Gas treatment apparatus and method

Abstract

To simplify recovery treatment of carbon dioxide by reducing energy cost in a gas treatment apparatus and method.SOLUTION: A gas treatment apparatus includes: an adsorption unit that is provided in a gas line through which air flows and adsorbs carbon dioxide contained in the air with an adsorbent; a concentration unit for desorbing and concentrating the carbon dioxide adsorbed by the adsorption unit; and a storage unit that stores the carbon dioxide concentrated by the concentration unit. The adsorption unit stops adsorption of the carbon dioxide when a predetermined switching time set in advance before the adsorbent reaches a breakthrough state is reached. After the adsorption of the carbon dioxide by the adsorption unit is stopped, the concentration unit causes suction force to act on a gas inlet side of the adsorption unit to desorb the carbon dioxide from the adsorption unit and concentrate the carbon dioxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY The present disclosure relates to gas treatment devices and methods for capturing and treating carbon dioxide. [Background technology]

[0002] One example of a technology for separating and capturing carbon dioxide (CO2) directly from the atmosphere (air) is DAC (Direct Air Capture). Such carbon dioxide capture technology is described, for example, in the following patent document. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 246383 [Patent Document 2] Patent Publication No. 2021-35654 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, when separating and recovering carbon dioxide from air, first, the air is passed through an adsorbent to allow the adsorbent to adsorb the carbon dioxide in the air. Next, the adsorbent with the adsorbed carbon dioxide is subjected to a heating treatment or a decompression treatment to recover the carbon dioxide adsorbed to the adsorbent. In other words, with conventional technology, a heating treatment or a decompression treatment is performed to separate and recover carbon dioxide from the adsorbent, which poses a problem of requiring a great deal of energy.

[0005] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a gas treatment device and method that simplifies the carbon dioxide recovery process by reducing energy costs. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the gas treatment device of the present disclosure comprises an adsorption unit that is provided in a gas line through which air flows and adsorbs carbon dioxide contained in the air using an adsorbent, a concentration unit that desorbs and concentrates the carbon dioxide adsorbed in the adsorption unit, and a storage unit that stores the carbon dioxide concentrated in the concentration unit, wherein the adsorption unit stops adsorbing the carbon dioxide when a predetermined switching time is reached before the adsorbent reaches a breakthrough state, and the concentration unit applies a suction force to the gas inlet side of the adsorption unit after the adsorption of the carbon dioxide by the adsorption unit has stopped, thereby desorbing and concentrating the carbon dioxide from the adsorption unit.

[0007] The gas treatment method disclosed herein also includes the steps of: adsorbing carbon dioxide contained in the air with an adsorbent in an adsorption tower; switching the adsorption tower that adsorbs the carbon dioxide when a predetermined switching time is reached before the adsorbent reaches a breakthrough state; and desorbing, concentrating, and storing the carbon dioxide adsorbed by the adsorbent in the adsorption tower before the switching. [Effects of the Invention]

[0008] According to the gas treatment device and method of the present disclosure, it is possible to reduce energy costs and thereby simplify the carbon dioxide recovery process. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of the gas treatment device of this embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the treatment of radioactive gas by the gas treatment device. [Figure 3] FIG. 3 is a schematic diagram showing the air treatment by the gas treatment device. [Figure 4] FIG. 4 is a schematic diagram showing the principle of carbon dioxide recovery treatment by the gas treatment device of this embodiment. [Figure 5] FIG. 5 is a schematic diagram showing the carbon dioxide recovery process using a gas treatment device. [Figure 6]FIG. 6 is a schematic diagram showing the process of concentrating carbon dioxide using a gas treatment device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0011] <Gas treatment equipment> FIG. 1 is a schematic diagram showing the configuration of the gas treatment device of this embodiment.

[0012] In the first embodiment, as shown in Fig. 1, a nuclear power plant 10 has a nuclear reactor. In this embodiment, the nuclear reactor is a pressurized water reactor (PWR). However, the nuclear reactor is not limited to a pressurized water reactor, and may be a boiling water reactor (BWR) or the like.

[0013] The reactor containment vessel 11 houses a pressurized water reactor 12 and multiple (one shown in the figure) steam generators 13. The pressurized water reactor 12 and the steam generator 13 are connected via a high-temperature side supply pipe 14 and a low-temperature side supply pipe 15. A pressurizer 16 is provided on the high-temperature side supply pipe 14, and a primary system cooling water pump 17 is provided on the low-temperature side supply pipe 15.

[0014] The reactor containment vessel 11 is connected to a filter vent device 20, and a gas processing device 30 is connected to the filter vent device 20.

[0015] The filter vent device 20 is connected to the reactor containment vessel 11. For example, when a severe accident occurs, a large amount of radioactive gas is generated inside the reactor containment vessel 11. The filter vent device 20 releases and processes the radioactive gas from the reactor containment vessel 11. The radioactive gas is introduced into the filter vent device 20 from the reactor containment vessel 11. The radioactive gas includes air, steam, cesium, iodine, radioactive fine particles, radioactive noble gases, etc. The filter vent device 20 captures and removes cesium, iodine, and radioactive fine particles from the radioactive gas.

[0016] The radioactive gas treated in the filter vent device 20 is introduced into the gas treatment device 30. The radioactive gas treated in the filter vent device 20 includes air, water vapor, radioactive noble gases, etc. The radioactive noble gases include xenon (Xe-133), krypton (Kr-85), etc. The gas treatment device 30 adsorbs and removes the radioactive noble gases from the radioactive gas, and concentrates and stores the radioactive noble gases. During this time, the concentrated radioactive noble gases are stored until they are ready for final disposal.

[0017] Air from a predetermined area is introduced into the gas treatment device 30. The air contains nitrogen, oxygen, carbon dioxide, etc. The gas treatment device 30 adsorbs and removes carbon dioxide from the air, and then concentrates and stores the carbon dioxide. During this time, the concentrated carbon dioxide is stored until it is ready for final disposal.

[0018] The reactor containment vessel 11 is connected to a filtered vent device 20 via a gas line L0. The filtered vent device 20 is connected to a switching valve 21 via a gas line (first gas line) L1. A concentration tank 22 is provided in the gas line L1. An intake section 23 is connected to the switching valve 21 via a gas line (second gas line) L2. A pump 24 is provided in the gas line L2. The switching valve 21 is connected to a gas processing device 30 via a gas line (gas supply line) L3. A dehumidification tower 25 is provided in the gas line L3.

[0019] The switching valve 21 switches between the gas line L1 and the gas line L2 with respect to the gas line L3. That is, when the gas line L1 and the gas line L3 are connected by the switching valve 21 and the gas line L2 is shut off, the radioactive gas treated in the filter vent device 20 is introduced into the gas treatment device 30. At this time, the radioactive gas is temporarily concentrated in the concentration tank 22, and then flows through the switching valve 21 into the dehumidification tower 25, where water vapor is removed before the radioactive gas is introduced into the gas treatment device 30.

[0020] On the other hand, when gas line L2 and gas line L3 are connected by switching valve 21, gas line L1 is shut off, and pump 24 is operated, air sucked through suction unit 23 is introduced into gas treatment device 30. At this time, the air flows through switching valve 21 to dehumidifying tower 25, where water vapor is removed before being introduced into gas treatment device 30.

[0021] The gas treatment device 30 selectively adsorbs and removes radioactive noble gases from gases containing radioactive noble gases introduced from gas lines L1 and L3, and concentrates and stores the radioactive noble gases. The gas treatment device 30 also selectively adsorbs and removes carbon dioxide from air introduced from gas lines L2 and L3, and concentrates and stores the carbon dioxide. The gas treatment device 30 includes an adsorption section 31, a concentration section 32, and a storage section 33.

[0022] The gas line L3 is connected downstream to a plurality of (three in this embodiment) branch lines L4, L5, and L6. The adsorption unit 31 has a plurality of (three in this embodiment) adsorption towers 41, 42, and 43. The branch lines L4, L5, and L6 are connected downstream to the inlets of the adsorption towers 41, 42, and 43. Although not shown, the adsorption towers 41, 42, and 43 each have a type of filter, for example, a container such as a tank, filled with an adsorbent. The adsorbent is, for example, a zeolite-based adsorbent, and suitable skeletal structures include FAU, LTA, MOR, and MFI.

[0023] When radioactive gas passes through the adsorption towers 41, 42, and 43, they selectively adsorb radioactive rare gases such as xenon and krypton contained in the radioactive gas. While the radioactive rare gases are selectively adsorbed through the adsorption towers 41, 42, and 43, unadsorbed air passes through them. When air passes through the adsorption towers 41, 42, and 43, they selectively adsorb carbon dioxide contained in the air. While the carbon dioxide is selectively adsorbed through the adsorption towers 41, 42, and 43, unadsorbed nitrogen (N2) and oxygen (O2) pass through them. The branch lines L4, L5, and L6 are provided with on-off valves (inlet switching valves) 44, 45, and 46.

[0024] Branch lines L7, L8, and L9 are connected to the outlets of the adsorption towers 41, 42, and 43. The branch lines L7, L8, and L9 are connected downstream to a single gas line L10. The branch lines L7, L8, and L9 are provided with on-off valves 47, 48, and 49. The gas line L10 is connected downstream to a chimney 50.

[0025] Branch lines L4, L5, L6 are connected to branch lines (concentration lines) L11, L12, L13 downstream of on-off valves 44, 45, 46, i.e., on the adsorption towers 41, 42, 43 sides, respectively. The branch lines L11, L12, L13 are connected downstream to a single gas line L14. On-off valves (separation switching valves) 51, 52, 53 are provided on the branch lines L11, L12, L13. A vacuum pump 54 is provided on the gas line L14. The vacuum pump 54 is capable of applying suction force to the inlets of the adsorption towers 41, 42, 43.

[0026] The downstream side of the gas line L14 is connected to a gas tank 55 that constitutes the storage section 33. The gas tank 55 is preferably a pressure tank. The gas tank 55 is connected to the gas line L3 by a circulation line L15. The downstream side of the circulation line L15 is connected to the gas line L3 between the dehumidification tower 25 and the on-off valves 44, 45, and 46. A circulation pump 56 is provided on the circulation line L15.

[0027] Branch lines L7, L8, and L9 are connected to branch lines L16, L17, and L18 upstream of on-off valves 47, 48, and 49, i.e., to the adsorption towers 41, 42, and 43. Branch lines L16, L17, and L18 are connected upstream to gas line L19. On-off valves 57, 58, and 59 are provided on branch lines L16, L17, and L18. An air treatment device 60 is connected upstream of gas line L19. A supply pump 61 is provided on gas line L19. Air treatment device 60 takes in external air to promote desorption during the desorption process. The supply pump 61 applies pressure to the outlets of adsorption towers 41, 42, and 43 via gas line L19 and branch lines L16, L17, L18, L7, L8, and L9, supplying air dried by air treatment device 60.

[0028] The concentration section 32 desorbs and concentrates the radioactive rare gases and carbon dioxide adsorbed in the adsorption section 31 (adsorption towers 41, 42, and 43). That is, the three adsorption towers 41, 42, and 43 are used for adsorption, for returning to atmospheric pressure, and for regeneration. For example, the adsorption tower 41 is used for adsorption, the adsorption tower 42 is used for returning to atmospheric pressure, and the adsorption tower 43 is used for regeneration. That is, the adsorption tower 41 is used for adsorption and adsorbs the radioactive rare gases and carbon dioxide. The adsorption tower 42 is used for returning to atmospheric pressure and is prepared for its next use as adsorption. The adsorption tower 43 is used for regeneration and is regenerated by desorbing and concentrating the adsorbed radioactive rare gases and carbon dioxide.

[0029] Therefore, the concentration section 32 is composed of branch lines L11, L12, and L13, a gas line L14, on-off valves 51, 52, and 53, and a vacuum pump 54. In addition to the above components, the concentration section 32 is also composed of branch lines L16, L17, and L18, a gas line L19, on-off valves 57, 58, and 59, an air treatment device 60, and a supply pump 61.

[0030] The storage unit 33 stores the radioactive rare gas and carbon dioxide concentrated in the concentration unit 32. That is, when the adsorption towers 41, 42, and 43 are used for regeneration, the radioactive rare gas and carbon dioxide adsorbed in the adsorption towers 41, 42, and 43 are desorbed and sent to a gas tank 55 serving as the storage unit 33. The gas tank 55 stores the radioactive rare gas and carbon dioxide sent from the adsorption towers 41, 42, and 43, thereby concentrating the radioactive rare gas and carbon dioxide.

[0031] In this embodiment, the above-mentioned switching valve 21, pump 24, on-off valves 44, 45, 46, 47, 48, 49, 51, 52, 53, vacuum pump 54, circulation pump 56, etc. are operated manually by an operator or automatically by a control device. In the case of automatic operation by the control device, when the control device detects a severe accident at the nuclear power plant 10, the switching valve 21 is used to introduce radioactive gas into the gas treatment device 30 for treatment. Furthermore, when the control device does not detect a severe accident at the nuclear power plant 10 or when a predetermined treatment signal is input, the control device introduces air into the gas treatment device 30 for treatment by using the switching valve 21.

[0032] In addition, in this embodiment, the adsorption unit 31 is configured with three adsorption towers 41, 42, and 43, but is not limited to this configuration. For example, the adsorption unit 31 may be configured with two adsorption towers, one of which is used for adsorption and the other for normal pressure return and regeneration. Alternatively, the adsorption unit 31 may be configured with four or more adsorption towers, with multiple adsorption towers used for adsorption, normal pressure return, and regeneration. Furthermore, although one gas tank 55 for storing a radioactive noble gas or carbon dioxide is provided as the storage unit 33, a tank for storing a radioactive noble gas and a tank for storing carbon dioxide may be provided separately.

[0033] <How to treat radioactive gas> First, we will explain the method of treating radioactive gas by operating the gas treatment device 30. Figure 2 is a schematic diagram showing the treatment of radioactive gas by the gas treatment device.

[0034] 2, in the gas treatment device 30, the adsorption unit 31 uses the adsorption tower 41 for adsorption. Therefore, the on-off valves 44 and 47 of the branch lines L4 and L7 are opened, and the on-off valves 45, 46, 48, and 49 of the branch lines L5, L6, L8, and L9 are closed.

[0035] If a severe accident occurs at the nuclear power plant 10, radioactive gas is generated inside the reactor containment vessel 11. At this time, the filter vent device 20 is activated. The filter vent device 20 releases and treats the radioactive gas from the reactor containment vessel 11. Vent gas is introduced from the reactor containment vessel 11 through a gas line L0 to the filter vent device 20, and the filter vent device 20 removes radioactive cesium, iodine, radioactive particulates, etc. contained in the vent gas. The vent gas treated by the filter vent device 20 is introduced into a gas line L1.

[0036] At this time, the switching valve 21 is operated to connect the gas line L1 and the gas line L3, and the radioactive gas treated in the filter vent device 20 is introduced into the gas line L1 and supplied to the gas treatment device 30 via the gas line L3. That is, the radioactive gas treated in the filter vent device 20 is temporarily concentrated in the concentration tank 22, then passes through the switching valve 21 and flows into the dehumidification tower 25, where water vapor is removed, before being supplied to the gas treatment device 30.

[0037] The radioactive gas supplied to the gas treatment device 30 from the gas line L1 is introduced into the adsorption tower 41 through the gas line L3 and the branch line L4. The adsorption tower 41 selectively adsorbs and removes radioactive rare gases (xenon, krypton) contained in the radioactive gas. While the radioactive rare gases are selectively adsorbed, the adsorption tower 41 allows air and other substances that have not been adsorbed to pass through, and the air and other substances are released into the atmosphere from the chimney 50 via the branch line L7 and the gas line L10.

[0038] When the amount of radioactive rare gas adsorbed in the adsorption tower 41 reaches a predetermined amount, the adsorption tower used for adsorption is switched. That is, the adsorption unit 31 uses the adsorption tower 42 for adsorption. To do this, the on-off valves 44 and 47 on the branch lines L4 and L7 are closed, and the on-off valves 45 and 48 on the branch lines L5 and L8 are opened. The radioactive gas treated in the filter vent device 20 is then introduced into the adsorption tower 42 from the gas line L3 through the branch line L5. The adsorption tower 42 adsorbs and removes radioactive rare gases (xenon and krypton) contained in the radioactive gas. The adsorption tower 42 passes air, etc. from which the radioactive rare gases have been removed, and the air, etc. is released into the atmosphere from the chimney 50 through the branch line L8 and the gas line L10. When the amount of radioactive rare gas adsorbed in the adsorption tower 42 reaches a predetermined amount, the adsorption tower used for adsorption is switched to the adsorption tower 43.

[0039] On the other hand, when radioactive gas is introduced into the adsorption tower 41 and radioactive rare gas adsorption is being performed, if the radioactive rare gas is adsorbed in the adsorption tower 43, the adsorption unit 31 performs regeneration of the adsorption tower 43. That is, the adsorption unit 31 uses the adsorption tower 43 for regeneration. To do this, the on-off valve 53 of the branch line L13 is opened, and the on-off valves 51 and 52 of the branch lines L11 and L12 are closed. Then, the vacuum pump 54 is driven. Furthermore, the on-off valves 57, 58, and 59 of the branch lines L16, L17, and L18 are closed, and the supply pump 61 is stopped.

[0040] Then, the vacuum pressure (suction force) of the vacuum pump 54 acts on the inlet of the adsorption tower 43 through the gas line L14 and the branch line L13. The adsorption tower 43 desorbs the adsorbed radioactive rare gas by the suction force acting on the inlet. The radioactive rare gas desorbed from the adsorption tower 43 is sent to the gas tank 55 of the storage unit 33 through the branch line L13 and the gas line L14 and stored therein.

[0041] Furthermore, after a predetermined time has elapsed since the start of regeneration treatment of the adsorption tower 43, the on-off valve 59 of the branch line L18 is opened and the supply pump 61 is driven. Then, the supply pump 61 supplies air dried in the air treatment device 60 to the outlet of the adsorption tower 43 via the gas line L19 and the branch lines L18 and L9. The adsorption tower 43 is backwashed by the pressure of the air supplied to the outlet, accelerating the desorption of the adsorbed radioactive rare gas.

[0042] When the regeneration process in the adsorption tower 43 is completed, the on-off valve 53 of the branch line L13 is closed and the vacuum pump 54 is stopped. In addition, the on-off valve 59 of the branch line L18 is closed and the supply pump 61 is stopped. Here, the adsorption tower 42 is used for restoring the pressure to normal pressure.

[0043] When the adsorption tower 41 is used for adsorption and the adsorption tower 43 is used for regeneration, the adsorption tower 42 is used for returning to normal pressure after the regeneration process is completed.

[0044] The adsorption section 31 sequentially uses the three adsorption towers 41, 42, and 43 for adsorption and then for regeneration, whereby the radioactive rare gas is stored in the gas tank 55 in a concentrated state.

[0045] Furthermore, if necessary, the circulation pump 56 is operated to return the radioactive rare gas stored in the gas tank 55 through the circulation line L15 to the gas line L3, and the radioactive rare gas is adsorbed in the adsorption towers 41, 42, and 43 of the adsorption section 31. When the concentration of the radioactive rare gas stored in the gas tank 55 is low, the circulation pump 56 is operated to circulate the radioactive rare gas through the circulation line L15 to the adsorption tower inlet of the adsorption section 31, and by performing adsorption and desorption again, a rare gas with a higher concentration can be stored in the gas tank 55.

[0046] <Air treatment method> Next, a description will be given of a method for treating air by operation of the gas treatment device 30. Fig. 3 is a schematic diagram showing the air treatment by the gas treatment device.

[0047] 3, in the gas treatment device 30, the adsorption unit 31 uses the adsorption tower 41 for adsorption. Therefore, the on-off valves 44 and 47 of the branch lines L4 and L7 are opened, and the on-off valves 45, 46, 48, and 49 of the branch lines L5, L6, L8, and L9 are closed.

[0048] When the nuclear power plant 10 is operating normally, no radioactive gas is generated inside the reactor containment vessel 11. At this time, the filter vent device 20 is not activated. At this time, the switching valve 21 is activated to connect the gas line L2 and the gas line L3, and air from a predetermined region is introduced into the gas line L2 and supplied to the gas treatment device 30 via the gas line L3. That is, the air from the predetermined region flows through the switching valve 21 to the dehumidification tower 25, where water vapor is removed, and then the air is supplied to the gas treatment device 30.

[0049] Air supplied to the gas treatment device 30 from gas line L2 passes through gas line L3 and branch line L4 and is introduced into the adsorption tower 41. The adsorption tower 41 selectively adsorbs and removes carbon dioxide contained in the air. While the adsorption tower 41 selectively adsorbs carbon dioxide, it passes unadsorbed nitrogen, oxygen, and the like, which are then released into the atmosphere from the chimney 50 via branch line L7 and gas line L10.

[0050] When the amount of carbon dioxide adsorbed in the adsorption tower 41 reaches a predetermined amount, the adsorption tower used for adsorption is switched. That is, the adsorption unit 31 uses the adsorption tower 42 for adsorption. To do this, the on-off valves 44 and 47 on the branch lines L4 and L7 are closed, and the on-off valves 45 and 48 on the branch lines L5 and L8 are opened. Air drawn in from a predetermined area is then introduced into the adsorption tower 42 through the gas line L3 and the branch line L5. The adsorption tower 42 adsorbs and removes carbon dioxide from the air. The adsorption tower 42 passes nitrogen and oxygen from which carbon dioxide has been removed, and the nitrogen and oxygen are released into the atmosphere from the chimney 50 through the branch line L8 and the gas line L10. When the amount of carbon dioxide adsorbed in the adsorption tower 42 reaches a predetermined amount, the adsorption tower used for adsorption is switched to the adsorption tower 43.

[0051] On the other hand, when air is introduced into the adsorption tower 41 to perform the carbon dioxide adsorption process, if carbon dioxide is adsorbed in the adsorption tower 43, the adsorption unit 31 performs a regeneration process on the adsorption tower 43. That is, the adsorption unit 31 uses the adsorption tower 43 for regeneration. To do this, the on-off valve 53 on the branch line L13 is opened, and the on-off valves 51 and 52 on the branch lines L11 and L12 are closed. Then, the vacuum pump 54 is driven. Furthermore, the on-off valves 57, 58, and 59 on the branch lines L16, L17, and L18 are closed, and the supply pump 61 is stopped.

[0052] Then, the vacuum pressure (suction force) of the vacuum pump 54 acts on the inlet of the adsorption tower 43 through the gas line L14 and the branch line L13. The adsorption tower 43 desorbs the adsorbed carbon dioxide due to the suction force acting on the inlet. The carbon dioxide desorbed from the adsorption tower 43 is sent to the gas tank 55 of the storage unit 33 through the branch line L13 and the gas line L14 and stored therein.

[0053] Furthermore, after a predetermined time has elapsed since the start of the regeneration process of the adsorption tower 43, the on-off valve 59 of the branch line L18 may be opened, the supply pump 61 may be driven, and the air dried in the air treatment device 60 may be supplied by the supply pump 61 to the outlet of the adsorption tower 43 from the gas line L19 and the branch lines L18 and L9.

[0054] When the regeneration process in the adsorption tower 43 is completed, the on-off valve 53 of the branch line L13 is closed and the vacuum pump 54 is stopped. In addition, the on-off valve 59 of the branch line L18 is closed and the supply pump 61 is stopped. Here, the adsorption tower 42 is used for restoring the pressure to normal pressure.

[0055] Then, the circulation pump 56 is operated to return the carbon dioxide stored in the gas tank 55 through the circulation line L15 to the gas line L3, and the carbon dioxide is adsorbed in the adsorption towers 41, 42, and 43 of the adsorption unit 31. When the concentration of carbon dioxide stored in the gas tank 55 is low, the circulation pump 56 is operated to circulate the carbon dioxide through the circulation line L15 to the adsorption tower inlet of the adsorption unit 31, and by performing adsorption and desorption again, carbon dioxide with an even higher concentration can be stored in the gas tank 55.

[0056] <Principle of carbon dioxide capture treatment> FIG. 4 is a schematic diagram showing the principle of carbon dioxide recovery treatment by the gas treatment device of this embodiment.

[0057] 4, the adsorption unit 31 has an adsorption tower 41 (42, 43), and the adsorption tower 41 is filled with zeolite as an adsorbent. When air passes through the adsorbent (zeolite) of the adsorption tower 41, carbon dioxide contained in the air is adsorbed.

[0058] Carbon dioxide is a linear molecule consisting of equivalent C=O bonds. Because carbon dioxide molecules have the same molecular size but opposite dipole moments, they cancel each other out, making the molecule nonpolar. However, the C=O bond is a π bond with high electron density, and the π electrons are attracted to the oxygen side, resulting in a partial negative charge. Because carbon dioxide has an electron imbalance within the molecule, electrostatic interactions occur between the C=O bond and the zeolite cation, resulting in strong adsorption to zeolite. On the other hand, nitrogen and oxygen are homonuclear diatomic molecules, meaning there is no distinction between the atoms within the molecule, resulting in nonpolar bonds. Therefore, nitrogen and oxygen do not generally interact electrostatically with zeolite, preventing strong adsorption. Consequently, zeolites have high selectivity for carbon dioxide among air components.

[0059] In the conventional gas treatment method (DAC), carbon dioxide is concentrated by adsorbing it sufficiently onto an adsorbent (zeolite), allowing it to break through, and then desorbing the carbon dioxide. During this process, the partial pressure of carbon dioxide during desorption and adsorption is 40 Pa (= concentration 400 ppm), so the carbon dioxide partial pressure must be reduced to 40 Pa or less. However, since this is difficult to achieve by vacuuming alone, a regeneration method is generally used in which heating is performed simultaneously with vacuuming.

[0060] In the gas treatment method of this embodiment, when air is passed through the adsorbent (zeolite) in the adsorption tower 41 to adsorb carbon dioxide, the carbon dioxide is not adsorbed by the entire amount of the adsorbent in the adsorption tower 41, but is instead adsorbed by a portion of the adsorbent in the adsorption tower 41 and recovered. Specifically, of the adsorbent filled in the adsorption tower 41, carbon dioxide is adsorbed by approximately one-quarter of the adsorbent from the inlet.

[0061] In the adsorption process, atmospheric air containing carbon dioxide is introduced into the adsorption tower 41. Then, the process is switched to the desorption process before the adsorption region of the adsorbent that has adsorbed carbon dioxide transitions to a breakthrough state. In the desorption process, the pressure is reduced at the inlet of the adsorption tower 41, and at this time, atmospheric components (nitrogen, oxygen, etc.) adsorbed by the adsorbent on the outlet side of the adsorption tower 41 are also desorbed and flow toward the inlet side, so the partial pressure of carbon dioxide on the inlet side of the adsorption tower 41 decreases, further accelerating the desorption of carbon dioxide.

[0062] The adsorbent in the adsorption tower 41 selectively adsorbs carbon dioxide, but any nitrogen or oxygen that slips through is adsorbed by the adsorbent on the outlet side of the adsorption tower 41. In the desorption process, by applying a reduced pressure to the inlet side of the adsorption tower 41, the carbon dioxide adsorbed on the adsorbent on the inlet side of the adsorption tower 41 is desorbed, and the nitrogen and oxygen adsorbed on the adsorbent on the outlet side of the adsorption tower 41 are also desorbed. The desorbed nitrogen and oxygen then contribute to lowering the partial pressure of carbon dioxide, further promoting the desorption of carbon dioxide. This eliminates the need for heat treatment as in conventional gas treatment methods.

[0063] <Examples of carbon dioxide capture processing> FIG. 5 is a schematic diagram showing a carbon dioxide recovery process using a gas treatment device, and FIG. 6 is a schematic diagram showing a carbon dioxide concentration process using a gas treatment device.

[0064] As shown in FIG. 5, in the gas treatment device 30, the adsorption unit 31 uses the adsorption tower 41 for adsorption. That is, the on-off valves 44 and 47 of the branch lines L4 and L7 are opened, and the on-off valves 46 and 49 of the branch lines L6 and L9 are closed. Air is introduced into the adsorption tower 41 from the branch line L4, and the adsorption tower 41 selectively adsorbs carbon dioxide using the adsorbent. At this time, the adsorption tower 41 adsorbs carbon dioxide sequentially from the adsorbent on the inlet (lower) side, and the adsorption area A of carbon dioxide increases toward the outlet (upper) side. In the adsorption tower 41, nitrogen and oxygen are adsorbed by the adsorbent on the outlet side.

[0065] Then, when the amount of carbon dioxide adsorbed in the adsorption tower 41 reaches a predetermined amount, the adsorption tower used for adsorption is switched. That is, when a predetermined switching time is reached before the adsorbent in the adsorption tower 41 reaches a breakthrough state, the adsorption tower is switched and the carbon dioxide adsorption process by the adsorption tower 41 is stopped. Here, the switching time is preferably when the actual adsorption range of carbon dioxide in the adsorbent reaches a range of 20% to 50% of the total adsorption range of the adsorbent. Furthermore, the switching time is more preferably when the actual adsorption range of carbon dioxide in the adsorbent reaches a range of 25% of the total adsorption range of the adsorbent.

[0066] Meanwhile, in the gas treatment device 30, the adsorption unit 31 uses the adsorption tower 43 for regeneration. That is, the on-off valve 53 of the branch line L13 is opened, and the on-off valve 51 of the branch line L11 is closed. Then, the vacuum pump 54 is driven. Then, the vacuum pressure of the vacuum pump 54 acts on the inlet of the adsorption tower 43 through the gas line L14 and the branch line L13. The adsorption tower 43 desorbs the adsorbed carbon dioxide by the suction force acting on the inlet. The carbon dioxide desorbed from the adsorption tower 43 is sent to the gas tank 55 of the storage unit 33 through the branch line L13 and the gas line L14 and stored therein.

[0067] At this time, a vacuum pressure acts on the inlet of the adsorption tower 41, causing the carbon dioxide adsorbed by the adsorbent on the inlet side of the adsorption tower 41 to be desorbed, and also causing the nitrogen and oxygen adsorbed by the adsorbent on the outlet side of the adsorption tower 41 to be desorbed. Then, the desorbed carbon dioxide flows toward the gas tank 55, and the desorbed nitrogen and oxygen flow toward the inlet side, which contributes to lowering the partial pressure of carbon dioxide and promotes the desorption of carbon dioxide.

[0068] However, it is difficult to increase the concentration of carbon dioxide to about 90% simply by introducing air into the adsorption tower 41 to adsorb carbon dioxide onto the adsorbent and then switching to the desorption process before the adsorption region transitions to a breakthrough state. Therefore, as shown in Fig. 6, the circulation pump 56 is operated to return the carbon dioxide stored in the gas tank 55 from the circulation line L15 to the gas line L3, and the carbon dioxide is adsorbed in the adsorption tower 41 being used for adsorption. By repeatedly returning the carbon dioxide from the gas tank 55 from the circulation line L15 to the adsorption tower 41 and adsorbing it, the concentration of carbon dioxide during desorption can be increased, and the carbon dioxide can be concentrated to a high concentration.

[0069] Although the adsorption towers are switched when the switching timing is reached before the adsorbent in the adsorption tower 41 reaches a breakthrough state, the switching timing may be delayed each time the process of returning carbon dioxide from the gas tank 55 to the adsorption tower 41 through the circulation line L15 and adsorbing it is repeated. For example, the first switching timing is set to the time when the adsorption region A in the adsorption tower has progressed to 20% from the inlet, and the second switching timing is set to the time when the adsorption region A in the adsorption tower has progressed to 30% from the inlet.

[0070] [Effects of this embodiment] The gas treatment device of the first embodiment comprises an adsorption section 31 that is provided in a gas line L3 through which air flows and that adsorbs carbon dioxide contained in the air using an adsorbent, a concentration section 32 that desorbs and concentrates the carbon dioxide adsorbed in the adsorption section 31, and a storage section 33 that stores the carbon dioxide concentrated in the concentration section 32. The adsorption section 31 stops adsorbing carbon dioxide when a predetermined switching time is reached before the adsorbent reaches a breakthrough state, and after the adsorption of carbon dioxide by the adsorption section 31 has stopped, the concentration section 32 applies suction force to the gas inlet side of the adsorption section 31 to desorb and concentrate the carbon dioxide from the adsorption section 31.

[0071] According to the gas treatment device of the first aspect, carbon dioxide can be recovered without the need for a heat treatment, and the carbon dioxide recovery process can be simplified by reducing energy costs.

[0072] The gas treatment device according to the second aspect is the gas treatment device according to the first aspect, and further, the switching time is when the actual carbon dioxide adsorption range of the adsorbent reaches 20% to 50% of the total adsorption range of the adsorbent, thereby making it possible to properly recover carbon dioxide contained in the air without causing it to flow downstream.

[0073] A gas treatment device according to a third aspect is the gas treatment device according to the first or second aspect, and further, the switching timing is the time when the actual adsorption range of carbon dioxide in the adsorbent reaches 25% of the total adsorption range of the adsorbent, thereby making it possible to properly recover carbon dioxide contained in the air without causing it to flow downstream.

[0074] A gas treatment device according to a fourth aspect is the gas treatment device according to any one of the first to third aspects, further comprising: the adsorption unit 31 including a plurality of adsorption towers 41, 42, 43 arranged in parallel on the gas line L3; and on-off valves 44, 45, 46 as inlet switching valves that switch the introduction of air into the plurality of adsorption towers 41, 42, 43; and the concentration unit 32 including branch lines L11, L12, L13 and a gas line L14 as concentration lines that desorb carbon dioxide adsorbed by the plurality of adsorption towers 41, 42, 43 and supply the carbon dioxide to the storage unit 33 for concentration; and on-off valves 51, 52, 53 as desorption switching valves that switch the desorption of carbon dioxide from the plurality of adsorption towers 41, 42, 43. Thus, by switching between the plurality of adsorption towers 41, 42, 43, it is possible to continuously perform carbon dioxide adsorption treatment and continuously perform carbon dioxide concentration treatment, thereby improving operability.

[0075] A gas treatment device according to a fifth aspect is the gas treatment device according to any one of the first to fourth aspects, and further includes a circulation line L15 that returns the carbon dioxide stored in the storage unit 33 to the adsorption unit 31, and delays the switching timing each time the process of returning the carbon dioxide stored in the storage unit 33 from the circulation line L15 to the adsorption unit 31 is repeated. This makes it possible to recover carbon dioxide at a high concentration.

[0076] A gas treatment device according to a sixth aspect is the gas treatment device according to any one of the first to fifth aspects, and further includes a gas line (first gas line) L1 through which a radioactive gas containing a radioactive noble gas flows, a gas line (second gas line) L2 through which air containing carbon dioxide flows, a gas line (gas supply line) L3 that supplies the radioactive gas or air to the adsorption unit 31, and a switching valve 21 that switches between the gas line L1 and the gas line L2 with respect to the gas line L3. This allows selective recovery of the radioactive noble gas or carbon dioxide as needed, thereby enabling effective use of the device.

[0077] A gas treatment method according to a seventh aspect includes the steps of: adsorbing carbon dioxide contained in air with an adsorbent in an adsorption tower; switching adsorption towers 41, 42, and 43 that adsorb carbon dioxide when a predetermined switching time is reached before the adsorbent reaches a breakthrough state; and desorbing, concentrating, and storing the carbon dioxide adsorbed by the adsorbent in the adsorption towers 41, 42, and 43 before switching. This allows carbon dioxide to be recovered without the need for a heating process, thereby reducing energy costs and simplifying the carbon dioxide recovery process. [Explanation of symbols]

[0078] 10. Nuclear Power Plant 11 Reactor containment vessel 12 Pressurized water reactor 13 Steam Generator 14 High temperature side feed piping 15 Low temperature side feed piping 16 Pressurizer 17 Primary cooling water pump 20 Filter vent device 21 Switching valve 22 Concentration Tank 23 Suction part 24 Pump 25 Dehumidification tower 30 Gas treatment equipment 31 Adsorption part 32 Concentration section 33 Storage section 41,42,43 Adsorption tower 44, 45, 46 On-off valve (inlet switching valve) 47, 48, 49 On-off valve 50 Chimney 51, 52, 53 On-off valve (separation switching valve) 54 Vacuum Pump 55 Gas Tank 56 Circulation Pump L0, L10, L19 gas lines L1 gas line (first gas line) L2 gas line (second gas line) L3 gas line (gas supply line) L4, L5, L6, L7, L8, L9, L16, L17, L18 branch lines L11, L12, L13 branch lines (concentration lines) L14 Gas line (concentration line)

Claims

1. an adsorption unit provided in a gas line through which air flows and configured to adsorb carbon dioxide contained in the air using an adsorbent; a concentration section that desorbs and concentrates the carbon dioxide adsorbed in the adsorption section; a storage section that stores the carbon dioxide concentrated in the concentration section; Equipped with the adsorption unit stops adsorption of the carbon dioxide when a predetermined switching time is reached before the adsorbent reaches a breakthrough state, the concentration unit, after the adsorption of the carbon dioxide by the adsorption unit has stopped, applies a suction force to a gas inlet side of the adsorption unit to desorb the carbon dioxide from the adsorption unit and concentrate it. Gas treatment equipment.

2. The switching time is a time when the actual adsorption area of ​​carbon dioxide in the adsorbent reaches a range of 20% to 50% of the total adsorption area of ​​the adsorbent. The gas treatment device of claim 1 .

3. The switching time is a time when the actual adsorption area of ​​carbon dioxide in the adsorbent reaches 25% of the total adsorption area of ​​the adsorbent. The gas treatment device of claim 2 .

4. The adsorption unit includes a plurality of adsorption towers provided in parallel on the gas line, and an inlet switching valve that switches the introduction of the air into the plurality of adsorption towers. The concentration unit includes a concentration line that desorbs the carbon dioxide adsorbed by the plurality of adsorption towers and supplies the carbon dioxide to the storage unit for concentration, and a desorption switching valve that switches the desorption of the carbon dioxide from the plurality of adsorption towers. The gas treatment device of claim 1 .

5. a circulation line for returning the carbon dioxide stored in the storage section to the adsorption section, and the switching timing is delayed each time the process of returning the carbon dioxide stored in the storage section from the circulation line to the adsorption section is repeated. The gas treatment device of claim 1 .

6. a first gas line through which a radioactive gas containing a radioactive noble gas flows, a second gas line through which air containing the carbon dioxide flows, a gas supply line that supplies the radioactive gas or the air to the adsorption unit, and a switching valve that switches between the first gas line and the second gas line for the gas supply line; The gas treatment device of claim 1 .

7. A step of adsorbing carbon dioxide contained in the air by an adsorbent in the adsorption tower; switching the adsorption tower that adsorbs the carbon dioxide when a predetermined switching time is reached before the adsorbent reaches a breakthrough state; a step of desorbing, concentrating, and storing the carbon dioxide adsorbed by the adsorbent in the adsorption tower before switching; A gas treatment method comprising:

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