JP2017068907A - Fuel battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery system that can reduce combustibility of liquid fuel according to the ambient condition.SOLUTION: A fuel battery system 1 includes: a direct methanol type fuel battery 2 for supplying liquid fuel containing methanol to an anode; a fuel supply device 3 which contains a fuel tank 31 for storing liquid fuel therein and supplies the liquid fuel from the fuel tank 31 to the anode; an emergency power load 94; a first opening/closing switch 92 for switching connection/disconnection between an external power load 100 and the fuel battery 2; a second opening/closing switch 93 for switching connection/disconnection between the emergency power load 94 and the fuel battery 2; and a control device 10 for controlling the second opening/closing switch 93 based on a temperature detection value so as to connect the emergency power load 94 to the fuel battery 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system including a direct methanol fuel cell.

  There is known a fire prevention system that supplies a nitrogen-rich cathode exhaust produced by a fuel cell to a room to reduce the oxygen content of the room (for example, Patent Document 1).

Special table 2009-515310

  In direct methanol fuel cells, liquid fuel containing methanol is used as the anode fuel. Therefore, even if the system is applied to a direct methanol fuel cell, the liquid fuel may be exposed to the surrounding high temperature environment. As described above, depending on the surrounding conditions, it is desirable to store the liquid fuel in a state in which the flammability is reduced.

  The problem to be solved by the present invention is to provide a fuel cell system capable of reducing the flammability of liquid fuel.

[1] A fuel cell system according to the present invention includes a direct methanol type fuel cell that supplies a liquid fuel containing methanol to an anode, and a fuel tank in which the liquid fuel is stored. Fuel supply means for supplying liquid fuel, emergency power load, external power load, first power supply switching means for switching between connection and disconnection of the fuel cell, the emergency power load and the fuel cell Second power supply switching means for switching between connection and disconnection, and control means for controlling the second power supply switching means to connect the emergency power load to the fuel cell based on a signal And a fuel cell system.

[2] In the above invention, the apparatus further includes a housing that houses the fuel cell system, and temperature detection means provided inside or outside the housing of the fuel cell system, wherein the temperature detection means detects The temperature may be output to the control means as the signal.

[3] In the above invention, a fuel supply unit that includes a fuel tank in which the liquid fuel is stored, supplies the liquid fuel from the fuel tank to the anode, and the fuel tank from the outside of the casing of the fuel cell system. Methanol supply means for supplying methanol to the fuel tank, wherein the methanol supply means has at least methanol supply switching means for switching between supply and shutoff of methanol from the outside to the fuel tank, and the control means May control the methanol supply switching means so as to cut off the supply of methanol from the outside to the fuel tank based on the signal.

[4] In the above invention, a fuel supply unit that includes a fuel tank in which the liquid fuel is stored, and that supplies the liquid fuel to the anode of the fuel cell from the fuel tank, and the control unit includes: When the fuel cell and the emergency power load are connected by the second power supply switching means, the fuel supply means may be controlled to increase the supply amount of the liquid fuel.

[5] In the above invention, the control unit may further include a constant voltage unit that outputs a voltage output from the fuel cell to the external power load and / or the emergency power load at a predetermined voltage. The constant voltage means may be controlled to lower the predetermined voltage.

[6] In the above invention, the control means disconnects the external power load and the fuel cell in accordance with the connection of the emergency power load and the fuel cell by the second power supply switching means. The first power supply switching means may be controlled to perform, and the electrical resistance value of the emergency power load may be smaller than the electrical resistance value of the external power load.

  In the present invention, the emergency power load is connected to the fuel cell by the second power supply switching means based on the signal. As described above, when the power load connected to the fuel cell is increased, the consumption of methanol in the liquid fuel is promoted, and the concentration of methanol contained in the liquid fuel is reduced, so that the flammability of the liquid fuel can be reduced. it can.

FIG. 1 is a block diagram showing a fuel cell system according to an embodiment of the present invention. FIG. 2 is a flowchart showing a data processing procedure in the control device according to the embodiment of the present invention. FIG. 3 is a graph (part 1) showing an operation of the fuel cell system according to the embodiment of the present invention. FIG. 4 is a graph (part 2) showing an operation of the fuel cell system according to the embodiment of the present invention.

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

  FIG. 1 is a block diagram showing a fuel cell system according to an embodiment of the present invention.

  The fuel cell system 1 in the present embodiment is a fuel cell system including a direct methanol fuel cell that generates power using methanol as a fuel. As shown in FIG. 1, a fuel cell 2, a fuel supply device 3, and an air supply A device 4, a methanol replenishment device 5, a water circulation device 6, a condenser 7, a temperature sensor 8, a power supply system 9, a control device 10, and a housing 11 are provided. Hereinafter, each configuration will be described with reference to FIG. The fuel cell system 1 in the present embodiment corresponds to an example of the “fuel cell system” in the present invention, and the “fuel supply device 3” in the present embodiment corresponds to an example of the “fuel supply unit” in the present invention. The “air supply device 4” in the embodiment corresponds to an example of the “oxidant supply unit” in the present invention, and the “methanol replenishment device 5” in the present embodiment corresponds to an example of the “methanol supply unit” in the present invention. The “temperature sensor 8” in the embodiment corresponds to an example of “temperature detection means” in the present invention.

  The fuel cell 2 includes a membrane electrode assembly (MEA) 21, a plate-like anode separator 22 and a cathode separator 23 that sandwich the membrane electrode assembly 21. The membrane electrode assembly 21 includes a substantially rectangular polymer electrolyte membrane 211 having hydrogen ion (cation) conductivity, a substantially rectangular anode catalyst layer 212, and a cathode catalyst layer 213, and further includes a substantially rectangular anode. A gas diffusion layer 214 and a cathode gas diffusion layer 215 are included. The anode catalyst layer 212 and the anode gas diffusion layer 214 constitute an anode, and the cathode catalyst layer 213 and the cathode gas diffusion layer 215 constitute a cathode. These anode and cathode serve as a pair of electrodes of the fuel cell 2.

  The fuel cell 2 shown in FIG. 1 is configured as a fuel cell having only one membrane electrode assembly 21 sandwiched between a pair of separators 22 and 23, but is not particularly limited to the above. For example, a plurality of cells composed of a pair of separators 22 and 23 and a membrane electrode assembly 21 sandwiched between them are stacked to form a stack, and the cells are connected directly or / and in parallel to form a fuel. The battery 2 may be configured. The “fuel cell 2” in the present embodiment corresponds to an example of the “fuel cell” in the present invention.

  The polymer electrolyte membrane 211 is not particularly limited, and a polymer electrolyte membrane mounted on a normal polymer electrolyte fuel cell can be used. For example, a polymer electrolyte membrane made of perfluorocarbon sulfonic acid (for example, nafion (trade name, registered trademark) manufactured by Dupont, USA, Acilex (trade name, registered trademark) manufactured by Asahi Kasei Co., Ltd., Japan Gore-Tex Corporation GSII (trade name, registered trademark, etc.) manufactured by KK) can be used.

  The anode catalyst layer 212 and the cathode catalyst layer 213 are composed of an electrode catalyst, conductive carbon particles (carbon powder) supporting the electrode catalyst, and a polymer electrolyte having hydrogen ion conductivity.

  As the conductive carbon particles which are carriers in the anode catalyst layer 212 and the cathode catalyst layer 213, it is preferable to use a carbon material having conductive pores. Examples of such a carbon material include carbon black, activated carbon, carbon fiber, and carbon tube. Examples of carbon black include channel black, furnace black, thermal black, and acetylene black. Activated carbon can be obtained by carbonizing and activating materials containing various carbon atoms.

  As an electrode catalyst in the anode catalyst layer 212 and the cathode catalyst layer 213, it is preferable to use platinum or a platinum alloy. Platinum alloys include platinum group metals other than platinum (ruthenium, rhodium, palladium, osmium, iridium), iron, titanium, gold, silver, chromium, manganese, molybdenum, tungsten, aluminum, silicon, rhenium, zinc, and tin. An alloy of platinum and one or more metals selected from the group is preferably used. The platinum alloy may contain an intermetallic compound of platinum and the metal. Furthermore, an electrode catalyst mixture obtained by mixing an electrode catalyst made of platinum and an electrode catalyst made of a platinum alloy may be used, or an electrode catalyst having the same configuration may be used for the anode and the cathode, or an electrode catalyst having a different configuration may be used. May be.

  As the anode gas diffusion layer 214 and the cathode gas diffusion layer 215 disposed outside the anode catalyst layer 212 and the cathode catalyst layer 213, various gas diffusion layers known in the art can be used. As the base material constituting these gas diffusion layers 214 and 215, in order to give gas permeability, the conductive material manufactured using carbon fine powder, carbon paper or carbon cloth having a developed structure structure. A porous substrate can be used. In order to improve drainage, for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PEA), tetra A water-repellent material (polymer) typified by a fluororesin such as fluoroethylene / ethylene copolymer (ETFE) may be dispersed inside the substrate, and the substrate may be subjected to a water-repellent treatment. Furthermore, in order to give electronic conductivity, you may comprise the said base material with electronic conductive materials, such as carbon fiber, a metal fiber, or carbon fine powder. Note that the gas diffusion layers having the same configuration or different gas diffusion layers may be used in the cathode and the anode.

  The pair of anode separator 22 and cathode separator 23 are members that are disposed outside the membrane electrode assembly 21 and mechanically fix the membrane electrode assembly 21. The surface of the anode separator 22 in contact with the membrane electrode assembly 21 is supplied with methanol as fuel to the anode, and discharges the electrode reaction product and the substance containing unreacted methanol from the reaction field to the outside. An anode channel (not shown) is formed. Similarly, an oxidant (air) is supplied to the cathode on the surface of the cathode separator 23 that is in contact with the membrane electrode assembly 21, and the electrode reaction product and the substance containing unreacted methanol are discharged from the reaction field to the outside. A cathode channel (not shown) for carrying away is formed.

  Although not shown, the anode channel and the cathode channel are formed by providing grooves on the surfaces of the anode separator 22 and the cathode separator 23 by a conventional method. Although not particularly limited, the anode flow path and the cathode flow path are composed of, for example, a plurality of straight upper groove portions and a plurality of U-turn groove portions that connect adjacent straight groove portions from upstream to downstream. It has a serpentine shape.

In the present embodiment, the liquid fuel of the fuel cell 2 is stored in the fuel tank 31 of the fuel supply device 3. Liquid fuel containing methanol is supplied from the fuel tank 31 to the inlet 241 of the anode flow path of the anode separator 22 described above via the pipe F1. On the other hand, air is supplied to the inlet 251 of the cathode flow path of the cathode separator 23 via the pipe F2. Thereby, in the anode,
[Equation 1]
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻
The chemical reaction occurs, and at the cathode,
[Equation 2]
3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O
A chemical reaction occurs. As a result, an electromotive force is generated between the anode and the cathode.

  Carbon dioxide produced at the anode and unreacted methanol that has not contributed to the reaction are returned to the fuel tank 31 from the outlet 242 of the anode flow path via the pipe F3. Similarly, water produced at the cathode and unreacted methanol that has permeated (crossed over) the membrane electrode assembly 21 from the outlet 252 of the cathode channel through the pipe F4 and the condenser 7 to the water circulation tank of the water circulation device 6. Return to 61. Incidentally, the condenser 7 has a function of liquefying water vapor generated at the cathode and returning it to the water circulation tank 61.

  In the present embodiment, the pipes F <b> 1 to F <b> 6 can adopt a specific structure according to the size and layout of the fuel cell system 1.

  The fuel supply device 3 includes a fuel tank 31, a pump 32, and a liquid concentration sensor 33. The fuel tank 31 includes a high-concentration methanol aqueous solution or methanol stock solution (hereinafter also referred to as high-concentration methanol) supplied from the external methanol tank 101, and water supplied from a water circulation tank 61 (described later) (slightly methanol is added). Liquid fuel is stored. The pump 32 supplies the liquid fuel from the fuel tank 31 to the inlet 241 of the anode flow path of the anode separator 22 described above via the pipe F1. The operation and stop of the pump 32 are controlled based on a control signal from the control device 10. The liquid concentration sensor 33 measures the concentration of methanol contained in the liquid fuel stored in the fuel tank 31 (hereinafter also referred to as “concentration detection value”). As the liquid concentration sensor 33, a known liquid concentration sensor can be used as appropriate. The measurement result by the liquid concentration sensor 33 is sent to the control device 10 as an output signal. The product discharged from the outlet 242 of the anode flow path of the fuel cell 2 and the unreacted liquid fuel are returned to the fuel tank 31 via the pipe F3. At this time, since the carbon dioxide gas which is a gas phase floats on the liquid surface, the fuel tank 31 separates the liquid phase methanol and the gas phase carbon dioxide, and the carbon dioxide gas is separated from the system via an exhaust pipe (not shown). Is discharged.

  The air supply device 4 is a device for sending air containing oxygen as an oxidant to the cathode of the fuel cell 2. The air supply device 4 includes a filter 41 and a blower 42. The filter 41 is provided to remove dust and the like contained in the air sucked from the outside of the housing 11, and is provided on the suction side of the blower 42. The blower 42 supplies air to the inlet 251 of the cathode channel of the cathode separator 23 described above via the pipe F2. The operation and stop of the blower 42 are controlled based on a control signal from the control measure 10.

  The methanol replenishing device 5 has a pump 51 and a shutoff valve 52. The pump 51 is provided outside the fuel cell system 1 and is connected to an external methanol tank 101 in which the above-described high-concentration methanol is stored as additional fuel via a pipe F5. The external methanol tank 101 has a fireproof structure. Additional fuel is supplied from the external methanol tank 101 to the fuel tank 31 by the pump 51. The operation and stop of the pump 51 are controlled based on a control signal from the control device 10.

  A shutoff valve 52 is provided on the suction side of the pump 51 in the pipe F5. The shutoff valve 52 supplies or shuts off additional fuel from the external methanol tank 101 to the fuel tank 31. The opening / closing operation of the shut-off valve 52 is controlled by a control signal from the control device 10. The shut-off valve 52 is not particularly limited. For example, an electromagnetic valve that opens and closes by moving a plunger by the magnetic force of a solenoid coil can be used. The arrangement of the shutoff valve 52 is not particularly limited to the above, and may be provided on the discharge side of the pump 51. The “shutoff valve 52” in the present embodiment corresponds to an example of “methanol supply switching means” in the present invention.

  The water circulation device 6 has a water circulation tank 61 and a pump 62. Water generated at the cathode of the fuel cell 2 and unreacted methanol that has permeated through the membrane electrode assembly 21 are supplied to the water circulation tank 61 from the outlet 252 of the cathode channel via the pipe F4 and the condenser 7. On the other hand, the water stored in the water circulation tank 61 is discharged toward the fuel tank 31 by the pump 62 provided in the pipe F6. The operation and stop of the pump 62 are controlled based on a control signal from the control device 10.

  The temperature sensor 8 is provided inside a housing 11 that houses various components of the fuel cell system 1. The temperature sensor 8 is used to detect the temperature around the fuel cell system 1, and outputs the detected temperature to the control device 10 as an electric signal (hereinafter also referred to as “temperature detection value”). . During operation, the temperature sensor 8 always performs signal output and temperature detection. As such a temperature sensor 8, for example, a known sensor such as an infrared sensor that can detect a temperature from room temperature to about 200 ° C. and can output this as an electrical signal can be used. The temperature sensor 8 may be provided outside the casing 11 of the fuel cell system 1. In this case, for example, a fire alarm installed in a building may be used as the temperature sensor 8. .

  The power supply system 9 that guides the power output from the fuel cell 2 to the outside of the housing 11 includes a power converter 91, a first open / close switch 92, a second open / close switch 93, an emergency power load 94, have. The power converter 91 converts a DC voltage output from the fuel cell 2 into a three-phase AC voltage in response to a control signal sent from the control device 10 and supplies the three-phase AC voltage to the external power load 100, and a DC A constant voltage circuit 911 including a constant voltage element such as a DC converter or a Zener diode. The constant voltage circuit 911 changes (drops) and supplies the voltage output from the fuel cell 2 to a constant voltage required by the external power load 100 in accordance with a control signal sent from the control device 10. When viewed from the fuel cell 2, a first open / close switch 92 is provided on the secondary side of the power converter 91, and the first open / close switch 92 is set according to a control signal sent from the control device 10. By switching, the fuel cell 2 and the external power load 100 are electrically connected or disconnected. The “constant voltage circuit 911” in the present embodiment corresponds to an example of the “constant voltage unit” in the present invention, and the “first open / close switch 92” in the present embodiment is the “first power supply switching unit” in the present invention. It corresponds to an example.

  Further, an emergency power load 94 is electrically connected to the secondary side of the power converter 91 in parallel with the external power load 100 via the second opening / closing switch 93. The emergency power load 94 according to the present embodiment is electrically connected to the fuel cell 2 in addition to the electrical connection between the fuel cell 2 and the external power load 100. As the emergency power load 94, a heating resistor or the like can be used. The operation of the second opening / closing switch 93 that electrically connects or disconnects the fuel cell 2 and the emergency power load 94 is controlled based on a control signal from the control device 10. As the second opening / closing switch 93, the same one as the first opening / closing switch 92 described above can be used. The “second opening / closing switch 93” in the present embodiment corresponds to an example of “second power supply switching unit” in the present invention.

  In the present embodiment, the emergency power load 94 is electrically connected to the fuel cell 2 in addition to the external power load 100 via the second opening / closing switch 93, but is not limited to this. Instead, the emergency power load 94 may be electrically connected to the fuel cell 2 instead of the external power load 100. This embodiment will be described as an example. The first open / close switch 92 is cut off and the second open / close switch 93 is electrically connected, so that the emergency power load 94 is replaced with a fuel cell instead of the external power load 100. 2 can be electrically connected. Although not particularly illustrated, one power supply switching means for switching between the electrical connection between the fuel cell and the external power load and the electrical connection between the fuel cell and the emergency power load may be provided. In this case, one power supply switching unit functions as the first and second power supply units of the present invention.

  The control device 10 is composed of, for example, a microcomputer including a CPU, ROM, RAM, A / D converter, input / output interface, and the like. Various sensors such as the temperature sensor 8 and the liquid concentration sensor 33 are connected to the control device 10 and can receive the detection signals thereof. The “control device 10” in the present embodiment corresponds to an example of “control means” in the present invention.

  Based on the temperature detection value received from the temperature sensor 8, the control device 10 determines whether or not the surroundings of the fuel cell system 1 are in a high temperature environment. The control device 10 stores in advance a lower limit value (hereinafter, also referred to as “first threshold value”) of an abnormal range as the ambient temperature of the fuel cell system 1. The control device 10 compares the first threshold value with the temperature detection value, and determines that the periphery of the fuel cell system 1 is a high-temperature environment when the temperature detection value is equal to or greater than the first threshold value. The first threshold value is preferably set in the range of 100 to 150 ° C. in view of the physical properties of methanol contained in the liquid fuel and the guaranteed temperature of the members constituting the fuel cell system. In this case, the above-described high temperature environment refers to an environment that belongs to a temperature region exceeding the first threshold.

  When it is determined that the surroundings of the fuel cell system 1 are in a high temperature environment, the control device 10 intentionally consumes the liquid fuel remaining in the fuel cell system 1 from the normal operation in the operation state of the fuel cell system 1. Transition to operation (hereinafter also referred to as “fuel consumption operation”). The fuel consumption operation is executed in order to consume the methanol contained in the liquid fuel by advancing the reactions shown in the above [Expression 1] and [Expression 2] in the fuel cell 2. Since methanol is flammable, it may cause an unintended rapid oxidation reaction when exposed to a high temperature environment. In the present invention, the consumption of liquid fuel is promoted, and the concentration of methanol contained in the liquid fuel is reduced, so that the liquid fuel is stored in a state where it is difficult to react even when exposed to a high temperature environment. .

  In this fuel consumption operation, in the fuel cell system 1, (1) control for electrically connecting the fuel cell 2 to the emergency power load 94, and (2) as additional fuel from the external methanol tank 101 to the fuel tank 31. And a control for stopping the supply of methanol. Details of the control performed by the control device 10 during the fuel consumption operation will be described later with reference to FIG.

  Further, the control device 10 of the present embodiment performs an operation that further promotes the consumption of the liquid fuel remaining in the fuel cell system 1 after the fuel cell system 1 shifts to the fuel consumption operation (hereinafter referred to as “rapid consumption operation”). (Also referred to as “)”.

  In this rapid consumption operation, (A) control for increasing the amount of liquid fuel supplied to the anode of the fuel cell 2, (B) control for increasing the amount of air supplied to the cathode of the fuel cell 2, and (C) fuel cell. 2 to control the voltage output from the power source 100 to the external power load 100 and the emergency power load 94 to be low. Details of the control performed by the control device 10 during the rapid consumption operation will be described later with reference to FIG.

  Further, the control device 10 determines whether or not to stop the fuel cell system 1 based on the detected concentration value of the liquid fuel stored in the fuel tank 31 output from the liquid concentration sensor 33. The control device 10 stores in advance a methanol concentration (hereinafter, also referred to as “second threshold”) at which the flammability of the liquid fuel is sufficiently reduced. The second threshold value is preferably a value at which the concentration of methanol volatilized from the liquid fuel is 200 ppm or less, although it depends on the methanol concentration of the set liquid fuel. The control device 10 compares the second threshold value with the concentration detection value, and if the concentration detection value is equal to or less than the second threshold value, it is determined that the concentration of methanol contained in the liquid fuel has sufficiently decreased, and the fuel cell A signal for stopping the system 1 is output.

  Next, a control procedure of the fuel cell system 1 according to the present embodiment will be described with reference to FIG. The following processing is executed by the control program of the fuel cell system 1 installed in the control device 10. The control of the fuel cell system 1 according to this embodiment is based on a signal from the temperature sensor 8 and shifts the fuel cell system 1 from the normal operation to the fuel consumption operation, and further from the fuel consumption operation to the rapid consumption operation. It is.

  First, in step ST1, the control device 10 reads the temperature detection value detected by the temperature sensor 8, and in step ST2, compares the read temperature detection value with the first threshold value. When the temperature detection value is larger than the first threshold value, the process proceeds to step ST3. On the other hand, when the temperature detection value is not more than the first threshold value, steps ST1 and ST2 are repeated.

  In step ST2, when it is determined that the temperature detection value is equal to or higher than the first threshold (that is, it is determined that the periphery of the fuel cell system 1 is in a high temperature environment), the control device 10 starts the fuel cell system 1 from the normal operation. Shift to fuel consumption operation. Below, the concrete control content of the fuel consumption operation which the fuel cell system 1 performs in step ST3 is demonstrated.

  As described above, in the fuel consumption operation (ie, step ST3), the control device 10 (1) performs control for electrically connecting the fuel cell 2 to the emergency power load 94, and (2) performs fuel from the external methanol tank 101. And a control for stopping the supply of high-concentration methanol as additional fuel to the tank 31.

  Here, first, the control device 10 outputs a signal for operating the second opening / closing switch 93 so as to electrically connect the emergency power load 94 to the fuel cell 2 in addition to the external power load 100. The load of the fuel cell 2 is increased by the addition of the emergency power load 94, and the current density applied to the fuel cell 2 is increased accordingly. For this reason, consumption of the liquid fuel is promoted in the fuel cell 2, and the concentration of methanol contained in the liquid fuel is reduced. When the emergency power load 94 is electrically connected to the fuel cell 2 instead of the external power load 100, the control device 10 outputs signals for operating the first and second on / off switches 92 and 93. To do.

  Further, the control device 10 outputs a signal for stopping the supply of high-concentration methanol as additional fuel stored in the external methanol tank 101 to the methanol replenishment device 5. Specifically, the control device 10 outputs a block signal to the cutoff valve 52 and outputs a stop signal to the pump 51. As a result, the supply of high-concentration methanol as additional fuel from the external methanol tank 101 to the fuel tank 31 is stopped. That is, the amount of methanol contained in the liquid fuel is steadily reduced by the amount consumed by the fuel cell 2.

  As described above, in this embodiment, when it is determined that the environment around the fuel cell system 1 is in a high temperature environment, the control device 10 intentionally consumes the liquid fuel remaining in the system of the fuel cell system 1 as the fuel consumption operation. The control which performs the operation which performs is performed, and the density | concentration of methanol in the system of the fuel cell system 1 is reduced. This reduces the flammability of the liquid fuel.

  Furthermore, in this embodiment, in step ST4, the control device 10 shifts the fuel cell system 1 from the fuel consumption operation to the rapid consumption operation. In the present embodiment, when the fuel cell system shifts to the fuel consumption operation, there is almost no time lag and the shift to the rapid consumption operation. Below, the specific control content of the rapid consumption operation which the fuel cell system 1 performs in step ST4 is demonstrated.

  As described above, in the rapid consumption operation (ie, step ST4), the control device 10 (A) controls to increase the amount of liquid fuel supplied to the anode of the fuel cell 2, and (B) air to the cathode of the fuel cell 2. And (C) control for lowering the voltage output from the fuel cell 2 to the external power load 100 and the emergency power load 94.

  Here, first, the control device 10 outputs a signal for increasing the flow rate of the liquid fuel discharged from the pump 32 of the fuel supply device 3 to the pump 32. In addition, the control device 10 outputs a signal for increasing the flow rate of the air discharged from the blower 42 of the air supply device 4 to the blower 42. Thereby, the flow volume of the reaction fluid (liquid fuel and air) supplied to the fuel cell 2 increases. As a result, the chemical reaction shown in the above [Equation 1] and [Equation 2] further proceeds, and the consumption of the liquid fuel in the fuel cell 2 is promoted. That is, the concentration of methanol contained in the liquid fuel is further reduced.

  Further, the control device 10 controls the constant voltage circuit 911 so that the voltage output from the fuel cell 2 to the external power load 100 and the emergency power load 94 becomes low. As a general characteristic of the fuel cell, when the voltage output from the fuel cell decreases, the current density tends to increase. On the other hand, when the current density output from the fuel cell increases, the output density tends to increase. Here, the current density output from the fuel cell 2 is increased and extended by controlling the constant voltage circuit 911 so as to reduce the voltage output from the fuel cell 2 using the above characteristics of the fuel cell. Increases the power density of the fuel cell 2. As described above, in the rapid consumption operation, by causing the fuel cell 2 to output a power density that is larger than the power density required in the normal operation, the fuel cell 2 is promoted to consume liquid fuel. The concentration of methanol contained in the fuel is further reduced.

  In step ST5, the control device 10 reads the concentration detection value of the liquid fuel stored in the fuel tank 31 from the liquid concentration sensor 33, and compares the concentration detection value with the second threshold value. If the detected concentration value is equal to or lower than the second threshold value, the concentration of methanol contained in the liquid fuel has sufficiently decreased, and the process proceeds to step ST6. On the other hand, when the detected density value is equal to or greater than the second threshold value, step ST5 is repeated.

  In step ST6, the fuel cell system 1 is stopped. Specifically, the control device 10 outputs a stop signal to the pump 32 and the blower 42 that are operating during the rapid consumption operation, and stops them. Further, the first and second on / off switches 92 and 93 are opened, and the electrical connection between the fuel cell 2 and the external power load 100 and the emergency power load 94 is cut off. Thereby, the fuel cell system 1 stops.

  As described above, in this embodiment, the liquid fuel is increased by electrically connecting the emergency power load 94 to the fuel cell 2 by the second opening / closing switch 93 based on the temperature detection value, thereby increasing the power load. Promotes the consumption of methanol in it. Thereby, since the methanol density | concentration contained in liquid fuel falls, the combustibility of liquid fuel can be reduced.

The actions and effects of this embodiment will be specifically described below. For example, in the fuel cell system 1 including the fuel cell 2 having the characteristics shown in FIG. 3, as a fuel consuming operation, an emergency power load 94 of 140 mW / cm ² is electrically connected and added from the external methanol tank 101. Control to stop the supply of fuel (methanol). In addition, liquid fuel (3 L, methanol concentration is 3 wt%) is circulated and supplied to the anode of the fuel cell at 3 L / min, and air is supplied to the cathode of the fuel cell at 200 L / min. In this case, when the concentration of methanol contained in the liquid fuel stored in the fuel tank 31 is plotted against the elapsed time from the start of the fuel consumption operation, a graph α as shown in FIG. 4 is obtained.

  As shown in FIG. 4, when 5 minutes have elapsed since the start of the fuel consumption operation, the concentration of methanol contained in the liquid fuel has decreased to 1 wt%, and when 15 minutes have elapsed since the start of the fuel consumption operation. The concentration of methanol contained in the liquid fuel has decreased to 0.5 wt%, and by executing the fuel consumption operation, the consumption of methanol in the liquid fuel is promoted and the concentration of methanol contained in the liquid fuel is reduced. be able to.

  Further, as the rapid consumption operation, the liquid fuel supply amount is increased to 6 L / min, and the air supply amount is controlled in the same manner as described above, as described above, with respect to the elapsed time from the start of the rapid consumption operation. When the concentration of methanol contained in the liquid fuel that can be stored in the fuel tank is plotted, a graph β as shown in FIG. 4 is obtained. Here, when the fuel cell system 1 shifts to the fuel consumption operation, it is assumed that there is almost no time lag and shifts to the rapid consumption operation.

  As shown in FIG. 4, the concentration of methanol contained in the liquid fuel is reduced to 0.5 wt% when 4 minutes have elapsed since the start of the rapid consumption operation. That is, by executing this rapid consumption operation, the consumption of methanol in the liquid fuel can be further promoted, and the concentration of methanol contained in the liquid fuel can be further reduced.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the present embodiment, control by the control device 10 is performed based on the temperature detection value detected by the temperature sensor 8, but the present invention is not limited to this, and the surroundings from the external device 102 shown in FIG. Control by the control device 10 may be performed based on a signal indicating an abnormality. In this case, “a signal indicating a surrounding abnormality from the external device 102” corresponds to an example of a “signal” of the present invention.

  In the case where the fuel cell system 1 is controlled based on a signal from a fire alarm installed in a building or a signal from the external device 102, for example, compared with a case where a temperature sensor is provided in the immediate vicinity of the housing. Since the execution time of the consumption operation or the rapid consumption operation can be secured for a long time, the operation and effect of the present invention can be made more effective.

  In the present embodiment, by using the constant voltage circuit 911, the voltage output from the fuel cell 2 is reduced to promote the consumption of liquid fuel in the fuel cell 2, but in addition, When the emergency power load 94 is electrically connected to the fuel cell 2 instead of the external power load 100, the electrical resistance value of the emergency power load 94 is smaller than the electrical resistance value of the external power load 100 By selecting, consumption of liquid fuel in the fuel cell 2 can be promoted. Since the above configuration is a simple configuration as compared with the configuration including the constant voltage circuit 911, the above-described operations and effects can be obtained relatively easily and inexpensively.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Fuel cell 21 ... Membrane electrode assembly 211 ... Polymer electrolyte membrane 212 ... Anode catalyst layer 213 ... Cathode catalyst layer 214 ... Anode gas diffusion Layer 215 ... Cathode gas diffusion layer 22 ... Anode separator 23 ... Cathode separator 241 ... Inlet 242 ... Outlet 251 ... Inlet 252 ... Outlet 3 ... Fuel supply device 31 .... Fuel tank 32 ... Pump 4 ... Air supply device 41 ... Filter 42 ... Blower 5 ... Methanol replenishing device 51 ... Pump 52 ... Shut-off valve 6 ... Water circulation device 61 ... Water circulation tank 62 ... Pump 7 ... Condenser 8 ... Temperature sensor 9 ... Power supply system 91 ... Power converter 911 ... Constant voltage circuit 92 ... First open / close switch 93 ... Second open / close switch 94 ... Emergency power load 10 ... Control device 11 ... Housing F1-F6 ... Pipe 100 ... External power load 101 ..External methanol tank 102 ... External equipment

Claims (6)

A fuel cell system including a direct methanol fuel cell that supplies a liquid fuel containing methanol to an anode,
A fuel supply unit including a fuel tank in which the liquid fuel is stored, and supplying the liquid fuel from the fuel tank to the anode;
Emergency power load,
First power supply switching means for switching between connection and disconnection of the external power load and the fuel cell;
Second power supply switching means for switching between connection and disconnection of the emergency power load and the fuel cell;
And a control means for controlling the second power supply switching means to connect the emergency power load to the fuel cell based on the signal. The fuel cell system according to claim 1,
A housing for housing the fuel cell system;
Temperature detecting means provided inside or outside the housing, and
The temperature detecting means outputs the detected temperature as the signal to the control means. The fuel cell system according to claim 1 or 2,
Methanol supply means for supplying methanol to the fuel tank from the outside of the casing of the fuel cell system,
The methanol supply means has at least methanol supply switching means for switching between supply and shutoff of methanol from the outside to the fuel tank,
The control means controls the methanol supply switching means so as to cut off the supply of methanol from the outside to the fuel tank based on the signal. The fuel cell system according to any one of claims 1 to 3,
The control means controls the fuel supply means so as to increase the supply amount of the liquid fuel when the fuel cell and the emergency power load are connected by the second power supply switching means. . The fuel cell system according to any one of claims 1 to 4, wherein
A constant voltage means for outputting a voltage output from the fuel cell to the external power load and / or the emergency power load at a predetermined voltage;
The control means operates the constant voltage means to lower the predetermined voltage based on the signal. A fuel cell system according to any one of claims 1 to 5,
The control means is configured to disconnect the external power load and the fuel cell in accordance with the connection of the emergency power load and the fuel cell by the second power supply switching means. Control the power supply switching means,
The fuel cell system according to claim 1, wherein an electrical resistance value of the emergency power load is smaller than an electrical resistance value of the external power load.

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