JP4886255B2 - Fuel cell device - Google Patents

Description

  The present invention relates to a direct methanol fuel cell device that reuses water discharged from an air electrode of a fuel cell and unreacted diluted fuel discharged from the fuel electrode of a fuel cell by returning them to a mixing tank.

In recent years, as a power source for an electronic device such as a portable computer, a small-sized fuel cell device that requires high output and does not require charging has attracted attention. Among these types of fuel cell devices , for example, direct methanol type fuel cell devices that circulate methanol aqueous solution (hereinafter DMFC: Direct Methanol Full Cell) are easier to handle than fuel cell devices that use hydrogen as fuel. In addition, since the entire system is simple, it is preferable as a power source for electronic equipment.

  A conventional DMFC includes a mixing tank that generates an aqueous methanol solution, a DMFC stack having a fuel electrode, an air electrode, and an electrolyte membrane, a fuel supply path that supplies an aqueous methanol solution to the fuel electrode of the DMFC stack, and air in the DMFC stack. And an air supply path for supplying air to the pole.

  In the fuel electrode of the DMFC stack, methanol reacts with water and is oxidized to generate carbon dioxide, hydrogen ions, and electrons. Hydrogen ions pass through the electrolyte membrane and reach the air electrode. At the air electrode, oxygen in the air combines with hydrogen ions and electrons and is reduced to produce water. At this time, electrons flow through an external circuit connected between the fuel electrode and the air electrode, and a power generation operation is performed.

According to the conventional DMFC, the water generated at the air electrode and the unreacted low-concentration methanol discharged from the fuel electrode return to the mixing tank as discharged substances. Water and low-concentration methanol mix with high-concentration methanol sent from the fuel cartridge in the mixing tank. As a result, the high-concentration methanol is diluted, and a methanol aqueous solution having a predetermined concentration is generated. Therefore, low-concentration methanol and water as emission substances are reused as fuel (see, for example, Patent Document 1).
JP 2004-296127 A

  In the conventional DMFC, the amounts of low-concentration methanol and water that return to the mixing tank vary depending on the use environment of the DMFC and the amount of power generation.

  Specifically, for example, when the amount of power generation is small under a humid usage environment, more water is generated at the air electrode of the DMFC stack. As a result, the amount of water returning from the DMFC stack to the mixing tank increases and the mixing tank becomes full. For this reason, there is no place for water to escape, so a maintenance call is required to temporarily stop the operation of the DMFC and encourage drainage of the mixing tank.

  Conversely, when the amount of power generation is large under a low humidity usage environment, less water is generated at the air electrode of the DMFC stack. As a result, the amount of water returning from the DMFC stack to the mixing tank decreases, and the water level in the mixing tank decreases. Therefore, it becomes impossible to make a methanol aqueous solution having a predetermined concentration, and the operation cannot be continued. Therefore, it is necessary to make a maintenance call for temporarily stopping the operation of the DMFC and urging the mixing tank to replenish water.

  An object of the present invention is to obtain a fuel cell device in which the amount of diluted fuel in a mixing tank can be easily controlled from the outside, and continuous operation is possible.

In order to achieve the above object, a fuel cell device according to one aspect of the present invention includes:
A fuel container containing fuel;
A fuel cell having a fuel electrode and an air electrode;
A mixing tank that generates diluted fuel by mixing the fuel supplied from the fuel container and the liquid emission material discharged from the fuel cell;
A fuel supply passage for supplying the diluted fuel produced in the mixing tank to the fuel electrode of the fuel cell,
An air supply path for supplying air to be subjected to power generation to the air electrode of the fuel cell,
A first spare container removably connected to the bottom of the mixing tank;
In place of the first auxiliary container, a second auxiliary container is removably connected to the bottom of the mixing tank.
When the first auxiliary container is connected to the mixing tank, the diluted fuel inside the mixing tank is taken out from the mixing tank. The second auxiliary container replenishes the mixing tank with diluted fuel when connected to the mixing tank.

According to the present invention, the first preliminary container is connected to the bottom of the mixing tank when the mixing tank shifts to a full state. Thereby, the diluted fuel in the mixing tank flows out to the first spare container, and the level of the diluted fuel in the mixing tank is lowered. When the diluted fuel in the mixing tank is insufficient , the second auxiliary container filled with the diluted fuel is connected to the bottom of the mixing tank. As a result, the diluted fuel in the second preliminary container flows into the mixing tank, and the level of the diluted fuel in the mixing tank rises.

  Therefore, the amount of diluted fuel in the mixing tank can be easily controlled from the outside, and the fuel cell device can be operated continuously.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 discloses an active DMFC 1 using, for example, methanol as a fuel. The DMFC 1 has a size that can be used as a power source of an electronic device such as the portable computer 2.

  The DMFC 1 includes an apparatus main body 3 and a placement unit 4. The apparatus main body 3 is formed in an elongated box shape along the width direction of the portable computer 2. The placement unit 4 projects from the front end of the apparatus main body 3 so that the rear end of the portable computer 2 can be placed. A power connector 5 is disposed on the upper surface of the mounting portion 4. The power connector 5 is electrically connected to the portable computer 2 when the portable computer 2 is placed on the placement unit 4.

  As shown in FIGS. 3 and 4, the apparatus main body 3 contains a fuel cartridge 6, a mixing tank 7, a DMFC stack 8, a first condenser 9, and a second condenser 10. The fuel cartridge 6 is an example of a fuel supply source, and contains, for example, high-concentration methanol as fuel. The fuel cartridge 6 is detachably supported at one end portion along the longitudinal direction of the apparatus main body 3 and can be replaced. The fuel cartridge 6 is covered with a cover 11. The cover 11 is detachably supported at one end of the apparatus main body 3 so that the fuel cartridge 6 can be easily replaced.

  The fuel cartridge 6 is connected to the mixing tank 7 via the first fuel supply pipe 12. The first fuel supply pipe 12 has a fuel pump 13 that sends high-concentration methanol from the fuel cartridge 6 to the mixing tank 7. The mixing tank 7 is for diluting high-concentration methanol to generate, for example, a methanol aqueous solution (diluted fuel) having a concentration of several percent to several tens percent, and is adjacent to the fuel cartridge 6.

  The DMFC stack 8 is an example of a fuel cell that generates power using a chemical reaction of methanol. The DMFC stack 8 includes a fuel electrode (anode) 14, an air electrode (cathode) 15, and an electrolyte membrane 16 interposed between the electrodes 14 and 15.

  The fuel electrode 14 of the DMFC stack 8 is connected to the mixing tank 7 via the second fuel supply pipe 18. The second fuel supply pipe 18 is an example of a fuel supply path, and is connected to one end of the fuel electrode 14. The second fuel supply pipe 18 has a liquid feed pump 19 that sends the aqueous methanol solution in the mixing tank 7 to the fuel electrode 14.

  The other end of the fuel electrode 14 is connected to the mixing tank 7 through a fuel return pipe 20. The fuel return pipe 20 is for returning unreacted aqueous methanol solution discharged from the fuel electrode 14 and carbon dioxide generated by the oxidation reaction at the fuel electrode 14 to the mixing tank 7. The unreacted aqueous methanol solution and carbon dioxide are one of the exhaust materials discharged from the fuel electrode 14. Immediately after being discharged from the fuel electrode 14, the aqueous methanol solution is affected by the heat during the power generation operation of the DMFC stack 8. The water temperature is 60 ° C or higher.

  The first condenser 9 is installed in the middle of the fuel return pipe 20. The first condenser 9 is for cooling the aqueous methanol solution returning from the fuel electrode 14 to the mixing tank 7. The first condenser 9 has a tube 21 through which an aqueous methanol solution flows and a plurality of heat radiation fins 22 thermally connected to the tube 21.

  The air electrode 15 of the DMFC stack 8 is connected to an intake port 25 via an air supply pipe 24. The intake port 25 is for taking in air for power generation from the atmosphere. The air supply pipe 24 is an example of an air supply path, and is connected to one end of the air electrode 15. The air supply pipe 24 has an air supply pump 26 that sends air taken from the intake port 25 to the air electrode 15.

  The second condenser 10 is connected to the other end of the air electrode 15 through the exhaust pipe 27. The second condenser 10 is for cooling discharged substances such as water vapor and water discharged from the air electrode 15, and is connected to the downstream end of the exhaust pipe 27. The second condenser 10 has a recovery tank 28. The recovery tank 28 is for storing water discharged from the air electrode 15 and water recovered from water vapor. The gas component from which moisture has been separated by the second condenser 10 is released from the second condenser 10 into the atmosphere.

  The recovery tank 28 is connected to the fuel return pipe 20 via a recovery pipe 29. The recovery pipe 29 has a recovery pump 30 that sends the water stored in the recovery tank 28 to the mixing tank 7 via the fuel return pipe 20.

  Further, the exhaust pipe 27 has a branch pipe 31 branched between the air electrode 15 and the second condenser 10. The upstream end of the branch pipe 31 is connected to the mixing tank 7. The branch pipe 31 is for guiding the carbon dioxide returned to the mixing tank 7 to the second condenser 10 via the exhaust pipe 27. The carbon dioxide led to the second condenser 10 is released from the second condenser 10 into the atmosphere.

  As shown in FIG. 4, the first condenser 9 and the second condenser 10 are installed at the other end of the apparatus main body 3, and are opposite to the fuel cartridge 6 with the DMFC stack 8 interposed therebetween. Is located. The first and second condensers 9 and 10 face each other with a space therebetween, and the first fan 33 and the second fan 34 are disposed between the condensers 9 and 10.

  The first fan 33 faces the first condenser 9. When the first fan 33 is operated, a flow of cooling air that passes through the first condenser 9 toward the first fan 33 is formed, and the first condenser 9 is cooled by the cooling air. The cooling air that has cooled the first condenser 9 is discharged from the discharge port 33 a of the first fan 33.

  The second fan 34 faces the second condenser 10. When the second fan 34 is operated, a flow of cooling air that passes through the second condenser 10 toward the second fan 34 is formed, and the second condenser 10 is cooled by the cooling air. The cooling air that has cooled the second condenser 10 is discharged from the discharge port 34 a of the second fan 34. Furthermore, even if impurities such as carbon dioxide discharged from the second condenser 10 are used, they are discharged from the discharge port 34a by multiplying the flow of the cooling air.

  As shown in FIGS. 1 and 4, the apparatus main body 3 has an exhaust port 35 at the other end. The exhaust port 35 faces the discharge ports 33 a and 34 a of the first and second fans 33 and 34. Impurities such as cooling air and carbon dioxide discharged from the discharge ports 33 a and 34 a are discharged out of the apparatus body 3 through the exhaust port 35.

  As shown in FIG. 3, the DMFC 1 has a control unit 36. The control unit 36 controls the power supplied to the portable computer 2 by controlling, for example, the concentration and amount of aqueous methanol solution generated in the mixing tank 7 and exchanging information with the portable computer 2. belongs to. The control unit 36 is housed in the placement unit 4 of the DMFC 1 and is electrically connected to the power connector 5 and the DMFC stack 8.

  The concentration of the methanol aqueous solution includes the amount of high-concentration methanol supplied from the fuel cartridge 6 to the mixing tank 7, the amount of unreacted methanol aqueous solution returned from the fuel electrode 14 of the DMFC stack 8 to the mixing tank 7, and the air of the DMFC stack 8. The amount of water returned from the pole 15 to the mixing tank 7 is adjusted by the control unit 36.

  Specifically, the mixing tank 7 includes a water level sensor 37 that detects the level of the aqueous methanol solution in the tank, a temperature sensor 38 that detects the temperature of the aqueous methanol solution, and a concentration sensor 39 that detects the concentration of the aqueous methanol solution. ing. Information on the aqueous methanol solution detected by each sensor 37, 38, 39 is sent to the control unit 36. The control unit 36 controls, for example, the fuel pump 13 and the recovery pump 30 based on information from the sensors 37, 38, and 39.

  As a result, the amount of high-concentration methanol flowing from the fuel cartridge 6 to the mixing tank 7 and the amount of water flowing from the recovery tank 28 to the mixing tank 7 are adjusted, and the concentration of the methanol aqueous solution becomes a value that can maintain the power generation performance satisfactorily. Be controlled.

  As shown in FIGS. 3 and 4, the mixing tank 7 that generates the aqueous methanol solution includes a coupler 41. The coupler 41 is for selectively detachably connecting the first and second spare cartridges 42 a and 42 b to the mixing tank 7, and is provided at the bottom of the mixing tank 7. The internal capacities of the first and second spare cartridges 42 a and 42 b are set to be, for example, about half of the internal capacity of the mixing tank 7.

The first spare cartridge 42a is used when taking out an excess aqueous methanol solution from the mixing tank 7, and the first spare cartridge 42a is empty from the beginning. On the other hand, the second spare cartridge 42b is used when the methanol aqueous solution is replenished to the mixing tank 7, and water or methanol diluted to a predetermined concentration is contained in the second spare cartridge 42b. Filled with aqueous solution.

  In a state where the first spare cartridge 42a or the second spare cartridge 42b is connected to the turnip 41, the inside of the mixing tank 7 and the first spare cartridge 42a or the second spare cartridge 42a are connected through a flow path (not shown) in the coupler 41. The inside of the spare cartridge 42b is in communication with each other. Therefore, the aqueous methanol solution can be circulated between the mixing tank 7 and the first auxiliary cartridge 42a or between the mixing tank 7 and the second auxiliary cartridge 42b. At the same time, the first spare cartridge 42 a or the second spare cartridge 42 b is covered with the removable cover 11 together with the mixing tank 7.

  Furthermore, the coupler 41 has a built-in shut-off valve (not shown). The shut-off valve shuts off the communication path when the first spare cartridge 42a or the second spare cartridge 42b is removed from the coupler 41, thereby preventing leakage of the methanol aqueous solution.

  Next, the power generation operation of the DMFC 1 will be described.

  The high-concentration methanol stored in the fuel cartridge 6 is sent to the mixing tank 7 by the fuel pump 13. The water recovered from the air electrode 15 of the DMFC stack 8 and the unreacted aqueous methanol solution (low concentration methanol) discharged from the fuel electrode 14 of the DMFC stack 8 are returned to the mixing tank 7. Therefore, the high-concentration methanol is mixed with water and the low-concentration methanol in the mixing tank 7 and diluted to generate a methanol aqueous solution having a predetermined concentration.

  The aqueous methanol solution generated in the mixing tank 7 is sent to the fuel electrode 14 of the DMFC stack 8 by the liquid feed pump 19. In the fuel electrode 14, methanol reacts with water and is oxidized to generate hydrogen ions, carbon dioxide, and electrons. Hydrogen ions pass through the electrolyte membrane 16 of the DMFC stack 8 and reach the air electrode 15.

  The carbon dioxide produced at the fuel electrode 14 is led to the first condenser 9 together with the unreacted methanol aqueous solution, and cooled by the cooling air blown from the first fan 33, and then the fuel return pipe 20. Is returned to the mixing tank 7. The carbon dioxide returned to the mixing tank 7 is vaporized in the mixing tank 7 and flows into the exhaust pipe 27 from the branch pipe 31.

  On the other hand, air to be used for power generation is taken in from the intake port 25 and is sent to the air electrode 15 of the DMFC stack 8 via the air feed pump 26. In the air electrode 15, oxygen in the air is combined with hydrogen ions and electrons and reduced to generate water vapor. At this time, electrons flow through an external circuit connected between the fuel electrode 14 and the air electrode 15 to perform a power generation operation.

  The water vapor generated at the air electrode 15 flows into the exhaust pipe 27 and joins the carbon dioxide from the mixing tank 7 in the exhaust pipe 27 and is guided to the second condenser 10. In the second condenser 10, the water vapor is cooled by the cooling air blown from the second fan 34 to become water. This water is temporarily stored in the recovery tank 28. The gas from which moisture is separated and containing impurities such as carbon dioxide is discharged from the second condenser 10 and the discharge port of the second fan 34 together with the cooling air that has passed through the second condenser 10. The gas is discharged from 34a toward the exhaust port 35.

  The water stored in the recovery tank 28 is returned to the mixing tank 7 via the recovery pump 30 and reused as water for diluting the high-concentration methanol.

  In the DMFC 1 operating in this manner, the amount of water returning from the recovery tank 28 to the mixing tank 7 varies depending on the usage environment, humidity, and power generation amount of the DMFC 1. For example, when DMFC 1 is used in a humid environment, the amount of water recovered in the recovery tank 28 increases and the amount of water returned from the recovery tank 28 to the mixing tank 7 increases.

  In the present embodiment, the water level of the mixing tank 7 is always detected by the water level sensor 37, and this water level is monitored by the control unit 36. Therefore, the control unit 36 notifies that the mixing tank 7 is full of water, for example, by sound or light when the water level in the mixing tank 7 exceeds a predetermined reference water level.

  When the notification that the mixing tank 7 is full is received, the cover 11 is removed from the apparatus main body 3 to expose the mixing tank 7 and the coupler 41. Next, as shown in FIG. 5, the empty first spare cartridge 42 a is connected to the coupler 41 of the mixing tank 7. Accordingly, as indicated by an arrow A in FIG. 5, the aqueous methanol solution in the mixing tank 7 flows out of the coupler 41 into the first auxiliary cartridge 42a due to gravity, and the level of the aqueous methanol solution in the mixing tank 7 is lowered.

  When the first spare cartridge 42a is full, the first spare cartridge 42a is removed from the coupler 41. The removed first spare cartridge 42a is preferably disposed of or stored for water supply.

  On the other hand, for example, when the DMFC 1 is used in a low humidity environment, the amount of water recovered in the recovery tank 28 decreases and the amount of water returned from the recovery tank 28 to the mixing tank 7 decreases. For this reason, when the water level in the mixing tank 7 falls below a predetermined water level, the control unit 36 notifies that there is too little methanol aqueous solution in the mixing tank 7 by sound or light, for example.

  When it is notified that the aqueous methanol solution in the mixing tank 7 is low, the cover 11 is removed from the apparatus body 3 to expose the mixing tank 7 and the coupler 41. Next, as shown in FIG. 6, the coupler 41 of the mixing tank 7 is connected to the second spare cartridge 42b filled with the aqueous methanol solution. As a result, as indicated by an arrow B in FIG. 6, the aqueous methanol solution in the second preliminary cartridge 42b flows into the mixing tank 7 from the coupler 41 by gravity, and the level of the aqueous methanol solution in the mixing tank 7 rises.

  When the methanol aqueous solution is supplied to the mixing tank 7, instead of the second spare cartridge 42b, for example, it is used when the methanol aqueous solution in the mixing tank 7 is discharged, and then stored for water supply. The spare cartridge 42a may be used.

  According to the DMFC 1 according to the present embodiment, the water level of the aqueous methanol solution in the mixing tank 7 can be adjusted from the outside of the DMFC 1 regardless of whether the mixing tank 7 is full or the aqueous methanol solution in the mixing tank 7 is too small. It can be easily controlled.

  In other words, drainage of the mixing tank 7 and water supply to the mixing tank 7 can be easily performed without using a dedicated jig, and the water level of the aqueous methanol solution in the mixing tank 7 can be maintained within an appropriate range. .

  For this reason, if the user attaches and detaches the first and second auxiliary cartridges 42a and 42b to and from the mixing tank 7 as required, it is possible to avoid the operation stop of the DMFC 1 due to excessive water or insufficient water. Therefore, the DMFC 1 can be operated continuously, and power can be stably supplied to the portable computer 2.

  Furthermore, according to the above configuration, when the methanol aqueous solution is replenished to the mixing tank 7 or the methanol aqueous solution is discharged from the mixing tank 7, the hand is not directly touched with methanol which is a kind of deleterious substance. Therefore, handling of the methanol aqueous solution becomes easy, and convenience for the user is enhanced.

  In addition, the coupler 41 of the mixing tank 7 is exposed to the outside of the DMFC 1 simply by removing the cover 11 from the apparatus main body 3. For this reason, the methanol aqueous solution in the mixing tank 7 can be discharged without decomposing the DMFC 1, and the methanol aqueous solution can be replenished in the mixing tank 7, thereby improving workability.

  The fuel cell device according to the present invention is not limited to a portable computer but can be implemented as a power source for other electronic devices such as a portable information terminal.

1 is a perspective view of a fuel cell device according to an embodiment of the present invention. The perspective view which shows the state which connected the portable computer to the fuel cell apparatus in embodiment of this invention. 1 is a block diagram of a fuel cell device according to an embodiment of the present invention. 1 is a cross-sectional view of a fuel cell device according to an embodiment of the present invention. FIG. 3 is a block diagram of the fuel cell device showing a state in which the first auxiliary cartridge is connected to the mixing tank that has become full in the embodiment of the present invention. In embodiment of this invention, when the water level of the methanol aqueous solution in a mixing tank falls, the block diagram of the fuel cell apparatus which shows the state which connected the 2nd auxiliary cartridge to this mixing tank.

Explanation of symbols

6 ... Fuel cartridge, 7 ... Mixing tank, 8 ... Fuel cell (DMFC stack), 14 ... Fuel electrode, 15 ... Air electrode, 18 ... Fuel supply path (second fuel supply pipe), 24 ... Air supply path (air) Supply pipe), 42a... First spare cartridge, 42b... Second spare cartridge .

Claims (4)

A fuel container containing fuel;
A fuel cell having a fuel electrode and an air electrode;
A mixing tank that generates diluted fuel by mixing the fuel supplied from the fuel container and the liquid emission material discharged from the fuel cell;
A fuel supply passage for supplying the diluted fuel produced in the mixing tank to the fuel electrode of the fuel cell,
An air supply path for supplying air to be subjected to power generation to the air electrode of the fuel cell,
A first auxiliary container that is removably connected to the bottom of the mixing tank and that, when connected to the mixing tank, takes the diluted fuel inside the mixing tank out of the mixing tank;
A second spare container removably connected to the bottom of the mixing tank in place of the first spare container and replenishing the mixing tank with diluted fuel when connected to the mixing tank;
A fuel cell device comprising: 2. The fuel cell device according to claim 1, wherein an inner volume of the first and second auxiliary containers is smaller than an inner volume of the mixing tank . 2. The fuel cell device according to claim 1, wherein the exhaust material is unreacted diluted fuel discharged from the fuel electrode of the fuel cell and water discharged from the air electrode of the fuel cell. 2. The apparatus main body provided with the fuel container, the fuel cell, and the mixing tank, and removably supported by the apparatus main body to cover the first spare container or the second spare container. And a fuel cell device further comprising a cover .

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