JP2000243417A - Fuel cell apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress reduction in output performance due to impurity mixed in a circulating path for supplying a gas by providing a removing means for removing an electric power generation inhibitor in the circulating path when a predetermined electric power generating condition in the circulating path for circulating and supplying at least one gas of first and second gases. SOLUTION: In this fuel cell apparatus, a hydrogen supply/exhaust system 10 and each fuel cell stack 2 construct a circulating path. The hydrogen supply/ exhaust system 10 is provided with a hydrogen common supply tube 11 and a hydrogen common exhaust tube 12. A check valve 13 accepts only a flow from the hydrogen common exhaust tube 12 to the hydrogen common supply tube 11. A purge valve 41 is generally closed and when opened, a gas in the hydrogen supply/exhaust system 10 is released. The impurity other than the hydrogen is accumulated in the hydrogen supply/exhaust system 10 or is attached on an electrode and then output performance is reduced with the lapse of time. Accordingly, the gas is released in the air for a predetermined period at a certain interval. When voltage or hydrogen concentration is decreased even within a predetermined period, purging is preformed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell device capable of effectively removing a power generation suppressing substance for suppressing generation of electric power.

[0002]

2. Description of the Related Art A fuel cell device is known as a device for directly extracting chemical energy of fuel as electric energy (electric power). This fuel cell device is constituted by one or more cells (fuel cells), and the cells sandwich an electrolyte membrane between a pair of electrodes, and form a gas passage on the outer surface of each electrode in cooperation with a defining member. Each is to be formed. Then, a first gas (for example, fuel gas (specifically, hydrogen or the like)) is supplied to one gas passage, and a second gas (which causes an electrochemical reaction with the first gas) is supplied to the other gas passage. For example, by supplying an oxidizing gas (specifically, air), electric power can be extracted from the pair of electrodes based on the electrochemical reaction of the first and second gases.

Such a fuel cell device has been improved. At present, as shown in JP-A-10-83824, when an electrode of a fuel cell (cell) is poisoned by CO and its output decreases, The fuel cell temperature is raised and the water vapor partial pressure of the reaction gas is kept constant to suppress a decrease in output performance. As shown in JP-A-7-272738, when the fuel cell is stopped, the fuel gas is changed to nitrogen. There has been proposed a method in which the generation of an electromotive force is immediately stopped by replacing the gas.

[0004] The present applicant has already proposed a fuel cell device which circulates and supplies at least one of the first and second gases to a cell through a circulation path. In this case, the unused gas can be reused based on the circulation path, and the gas can be effectively used.

[0005]

However, according to recent research, impurities (nitrogen, carbon monoxide, carbon dioxide, dust, etc.) as power generation suppressing substances enter the circulation path for some reason, It has been found that the impurities gradually accumulate due to the closed cycle of the circulation path and the impurities adhere to the electrode reaction surface. For this reason, the electrochemical reaction is hindered thereby, and the output performance is reduced with power generation (operation).

The present invention has been made in view of the above circumstances, and a technical problem thereof is that a fuel capable of suppressing a decrease in output performance caused by impurities mixed in a circulation path for supplying gas. It is to provide a battery device.

[0007]

In order to achieve the above technical object, according to the present invention (the first aspect of the present invention), electric power is obtained by causing an electrochemical reaction between a first gas and a second gas. In a fuel cell device comprising a cell and a circulation path for circulating and supplying at least one of the first and second gases to the cell, the power generation state of the circulation path is a predetermined state. The fuel cell apparatus further comprises a removing means for removing the power generation suppressing substance in the circulation path. Preferred embodiments of the first aspect are as described in the second and subsequent aspects.

[0008]

According to the first aspect of the present invention, when the power generation state is the predetermined state, the removing means removes the power generation suppressing substance in the circulation path, and the power generation in the circulation path is removed. The concentration of the inhibitor will be reduced. For this reason, it is possible to suppress a decrease in output due to the power generation suppressing substance with power generation.

According to the second aspect of the present invention, since the predetermined state is that the amount of the power generation suppressing substance in the circulation path is equal to or more than the predetermined value, the power generation suppressing which affects the output decrease. The power generation suppressing substance can be removed by accurately grasping the mixed amount of the substance, and a decrease in the output generated in advance can be suppressed in advance.

According to the third aspect of the present invention, since the power generation degree of the cell is equal to or less than the predetermined value in the predetermined state, it is possible to avoid frequent removal of the power generation suppressing substance. .

According to the fourth aspect of the present invention, the removing means is an air release valve that opens the circulation path to the atmosphere when the power generation state is the predetermined state. Sometimes, simply by opening the air release valve, the power generation suppressing substance can be released to the atmosphere using the gas pressure in the circulation path, and the amount of the power generation suppression substance in the circulation path can be reduced. For this reason, with a very simple configuration,
It is possible to suppress a decrease in output due to the power generation suppressing substance.

According to the invention described in claim 5, the circulation path is provided with a gas replenishing device for replenishing at least one of the first and second gases when the power generation state is the predetermined state. Therefore, even if the air release valve is opened, the gas is replenished and the gas pressure in the circulation path is maintained at a constant level, and the output is temporarily reduced with the opening of the air release valve. It is possible to suppress the decrease.

According to the sixth aspect of the present invention, the removing means is an adsorbing means for adsorbing the power generation suppressing substance when the power generation state is the predetermined state. As a result, the gas can be prevented from being discarded from the circulation path with the work of removing the power generation suppressing substance.

According to the seventh aspect of the present invention, the adsorbing means is provided to the circulation path via the bypass path attached to the circulation path, and the power generation state is predetermined in the bypass path. Since the switching valve for switching to the flow to the suction means in the state is provided, the same operation and effect as in the sixth aspect can be obtained with a specific configuration.

According to the invention described in claim 8, as the removing means, an air release valve for opening the circulation path to the atmosphere when the power generation state is the predetermined state, and the power generation valve when the power generation state is the predetermined state. An adsorbing means for adsorbing the suppressing substance; and a gas replenishing device for replenishing at least one of the first and second gases when the power generation state is in a predetermined state, in the circulation path. Therefore, the same function and effect as those of the fourth to sixth aspects can be obtained at the same time.

According to the ninth aspect, one of the first and second gases is hydrogen, and the first and second gases are hydrogen.
Since the other gas of the second gas is an oxygen-containing gas and only hydrogen is circulated and supplied to the cell through a circulation path, the fuel cell may have the most general basic configuration as a fuel cell. Thus, the same function and effect as those of the first aspect can be obtained.

According to the tenth aspect of the present invention, the removing means is an adsorbing means for adsorbing the power generation suppressing substance when the power generation state is a predetermined state, and the adsorbing means is formed of a palladium thin film. Therefore, in the most common basic configuration of a fuel cell using hydrogen as a fuel gas, the adsorption means (palladium thin film) adsorbs a power generation suppressing substance other than hydrogen and allows hydrogen to pass therethrough. In removing the power generation suppressing substance, hydrogen can be used effectively without discarding hydrogen.

According to the eleventh aspect of the present invention, since the cell includes one or more cells,
In addition to a single cell, the same function and effect as those of the first to tenth aspects can be obtained for a fuel cell stack in which a plurality of cells are assembled.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a fuel cell device according to an embodiment, and the fuel cell device 1 includes four fuel cell stacks 2. As shown in FIG. 2, each fuel cell stack 2 is configured by stacking a plurality of solid polymer fuel cells (hereinafter, referred to as cells) 3, and each cell 3 has a polymer electrolyte membrane 4. Gas passages 8 and 9 are formed between the pair of electrodes 5 and 6 on the outer surfaces of the electrodes 5 and 6 in cooperation with the defining member 7. Then, one gas passage 8 is supplied with hydrogen (fuel gas) as a first gas, and the other gas passage 9 is supplied with air (oxidizing gas) as a second gas that causes an electrochemical reaction with hydrogen. It is supposed to be.

As shown in FIG. 1, a hydrogen supply / discharge system 10 is associated with each fuel cell stack 2, and the hydrogen supply / discharge system 10 and each fuel cell stack 2 constitute a circulation path. . This hydrogen supply / discharge system 10 is connected to each fuel cell stack 2
A common hydrogen supply pipe 11 and a common hydrogen discharge pipe 12 are provided for associating the common hydrogen supply pipe 11 and the common hydrogen discharge pipe 12 with the common hydrogen supply pipe 11 and the common hydrogen discharge pipe 12. Is connected via a check valve 13 that allows only the flow of

The hydrogen common supply pipe 11 has a hydrogen supply port 14 and supply branch pipes 15a to 15d. One end of the hydrogen supply port 14 is connected to the hydrogen common supply pipe 11 on the downstream side of the check valve 13, and the other end is connected to a hydrogen gas cylinder 45 filled with hydrogen. A regulator 21 is interposed in the hydrogen supply port 14. The regulator 21 serves to maintain the pressure in the hydrogen supply / discharge system 10 (in the hydrogen common supply pipe 11 and the hydrogen common discharge pipe 12) at a predetermined pressure. When the pressure in the hydrogen supply / discharge system 10 becomes lower than a predetermined pressure, the valve is opened to replenish the hydrogen in the hydrogen gas cylinder 45 into the hydrogen common supply pipe 11. The supply branch pipes 15a to 15d correspond to the fuel cell stack 2, and the respective supply branch pipes 15a to 15d
Accordingly, hydrogen is supplied to one gas passage 8 of each cell 3 in each fuel cell stack 2.

On the other hand, the hydrogen common discharge pipe 12 is provided at one end thereof with four discharge branch pipes 17a to 17d, and at the other end thereof, in order toward the check valve 13, a hydrogen circulation pump 20 and a purge valve. 41, three-way valve 4
2 are provided. Four discharge branch pipes 17a to 17d
Corresponds to each fuel cell stack 2, and hydrogen in one gas passage 8 of each cell 3 in each fuel cell stack 2 is discharged by each discharge branch pipe 17 a to 17 d. I have. In this case, supply to one gas passage 8 of each cell 3 in each fuel cell stack 2 or discharge from one gas passage of each cell 3 is performed through a common passage (not shown) inside each fuel cell stack 2. It is supplied or discharged through the apparatus, but the details thereof are already known, so that further description is omitted. Hydrogen circulation pump 20
Is for forced circulation of hydrogen, whereby hydrogen in a pressurized state can be supplied to each fuel cell stack 2. The purge valve 41 has a function of releasing the gas in the hydrogen supply / discharge system 10 by communicating the inside of the hydrogen supply / discharge system 10 with the atmosphere when the valve is opened, while the purge valve 41 is normally closed. I have. The three-way valve 42 is connected to the hydrogen common discharge pipe 1.
2, the first connection port is connected to the purge valve 41 side, the second connection port is connected to the check valve 13 side, and the third connection port is connected to the hydrogen supply port 14 with the regulator. It is connected to a bypass pipe 43 connected on the upstream side of 21. The three-way valve 42 can selectively connect the purge valve 41 side and the check valve 13 side or the purge valve 41 side and the bypass pipe 43 side by the switching thereof. In addition to flowing into the common hydrogen supply pipe 11 via the pipe 13, it is also possible to flow into the bypass pipe 43. In this case, the bypass pipe 43
, A palladium thin film device 19 as an adsorption means and a check valve 46 are sequentially provided toward the hydrogen supply port 14. The palladium thin film device 19 is composed of a palladium thin film, and is composed of a gas containing impurities other than hydrogen (for example, nitrogen,
It has a function of removing only hydrogen while removing carbon dioxide, carbon monoxide, dust, etc.), and the check valve 46 allows the hydrogen that has passed through the palladium thin film device 19 to flow into the hydrogen supply port 14. On the other hand, it has a function of preventing the hydrogen from the hydrogen gas cylinder 45 from flowing into the palladium thin film device 19 side.

As shown in FIG. 1, each fuel cell stack 2 is associated with an air supply / discharge system 22. The air supply / discharge system 22 is used for associating with each fuel cell stack 2. A common air supply pipe 23 and a common air discharge pipe 24 are provided. One end of the common air supply pipe 23 is an air supply port 25 for taking in air, and the common air supply pipe 23 is cooled from the air supply port 25 toward the other end of the common air supply pipe 23 in order. A compressor 26 and a compressor (rotary pump) 27 are interposed. The cooler 26 adjusts the temperature of the air supplied to each fuel cell stack 2. The compressor 27 adjusts the number of revolutions to suck the outside air and supply the air to each of the fuel cell stacks 2, and adjusts the pressure and the like of the supplied air to adjust the electrochemical reaction in each of the fuel cell stacks 2. Is adjusted according to the required power (see FIG. 5). At the other end of the common air supply pipe 23, four supply branch pipes 28a to 28d are provided. The four supply branch pipes 28 a to 28 d correspond to the fuel cell stacks 2, and the air is supplied to the other gas passages 9 of the cells 3 in each fuel cell stack 2 by the supply branch pipes 28 a to 28 d. Is to be supplied.

On the other hand, the air common discharge pipe 24 has one end serving as an air discharge port 30 opening to the atmosphere, and the other end of the air common discharge pipe 24 has four discharge branch pipes 31a to 31a.
31d. Four discharge branch pipes 31a to 31d
Corresponds to each of the fuel cell stacks 2, and the air is discharged from the other gas passage 9 of each cell 3 in each fuel cell stack 2 by each of the discharge branch pipes 31a to 31d. . Also in this case, the supply to the other gas passage 9 of each cell 3 in each fuel cell stack 2 or the discharge from the other gas passage 9 of each cell 3 is performed by a common passage inside each fuel cell stack 2 (not shown). ) Is supplied or discharged, but the details thereof are already known, so that further description is omitted.

A cooling system 32 is associated with each fuel cell stack 2 as shown in FIG. Cooling system 3
2 constitutes a circulation path 33 that circulates cooling water in cooperation with each fuel cell stack 2, and includes a cooling water heater 40, a circulation pump 34, a cooling water valve 35, and a cooler. 36 are provided. The cooling system 32
Is provided with a bypass path 37 for bypassing the cooler 36, and the bypass path 37 is provided with a cooling water bypass valve 38. Thereby, these elements 33 to
By adjusting the temperature of the cooling water by using 38 and 40, the temperature of each fuel cell stack 2 can be adjusted.

In the present embodiment, the hydrogen supply / discharge system 10 is controlled by a control unit U as control means, as shown in FIGS. The control unit U includes voltage signals from voltage sensors V1 to V4 for measuring the voltage of each fuel cell stack 2, a hydrogen supply / discharge system 10
A hydrogen concentration signal from a hydrogen concentration detection sensor 44 for detecting the hydrogen concentration in the chamber, and various other signals from various sensors ES are input. From the control unit U, the purge valve 41 and the three-way valve 42 are A control signal is to be output.

The control unit U generally performs the following control. That is, if impurities other than hydrogen are accumulated in the hydrogen supply / discharge system 10 or adhere to the electrode 5, the output performance of each fuel cell stack 2 (cell 3) decreases with time. The gas (hydrogen and other impurities) in the hydrogen supply / discharge system 10 is discharged for a predetermined time (for example, α seconds (0 <α≪) every predetermined time (for example, every a minutes (0 <a)).
a)) only released to the atmosphere (hereinafter referred to as purge)
While the released and deficient hydrogen is replenished into the hydrogen supply / discharge system 10, if the voltage of each fuel cell stack 2 drops from a predetermined state within the fixed time, or if the hydrogen supply / discharge system 1
When the hydrogen concentration in 0 is reduced from a predetermined state, it is determined that impurities other than hydrogen are accumulated in the hydrogen supply / discharge system 10 and purging is to be performed. In addition, in replenishment of hydrogen due to purging, the remaining hydrogen in the hydrogen supply / discharge system 10 is recovered, and the hydrogen is also used as replenishment hydrogen.
We are trying to reduce the amount of hydrogen used.

Next, the above control will be described with reference to the flowchart shown in FIG. still. S indicates a step.
First, in S1, various data such as the voltage from each fuel cell stack 2 and the hydrogen concentration in the hydrogen supply / discharge system 10 from the hydrogen concentration detection sensor 44 are input, and in the next S2, a count is added by a timer. . Then, in the next S3, it is determined whether or not a certain time T10 has elapsed since the timer started counting the elapsed time T. In principle, this is done by purging at regular intervals,
This is performed in order to obtain a determination to release impurities as a power generation suppressing substance from the hydrogen supply / discharge system 10 (circulation path).

If the determination in S3 is YES, the timer is reset, the purge valve 41 is opened (opened to the atmosphere), purge is performed for a predetermined time, and impurities in the hydrogen supply / discharge system 10 are released to the atmosphere. Released (S4, S
5). At this time, the three-way valve 42 is
In synchronism with this, the purge valve 41 is switched so as to communicate with the bypass pipe 43 instead of the check valve 13, whereby the gas (hydrogen passing through the purge valve 41 and reaching the three-way valve 42) is switched. At this time, the pressure in the hydrogen supply / discharge system 10 is reduced due to the purge, and the hydrogen common supply pipe 11
Fresh hydrogen flowing into the inside (hydrogen gas cylinder 4
5) and flows into the hydrogen common supply pipe 11 together with the fresh hydrogen. In this case, the gas flowing into the bypass pipe 43 passes through the palladium thin film device 19 and the palladium thin film device 1
The hydrogen from which the impurities have been removed by 9 is supplied again into the hydrogen common supply pipe 11 as supplementary hydrogen. For this reason, the pressure in the circulation path including the hydrogen supply / discharge system 10 is kept constant even during the execution of the purge by the fresh hydrogen and the hydrogen recovered from the bypass pipe 43 to suppress the decrease in the output. In addition, the reuse of the recovered hydrogen makes it possible to reduce the usage of hydrogen as much as possible. Thereafter, with the end of the purge, the three-way valve 42 is switched to the original state, and the hydrogen supply / discharge system 10 returns to the original closed cycle state.

When S3 is NO, that is, when the fixed time T10 has not elapsed since the previous purge,
In S7, it is determined whether the current of each fuel cell stack 2 is constant. This is to determine whether or not the output performance is reduced under a steady state, and to increase the reliability of the determination. When S7 is NO, the purge valve 41 is closed, and when S7 is YES, whether or not the voltage of each fuel cell stack 2 has dropped from a predetermined state is determined. It is determined whether the concentration has decreased from the predetermined state (whether the impurity concentration has relatively increased) (S9, S10). This is to determine whether or not impurities are accumulated in the hydrogen supply / discharge system 10 or whether or not impurities are attached to the electrode 5 to obtain a determination as to whether or not it is necessary to perform purging.

When both S9 and S10 are NO, the process proceeds to S8, and when either S9 or S10 is YES, in S11, the elapsed time T is set to a predetermined time T10 from the start of the previous timer count. It is determined whether or not it is longer than a predetermined time T20 that is shorter than T20.
This is because a case where only a short time has elapsed since the previous purge is determined as an abnormality of the fuel cell stack 2. When S11 is NO, it is determined in S12 that the corresponding fuel cell stack 2 is abnormal, and S11
If the answer is YES, the program proceeds to S4, where the purging as described above is performed (S5, S6).

Therefore, in this embodiment, the purging is not only performed in principle every time the fixed time T10 elapses, but even if the elapsed time T is equal to or less than the fixed time T10, the voltage drop in each fuel cell stack 2 is reduced. Alternatively, purging is performed by detecting a decrease in the hydrogen concentration in the hydrogen supply / discharge system 10, so that accumulation of impurities in the circulation path including the hydrogen supply / discharge system 10 can be suppressed. For this reason,
It is possible to suppress a decrease in output performance based on impurities accumulated in the circulation path.

Although the embodiments have been described above, the present invention includes the following. (1) An electromagnetic valve is provided in place of the regulator 21, and the opening and closing of the electromagnetic valve is controlled by the control unit U. (2) Circulating and supplying not only hydrogen but also oxidizing gas as the second gas to the fuel cell stack 2. (3) Instead of the hydrogen gas cylinder 45, a reformer, for example, a reformer that generates hydrogen using methanol is used. (4) Use the fuel cell device as a power source for a vehicle or the like. (5) Even after the purge valve 41 is closed in S8, the three-way valve 4
Part of the gas that has reached 2 is supplied to the palladium thin film device 19.

It should be noted that the object of the present invention is not limited to what is explicitly specified, but also implicitly includes providing what substantially corresponds to what is described as preferable or advantageous.

[Brief description of the drawings]

FIG. 1 is an overall system diagram according to an embodiment.

FIG. 2 is an explanatory view conceptually showing a cell (fuel cell) structure.

FIG. 3 is a diagram showing an input / output relationship with respect to a control unit.

FIG. 4 is a flowchart illustrating a control example by a control unit U;

FIG. 5 is a diagram showing characteristics of the number of revolutions of the compressor with respect to required power.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel cell device 2 Fuel cell stack 3 Cell 10 Hydrogen supply / discharge system 19 Palladium thin film device 41 Purge valve 42 Three-way valve 44 Hydrogen concentration detection sensor 45 Hydrogen gas cylinder U Control unit V1 Voltage sensor V2 Voltage sensor V3 Voltage sensor V4 Voltage sensor

Claims (11)

[Claims] A cell for obtaining an electric power by performing an electrochemical reaction between a first gas and a second gas;
A fuel cell device provided with a circulation path for circulating and supplying at least one gas of the second gas, wherein a power generation suppressing substance in the circulation path is removed from the circulation path when the power generation state is a predetermined state. A fuel cell device comprising a removing unit. 2. The fuel cell device according to claim 1, wherein the predetermined state is that an amount of the power generation suppressing substance in the circulation path is equal to or more than a predetermined value. 3. The fuel cell device according to claim 1, wherein the predetermined state is such that a power generation degree of the cell is equal to or less than a predetermined value. 4. The fuel cell device according to claim 1, wherein the removing unit is an air release valve that opens the circulation path to the atmosphere when the power generation state is a predetermined state. 5. The gas supply device according to claim 4, wherein the circulation path includes a gas replenishing device that replenishes at least one of the first and second gases when the power generation state is a predetermined state. A fuel cell device characterized by the above-mentioned. 6. The fuel cell device according to claim 1, wherein the removal unit is an adsorption unit that adsorbs the power generation suppressing substance when the power generation state is a predetermined state. 7. The method according to claim 6, wherein the suction means is provided to the circulation path via a bypass passage provided in the circulation path, and the power generation state in the bypass path is a predetermined state. A switching valve for switching the flow to the adsorption means. 8. An air release valve according to claim 1, wherein said removing means opens said circulation path to atmosphere when a power generation state is a predetermined state, and said power generation suppressing substance when said power generation state is a predetermined state. And a gas replenishing device for replenishing at least one of the first gas and the second gas when the power generation state is in a predetermined state. A fuel cell device. 9. The cell according to claim 1, wherein one of the first and second gases is hydrogen, and the other of the first and second gases is an oxygen-containing gas. Wherein only hydrogen is circulated and supplied through the circulation path. 10. The method according to claim 9, wherein the removal unit is an adsorption unit that adsorbs the power generation suppressing substance when the power generation state is a predetermined state, and the adsorption unit is formed of a palladium thin film. Characteristic fuel cell device. 11. The fuel cell device according to claim 1, wherein the cell includes one or more cells.