JP2013211105A - Fuel cell power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell power generation system that is operable for a long period of time with a simpler system configuration.SOLUTION: A fuel cell system includes an alkali stack 12 and an acid stack 13. Liquid fuel that is stored in a common fuel tank 11 is circulated and supplied to respective anodes of the alkali stack 12 and the acid stack 13. An exhaust opening of a cathode of the acid stack 13 and an intake opening of a cathode of the alkali stack 12 are connected in such a manner that exhaust gas from the cathode of the acid stack 13 is supplied to the cathode of the alkali stack 12.

Description

  The present invention relates to a fuel cell system that generates power using liquid fuel as fuel.

  Recent advances in electronic technology increase the amount of information, and it is necessary to process the increased information faster and with higher functionality, so a high power density and high energy density power supply, that is, continuous drive time Need a long power supply.

  There is a growing need for small generators that do not require charging, that is, micro-generators that can be easily refueled. Against this background, the importance of fuel cells is being studied.

  A fuel cell is a generator that is composed of at least a solid or liquid electrolyte and an anode and a cathode, which are a pair of electrodes that induce a desired electrochemical reaction, and converts the chemical energy of the fuel directly into electrical energy with high efficiency. is there.

  In such fuel cells, those using a solid polymer electrolyte membrane as the electrolyte membrane and using hydrogen as fuel are called polymer electrolyte fuel cells (PEFC), and those using methanol as fuel are directly methanol. It is called a direct fuel fuel cell (DMFC). Among them, DMFCs that use liquid fuels are attracting attention as being effective as small portable or portable power sources because of the high volumetric energy density of the fuel.

  Here, many of the solid polymer electrolyte membranes used in membrane / electrode assemblies (MEAs), which are the power generation parts of DMFCs currently being developed, are proton exchanges in which sulfonic acid groups are introduced as ion exchange groups. Type electrolyte membrane, which is called an acid type. In addition to an acid DMFC using a proton exchange electrolyte membrane, there is an alkaline fuel cell (AFC) using an anion exchange electrolyte membrane having an anion exchange group represented by an amine group.

  Patent Document 1 discloses a fuel cell system in which acid DMFC and AFC are combined.

JP 2010-49912 A

The battery reaction of acid DMFC using a proton exchange electrolyte membrane is expressed by (Formula 1) to (Formula 3).
Anode: CH ₃ OH + H ₂ O => CO ₂ + 6H ⁺ + 6e ⁻ (Formula 1)
Cathode: 3/2 O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O (Formula 2)
Whole: CH ₃ OH + 3 / 2O ₂ ⇒CO ₂ + 2H ₂ O (Formula 3)

  As shown in (Formula 1), acid DMFC requires water for the reaction at the anode. For this reason, in an acid type DMFC, it is necessary to supply water to the anode with a water cartridge, or to recover the water produced by the cathode reaction of (Formula 2) using a heat exchanger and supply it to the anode. there were.

On the other hand, there is an alkaline fuel cell (AFC) using an anion exchange type electrolyte membrane having an anion exchange group represented by an amine group in addition to the acid type DMFC. The battery reaction formula of AFC is represented by (Formula 4) to (Formula 6).
Anode: CH ₃ OH + 6OH ⁻ → CO ₂ + 5H ₂ O + 6e ⁻ (Formula 4)
Cathode: 3 / 2O ₂ + 3H ₂ O + 6e ⁻ → 6OH ⁻ (Formula 5)
Whole: CH ₃ OH + 3 / 2O ₂ ⇒CO ₂ + 2H ₂ O (Formula 6)

  In the AFC using the anion exchange type electrolyte membrane, contrary to the acid type DMFC, water is required for the reaction at the cathode as shown in (Formula 5). Therefore, it is necessary to humidify the gas containing oxygen supplied to the cathode using a humidifier. In addition, a large amount of water is generated by power generation at the anode (Formula 4). Therefore, if the operation is continued in AFC, there is a problem that the methanol concentration decreases due to generation of water, and the amount of liquid in the fuel tank increases and overflows.

  As described above, both the acid type DMFC and AFC have problems such as ensuring the supply source of water necessary for the reaction and treating the water generated by the reaction, making the system more complex, larger, and less convenient. There has been a demand for a fuel cell system having a simple configuration that does not have a water treatment apparatus such as a water supply or a water recovery mechanism.

  In the fuel cell system described in Patent Document 1, a system configuration is proposed in which water generated at the anode of the AFC is supplied to the anode of the acid DMFC, thereby suppressing a decrease in methanol concentration and an increase in the amount of liquid in the fuel tank. can do. On the other hand, the cathode is configured to have a line for supplying air that is not wet to the acid DMFC from the outside and a line for supplying air that is wet to the AFC from the outside. Therefore, it is necessary to provide a humidifier for humidifying the air in the air supply line to the AFC, which is insufficient from the viewpoint of simplification and miniaturization of the fuel cell system.

  An object of the present invention is to provide a fuel cell system that can be operated for a long time with a simpler system configuration.

  The fuel cell system according to the present invention includes an anion exchange electrolyte membrane, an alkali stack in which a plurality of membrane electrode assemblies each composed of an anode and a cathode electrode disposed on both sides of the anion exchange electrolyte membrane, and a proton exchange An electrolyte stack, an anode disposed on both sides of the proton exchange electrolyte membrane, and an acid stack in which a plurality of membrane electrode assemblies composed of cathode electrodes are laminated, and the anode of the alkali stack and the acid stack The acid stack cathode exhaust port and the alkali stack so that liquid fuel stored in a common fuel tank is circulated and supplied to the cathode of the alkali stack. This is characterized in that an intake port of the cathode is connected.

  The present invention can provide a fuel cell system that can be operated for a long time with a simpler system configuration.

1 is a schematic diagram of a fuel cell system according to the present invention. 1 is a schematic diagram of a fuel cell system according to the present invention. 1 is a schematic diagram of a fuel cell system according to the present invention. 1 is a schematic diagram of a fuel cell system according to the present invention. 1 is a schematic diagram of a fuel cell system according to the present invention.

  A first embodiment according to the fuel cell system of the present invention will be described. The fuel cell system targeted by the present invention includes an anion exchange electrolyte membrane, an alkali stack in which a plurality of membrane electrode assemblies composed of anodes and cathodes arranged on both sides of the anion exchange electrolyte membrane, and a proton It includes an exchange electrolyte membrane and an acid stack in which a plurality of membrane electrode assemblies composed of anodes and cathodes arranged on both sides of the proton exchange electrolyte membrane are stacked, and generates electricity in both the alkali stack and the acid stack. System. The fuel cell system of the present embodiment is characterized in that the liquid fuel stored in a common fuel tank is circulated and supplied to the anodes of the alkali stack and the acid stack. Further, the exhaust port of the acid stack cathode and the intake port of the alkali stack cathode are connected so that the exhaust gas from the acid stack cathode is supplied to the alkaline stack cathode.

  In this way, the liquid fuel stored in the common fuel tank is circulated and supplied to the anode of the alkali stack and the acid stack, so that the water generated in the anode reaction of the alkali stack is used for the anode reaction of the acid stack. Can do. Thereby, a water recovery mechanism for recovering water discharged from the alkali stack and a water supply mechanism for supplying water to the anode of the acid stack can be omitted. Also, the acid stack cathode reaction was generated by connecting the acid stack cathode exhaust port to the alkali stack cathode intake port so that the exhaust from the acid stack cathode was supplied to the alkali stack cathode. Water can be used for the cathodic reaction of the alkaline stack. Thereby, it is not necessary to humidify the oxidant gas supplied to the cathode of the alkali stack, and the humidifier required in the conventional oxidant gas supply mechanism of the alkali stack can be omitted. As described above, in the fuel cell system of this embodiment, water generated by the alkaline stack anode reaction and the acid stack cathode reaction can be effectively utilized in the acid stack anode reaction and the alkaline stack cathode reaction with a simple system configuration. Can do. In addition, by effectively using the water generated and consumed by the power generation reaction of the acid stack and alkali stack between them, it is possible to moderate the decrease in the concentration of liquid fuel and increase in the amount of liquid in the tank for a long time. Driving is possible.

  Next, a second embodiment of the fuel cell system of the present invention will be described. As a result of investigations by the present inventors, it has been found that the fuel cell system of the first embodiment has the following problems. The liquid fuel discharged from the acid stack and the alkali stack and the water generated in the acid stack contain ion exchange groups eluted from the electrolyte membrane. The eluting ion exchange group is a proton exchange group such as a sulfonic acid group in the case of an acid stack, and an anion exchange group such as a quaternary amine group in the case of an alkali stack. Here, when the liquid fuel discharged from the anode of the alkali stack is supplied to the anode of the acid stack, the anion exchange group eluted from the anion exchange type electrolyte membrane is supplied to the anode of the acid stack in a state of being mixed in the liquid fuel, The proton exchange group of the proton exchange type electrolyte membrane of the acid stack and the anion exchange group contained in the liquid fuel are combined. Similarly, when water produced at the cathode of the acid stack is supplied to the cathode of the alkali stack, the proton exchange group contained in the water is bonded to the anion exchange group of the anion exchange type electrolyte membrane. As a result, there is a problem that the power generation performance is deteriorated due to a decrease in the ionic conductivity of the electrolyte membrane. Note that the alkaline stack tends to elute the ion-exchange groups into the liquid fuel and produced water more than the acid stack, especially when the liquid fuel discharged from the alkaline stack anode is supplied to the acidic stack anode. The problem of performance degradation is large.

  In the fuel cell system of the present embodiment, in the fuel cell of the first embodiment, an ion removal unit that removes ion exchange groups is provided in either the fuel tank or the fuel supply line that supplies the liquid fuel to the acid stack. It is characterized by that. By removing the ion exchange group in the liquid fuel by the ion removing unit, the bond between the anion exchange group and the proton exchange group is suppressed, and a decrease in the ionic conductivity of the electrolyte membrane can be suppressed. In addition, since the cathode has the same problem as described above, it is preferable to provide the ion removing unit also in a pipe connecting the exhaust port of the cathode of the acid stack and the intake port of the cathode of the alkali stack. As the ion removal unit, any ion exchange membrane can be used as long as it can remove the ion exchange group.

  The fuel cell system according to this embodiment can be operated for a longer time than the fuel cell system according to the first embodiment.

  Hereinafter, embodiments of the present invention will be specifically described using examples.

Example 1
A fuel cell system that uses methanol as fuel will be described as an example of a fuel cell system that generates power using liquid fuel as fuel. An example of the basic configuration of the fuel cell system according to this embodiment is shown in FIG. The fuel cell system includes an alkali stack 12 in which single cells using an anion exchange type electrolyte membrane as a power generation unit are laminated, an acid stack 13 in which single cells using a proton exchange type electrolyte membrane are laminated, an alkali stack 12 and an acid stack 13. A fuel tank 11 for supplying fuel to the fuel and collecting unreacted residual fuel, a fuel pump 15 for circulating and supplying liquid fuel, a blower 17 for supplying air to the alkali stack 12 and the acid stack 13, and an alkali A fuel drain collection line 16 for collecting residual fuel discharged from the stack 12 and the acid stack 13, a methanol concentration sensor 25 for detecting the methanol concentration in the fuel tank 11, and a liquid amount in the fuel tank 11 are monitored. Water level sensor 26, methanol concentration sensor 25 and water level sensor 26 Monitoring and controlling operation / stop of the high-concentration methanol supply pump 22 for supplying high-concentration methanol from the high-concentration methanol cartridge 21 to the fuel tank 11, and controlling the power generation amount of the alkali stack 12 and the acid stack 13 A monitor / control circuit 24 for performing system control such as

The alkali stack 12 includes a membrane electrode assembly (MEA) having an anode electrode and a cathode electrode sandwiched between an anion exchange type solid polymer electrolyte membrane whose ion conductive group is represented by OH ⁻ , and an anode electrode and a cathode electrode. A plurality of single cells each including a separator for supplying liquid fuel and oxidant gas are stacked in series. Electric power is generated by supplying a methanol aqueous solution as a fuel and air or oxygen as an oxidant gas to the alkali stack 12. On the other hand, the acid stack 13 includes a membrane electrode assembly (MEA) in which an anode electrode and a cathode electrode are formed with a proton exchange type solid polymer electrolyte membrane whose ion conductive group is represented by SO ₄ ^2- in between, and an anode A plurality of single cells composed of a separator for supplying liquid fuel and oxidant gas to the electrode and the cathode electrode are stacked in series. Like the alkali stack 12, an aqueous methanol solution as fuel and air as oxidant gas Alternatively, power is generated by supplying oxygen.

  First, regarding the anode side, as shown in (Formula 4), in the alkali stack 12 which is AFC, water is generated by a methanol oxidation reaction on the anode side. Therefore, when the alkali stack 12 is operated alone for a long time, there are problems that the methanol concentration decreases due to the generation of water, and the amount of liquid in the tank increases and overflows. On the other hand, as shown in FIG. 1, when the anode discharge liquid of the alkali stack 12 is supplied to the anode of the acid stack 13, water is required for the methanol oxidation reaction as shown in (Formula 1). In step 12, water generated by power generation is consumed to generate power. Furthermore, when protons generated by the methanol oxidation reaction shown in (Formula 1) migrate to the cathode through the proton exchange electrolyte membrane, water can also be transferred to the cathode side as water accompanied by protons. Consume.

  Next, regarding the cathode side, as shown in (Formula 2), in the acid stack 13, water is generated by the reaction at the cathode. On the other hand, as shown in (Formula 5), the alkali stack 12 requires water for the reaction at the cathode. Therefore, when the alkali stack 12 is operated alone, it is necessary to humidify the oxidant gas supplied to the alkali stack 12 with a humidifier. On the other hand, in the fuel cell system of this embodiment, as shown in FIG. 1, the cathode exhaust port of the acid stack 13 and the cathode intake port of the alkali stack 12 are connected to generate by the cathode reaction of the acid stack 13. The generated water is supplied to the cathode of the alkali stack 12. Thereby, it becomes possible to omit the humidifier conventionally required, and the system can be simplified.

  In the fuel cell system of this embodiment, the power generation amount of each stack is controlled by adjusting the electrode area and the number of stacks of the cells of the alkaline stack 12 and the acid stack 13, and the monitor / control circuit 24 is used to control the alkaline stack. By controlling the power generation amount of the acid stack 12 and the acid stack 13 respectively, the amount of water generated by the power generation in the alkali stack 12 and the amount of water consumed as power generation and proton-entrained water in the acid stack 13 are balanced. The fuel cell system can be operated for a long time without overflowing the liquid fuel from the fuel tank 11. Specifically, from the relationship between the amount of water generated and consumed in the alkali stack 12, the amount of water generated and consumed in the acid stack 13, and the amount of water moving as proton-accompanying water, the alkali stack 12 Preferably, the power generation amount of the acid stack 13 is made the same, or the power generation amount is controlled so that the power generation amount of the acid stack 13 becomes large.

(Example 2)
FIG. 2 shows a system in which an ion exchange resin layer 21 serving as an ion removing unit is introduced into an anode pipe and a cathode pipe between the alkali stack 12 and the acid stack 13 of the fuel cell system shown in FIG. About the liquid fuel discharged | emitted from the anode of the alkali stack 12, mixing of the anion exchange group eluted from the anion exchange type electrolyte membrane and the electrode binder is inevitable. Further, regarding the exhaust gas discharged from the cathode of the acid stack 13, it is inevitable that proton exchange groups eluted from the proton exchange electrolyte membrane or the electrode binder are mixed. When these flow into the downstream stack, a neutralization reaction occurs in each electrolyte membrane or electrode binder, and the performance of the stack deteriorates. As shown in FIG. 2, the life of the fuel cell system can be extended by introducing a system for trapping harmful substances eluted by introducing the ion exchange resin 21.

  Further, in the configuration shown in FIG. 2, if an ion exchange resin is further provided in the fuel drainage recovery line 16 or the fuel tank 11, the proton exchange groups contained in the drainage discharged from the anode of the acid stack 13 are used. The neutralization reaction in the alkali stack 12 can be prevented, and is more preferable.

(Example 3)
FIG. 3 is a diagram showing a system in which an ion exchange resin layer 21 for removing anion exchange groups and proton exchange groups eluted from the alkali stack 12 and the acid stack 13 is installed in the fuel tank 11. In this embodiment, if the anode outlet of the alkali stack 12 and the anode inlet of the acid stack 13 are directly connected, the anion exchange groups eluted from the alkali stack 12 will be mixed into the acid stack 13, so that different fuel pumps are used. 15 is used to circulate and supply liquid fuel from the fuel tank 11 to each stack. In this way, even when the line for circulating and supplying the liquid fuel is separated by the alkali stack 12 and the acid stack 13, the fuel tank 11 is common, so that the water generated at the anode of the alkali stack 12 passes through the fuel tank. Since it is used in the oxidation reaction of the anode of the acid stack 13, the fuel cell system can be operated for a long time without overflowing the liquid fuel from the fuel tank 11 as in the first and second embodiments. Further, by providing the ion exchange resin layer 27 in the fuel tank 11, it is possible to extend the system life as in the fuel cell system of the second embodiment. Further, the configuration of the present embodiment has an advantage that neutralization reaction due to ion exchange groups can be suppressed in both the alkali stack 12 and the acid stack 13 only by providing the ion exchange resin layer 27 in the fuel tank 11.

Example 4
FIG. 4 shows an ion exchange resin layer 21 in the fuel tank shown in FIG. 3 for a fuel cell system that supplies liquid fuel to the alkali stack 12 and the acid stack 13 using two fuel pumps 15 from the fuel tank 11. Instead, it is a diagram showing a system installed in each fuel supply line 14. By adopting the configuration of the present embodiment, it is possible to extend the life of the system as in the fuel cell system shown in FIGS. Further, the ion exchange group removal efficiency is higher when the ion exchange resin layer is provided in each fuel supply line 14 than when the ion exchange resin layer is provided in the fuel tank as shown in FIG. Improvement can be expected.

(Example 5)
FIG. 5 is an example of another embodiment of the fuel cell system according to the present invention. In this fuel cell system, the fuel waste liquid discharged from the alkali stack 12 is separated into a gas part and a liquid part using a gas-liquid separator 28, and the gas part separated by the gas-liquid separator 28 is separated into a downstream acid stack. 13, the anion exchange groups eluted from the alkali stack 12 are prevented from being mixed into the acid stack 13.

  The fuel cell system of the present embodiment includes an alkali stack 12 in which single cells using an anion exchange type electrolyte membrane as a power generation unit are stacked, an acid stack 13 in which single cells using a proton exchange type electrolyte membrane are stacked, and an alkali stack. 12 and a fuel tank 11 for supplying liquid fuel to the acid stack 13 and recovering unreacted residual fuel, a fuel pump 15 for circulating and supplying the liquid fuel, and fuel exhaust liquid discharged from the alkali stack 12 as gas. Gas-liquid separator 28 for separating the gas part into a liquid part, a fuel exhaust gas supply line 29 for supplying the gas part separated by the gas-liquid separator 28 to the acid stack 13, and a liquid part separated by the gas-liquid separator 28 A blower for supplying air to the fuel drainage recovery line 16 for returning the fuel to the fuel tank 11, the alkali stack 12 and the acid stack 13 7, a fuel exhaust gas recovery line 31 for recovering the residual fuel discharged from the acid stack 13, a thermocouple 30 for measuring the temperature of the alkali stack 12, and a methanol concentration sensor 25 for detecting the methanol concentration in the fuel tank 11. The high concentration methanol for monitoring the water level sensor 26, the methanol concentration sensor 25 and the water level sensor 26 for monitoring the amount of liquid in the fuel tank 11 and supplying the high concentration methanol from the high concentration methanol cartridge 21 to the fuel tank 11 It has a monitor / control circuit 24 for performing system control such as controlling the operation / stop of the supply pump 22 and controlling the power generation amount of the alkali stack 12 and the acid stack 13.

  The fuel cell system of this embodiment is characterized in that a part of the liquid fuel is gasified and supplied to the acid stack 13. The temperature of the alkali stack 12 is measured using a thermocouple 30, and the acid stack 13 The temperature of the alkali stack 12 is controlled using a monitor / control circuit 24 so that methanol and water required for power generation can be gasified by the alkali stack 12. As a method for controlling the temperature, it is conceivable to change the power generation amount of the alkali stack 12 or change the concentration of methanol to be supplied. The measurement of the temperature of the alkali stack 12 is not limited to a thermocouple, and other temperature sensors can be used.

  Even in the configuration of the present embodiment, since harmful substances can be prevented from being mixed into each stack, it is possible to extend the life of the system as in the fuel cell systems shown in Embodiments 2 to 4.

  As the liquid fuel used in the fuel cell system of this embodiment, it is preferable to use a fuel having a boiling point lower than that of water in order to gasify the required amount of fuel and water in the alkaline stack 12. Examples of such fuel include ethanol (boiling point 78.4 ° C.) and 2-propanol (boiling point 82.4 ° C.) in addition to methanol (boiling point 64.6 ° C.).

  In Examples 1 to 5, a direct methanol fuel cell using methanol as a fuel has been described as an example. However, the present invention uses other liquid fuels such as a direct ethanol fuel cell using ethanol as a fuel. However, the present invention is not limited to a direct methanol fuel cell.

  The present invention relates to a fuel cell system that generates power using liquid fuel as a fuel, and is used in a fuel cell system that generates power using liquid fuel as a fuel, an electronic device equipped with a fuel cell that generates power using liquid fuel as a power source, and the like. it can.

DESCRIPTION OF SYMBOLS 11 Fuel tank 12 Alkali stack 13 Acid stack 14 Fuel supply line 15 Fuel pump 16, 31 Fuel exhaust liquid recovery line 17 Blower 18 Intake line 19, 20 Exhaust port 21 High concentration methanol cartridge 22 High concentration methanol supply pump 23 High concentration methanol supply Line 24 Monitor / control circuit 25 Methanol concentration sensor 26 Water level sensor 27 Ion exchange resin layer 28 Gas-liquid separator 29 Fuel exhaust gas supply line 30 Thermocouple

Claims (13)

An alkali stack in which a plurality of membrane electrode assemblies composed of an anion exchange electrolyte membrane, an anode and a cathode electrode arranged on both sides of the anion exchange electrolyte membrane are stacked, a proton exchange electrolyte membrane, and the proton exchange A fuel cell system comprising an acid stack in which a plurality of membrane electrode assemblies composed of an anode and a cathode arranged on both sides of a type electrolyte membrane are laminated,
A liquid fuel stored in a common fuel tank is circulated and supplied to the anode of the alkali stack and the acid stack,
A fuel cell characterized in that an exhaust port of the cathode of the acid stack and an intake port of the cathode of the alkaline stack are connected so that exhaust gas from the cathode of the acid stack is supplied to the cathode of the alkali stack. system.   2. The fuel cell system according to claim 1, further comprising an ion removing unit that removes an ion exchange group in either the fuel tank or a fuel supply line that supplies liquid fuel to the acid stack.   3. The fuel cell system according to claim 2, wherein the ion removing unit is an ion exchange resin.   2. The fuel cell system according to claim 1, further comprising an ion removing unit that removes an ion exchange group in a pipe connecting the exhaust port of the cathode of the acid stack and the intake port of the cathode of the alkali stack.   2. The fuel cell system according to claim 1, wherein a fuel discharge port of the anode of the alkali stack and a fuel supply port of the anode of the acid stack are connected to supply the fuel discharged from the alkali stack to the acid stack.   6. The fuel cell system according to claim 5, further comprising an ion removing unit that removes an ion exchange group in a fuel supply line connecting the fuel discharge port of the alkali stack and the fuel supply port of the acid stack.   6. The gas stack according to claim 5, further comprising a gas-liquid separator in a fuel supply line connecting the fuel discharge port of the alkali stack and the fuel supply port of the acid stack, and the gas component separated by the gas-liquid separator is supplied to the acid stack. The fuel cell system is characterized in that the liquid component separated by the gas-liquid separator is returned to the fuel tank.   8. The fuel cell system according to claim 7, wherein the alkaline stack performs power generation at a temperature at which a predetermined amount of liquid fuel and water are gasified.   9. The fuel cell system according to claim 8, wherein a temperature of the alkaline stack is controlled by adjusting a power generation amount of the alkaline stack or a concentration of liquid fuel supplied to the alkaline stack.   8. The fuel cell system according to claim 7, further comprising an ion removing unit that removes an ion exchange group in at least one of the fuel tank and the line that circulates and supplies the liquid fuel.   2. The line according to claim 1, wherein a line for circulating liquid fuel from the fuel tank to the alkaline stack and a line for circulating liquid fuel from the fuel tank to the acid stack are separately provided. Fuel cell system.   12. The fuel cell system according to claim 11, further comprising an ion removing unit that removes ion exchange groups in the fuel tank.   12. The fuel cell system according to claim 11, further comprising an ion removing unit that removes ion exchange groups in a fuel supply line that supplies liquid fuel from the fuel tank to the acid stack.