JP2005293936A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell, where activation time is shortened and temperature during operation is stabilized. <P>SOLUTION: In the fuel cell 100 for generating power by the electrochemical reaction between fuel and oxidizer, a fuel battery cell 12 for generating power by the electrochemical reaction and a temperature control cell 14 for heating and cooling the fuel battery cell 12 are laminated for composing a fuel cell body 10, methanol is introduced to the temperature control cell 14 for increasing temperature in the fuel cell body 10, and air is introduced to the temperature control cell 14 when decreasing temperature in the fuel cell body 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell, and more particularly to shortening the startup time of the fuel cell and stabilizing the temperature during operation.

  A fuel cell is a device that generates electrical energy from fuel and an oxidant, and can achieve high power generation efficiency. The main feature of the fuel cell is direct power generation that does not go through the process of thermal energy or kinetic energy as in the conventional power generation method. Therefore, high power generation efficiency can be expected even on a small scale, and there is little emission of nitrogen compounds. In addition, noise and vibration are also small, so the environment is good. In this way, fuel cells can effectively use the chemical energy of fuels and have environmentally friendly characteristics, so they are expected as energy supply systems for the 21st century, and are used on a large scale from space to automobiles and portable devices. It is attracting attention as a promising new power generation system that can be used in various applications from power generation to small-scale power generation, and technological development is in full swing toward practical application.

  Particularly in recent years, direct methanol fuel cells (DMFC) have attracted attention as one form of fuel cells. In DMFC, methanol as a fuel is directly supplied to an anode without being reformed, and electric power is obtained by an electrochemical reaction between methanol and oxygen. Methanol has a higher energy per unit volume than hydrogen, is suitable for storage, and has a low risk of explosion, and is expected to be used as a power source for automobiles and portable devices.

However, when the temperature of the fuel cell is lowered at the time of start-up or the like, the fuel cell has a problem that the power generation efficiency is lowered. For such a problem, a temperature raising means is provided in the fuel or oxidant supply system. Measures have been taken (see Patent Document 1).
JP 2002-373684 A

  However, the above fuel cell has a problem that the entire system becomes large because the temperature raising means is provided in the supply system. In addition, if a heater or the like is used as the temperature raising means, the generated power is consumed, resulting in a problem that the power generation efficiency of the entire fuel cell is lowered.

  Furthermore, if the temperature of the fuel cell rises excessively, in the fuel cell using the electrolyte membrane, drying of the electrolyte membrane proceeds, which may cause a decrease in power generation efficiency and a decrease in durability of the fuel cell.

  The present invention has been made in view of this point, and an object of the present invention is to provide a fuel cell having both functions of shortening the startup time and stabilizing the temperature during operation.

  In order to achieve the above object, a fuel cell according to claim 1 of the present invention is a fuel cell that generates electric power by an electrochemical reaction between a fuel and an oxidant, a fuel cell that generates electric power by an electrochemical reaction, and a fuel cell A temperature control cell for heating the cell is laminated.

  According to the first aspect of the present invention, since the fuel cell that generates power by electrochemical reaction and the temperature control cell that heats the fuel cell are stacked, the fuel cell having a heating function is compactly configured. In addition, since both the cells are stacked, the fuel cell can be directly heated by the temperature control cell to shorten the startup time.

  A fuel cell according to claim 2 of the present invention is the fuel cell according to claim 1, wherein the temperature control cell includes a combustion catalyst that undergoes a combustion reaction with the fuel.

  According to the second aspect of the present invention, since the temperature control cell includes the combustion catalyst that undergoes a combustion reaction with the fuel, the reaction heat generated by the combustion reaction is supplied to the fuel cell by supplying the fuel to the temperature control cell. can do.

  The fuel cell according to claim 3 of the present invention is the fuel cell according to claim 1 or 2, characterized in that a fluid for cooling the fuel cell flows through the temperature control cell.

  According to the third aspect of the present invention, since the fluid for cooling the fuel cell flows in the temperature control cell, the temperature of the fuel cell can be stabilized during operation.

  A fuel cell according to a fourth aspect of the present invention is the fuel cell according to any one of the first, second, and third aspects, further comprising a fluid circulation circuit that connects the fuel cell and the temperature control cell, The distributed fluid is introduced into the fuel cell, and power is generated by an electrochemical reaction.

  According to claim 4 of the present invention, a fluid circulation circuit that connects the fuel cell and the temperature control cell is provided, and the fluid that has circulated through the temperature control cell is introduced into the fuel cell, and power is generated by an electrochemical reaction. The fuel or air that contributes to heating or cooling in the temperature control cell can be used as a raw material for the electrochemical reaction in the fuel cell, and the reaction heat can be recovered again.

  A fuel cell according to claim 5 of the present invention is the fuel cell according to any one of claims 1, 2, 3 or 4, wherein the fuel cell supplies a methanol aqueous solution to the anode of the fuel cell. It is characterized by being.

  According to claim 5 of the present invention, since the fuel cell is a direct methanol fuel cell that supplies an aqueous methanol solution to the anode of the fuel cell, in a fuel cell that is expected to be used for a power source of an automobile or a portable device, In addition to being able to reduce the size, it is possible to shorten the start-up time and stabilize the temperature during operation.

  As described above, according to the first aspect of the present invention, the fuel cell having the heating function can be configured in a compact manner, and the startup time can be shortened. Furthermore, according to the second aspect, by using the reaction heat generated by the combustion reaction of the combustion catalyst, it is possible to shorten the start-up time without consuming electric power by a heater or the like.

  Further, according to claim 3, it is possible to provide a fuel cell having both functions of shortening the startup time and stabilizing the temperature during operation. According to the fourth aspect of the present invention, fuel or air can be used without waste as a raw material for electrochemical reaction, and reaction heat can be recovered again.

  Finally, according to claim 5, in a direct methanol fuel cell that is expected to be particularly downsized for portable devices, a direct methanol fuel cell that is compact, has a short start-up time, and can be stably operated is provided. Is possible.

  FIG. 1 is a schematic diagram showing a main part of a fuel cell 100 according to an embodiment of the present invention. A fuel cell main body 10 is configured by laminating a plurality of fuel cells 12 and temperature control cells 14. The fuel cells 12 and the temperature control cells 14 may be alternately stacked one by one, or several fuel cells 12 are stacked to form a fuel cell unit. May be laminated alternately. Further, both ends of the fuel cell 12 may be sandwiched by the temperature control cell 14 after being stacked.

  Unlike the structure in which the membrane-electrode assembly (MEA) (not shown) is sandwiched between the separators as in the fuel battery cell 12, the temperature control cell 14 does not have the MEA, and only the flow path is formed only by the separator. It has been configured. When a substance that causes a combustion reaction is introduced, for example, by applying a combustion catalyst to the separator wall or by introducing a combustion catalyst into the flow path, a fluid substance that does not cause a combustion reaction is introduced. When this is done, it acts as a cooling means for removing heat from the surrounding fuel cells 12 and discharging the heat out of the fuel cell body 10.

  A fuel supply port 16, an oxidant supply port 18, a fuel discharge port 20, and an oxidant discharge port 22 are provided at the end of the fuel cell main body 10. Although not shown, a fuel supply manifold, an oxidant supply manifold, a fuel discharge manifold, and an oxidant discharge manifold are provided inside the fuel cell main body 10 in the cell stacking direction. Then, fuel and oxidant are supplied to each fuel battery cell 12, and exhaust fuel, exhaust oxidant, generated water and the like discharged from each fuel battery cell 12 are discharged from the discharge manifold through the discharge port.

  In implementing the present invention, the fuel cell 100 uses a direct methanol fuel cell using methanol as a fuel supply source and air as an oxidant supply source, and exhaust methanol, exhaust carbon dioxide and the like are discharged from the fuel discharge port 20. Exhaust air, generated water, and the like are discharged from the oxidant discharge port 22. These are introduced into the circulation tank 28 through the fuel discharge pipe 24 and the oxidant discharge pipe 26. The circulation tank 28 serves as a dilution means for the high-concentration methanol introduced from the high-concentration methanol tank 30, or carbon dioxide and exhaust gas. It is also used as gas-liquid separation means for selectively discharging air.

  The methanol stored in the circulation tank 28 is adjusted to about 0.1 N, and is supplied from the fuel supply port 16 to the anode of each fuel cell 12 through the fuel supply pipe 34 by the first fuel supply pump 32. On the other hand, the air sent out by the first oxidant supply pump 36 is supplied from the oxidant supply port 18 to the cathode of each fuel cell 12 through the oxidant supply pipe 38.

  The temperature control cell 14 is coated or introduced with a combustion catalyst that causes a combustion reaction with methanol. The combustion catalyst may be a material having a high methanol oxidation reaction activity, and examples thereof include a platinum group element (for example, platinum, ruthenium, rhodium, palladium, iridium, osmium) and a copper-zinc oxide catalyst. In addition, the catalyst particles may be composed of the catalyst alone. In addition, supported catalyst particles in which the catalyst is supported on carbon black such as furnace black or acetylene black, or ceramics such as alumina, zirconia, or titania. But it ’s okay.

  In the first embodiment, when the output from the fuel cell 100 is low, when the temperature of the fuel cell main body 10 is low, or when the temperature of the fuel cell main body 10 needs to be increased, such as when the fuel cell 100 is started up, A method will be described.

  As shown in FIG. 2, when raising the temperature of the fuel cell main body 10, methanol is supplied to each temperature control cell 14 through the temperature control fluid supply pipe 40. The methanol supplied to each temperature control cell 14 undergoes a combustion reaction with the combustion catalyst in the temperature control cell 14, and the temperature of the temperature control cell 14 rises. As a result, the temperature of the entire fuel cell body 10 rises. Further, the exhausted methanol from the temperature control cell 14 passes through the temperature control fluid discharge pipe 42 and is supplied from the fuel supply port 16 to each fuel cell 12. Since this waste methanol contains unreacted methanol and the temperature is rising, it is possible to contribute to power generation at the anode, and it is also possible to warm the fuel cell 12 directly.

  The temperature control fluid supply pipe 40 connects the fuel supply pipe 34 downstream of the first fuel supply pump 32 and each temperature control cell 14. When there is no need to raise the temperature of the fuel cell main body 10, each temperature control cell 14. The temperature control fluid supply pipe 40 is provided with a first valve 44 so that methanol is not supplied to the pipe. On the other hand, the second valve 46 is also provided downstream of the fuel supply pipe 34 from the point where the temperature control fluid supply pipe 40 branches. When the first valve 44 is closed, the second valve 46 is opened and the second tank 46 is opened. Methanol is directly supplied to each fuel cell 12 through the first fuel supply pump 32. When the first valve 44 is open, the second valve 46 is closed, and the methanol is supplied from the circulation tank 28 to each fuel cell 12 through the first fuel supply pump and each temperature control cell 14. .

  In the second embodiment, in addition to the operation method when the temperature of the fuel cell main body 10 needs to be raised, the temperature of the fuel cell main body 10 is adjusted during normal operation of the fuel cell 100 or when the fuel cell 100 is stopped. An operation method when it is necessary to reduce the speed will be described.

  First, when the temperature of the fuel cell main body 10 is raised, methanol is supplied to each temperature control cell 14 through the temperature control fluid supply pipe 40 as shown in FIG. The methanol supplied to each temperature control cell 14 undergoes a combustion reaction with the combustion catalyst in the temperature control cell 14, and the temperature of the temperature control cell 14 rises. As a result, the temperature of the entire fuel cell body 10 rises. Further, the exhausted methanol from the temperature control cell 14 passes through the temperature control fluid discharge pipe 42 and is supplied from the fuel supply port 16 to each fuel cell 12. Since this waste methanol contains unreacted methanol and the temperature is rising, it is possible to contribute to power generation at the anode, and it is also possible to warm the fuel cell 12 directly.

  The temperature control fluid supply pipe 40 connects the fuel supply pipe 34 downstream of the first fuel supply pump 32 and each temperature control cell 14. When there is no need to raise the temperature of the fuel cell body 10, each temperature control cell 14. The temperature control fluid supply pipe 40 is provided with a first valve 44 so that methanol is not supplied to the pipe. On the other hand, the second valve 46 is also provided downstream of the fuel supply pipe 34 from the point where the temperature control fluid supply pipe 40 branches. When the first valve 44 is closed, the second valve 46 is opened and the second tank 46 is opened. Methanol is directly supplied to each fuel cell 12 through the first fuel supply pump 32. When the first valve 44 is open, the second valve 46 is closed, and the methanol is supplied from the circulation tank 28 to each fuel cell 12 through the first fuel supply pump and each temperature control cell 14. .

  Next, when the temperature of the fuel cell main body 10 is lowered, air is supplied to each temperature control cell 14 through the temperature control fluid supply pipe 40 as shown in FIG. The air supplied to each temperature control cell 14 takes heat from the surrounding fuel cells 12 and the temperature of the surrounding fuel cells 12 decreases. The exhaust air from the temperature control cell 14 passes through the temperature control fluid discharge pipe 42 and is supplied from the oxidant supply port 18 to each fuel cell 12. At this time, the temperature of the exhaust air is warmed by heat exchange in the temperature control cell 14, but is lower than the temperature of the fuel cell main body 10, so that the fuel cell 12 is further cooled. Thereby, the temperature of the whole fuel cell main body 10 falls.

  This temperature control fluid supply pipe 40 connects the oxidant supply pipe 38 downstream of the first oxidant supply pump 36 and each temperature control cell 14, and each temperature control is performed when it is not necessary to lower the temperature of the fuel cell main body 10. The temperature control fluid supply pipe 40 is provided with a third valve 48 so that air is not supplied to the cell 14. At this time, since both methanol and air are supplied to each temperature control cell 14 through the same temperature control fluid supply pipe 40, the temperature control fluid supply pipe 40 includes the first valve 44 and the third valve. 48. The piping for methanol and the piping for air are merged on both downstream sides of 48, and the temperature control fluid supply piping 40 is shared.

  On the other hand, a fourth valve 50 is provided downstream of the oxidant supply pipe 38 from the point where the temperature control fluid supply pipe 40 branches, and when the third valve 48 is closed, the fourth valve 50 is opened and the first oxidation is performed. Air is directly supplied to each fuel cell 12 from the agent supply pump 36. When the third valve 48 is open, the fourth valve 50 is closed, and the air is supplied from the first oxidant supply pump 36 to the fuel battery cells 12 through the temperature control cells 14 and the temperature control fluid discharge pipes 42. Is supplied.

  The temperature control fluid discharge pipe 42 is also configured such that both methanol and air are supplied to each fuel cell 12 through the same temperature control fluid discharge pipe 42. The gas is branched and separated into a methanol pipe connected to the fuel supply port 16 and an air pipe connected to the oxidant supply port 18. A fifth valve 52 is provided in the temperature control fluid discharge pipe 42 for methanol downstream of the branch point, and a sixth valve 54 is provided in the temperature control fluid discharge pipe 42 for air, so that the temperature of the fuel cell main body 10 is increased. When it is desired to increase the temperature, that is, when methanol flows through the temperature control cell 14, the fifth valve 52 is opened and the sixth valve 54 is closed. Conversely, when the temperature of the fuel cell body 10 is to be decreased, that is, When air flows through the temperature control cell 14, each valve is controlled so that the fifth valve 52 is closed and the sixth valve 54 is opened.

  The control of the valves as shown in FIGS. 3 and 4 is such that the temperature of the fuel cell main body 10 reaches about 50 ° C. when heated, and the temperature of the fuel cell main body 10 exceeds about 80 ° C. when cooled. Sometimes do. That is, when the temperature of the fuel cell main body 10 is stable between about 50 to 80 ° C., methanol or air only needs to be supplied to the fuel cell 12, that is, the flow of the temperature control fluid is stopped. Thus, the opening and closing of the valves 44, 46, 48, 50, 52, 54 may be controlled.

  The opening and closing of each valve in Example 2 is summarized as shown in Table 1 above.

  In Examples 1 and 2, a valve for opening and closing is provided in each pipe, but the valve may be controlled to open and close as shown in Table 1 using a three-way valve or a four-way valve.

  FIG. 5 is a schematic view showing a main part of a fuel cell 100 according to another embodiment of the present invention, and a first fuel supply pump 32 for supplying methanol or air to the anode or cathode of each fuel cell 12. And the first oxidant supply pump 36, the second fuel supply pump 56 for supplying high concentration methanol from the high concentration methanol tank 30 to the circulation tank 28, and the high concentration from the high concentration methanol tank 30 to each temperature control cell 14. A third fuel supply pump 58 for supplying methanol and a second oxidant supply pump 60 for supplying air to each temperature control cell 14 are provided. The substance discharged from each temperature control cell 14 is connected to be introduced into the circulation tank 28 through the heating / cooling discharge pipe 42.

  In this embodiment, when raising the temperature of the fuel cell main body 10, the second oxidant supply pump 60 is operated together with the third fuel supply pump 58, and the temperature control cell 14 is passed through the temperature control fluid supply pipe 40. Supply methanol and air at concentrations. The high-concentration methanol and air supplied to each temperature control cell 14 undergo a combustion reaction with the combustion catalyst in the temperature control cell 14, and the temperature of the temperature control cell 14 rises more rapidly than in the first embodiment. Then, the exhausted methanol from the temperature control cell 14 passes through the heating / cooling discharge pipe 42 and is introduced into the circulation tank 28.

  On the other hand, when the temperature of the fuel cell main body 10 is lowered, the third fuel supply pump 58 is stopped and only the second oxidant supply pump 60 is operated. The air supplied to each temperature control cell 14 through the temperature control fluid supply pipe 40 takes heat from the surrounding fuel cells 12 and the temperature of the surrounding fuel cells 12 is lowered. The exhaust air from the temperature control cell 14 passes through the heating / cooling discharge pipe 42 and is introduced into the circulation tank 28 and discharged to the outside.

  Further, when the temperature of the fuel cell main body 10 is stably operated at a predetermined temperature, the third fuel supply pump 58 and the second oxidant supply pump 60 may be stopped so as not to consume extra power. . The operating states of the third fuel supply pump 58 and the second oxidant supply pump 60 in Example 3 are summarized as shown in Table 2.

  FIG. 6 is a schematic diagram showing a main part of a fuel cell 100 according to still another embodiment of the present invention. A second embodiment for supplying high-concentration methanol from the high-concentration methanol tank 30 to the circulation tank 28 in Example 3. The fuel supply pump 56 and the third fuel supply pump 58 for supplying high-concentration methanol from the high-concentration methanol tank 30 to each temperature control cell 14 are made common. Then, a high concentration methanol supply pipe 62 for supplying high concentration methanol from the high concentration methanol tank 30 to the circulation tank 28 via the second fuel supply pump 56 and a downstream side of the second fuel supply pump 56 are branched. A temperature control fluid supply pipe 40 for supplying high-concentration methanol to the temperature control cell 14 is provided.

  Similarly, the first oxidant supply pump 36 for supplying air to the cathode of each fuel cell 12 and the second oxidant supply pump 60 for supplying air to each temperature control cell 14 are made common to supply the first oxidant. An oxidant supply pipe 38 that supplies air from the pump 36 to each fuel cell 12, and a temperature control fluid supply pipe 40 that branches from the downstream side of the first oxidant supply pump 36 and supplies air to each temperature control cell 14. And provide.

  A seventh valve 64 and an eighth valve 66 are provided upstream of the point where the temperature control fluid supply pipe 40 for supplying high concentration methanol and the temperature control fluid supply pipe 40 for supplying air join, When the temperature of the fuel cell body 10 is raised, both the seventh valve 64 and the eighth valve 66 are opened so that high-concentration methanol and air are supplied to each temperature control cell 14. The fuel cell body 10 is heated by a combustion reaction of high-concentration methanol and air supplied to. When the temperature of the fuel cell body 10 is lowered, the seventh valve 64 is closed and only the eighth valve 66 is opened so that only air is supplied to each temperature control cell 14 and supplied to each temperature control cell 14. The taken air takes heat from the surrounding fuel cells 12 and cools the fuel cell body 10. Then, when the temperature of the fuel cell main body 10 is stably operated at a predetermined temperature, the seventh valve 64 and the eighth valve 66 may be closed. The opening and closing of the seventh valve 64 and the eighth valve 66 in Example 4 are summarized as shown in Table 3.

  In this embodiment, open / close valves are arranged in the respective pipes, but the present invention is not limited to open / close valves as long as the methanol and air flow paths of the respective embodiments can be realized.

  Further, the temperature control fluid supply pipe 40 for supplying the temperature control fluid to each temperature control cell 14 is made thinner than the fuel supply pipe 34 and the oxidant supply pipe 38 for supplying methanol or air to each fuel cell 12. Although it is considered that it is easy to balance the heat supply, this can be realized not only by adjusting the diameter of the pipe but also by adjusting the valve opening and closing time, the pump supply amount, and the like.

1 is a schematic diagram showing a fuel cell according to an embodiment of the present invention. It is a schematic diagram which shows the fluid circuit of the fuel cell which concerns on Example 1 of this invention. It is a schematic diagram which shows the fluid circuit when heating the fuel cell which concerns on Example 2 of this invention. It is a schematic diagram which shows the fluid circuit when cooling the fuel cell which concerns on Example 2 of this invention. It is a schematic diagram which shows the fluid circuit of the fuel cell which concerns on Example 3 of this invention. It is a schematic diagram which shows the fluid circuit of the fuel cell which concerns on Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell main body 12 ... Fuel cell 14 ... Temperature control cell 16 ... Fuel supply port 18 ... Oxidant supply port 20 ... Fuel discharge port 22 ... Oxidant discharge Outlet 24 ... Fuel discharge pipe 26 ... Oxidant discharge pipe 28 ... Circulation tank 30 ... High concentration methanol tank 32 ... First fuel supply pump 34 ... Fuel supply pipe 36 ... First oxidant supply pump 38 ... Oxidant supply pipe 40 ... Temperature control fluid supply pipe 42 ... Temperature control fluid discharge pipe 44 ... First valve 46 ... Second valve 48 ... 3rd valve 50 ... 4th valve 52 ... 5th valve 54 ... 6th valve 56 ... 2nd fuel supply pump 58 ... 3rd fuel supply pump 60 ... 2nd oxidizing agent Supply pump 62 ... High concentration methanol supply Tube 64 ... seventh valve 66 ... eighth valve 100 ... fuel cell

Claims (5)

In a fuel cell that generates electricity by an electrochemical reaction between a fuel and an oxidant,
A fuel cell that generates electricity by an electrochemical reaction;
A temperature control cell for heating the fuel cell;
A fuel cell, characterized by being laminated.   The fuel cell according to claim 1, wherein the temperature control cell includes a combustion catalyst that undergoes a combustion reaction with fuel.   The fuel cell according to claim 1 or 2, wherein a fluid for cooling the fuel cell flows in the temperature control cell. A fluid circulation circuit that connects the fuel cell and the temperature control cell;
4. The fuel cell according to claim 1, wherein the fluid flowing through the temperature control cell is introduced into the fuel cell and power is generated by an electrochemical reaction. 5. 5. The fuel cell according to claim 1, wherein the fuel cell is a direct methanol fuel cell that supplies a methanol aqueous solution to an anode of the fuel cell. 6.

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