JP2008171655A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of restraining itself from freezing due to moisture contained in fuel offgas, and further, capable of easily arranging auxiliary machines or the like in a fuel offgas circulation channel. <P>SOLUTION: The system is provided with a fuel gas supply channel 61 supplying fuel gas, a fuel cell 1 made by fixing to an end plate 9a a stack main body 3 generating power by electrochemical reaction of the fuel gas supplied to an inner manifold 21 from the fuel gas supply channel 61 with oxidizing gas, and a fuel offgas circulation channel 69 sending the fuel offgas exhausted from the stack main body 3 back to the fuel gas supply channel 61. The fuel offgas circulation channel 69, after being arranged outside the fuel cell 1, joins the fuel gas supply channel 61 inside the end plate 9a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell that generates power upon receiving a reaction gas.

  In recent years, a fuel cell system using a fuel cell that generates power by an electrochemical reaction between a fuel gas and an oxidizing gas as an energy source has attracted attention. A fuel cell used in this fuel cell system is usually configured by fixing between end plates disposed at both ends in a stacking direction of a stack body in which a plurality of single cells are stacked with a tension plate or the like.

  In the fuel cell system, in order to reuse the fuel gas component remaining in the fuel off-gas after passing through the stack of the fuel gas supplied through the fuel gas supply path, the fuel off-gas circulation in which the fuel off-gas is again introduced into the fuel gas supply path It has a road. And there exists a technique which provides such a fuel off-gas circulation path in an end plate entirely (for example, refer patent document 1).

In this technology, by providing a fuel off-gas circulation path in the end plate that is heated by heat generated by the power generation of the stack, it is possible to suppress freezing that occurs when the fuel off-gas containing a lot of water joins the low-temperature fuel gas. It has become.
JP 2001-143734 A

  However, if the fuel off-gas circulation path is provided entirely in the end plate as described above, it becomes difficult to place the auxiliary equipment to be disposed in the fuel off-gas circulation path.

  Therefore, the present invention provides a fuel cell system that can suppress freezing due to moisture contained in the fuel off-gas, and can easily arrange auxiliary equipment in the fuel off-gas circulation path. With the goal.

  In order to achieve the above object, a fuel cell system of the present invention includes a stack body having a plurality of cells that generate power by an electrochemical reaction between a fuel gas and an oxidizing gas, and the stack body disposed on both sides in the stacking direction of the stack body. A fuel cell having an end plate sandwiching the main body; a fuel gas supply path for supplying fuel gas from a fuel supply source to the stack body; and a fuel off-gas discharged from the stack body in the fuel gas supply path A fuel cell system comprising a fuel off-gas circulation path for returning again, wherein the fuel off-gas circulation path extends outside the fuel cell and then merges with the fuel gas supply path in the end plate It is.

  According to such a configuration, the fuel off-gas flowing through the fuel off-gas circulation path merges with the fuel gas flowing through the fuel gas supply path in the end plate heated by the heat generated by the power generation of the stack body. Even if the fuel gas from the source is at a low temperature, freezing of moisture contained in the fuel off-gas can be suppressed. In addition, it is possible to easily arrange the auxiliary equipment in a portion of the fuel off-gas circulation path that extends outside the fuel cell.

  In the stack body, the fuel gas supply path and each cell communicate with each other to supply fuel gas to each cell, and the fuel off-gas circulation path and each cell communicate with each other. And a second internal manifold that discharges fuel off-gas from each cell.

  The end plate may have an internal passage that communicates the fuel off-gas circulation path extending to the outside of the fuel cell and an intermediate position of the fuel gas supply path in the end plate.

  The fuel cell of the present invention includes a stack body having a plurality of cells that generate power by an electrochemical reaction between a fuel gas and an oxidizing gas, and an end that is disposed on both sides of the stack body in the stacking direction and sandwiches the stack body. A fuel gas supply path for supplying fuel gas from a fuel supply source to the stack body, and a fuel off-gas circulation path for returning the fuel off-gas discharged from the stack body to the fuel gas supply path again. In the fuel cell to be connected, the end plate has an internal passage that allows communication between the outside and the middle position of the fuel gas supply passage in the end plate.

  According to this configuration, if one end of the fuel off-gas circulation path is connected to one end of the internal passage, more specifically, one end of the fuel off-gas circulation path is connected to one end of the internal passage that opens to the outer surface of the end plate, In the end plate heated by the heat generated by power generation, the fuel off-gas flowing through the fuel off-gas circulation path merges with the fuel gas flowing through the fuel gas supply path. Even at a low temperature, freezing of moisture contained in the fuel off-gas can be suppressed. In addition, it is possible to easily arrange the auxiliary equipment in a portion of the fuel off-gas circulation path that extends outside the fuel cell.

  In the stack body, the fuel gas supply path and each cell communicate with each other to supply fuel gas to each cell, and the fuel off-gas circulation path and each cell communicate with each other. And a second internal manifold that discharges fuel off-gas from each cell.

  According to the present invention, it is possible to provide a fuel cell system that can suppress freezing due to moisture contained in the fuel off-gas and can easily arrange auxiliary equipment in the fuel off-gas circulation path. Can do.

  Next, an embodiment of a fuel cell system according to the present invention will be described with reference to the drawings. FIG. 1 is a system configuration diagram of a fuel cell system. This fuel cell system is an in-vehicle power generation system for fuel cell vehicles, a power generation system for any moving body such as a ship, an aircraft, a train, or a walking robot, and a stationary power generation system used for a building (house, building, etc.). It can be applied to power generation systems.

  The fuel cell system includes a fuel cell 1 that receives supply of reaction gases (oxidation gas and fuel gas) and generates electric power by an electrochemical reaction to generate electric power, and air gas as oxidation gas to the fuel cell 1 An oxidizing gas piping system 30 for adjusting supply, a fuel gas piping system 40 for adjusting gas supply of hydrogen gas as fuel gas, and a refrigerant piping system 80 for cooling the fuel cell 1 are provided.

  The oxidizing gas piping system 30 includes an air supply piping 32 that supplies the air humidified by the humidifying module 31 to the fuel cell 1, an exhaust piping 33 that guides the oxidizing off-gas discharged from the fuel cell 1 to the humidifying module 31, and a humidifying module. 31 and a discharge pipe 34 for guiding the oxidizing off gas to the outside.

  The air supply pipe 32 is provided with a compressor 35 that takes in the oxidizing gas in the atmosphere and pumps it to the humidification module 31, and the exhaust pipe 33 has an exhaust valve that adjusts the amount of oxidizing off-gas discharged from the fuel cell 1. 36 is provided. Further, a muffler 37 for silencing is provided at the end position of the discharge pipe 34.

  The fuel gas piping system 40 includes a hydrogen tank 41 as a fuel supply source storing hydrogen gas at a pressure higher than normal pressure (for example, 70 MPa), and a fuel supply for supplying the hydrogen gas in the hydrogen tank 41 to the fuel cell 1. A pipe 42, a circulation pipe 44 that returns hydrogen off-gas as fuel off-gas discharged from the fuel cell 1 to the fuel cell 1, and an exhaust pipe 43 that branches from the circulation pipe 44 and exhausts the hydrogen off-gas to the outside. ing.

  The fuel supply pipe 42 includes a shutoff valve 45 that shuts off or allows the supply of hydrogen gas from the hydrogen tank 41, a pressure regulating valve 46 that adjusts the pressure of the hydrogen gas when the shutoff valve 45 allows the supply of hydrogen gas, A shutoff valve 47 that shuts off or allows supply is provided.

  The circulation pipe 44 is provided with a shut-off valve 48 that shuts off or allows discharge of the hydrogen off-gas from the fuel cell 1 and a gas-liquid separator 49 that gas-liquid separates the hydrogen off-gas discharged from the fuel cell 1. . A drain valve 50 is connected to the gas-liquid separator 49, and the drain valve 50 is connected to the discharge pipe 34 via a drain pipe 51. The drain valve 50 discharges the water collected by the gas-liquid separator 49 to the outside through the discharge pipe 34.

  The circulation pipe 44 adjusts the circulation of the gas discharged from the fuel cell 1 by sucking, pressurizing, and discharging the hydrogen off-gas in the circulation pipe 44 discharged from the fuel cell 1 to the fuel cell 1 side again. A circulation pump 52 is provided. Further, an exhaust pipe 43 that branches from the downstream side of the circulation pump 52 of the circulation pipe 44 includes an exhaust valve 53 that blocks or allows discharge of hydrogen off-gas through the exhaust pipe 43, and a branch pipe from which the hydrogen off-gas flows from the discharge pipe 34. And a diluter 55 for diluting with an oxidizing off-gas introduced through 54.

  The gas diluted by the diluter 55 is discharged to the outside through the pipe 56 and the discharge pipe 34 while being silenced by the muffler 37. A check valve 57 for preventing the backflow of hydrogen gas to the circulation pipe 44 is provided downstream of the exhaust pipe 43 of the circulation pipe 44.

  In such a fuel cell system, the hydrogen gas supplied from the hydrogen tank 41 through the fuel supply pipe 42 to the fuel cell 1 after being adjusted by the pressure regulating valve 46, and the humidification module 31 through the air supply pipe 32 by pressure feeding by the compressor 35. The oxidizing gas humidified in step 1 and introduced into the fuel cell 1 causes an electrochemical reaction in the fuel cell 1 to generate power.

  Further, the hydrogen off-gas from the fuel cell 1 is introduced into the gas-liquid separator 49 of the circulation pipe 44 and is again introduced into the fuel cell 1 by the circulation pump 52. Further, when the exhaust valve 53 is opened at an appropriate timing, the hydrogen off-gas from the fuel cell 1 is introduced into the diluter 55 from the exhaust pipe 43, and the oxidized off-gas discharged from the fuel cell 10 in the diluter 55. It is diluted and discharged to the outside through the discharge pipe 34.

  The refrigerant pipe system 80 includes a refrigerant pipe 81 communicating with a cooling flow path in the fuel cell 1, a cooling pump 82 provided in the refrigerant pipe 81, a radiator 83 that cools the refrigerant discharged from the fuel cell 1, and a radiator. A bypass pipe 84 that bypasses 83, and a switching valve 85 that sets the flow of cooling water to the radiator 83 and the bypass pipe 84.

  Next, the fuel cell 1 will be further described with reference to FIGS. 2 and 3. As shown in FIG. 2, the fuel cell 1 includes a stack body 3 in which a plurality of cells 2 that are basic power generation units are stacked, and a frame 5 that supports the stack body 3. A terminal plate 7 is disposed at one end of the stack body 3 along the stacking direction of the cells 2, and an insulating plate 8 is disposed outside the terminal plate 7. Further, an end plate 9a constituting the frame 5 is arranged on the outer side.

  A terminal plate 7 is disposed at the other end of the stack body 3, an insulating plate 8 is disposed outside the stack plate 3, and a pressure plate 13 is disposed outside the terminal plate 7. Each terminal plate 7 is provided with an output terminal 6. An end plate 9b constituting the frame 5 is disposed outside the pressure plate 13 so as to be separated from the pressure plate 13, and a spring member 14 is interposed between the pressure plate 13 and the end plate 9b. ing.

  Between the two end plates 9 a and 9 b arranged on both sides of the stack body 3, a plurality of tension plates 11 are installed along the stacking direction of the cells 2. Both end portions of each tension plate 11 are fixed to the upper end surface and lower end surface of each end plate 9a, 9b by bolts 12, respectively, and constitutes a frame 5 together with the two end plates 9a, 9b.

  When the two end plates 9 a and 9 b are connected via the plurality of tension plates 11, a compression force is introduced into the spring member 14, and the spring member 14 is stacked in the cell 2 stacking direction with respect to the stack body 3. An urging force is applied to. The plurality of cells 2 are fastened (held) by this urging force. The tension plate 11 bears a reaction force against the urging force of the spring member 14, whereby a tension acts on the tension plate 11.

  As shown in FIG. 3, the cell 2 includes an MEA (Membrane-Electrode Assembly) 15 in which a pair of electrodes 15 b are disposed on both surfaces of an electrolyte membrane 15 a made of an ion exchange membrane, and a pair of separators disposed on both surfaces of the MEA 15. 16 and 17. Each of the separators 16 and 17 is made of a gas-impermeable base material and has conductivity.

  The separators 16 and 17 are provided with oxidizing gas manifolds 16a and 17a for supplying an oxidizing gas (usually air) to the electrodes 15b, hydrogen gas manifolds 16b and 17b for supplying hydrogen gas, and a refrigerant (usually normal). Is formed with refrigerant manifolds 16c and 17c for circulating water.

  The oxidizing gas manifold 16a, the refrigerant manifold 16c, and the hydrogen gas manifold 16b are arranged in a line along both side edges of the separator 16, respectively. Further, the oxidizing gas manifold 17a, the refrigerant manifold 17c, and the hydrogen gas manifold 17b are arranged in a line along both side edges of the separator 17, respectively. Each of the manifolds described above is continuous in the stacking direction of the cells 2.

  The separator 16 is formed with a plurality of recesses 16d serving as a hydrogen gas flow path on a side surface facing one electrode 15b of the MEA 15, and a plurality of recesses 16f serving as a coolant flow path is formed on the opposite side surface. Is formed. Each recess 16d communicates with a hydrogen gas manifold 16b formed adjacent to one side edge of the separator 16 and a hydrogen gas manifold 16b formed adjacent to the other side edge via a groove 16e. ing.

  Each recess 16f communicates with a refrigerant manifold 16c formed adjacent to one side edge of the separator 16 and a refrigerant manifold 16c formed adjacent to the other side edge via a groove 16g. ing.

  In the separator 17, a plurality of recesses 17 d serving as a flow path for oxidizing gas are formed on a side surface facing the other electrode 15 b of the MEA 15, and a plurality of recesses 17 f serving as a coolant flow path are formed on the opposite side surface. Is formed. Each recess 17d communicates with the oxidizing gas manifold 17a formed adjacent to one side edge of the separator 17 and the oxidizing gas manifold 17b formed adjacent to the other side edge through a groove portion 17e. ing.

  Each recess 17f communicates with a refrigerant manifold 17c formed adjacent to one side edge of the separator 17 and a refrigerant manifold 17c formed adjacent to the other side edge through a groove portion 17g. ing.

  A seal member 18a is provided between the separator 16 and the MEA 15 so as to surround the recess 16d, the groove 16e, and the hydrogen gas manifold 16b communicating with the groove 16e. Further, between the separator 16 and the MEA 15, a seal member 18b is provided around the oxidizing gas manifold 16a, and a seal member 18c is provided around the refrigerant manifold 16c.

  A seal member 19a is provided between the separator 17 and the MEA 15 so as to surround the recess 17d, the groove 17e, and the oxidizing gas manifold 17a communicating with the groove 17e. Between the separator 16 and the MEA 15, a seal member 19b is provided around the hydrogen gas manifold 16b, and a seal member 19c is provided around the refrigerant manifold 17c.

  A seal member 20a is provided between the separator 16 and a cell (not shown) adjacent to the separator 16 so as to surround the recess 16f, the groove 16g, and the refrigerant manifold 16c communicating with the groove 16g. Between the separator 16 and the same cell, a sealing member 20b is provided around the oxidizing gas manifold 16a, and a sealing member 20c is provided around the hydrogen gas manifold 16b. Each of the sealing members is in close contact with the separator and prevents leakage of oxidizing gas, hydrogen gas, and refrigerant.

  That is, the stack body 3 includes an internal manifold (first internal manifold) 21 shown in FIG. 2 in which the inlet-side hydrogen gas manifolds 16b and 17b communicate with each other in the stacking direction, and the outlet-side hydrogen gas manifolds 16b and 16b. 17b has an internal manifold (second internal manifold) 22 that communicates in the stacking direction.

  Furthermore, although not shown, an internal manifold in which the inlet side oxidizing gas manifolds 16a and 17a communicate with each other in the stacking direction, an inner manifold in which each of the outlet side oxidizing gas manifolds 16a and 17a communicate with each other in the stacking direction, and an inlet port It also has an internal manifold in which the refrigerant manifolds 16c and 17c on the side communicate in the stacking direction and an internal manifold in which the refrigerant manifolds 16c and 17c on the outlet side communicate in the stacking direction.

  The end plate 9a disposed at one end of the stack body 3 communicates with the internal manifold 21 on the inlet side on one side and communicates with the fuel supply pipe 42 on the other side (fuel gas flow path in the end plate) 60. Is formed. The communication path 60 and the fuel supply pipe 42 constitute a hydrogen gas supply path (fuel gas supply path) 61 for supplying hydrogen gas from the hydrogen tank 41 to the stack body 3. The end plate 9a is formed with a communication passage 62 that communicates with the internal manifold 22 on the outlet side on one side and communicates with the circulation pipe 44 on the other side.

  Further, the end plate 9a has a communication passage 63 shown in FIG. 4 in which one side communicates with an internal manifold including the oxidizing gas manifolds 16a and 17a on the inlet side, and the other side communicates with the air supply pipe 32. The communication passage 64 communicates with the internal manifold composed of the oxidizing gas manifolds 16a and 17a, the other side communicates with the exhaust pipe 33, the one side communicates with the internal manifold composed of the refrigerant manifolds 16c and 17c on the inlet side, and the other side supplies the refrigerant pipe 81. A communication path 65 that communicates with the refrigerant passages 16 is formed, and a communication path 66 that communicates with the internal manifold including the refrigerant manifolds 16 c and 17 c on one side and the other side communicates with the discharge side of the refrigerant pipe 81.

  In the present embodiment, as shown in FIG. 2, one end communicates with the intermediate position of the communication path 60 in the end plate thickness direction, and the other side communicates with the return side of the circulation pipe 44 in the end plate 9 a. An internal passage 68 is formed. As a result, the hydrogen off-gas circulation path (fuel off-gas circulation path) 69 formed by the internal passage 68 and the circulation pipe 44 is once disposed in the outside of the fuel cell 1 at a portion constituted by the circulation pipe 44. The portion constituted by the internal passage 68 joins the hydrogen gas supply path 61 in the end plate 9a.

  Here, as shown in FIG. 4A, the end plate 9a is formed with inlet-side communication passages 60, 63, 65 along one side edge, and along the opposite side edge. Since the outlet side communication passages 62, 64, 66 are formed, the internal passage 68 is formed so as not to interfere with these. That is, the hole 71 connected to the circulation pipe 44 is formed in the center portion between the communication passages 60, 63, 65 and the communication passages 62, 64, 66 in the end plate 9a from the side opposite to the stack body 3 as shown in FIG. ) To the middle of the plate thickness, so as to obliquely intersect this edge from the plate thickness intermediate position on one side edge of the end plate 9a and perpendicular to the hole 71 through the communication path 60 An internal passage 68 is formed by opening a hole 72 in the hole 72 and closing the outer opening of the hole 72 with a closing member 73. In this way, the internal passage 68 can be easily formed.

  Alternatively, as shown in FIG. 5, a hole connected to the circulation pipe 44 at a position biased toward the communication path 60 between the communication paths 60, 63, 65 and the communication paths 62, 64, 66 in the end plate 9a. 71 is drilled from the side opposite to the stack body 3 to the middle of the plate thickness, and the end plate 9a has a hole portion that is perpendicular to the edge portion from the middle position of the edge portion on the one side and passes through the communication path 60. The internal passage 68 may be formed by forming a hole 72 so as to be orthogonal to 71 and closing the outer opening of the hole 72 with a closing member 73.

  Alternatively, as shown in FIG. 6, a hole 71 connected to the circulation pipe 44 is formed at the center portion between the communication passages 60, 63, 65 and the communication passages 62, 64, 66 in the end plate 9 a. Is drilled from the opposite side to the middle of the plate thickness, and between the communication channels 60, 63, 65 and the communication channels 62, 64, 66 from the plate thickness intermediate position of the other edge of the end plate 9a on the communication channel 60 side. A hole 74 is formed so as to extend along the arrangement direction of the communication passages 60, 63, 65 and to be orthogonal to the hole 71, and from the plate thickness intermediate position of the above-mentioned one side edge of the end plate 9 a. A hole 75 is formed so as to be orthogonal to the edge and through the communication path 60 to be orthogonal to the hole 74, and the outer opening of the hole 74 is closed with a closing member 76. The inner opening 68 may be formed by closing the outer opening with a closing member 77.

  Alternatively, as shown in FIG. 7, a hole 78 connected to the circulation pipe 44 is formed so as to directly communicate with the communication path 60 from the plate thickness intermediate position of the other edge on the communication path 60 side of the end plate 9a. The internal passage 68 may be formed.

  According to the fuel cell system described above, even if the high-pressure hydrogen gas released from the hydrogen tank 41 is lowered in temperature by adiabatic expansion, the hydrogen off-gas flowing through the hydrogen off-gas circulation path 69 is used for power generation of the fuel cell 1. Accordingly, the hydrogen gas flowing through the hydrogen gas supply path 61 is joined in the heated end plate 9a, so that freezing due to moisture contained in the hydrogen off-gas can be suppressed by heating by the end plate 9a.

  In addition, since the hydrogen off-gas circulation path 69 is arranged outside the fuel cell 1 and merges with the hydrogen gas supply path 61 in the end plate 9a, a shut-off valve 48 is provided at a portion arranged outside the fuel cell 1. Auxiliaries such as the gas-liquid separator 49, the circulation pump 52, and the check valve 57 can be easily arranged.

1 is an overall configuration diagram showing an embodiment of a fuel cell system according to the present invention. It is sectional drawing of the fuel cell used for the fuel cell system. It is a disassembled perspective view of the cell which comprises the fuel cell. It is the front view (a) and sectional drawing (b) of the end plate of the fuel cell. It is a front view of the modification of the end plate of the fuel cell. It is a front view of the modification of the end plate of the fuel cell. It is a front view of the modification of the end plate of the fuel cell.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 3 ... Stack main body, 9a ... End plate, 21 ... Internal manifold (1st internal manifold), 22 ... Internal manifold (2nd internal manifold), 41 ... Hydrogen tank (fuel supply source), 60 ... communication passage (fuel gas passage in the end plate), 61 ... hydrogen gas supply passage (fuel gas supply passage), 68 ... internal passage, 69 ... hydrogen off-gas circulation passage (fuel off-gas circulation passage).

Claims (5)

A fuel cell comprising: a stack body having a plurality of cells that generate power by an electrochemical reaction between a fuel gas and an oxidizing gas; and an end plate disposed on both sides of the stack body in the stacking direction to sandwich the stack body;
A fuel gas supply path for supplying fuel gas from a fuel supply source to the stack body;
A fuel off-gas circulation path for returning the fuel off-gas discharged from the stack body back to the fuel gas supply path,
The fuel off-gas circulation path extends outside the fuel cell and then joins the fuel gas supply path in the end plate. The fuel cell system according to claim 1, wherein
In the stack body, the fuel gas supply path and each cell communicate with each other to supply fuel gas to each cell, and the fuel off-gas circulation path and each cell communicate with each other. And a second internal manifold for discharging fuel off-gas from each cell. The fuel cell system according to claim 1 or 2,
The said end plate is a fuel cell system which has an internal passage which connects the said fuel off-gas circulation path extended outside the said fuel cell, and the middle position of the said fuel gas supply path in the said end plate. A stack body having a plurality of cells that generate power by an electrochemical reaction between a fuel gas and an oxidizing gas, and an end plate disposed on both sides in the stacking direction of the stack body to sandwich the stack body,
A fuel cell connected to a fuel gas supply path for supplying fuel gas from a fuel supply source to the stack body, and a fuel offgas circulation path for returning the fuel offgas discharged from the stack body back to the fuel gas supply path; There,
The said end plate is a fuel cell which has an internal channel | path which enables the exterior and the middle position of the fuel gas supply path in the said end plate to communicate. The fuel cell according to claim 4, wherein
In the stack body, the fuel gas supply path and each cell communicate with each other to supply fuel gas to each cell, and the fuel off-gas circulation path and each cell communicate with each other. And a second internal manifold that discharges fuel off-gas from each cell.

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