Fuel Cell Systems

Abstract

The fuel cell system according to the present disclosure includes a fuel cell having an anode and a cathode, a branching section that branches anode off-gas discharged from the anode into a branched gas and a recycled gas, a separation device having a plurality of separation units that separate specific gas components from the branched gas, a compressor that pressurizes the branched gas, a pressure gauge that measures the pressure of the branched gas introduced into the separation device, a pressure regulator that adjusts the pressure of the branched gas, a gas information acquisition section that acquires a composition and flow rate of the branched gas, and a distribution mechanism that distributes the branched gas to the plurality of separation units.

Description

[Technical field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] Patent Document 1 discloses a technology for separating carbon dioxide from anode off-gas discharged from the anode of a fuel cell. Specifically, the anode off-gas is introduced into a separation section having a separation membrane. The separation membrane in Patent Document 1 has the property of being easily permeable to carbon dioxide and water, but being difficult to permeate other components. Therefore, the carbon dioxide concentration of the gas that has permeated the separation membrane is higher than that of the anode off-gas. The remaining gas of the anode off-gas that has not permeated the separation membrane contains combustible components such as hydrogen. This gas is reused as regenerated fuel gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-139858 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when the fuel cell is operating at partial load, the flow rate of the anode off-gas introduced into the separation section is reduced compared to when the fuel cell is operating at rated load. Other factors may also reduce the flow rate of the anode off-gas introduced into the separation section. When the flow rate of the anode off-gas is reduced, the area of ​​the separation membrane for the anode off-gas per unit flow rate increases relatively. This causes an increase in the permeation amount of components that are less likely to permeate the separation membrane than carbon dioxide, such as hydrogen. As a result, a problem occurs in that the concentration of carbon dioxide contained in the recovered gas is reduced.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a fuel cell system that can suppress a decrease in the carbon dioxide concentration of the separated gas when the flow rate of the gas introduced into the separation membrane changes. [Means for solving the problem]

[0006] One aspect of a fuel cell system according to the present disclosure includes a fuel cell having an anode and a cathode, a branching section that branches anode off-gas discharged from the anode into a branched gas and a recycled gas, a separation device having a plurality of separation units that separate specific gas components from the branched gas, a compressor that pressurizes the branched gas, a pressure gauge that measures the pressure of the branched gas introduced into the separation device, a pressure regulator that adjusts the pressure of the branched gas, a gas information acquisition section that acquires a composition and flow rate of the branched gas, and a distribution mechanism that distributes the branched gas to the plurality of separation units. Effect of the Invention

[0007] According to the fuel cell system of the present disclosure, when the flow rate of the gas introduced into the separation membrane changes, it is possible to suppress a decrease in the carbon dioxide concentration of the separated gas. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a configuration of a fuel cell system according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing the configuration of a separation device of the fuel cell system shown in FIG. [Diagram 3] FIG. 4 is a diagram showing a modified example of the configuration of the separation device according to the first embodiment. [Figure 4] FIG. 11 is a diagram showing the configuration of a fuel cell system according to a second embodiment. [Diagram 5] FIG. 11 is a diagram showing the configuration of a fuel cell system according to a third embodiment. [Figure 6] FIG. 11 is a diagram showing the configuration of a fuel cell system according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the scope of the present disclosure is not limited to the following embodiments, and may be modified as desired within the scope of the technical concept of the present disclosure.

[0010] Embodiment 1 Fig. 1 is a schematic diagram of a fuel cell system 100 according to embodiment 1. As shown in Fig. 1, the fuel cell system 100 includes a supply path 1, a raw material flow meter 1a, a mixer 2, a reformer 3, a fuel cell 4, a steam generator 7, a condensation tank 9, a branching section 10, a compressor 12, a temperature regulator 13, a control device 19, a pressure gauge 20, a control valve 21, a thermometer 22, and a gas separation device D.

[0011] Although details will be described later, the gas separation device D (hereinafter simply referred to as the separation device D) has a function of separating a process gas containing carbon dioxide into a carbon dioxide rich gas G11 having a high carbon dioxide concentration and a regenerated fuel gas G12 having a low carbon dioxide concentration. The process gas in this embodiment is an anode off-gas discharged from the anode 4A of the fuel cell 4. However, the present disclosure may be applied to a process gas other than the anode off-gas. In other words, the fuel cell system 100 may be applied to a process gas other than that discharged from the fuel cell 4.

[0012] Other examples of the process gas containing carbon dioxide include exhaust gas from a factory and exhaust gas from a power plant. Also, exhaust gas from a reforming reaction system that produces hydrogen from a hydrocarbon fuel, such as the reformer 3, may be used as the process gas. In the present embodiment, the following description will be given taking "anode off-gas G" as an example of the process gas.

[0013] The supply path 1 supplies the raw material to the mixer 2. As the raw material, a carbon-containing material such as a hydrocarbon can be used. An example of the hydrocarbon is methane. In the following, the case where the raw material is methane will be described, but the raw material is not limited to methane. The supply path 1 is provided with a raw material flow meter 1a. The raw material flow meter 1a measures the flow rate of the raw material supplied to the mixer 2. The measurement result of the raw material flow meter 1a may be input to, for example, the operating state acquisition unit 18 and the control device 19. A raw material supply system 2a is connected to the mixer 2. The raw material is mixed with a recycle gas G2 and steam described later in the mixer 2, and is introduced into the reformer 3 via the raw material supply system 2a.

[0014] The reformer 3 generates a reformed gas by a steam reforming reaction or a carbon dioxide reforming reaction. The reformed gas contains hydrogen. The steam reforming reaction follows, for example, the following formulas (I) and (II). CH 4 +H 2 O→CO+3H 2 (I) CO+H 2 O→CO 2 +H 2 (II) The carbon dioxide reforming reaction follows, for example, the following formulas (III) and (IV). CH 4 +CO 2 →2CO+2H 2 (III) 2CO+2H 2 O→2CO 2 +2H 2 (IV)

[0015] The reformer 3 preferably has at least one of a steam reforming catalyst and a carbon dioxide reforming catalyst. In addition, it is more preferable that the reformer 3 has both a steam reforming catalyst and a carbon dioxide reforming catalyst. The steam reforming catalyst promotes the steam reforming reaction. The carbon dioxide reforming catalyst promotes the carbon dioxide reforming reaction. Examples of the steam reforming catalyst include Ni-supported alumina and Ru-supported alumina. Examples of the carbon dioxide reforming catalyst include Ni-supported yttria and Pt-supported yttria.

[0016] The steam reforming catalyst and the carbon dioxide reforming catalyst may be mixed and packed into the reformer 3. The steam reforming catalyst and the carbon dioxide reforming catalyst may form different layers and be packed into the reformer 3. The steam reforming catalyst and the carbon dioxide reforming catalyst may be packed into the reformer 3 so that they are located in appropriate temperature zones for the respective catalysts to function, for example.

[0017] The temperature inside the reformer 3 is set so that at least one of the steam reforming reaction and the carbon dioxide reforming reaction proceeds. A temperature distribution suitable for each reaction may be set inside the reformer 3 so that both the steam reforming reaction and the carbon dioxide reforming reaction proceed. A combustor 3a is thermally connected to the reformer 3. The combustor 3a burns fuel to generate heat so that the inside of the reformer 3 is in an appropriate temperature range. The fuel for the combustor 3a may be the cathode offgas discharged from the cathode 4B, the regenerated fuel gas G12 discharged from the separation device D, or the like. The regenerated fuel gas G12 will be described later.

[0018] The air supply system 5 supplies air to the fuel cell 4. The air supplied from the air supply system 5 is an oxygen-containing gas. The oxygen-containing gas contains oxygen (O 2). The air supply system 5 is provided with an air supply blower 5a for causing air to flow toward the fuel cell 4. The air supply system 5 is also provided with a heat exchanger 17. The heat exchanger 17 exchanges heat between the air flowing in the air supply system 5 and the combustion off-gas discharged from the combustor 3a. This makes it possible to use the exhaust heat of the combustor 3a to heat the air introduced into the cathode 4B.

[0019] The fuel cell 4 has an anode 4A and a cathode 4B. The reformed gas obtained in the reformer 3 is supplied to the anode 4A of the fuel cell 4. Air supplied from an air supply system 5 is supplied to the cathode 4B of the fuel cell 4. The fuel cell 4 uses hydrogen (H 2 The reformed gas containing the fuel cell 4 reacts with air (an oxidant) to generate electricity, thereby generating electrical energy. A fuel cell system 100 including the fuel cell 4 can also be called a power generation system.

[0020] The fuel cell 4 may be, for example, a solid oxide fuel cell. In the case of a solid oxide fuel cell, the reaction at the anode 4A follows formula (V) below, and the reaction at the cathode 4B follows formula (VI) below. H 2 +O 2- →H 2 O+2e - (V) 1 / 2O 2 +2e - →O 2- (VI)

[0021] Anode off-gas G is discharged from the anode 4A of the fuel cell 4. The anode off-gas G may be, for example, hydrogen (H 2 ), carbon dioxide (CO 2 ), water vapor (H 2 O), carbon monoxide (CO), and methane (CH 4The anode off-gas system 6 extracts anode off-gas G from the anode 4A of the fuel cell 4 and guides it to a branching section 10. In the anode off-gas system 6, a water vapor generator 7, a heat recovery device 6a, and a condensation tank 9 are arranged in a portion between the fuel cell 4 and the branching section 10.

[0022] The condensation tank 9 can condense a portion of the water vapor contained in the anode off-gas G. The water obtained in the condensation tank 9 is supplied to the water vapor generator 7 via a pump 23a and a flow rate controller 23. The pump 23a generates power for causing the water to flow from the condensation tank 9 toward the water vapor generator 7. The flow rate controller 23 controls the flow rate of the water supplied to the water vapor generator 7. The measurement result of the flow rate controller 23 may be input to, for example, the operation state acquisition unit 18 and the control device 19.

[0023] The water vapor generator 7 heats the water supplied from the condensation tank 9 by heat exchange with the anode off-gas G. As a result, the water vapor generator 7 obtains water vapor. The water vapor generator 7 has an auxiliary heater 7a. The auxiliary heater 7a is, for example, a heater. When the amount of heat required for evaporating water is insufficient only through heat exchange with the anode off-gas G, the auxiliary heater 7a may be used to heat the water. The water vapor obtained by the water vapor generator 7 is introduced into the mixer 2 from a water vapor supply system 8.

[0024] The heat recovery device 6a is located upstream of the condensation tank 9 and can recover heat from the anode off-gas G. This allows, for example, the anode off-gas G to be set to a temperature equal to or lower than the heat-resistant temperature of a recycle gas blower 16a (described later). A branching section 10 is disposed downstream of the condensation tank 9. At the branching section 10, the anode off-gas system 6 branches into a branch gas system 11 and a recycle gas system 16. The recycle gas system 16 supplies at least a portion of the anode off-gas G to the mixer 2 as a recycle gas G2.

[0025] The branching section 10 can change the distribution ratio of the anode off-gas G to the branch gas system 11 and the recycle gas system 16. The branching section 10 may have, for example, a control valve for changing the distribution ratio. More specifically, the control valve may change the ratio of the flow path cross-sectional area to the branch gas system 11 and the flow path cross-sectional area to the recycle gas system 16 in the branching section 10. In addition, a thermocouple may be provided inside the condensation tank 9 to measure the condensation temperature, thereby making it possible to know the amount of water vapor in the gas. In addition, the measurement result may be input to, for example, the control device 19. However, the structure for changing the distribution ratio in the branching section 10 is not limited to the above and can be appropriately changed.

[0026] The recycled gas system 16 is provided with a recycled gas blower 16a and a recycled gas flowmeter 16b. The recycled gas blower 16a generates power to cause the recycled gas G2 to flow from the branching portion 10 toward the mixer 2. The recycled gas flowmeter 16b measures the flow rate of the recycled gas G2 supplied to the mixer 2. In this manner, the recycled gas system 16 circulates the recycled gas G2 to the raw material supply system 2a. Moreover, the mixer 2 may be an ejector. In this case, since the recycled gas G2 can be sucked in using steam as a driving fluid, the recycled gas blower 16a becomes unnecessary, and the auxiliary power can be reduced.

[0027] The branch gas system 11 supplies at least a portion of the anode off-gas G to the separation device D as a branch gas G1. The branch gas system 11 is provided with a gas information acquisition unit 11a, a compressor 12, and a temperature regulator 13. The gas information acquisition unit 11a acquires information on the branch gas G1. The "information on the branch gas G1" is, for example, the composition, flow rate, pressure, temperature, etc. The information on the composition of the branch gas G1 may include, for example, the partial pressure of carbon dioxide. Since the branch gas G1 is a part of the anode off-gas G, it can also be said that the gas information acquisition unit 11a acquires information on the anode off-gas G.

[0028] The gas information acquisition unit 11a has a sensor or the like according to the type of information to be acquired. For example, when acquiring a composition, the gas information acquisition unit 11a may have a near-infrared spectroscopic sensor. For example, when acquiring a flow rate, pressure, temperature, or the like, the gas information acquisition unit 11a may have a flowmeter, a pressure gauge, a thermometer, or the like. The gas information acquisition unit 11a may have a plurality of types of sensors as described above. However, the gas information acquisition unit 11a may calculate the composition and flow rate of the branch gas G1 based on the operating state of the fuel cell 4 acquired by the operating state acquisition unit 18, the raw material flow rate acquired by the raw material flow meter 1a, the condensation temperature in the condensation tank 9, and the distribution ratio of the anode off-gas G in the branch unit 10.

[0029] The compressor 12 can increase the pressure of the branch gas G1 supplied to the separation device D. The compressor 12 may be, for example, a blower. The pressure of the branch gas G1 in the separation device D can be changed by adjusting the output of the compressor 12. Therefore, the compressor 12 can function as a pressure regulator Cp that adjusts the pressure of the branch gas G1 in the separation device D. The temperature regulator 13 can adjust the temperature of the branch gas G1 supplied to the separation device D.

[0030] In the example of FIG. 1, the temperature regulator 13 has a pump 13a and a heat exchanger 13b. In the heat exchanger 13b, heat exchange is performed between the refrigerant and the branched gas G1. The pump 13a generates power for the refrigerant to flow in the heat exchanger 13b. By changing the output of the pump 13a, the flow rate of the refrigerant flowing in the heat exchanger 13b changes. Therefore, by adjusting the output of the pump 13a, the amount of heat exchanged between the refrigerant and the branched gas G1 in the heat exchanger 13b can be adjusted. This allows the temperature regulator 13 to adjust the temperature of the branched gas G1. However, the configuration of the temperature regulator 13 is not limited to the above, and can be changed as appropriate as long as it can adjust the temperature of the branched gas G1.

[0031] In this embodiment, the separation device D has a plurality of carbon dioxide separation units 14 (hereinafter simply referred to as separation units 14). 2, this embodiment has four separation units 14. The four separation units 14 are referred to as a first separation unit 141, a second separation unit 142, a third separation unit 143, and a fourth separation unit 144, respectively. The separation units 14 are arranged in parallel. That is, when the branch gas G1 is introduced into each of the separation units 14, the separation process of the introduced branch gas G1 is performed simultaneously. Each separation unit 14 has a separation membrane S that selectively allows carbon dioxide to permeate. Also, the separation unit 14 has an introduction chamber R1 and a recovery chamber R2 that are partitioned by the separation membrane S. The separation membrane S is formed of, for example, a polymer. The number of separation units 14 included in the separation device D is not limited to four, but may be two or more.

[0032] As shown in FIG. 2, a branched gas G1 flowing from a branching portion 10 through a branched gas system 11 is distributed to a plurality of separation units 14 by a distribution mechanism DM. The distribution mechanism DM is controlled by a control device 19. The control device 19 controls the distribution mechanism DM based on information from a pressure gauge 20 and the gas information acquisition unit 11a, and distributes the branched gas G1 to a plurality of separation units . The distribution mechanism DM includes a plurality of shutoff valves, and the control device 19 distributes the branched gas G1 to the separation units 14 by opening and closing the shutoff valves. More specifically, the distribution mechanism DM includes a distribution shutoff valve Vi provided in each line that introduces the branched gas G1 into the separation unit 14, and a recovery shutoff valve Vo provided in each line that discharges gas from the introduction chamber R1 of the separation unit 14. In the following explanation, the distribution shutoff valves Vi provided respectively in the lines leading to the first to fourth separation units 141, 142, 143, 144 will be referred to as the first to fourth distribution shutoff valves V1i, V2i, V3i, V4i, and the recovery shutoff valves Vo provided respectively in the lines leading to the gas from the introduction chamber R1 of the first to fourth separation units 141, 142, 143, 144 will be referred to as the first to fourth recovery shutoff valves V1o, V2o, V3o, V4o. The distributed gases GD introduced from the first to fourth distribution cutoff valves V1i, V2i, V3i, and V4i to the separation units 14 are referred to as first to fourth distributed gases GD1, GD2, GD3, and GD4, respectively.

[0033] Next, a method for separating carbon dioxide in each separation unit 14 will be described. First, a method of separating carbon dioxide in the first separation unit 141 will be described when all distribution cutoff valves Vi and all recovery cutoff valves Vo are opened and the branched gas G1 is evenly distributed by the four distribution cutoff valves Vi. That is, in this case, 1 / 4 of the branched gas G1 is distributed to each separation unit 14. The branched gas G1 is first introduced into the introduction chamber R1 of the first separation unit 141. Inside the introduction chamber R1, the branched gas G1 comes into contact with the separation membrane S. The branched gas G1 comes into contact with the separation membrane S at a pressure adjusted by the pressure regulator Cp. As a result, carbon dioxide contained in the branched gas G1 permeates the separation membrane S and moves to the recovery chamber R2. Depending on conditions such as the type and pressure of the separation membrane S, components other than carbon dioxide may also permeate the separation membrane S.

[0034] In the first separation unit 141, the gas that permeates the separation membrane S from the inlet chamber R1 and moves to the recovery chamber R2 is referred to as a first carbon dioxide rich gas GD11. Also, the gas that does not permeate the separation membrane S and remains is referred to as a first regenerated fuel gas GD12. That is, the first separation unit 141 uses the separation membrane S to separate the first distributed gas GD1 into the first carbon dioxide rich gas GD11 and the first regenerated fuel gas GD12. Similarly, in the second to fourth separation units 142, 143, and 144, the separation membrane S is used to separate the branched gas G1 into second to fourth carbon dioxide rich gases GD21, GD31, and GD41 and second to fourth regenerated fuel gases GD22, GD32, and GD42.

[0035] In this specification, the gas that permeates the separation membrane S from the introduction chamber R1 of the first to fourth separation units 141, 142, 143, and 144 and moves to the recovery chamber R2 is referred to as carbon dioxide-rich gas G11. Moreover, among the gases that do not permeate the separation membrane S and remain in the first to fourth separation units 141, 142, 143, and 144, the gas that passes through the recovery cutoff valve Vo is referred to as regenerated fuel gas G12. That is, the separation unit 14 separates the branch gas G1 into the carbon dioxide-rich gas G11 and the regenerated fuel gas G12 using the separation membrane S.

[0036] The carbon dioxide-rich gas G11 has a higher concentration of carbon dioxide than the branch gas G1 before being separated by the separation unit 14. The recycled fuel gas G12 has a lower concentration of carbon dioxide than the branch gas G1 before being separated by the separation unit 14. The recycled fuel gas G12 also contains combustible components such as hydrogen, carbon monoxide, and methane. Therefore, the recycled fuel gas G12 can be used as a fuel. As shown in FIG. 1 and FIG. 2, in this embodiment, the regenerated fuel gas G12 is used as fuel in the combustor 3a of the reformer 3. The introduction chamber R1 of each of the separation units 141-144 is connected to a regenerated fuel gas system 14b. The first to fourth regenerated fuel gases GD12, GD22, GD32, and GD42 discharged from each of the separation units 141-144 pass through the recovery shutoff valve Vo from the introduction chamber R1 and are discharged to the regenerated fuel gas system 14b. The combustor 3a is connected to the downstream side of the regenerated fuel gas system 14b. With this configuration, the regenerated fuel gas G12 is supplied from the introduction chamber R1 to the combustor 3a and reused as fuel.

[0037] As shown in FIG. 1 and FIG. 2, a carbon dioxide capture system 14a is connected to the recovery chamber R2 of each of the separation units 141-144. The first to fourth carbon dioxide rich gases GD11, GD21, GD31, and GD41 discharged from each of the separation units 141-144 are discharged from the recovery chamber R2 to the carbon dioxide capture system 14a. A vacuum pump 15 is disposed in the carbon dioxide capture system 14a. The vacuum pump 15 sucks the carbon dioxide rich gas G11 in the recovery chamber R2 through the carbon dioxide capture system 14a. The carbon dioxide rich gas G11 thus recovered may be reused for other purposes. The vacuum pump 15 may not be provided.

[0038] The pressure gauge 20 measures the pressure of the regenerated fuel gas G12 in the portion of the regenerated fuel gas system 14b between the separation unit 14 and the regulating valve 21. From the measurement result of the pressure gauge 20, the pressure of the branched gas G1 supplied to the separation unit 14 can be indirectly known. Note that, if the pressure of the branched gas G1 supplied to the separation unit 14 can be measured directly or indirectly, the position of the pressure gauge 20 can be changed as appropriate.

[0039] The thermometer 22 measures the temperature of the branched gas G1 in the portion between the temperature regulator 13 and the separation unit 14 in the branched gas system 11. The position of the thermometer 22 can be changed as appropriate as long as it can measure the temperature of the branched gas G1 supplied to the separation unit 14.

[0040] The regulating valve 21 is provided in the regenerated fuel gas system 14b. The pressure in the introduction chamber R1 can be adjusted by opening and closing the regulating valve 21. For example, when the aperture of the regulating valve 21 is increased, the regenerated fuel gas G12 flows more easily from the introduction chamber R1 to the combustor 3a. As a result, the pressure in the introduction chamber R1 decreases. Conversely, when the aperture of the regulating valve 21 is decreased, the pressure in the introduction chamber R1 increases. Therefore, the regulating valve 21 can function as a pressure regulator Cp that adjusts the pressure of the branched gas G1 in the introduction chamber R1.

[0041] As shown in Fig. 1, the fuel cell system 100 includes an operating state acquisition unit 18 and a control device 19. The operating state acquisition unit 18 acquires the operating state of the fuel cell 4. The operating state is, for example, the state of the output of the fuel cell 4 relative to the rated output. The operating state acquisition unit 18 may include, for example, an ammeter and a voltmeter for measuring the output of the fuel cell 4. The operating state acquisition unit 18 inputs the operating state of the fuel cell 4 to the control device 19.

[0042] Various information is input to the control device 19 from a pressure gauge 20, a thermometer 22, a recycled gas flowmeter 16b, an operating state acquisition unit 18, an operation time acquisition unit 24 (described later), etc. Based on this information, the control device 19 controls the temperature regulator 13, the pressure regulator Cp, the distribution mechanism DM, etc. The control device 19 may control the distribution ratio of the branch gas G1 and the recycled gas G2 in the branch section 10.

[0043] Here, when the fuel cell 4 is in partial load operation, the flow rate of the anode off-gas G decreases. As a result, the flow rate of the branched gas G1 supplied to the separation unit 14 may decrease. When the flow rate of the branched gas G1 decreases, the area of ​​the separation membrane S per unit flow rate of the branched gas G1 increases in the separation unit 14. As a result, hydrogen and other substances having a smaller permeability coefficient than carbon dioxide also easily permeate the separation membrane S, and the carbon dioxide concentration in the carbon dioxide-rich gas G11 decreases. Furthermore, the amount of combustible components such as hydrogen contained in the regenerated fuel gas G12 decreases, which causes a problem of a decrease in the power generation efficiency of the entire system. Therefore, in this embodiment, when the flow rate of the branch gas G1 supplied to the separation unit 14 decreases, some of the multiple distribution shutoff valves Vi are closed according to the flow rate to adjust the number of separation units 14 in use.

[0044] Hereinafter, a method in this embodiment in which the control device 19 controls the number of separation units 14 in use so that the separation performance of the separation units 14 does not decrease when the output of the fuel cell 4 fluctuates will be specifically described. The branched gas G1 is distributed to all or some of the separation units 14 according to the pressure acquired by the pressure gauge 20 and information on the flow rate of the branched gas G1 from the gas information acquisition unit 11a. Specifically, the control device 19 controls the open / close states of the distribution cutoff valve Vi and the recovery cutoff valve Vo by the distribution mechanism DM. This control may be further performed based on the temperature acquired by the thermometer 22, the flow rate of the recycled gas G2 acquired by the recycled gas flowmeter 16b, the operating state of the fuel cell 4 acquired by the operating state acquisition unit 18, and the like.

[0045] For example, the control device 19 holds the carbon dioxide concentration or flow rate of the carbon dioxide-rich gas G11 obtained by the separation unit 14 as a target value. The control device 19 may control the open / close states of the distribution cutoff valve Vi and the recovery cutoff valve Vo of the distribution mechanism DM so as to satisfy these target values. As an example, first, when the flow rate of the branch gas G1 is equal to or greater than a first threshold, all the distribution cutoff valves Vi are in an open state so that the branch gas G1 is introduced into all of the separation units 14. When the flow rate of the branch gas G1 is equal to or greater than the first threshold, it includes, for example, the flow rate of the branch gas G1 when the fuel cell is in a rated output state. The flow rate of the branched gas G1 decreases when the output of the fuel cell 4 decreases. To compensate for this decrease, the control device 19 may execute the following control.

[0046] When the flow rate of the branch gas G1 falls below a first threshold, one of the multiple distribution shutoff valves Vi is closed to prevent gas separation in one separation unit 14 connected to the closed distribution shutoff valve Vi. For example, the first threshold is determined based on a target value of the carbon dioxide concentration or flow rate of the carbon dioxide-rich gas G11, and may be, for example, 3 / 4 of the flow rate of the branch gas G1 at rated output.

[0047] When the gas flow rate falls below the first threshold, for example, the fourth distribution cutoff valve V4i is closed and the branched gas G1 is introduced into the first to third separation units 141 to 143. This makes it possible to prevent an excessive increase in the area of ​​the separation membrane S for the branched gas G1 per unit flow rate in the first to third separation units 141 to 143. This makes it possible to prevent an increase in the permeation amount of a component that is less likely to permeate the separation membrane S than carbon dioxide, such as hydrogen, and to prevent a decrease in the concentration of carbon dioxide contained in the carbon dioxide-rich gas G11.

[0048] In this way, when the flow rate of the branch gas G1 falls below the first threshold, one of the separation units 14 is shut off. Furthermore, when the flow rate of the branch gas G1 decreases, the number of separation units 14 to which the branch gas G1 is introduced is reduced. When the threshold value of the flow rate of the branch gas G1 when two of the separation units 14 are shut off is set as the second threshold, and the threshold value of the flow rate of the branch gas G1 when three separation units 14 are shut off is set as the third threshold, these threshold values ​​satisfy the relationship of first threshold>second threshold>third threshold. For example, the second threshold value may be 2 / 4 of the flow rate of the branch gas G1 at rated output, and the third threshold value may be 1 / 4 of the flow rate of the branch gas G1 at rated output. Note that the second and third threshold values ​​may be determined based on a target value of the carbon dioxide concentration or flow rate of the carbon dioxide rich gas G11.

[0049] Based on these first to third thresholds, when the flow rate of the branched gas G1 falls below the threshold, the distribution shutoff valves Vi connected to the separation units 14, the number of which corresponds to the threshold, are closed. When the flow rate of the branched gas G1 becomes equal to or greater than the threshold, the distribution shutoff valves Vi connected to the separation units 14, the number of which corresponds to each threshold, are opened. The open / closed state of the recovery cutoff valve Vo may be controlled by the control device 19 in accordance with the opening / closing of the corresponding distribution cutoff valve Vi.

[0050] In addition, when changing the pressure of the distributed gas GD in each separation unit 14, the control device 19 may perform the following control. By increasing the opening of the regulating valve 21 serving as the pressure regulator Cp, the regenerated fuel gas G12 can easily flow from the separation unit 14 to the combustor 3a. Alternatively, by decreasing the rotation speed of the compressor 12 serving as the pressure regulator Cp, the pressure applied to the branched gas G1 in the branched gas system 11 can be reduced. As a result, the pressure of the branched gas G1 in the separation unit 14 (the total pressure of the distributed gas GD) can be changed.

[0051] In this manner, the control device 19 controls the distribution mechanism DM and the pressure regulator Cp using the carbon dioxide concentration or flow rate of the carbon dioxide rich gas G11 obtained by the separation unit 14 as a target value.

[0052] <Uniformity of Operation Times of Separation Units 14 by Operation Time Acquisition Unit 24> In the above example, the fourth separation unit 144 is shut off when the flow rate of the branched gas G1 becomes equal to or less than the first threshold. However, if the fourth separation unit 144 is always shut off when the flow rate of the branched gas G1 becomes equal to or less than the first threshold, the operation time of the first to third separation units 141 to 143 becomes longer than the operation time of the fourth separation unit 144. The separation membrane S may need to be replaced when it exceeds a specified usage time, and only the separation membrane S of the first to third separation units 141 to 143 that have been in operation for a long time may need to be replaced. Therefore, in this embodiment, an operation time acquisition unit 24 (see FIG. 2) is provided that acquires operation times of the plurality of separation units 14. When the flow rate of the branched gas G1 falls below a threshold, the separation units 14 to be shut off are switched based on information from the operation time acquisition unit 24, and the operation times of the separation units 14 are controlled to be equal to each other. The operation time acquisition unit 24 may be provided inside the control device 19, or the operation time acquisition unit 24 and the control device 19 may be realized by the same hardware.

[0053] For example, when a certain time has elapsed since the fourth separation unit 144 was shut off, the distribution shutoff valve V4i of the fourth separation unit 144 is opened, and the distribution shutoff valve Vi of the separation unit 14 with the longest accumulated operating time is closed. Thereafter, every time a certain time elapses, the distribution shutoff valve Vi of the separation unit 14 that was shut off is opened, and the distribution shutoff valve Vi of the separation unit 14 with the longest accumulated operating time is closed. Similarly, in the case where multiple separation units 14 are shut off, the control device 19 controls the opening and closing of the distribution shutoff valve Vi of the separation unit 14 to which the branch gas G1 is introduced based on the operating times of the multiple separation units 14 acquired by the operating time acquisition unit 24, so that the operating times of each separation unit 14 are equalized. Specifically, the control device 19 controls the distribution mechanism DM based on the operation times of the multiple separation units 14 acquired by the operation time acquisition unit 24 so that the operation times of the multiple separation units 14 are uniform, thereby controlling the opening and closing of the above-mentioned distribution shut-off valve Vi.

[0054] <Adjustment of the operating pressure of the separation unit when opening and closing the distribution shutoff valve Vi> When the flow rate of the branch gas G1 falls below the first threshold and the distribution shutoff valve V4i is closed, the flow rate of the gas flowing through the fourth separation unit 144 changes, for example, from ¼ the flow rate of the branch gas G1 to zero. When the distribution shutoff valve V4i is controlled in two patterns, an open state and a closed state, a sudden decrease in the flow rate may occur in the fourth separation unit 144. Also, a sudden increase in the flow rate may occur in the first to third separation units 141 to 143 other than the fourth separation unit 144. Hereinafter, the condition where such a sudden change in flow rate occurs and the operating pressure of the separation unit 14 changes suddenly is referred to as a discontinuous condition. Since the separation capacity of the separation unit 14 may decrease under the discontinuous condition, in this embodiment, the pressure regulator Cp is controlled, and the control device 19 controls the distribution mechanism DM so that the change in flow rate in the separation unit 14 becomes gradual. For example, when the first to third separation units 141 to 143 are operating, and the control device 19 detects that the flow rate of the branched gas G1 measured by the gas information acquisition unit 11a has exceeded a first threshold value, and starts introducing the branched gas G1 into the fourth separation unit 144, the control device 19 may perform the following first or second example control.

[0055] In the first example, first, before opening the fourth distribution shutoff valve V4i, the operating pressure in the first to third separation units 141 to 143 is increased by controlling the pressure regulator Cp. After that, the opening degree of the fourth distribution shutoff valve V4i is gradually increased. The opening degree of the fourth distribution shutoff valve V4i may be increased continuously from 0% to 100% within a certain time, or may be increased in steps of several percent each. As the opening degree of the fourth distribution shutoff valve V4i increases and the operating pressure in the fourth separation unit 144 increases, the gas flowing toward the first to third separation units 141 to 143 decreases, so that the operating pressure in the first to third separation units 141 to 143 decreases to a certain pressure. After the operating pressures of the four separation units 14 become equal, the pressure regulator Cp may be controlled as necessary to reduce the pressure of the branch gas G1.

[0056] In the second example, the fourth distribution cutoff valve V4i is opened and at the same time the operating pressures in the first to third separation units 141 to 143 are reduced by controlling the pressure regulator Cp. After that, the operating pressures of the first to fourth separation units 141 to 144 are increased to a constant pressure. After the operating pressures of the four separation units 14 become equal, the pressure regulator Cp may be controlled as necessary to increase the pressure of the branched gas G1.

[0057] In the first and second examples, by controlling the operating pressure of the separation unit 14 using the pressure regulator Cp, it is possible to distribute the branched gas G1 to multiple separation units 14 according to a threshold value while suppressing a decrease in separation capacity due to a sudden change in the operating pressure in the separation unit 14. Incidentally, even when one of the distribution cutoff valves Vi is closed, the pressure regulator Cp can be controlled based on the first or second example to prevent a discontinuous state.

[0058] <Serial arrangement of separation units 14> In the separation device D, a mechanism is provided for introducing gas discharged from one separation unit 14 into another separation unit 14, and thus, a plurality of separation units 14 are provided in series. In this embodiment, a check valve NV is provided for introducing gas discharged from the introduction chamber R1 into another separation unit 14. As a result, gas separation processing is sequentially performed on a portion of the branched gas G1 by the plurality of separation units 14. Thus, in the example shown in FIG. 2, in addition to the plurality of separation units 14 being provided in parallel, the plurality of separation units 14 are also provided in series. 2, a check valve NV is provided that is connected from the introduction chamber R1 of one separation unit 14 to the line of the distributed gas GD leading to the introduction chamber R1 of the other separation unit 14. Thus, the gas in the introduction chamber R1 is introduced into the introduction chamber R1 of the other separation unit 14 through the check valve NV.

[0059] More specifically, in the example shown in Figure 2, there are provided a first check valve NV1 connected from the inlet chamber R1 of the first separation unit 141 to the line of the distribution gas GD2 introduced into the second separation unit 142, a second check valve NV2 connected from the inlet chamber R1 of the second separation unit 142 to the line of the distribution gas GD3 introduced into the third separation unit 143, and a third check valve NV3 connected from the inlet chamber R1 of the third separation unit 143 to the line of the distribution gas GD4 introduced into the fourth separation unit 144.

[0060] For example, a case will be described in which the first distribution shutoff valve V1i is opened, the second to fourth distribution shutoff valves V2i, V3i, and V4i are closed, the first to third recovery shutoff valves V1o, V2o, and V3o are closed, and the fourth recovery shutoff valve V4o is opened. A portion of the first regenerated fuel gas GD12 led out from the first check valve NV1 of the first separation unit 141 is further gas-separated in the second to fourth separation units 142 to 144 and is discharged toward the fourth recovery shutoff valve V4o or the inlet line for the carbon dioxide-rich gas G11.

[0061] In this way, when multiple separation units 14 are arranged in series, a portion of the first to third regenerated fuel gases GD12 to GD32 is again subjected to gas separation processing by the separation membrane S. This makes it possible to further increase the carbon dioxide concentration contained in the carbon dioxide-rich gas G11 discharged from the separation device D, and to further increase the concentration of hydrogen and other elements contained in the regenerated fuel gas G12.

[0062] It is not essential to provide a check valve NV, and the check valve NV may be omitted and the multiple separation units 14 may be arranged only in parallel, not connected in series, as shown in Fig. 3. Furthermore, at least two or more of the multiple separation units 14 may be connected by the check valve NV.

[0063] The separation device D in this embodiment separates the process gas (anode off-gas G) into a carbon dioxide-rich gas G11 and a regenerated fuel gas G12. However, the process gas to be separated by the separation device D may not contain flammable components such as hydrogen. Therefore, the residual gas after the carbon dioxide-rich gas G11 is separated from the process gas may not contain flammable components. In other words, the separation device D may separate the process gas into a carbon dioxide-rich gas G11 with an increased carbon dioxide concentration and a regenerated fuel gas G12 with a reduced carbon dioxide concentration and an increased hydrogen concentration.

[0064] As described above, the fuel cell system 100 of the present disclosure includes a fuel cell 4 having an anode 4A and a cathode 4B, a branching section 10 that branches the anode off-gas G discharged from the anode 4A into a branched gas G1 and a recycled gas G2, a separation device D having a plurality of separation units 14 that separate specific gas components from the branched gas G1, a compressor 12 that pressurizes the branched gas G1, a pressure gauge 20 that measures the pressure of the branched gas G1 introduced into the separation device D, a pressure regulator Cp that adjusts the pressure of the branched gas G1, a gas information acquisition section 11a that acquires the composition and flow rate of the branched gas G1, and a distribution mechanism DM that distributes the G1 branched gas to the plurality of separation units 14.

[0065] According to the fuel cell system 100 having such a configuration, when the flow rate of the process gas supplied to the separation device D changes, it is possible to adjust the flow rate of the process gas distributed to each separation unit 14 by the distribution mechanism DM so as not to decrease the carbon dioxide concentration of the carbon dioxide-rich gas G11. Therefore, it is possible to adjust the operating pressure of the gas separation process in the separation unit 14. The control based on the flow rate and pressure has a small time constant, that is, the control based on the flow rate and pressure has a high response speed. Therefore, by controlling the gas separation process by dividing the branch gas G1 into the multiple separation units 14 as in the present embodiment, it is possible to suitably bring the concentration or recovery amount of carbon dioxide close to the target value.

[0066] The system further includes a control device 19 for controlling the distribution mechanism DM. The control device 19 controls the distribution mechanism DM based on information from a pressure gauge 20 and a gas information acquisition unit 11a, and distributes the branched gas G1 to a plurality of separation units . This allows the branched gas G1 to be distributed and introduced into the plurality of separation units 14, thereby enabling gas separation processing at an appropriate flow rate and pressure of the branched gas G1 in each separation unit 14.

[0067] Further, the separation units 14 are arranged in parallel, the distribution mechanism DM includes a distribution shutoff valve Vi, and the control device 19 distributes the branched gas G1 to the separation units 14 by opening and closing the distribution shutoff valve Vi. Since a plurality of separation units 14 are arranged in parallel, it is possible to simultaneously perform gas separation processing in the plurality of separation units 14. In addition, by opening and closing the distribution shutoff valve Vi according to the flow rate of the branch gas G1, it is possible to perform gas separation processing at an appropriate flow rate and pressure of the branch gas G1 in each separation unit 14.

[0068] Furthermore, at least two separation units 14 included in the separation unit 14 are arranged in series. This allows a portion of the branched gas G1 to be treated multiple times by the separation membrane S, so that the concentrations of the gases to be recovered in the carbon dioxide rich gas G11 and the regenerated fuel gas G12 can be increased.

[0069] In addition, the distribution mechanism DM distributes the branched gas G1 to all of the multiple separation units 14 when the flow rate of the branched gas G1 acquired by the gas information acquisition unit 11a is equal to or greater than a threshold value, and distributes the branched gas G1 to some of the multiple separation units 14 when the flow rate of the branched gas G1 acquired by the gas information acquisition unit 11a is below the threshold value. This allows the number of separation units 14 into which the branch gas G1 is introduced to be adjusted based on the threshold value. This makes it possible to prevent an excessive increase in the area of ​​the separation membrane S for the branch gas G1 per unit flow rate in the separation unit 14. This prevents an increase in the permeation amount of a component that is less permeable through the separation membrane S than carbon dioxide, such as hydrogen, and prevents a decrease in the concentration of carbon dioxide contained in the carbon dioxide-rich gas G11.

[0070] The control device 19 further includes an operation time acquisition unit 24 that acquires the operation times of the multiple separation units 14, and controls the distribution mechanism DM based on the operation times of the multiple separation units 14 acquired by the operation time acquisition unit 24, so that the operation times of the multiple separation units 14 are uniform. This allows the usage time of the separation membrane S included in each of the multiple separation units 14 to be equal. Therefore, the timing for replacement or maintenance of the separation membrane S based on the accumulated usage time of the separation membrane S can be set to the same period.

[0071] Moreover, by controlling the pressure regulator Cp to change the pressure of the branch gas G1, the operating pressure of the separation unit 14 is adjusted when the open / closed state of the distribution cutoff valve Vi is changed. This makes it possible to prevent the operating pressure of the separation unit 14 from changing suddenly when the distribution shutoff valve Vi is opened or closed, thereby making it possible to prevent a decrease in the gas separation capacity of the separation unit 14 due to a sudden change in the operating pressure.

[0072] It also has a vacuum pump that sucks in the carbon dioxide rich gas G11 discharged from the separation device D. According to this configuration, the pressure ratio between the introduction chamber R1 and the recovery chamber R2 can be increased, and the performance of the separation membrane S can be improved. Furthermore, the carbon dioxide rich gas G11 can be prevented from accumulating in the recovery chamber R2. Therefore, the phenomenon in which the permeation of carbon dioxide in the separation membrane S stagnates due to the high carbon dioxide concentration in the recovery chamber R2 can be prevented.

[0073] Embodiment 2 Next, a fuel cell system 100A according to a second embodiment will be described with reference to Fig. 4. The basic configuration of the fuel cell system 100A is similar to that of the fuel cell system 100 according to the first embodiment, so differences will be mainly described.

[0074] 4, the fuel cell system 100A according to this embodiment further includes a temperature detection mechanism 30 provided in the combustor 3a. The temperature detection mechanism 30 measures the temperature of the combustor 3a. Temperature information from the temperature detection mechanism 30 is input to the control device 19.

[0075] The combustor 3a burns fuel to generate heat so as to maintain an appropriate temperature range inside the reformer 3. As described above, the regenerated fuel gas G12 discharged from the separation device D is used as fuel for the combustor 3a. In this embodiment, the combustion temperature of the combustor 3a is measured by the temperature detection mechanism 30, and the control device 19 estimates the amount of gas separated in the separation device D (the amount of regenerated fuel gas G12) based on the temperature information from the temperature detection mechanism 30. Then, the amount of gas separated in the separation device D is controlled according to the estimated amount of gas separated. The amount of gas separated in the separation device D is controlled by the distribution mechanism DM or the pressure regulator 21. For example, when the combustion temperature is lower than the target value, the control device 19 may control the distribution mechanism DM or the pressure regulator 21 so as to increase the amount of regenerated fuel gas G12, thereby increasing the amount of gas separated in the separation device D. When the combustion temperature is higher than the target value, the control device 19 may control the distribution mechanism DM or the pressure regulator 21 so as to decrease the amount of regenerated fuel gas G12, thereby decreasing the amount of gas separated in the separation device D.

[0076] The fuel cell system 100A in this embodiment has a reformer 3 that produces hydrogen from a hydrocarbon fuel, and a combustor 3a that is thermally connected to the reformer, and supplies the regenerated fuel gas G12, which has a higher hydrogen concentration than the branched gas G1 and is discharged from a separation device D, to the combustor 3a. The distribution mechanism DM or the pressure regulator 21 is controlled based on information from a temperature detection mechanism 30 provided in the combustor 3a. According to this configuration, the regenerated fuel gas G12, which has a lower carbon dioxide concentration and a higher hydrogen concentration than the process gas, can be efficiently reused as fuel for the combustor 3a, thereby further improving the power generation efficiency of the entire system.

[0077] Embodiment 3 Next, a fuel cell system 100B according to a third embodiment will be described with reference to Fig. 5. The basic configuration of the fuel cell system 100B is similar to that of the fuel cell system 100 of the first embodiment, so the following description will focus on the differences.

[0078] As shown in FIG. 5, the fuel cell system 100B further includes a fuel synthesis reaction mechanism 40 that produces a synthetic fuel from carbon dioxide. The carbon dioxide-rich gas G11 separated from the branched gas G1 by the separation device D and introduced into the carbon dioxide capture system 14a is supplied to the fuel synthesis reaction mechanism 40 together with hydrogen gas supplied from the outside. The hydrogen gas supplied from the outside is hydrogen generated separately by water electrolysis, or hydrogen stored and transported by other generation methods, etc. The carbon and hydrogen in the carbon dioxide-rich gas G11 react to produce a synthetic fuel (e.g., methane), which is a hydrocarbon-based fuel.

[0079] The fuel cell system 100B in this embodiment further includes a fuel synthesis reaction mechanism 40 that produces synthetic fuel from carbon dioxide, and a carbon dioxide capture system 14a that supplies the carbon dioxide-rich gas G11 separated from the branch gas G1 by the separation device D to the fuel synthesis reaction mechanism 40. According to this, the carbon dioxide rich gas G11 discharged from the separation device D can be used to synthesize synthetic fuel.

[0080] Embodiment 4 Next, a fuel cell system 100C according to a third embodiment will be described with reference to Fig. 6. The basic configuration of the fuel cell system 100C is similar to that of the fuel cell system 100B according to the third embodiment, so differences will be mainly described.

[0081] As shown in FIG. 6, the fuel cell system 100C further includes a co-electrolysis cell 50 between the carbon dioxide capture system 14a and the fuel synthesis reaction mechanism 40. The co-electrolysis cell 50 receives the carbon dioxide-rich gas G11 that has been separated from the branched gas G1 by the separation device D and introduced into the carbon dioxide capture system 14a. In the co-electrolysis cell 50, a synthesis gas containing hydrogen and carbon monoxide is produced from the carbon dioxide-rich gas G11. The synthesis gas is introduced into the fuel synthesis reaction mechanism 40, where a synthetic fuel (e.g., methane or higher hydrocarbons) is produced from the synthesis gas containing hydrogen and carbon monoxide.

[0082] According to this embodiment, a co-electrolysis cell 50 for producing synthesis gas containing hydrogen and carbon monoxide is further provided between the carbon dioxide capture system 14a and the fuel synthesis reaction mechanism 40. This allows the fuel synthesis reaction mechanism 40 to use hydrogen produced in the co-electrolysis cell 50 instead of hydrogen supplied from an external source as in the third embodiment.

[0083] Carbon recycling can be achieved by turning the carbon components used as raw materials into synthetic fuel.

[0084] The technical scope of the present disclosure is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present disclosure.

[0085] For example, a shift reaction section 61 for converting carbon monoxide into carbon dioxide and a shift reaction heat exchange section 62 for exchanging heat between the heat of the shift reaction section and steam may be provided between the branching section 10 and the compressor 12 for boosting the pressure of the branched gas G1 supplied to the separation device D. The steam used for the heat exchange may be the steam supplied to the reformer 3. In the shift reaction section 61 and the shift reaction heat exchange section 62, the concentration of each gas in the branched gas G1 changes due to the shift reaction. For this reason, it is preferable that the shift reaction section 61 and the shift reaction heat exchange section 62 are disposed upstream of the gas information acquisition section 11a. Furthermore, in the shift reaction section 61, the higher the water vapor partial pressure, the more the reaction proceeds in the direction of producing carbon dioxide, so it is more preferable to provide the shift reaction section 61 in an appropriate temperature region between the water vapor generator 7 and the condensation tank 9. The shift reaction makes it possible to reduce the carbon monoxide concentration and increase the carbon dioxide and hydrogen concentrations in the branched gas G1 before it is introduced into the separation device D. This makes it possible to further increase the carbon dioxide or hydrogen concentrations in the carbon dioxide-rich gas G11 and regenerated fuel gas G12 discharged from the separation device D.

[0086] In addition, in the first embodiment, the compressor 12 and the regulating valve 21 function as the pressure regulator Cp. However, the function of the pressure regulator Cp may be realized by only one of the compressor 12 and the regulating valve 21. In addition, the fuel cell system 100 may not include the branching section 10, and the entire amount of the anode off-gas G may be supplied directly to the separation device D.

[0087] In the above embodiment, the control device 19 controls the temperature regulator 13 and the pressure regulator Cp. The functions of the control device 19 are realized by a processor such as a CPU (Central Processing Unit) executing a program stored in a program memory. Some or all of these functions may be realized by hardware such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array), or may be realized by software and hardware working together. The functions of the control device 19 may be realized by one piece of hardware. Alternatively, the hardware that controls the temperature regulator 13 may be different from the hardware that controls the pressure regulator Cp.

[0088] In addition, the above-described embodiments and modifications may be combined as appropriate. [Explanation of symbols]

[0089] 3...Reformer 3a...Combustor 4...Fuel cell 4A...Anode 4B...Cathode 10...Branch section 11...Branch gas system 11a...Gas information acquisition section 13...Temperature regulator 14...Separation unit 14a...Carbon dioxide capture system 15...Vacuum pump 18...Operation status acquisition section 19...Control device 22...Thermometer 24...Operation time acquisition section 30...Temperature detection mechanism 40...Fuel synthesis reaction mechanism 50...Co-electrolysis cell 61...Shift reaction section 62...Shift reaction heat exchange section 100, 100A, 100B, 100C...Fuel cell system Cp...Pressure regulator D...Separator DM...Distribution mechanism G...Anode off-gas (process gas) G1...Branch gas G2...Recycled gas G11...Carbon dioxide-rich gas G12...Regenerated fuel gas (residual gas) Vi...Distribution shutoff valve NV...Check valve

Claims

1. A fuel cell having an anode and a cathode, A branching section that splits the anode off-gas discharged from the anode into branched gas and recycled gas, A separation device having multiple separation units for separating specific gas components from the aforementioned branched gas, A compressor for pressurizing the aforementioned branched gas, A pressure gauge for measuring the pressure of the branched gas introduced into the separation device, A pressure regulator for adjusting the pressure of the aforementioned branch gas, A gas information acquisition unit that acquires the composition and flow rate of the aforementioned branch gas, A fuel cell system comprising a distribution mechanism for distributing the branched gas to the plurality of separation units.

2. The device further comprises a control device for controlling the distribution mechanism, The fuel cell system according to claim 1, wherein the control device controls the distribution mechanism based on information from the pressure gauge and the gas information acquisition unit, and distributes the branched gas to the plurality of separation units.

3. The aforementioned plurality of separation units are arranged in parallel, The distribution mechanism includes a distribution shutoff valve. The fuel cell system according to claim 2, wherein the control device distributes the branched gas to the separation unit by opening and closing the distribution shutoff valve.

4. The fuel cell system according to claim 3, wherein at least two of the separation units included in the separation unit are arranged in series.

5. The distribution mechanism is, If the flow rate of the branched gas acquired by the gas information acquisition unit is equal to or greater than a threshold, the branched gas is distributed to all of the plurality of separation units. The fuel cell system according to any one of claims 1 to 4, wherein if the flow rate of the branched gas acquired by the gas information acquisition unit falls below a threshold, the branched gas is distributed to a portion of the plurality of separation units.

6. The system further includes an operating time acquisition unit that acquires the operating time of the plurality of separation units, The fuel cell system according to any one of claims 1 to 4, wherein the control device for controlling the distribution mechanism controls the distribution mechanism based on the operating times of the plurality of separation units acquired by the operating time acquisition unit so that the operating times of the plurality of separation units become uniform.

7. The fuel cell system according to claim 3, wherein the operating pressure of the separation unit is adjusted when the open / closed state of the distribution shutoff valve is changed by controlling the pressure regulator to change the pressure of the branched gas.

8. A reformer that produces hydrogen from hydrocarbon fuels, The reformer and the combustor are thermally connected, A fuel cell system according to any one of claims 1 to 4 and 7, comprising supplying a regenerated fuel gas with a higher hydrogen concentration than the branched gas discharged from the separation device to the combustor, and controlling the distribution mechanism or the pressure regulator based on information from a temperature detection mechanism provided in the combustor.

9. The fuel synthesis reaction mechanism that produces synthetic fuel from carbon dioxide, A fuel cell system according to any one of claims 1 to 4 and 7, further comprising a carbon dioxide recovery system that supplies carbon dioxide-rich gas separated from the branch gas by the separation device to the fuel synthesis reaction mechanism.

10. The fuel cell system according to claim 9, further comprising a co-electrolytic cell that generates a synthesis gas containing hydrogen and carbon monoxide between the carbon dioxide recovery system and the fuel synthesis reaction mechanism.

11. The system comprises a shift reaction section for converting carbon monoxide to carbon dioxide between the branching section and a compressor for increasing the pressure of the branched gas supplied to the separation device, and a shift reaction heat exchange section for performing heat exchange between the heat of the shift reaction section and water vapor. The fuel cell system according to any one of claims 1 to 4 and 7, wherein the steam used for the heat exchange is steam supplied to a reformer that generates hydrogen from a hydrocarbon fuel.

12. A fuel cell system according to any one of claims 1 to 4 and 7, further comprising a vacuum pump for sucking up carbon dioxide-rich gas discharged from the separation device.

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