JP2004171974A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a specific fuel cell system for using discharged water from fuel cells, and to improve reliability and service life of the system. <P>SOLUTION: A recovery container 1 is used as both a container for a heat recovering heat medium and a humidifier for an oxidizing agent gas of fuel cells 6, and stores water discharged from the fuel cells including pure water generated in the fuel cells. An inlet pipe 4, through which the water from the fuel cells is supplied to the recovery container 1, is connected to the under part of the recovery container 1. An outlet pipe 5 is connected to the recovery container 1 at a position upper than the fluid level by the static pressure value of the oxidizing agent gas supplied into the recovery container 1 on the way of the inlet pipe 4 and lower than an upper plate 12 of the recovery container 1. This can keep the interior of the fuel cells clean, and realizes simplification and cost reduction of the system. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides one or both of the purified water or the condensed water derived from the reducing agent gas used for fuel humidification including pure water generated by the reaction at the time of power generation in the fuel cell, and the recovered water in the system using the purified water in the system. The present invention relates to a technology for achieving simplification of a fuel cell system, improvement of durability, and reduction of power consumption by supplying or reusing.
[0002]
[Prior art]
A fuel cell is provided with a pair of electrodes on both sides of an electrolyte which is an ion conductor, supplies an oxidizing agent to one electrode and a reducing agent to the other electrode, and electrochemically generates power. In general, there are various types of fuel cells depending on the fuel supply method and the type of electrolyte used.In particular, in recent years, research on solid polymer electrolytes has been advanced, and the operating temperature is as low as 100 ° C. or less and the current density is high, so that a small Practical application is expected.
[0003]
For proton conduction related to power generation by the solid polymer, the solid polymer electrolyte must always keep appropriate water.
Further, in order to obtain a hydrogen-containing gas as a reducing agent, it is necessary to supply water even when an alcohol, an ether, a hydrocarbon-based fuel, or the like is obtained by using a technique such as steam reforming.
[0004]
In response to such a need for water, conventional technologies include a fuel cell system that reuses water contained in a fuel gas off-gas and an oxidant gas off-gas. (For example, see Patent Document 1)
[0005]
There is also a fuel cell system that collects water in off-gas contained in off-gas of reducing agent gas and off-gas of oxidizing gas discharged from a fuel cell and reuses it as reforming raw material and humidified water. (For example, Patent Document 2)
[0006]
However, in this case, the water in the fuel gas off-gas and the oxidizing gas off-gas is condensed, stored in one storage unit, and reused as the humidifying water for the reforming raw material, the fuel gas, and the oxidizing gas. Since impurities are contained therein, if they are reused as they are, the performance of the fuel cell will be reduced.
[0007]
In order to solve this, there is a method in which condensed water of a reducing agent gas is collected and used as reforming raw water. (For example, Patent Document 3)
There is also a method in which the recovered water is desalted and then supplied to a fuel cell. (For example, Patent Document 4) However, it is not practical to manufacture the fuel cell system at low cost and compactly as in a home fuel cell system.
[0008]
As a conventional technique for recovering heat generated in a fuel cell during power generation, there is a method in which heat is exchanged once with purified water, and then the purified water having a high temperature is exchanged again with city water. The reason why purified water is used is that when a heat medium having high conductivity is used, current may leak from the fuel cell, but if the circulation is continued for a long time in a closed loop, the conductivity gradually increases. There's a problem.
[0009]
[Patent Document 1]
JP-A-6-325780 [Patent document 2]
JP-A-9-17438 [Patent Document 3]
Japanese Patent Application Laid-Open No. 2000-223144 [Patent Document 4]
JP 2000-331703 A
[Problems to be solved by the invention]
One of the issues for practical use of a home fuel cell cogeneration system is to establish a simple method for collecting and reusing water discharged from a fuel cell. The present invention provides a specific system that uses water discharged from a fuel cell, and at the same time, greatly contributes to improvement of the reliability of the system and prolonging its life.
[0011]
[Means to solve the problem]
The present invention focuses on this point and solves the above-mentioned problems.In view of the structure of the system, the humidified gas discharged from the fuel cell is condensed and water is collected without requiring special power, and the water in the purified water container is collected. The liquid level is kept constant, and the fuel cell can be reused for the same or another use while keeping the inside of the fuel cell clean without contact between the oxidizing gas and the reducing agent gas. .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 1, the basic structure of the present invention is as follows. In order to obtain a humidified gas from a collection container 1 such as a gas humidifier, a gas 2 is introduced into the liquid in the collection container 1 so that the liquid at ambient temperature can be obtained. Is obtained. This is introduced into the fuel cell as humidified gas 3. At this time, since the inside of the recovery container 1 has a constant static pressure due to the supply of the gas 2, the liquid level position in the container decreases by the static pressure, and at the same time, the liquid level position of the introduction pipe 4 increases.
[0013]
This relationship is expressed by h = (P1−P2) / (ρ · g). When P2 is determined (such as atmospheric pressure), the inside of the container is determined by the supply of gas 2 and the pressure loss of the downstream fuel cell and the like. H is determined by the pressure P1.
[0014]
Accordingly, by disposing the discharge pipe 5 at a position higher by h, it is possible to prevent the liquid level of the introduction pipe 4 raised by the gas input 2 from being wastefully discharged. Also, by introducing the gas discharged from the fuel cell through the introduction pipe 4 through the condenser, water can be collected in the collection container 1 and reused, and the surplus is discharged from the exhaust and the discharge pipe 5. Since the liquid is discharged, the liquid level position is always kept constant. Further, the entire amount of the gas can be introduced into the fuel cell after humidification without structurally discharging the gas from the introduction pipe 4.
[0015]
【Example】
Next, an embodiment in which the present invention is applied to a fuel cell system will be described with reference to FIGS. 2 to 4. First, in FIG. 2, the fuel cell 6 generates heat during operation, and as a result, a heat recovery heat medium container and an oxidizing agent. Although the temperature of the recovery container 1 which also serves as a gas humidifier rises, the liquid sending means 7 for heat exchange between purified water and city water receives a signal from the temperature detecting means 8 to purify the temperature of the recovery container 1 to be constant. It controls the supply of water.
[0016]
According to the first invention of the present application, the heat recovery heat medium container and the oxidizing gas humidifier are also used in the recovery container 1, and the oxidizing gas exhaust gas discharged from the fuel cell including the pure water generated in the fuel cell 1 is discharged to the condenser 9. The condensed water is collected in the collection container 1 via the fuel cell, and at the same time, the cooling pump 10 for heat recovery of the fuel cell 6 is always operated, so that the humidified state of the oxidizing gas always introduced into the fuel cell is changed at the temperature of the fuel cell 6 It can be introduced as an oxidizing gas saturated with water.
[0017]
When the fuel cell 6 is in the power generation state, the oxidant exhaust gas contains humidified water when the oxidant gas is humidified and pure water generated in the fuel cell 6. When the discharge pipe 5 is provided to keep the amount constant, the amount of power generation is large, and when the amount of recovered water is large, excess liquid water is discharged from the discharge pipe 5 together with the oxidant exhaust gas. It is diluted with water and can always maintain a clean state.
[0018]
Conversely, when the power level is small and the amount of generated water is small and the water level of the recovery vessel 1 cannot be maintained due to loss of recovery of condensed water in the oxidizing exhaust gas, the liquid level detection means 11 installed in the recovery vessel 1 Upon receiving the signal, the liquid supply means 7 for replenishing the purified water is opened and closed. With this structure, the inside of the recovery container 1 is diluted with clean water, so that the electrolyte membrane of the fuel cell 1 is not adversely affected, and current leakage from the fuel cell 6 due to an increase in the ion concentration of water in the recovery container 1 is performed. There is also the effect of avoiding. Furthermore, the use of the container also has the effect of reducing the number of the liquid level detecting means 11 and the number of the purified water replenishing means.
[0019]
According to the second aspect of the present invention, when an oxidizing gas is obtained as shown in FIG. 1, when the oxidizing gas 2 is introduced into the water in the collection container 1, a saturated gas of the present liquid at an ambient temperature is obtained. This is introduced into the fuel cell 6 as the humidified oxidant gas 3. At this time, since the inside of the collection container 1 has a constant static pressure due to the supply of the oxidizing gas 2, the liquid level position in the collection container 1 decreases by the static pressure, and at the same time, the liquid level position of the introduction pipe 4 increases.
[0020]
This relationship is represented by h = (P1−P2) / (ρ · g). When P2 is determined (such as atmospheric pressure), the supply of the oxidizing gas 2 and the downstream fuel cell 6 and the condenser H is determined by the pressure P1 in the collection container 1 determined by a pressure loss such as 9. By arranging the discharge pipe 5 at a position higher by h and at a position lower than the upper surface plate 12 of the collection container 1, wasteful discharge of the liquid level of the introduction pipe 4 caused by the input gas 2 is achieved. Can be prevented.
[0021]
Also, by introducing the gas discharged from the fuel cell 6 through the introduction pipe 4 through the condenser 9, water can be collected in the collection container 1 and reused. , The liquid level is always kept constant. Further, the entire amount of the gas can be introduced into the fuel cell 6 after humidification without structurally discharging the gas from the discharge pipe 5.
[0022]
Needless to say, as shown in FIG. 2, the oxidizing gas supply means 13 should be located above the water surface position in order to prevent the inflow of water when stopped.
[0023]
The reducing agent gas exhibits the same effect as the second invention of the present application. In the steam reforming of hydrocarbons, water is usually supplied in an excessive composition for the purpose of preventing coking, and reforming is performed. As a result, since the generated reducing agent gas contains a very large amount of unreacted water, the temperature of the reformed gas is lowered since it needs to be supplied to the fuel cell 6 in an appropriate water-containing state. The condensed water collected in 9 is discharged from the discharge pipe 5 without discharging the reducing agent gas.
[0024]
As shown in FIG. 3, in the third invention of this application, the condensing container 14 in the reducing agent gas (H2 containing gas) is placed in the collecting container 1 and one end is taken out from below the water level position of the condensing container 14. The other end of the pipe 15 is located above the water level position of the condensing container 14 and below the top plate 16 of the condensing container 14 above the liquid level position of the reforming fuel water container 17 having the reforming fuel water. It has an open structure.
[0025]
The discharge pipe 5 in the middle of the introduction pipe 4 from the recovery container 1 is also connected to a position above the liquid level of the fuel water container 17 for reforming and below the top plate 12 of the recovery container 1.
[0026]
With this structure, the effect of the third invention of the present application is exhibited, and the condensing container 14 for the reducing agent gas is located in the collecting container 1, and the heat recovery and the temperature detecting means 8 in the fuel cell 1 by the cooling pump 10 are performed. The fuel cell 1, the humidifying temperature of the oxidizing gas and the condensing temperature of the reducing agent gas are relatively close to each other by the liquid sending means 7 which operates / stops in response to a signal from the controller. As a result, the wet state of the electrolyte of the fuel cell 6 is improved, so that stable operation of the fuel cell 6 can be realized.
[0027]
Further, when the liquid level in the reforming fuel water container 17 drops, the liquid sending means 7 provided in the recovery container 1 is opened by a signal from the liquid level detecting means 11 arranged in the reforming fuel water container 17. Replenish the purified water. As a result, the liquid level in the recovery vessel 1 rises, and the water level in the introduction pipe 4, including the static pressure component by the oxidizing gas supply means 13, rises in the discharge pipe 5 where the reforming fuel water vessel 17 is connected. When it reaches the height, it flows into the water container 17 for reformed fuel. When the liquid level in the reforming fuel water container 17 becomes a sufficient amount, the liquid sending means 7 for replenishing purified water is closed by a signal from the liquid level detecting means 11.
Thereby, it is possible to keep the water in the collection container 1 always in a clean state.
[0028]
FIG. 4 shows a state in which the discharge pipe 5 in the middle of the introduction pipe 4 from the recovery vessel 1 is positioned above the liquid level position of the reforming fuel water vessel 17 and below the upper surface plate 12 of the recovery vessel 1 as shown in FIG. This is the structure connected to the position.
[0029]
With this structure, while retaining the effects of the first and second aspects of the present invention, the surplus water from the recovery container 1 can be reused as the reforming fuel water via the supply pump 18 and the reforming fuel water can be reused. Does not flow back from the reforming fuel water container 17 to the recovery container 1 and does not contaminate the recovery container 1.
[0030]
Further, when the liquid level in the reforming fuel water container 17 drops, the liquid sending means 7 provided in the recovery container 1 is opened by a signal from the liquid level detecting means 11 arranged in the reforming fuel water container 17. Replenish the purified water. As a result, the liquid level in the recovery vessel 1 rises, and the water level in the introduction pipe 4, including the static pressure component by the oxidizing gas supply means 13, rises in the discharge pipe 5 where the reforming fuel water vessel 17 is connected. When it reaches the height, it flows into the water container 17 for reformed fuel. When the liquid level in the reforming fuel water container 17 becomes a sufficient amount, the liquid sending means 7 for replenishing purified water is closed by a signal from the liquid level detecting means 11.
This makes it possible to always keep the water in the collection container 1 clean as described above.
[0031]
Also, the oxidant exhaust gas from the fuel cell 1 condenses water through the condenser 9 and is collected in the collection container 1 by the introduction pipe 4, while the excess water and the oxidant gas exhaust gas are sent to the reforming fuel water container 17. Inflow, water is reused for reforming, and oxidant gas exhaust is discharged from the oxidant gas exhaust point and excess water from the overflow port 19.
[0032]
Although the oxidizing gas exhaust gas always flows into the reforming fuel water container 17, the reducing agent gas does not flow into the reforming fuel water container 17 due to its structure. Both the condensed water derived from the oxidizing gas and the condensed water derived from the reducing agent gas can be reused for reforming without causing an explosive atmosphere.
[0033]
A heat exchanger 20 is provided at an inner bottom portion of the collection container 1, and exchanges heat with high-temperature water in the collection container 1 to send heat to a heat use unit 23 through a circulation path 22 provided with a circulation pump 21. Here, various types of heat are used to improve the efficiency.
[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to collect and reuse the condensed water derived from the oxidant consumption gas discharged from the fuel cell and the condensed water derived from the reducing gas without waste in the structure of the system. In addition, the inside of the fuel cell can be kept clean, and the system can be simplified and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram of the present invention.
FIG. 2 is a configuration diagram of a fuel cell system showing one embodiment of the present invention.
FIG. 3 is a configuration diagram showing another embodiment of the present invention.
FIG. 4 is a configuration diagram showing still another embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 collection container 4 introduction pipe 5 discharge pipe 6 fuel cell 8 liquid level detecting means 12, 16 top plate 14 condensing vessel 15 communication pipe 17 fuel reforming water vessel

Claims (5)

A heat recovery heat medium container for the fuel cell, and a humidifier for the oxidizing gas, which also serves as a recovery container for storing water discharged from the fuel cell, including pure water generated by the fuel cell,
A fuel cell system wherein the water stored in the recovery container is reused for a heat medium for fuel cell heat recovery and humidifying water for oxidizing gas. An inlet pipe for supplying water from the fuel cell to the recovery vessel is connected to the lower part of the recovery vessel, and furthermore, the middle of the introduction pipe is a static pressure of the oxidizing gas supplied to the recovery vessel from the liquid level. 2. The fuel cell system according to claim 1, wherein a discharge pipe is provided at a position above and below a top plate of the collection container. In the recovery container, a condensing container for condensing water in the reducing agent gas is provided.A lower pipe of the condensing container is connected to a supply pipe of the reducing agent gas, and one end of a connecting pipe is connected to the other end. 3. The structure of the fuel cell system according to claim 1, wherein the fuel cell system is opened above the liquid level by an amount corresponding to the static pressure of the reducing agent gas and below the upper plate of the condensation vessel. 4. The fuel cell system according to claim 3, wherein the connecting pipe is connected above a water level position of the fuel reforming water container, and condensed surplus water is reused as fuel reforming water. The fuel reforming water container is connected to the discharge pipe in the middle of the introduction pipe above a water level position, and is provided with a liquid level detecting means, and the supply of pure water to the recovery vessel is controlled by the water level detecting means. The fuel cell system according to claim 4, wherein:

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