Separation system

Abstract

To provide a separation system that has high energy efficiency and can be promptly started.SOLUTION: A separation system 1 is provided with a plurality of separators connected to each other, and a heat exchange circuit 50. The plurality of separators include: a first separator 10 into which fluid containing a hydrogen isotope flows and which flows fluid that is lower in hydrogen isotope content rate than the fluid containing the hydrogen isotope; a second separator 20 which is provided at a downstream side of the first separator 10, and generates electric power using the liquid flown out of the first separator 10. The heat exchange circuit 50 has a first connection circuit 51 that supplies a heat exchange medium from the second separator 20 to the first separator 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a separation system.

Background Art

[0002] In recent years, research and development on fuel cells that contribute to energy efficiency have been carried out to enable more people to access affordable, reliable, sustainable, and advanced energy. For example, as a technique for enriching deuterium and tritium, which are hydrogen isotopes, a method is known in which a plurality of fuel cells connected in series are used, power generation is independently performed in each fuel cell, and hydrogen isotopes are separated from a gas containing hydrogen isotopes and taken out as liquid water containing hydrogen isotopes (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a system for separating hydrogen isotopes, it is required to start up the system quickly with high energy efficiency. An object of the present invention is to provide a separation system that can be started up quickly with high energy efficiency, and thus contributes to energy efficiency improvement.

Means for Solving the Problems

[0005] The present invention has the following aspects. [1] A separation system according to an aspect of the present invention is a separation system including a plurality of connected separation devices and a heat exchange circuit. The plurality of separation devices include a first separation device into which a fluid containing hydrogen isotopes flows and from which a fluid having a lower hydrogen isotope content than the fluid flows out, and a second separation device provided downstream of the first separation device and generating electricity by the fluid flowing out from the first separation device. The heat exchange circuit has a first connection circuit for supplying a heat exchange medium from the second separation device to the first separation device. According to this configuration, at the start of the separation system, waste heat can be supplied from the second separation device that generates electricity to the first separation device, and the separation system can be started up quickly with high energy efficiency.

[0006] [2] In the aspect of [1] above, the separation system may further include a humidifier for humidifying the fluid supplied to the first separation device, and the heat exchange circuit may further have a second connection circuit for supplying the heat exchange medium from the first separation device or the second separation device to the humidifier. According to this configuration, the waste heat generated in the second separation device can be added to the first separation device and also supplied to the humidifier, so that the waste heat can be utilized more effectively.

[0007] [3] In the aspect of [2] above, the separation system may further include a water electrolysis device for electrolyzing water and provided upstream of the first separation device, and a control unit. The control unit may start the second separation device after starting the water electrolysis device at the start of the separation system. According to this configuration, electricity can be generated in the second separation device by the gas generated by the electrolysis of water, and an efficient separation system can be started up.

[0008] [4] In the aspect of [3] above, when starting the separation system, the control unit operates the second separation device in a heating mode that prioritizes heat generation over the operation state of the second separation device after at least one of the first separation device, the humidifier, and the heat exchange circuit reaches a predetermined temperature, until at least one of the first separation device, the humidifier, and the heat exchange circuit reaches the predetermined temperature. According to this configuration, the first separation device, the second separation device, and the humidifier can be efficiently warmed up when starting the separation system, and the separation system can be started more quickly.

[0009] [5] In the aspect of [4] above, the heat exchange circuit further includes a third connection circuit that supplies the heat exchange medium from the humidifier to the second separation device, and a radiator provided in the third connection circuit. The control unit starts the radiator after at least one of the first separation device, the humidifier, and the heat exchange circuit reaches the predetermined temperature, and may start the first separation device while operating the second separation device in a power generation mode that prioritizes power generation over the heating mode. According to this configuration, the separation system can be operated in a temperature range suitable for the operation of the separation system, and power generation by the second separation device can be performed while ensuring the separation performance of the first separation device.

[0010] Further, another aspect of the present invention is as follows. [6] A method for starting a separation system according to an aspect of the present invention includes a plurality of connected separation devices, a heat exchange circuit, a water electrolysis device for electrolyzing water, and a control unit. The plurality of separation devices include a first separation device into which a fluid containing hydrogen isotopes flows and from which a fluid having a lower hydrogen isotope content than the fluid flows out, and a second separation device provided downstream of the first separation device and generating power using the fluid flowing out from the first separation device. The heat exchange circuit has a first connection circuit for supplying a heat exchange medium from the second separation device to the first separation device. The water electrolysis device is provided upstream of the first separation device. The method for starting the separation system is such that, after starting the water electrolysis device when starting the separation system by the control unit, the second separation device is started, and a heat exchange medium is supplied from the second separation device to the first separation device. According to this configuration, when starting the separation system, waste heat can be supplied from the second separation device that generates power to the first separation device, and the separation system can be started quickly with high energy efficiency. In addition, power generation of the second separation device can be performed using the gas generated by electrolysis of water, enabling efficient startup of the separation system.

[0011] [7] In the aspect of [6] above, the separation system further includes a humidifier for humidifying the fluid supplied to the first separation device. The heat exchange circuit further has a second connection circuit for supplying the heat exchange medium from the first separation device or the second separation device to the humidifier. The control unit may supply the heat exchange medium from the first separation device or the second separation device to the humidifier when starting the separation system. According to this configuration, the waste heat generated in the second separation device can be added to the first separation device and also supplied to the humidifier, so that the waste heat can be utilized more effectively.

[0012] [8] In the aspect of [7] above, when starting the separation system, the control unit operates the second separation device in a heating mode that prioritizes heat generation over the operation state of the second separation device after at least one of the first separation device, the humidifier, and the heat exchange circuit reaches a predetermined temperature, until at least one of the first separation device, the humidifier, and the heat exchange circuit reaches the predetermined temperature. According to this configuration, the first separation device, the second separation device, and the humidifier can be efficiently warmed up when starting the separation system, and the separation system can be started more quickly.

[0013] [9] In the aspect of [8] above, the heat exchange circuit further includes a third connection circuit that supplies the heat exchange medium from the humidifier to the second separation device, and a radiator provided in the third connection circuit. After at least one of the first separation device, the humidifier, and the heat exchange circuit reaches the predetermined temperature, the control unit starts the radiator and starts the first separation device while operating the second separation device in a power generation mode that prioritizes power generation over the heating mode. According to this configuration, the separation system can be operated in a temperature range suitable for the operation of the separation system, and power generation in the second separation device can be performed while ensuring the separation performance in the first separation device.

Effects of the Invention

[0014] According to the present invention, a separation system that can be started quickly with high energy efficiency can be provided.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0016] Hereinafter, the separation system and startup method according to embodiments of the present invention will be described in detail with appropriate reference to FIGS. 1 and 2. In the present invention, among the three isotopes of hydrogen, deuterium ( 2 H or D) with a mass number of 2 and tritium ( 3 H or T) with a mass number of 3 are collectively referred to as "hydrogen isotopes", and hydrogen ( 1 H or H) with a mass number of 1 is referred to as "light hydrogen". In addition, gas and liquid are collectively referred to as "fluid". In the present invention, those containing liquid in gas or those containing gas in liquid are also included in the fluid. As the fluid, gas or those containing liquid in gas are preferable. In addition, until a series of operations performed when starting the separation system of the present invention are completed is referred to as "starting of the separation system". Specifically, from when the water electrolysis device described later starts up to when the first separation device described later starts up is referred to as "starting of the separation system". Also, the operation of the separation system after startup is referred to as "operation of the separation system". In addition, each drawing used in the following description may, for the sake of clarity of its features, show the characteristic parts enlarged for convenience, and the dimensional ratios of each component may be different from the actual ones. Also, the materials, dimensions, etc. exemplified in the following description are just examples, and the present invention is not limited to them, and it can be appropriately changed and implemented within the scope of not changing its gist.

[0017] "Separation system" FIG. 1 is a configuration diagram schematically showing an example of the separation system of the present invention. The separation system 1 shown in FIG. 1 includes a connected first separation device 10 and second separation device 20, a water electrolysis device 30, a humidifier 40, a heat exchange circuit 50, and a control unit 80. The water electrolysis device 30, the humidifier 40, the first separation device 10, and the second separation device 20 are connected in this order from the upstream side by a hydrogen supply flow path 60 and an oxygen supply flow path 70.

[0018] <First separation device> The first separation device 10 is a device into which a fluid containing hydrogen isotopes (hereinafter also referred to as "first fluid") flows and from which a fluid having a lower hydrogen isotope content than the first fluid (hereinafter also referred to as "second fluid") flows out. The first separation device 10 includes a first fuel cell 11. The first separation device 10 also has a flow path (not shown) through which a heat exchange medium for heating or cooling the first fuel cell 11 passes. In this specification, the inlet of the flow path through which the heat exchange medium passes is also referred to as the "medium inlet", and the outlet of the flow path is also referred to as the "medium outlet".

[0019] The first fuel cell 11 is for separating hydrogen isotopes from the first fluid. As the first fuel cell 11, a known fuel cell can be used. As a specific example, the first fuel cell 11 includes an electrolyte membrane, and on both surfaces of the electrolyte membrane, an anode catalyst layer and an anode flow path are provided in this order on the first surface, and a cathode catalyst layer and a cathode flow path are provided in this order on the second surface. The first fuel cell 11 also has a pair of separators that sandwich the electrolyte membrane, the anode catalyst layer and the anode flow path, and the cathode catalyst layer and the cathode flow path.

[0020] The electrolyte membrane has an electrolyte. When the first separation device 10 operates, light hydrogen and hydrogen isotopes contained in the first fluid diffuse from the anode catalyst layer to the cathode catalyst layer through the electrolyte membrane. The electrolyte membrane is not particularly limited as long as it has an electrolyte, but a solid polymer membrane is preferred because light hydrogen and hydrogen isotopes can easily diffuse, an isotope exchange reaction (HD + H2O ⇔ H2 + HDO) easily occurs at the interface between the electrolyte membrane and the cathode catalyst layer, and the reaction efficiency also increases. Examples of the solid polymer membrane include a proton-conductive solid polymer membrane and an anion-conductive solid polymer membrane.

[0021] The anode catalyst layer is provided on the first surface of the electrolyte membrane. Examples of the catalyst included in the anode catalyst layer include noble metals such as platinum and ruthenium, transition metals such as nickel and cobalt, and their alloys and oxides. Among these, platinum is preferable because the isotope exchange reaction (H2 + D2 ⇔ 2DH) is likely to occur and the reaction efficiency is increased. The anode flow path is provided on the surface of the anode catalyst layer opposite to the electrolyte membrane. The anode flow path is the region between the anode catalyst layer and the separator.

[0022] The cathode catalyst layer is provided on the second surface of the electrolyte membrane. Examples of the catalyst included in the cathode catalyst layer include noble metals such as platinum and ruthenium, transition metals such as nickel and cobalt, and their alloys and oxides. Among these, platinum is preferable because the isotope exchange reaction is likely to occur in the cathode catalyst layer and at the interface between the electrolyte membrane and the cathode catalyst layer, and the reaction efficiency is increased. In particular, from the viewpoint that the isotope exchange reaction is more likely to occur and the reaction efficiency is further increased, it is preferable that the electrolyte membrane is a solid polymer membrane and the anode catalyst layer and the cathode catalyst layer contain platinum. The cathode flow path is provided on the surface of the cathode catalyst layer opposite to the electrolyte membrane. The cathode flow path is the region between the cathode catalyst layer and the separator.

[0023] The separators are respectively provided outside the anode flow path and the cathode flow path. Examples of the separator include styrene, titanium, carbon, and the like.

[0024] When the electrolyte membrane, the anode catalyst layer, the anode flow path, the cathode catalyst layer, the cathode flow path, and the separator are regarded as one cell (fuel cell), the first fuel cell 11 may be composed of one fuel cell or may be an assembly of a plurality of fuel cells (fuel cell stack).

[0025] <Second separation device> The second separation device 20 is provided downstream of the first separation device 10 and is a device that generates electricity using the second fluid flowing out from the first separation device 10. That is, the separation system 1 shown in FIG. 1 is also a separation and power generation system. The second separation device 20 includes a second fuel cell 21. Further, the second separation device 20 has a flow path (not shown) through which a heat exchange medium for heating or cooling the second fuel cell 21 passes.

[0026] The second fuel cell 21 is for generating electricity using the second fluid and oxygen while generating water. During power generation, hydrogen isotopes are separated from the second fluid. As the second fuel cell 21, a known fuel cell can be used. As a specific example, the second fuel cell 21 includes an electrolyte membrane, and on both sides of the electrolyte membrane, an anode catalyst layer and an anode flow path are provided in this order on the first surface, and a cathode catalyst layer and a cathode flow path are provided in this order on the second surface. Further, the second fuel cell 21 has an electrolyte membrane, an anode catalyst layer and an anode flow path, a cathode catalyst layer and a cathode flow path, and a pair of separators sandwiching them.

[0027] The electrolyte membrane, anode catalyst layer, anode flow path, cathode catalyst layer, cathode flow path, and separator constituting the second fuel cell 21 may be the same as those of the electrolyte membrane, anode catalyst layer, anode flow path, cathode catalyst layer, cathode flow path, and separator constituting the first fuel cell 11 provided in the first separation device 10, respectively. The second fuel cell 21 may be composed of one fuel cell unit or may be an assembly of a plurality of fuel cell units (fuel cell stack).

[0028] <Water electrolysis device> The water electrolysis device 30 is provided upstream of the first separation device 10 and is a device for electrolyzing water. As the water electrolysis device 30, a known water electrolysis device can be used, and examples thereof include a polymer electrolyte water electrolysis device and an alkaline water electrolysis device. Among these, an alkaline water electrolysis device is preferable because a large amount of hydrogen gas can be generated.

[0029] The raw material decomposed by the water electrolysis device 30 at the start of the separation system 1, that is, water, is not particularly limited, and it may be water containing hydrogen isotopes or water not containing hydrogen isotopes. Specifically, tap water, pure water, wastewater containing hydrogen isotopes, wastewater not containing hydrogen isotopes, etc. can be mentioned.

[0030] <Humidifier> The humidifier 40 is provided between the water electrolysis device 30 and the first separation device 10 and humidifies the fluid supplied to the first separation device 10. Specifically, the humidifier 40 humidifies the fluid containing hydrogen among the hydrogen and oxygen generated by the electrolysis of water in the water electrolysis device 30. The fluid containing hydrogen humidified by the humidifier 40 is supplied in the order of the anode flow path of the first fuel cell 11 and the anode flow path of the second fuel cell 21. The humidifier 40 is not particularly limited as long as it can generate water vapor. The humidifier 40 has a flow path (not shown) through which a heat exchange medium for heating or cooling the humidifier 40 passes.

[0031] In the humidifier 40, in addition to the fluid containing hydrogen, the fluid containing oxygen may be humidified. The fluid containing oxygen humidified by the humidifier 40 is supplied in the order of the cathode flow path of the first fuel cell 11 and the cathode flow path of the second fuel cell 21. When both the fluid containing hydrogen and the fluid containing oxygen are humidified, it is preferable that each fluid is humidified by a separate humidifier. In addition, in order to prevent the fluid containing hydrogen and the fluid containing oxygen from being mixed in the humidifier, for example, when each flow path is provided in the humidifier, the fluid containing hydrogen and the fluid containing oxygen may be humidified by one humidifier.

[0032] <Heat exchange circuit> The heat exchange circuit 50 includes a first connection circuit 51, a second connection circuit 52, a third connection circuit 53, a radiator 54, and a first pump 55. The first connection circuit 51 is a pipe for supplying a heat exchange medium from the second separation device 20 to the first separation device 10. That is, the second separation device 20 and the first separation device 10 are connected by the first connection circuit 51. One end of the first connection circuit 51 is connected to the medium outlet of the second separation device 20, and the other end is connected to the medium inlet of the first separation device 10. In this example, the second connection circuit 52 is a pipe for supplying a heat exchange medium from the first separation device 10 to the humidifier 40. That is, the first separation device 10 and the humidifier 40 are connected by the second connection circuit 52. One end of the second connection circuit 52 is connected to the medium outlet of the first separation device 10, and the other end is connected to the medium inlet of the humidifier 40. The third connection circuit 53 is a pipe for supplying a heat exchange medium from the humidifier 40 to the second separation device 20. That is, the humidifier 40 and the second separation device 20 are connected by the third connection circuit 53. One end of the third connection circuit 53 is connected to the medium outlet of the humidifier 40, and the other end is connected to the medium inlet of the second separation device 20. The radiator 54 is provided in the third connection circuit 53. The radiator 54 is not particularly limited as long as it can dissipate heat of the heat exchange medium, and a known radiator can be used. The first pump 55 is provided downstream of the radiator 54 in the third connection circuit 53.

[0033] The heat exchange medium circulates among the second separation device 20, the first separation device 10, and the humidifier 40 via the heat exchange circuit 50. Examples of the heat exchange medium include water, air, ethylene glycol, and the like.

[0034] <Hydrogen supply flow path> The hydrogen supply channel 60 is a pipe for supplying a fluid containing hydrogen (hereinafter also referred to as "fluid (F1)") among the hydrogen and oxygen generated by the electrolysis of water in the water electrolysis device 30 to the second separation device 20. The hydrogen supply channel 60 includes a first hydrogen supply channel 61, a second hydrogen supply channel 62, a third hydrogen supply channel 63, and a second pump 64. The first hydrogen supply channel 61 is a pipe for supplying the fluid (F1) generated in the water electrolysis device 30 from the water electrolysis device 30 to the humidifier 40. That is, the water electrolysis device 30 and the humidifier 40 are connected by the first hydrogen supply channel 61. The second hydrogen supply channel 62 is a pipe for supplying the fluid (F1) from the humidifier 40 to the first separation device 10. That is, the humidifier 40 and the first separation device 10 are connected by the second hydrogen supply channel 62. One end of the second hydrogen supply channel 62 is connected to the humidifier 40, and the other end is connected to the inlet of the anode channel of the first fuel cell 11. The third hydrogen supply channel 63 is a pipe for supplying the fluid (F1) from the first separation device 10 to the second separation device 20. That is, the first separation device 10 and the second separation device 20 are connected by the third hydrogen supply channel 63. One end of the third hydrogen supply channel 63 is connected to the outlet of the anode channel of the first fuel cell 11, and the other end is connected to the inlet of the anode channel of the second fuel cell 21. The second pump 64 is provided in the first hydrogen supply channel 61. Note that since hydrogen is generated in the water electrolysis device 30, the fluid flows downstream due to the pressure difference at that time. Therefore, it is not always necessary to provide the second pump 64, and the hydrogen supply channel 60 may not have the second pump 64.

[0035] <Oxygen supply channel> The oxygen supply channel 70 is a pipe for supplying a fluid containing oxygen (hereinafter also referred to as "fluid (F2)") among the hydrogen and oxygen generated by the electrolysis of water in the water electrolysis device 30 to the second separation device 20. The oxygen supply passage 70 includes a first oxygen supply passage 71, a second oxygen supply passage 72, a third oxygen supply passage 73, and a third pump 74. The first oxygen supply passage 71 is a pipe for supplying the fluid (F2) generated in the water electrolysis device 30 from the water electrolysis device 30 to the humidifier 40. That is, the water electrolysis device 30 and the humidifier 40 are connected by the first oxygen supply passage 71. The second oxygen supply passage 72 is a pipe for supplying the fluid (F2) from the humidifier 40 to the first separation device 10. That is, the humidifier 40 and the first separation device 10 are connected by the second oxygen supply passage 72. One end of the second oxygen supply passage 72 is connected to the humidifier 40, and the other end is connected to the inlet of the cathode passage of the first fuel cell 11. The third oxygen supply passage 73 is a pipe for supplying the fluid (F2) from the first separation device 10 to the second separation device 20. That is, the first separation device 10 and the second separation device 20 are connected by the third oxygen supply passage 73. One end of the third oxygen supply passage 73 is connected to the outlet of the cathode passage of the first fuel cell 11, and the other end is connected to the inlet of the cathode passage of the second fuel cell 21. The third pump 74 is provided in the first oxygen supply passage 71. Note that since oxygen is generated in the water electrolysis device 30, the fluid flows downstream due to the pressure difference at that time. Therefore, it is not always necessary to provide the third pump 74, and the oxygen supply passage 70 may not have the third pump 74. In the separation system 1 of the present embodiment, the fluid (F2) passes through the humidifier 40 and the first separation device 10 and is supplied to the second separation device 20, but the fluid (F2) may be directly supplied from the water electrolysis device 30 to the second separation device 20. Further, the fluid (F2) that has passed through the humidifier 40 may be supplied to the second separation device 20 without passing through the first separation device 10, or the fluid (F2) may be supplied in the order of the first separation device 10 and the second separation device 20 without passing through the humidifier 40.

[0036] <Control unit> The control unit 80 controls the operations of the first separation device 10, the second separation device 20, the water electrolysis device 30, the radiator 54, the first pump 55, the second pump 64, the third pump 74, and the like. Specifically, when starting up the separation system 1, the control unit 80 starts the second separation device 20 after starting the water electrolysis device 30. At this time, the second pump 64 and the third pump 74 are also started.

[0037] Also, when starting up the separation system 1, the control unit 80 sets the second separation device 20 to a heating mode that prioritizes heat generation over normal operation until at least one of the first separation device 10, the humidifier 40, and the heat exchange circuit 50 reaches a predetermined temperature (hereinafter also referred to as "temperature T"). Then, the first pump 55 is started to circulate the heat exchange medium among the second separation device 20, the first separation device 10, and the humidifier. In the present invention, the normal operation of the second separation device 20 refers to the operating state of the second separation device 20 after at least one of the first separation device 10, the humidifier 40, and the heat exchange circuit 50 reaches the temperature T, that is, the "power generation mode" in which power generation is prioritized. Note that power generation is also performed in the heating mode. Also, the fact that at least one of the first separation device 10, the humidifier 40, and the heat exchange circuit 50 reaches the temperature T means that, for example, the temperature of the heat exchange medium flowing through at least one of the first connection circuit 51, the second connection circuit 52, and the third connection circuit 53 reaches the temperature T.

[0038] Also, after at least one of the first separation device 10, the humidifier 40, and the heat exchange circuit 50 reaches the temperature T, the control unit 80 starts the radiator 54, sets the second separation device 20 to the power generation mode that prioritizes power generation over the heating mode, and starts the first separation device 10.

[0039] <Starting method of the separation system> An example of the starting method of the separation system 1 described above will be described below with reference to FIG. 2. FIG. 2 is a flowchart showing an example of the flow of the starting method of the separation system 1.

[0040] First, the control unit 80 activates the water electrolysis device 30 (step S1). Also, the control unit 80 activates the second pump 64 to supply the fluid (F1) containing hydrogen generated in the water electrolysis device 30 to the humidifier 40, the first separation device 10, and the second separation device 20 in this order through the hydrogen supply passage 60. The fluid (F1) passes through the humidifier 40, the anode passage of the first fuel cell 11, and the anode passage of the second fuel cell 21 in this order. When the fluid (F1) passes through the humidifier 40, it is preferable to humidify the fluid (F1). By humidifying the fluid (F1), deterioration of the second fuel cell 21 can be suppressed. The hydrogen contained in the fluid (F1) may be light hydrogen, may be a hydrogen isotope, or may be both.

[0041] Also, the control unit 80 activates the third pump 74 to supply the fluid (F2) containing oxygen generated in the water electrolysis device 30 to the humidifier 40, the first separation device 10, and the second separation device 20 in this order through the oxygen supply passage 70. The fluid (F2) passes through the humidifier 40, the cathode passage of the first fuel cell 11, and the cathode passage of the second fuel cell 21 in this order. When the fluid (F2) passes through the humidifier 40, it is preferable to humidify the fluid (F2). By humidifying the fluid (F2), deterioration of the second fuel cell 21 can be suppressed.

[0042] Next, in the second separation device 20, it is determined whether or not the pressure on the anode side (anode pressure) across the electrolyte membrane of the second fuel cell 21 has reached a predetermined value (step S2). Specifically, it is determined whether or not the pressure on the anode side of the second fuel cell 21 has reached a pressure at which power generation is possible. The pressures on the anode side and the cathode side can be controlled by adjusting the flow rates of the fluid (F1) and the fluid (F2) with the second pump 64 and the third pump 74. For example, by making the flow rate of the fluid (F1) larger than the flow rate of the fluid (F2), the anode side is more likely to be at a higher pressure than the cathode side.

[0043] When the anode pressure reaches a predetermined value, the control unit 80 activates the second separation device 20 (step S3). Further, the control unit 80 activates the first pump 55, and supplies the heat exchange medium in the order of the second separation device 20 to the first separation device 10, the first separation device 10 to the humidifier 40, and the humidifier 40 to the second separation device 20 via the heat exchange circuit 50 to circulate the heat exchange medium.

[0044] Next, it is determined whether or not the power generation amount of the second separation device 20 has reached a predetermined value (step S4).

[0045] When the power generation amount of the second separation device 20 reaches a predetermined value, the control unit 80 sets the second separation device 20 to the heating mode until at least one of the first separation device 10, the humidifier 40, and the heat exchange circuit 50 reaches a predetermined value (temperature T) (step S5). To set the second separation device 20 to the heating mode, for example, the flow rate of the fluid (F1) may be made larger than the flow rate of the fluid (F2). Also, the flow rate of the fluid (F2) may be reduced from the flow rate in the power generation mode, or a heater or the like may be attached to the second separation device 20 to warm it, so that the heating mode can be set. By setting the second separation device 20 to the heating mode, the heat exchange medium supplied to the second separation device 20 is quickly heated and discharged from the second separation device 20, and is supplied to the first separation device 10 and the humidifier 40 in this order, so that the first separation device 10 and the humidifier 40 are quickly warmed.

[0046] Next, it is determined whether or not at least one of the first separation device 10, the humidifier 40, and the heat exchange circuit 50 has reached the temperature T (step S6). Specifically, it is determined whether or not the temperature of the heat exchange medium flowing through at least one of the first connection circuit 51, the second connection circuit 52, and the third connection circuit 53 has reached a predetermined value (temperature T).

[0047] When at least one of the first separator 10, the humidifier 40, and the heat exchange circuit 50 reaches the temperature T, the control unit 80 activates the radiator 54 and sets the second separator 20 to a power generation mode that prioritizes power generation over the heating mode (step S7). By activating the radiator 54, the heat exchange medium is cooled when passing through the radiator 54, so that overheating of the first separator 10, the humidifier 40, and the heat exchange circuit 50 can be suppressed. It is preferable to cool the heat exchange medium so that the temperature of the heat exchange medium when passing through the upstream of the radiator 54 in the third connection circuit 53 can be maintained at or below the temperature T.

[0048] Next, the control unit 80 activates the first separator 10 (step S8). The activation of the first separator 10 completes the activation of the separation system 1.

[0049] <Operation of the separation system> By activating the first separator 10, the separation system 1 operates. First, in the water electrolysis device 30, for example, water containing hydrogen isotopes is electrolyzed. The fluid (first fluid) containing hydrogen isotopes obtained by this electrolysis flows into the inlet of the anode channel of the first fuel cell 11 of the first separator 10. At this time, the first fluid may be passed through the humidifier 40 and then flow into the anode channel of the first fuel cell 11, or may flow directly from the water electrolysis device 30 into the anode channel of the first fuel cell 11. Separately, the fluid (F2) containing oxygen obtained by electrolysis flows into the inlet of the cathode channel of the first fuel cell 11 of the first separator 10. At this time, it is preferable to pass the fluid (F2) through the humidifier 40, humidify it, and then flow it into the cathode channel of the first fuel cell 11. In this case, the fluid (F2) contains oxygen and water vapor. Also, nitrogen may be contained in the fluid (F2).

[0050] In the first separation device 10, a part of the light hydrogen and hydrogen isotopes contained in the first fluid flowing into the anode flow path moves from the anode flow path to the anode catalyst layer, and further passes through the electrolyte membrane from the anode catalyst layer and moves to the cathode catalyst layer. The light hydrogen and hydrogen isotopes that have moved to the cathode catalyst layer undergo an isotope exchange reaction with the water vapor (H2O) contained in the fluid (F2) that has moved from the cathode flow path to the cathode catalyst layer in the cathode catalyst layer and at the interface between the electrolyte membrane and the cathode catalyst layer, generating D2O and HDO. The light hydrogen and hydrogen isotopes contained in the first fluid that have not moved to the cathode catalyst layer flow out from the outlet of the anode flow path as a second fluid that is a fluid with a lower hydrogen isotope content than the first fluid. Note that the isotope exchange reaction also occurs on the surface of the anode catalyst layer.

[0051] A part of the second fluid flowing out from the anode flow path of the first fuel cell 11 may be returned to the anode flow path of the first fuel cell 11, or all of it may be supplied to the second separation device 20 and used for power generation. If the second fluid is used for power generation, the light hydrogen and hydrogen isotopes contained in the second fluid can be consumed.

[0052] The fluid (F2) passing through the cathode flow path of the first fuel cell 11 without being used in the above isotope exchange reaction, and the D2O, HDO, and H2 generated by the isotope exchange reaction and moving to the cathode flow path flow out from the outlet of the cathode flow path of the first fuel cell 11 as the fluid (F3). The fluid (F3) flowing out from the cathode flow path of the first fuel cell 11 may be subjected to gas-liquid separation, or may be recovered as water containing D2O. When the fluid (F3) is subjected to gas-liquid separation, the gas separated from the fluid (F3) is discharged. The liquid separated from the fluid (F3) may be supplied to the water electrolysis device 30, or may be recovered as water containing D2O.

[0053] In the second separation device 20, first, at least a part of the second fluid flowing out from the anode flow path of the first fuel cell 11 flows into the inlet of the anode flow path of the second fuel cell 21. Separately, oxygen is introduced into the inlet of the cathode flow path of the second fuel cell 21. As the oxygen flowing into the cathode flow path of the second fuel cell 21 during the operation of the separation system 1, a fluid (F2) containing oxygen generated by the water electrolysis device 30 can be used. In this case, the fluid (F2) is directly supplied from the water electrolysis device 30 to the cathode flow path of the second fuel cell 21.

[0054] A part of the light hydrogen and hydrogen isotopes contained in the second fluid flowing into the anode flow path of the second fuel cell 21 moves from the anode flow path to the anode catalyst layer in an ionic state, and further passes through the electrolyte membrane from the anode catalyst layer and moves to the cathode catalyst layer. The light hydrogen ions and hydrogen isotope ions that have moved to the cathode catalyst layer of the second fuel cell 21 react with the oxygen that has moved from the cathode flow path to the cathode catalyst layer in the cathode catalyst layer and at the interface between the electrolyte membrane and the cathode catalyst layer to generate water (H2O and D2O). The second separation device 20 generates electricity by this reaction. In this way, the second fluid flowing out of the anode flow path of the first fuel cell 11 is used for power generation and consumed.

[0055] A fluid (F4) with a lower hydrogen isotope content than the second fluid, which has not been used for power generation, flows out from the outlet of the anode flow path of the second fuel cell 21. The discharged fluid (F4) may be discharged, or at least a part of the fluid (F4) may be returned to the anode flow path of the second fuel cell 21. On the other hand, the water (H2O and D2O) generated in the cathode catalyst layer etc. of the second fuel cell 21 and moving to the cathode flow path flows out from the outlet of the cathode flow path of the second fuel cell 21 as a fluid (F5). The water (H2O and D2O), which is the fluid (F5) flowing out from the cathode flow path of the second fuel cell 21, may be supplied to the water electrolysis device 30, discharged, or recovered as water containing D2O. It should be noted that the fluid discharged in the present invention is appropriately treated after discharge.

[0056] <Advantages and effects> In the separation system and its startup method of the present embodiment described above, when starting the separation system, the heat exchange medium heated by the second separation device is supplied to the first separation device. When the separation system is in operation, in order to efficiently separate hydrogen isotopes from the first fluid, it is necessary to heat the first separation device to a temperature suitable for the isotope exchange reaction. However, in the present embodiment, the waste heat generated in the second separation device can be used to heat the first separation device, and the first separation device can be quickly heated. At this time, by setting the second separation device to the heating mode until at least one of the first separation device, the humidifier, and the heat exchange circuit reaches the temperature T, the heat exchange medium supplied from the second separation device to the first separation device can be quickly heated, and the first separation device can be heated more quickly. Moreover, the second separation device can also be quickly heated to a temperature suitable for power generation, and the separation system can be started more quickly. Further, after at least one of the first separation device, the humidifier, and the heat exchange circuit reaches the temperature T, by switching the second separation device from the heating mode to the power generation mode, the separation system can be operated in a temperature range suitable for the operation of the separation system, and power generation by the second fluid in the second separation device can be performed while ensuring the separation performance in the first separation device. Therefore, according to the separation system and its startup method of the present embodiment, the separation system can be started up quickly with high energy efficiency. And by extension, it can contribute to the improvement of energy efficiency.

[0057] Also, when starting the separation system, if the fluid (fluid (F2)) sequentially supplied to the first separation device and the second separation device is humidified, deterioration of the electrolyte membrane constituting the fuel cell provided in each separation device can be suppressed. In addition, the isotope exchange reaction after starting the first separation device becomes more likely to proceed, the separation coefficient for separating hydrogen isotopes from the first fluid is improved, and the separation efficiency is increased. When starting the separation system, if the heat exchange medium heated by the second separation device is also supplied to the humidifier and the humidifier is pre-heated, the heated fluid (F2) can be supplied to the first separation device, so the first separation device can be heated more quickly. Also, the isotope exchange reaction after starting the first separation device becomes more likely to proceed, and the separation efficiency is further increased. In this way, the waste heat generated by the second separation device can be effectively utilized for heating the first separation device and the humidifier.

[0058] <Other embodiments> The separation system and its startup method of the present invention are not limited to those described above. For example, in the separation system 1 shown in FIG. 1, one end of the second connection circuit 52 is connected to the medium outlet of the first separation device 10, but one end of the second connection circuit 52 may be connected to the medium outlet of the second separation device 20. That is, the second separation device 20 and the humidifier 40 may be connected by the second connection circuit 52. Also, the first connection circuit 51 may branch in the middle, one end of the first connection circuit 51 is connected to the medium outlet of the second separation device 20, one of the other ends is connected to the medium inlet of the first separation device 10, and the other of the other ends is connected to the medium inlet of the humidifier 40.

[0059] Also, at the time of starting up the separation system 1, the fluid (F1) and the fluid (F2) may be directly supplied from the water electrolysis device 30 or the humidifier 40 to the second separation device 20 without passing through the first separation device 10.

[0060] Also, in the separation system 1 shown in FIG. 1, two separation devices are provided, but the separation system 1 may be provided with three or more separation devices connected together. In this case, among the three or more separation devices, as long as at least the most upstream separation device is the first separation device 10 and the most downstream separation device is the second separation device 20, the remaining separation devices may be the first separation device 10 or the second separation device 20. In particular, it is more preferable that only the most downstream is provided with the second separation device 20.

Explanation of reference numerals

[0061] 1 Separation system 10 First separation device 11 First fuel cell 20 Second separation device 21 Second fuel cell 30 Water electrolysis device 40 Humidifier 50 Heat exchange circuit 51 First connection circuit 52 Second connection circuit 53 Third connection circuit 54 Radiator 55 First pump 60 Hydrogen supply flow path 61 First hydrogen supply flow path 62 Second hydrogen supply flow path 63 Third hydrogen supply flow path 64 Second pump 70 Oxygen supply flow path 71 First oxygen supply flow path 72 Second oxygen supply flow path 73 Third oxygen supply flow path 74 Third pump 80 Control unit

Claims

Claims 1. A separation system for separating a hydrogen isotope from a fluid containing a hydrogen isotope, comprising: the separation system includes a plurality of connected separation devices; and a heat exchange circuit; the plurality of separation devices include a first separation device into which a first fluid containing light hydrogen and the hydrogen isotope flows and a second fluid having a lower hydrogen isotope content than the first fluid flows out, and a second separation device provided downstream of the first separation device and generating power by the second fluid flowing out from the first separation device; the first separation device includes a first fuel cell; the second separation device includes a second fuel cell; in the first fuel cell, a part of the light hydrogen and the hydrogen isotope contained in the first fluid undergoes an isotope exchange reaction with separately introduced steam in the first fuel cell to generate D2O and HDO, and the remainder flows out of the first fuel cell as the second fluid; a fluid (F3) containing the D2O and the HDO generated by the first fuel cell flows out of the first fuel cell; in the second fuel cell, a part of the light hydrogen and the hydrogen isotope contained in the second fluid reacts with separately introduced oxygen in the second fuel cell in an ionic state to generate H2O and D2O, and the remainder flows out of the second fuel cell as a fluid (F4) having a lower hydrogen isotope content than the second fluid; a fluid (F5) containing the H2O and the D2O generated by the second fuel cell flows out of the second fuel cell; the heat exchange circuit has a first connection circuit for supplying a heat exchange medium from the second separation device to the first separation device; at the start-up of the separation system, the heat exchange medium heated by the second separation device is supplied to the first separation device by the first connection circuit to heat the first separation device. A separation system. Claims 2. The separation system according to claim 1, further comprising a humidifier for humidifying the fluid supplied to the first separation device. The heat exchange circuit further has a second connection circuit for supplying the heat exchange medium from the first separation device or the second separation device to the humidifier. Claims 3. The separation system according to claim 1, further comprising a water electrolysis device provided upstream of the first separation device for electrolyzing water; and a control unit. The separation system according to claim 2, wherein the control unit starts the second separation device after starting the water electrolysis device when the separation system is started.

4. The separation system according to claim 3, wherein the control unit sets the second separation device to a heating mode that prioritizes heat generation over the operating state of the second separation device after at least one of the first separation device, the humidifier, and the heat exchange circuit reaches a predetermined temperature when the separation system is started.

5. The heat exchange circuit further includes a third connection circuit that supplies the heat exchange medium from the humidifier to the second separation device, and a radiator provided in the third connection circuit. The separation system according to claim 4, wherein the control unit starts the radiator after at least one of the first separation device, the humidifier, and the heat exchange circuit reaches the predetermined temperature, and starts the first separation device while setting the second separation device to a power generation mode that prioritizes power generation over the heating mode.

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