Gas Recovery Device

Abstract

To provide a gas recovery apparatus that can suppress power consumption during normal operation and can reliably maintain a valve fully closed even if power is lost during a desorption step.SOLUTION: A carbon dioxide recovery apparatus 1 comprises: a reactor 11 having an adsorbent 12 therein and performing an adsorption step of adsorbing a gas to be recovered into the adsorbent 12 and a desorption step of desorbing the gas to be recovered from the adsorbent 12 by heating the surrounding area of the adsorbent 12 under reduced pressure; a fan 61 for supplying gas into the reactor 11; and butterfly type third valve 23 and fourth valve 24 provided in the gas inlet and outlet of reactor 11, and having plate-shaped valve bodies 23a and 24a that rotate around rotation axes 23b and 24b. When viewed from the normal direction of the plate surfaces of the valve bodies 23a and 24a, the rotation centers of the rotation axes 23b and 24b are offset from the center positions of the valve bodies 23a and 24a.SELECTED DRAWING: Figure 5-1

Description

[Technical Field]

[0001] The present disclosure relates to a gas recovery device. [Background technology]

[0002] A known gas capture device is, for example, direct air capture (DAC), which captures carbon dioxide (CO2) from the atmosphere in order to reduce the CO2 concentration in the atmosphere, etc. In a DAC system, for example, a gas such as air containing CO2 is drawn into a reactor holding an adsorbent, and the adsorbent is adsorbed onto the adsorbent, and the adsorbed CO2 is desorbed by heating the adsorbent under reduced pressure, thereby capturing the CO2.

[0003] In the CO2 desorption and adsorbent regeneration process for the CO2 adsorbent in the CO2 adsorption / desorption reactor of the DAC system, the pressure inside the reactor housing that houses the adsorbent is reduced to, for example, an absolute pressure of 20 kPa to 1 kPa, and at the same time, the adsorbent is heated to, for example, about 80 to 100°C using a heat exchanger placed in contact with the adsorbent to promote CO2 desorption.

[0004] In this case, when a butterfly valve is used as the air intake, exhaust, and sealing valve, and when a biasing means (return spring) is used to bias the valve body in the direction indicated, the abutment position (biasing direction) of the return spring should be set to the fully open side.

[0005] The CO2 adsorption process, which requires the valve to be kept fully open, takes longer than the CO2 desorption process, which requires the valve to be kept fully closed. Therefore, by relying on the force of the return spring to keep the valve fully open using an electric motor and gear mechanism during the adsorption process, it is possible to minimize the power consumption of the electric motor throughout the entire adsorption / desorption process. Therefore, setting the return spring as described above, i.e., setting the return spring's abutment position (biasing direction) to the fully open side, is an effective measure.

[0006] Patent Document 1 discloses a technology in which a butterfly valve can be opened and closed without the rotation axis of the valve shaft and the valve plate being aligned, thereby reducing costs by using a flat valve plate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-216184 Summary of the Invention [Problem to be solved by the invention]

[0008] However, if the return spring's abutment position (biasing direction) is set to the fully open side, if power is lost due to a lightning strike or other cause, there is a possibility that the return spring will cause the valve to open as soon as the motor torque stops maintaining the fully closed position, because the valve is abutted on the fully open side.

[0009] When solid amines are used as adsorbents, it is known that exposure to oxygen at high temperatures causes the solid amines to oxidize and deteriorate, significantly reducing their CO2 adsorption capacity. Adsorbent deterioration is something that should be avoided, both in terms of operational costs and maintaining CO2 capture volume. Therefore, in the event of a power outage, it is necessary to ensure that the valve remains fully closed during the desorption process until the temperature inside the reactor drops to a temperature where oxidation damage to the solid amine adsorbent is minimal, such as 60°C.

[0010] The object of the present disclosure is to provide a gas recovery device that can reduce power consumption during normal operation and can reliably maintain the valve fully closed even if power is lost while the desorption process is being performed. [Means for solving the problem]

[0011] The present disclosure solves the above-mentioned problems by the following means: For ease of understanding, the following description will be given with reference numerals corresponding to the embodiments of the present disclosure, but the present disclosure is not limited to these.

[0012] The first disclosure is a gas recovery device (1) including a reactor (11) having an adsorbent (12) therein and performing an adsorption process in which a gas containing a gas to be recovered is drawn into the adsorbent (12) to adsorb the gas to be recovered, and a desorption process in which the adsorbent (12) is heated under reduced pressure around the adsorbent (12) to desorb the gas to be recovered from the adsorbent (12); a fan (61) that supplies gas into the reactor (11); and butterfly-type valves (23, 24) that are provided at the gas inlet and outlet of the reactor (11) and have plate-shaped valve bodies (23a, 24a) that rotate around rotation axes (23b, 24b), where the rotation centers of the rotation axes (23b, 24b) are offset from the central positions of the valve bodies (23a, 24a) when viewed from the normal direction to the plate surfaces of the valve bodies (23a, 24a).

[0013] The second disclosure is the gas recovery device (1) according to the first disclosure, wherein the valve has a return spring (23c, 24c) that biases the valve body (23a, 24a) in the opening direction.

[0014] The third disclosure is a gas recovery device (1) according to the second disclosure, wherein the offset amount of the rotary shaft (23b, 24b) is Δd(m), and the torque of the return spring (23c, 24c) toward the opening side when the valve body (23a, 24a) is fully closed is T sc (Nm), the radius of the seal circle when the valve bodies (23a, 24a) are fully closed is R (m), and the pressure difference between the inside and outside of the reactor (11) in the desorption step is ΔP (Pa),

number

[0015] A fourth disclosure is the gas recovery apparatus (1) according to any one of the first to third disclosures, wherein the adsorbent (12) is a solid amine and the gas to be recovered is carbon dioxide. [Effects of the Invention]

[0016] According to the present disclosure, a gas recovery device can be provided that can reduce power consumption during normal operation and can reliably maintain the valve fully closed even if power is lost while the desorption process is being performed. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing a configuration relating to the flow of liquid in a carbon dioxide recovery device 1, which is a gas recovery device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing a configuration relating to gas flow in a reactor 11 of the carbon dioxide recovery device 1 of the present embodiment. [Figure 3] FIG. 2 is a diagram showing an example of a connection configuration between a reactor 11 and a fan 61. [Figure 4] FIG. 2 is a diagram showing an example of the configuration of a reactor 11. [Figure 5-1] 2 is a diagram showing an example of the internal configuration of a third valve 23. FIG. [Figure 5-2] 10 is a diagram showing an example of the internal configuration of a fourth valve 24. FIG. [Figure 6] FIG. 1 is a schematic diagram showing a butterfly valve. [Figure 7-1] FIG. 7 is an enlarged view of the rubber seal and its surroundings in FIG. 6. [Figure 7-2] FIG. 7 is an enlarged view of the rubber seal and its surroundings in FIG. 6. [Figure 8] FIG. 1 is a schematic diagram showing a butterfly-type valve in which the rotation axis is shifted from the center plane of the seal rubber in the normal direction to the plate surface of the valve body. [Figure 9-1] FIG. 9 is an enlarged view of the rubber seal and its surroundings in FIG. 8. [Figure 9-2] FIG. 9 is an enlarged view of the rubber seal and its surroundings in FIG. 8. [Figure 10] 7 is a diagram showing the valve shown in FIG. 6 as seen from the front (in the normal direction to the plate surface of the valve body) together with a diagram as seen from the direction in which the rotation axis extends. [Figure 11-1] 10 is a diagram showing a valve in which the center of rotation of the rotation axis is offset from the center position of the valve body when viewed from the normal direction of the plate surface of the valve body. FIG. [Figure 11-2] This figure shows a valve in which the center of rotation of the rotation axis is offset from the center position of the valve body when viewed from the normal direction of the plate surface of the valve body, and the position of the rotation axis is further shifted from the center plane of the seal rubber in the normal direction of the plate surface of the valve body. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] <Overall structure> Fig. 1 is a schematic diagram showing the configuration related to the flow of liquid in a carbon dioxide capture device 1, which is a gas capture device according to one embodiment of the present invention. Fig. 2 is a schematic diagram showing the configuration related to the flow of gas in a reactor 11 of the carbon dioxide capture device 1 of this embodiment. Note that the configuration related to the flow of gas in the carbon dioxide capture device 1 is omitted from Fig. 1. Note that the following description will be given using the carbon dioxide capture device 1, which is an example of a gas capture device, as an example, but the configuration for metering control using a valve according to the present disclosure can be similarly applied to the case of capturing gases other than carbon dioxide.

[0020] The carbon dioxide capture device 1 of this embodiment is applied to, for example, direct air capture (DAC) technology that captures carbon dioxide from the atmosphere in order to reduce the carbon dioxide concentration in the atmosphere. The carbon dioxide captured by the carbon dioxide capture device 1 is stored underground or reused as fuel or material.

[0021] As shown in Figures 1 and 2, the carbon dioxide recovery device 1 of this embodiment includes a reactor unit 10, a fan 61, a vacuum pump 62, a carbon dioxide recovery pump 63, a heat exchange device 80 having a heat source device 81 consisting of a heat pump, and a control device 90.

[0022] The reactor unit 10 is configured by arranging a plurality of reactors 11 in parallel, each of which adsorbs carbon dioxide. In this embodiment, a total of 16 reactors 11 are arranged by a pair of left and right reactor units 10.

[0023] As shown in FIG. 2, the reactor 11 is a carbon dioxide capture reactor including an adsorbent 12, a first valve 21, a second valve 22, a third valve 23, a fourth valve 24, and an adsorbent temperature sensor 27.

[0024] The adsorbent 12 is placed inside the reactor 11 to adsorb carbon dioxide. The adsorbent 12 is a particulate material that has the property of adsorbing carbon dioxide at low temperatures (for example, in the range of -30°C to 50°C) and desorbing (releasing) carbon dioxide at high temperatures (for example, in the range of 50°C to 110°C) when the ambient carbon dioxide concentration is low. Examples of such adsorbent 12 include solid amine carbon dioxide adsorbents formed by supporting amine on a porous material such as silica.

[0025] The first valve 21 is an on-off valve arranged at the connection between the reactor 11 and a carbon dioxide line 103 that captures carbon dioxide. A carbon dioxide capture pump 63 is arranged in the carbon dioxide line 103. The second valve 22 is an on-off valve arranged at the connection between the reactor 11 and a vacuum line 102 in which a vacuum pump 62 is arranged. The third valve 23 is a butterfly-type valve arranged at the inlet that takes in air and the like into the reactor 11. The fourth valve 24 is a butterfly-type valve arranged at the connection between the adsorption line 101 and the reactor 11. A fan 61 is arranged in the adsorption line 101.

[0026] The first valve 21, second valve 22, third valve 23, and fourth valve 24 are all controlled to open and close by a control device 90. The first valve 21, second valve 22, third valve 23, and fourth valve 24 are each configured, for example, by a normally open butterfly valve. The specific configurations of the third valve 23 and fourth valve 24 will be described later.

[0027] FIG. 3 is a diagram showing an example of a connection between the reactor 11 and the fan 61. FIG. 4 is a diagram showing an example of the configuration of the reactor 11, and also shows a portion of the interior of the reactor 11. In the example shown in FIG. 3, a total of 16 reactors 11 are provided on two opposing sides in a direction perpendicular to the extension direction (longitudinal direction) of the piping that is the adsorption line 101, with eight reactors 11 on each side. These reactors 11 are arranged in parallel with the adsorption line 101, with the fourth valve 24 connected to the adsorption line 101. In other words, the adsorption line 101 is branched and connected to each of the reactors 11. Note that the arrangement of the reactors 11 with respect to the adsorption line 101 shown in FIG. 3 is merely an example, and other arrangements may also be used.

[0028] As shown in Fig. 4, the reactor 11 includes a box-shaped housing 15, and a third valve 23 and a fourth valve 24 provided on two opposing surfaces of the housing 15. The housing 15 is a box-shaped member and includes an adsorbent 12 therein. As shown in Fig. 4, the adsorbent 12 is filled between the fins of a support that includes a plurality of thin plate-like fins and tubes (pipes) (not shown) and is stacked in a bellows shape.

[0029] One fan 61 is provided at the point where the branched portions of the adsorption line 101 converge. When driven, the fan 61 generates a gas flow from "intake" to "exhaust" in each of the multiple reactors 11 arranged upstream of the adsorption line 101. This supplies atmospheric air into the reactor 11.

[0030] For ease of understanding, Fig. 2 shows an example in which one third valve 23 and one fourth valve 24 are provided in one reactor 11. However, as shown in Figs. 3 and 4, two or more third valves 23 and four fourth valves 24 may be provided in one reactor 11.

[0031] 2, the adsorbent temperature sensor 27 measures the temperature of the adsorbent 12. The measurement information of the adsorbent temperature sensor 27 is transmitted to the control device 90.

[0032] The vacuum line 102 is branched and connected to each of the reactors 11. The vacuum pump 62 is disposed at the point where the branched portions of the vacuum line 102 converge. When the vacuum pump 62 is driven, it sucks gas from the inside of the reactor 11 through the vacuum line 102, bringing the inside of the reactor 11 into a vacuum state or a state close to a vacuum state.

[0033] The carbon dioxide line 103 branches off and is connected to each of the reactors 11. A carbon dioxide capture pump 63 is disposed at the point where the branched portions of the carbon dioxide line 103 converge. The carbon dioxide capture pump 63 applies suction force to the carbon dioxide flowing through the carbon dioxide line 103, and stores the captured carbon dioxide in a tank (not shown) for storing carbon dioxide.

[0034] Returning to Fig. 1, the heat exchanger 80 will be described. The heat exchanger 80 supplies thermal energy for heating the interior of each reactor 11 of the reactor unit 10 to a predetermined temperature when the reactor 11 performs the desorption step. The heat exchanger 80 also recovers unnecessary thermal energy when each reactor 11 performs the adsorption step.

[0035] The heat exchanger 80 of this embodiment includes a heat source device 81, a cold water tank 82, a cold water line 111, a hot water tank 83, a hot water line 112, and a three-way valve 30.

[0036] The heat source device 81 exchanges heat between the heat medium flowing in the cold water line 111 and the heat medium flowing in the hot water line 112. The heat source device 81 is, for example, a heat pump. The heat medium is, for example, a liquid such as water. Due to the heat transfer that occurs in the heat source device 81, the heat medium flowing in the cold water line 111 is cooled and the heat medium flowing in the hot water line 112 is heated.

[0037] The cold water tank 82 stores the heat medium flowing through the cold water line 111. The heat medium flowing through the cold water line 111 is stored in the cold water tank 82 and then sent to the heat source device 81. The heat medium cooled in the heat source device 81 is returned to the cold water tank 82 and then sent to each reactor 11 through the cold water line 111. A water pump 821 for circulating in the heat source device is arranged between the cold water tank 82 and the heat source device 81 on the cold water line 111. When the water pump 821 for circulating in the heat source device is driven, the heat medium flowing in the cold water line 111 circulates between the cold water tank 82 and the heat source device 81.

[0038] The cold water line 111 is branched and connected to the upstream and downstream sides of each reactor 11, connecting the cold water tank 82 with each reactor 11. A first cold water circulation water pump 822 and a second cold water circulation water pump 823 are disposed in the cold water line 111 between the cold water tank 82 and each reactor 11. A circulation line 824 is disposed in the cold water line 111, returning from the downstream side of the second cold water circulation water pump 823 to the upstream side. A circulation valve 825 is disposed in this circulation line 824.

[0039] The hot water tank 83 stores the heat medium flowing through the hot water line 112. The heat medium flowing through the hot water line 112 is stored in the hot water tank 83 and then sent to the heat source device 81. The heat medium heated in the heat source device 81 is returned to the hot water tank 83 and then sent to each reactor 11 through the hot water line 112. A water pump 831 for circulating in the heat source device is arranged between the hot water tank 83 and the heat source device 81 in the hot water line 112. When the water pump 831 for circulating in the heat source device is driven, the heat medium flowing in the hot water line 112 circulates between the hot water tank 83 and the heat source device 81.

[0040] The hot water line 112 is branched and connected to the upstream and downstream sides of each reactor 11, connecting the hot water tank 83 with each reactor 11. A first hot water circulation water pump 832 and a second hot water circulation water pump 833 are disposed in the hot water line 112 between the hot water tank 83 and each reactor 11. A circulation line 834 is disposed in the hot water line 112, returning from the downstream side of the second hot water circulation water pump 833 to the upstream side. A circulation valve 835 is disposed in this circulation line 834.

[0041] The three-way valve 30 is connected to the cold water line 111, the hot water line 112, and the reactor 11. The three-way valve 30 is disposed on each of the upstream and downstream sides of the reactor 11. The three-way valve 30 is configured to be switchable among a cold water connection state in which the cold water line 111 is connected to the reactor 11, a hot water connection state in which the hot water line 112 is connected to the reactor 11, and a cut-off state in which the connection between the cold water line 111 and the hot water line 112 and the reactor 11 is cut off.

[0042] The flow path switching of the three-way valve 30 is controlled by the control device 90. The heat medium is introduced into the reactor 11 through the three-way valve 30 arranged on the upstream side, and the heat medium is returned to the heat source device 81 side through the three-way valve 30 arranged on the downstream side.

[0043] Next, the control device 90 will be described. The control device 90 controls the operation of each part of the carbon dioxide capture device 1. The control device 90 controls the operation of devices used for carbon dioxide adsorption and desorption, such as driving and stopping. The control device 90 controls the opening and closing of the first valve 21, second valve 22, third valve 23, and fourth valve 24 provided in each reactor 11. The control device 90 also controls the driving of the fan 61, vacuum pump 62, carbon dioxide capture pump 63, heat source unit circulating water pump 821, first cold water circulating water pump 822, second cold water circulating water pump 823, heat source unit circulating water pump 831, first hot water circulating water pump 832, second hot water circulating water pump 833, etc., and controls the opening and closing of circulation valve 825 and circulation valve 835.

[0044] The control device 90 is, for example, a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The control device 90 may be configured as one device or as multiple devices.

[0045] <Carbon dioxide capture> Next, the control for recovering carbon dioxide by the control device 90 will be described. The carbon dioxide recovery device 1 alternately performs an adsorption process in which the adsorbent 12 in the reactor 11 adsorbs carbon dioxide in a gas such as the air that has been taken in, and a desorption process in which the carbon dioxide adsorbed by the adsorbent 12 is desorbed, and the desorbed carbon dioxide is compressed and stored in a tank (not shown), thereby removing and recovering carbon dioxide from the air. In this embodiment, the adsorption process and the desorption process are performed with a ratio of adsorption process time:desorption process time=7:1.

[0046] The adsorption step is a step of adsorbing carbon dioxide to the adsorbent 12 in the reactor 11. In the adsorption step, the third valve 23 and the fourth valve 24 of the reactor 11 are opened, and the first valve 21 and the second valve 22 are closed. The fan 61 is driven to generate a gas flow from upstream to downstream, and a gas containing carbon dioxide (e.g., atmospheric air) is drawn in through the third valve 23. The drawn in gas passes through the adsorbent 12 in the reactor 11. At this time, the inside of the reactor 11 is at room temperature (25°C), and the carbon dioxide in the gas is adsorbed by the adsorbent 12. Gases other than carbon dioxide, such as nitrogen and oxygen, are exhausted to the outside of the carbon dioxide recovery device 1 through the fourth valve 24 and the adsorption line 101.

[0047] The desorption step is a step of desorbing carbon dioxide from the adsorbent 12 in the reactor 11. In the desorption step, the first valve 21, the third valve 23, and the fourth valve 24 of the reactor 11 are closed, and the second valve 22 is opened. The vacuum pump 62 is operated to suck air into the reactor 11 and reduce the pressure to create a vacuum state or a near-vacuum state. At the same time, the heat exchanger 80 causes a heat medium, which serves as a heat source, to flow through the reactor 11 to supply thermal energy and raise the temperature of the adsorbent 12 in the reactor 11.

[0048] By controlling the temperature rise of the adsorbent 12, the adsorbent 12 is also heated to a predetermined temperature (e.g., 80°C) sufficient for the desorption step, and the carbon dioxide adsorbed in the adsorbent 12 is desorbed. Next, the second valve 22, the third valve 23, and the fourth valve 24 are closed, the first valve 21 is opened, and the carbon dioxide recovery pump 63 is driven, and the desorbed carbon dioxide is stored in a tank (not shown) through the carbon dioxide line 103. In this embodiment, each step is controlled so that 12 of the 16 reactors 11 perform the adsorption step and the remaining four perform the desorption step.

[0049] FIG. 5-1 illustrates an example of the internal configuration of the third valve 23. In FIG. 5-1, the right side of the third valve 23 is the atmospheric inlet, and the reactor 11 is connected to the left side of the third valve 23. In FIG. 5-1, the white arrow indicates the gas flow direction during the adsorption process. Also, in FIG. 5-1, the black arrow indicates the direction of the force that the valve body 23a receives from the atmospheric air due to a pressure difference when the reactor 11 is in a vacuum state during the desorption process. As shown in FIG. 5-1, the third valve 23 includes a valve body 23a, a rotating shaft 23b, a return spring 23c, and an actuator (not shown) (e.g., an electric motor that transmits rotational force via a reduction mechanism) that is driven and controlled by the control device 90. The valve body 23a is formed in a substantially disk shape, and a seal rubber 23d is attached to the entire outer periphery of its outer periphery. The rotating shaft 23b is integrally attached to the valve body 23a and serves as the center of rotation when the valve body 23a rotates to open and close. The return spring 23c is a torsion coil spring with fixed ends attached to the housing 23e and the rotating shaft 23b of the third valve 23, and urges the valve body 23a and the rotating shaft 23b in the opening direction. This eliminates the need to operate the actuator during the adsorption process, thereby reducing the power consumption of the third valve 23 during the adsorption process. In the third valve 23 configured as described above, the valve body 23a, which is rotated by the actuator, rotates between a fully closed state and a fully open state. This allows the third valve 23 to switch between blocking and venting the atmosphere flowing into the reactor 11.

[0050] FIG. 5-2 illustrates an example of the internal configuration of the fourth valve 24. In FIG. 5-2, the right side of the fourth valve 24 is the fan 61 side (atmospheric side), and the reactor 11 is connected to the left side of the fourth valve 24. In FIG. 5-2, the white arrow indicates the gas flow direction during the adsorption process. Also, in FIG. 5-2, the black arrow indicates the direction of the force that the valve body 24a receives from the atmosphere due to a pressure difference when the reactor 11 is in a vacuum state during the desorption process. As shown in FIG. 5-2, the fourth valve 24 includes the valve body 24a, a rotating shaft 24b, a return spring 24c, and an actuator (not shown) (e.g., an electric motor that transmits rotational force via a reduction mechanism) driven and controlled by the control device 90. The valve body 24a is formed in a substantially disk shape, and a seal rubber 24d is attached to the entire outer periphery of its outer periphery. The rotating shaft 24b is integrally attached to the valve body 24a and serves as the center of rotation when the valve body 24a rotates to open or close. The return spring 24c is a torsion coil spring with fixed ends attached to the housing 24e and the rotating shaft 24b of the fourth valve 24, and urges the valve body 24a and the rotating shaft 24b in the opening direction. This eliminates the need to operate the actuator during the adsorption process, thereby reducing the power consumption of the fourth valve 24 during the adsorption process. In the fourth valve 24 configured as described above, the valve body 24a, which is rotated by the actuator, rotates between a fully closed state and a fully open state. This allows the fourth valve 24 to switch between blocking and venting the atmosphere exhausted from the reactor 11.

[0051] In this embodiment, in both the third valve 23 and the fourth valve 24, the rotation centers of the rotary shafts 23b, 24b are offset from the center position O of the valve bodies 23a, 24a when viewed from the normal direction to the plate surfaces of the valve bodies 23a, 24a. In other words, when viewed from the extension direction of the rotary shafts 23b, 24b, the rotation centers of the rotary shafts 23b, 24b are offset from the center position O of the valve bodies 23a, 24a in the radial direction of the valve bodies 23a, 24a. The amount of offset is indicated as Δd in FIGS. 5-1 and 5-2.

[0052] Due to the offset arrangement of the rotating shafts 23b and 24b, the distance from the rotation center of the rotating shafts 23b and 24b to the seal rubbers 23d and 24d differs between the upper and lower sides of the rotating shafts 23b and 24b in Figures 5-2 and 5-3. During the desorption process indicated by the black arrows in Figures 5-1 and 5-2, when the reactor 11 is in a vacuum state, the force exerted by the atmosphere on the valve bodies 23a and 24a acts evenly on the plate surfaces of the valve bodies 23a and 24a. The force exerted by the atmosphere above the rotation center of the rotating shafts 23b and 24b in the figures generates a torque that rotates the valve bodies 23a and 24a in the closing direction. On the other hand, the force exerted by the atmosphere below the rotation center of the rotating shafts 23b and 24b in the figures generates a torque that rotates the valve bodies 23a and 24a in the opening direction.

[0053] On the upper side of the figure, the rotating shafts 23b, 24b are offset so that the distance from the rotation center of the rotating shafts 23b, 24b to the seal rubbers 23d, 24d is longer. In other words, the rotating shafts 23b, 24b are offset so that a rotational torque is generated in the direction of closing the valve bodies 23a, 24a when uniform pressure is applied to the plate surfaces of the valve bodies 23a, 24a from the atmosphere. Therefore, when the reactor 11 is in a vacuum state during the desorption step, the force that the valve bodies 23a, 24a receive from the atmosphere causes the valve bodies 23a, 24a to receive a force that rotates them in the closing direction.

[0054] If the force acting from the atmosphere to close the valve bodies 23a, 24a is greater than the force acting from the return springs 23c, 24c to open the valve bodies 23a, 24a, the valve bodies 23a, 24a can be maintained closed even if the actuator's driving force to close the valve bodies 23a, 24a is lost during a power outage or other event. In this embodiment, the force acting from the atmosphere to close the valve bodies 23a, 24a is greater than the force acting from the return springs 23c, 24c to open the valve bodies 23a, 24a. This allows the valve bodies 23a, 24a to be maintained closed even if the actuator's driving force to close the valve bodies 23a, 24a is lost during a power outage or other event. This prevents oxidation degradation of the adsorbent in such cases.

[0055] As described above, the carbon dioxide capture device 1 of this embodiment is provided with return springs 23c and 24c, which bias the valve bodies 23a and 24a in an opening direction during normal operation, thereby reducing power consumption during normal operation. Furthermore, the rotational shafts 23b and 24b are offset so that a rotational torque is generated in a direction that closes the valve bodies 23a and 24a when uniform pressure is applied to the plate surfaces of the valve bodies 23a and 24a from the atmospheric side. This allows the valve bodies 23a and 24a to remain closed even if the driving force of the actuator in the closing direction of the valve bodies 23a and 24a is lost during a power outage or other such event. Therefore, oxidation degradation of the adsorbent can be prevented even during a power outage.

[0056] As described above, the carbon dioxide capture device 1 of this embodiment can reliably maintain the valve body fully closed even if power is lost during the desorption process, thereby eliminating the risk of oxidative degradation of the adsorbent. Furthermore, the valve body can remain fully closed even if the power input to the motor that drives the valve body is reduced to zero while the valve body is held fully closed. This limits power input to the motor to only during transient operations of opening and closing the valve body, contributing to a significant reduction in power consumption. Furthermore, because there is no need to replace the adsorbent due to deterioration, the system can be quickly restarted when power is later restored.

[0057] <Example> The effectiveness of the valve of this embodiment will be explained below using specific numerical examples. Note that the numerical values ​​explained below are only examples, and various numerical values ​​are possible as long as the operating principle is satisfied. In addition, in the following explanation, no distinction is made between the third valve 23 and the fourth valve 24, and the reference numerals of the various parts will be omitted as appropriate to provide a more generalized example.

[0058] In a circular butterfly valve, which functions by rotating the valve's rotating shaft with an actuator, if the differential pressure is 90 kPa due to reduced pressure, offsetting the rotating shaft by 2.05% from the center will cause a torque of 3 Nm to act due to the differential pressure, countering the return spring torque set at 2 Nm and reliably maintaining the valve fully closed. After the heating state in the desorption process is terminated and the temperature is lowered as a preliminary step before transitioning to the adsorption process, the normal pressure return valve is opened when transitioning to the adsorption process, quickly releasing the reduced pressure and allowing the motor to immediately operate the valve normally. In the event of a power loss, the reduced pressure environment inside the reactor during the desorption process at high temperatures will act as a torque to maintain the valve fully closed, reliably preventing the opportunity for oxidation degradation due to the intrusion of external air.

[0059] The operating mechanism of the valve of this embodiment will be explained using specific numerical examples. Figure 6 is a schematic diagram of a butterfly-type valve. Figures 7-1 and 7-2 are enlarged views of the rubber seal and its surroundings in Figure 6. In the example of Figure 6, a rubber seal is installed in the outer peripheral groove of a circular butterfly valve with a radius of 75 mm. The rubber seal is 5 mm thick, the groove depth is 2.5 mm, and the outer radius of the rubber attached to the groove is 77.5 mm. When fully closed, the seal rubber deforms by 0.5 mm, and at this time, the outer radius of the rubber is 77 mm, which is equal to the inner radius of the air passage. Therefore, the differential pressure acting on the valve surface when fully closed is equivalent to the differential pressure acting on a flat disk with a radius of 77 mm. For example, when the differential pressure ΔP is 90 kPa, the force F (N) acting on a flat disk with a radius of 77 mm is given by:

[0060] F=π×0.077 2 ×90000=1676.39N

[0061] As shown in Figure 6, the rotating shaft passes through the center of the valve, and when fully closed, it comes into contact with the inner wall of the air passage as shown in Figures 7-1 and 7-2, causing the seal rubber to compress by 0.5 mm, thereby achieving sealing performance. Figures 7-1 and 7-2 are examples of the state of the seal part.

[0062] However, if the rotating shaft were to be on the same plane as the center plane of the seal rubber, as shown in Figure 6, the seal may be insufficient where the shaft and seal intersect, making it difficult to maintain a vacuum. Therefore, it is well known that in practice, the rotating shaft is positioned at a certain distance from the center plane of the seal rubber in the normal direction to the plate surface of the valve body, as shown in Figure 8. Figure 8 is a schematic diagram showing a butterfly-type valve in which the rotating shaft is shifted from the center plane of the seal rubber in the normal direction to the plate surface of the valve body. Figures 9-1 and 9-2 are enlarged views of the rubber seal and its vicinity in Figure 8. In this embodiment, as shown in Figures 5-1 and 5-2, the rotating shafts 23b and 24b are positioned away from the plate surfaces of the valve bodies 23a and 24a in the normal direction.

[0063] Note that the discussion of the torque around the shaft when the valve is fully closed is not affected by the distance from the center plane of the disk of the valve body to the axis of rotation (see Figures 11-1 and 11-2). Therefore, for simplicity, the explanation will be given using the valve model in Figure 6.

[0064] A more detailed explanation will be given using the values ​​of the valve shown in Figure 6. Figure 10 shows the valve shown in Figure 6 as viewed from the front (normal to the valve body's plate surface) together with a view from the direction of the rotation axis. Figure 11-1 shows a valve in which the center of rotation of the rotation axis is offset from the center of the valve body when viewed normal to the valve body's plate surface. Figure 11-2 shows a valve in which the center of rotation of the rotation axis is offset from the center of the valve body when viewed normal to the valve body's plate surface, and the rotation axis is further shifted from the center plane of the seal rubber in the normal to the valve body's plate surface. When the valve is fully closed and the reactor interior is depressurized, if the differential pressure ΔP across the valve is 90 kPa, as previously described, the force F (N) acting on the 77 mm flat disk is as follows:

[0065] F=π×0.077 2 ×90000=1676.39N

[0066] The radius of the seal circle when fully closed is R = 77.0 mm, and the differential pressure before and after acts perpendicular to the disk plane formed by this radius. As shown in Figure 10, for example, one end of the return spring is fixed to a reference fixed point on the housing side, and the other end is installed on the rotating shaft side, and the torque of the spring acts so that the valve rotates toward the fully open side. Note that the reason why the spring torque acts toward the fully open side is that in the carbon dioxide capture device 1 of this embodiment, the length of the adsorption process, which requires the valve to be open, is longer than the desorption process, which requires the valve to be fully closed, and therefore it is advantageous to reduce power consumption by setting the driving force of the motor that drives the valve to 0 in the fully open position.

[0067] Although not shown, the stopper that determines the fully closed and fully open positions is realized by mechanically determining the position between the rotating shaft and the reactor housing. When the rotating shaft of the valve passes through the center of the valve's seal circle as shown in Figure 6, in the fully closed state, the differential pressure ΔP acting on the area projected onto the circle is the same area of ​​the same shape above and below the central axis of the rotating shaft: (πR 2 ) / 2.

[0068] In addition, the torque T (N) around the central axis due to the pressure difference ΔP is balanced around the central axis because the torque Tu due to the area Su above the rotating shaft in the figure and the torque Td due to the area Sd below the rotating shaft in the figure are the same in magnitude (Fig. 10). Note that the torque T generated above the rotating shaft in the figure due to the pressure difference ΔP is u is expressed as ((2R 3 ) / 3)×ΔP.

[0069]

number

[0070] When the rotation axis is located at the center of the seal circle (the circle formed by the annular seal rubber when viewed from the normal direction of the plate surface of the valve body (hereinafter also referred to as "viewing the valve body from the front")), the torque around the axis due to the upper and lower semicircular areas is balanced as shown in equation (2), when the force F=πR due to the differential pressure ΔP due to the entire area of ​​the circle is 2 This is because when the "center point of the circle" which is the point of action of ΔP (center of the differential pressure load) is viewed from the front of the valve body (normal to the plate surface of the valve body), the "center point of the circle" and the rotation axis coincide.

[0071] When the valve body is viewed from the front, if the rotation axis is offset by Δd from the center point of the disc shape of the valve body, the rotation axis will be separated by Δd from the point of action of the force F caused by the differential pressure, and a torque will be generated around the axis, but this torque T is nothing other than FΔd (proof omitted). Therefore, the torque T caused by the differential pressure when the offset amount Δd is p is expressed as the following equation (3).

[0072] T p =FΔd=πR 2 ΔPΔd···Eq.(3)

[0073] By slightly offsetting the rotation axis from the center of the disk of the valve body when viewed from the front, it is possible to generate torque due to the pressure difference when the pressure is reduced during the desorption process, which closes the valve. If this generated torque is large enough to overcome the torque of the return spring, the valve can be kept fully closed even if power is lost.

[0074] In the carbon dioxide capture device of this embodiment, the rotation axis of the valve body is offset from the center of the disk of the valve body, so that the valve can be kept closed by the pressure difference when the reactor is depressurized. The relationship between each parameter required to keep the valve closed by this pressure difference is explained below. Each parameter of the butterfly valve is defined as follows:

[0075] The radius of the circular valve body when viewed from the front is R (m). This radius R is the effective radius taking into account the uniform deformation of the rubber seal installed in the peripheral groove of the disc-shaped valve body in the circumferential direction when the valve is fully closed.

[0076] The pressure difference between the inside and outside of the reactor during the desorption process is ΔP (Pa). The pressure outside the reactor is usually atmospheric pressure, and if the internal pressure is about 1 to 20 kPa, the pressure difference ΔP at around sea level is about 80 to 100 kPa.

[0077] The offset of the rotation axis of the valve body is Δd (m). Δd is the distance (offset) from the center of the disk to the rotation axis, as observed when the valve body is viewed from the front of the disk.

[0078] The torque of the return spring to the opening side when the valve is fully closed is T sc (Nm). The fully open position of the valve body is the default position.

[0079] The spring constant of the return spring is k (Nm / rad). The shaft friction of the rotary shaft of the valve body is T f (Nm). The coefficient of increase in shaft friction over time is η (>1).

[0080] The valve angle when the valve body is fully closed is θ c (rad) where the angle θ when fully closed c is set to 0 (rad).

[0081] The valve angle when the valve body is fully open is θ o (rad) where the full closing angle θ c Fully open angle θ o is generally +π / 2 (rad).

[0082] When the valve body is fully closed, the torque that tries to turn the valve body to the open side is the spring torque T defined above. sc Only.

[0083] T sc ...Equation (4)

[0084] Furthermore, when the valve body is fully closed, the torque that tries to rotate the valve body in the closing direction is the differential pressure torque Tp. If the rotation axis is offset by +Δd from the point of action of the force F caused by the differential pressure, i.e., the center point of the disk of the valve body, a differential pressure torque Tp for the offset amount Δd is generated around the axis.

[0085] T p =FΔd=πR 2 ΔPΔd···Equation (3): Reprinted

[0086] Furthermore, the valve body movement when opening is controlled by the shaft friction ηT f Therefore, the total torque acting around the rotation axis to prevent the valve from opening when the valve is fully closed is expressed as follows:

[0087] T p +ηT f ...Equation (5)

[0088] If the torque expressed by equation (5) overcomes the torque of the return spring (equation (4)), the valve body will be maintained fully closed in the fully closed position without using motor torque. In other words, if the following equation (6) is satisfied, the valve body will be maintained fully closed (held in the fully closed position).

[0089] T p +ηT f >T sc ...Equation (6)

[0090] By applying equations (3) and (4) to equation (6), we obtain the following equation (6').

[0091] πR 2 ΔPΔd+ηT f >T sc ...Formula (6')

[0092] From equation (6'), we obtain the following equation (6'').

[0093]

number

[0094] If an offset amount Δd of the rotating shaft is given that satisfies equation (6''), the fully closed state can be maintained when fully closed. However, in reality, in an environment where a unidirectional (DC) torque called spring torque is constantly applied, and an AC vibration environment exists due to the circular excitation mode of the stator excited by the air intake fan, the effect of fixing the shaft by friction may become uncertain in a time domain exceeding several tens of seconds or several minutes. Therefore, the possibility of a slight drift to the open side due to the spring torque cannot be denied. For this reason, when a long-term release process is performed, ηT in equation (6'') f should be set to 0. Therefore, it should be noted that the following equation (6''') should be adopted as the requirement equation for Δd.

[0095]

number

[0096] In addition, T in equation (6'') f This includes not only the friction of the rotating shaft, but also the friction of the reduction mechanism and the friction of the electric motor connected via the reduction mechanism.

[0097] Next, we will explain the operation of the valve body when it is in the fully open position. When the valve body is fully open, the spring torque T so is the spring torque T when fully closed sc and spring constant k, valve angle θ when fully closed c =0(rad), fully open angle θ o (usually π / 2), it is shown by the following equation (7).

[0098] T so =T sc -k(θ o -θ c )=T sc -kθ o ...Equation (7)

[0099] During the adsorption process, the valve body is normally pushed to the fully open position. so is the full-throttle torque that provides sufficient toughness against disturbances caused by air flow from the air fan without using the torque of the motor. so However, if the spring constant of the return spring is increased, the torque T acting on the opening side when the valve is fully closed increases. sc becomes excessively large, and the work done by the motor to close the valve when transitioning from the adsorption process to the desorption process increases, leading to an increase in the motor size. On the other hand, if the spring constant of the return spring is reduced, the spring torque T sc T so However, with a small spring constant, the same set load T soTherefore, the spring structure of the return spring must be large, leading to an increase in the size of the entire structure. It is necessary to set an appropriate spring constant for the return spring, taking this relationship into consideration.

[0100] As a more specific example of numerical values, the following numerical values ​​will be described. The radius of the circular valve body is R = 0.077 (m). The differential pressure inside and outside the reactor during the desorption process is ΔP = 90 (kPa). Torque T when the return spring is fully closed sc =2 (Nm). The spring constant of the return spring is k=2 / π(Nm / rad). Friction around the shaft Tf = 0.2 (Nm). However, this is not required for (6''). · Shaft friction increase coefficient η = 2.5. However, this is not necessary at (6''). Valve angle θ when valve is fully closed c =0(rad). Valve angle θ when valve is fully open o =π / 2 (rad).

[0101] Applying the above to (6'''), we obtain the following equation:

[0102]

number

[0103] The minimum value of Δd is 1.19 mm, which is 1.55% of the effective radius R of the valve body. We will refer to this as "the offset Δd is 1.55%." In the above numerical example, setting the offset Δd to a value greater than 1.55% (1.19 mm) makes it possible to reliably maintain a fully closed state during the disengagement process. However, in practice, factors such as manufacturing variations in spring load must be taken into consideration. Therefore, it is necessary to set an appropriate margin of 1.19 mm, such as 20%, and set the offset Δd to 1.86% (1.19 x 1.2 = 1.43 mm).

[0104] As an extreme numerical setting, if the spring load of the return spring when fully closed is increased by 10 times and the spring constant of the return spring is increased by 10 times, and an extremely strong torque is applied to the fully open side, in other words, for the above numerical example, if the torque when the return spring is fully closed is set to Tsc = 20 (Nm) and the spring constant of the return spring is set to k = 20 / π (Nm / rad), the following relationship can be obtained from (6''').

[0105] Δd>11.93(mm)

[0106] In this case, since the offset amount Δd is greater than 15.49% (1.93 mm) from (6'''), it is necessary to set a margin of 20% for 11.93 mm, for example, and set the offset amount Δd to 18.59% (11.93 x 1.2 = 14.32 mm).

[0107] In both of the above numerical examples, the offset Δd is within a range that allows for spatially smooth valve operation and is easy to achieve. Therefore, by providing the offset Δd, the valve body can be reliably maintained in a fully closed state during the desorption process. [Explanation of symbols]

[0108] 1. Carbon dioxide capture device 10 Reactor Unit 11. Reactor 12 Adsorbent 15 Case 21 First valve 22 Second valve 23 Third valve 23a Valve body 23b Rotation axis 23c Return spring 23d seal rubber 23e case 24 4th valve 24a valve body 24b Rotation axis 24c return spring 24d seal rubber 24e case 27 Adsorbent temperature sensor 61 fans 62 Vacuum pump 63 Carbon dioxide capture pump 80 Heat exchange equipment 81 Heat source equipment 90 Control device 101 suction line 102 Vacuum Line 103 Carbon Dioxide Line

Claims

1. a reactor having an adsorbent therein, which performs an adsorption step of sucking a gas containing the gas to be recovered into the adsorbent to adsorb the gas to be recovered, and a desorption step of heating the adsorbent under a reduced pressure around the adsorbent to desorb the gas to be recovered from the adsorbent; a fan for supplying gas into the reactor; a butterfly valve provided at the gas inlet and outlet of the reactor, the valve body being a plate-like valve that rotates around a rotation axis; A gas recovery device comprising: The valve has a return spring that biases the valve body in an opening direction, a gas recovery device in which the center of rotation of the rotary shaft is offset from the center position of the valve body when viewed from the normal direction of the plate surface of the valve body so that a rotational torque in the closing direction greater than the rotational torque in the opening direction of the return spring is generated in the valve body due to the internal / external pressure differential generated in the desorption process.

2. 2. The gas recovery device according to claim 1, The offset amount of the rotation axis is Δd (m), The torque of the return spring toward the opening side when the valve body is fully closed is T ｓｃ (Nm), The radius of the seal circle when the valve body is fully closed is R (m), The pressure difference between the inside and outside of the reactor in the desorption step is ΔP (Pa), Then, [Equation 1] Gas recovery equipment that satisfies the above requirements.

3. The gas recovery device according to claim 1 or 2, The adsorbent is a solid amine, A gas recovery device, wherein the gas to be recovered is carbon dioxide.

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