JP2005235519A - Fuel cell, fuel cell system, and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell and a fuel cell system capable of enhancing reaction efficiency. <P>SOLUTION: Gas liquid separating membrane 9 is arranged on the outside of a fuel chamber 31. A supply control means 105 monitors a methanol concentration detecting signal from a methanol concentration detecting means 106, and supplies methanol from a methanol tank 101 to the fuel chamber 31 when methanol concentration drops to a prescribed value or less. Since carbon dioxide generated by reaction of methanol with water in the fuel chamber 31 can be exhausted by the gas liquid separating membrane 9, a contact area of a methanol aqueous solution with an anode electrode 3 can favorably be ensured, and reaction efficiency can be enhanced. Since a generating current value can be ensured without circulation of the methanol aqueous solution in the fuel chamber 31, the amounts of necessary methanol and pure water can be minimized, a fuel cell system 100 is miniaturized, and driving for a long time with small amounts of methanol and pure water can be made possible. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell, a fuel cell system, and an apparatus that obtain electric energy by directly supplying methanol.

A fuel cell continuously supplies fuel and oxygen from the outside and reacts electrochemically to extract electric energy. Fuel cells have been attracting attention in recent years because environmental problems have become more prominent because they are more efficient and emit less carbon dioxide than other power generation methods.
For example, a polymer electrolyte fuel cell (PEFC) can operate at a low temperature, has a short start-up time, and can be downsized. This polymer electrolyte fuel cell is equipped with a MEA (Membrane Electrode Assembly) having a structure in which a polymer solid electrolyte membrane is sandwiched between an air side electrode and a fuel side electrode, and supplies air (oxygen) to the air side electrode. By supplying a fuel such as methanol or reformed hydrogen to the side electrode, an electrochemical reaction occurs and electric power is generated (for example, Patent Document 1).
Among the polymer electrolyte fuel cells, the direct methanol fuel cell (DMFC), in particular, stores hydrogen, unlike PEFC, in order to supply methanol directly to the fuel cell to obtain electrical energy. There is no need for a container or a reformer for reforming the fuel and taking out hydrogen. For this reason, direct methanol fuel cells are expected to replace conventional primary batteries and secondary batteries as portable power sources for portable devices such as mobile phones and laptop computers that need to be used continuously for a long time. Has been.

JP-A-8-162132

In a direct methanol fuel cell, when an aqueous methanol solution is supplied as fuel to the reaction chamber on the anode electrode side, water and methanol react on the anode electrode side to generate carbon dioxide, protons, and electrons. In this case, when the generated carbon dioxide is accumulated in the reaction chamber, there is a problem that the amount of methanol that contacts the anode electrode is reduced, and the reaction efficiency is lowered. Therefore, conventionally, by circulating an aqueous methanol solution and constantly exchanging the liquid in the reaction chamber, carbon dioxide is discharged together with the aqueous methanol solution, or a groove is provided in the reaction chamber wall to discharge the carbon dioxide. Proposals have been made for structures that encourage
However, even if such a structure is adopted, it is difficult to exhaust carbon dioxide in the reaction chamber sufficiently and reliably. Therefore, it is difficult to carry out the reaction of methanol sufficiently efficiently. Improvement is desired.

  An object of the present invention is to provide a fuel cell and a fuel cell system capable of increasing reaction efficiency.

The fuel cell of the present invention is provided with a polymer solid electrolyte membrane having proton conductivity, an anode electrode and a cathode electrode provided on both sides of the polymer solid electrolyte membrane, and adjacent to the anode electrode and the cathode electrode, respectively. A fuel cell that obtains electric energy by directly supplying methanol to the anode side reaction chamber, the cathode side reaction chamber, and the anode side reaction chamber, and is formed outside the anode side reaction chamber after the reaction of methanol and water. A gas-liquid separation membrane for separating carbon dioxide is provided.
According to this invention, since the gas-liquid separation membrane is provided outside the anode-side reaction chamber, the aqueous methanol solution does not pass through the gas-liquid separation membrane and remains in the anode-side reaction chamber, while it is generated in the anode-side reaction chamber. Carbon dioxide passes through the gas-liquid separation membrane and is discharged outside. Therefore, carbon dioxide in the methanol aqueous solution is surely discharged, the contact area of the methanol aqueous solution with the anode electrode is ensured, and the reaction efficiency is good.
In addition, since carbon dioxide is discharged by the gas-liquid separation membrane, conventional measures such as groove formation and circulation of aqueous methanol solution at a certain flow rate are not required, and the structure of the fuel cell is simplified.

  The fuel cell system of the present invention includes the fuel cell described above, methanol supply means for supplying methanol to the anode reaction chamber, water supply means for supplying water to the anode reaction chamber, and methanol concentration in the anode reaction chamber. A supply control means for controlling the methanol supply means and the water supply means so as to be within a predetermined range is provided.

According to this invention, since the fuel cell system includes the fuel cell described above, carbon dioxide can be discharged by the gas-liquid separation membrane. For this reason, it is not necessary to circulate the aqueous methanol solution at a certain flow rate in order to discharge the carbon dioxide in the anode side reaction chamber.
Here, in the anode side reaction chamber, when the reaction between methanol and water proceeds, the methanol concentration in the methanol aqueous solution decreases, and if this is left as it is, the reaction efficiency decreases. In the present invention, the supply control means controls the methanol supply means and the water supply means to supply the optimal concentration of methanol or aqueous methanol solution so as to replenish the reduced amount of methanol. By this control, the methanol concentration in the anode reaction chamber is maintained within a predetermined range, so that a reduction in reaction efficiency is prevented and the reaction efficiency is improved.
In addition, when the fuel supply control means adjusts the methanol concentration of the aqueous methanol solution, not only when supplying the methanol aqueous solution in which methanol and water are mixed in advance to the anode side reaction chamber, the methanol and water are separately supplied to the anode side. The case of supplying to the reaction chamber and the case of supplying only methanol without supplying water from the water supply means are also included.

  In addition, since the supply control unit controls the methanol supply unit and the water supply unit so that the methanol concentration in the anode side reaction chamber is within the predetermined range, the reaction efficiency of methanol and water in the anode side reaction chamber is maintained well. The And since the fuel cell system is provided with a methanol supply means and a water supply means separately, by changing the ratio of these supply amounts, only methanol, water only, or aqueous methanol solution of any concentration in the anode side reaction chamber Can be supplied. Therefore, the control of the methanol concentration in the anode side reaction chamber becomes flexible, and it becomes possible to cope with various configurations and use conditions of the fuel cell system.

In the present invention, methanol amount detection means for detecting the amount of methanol in the anode side reaction chamber is provided, and the supply control means controls the methanol supply means and the water supply means based on the methanol amount detection signal from the methanol amount detection means. It is desirable.
According to this invention, since the methanol amount detection means detects the amount of methanol in the anode side reaction chamber, the supply control means may supply the amount of methanol corresponding to this detection signal, and the amount of methanol in the anode side reaction chamber can be determined. It becomes easy to control within a predetermined range.

In the present invention, the methanol amount detection means is one or both of a methanol concentration detection means for detecting the concentration of the methanol aqueous solution in the anode reaction chamber and a current value detection means for detecting the current value generated in the fuel cell. It is desirable to be.
According to this invention, the supply control means monitors the concentration and / or current value of the methanol aqueous solution detected by one or both of the methanol concentration detection means and the current value detection means, and based on these detection signals. Control the methanol supply means and the water supply means. When using the methanol concentration detection means, the methanol concentration in the anode reaction chamber is directly detected, enabling control based on a more accurate detection signal, and maintaining good reaction efficiency in the anode reaction chamber. It becomes. Further, when the current value detecting means is used, it is only necessary to detect the current value obtained by the external load connected to the fuel cell, so that it is possible to divert the existing configuration, and the configuration of the fuel cell system is It will be easy. When these are combined, the amount of methanol in the anode reaction chamber can be detected in a complex manner, and a more accurate detection signal can be obtained.

In the present invention, the supply control means controls the methanol supply means and the water supply means to supply methanol or an aqueous methanol solution to the anode side reaction chamber when the methanol amount detection signal from the methanol amount detection means is not more than a predetermined value. It is desirable to perform control.
According to this invention, since the supply control means supplies methanol or an aqueous methanol solution when the detection signal of the amount of methanol is equal to or less than the predetermined value, the amount of methanol in the anode reaction chamber does not decrease below the predetermined value and is good. Reaction efficiency is maintained.
In the case where only methanol is supplied to the anode side reaction chamber, the water supply means may be controlled so as not to supply water to the anode side reaction chamber.

In the present invention, it is desirable that the supply control means outputs a methanol aqueous solution supply command for supplying a predetermined amount of a methanol aqueous solution having a predetermined concentration every predetermined time.
According to this invention, since the supply control means outputs a methanol aqueous solution supply command every predetermined time, it is not necessary to monitor the amount of methanol in the anode side reaction chamber, and the configuration of the supply control means is simplified. This is particularly useful when the consumption rate of methanol in the anode reaction chamber can be predicted in advance.

In the present invention, it is desirable that the supply control means outputs a liquid exchange command for supplying water from the water supply means to the anode reaction chamber every predetermined time and replacing the liquid in the anode reaction chamber with water.
According to the present invention, if the required amount of methanol or aqueous methanol solution is supplied to the anode side reaction chamber to maintain the methanol concentration in the anode side reaction chamber, the methanol aqueous solution is not circulated or even slightly circulated. As the period is used, byproducts such as formic acid, formaldehyde, and carbon monoxide may accumulate in the anode reaction chamber. Even in such a case, the supply control means outputs a liquid exchange command every predetermined time, so that by-products in the anode side reaction chamber are discharged every predetermined time, thereby reliably preventing a reduction in the reaction efficiency of methanol and water. Is done.

The apparatus of the present invention includes the above-described fuel cell or the above-described fuel cell system.
According to this invention, since the apparatus includes the above-described fuel cell or the above-described fuel cell system, it is possible to achieve the same effect as the above-described effect, and the gas-liquid separation membrane improves the discharge of carbon dioxide, The reaction efficiency between methanol and water is improved.

  According to the fuel cell, fuel cell system and apparatus of the present invention, the gas-liquid separation membrane discharges carbon dioxide generated in the anode reaction chamber satisfactorily, thereby improving the reaction efficiency between methanol and water.

  Hereinafter, each embodiment of the present invention will be described with reference to the drawings. In the second embodiment and later described below, the same reference numerals are given to the same components and components having the same functions as those in the first embodiment described below, and description thereof will be simplified or omitted.

[First embodiment]
FIG. 1 is a side sectional view of a fuel cell 1 according to the first embodiment of the present invention. In FIG. 1, a fuel cell 1 is a direct methanol fuel cell (DMFC), and a fuel cell 10 is housed in a case 11. In the present embodiment, for the sake of simplification of explanation, a fuel cell 1 composed of a single fuel cell 10 is illustrated as shown in FIG. 1. Of course, the fuel cell 1 is replaced with the fuel cell 10. A stack structure in which a plurality of sheets are stacked may be used.

  The fuel cell 10 includes a polymer solid electrolyte membrane 2, an anode electrode 3 and a cathode electrode 4 integrally formed on both surfaces of the polymer solid electrolyte membrane 2, and a fuel diffusion layer disposed on the anode electrode 3 side. 5, the air diffusion layer 6 disposed on the cathode electrode 4 side, and the fuel diffusion layer 5 and the air diffusion layer 6, respectively, and the electric energy generated between the anode electrode 3 and the cathode electrode 4. Current collectors 7 and 8 to be taken out and a gas-liquid separation membrane 9 disposed on the anode electrode 3 side are provided. The fuel cell 10 is housed in a case 11 and is sandwiched from both sides of the polymer solid electrolyte membrane 2 by a gasket 12. Thereby, the inside of the case 11 is sealed and separated on the anode electrode 3 side and the cathode electrode 4 side with the polymer solid electrolyte membrane 2 interposed therebetween.

A fuel supply port 111 for supplying fuel to the inside of the case 11 and a fuel discharge port 112 for discharging the fuel that has finished the reaction at the anode electrode 3 are formed on the anode electrode 3 side of the case 11. Has been. A plurality of air holes 113 for supplying air into the case 11 are formed on the case 11 on the cathode electrode 4 side. Here, a region between the inner wall of the case 11 and the anode electrode 3 is configured to be liquid-tight and serves as a fuel chamber 31 as an anode-side reaction chamber to which fuel is supplied. A region between the inner wall of the case 11 and the cathode electrode 4 is an air chamber 41 as a cathode side reaction chamber to which air is supplied. The air supply to the air chamber 41 is naturally aspirated, and the air chamber 41 is opened to the atmosphere through the air holes 113 so that the air is supplied to the air chamber 41. Note that a methanol (CH ₃ OH) aqueous solution is supplied as the fuel.

  A substantially rectangular anode electrode 3 and cathode electrode 4 are integrally formed on both surfaces of the polymer solid electrolyte membrane 2 within a predetermined range separated by a predetermined width from the outer edge. The solid polymer electrolyte membrane 2 is formed by impregnating a porous solid portion of a stretched porous polytetrafluoroethylene (PTFE) film with a solid polymer electrolyte resin composed of a proton conductive polymer. It is configured. As the polymer solid electrolyte resin, for example, a perfluorosulfonic acid polymer such as a Nafion membrane (trademark of DuPont), a fluorine polymer, a hydrocarbon polymer, or the like can be employed. In some cases, a catalyst such as platinum, carbon powder, various ceramic powders and the like may be added to the solid polymer electrolyte resin as long as electronic conductivity does not occur.

  In addition, a stretched porous polytetrafluoroethylene (PTFE) film is obtained by stretching and porous PTFE lumps, and is a microscopic structure that connects many micronodules and three-dimensionally connects the micronodules. It is a porous PTFE film having a structure composed of fibers, and a large number of holes penetrating in the thickness direction are formed in this film. In the present embodiment, the stretched porous PTFE film has a thickness of 1 to 100 μm, preferably 3 to 30 μm, a pore diameter of 0.05 to 5 μm, preferably 0.5 to 2 μm, and a porosity of 60% to 98. %, Preferably 80 to 92%. If the film thickness is too thin, short circuits and gas leaks (cross leaks) are likely to occur, and if it is too thick, the electrical resistance increases. If the pore size is too small, it is difficult to impregnate the polymer solid electrolyte resin. If it is too large, the holding power of the polymer solid electrolyte resin is weakened, and the reinforcing effect is also weakened. If the porosity is too small, the resistance of the polymer solid electrolyte membrane is increased. If it is too large, the strength of PTFE itself is generally weakened and a reinforcing effect cannot be obtained.

The anode electrode 3 and the cathode electrode 4 are composed of a carbon catalyst electrode film carrying a catalyst for decomposing methanol. Here, platinum etc. are employable as a catalyst, for example. On the anode electrode 3 side, in order to prevent poisoning of carbon monoxide CO, which is an intermediate product generated by the reaction between methanol and the catalyst, at least the catalyst on the anode electrode 3 side includes an alloy of platinum and ruthenium, etc. Is more preferable.
Here, the polymer solid electrolyte membrane 2, the anode electrode 3, and the cathode electrode 4 are integrally formed to form a membrane electrode assembly 20.
The fuel diffusion layer 5 and the air diffusion layer 6 are porous membranes made of mesh metal foam (for example, steel wool) and diffuse the supplied fuel and oxygen to the anode electrode 3 and the cathode electrode 4, respectively. The fuel diffusion layer 5 and the air diffusion layer 6 may be made of aluminum, stainless steel or the like, respectively, a porous metal material such as sponge titanium, carbon paper supported on carbon, carbon cloth, or the like. It may be.
Further, lead wires (not shown) are connected to the current collectors 7 and 8, respectively, and are connected to an external load.

  On the outside of the fuel chamber 31, that is, on the surface of the current collector 7 opposite to the side where the fuel diffusion layer 5 is provided, the gas-liquid separation film 9 is disposed over the entire surface. The gas-liquid separation membrane 9 is made of a porous material having a plurality (a large number) of holes (passes) penetrating in the thickness direction, such as ceramics, and has a property of allowing gas to pass but not liquid. Further, a plurality of (many) discharge holes 114 for discharging carbon dioxide discharged from the fuel chamber 31 through the gas-liquid separation membrane 9 to the outside are formed at positions facing the gas-liquid separation membrane 9 in the case 11. Has been.

In operating such a fuel cell 1, it is necessary to construct a fuel cell system including a methanol aqueous solution supplying means.
FIG. 2 shows a schematic configuration diagram of a fuel cell system 100 in which the fuel cell 1 is incorporated. In FIG. 2, the fuel cell system 100 includes the above-described fuel cell 1, a methanol tank 101 that stores methanol supplied to the fuel chamber 31, and methanol diluted to a predetermined concentration for reaction in the fuel chamber 31. A pure water tank 102 that stores pure water as water to be provided, a mixer 103 that mixes methanol and pure water, a pump 104 that feeds an aqueous methanol solution mixed in the mixer 103 to the fuel chamber 31, methanol and Supply control means 105 for controlling the supply operation of pure water, methanol concentration detection means 106 as a methanol amount detection means for detecting the methanol concentration in the fuel chamber 31, and a waste liquid tank for storing waste liquid discharged from the fuel chamber 31 107.

The methanol tank 101 and the pure water tank 102 include valves 101A and 102A that can open and close the flow path to the fuel chamber 31. These valves 101 </ b> A and 102 </ b> A are electrically connected to the supply control means 105, and can be individually opened and closed by commands from the supply control means 105, and their opening degrees can also be adjusted.
The mixer 103 is a mixing unit that mixes methanol from the methanol tank 101 and pure water from the pure water tank 102 to create a methanol aqueous solution in which methanol is uniformly dispersed. When only methanol or pure water is supplied to the fuel chamber 31, the mixer 103 only mixes one kind of liquid, and the liquid passes substantially without performing its function. Become.
The pump 104 is connected to the fuel supply port 111, and feeds methanol, pure water, or a methanol aqueous solution mixed in the mixer 103 simply passed through the mixer 103 to the fuel chamber 31. The pump 104 is electrically connected to the supply control means 105, and ON / OFF of the pump 104 is controlled by a liquid feed command signal from the supply control means 105.

Here, in the present embodiment, the methanol supply means of the present invention is configured by including the methanol tank 101, the valve 101A, and the pump 104, and the pure water tank 102, the valve 102A, and the pump 104 are included in the present invention. A water supply means is configured.
The methanol tank 101 and the pure water tank 102 are preferably configured so that the interior of the integral case is partitioned. For example, the methanol tank 101 and the pure water tank 102 can be easily and simultaneously formed in a so-called cartridge system. A replaceable structure is desirable.

Based on the methanol concentration detection signal from the methanol concentration detection unit, the supply control unit 105 maintains the methanol supply unit and the water so as to maintain the concentration of the aqueous methanol solution in the fuel chamber 31 at a predetermined value M or higher. Control the supply means.
Here, the predetermined value M is preferably set within a range in which the reaction efficiency between methanol and the catalyst in the fuel chamber 31 is good and the crossover of the polymer solid electrolyte membrane 2 is well prevented. It is set as appropriate in consideration of the capacity of the fuel cell 1, the material of the polymer solid electrolyte membrane 2, the performance, and the like. For example, it is set within the range of 3% to 5% or 1 mol / l to 8 mol / l.
In addition, the supply control means 105 incorporates a liquid replacement timer (not shown) in order to replace the liquid in the fuel chamber 31 with pure water every predetermined time t1. The predetermined time t1 is set so that reaction efficiency does not decrease by a predetermined value or more due to accumulation of by-products such as formic acid, formaldehyde, and carbon monoxide, which are generated by the reaction of methanol and water in the fuel chamber 31. It is preferably set in consideration of the capacity, load, usage time, capacity of the waste liquid tank 107, and the like of the fuel cell 1 and the fuel chamber 31, and is set, for example, between 10 minutes and 1 hour.

The methanol concentration detection means 106 detects the methanol concentration of the aqueous methanol solution filled in the fuel chamber 31, and can employ any system such as an infrared transmission absorption type optical methanol concentration sensor.
The waste liquid tank 107 is connected to the fuel discharge port 112 and stores the waste liquid discharged from the fuel chamber 31. The waste liquid tank 107 may be provided separately from the methanol tank 101 and the pure water tank 102 so as to be individually replaceable. Further, it may be formed integrally with the methanol tank 101 and the pure water tank 102. In this case, when the methanol tank 101 and the deionized water tank 102 are used up and replaced in advance, the waste liquid tank 107 can also be replaced at the same time, so that the replacement operation is simplified and handling is improved.

Next, the operation of the fuel cell system 100 will be described.
FIG. 3 is a flowchart showing the operation of the fuel cell system 100. As shown in FIG. 3, first, when the fuel cell system 100 is started, in step S11, the methanol aqueous solution is filled into the fuel chamber 31 by an initial methanol aqueous solution supply command output from the supply control means 105. In response to this command signal, the valves 101A and 102A are opened, and methanol and pure water are fed, respectively. At this time, the opening degree of the valves 101A and 102A is set in advance so that the concentration of the methanol aqueous solution becomes equal to or higher than the predetermined value M. Methanol and pure water are uniformly mixed by the mixer 103 and supplied to the fuel chamber 31 by the pump 104.

In the fuel chamber 31, the methanol aqueous solution causes an oxidation reaction of the following formula (1) by the catalyst of the anode electrode 3, and this reaction generates carbon dioxide CO ₂ , protons H ^+, and electrons e ⁻ .
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
Proton H ⁺ passes through the polymer solid electrolyte membrane 2 and moves to the cathode electrode 4 side, whereby a voltage is generated across the current collectors 7 and 8. When the proton H ⁺ reaches the cathode electrode 4 side, the electron e ⁻ that has reached the cathode electrode 4 after working through an external load is converted into oxygen O ₂ in the air in the air chamber 41 by the catalyst of the cathode electrode 4. The reaction causes a reduction reaction of formula (2).
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)
The carbon dioxide CO ₂ generated on the anode electrode 3 side is separated by the gas-liquid separation membrane 9 immediately after being generated, and is discharged to the outside through the discharge hole 114. Moreover, the water produced | generated by the cathode electrode 4 side is discharged | emitted from the air hole 113 as water vapor | steam.

In step S12 of FIG. 3, the supply control means 105 determines whether or not a predetermined time t1 has elapsed with a built-in liquid replacement timer. If the predetermined time t1 has not elapsed, the process proceeds to step S13, and the methanol concentration detecting means 106 is measured. The methanol concentration detector 106 measures the concentration of the aqueous methanol solution in the fuel chamber 31 and outputs a detection signal to the supply controller 105.
In step S14 of FIG. 3, the supply control unit 105 determines whether or not the methanol concentration detection signal from the methanol concentration detection unit 106 is equal to or greater than a predetermined value M. If the methanol concentration detection signal is greater than or equal to the predetermined value M, the process returns to step S12.

  On the other hand, if the methanol concentration detection signal is smaller than the predetermined value M in step S14, the process proceeds to step S15, and the supply control means 105 outputs a methanol supply command to the valve 101A and the pump 104. In response to this methanol supply command, the valve 101 A is opened, the pump 104 is driven, and methanol is supplied from the methanol tank 101 to the fuel chamber 31 via the mixer 103 and the pump 104. The supply control means 105 monitors the methanol concentration in the fuel chamber 31 in steps S16 and S17, and when the methanol concentration detection signal becomes equal to or greater than the predetermined value M, the supply control means 105 proceeds to step S18 and outputs a methanol supply stop command. Thus, the valve 101A is closed, the pump 104 is stopped, and the process returns to step S12. By this operation, the supply of methanol to the fuel chamber 31 is stopped, and the methanol concentration of the aqueous methanol solution in the fuel chamber 31 is maintained within a predetermined range around the predetermined value M.

  FIG. 4 is a conceptual diagram showing the concentration of the aqueous methanol solution in the fuel chamber 31 with respect to time t. As shown in FIG. 4, in the fuel chamber 31, methanol is consumed by the reaction, so that the methanol concentration in the fuel chamber 31 decreases with time t, resulting in a water-rich condition. However, when the methanol concentration becomes equal to or less than the predetermined value M, the supply control means 105 controls the methanol supply means to supply methanol to the fuel chamber 31, so that the methanol concentration rises, and by repeating this, the inside of the fuel chamber 31 is increased. The methanol concentration of the aqueous methanol solution is appropriately maintained.

Here, in this embodiment, since the methanol aqueous solution in the fuel chamber 31 is not circulated, when methanol and water are reacted for a long time, intermediate products such as formic acid, formaldehyde, and carbon monoxide accumulate. These intermediate products are often dissolved in an aqueous solution and are not separated by the gas-liquid separation membrane 9.
Therefore, when it is determined in step S12 that the predetermined time t1 has elapsed, the process proceeds to step S19, and the supply control means 105 outputs a liquid exchange command signal to the valve 102A and the pump 104. By this liquid exchange command signal, pure water is supplied from the pure water tank 102 to the fuel chamber 31 via the mixer 103 and the pump 104. The aqueous methanol solution and a small amount of intermediate product filled in the fuel chamber 31 are pushed out into the pure water and discharged, and stored in the waste liquid tank 107 as waste liquid.
When the supply of the predetermined amount of pure water is completed, the supply control means 105 resets the built-in liquid replacement timer in step S20, and proceeds to step S13.

  By repeating the above cycle, the required methanol and / or pure water is supplied to the fuel chamber 31, and the methanol concentration in the fuel chamber 31 is maintained within a predetermined range. Further, when the methanol in the methanol tank 101 and the pure water in the pure water tank 102 run out, methanol and pure water are added to the methanol tank 101 and the pure water tank 102, respectively, or the methanol tank 101 and the pure water are added. The entire tank 102 may be replaced. Similarly, when a predetermined amount or more of waste liquid is stored in the waste liquid tank 107, the waste liquid in the waste liquid tank 107 may be discarded or the whole waste liquid tank 107 may be replaced.

According to such a first embodiment, the following effects can be obtained.
(1) The gas-liquid separation membrane 9 is disposed outside the fuel chamber 31 by disposing the gas-liquid separation membrane 9 so as to face the current collector 7. For this reason, carbon dioxide immediately after being generated by the reaction in the fuel chamber 31 can be discharged by the gas-liquid separation membrane 9. Therefore, a sufficient contact area of the aqueous methanol solution with the anode electrode 3 can be ensured in the fuel chamber 31, and the reaction efficiency of the fuel cell 1 can be improved. Thereby, a favorable power generation amount can be ensured over a long period of time.
Further, since carbon dioxide is discharged by the gas-liquid separation membrane 9, unlike the conventional case, it is not necessary to circulate the methanol aqueous solution. Therefore, almost all of the supplied methanol can be used for the reaction, and the usable time of the fuel cell system 100 can be lengthened. On the other hand, the amount of methanol required for power generation for a predetermined time can be reduced, so that the fuel cell system 100 can be reduced in size and weight.

(2) Since the supply control means 105 controls to supply methanol from the methanol tank 101 when the methanol concentration becomes a predetermined value M or less, the methanol concentration in the fuel chamber 31 can always be maintained at an appropriate concentration. . Thereby, even when the fuel cell system 100 is used for a long time, good reaction efficiency can be maintained.
(3) Since the supply control means 105 adjusts the methanol concentration in the fuel chamber 31 to supply only methanol instead of the aqueous methanol solution, the amount of pure water used can be suppressed to the minimum. Therefore, the size reduction of the pure water tank 102 can be promoted, and the fuel cell system 100 can be reduced in size and weight.

 (4) Since the methanol aqueous solution in the fuel chamber 31 is exchanged with pure water every predetermined time t1, by-products generated during the reaction between methanol and water can be eliminated, and the reaction efficiency is improved over a long period of time. Can hold. In addition, by performing such pure water supply control, pure water is required only when the aqueous methanol solution is first filled and when this water exchange is performed. Compared to, the required amount of pure water can be greatly reduced. Therefore, the pure water tank 102 and the waste liquid tank 107 can be reduced in size, and the reduction in size and weight of the fuel cell system 100 can be further promoted. Conversely, the fuel cell system 100 can be used for a longer time with the same amount of pure water.

 (5) The methanol concentration detection means 106 is provided, and the supply control means 105 directly monitors the methanol concentration in the fuel chamber 31 to control the methanol supply means and the water supply means, so the methanol concentration in the fuel chamber 31 is directly detected. Control can be performed based on a more accurate detection signal obtained in this way, and more accurate and reliable control can be performed.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the second embodiment, a predetermined amount of methanol is supplied every predetermined time t2.
FIG. 5 shows a schematic configuration diagram of a fuel cell system 100 according to the second embodiment. In FIG. 5, the supply control means 105 has a built-in water exchange timer similar to that of the first embodiment, and a methanol supply timer (not shown) for supplying methanol every predetermined time t2. Also built in.
Here, the predetermined time t2 is preferably set to a time until the methanol concentration in the fuel chamber 31 becomes a predetermined value M or less from the value at the start of operation by using the fuel cell 1. It is set as appropriate in consideration of the external load, the capacity of the fuel cell 1, the setting of the methanol concentration at the start of operation in the fuel chamber 31, the consumption rate of methanol, etc., for example, between 5 minutes and 10 minutes. .
Further, unlike the first embodiment, the fuel cell system 100 of the second embodiment does not include a methanol concentration detection means.

Such a fuel cell system operates as follows.
FIG. 6 is a flowchart showing the operation of the fuel cell system 100 according to the second embodiment. In FIG. 6, the supply control means 105 performs control to supply the methanol aqueous solution to the fuel chamber 31 and fill the fuel chamber 31 in step S21 as in the first embodiment.
Next, when the predetermined time t1 has not elapsed in step S22, in step S23, the supply control means 105 determines whether or not the predetermined time t2 has elapsed with the built-in methanol supply timer. If the predetermined time t2 has not elapsed, the process returns to step S22. When the predetermined time t2 has elapsed in step S23, the supply control means 105 outputs a methanol supply command signal to the valve 101A and the pump 104 in step S24. By this signal, the valve 101A is opened and the pump 104 is driven, whereby methanol is supplied to the fuel chamber 31. Supply control means 105 opens valve 101A for a predetermined time to supply a predetermined amount of methanol, then closes valve 101A, stops pump 104, and stops the supply of methanol.
In step S25, the methanol supply timer is reset, and the process returns to step S22. By this control, a predetermined amount of methanol is supplied into the fuel chamber 31 every predetermined time t2.
In steps S22, S26, and S27, as in the first embodiment, when the usage time of the fuel cell 1 has passed the predetermined time t1, the methanol solution in the fuel chamber 31 is replaced with pure water.

According to such a second embodiment, in addition to the same effects as the effects (1), (3) and (4) of the first embodiment, the following effects can be obtained.
(6) Since the supply control unit 105 performs control to supply a predetermined amount of methanol every predetermined time t2, unlike the first embodiment, a detection unit such as the methanol concentration detection unit 106 is not necessary. Therefore, the configuration of the supply control means 105 can be simplified and the number of parts can be reduced, so that the manufacturing cost of the fuel cell system 100 can be reduced.
Moreover, since it is not necessary to adjust the methanol supply amount according to the measured value, the responsiveness can be improved. Such control is particularly effective when the consumption rate of methanol is known in advance, such as when the fuel cell system 100 is used under a condition where the external load is constant.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
The water supply means is not limited to one using only pure water stored in the pure water tank. That is, for example, pure water is generated by the reaction on the cathode side of the fuel cell, and this may be reused. In this case, as shown in FIG. 7, the cathode-side air chamber 41 and the pure water tank 102 are connected, and the pure water generated in the state of water vapor in the air chamber 41 is recovered to obtain the pure water tank. It may be returned to 102 and reused as pure water supplied to the fuel chamber 31. According to such a configuration, it is possible to reduce the amount of pure water stored in the pure water tank, and on the contrary, it is possible to operate for a longer time with a predetermined amount of pure water, and the life of the fuel cell system 100 is prolonged. .

  Since the liquid that has been reacted on the anode side is mostly water, as shown in FIG. 7, this liquid may be returned to the pure water tank without being stored in the waste liquid tank. In this case, the reaction-finished liquid contains some by-products and unreacted methanol, but since the amount is very small, the reaction efficiency in the fuel chamber 31 due to these by-products and the like. As long as there is no adverse effect on the water, it is possible to recycle pure water. Thereby, the whole capacity | capacitance of the pure water tank 102 can be made still smaller, and the lifetime of the fuel cell system 100 can be lengthened more.

  The supply control means is not limited to controlling the supply of the methanol stock solution to the anode side reaction chamber. You may comprise so that the control hold | maintained within the range may be performed. In this case, since methanol is dispersed in water to some extent in advance, methanol is more easily dispersed more uniformly in the fuel chamber, and the reaction at the anode electrode is improved.

  Further, the methanol stock solution or aqueous methanol solution supplied to the anode side reaction chamber is not limited to a constant concentration. For example, the fuel cell system is configured so that the concentration of the methanol aqueous solution can be adjusted, so that the methanol concentration in the anode side reaction chamber is adjusted. A methanol aqueous solution having a corresponding concentration may be supplied. In this case, the opening of the valves of the methanol tank and the pure water tank can be adjusted, and the opening of these valves may be adjusted by the supply control means.

Further, the supply control means performs control to supply methanol or an aqueous methanol solution when the methanol concentration in the anode reaction chamber becomes a predetermined value or less. For example, when the methanol concentration becomes a predetermined value or more, You may control to supply only and dilute.
The supply control means is not limited to supplying methanol or an aqueous methanol solution only when the methanol concentration in the anode side reaction chamber becomes a predetermined value or less. For example, the supply aqueous solution always supplies a constant amount of methanol aqueous solution into the anode side reaction chamber. You may perform what is called circulation control which always replaces methanol aqueous solution. In this case, if the circulation amount of the aqueous methanol solution is sufficiently large, by-products are also discharged together with the circulating aqueous methanol solution, so water exchange work for exchanging the liquid in the fuel chamber with water every predetermined time is unnecessary. It may become.

  The supply control means is not limited to having only a set value as a lower limit value for supplying methanol when the methanol concentration is equal to or lower than a predetermined value set in advance. For example, the set value of the methanol concentration is set to an upper limit value and a lower limit value. The supply amount of the methanol stock solution or aqueous methanol solution may be controlled so that the methanol concentration in the anode reaction chamber is within this predetermined range. In this case, for example, the supply of methanol may be started when the methanol concentration becomes equal to or lower than the lower limit value of the predetermined range, and the supply of methanol may be stopped when the methanol concentration becomes equal to or higher than the upper limit value of the predetermined range. According to such control, since there is a range in the setting of the methanol concentration, the frequency of methanol supply is reduced and the control is stabilized.

  Furthermore, the supply control means is not limited to the so-called feedback control that monitors the methanol concentration while supplying methanol and stops the supply when the methanol concentration exceeds a predetermined value. When the value is less than or equal to a predetermined value, feedforward control for supplying a predetermined amount of methanol or aqueous methanol solution may be performed. In this case, since it is not necessary to monitor the methanol concentration during the supply of methanol, the control by the supply control means becomes easier.

  The detection of the methanol concentration by the methanol concentration detection means is not limited to the constant detection, and may be detected, for example, every predetermined time. In this case, compared with the case where the methanol concentration is always detected, the power consumed for detection can be reduced, and the power saving of the fuel cell system can be promoted.

The methanol amount detecting means is not limited to directly measuring the methanol concentration in the anode side reaction chamber, and may be, for example, a current value detecting means for detecting a current value generated in the fuel cell. In this case, when the methanol concentration in the anode side reaction chamber is lowered, the reaction efficiency is also lowered, so that the generated current value is also lowered. Therefore, the supply control means may monitor the current value detected by the current value detection means, and supply the methanol stock solution or aqueous methanol solution when the current value falls below a predetermined value or a predetermined range. According to such a configuration, it is only necessary to measure the value of the current flowing through the external load, so that the configuration that originally exists can be used, the configuration of the methanol amount detection means becomes simple, and the fuel cell system can be manufactured at low cost.
The methanol amount detection means may be configured by combining a plurality of detection means such as a methanol concentration detection means and a current value detection means. In this case, since the amount of methanol can be detected in combination from a plurality of detection signals, more accurate control of the amount of methanol can be performed.
The methanol amount detecting means is not limited to the methanol concentration detecting means for detecting the methanol concentration and the current value detecting means for detecting the current value generated in the fuel cell, and any other method can be adopted.

  Since the fuel cell or fuel cell system of the present invention can promote downsizing, it can be applied to portable devices such as mobile phones and notebook computers, cars, and any other devices.

The best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations.
Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

1 is a side sectional view showing a fuel cell according to a first embodiment of the present invention. 1 is a schematic configuration diagram showing a fuel cell system according to a first embodiment. The flowchart which shows operation | movement of the fuel cell system concerning 1st embodiment. The figure which shows the density | concentration of the methanol aqueous solution in the fuel chamber concerning 1st embodiment. The schematic block diagram which shows the fuel cell system concerning 2nd embodiment. The flowchart which shows operation | movement of the fuel cell system concerning 2nd embodiment. The figure which shows the modification of the fuel cell system of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Polymer solid electrolyte membrane, 3 ... Anode electrode, 4 ... Cathode electrode, 5 ... Fuel diffusion layer, 6 ... Air diffusion layer, 7, 8 ... Current collector, 9 ... Gas-liquid separation membrane, DESCRIPTION OF SYMBOLS 31 ... Fuel chamber (anode side reaction chamber), 41 ... Air chamber, 100 ... Fuel cell system, 101 ... Methanol tank (methanol supply means), 101A, 102A ... Valve, 102 ... Pure water tank (water supply means), 103 ... Mixer, 104 ... Pump, 105 ... Supply control means, 106 ... Methanol concentration detection means (methanol amount detection means).

Claims (8)

A polymer solid electrolyte membrane having proton conductivity;
An anode electrode and a cathode electrode respectively provided on both sides of the polymer solid electrolyte membrane;
An anode side reaction chamber and a cathode side reaction chamber respectively provided adjacent to the anode electrode and the cathode electrode;
A fuel cell that obtains electric energy by directly supplying methanol to the anode reaction chamber,
A fuel cell, characterized in that a gas-liquid separation membrane for separating carbon dioxide produced after the reaction between methanol and water is provided outside the anode side reaction chamber. A fuel cell according to claim 1;
Methanol supply means for supplying methanol to the anode reaction chamber;
Water supply means for supplying water to the anode reaction chamber;
A fuel cell system comprising: a supply control means for controlling the methanol supply means and the water supply means so that the methanol concentration in the anode reaction chamber is within a predetermined range. The fuel cell system according to claim 2, wherein
A methanol amount detecting means for detecting the amount of methanol in the anode reaction chamber;
The fuel cell system, wherein the supply control means controls the methanol supply means and the water supply means based on a methanol amount detection signal from the methanol amount detection means. The fuel cell system according to claim 2 or 3,
The methanol amount detection means is one or both of a methanol concentration detection means for detecting the concentration of the aqueous methanol solution in the anode reaction chamber and a current value detection means for detecting a current value generated in the fuel cell. A fuel cell system. In the fuel cell system according to claim 3 or 4,
The supply control means controls the methanol supply means and the water supply means to supply methanol or an aqueous methanol solution to the anode reaction chamber when a detection signal of the methanol amount from the methanol quantity detection means is a predetermined value or less. A fuel cell system characterized by performing supply control. The fuel cell system according to any one of claims 2 to 5,
The fuel supply system is characterized in that the supply control means outputs a methanol supply command for supplying a predetermined amount of methanol or a methanol aqueous solution having a predetermined concentration every predetermined time. The fuel cell system according to any one of claims 2 to 6,
The supply control means supplies water from the water supply means to the anode side reaction chamber every predetermined time and outputs a liquid exchange command for replacing the liquid in the anode side reaction chamber with water. Fuel cell system.   An apparatus comprising the fuel cell according to claim 1 or the fuel cell system according to any one of claims 2 to 7.

Images