JPH06203865A - Fuel cell system - Google Patents

Abstract

PURPOSE:To eliminate the need for operations such as replacing a cylinder and to purge combustible gas without depending on manual work by providing an exhaust gas burner for subjecting fuel exhaust gas to combustion process and an oxygen gas removing device or the like for separating inert gas. CONSTITUTION:Fuel exhaust gas exhausted from a fuel cell main body 2 is subjected to combustion process by an exhaust gas burner 12. Oxygen gas is separated from generated burner exhaust gas by an oxygen gas removing device 8 so that the exhaust gas is separated into inert gas. Since the inert gas is always stored in a tank 6 as purging gas for combustible gas retained in a fuel cell system, the inert gas in the tank 6 does not become insufficient. Therefore, the need for conventional troublesome operations such as replacing the tank 6 is eliminated, so the combustible gas can be purged very easily. Furthermore, a valve 7 is provided which is opened when operation of the main body 2 is stopped and which is also opened when purging of the combustible gas is terminated, thereby enabling purging without depending on manual work.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to fuel cell systems and, more particularly, to improvements in their purge systems.

[0002]

2. Description of the Related Art Fuel cells are a type of new power generator. The mechanism is such that hydrogen obtained by reforming a fuel such as natural gas is electrochemically reacted with oxygen in the air to directly generate power, which is also called chemical power generation. The principle of the fuel cell utilizes a reverse reaction of water electrolysis, that is, a mechanism in which hydrogen and oxygen are combined to generate electricity and water. In fact, the water produced at the same time as power generation can be recovered and used.

Regarding the mechanism of the fuel cell, an ordinary primary battery does not come and go because the reactants contained therein do not come and go, and eventually the life of the fuel cell is exhausted. However, the fuel cell continuously supplies the reactants and discharges the products. Thus, it can be described as a battery that continuously generates electricity. The main features of the fuel cell are as follows. Since it is direct power generation that does not go through the process of thermal energy or kinetic energy like the conventional power generation method, high power generation efficiency can be expected even on a small scale. The heat generated by power generation is easy to use for hot water supply and cooling and heating, which increases the overall energy efficiency. Emissions of nitrogen compounds are small, and noise and vibration are also small, so it is environmentally friendly.

As described above, the fuel cell power generation can utilize the chemical energy of the fuel effectively and has the property of being environmentally friendly. Therefore, the fuel cell power generation is expected as a city-type energy supply system for the 21st century, and it is a technology for practical use. Development is in full swing. In general, a fuel cell system is mainly composed of a fuel cell main body for generating electricity, and a reformer for steam reforming a fuel for supplying hydrogen-rich gas to the fuel cell main body and a direct current generated from the fuel cell main body. It is composed of peripheral devices such as an inverse conversion device (inverter or orthogonal conversion device) for converting the electric current into an alternating current, and a passage connecting these peripheral devices.

By the way, in the fuel cell system configured as described above, when the operation is stopped, the fuel cell system (in particular, the reformer, the fuel cell body, the passage)
Inflammable gas (gas mainly containing hydrogen) remains inside. If the fuel cell system is left with the flammable gas remaining in this way, the fuel cell body and the reformer are devices that perform chemical reactions. There is a possibility that corrosion will proceed and an unintended reaction will occur. Further, when a large amount of combustible gas remains in the fuel cell system, it may be subject to regulations such as the High Pressure Gas Control Law. Therefore, it is necessary to discharge the combustible gas remaining in the fuel cell system during the operation stop to the outside of the fuel cell system.

Therefore, conventionally, a fuel cell system and a cylinder storing an inert gas (usually a nitrogen cylinder)
And the reformer from the cylinder during the operation stop,
The inflammable gas remaining in the fuel cell system was purged by supplying an inert gas to the fuel cell main body, passages and the like.

[0007]

However, in the above-mentioned conventional fuel cell system, since the nitrogen gas stored in the nitrogen cylinder is finite, the nitrogen gas in the cylinder will be discharged as the flammable gas is purged. Reduced and nitrogen cylinders need to be replaced with new ones. Therefore,
Since labor is required to replace the cylinder, there is a problem that it is very troublesome and the workability is poor.

The present invention has been made in view of the above problems, and does not require any troublesome work such as exchanging a cylinder that stores an inert gas for purging, and can burn combustible gas without human labor. An object is to provide a very excellent fuel cell system that can be purged.

[0009]

In order to solve the above problems, the present invention provides a reformer for reforming a fuel to produce hydrogen, hydrogen produced by the reformer, and oxygen in the air. A fuel cell body for electrochemically reacting to generate electricity, an exhaust gas burner for burning the fuel exhaust gas discharged from the fuel cell body, and an oxygen gas from the burner exhaust gas burned by the exhaust gas burner. An oxygen gas removing device for removing the inert gas, a tank for storing the inert gas separated by the oxygen gas removing device, a passage connecting the tank and the reformer, and an intermediate part of the passage And when the operation of the fuel cell main body is stopped, the valve is opened to expel the inflammable gas remaining in the fuel cell system by the inactive gas in the tank, while the inflammable gas is inactive. Place with gas Is the is characterized in that a valve that is configured to close the.

[0010]

With the above structure, the fuel exhaust gas discharged from the fuel cell body is burned by the exhaust gas burner. In addition, the burner exhaust gas generated at this time has the oxygen gas removed by an oxygen gas removal device, and is thus an inert gas (N ₂ gas and C ₂
Mixed gas with O ₂ gas). Furthermore, since this inert gas is always stored in the tank as a gas for purging the flammable gas remaining in the fuel cell system, the inert gas in the tank does not run short. Therefore, it is possible to purge the flammable gas very easily, since the troublesome work such as the replacement of the tank as in the conventional case is not necessary.

In addition, since the valve provided in the middle of the passage connecting the tank and the reformer is configured to open when the operation of the fuel cell main body is stopped, the operation of the fuel cell main body is stopped. Then, the valve is automatically opened, and the inert gas can be supplied from the tank to the reformer, and further to the entire fuel cell system such as the fuel cell main body. Further, since the valve is configured to be closed when the purging of the combustible gas is completed, the combustible gas remaining in the fuel cell system can be purged very easily without manual labor. .

[0012]

FIG. 1 is a schematic configuration diagram of a 3 kw class small-sized fuel cell system used as a household power source or the like according to an embodiment of the present invention, in which a raw material gas is steam-reformed to produce a hydrogen-rich gas. A pouch 1, a fuel cell body 2 that electrochemically reacts hydrogen-rich gas produced in the reformer 1 with oxygen in the air to generate electricity, and a fuel cell body 2
And a passage B connecting the reformer 1 with the raw material gas, and a passage B for supplying the raw material gas to the reformer 1, and a raw material gas provided in the middle of the passage B for supplying the raw material gas to the reformer 1. Source gas supply valve 3 for varying the amount, and the fuel cell main body 2
An air supply fan 4 for supplying air to the fuel cell, a passage C connecting the air supply fan 4 and the fuel cell main body 2, and an exhaust gas burner 12 for combusting the fuel exhaust gas discharged from the fuel cell main body 2. A passage G connecting the exhaust gas burner 12 and the fuel cell main body 2; a passage H through which the burner exhaust gas burned by the exhaust gas burner 12 flows; and a passage G provided in the middle of the passage H. A heat exchanger 13 for exchanging heat to remove water vapor,
The oxygen gas removing device 8 for removing oxygen gas from the burner exhaust gas after removing steam by the heat exchanger 13 to separate the inert gas, and the burner exhaust gas after removing steam by the heat exchanger 13 are A passage J for supplying the oxygen gas removing device 8, a three-way valve 14 provided at a branch point of the passage J and the passage H, and an inert gas tank 6 for storing the inert gas separated by the oxygen gas removing device 8. And a pressure sensor 6a for detecting the gas pressure in the inert gas tank 6,
A passage E connecting the oxygen gas removing device 8 and the inert gas tank 6, and a passage E provided in the middle of the passage E,
A pressure compressor 9 for compressing the inert gas separated by the oxygen gas removing device 8 to supply it into the inert gas tank 6, and an inert gas stored in the inert gas tank 6 to the reformer 1 And a passage D for supplying the fuel cell main body 2 to the fuel cell main body 2
Generated from the fuel cell main body 2 and the inert gas supply valve 7 that opens when the operation of No. 1 stops and closes when the purging of the combustible gas ends, the switch 10 that operates the oxygen gas removing device 8 It is composed of a quadrature conversion device (inverter) 5 for converting a direct current into an alternating current, and peripheral devices such as a control device 11 for controlling these components.

The fuel cell body 2 comprises a phosphoric acid electrolyte 2a.
It has a structure in which a fuel electrode (negative electrode) 2b and an air electrode (positive electrode) 2c are arranged on both sides via a fuel cell, and the hydrogen rich gas supplied from the reformer 1 is supplied to the fuel electrode 2b via a passage A. Meanwhile, the air supplied from the air supply fan 4 is supplied to the oxidant electrode 2c through the passage C. The electrochemical reaction in the fuel cell body 2 is performed as shown in Chemical formula 1.

[0014]

[Chemical 1]

The reformer 1 is a device for steam-reforming a raw material gas (for example, natural gas) supplied through the passage B into a hydrogen-rich gas. The hydrogen-rich gas reformed here passes through the passage A and the fuel electrode 2 of the fuel body 1.
b. The steam reforming reaction here is carried out as follows. CH ₄ + 2H ₂ O → 4H ₂ + CO _{2 The} exhaust gas burner 12 burns the fuel exhaust gas discharged from the fuel cell body 2. At this time, the burner exhaust gas discharged is normally discharged into the atmosphere through the passage H, but is used to separate the purging inert gas by switching the three-way valve 14. The combustion heat generated during the combustion process is used to heat the reformer 1.

The heat exchanger 13 exchanges heat with the burner exhaust gas discharged from the exhaust gas burner 12 to remove water vapor. At this time, the removed steam is used for cogeneration such as hot water supply. The burner exhaust gas from which the water vapor has been removed is normally discharged into the atmosphere via the passage H. The oxygen gas removing device 8 includes the heat exchanger 1
3 is a device for removing oxygen gas from the burner exhaust gas after removing the steam in 3 to separate the inert gas. Although not shown, a compressor for compressing the burner exhaust gas and introducing it into the device, and this compressor It is mainly composed of an adsorption tank for separating oxygen gas from the compressed burner exhaust gas.

Here, assuming that the total volume of the combustible gas remaining in the fuel cell system is about 11 liters, in order to completely purge the combustible gas, about 2 times the combustible gas is required. Double the volume of inert gas is needed, ie about 23 liters of inert gas. In this case, assuming that the pressure of the inert gas tank 6 is about 9 atm, the inert gas tank 6 having a volume of about 2.5 liters (23/9) is required. The pressure in the inert gas tank 6 needs to be lower than 10 atm because of restrictions such as the High Pressure Gas Control Law.

The valve 7 provided in the middle of the passage D connecting the reformer 1 and the inert gas tank 6 is based on a valve opening command from the controller 11 when the operation of the fuel cell main body 2 is stopped. The valve 7 is configured to be automatically opened. When the valve 7 is opened, the reformer 1 and the passage for connecting the reformer 1 and the fuel cell main body 2 via the passage D. As a result of the supply of A or the inert gas into the fuel cell main body 2, the combustible gas remaining in the fuel cell system is purged. Further, since the valve 7 is configured to be closed based on the valve closing command from the control device 11 after completion of the purge, it is possible to prevent wasteful consumption of the inert gas after completion of the purge. You can Here, the purged combustible gas is discharged to the atmosphere after being processed by the combustible gas processing device or introduced into the exhaust gas burner 12 of the reforming device 1 for processing.

The three-way valve 14 is provided at a branch point between the passage H and the passage J, and based on a command from the control device 11,
It is switched to supply the burner exhaust gas to the passage H side or the passage J side. For example, when the gas pressure in the inert gas tank 6 becomes lower than a certain pressure, the oxygen gas removing device 8
While the burner exhaust gas is switched to the passage J side, if the gas pressure is equal to or higher than a certain pressure, the burner exhaust gas is switched to the passage H side so as to be discharged into the atmosphere.

The switch 10 is an ON / OFF switch for operating and stopping the oxygen gas removing device 8.
It is a switch and operates based on a command from the control device 11. For example, it is turned on when the gas pressure in the inert gas tank 6 becomes lower than a certain pressure, while it is turned off when the gas pressure is a certain pressure or more. A passage D connecting the reformer 1 and the inert gas tank 6 branches into a passage F on the downstream side of the valve 7, and the passage F connects the air supply fan 4 and the cathode 2c. They join in the middle of the passage C. With such a configuration, the cathode 2c can be formed using the inert gas supplied through the passage F.
The residual oxygen remaining inside can also be purged. [Other Matters] In the above embodiment, the phosphoric acid fuel cell was used as the fuel cell main body 2, but it is of course possible to use a molten carbonate fuel cell, a solid oxide fuel cell, or the like. . Further, the residual oxygen remaining in the cathode 2c was also purged with an inert gas, but this treatment is not always necessary.

[0021]

As described above, according to the present invention, the fuel exhaust gas discharged from the fuel cell body is burned by the exhaust gas burner. Further, the burner exhaust gas generated at this time is separated into an inert gas by removing the oxygen gas by the oxygen gas removing device. Furthermore, since this inert gas is always stored in the tank as a gas for purging the flammable gas remaining in the fuel cell system, the inert gas in the tank does not run short. Therefore, since it is not necessary to perform a troublesome work such as replacing the tank as in the conventional case,
Combustible gas can be purged very easily.

In addition, since the valve provided in the middle of the passage connecting the tank and the reformer is configured to open when the operation of the fuel cell main body is stopped, the operation of the fuel cell main body is stopped. Then, the valve is automatically opened, and the inert gas can be supplied from the tank to the reformer, and further to the entire fuel cell system such as the fuel cell main body. Further, since the valve is configured to be closed when the purging of the combustible gas is completed, the combustible gas remaining in the fuel cell system can be purged very easily without manual labor. Such an excellent effect.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a 3 kw class small-sized fuel cell system according to an embodiment of the present invention.

[Explanation of symbols]

 1 reformer 2 fuel cell body 6 tank 7 valve 8 oxygen gas removal device 12 exhaust gas burner D passage

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Eiji Tateyama 2-18 Keihan Hondori, Moriguchi-shi Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. A reformer for reforming a fuel to produce hydrogen, and a fuel cell body for electrochemically reacting hydrogen produced by the reformer with oxygen in the air to generate electricity. An exhaust gas burner that burns the fuel exhaust gas discharged from the fuel cell main body, and an oxygen gas removal device that removes oxygen gas from the burner exhaust gas burned by the exhaust gas burner to separate an inert gas. A tank for storing the inert gas separated by the oxygen gas removing device; a passage connecting the tank and the reformer; and a passage provided in the middle of the passage and stopping the operation of the fuel cell main body. Then, the valve configured to open to expel the combustible gas remaining in the fuel cell system by the inert gas in the tank, and close the valve when the combustible gas is replaced with the inert gas. When, Fuel cell system characterized by comprising.