JP2005209573A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make high speed and uniform warming up of a fuel cell compatible with power generation efficiency in a fuel cell system. <P>SOLUTION: An anode passage 113 through which supply gas to an anode 112 flows and a cathode passage 115 through which supply gas to a cathode flows are installed in parallel or almost in parallel. During power generation of the fuel cell 110, flow of gas in the anode passage 113 and flow of gas in the cathode passage 115 are made opposite, and in the warming up of the fuel cell 110, flow of gas in the anode passage 113 and flow of gas in the cathode passage 115 are made parallel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electricity by supplying a fuel gas to an anode and supplying an oxidizing gas to a cathode, and in particular, warms up the fuel cell by supplying a high-temperature gas to the anode. The present invention relates to a fuel cell system having a warm-up function.

  A general fuel cell has a structure in which a pair of electrodes are arranged with an electrolyte that permeates hydrogen ions, a fuel gas containing hydrogen is supplied to the anode, and an oxidizing gas containing oxygen is supplied to the cathode. Thus, an electrochemical reaction occurs in both electrodes, and an electromotive force is generated.

  A fuel cell has an operating temperature for obtaining sufficient battery performance, and this operating temperature is determined by the type of electrolyte membrane. For example, solid polymer type (PEM) is about 80 ° C., phosphoric acid type (PAFC) is about 200 ° C., molten carbonate type (MCFC) is 600 to 800 ° C., and solid oxide type (SOFC) is 800 to 1000 ° C. Becomes the operating temperature. In the hydrogen separation membrane type (HMFC) proposed by the present applicant in the prior application (Japanese Patent Application No. 2003-064478, Japanese Patent Application No. 2003-072994, Japanese Patent Application No. 2003-204734), the operating temperature is 400 to 600 ° C. This hydrogen separation membrane fuel cell specifically includes an electrolyte membrane having a structure in which a hydrogen separation membrane (for example, a membrane in which palladium is laminated on vanadium) is laminated on a proton conductive material (eg, zirconia ceramics). It is what is used.

  As described above, most of the currently proposed fuel cells have an operating temperature higher than room temperature. The fuel cell is warmed up by the internal reaction heat, but it is necessary to forcibly warm up from the outside to reach the operating temperature in order to obtain the desired battery performance immediately after startup. There is. As a technique for warming up the fuel cell, for example, a technique proposed in Patent Document 1 is known.

The system described in Patent Document 1 includes a reformer. During power generation of the fuel cell, fuel gas to be supplied to the anode is generated by reforming the hydrocarbon raw material by the reformer, and cathode offgas discharged from the cathode is supplied to the reformer as reforming air. In this system, at the time of start-up, the amount of air supplied to the reformer via the cathode is adjusted to be several times the stoichiometric air-fuel ratio, so that the hydrocarbon-based raw material is completely oxidized by lean combustion, thereby generating steam. High temperature gas containing is generated. The fuel cell is forcibly warmed up by supplying the high temperature gas to the anode.
JP 2003-151599 A

  By the way, various formats have been proposed for the direction of gas flow in the fuel cell. For example, there are some in which the flow direction of the oxidizing gas in the cathode is orthogonal to the flow direction of the fuel gas in the anode, and others in parallel. In the technique described in Patent Document 1, the flow direction of the oxidizing gas in the cathode and the flow direction of the fuel gas in the anode are parallel and opposite to each other.

  The direction of gas flow in the fuel cell greatly affects the power generation efficiency of the fuel cell during power generation. That is, as described above, the electromotive force is generated by the electrochemical reaction at both electrodes, but the concentration of the reaction component in the gas flowing through both electrodes gradually changes with the electrochemical reaction. For this reason, depending on the relationship of the flow direction of the gas flowing through the two electrodes, there may be a difference in the reactivity of the electrochemical reaction due to a change in the concentration of the reaction component in the gas, and the current density distribution may be biased There is. From the viewpoint of power generation efficiency, it is better that the current density distribution is uniform, and it is desirable that the gas flow direction be set so that the current density distribution is uniform.

  Further, the gas flow direction in the fuel cell greatly affects the warm-up efficiency of the fuel cell during warm-up. During warm-up, high temperature gas is supplied to the anode, while normal temperature gas is supplied to the cathode. Thus, when there is a temperature difference in the gas flowing through both electrodes, there is a possibility that the amount of heat supplied to the electrolyte membrane may be biased in-plane depending on the relationship in the flow direction. If the amount of heat supplied is uneven in the surface, it will not only take time to reach the operating temperature, but also a temperature difference will occur in the surface, making it impossible to achieve sufficient battery performance. End up. For this reason, from the viewpoint of warm-up efficiency (high-speed and uniform warm-up), it is desirable that the gas flow direction be set so that the amount of supplied heat is uniform in the plane.

  From the above, in determining the gas flow direction in the fuel cell, it is necessary to consider both the power generation efficiency during power generation and the warm-up efficiency during warm-up. However, in the conventional techniques including the technique described in Patent Document 1, the examination based on the different requirements of the power generation efficiency and the warm-up efficiency has not been made regarding the gas flow direction in the fuel cell. For this reason, even if a uniform current density distribution is obtained at the time of power generation and high power generation efficiency is obtained, the supply heat quantity is uneven in the surface at the time of warm-up, and the fuel cell is warmed up at high speed and uniformly. There was a possibility that could not.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel cell system capable of achieving both high-speed and uniform fuel cell warm-up and high power generation efficiency. To do.

In order to achieve the above object, a first invention includes a fuel cell having an anode and a cathode. During power generation of the fuel cell, a fuel gas containing hydrogen is supplied to the anode and oxygen is contained in the cathode. In the fuel cell system in which an oxidizing gas is supplied and when the fuel cell is warmed up, a high-temperature gas is supplied to the anode.
An anode flow path provided in the anode and through which a supply gas to the anode flows;
A cathode channel provided in the cathode in parallel or substantially in parallel with the anode channel, and through which a supply gas to the cathode flows;
Gas flow switching means capable of switching the relationship between the gas flow in the anode flow path and the gas flow in the cathode flow path from parallel flow to counter flow, and from counter flow to parallel flow,
During power generation of the fuel cell, the relationship between the gas flow in the anode flow channel and the gas flow in the cathode flow channel is an opposing flow,
When the fuel cell is warmed up, the relationship between the gas flow in the anode flow channel and the gas flow in the cathode flow channel is a parallel flow.

The second invention is the first invention, comprising a reformer for reforming the hydrocarbon raw material to produce fuel gas,
During power generation of the fuel cell, fuel gas is supplied from the reformer to the anode,
When the fuel cell is warmed up, high temperature gas generated by lean combustion of the hydrocarbon raw material in the reformer is supplied to the anode.

Further, in a third invention according to the second invention, during power generation of the fuel cell, a cathode off gas discharged from the cathode is supplied to the reformer as reforming air for a hydrocarbon raw material,
When the fuel cell is warmed up, the cathode off-gas discharged from the cathode is supplied to the reformer as lean combustion air for hydrocarbon raw material.

  According to a fourth invention, in any one of the first to third inventions, the gas flow switching means connects a connection destination of the gas supply source to the cathode to the cathode channel. It includes a switching valve for switching between one end and the other end, or for switching a connection destination of the gas supply source to the anode to the anode flow path between the one end and the other end of the anode flow path. It is said.

  According to the first to third inventions, high power generation efficiency can be obtained by making the relationship between the gas flow in the anode flow path and the gas flow in the cathode flow path opposite to each other during power generation of the fuel cell. At the same time, when the fuel cell is warmed up, the relationship between the gas flow in the anode flow channel and the gas flow in the cathode flow channel is made parallel, whereby the fuel cell can be warmed up uniformly at high speed. That is, according to the present invention, both high-speed and uniform warm-up of the fuel cell and high power generation efficiency can be achieved.

  Further, according to the fourth invention, the relationship between the gas flow in the anode flow path and the gas flow in the cathode flow path is switched from the parallel flow to the counter flow and from the counter flow to the parallel flow with a simple configuration. Can do.

Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram of a fuel cell system as Embodiment 1 of the present invention. As shown in FIG. 1, this fuel cell system includes a reformer 100 that reforms a hydrocarbon raw material (hereinafter referred to as fuel) to generate a fuel gas containing hydrogen (hereinafter referred to as reformed gas), a reformer 100, A fuel cell 110 that generates power using the reformed gas generated by the mass device 100 is provided. Hereinafter, the structures and functions of the fuel cell 110 and the reformer 100 will be described.

The fuel cell 110 has a structure in which an electrolyte membrane 116 is sandwiched between two electrodes, that is, an anode 112 and a cathode 114. When the reformed gas containing hydrogen is supplied to the anode 112, a chemical reaction of the following formula (1) occurs to generate hydrogen ions.
H ₂ → 2H ⁺ + 2e ⁻ (1)
The generated hydrogen ions are supplied to the cathode 114 through the electrolyte membrane 116. When an oxidizing gas containing oxygen is supplied to the cathode 114, a chemical reaction of the following formula (2) occurs, and water (water vapor) is generated from the hydrogen ions and oxygen generated at the anode 102.
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
When the above reaction occurs continuously at both the anode 112 and the cathode 114, an electromotive force is generated between the anode 112 and the cathode 114, and this becomes the generated power of the fuel cell 110. As the fuel cell 110 according to the present fuel cell system, any of solid polymer type, phosphoric acid type, molten carbonate type, solid oxide type, and hydrogen separation membrane type fuel cell may be adopted. The fuel cell 110 is provided with an electrolyte membrane 116 corresponding to its type.

The reformer 100 includes a reforming unit that includes a catalyst and a heating unit that heats the reforming unit. For example, when gasoline (the main component is C ₈ H ₁₈ ) is supplied as the fuel, the reforming of the fuel is performed by the chemical reaction of the following formulas (3) and (4) in the reforming unit.
C ₈ H ₁₈ + 8H ₂ O → 17H ₂ + 8CO (3)
C ₈ H ₁₈ + 4O ₂ → 9H ₂ + 8CO (4)
The reaction represented by the above formula (3) is called a steam reforming reaction and is an endothermic reaction. The reaction represented by the formula (4) is called a partial oxidation reaction and is an exothermic reaction. A catalyst is provided to promote these reactions. Although it is considered that both reactions occur simultaneously in the reforming section, the main is the steam reforming reaction, and the entire reforming reaction in the reforming section is an endothermic reaction. For this reason, in order to promote the reforming reaction, it is necessary to supply heat, and as heat for that purpose, combustion heat of the heating fuel is supplied from the heating unit. In FIG. 1, the supply system of heating fuel and combustion air to the heating unit is not shown. In addition, the reformer 100, the CO produced by the reforming reaction shift unit and to shift the CO ₂ is reacted with water and CO selective oxidation unit to be transformed into CO ₂ also provided to oxidize CO However, since these are not the main part of the present invention, detailed description thereof is omitted.

  In this fuel cell system, cathode off gas discharged from the cathode 114 of the fuel cell 110 is supplied as air for reforming in the reformer 100. The reforming reaction in the reformer 100 requires water (steam) and oxygen as shown in the above formulas (3) and (4), but the cathode offgas includes the above formula (2). As shown in FIG. 4, a large amount of moisture generated by the oxidation reaction at the cathode 114 is contained. Further, the cathode off gas contains a large amount of unreacted oxygen. Therefore, by supplying the cathode off-gas as reforming air to the reformer 100, a dedicated evaporator for generating water vapor becomes unnecessary, and the system can be miniaturized.

The reformer 100 is also used as a hot gas supply source for warming up the fuel cell 110. During power generation of the fuel cell 110, the supply amount of the cathode off gas is adjusted so that the chemical reaction of the above formulas (3) and (4) occurs, but when the fuel cell 110 is warmed up, the following (5) The supply amount of the cathode off gas is adjusted so that the chemical reaction of the formula occurs.
C ₈ H ₁₈ + (25/2) O ₂ → 8CO ₂ + 9H ₂ O (5)
That is, the supply amount of the cathode off gas is adjusted so as to be leaner than the stoichiometric air-fuel ratio in relation to the fuel supply amount. Thereby, the combustion of the fuel in the reforming section becomes lean combustion, and the complete oxidation reaction represented by the above formula (5) occurs. Since this complete oxidation reaction is an exothermic reaction, the generated combustion gas is at a high temperature, and the fuel cell 110 is warmed up by supplying this high-temperature combustion gas to the anode 112 of the fuel cell 110.

Next, the flow of the supply gas in the fuel cell system will be described.
In the anode 112 of the fuel cell 110, a gas flow path (hereinafter referred to as an anode flow path) 113 through which a supply gas to the anode 112 flows is provided. On the other hand, a gas flow path (hereinafter referred to as a cathode flow path) 115 through which a supply gas to the cathode 114 flows is provided in the cathode 114 of the fuel cell 110. In this fuel cell system, the anode channel 113 and the cathode channel 115 are provided in parallel.

  Supply gas from the reformer 100 to the anode 112 of the fuel cell 110, that is, reformed gas during power generation and high-temperature gas during warm-up, is supplied to one end (hereinafter referred to as the left end according to the figure) 113a of the anode flow path 113. Is done. The supply gas passes through the anode passage 113 and is discharged to the outside as an anode off gas from the other end (hereinafter, referred to as a right end according to the drawing) 113b. That is, the gas flow direction in the anode channel 113 is constant, and always flows from the left end 113a to the right end 113b during power generation and warm-up.

  Two three-way valves (switching valves) 140 and 150 are arranged in the air supply system to the cathode 114. The three-way valve 140 has three ports 141, 142, and 143, and the communication destination of the first port 141 can be switched between the second port 142 and the third port 143. The same is true for the other three-way valve 150, and the communication destination of the first port 151 can be switched between the second port 152 and the third port 153. The first port 141 of one three-way valve 140 is connected to one end (hereinafter referred to as the right end in accordance with the drawing) 115a of the cathode flow path 115, and the first port 151 of the other three-way valve 150 is connected to the other end of the cathode flow path 115. It is connected to 115b (hereinafter referred to as the left end according to the figure). The second ports 142 and 152 of the three-way valves 140 and 150 are connected to an air pump 120 that is an air supply source to the cathode 114, and the third ports 143 and 153 of the three-way valves 140 and 150 are Each is connected to the air inlet of the reformer 100.

  By connecting the cathode 114, the air pump 120, and the reformer 100 via the three-way valves 140, 150, the flow direction of the gas flowing through the cathode channel 115 is controlled by switching the communication state of the three-way valves 140, 150. can do. In this fuel cell system, as shown in FIGS. 2 and 3, the flow direction of the gas flowing through the cathode flow path 115 is switched between when the fuel cell 110 generates power and when it is warmed up.

  FIG. 2 is a diagram showing a gas flow during power generation in the fuel cell system. During power generation of the fuel cell, in the three-way valve 140 connected to the right end 115a of the cathode channel 115, the first port 141 and the second port 142 communicate with each other, and in the three-way valve 150 connected to the left end 115b of the cathode channel 115, The first port 151 and the third port 153 communicate with each other. As a result, the gas supplied from the air pump 120 flows into the right end 115a of the cathode channel 115 via the three-way valve 140, flows in the cathode channel 115 from the right end 115a to the left end 115b, and is discharged as cathode off-gas from the left end 115b. Is done. The discharged cathode off gas is supplied to the reformer 100 via the three-way valve 150 as reforming air.

  On the other hand, FIG. 3 is a diagram showing a gas flow when the fuel cell system is warmed up. When the fuel cell is warmed up, the three-way valve 140 connected to the right end 115a of the cathode channel 115 communicates with the first port 141 and the third port 143 and is connected to the left end 115b of the cathode channel 115. In 150, the first port 151 and the second port 152 communicate with each other. As a result, the gas supplied from the air pump 120 flows into the left end 115b of the cathode flow path 115 via the three-way valve 150, flows in the cathode flow path 115 from the left end 115b to the right end 115a, and is discharged as cathode off-gas from the right end 115a. Is done. The discharged cathode off gas is supplied to the reformer 100 through the three-way valve 140 as lean combustion air.

  As a result of controlling the flow direction of the gas flowing through the cathode flow path 115, when the fuel cell 110 generates power, the relationship between the gas flow in the anode flow path 113 and the gas flow in the cathode flow path 115 becomes an opposite flow, When the fuel cell 110 is warmed up, the relationship between the gas flow in the anode flow path 113 and the gas flow in the cathode flow path 115 is a parallel flow. By switching the flow relationship between power generation and warm-up in this way, the following effects can be obtained.

  First, FIG. 4 is a diagram comparing the temperature distribution in the fuel cell 110 during power generation between the parallel flow and the counter flow. The graph shown on the left of FIG. 4 is the temperature distribution in the case of counter flow, and the graph shown on the right of FIG. 4 is the temperature distribution in the case of parallel flow. Both are in steady state. In the graph, the flow direction of the gas (anode gas) in the anode flow path 113 and the flow direction of the gas (cathode gas) in the cathode flow path 115 are indicated by arrows, respectively. From the viewpoint of the temperature distribution of the fuel cell 110 at the time of power generation, there is no significant difference between parallel flow and counter flow.

  However, from the viewpoint of the current density distribution of the fuel cell 110 during power generation, a large difference occurs between the parallel flow and the counter flow as described below. FIG. 5 is a diagram comparing the current density distribution in the fuel cell 110 during power generation between the parallel flow and the counter flow. The graph shown on the left of FIG. 5 is the current density distribution in the case of counterflow, and the graph shown on the right of FIG. 5 is the current density distribution in the case of parallel flow. Both are in steady state. In the graph, the flow direction of the gas (anode gas) in the anode flow path 113 and the flow direction of the gas (cathode gas) in the cathode flow path 115 are indicated by arrows, respectively. As can be seen by comparing the two graphs, in the case of counter flow, a substantially uniform current density distribution is obtained in the gas flow direction, whereas in the case of parallel flow, the current density distribution is biased and the upstream On the side, the current density is very high, while on the downstream side, the current density is greatly reduced.

  The following can be considered as the cause of the bias in the current density distribution in the parallel flow. In the case of parallel flow, both the hydrogen concentration in the anode channel 113 and the oxygen concentration in the cathode channel 115 are high on the upstream side of the anode channel 113 (upstream side in the graph). For this reason, the electrochemical reaction shown by the above formulas (1) and (2) occurs violently and many electrons are generated. However, since the hydrogen concentration and the oxygen concentration both decrease with the reaction, the reactivity of the electrochemical reaction described above greatly decreases as it goes downstream. On the other hand, in the case of the counter flow, the oxygen concentration in the cathode channel 115 is low on the upstream side of the anode channel 113 having a high hydrogen concentration, and conversely on the upstream side of the cathode channel 115 having a high oxygen concentration. Since the hydrogen concentration in the anode channel 113 is low, the electrochemical reaction described above occurs at a substantially constant reactivity along the flow direction.

  The fuel cell 110 can obtain higher power generation efficiency when there is no bias in the current density distribution than when there is a bias in the current density distribution. As can be seen by comparing the two graphs in FIG. 5, the countercurrent flow is overwhelmingly balanced in the current density distribution. Therefore, as in the present fuel cell system, the three-way valve 140, so that the relationship between the gas flow in the anode flow channel 113 and the gas flow in the cathode flow channel 115 is a counter flow during power generation of the fuel cell 110. By switching 150, high power generation efficiency can be realized.

  Next, FIG. 6 is a diagram comparing the temperature distribution in the fuel cell 110 after a certain time has elapsed from the start of warm-up between parallel flow and counterflow. The graph shown on the left of FIG. 6 is the temperature distribution in the case of counter flow, and the graph shown on the right of FIG. 6 is the temperature distribution in the case of parallel flow. Both are in steady state. In the graph, the flow direction of the gas (anode gas) in the anode flow path 113 and the flow direction of the gas (cathode gas) in the cathode flow path 115 are indicated by arrows, respectively. As can be seen from the comparison of the two graphs, the temperature distribution is uneven in the case of counter flow, while the temperature on the upstream side is very high while the temperature is greatly reduced on the downstream side, In this case, a substantially uniform temperature distribution can be obtained in the gas flow direction.

  During the warm-up, high temperature gas is supplied to the anode channel 113. The supplied gas flows from the left end 113 a to the right end 113 b of the anode channel 113, but naturally the amount of heat received from the gas is higher on the upstream side of the anode channel 113. Therefore, normally, the upstream side (left end 113a side) of the anode channel 113 is likely to be hotter than the downstream side (right end 113b side), and a large temperature gradient is likely to be formed from the upstream side to the downstream side. However, since the gas flowing through the cathode channel 115 is low temperature (normal temperature), in the case of parallel flow, heat is taken away from the electrolyte membrane 116 by the gas flowing through the cathode channel 115 on the upstream side of the high temperature, and the heat taken away. Is carried to the low temperature downstream side by the gas flow in the cathode channel 115. As a result, heat conduction from the upstream side to the downstream side is promoted, the deviation of the temperature distribution in the gas flow direction is eliminated, and a substantially uniform temperature distribution as shown in the graph is realized. On the other hand, in the case of the counter flow, the gas in the cathode channel 115 flows from the low temperature side to the high temperature side, so that the effect of promoting heat conduction by the gas flow cannot be obtained. For this reason, as shown in the graph, a large temperature gradient is generated from the upstream side to the downstream side of the anode channel 113.

  In order for the fuel cell 110 to exhibit sufficient battery performance, the entire fuel cell 110 needs to be warmed up to the operating temperature equally. For this purpose, it is necessary to raise the temperature of the entire fuel cell 110 uniformly. In this respect, as can be seen by comparing the two graphs of FIG. 6, the parallel flow is clearly superior to the counter flow, and the temperature of the entire fuel cell 110 can be increased substantially uniformly. Further, as a method for promoting the warm-up of the fuel cell 110, it is conceivable to raise the temperature of the supply gas to the anode flow path 113, but in the case of the counter flow, the inlet temperature of the anode flow path 113 is the material temperature. The allowable temperature may be exceeded. For this reason, in the case of counterflow, the temperature of the supply gas to the anode flow path 113 must be made lower than in the case of parallel flow. In other words, by using parallel flow, the gas supplied to the anode flow path 113 can be heated to a higher temperature, and the warm-up speed can be increased. Therefore, as in the present fuel cell system, when the fuel cell 110 is warmed up, the three-way valve 140 is such that the relationship between the gas flow in the anode flow path 113 and the gas flow in the cathode flow path 115 is parallel. , 150 can be switched to achieve high-speed and uniform warm-up of the fuel cell 110.

  As described above, according to the present fuel cell system, the relationship between the gas flow in the anode flow path 113 and the gas flow in the cathode flow path 115 is changed from a counter flow during power generation to a parallel flow during warm-up. By switching to, it is possible to achieve both high-speed and uniform warm-up of the fuel cell 110 and high power generation efficiency during power generation.

Embodiment 2.
The second embodiment of the present invention will be described below with reference to FIG. In addition, about the site | part same as Embodiment 1 mentioned above, the same code | symbol is attached | subjected and shown in the figure, and the description shall be abbreviate | omitted.

  The fuel cell system of this embodiment is characterized in that two air pumps 160 and 170 are provided as air supply sources to the cathode 114. One is an air pump 160 that is activated during power generation of the fuel cell 110, and is connected to the second port 142 of the three-way valve 140 connected to the right end 115a of the cathode channel 115. The other is an air pump 170 that is operated when the fuel cell 110 is warmed up, and is connected to the second port 152 of the three-way valve 150 connected to the left end 115b of the cathode flow path 115.

  During power generation of the fuel cell, the three-way valve 140 connected to the right end 115a of the cathode channel 115 communicates with the first port 141 and the second port 142, and the three-way valve 150 connected to the left end 115b of the cathode channel 115 The first port 151 and the third port 153 communicate with each other. As a result, the gas supplied from the air pump 160 flows into the right end 115a of the cathode channel 115 via the three-way valve 140, flows in the cathode channel 115 from the right end 115a to the left end 115b, and is discharged from the left end 115b as cathode off gas. The The discharged cathode off gas is supplied to the reformer 100 via the three-way valve 150 as reforming air.

  On the other hand, when the fuel cell is warmed up, the three-way valve 140 connected to the right end 115a of the cathode channel 115 communicates with the first port 141 and the third port 143 and is connected to the left end 115b of the cathode channel 115. In the three-way valve 150, the first port 151 and the second port 152 communicate with each other. As a result, the gas supplied from the air pump 170 flows into the left end 115b of the cathode flow path 115 through the three-way valve 150, flows in the cathode flow path 115 from the left end 115b to the right end 115a, and is discharged from the right end 115a as the cathode off gas. The The discharged cathode off gas is supplied to the reformer 100 through the three-way valve 140 as lean combustion air.

  Therefore, also with the present fuel cell system, the relationship between the gas flow in the anode flow channel 113 and the gas flow in the cathode flow channel 115 can be made to be an opposite flow during power generation, as in the first embodiment. When warming up, it can be parallel flow.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the anode channel 112 and the cathode channel 114 are provided in parallel. However, in the present invention, the two channels do not have to be completely parallel, and the flow direction is switched. As long as the above effects can be obtained, there may be a certain degree of angular deviation. That is, it may be substantially parallel.

  In the above-described embodiment, the gas flow in the cathode flow path 114 is switched between power generation and warm-up, but the gas flow in the anode flow path 112 may be switched. .

  In the above-described embodiment, the cathode off gas is supplied to the reformer 100. However, the present invention is also applied to a fuel cell system including a dedicated evaporator for supplying water vapor to the reformer. Is possible. Furthermore, the fuel cell system to which the present invention is applicable may be any fuel cell system in which a fuel gas containing hydrogen is supplied to the anode during power generation and a high-temperature gas is supplied to the anode during warm-up. It is not limited to the provided fuel cell system.

It is a figure which shows schematic structure of the fuel cell system as Embodiment 1 of this invention. It is a figure which shows the flow of the gas at the time of the electric power generation of the fuel cell system as Embodiment 1 of this invention. It is a figure which shows the gas flow at the time of warming-up of the fuel cell system as Embodiment 1 of this invention. It is the figure which compared the temperature distribution in the fuel cell at the time of electric power generation with a parallel flow and a counterflow. It is the figure which compared the current density distribution in the fuel cell at the time of electric power generation by the parallel flow and the counterflow. It is the figure which compared the temperature distribution in the fuel cell after a fixed time progress from a warming-up start by a parallel flow and a counterflow. It is a figure which shows schematic structure of the fuel cell system as Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Reformer 110 Fuel cell 112 Anode 113 Anode channel 114 Cathode 115 Cathode channel 116 Electrolyte membrane 120,160,170 Air pump 140,150 Three-way valve

Claims (4)

A fuel cell having an anode and a cathode, and at the time of power generation of the fuel cell, a fuel gas containing hydrogen is supplied to the anode and an oxidizing gas containing oxygen is supplied to the cathode, and when the fuel cell is warmed up, In the fuel cell system in which high temperature gas is supplied to the anode,
An anode flow path provided in the anode and through which a supply gas to the anode flows;
A cathode channel provided in the cathode in parallel or substantially in parallel with the anode channel, and through which a supply gas to the cathode flows;
Gas flow switching means capable of switching the relationship between the gas flow in the anode flow path and the gas flow in the cathode flow path from parallel flow to counter flow, and from counter flow to parallel flow,
During power generation of the fuel cell, the relationship between the gas flow in the anode flow channel and the gas flow in the cathode flow channel is an opposing flow,
When the fuel cell is warmed up, the relationship between the gas flow in the anode flow path and the gas flow in the cathode flow path is a parallel flow. Equipped with a reformer that reforms hydrocarbon feedstock to produce fuel gas,
During power generation of the fuel cell, fuel gas is supplied from the reformer to the anode,
2. The fuel cell system according to claim 1, wherein when the fuel cell is warmed up, a high-temperature gas generated by lean combustion of a hydrocarbon raw material in the reformer is supplied to the anode. During power generation of the fuel cell, cathode off-gas discharged from the cathode is supplied to the reformer as air for reforming hydrocarbon raw material,
3. The fuel cell system according to claim 2, wherein when the fuel cell is warmed up, cathode off-gas discharged from the cathode is supplied to the reformer as lean combustion air for a hydrocarbon raw material.   The gas flow switching means switches the connection destination of the gas supply source to the cathode to the cathode flow path between one end and the other end of the cathode flow path, or the gas supply source to the anode The fuel cell system according to any one of claims 1 to 3, further comprising a switching valve that switches a connection destination to the anode flow path between one end and the other end of the anode flow path.

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