JP2006253041A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent invasion of water into a control valve in a fuel cell system having a circulation passage. <P>SOLUTION: The fuel cell system 10 comprises a fuel cell 12, a hydrogen tank 14, an anode exhaust passage 30, a circulation pump 18, and a control valve 24. The control valve 24 shuts off supply of hydrogen gas. The control valve 24 is arranged at the perpendicularly upper part than a converging part S of the anode exhaust gas circulated through the circulation pump 18 and prevents invasion of water. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system having a circulation path for recirculating exhaust gas discharged from an anode of a fuel cell to the anode.

  Hydrogen gas is known as a fuel gas supplied to the anode of a fuel cell. When supplying hydrogen gas, more hydrogen gas is supplied than the theoretical amount of hydrogen necessary to obtain the desired power. By making the hydrogen gas rich, the power generation efficiency is maintained and impurities are efficiently discharged from the fuel gas flow path in the fuel cell. Impurities are water vapor generated by an electrochemical reaction, and can be discharged to the fuel cell side by increasing the flow rate of hydrogen gas. On the other hand, since hydrogen gas is supplied excessively, the exhaust gas contains a large amount of hydrogen gas that does not contribute to the electrochemical reaction. Therefore, conventionally, a system for circulating exhaust gas discharged from the fuel cell in addition to hydrogen gas supplied to the anode of the fuel cell has been proposed.

  In the following patent document, a system configuration that circulates exhaust gas, and a water permeable membrane dehumidifier that moves water from a liquid with a high water content to a liquid with a low water content are provided in the circulation channel, and flows through the circulation channel A configuration for removing moisture from hydrogen gas by moving liquid moisture to a water permeable membrane dehumidifier is disclosed.

JP 2004-71348 A

  The exhaust gas discharged and circulated from the fuel cell contains water vapor as the generated water permeates through the solid polymer electrolyte membrane. When this water vapor condenses and freezes in a sub-freezing environment, the gas flow path There is a problem that the opening / closing control of various valves provided in the valve becomes impossible, or the opening / closing speed is lowered due to moisture accumulated in the valve, or the corrosion of the valve proceeds. In the above prior art, although the moisture is removed, a dehumidifier or the like is interposed, so that the configuration becomes complicated. Moreover, it cannot respond to condensation or freezing when the operation of the dehumidifier is stopped.

  An object of the present invention is to provide a fuel cell system that can prevent a malfunction of a valve due to condensation or freezing of water while having a simple configuration.

  The present invention includes a fuel gas supply unit that supplies fuel gas from a fuel gas supply source to an anode of a fuel cell via a supply path, and exhaust gas discharged from the fuel cell to the supply path via a circulation path. A fuel cell system having a gas circulation part to be joined, wherein a valve for controlling the supply of the fuel gas is disposed in the supply path, and the valve is more vertically than the joining part of the fuel gas and the exhaust gas. It is characterized by being disposed above.

  The present invention also provides a fuel gas supply unit for supplying fuel gas from a fuel gas supply source to the anode of the fuel cell via a supply path, and supplying the exhaust gas discharged from the fuel cell via a circulation path. A fuel cell system having a gas circulation part to be merged with a passage, wherein a valve for controlling the supply of the exhaust gas is disposed in the circulation path, and the valve is provided by a joining part of the fuel gas and the exhaust gas. Is also arranged vertically above.

  In a fuel cell system having a circulation path, water vapor is contained in the circulated exhaust gas, which tends to condense and accumulate moisture in the supply path on the anode side. During the operation of the system, the fuel gas is flowing toward the fuel cell side, so that the moisture also flows to the fuel cell side. However, when the system is stopped, the condensed moisture flows backward (assuming the fuel cell side is downstream). Will invade. In the present invention, the valve disposed in either the supply path or the circulation path is disposed vertically above the merging portion (the valve is disposed at a position higher than the merging portion), so that moisture can easily enter. To prevent. In the present invention, a valve for adjusting the flow of the fuel gas is provided in at least one of the supply path and the circulation path, and this valve may be disposed vertically above the junction between the supply path and the circulation path.

  According to the present invention, it is possible to prevent moisture from entering the valve with a simple configuration without using a moisture barrier filter, a dehumidifier, or the like, and to ensure the operation of the valve.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
<Basic configuration>
First, the basic configuration of the fuel cell system will be described. FIG. 1 shows a system configuration diagram of the fuel cell system. The fuel cell system 10 includes a fuel cell 12, a hydrogen tank 14, a blower 16, and a circulation pump 18.

  The hydrogen tank 14 is a supply source that stores hydrogen gas and supplies hydrogen gas to the system, and is connected to the fuel cell 12 via a fuel gas supply path 20. A regulator 22 is disposed in the vicinity of the hydrogen tank 14 in the fuel gas supply path 20. A control valve 24 is disposed on the downstream side of the regulator 22. The regulator 22 adjusts the flow rate of the gas supplied from the hydrogen tank 14 to the fuel cell 12, and the control valve 24 functions as a cutoff valve that controls the supply / hydrogenation (ON / OFF) of the supply of hydrogen gas. The pressure of the hydrogen gas is adjusted to, for example, about 200 kPa by the regulator 22. Hydrogen gas as fuel gas is supplied to the anode of the fuel cell 12.

  The fuel cell 12 is a solid polymer electrolyte type fuel cell, and has a stack structure in which a plurality of single cells as constituent units are stacked. Hydrogen gas is supplied to the anode of each unit cell, and oxidizing gas (air) containing oxygen is supplied to the cathode. At the anode, hydrogen gas is ionized and moves in the solid polymer electrolyte, and electrons move to the cathode through an external load, and react with oxygen at the cathode to produce water. Electric energy is generated by this electrochemical reaction.

  The blower 16 is connected to the fuel cell 12 via the oxidizing gas supply path 26 and supplies air to the cathode of the fuel cell 12. The exhaust gas after being subjected to the electrochemical reaction is discharged to the outside through the cathode exhaust gas passage 28.

  On the other hand, the remaining hydrogen gas (anode exhaust gas) subjected to the electrochemical reaction in the fuel cell 12 is discharged to the anode exhaust gas passage 30. The anode exhaust gas path 30 is connected to the fuel gas supply path 20 via the circulation pump 18. The remaining hydrogen gas is mixed with hydrogen gas (fresh hydrogen gas) from the hydrogen tank 14 at the junction S (connection point) by the circulation pump 18 and supplied again to the anode of the fuel cell 12. The anode exhaust gas path 30 functions as a circulation path. The supply path 20 from the junction S to the fuel cell 12 is referred to as a supply path (mixed gas supply path) 32 for convenience.

  Conventionally, the control valve 24 may be disposed on the downstream side (fuel cell 12 side) of the merging portion S. For this reason, moisture generated by condensation of water vapor is accumulated in the control valve, and the speed of the opening / closing control decreases. It was impossible to control opening and closing due to corrosion, corrosion, or freezing of water in a sub-freezing environment. As described above, the control valve 24 of the present embodiment is disposed upstream of the merging portion S and vertically above the merging point, so that the control valve 24 is not only operating but also stopped. Also, the condensed water is prevented from reaching the valve.

<Arrangement of control valve>
FIG. 2 shows the arrangement position of the control valve 24. In the figure, the XY plane indicates a horizontal plane, and the Z axis indicates a vertical direction. An anode exhaust gas passage 30 and a supply passage 32 connected to the circulation pump 18 are disposed in the lower part (vertically below) of the system. The control valve 24 is disposed vertically above the junction S, that is, vertically above the anode exhaust gas passage 30 and the supply passage 32. The control valve 24 and the junction S are connected by, for example, a pipe having a curvature.

  As described above, the control valve 24 is disposed vertically above the junction S, and a difference in height is formed between the control valve 24 and the junction S, so that the water vapor in the anode exhaust gas is condensed and moisture. Even if this occurs, the moisture does not reach the control valve 24, and a decrease in opening / closing speed due to moisture, corrosion, and inoperability due to moisture freezing can be prevented. Even when there is no difference in height between the control valve 24 and the junction S, water is not accumulated in the control valve 24 due to the pressure of hydrogen gas during the system operation, but flows to the fuel cell 12 side. When the operation stops, moisture enters the control valve 24. By forming a height difference with the control valve 24 disposed vertically upward, it is possible to easily and reliably prevent moisture from entering even when the system operation is stopped. In this embodiment, in order to prevent moisture from entering due to gravity, configurations such as a moisture removal filter and a dehumidifier are not required.

  The height difference between the control valve 24 and the merging portion S can be arbitrarily set, and may be set according to the pipe diameter and the expected moisture amount. An example of the height difference is about 50 mm. Further, the arrangement position of the control valve 24 is not fixed and may be arranged to be adjustable in the vertical direction.

<Specific arrangement of control valves>
FIG. 3 shows a more specific arrangement of the control valve 24. In the figure, “UP” in the three-axis directions indicates the vertical direction, “RH” indicates the vehicle left-right direction in the horizontal plane, and “FR” indicates the vehicle front-rear direction in the horizontal plane. Hydrogen gas supplied from a hydrogen tank (not shown) is supplied to the control valve 24 via the supply path 20. The control valve 24 is controlled to open and close by control from the in-vehicle microcomputer, and controls supply / shielding of hydrogen gas. Hydrogen gas from the control valve 24 is supplied to the merging section S through a pipe. The control valve 24 is disposed on the “UP” side, that is, vertically above the junction S, and a height difference is formed between the control valve 24 and the junction S.

  On the other hand, the anode exhaust gas discharged from the anode of the fuel cell 12 is supplied to the circulation pump 18. The circulation pump 18 supplies anode exhaust gas to the merging section S via the anode exhaust gas passage 30. Fresh hydrogen gas and anode exhaust gas are mixed at the junction S. A pressure sensor 34 is disposed in the vicinity of the merging portion S and downstream of the merging portion S, and the pressure of the mixed gas is measured. The pressure of the mixed gas is supplied from the sensor 34 to the microcomputer, and the pressure on the supply path 20 side and the anode exhaust gas path 30 side is adjusted so that the pressure of the mixed gas becomes a desired value. The mixed gas is supplied to the anode of the fuel cell 12 through the supply path 32.

Second Embodiment
FIG. 4 shows a basic configuration of the present embodiment. In the first embodiment, the control valve 24 is disposed in the supply passage 20, but in the present embodiment, the control valve 36 is further disposed in the anode exhaust gas passage 30. In addition to functioning as a valve that shuts off the anode exhaust gas, the control valve 36 may function as a switching valve that switches the anode exhaust gas to another system. A configuration for causing the control valve 36 to function as a switching valve is disclosed in Japanese Patent Application Laid-Open No. 2004-186065. In this publication, a separation chamber for removing an impurity rich gas having higher impurities from the anode exhaust gas is provided, and the control valve 36 is switched to guide the anode exhaust gas to the separation chamber. The anode exhaust gas from which impurities have been removed in the separation chamber is mixed with fresh hydrogen gas at another junction S ′ (not shown) different from the junction S. When a path that circulates through the separation chamber is referred to as a bypass path, and a path that circulates without passing through the separation chamber is referred to as a main path, the control valve 36 is a valve that switches between the main path and the bypass path. The control valve 36 switches between the main path and the bypass path at predetermined time intervals.

  In such a configuration, similarly to the control valve 24, the control valve 36 is also arranged vertically above the merging portion S and forms a height difference with the merging portion. This prevents moisture condensed while the system operation is stopped from entering the control valve 36 and ensures the operation of the control valve 36.

<Third Embodiment>
FIG. 5 shows the arrangement of the anode exhaust gas passage 30 and the supply passage 32 in the third embodiment. In the above embodiment, attention is paid to the height difference between the merging portion S and the control valve 24 or the control valve 36, and the anode exhaust gas passage 30 and the supply passage 32 are arranged in the same horizontal plane (the lowest part of the fuel cell system). However, in this embodiment, the anode exhaust gas passage 30 and the supply passage 32 are inclined. The anode exhaust gas passage 30 and the supply passage 32 are inclined so as to be low on the fuel cell 12 side (vertically below in the Z direction) and high on the circulation pump 18 side (vertically above in the Z direction). When the merging portion S is used as a reference, it can be said that the upstream side is arranged high and the downstream side is arranged low. Since the control valve 36 is disposed on the upstream side of the junction S, the control valve 36 is naturally disposed vertically above the junction S. Also with this arrangement method, it is possible to prevent moisture condensed when the system operation is stopped from flowing back and entering the control valve 36. The same applies to the supply path 20, and the supply path 20 can be disposed so as to be inclined so that the upstream side becomes higher.

<Fourth embodiment>
FIG. 6 shows still another basic configuration of the present embodiment. A purge valve 40 for discharging the anode exhaust gas to the outside without circulating it is disposed in the anode exhaust gas passage 30. Impurities other than hydrogen may be mixed in the anode exhaust gas. For example, nitrogen gas or produced water permeates through the electrolyte membrane from the cathode of the fuel cell 12 to the anode and enters the anode exhaust gas. Therefore, if the anode exhaust gas is continuously circulated, the hydrogen concentration gradually decreases, causing a decrease in power generation reaction. Therefore, a pipe is branched from the anode exhaust gas path 30 which is a circulation path, and a purge valve 40 is disposed in this branch path. The purge valve 40 is normally closed and shuts off the circulation path leading to the junction S when a predetermined condition, for example, when the operation time reaches a certain time or when the hydrogen concentration falls below a predetermined value, 40 is opened, and impurities such as nitrogen gas and water contained in the anode exhaust gas are discharged to the outside. Both the gas discharged from the purge valve 40 and the cathode exhaust gas are processed by the diluter 42 and then discharged to the outside.

  In such a configuration, the purge valve 40 is disposed vertically above the merging portion S to form a height difference with the merging portion. This prevents water condensed while the system operation is stopped from entering the purge valve 40 and ensures the operation of the purge valve 40. Both the control valve 24 and the purge valve 40 may be arranged vertically above the junction S.

It is a basic lineblock diagram of an embodiment. It is arrangement | positioning explanatory drawing of a control valve. It is a perspective view of a fuel cell system. It is a basic composition figure of other embodiments. It is arrangement | positioning explanatory drawing of the control valve of other embodiment. It is a basic composition figure of other embodiments.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell system, 12 Fuel cell, 14 Hydrogen tank, 16 Blower, 18 Circulation pump, 20 Supply path (fuel gas supply path), 22 Regulator, 24 Control valve, 26 Oxidation gas supply path, 28 Cathode exhaust gas path, 30 Anode Exhaust gas path (circulation path), 32 supply path (mixed gas supply path), 40 purge valve.

Claims (6)

A fuel gas supply unit for supplying fuel gas from a fuel gas supply source to the anode of the fuel cell via a supply path;
A gas circulation unit that joins exhaust gas discharged from the fuel cell to the supply path via a circulation path;
A fuel cell system comprising:
A valve for adjusting the flow of fuel gas in at least one of the supply path and the circulation path;
The fuel cell system, wherein the valve is disposed vertically above a junction of the supply path and the circulation path. The system of claim 1, wherein
A valve for controlling the supply of the fuel gas is disposed in the supply path;
The valve is disposed vertically above a junction of the fuel gas and the exhaust gas. The fuel cell system. The system of claim 1, wherein
A valve for controlling the supply of the exhaust gas is disposed in the circulation path;
The valve is disposed vertically above a junction of the fuel gas and the exhaust gas. The fuel cell system. The system of claim 1, wherein
A purge valve for discharging the exhaust gas to the outside under a predetermined condition is disposed in the circulation path,
The valve is disposed vertically above a junction of the fuel gas and the exhaust gas. The fuel cell system. In the system in any one of Claims 1-4,
The fuel cell system according to claim 1, wherein at least a part of the circulation path including the merging portion is inclined so that the fuel cell side is vertically downward. The system of claim 1, wherein
The fuel cell system according to claim 1, wherein the valve is a shutoff valve that shuts off the fuel gas.

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