is performed, in which the on-off valve 61 is changed from the closed state to the open state, the on-off valve 35 is maintained in the open state, and the suction pump 41 is driven. Then, the desorbed gas passes through the bypass line 34 and is supplied to the acidic gas adsorption device 1. This replaces the target gas in the interior of the acidic gas adsorption device 1 (typically, the gas flow path 16) with the desorbed gas. After the replacement time has elapsed, the desorption step is carried out, and the on-off valve 35 is changed from the open state to the closed state while the on-off valve 61 is kept open. As a result, the desorbed gas is restricted from passing through the bypass line 34, and passes through the resistor 5 and is supplied to the acidic gas adsorption device 1 heated to the desorption temperature. This makes it possible to equalize the flow rate of the desorbed gas flowing through each acidic gas adsorption device 1, and to smoothly recover the recovered gas containing the acidic gas and the desorbed gas.

[0074] The acid gas recovery system according to the embodiment of the present invention is used for separating and recovering acid gases, and can be particularly suitably used in a carbon dioxide capture, utilization, and storage (CCUS) cycle.

[0075] REFERENCE SIGNS LIST 1 Acid gas adsorption device 1a Carbon dioxide adsorption device 3 Fluid supply line 32 Branching section 33 Diversion section 34 Bypass line 100 Acid gas recovery system 100a Carbon dioxide recovery system

Claims

1. A plurality of acid gas adsorption devices including an acid gas adsorbent; A fluid supply line for distributing and supplying fluid to each of the plurality of acid gas adsorption devices; an acid gas recovery system comprising: The acid gas recovery system includes an adsorption step of supplying a gas to be treated containing acid gas to the plurality of acid gas adsorption devices and adsorbing the acid gas on the acid gas adsorbent; a desorption step of heating the plurality of acid gas adsorption devices to desorb the acid gas from the acid gas adsorbent and supplying the desorbed gas to the plurality of acid gas adsorption devices; can be implemented, The fluid supply line includes a branch portion; and a plurality of shunt portions connecting the branch portion to each of the plurality of acid gas adsorption devices; A resistor is provided in each of the plurality of shunt portions, In the desorption step, the flow path resistance of the resistor is greater than the flow path resistance of each of the plurality of acid gas adsorption devices. An acid gas recovery system.

2. The acid gas is carbon dioxide. The acid gas recovery system according to claim 1.

3. The resistor is capable of varying the flow path resistance, In the adsorption step, the flow path resistance of the resistor is smaller than the flow path resistance of each of the plurality of acid gas adsorption devices. The acid gas recovery system according to claim 1 or 2.

4. The acid gas recovery system according to claim 3, further comprising a control unit capable of controlling the flow path resistance of the resistor.

5. The acid gas recovery system according to claim 1 or 2, further comprising a bypass line capable of bypassing the resistor.