Carbon dioxide recovery system

Abstract

To provide an art which can inhibit contact between a solid adsorbent supporting amine and a sulfur oxide with a simple structure.SOLUTION: A carbon dioxide recovery system recovers carbon dioxide from exhaust gas containing carbon dioxide and water and includes: a first solid adsorbent supporting amine capable of adsorbing carbon dioxide; and an adsorber which is filled with the first solid absorbent and into which the exhaust gas flows. A space at the upstream side of the first solid adsorbent in the adsorber is filled with a second solid adsorbent capable of adsorbing a sulfur oxide. The exhaust gas flowing into the adsorber passes through the second solid adsorbent and then passes through the first solid adsorbent.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a carbon dioxide capture system. [Background technology]

[0002] Zeolite 13X (Na-containing X-type zeolite) has been used as a solid adsorbent to adsorb and capture carbon dioxide from exhaust gas. However, because zeolite 13X has the property of adsorbing water, when it is used to capture carbon dioxide from exhaust gas that contains a lot of water, a process of dehydrating the exhaust gas in advance is required.

[0003] In contrast, there are adsorbents that use amines, which can adequately exhibit carbon dioxide adsorption even when exhaust gas contains a large amount of water. It is known that the adsorption of carbon dioxide by amines is inhibited by acidic gases such as sulfur oxides (SOx) contained in exhaust gas (see, for example, Non-Patent Document 1). For this reason, when using amines to capture carbon dioxide from exhaust gas, a process of desulfurizing the exhaust gas in advance is required. Patent Documents 1 and 2 disclose a method for capturing carbon dioxide by desulfurizing exhaust gas and using an aqueous solution of an amine compound as an adsorbent.

[0004] On the other hand, Patent Document 3 discloses a CO2 separation and capture device that includes a harmful component removal section that removes sulfur oxides and the like from exhaust gas, and a CO2 separation and capture section that separates and captures carbon dioxide from the exhaust gas from which sulfur oxides and the like have been removed, and also cites a solid adsorbent material in which an amine compound is supported on a porous material as an example of a CO2 absorbent material provided inside the CO2 separation and capture section. Such solid adsorbents are being studied from the viewpoint of ease of handling. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2010-516596 [Patent Document 2] JP 2020-195998 A [Patent Document 3] Patent Publication No. 2021-195270 [Non-patent literature]

[0006] [Non-Patent Document 1] Alexander P. Hallenbeck and John R. Kitchin. Effects of O2 and SO2 on the Capture Capacity of a Primary-Amine Based Polymeric CO2 Sorbent Industrial & Engineering Chemistry Research 2013 v.52 no.31 pp. 10788-10794 Summary of the Invention [Problem to be solved by the invention]

[0007] In the adsorption of carbon dioxide from exhaust gas using a solid adsorbent, it is preferable to desulfurize the exhaust gas in advance in order to suppress contact between the sulfur oxides and the solid adsorbent. However, in Patent Document 3, since the harmful component removal section and the CO2 separation and capture section are separately provided, there is a concern that the CO2 separation and capture device will become large and complicated. For this reason, there has been a demand for a technology that can suppress contact between the amine-supported solid adsorbent and the sulfur oxides with a simple structure.

[0008] The present invention has been made to solve at least part of the above-mentioned problems, and has an object to provide a technique capable of suppressing contact between a solid adsorbent material carrying an amine and sulfur oxides with a simple structure. [Means for solving the problem]

[0009] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0010] (1) According to one aspect of the present invention, there is provided a carbon dioxide capture system, comprising: a first solid adsorbent material carrying an amine capable of adsorbing carbon dioxide; and an adsorber in which the first solid adsorbent material is packed and into which the exhaust gas flows, the adsorber is packed on the upstream side of the first solid adsorbent material with a second solid adsorbent material capable of adsorbing sulfur oxides, and the exhaust gas that has flowed into the adsorber passes through the second solid adsorbent material and then the first solid adsorbent material.

[0011] According to this configuration, the second solid adsorbent capable of adsorbing sulfur oxides is packed upstream of the first solid adsorbent inside the adsorber into which the exhaust gas flows, so that the sulfur oxides contained in the exhaust gas can be adsorbed by the second solid adsorbent before coming into contact with the first solid adsorbent. Therefore, the sulfur oxides that inhibit the adsorption of carbon dioxide by the first solid adsorbent can be prevented from coming into contact with the first solid adsorbent, so that the carbon dioxide adsorption performance of the first solid adsorbent can be maintained. In addition, according to this configuration, the first solid adsorbent and the second solid adsorbent are packed in the same adsorber, which is a simple structure, so that it is possible to prevent the carbon dioxide capture system from becoming large and complicated while preventing the sulfur oxides from coming into contact with the first solid adsorbent.

[0012] (2) In the carbon dioxide recovery system of the above aspect, the second solid adsorbent material may be a Na-containing Y-type zeolite. According to this configuration, since the Na-containing Y-type zeolite has a relatively low carbon dioxide adsorption capacity and a relatively high sulfur oxide adsorption capacity, the sulfur oxides contained in the exhaust gas can be adsorbed by the second solid adsorbent while suppressing the influence on the adsorption of carbon dioxide by the first solid adsorbent, and as a result, the amount of carbon dioxide adsorbed by the first solid adsorbent can be secured.

[0013] (3) In the carbon dioxide capture system of the above aspect, a value obtained by dividing a volume of the second solid adsorbent material filled inside the adsorber by a total volume obtained by adding up a volume of the first solid adsorbent material and a volume of the second solid adsorbent material filled inside the adsorber may be 0.1 or more and 0.3 or less. This configuration can particularly suppress the deterioration of the carbon dioxide adsorption performance that occurs when the first solid adsorbent material repeatedly adsorbs and desorbs carbon dioxide.

[0014] (4) The carbon dioxide capture system of the above embodiment may further include a plurality of the adsorbers, an exhaust gas supply passage that supplies the exhaust gas to the inside of each of the adsorbers, a purge gas supply passage that supplies a purge gas to the inside of each of the adsorbers, and a control unit that controls the carbon dioxide capture system, wherein the control unit executes a step of switching a path through which the exhaust gas flows in the exhaust gas supply passage to supply the exhaust gas to the inside of each of the adsorbers, and a step of switching a path through which the purge gas flows in the purge gas supply passage to supply the purge gas to the inside of each of the adsorbers. According to this configuration, it is possible to perform adsorption and desorption of carbon dioxide in each adsorber, thereby increasing the amount of carbon dioxide captured by the carbon dioxide capture system.

[0015] (5) The carbon dioxide capture system of the above aspect may further include a heat medium flow path through which a heat medium that exchanges heat with the first solid adsorbent material and the second solid adsorbent material flows, and a flow direction of the heat medium in a portion of the heat medium flow path that is disposed inside the adsorber may be opposite to a flow direction of the exhaust gas inside the adsorber. The second solid adsorbent material that adsorbs sulfur oxides tends to exhibit its ability to adsorb sulfur oxides favorably under relatively low temperature conditions. According to this configuration, the heat transfer medium whose temperature has been lowered by heat exchange with the first solid adsorbent material flows into the second solid adsorbent material, so that the amount of sulfur oxides adsorbed by the second solid adsorbent material can be increased.

[0016] (6) The carbon dioxide capture system of the above aspect may further include a reactor connected to the adsorber and containing a catalyst for synthesizing hydrocarbons using carbon dioxide and hydrogen. According to this configuration, the carbon dioxide recovered from the exhaust gas can be used to synthesize hydrocarbons, thereby making it possible to reduce the carbon dioxide contained in the exhaust gas and to recover hydrocarbons that can be used for combustion, etc.

[0017] The present invention can be realized in various forms, for example, as a carbon dioxide capture method, a control method for a carbon dioxide capture system, a computer program for executing these systems and methods, a server device for distributing this computer program, a non-transitory storage medium on which a computer program is stored, etc. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is an explanatory diagram illustrating a configuration of a carbon dioxide capture system according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram showing in detail the configuration of the suction unit and its surroundings. [Diagram 3] 10 is a flowchart showing the procedure of a collection process executed by a control unit. [Figure 4] FIG. 1 is an explanatory diagram showing the carbon dioxide recovery ratio that varies depending on the volume ratio, etc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] First Embodiment 1 is an explanatory diagram illustrating the configuration of a carbon dioxide capture system 1 according to a first embodiment of the present invention. The carbon dioxide capture system 1 is a system that captures carbon dioxide from exhaust gas containing carbon dioxide and water, and synthesizes hydrocarbons using the captured carbon dioxide. The carbon dioxide capture system 1 includes a control unit 10, a combustor 20, a dehumidifier 30, an adsorber 40, a reactor 80, and a dehumidifier 90.

[0020] The control unit 10 is a computer including a ROM, a RAM, and a CPU, and performs various controls of the carbon dioxide capture system 1. The combustor 20 is, for example, a combustion furnace in a factory, and discharges exhaust gas by combustion. This exhaust gas contains nitrogen and oxygen in addition to carbon dioxide and water. The dehumidifier 30 is connected to the combustor 20, and dehumidifies the exhaust gas discharged from the combustor 20. The adsorber 40 is connected to the dehumidifier 30, and allows the exhaust gas sent from the dehumidifier 30 to flow therein, and adsorbs the carbon dioxide contained in the exhaust gas.

[0021] Fig. 2 is an explanatory diagram showing in detail the configuration around the adsorber 40. The carbon dioxide capture system 1 includes an exhaust gas supply passage 50, an exhaust gas discharge passage 55, a purge gas supply source 60, a purge gas supply passage 70, a mixed gas delivery passage 75, and a heat medium passage HC, in addition to the configuration shown in Fig. 1.

[0022] The exhaust gas supply passage 50 is a gas passage that supplies exhaust gas from the combustor 20 to the inside of the first adsorber 40A and the inside of the second adsorber 40B, and is formed by a plurality of pipes. In addition to the dehumidifier 30, the pipes that form the exhaust gas supply passage 50 are provided with a first exhaust gas supply valve 52A and a second exhaust gas supply valve 52B. The first exhaust gas supply valve 52A and the second exhaust gas supply valve 52B can open and close each of the passages that supply exhaust gas to the first adsorber 40A or the second adsorber 40B in the exhaust gas supply passage 50. These valves can not only open and close each passage, but also adjust the flow rate in each passage. The opening and closing of the first exhaust gas supply valve 52A and the second exhaust gas supply valve 52B is controlled by the control unit 10.

[0023] The carbon dioxide capture system 1 includes a first adsorber 40A and a second adsorber 40B as the adsorbers 40. The first adsorber 40A and the second adsorber 40B are collectively referred to as the adsorbers 40. In this embodiment, the first adsorber 40A and the second adsorber 40B are each composed of a cylindrical portion filled with first solid adsorbent materials 41A, 41B and second solid adsorbent materials 42A, 42B, which will be described later, and hemispherical portions connected to both ends of the cylindrical portion.

[0024] The first adsorber 40A is filled with a first solid adsorbent 41A, and exhaust gas flows into the first adsorber 40A through an exhaust gas supply passage 50. The first solid adsorbent 41A is an adsorbent carrying an amine capable of adsorbing carbon dioxide. The first solid adsorbent 41A is formed by filling the first adsorber 40A with a pellet-shaped member carrying an amine. The second adsorber 40B is filled with a first solid adsorbent 41B similar to the first solid adsorbent 41A in the first adsorber 40A. The first solid adsorbent 41A and the first solid adsorbent 41B are collectively referred to as the first solid adsorbent 41.

[0025] The pellet-shaped member that serves as the base of the first solid adsorbent 41 is produced by the following procedure. First, pentaethylenehexamine (PEHI) is synthesized by adding formaldehyde while stirring pentaethylenehexamine at room temperature and then drying. Next, the prepared PEHI / ethanol solution (PEHI concentration 20-30 wt%) is dropped onto a pellet-shaped silica carrier at room temperature for 2 hours to impregnate the silica carrier, followed by drying under reduced pressure at 80°C. This process is repeated until the amine carrying rate in the silica carrier reaches 35 wt%, thereby producing a pellet-shaped member that serves as the base of the first solid adsorbent 41.

[0026] The inside of the first adsorber 40A is filled with a second solid adsorbent 42A capable of adsorbing sulfur oxides upstream of the first solid adsorbent 41A. The upstream side here means the upstream side in the flow direction in which the exhaust gas flows into the adsorber 40 from the exhaust gas supply passage 50 and then is discharged from the adsorber 40 via the exhaust gas discharge passage 55 described later. The second solid adsorbent 42A is formed by filling the inside of the first adsorber 40A with pellet-shaped Na-containing Y-type zeolite. The Na-containing Y-type zeolite is a faujasite-type zeolite containing Na as a metal element (cation). In this way, the first solid adsorbent 41A and the second solid adsorbent 42A are both filled inside the first adsorber 40A. The second adsorber 40B is filled with a second solid adsorbent 42B similar to the second solid adsorbent 42A in the first adsorber 40A. The second solid adsorbent material 42A and the second solid adsorbent material 42B are collectively referred to as the second solid adsorbent material 42. Therefore, it can be said that the first solid adsorbent material 41 and the second solid adsorbent material 42 are filled inside the adsorber 40 such that the exhaust gas that has flowed into the adsorber 40 passes through the second solid adsorbent material 42 and then passes through the first solid adsorbent material 41.

[0027] It is known that the adsorption of carbon dioxide by the amine contained in the first solid adsorbent 41 is inhibited by acid gases such as sulfur oxides (SOx) contained in the exhaust gas. For this reason, the second solid adsorbent 42 capable of adsorbing sulfur oxides is filled upstream of the first solid adsorbent 41 inside the adsorber 40. In this embodiment, the volumes of the first solid adsorbent 41 and the second solid adsorbent 42 are set so that the value (volume ratio) obtained by dividing the volume of the second solid adsorbent 42 filled inside the adsorber 40 by the total volume of the first solid adsorbent 41 and the second solid adsorbent 42 filled inside the adsorber 40 is within the range of 0.1 or more and 0.3 or less. In this embodiment, the first solid adsorbent 41 and the second solid adsorbent 42 are fitted inside the same cylindrical part of the adsorber 40, so that the shapes of the first solid adsorbent 41 and the second solid adsorbent 42 are shapes having approximately the same cross-sectional area but different heights. In other words, the first solid adsorbent material 41 and the second solid adsorbent material 42 are formed so that when the total height of the first solid adsorbent material 41 and the second solid adsorbent material 42 is taken as 1, the height of the second solid adsorbent material 42 is within the range of 0.1 or more and 0.3 or less.

[0028] The exhaust gas discharge flow path 55 is a gas flow path for discharging the remaining gas of the exhaust gas that has not been adsorbed by the first solid adsorbent 41 to the outside of the carbon dioxide capture system 1. A first exhaust gas discharge valve 57A and a second exhaust gas discharge valve 57B are provided in the piping forming the exhaust gas discharge flow path 55. The first exhaust gas discharge valve 57A and the second exhaust gas discharge valve 57B can open and close each flow path of the exhaust gas discharge flow path 55 that discharges the exhaust gas from the first adsorber 40A or the second adsorber 40B. These valves can not only open and close each flow path but also adjust the flow rate in each flow path. The opening and closing of the first exhaust gas discharge valve 57A and the second exhaust gas discharge valve 57B is controlled by the control unit 10.

[0029] A carbon dioxide sensor 59 is provided in a pipe forming a downstream side of a position where the flow paths for discharging exhaust gas from the first adsorber 40A or the second adsorber 40B join together in the exhaust gas discharge flow path 55. The carbon dioxide sensor 59 detects the concentration of carbon dioxide in the gas discharged from the adsorber 40.

[0030] The purge gas supply source 60 is a tank that stores a purge gas. The purge gas includes hydrogen. The purge gas supply passage 70 is a gas passage that supplies gas from the purge gas supply source 60 to the inside of the first adsorber 40A and the inside of the second adsorber 40B, and is formed of a plurality of pipes. The pipes that form the purge gas supply passage 70 are provided with a first purge gas supply valve 72A and a second purge gas supply valve 72B. The first purge gas supply valve 72A and the second purge gas supply valve 72B can open and close each of the passages that supply purge gas to the first adsorber 40A or the second adsorber 40B in the purge gas supply passage 70. These valves can not only open and close each passage, but also adjust the flow rate in each passage. The opening and closing of the first purge gas supply valve 72A and the second purge gas supply valve 72B is controlled by the control unit 10. When one of the first purge gas supply valve 72A and the second purge gas supply valve 72B is opened to supply purge gas to the first adsorption device 40A and the second adsorption device 40B, the carbon dioxide adsorbed in the first solid adsorbent material 41A or the first solid adsorbent material 41B is desorbed.

[0031] The mixed gas delivery passage 75 is a gas passage for delivering the mixed gas to the reactor 80, and is formed of a plurality of pipes. The mixed gas is a gas discharged from the first adsorber 40A or the second adsorber 40B by supplying a purge gas, and is a gas containing carbon dioxide and hydrogen desorbed from the first solid adsorbent 41A or the first solid adsorbent 41B. The pipes forming the mixed gas delivery passage 75 are provided with a first mixed gas delivery valve 77A and a second mixed gas delivery valve 77B. The first mixed gas delivery valve 77A and the second mixed gas delivery valve 77B can open and close each of the passages in the mixed gas delivery passage 75 that deliver the mixed gas from the first adsorber 40A or the second adsorber 40B. These valves can not only open and close each passage, but also adjust the flow rate in each passage. The opening and closing of the first mixed gas delivery valve 77A and the second mixed gas delivery valve 77B is controlled by the control unit 10.

[0032] The heat medium flow path HC is a flow path through which the heat medium that exchanges heat with the first solid adsorbent 41 and the second solid adsorbent 42 flows, and is formed of a plurality of pipes. A part of the heat medium flow path HC is disposed inside the adsorber 40. In detail, the first adsorber 40A and the second adsorber 40B are both double-tube, and a part of the heat medium flow path HC is disposed between the outer tube and the inner tube of the double tube. In addition, another part of the heat medium flow path HC is also disposed at a position where the heat medium can exchange heat with the reactor 80 (not shown), and the heat medium is heated by the reaction heat generated when the hydrocarbons are synthesized in the reactor 80. That is, the heat medium heated by the reactor 80 flows through the heat medium flow path HC and warms the first solid adsorbents 41A, 41B and the second solid adsorbents 42A, 42B in the first adsorber 40A and the second adsorber 40B.

[0033] The piping forming the heat medium flow passage HC is provided with a first flow passage switching valve V1 and a second flow passage switching valve V2. The first flow passage switching valve V1 and the second flow passage switching valve V2 are both three-way valves, and switch the path through which the heat medium flows in the heat medium flow passage HC between a path passing through the first adsorber 40A (between the outer pipe and the inner pipe) and a path passing through the second adsorber 40B (between the outer pipe and the inner pipe). For example, when the path through which the heat medium flows is switched to a path passing through the first adsorber 40A, heat exchange is performed between the first adsorber 40A and the heat medium by the heat medium flowing through the first adsorber 40A. The switching of the path by the first flow passage switching valve V1 and the second flow passage switching valve V2 is controlled by the control unit 10. The piping forming the heat medium flow passage HC may be provided with a pump capable of promoting the flow of the heat medium and changing the flow direction.

[0034] In this embodiment, the flow direction of the heat medium in the portion of the heat medium flow path HC arranged inside the adsorber 40 is a reverse direction RD (illustrated in FIG. 2) to the flow direction of the exhaust gas inside the adsorber 40. Since the flow direction of the exhaust gas is the direction in which the exhaust gas passes through the second solid adsorbent material 42 and then passes through the first solid adsorbent material 41 inside the adsorber 40, the reverse direction RD is the flow direction in which the heat medium heated by the reaction heat of the reactor 80 exchanges heat with the first solid adsorbent material 41 and then exchanges heat with the second solid adsorbent material 42 inside the heat medium flow path HC.

[0035] Returning to the explanation of FIG. 1 , the reactor 80 is connected to the adsorber 40, and contains a catalyst (not shown) that synthesizes hydrocarbons using carbon dioxide and hydrogen. The carbon dioxide and hydrogen used in the synthesis of hydrocarbons in the reactor 80 are the carbon dioxide and hydrogen contained in the mixed gas. The dehumidifier 90 is connected to the reactor 80, and dehumidifies the hydrocarbons synthesized in the reactor 80. The dehumidifier 90 is also connected to the combustor 20, and the dehumidified hydrocarbons are used for combustion in the combustor 20.

[0036] 3 is a flowchart showing the procedure of the capture process executed by the control unit 10 in the carbon dioxide capture system 1. The capture process is a process in which carbon dioxide is captured by adsorbing carbon dioxide to the first solid adsorbent material 41 and then desorbing the carbon dioxide from the first solid adsorbent material 41. Here, the capture process targeted at the first adsorption device 40A will be described. When the capture process is started, the control unit 10 opens the first exhaust gas supply valve 52A and the first exhaust gas discharge valve 57A (step S11). It is assumed that the first purge gas supply valve 72A and the first mixed gas delivery valve 77A are closed at the time when the capture process is started.

[0037] By the process of step S11, exhaust gas flows from the combustor 20 into the first adsorber 40A through the exhaust gas supply passage 50. The exhaust gas that flows in first passes through the second solid adsorbent 42A. At this time, sulfur oxides contained in the exhaust gas are adsorbed by the second solid adsorbent 42A. The exhaust gas that has passed through the second solid adsorbent 42A then passes through the first solid adsorbent 41A. At this time, carbon dioxide contained in the exhaust gas is adsorbed by the first solid adsorbent 41A. The exhaust gas that has passed through the first solid adsorbent 41A (the remaining gas that has not been adsorbed by the first solid adsorbent 41A and the second solid adsorbent 42A) is discharged from the exhaust gas discharge passage 55 to the outside of the carbon dioxide capture system 1. The gas discharged to the outside mainly contains nitrogen and oxygen.

[0038] After opening the first exhaust gas supply valve 52A and the first exhaust gas discharge valve 57A (step S11), the control unit 10 determines whether the concentration of carbon dioxide in the gas discharged from the adsorber 40 is greater than 1% (step S12). The concentration of carbon dioxide in the gas discharged from the adsorber 40 is detected by the carbon dioxide sensor 59. If the concentration of carbon dioxide is 1% or less (step S12: NO), the control unit 10 repeats the process of step S12.

[0039] If the concentration of carbon dioxide is greater than 1% (step S12: YES), the control unit 10 closes the first exhaust gas supply valve 52A and the first exhaust gas discharge valve 57A (step S13). By the process of step S13, the inflow of exhaust gas from the combustor 20 to the first adsorber 40A is stopped.

[0040] Next, the control unit 10 opens the first purge gas supply valve 72A and the first mixed gas delivery valve 77A (step S14). By the process of step S14, the purge gas flows from the purge gas supply source 60 through the purge gas supply passage 70 into the first adsorption device 40A. The carbon dioxide adsorbed in the first solid adsorbent material 41A is desorbed from the flowing purge gas. The mixed gas, which is a mixture of the desorbed carbon dioxide and the purge gas, is delivered from the first adsorption device 40A to the reactor 80 through the mixed gas delivery passage 75.

[0041] After opening the first purge gas supply valve 72A and the first mixed gas delivery valve 77A (step S14), the control unit 10 determines whether a set time has elapsed since the process of step S14 was executed (step S15). The set time is preferably set in consideration of the time required for the carbon dioxide adsorbed by the first solid adsorbent material 41A to be desorbed. If the set time has not elapsed since the process of step S14 was executed (step S15: NO), the control unit 10 repeats the process of step S15.

[0042] If the set time has elapsed since the process of step S14 was executed (step S15: YES), the control unit 10 closes the first purge gas supply valve 72A and the first mixed gas delivery valve 77A (step S16). The process of step S16 stops the inflow of purge gas from the purge gas supply source 60 to the first adsorption device 40A. Thereafter, the control unit 10 ends the recovery process for the first adsorption device 40A.

[0043] In the second adsorber 40B, a recovery process similar to that of the first adsorber 40A is performed. In detail, in the recovery process targeted at the second adsorber 40B, the second exhaust gas supply valve 52B and the second exhaust gas exhaust valve 57B are used instead of the first exhaust gas supply valve 52A and the first exhaust gas exhaust valve 57A, and the second purge gas supply valve 72B and the second mixed gas delivery valve 77B are used instead of the first purge gas supply valve 72A and the first mixed gas delivery valve 77A, thereby performing a recovery process similar to that of the first adsorber 40A.

[0044] When the process steps S11 to S13 of the recovery process are defined as an adsorption process and the process steps S14 to S16 are defined as a desorption process, the control unit 10 controls the recovery process for each of the first adsorption device 40A and the second adsorption device 40B so that different processes are performed for each of them. In other words, when one of the adsorption process and the desorption process is performed for the first adsorption device 40A, the control unit 10 controls so that the other process is performed for the second adsorption device 40B. Therefore, for example, even if the process of step S13 has been completed in the recovery process for the first adsorption device 40A, if the process of step S16 has not yet been completed in the recovery process for the second adsorption device 40B, the process of step S14 is not started in the recovery process for the first adsorption device 40A until the process of step S16 is completed. That is, after the adsorption step in the recovery process targeted for the first adsorber 40A is completed and the desorption step in the recovery process targeted for the second adsorber 40B is completed, the desorption step in the recovery process targeted for the first adsorber 40A is started and the adsorption step in the recovery process targeted for the second adsorber 40B is started. In this manner, the control unit 10 executes a step of switching the path through which the exhaust gas flows in the exhaust gas supply flow passage 50 to supply the exhaust gas to the inside of each adsorber (the first adsorber 40A, the second adsorber 40B) (adsorption step), and a step of switching the path through which the purge gas flows in the purge gas supply flow passage 70 to supply the purge gas to the inside of each adsorber (the first adsorber 40A, the second adsorber 40B) (desorption step).

[0045] FIG. 4 is an explanatory diagram showing the carbon dioxide recovery ratio that varies depending on the volume ratio of the second solid adsorbent 42 and the like. In FIG. 4, the horizontal axis shows the volume ratio of the second solid adsorbent 42. The volume ratio of the second solid adsorbent 42 is a value obtained by dividing the volume of the second solid adsorbent 42 filled inside the adsorber 40 by the total volume obtained by adding up the volume of the first solid adsorbent 41 filled inside the adsorber 40 and the volume of the second solid adsorbent 42. The vertical axis shows the carbon dioxide recovery ratio. The carbon dioxide recovery ratio is a value obtained by dividing the average value of the amount of carbon dioxide recovered during the desorption process of the second cycle and the amount of carbon dioxide recovered during the desorption process of the third cycle by the amount of carbon dioxide recovered during the desorption process of the 800th cycle when 800 cycles of the adsorption process and the desorption process are repeated for the adsorber 40 as a durability test, where one cycle is a 15-minute adsorption process followed by a 15-minute desorption process. In the adsorption process, nitrogen was used as the balance gas, and simulated exhaust gas containing water (3%), sulfur oxides (1 ppm), oxygen (3%) and carbon dioxide (10%) was pumped at a space velocity (SV) of 6,200 h- 1 In the desorption step, nitrogen gas containing hydrogen (3%) was allowed to flow into the adsorber 40.

[0046] In Fig. 4, points E1 to E4 and points C1 to C4 indicate the recovery amount ratio of carbon dioxide at each volume ratio. Point E1 indicates the recovery amount ratio in the adsorber 40 with a volume ratio of 0.2. Point E2 indicates the recovery amount ratio in the adsorber 40 with a volume ratio of 0.1. Point E3 indicates the recovery amount ratio in the adsorber 40 with a volume ratio of 0.15. Point E4 indicates the recovery amount ratio in the adsorber 40 with a volume ratio of 0.3.

[0047] Point C1 indicates the recovery amount ratio in the adsorber 40 in which the second solid adsorbent 42 is not filled and only the first solid adsorbent 41 is filled (volume ratio 0). Point C2 indicates the recovery amount ratio in the adsorber 40 in which the solid adsorbent is a mixture of a pellet-shaped member carrying an amine and a pellet-shaped Na-containing Y-type zeolite, but the volume ratio is 0.2. In other words, point C2 indicates the recovery amount ratio in the adsorber 40 in which the first solid adsorbent 41 and the second solid adsorbent 42 are not filled separately but are integrally filled. Point C3 indicates the recovery amount ratio in the adsorber 40 in which the volume ratio is 0.4. Point C4 indicates the recovery amount ratio in the adsorber 40 in which the volume ratio is 0.5.

[0048] From a comparison between point C1 and points E1 to E4, it was confirmed that the deterioration of the carbon dioxide adsorption performance during the durability test of up to 800 cycles can be suppressed by filling a certain amount of the second solid adsorbent 42 upstream of the first solid adsorbent 41 inside the adsorber 40. Furthermore, from a comparison between points C1, C3, C4 and points E1 to E4, it was confirmed that the range in which the suppression effect can be particularly obtained is a volume ratio of the second solid adsorbent 42 to the first solid adsorbent 41 of 0.1 or more and 0.3 or less. As shown by points C3 and C4, when the volume of the second solid adsorbent 42 becomes large (the amount of Na-containing Y-type zeolite increases), the proportion of the volume of the second solid adsorbent 42 in the adsorber 40 increases, and the amount of carbon dioxide recovery decreases, which is not preferable. In addition, a comparison of points C2 and E1 confirmed that when pellet-shaped Na-containing Y-type zeolite is mixed with a pellet-shaped material carrying an amine, it becomes difficult to suppress the decline in carbon dioxide adsorption performance.

[0049] According to the carbon dioxide capture system 1 of the first embodiment described above, the second solid adsorbent 42 capable of adsorbing sulfur oxides is filled upstream of the first solid adsorbent 41 inside the adsorber 40 into which the exhaust gas flows, so that the sulfur oxides contained in the exhaust gas can be adsorbed by the second solid adsorbent 42 before coming into contact with the first solid adsorbent 41. Therefore, it is possible to suppress the sulfur oxides that inhibit the adsorption of carbon dioxide by the first solid adsorbent 41 from coming into contact with the first solid adsorbent 41, so that the adsorption performance of carbon dioxide by the first solid adsorbent 41 can be maintained. Furthermore, according to the carbon dioxide capture system 1 of the first embodiment, since it has a simple structure in which the first solid adsorbent 41 and the second solid adsorbent 42 are filled in the same adsorber 40, it is possible to suppress the contact of the sulfur oxides with the first solid adsorbent 41 while avoiding the carbon dioxide capture system 1 from becoming large and complicated.

[0050] Moreover, in the carbon dioxide capture system 1 of the first embodiment, the second solid adsorbent material 42 is Na-containing Y-type zeolite. Since Na-containing Y-type zeolite has a relatively low adsorption capacity for carbon dioxide and a relatively high adsorption capacity for sulfur oxides, it is possible to cause the second solid adsorbent material 42 to adsorb the sulfur oxides contained in the exhaust gas while suppressing any influence on the adsorption of carbon dioxide by the first solid adsorbent material 41. As a result, the amount of carbon dioxide adsorbed by the first solid adsorbent material 41 can be secured.

[0051] Furthermore, in the carbon dioxide capture system 1 of the first embodiment, the volume ratio of the second solid adsorbent material 42 to the total volume of the first solid adsorbent material 41 and the second solid adsorbent material 42 is not less than 0.1 and not more than 0.3. Therefore, as described in Fig. 4, it is possible to particularly suppress a decrease in the adsorption performance of carbon dioxide that occurs when adsorption and desorption of carbon dioxide are repeated in the first solid adsorbent material 41.

[0052] Moreover, the carbon dioxide capture system 1 of the first embodiment includes a plurality of adsorbers 40, and the control unit 10 executes a step (adsorption step) of switching the path through which the exhaust gas flows in the exhaust gas supply passage 50 to supply the exhaust gas to the inside of each of the adsorbers (the first adsorber 40A, the second adsorber 40B), and a step (desorption step) of switching the path through which the purge gas flows in the purge gas supply passage 70 to supply the purge gas to the inside of each of the adsorbers (the first adsorber 40A, the second adsorber 40B). This makes it possible to perform adsorption and desorption of carbon dioxide in each of the adsorbers 40. As a result, the amount of carbon dioxide captured by the carbon dioxide capture system 1 can be increased.

[0053] Furthermore, in the carbon dioxide capture system 1 of the first embodiment, the flow direction of the heat medium in the portion of the heat medium flow path HC arranged inside the adsorber 40 is the opposite direction RD to the flow direction of the exhaust gas inside the adsorber 40. The second solid adsorbent material 42 that adsorbs sulfur oxides tends to exhibit its ability to adsorb sulfur oxides favorably under relatively low temperature conditions. According to the carbon dioxide capture system 1 of the first embodiment, the heat medium whose temperature has been reduced by heat exchange with the first solid adsorbent material 41 flows to the second solid adsorbent material 42, so that the amount of sulfur oxides adsorbed by the second solid adsorbent material 42 can be increased.

[0054] Furthermore, in the carbon dioxide capture system 1 of the first embodiment, the reactor 80 contains a catalyst that synthesizes hydrocarbons using carbon dioxide and hydrogen. Therefore, the carbon dioxide captured from the exhaust gas can be used to synthesize hydrocarbons. Therefore, it is possible to reduce the carbon dioxide contained in the exhaust gas and to capture hydrocarbons that can be used for combustion, etc.

[0055] <Modifications of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit and scope of the invention. For example, the following modifications are also possible.

[0056] In the above embodiment, a heat exchanger capable of exchanging heat with the exhaust gas discharged from the combustor 20 may be provided between the combustor 20 and the dehumidifier 30. Also, the dehumidifier 30 does not need to be provided, and the exhaust gas from the combustor 20 may be supplied to the adsorber 40 without passing through the dehumidifier 30.

[0057] In the above embodiment, the second solid adsorbent 42 is Na-containing Y-type zeolite, but is not limited thereto. As described above, since the volume ratio of the second solid adsorbent 42 to the total volume of the first solid adsorbent 41 and the second solid adsorbent 42 is preferably 0.1 or more and 0.3 or less, the amount of the second solid adsorbent 42 filled in the adsorber 40 is smaller than that of the first solid adsorbent 41. Therefore, any material may be used as long as it has the property of adsorbing sulfur oxides, and may be, for example, zeolite 13X. Of course, among materials having the property of adsorbing sulfur oxides, a material having the property of not easily adsorbing carbon dioxide is more preferable.

[0058] In the above embodiment, the purge gas contains hydrogen, but it does not have to contain hydrogen as long as it can desorb the carbon dioxide adsorbed in the first solid adsorbent material 41. In such a case, the hydrogen used for synthesizing hydrocarbons in the reactor 80 is supplied to the reactor 80 separately.

[0059] In the above embodiment, both the first adsorption device 40A and the second adsorption device 40B are double-tube structures, and a part of the heat medium flow path HC is disposed between the outer tube and the inner tube of the double tube, but this is not limited to the above. For example, both the first adsorption device 40A and the second adsorption device 40B may have a multi-tube structure in which a large number of thin inner tubes are disposed inside a large outer tube, and the large number of inner tubes may correspond to a part of the heat medium flow path HC.

[0060] In the above embodiment, the other part of the heat medium flow path HC is also disposed at a position where the heat medium can exchange heat with the reactor 80, but it does not have to be disposed at such a position. In such a case, it is assumed that a device for heating the heat medium is provided instead of the reactor 80.

[0061] In the above embodiment, the carbon dioxide recovered by supplying a purge gas to the adsorber 40 is used for the synthesis of hydrocarbons in the reactor 80, but this is not limiting. For example, the carbon dioxide recovered by supplying a purge gas to the adsorber 40 may be stored in a tank or the like and used as a raw material for chemical products or a raw material for beverages.

[0062] In the above embodiment, the execution of closing the first exhaust gas supply valve 52A and the first exhaust gas discharge valve 57A (step S13) by the control unit 10 is based on the concentration of carbon dioxide detected by the carbon dioxide sensor 59, but this is not limited to the above. For example, the execution of step S13 by the control unit 10 may be based on the lapse of a set time since the control unit 10 executed the process of step S11. Such a set time is preferably set in consideration of the time required for the first solid adsorbent material 41 to adsorb a sufficient amount of carbon dioxide.

[0063] Although the present aspect has been described above based on the embodiment and modified examples, the above-mentioned embodiment of the aspect is intended to facilitate understanding of the present aspect and does not limit the present aspect. The present aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents are included in the present aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0064] The present invention can also be realized in the following forms. [Application example 1] A carbon dioxide capture system for capturing carbon dioxide from an exhaust gas containing carbon dioxide and water, comprising: a first solid adsorbent material carrying an amine capable of adsorbing carbon dioxide; an adsorber in which the first solid adsorbent material is filled and into which the exhaust gas flows, a second solid adsorbent capable of adsorbing sulfur oxides is filled in the adsorber upstream of the first solid adsorbent, the exhaust gas that has flowed into the adsorber passes through the second solid adsorbent material and then passes through the first solid adsorbent material. [Application example 2] The carbon dioxide capture system according to Application Example 1, The carbon dioxide capture system, wherein the second solid adsorbent material is a Na-containing Y-type zeolite. [Application example 3] The carbon dioxide capture system according to Application Example 1 or Application Example 2, a value obtained by dividing a volume of the second solid adsorbent material filled inside the adsorber by a total volume obtained by adding up a volume of the first solid adsorbent material and a volume of the second solid adsorbent material filled inside the adsorber is 0.1 or more and 0.3 or less. [Application example 4] The carbon dioxide capture system according to any one of Application Examples 1 to 3, further comprising: A plurality of said adsorbents; an exhaust gas supply passage that supplies the exhaust gas to an interior of each of the adsorbers; a purge gas supply passage for supplying a purge gas to the inside of each of the adsorbers; A control unit that controls the carbon dioxide capture system, The control unit executes the steps of: switching a path through which the exhaust gas flows in the exhaust gas supply flow passage to supply the exhaust gas to the inside of each of the adsorbers; and switching a path through which the purge gas flows in the purge gas supply flow passage to supply the purge gas to the inside of each of the adsorbers. [Application example 5] The carbon dioxide capture system according to any one of Application Examples 1 to 4, further comprising: a heat medium flow path through which a heat medium that exchanges heat with the first solid adsorbent material and the second solid adsorbent material flows, a flow direction of the heat medium in a portion of the heat medium flow path disposed inside the adsorber is opposite to a flow direction of the exhaust gas inside the adsorber. [Application Example 6] The carbon dioxide capture system according to any one of Application Examples 1 to 5, further comprising: A carbon dioxide capture system comprising a reactor connected to the adsorber and containing a catalyst for synthesizing hydrocarbons using carbon dioxide and hydrogen. [Explanation of symbols]

[0065] 1. Carbon dioxide capture system 10...Control section 20…Combustor 30...Dehumidifier 40...Adsorber 40A…First suction unit 40B…Second adsorption device 41...First solid adsorbent 41A…First solid adsorbent 41B…First solid adsorbent 42...Second solid adsorbent 42A…Second solid adsorbent 42B…Second solid adsorbent 50...Exhaust gas supply passage 52A…First exhaust gas supply valve 52B…Second exhaust gas supply valve 55...Exhaust gas discharge passage 57A…First exhaust gas discharge valve 57B…Second exhaust gas discharge valve 59...Carbon dioxide sensor 60…Purge gas supply source 70...Purge gas supply passage 72A…First purge gas supply valve 72B…Second purge gas supply valve 75...Mixed gas delivery passage 77A…First mixed gas delivery valve 77B…Second mixed gas delivery valve 80…Reactor 90...Dehumidifier HC…heat medium flow path V1: First flow path switching valve V2: Second flow path switching valve

Claims

1. A carbon dioxide capture system for capturing carbon dioxide from an exhaust gas containing carbon dioxide and water, comprising: a first solid adsorbent material carrying an amine capable of adsorbing carbon dioxide; an adsorber in which the first solid adsorbent material is filled and into which the exhaust gas flows, a second solid adsorbent capable of adsorbing sulfur oxides is filled in the adsorber upstream of the first solid adsorbent, the exhaust gas that has flowed into the adsorber passes through the second solid adsorbent material and then passes through the first solid adsorbent material.

2. 2. The carbon dioxide capture system of claim 1, The carbon dioxide capture system, wherein the second solid adsorbent material is a Na-containing Y-type zeolite.

3. 2. The carbon dioxide capture system of claim 1, a value obtained by dividing a volume of the second solid adsorbent material filled inside the adsorber by a total volume obtained by adding up a volume of the first solid adsorbent material and a volume of the second solid adsorbent material filled inside the adsorber is 0.1 or more and 0.3 or less.

4. 2. The carbon dioxide capture system of claim 1, further comprising: A plurality of said adsorbents; an exhaust gas supply passage that supplies the exhaust gas to an interior of each of the adsorbers; a purge gas supply passage for supplying a purge gas to the inside of each of the adsorbers; A control unit that controls the carbon dioxide capture system, The control unit executes the steps of: switching a path through which the exhaust gas flows in the exhaust gas supply flow passage to supply the exhaust gas to the inside of each of the adsorbers; and switching a path through which the purge gas flows in the purge gas supply flow passage to supply the purge gas to the inside of each of the adsorbers.

5. 2. The carbon dioxide capture system of claim 1, further comprising: a heat medium flow path through which a heat medium that exchanges heat with the first solid adsorbent material and the second solid adsorbent material flows, a flow direction of the heat medium in a portion of the heat medium flow path disposed inside the adsorber is opposite to a flow direction of the exhaust gas inside the adsorber.

6. The carbon dioxide capture system according to any one of claims 1 to 5, further comprising: A carbon dioxide capture system comprising a reactor connected to the adsorber and containing a catalyst for synthesizing hydrocarbons using carbon dioxide and hydrogen.

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