JP2009054290A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of efficiently exhausting non-reactive fluid not served for power generation reaction in a fuel cell. <P>SOLUTION: The fuel cell 100 is provided with a plurality of power generating modules 110 including an electrolyte film pinched by electrodes, a hydrogen exhausting manifold 122 coupled with each of the plurality of power generating modules 110 for exhausting exhaust gas, and a plurality of branched flow channels 130 branched from the hydrogen-exhausting manifold 122. Each of the plurality of branched flow channels 130 is provided with a gas injection valve 131. A control part 600 is able to control an exhaust gas exhaust volume from each of the plurality of power generating modules 110 by controlling valve switching of the gas injection valve 131. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

The fuel cell generates power by receiving supply of hydrogen and oxygen as reaction gases. In a fuel cell, if a non-reactive fluid containing water generated by a power generation reaction or a non-reactive gas (such as N ₂ gas) that is not used for the power generation reaction stays in a power generation region where power generation is performed, There is a possibility that the efficiency of power generation is reduced by obstructing the flow of the reactive gas in the region. Until now, various techniques have been proposed for discharging the non-reacting fluid to the outside of the fuel cell (Patent Document 1, etc.).

JP 2004-536438 A JP 2005-203143 A JP 2006-155997 A JP 2005-100827 A JP 2005-209427 A

  By the way, in general, a fuel cell generates power with a plurality of power generation modules, and collects electricity generated by each power generation module to obtain the output of the fuel cell. Further, the retention of the non-reacting fluid described above occurs in some power generation modules, and other power generation modules can usually generate power normally. Therefore, it is preferable that the non-reacting fluid is discharged from the power generation module having a reduced power generation efficiency. However, the reality is that until now there has not been enough ingenuity to meet these requirements.

  An object of the present invention is to provide a technique for efficiently discharging a non-reacting fluid that is not subjected to a power generation reaction in a fuel cell.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A fuel cell system having a plurality of power generation modules including an electrolyte membrane sandwiched between electrodes, and an exhaust manifold for discharging exhaust gas connected to each of the plurality of power generation modules. A fuel cell, a plurality of branch exhaust passages branched from the exhaust manifold, each having a valve, and a control unit that controls the opening and closing of the valve to control the exhaust amount of the exhaust gas from each branch exhaust passage A fuel cell system comprising: According to this fuel cell system, the amount of exhaust gas discharged can be controlled for each of the plurality of branch exhaust passages. Therefore, the amount of exhaust gas discharged from a specific power generation module can be controlled. That is, the exhaust gas emission amount from a specific power generation module can be selectively increased from a plurality of power generation modules, and the discharge process of the non-reactive fluid can be performed efficiently.

[Application Example 2] The fuel cell system according to Application Example 1, wherein the control unit opens only some of the plurality of branch exhaust passages and closes the other branch exhaust passages. system. According to this fuel cell system, the amount of exhaust gas discharged from the power generation module in the vicinity of the opened valve can be increased.

[Application Example 3] The fuel cell system according to Application Example 1 or Application Example 2, further comprising an exhaust connection pipe connected to an end of the exhaust manifold, wherein the plurality of branch exhaust passages are Fuel cell system connected to exhaust connection piping. According to this fuel cell system, the exhaust gas from the exhaust manifold and the exhaust gases from the plurality of branch exhaust passages can be mixed and discharged simultaneously. Therefore, the non-reacting fluid discharge process can be executed more efficiently.

Application Example 4 The fuel cell system according to Application Example 1 or Application Example 3, wherein the exhaust manifold is an anode exhaust gas exhaust manifold for discharging anode exhaust gas. According to this fuel cell system, the discharge process of the non-reacting fluid from the anode side of the fuel cell can be executed efficiently.

Application Example 5 The fuel cell system according to any one of Application Examples 1 to 4, further including a voltage detection unit for detecting voltages of the plurality of power generation modules, wherein the control unit includes: Branch exhaust provided closest to the low-voltage power generation module among the plurality of branch exhaust flow paths when a low-voltage power generation module exhibiting a voltage drop of a predetermined value or more is detected among the plurality of power generation modules. A fuel cell system that opens the valve of the flow path. According to this fuel cell system, it is possible to increase the amount of exhaust gas discharged from the low voltage power generation module among the plurality of power generation modules. Therefore, when the power generation module is at a low voltage due to the non-reacting fluid, it is possible to recover the voltage of the low voltage power generation module while suppressing an increase in exhaust gas emission from other power generation modules. .

Application Example 6 In the fuel cell system according to Application Example 5, the anode exhaust gas discharged from the fuel cell is discharged outside the fuel cell system without being recirculated to the fuel cell. The anode exhaust gas contains a nitrogen gas component. According to this fuel cell system, when power generation is performed with a hydrogen supply amount that is slightly smaller than the oxygen supply amount, even if nitrogen stays in any power generation module, the exhaust gas emission amount of the power generation module is increased. I can do it. Therefore, nitrogen can be efficiently discharged.

  The present invention can be realized in various forms, for example, in the form of a fuel cell, a fuel cell system including the fuel cell, a vehicle equipped with the fuel cell system, and the like. .

A. First embodiment:
FIG. 1 is a schematic diagram showing the configuration of a fuel cell system as an embodiment of the present invention. The fuel cell system 1000 includes a fuel cell 100, a hydrogen supply system 200, an oxygen supply system 300, a hydrogen discharge system 400, an oxygen discharge system 500, and a control unit 600.

  The fuel cell 100 is a polymer electrolyte fuel cell that generates power by receiving supply of hydrogen and oxygen as reaction gases. The fuel cell 100 may not be a polymer electrolyte fuel cell, and the present invention can be applied to any of various types of fuel cells.

  The fuel cell 100 has a so-called stack structure in which a plurality of power generation modules 110 are stacked. Here, in this specification, the “power generation module” means one membrane electrode assembly (described later) and a gas flow path (described later) for a reactive gas adjacent to two electrode surfaces of the membrane electrode assembly. The component part of the fuel cell which produces electric power including these is meant.

  The fuel cell 100 is provided with a plurality of gas manifolds 121 to 124 for supplying and discharging reaction gases. Specifically, a hydrogen supply manifold 121 for supplying hydrogen, a hydrogen discharge manifold 122 for discharging hydrogen, an oxygen supply manifold 123 for supplying oxygen, and an oxygen discharge manifold 124 for discharging oxygen are provided. It has been. The gas manifolds 121 to 124 are provided along the stacking direction of the power generation modules 110 and communicate with gas flow paths provided in the electrodes of the power generation modules 110.

  The fuel cell 100 is provided with a plurality of branch passages 130 branched from the hydrogen discharge manifold 122 and communicating from the side surface of the fuel cell 100 to the outside at substantially equal intervals. Here, the “side surface of the fuel cell 100” means a surface along the stacking direction of the power generation modules 110. A gas injection valve 131 is provided in each of the plurality of branch flow paths 130. The gas injection valve 131 is provided so that anode exhaust gas can be ejected from the hydrogen discharge manifold 122 toward the hydrogen discharge pipe 410. The gas injection valve 131 can adjust the amount of gas ejection according to the valve opening time.

  Further, the fuel cell 100 is provided with an FC voltage detection unit 140 that measures a power generation voltage for each power generation module 110. The FC voltage detection unit 140 outputs the measurement result to the control unit 600.

  The hydrogen supply system 200 supplies hydrogen gas, which is a fuel gas, to the fuel cell 100. The hydrogen supply system 200 includes a hydrogen tank 210 and a hydrogen supply pipe 220. The hydrogen tank 210 stores high-pressure hydrogen. The hydrogen supply pipe 220 connects the hydrogen tank 210 and the hydrogen supply manifold 121 of the fuel cell 100. The hydrogen supply pipe 220 is provided with a hydrogen cutoff valve 221 on the upstream side and a regulator 222 for adjusting the hydrogen pressure on the downstream side.

  The oxygen supply system 300 supplies high-pressure air that is an oxidizing gas to the fuel cell. The oxygen supply system 300 includes an air compressor 310 and an oxygen supply pipe 320. The oxygen supply pipe 320 connects the air compressor 310 and the oxygen supply manifold 123 of the fuel cell 100. The oxygen supply system 300 may be provided with a humidifying unit (not shown) for humidifying the supplied high-pressure air.

  The hydrogen discharge system 400 includes a hydrogen discharge pipe 410 connected to the end 122e of the hydrogen discharge manifold 122 of the fuel cell 100. Usually, the anode exhaust gas containing hydrogen that has not been subjected to the reaction is discharged from the end 122e of the hydrogen discharge manifold to the outside of the fuel cell system 1000 through the hydrogen discharge pipe 410. Note that the flow of the anode exhaust gas from the end 122e is controlled by the hydrogen discharge valve 411.

  The hydrogen discharge pipe 410 is connected to a plurality of branch flow paths 130 provided on the side surface of the fuel cell 100 on the downstream side of the hydrogen discharge valve 411. Part of the anode exhaust gas is discharged to the hydrogen discharge pipe 410 by the gas injection valve 131 via any one of the plurality of branch flow paths 130 in a predetermined case. Details of the exhaust processing by the gas injection valve 131 will be described later.

  The hydrogen discharge pipe 410 is provided with a diluter 412 on the downstream side of the connecting portion 413 with the plurality of branch flow paths 130. The diluter 412 is for reducing the hydrogen concentration in the anode exhaust gas by mixing the anode exhaust gas and another gas, and enabling the anode exhaust gas to be discharged into the atmosphere. The diluter 412 reduces the hydrogen concentration in the anode exhaust gas even when the exhaust amount of the anode exhaust gas is increased by exhaust processing by the gas injection valve 131 described later, and the hydrogen flammability limit value (about 4%) ).

  The oxygen discharge system 500 includes an oxygen discharge pipe 510 connected to the oxygen discharge manifold 124 of the fuel cell 100. Cathode exhaust gas containing oxygen that has not been used for the reaction discharged from the fuel cell 100 flows into the oxygen discharge pipe 510. The oxygen exhaust pipe 510 may discharge the cathode exhaust gas directly to the outside of the system, or may be connected to the pipe of the oxygen supply system 300 to circulate the cathode exhaust gas in the system.

  The control unit 600 is configured as a logic circuit centered on a microcomputer, and includes a central processing unit (not shown), a storage device (not shown), and the like. The control unit 600 is connected to the hydrogen cutoff valve 221, the air compressor 310, the hydrogen discharge valve 411, the gas injection valve 131, and the like via signal lines, and controls the fuel cell system 1000. When the fuel cell 100 generates power, the control unit 600 executes a nitrogen discharge process described later based on the output value from the FC voltage detection unit 140.

  By the way, the fuel cell system 1000 of the present embodiment is a so-called anode circulation-less system in which the operation of the fuel cell 100 is continued without recirculating hydrogen in the anode exhaust gas to the fuel cell 100. The controller 600 operates the fuel cell 1000 by setting the amount of hydrogen supplied to the fuel cell 100 to a minute amount compared to the amount of oxygen supplied. Specifically, the ratio between the hydrogen supply amount and the oxygen supply amount may be, for example, 1: 100. Thereby, the amount of hydrogen discharged from the fuel cell 100 without being subjected to the reaction is reduced, and the utilization efficiency of hydrogen is improved.

  FIG. 2A1 is a schematic diagram showing the membrane electrode assembly 10 included in the power generation module 110 of the fuel cell 100. FIG. The membrane electrode assembly 10 is provided with a seal portion 12 on the outer peripheral edge of a power generation region 11 which is a region subjected to a power generation reaction. The power generation region 11 has a substantially rectangular shape. The seal portion 12 has a protruding portion 12e at the center of the short sides facing each other across the power generation region 11. Accordingly, rectangular recesses 13 that constitute the gas manifolds 121 to 124 (FIG. 1) when assembled as the fuel cell 100 are provided at the four corners of the membrane electrode assembly 10.

  FIG. 2A2 is a cross-sectional view of the membrane electrode assembly 10 taken along the line A2-A2 shown in FIG. The power generation region 11 of the membrane electrode assembly 10 includes an electrolyte membrane 14 and an anode 15 and a cathode 16 disposed on both surfaces of the electrolyte membrane 14.

  The electrolyte membrane 14 is a solid polymer that exhibits good proton conductivity in a wet state. A gas diffusion layer (not shown) is provided on the outer surfaces of the two electrodes 15 and 16 that are not in contact with the electrolyte membrane 14 so as to spread the reaction gas over the entire surface, and the power contact reaction is promoted on the surfaces in contact with the electrolyte membrane 14. For this purpose, a catalyst layer (not shown) carrying a catalyst such as platinum is provided.

  The seal portion 12 is formed so as to cover the outer peripheral end portion 14 e of the electrolyte membrane 14 and the outer peripheral end portions 15 e and 16 e of the two electrodes 15 and 16. The outer peripheral end portion 14e of the electrolyte membrane 14 protrudes from the two electrode end portions 15e and 16e, thereby suppressing the occurrence of reaction gas cross leak at the electrode end portions 15e and 16e.

  When assembled as the fuel cell 100, a gas flow path member 17 is disposed on the outer surfaces of the two electrodes 15 and 16 of the membrane electrode assembly 10 to distribute the reaction gas over the entire electrodes. The gas flow path member 17 can be composed of a porous member having conductivity. The gas flow path member 17 also functions as a conductive path for the generated electricity.

  FIG. 2B is a schematic diagram showing the separator 20 used in the power generation module 110 of the fuel cell 100. The separator 20 is a plate-like member having substantially the same shape as the membrane electrode assembly 10, and the rectangular recess 13 is provided in the same manner as the membrane electrode assembly 10. In addition, as the separator 20, it can comprise with the thin plate-shaped member (for example, metal plate) which has electroconductivity.

  The two surfaces of the separator 20 are each provided with a guide channel groove 21 that is a channel for guiding the reaction gas. The guide channel groove 21 provided on the first surface is configured as a plurality of grooves meandering along the entire separator 20 and connects the two rectangular recesses 13 located at opposing positions. The guide channel groove 21 provided on the second surface not shown is the same as the guide channel groove 21 provided on the first surface except that the remaining two rectangular recesses 13 are connected. Is provided.

  FIG. 3 is a schematic diagram showing a process of assembling the membrane electrode assembly 10 and the separator 20 described above as the fuel cell 100. The plurality of membrane electrode assemblies 10 and the separators 20 are alternately stacked and housed in a battery housing 30 that is a hollow, substantially rectangular parallelepiped. A gas flow path member 17 is disposed in the power generation region 11 of the membrane electrode assembly 10. The battery casing 30 can be made of, for example, stainless steel (SUS).

  The contact portions between the end surfaces of the membrane electrode assembly 10 and the separator 20 and the inner wall surface of the battery housing 30 are sealed by an insulating member. The four spaces surrounded by the end surfaces of the rectangular recesses 13 of the laminated membrane electrode assembly 10 and the separator 20 and the inner wall surface of the battery housing 30 constitute gas manifolds 121 to 124. The laminated membrane electrode assembly 10 and the separator 20 are subjected to a fastening load in the lamination direction by a fastening member (not shown).

  FIG. 4 is a schematic perspective view showing the completed fuel cell 100. Each of the gas manifolds 121 to 124 is connected to the hydrogen supply pipe 220, the oxygen supply pipe 320, the hydrogen discharge pipe 410, and the oxygen discharge pipe 510 described in FIG. The hydrogen discharge pipe 410 runs side by side with the hydrogen discharge manifold 122 by turning back into a U shape from the connection portion with the hydrogen discharge manifold 122. Note that only the connecting end portions of the oxygen manifolds 123 and 124 are shown.

  On the side surface of the fuel cell 100, a plurality of branch flow paths 130 including gas injection valves 131 branched from the hydrogen discharge manifold 122 are arranged in the stacking direction at substantially equal intervals. The plurality of branch flow paths 130 connect the hydrogen discharge manifold 122 and the hydrogen discharge pipe 410 at a portion where the hydrogen discharge manifold 122 and the hydrogen discharge pipe 410 run side by side.

  In FIG. 4, the flow of hydrogen in the fuel cell 100 is schematically shown by broken-line arrows. The hydrogen that has flowed into the hydrogen supply manifold 121 via the hydrogen supply pipe 220 is guided by the guide channel groove 21 provided in the separator 20 and flows through the power generation region 11 on the anode side of each membrane electrode assembly 10. The anode exhaust gas flows from the power generation region 11 on the anode side of each membrane electrode assembly 10 into the hydrogen discharge manifold 122 through the induction channel groove 21 and further flows into the hydrogen discharge pipe 410. The same applies to the flow of oxygen in the fuel cell 100.

  FIG. 5 is a schematic cross-sectional view showing a part of the internal configuration of the fuel cell 100. In FIG. 5, arbitrary three power generation modules 110 of the fuel cell 100 are illustrated, but for convenience of explanation, “power generation module 110 </ b> A” and “power generation module” are sequentially illustrated from the left toward the paper surface. 110B ”and“ power generation module 110C ”. In FIG. 5, the flow of hydrogen in the fuel cell 100 is illustrated by arrows.

  Here, it is assumed that the pressure loss of the gas flow path on the anode side of the power generation module 110B is larger than the pressure loss of the gas flow paths on the anode side of the other power generation modules 110A and 110C. Here, the “gas channel” refers to the guide channel groove 21 provided in each separator 20, the gas channel member 17 disposed on the electrode surface of the membrane electrode assembly 10, and the electrodes 15 and 16. It is a general term for a region where gas flows in a power generation module, including a gas diffusion layer provided.

  When the fuel cell 100 is operated under this assumption, the amount of hydrogen flowing from the hydrogen supply manifold 121 to the gas flow path on the anode side of the power generation module 110B is the gas flow path on the anode side of the other power generation modules 110A and 110C. Less than the amount of hydrogen flowing into Accordingly, the amount of anode exhaust gas discharged from the power generation module 110B to the hydrogen discharge manifold 122 is reduced accordingly, and the anode exhaust gas flows backward from the hydrogen discharge manifold 122 to the gas flow path on the anode side of the power generation module 110B. There is a case (dashed arrow Cf).

  By the way, high-pressure air is supplied as an oxidizing gas to the cathode side of the fuel cell 100, but non-reactive gas (mainly nitrogen) that is not used for the reaction flows to the anode side through the electrolyte membrane 14. It is known to leak. The nitrogen leaked to the anode side is discharged together with hydrogen that has not been subjected to the reaction as an anode exhaust gas if the exhaust is normally performed in each power generation module.

  However, in the power generation module 110 in which the backflow of the anode exhaust gas is generated as in the power generation module 110B described above, as shown in the hatched area NA in the figure, nitrogen stays in the power generation area without being discharged. Further, the retention amount increases with time.

  In the power generation module 110 in which this “nitrogen retention” has occurred, the flow of hydrogen in the power generation region is hindered by nitrogen, so that the power generation efficiency decreases. Furthermore, if the nitrogen retention amount increases significantly, the power generation module 110 may stop power generation.

  In the anode circulation-less system, the supply amount of hydrogen is extremely small relative to the supply amount of oxygen, and a pressure difference is generated in the gas flow path between the anode side and the cathode side, so that nitrogen leaks to the anode side. Cheap. Therefore, the retention of nitrogen in the anode-side power generation region described above is likely to occur in an anode circulation-less system such as the fuel cell system 1000 of the present embodiment.

  FIG. 6 is a schematic diagram showing a gas flow in the fuel cell 100 when one gas injection valve 131 of the plurality of branch flow paths 130 is opened. FIG. 6 is substantially the same as FIG. 5 except that the arrows indicating the gas flow are different.

  When the gas injection valve 131 of the branch flow path 130n closest to the power generation module 110B in which nitrogen stays out of the plurality of branch flow paths 130 provided in the hydrogen discharge manifold 122 is opened, the flow of hydrogen is as shown in FIG. It changes like the arrow shown. That is, a part of the anode exhaust gas of the hydrogen discharge manifold 122 is injected into the hydrogen discharge pipe 410 through the branch flow path 130n, so that the backflow of the anode exhaust gas to the power generation module 110B is eliminated and stays in the power generation module 110B. Nitrogen is exhausted.

  Thus, according to the fuel cell 100 provided with the plurality of branch channels 130, the exhaust gas can be selectively discharged from any one of the plurality of branch channels 130. The exhaust gas emission amount of any power generation module 110 can be increased. Therefore, the amount of exhaust gas discharged from the power generation module in which nitrogen is retained can be increased to eliminate the retention of nitrogen.

  FIG. 7 is a flowchart showing a processing procedure performed by the control unit 600 when the fuel cell system 1000 is operated. In step S <b> 10, the control unit 600 performs a process for supplying the reaction gas to the fuel cell 100. Specifically, the hydrogen shutoff valve 221 of the hydrogen supply system 200 is opened, and the air compressor 310 of the oxygen supply system 300 is started (FIG. 1). The control unit 600 opens the hydrogen discharge valve 411 when the hydrogen discharge valve 411 of the hydrogen discharge system 400 is closed. The supply amount of hydrogen and oxygen is controlled in response to an output request from an external load (not shown) connected to the fuel cell system 1000.

  When the fuel cell 100 starts power generation, the control unit 600 monitors whether any of the power generation modules 110 of the fuel cell 100 has nitrogen retention (step S20). Specifically, the control unit 600 detects the retention of nitrogen from the change in the voltage value of each power generation module 110 measured by the FC voltage detection unit 140 provided in the fuel cell 100.

  FIG. 8 is an example of a graph showing a temporal change in the voltage value detected by the FC voltage detection unit 140 in the power generation module 110 in which nitrogen retention occurs. In the power generation module 110 in which stagnation of nitrogen occurs, the power generation voltage continuously decreases as time passes.

  Therefore, the control unit 600 calculates the average value (average voltage value Va) of the power generation voltages of all the power generation modules 110 of the fuel cell 100 at each time in step S20 (FIG. 7), and the voltage from the average voltage value Va. The power generation module 110 whose value is decreasing is detected. Then, the control unit 600 obtains a difference (voltage drop amount Vd) between the voltage value of the power generation module 110 and the average voltage value Va, and calculates a ratio of the voltage drop amount Vd to the average voltage value Va (voltage drop rate Vdr). To do. The control unit 600 determines that the stagnation of nitrogen occurs in the power generation module 110 whose voltage drop rate Vdr is greater than a predetermined value (for example, 5%).

  When the power generation module 110 in which nitrogen retention has occurred is detected, the control unit 600 executes “nitrogen discharge processing” (steps S30 to S60) described below. As step S30, the control unit 600 calculates a nitrogen retention amount in the power generation module 110.

  FIG. 9 is a graph showing the nitrogen retention amount with respect to the voltage drop rate Vdr in the power generation module 110. This graph is obtained in advance by experiments or the like and stored in the storage device of the control unit 600 as a nitrogen retention amount map. Control unit 600 obtains nitrogen retention amount Nq corresponding to voltage drop rate Vdr obtained in step S20 from this nitrogen retention amount map.

  FIG. 10 is a graph showing the optimum gas discharge amount from the branch flow path 130 for eliminating the nitrogen retention with respect to the nitrogen retention amount. This graph is obtained in advance by experiments or the like, and is stored as an exhaust gas amount map in the storage device of the control unit 600. As this exhaust gas amount map, a map corresponding to each power generation module 110 may be prepared. The controller 600 determines an exhaust gas amount Eq to be exhausted from the plurality of branch passages 130 corresponding to the nitrogen retention amount Nq obtained in step S30 from the exhaust gas amount map (step S40).

  FIG. 11 is a graph showing the relationship between the opening time of the gas injection valve 131 in the branch flow path 130 and the amount of gas injected. This graph is determined by the characteristics of each gas injector 131 and is stored in the storage device of the control unit 600 as a gas injector characteristic map. The control unit 600 obtains the valve opening time Te of the gas injection valve 131 necessary for discharging the exhaust gas amount Eq determined in step S40, using this gas injection valve characteristic map (step S50).

  In step S60, the control unit 600 opens the gas injection valve 131 in accordance with the valve opening time Te obtained in step S50, and discharges the anode exhaust gas containing stagnant nitrogen to the hydrogen discharge pipe 410 by a predetermined gas amount.

  Thus, according to the fuel cell system 1000 of the present embodiment, only some valves (valves) of the plurality of branch flow paths 130 are opened to discharge nitrogen gas. Therefore, the nitrogen discharge process can be executed for a plurality of power generation modules 110 constituting the fuel cell 100, in which nitrogen stays and power generation efficiency is reduced. Further, in this embodiment, an increase in the amount of exhaust from the other power generation module 110 that has not been reduced in power generation efficiency due to the nitrogen exhaust treatment can be suppressed, so that the utilization efficiency of hydrogen can be improved.

B. Second embodiment:
FIG. 12 is a schematic diagram showing the configuration of a fuel cell system as a second embodiment of the present invention. FIG. 12 is almost the same as FIG. 1 except that a plurality of branch flow paths 130 are connected to the oxygen exhaust pipe 510.

  In the fuel cell system 1000A, similarly to the fuel cell system 1000 of the first embodiment, the nitrogen discharge process can be executed via the oxygen discharge pipe 510 for the power generation module 110 in which the retention of nitrogen occurs. . Further, in this fuel cell system 1000A, the anode exhaust gas discharged together with nitrogen from the plurality of branch flow paths 130 flows to the oxygen discharge pipe even when nitrogen discharge processing from the plurality of branch flow paths 130 is performed. Mixed with a large amount of air (eg 1000 NL / min air). Therefore, unlike the hydrogen discharge system 400, the anode exhaust gas can be discharged without providing a diluter in the oxygen discharge distribution 510. However, like the hydrogen discharge pipe 410, the oxygen discharge pipe 510 may be provided with a diluter.

  Since the anode exhaust gas from the plurality of branch passages 130 is discharged from the oxygen discharge pipe 510, the anode exhaust gas discharged from the hydrogen discharge pipe 410 is reduced as compared with the first embodiment. Therefore, the diluter 412 of the hydrogen discharge system 400 can be smaller than that of the first embodiment, and thus the size of the system can be reduced.

C. Third embodiment:
FIG. 13 is a schematic diagram showing the configuration of a fuel cell system as a third embodiment of the present invention. FIG. 13 is substantially the same as FIG. 1 except that the hydrogen discharge pipe 410 is not directly connected to the hydrogen discharge manifold 122. That is, the hydrogen discharge pipe 410 is connected to the hydrogen discharge manifold 122 only through the plurality of branch flow paths 130.

  The fuel cell system 1000B is a fuel cell system that performs so-called anode dead end operation. Here, the “anode dead end operation” refers to an operation in which power generation is continued in a state where fuel gas is not discharged from the anode side while supply of fuel gas to the anode side is continued. In the fuel cell system 1000 of the first embodiment, when the power generation is continued, the discharge of hydrogen that has not been subjected to the reaction is performed in small amounts but continuously. However, since the fuel cell system 1000B of the third embodiment does not continuously discharge such hydrogen, the hydrogen discharge pipe 410 and the hydrogen discharge manifold 122 can be disconnected.

  By the way, it is known that even in a fuel cell that performs such an anode dead end operation, if power generation is continued, nitrogen may stay in the power generation region and inhibit the power generation reaction. In addition, when the anode exhaust gas path from the anode side is omitted, it is difficult to discharge the stagnant nitrogen. Therefore, in the third embodiment, the retained nitrogen discharge process is executed by the plurality of branch flow paths 130 as in the first embodiment. Thereby, the retention of nitrogen can be eliminated for each power generation module 110, and the anode dead end operation can be continued satisfactorily. If this anode dead end operation is performed, the utilization efficiency of hydrogen during power generation can be improved.

D. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

D1. Modification 1:
In the above embodiment, the fuel cell 100 is used in an anode circulation-less system, but may be used in other fuel cell systems. For example, it may be used in a system in which hydrogen in the anode exhaust gas is recycled to the fuel cell without being discharged to the outside.

  In this case, the plurality of branch flow paths 130 may be provided not in the hydrogen discharge manifold 122 but in the oxygen discharge manifold 124. Thus, for example, excess water generated on the cathode side may be discharged from the plurality of branch channels 130 as a non-reactive fluid.

D2. Modification 2:
In the above embodiment, the plurality of branch flow paths 130 are provided with the gas injection valve 131, but the gas injection valve 131 may not be provided. For example, instead of the gas injection valve 131, the plurality of branch flow paths 130 may be provided with a flow rate adjustment valve capable of adjusting the gas flow rate. Alternatively, the plurality of branch channels 130 may be provided with simple valves. That is, the non-reacted fluid discharge process may be executed without adjusting the flow rate of the exhaust gas, and the control unit 600 may open the valve for a predetermined time. Even with such a configuration, the nitrogen discharge process can be executed by the plurality of branch channels 130.

  Moreover, in the said Example, although the gas injection valve 131 was able to control the gas flow rate ejected by the open time of a valve, it is good also as what adjusts a gas flow rate with the opening degree of a valve. This further enables fine control of the discharge flow rate by the gas injection valve 131.

D3. Modification 3:
In the above embodiment, the plurality of branch channels 130 are provided on the side surface of the fuel cell 100 at substantially equal intervals, but may not be provided at equal intervals. For example, it is good also as what is provided only in the vicinity of the electric power generation module 110 which tends to produce nitrogen retention.

D4. Modification 4:
In the above embodiment, the nitrogen discharge process is executed when the voltage drop rate Vdr becomes larger than a predetermined value. However, when a low voltage power generation module that shows a voltage drop higher than a predetermined value is detected, the nitrogen discharge process is performed. It is good also as what performs a process. Moreover, it is good also as what performs the discharge | emission process of nitrogen by conditions other than a voltage fall.

D5. Modification 5:

  In the embodiment described above, the control unit 600 detects the retention of nitrogen by a decrease in the generated voltage. However, the control unit 600 may detect the retention of nitrogen by another method. Moreover, it is good also as what performs the discharge process by the some branch flow path 130, without detecting the stay of nitrogen. For example, the control unit 600 may repeat control to open the gas injection valves 131 of the plurality of branch flow paths 130 one by one at a predetermined time interval while the fuel cell system 1000 continues operation. good. With such a configuration, the discharge process is sequentially performed on each of the power generation modules 110, so that the possibility of stagnation of nitrogen can be reduced.

D6. Modification 6:
In the above embodiment, the plurality of branch flow paths 130 are connected to the hydrogen discharge pipe 410 or the oxygen discharge pipe 510, but the fuel cell is directly connected to the plurality of branch flow paths 130 without being connected to these discharge pipes. The exhaust gas may be discharged to the outside.

D7. Modification 7:
In the above-described embodiment, only the flow path in which the gas injection valve 131 is opened by the control unit 600 among the multiple branch flow paths 130 discharges the exhaust gas. It is good also as what is discharging. In this case, when the power generation module 110 in which the non-reactive gas stays is generated, the discharge amount from the branch channel other than the branch channel closest to the power generation module 110 may be suppressed. As a result, the amount of gas discharged from the branch channel closest to the power generation module 110 can be increased.

D8. Modification 8:
In the above embodiment, the gas manifolds 121 to 124 of the fuel cell 100 are provided between the outer peripheral end faces of the membrane electrode assembly 10 and the separator 20 and the inner wall surface of the battery housing 30. And it may be provided as a through hole in the outer peripheral edge of the separator. In this case, the plurality of branch flow paths 130 may be provided as flow paths communicating from the outer peripheral end face of the membrane electrode assembly 10 or the separator 20 to the hydrogen discharge manifold 122.

Schematic which shows the structure of the fuel cell system of 1st Example. Schematic which shows the structure of a membrane electrode assembly and a separator. Schematic which shows the assembly | attachment process of a fuel cell. The schematic perspective view which shows the completed fuel cell. The schematic sectional drawing for demonstrating the flow of the gas in a fuel cell. The schematic diagram for demonstrating the exhaust_gas | exhaustion from a branch flow path. The flowchart which shows the process sequence which a control part performs in the case of a driving | operation of a fuel cell system. The graph which shows an example of the time change of the power generation voltage in the power generation module in which the retention of nitrogen has arisen. The graph which shows the relationship between a voltage fall rate and nitrogen retention. The graph for determining the exhaust gas amount from the branch flow path with respect to the nitrogen residence amount. The graph which shows the relationship between the amount of exhaust gas, and the open time of a flow regulating valve. Schematic which shows the structure of the fuel cell system of 2nd Example. Schematic which shows the structure of the fuel cell system of 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Membrane electrode assembly 11 ... Electric power generation area 12 ... Seal part 12e ... Protrusion part 13 ... Rectangular recessed part 14 ... Electrolyte membrane 14e ... Outer peripheral edge part 15 ... Anode 15e, 16e ... Electrode edge part 16 ... Cathode 17 ... Gas flow path member DESCRIPTION OF SYMBOLS 20 ... Separator 21 ... Guidance channel groove 30 ... Battery casing 100 ... Fuel cell 1000, 1000A, 1000B ... Fuel cell system 110, 110A, 110B, 110C ... Power generation module 121-124 ... Gas manifold 122e ... End of hydrogen discharge manifold Portion 130 ... Plural branch passages 130n ... Branch passage 131 ... Gas injection valve 140 ... FC voltage detection unit 200 ... Hydrogen supply system 210 ... Hydrogen tank 220 ... Hydrogen supply piping 221 ... Hydrogen shutoff valve 222 ... Regulator 300 ... Oxygen supply System 310 ... Air compressor 320 ... Oxygen supply piping DESCRIPTION OF SYMBOLS 400 ... Hydrogen discharge system 410 ... Hydrogen discharge piping 411 ... Hydrogen discharge valve 412 ... Diluter 413 ... Connection part 500 ... Oxygen discharge system 510 ... Oxygen discharge piping 600 ... Control part

Claims (6)

A fuel cell system,
A plurality of power generation modules including an electrolyte membrane sandwiched between electrodes;
An exhaust manifold connected to each of the plurality of power generation modules for discharging exhaust gas;
A fuel cell having
A plurality of branch exhaust passages branched from the exhaust manifold, each having a valve;
A control unit for controlling the opening and closing of the valve to control the exhaust amount of the exhaust gas from each branch exhaust passage;
A fuel cell system comprising: The fuel cell system according to claim 1, wherein
The control unit is a fuel cell system that opens only some valves of the plurality of branch exhaust passages and closes valves of other branch exhaust passages. The fuel cell system according to claim 1 or 2, further comprising:
An exhaust connection pipe connected to an end of the exhaust manifold;
The fuel cell system, wherein the plurality of branch exhaust passages are connected to the exhaust connection pipe. A fuel cell system according to any one of claims 1 to 3,
The exhaust manifold is an anode exhaust gas exhaust manifold for discharging anode exhaust gas. The fuel cell system according to any one of claims 1 to 4, further comprising:
A voltage detection unit for detecting voltages of the plurality of power generation modules;
The control unit is located closest to the low-voltage power generation module among the plurality of branch exhaust passages when a low-voltage power generation module showing a voltage drop of a predetermined value or more is detected among the plurality of power generation modules. A fuel cell system that opens a valve of a provided branch exhaust passage. The fuel cell system according to claim 5, wherein
The anode exhaust gas discharged from the fuel cell is discharged outside the fuel cell system without being recirculated to the fuel cell,
The fuel cell system, wherein the anode exhaust gas includes a nitrogen gas component.

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