JP4175983B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system that uses an organic liquid fuel and a fuel supply device that can be used in the fuel cell system.

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 the negative electrode without being reformed, and electric power is obtained by an electrochemical reaction between methanol and oxygen. Methanol has higher energy per unit volume than hydrogen, is suitable for storage, and has a low risk of explosion, etc., so it is expected to be used as a power source for automobiles and portable devices (for example, , See Patent Document 1).
JP 2001-185185 A

  In order to use a fuel cell as a power source for a portable device, it is necessary to further reduce the size and weight of the fuel cell. In the conventional DMFC, many auxiliary devices such as a tank for diluting methanol and a pump for supplying methanol to the fuel cell are required to drive the fuel cell. There is a need for a technique for reducing the size and weight of the fuel cell system by simplifying the configuration of the class.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique for realizing a reduction in size or weight of a fuel cell system. Another object of the present invention is to provide a technique for reducing the power consumption of auxiliary equipment in a fuel cell system.

  One embodiment of the present invention relates to a fuel cell system. The fuel cell system includes a fuel cell device that operates with an organic liquid fuel, and a fuel supply device that supplies the organic liquid fuel to the fuel cell device, wherein the fuel supply device stores the organic liquid fuel. A chamber and a dilution chamber for holding an organic liquid fuel having a lower concentration than the storage chamber, the organic liquid fuel having a structure separated from the storage chamber by the diaphragm capable of moving to the dilution chamber, To do. As a result, auxiliary equipment such as a dilution tank and pump can be omitted, so that the fuel cell system can be reduced in size and weight, and power consumption required for driving the auxiliary equipment can be reduced. it can.

  The said diaphragm may be comprised with the material which permeate | transmits the said organic liquid fuel. The diaphragm may include a polymer material and allow the organic liquid fuel to permeate from the storage chamber to the dilution chamber. Thereby, the organic liquid fuel stored in the storage chamber can be transmitted to the dilution chamber and supplied to the fuel cell device.

  The fluid discharged from the fuel cell device may be returned to the dilution chamber, and the gas component of the fluid may be gas-liquid separated in the dilution chamber and exhausted outside the system. Thereby, it is not necessary to provide a gas-liquid separation tank separately, and the system configuration can be simplified.

  The fuel cell system includes concentration detecting means for detecting the concentration of the organic liquid fuel in the dilution chamber, a valve provided in a pipe for exhausting the gas component, and a control unit for controlling opening and closing of the valve. When the concentration of the organic liquid fuel in the dilution chamber detected by the concentration detection means is higher than a predetermined value, the control unit closes the valve and suppresses the exhaust of the gas component, and closes the diaphragm near the diaphragm. By accumulating gas components, liquid contact between the storage chamber and the dilution chamber may be prevented, and movement of the organic liquid fuel from the storage chamber to the dilution chamber may be suppressed. Thereby, the density | concentration of the organic liquid fuel of a dilution chamber can be kept appropriate.

  The fuel cell system further includes a liquid level detection unit that detects a liquid level in the dilution chamber, and the control unit detects when the liquid level in the dilution chamber detected by the liquid level detection unit is lower than a predetermined value. In addition, the gas component may be exhausted outside the system by opening the valve. Thereby, it is possible to prevent excessive accumulation of gas components in the dilution chamber, and it is possible to prevent damage to the fuel supply device and the diaphragm. Moreover, the situation where fuel supply stops can be prevented.

  The storage chamber of the fuel supply apparatus may further include a filling port for filling the organic liquid fuel from outside the system. As a result, the organic liquid fuel can be replenished without removing the fuel supply device from the system, and the maintainability can be improved.

The fuel cell system, an organic liquid fuel held in front Symbol dilution chamber, characterized in that it further includes a supply port for supplying the fuel cell system.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between a method, an apparatus, a system, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to provide a technique for reducing the size or weight of a fuel cell system.

(First embodiment)
FIG. 1 shows an overall configuration of a fuel cell system 10 according to the first embodiment. The fuel cell system 10 supplies the fuel cell device 20, the fuel tank 30 which is an example of a fuel supply device for supplying organic liquid fuel to the fuel cell device 20, and the organic liquid fuel in the fuel tank 30 to the fuel cell device 20. And a pump 40 for supplying air to the fuel cell device 20. The fuel cell device 20 includes a membrane electrode assembly (hereinafter referred to as “MEA”) in which a solid polymer electrolyte membrane having hydrogen ion conductivity such as Nafion (registered trademark) is disposed between a positive electrode layer and a negative electrode layer. And a stack in which a plurality of layers are stacked with a conductive separator interposed therebetween. Organic liquid fuels such as alcohols such as methanol and ethanol and ethers are directly supplied to the negative electrode (fuel electrode) of the MEA without modification, and air is supplied to the positive electrode (air electrode) of the MEA. Is done. And electric power is taken out by the electrochemical reaction of the organic liquid fuel and oxygen in MEA.

  The fuel tank 30 has a structure in which a storage chamber 32 for storing a high concentration organic liquid fuel and a dilution chamber 34 for storing a low concentration organic liquid fuel diluted with water are separated by a diaphragm 36. The diaphragm 36 is made of a material that allows the organic liquid fuel stored in the storage chamber 32 to permeate into the dilution chamber 34, and is stored by the concentration gradient of the organic liquid fuel between the storage chamber 32 and the dilution chamber 34. The organic liquid fuel moves from the chamber 32 to the dilution chamber 34, and the low-concentration organic liquid fuel diluted in the dilution chamber 34 is supplied to the fuel cell device 20.

  During operation of the fuel cell system 10, low-concentration organic liquid fuel is supplied to the fuel cell device 20 through the pump 40 from the supply port 60 provided in the dilution chamber 34 of the fuel tank 30. When high concentration organic liquid fuel is supplied to the fuel electrode of the fuel cell device 20 as it is, the organic liquid fuel passes through the solid polymer electrolyte membrane of the MEA and moves to the air electrode side, and the organic liquid fuel reacts on the air electrode side. As a result, back electromotive force may be generated. Therefore, the low-concentration organic liquid fuel diluted in the dilution chamber 34 is supplied to the fuel cell device 20 in this way.

  At the fuel electrode of each MEA of the fuel cell device 20, the organic liquid fuel and water react to generate carbon dioxide and hydrogen ions. The unreacted organic liquid fuel and the product such as carbon dioxide generated by the reaction are returned to the receiving port 62 provided in the dilution chamber 34 of the fuel tank 30 through the pipe 70.

  Air taken in by the air pump 50 from the suction port 80 is supplied to the air electrode of each MEA of the fuel cell device 20. At the air electrode, oxygen and hydrogen ions in the air react to produce water. Unreacted air and water generated by the reaction are returned to the receiving port 66 provided in the dilution chamber 34 of the fuel tank 30 via the pipe 72.

  In the dilution chamber 34, the liquid and the gas are separated, the gas is discharged from the discharge port 68, and is discharged outside the system through the pipe 74 and the exhaust port 82. During the operation of the fuel cell system 10, water generated at the air electrode of the fuel cell device 20 is returned to the dilution chamber 34, and the organic liquid fuel stored in the dilution chamber 34 is diluted. As a result, a concentration gradient with the organic liquid fuel in the storage chamber 32 is generated, and the organic liquid fuel passes through the diaphragm 36 and is replenished to the dilution chamber 34. Thus, the high-concentration organic liquid fuel stored in the storage chamber 32 gradually permeates the dilution chamber 34 as the fuel cell system 10 operates, and is diluted in the dilution chamber 34 and supplied to the fuel cell device 20. The

  A valve 86 is provided in the pipe 74 for discharging the gas separated from the gas and liquid in the dilution chamber 34, and the opening and closing of the valve 86 is controlled by the control unit 94. The dilution chamber 34 is provided with a concentration sensor 90 which is an example of a concentration detection means for detecting the concentration of the organic liquid fuel in the dilution chamber 34. The control unit 94 acquires the concentration of the organic liquid fuel in the dilution chamber 34 detected by the concentration sensor 90. When the concentration is higher than the optimum concentration for the operation of the fuel cell device 20, the control unit 94 closes the valve 86 and dilutes the chamber. The exhaust of the gas component in 34 is suppressed. Then, since a gas component accumulates in the vicinity of the diaphragm 36, liquid contact between the storage chamber 32 and the dilution chamber 34 is hindered, and movement of the organic liquid fuel from the storage chamber 32 to the dilution chamber 34 is suppressed. Thereby, it can prevent that the density | concentration of the organic liquid fuel in the dilution chamber 34 becomes high too much, and can maintain a density | concentration appropriately.

  The dilution chamber 34 is provided with a liquid level sensor 92 which is an example of a liquid level detecting means for detecting the liquid level in the dilution chamber 34. The control unit 94 acquires the liquid level in the dilution chamber 34 detected by the liquid level sensor 92. When the liquid level becomes lower than a predetermined value, the control unit 94 opens the valve 86 to exhaust the gas component out of the system. Thereby, it is possible to prevent excessive accumulation of gas components in the dilution chamber 34 and to prevent damage to the fuel tank 30 and the diaphragm 36. Moreover, the situation where fuel supply stops can be prevented.

  When the concentration of the organic liquid fuel in the fuel tank 30 is lower than the concentration of the organic liquid fuel to be supplied to the fuel cell device 20, the fuel tank 30 needs to be replaced. In order to determine the replacement time, a concentration sensor for detecting the concentration of the organic liquid fuel in the fuel tank 30 may be provided. The used fuel tank 30 may be collected and recycled. A business model is established in which the provider of the fuel tank 30 collects the used fuel tank 30 from the user, refills the storage chamber 32 with the organic liquid fuel, and puts the fuel tank 30 on the market again.

  In the conventional fuel cell system, the high-concentration organic liquid fuel stored in the fuel tank is sent to a dilution tank or the like by using a pump, and once diluted by adding water, the fuel cell device 20 is then pumped by the pump. Had to supply. In this case, it is necessary to provide a separate dilution tank, and electric power for driving the pump is required. However, in the present embodiment, by providing the dilution chamber 34 separated by the diaphragm 36 in the fuel tank 30, the configuration such as the dilution tank and the configuration such as the pump for supplying the liquid organic fuel to the dilution tank Is omitted. Thereby, a fuel cell system can be reduced in size and weight, and power consumption can be reduced.

  The diaphragm 36 is made of a material that transmits organic liquid fuel. For example, fluoropolymer electrolyte membranes used for electrolyte membranes such as Nafion (registered trademark), water-permeable or hydrophilic polymers such as polyvinylpyrrolidone, polyvinyl alcohol, polybenzimidazole, porous water-repellent polymers, mesopores or It may be a carbon material having micropores, a material such as zeolite, mordenite, or silica, or a composite material combining these materials. As porous water-repellent polymer, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy resin, tetra A fluororesin such as fluoroethylene-ethylene copolymer, polychlorotrifluoroethylene, or polyether sulfone may be used. The porous water repellent polymer may have any pore structure. Moreover, you may use the material in which the porous site | part was provided in a part of precise | minute water-repellent polymer diaphragm.

(Second Embodiment)
FIG. 2 shows the overall configuration of the fuel cell system 10 according to the second embodiment. In the fuel cell system 10 of the present embodiment, the diaphragm 36 that separates the storage chamber 32 and the dilution chamber 34 of the fuel tank 30 is configured in a bag shape, and high concentration organic liquid fuel is supplied to the storage chamber 32 from outside the system. A filling port 84 for filling is provided. Other configurations are the same as those of the first embodiment, and the same reference numerals are given to the same configurations.

  Since the diaphragm 36 is configured in a bag shape, the high-concentration organic liquid fuel in the storage chamber 32 and the low-concentration organic liquid fuel in the dilution chamber 34 can be obtained regardless of the orientation of the fuel cell system 10. Contact is made through the diaphragm 36. Therefore, regardless of the installation direction, the organic liquid fuel can be supplied to the fuel cell device 20 and operated for a long time. This technique is particularly effective when the fuel cell system 10 is mounted on a portable device or the like. The diaphragm 36 may be fixed in the fuel tank 30 or may not be fixed.

  Also in the present embodiment, as in the case of the first embodiment, the controller 94 controls the opening and closing of the valve 86 based on the sensor values acquired from the concentration sensor 90 and the liquid level sensor 92, thereby diluting. The amount of gas and the liquid level in the chamber 34 can be controlled, and the permeation of the organic liquid fuel from the storage chamber 32 to the dilution chamber 34 can be controlled. Thereby, the density | concentration of the organic liquid fuel supplied to the fuel cell apparatus 20 from the dilution chamber 34 can be controlled appropriately.

  The storage chamber 32 is configured so that a high-concentration organic liquid fuel can be filled from outside the system through the filling port 84. Thereby, the organic liquid fuel can be replenished without taking the fuel tank 30 out of the system, so that the maintenance is excellent. Similarly, in the fuel cell system 10 of the first embodiment shown in FIG. 1, the fuel tank 30 may be provided with a filling port for filling the organic liquid fuel from outside the system.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

It is a figure showing the whole fuel cell system composition concerning a 1st embodiment. It is a figure which shows the whole structure of the fuel cell system which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell system, 20 Fuel cell apparatus, 30 Fuel tank, 32 Storage chamber, 34 Dilution chamber, 36 Diaphragm, 40 Pump, 50 Air pump, 60 Supply port, 62,66 Receiving port, 68 Outlet port, 80 Suction port, 82 Exhaust port, 84 filling port, 86 valve, 90 concentration sensor, 92 liquid level sensor, 94 control unit.

Claims (7)

A fuel cell device operating with an organic liquid fuel;
A fuel supply device for supplying the organic liquid fuel to the fuel cell device,
The fuel supply device includes:
A storage chamber for storing the organic liquid fuel and a dilution chamber for holding the organic liquid fuel having a lower concentration than the storage chamber are separated by a diaphragm capable of moving the organic liquid fuel from the storage chamber to the dilution chamber. structure have a,
The fluid discharged from the fuel cell device is returned to the dilution chamber,
A gas component of the fluid is gas-liquid separated in the dilution chamber and exhausted out of the system.   The fuel cell system according to claim 1, wherein the diaphragm is made of a material that allows the organic liquid fuel to pass therethrough.   The fuel cell system according to claim 1, wherein the diaphragm includes a polymer material. Concentration detecting means for detecting the concentration of the organic liquid fuel in the dilution chamber;
A valve provided in a pipe for exhausting the gas component;
A control unit for controlling the opening and closing of the valve,
When the concentration of the organic liquid fuel in the dilution chamber detected by the concentration detection unit is higher than a predetermined value, the control unit closes the valve to suppress the exhaust of the gas component, and closes the gas near the diaphragm. preventing the contact of the liquid between said dilution chamber and said reservoir chamber by storing components, according to claim 1, characterized in that to suppress the movement of the organic liquid fuel to the dilution chamber from said storage chamber Fuel cell system. Further comprising a liquid level detecting means for detecting the liquid level of the dilution chamber,
The control unit opens the valve to exhaust the gas component out of the system when the liquid level in the dilution chamber detected by the liquid level detection unit is lower than a predetermined value. 5. The fuel cell system according to 4 . The fuel cell system according to any one of claims 1 to 5, further comprising a filling port for filling the organic liquid fuel from the outside of the system into the storage compartment of the fuel supply device. The fuel cell system according to any one of claims 1 to 6, further comprising a supply port for supplying the organic liquid fuel held in the dilution chamber to the fuel cell device .

Images