Carbon dioxide recovery system and moving body including carbon dioxide recovery system

Abstract

This carbon dioxide recovery system includes: a carbon dioxide recovery device that includes a refrigerant flow path passing through a solidification space into which target gas flows; an energy conversion system that includes a fuel flow path that connects, to an energy conversion device, a fuel tank that stores a fluid fuel at a temperature lower than the sublimation temperature of carbon dioxide; a first branch flow path that connects the fuel flow path to an inlet of the refrigerant flow path; a second branch flow path that connects an outlet of the refrigerant flow path to the fuel flow path; a regulating valve that regulates the flow rate of the fuel in the refrigerant flow path; a sensor; and a processing circuit that controls the regulating valve on the basis of a detection signal from the sensor.

Description

Carbon dioxide recovery system and mobile body equipped with the carbon dioxide recovery system

[0001] The present disclosure relates to a carbon dioxide recovery system and a mobile body equipped with the carbon dioxide recovery system.

[0002] In the carbon dioxide recovery device disclosed in Patent Document 1, carbon dioxide is solidified with a refrigerant below the solidification temperature of carbon dioxide and recovered as dry ice.

[0003] Japanese Patent Application Laid-Open No. 2009-242157

[0004] In the carbon dioxide recovery device disclosed in Patent Document 1, liquefied nitrogen is used as the refrigerant. Since liquid nitrogen is cooled by a refrigerator, energy is used only for cooling the liquid nitrogen.

[0005] One aspect of the present disclosure aims to effectively utilize energy to recover carbon dioxide.

[0006] A carbon dioxide recovery system according to one aspect of the present disclosure is a carbon dioxide recovery system that recovers carbon dioxide from a target gas, including a solidification tank having a solidification space into which the target gas flows, and a refrigerant flow path that passes through the solidification space and has an inlet and an outlet, a carbon dioxide recovery device that solidifies carbon dioxide contained in the target gas, an energy conversion system including a fuel tank that stores a fluid fuel at a temperature lower than the sublimation temperature of carbon dioxide and a fuel flow path connecting the fuel tank to an energy conversion device, a first branch flow path connecting the fuel flow path to the inlet of the refrigerant flow path, a second branch flow path connecting the outlet of the refrigerant flow path to the fuel flow path, a regulating valve that regulates the flow rate of the fuel in the refrigerant flow path, a sensor that detects at least one selected from the group consisting of the flow rate of the target gas flowing into the solidification space, the concentration of carbon dioxide contained in the target gas flowing into the solidification space, the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, and the temperature of the solidification space, and outputs a detection signal, and a processing circuit that controls the regulating valve based on the detection signal of the sensor.

[0007] A mobile body according to one aspect of this disclosure comprises the carbon dioxide capture system and the energy conversion device, the energy conversion device being a power source.

[0008] According to one aspect of this disclosure, energy can be used effectively to recover carbon dioxide.

[0009] Figure 1 is a schematic diagram of a carbon dioxide capture system according to an embodiment. Figure 2 is a schematic diagram of a carbon dioxide capture system of a first modified example. Figure 3 is a schematic diagram of a carbon dioxide capture system of a second modified example. Figure 4A is a block diagram showing an example of the carbon dioxide capture system of Figure 1 mounted on a mobile vehicle. Figure 4B is a block diagram showing an example of the carbon dioxide capture system of Figure 2 mounted on a mobile vehicle. Figure 4C is a block diagram showing an example of the carbon dioxide capture system of Figure 1 mounted on a mobile vehicle.

[0010] Embodiments will be described below with reference to the drawings.

[0011] Figure 1 is a schematic diagram of a carbon dioxide capture system 1 according to an embodiment. As shown in Figure 1, carbon dioxide is captured from a target gas in the carbon dioxide capture system 1. The target gas may be exhaust gas from a power plant flue, air in the atmosphere, or exhaust gas from a mobile vehicle. The carbon dioxide capture system 1 is installed on the ground, but may also be mounted on a mobile vehicle. The carbon dioxide capture system 1 comprises a carbon dioxide capture device 2 and an energy conversion system 3.

[0012] The carbon dioxide recovery device 2 recovers carbon dioxide from the target gas using the TSS method (Thermal Swing Sublimation). The TSS method utilizes the property that carbon dioxide solidifies when its temperature falls below the sublimation temperature of -78.5°C. By cooling the target gas to an extremely low temperature, carbon dioxide is recovered from the target gas as dry ice. The carbon dioxide recovery device 2 includes a target gas flow path 11, a mist eliminator 12, a blower 13, a moisture separator 14, a dryer 15, a heat exchanger 16, and a sublimator 17, etc.

[0013] The target gas flow path 11 includes a flow path that directs the target gas from an external source toward the sub-meter 17. When the carbon dioxide capture system 1 is installed in a ground facility, for example, atmospheric air or exhaust gas from a power plant flue flows into the target gas flow path 11 as the target gas.

[0014] The mist eliminator 12 is positioned in the target gas flow path 11. The target gas that flows into the target gas flow path 11 from outside the carbon dioxide recovery device 2 flows into the mist eliminator 12. The mist eliminator 12 separates the liquid mist contained in the target gas from the gas. The mist eliminator 12 is equipped with, for example, a mesh through which the target gas containing the mist passes, and the mist is separated from the target gas by colliding with and adhering to the mesh.

[0015] The blower 13 is positioned downstream of the mist eliminator 12 in the target gas flow path 11. The blower 13 generates a flow of the target gas from upstream to downstream in the target gas flow path 11. The blower 13 may be positioned in a location in the target gas flow path 11 different from the location shown in Figure 1.

[0016] The moisture separation device 14 is positioned downstream of the blower 13 in the target gas flow path 11. The moisture separation device 14 separates any liquid remaining in the target gas flowing out of the mist eliminator 12 from the target gas. The moisture separation device 14, for example, includes a porous basket that rotates at high speed, and separates the liquid from the target gas flowing into the porous basket by centrifugal force.

[0017] The dryer 15 is positioned downstream of the moisture separator 14 in the target gas flow path 11. The dryer 15 may be, for example, a bubbling dryer that includes a dewatering tower storing liquid refrigerant. In the dryer 15, the target gas is cooled by passing it as bubbles through the liquid refrigerant in the dewatering tower, and the moisture in the target gas is collected in the liquid refrigerant.

[0018] The heat exchanger 16 is located downstream of the dryer 15 in the target gas flow path 11. The heat exchanger 16 includes a cooler that cools the target gas that has been heated in the dryer 15. The refrigerant for the heat exchanger 16 may be the cooled target gas discharged from the sublimeter 17.

[0019] The sublimeter 17 is positioned downstream of the heat exchanger 16 in the target gas flow path 11. The sublimeter 17 includes a solidification tank 18 and a refrigerant flow path 19. The solidification tank 18 has a solidification space S into which the target gas flowing from the heat exchanger 16 flows. The refrigerant flow path 19 passes through the solidification space S and has an inlet 19a and an outlet 19b. The refrigerant flow path 19 includes, for example, an internal flow path of a refrigerant tube 20. The refrigerant tube 20 may be, for example, a finned tube having a tube and a number of fins protruding from the outer surface of the tube.

[0020] A fluid at a temperature lower than the sublimation temperature of carbon dioxide flows as a refrigerant through the refrigerant channel 19. In this embodiment, a cryogenic liquefied fuel, described later, flows as a refrigerant through the refrigerant channel 19. The coldness of the refrigerant channel 19 cools the target gas in the solidification space S to a temperature lower than the sublimation temperature of carbon dioxide. As a result, the carbon dioxide contained in the target gas in the solidification space S solidifies, and the solidified carbon dioxide is recovered as dry ice. The target gas from which the carbon dioxide has been removed is discharged to the outside from the solidification tank 18. For example, the target gas discharged from the solidification tank 18 is released into the atmosphere.

[0021] The energy conversion system 3 converts the chemical energy of a fluid fuel into a different type of energy. The energy conversion system 3 includes a fuel tank 21, an energy conversion device 22, a fuel flow path 24, a self-pressurizing structure 25, an evaporator 26, a heater 27, a buffer tank 28, and a pressure regulating valve 29, etc.

[0022] The fuel tank 21 stores the fluid fuel F at a temperature lower than the sublimation temperature of carbon dioxide. In this embodiment, the fuel tank 21 stores the fuel F, which liquefies at extremely low temperatures and vaporizes at room temperature, in the liquid phase. Therefore, the fuel tank 21 has an insulating structure that blocks heat input from the outside. Specifically, the fuel tank 21 stores liquefied hydrogen as the fuel F. The fuel F stored in the fuel tank 21 may be a gas as long as it is at a temperature lower than the sublimation temperature of carbon dioxide. The fuel F is not limited to liquefied hydrogen, but may be, for example, liquefied natural gas (LNG).

[0023] The energy conversion device 22 converts the chemical energy of a fuel into pressure energy by burning the fluid fuel. In this embodiment, the energy conversion device 22 includes a combustor 32. The combustor 32 is, for example, part of a gas turbine 23. The gas turbine 23 comprises a compressor 31, a combustor 32, a turbine 33, a rotating shaft 34, and a casing 35. The compressor 31 and the turbine 33 are connected to each other by the rotating shaft 34. In the gas turbine 23, air introduced into the casing 35 from the outside is compressed by the compressor 31, and the compressed air is led to the combustor 32. In the combustor 32, the fuel is burned together with the compressed air, and the pressure energy of the high-pressure combustion gas obtained is extracted as rotational power in the turbine 33. That is, the gas turbine 23 converts the chemical energy of a fuel into kinetic energy by burning the fluid fuel.

[0024] The rotating shaft of the gas turbine 23 is connected, for example, to a generator 58. The rotational power output by the gas turbine 23 drives the generator.

[0025] The fuel passage 24 connects the storage space of the fuel tank 21 to the combustor 32 of the gas turbine 23. The fuel passage 24 includes a passage defined by pipes. The energy conversion system 3 includes pipes that define the fuel passage 24. The fuel F in the fuel tank 21 flows through the fuel passage 24 and is supplied to the combustor 32.

[0026] The self-pressurizing structure 25 generates pressure to deliver the fuel F stored in the fuel tank 21 to the fuel passage 24. The self-pressurizing structure 25 includes a pressurizing passage 41, a pressurizer 42, and a control valve 43. The pressurizing passage 41 has an inlet connected to the lower part of the storage space of the fuel tank 21 and an outlet connected to the upper part of the storage space of the fuel tank 21. The pressurizer 42 is located in the pressurizing passage 41. The control valve 43 is located in the pressurizing passage 41.

[0027] The pressurizer 42 includes, for example, a heat exchanger that heats and vaporizes the liquefied hydrogen flowing through the pressurizing channel 41. When the hydrogen vaporized and expanded in the pressurizer 42 is supplied to the upper part of the storage space of the fuel tank 21, the storage space of the fuel tank 21 is pressurized. The increase in pressure in the storage space of the fuel tank 21 causes the liquefied hydrogen in the storage space of the fuel tank 21 to be sent to the fuel channel 24. The control valve 43 is opened when pressurization of the storage space of the fuel tank 21 is required, and the control valve 43 is closed when pressurization of the storage space of the fuel tank 21 is not required.

[0028] The evaporator 26 is located downstream of the fuel tank 21 in the fuel flow path 24. The evaporator 26 includes a heat exchanger that vaporizes the liquefied hydrogen sent from the fuel tank 21 into the fuel flow path 24.

[0029] The heater 27 is located downstream of the evaporator 26 in the fuel flow path 24. The heater 27 heats the low-temperature fuel vaporized in the evaporator 26 to room temperature.

[0030] The buffer tank 28 is located downstream of the heater 27 in the fuel flow path 24. The buffer tank 28 temporarily stores the fuel flowing out of the heater 27 when the pressure regulating valve 29 (described later) is closed.

[0031] The pressure regulating valve 29 is located downstream of the buffer tank 28 in the fuel passage 24. The pressure regulating valve 29 reduces the fuel pressure so that the pressure of the fuel supplied from the buffer tank 28 reaches a predetermined specified pressure P1. The pressure regulating valve 29 may be a valve that adjusts the pressure mechanically, but it may also be a valve that adjusts the pressure by electrical control.

[0032] A fuel injector 36 is located downstream of the pressure regulating valve 29 in the fuel passage 24. The fuel injector 36 is a fuel injection valve. The fuel injector 36 discharges the fuel supplied from the pressure regulating valve 29 to the combustor 32 of the gas turbine 23.

[0033] The carbon dioxide recovery system 1 is structured to utilize the low-temperature fuel from the energy conversion system 3 as a refrigerant for the carbon dioxide recovery device 2. Specifically, the carbon dioxide recovery system 1 includes a first branch channel 4, a second branch channel 5, a control valve 6, and a check valve 7.

[0034] The first branch channel 4 connects the fuel channel 24 of the energy conversion system 3 to the inlet 19a of the refrigerant channel 19 of the carbon dioxide recovery device 2. The first branch channel 4 includes a channel defined by a first pipe. The carbon dioxide recovery system 1 includes a first pipe that defines the first branch channel 4. The second branch channel 5 connects the outlet 19b of the refrigerant channel 19 of the carbon dioxide recovery device 2 to the fuel channel 24 of the energy conversion system 3. The second branch channel 5 includes a channel defined by a second pipe. The carbon dioxide recovery system 1 includes a second pipe that defines the second branch channel 5. The first branch channel 4 and the second branch channel 5 branch off from the portion of the fuel channel 24 between the fuel tank 21 and the evaporator 26. The point where the second branch channel 5 connects to the fuel channel 24 is downstream of the point where the first branch channel 4 connects to the fuel channel 24. The first branch channel 4 and the second branch channel 5 may branch off from the portion of the fuel channel 24 between the evaporator 26 and the heater 27.

[0035] The control valve 6 is located in the first branch passage 4. The control valve 6 may also be located in the second branch passage 5. The check valve 7 is located in the first branch passage 4. The check valve 7 allows flow from the fuel passage 24 to the inlet 19a of the refrigerant passage 19 via the first branch passage 4, and blocks flow from the inlet 19a of the refrigerant passage 19 to the fuel passage 24 via the first branch passage 4. Instead of the check valve 7, a check valve may be located in the second branch passage 5. If a check valve is located in the second branch passage 5, the check valve located in the second branch passage 5 allows flow from the outlet 19b of the refrigerant passage 19 to the fuel passage 24 via the second branch passage 5, and blocks flow from the fuel passage 24 to the outlet 19b of the refrigerant passage 19 via the second branch passage 5.

[0036] When the control valve 6 is open, a portion of the liquefied hydrogen flowing from the fuel tank 21 to the fuel passage 24 flows into the inlet 19a of the refrigerant passage 19 via the first branch passage 4. The flow rate of liquefied hydrogen in the refrigerant passage 19 can be adjusted by adjusting the opening of the control valve 6. The cold energy of the liquefied hydrogen flowing through the refrigerant passage 19 cools and solidifies the carbon dioxide in the target gas present in the solidification space S of the solidification tank 18 of the sublimeter 17. This allows the carbon dioxide to be recovered as a solid. The target gas from which the carbon dioxide has been removed is discharged to the outside of the solidification tank 18.

[0037] The liquefied hydrogen that flows through the refrigerant channel 19 flows out from the outlet 19b of the refrigerant channel 19 and returns to the fuel channel 24 via the second branch channel 5. In this way, the hydrogen fuel used to solidify carbon dioxide is returned to the fuel channel 24 and used for combustion in the gas turbine 23, so no fuel is wasted. Furthermore, the hydrogen fuel flowing through the refrigerant channel 19 of the sublimeter 17 is heated by heat exchange before returning to the fuel channel 24 via the second branch channel 5, thus reducing the thermal energy required for the evaporator 26 to vaporize the hydrogen fuel.

[0038] The carbon dioxide capture system 1 comprises a first controller 8 and a second controller 9. The first controller 8 mainly controls the carbon dioxide capture device 2. The second controller 9 mainly controls the energy conversion system 3. The first controller 8 and the second controller 9 may be integrated into a single controller.

[0039] The first controller 8 includes a processing circuit 8a and an I / O interface. Specifically, the first controller 8 includes a processor, system memory, storage memory, and driver circuitry. The processor may include a CPU. The system memory may include volatile memory. The storage memory may include non-volatile memory. The storage memory may be a hard disk, flash memory, or a combination thereof. The storage memory stores a control program. An example of a processing circuit 8a is a configuration in which the processor executes a control program read from the storage memory to the system memory. The I / O interface includes at least one of a digital interface and an analog interface. When the processing circuit 8a receives detection signals from the sensors 51, 52, and 53 (described later) as analog signals, the processing circuit 8a converts the analog signals to digital signals.

[0040] Similarly, the second controller 9 includes a processing circuit 9a and an I / O interface. Specifically, the second controller 9 includes a processor, system memory, storage memory, and driver circuitry. The processor may include a CPU. The system memory may include volatile memory. The storage memory may include non-volatile memory. The storage memory may be a hard disk, flash memory, or a combination thereof. The storage memory stores a control program. An example of a processing circuit 9a is a configuration in which the processor executes a control program read from the storage memory to the system memory. The I / O interface includes at least one of a digital interface and an analog interface. When the processing circuit 9a receives detection signals from the sensors 54, 55, and 56 (described later) as analog signals, the processing circuit 9a converts them from analog signals to digital signals.

[0041] The carbon dioxide recovery device 2 includes a flow sensor 51, a carbon dioxide concentration sensor 52, and a temperature sensor 53. The detection signals output from these sensors 51, 52, and 53 may be digital or analog signals.

[0042] The flow rate sensor 51 detects the flow rate of the target gas flowing into the solidification space S of the sublimator 17. In the present embodiment, the flow rate sensor 51 is disposed upstream of the mist eliminator 12 in the target gas flow path 11, but it may be disposed at any location in the target gas flow path 11. For example, the flow rate sensor 51 may be disposed in a portion between the heat exchanger 16 and the sublimator 17 in the target gas flow path 11.

[0043] The carbon dioxide concentration sensor 52 detects the concentration of carbon dioxide contained in the target gas flowing into the solidification space S of the sublimator 17. In the present embodiment, the carbon dioxide concentration sensor 52 is disposed upstream of the mist eliminator 12 in the target gas flow path 11, but it may be disposed at any location in the target gas flow path 11. The position of the carbon dioxide concentration sensor 52 is not particularly limited. For example, the carbon dioxide concentration sensor 52 may be disposed in a portion between the heat exchanger 16 and the sublimator 17 in the target gas flow path 11.

[0044] The temperature sensor 53 detects the temperature of the refrigerant flow path 19, the temperature of the liquefied hydrogen in the refrigerant flow path 19, or the temperature of the solidification space S. That is, the temperature sensor 53 detects a temperature correlated with the temperature of the target gas present in the solidification space S of the solidification tank 18. The detection unit of the temperature sensor 53 may be disposed inside the refrigerant flow path 19, may be disposed so as to contact the tube defining the refrigerant flow path 19, or may be disposed in the solidification space S outside the tube defining the refrigerant flow path 19.

[0045] The energy conversion system 3 includes a pressure sensor 54, a flow rate sensor 55, and a rotational speed sensor 56. The detection signals output from these sensors 54, 55, 56 may be digital signals or analog signals. The pressure sensor 54 detects the pressure between the buffer tank 28 and the pressure regulating valve 29 in the fuel flow path 24. The flow rate sensor 55 detects the flow rate of a portion between the pressure regulating valve 29 and the fuel injector 36 in the fuel flow path 24. The rotational speed sensor 56 detects the rotational speed of the rotary shaft 34 of the gas turbine 23.

[0046] The processing circuit 8a of the first controller 8 controls the control valve 6 based on the detection signals of the flow rate sensor 51, the carbon dioxide concentration sensor 52, and the temperature sensor 53. The processing circuit 9a of the second controller 9 controls the control valve 43 of the self-pressurizing structure 25 based on the detection signal of the pressure sensor 54, and controls the fuel injector 36 based on the detection signal of the rotational speed sensor 56.

[0047] The processing circuit 8a of the first controller 8 is communicably connected to the processing circuit 9a of the second controller 9. When the processing circuit 8a receives a signal indicating that the energy conversion system 3 is in an operating state from the processing circuit 9a, it controls the control valve 6 to open the control valve 6 and starts the operation of the carbon dioxide recovery device 2. When the processing circuit 8a receives a signal indicating that the operation of the energy conversion system 3 has stopped from the processing circuit 9a, it controls the control valve 6 to close the control valve 6 and stops the operation of the carbon dioxide recovery device 2.

[0048] For example, when the processing circuit 8a receives a signal indicating that the gas turbine 23 has started from the processing circuit 9a, it may control the control valve 6 to open the control valve 6 from the closed state. When the processing circuit 8a receives a signal indicating that the rotational speed of the rotating shaft 34 of the gas turbine 23 has reached a predetermined rotational speed indicating steady operation from the processing circuit 9a, it may control the control valve 6 to open the control valve 6 from the closed state.

[0049] When conditions other than the flow rate detected by the flow rate sensor 51 are the same, when the flow rate detected by the flow rate sensor 51 increases, the processing circuit 8a controls the control valve 6 to increase the opening degree of the control valve 6. As a result, when the flow rate of the target gas flowing into the solidification space S of the sublimator 17 increases, the flow rate of liquefied hydrogen in the refrigerant flow path 19 increases and the solidification space S is sufficiently cooled, so that carbon dioxide in the target gas is appropriately solidified.

[0050] When all other conditions are the same except for the carbon dioxide concentration detected by the carbon dioxide concentration sensor 52, the processing circuit 8a controls the control valve 6 to increase its opening when the carbon dioxide concentration detected by the carbon dioxide concentration sensor 52 increases. As a result, when the carbon dioxide concentration of the target gas flowing into the solidification space S of the sublimeter 17 increases, the flow rate of liquefied hydrogen in the refrigerant flow path 19 increases, and the solidification space S is sufficiently cooled, so that the carbon dioxide in the target gas is properly solidified.

[0051] The processing circuit 8a controls the control valve 6 to maintain a state where the temperature T detected by the temperature sensor 53 is lower than the sublimation temperature of carbon dioxide, which is -78.5°C. For example, if all other conditions are the same, the processing circuit 8a increases the opening of the control valve 6 when the temperature T increases, and decreases the opening of the control valve 6 when the temperature T decreases. Through this control of the control valve 6, the temperature of the solidification space S in the sublimeter 17 is appropriately managed, and the carbon dioxide in the target gas is properly solidified.

[0052] As described above, the flow rate of the refrigerant flow path 19 of the carbon dioxide recovery device 2 is adjusted based on at least one of the flow rate detected by the flow sensor 51, the carbon dioxide concentration detected by the carbon dioxide concentration sensor 52, and the temperature detected by the temperature sensor 53, thereby enabling efficient recovery of carbon dioxide from the target gas. Furthermore, the flow rate of the refrigerant flow path 19 can be optimized by adjusting it not only based on the flow rate of the target gas detected by the flow sensor 51 and the concentration of carbon dioxide contained in the target gas detected by the carbon dioxide concentration sensor 52, but also based on the temperature detected by the temperature sensor 53. Note that one or two of the flow sensor 51, carbon dioxide concentration sensor 52, and temperature sensor 53 may be omitted.

[0053] The processing circuit 8a receives the operating status of the gas turbine 23 from the processing circuit 9a and controls the control valve 6 based on the received operating status. For example, if the processing circuit 8a determines that even if the opening of the control valve 6 is maximized to maximize the fuel flow rate in the refrigerant flow path 19 while the gas turbine 23 is operating, the temperature detected by the temperature sensor 53 will not become lower than the sublimation temperature of carbon dioxide, it may control the control valve 6 to close it. This prevents the wasteful flow of fuel from the energy conversion system 3 into the refrigerant flow path 19 when the carbon dioxide recovery device 2 cannot be operated properly.

[0054] If the processing circuit 8a determines that the operating state of the energy conversion system 3 is in a state where it cannot achieve the output required for the gas turbine 23, it may control the control valve 6 to close it. The processing circuit 8a may receive information indicating the operating state of the energy conversion system 3 from the processing circuit 9a, or it may receive it directly from sensors placed in the energy conversion system 3.

[0055] For example, if the processing circuit 8a determines that the pressure or flow rate of the fuel flowing through the fuel passage 24 of the energy conversion system 3 is less than the required value, it may control the control valve 6 to close it. This suppresses a decrease in the capacity of the energy conversion system 3 caused by the distribution of fuel from the energy conversion system 3 to the carbon dioxide recovery device 2.

[0056] Specifically, if the processing circuit 8a determines that the fuel pressure detected by the pressure sensor 54 is less than a predetermined pressure P2, it may control the control valve 6 to close the control valve 6. The predetermined pressure P2 is set to a value greater than or equal to the specified pressure P1 mentioned above. If the processing circuit 8a determines that the fuel flow rate detected by the flow rate sensor 55 is less than the flow rate required by the processing circuit 9a, it may control the control valve 6 to close the control valve 6.

[0057] As described above, depending on the operating state of the energy conversion system 3, the amount of fuel flowing from the fuel passage 24 to the refrigerant passage 19 is restricted, thereby maintaining proper operation of the gas turbine 23. In other words, by prioritizing the operation of the energy conversion device 22 over the carbon dioxide recovery device 2, the energy conversion device 22 can be operated stably.

[0058] Figure 2 is a schematic diagram of the first modified carbon dioxide capture system 101. In the carbon dioxide capture system 101, components common to the previously described embodiment are denoted by the same reference numerals and their explanation is omitted. As shown in Figure 2, in the first modified carbon dioxide capture system 101, a reciprocating engine, an internal combustion engine 60, is used as the energy conversion device 122 of the energy conversion system 103. The internal combustion engine 60 converts the chemical energy of the fuel into kinetic energy by burning the fluid fuel. The carbon dioxide capture system 101 is installed on the ground, but it may also be mounted on a mobile body.

[0059] The internal combustion engine 60 includes a cylinder 61, a piston 62, a crankshaft 63, a connecting rod 64, an intake valve 65, and an exhaust valve 66, etc. The cylinder 61 has a combustion chamber 61a, an intake port 61b that guides intake air into the combustion chamber 61a, and an exhaust port 61c that guides exhaust air from the combustion chamber 61a to the outside. The combustion chamber 61a is defined by a piston 62 that is slidably housed in the cylinder 61. A spark plug is attached to the cylinder 61 to ignite the hydrogen gas in the combustion chamber 61a. The piston 62 is mechanically connected to the crankshaft 63 via a connecting rod 64. The internal combustion engine 60 is provided with a rotational speed sensor 72 that detects the rotational speed of the crankshaft 63.

[0060] An intake passage 68 is fluidly connected to the intake port 61b of the internal combustion engine 60. The intake passage 68 guides air, which has been purified by the air cleaner, to the intake port 61b. A throttle valve 69 is located in the intake passage 68. The amount of intake air supplied to the internal combustion engine 60 is regulated by the throttle valve 69. The throttle valve 69 is driven by a valve motor 70. The intake port 61b is opened and closed by an intake valve 65. The exhaust port 61c is opened and closed by an exhaust valve 66. A fuel injector 71 is attached to the cylinder 61 to directly inject hydrogen gas into the combustion chamber 61a.

[0061] The crankshaft 63 of the internal combustion engine 60 is connected, for example, to a generator 58. The rotational power output by the internal combustion engine 60 drives the generator 58.

[0062] The processing circuit 109a of the second controller 109 controls the control valve 43 of the self-pressurizing structure 25 based on the detection signal of the pressure sensor 54, and controls the fuel injector 71 and valve motor 70 based on the detection signal of the rotation speed sensor 72.

[0063] When the control valve 6 is open under the control of the processing circuit 8a, a portion of the liquefied hydrogen flowing from the fuel tank 21 of the energy conversion system 103 to the fuel flow path 24 flows through the refrigerant flow path 19 via the first branch flow path 4, and the carbon dioxide in the target gas of the solidification space S of the sublimeter 17 is cooled and solidified. The liquefied hydrogen that has flowed through the refrigerant flow path 19 returns to the fuel flow path 24 via the second branch flow path 5. In this way, the hydrogen fuel used to solidify carbon dioxide is returned to the fuel flow path 24 and used for combustion in the internal combustion engine 60, so no fuel is wasted. The other components of the carbon dioxide recovery system 101 are the same as those of the embodiment described above, so their description is omitted.

[0064] Figure 3 is a schematic diagram of the second modified carbon dioxide capture system 201. In the carbon dioxide capture system 201, components common to the previously described embodiment are denoted by the same reference numerals and their explanation is omitted. As shown in Figure 3, in the second modified carbon dioxide capture system 201, a fuel cell 80 is used as the energy conversion device 222 of the energy conversion system 203. The fuel cell 80 converts the chemical energy of hydrogen fuel into electrical energy by chemically reacting hydrogen fuel with oxygen. The carbon dioxide capture system 201 is installed on the ground, but it may also be mounted on a mobile device.

[0065] In the fuel passage 24 of the energy conversion system 203, a fuel supply valve 81 is located downstream of the pressure regulating valve 29 to supply hydrogen gas to the fuel cell 80. The processing circuit 209a of the second controller 209 controls the regulating valve 43 of the self-pressurizing structure 25 based on the detection signal from the pressure sensor 54. The processing circuit 209a controls the fuel supply valve 81 to open it in response to a power generation command. Other configurations in the carbon dioxide capture system 201 are the same as in the embodiment described above, so their description is omitted.

[0066] Figures 4A, 4B, and 4C show examples in which carbon dioxide capture systems 1, 101, and 201 are mounted on mobile units 1000, 1100, and 1200, respectively. In mobile units 1000, 1100, and 1200, energy conversion devices 22, 122, and 222 are power sources. Mobile units 1000, 1100, and 1200 include, for example, ships, vehicles, trucks, buses, passenger cars, or heavy machinery.

[0067] Figure 4A is a block diagram showing an example in which the carbon dioxide capture system 1 of Figure 1 is mounted on a mobile body 1000. As shown in Figure 4A, the mobile body 1000 comprises the carbon dioxide capture system 1 including a gas turbine 23, and a propeller 1001 connected to the gas turbine 23 to generate thrust for the mobile body 1000. The propeller 1001 is an example of a thrust generator that generates thrust for the mobile body 1000. The propeller 1001 is driven by the gas turbine 23 of the carbon dioxide capture system 1. That is, the rotational power output by the gas turbine 23 is used for the drive part of the mobile body 1000. In the mobile body 1000, exhaust gas from the gas turbine 23 flows into the target gas flow path 11 of the carbon dioxide capture system 1 as the target gas. Atmospheric air may also flow into the target gas flow path 11 of the carbon dioxide capture system 1 as the target gas.

[0068] Figure 4B is a block diagram showing an example in which the carbon dioxide capture system 101 of Figure 2 is mounted on a mobile body 1100. As shown in Figure 4B, the mobile body 1100 comprises the carbon dioxide capture system 101 including an internal combustion engine 60, a transmission 1101 that changes the driving force from the internal combustion engine 60, and wheels 1102 that generate propulsion for the mobile body 1100 by the driving force output from the transmission 1101. The wheels 1102 are an example of a propulsion force generator that generates propulsion for the mobile body 1100. The wheels 1102 are driven by the internal combustion engine 60 of the carbon dioxide capture system 101. That is, the rotational power output by the internal combustion engine 60 is used for the drive part of the mobile body 1100. In the mobile body 1100, exhaust gas from the internal combustion engine 60 flows into the target gas passage 11 of the carbon dioxide capture system 101 as the target gas. Atmospheric air may also flow into the target gas passage 11 of the carbon dioxide capture system 101 as the target gas.

[0069] Figure 4C is a block diagram showing an example in which the carbon dioxide capture system 201 of Figure 1 is mounted on a mobile body 1200. As shown in Figure 4C, the mobile body 1200 comprises a carbon dioxide capture system 201 including a fuel cell 80, a battery 1201 for storing electricity from the fuel cell 80, an electric motor 1203 driven by electricity from the battery 1201, an inverter 1202 for controlling the electricity supplied from the battery 1201 to the electric motor 1203, and wheels 1204 that generate propulsion for the mobile body 1200 by the driving force output from the electric motor 1203. In the mobile body 1200, the power source may include the electric motor 1203 in addition to the fuel cell 80.

[0070] The propulsion generators and carbon dioxide capture systems in the mobile bodies 1000, 1100, and 1200 can be in different combinations. For example, the mobile body 1000 in Figure 4A may be combined with the mobile body 1100 in Figure 4B, and the wheels 1102 may be driven by a gas turbine 23. For example, the mobile body 1100 in Figure 4B may be combined with the mobile body 1000 in Figure 4A, and the propeller 1001 may be driven by an internal combustion engine 60. For example, the mobile body 1200 in Figure 4C may be combined with the mobile body 1000 in Figure 4A, and the propeller 1001 may be driven by an electric motor 120.

[0071] As described above, the embodiments have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to the embodiments described above and can be applied to embodiments that have been modified, replaced, added, or omitted as appropriate. It is also possible to combine the components described in the embodiments to create new embodiments. For example, some components or methods in one embodiment may be applied to other embodiments, and some components in an embodiment can be separated from other components in that embodiment and extracted as appropriate. Among the components described in the attached drawings and detailed description are not only components that are essential for solving the problem, but also components that are not essential for solving the problem, in order to illustrate the technology.

[0072] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, dedicated processors, integrated circuits, ASICs (Application Specific Integrated Circuits), FPGAs (Field Programmable Gate Arrays), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions, or hardware programmed to perform the enumerated functions. The hardware may be hardware disclosed herein, or other known hardware that is programmed or configured to perform the enumerated functions. If the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or the processor.

[0073] [Embodiment] The embodiments described above are specific examples of the following embodiments.

[0074] (Aspect 1) A carbon dioxide recovery system for recovering carbon dioxide from a target gas, comprising: a solidification tank having a solidification space into which the target gas flows; a refrigerant flow path passing through the solidification space and having an inlet and an outlet, for solidifying the carbon dioxide contained in the target gas; an energy conversion system including a fuel flow path connecting a fuel tank for storing a fluid fuel at a temperature lower than the sublimation temperature of carbon dioxide to an energy conversion device; a first branch flow path connecting the fuel flow path to the inlet of the refrigerant flow path; a second branch flow path connecting the outlet of the refrigerant flow path to the fuel flow path; a control valve for adjusting the flow rate of the fuel in the refrigerant flow path; a sensor that detects at least one selected from the group consisting of the flow rate of the target gas flowing into the solidification space, the concentration of carbon dioxide contained in the target gas flowing into the solidification space, the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, and the temperature of the solidification space, and outputs a detection signal; and a processing circuit that controls the control valve based on the detection signal from the sensor.

[0075] According to Embodiment 1, carbon dioxide can be recovered in a solid state by using the cold energy of the low-temperature fuel supplied to the energy conversion device to cool and solidify the carbon dioxide in the target gas in the solidification space of the carbon dioxide recovery device. Furthermore, since the fuel used to solidify the carbon dioxide is returned to the fuel flow path of the energy conversion system, no fuel is wasted. In addition, since the flow rate of the refrigerant flow path of the carbon dioxide recovery device is adjusted based on at least one of the flow rate of the target gas, the carbon dioxide concentration of the target gas, the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, and the temperature of the solidification space, carbon dioxide can be recovered efficiently from the target gas. Therefore, the efficiency of the system for recovering carbon dioxide from a target gas can be increased.

[0076] (Aspect 2) The carbon dioxide recovery system according to aspect 1, wherein the processing circuit controls the control valve based on the operating state of the energy conversion system.

[0077] According to embodiment 2, the flow rate of fuel from the fuel passage to the refrigerant passage is adjusted in response to changes in the operating state of the energy conversion system, thereby maintaining proper operation of the energy conversion device. In other words, by prioritizing the operation of the energy conversion device over the operation of the carbon dioxide capture device, the energy conversion device can be operated stably.

[0078] (Aspect 3) The carbon dioxide recovery system according to aspect 1 or 2, wherein the fuel includes liquefied hydrogen, and the energy conversion device includes a fuel cell, a combustor, or an internal combustion engine.

[0079] According to embodiment 3, liquefied hydrogen used as fuel for fuel cells, combustors, or internal combustion engines can be used as a refrigerant for carbon dioxide recovery devices.

[0080] (Aspect 4) The carbon dioxide recovery system according to any one of aspects 1 to 3, wherein the processing circuit controls the control valve to increase the flow rate of the fuel in the refrigerant flow path when the flow rate of the target gas flowing into the solidification space or the carbon dioxide concentration contained in the target gas flowing into the solidification space increases.

[0081] According to embodiment 4, the control valve is controlled to increase the flow rate of fuel in the refrigerant flow path in accordance with the increase in carbon dioxide in the target gas, thereby enabling proper solidification of carbon dioxide in the target gas.

[0082] (Aspect 5) The carbon dioxide recovery system according to any one of aspects 1 to 4, wherein the processing circuit controls the control valve to adjust the flow rate of the fuel in the refrigerant flow path so that at least one of the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, and the temperature of the solidification space is kept lower than the sublimation temperature of carbon dioxide.

[0083] According to embodiment 5, carbon dioxide in the target gas can be properly solidified by temperature control through the control of a control valve.

[0084] (Aspect 6) A carbon dioxide recovery system according to any one of aspects 1 to 5, wherein the processing circuit controls the control valve to adjust the flow rate of the fuel in the refrigerant flow path based on the flow rate of the target gas flowing into the solidification space, or the carbon dioxide concentration contained in the target gas flowing into the solidification space, the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, or the temperature of the solidification space.

[0085] According to embodiment 6, the flow rate of the refrigerant flow path is adjusted not only based on the flow rate of the target gas flowing into the solidification space, or the carbon dioxide concentration contained in the target gas flowing into the solidification space, but also based on the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, or the temperature of the solidification space, thus further optimizing the flow rate of the refrigerant flow path.

[0086] (Aspect 7) The carbon dioxide recovery system according to aspect 2 or 3, wherein the processing circuit closes the control valve when the energy conversion device is operating and the control valve is controlled to maximize the flow rate of the fuel in the refrigerant flow path, if the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, or the temperature of the solidification space does not fall below the sublimation temperature of carbon dioxide.

[0087] According to embodiment 7, when the carbon dioxide recovery device cannot be operated properly, it is possible to suppress the wasteful flow of fuel from the energy conversion device into the refrigerant flow path.

[0088] (Aspect 8) A mobile body comprising a carbon dioxide capture system according to any one of aspects 1 to 7, and the energy conversion device, wherein the energy conversion device is a power source.

[0089] According to embodiment 8, carbon dioxide can be recovered in a solid state by utilizing the cold energy of the cryogenic fuel supplied to the power source of the mobile vehicle. Therefore, the location where carbon dioxide is recovered can be easily changed by moving the vehicle.

[0090] 1, 101, 201 Carbon dioxide capture system 2 Carbon dioxide capture device 3, 103, 203 Energy conversion system 4 First branch channel 5 Second branch channel 6 Control valve 8a, 9a Processing circuit 17 Sublimeter 18 Solidification tank 19 Refrigerant channel 19a Inlet 19b Outlet 21 Fuel tank 22, 122, 222 Energy conversion device 23 Gas turbine 24 Fuel channel 32 Combustor 51 Flow sensor 52 Carbon dioxide concentration sensor 53 Temperature sensor 60 Internal combustion engine 80 Fuel cell S Solidification space

Claims

1. A carbon dioxide recovery system for recovering carbon dioxide from a target gas, comprising: a solidification tank having a solidification space into which the target gas flows; a refrigerant flow path passing through the solidification space and having an inlet and an outlet, for solidifying the carbon dioxide contained in the target gas; an energy conversion system including a fuel flow path connecting a fuel tank for storing a fluid fuel at a temperature lower than the sublimation temperature of carbon dioxide to an energy conversion device; a first branch flow path connecting the fuel flow path to the inlet of the refrigerant flow path; a second branch flow path connecting the outlet of the refrigerant flow path to the fuel flow path; a control valve for adjusting the flow rate of the fuel in the refrigerant flow path; a sensor that detects at least one selected from the group consisting of the flow rate of the target gas flowing into the solidification space, the concentration of carbon dioxide contained in the target gas flowing into the solidification space, the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, and the temperature of the solidification space, and outputs a detection signal; and a processing circuit that controls the control valve based on the detection signal from the sensor.

2. The carbon dioxide recovery system according to claim 1, wherein the processing circuit controls the control valve based on the operating state of the energy conversion system.

3. The carbon dioxide recovery system according to claim 1 or 2, wherein the fuel includes liquefied hydrogen, and the energy conversion device includes a fuel cell, a combustor, or an internal combustion engine.

4. The carbon dioxide recovery system according to claim 1 or 2, wherein the processing circuit controls the control valve to increase the flow rate of the fuel in the refrigerant flow path when the flow rate of the target gas flowing into the solidification space or the carbon dioxide concentration contained in the target gas flowing into the solidification space increases.

5. The carbon dioxide recovery system according to claim 1 or 2, wherein the processing circuit controls the control valve to adjust the flow rate of the fuel in the refrigerant flow path so that at least one of the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, and the temperature of the solidification space is kept lower than the sublimation temperature of carbon dioxide.

6. The carbon dioxide recovery system according to claim 1 or 2, wherein the processing circuit controls the control valve to adjust the flow rate of the fuel in the refrigerant flow path based on the flow rate of the target gas flowing into the solidification space, or the carbon dioxide concentration contained in the target gas flowing into the solidification space, the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, or the temperature of the solidification space.

7. The carbon dioxide recovery system according to claim 2, wherein the processing circuit closes the control valve if, while the energy conversion device is in operation, the control valve is controlled to maximize the flow rate of the fuel in the refrigerant flow path, but the temperature of the refrigerant flow path, the temperature of the fuel in the refrigerant flow path, or the temperature of the solidification space does not fall below the sublimation temperature of carbon dioxide.

8. A mobile body comprising a carbon dioxide capture system according to claim 1 or 2, and the energy conversion device, wherein the energy conversion device is a power source.

Images