Acid 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

[Technical Field]

[0001] This invention relates to an acid gas recovery system. [Background technology]

[0002] In recent years, efforts have been made to separate and recover acidic gases contained in the atmosphere in order to reduce environmental impact. One example of such acidic gas is carbon dioxide (hereinafter sometimes referred to as CO2), which is a major cause of global warming. A representative example of such efforts is the Carbon dioxide Capture, Utilization and Storage (CCUS) cycle. As a carbon dioxide adsorption device used for such carbon dioxide separation and recovery, a gas separation unit equipped with an adsorption layer filled with pelletized carbon dioxide adsorbent has been proposed (see, for example, Patent Document 1). In the gas separation unit, the pelletized carbon dioxide adsorbent adsorbs CO2 from the gas fluid passing through the adsorption layer at a predetermined adsorption temperature, and desorbs the adsorbed CO2 when heated to a desorption temperature exceeding the adsorption temperature. To provide an inexpensive CO2 recovery system, it is conceivable to reduce the number of CO2 supply blowers and distribute the desorbed gas to each of the multiple CO2 adsorption devices. However, the flow resistance (pressure loss) of the multiple CO2 adsorption devices may differ from one another. In this case, during the desorption process, the flow rate of the desorbed gas to the CO2 adsorption device with relatively low flow resistance becomes relatively high, while the flow rate of the desorbed gas to the CO2 adsorption device with relatively high flow resistance becomes relatively low. As a result, temperature variations occur among the multiple CO2 adsorption devices depending on the flow rate of the desorbed gas, and there is a risk that the temperature of the CO2 adsorption device with relatively low flow resistance will rise excessively. If the temperature of the CO2 adsorption device rises excessively, the CO2 adsorbent material will deteriorate due to volatilization and thermal decomposition, reducing its CO2 adsorption capacity. In addition, the CO2 adsorption device with relatively high flow resistance will have a low temperature and will not reach the temperature necessary for CO2 desorption, resulting in a decrease in its CO2 adsorption capacity. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2014 / 170184 [Overview of the project] [Problems that the invention aims to solve]

[0004] The main objective of the present invention is to provide an acid gas recovery system that can improve the amount of acid gas adsorbed and suppress the deterioration of the acid gas adsorbent. [Means for solving the problem]

[0005] [1] An acid gas recovery system according to an embodiment of the present invention comprises a plurality of acid gas adsorption devices and a fluid supply line. Each of the plurality of acid gas adsorption devices contains an acid gas adsorbent. The fluid supply line distributes and supplies fluid to each of the plurality of acid gas adsorption devices. The fluid supply line comprises a branching section and a plurality of flow diversion sections. Each of the flow diversion sections connects the branching section to each of the plurality of acid gas adsorption devices. Each of the flow diversion sections is provided with a resistor. [2] In the acid gas recovery system described in [1] above, the acid gas may be carbon dioxide. [3] In the acid gas recovery system described in [1] or [2] above, it may be possible to perform an adsorption step of supplying a gas to be treated containing the acid gas to the plurality of acid gas adsorption devices to adsorb the acid gas onto the acid gas adsorbent; and 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. In the desorption step, the flow resistance of the resistor may be greater than the flow resistance of each of the plurality of acid gas adsorption devices. [4] In the acid gas recovery system described in [3] above, the resistor may have a variable flow resistance. In the adsorption step, the flow resistance of the resistor is smaller than the flow resistance of each of the plurality of acid gas adsorption devices. [5] The acid gas recovery system described in [4] above may further include a control unit. The control unit can control the flow resistance of the resistor. [6] The acid gas recovery system described in any of [3] to [5] above may further include a bypass line that can bypass the resistor. [Effects of the Invention]

[0006] According to embodiments of the present invention, an acid gas recovery system can be realized that can improve the amount of acid gas adsorbed and suppress the deterioration of the acid gas adsorbent. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram of an acidic gas recovery system according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of one embodiment of the acid gas adsorption device included in the acid gas recovery system shown in Figure 1. [Figure 3] Figure 3 is a schematic perspective view of another embodiment of the acid gas adsorption device included in the acid gas recovery system of Figure 1. [Figure 4] Figure 4 is a schematic cross-sectional view of the acid gas adsorption apparatus shown in Figure 3. [Figure 5] Figure 5 is a schematic diagram of an acidic gas recovery system according to another embodiment of the present invention. [Modes for carrying out the invention]

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

[0009] A. Outline of the Acid Gas Recovery System Figure 1 is a schematic diagram of an acidic gas recovery system according to one embodiment of the present invention. The illustrated example of the acid gas recovery system 100 comprises a plurality of acid gas adsorption devices 1 and a fluid supply line 3. Each of the plurality of acid gas adsorption devices 1 contains an acid gas adsorbent. The fluid supply line 3 distributes and supplies fluid to each of the plurality of acid gas adsorption devices 1. The fluid supply line 3 comprises a branching section 32 and a plurality of flow diversion sections 33. Each of the plurality of flow diversion sections 33 connects the branching section 32 to each of the plurality of acid gas adsorption devices 1. Each of the plurality of flow diversion sections 33 is provided with a resistor 5. The acid gas recovery system 100 can typically perform 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 multiple acid gas adsorption devices 1, and the acid gas is adsorbed onto the acid gas adsorbent. In the desorption process, the multiple acid gas adsorption devices 1 are heated to desorb the acid gas from the acid gas adsorbent, and the desorbed gas is supplied to the multiple acid gas adsorption devices 1. According to one embodiment of the present invention, a plurality of acid gas adsorption devices 1 are connected to a fluid supply line 3 in parallel. The fluid supply line 3 can distribute and supply the gas to be treated to each of the plurality of acid gas adsorption devices 1 during the adsorption process. As a result, the acid gas can be adsorbed collectively by the acid gas adsorbents of the plurality of acid gas adsorption devices 1, and the number of blowers for supplying the acid gas can be reduced, thus providing an inexpensive acid gas recovery system. Furthermore, during the desorption process, the plurality of acid gas adsorption devices 1 are heated, and the fluid supply line 3 distributes and supplies the desorbed gas to each of the plurality of acid gas adsorption devices 1. However, the flow path resistances (pressure losses) of multiple acid gas adsorption devices may differ from each other. 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 large, and the flow rate of the desorbed gas to the acid gas adsorption device with a relatively large flow path resistance becomes relatively small. Then, temperature unevenness occurs among the multiple acid gas adsorption devices according to the flow rate of the desorbed gas, and there is a risk that the temperature of the acid gas adsorption device with a relatively small flow path resistance may rise excessively. When the temperature of the acid gas adsorption device rises excessively, it deteriorates due to volatilization and thermal decomposition of the acid gas adsorbent, and the adsorption capacity of the acid gas decreases. Also, in the acid gas adsorption device with a relatively large flow path resistance, the temperature is low and does not reach the temperature required for acid gas desorption, resulting in a decrease in the adsorption capacity of the acid gas. In this regard, in one embodiment of the present invention, a resistor 5 is provided in a flow dividing portion 33 that connects a branching portion 32 and each acid gas adsorption device 1. Therefore, the flow rate of the desorbed gas flowing through each acid gas adsorption device 1 depends on the flow path resistance of the resistor 5 rather than the flow path resistances (pressure losses) of the multiple acid gas adsorption devices 1. As a result, in the desorption process, it is possible to equalize the flow rate of the desorbed gas flowing through each acid gas adsorption device 1, and it is possible to suppress the excessive rise in the temperature of the acid gas adsorption device 1 and, consequently, the deterioration of the acid gas adsorbent.

[0010] In one embodiment, the flow path resistance of the resistor 5 in the desorption process is larger than the respective flow path resistances of the multiple acid gas adsorption devices 1. The flow path 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 path resistance is a pressure loss resistance and can be measured, for example, by a differential pressure gauge installed before and after the resistor and before and after the acid gas adsorption device. The difference between the flow path resistance of the resistor 5 and the flow path 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 path resistance of the resistor in the desorption step and / or the flow path resistance between the resistor and the acid gas adsorption device is not less than the above lower limit, the influence of the flow path resistance of the acid gas adsorption device on the flow rate of the desorbed gas can be stably suppressed. If the difference between the flow path resistance of the resistor in the desorption step and / or the flow path resistance between the resistor and the acid gas adsorption device is not more than the above upper limit, the desorbed gas can be supplied to the acid gas adsorption device within an energy - practically applicable range in the desorption step.

[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, preferably 0.023 to 1.500. The friction loss coefficient is typically obtained from the Colebrook equation or the Moody diagram.

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

[0013] In one embodiment, the flow path resistance of the resistor 5 is variable. The lower the flow path resistance of the resistor 5 in the adsorption step, the more preferable it is, and typically it is smaller than the flow path resistance of the resistor 5 in the desorption step. The flow path resistance of the resistor 5 in the adsorption step is, for example, 20 kPaG (gauge pressure) or less, preferably 1 kPaG or less, more preferably 0.1 kPaG or less, still more preferably 0.08 kPaG or less, particularly preferably 0.0008 kPaG or less. If the flow path resistance of the resistor in the adsorption step is not more than the above upper limit, the gas to be treated can be efficiently supplied to each acid gas adsorption device in the adsorption step. The lower limit of the flow path resistance of the resistor in the adsorption step is, for example, 0.0001 kPaG or more, or for example 0.01 kPaG or more. In one embodiment, the flow path resistance of the resistor 5 in the adsorption step is smaller than the flow path resistance of each of the plurality of acid gas adsorption devices 1. Thereby, the gas to be treated can be supplied to the acid gas adsorption device more efficiently.

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

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

[0016] Furthermore, as shown in Figure 5, the acidic gas recovery system 100 may also 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 acidic gas adsorption device via the bypass line. In this case, the flow path resistance (pressure loss) of the resistor 5 may be constant in both the adsorption and desorption processes. When the flow path resistance of the resistor 5 is constant, its 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] Examples of acidic gases included in the gas to be treated include carbon dioxide (CO2), hydrogen sulfide, sulfur dioxide, nitrogen dioxide, dimethyl sulfide (DMS), and hydrogen chloride. 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 also contain nitrogen in addition to CO2. Typically, the CO2-containing gas is air (atmosphere). The CO2 concentration in the CO2-containing gas is, for example, 100 ppm (by volume) or more and 2% by volume or less. The following section details the case where the acidic gas is carbon dioxide (CO2).

[0018] B. Details of the Acid Gas Recovery System Next, with reference to Figure 1, the details of the acid gas recovery system 100 will be described. The illustrated example of the acid gas recovery system 100 includes, in addition to the above-mentioned multiple acid gas adsorption devices 1, fluid supply line 3, and multiple resistors 5, an acid gas supply blower 2, a desorption gas supply unit 6, and a recovery unit 4. When the gas to be processed by the acid gas adsorption device is a CO2-containing gas, the acid gas adsorption device 1 is a carbon dioxide adsorption device 1a. The illustrated example of the acid gas recovery system 100 includes four acid gas adsorption devices 1, but the number of acid gas adsorption devices 1 is not limited to this. The number of acid gas adsorption devices 1 may be, for example, two or more, preferably four or more, and for example, ten or less.

[0019] B-1. First Embodiment of Acid Gas Adsorption Apparatus As shown in Figure 2, in one embodiment, the acid gas adsorption device 1 comprises a plurality of adsorption material layers 71.

[0020] Multiple adsorbent layers 71 are stacked with spacing between them 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. Among the multiple adsorbent layers 71, the spacing between adjacent adsorbent layers 71 is, for example, 0.5 cm or more and 1.5 cm or less.

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

[0022] The flexible fiber member 73 allows the passage of gas and restricts the passage of pellet-shaped adsorbent. Typically, the flexible fiber member 73 is formed in a hollow shape (bag 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 preferably polyethylene terephthalate fibers, polyethylene fibers, and cellulose fibers. The thickness of the flexible fiber member 73 is, for example, 25 μm to 500 μm.

[0023] Multiple pellet-shaped adsorbents 72 are filled inside a flexible fiber member 73 having a hollow shape (bag shape). The pellet-shaped adsorbents 72 function as acid gas adsorbents, and typically function 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 nanofiberized cellulose. The average primary particle diameter of the pellet-shaped adsorbents 72 is, for example, 60 μm to 1200 μm. The filling ratio of the pellet-shaped adsorbents 72 in the adsorbent layer 71 can be any appropriate value.

[0024] The illustrated example of the acid gas adsorption apparatus 1 further includes a plurality of spacers 74. The spacers 74 are sandwiched between adjacent 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 roughly zigzag shape when viewed from a direction perpendicular to the thickness direction of the adsorbent layers 71 (the depth direction of the paper in Figure 1).

[0025] An example of such an acidic gas adsorption apparatus 1 is the gas separation unit described in International Publication No. 2014 / 170184. The entire description of this publication is incorporated herein by reference.

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

[0027] The structure of the substrate 10 is not particularly limited and can be, for example, a honeycomb structure, a filter structure such as a filter cloth, or a pellet structure. The acidic gas adsorption layer 15 is not particularly limited as long as it is placed on the surface of the substrate 10.

[0028] B-2-1. Substrate (honeycomb-shaped substrate) In one embodiment, the base material 10 is a honeycomb-shaped base material 10a. The honeycomb-shaped base material 10a includes partition walls 13 that define a plurality of cells 14. Cell 14 extends along the length (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 Figure 4). Cell 14 has any suitable shape in a cross-section perpendicular to the length direction of the honeycomb substrate 10a. Examples of cell cross-sectional shapes include triangles, quadrilaterals, pentagons, polygons with hexagons or more, circles, and ellipses. The cross-sectional shapes and sizes of the cells may all be the same, or at least some may differ. Among such cell cross-sectional shapes, hexagons and quadrilaterals are preferred, and squares, rectangles, or hexagons are more preferred.

[0029] The cell density (i.e., the number of cells per unit area) in a cross-section perpendicular to the longitudinal direction of the honeycomb substrate can be appropriately set depending on the purpose. For example, the cell density could be 4 cells / cm². 2 ~320 cells / cm 2 This is possible. If the cell density is within this range, sufficient strength and effective GSA (geometric surface area) of the honeycomb substrate can be ensured.

[0030] The honeycomb substrate 10a has any suitable shape (overall shape). Examples of honeycomb substrate shapes include a cylindrical shape with a circular base, an elliptical columnar shape with an elliptical base, a prismatic columnar shape with a polygonal base, and a columnar shape with an irregular base. The honeycomb substrate 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 in the center of a cross-section in a direction perpendicular to the length direction.

[0031] The honeycomb-shaped substrate 10a typically comprises an outer peripheral wall 11 and a partition wall 13 located inside the outer peripheral wall 11. In the illustrated example, the outer peripheral wall 11 and the partition wall 13 are formed integrally. The outer peripheral wall 11 and the partition wall 13 may be separate components.

[0032] The outer periphery wall 11 has a cylindrical shape. The thickness of the outer periphery wall 11 can be set arbitrarily and appropriately. For example, the thickness of the outer periphery wall 11 is 0.1 mm to 10 mm.

[0033] The partition wall 13 defines multiple cells 14. More specifically, the partition wall 13 has a first partition wall 13a and a second partition wall 13b that are orthogonal to each other, and the first partition wall 13a and the second partition wall 13b define multiple cells 14. The cross-sectional shape of the cells 14 is rectangular, except for the parts where the first partition wall 13a and the second partition wall 13b are in contact with the outer periphery wall 11. Note that the configuration of the partition wall is not limited to the partition wall 13 described above. The partition wall may have a first partition wall extending in the radial direction and a second partition wall extending in the circumferential direction, and these may define multiple cells.

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

[0035] The porosity of the partition wall 13 can be appropriately set depending on the purpose. The porosity of the partition wall 13 is, for example, 15% or more, preferably 20% or more, and for example, 70% or less, preferably 45% or less. The porosity can be measured, for example, by the mercury intrusion method. The bulk density of the partition walls 13 can be appropriately set depending on the purpose. For example, their bulk density may be 0.10 g / cm³. 3 Preferably 0.20 g / cm³ 3 That's all, for example, 0.60 g / cm³ 3 The following is preferably 0.50 g / cm³ 3 The following applies. Note that bulk density can be measured, for example, by the mercury intrusion method.

[0036] Typical materials for the partition wall 13 include ceramics. Examples of ceramics include silicon carbide, silicon-silicon carbide composite materials, cordierite, mullite, alumina, silicon nitride, spinel, silicon carbide-cordierite composite materials, lithium aluminum silicate, and aluminum titanate. The materials constituting the partition wall can be used individually or in combination. Among the materials constituting the partition wall, cordierite, alumina, mullite, silicon carbide, silicon-silicon carbide composite materials, and silicon nitride are preferred, and silicon carbide and silicon-silicon carbide composite materials are preferred.

[0037] Such a honeycomb-shaped substrate 10a is typically manufactured by the following method. First, a binder and water or an organic solvent are added as needed to the material powder containing the ceramic powder described above, 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 needed to produce the honeycomb-shaped substrate 10a. When firing, for example, it is fired at 1200°C to 1500°C. The firing time is, for example, 1 hour to 20 hours.

[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 channel 16 is formed in the portion of the cross-section of the cell 14 where the acidic gas adsorption layer 15 is not formed (typically the central portion). The acidic gas adsorption layer 15 may be formed on the entire inner surface of the partition wall 13 (i.e., surrounding the gas channel 16) as shown in the illustrated example, or it may be formed on a part of the surface of the partition wall. When the acidic gas adsorption layer 15 is formed on the entire inner surface of the partition wall 13, the removal efficiency of acidic gases (typically CO2) can be improved.

[0039] The gas flow path 16 extends from the first end face E1 (inlet end face) to the second end face E2 (outlet end face), similar to the cell 14. The cross-sectional shape of the gas flow path 16 can be the same as that of the cell 14 described above, preferably a hexagon or quadrilateral, and more preferably a square, rectangle or hexagon. The cross-sectional shape and size of the gas flow path 16 may all be the same, or at least some may differ. Typically, the gas to be treated as described above flows through cell 14 (more specifically, gas flow path 16) during the adsorption process. In one embodiment, the desorbed gas flows through cell 14 (more specifically, gas flow path 16) during the desorption process.

[0040] The acidic gas adsorption layer 15 contains an acidic gas adsorbent corresponding to 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 contains a carbon dioxide adsorbent as an example of an acidic gas adsorbent.

[0041] As the carbon dioxide adsorbent, any suitable compound capable of adsorbing and desorbing CO2 can be used. Examples of carbon dioxide adsorbents include nitrogen-containing compounds (described later); 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; organometallic structures (MOFs) such as MOF-74, MOF-200, and MOF-210; zeolites; activated carbon; nitrogen-doped carbon; and ionic liquids. The carbon dioxide adsorbents can be used individually or in combination.

[0042] Among carbon dioxide adsorbents, nitrogen-containing compounds and ionic liquids are preferred. 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 with added amino groups; organic polymers having primary to tertiary amino groups such as linear polyethyleneimine and branched polyethyleneimine with added primary to tertiary amino groups; piperazine compounds such as 1-(2-hydroxyethyl)piperazine; amide compounds such as polyamidoamine; polyvinylamine; and organic / inorganic compounds with added amino groups as substituents. Among nitrogen-containing compounds, preferred examples include methyldiethylamine, monoethanolamine, cyclic amine, diethanolamine, tetraethylenepentamine, ethyleneimine, linear polyethyleneimine, branched polyethyleneimine, and organic / inorganic compounds to which amino acids are attached as substituents.

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

[0044] Ionic liquids are more preferably used in combination with carbon dioxide adsorbents other than ionic liquids (hereinafter referred to as "other carbon dioxide adsorbents"). In this case, the ionic liquid coats the other carbon dioxide adsorbent (for example, a nitrogen-containing compound). This improves the performance and extends the lifespan of the carbon dioxide adsorbent. 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, and for example, 0.1 parts by mass or less, preferably 0.05 parts by mass or less, per 1 part by mass of the other carbon dioxide adsorbent. When the content ratio of the ionic liquid is within the above range, the performance of the carbon dioxide adsorbent and its lifespan can be stably improved and 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 channel. Including a porous carrier in the carbon dioxide adsorption layer can suppress the detachment of the carbon dioxide adsorbent from the carbon dioxide adsorption layer during the adsorption and / or desorption process.

[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; zeolite; carbon nanotubes; fluorinated resins such as polyvinylidene fluoride (PVDF); and the like. Preferably, metal-organic frameworks (MOFs), PVDF, activated carbon, zeolite, mesoporous silica, and mesoporous alumina are mentioned. The porous support can be used alone or in combination. Preferably, a material different from the carbon dioxide adsorbent is employed for the porous support.

[0047] The BET specific surface area of the porous support is, for example, 50 m 2 / g or more, preferably 500 m 2 / g or more. If the surface area of the porous support is at least the above lower limit, the carbon dioxide adsorbent can be stably supported, and the CO2 recovery rate can be improved. The upper limit of the BET specific surface area of the porous support is typically 2000 m 2 / g or less.

[0048] When the carbon dioxide adsorption layer contains a carbon dioxide adsorbent and a porous support, the total content ratio of the carbon dioxide adsorbent and the porous support 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 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, and for example, 99% by mass or less. The content ratio of the porous support is, for example, 0.01 part by mass or more, preferably 0.3 part by mass or more, and for example, 0.7 part by mass or less, preferably 0.5 part by mass or less, based on 1 part by mass of the carbon dioxide adsorbent. When the content ratio of the porous support is within the above range, the carbon dioxide adsorbent can be more stably supported.

[0049] Furthermore, the carbon dioxide adsorption layer may consist solely of carbon dioxide adsorbent material. In this case, the carbon dioxide adsorbent material is directly supported on the partition wall 13 and faces the gas flow path. When the carbon dioxide adsorption layer consists solely of carbon dioxide adsorbent material, the content ratio of carbon dioxide adsorbent material in the carbon dioxide adsorption layer is typically between 95.0% by mass and 100% by mass. When the content ratio of carbon dioxide adsorbent material is within the above range, a stable and excellent CO2 recovery rate can be ensured.

[0050] Such carbon dioxide adsorption layers are typically prepared by the following method: A solution of the carbon dioxide adsorbent is prepared by dissolving the carbon dioxide adsorbent in a solvent. If necessary, the porous carrier described above is added to the solvent. The order in which the carbon dioxide adsorbent and the porous carrier are added is not particularly limited. After that, the carbon dioxide adsorbent solution is applied to the substrate (specifically, the partition wall), the coating is dried, and if necessary, sintered to form a carbon dioxide adsorption layer. Alternatively, a dispersion containing a carbon dioxide adsorbent other than an ionic liquid and a porous carrier is applied to the 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 adsorption layer.

[0051] Although not shown in the figures, the acid gas adsorption apparatus 1 may include a heating element in addition to the substrate 10 and the acid gas adsorption layer 15. The heating element is capable of heating the substrate 10. Typically, the heating element is in contact with the substrate 10. If the acid gas adsorption apparatus is equipped with a heating element, the temperature of the acid gas adsorption apparatus can be smoothly raised to the desorption temperature during the desorption process.

[0052] Although not shown in the figures, the acid gas adsorption device 1 may also include a case. The case has a cylindrical shape (hollow shape) that extends in the direction of passage of the gas to be treated. Examples of cylindrical shapes include a cylindrical shape and a rectangular cylindrical 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 Figure 2), and in another embodiment, it houses a base material 10 and an acid gas adsorption layer 15 (see Figures 3 and 4).

[0053] B-3. ​​Blower for supplying acidic gases As shown in Figure 1, the acid gas supply blower 2 is configured to supply the gas to be treated (typically a CO2-containing gas) to multiple acid gas adsorption devices 1 during the adsorption process. The acid gas supply blower 2 in the illustrated example is capable of blowing the gas to be treated, which includes acid gas, toward multiple acid gas adsorption devices 1. The acid gas supply blower 2 can adopt any appropriate configuration.

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

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

[0056] B-6. Desorption gas supply unit The desorption gas supply unit 6 is configured to supply desorption gas to the acid gas adsorption device 1 during the desorption process. 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 desorption gas to the fluid supply line 3. The downstream end of the desorption gas supply line 62 in the direction of desorption gas supply is connected to the connection part 31. If the desorption gas is a recovered gas (described later), the upstream end of the desorption gas supply line 62 in the direction of desorption gas supply is connected to an intermediate tank that stores the desorption gas (typically the recovered gas), although this is not shown. The on-off valve 61 is provided on the desorption gas supply line 62 and can open and close the desorption gas supply line 62. Examples of the on-off valve 61 include a ball valve, a gate valve, and a butterfly valve, with a butterfly valve being preferred.

[0057] B-7. Recovery Unit The recovery unit 4 is configured to recover the acidic gas desorbed in the desorption process. The illustrated recovery unit 4 includes a suction pump 41 and a discharge line 42. The suction pump 41 is capable of drawing gas from within the acidic gas adsorption device. For example, a vacuum pump can be used as the suction pump 41. The discharge line 42 is typically a pipe through which gas discharged from multiple acidic gas adsorption devices 1 and heading toward the suction pump 41 passes. The upstream end of the discharge line 42 in the direction of gas passage is branched into the same number of lines as the multiple acidic gas adsorption devices 1, and connected to each acidic gas adsorption device 1. In one embodiment, the upstream end (branching section) of the discharge line 42 is connected to the outlet of the case provided by each acidic gas adsorption device 1. The downstream end of the discharge line 42 in the direction of gas passage is connected to the suction pump 41 after the above-mentioned branching sections merge.

[0058] B-8. Detour Line As shown in Figure 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 in the adsorption process bypasses the resistor 5 and is supplied to the acid gas adsorption device 1. Typically, the bypass line 34 is 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 each of the plurality of diversion sections 33. The upstream end of the bypass line 34 in the direction of gas passage is connected to the portion of the diversion section 33 between the branch section 32 and the resistor 5. The downstream end of the bypass line 34 in the direction of gas passage is connected to the portion of the diversion section 33 between the resistor 5 and the acid gas adsorption device 1. In the illustrated example, a shut-off valve 35 is provided in the bypass line 34. The shut-off valve 35 can open and close the bypass line 34. Examples of the shut-off valve 35 include a ball valve, a gate valve, and a butterfly valve, with a butterfly valve being preferred. Such an 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 fluctuations in the flow resistance of the resistor 5.

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

[0060] In the acid gas recovery system 100, an adsorption process is performed first. In the adsorption process, the on / off valve 61 is closed and the acid gas supply blower 2 is driven. As a result, the gas to be treated is sent out by the acid gas supply blower 2 and distributed and supplied to each of the multiple acid gas adsorption devices 1 via the fluid supply line 3. The temperature of each acid gas adsorption device in the adsorption process is pre-adjusted to the adsorption temperature. Furthermore, the flow resistance of the resistor in the adsorption process is preferably pre-set to be below the upper limit of the flow resistance of the resistor in the adsorption process as described above. In the illustrated example, the flow 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 multiple acid gas adsorption devices is, for example, 0°C to 50°C, and 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 acid gas adsorption device. The pressure of the gas to be treated is, for example, 0.3 × 10⁻⁶ 5 PaA (absolute pressure) or higher: 2.0 × 10 5 The pressure is less than or equal to PaA. The flow rate of the gas to be treated, delivered by the acid gas supply blower, is, for example, between 1.0 m / sec and 30 m / sec, and the flow rate of the gas to be treated, supplied to each acid gas adsorption device, is, for example, between 0.5 m / sec and 5 m / sec.

[0062] The temperature of each acidic gas adsorption apparatus in the adsorption process (adsorption temperature) 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 process (adsorption time) is, for example 15 minutes or more, preferably 30 minutes or more, and for example 3 hours or less, preferably 2 hours or less. When the adsorption temperature and / or adsorption time are within the above range, the acidic gas adsorbent can efficiently adsorb acidic gases.

[0063] After the adsorption time described above has elapsed, the operation of the acid gas supply blower 2 is stopped, and the adsorption process is completed.

[0064] The acid gas recovery rate in the adsorption process (= 100 - (acid gas concentration in the target gas that has passed through the multiple acid gas adsorption devices / acid gas concentration in the target gas before supplying to the multiple acid 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 replacement process is performed in the acid gas recovery system 100. In the replacement process, the on-off valve 61 is changed from a closed state to an open state, and the suction pump 41 is driven. As a result, the desorbed gas is supplied to the fluid supply line 3 through the desorbed gas supply line 62, and the fluid supply line 3 distributes and supplies it to each of the multiple acid gas adsorption devices 1. In this way, the inside of the acid 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 displacement process, the temperature range of the desorbed gas supplied to each acidic gas adsorption device is the same as the adsorption temperature range described above. The pressure of the desorbed gas is, for example, 0.1 × 10⁻⁶. 4 PaA (absolute pressure) or higher: 1.0 × 10 4 It is less than or equal to PaA, and also, for example, 0.1 × 10⁻⁶ 4 PaA or higher 5.0 × 10 4The PaA is less than or equal to the specified value. The duration of the substitution process (hereinafter referred to as the substitution time) is, for example, between 1 minute and 30 minutes.

[0067] In addition, during the substitution process, a purge gas different from the desorbed gas may be introduced into the acid gas adsorption device to replace the gas being treated with the purge gas inside the acid gas adsorption device. In this case, the pressure of the purge gas may be, for example, 0.1 × 10⁻⁶. 4 PaA or higher 11 x 10 4 The pressure is below PaA. The displacement time is, for example, between 1 minute and 30 minutes. Examples of purge gases include water vapor, carbon dioxide, nitrogen, and argon.

[0068] Subsequently, in the acid gas recovery system 100, a desorption process is carried out following the displacement process. In the desorption process, typically, multiple acidic gas adsorption devices 1 are heated to a desorption temperature exceeding the adsorption temperature. Alternatively, heating of the acidic gas adsorption devices may be started midway through the substitution process. Furthermore, the flow resistance of the multiple resistors is preferably set to be above the lower limit of the flow resistance of the resistors in the desorption step described above. In the illustrated example, a signal is transmitted from the control unit 9 to each resistor 5, and based on this signal, the flow resistance of each resistor 5 is changed as described above. Next, the desorbed gas is supplied to the multiple acid gas adsorption devices 1 that have been heated to the desorption temperature. More specifically, in the desorption step, the multiple acid gas adsorption devices 1 are heated to the desorption temperature, maintained at the desorption temperature for a predetermined desorption time, and the desorbed gas is supplied to each acid gas adsorption device. In the illustrated example, by maintaining the operation of the suction pump 41, the desorbed gas is uniformly distributed and supplied to each of the multiple acid gas adsorption devices 1 by 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 the recovered gas.

[0069] Preferably, the desorbed gas is the recovered gas previously recovered by an acid gas recovery system. By using the recovered gas as the desorbed gas, the acid 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 desorbed 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 apparatus in the desorption process (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 process (the desorption time during which the acid gas adsorption device is maintained at the desorption temperature) is, for example, 1 minute or more, preferably 5 minutes or more, and for example, 1 hour or less, preferably 30 minutes or less. When the desorption temperature and / or desorption time are within the above range, the acid gas can be desorbed more smoothly from the acid gas adsorbent.

[0071] As described above, when the temperature of each acid gas adsorption device reaches the desorption temperature, the acid gas held by the acid gas adsorbent is desorbed (released) from the acid gas adsorbent. The desorbed acid gas is discharged from the acid gas adsorption device 1 along 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 as described above, it may be resupplied to the acid gas adsorption device as desorbed gas, or it can be used as a raw material for various industrial products (for example, as a raw material for hydrocarbon fuels).

[0072] Subsequently, the acid gas recovery system 100 performs the adsorption process again as needed. More specifically, after stopping the operation of the suction pump 41, the adsorption process described above is performed again. In this way, the acid gas recovery system 100 allows for the sequential repetition of the adsorption process, the displacement process, and the desorption process.

[0073] Furthermore, as shown in Figure 5, if the acid gas recovery system 100 is equipped with a bypass line 34, in the adsorption process, the on-off valve 61 is closed and the on-off valve 35 is opened to drive the acid gas supply blower 2. As a result, due to the flow resistance of the resistor 5, the flow rate of the gas to be treated passing through the bypass line 34 becomes greater than the flow rate of the gas to be treated passing through the diversion section 33. Therefore, the gas to be treated described above passes through the bypass line 34 and is smoothly supplied to the acid gas adsorption device 1. Subsequently, after the adsorption time described above has elapsed, the operation of the acid gas supply blower 2 is stopped. Next, a replacement process is performed, changing the on-off valve 61 from the closed state to the open state, maintaining the on-off valve 35 in the open state, and driving the suction pump 41. Then, the desorbed gas described above passes through the bypass line 34 and is supplied to the acid gas adsorption device 1. As a result, the inside of the acid gas adsorption device 1 (typically the gas flow path 16) is replaced with the desorbed gas from the gas to be treated. After the above-mentioned substitution time has elapsed, the desorption process is performed, and while the on-off valve 61 is kept in the open state, the on-off valve 35 is changed from the open state to the closed state. As a result, the desorbed gas is restricted from passing through the bypass line 34 and is supplied to the acid gas adsorption device 1, which is heated to the above-mentioned desorption temperature, by passing through the resistor 5. Therefore, the flow rate of the desorbed gas flowing through each acid gas adsorption device 1 can be made uniform, and the recovered gas containing the acid gas and desorbed gas can be recovered smoothly. [Industrial applicability]

[0074] The acid gas recovery system according to the embodiment of the present invention can be used for the separation and recovery of acid gases, and is particularly suitable for use in the carbon dioxide capture, utilization, and storage (CCUS) cycle. [Explanation of Symbols]

[0075] 1. Acid gas adsorption device 1a Carbon dioxide adsorption device 3. Fluid supply line 32 Branching point 33 Diversion section 34 Detour Line 100 Acid Gas Recovery System 100a carbon dioxide capture system

Claims

1. Multiple acid gas adsorption devices containing acid gas adsorbents; An acid gas recovery system comprising: a fluid supply line for distributing and supplying a fluid to each of the plurality of acid gas adsorption devices; The acid gas recovery system is capable of performing an adsorption step of supplying a gas to be treated containing acid gas to a plurality of acid gas adsorption devices to adsorb the acid gas onto the acid gas adsorbent; and 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. The fluid supply line comprises: a branching section; and a plurality of flow distribution sections connecting the branching section to each of the plurality of acid gas adsorption devices; Each of the aforementioned plurality of flow dividers is provided with a resistor, In the desorption step, the flow resistance of the resistor is greater than the flow resistance of each of the multiple acid gas adsorption devices. The aforementioned resistor is an orifice plate, a nonwoven fabric, a control valve, or a heat exchanger, in an acid gas recovery system.

2. The acidic gas recovery system according to claim 1, wherein the acidic gas is carbon dioxide.

3. The resistor has a variable flow resistance, The acid gas recovery system according to claim 1 or 2, wherein in the adsorption step, the flow resistance of the resistor is smaller than the flow resistance of each of the plurality of acid gas adsorption devices.

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

5. The acidic gas recovery system according to claim 1 or 2, further comprising a bypass line that can bypass the resistor.

Images