JP2008204791A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove ions in a cooling liquid in early stages in a fuel cell system having an ion adsorbing device. <P>SOLUTION: In a fuel cell system equipped with the ion adsorbing device 41 having anion exchange resin 51 and cation exchange resin 52 adsorbing ions in the cooling liquid, the ion adsorbing device 41 has an anode 53 arranged in the vicinity of the anion exchange resin 51 and a cathode 54 arranged in the vicinity of the cation exchange resin 52, and in a stop state of power generation of the fuel cell 1, a circulation pump 33 is operated on a power supplied from a secondary battery 2, and ions in the cooling liquid are adsorbed in early stage by applying voltage to the anode 53 and the cathode 54 with an ion adsorbing means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electric energy by a chemical reaction between hydrogen and oxygen, and is effective when applied to a moving body such as a vehicle, a ship, and a portable generator.

  2. Description of the Related Art Conventionally, a fuel cell system that generates power using an electrochemical reaction between hydrogen and air (oxygen) is known. A fuel cell generates heat with power generation. Therefore, in the fuel cell system, a cooling system is provided in order to keep the temperature of the fuel cell constant by circulating a coolant through the fuel cell and releasing the heat of the fuel cell to the outside with a radiator. In addition, the cooling system is provided with an ion adsorption device for removing ions such as metals eluted into the coolant from a radiator, a fuel cell stack, a coolant pipe, and the like.

  However, during the shutdown of the fuel cell, the circulation of the coolant also stops, so that ions such as metals that have eluted into the coolant from the radiator, fuel cell stack, coolant pipe, etc. elute, and the conductivity of the coolant Rises. Therefore, a fuel cell system is known in which the coolant in the coolant pipe is made to flow even when power generation of the fuel cell is stopped, and ions being cooled are removed by an ion adsorption device (see, for example, Patent Document 1). .

In this prior art, the fuel cell system causes the coolant in the coolant pipe to flow by operating the circulation pump while the fuel cell is stopped by the secondary battery. Further, the temperature of the coolant is changed by the heat stored during the fuel cell operation to cause natural convection to flow the coolant.
JP 2005-50731 A

  However, in vehicles and the like, the capacity of the secondary battery that can be used while the fuel cell is stopped is limited, and if the capacity of the secondary battery decreases, the circulation pump cannot be operated for a long time, and the coolant There was a problem that the electrical conductivity of the film increased.

  Also, even when natural convection is caused by giving a temperature difference to the coolant, if the amount of heat stored during fuel cell operation decreases with time, the coolant cannot be given a temperature difference and convection Therefore, there has been a problem that the conductivity of the coolant increases.

  In view of the above points, an object of the present invention is to quickly remove ions in a coolant in a fuel cell system including an ion adsorption device.

  In order to achieve the above object, in the present invention, a fuel cell (1) for obtaining electric power by electrochemically reacting an oxidant gas and a fuel gas, and a coolant path for circulating a coolant to the fuel cell (1). (30), a circulating pump (33) provided in the coolant path (30) for circulating the coolant, and an ion having an anion exchange resin (51) and a cation exchange resin (52) that adsorb ions in the coolant In a fuel cell system comprising an adsorption device (41) and a secondary battery (2) that can be charged by receiving power from the fuel cell (1), the ion adsorption device (41) comprises an anion exchange resin (51). In the vicinity of the cation exchange resin (52) and the cathode (54) in the vicinity of the cation exchange resin (52), the secondary battery (2) in the power generation stop state of the fuel cell (1) ) Actuating the pump (33), and characterized in that it comprises an ion attracting means for attracting the ions in the cooling liquid by applying a voltage to the anode (53) and the cathode (54).

  Thereby, even when the power generation of the fuel cell (1) is stopped, the flow of the coolant by the circulation pump (33) and the application of the voltage to the ion adsorber (41) can adsorb ions in the coolant at an early stage. Therefore, the adsorption efficiency can be improved. Further, since the operation time of the circulation pump (33) can be shortened, energy efficiency can be improved.

  In addition, a conductivity detection means for detecting the conductivity of the coolant is provided, and the ion adsorption means operates the circulation pump (33) when the conductivity detected by the conductivity detection means is larger than a predetermined value. When the voltage is applied to the anode (53) and the cathode (54), the flow of the cooling liquid by the circulation pump (33) and the ion adsorption device (41) when the conductivity of the cooling liquid is equal to or higher than a predetermined value. Therefore, the ion adsorption efficiency can be further improved.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, a fuel cell system according to a first embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the fuel cell system is applied to an electric vehicle (fuel cell vehicle) that runs using the fuel cell 1 as a power source.

  FIG. 1 is a conceptual diagram of the fuel cell system according to the first embodiment. As shown in FIG. 1, the fuel cell system includes a fuel cell 1 that generates electric power using an electrochemical reaction between hydrogen and oxygen. The fuel cell 1 is configured to supply electric power to an electrical device such as a secondary battery 2 and a travel motor (not shown).

  In the first embodiment, a solid polymer electrolyte fuel cell is used as the fuel cell 1, and there are a plurality of cells composed of an MEA having electrodes joined to both sides of the electrolyte membrane and a pair of separators sandwiching the MEA. These are stacked and electrically connected in series. In the fuel cell 1, the following electrochemical reaction between hydrogen and oxygen occurs to generate electric energy.

(Hydrogen electrode side) H ₂ → 2H ⁺ + 2e ⁻
(Oxygen electrode side) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
The fuel cell 1 and the secondary battery 2 are electrically connected via a DC-DC converter (not shown) capable of transmitting power in both directions. This DC-DC converter controls the flow of power from the fuel cell 1 to the secondary battery 2 or from the secondary battery 2 to the fuel cell 1. When the power generation of the fuel cell 1 is stopped, it is possible to supply electric power from the secondary battery 2 to an electric device or the like.

  The fuel cell system is provided with a hydrogen supply path 10 through which hydrogen supplied to the hydrogen electrode of the fuel cell 1 passes and a hydrogen discharge path 11 through which hydrogen electrode side exhaust gas discharged from the hydrogen electrode of the fuel cell 1 passes. ing. A hydrogen supply device 12 for supplying hydrogen to the hydrogen electrode of the fuel cell 1 is provided at the most upstream portion of the hydrogen supply path 10. In the first embodiment, a hydrogen tank filled with high-pressure hydrogen is used as the hydrogen supply device 12.

  The hydrogen supply path 10 is provided with a first shut valve 13, a pressure regulating valve 14, and a second shut valve 15 in order from the upstream side. When supplying hydrogen to the fuel cell 1, the first shut valve 13 and the second shut valve 15 are opened, and a desired hydrogen pressure is supplied to the fuel cell 1 by the pressure regulating valve 14. When the vehicle is stopped, the first shut valve 13 and the second shut valve 15 are closed for safety.

  A third shut valve 16 is provided in the hydrogen discharge path 11. By opening the third shut valve 16 as necessary, it passes through the electrolyte membrane from the unreacted hydrogen, vapor (or water) and air electrode side through the hydrogen discharge path 11 from the hydrogen electrode side of the fuel cell 1. Impurities such as nitrogen and oxygen mixed on the hydrogen electrode side are discharged.

  The fuel cell system includes an air supply path 20 through which air supplied to an air electrode (oxygen electrode) of the fuel cell 1 passes, and an air discharge through which air electrode side exhaust gas discharged from the air electrode of the fuel cell 1 passes. A path 21 is provided. The air supply path 20 is provided with an air supply device 22 for supplying air. In the first embodiment, an air compressor is used as the air supply device 22. The air supply device 22 is mechanically connected to a compressor motor. The air discharge path 21 is provided with a pressure regulating valve 23 that adjusts the exhaust pressure of air so as to be a desired pressure.

  The fuel cell 1 is a heating element that generates heat by the electrochemical reaction during power generation. The fuel cell 1 needs to be maintained at a constant temperature (for example, about 70 ° C.) during operation to ensure power generation efficiency. Moreover, since the electrolyte membrane inside the fuel cell 1 exceeds the predetermined allowable upper limit temperature and is destroyed by the high temperature, it is necessary to keep the temperature of the fuel cell 1 below the allowable temperature.

  Therefore, the fuel cell system is provided with a cooling system for cooling the fuel cell 1. The cooling system is provided with a coolant path 30 that circulates a coolant (heat medium) in the fuel cell 1, a circulation pump 33 that circulates the coolant, and a radiator 31 (a radiator) that includes a fan 32.

  The coolant path 30 is provided with a bypass path 34 for bypassing the coolant to the radiator 31. A flow path switching valve 45 for adjusting the flow rate of the coolant flowing through the bypass path 34 is provided at the junction of the coolant path 30 and the bypass path 34.

  Further, in the configuration of the present embodiment, since the coolant directly contacts the inside of the fuel cell 1, if the conductivity of the coolant is large, an electric shock due to electric leakage and a decrease in fuel cell system efficiency are caused. For this reason, in the present embodiment, an ion adsorption path 40 is provided in the coolant path 30, and an ion adsorption device 41 is disposed in the ion adsorption path 40. Here, the ion adsorption path 40 has a smaller cross-sectional area than the cooling liquid path 30 so that the main flow of the cooling liquid flows into the cooling liquid path 30.

  The ion adsorption device 41 has an anion exchange resin and a cation exchange resin, adsorbs ions eluted into the coolant from the radiator 31, the fuel cell 1, the coolant path 30, and the like, and suppresses an increase in the conductivity of the coolant. be able to.

  A specific configuration of the ion adsorption device 41 will be described with reference to FIG. FIG. 2A shows a cross-sectional view of the side surface of the ion adsorption device 41, and FIG. 2B shows a cross-sectional view taken along the line AA of FIG.

  As shown in FIGS. 2A and 2B, the ion adsorption device 41 of the present embodiment includes a cylindrical container 50 formed of a conductive material. The container 50 is provided with a coolant inlet 40a and a coolant outlet 40b on both side surfaces in the coolant flow direction. The coolant inlet 40 a and the coolant outlet 40 b are connected to the ion adsorption path 40. The container 50 has a larger cross-sectional area than the ion adsorption path 40 in order to increase the surface area for adsorbing ions.

  The container 50 is filled with a cation exchange resin 52 that adsorbs cations so as to be in contact with the inner wall of the container 50, and is further filled with an anion exchange resin 51 that adsorbs anions inside the cation exchange resin 52. In the center of the anion exchange resin 51, an anode 53, which is a cylindrical conductive material extending in the flow direction of the coolant, is embedded. Here, the container 50 is made of a conductive material and corresponds to the cathode 54 of the present invention.

  At the boundary between the anion exchange resin 51 and the cation exchange resin 52, a mesh-like partition member 55 for separating the anion exchange resin 51 and the cation exchange resin 52 and preventing them from flowing out into the ion adsorption path 40 is provided. ing. In addition, a predetermined gap is provided between both side surfaces of the container 50 in the coolant flow direction and the mesh-like partition member 55. By providing the predetermined gap, the inflowing coolant can be dispersed and the coolant can be passed through both the anion exchange resin 51 and the cation exchange resin 52.

  In such a configuration, ions can be adsorbed early by the anion exchange resin 51 and the cation exchange resin 52 by applying a voltage to the anode 53 and the cathode 54. In addition, in order to improve vehicle mountability, the physique of the ion adsorption device 41 can be reduced in size by reducing the filling amount of the anion exchange resin 51 and the cation exchange resin 52 filled in the ion adsorption device 41. .

  Here, since the Coulomb force F applied to the ions is proportional to the intensity E of the electric field, the Coulomb force F can be increased by increasing the voltage or decreasing the distance between the electrodes. You can increase the speed. However, it is desirable that the applied voltage be, for example, about 14 V in order to prevent electric shock.

  Returning to FIG. 1, the ion adsorption path 40 is provided with a conductivity sensor 42 for detecting the conductivity of the coolant. In the present embodiment, the conductivity sensor 42 measures the resistance value by passing a minute current through the coolant, and detects the conductivity of the coolant by converting the measured resistance value into the conductivity. Yes. Here, the conductivity sensor 42 corresponds to the conductivity detecting means in the present invention.

  The fuel cell system is provided with a control unit (ECU) 100 that performs various controls. The control unit 100 is configured by a known microcomputer including a CPU, a ROM, a RAM, an I / O, and the like, and executes processing such as various calculations according to a program stored in the ROM. The controller 100 is input with required power signals from various loads and the conductivity signal from the conductivity sensor 42. Moreover, the control part 100 is comprised so that a control signal may be output to the flow-path switching valve 35, the circulation pump 33, etc. based on a calculation result.

  The control unit 100 also monitors the conductivity of the coolant at an appropriate cycle by the conductivity sensor 42 even when the fuel cell 1 is in the power generation stop state. Even when the power generation of the fuel cell 1 is stopped, when the conductivity of the coolant exceeds a predetermined value set in advance, the circulation pump 33 is operated by the power supply of the secondary battery 2, and the anode 53 and the cathode An ion adsorption control process of applying a voltage to 54 is performed. Here, the ion adsorption control corresponds to the ion adsorption means in the present invention.

  Next, ion adsorption control of the cooling system of this embodiment will be described with reference to FIG. FIG. 3 is a flowchart illustrating ion adsorption control of the fuel cell system. The ion adsorption control of the fuel cell system is performed when the power generation of the fuel cell 1 is stopped, and the coolant circulation pump 33 of the fuel cell 1 is not operated.

  First, in S10, the conductivity ρ of the coolant is detected by the conductivity sensor 42.

  Next, in S20, it is determined whether or not the detected conductivity ρ is equal to or greater than a predetermined value ρ1. Here, the predetermined value ρ1 is a preset value and is stored in a ROM or the like.

  If it is determined in S20 that the conductivity ρ is equal to or greater than the predetermined value ρ1, the circulation pump 33 is operated by supplying power from the secondary battery 2 in S30. Here, when the circulation pump 33 is operating, the operation of the circulation pump 33 is continued. By operating the circulation pump 33, the cooling liquid can be supplied to the ion adsorption device 41, and ions contained in the cooling liquid can be adsorbed to the anion exchange resin 51 and the cation exchange resin 52 of the ion adsorption device 41. it can.

  In S <b> 40, the power is supplied from the secondary battery 2 and applied to the electrodes 53 and 54 of the ion adsorption device 41. Ions existing in the coolant circulating in the coolant path 30 are adsorbed by the anode 53 and the cathode 54 of the ion adsorption device 41. The ion adsorption device 41 in this embodiment can adsorb anions at the anode 53 and adsorb cations at the cathode 54.

  Thereby, by the flow of the cooling liquid by the circulation pump 33 and the application of the voltage to the ion adsorption device 41, the ions in the cooling liquid can be removed at an early stage, and the ion adsorption efficiency can be improved.

  When it is determined that the conductivity ρ detected in S20 is smaller than the predetermined value ρ1, the circulation pump 33 is deactivated in S50. Here, when the operation of the circulation pump 33 is stopped, the operation stop of the circulation pump 33 is continued.

  In S60, application to the electrodes 53 and 54 of the ion adsorption device 41 is stopped. In the ion adsorption apparatus 41 in the present embodiment, the anode 53 is disposed in the center filled with the anion exchange resin 51 and the cathode 54 is disposed outside the cation exchange resin 52. The anion can be adsorbed by the anion exchange resin 51 and the cation can be adsorbed by the cation exchange resin 52 even if the cation is stopped.

  Thereby, since the ions adsorbed by the electrodes 53 and 54 are adsorbed by the anion exchange resin and the cation exchange resin, the conductivity of the coolant can be lowered.

  As described above, even when the power generation of the fuel cell 1 is stopped, the adsorption efficiency is improved because ions in the cooling liquid can be adsorbed early by the flow of the cooling liquid by the circulation pump 33 and the application of the voltage to the ion adsorption device 41. Can be made. Further, when the conductivity detected by the conductivity sensor 42 is equal to or higher than a predetermined value, the flow of the coolant by the circulation pump 33 and the application of a voltage to the ion adsorbing device 41, the operation time of the circulation pump 33 is shortened. Therefore, energy efficiency can be improved.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In this 2nd Embodiment, the structure of the ion adsorption apparatus 41 differs compared with 1st Embodiment. Therefore, only different parts from the first embodiment will be described.

  FIG. 4 shows a cross-sectional view of the ion adsorption device 41 used in the second embodiment, FIG. 4 (a) shows a cross-sectional view of the side surface of the ion adsorption device 41, and FIG. FIG. 4B is a sectional view taken along line BB in FIG.

  As shown in FIGS. 4A and 4B, an ion adsorption device 41 according to the second embodiment includes an anion exchange resin 51 and a cation exchange resin 52 in a rectangular container 50 formed of a conductive material. In a state of being partitioned by a mesh-like partition member 55. The anion exchange resin 51 is filled in the upper part of the container 50, and the upper surface of the container on the anion exchange resin 51 side is the anode 53. The cation exchange resin 52 is filled in the lower part of the container 50, and the lower surface of the container 50 made of a conductive material is a cathode 54.

  Even with the configuration as described above, the same effects as those of the first embodiment can be obtained.

(Other embodiments)
In the first embodiment, the configuration is such that ions in the coolant can be adsorbed early in the power generation stop state of the fuel cell 1. However, in the power generation state of the fuel cell 1, the ion adsorption device 41 is powered by the power from the fuel cell 1. The adsorption efficiency of ions in the coolant may be improved by applying a voltage to. Since the circulation pump 33 is operating in the power generation state of the fuel cell 1, the ion adsorption control is executed by skipping the operation start / stop processing of the circulation pump 33 of S30 and S50 shown in FIG. Can do.

  Moreover, in the said 1st Embodiment, although it was set as the structure which provides the ion adsorption apparatus 41 in the path | route 40 for ion adsorption, not only this but the structure provided in the cooling fluid path | route 30 is good.

  In the first embodiment, the conductivity sensor 42 is configured to detect the conductivity of the coolant by measuring the resistance value by passing a minute current through the coolant and converting the resistance value into the conductivity. However, the present invention is not limited to this, and any configuration can be used as long as the conductivity of the coolant can be detected.

  In addition, the process of determining whether or not to control to adsorb ions is performed based on the magnitude of the conductivity detected by the conductivity sensor 42. However, the present invention is not limited to this. For example, the insulation resistance between the fuel cell and the vehicle body When the detection result is equal to or less than a predetermined value, the determination process may be performed to control to adsorb ions.

It is a conceptual diagram which shows the whole structure of the fuel cell system of the said 1st Embodiment. It is sectional drawing of the ion adsorption apparatus of the said 1st Embodiment. It is a flowchart which shows the content of the ion adsorption control of the said 1st Embodiment. It is sectional drawing of the ion adsorption apparatus of the said 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Secondary battery, 30 ... Coolant liquid path | route, 33 ... Circulation pump, 40 ... Path | route for ion adsorption, 41 ... Ion adsorption apparatus, 42 ... Conductivity sensor.

Claims (2)

A fuel cell (1) for obtaining electric power by electrochemically reacting an oxidant gas and a fuel gas;
A coolant path (30) for circulating coolant through the fuel cell (1);
A circulation pump (33) provided in the coolant path (30) for circulating the coolant;
An ion adsorption device (41) having an anion exchange resin (51) and a cation exchange resin (52) for adsorbing ions in the cooling liquid;
A secondary battery (2) that can be charged by receiving power from the fuel cell (1);
In a fuel cell system comprising:
The ion adsorption device (41) includes an anode (53) disposed in the vicinity of the anion exchange resin (51) and a cathode (54) disposed in the vicinity of the cation exchange resin (52). ,
In the power generation stop state of the fuel cell (1), the circulation pump (33) is operated by supplying power from the secondary battery (2), and a voltage is applied to the anode (53) and the cathode (54). A fuel cell system comprising ion adsorption means for adsorbing the ions in the coolant. Comprising conductivity detecting means for detecting the conductivity of the coolant;
The ion adsorbing means operates the circulation pump (33) when the conductivity detected by the conductivity detecting means is larger than a predetermined value, and causes the anode (53) and the cathode (54) to operate. 2. The fuel cell system according to claim 1, wherein a voltage is applied.

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