JP2005222823A - Fuel cell power generation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generation method of a fuel cell with improved operability for a user at starting. <P>SOLUTION: At starting of changing over from a power generation operation suspending period to a power generation operation period, at least a part of water remaining at a fuel electrode of a cell during the power generation operation suspending period or fuel solution with a density not generating cross-over is collected and preserved, and further, the density of the fuel solution is put back to an appropriate density by supplying fuel liquid to start power generation operation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell that generates power using a solid electrolyte membrane.

This type of direct methanol fuel cell stack 1A (MEA = Membrane Electrode Assembly) is configured as shown in FIG.
The cell stack 1A of the fuel cell has electrode catalyst layers 3 and 4 formed on both sides of the solid electrolyte membrane 2, and an aqueous methanol solution on one side of the solid electrolyte membrane 2 via the electrode catalyst layer 3 on one side of the solid electrolyte membrane 2. 5 is supplied, and oxygen 6 is supplied to the electrode catalyst layer 4 on the other side of the solid electrolyte membrane 2 (Non-patent Document 1).

This power generation principle will be described.
In the cell stack 1 </ b> A, the fuel electrode 7 having the electrode catalyst layer 3 is formed on one side of the solid electrolyte membrane 2, and the air electrode 8 having the electrode catalyst layer 4 is formed on the other side of the solid electrolyte membrane 2. When an aqueous methanol solution of fuel is supplied to the fuel electrode 7, a chemical reaction proceeds at the fuel electrode 7 to generate carbon dioxide, protons, and electrons.

CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻
Among these, protons permeate through the solid electrolyte membrane 2 and electrons pass through an external circuit. Then, a chemical reaction proceeds between the protons, the electrons, and oxygen supplied to the air electrode 8 at the air electrode 8. Is generated.

  The theoretical concentration of methanol and water in the aqueous methanol solution supplied to the fuel electrode 7 is 1: 1 (64 wt% methanol aqueous solution) in molar ratio, but the solid electrolyte membrane 2 permeates the methanol and reaches the air electrode 19 ( Since the battery output is reduced by methanol crossover), the actual optimum concentration is about 3 to 30% by weight, and when methanol and water generate a power generation reaction, the water is in a surplus state.

  In order to supply the methanol aqueous solution fuel, the liquid chamber of the fuel electrode 7 is filled with the methanol aqueous solution, and the fuel liquid static type system (passive type) that supplies the fuel directly from the tank to the liquid chamber of the fuel electrode 7 according to the amount of consumption. ) And a fuel liquid circulation system (active type) in which methanol aqueous fuel is circulated through the liquid chamber of the fuel electrode 7 and methanol fuel is supplied from the methanol fuel tank according to the amount of consumption in the circulation tank. Yes (Patent Document 1) (Patent Document 2).

  Comparing these two methods, the passive type is suitable for miniaturization because it does not require a portion for circulating the fuel, but the methanol aqueous solution reacts with the electrode catalyst layer 3 of the fuel electrode 7 and the methanol is consumed. Then, there is a problem that the battery output decreases as the methanol concentration decreases. Since the active type circulates in the liquid chamber of the fuel electrode 7, the active type has an advantage that an output concentration about 3 to 5 times that of the passive type can be obtained.

  FIG. 7 quotes (Patent Document 2), where high-concentration methanol is set in a methanol storage tank 9, and the methanol storage tank 9 is connected to a circulation tank 11 via a fuel + water injection device 10. Yes. A circulation path is formed so that the aqueous methanol solution 5 taken out from the circulation tank 11 by the pump 12 returns to the circulation tank 11 via the fuel electrode 7 and the heat exchanger 13 of the cell stack 1A. Air is supplied to the air electrode 8 of the cell stack 1 </ b> A via the oxidant supply device 14.

  As a result, in the cell stack 1A, the methanol aqueous solution causes a battery reaction to consume methanol and generate carbon dioxide. The mixed fluid of the low-concentration methanol liquid and the gas returns to the circulation tank 11, the liquid and the carbon dioxide gas are separated by gravity in the circulation tank 11, and the carbon dioxide gas is discharged from above the circulation tank 11. On the other hand, methanol and water are consumed by the cell reaction and fuel is reduced. Therefore, a predetermined amount is injected from the fuel + water injection device 10 into the circulation tank 11 at a concentration that provides the optimum methanol fuel.

  The water generated by the reaction by supplying air to the air electrode 8 of the cell stack 1A via the oxidant supply device 14 is recovered by the water recovery device 15 and returned to the fuel + water injection device 10, and again. It is used as water to be supplied to the fuel electrode 7. As the oxidant supply device 14, an air pump is generally used.

  In this way, a methanol aqueous solution having a concentration suitable for power generation operation is circulated in the fuel electrode 7 and air is supplied to the air electrode 8 for continuous operation. Consider the waiting state before starting.

  If the methanol aqueous solution is filled in the fuel electrode during the rest period of the power generation operation before the start of use, methanol is consumed due to a discharge phenomenon during the rest period and carbon dioxide is generated, which is not suitable for long-term storage.

  In addition, a start-up method may be considered in which the methanol aqueous solution is not supplied to the fuel electrode during the suspension period, and the methanol aqueous solution is supplied to the fuel electrode at the time of start-up. Since the rated performance cannot be obtained until the electrode catalyst layer 3 of the fuel electrode 7 becomes sufficiently familiar, there is a problem that the startup performance at the time of startup is poor.

  Further, since water is not recovered in the water recovery device 15 at the start of use, when using high-concentration fuel, a diluent or water is injected into the fuel cell device in advance at the time of shipment from the factory, or the fuel at the start of use. It is assumed that an operation of supplying a diluent or water from the outside into the battery device is required.

(Patent Document 3) discloses that water or fuel is present in the fuel electrode during the suspension period of power generation operation, and the electrode catalyst layer of the fuel electrode is not dried during long-term storage and suspension. A method is described that can improve start-up performance.
Industrial Research Committee “Electronic Materials” February 2003, p. 31 “Portable Small Fuel Cell” (Nobuyuki Kamiya) Japanese Patent No. 2939978 Special table hei 10-507572 JP 2003-77512 A

  A method for a consumer to start using a fuel cell in which water or a methanol aqueous solution having a concentration that does not cause crossover is present in the fuel electrode is not specifically described in (Patent Document 3) and the like. There is a need to improve consumer operability when starting to use batteries.

  An object of this invention is to provide the specific fuel cell power generation method which can improve the operativity of consumers at the time of the start of use of a fuel cell.

  In the fuel cell power generation method according to claim 1 of the present invention, water or a fuel aqueous solution having a concentration that does not cause crossover is present in the fuel electrode of the cell during the suspension period of the power generation operation. When the fuel liquid is supplied from the tank to the fuel electrode and air is supplied to the air electrode of the cell to generate power, at the time of start-up that shifts from the power generation operation suspension period to the power generation operation period, Collect and store at least a portion of the water or fuel aqueous solution at a concentration that does not cause crossover that existed in the fuel electrode, and supply the fuel liquid to generate an appropriate concentration of the fuel aqueous solution at the fuel electrode. When the operation is started and the aqueous fuel solution in the fuel electrode is diluted, the stored water or the aqueous fuel solution having a concentration that does not cause crossover is supplied to the fuel electrode. Which comprises carrying out the adjustment of the degree.

  The fuel cell power generation method according to claim 2 of the present invention is the fuel cell power generation method according to claim 1, wherein after supplying the fuel liquid to the fuel electrode, the liquid in the fuel electrode is forcibly moved and mixed to mix the aqueous fuel solution in the fuel electrode. It is characterized in that the density of the liquid is adjusted to an appropriate density.

  According to a third aspect of the present invention, there is provided a fuel cell power generation method in which the fuel electrode in the fuel supply channel in which the first and second fuel tanks are disposed on both sides of the fuel electrode in the center During the suspension period of operation, water or a fuel aqueous solution with a concentration that does not cause crossover is present, and at the time of start-up to shift from the suspension period of power generation operation to the power generation operation period, it exists in the fuel electrode of the cell during the suspension period of power generation operation At least a part of the water or the aqueous fuel solution having a concentration that does not cause crossover is collected and stored, and further supplied with a fuel liquid and between the first fuel tank and the second fuel tank via the fuel electrode. The fuel liquid in the fuel supply passage is forcibly moved and mixed to start the power generation operation with the concentration of the aqueous fuel solution at the fuel electrode set to an appropriate concentration, and to dilute the aqueous fuel solution in the fuel electrode. Which comprises carrying out the adjustment of the concentration by supplying a fuel aqueous solution of concentration the storage to have water or crossover does not occur in the fuel electrode to.

  According to the fuel cell power generation method of the present invention, at the time of start-up that shifts from the power generation operation suspension period to the power generation operation period, the fuel having a concentration that does not cause water or crossover that was present in the fuel electrode of the cell during the power generation operation suspension period When at least a part of the aqueous solution is collected and stored, and the aqueous fuel solution in the fuel electrode is diluted, the stored water or the aqueous fuel solution having a concentration that does not cause crossover is supplied to the fuel electrode. Since adjustment is performed, water generated by the power generation reaction cannot be recovered, for example, even when concentration adjustment is performed at the beginning of power generation operation, water or a fuel aqueous solution having a concentration that does not cause crossover is supplied from the outside. It is not necessary for the consumer to perform this operation.

Hereinafter, the fuel cell power generation method of the present invention will be described based on specific embodiments.
(Embodiment 1)
1 to 3 show (Embodiment 1) of the present invention.

  In FIG. 1, the fuel cell device of this embodiment includes a cell 1, first and second fuel tanks C1 and C2, a single air pump AP, a buffer tank B1, and a water storage tank C3. The methanol storage container C4, a piping path connecting between them, and a valve or a gas-liquid separator connected to the piping path are combined.

  As described in the prior art, the cell 1 is configured by forming the electrode catalyst layers 3 and 4 on both sides with the solid electrolyte membrane 2 at the center, and the fuel electrode 7 of the cell 1 at the center and on both sides thereof. The first and second fuel tanks C1 and C2 are arranged, the first fuel tank C1 and the fuel electrode 7 are connected by the first fuel supply channel 16, and the second fuel tank C2 and the fuel are connected. The poles 7 are connected by a second fuel supply channel 17.

  Here, the first and second fuel tanks C1 and C2 are constituted by meandering thin serpentine fuel tanks as shown in FIG. For example, the first glass substrate 18 having a recess that becomes a part of a meandering path, and the recesses of the first glass substrate 18 having a recess that becomes a part of a meandering path are symmetrical. The two glass substrates 19 are bonded to each other so that the respective concave portions are inside. 20 is an air inlet and 21 is a liquid inlet / outlet.

  A first gas-liquid separator L1 is interposed at the fuel outlet (hereinafter referred to as section S42) of the first fuel tank C1, and the fuel outlet (hereinafter referred to as section S52) of the second fuel tank C2. Is provided with a second gas-liquid separator L2. A first filter F1 of a hydrophobic porous membrane is interposed in the air inlet (hereinafter referred to as section S41) of the first fuel tank C1, and the air inlet (hereinafter referred to as section S51) of the second fuel tank C2. Also includes a second filter F2 of a hydrophobic porous membrane.

  The air supply flow path for supplying air to the air electrode 8 of the cell 1 connects one end of the air electrode 8 and the buffer tank B1 with a pipe line 22 and connects the other end of the air electrode 8 to the third gas-liquid separator L3. And one end of a water storage tank C3 through a valve V11. One end of the water storage tank C3 is connected to the second fuel supply channel 17 through a valve V6. Similarly to the first and second fuel tanks C1 and C2, the water storage tank C3 is constituted by a meandering thin serpentine tank. In any of the tanks C1, C2, and C3, the meniscus formed in the flow path may be broken due to an impact such as a drop when the flow path diameter is increased. The meniscus is thin enough not to collapse.

  A buffer tank B1 whose internal pressure is pressurized so as to maintain a target value by the air pump AP is connected to the air inlet of the first fuel tank C1 via the valve V1 and the first filter F1, and is buffered. A tank B1 is connected to the air inlet of the second fuel tank C2 via a valve V3 and the second filter F2. A connection point between the valve V1 and the first filter F1 is connected to the atmosphere via the valve V2. A connection point between the valve V3 and the second filter F2 is connected to the atmosphere via the valve V4.

  The methanol storage container C4 is formed with a sealed chamber 24 for accommodating a flexible bag 23 filled with high-concentration methanol, and this sealed chamber 24 is connected to the buffer tank B1 via a valve V8. . The sealed chamber 24 is opened to the atmosphere via a valve V9. The fuel outlet of the bag 23 is connected to the first fuel supply channel 16 via a filter F3 and a valve V5 for preventing contamination. A surplus water tank C5 is attached to the methanol storage container C4.

  The surplus water tank C5 is connected to the other end of the water storage tank C3 via the valve V7. The other end of the water storage tank C3 is connected to the buffer tank B1 through a first filter F4 of a hydrophobic porous membrane and a valve V10.

  Further, the section S42 (fuel outlet of the first fuel tank C1), the section S52 (fuel outlet of the second fuel tank C2), the section S41 (air inlet of the first fuel tank C1), the section S51. As shown in FIG. 3, electrodes P1 and P2 as level meters are respectively laid at the (air inlet of the second fuel tank C2), and an aqueous methanol solution is interposed between the electrodes P1 and P2. The electrical resistance value is discriminated from the state in which the aqueous methanol solution is no longer present.

  In this embodiment, electrodes P1 and P2 are provided in sections S41 and S42, respectively, as a first sensor for detecting the liquid level of the fuel liquid in the first fuel tank C1, and the fuel liquid in the second fuel tank C2 is provided. As a second sensor for detecting the liquid level, electrodes P1 and P2 are provided in sections S51 and S52, respectively. Similarly to the first and second sensors, electrodes P1 and P2 are provided as a third sensor in a section S61 between the valve V6 and the water storage tank C3.

  All of the tanks C1, C2, and C3 are configured using a liquid repellent treatment for the inside of the flow path or a liquid repellent material for the flow path pipe. The purpose of this is to improve this point because if the wetting of the channel wall surface is high, a water film remains on the wall surface and the fuel transfer efficiency deteriorates. More specifically, using a fluorine-based liquid repellent treatment or a fluorine-based pipe material inside the flow paths of the tanks C1, C2, C3, the fuel can move without leaving a water film and droplets on the flow path partition walls. Smooth, good movement efficiency and clear liquid level detection.

  Each of the valves V1 to V11 is an electromagnetic valve that can be electrically switched between open and closed states according to the operating state. More preferably, when a set pulse voltage is applied at the switching timing of the open and closed state, The flow path is self-maintained until the reset pulse voltage is applied after the voltage disappears, and when the reset pulse voltage is applied, the reset pulse voltage disappears and the set pulse voltage is applied thereafter. A latching type solenoid valve that is self-maintained in a closed state is preferable for reducing power consumption. In FIG. 1, each of the valves V1 to V11 is supplied with the set pulse voltage and the reset pulse voltage from the controller 25 according to each operation state. Is applied. The controller 25 is provided with a start-up battery for operating various valves and the like at start-up.

This will be described in the following states.
"Power generation suspension period"
"On startup"
"Power generation operation"
The fuel cell device shipped from the factory enters the “power generation operation” state through the “power generation operation suspension period” and “start-up” states, but is necessary for power generation in order to clarify the operation of each component in FIG. First, a “power generation operation” state in which a methanol aqueous solution having an appropriate and appropriate concentration exists in the fuel electrode 7 will be described, and then a “power generation operation suspension period” and a “start-up” state will be described.

"Power generation operation"
a. Standby stage After the first fuel tank C1 is empty and the second fuel tank C2 is filled with an aqueous methanol solution having an appropriate concentration necessary for power generation, the controller 25 executes the next operation first stage.

  When the first fuel tank C1 is empty and the second fuel tank C2 is full, the controller 25 sets the valves V1, V3 to the closed state and the valves V2, V4 to the closed state. From the electrical continuity of the electrodes P1, P2 of S41, S42, S51, S52, it is checked whether the first fuel tank C1 is empty and the second fuel tank C2 is full.

  Specifically, the methanol levels of the sections S41 and S42 at both ends of the first fuel tank C1 cannot detect methanol (hereinafter, this methanol-free state is referred to as “Low”), both ends of the second fuel tank C2. It is checked whether the methanol level in the sections S51 and S52 in the state where methanol is detected (hereinafter, the state with methanol is referred to as “Hi”).

  When the first fuel tank C1 is empty and the second fuel tank C2 is not full, the controller 25 closes the valves V2 and V3 and opens the valves V1 and V4, and opens the valves from the buffer tank B1. Pressurized air is sent to the first fuel tank C1 through V1 and the filter F1, and the methanol aqueous solution remaining in the first fuel tank C1 is used as the first fuel supply channel 16, the fuel electrode 7, and the second fuel. The air that has been moved to the second fuel tank C2 through the supply flow path 17 and the gas-liquid separator L2 and is pushed out from the second fuel tank C2 is released from the filter F2 to the atmosphere via the valve V4.

  If the second fuel tank C2 does not become full at the end of the standby stage, it is determined that the methanol aqueous solution is insufficient, and the controller 25 detects this and detects the first fuel supply channel 16. Control is performed to instruct the injection of high-concentration methanol and to inject water into the second fuel supply channel 17.

b. First stage of operation In this state, the valves V1, V4 are closed and the valves V2, V3 are set to the open state, and the pressurized air is supplied from the buffer tank B1 to the second fuel tank C2 via the valve V3 and the filter F2. On the other hand, in the first fuel tank C1, the internal air is released to the atmosphere through the filter F1 and the valve V2, so that the first fuel tank C1 is separated from the second fuel tank C2 by the gas-liquid separator L2. The methanol aqueous solution pushed out to the fuel supply flow path 17 passes through the fuel electrode 7, and methanol and water are consumed by passing through the fuel electrode 7, and carbon dioxide gas is generated to form a gas-liquid mixed flow. The aqueous methanol solution is further gas-liquid separated by the gas-liquid separator L1 through the first fuel supply flow path 16, and the carbon dioxide gas in the gas-liquid mixed flow is separated by the gas-liquid separator L1 and discharged to the atmosphere. . Only the methanol aqueous solution remaining in the gas-liquid separation flows into the first fuel tank C1 via the gas-liquid separator L1.

Due to such a flow path configuration, a flow path liquid level boundary is formed in the first fuel tank C1, and the liquid level passes through the section S42 and moves toward the section S41.
In the first stage of operation, air is continuously supplied from the buffer tank B1 to the air electrode 8, and the air that has passed through the air electrode 8 is separated by the gas-liquid separator L3 and discharged to the atmosphere.

  The controller 25 that has detected that the aqueous methanol solution has reached section S41 switches to the next operation second stage. However, if the aqueous methanol solution does not reach the section S41, it is determined that a predetermined amount of aqueous methanol solution has been consumed, and the controller 25 detects this and injects high-concentration methanol into the first fuel supply channel 16. Instruct and control to inject water into the second fuel supply flow path 17.

c. Second Operation Stage This second operation stage switches to an operation stage that moves the aqueous methanol solution from the first fuel tank C1 to the second fuel tank C2. Specifically, the valves V2 and V3 are closed and the valves V1 and V4 are set to open, and pressurized air is sent from the buffer tank B1 to the first fuel tank C1 via the valve V1 and the filter F1, while In the second fuel tank C2, since the internal air is released to the atmosphere via the filter F2 and the valve V4, the first fuel supply is performed after gas-liquid separation from the first fuel tank C1 by the gas-liquid separator L1. The methanol aqueous solution pushed out to the flow path 16 passes through the fuel electrode 7, and methanol and water are consumed by passing through the fuel electrode 7, and the methanol aqueous solution that is generated as carbon dioxide gas and becomes a gas-liquid mixed flow is the first. The gas-liquid separator L2 further gas-liquid-separates through the fuel supply flow path 17, and the gas-liquid mixed flow carbon dioxide gas is separated by the gas-liquid separator L2 and discharged to the atmosphere. Only the methanol aqueous solution remaining in the gas-liquid separation flows into the first fuel tank C2 via the gas-liquid separator L2. Similar to the first stage of operation, the second fuel tank C2 also has a flow path liquid level boundary, and the liquid level passes through the section S52 and moves toward the section S51.

  In the second stage of operation, air is continuously supplied from the buffer tank B1 to the air electrode 8, and the air that has passed through the air electrode 8 is separated by the gas-liquid separator L3 and discharged to the atmosphere.

  The controller 25 that has detected that the aqueous methanol solution has reached the section S51 switches to the operation first stage again. However, if the aqueous methanol solution does not reach section S51, it is determined that a predetermined amount of aqueous methanol solution has been consumed, and the controller 25 detects this and injects high-concentration methanol into the first fuel supply channel 16. Instruct and control to inject water into the second fuel supply flow path 17.

In the case of injecting high-concentration methanol When injecting high-concentration methanol, the valves V5 and V9 are closed and the valve V8 is opened, so that the methanol storage container C4 is sealed from the buffer tank B1 through the valve V8. Pressurized air is supplied to the chamber 24, and the pressure of the supplied pressurized air is applied to the bag 23. This state is referred to as a standby state. Then, by opening the valve V5, the bag 23 is crushed according to the pressure of the supplied pressurized air, and the bag 23 is passed through the filter F3 and the valve V5 to the first fuel supply channel 16. High concentration methanol is injected. The injection at this time is performed until the controller 25 detects whether or not each section S41, S42, S51, S52 is full in each stage.

In the case of water injection During the repeated operation of the operation first stage and the operation second stage, water is stored in the water storage tank C3 as follows. That is, when the valves V7 and V11 are set in the open state and the valves V10 and V6 are set in the closed state, the water + unreacted air mixed fluid that has passed through the air electrode 8 of the cell flows into the gas-liquid separator L3, and unreacted air Is discharged to the atmosphere, and only water passes through the hydrophilic filter of the gas-liquid separator L3, passes through the valve V11, and is stored in the water storage tank C3. When water is fed into the water storage tank C3, the gas-liquid level in the water storage tank C3 moves toward the surplus water tank C5 as the water increases. The surplus water tank C5 is specifically composed of a porous material provided outside the sealed chamber 24 of the methanol storage container C4, and surplus water exceeding the capacity of the water storage tank C3 It is absorbed and held in the porous material of C5, and is evaporated from the porous material to the atmosphere and discharged.

  The injection of water from the water storage tank C3 to the second fuel supply channel 17 is performed as follows. In this case, the controller 25 sets the valves V7 and V11 to the closed state and the valves V6 and V10 to the open state. When the valve V8 is set to the closed state, pressurized air is supplied from the buffer tank B1 to the water storage tank C3 through the valve V10 and the filter F4, and the water stored in the water storage tank C3 is supplied to the valve V6. And injected into the second fuel supply channel 17. The injection at this time is performed until the controller 25 detects whether or not each section S41, S42, S51, S52 is full in each stage. When the injection is finished, the controller 25 returns the valves V7 and V11 to the open state and the valves V10 and V6 to the closed state.

  The timings of the “injection of high-concentration methanol” and the “injection of water” are as follows. For example, when methanol and water are consumed in the fuel electrode 7, When the fuel is transported from the fuel tank C1, the sections S51 and S52 do not become “Hi” even if the sections S41 and S42 become “Low”. At this time, when the controller 25 looks at the methanol concentration and determines that the concentration is low, high concentration methanol is injected, and when it is determined that the concentration is high, water is injected.

  The methanol concentration detection may be performed by directly reading the output of a methanol concentration sensor (not shown) provided in at least one of the first fuel supply channel 16 and the second fuel supply channel 17 or by generating power in the cell. Read indirectly from force.

  The high-concentration methanol and water injected into the first fuel supply flow path 16 and the second fuel supply flow path 17 in this way are quickly brought about by repeated operation of the operation first stage and operation second stage. Mix evenly.

  The volume of the first fuel tank C1 and the second fuel tank C2 is from the first fuel supply flow path 16 to the second fuel supply flow path 17 including the flow path of the fuel electrode 7 of the cell 1. It is preferably equal to or more than the channel volume. This is because the fuel in the cell 1 is changed in one direction.

  As described above, in the fuel cell device in which the fuel is supplied to the fuel electrode 7 of the cell 1 by the bidirectional operation of the operation first stage and the operation second stage, the current-voltage characteristic of the cell 1 is improved. Measurements were made. As a result, changes in current and voltage at the timing of switching between the operation first stage and the operation second stage were not detected. The change is expected to be less than 1 mW.

  Further, in one direction, there continuously occurs a state in which no gas is present at the fuel electrode inlet of the cell 1 and the methanol concentration is rich, and the outlet has a large amount of gas and a low methanol concentration. Since the power generation output at the inlet side is high and the power generation output at the outlet is low, the life on the inlet side of the air electrode is low, and the concentration on the inlet side is always high, so methanol crossover occurs and the output does not increase. By making them bidirectional as in the above, the output of the MEA film is averaged, and the load on the MEA is also averaged. Since the methanol concentration at the inlet and outlet is switched between low and high, methanol crossover is reduced.

  As a result, when the output increases and bubbles are discharged, the discharge capacity of the bubbles at the outlet is reduced if it is in one direction. Since the liquid is switched to the inlet even if the pressure drops, it is excellent in the ability to discharge bubbles due to the force of the liquid flow, and it is difficult to cause a shortage of fluid fuel supply, and a stable operation can be expected over a long period of time.

  In addition, since the air pump AP that sends air to the air electrode 8 is also used for fuel supply at the fuel electrode 7, a liquid pump provided separately from the air pump AP that sends air to the air electrode 8 as in the prior art. Compared with the case where fuel is supplied to the fuel electrode 7, the apparatus can be reduced in size and weight by a single motor. Further, when the fuel is supplied to the fuel electrode 7 using the liquid pump, it cannot be started unless the priming water is given. In this embodiment, the air pump AP for sending air to the air electrode 8 is provided with the fuel electrode 7. Because it is also used for fuel supply in the above, the priming water is unnecessary and a reliable start-up can be realized.

  In addition, since the air pump AP for sending air to the air electrode 8 is used for injecting high-concentration methanol from the methanol storage container C4 to the first fuel supply flow path 16, it has a special resistance to methanol. It is not necessary to use a pump made of material, and it is suitable for a small amount of methanol. Even when the fuel cell is reversed and the air contacts the methanol outlet of the methanol storage container C4, methanol can be reliably injected.

  In the case of a weight separation type circulation tank, the portable fuel cell may be turned upside down, and carbon dioxide gas cannot be discharged. Since the liquid level fluctuates, the liquid level sensor malfunctions. Further, when there is vibration, the circulation tank is shuffled and a large amount of bubbles are mixed into the liquid, causing the air pump to malfunction. In the above embodiment, the first and second fuel tanks are used. Since the shapes of C1 and C2 are formed by pipes, the liquid levels of methanol and air are constant regardless of the attitude of the fuel cell, and stable operation can be expected.

Explains the “power generation operation suspension period” that exists before the above “power generation operation” and the “start-up” state executed between this “power generation operation suspension period” and “power generation operation” To do.
"Power generation suspension period"
In the rest period of the power generation operation from the factory shipment to the start of use by the consumer, in this fuel cell device, all the valves V1 to V11 are set in the closed state, the first fuel tank C1 is in the empty state, The second fuel tank C2 is filled with water through the one fuel supply channel 16, the fuel electrode 7, and the second fuel supply channel 17. The water storage tank C3 is empty, for example. The methanol storage container C4 may be either before or after mounting.

  As described above, during the rest period of the power generation operation, no aqueous methanol solution exists in the fuel electrode 7, and the electrode catalyst layer of the fuel electrode is dried during long-term storage and rest due to being wet with water. The startup performance at startup can be improved.

Starting At the time of starting to shift from the suspension period of power generation operation to the power generation operation period, when the controller 25 is instructed to start, the controller 25 that recognizes this instructs the first fuel tank C1, the first fuel supply channel 16, and the fuel electrode. 7 and a flow path formed by a pipe 26 connecting the valve V6 and the water storage tank C3 and a water storage tank C3 for collecting a part of the water filled in the second fuel supply path 17 Is implemented as a tank.

  Specifically, when the valves V1, V6, V7 are opened, the valves V2, V3, V4, V5, V8, V9, V10, V11 are closed and the air pump AP is turned on, the cell is passed through the buffer tank B1. Air is sent to one air electrode 8, pressurized air is sent from the valve V 1 to the first fuel tank C 1 via the filter F 1, and the first fuel supply channel 16 and the air electrode 7 are filled. Water is sent to the water storage tank C3 via the valve V6.

  When the controller 25 detects that the water has reached the section S61, the controller 25 assumes that the fixed amount of water has been collected, and opens the valve V4 while keeping the valve V1 open, and opens the valves V2, V3, V5, V6, V7, By closing V8, V9, V10, and V11, the water remaining in the first fuel tank C1 is moved from the first gas-liquid separator L1 to the second fuel tank C2 via the fuel electrode 7.

  The controller 25 determines that the movement to the second fuel tank C2 of water has ended because the section S42 no longer detects water, and opens the valves V5 and V8 while keeping the valves V1 and V4 open. By closing the valves V2, V3, V6, V7, V9, V10, V11, pressurized air is supplied from the buffer tank B1 to the sealed chamber 24 of the methanol storage container C4 via the valve V8, and the supplied pressurization is performed. The pressure of air acts on the bag 23, and the bag 23 is crushed according to the pressure of the supplied pressurized air, and the high-concentration methanol is supplied to the first fuel supply channel 16 through the filter F3 and the valve V5. Is injected. This injection is performed until the controller 25 detects that the liquid has reached between the electrodes P1 and P2 of the section S51 of the second fuel tank C2 and the electrodes P1 and P2 are conducted.

  For fuel agitation at startup, the controller 25 detects the liquid from the second fuel tank C2 toward the first fuel tank C1 with the valves V3 and V2 opened and the valves V1 and V4 closed. Move the fuel until Next, the controller 25 closes the valves V3 and V2 and opens the valves V1 and V4. From the first fuel tank C1 toward the second fuel tank C2, fuel is supplied until the section S53 detects liquid. Move. By repeating such an operation several times, water and high-concentration methanol can be rapidly stirred at an interval shorter than the movement of the liquid in the “power generation operation”.

  Thus, at the “start-up”, a part of the water that has entered the fuel electrode 7 during the “power generation operation suspension period” is recovered to the water storage tank C3 side, and the first fuel is supplied from the methanol storage container C4. Since the controller 25 automatically prepares a methanol aqueous solution having a concentration necessary for “power generation operation” by injecting high-concentration methanol into the flow path 16, the operability of the consumer at the start of use of the fuel cell is good. .

Further, the collected water is not discarded but stored on the side of the water storage tank C3 and effectively used for diluting the methanol aqueous solution in the “power generation operation” state.
Further, as described above, high-concentration methanol is injected into the first fuel supply channel 16 at the “start-up” time, and then moved between the first fuel tank C1 and the second fuel tank C2, so that water and high Since the methanol concentration is agitated, the output voltage rises quickly in the transition period from the start of startup to the power generation state.

(Embodiment 2)
4 and 5 show (Embodiment 2).
In (Embodiment 1), the cell 1 is applied to a fuel cell that sends fuel in both directions. FIG. 4 and FIG. This shows a case where the present invention is implemented in a fuel cell in which fuel is circulated in one direction. Components having the same functions as those in FIG.

In FIG. 4, an electromagnetic valve V <b> 100 is interposed between the fuel electrode 7 and the heat exchanger 13, and an electromagnetic valve V <b> 200 is interposed between the fuel electrode 7 and the water recovery device 15.
In the “power generation operation suspension period”, water is filled between the bottom of the circulation tank 11 and the pump 12, the fuel electrode 7, and the electromagnetic valve V100 from the circulation tank 11 as shown by a thick line in FIG. Water is also filled between the fuel electrode 7 and the electromagnetic valve V200.

  At the “start-up”, the controller 25 switches the electromagnetic valve V200 to the open state while the electromagnetic valve V100 is closed, and operates the pump 12 to fill the fuel electrode 7 during the suspension period of the power generation operation. The collected water is collected in the water collecting device 15. Further, the water recovered in the water recovery device 15 is used to dilute the high-concentration methanol supplied from the methanol storage tank 9 by the fuel + water injection device 10 and becomes a methanol aqueous solution having a concentration suitable for power generation operation. It is supplied to the circulation tank 11.

  When the operation at the start-up is completed, the controller 25 closes the electromagnetic valve V200 and switches the electromagnetic valve V100 to an open state to operate the pump 12 to operate the circulation tank 11, the pump 12, the fuel electrode 7, and the heat exchanger 13. The aqueous methanol solution is circulated through the path of the circulation tank 11.

In this way, at the “start-up” time, the water that has entered the fuel electrode 7 during the “power generation operation suspension period” is recovered by the water recovery device 15, so that the operability of the consumer when starting to use the fuel cell is improved. It is good.
Further, the collected water at this “start-up” is not discarded but stored in the water recovery device 15 and effectively used for diluting the methanol aqueous solution in the “power generation operation” state.

  In each of the above embodiments, water is contained in the fuel electrode 7 during the “power generation operation suspension period”. This is the same even in a low-concentration aqueous methanol solution in which methanol crossover does not occur.

  The present invention can improve the reliability and reduce the size and weight of a fuel cell, and is useful for various portable devices that use this type of fuel cell as a power source.

1 is a block diagram of a fuel cell for carrying out the fuel cell power generation method of the present invention (Embodiment 1). Plan view of first and second fuel tanks C1, C2 of the fuel cell device 2 is an enlarged cross-sectional view of the main part of FIG. Explanatory drawing of the idle period of the electric power generation operation of the fuel cell of Embodiment 2 which implements the fuel cell power generation method of the present invention Explanatory drawing at the time of starting of the fuel cell for carrying out the fuel cell power generation method of the present invention (Embodiment 2) Expanded sectional view of a cell for explaining a power generation system of a fuel cell Configuration diagram of conventional fuel cell

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cell 2 Solid electrolyte membrane 3, 4 Electrode catalyst layer 7 Fuel electrode 8 Air electrode 16 1st fuel supply flow path 17 2nd fuel supply flow path 18 1st glass substrate 19 2nd glass substrate 20 Air inlet 21 Liquid inlet / outlet 23 Bag 24 Sealed chamber 25 Controller V1 to V11 Valve AP Air pump B1 Buffer tank C1, C2 First and second fuel tank C3 Water storage tank C4 Methanol storage container C5 Surplus water tank S41 First fuel tank C1 Air inlet S42 Fuel outlet S51 of the first fuel tank C1 Air inlet S52 of the second fuel tank C2 Fuel outlet L1 of the second fuel tank C2 First gas-liquid separator L2 Second gas-liquid separator L3 First 3 gas-liquid separator F1 first filter F2 second filter

Claims (3)

During the suspension period of power generation operation, water or a fuel aqueous solution having a concentration that does not cause crossover is present in the fuel electrode of the cell, and during the power generation operation period, fuel liquid is supplied from the fuel tank to the fuel electrode, When generating air by supplying air to the air electrode,
At the time of start-up to shift from the power generation operation suspension period to the power generation operation period, at least a part of the water or the aqueous fuel solution having a concentration that does not cause crossover that existed in the fuel electrode of the cell during the power generation operation suspension period is collected and stored. When the fuel liquid is further supplied to start the power generation operation by setting the concentration of the aqueous fuel solution in the fuel electrode to an appropriate concentration and diluting the aqueous fuel solution in the fuel electrode, the stored water or crossover A fuel cell power generation method for adjusting a concentration by supplying a fuel aqueous solution having a concentration that does not occur to the fuel electrode. 2. The fuel cell power generation method according to claim 1, wherein after supplying the fuel liquid to the fuel electrode, the liquid of the fuel electrode is forcibly moved and mixed to adjust the concentration of the aqueous fuel solution in the fuel electrode to an appropriate concentration. Concentration at which water or crossover does not occur in the fuel electrode in the fuel supply channel in which the fuel electrode of the cell is in the center and the first and second fuel tanks are arranged on both sides of the cell. In the presence of an aqueous fuel solution,
At the time of start-up to shift from the power generation operation suspension period to the power generation operation period, at least a part of the water or the aqueous fuel solution having a concentration that does not cause crossover that existed in the fuel electrode of the cell during the power generation operation suspension period is collected and stored. Further, the fuel liquid is supplied, and the fuel liquid in the fuel supply flow path is forcibly moved and mixed between the first fuel tank and the second fuel tank via the fuel electrode, and mixed with the aqueous fuel solution in the fuel electrode In the case of diluting the aqueous fuel solution in the fuel electrode by starting the power generation operation with an appropriate concentration, the stored water or the aqueous fuel solution having a concentration that does not cause crossover is supplied to the fuel electrode. A fuel cell power generation method for performing the adjustment.

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