JP7036318B2 - Ammonia decomposition method and fuel cell system - Google Patents

Description

The present invention relates to an ammonia decomposition method and a fuel cell system, and more particularly, an ammonia decomposition method effective for decomposing ammonia contained in a liquid fuel circulating in a fuel cell system, and a fuel using the ammonia decomposition method. Regarding the battery system.

Conventionally, ammonia may be generated from various devices that consume nitrogen compounds, such as fuel cells that use hydrazine as a liquid fuel. From the viewpoint of the global environment, such ammonia is usually required to be detoxified before being released into the atmosphere.

As a method for treating ammonia, for example, a method of decomposing ammonia into nitrogen and hydrogen using a plasma reactor is known.

More specifically, for example, a pair of electrodes are placed facing each other in an aqueous hydrazine solution containing ammonia at a concentration of 0.001 to 1 mol% (that is, 0.0014 to 1.4% by mass). The electrode is energized and the hydrazine aqueous solution is boiled in the vicinity of the electrode to generate a gas phase between the electrodes, and plasma is generated in the gas phase under the condition that insulation failure occurs in the gas phase, and the hydrazine aqueous solution contains the hydrazine aqueous solution. A method for decomposing ammonia has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-148745

On the other hand, when ammonia is decomposed in an aqueous solution of hydrazine, not only ammonia but also hydrazine may be decomposed, and as a result, nitrogen oxides and the like may be generated, which may require further purification treatment.

The present invention is an ammonia decomposition method capable of suppressing the decomposition of hydrazine and efficiently decomposing ammonia, and a fuel cell system using the ammonia decomposition method.

The present invention [1] comprises a concentration step of adjusting the ammonia concentration of the hydrazine aqueous solution to 2.0% by mass or more by concentrating the hydrazine aqueous solution containing ammonia, and arranging a pair of electrodes facing each other in the hydrazine aqueous solution. In the preparatory step, the electrode is energized and the hydrazine aqueous solution is boiled in the vicinity of the electrode to generate a gas phase between the electrodes, and plasma is generated in the gas phase under the condition that insulation failure occurs in the gas phase. The present invention comprises a method for decomposing ammonia, which comprises a decomposing step of decomposing ammonia contained in the aqueous hydrazine solution.

The present invention [2] is a fuel cell system capable of decomposing ammonia by the ammonia decomposition method according to the above [1], wherein a fuel cell to which a liquid fuel containing hydrazine is supplied and a fuel in which the liquid fuel is stored are stored. The tank, the fuel supply path for supplying liquid fuel from the fuel tank to the fuel cell, the fuel discharge path for discharging the discharge liquid from the fuel cell, and the discharge liquid being transported from the fuel discharge path to the fuel tank. A gas-liquid separator interposed between the fuel discharge path and the return path, a water separation means interposed in the return path for separating water from the liquid fuel, and the fuel tank. It comprises a fuel cell system comprising a pair of electrodes arranged opposed therein and a plasma generator comprising a power source for energizing the electrodes.

In the ammonia decomposition method and the fuel cell system of the present invention, first, the ammonia concentration in the hydrazine aqueous solution (liquid fuel) containing ammonia is adjusted to 2.0% by mass or more, and then the hydrazine aqueous solution (liquid fuel) is energized. As a result, a gas phase (bubbles) is generated in the hydrazine aqueous solution, and plasma is generated in the gas phase under the condition that the insulation is destroyed by the gas phase (bubbles).

As a result, ammonia in the hydrazine aqueous solution can be efficiently decomposed while suppressing the decomposition of hydrazine.

FIG. 1 is a schematic view of an ammonia decomposition apparatus used for carrying out one embodiment of the ammonia decomposition method of the present invention. FIG. 2 is a schematic diagram of a fuel cell system in which the ammonia decomposition apparatus shown in FIG. 1 is used. FIG. 3 is a schematic configuration diagram showing a concentrator mounted on the fuel cell system shown in FIG. 2.

1. 1. Ammonia decomposition method and ammonia decomposition device In the ammonia decomposition method of the present invention, as will be described in detail later, ammonia is generated by generating plasma in a hydrazine aqueous solution containing ammonia after adjusting the concentration of ammonia in the hydrazine aqueous solution. (NH ₃ , NH ₄ ⁺ ) is decomposed into nitrogen (N ₂ ) and hydrogen (H ₂ ).

The hydrazine aqueous solution is an aqueous solution of hydrazine and contains hydrazine, water and ammonia.

Examples of hydrazine include anhydrous hydrazine (NH ₂ NH ₂ ), hydrated hydrazine (NH ₂ NH ₂ · H ₂ O), carbonated hydrazine ((NH ₂ NH ₂ ) ₂ CO ₂ ), and hydrazine sulfate (NH ₂ NH ₂ ). -H ₂ SO ₄ ), monomethylhydrazine (CH ₃ NHNH ₂ ), dimethylhydrazine ((CH ₃ ) ₂ NNH ₂ , CH ₃ NHNHCH ₃ ), carboxylic hydrazine ((NHNH ₂ ) ₂ CO) and the like. These hydrazines can be used alone or in combination of two or more. Preferred examples of hydrazine include anhydrous hydrazine (NH ₂ NH ₂ ) and hydrated hydrazine (NH ₂ NH ₂ · H ₂ O).

In the hydrazine aqueous solution containing ammonia, the concentration of hydrazine (concentration before concentration described later) is not particularly limited, but is, for example, 1.0% by mass or more, preferably 2.0% by mass, based on the total amount of the hydrazine aqueous solution. % Or more, for example, 20.0% by mass or less, preferably 15.0% by mass or less.

Further, in the hydrazine aqueous solution containing ammonia, the concentration of ammonia (concentration before concentration described later) is, for example, 0.001% by mass or more, preferably 0.01% by mass or more, based on the total amount of the hydrazine aqueous solution. Yes, for example, less than 2.0% by mass, preferably 1.5% by mass or less, more preferably 1.4% by mass or less, still more preferably 0.14% by mass or less.

Further, a known additive (alkali metal hydroxide such as sodium hydroxide or potassium hydroxide) may be added to the hydrazine aqueous solution at an appropriate ratio, if necessary.

Such an aqueous solution of hydrazine containing ammonia is treated by, for example, the ammonia decomposition apparatus 50 shown in FIG.

In FIG. 1, the ammonia decomposition device 50 includes a concentration device 51, a plasma reaction vessel 52, and a plasma generator 53.

The concentrator 51 includes a storage tank 54 for accumulating the hydrazine aqueous solution, a water separation pipe 55 arranged so as to pass through the storage tank 54, and a blower 56 for supplying air into the water separation pipe 55. It is provided with a concentrate transport line 57 as a transport route for transporting the hydrazine aqueous solution from the storage tank 54 to the plasma reaction vessel 52.

The storage tank 54 is a closed container capable of storing the hydrazine aqueous solution, and is made of a material resistant to the hydrazine aqueous solution. An aqueous solution of hydrazine containing ammonia is stored inside the storage tank 54.

Further, although not shown, the storage tank 54 is provided with an ammonia densitometer capable of measuring the ammonia concentration in the hydrazine aqueous solution.

The water separation pipe 55 includes, for example, a hollow fiber (hollow fiber membrane) made of a water separation membrane.

The water separation membrane is a membrane that allows water to permeate while blocking ammonia and hydrazine, and is, for example, a carbon membrane, a hydrophobic porous membrane (for example, a polytetrafluoroethylene porous membrane, a polyethylene porous membrane, a polypropylene porous membrane). Membrane, etc.). The pore size of the water separation membrane is not particularly limited, and is appropriately set within a range that blocks ammonia and hydrazine and allows water to permeate.

The inner diameter of the hollow fiber (hollow fiber membrane) made of a water separation membrane is, for example, 200 μm or more, preferably 250 μm or more, and for example, 900 μm or less, preferably 850 μm or less.

Although not shown in FIG. 1, the water separation tube 55 is preferably formed as a bundle of hollow fibers (hollow fiber membranes) made of a water separation membrane. Specifically, by bundling a plurality of (for example, 500 to 2500) hollow fibers made of a water separation membrane, a collecting tubular water separation tube 55 can be obtained.

The water separation pipe 55 is arranged so as to pass through the storage tank 54, and is immersed in a hydrazine aqueous solution containing ammonia.

The blower 56 includes a blower pump 58 and a blower line 59, and can supply air to the blower line 59 by driving the blower pump 58.

The water separation pipe 55 is arranged in the middle of the flow direction of the blower line 59 so as to intervene in the blower line 59. As a result, air can be supplied from the blower pump 58 to the water separation pipe 55 via the blower line 59.

The concentrated liquid transport line 57 has an upstream end connected to a storage tank 54 and a downstream end connected to a plasma reaction vessel 52 described later.

Further, an on-off valve 60 is provided in the middle of the flow direction of the concentrated liquid transport line 57.

The on-off valve 60 is a valve for opening and closing the concentrated liquid transport line 57, and a known on-off valve such as a solenoid valve is used. By opening and closing the on-off valve 60 in this way, the hydrazine aqueous solution in the storage tank 54 can be transported to the plasma reaction vessel 52 at an arbitrary timing.

The plasma reaction vessel 52 is a heat-resistant and pressure-resistant vessel that can be sealed, and is made of a material that is stable against an aqueous hydrazine solution containing ammonia. The shape and size of the plasma reaction vessel 52 are not particularly limited, and are appropriately set according to the purpose and application.

The plasma generator 53 includes a power supply 61 and a pair of electrodes 62.

The power supply 61 is not particularly limited as long as it can energize the electrode 62 to generate plasma in the hydrazine aqueous solution, and examples thereof include known pulse power supplies. The pulse power supply is usually adjustable in pulse voltage, pulse width and pulse repetition frequency to any value and is electrically connected to a pair of electrodes 62 via wiring.

The pair of electrodes 62 are formed in, for example, a plate shape, a rod shape, or the like. In FIG. 1, the electrode 62 is formed in a rod shape. Examples of the electrode material forming the electrode 62 include nickel, copper, stainless steel, tungsten and the like, and preferably tungsten. Further, the pair of electrodes 62 are fixed to the plasma reaction vessel 52 so as to penetrate the peripheral side surface of the plasma reaction vessel 52, and are separated from each other by a predetermined distance so that the end faces face each other in the plasma reaction vessel 52. Are arranged facing each other.

The distance between the end faces of the pair of electrodes 62 is, for example, 0.5 mm or more, preferably 0.8 mm or more, and for example, 1.5 mm or less, preferably 1.2 mm or less.

The cross-sectional shape of the electrodes 62 (that is, the shape of the facing surfaces of the pair of electrodes 62) is not particularly limited, but various shapes such as a substantially circular cross-sectional view and a substantially square cross-sectional view are adopted. .. As the cross-sectional shape of the electrode 62, a substantially circular shape in cross-sectional view is preferable.

The size of the electrode 62 is, for example, when the electrode 62 has a substantially circular shape in cross section, its diameter (that is, the diameter of the facing surface of the pair of electrodes 62) is 0.1 mm or more, preferably 0.2 mm or more. It is 1.0 mm. Further, for example, when the electrode 62 has a substantially quadrangular cross-sectional view, the length of one side thereof (that is, the length of one side of the facing surface of the pair of electrodes 62) is 0.1 mm or more, preferably 0. It is 2 mm or more and 1.0 mm.

Further, the cross-sectional area of the electrodes 62 (that is, the area of the facing surfaces of the pair of electrodes 62) is 0.007 mm ² or more, preferably 0.03 mm ² or more, for example, 1 mm ² or less, preferably 0. It is 8.8 mm ² or less.

When the size of the electrode 62 is within the above range, a gas phase (bubbles) can be satisfactorily generated in the hydrazine aqueous solution containing ammonia, and dielectric breakdown due to the gas phase (bubbles) can be caused in the solution.

Hereinafter, the plasma decomposition method using the ammonia decomposition device 50 will be described in detail.

In this method, first, the hydrazine aqueous solution containing ammonia is concentrated by the concentrating device 51, whereby the ammonia concentration of the hydrazine aqueous solution is adjusted (concentration step).

More specifically, in this step, in the concentrator 51, the hydrazine aqueous solution is stored in the storage tank 54, and the water separation pipe 55 is immersed in the hydrazine aqueous solution.

In such a state, when the blower pump 58 of the blower 56 is driven and air is supplied to the water separation tube 55 (hollow fiber membrane) via the blower line 59, the water contained in the hydrazine aqueous solution around the water separation tube 55 is contained. Is steamed, and the steam passes through the hollow fiber membrane of the water separation tube 55.

As a result, water is introduced into the water separation pipe 55, while hydrazine and ammonia are not vaporized and remain in the storage tank 54. The water vapor introduced into the water separation pipe 55 is discharged while being mixed with air.

As a result, a part of water is separated from the hydrazine aqueous solution, and ammonia and hydrazine are concentrated.

In this method, preferably, the ammonia concentration of the hydrazine aqueous solution in the storage tank 54 is monitored by an ammonia concentration meter (not shown), and the hydrazine aqueous solution is concentrated by the above method until the predetermined ammonia concentration is reached.

The ammonia concentration after concentration is higher than the ammonia concentration before concentration, and is 2.0% by mass or more, preferably 2.5% by mass or more, more preferably 3.0% by mass, based on the total amount of the hydrazine aqueous solution. The above is more preferably 3.5% by mass or more, further preferably 4.0% by mass or more, still more preferably 4.5% by mass or more, and particularly preferably 5.0% by mass or more, and is usually used. It is 20.0% by mass or less, preferably 10.0% by mass or less.

The concentration of hydrazine after concentration is not particularly limited, but is higher than the concentration of hydrazine before concentration, for example, 2.0% by mass or more, preferably 5.0% by mass or more, for example, 25. It is 0% by mass or less, preferably 20.0% by mass or less.

Then, in this step, the hydrazine aqueous solution enriched with ammonia is transported from the storage tank 54 to the plasma reaction vessel 52 via the concentrated liquid transport line 57 by opening the on-off valve 60 of the concentrated liquid transport line 57. do.

As a result, the hydrazine aqueous solution (ammonia concentrate) containing ammonia is stored in the plasma reaction vessel 52.

Next, in this method, a pair of electrodes 62 are arranged to face each other in an aqueous solution of hydrazine (ammonia concentrate) containing ammonia (preparation step).

That is, the hydrazine aqueous solution containing ammonia is transported into the plasma reaction vessel 52 in which the electrodes 62 are arranged to face each other, so that the pair of electrodes 62 are arranged to face each other in the hydrazine aqueous solution.

Next, in this method, the electrode 62 is energized and the hydrazine aqueous solution is boiled in the vicinity of the electrode 62 to generate a gas phase (air bubbles) between the electrodes 62, and insulation destruction due to the gas phase (air bubbles) occurs in the solution. Under the conditions, plasma is generated in the gas phase (air bubbles) to decompose the ammonia contained in the hydrazine aqueous solution (decomposition step).

Specifically, the following are conditions for generating a gas phase (bubbles) due to boiling in an aqueous solution of hydrazine containing ammonia in the decomposition step and causing dielectric breakdown due to the gas phase (bubbles) in the solution. Satisfaction of at least one or more of the conditions (a) to (c) can be mentioned.

(A) Electrode size The size of the pair of electrodes 62 is within the above range. Specifically, when the electrode 62 has a substantially circular shape in cross section, its diameter (that is, the diameter of the facing surfaces of the pair of electrodes 62) is set to, for example, 0.1 mm or more, preferably 0.2 mm or more. Also, for example, it is set to 1.0 mm or less.

When the size of the electrode 62 is within the above range, a gas phase (bubble) can be more reliably generated in the hydrazine aqueous solution containing ammonia, and dielectric breakdown due to the gas phase (bubble) can be caused in the solution. Therefore, ammonia in the hydrazine aqueous solution can be reliably decomposed.

(B) Frequency Of the energization conditions by the electrode 62 (pulse power supply), the pulse repetition frequency is adjusted to an appropriate range.

Specifically, the repetition frequency of the pulse is, for example, 20 kHz or more, for example, 300 kHz or less, preferably 100 kHz or less, and more preferably 50 kHz or less.

When the repetition frequency of the pulse is in the above range, a gas phase (bubble) can be more reliably generated in the hydrazine aqueous solution containing ammonia, and insulation destruction due to the gas phase (bubble) can be caused in the solution. Therefore, ammonia in the hydrazine aqueous solution can be reliably decomposed.

(C) Conductance of the solution The conductance (easiness of current flow) of the hydrazine aqueous solution containing ammonia is adjusted to an appropriate range.

Specifically, the conductance of the aqueous solution of hydrazine containing ammonia is, for example, 0.01 S / m or more, preferably 0.05 S / m or more, and for example, 10 S / m or less, preferably 5 S / m or less. Is.

If the conductance of the aqueous solution of hydrazine containing ammonia is within the above range, a gas phase (bubble) is more reliably generated in the aqueous solution of hydrazine containing ammonia, and insulation destruction due to the gas phase (bubble) is caused in the solution. Can be done. Therefore, ammonia in the hydrazine aqueous solution can be reliably decomposed.

The method for adjusting the conductance is not particularly limited, and a known method can be adopted. Specifically, for example, a known additive such as an acid or an alkali is added to improve the conductivity of the solution. Examples thereof include a method of allowing the solution to be removed, and a method of removing ions in the solution with an ion adsorbing resin or the like to reduce the conductivity.

Further, in this ammonia decomposition method, it is sufficient that at least one or more of the above conditions (a) to (c) are satisfied, but preferably all of the above conditions (a) to (c) are satisfied. Meet is mentioned. If all of the above conditions (a) to (c) are satisfied, a gas phase (bubbles) is generated in the hydrazine aqueous solution containing ammonia, and dielectric breakdown due to the gas phase (bubbles) occurs in the solution. Can be made to. Therefore, ammonia in the hydrazine aqueous solution can be reliably decomposed.

The conditions other than the above (a) to (c) are not particularly limited and are appropriately set according to the purpose and application.

Specifically, the amount of the hydrazine aqueous solution containing ammonia is, for example, 10 mL or more, preferably 20 mL or more, and for example, 100 L or less, preferably 50 L or less.

Further, among the energization conditions by the electrode 62 (pulse power supply), the pulse voltage is, for example, 1 kV or more, preferably 3 kV or more, and for example, 20 kV or less, preferably 15 kV or less.

The pulse width is, for example, 0.1 μs or more, preferably 1 μs or more, and for example, 10 μs or less, preferably 5 μs or less.

The irradiation time (energization time) is, for example, 5 minutes or more, preferably 30 minutes or more, and for example, 6 hours or less, preferably 2 hours or less.

Then, by energizing under such conditions, the hydrazine aqueous solution containing ammonia boils, a gas phase (bubbles) is generated in the solution, and insulation destruction due to the gas phase (bubbles) occurs in the solution. At this time, the ammonia in the hydrazine aqueous solution moves into the gas phase (bubbles) and is gasified (ammonia gasification).

In such a state, since the hydrazine aqueous solution containing ammonia is energized by the plasma generator 53, the ammonia gas in the gas phase (bubbles) is plasma-treated and decomposed into nitrogen and hydrogen.

That is, in such an ammonia decomposition method, a gas phase (bubbles) is generated in the solution by energization, and plasma is generated in the gas phase (bubbles) under the condition that dielectric breakdown in the gas phase is caused in the solution. .. At this time, the ammonia contained in the solution moves into the gas phase (bubbles), and the ammonia is decomposed in the gas phase (bubbles).

According to such an ammonia decomposition method, ammonia can be decomposed efficiently at low cost in an aqueous hydrazine solution containing ammonia.

Further, by satisfying at least one of the above-mentioned conditions (a) to (c), it is possible to surely cause dielectric breakdown in the hydrazine aqueous solution containing ammonia. .. Therefore, ammonia in the hydrazine aqueous solution can be reliably decomposed.

In particular, in the above-mentioned ammonia decomposition method, first, the ammonia concentration in the hydrazine aqueous solution containing ammonia is adjusted to 2.0% by mass or more, and then the gas phase (bubbles) is contained in the hydrazine aqueous solution by energizing the hydrazine aqueous solution. ) Is generated, and plasma is generated in the gas phase under the condition that the insulation is destroyed by the gas phase (air bubbles).

In other words, when plasma is generated, the ammonia concentration in the hydrazine aqueous solution is adjusted to 2.0% by mass or more.

As a result, ammonia in the hydrazine aqueous solution can be efficiently decomposed while suppressing the decomposition of hydrazine.

In the above-mentioned ammonia decomposition method and ammonia decomposition apparatus, water is separated from the hydrazine aqueous solution by a water separation membrane and a blower to concentrate ammonia, but the concentration method in the concentration step is not particularly limited, and a known method is adopted. can do.

Therefore, such an ammonia decomposition method can be used in various industrial fields, and can be particularly preferably used in a fuel cell using hydrazine as a liquid fuel.

2. 2. Overall Configuration of Fuel Cell System In FIG. 2, the electric vehicle 1 is a hybrid vehicle that selectively uses a fuel cell and a battery as a power source, and is equipped with the fuel cell system 2.

The fuel cell system 2 is a fuel cell system capable of decomposing ammonia by the above-mentioned ammonia decomposition method. The fuel cell system 2 includes a fuel cell 3, a fuel supply / discharge unit 4, an air supply / discharge unit 5, an ammonia decomposition device 50, a control unit 6, and a power unit 7.

(1) Fuel Cell The fuel cell 3 is, for example, an anion exchange type fuel cell or a cation exchange type fuel cell in which liquid fuel is directly supplied and discharged, and is arranged on the lower center side of the electric vehicle 1. Examples of the liquid fuel include liquid fuels containing hydrazine as a fuel compound, and specific examples thereof include an aqueous solution of hydrazine. Further, a known additive (alkali metal hydroxide such as sodium hydroxide or potassium hydroxide) may be added to the liquid fuel in an appropriate ratio, if necessary.

In the following, the liquid fuel supplied to the fuel cell 3 is the supply liquid, while the liquid fuel discharged from the fuel cell 3 (reaction products of the liquid fuel supplied to the fuel cell 3 (nitrogen gas, ammonia, etc.)). And the reaction-generated water) as the discharge liquid, and distinguish them from each other.

In the fuel cell 3, the unit cell 28 (fuel cell) having the electrolyte layer 8, the anode 9 arranged on one side of the electrolyte layer 8, and the cathode 10 arranged on the other side of the electrolyte layer 8 is a separator. It is formed in a stack structure in which a plurality of layers are stacked via (not shown). That is, a plurality of unit cells 28 in which the anode 9 and the cathode 10 are arranged to face each other via the electrolyte layer 8 are stacked. Note that, in FIG. 2, among the plurality of stacked unit cells 28, only the unit cell 28 arranged in the middle of the front-rear direction of the electric vehicle 1 is shown in an enlarged manner, and the other unit cells 28 are simplified and described. ing.

The electrolyte layer 8 is, for example, a layer on which an anion component or a cation component can move, and is formed by using an anion exchange membrane or a cation exchange membrane. The electrolyte layer 8 is preferably formed using an anion exchange membrane.

The anode 9 has an anode electrode 11 as a fuel side electrode and a fuel supply member 12 for supplying a liquid fuel (supply liquid) to the anode electrode 11.

The anode electrode 11 is formed on one surface of the electrolyte layer 8. Examples of the electrode material of the anode electrode 11 include a porous carrier on which a catalyst is supported (catalyst-supported porous carrier) and the like.

The fuel supply member 12 is also used as a separator and is made of a gas-impermeable conductive member. The fuel supply member 12 is formed with a knot-shaped groove recessed from the surface thereof. The surface of the fuel supply member 12 in which the groove is formed is in direct contact with the anode electrode 11. As a result, between one surface of the anode electrode 11 and the other surface of the fuel supply member 12 (the surface on which the groove is formed), a fuel supply path for bringing the liquid fuel (supply liquid) into contact with the entire anode electrode 11 13 is formed.

In the fuel supply path 13, a fuel supply port 15 for allowing the liquid fuel (supply liquid) to flow into the anode 9 is formed on one end side (lower side), and the liquid fuel (discharge liquid) is discharged from the anode 9. The fuel discharge port 14 of the above is formed on the other end side (upper side).

The cathode 10 has a cathode electrode 16 as an oxygen side electrode and an air supply member 17 for supplying air (oxygen) to the cathode electrode 16.

The cathode electrode 16 is formed on the other surface of the electrolyte layer 8.

Examples of the electrode material of the cathode electrode 16 include a catalyst-supported porous carrier exemplified as the electrode material of the anode electrode 11.

The air supply member 17 is also used as a separator and is made of a gas-impermeable conductive member. The air supply member 17 is formed with a knot-shaped groove recessed from the surface thereof. The surface of the air supply member 17 in which the groove is formed is in direct contact with the cathode electrode 16. As a result, an air supply path 18 for bringing air into contact with the entire cathode electrode 16 is formed between the other surface of the cathode electrode 16 and one surface of the air supply member 17 (the surface on which the groove is formed). ..

In the air supply path 18, an air supply port 19 for allowing air to flow into the cathode 10 is formed on the other end side (upper side), and an air discharge port 20 for discharging air from the cathode 10 is formed on one end side (lower side). Is formed on the side).

Further, in such a fuel cell 3, one separator that separates a plurality of unit cells 28 each has the fuel supply member 12 and the air supply member 17. In other words, the separator acts as a fuel supply member 12 on one side thereof and as an air supply member 17 on the other side.

(2) Fuel supply / discharge section The fuel supply / discharge section 4 includes a high-concentration fuel tank 22 for storing a liquid fuel containing a high concentration of hydrazine (high-concentration liquid fuel), a high-concentration fuel tank 22, and a fuel cell 3. A circulating fuel tank 47 as a fuel tank arranged between the two, and a high-concentration fuel supply line 45 for supplying liquid fuel (primary (high-concentration) supply liquid) from the high-concentration fuel tank 22 to the circulating fuel tank 47. A fuel supply line 30 as a fuel supply path for supplying a supply liquid (secondary (low concentration) supply liquid) from the circulating fuel tank 47 to the fuel cell 3 (specifically, the fuel supply path 13), and the fuel cell 3 (specifically, the fuel cell 3 (specifically, the fuel supply line 13). Specifically, a fuel discharge line 31 as a fuel discharge path for discharging the discharge liquid from the fuel supply path 13) and a return line 32 as a return path for transporting the discharge liquid from the fuel discharge line 31 to the circulating fuel tank 47. It is equipped with.

A fuel cell 3 is interposed between the fuel supply line 30 and the fuel discharge line 31, and a gas-liquid separator 23 (described later) is located between the fuel discharge line 31 and the recirculation line 32. Is intervening.

The high-concentration fuel tank 22 is arranged behind the fuel cell 3 and behind the electric vehicle 1. The high-concentration fuel tank 22 stores a high-concentration aqueous solution of hydrazine as a liquid fuel.

The upstream end of the high-concentration fuel supply line 45 is connected to the high-concentration fuel tank 22, and the downstream end of the high-concentration fuel supply line 45 is connected to the circulating fuel tank 47.

Further, the high concentration fuel supply line 45 is provided with a first supply pump 33 and a fuel supply valve 34.

As the first supply pump 33, a known liquid feed pump such as a rotary pump such as a rotary pump or a gear pump, a reciprocating pump such as a piston pump or a diaphragm pump is used. The first supply pump 33 is electrically connected to the control unit 29 (described later) (see the broken line in FIG. 2). As a result, the control signal from the control unit 29 (described later) is input to the first supply pump 33, and the control unit 29 (described later) controls the drive and stop of the first supply pump 33.

Further, the fuel supply valve 34 is a valve for opening and closing the high-concentration fuel supply line 45, and a known on-off valve such as a solenoid valve is used. Further, the fuel supply valve 34 is electrically connected to the control unit 29 (described later) (see the broken line in FIG. 2). As a result, the control signal from the control unit 29 (described later) is input to the fuel supply valve 34, and the control unit 29 (described later) controls the opening and closing of the fuel supply valve 34.

By driving the first supply pump 33 and opening and closing the fuel supply valve 34, the liquid fuel (primary (high concentration) supply liquid) is supplied to the high concentration fuel tank 22 via the high concentration fuel supply line 45. Is supplied to the circulating fuel tank 47.

The circulating fuel tank 47 is a tank for storing liquid fuel, and is made of a material resistant to the above-mentioned liquid fuel.

A downstream end of the recirculation line 32 (described later) is connected to the circulating fuel tank 47, and the discharged liquid is supplied via the recirculation line 32, which will be described in detail later. As a result, in the circulating fuel tank 47, the liquid fuel (primary supply liquid) transported from the high-concentration fuel tank 22 and the discharged liquid discharged from the fuel cell 3 are mixed at an appropriate ratio, and the fuel cell 3 is mixed. The concentration of the liquid fuel (secondary supply liquid) supplied to the vehicle is adjusted.

The upstream end of the fuel supply line 30 is connected to the circulating fuel tank 47, and the downstream end of the fuel supply line 30 is connected to the fuel cell 3 (specifically, the fuel supply path 13 of the anode 9). There is.

Further, the fuel supply line 30 is provided with a second supply pump 35.

As the second supply pump 35, the above-mentioned known liquid feeding pump is used. The second supply pump 35 is electrically connected to the control unit 29 (described later) (see the broken line in FIG. 2). As a result, the control signal from the control unit 29 (described later) is input to the second supply pump 35, and the control unit 29 (described later) controls the drive and stop of the second supply pump 35.

By driving the second supply pump 35 in this way, the liquid fuel (secondary (low concentration) supply liquid) containing hydrazine at a relatively low concentration is supplied from the circulating fuel tank 47 to the fuel cell 3 via the fuel supply line 30. Is supplied to.

The upstream end of the fuel discharge line 31 is connected to the fuel cell 3 (specifically, the fuel supply path 13 of the anode 9), and the downstream end is connected to the gas-liquid separator 23. ing.

Through such a fuel discharge line 31, the discharge liquid is discharged from the fuel cell 3 and transported to the gas-liquid separator 23.

The gas-liquid separator 23 is composed of, for example, a hollow container, and two bottom flow ports 24 for circulating the inside and outside of the gas-liquid separator 23 are formed below the hollow container.

Further, on the upper part of the gas-liquid separator 23, one upper distribution port 25 for circulating the inside and outside of the gas-liquid separator 23 is formed.

In the gas-liquid separator 23, the two bottom flow ports 24 are located rearward in the front-rear direction of the electric vehicle 1 and above the vertical direction of the electric vehicle 1 with respect to the fuel cell 3, respectively. It is connected to (described later).

A gas discharge pipe 26 for discharging the gas (gas) separated by the gas-liquid separator 23 is connected to the upper distribution port 25. The gas discharge pipe 26 is connected to the upper distribution port 25. Further, a gas discharge valve 27 is provided in the middle of the gas discharge pipe 26.

The gas discharge valve 27 is a valve for opening the gas discharge pipe 26 to release the pressure in the gas-liquid separator 23, and a known on-off valve such as a solenoid valve is used. The gas discharge valve 27 is electrically connected to the control unit 29 (described later) (see the broken line in FIG. 2). As a result, a control signal from the control unit 29 (described later) is input to the gas discharge valve 27, and the control unit 29 (described later) controls the opening and closing of the gas discharge valve 27.

The upstream end of the reflux line 32 is connected to the gas-liquid separator 23, and the downstream end of the recirculation line 32 is connected to the upper wall of the circulating fuel tank 47.

As a result, the discharged liquid transported in the fuel discharge line 31 is transported to the circulating fuel tank 47 via the gas-liquid separator 23 and the reflux line 32, and further via the storage tank 54 described later. Then, in the circulating fuel tank 47, the liquid fuel (primary supply liquid) transported from the high-concentration fuel tank 22 is mixed, the concentration is adjusted, and then the fuel cell 3 is used as the supply liquid (secondary supply liquid). By returning, a closed line (closed flow path) that circulates through the anode 9 is formed. That is, the circulating fuel tank 47, the fuel supply line 30, the fuel supply line 13, the fuel discharge line 31, the gas-liquid separator 23, the reflux line 32, and the storage tank 54 (described later) form a closed line (closed flow path). ..

(3) Air supply / discharge section The air supply / discharge section 5 has an air supply line 41 for supplying air to the fuel cell 3 (cathode 10) and an air discharge for discharging the air discharged from the cathode 10 to the outside. It is equipped with a line 42.

One end side (upstream side) of the air supply line 41 is open to the atmosphere, and the other end side (downstream side) is connected to the air supply port 19. An air supply pump 43 is interposed in the middle of the air supply line 41, and an air supply valve 44 is provided on the downstream side thereof.

Further, the air supply pump 43 is electrically connected to the control unit 29 (described later), a control signal from the control unit 29 (described later) is input to the air supply pump 43, and the control unit 29 (described later) receives the control signal. , Controls the drive and stop of the air supply pump 43.

The air supply valve 44 is a valve for opening and closing the air supply line 41, and a known on-off valve such as a solenoid valve is used.

Further, each of the air supply valves 44 is electrically connected to the control unit 29 (described later), and a control signal from the control unit 29 (described later) is input to the air supply valve 44 to be input to the control unit 29 (described later). ) Controls the opening and closing of the air supply valve 44.

Further, as will be described later, the air supply line 41 is arranged so as to pass through the storage tank 54 (described later) on the downstream side of the air supply pump 43 and the air supply valve 44.

One end side (upstream side) of the air discharge line 42 is connected to the air discharge port 20, and the other end side (downstream side) is a drain.

(4) Ammonia Decomposition Device The ammonia decomposition device 50 is provided in the fuel cell system 2 for decomposing ammonia in the liquid fuel (that is, the hydrazine aqueous solution).

The ammonia decomposition device 50 is interposed in the recirculation line 32, and includes a concentration device 51 as a water separation means for separating water from the liquid fuel, and a plasma generator 53 for generating plasma in the circulating fuel tank 47. I have.

As shown in FIG. 3, the concentrator 51 has a storage tank 54 for accumulating liquid fuel and a water separation pipe 55 interposed in the air supply line 41 and arranged so as to pass through the storage tank 54. I have.

The storage tank 54 is the same as the storage tank 54 of the ammonia decomposition apparatus 50 shown in FIG. 1, is a closed container capable of retaining liquid fuel, and is made of a material resistant to the liquid fuel described above.

Further, in the fuel cell system 2, the storage tank 54 is interposed in the reflux line 32 as shown in FIG. Specifically, the reflux line 32 is divided by the storage tank 54. Further, the reflux line 32 is connected to the upper wall of the storage tank 54, and the reflux line 32 is also connected to the bottom wall of the storage tank 54. Liquid fuel is temporarily retained in such a storage tank 54 by the operation of the fuel cell system 2.

The water separation pipe 55 is the same as the water separation pipe 55 of the ammonia decomposition apparatus 50 shown in FIG. 1, and includes a hollow fiber (hollow fiber membrane) made of a water separation membrane. Preferably, it is formed as a bundle of hollow fibers (hollow fiber membranes) made of a water separation membrane. Specifically, by bundling a plurality of (for example, 500 to 2500) hollow fibers made of a water separation membrane, a collecting tubular water separation tube 55 can be obtained.

The water separation pipe 55 is arranged in the storage tank 54 so as to be interposed in the air supply line 41 (see the thick broken line in FIG. 3).

More specifically, the water separation pipe 55 is arranged singularly or plurally (one in FIG. 3) in the storage tank 54, and is immersed in a liquid fuel (not shown).

Further, in the ammonia decomposition apparatus 50, the circulation line 32 is also used as the concentrated liquid transport line 57 shown in FIG. 1 on the downstream side of the storage tank 54.

An on-off valve 60 is provided on the downstream side of the storage tank 54 in the middle of the flow direction of the circulation line 32 (concentrate transport line 57).

The on-off valve 60 is a valve for opening and closing the concentrated liquid transport line 57, and a known on-off valve such as a solenoid valve is used. Further, the on-off valve 60 is electrically connected to the control unit 29 (described later) (see the broken line in FIG. 2). As a result, the control signal from the control unit 29 (described later) is input to the on-off valve 60, and the control unit 29 (described later) controls the opening and closing of the on-off valve 60.

Further, although not shown, the storage tank 54 is provided with an ammonia concentration meter capable of measuring the ammonia concentration of the liquid fuel (hydrazine aqueous solution) in the storage tank 54, and monitors the ammonia concentration in the storage tank 54. It is possible, and the ammonia concentration can be input to the control unit 29.

The plasma generator 53 includes a pair of electrodes 62 arranged to face each other in the circulating fuel tank 47, and a power supply 61 for energizing each electrode 62.

The pair of electrodes 62 is the same as the pair of electrodes 62 of the ammonia decomposition apparatus 50 shown in FIG. 1, and is fixed to the circulating fuel tank 47 so as to penetrate the peripheral side wall of the circulating fuel tank 47 and circulates. In the fuel tank 47, they are arranged so as to face each other at predetermined intervals so that the end faces face each other.

Further, the power supply 61 is the same as the power supply 61 of the ammonia decomposition apparatus 50 shown in FIG. 1, and examples thereof include a known pulse power supply. The pulse power supply is usually adjustable in pulse voltage, pulse width and pulse repetition frequency to any value and is electrically connected to a pair of electrodes 62 via wiring.

That is, the circulating fuel tank 47 shown in FIG. 2 is also used as the plasma reaction vessel 52, and the pair of electrodes 62 are fixed to the peripheral wall thereof, and the power supply 61 and the electrodes 62 are connected to each other to generate a plasma generator. 53 is configured.

(5) Control unit The control unit 6 includes a control unit 29.

The control unit 29 is a control unit (for example, an ECU: Electronic Control Unit) that executes electrical control in the electric vehicle 1, and is composed of a microcomputer including a CPU, a ROM, a RAM, and the like.

The control unit 6 will be described in detail later, but for example, driving and stopping of the first supply pump 33, the second supply pump 35, etc., and for example, the fuel supply valve 34, the gas discharge valve 27, the air supply valve 44, and the on-off valve. The opening and closing of 60 and the like is appropriately controlled.

(6) Power unit The power unit 7 includes a motor 37 for converting the electric energy output from the fuel cell 3 into mechanical energy as the driving force of the electric vehicle 1, and an inverter 38 electrically connected to the motor 37. A power battery 40 for storing the regenerative energy of the motor 37 and a DC / DC converter 36 are provided.

The motor 37 is arranged in front of the fuel cell 3 and in front of the electric vehicle 1. Examples of the motor 37 include known three-phase motors such as a three-phase induction motor and a three-phase synchronous motor.

The inverter 38 is arranged between the motor 37 and the fuel cell 3. The inverter 38 is a device that converts DC power generated by the fuel cell 3 into AC power, and examples thereof include a power conversion device incorporating a known inverter circuit. Further, the inverter 38 is electrically connected to the fuel cell 3 and the motor 37 by wiring, respectively.

Examples of the power battery 40 include known secondary batteries such as nickel-metal hydride batteries having a rated voltage of about 100 V and lithium-ion batteries. Further, the power battery 40 is connected to the wiring between the inverter 38 and the fuel cell 3, whereby the electric power from the fuel cell 3 can be stored and the electric power can be supplied to the motor 37.

The DC / DC converter 36 is arranged between the power battery 40 and the fuel cell 3. The DC / DC converter 36 has a function of raising and lowering the output voltage of the fuel cell 3 and has a function of adjusting the electric power of the fuel cell 3 and the input / output electric power of the power battery 40.

The DC / DC converter 36 is electrically connected to the control unit 29 (see the broken line in FIG. 2), whereby the fuel cell 3 responds to the input of the output control signal output from the control unit 29. Controls the output (output voltage) of.

Further, the DC / DC converter 36 is electrically connected to the fuel cell 3 and the power battery 40 by wiring, and is electrically connected to the inverter 38 by branching of the wiring.

As a result, the power from the DC / DC converter 36 to the motor 37 is converted from the DC power to the three-phase AC power in the inverter 38 and supplied to the motor 37 as the three-phase AC power.

3. 3. Power generation by the fuel cell system In the fuel cell system 2 described above, the fuel supply valve 34 is opened under the control of the control unit 29, and the first supply pump 33 is driven, so that the liquid stored in the high-concentration fuel tank 22 is stored. Fuel (primary supply liquid) is supplied to the circulating fuel tank 47 via the high-concentration fuel supply line 45. Further, under the control of the control unit 29, the second supply pump 35 is driven, and the liquid fuel (secondary supply liquid) in the circulating fuel tank 47 is supplied to the anode 9 via the fuel supply line 30. On the other hand, the air supply valve 44 is opened and the air supply pump 43 is driven, so that air is supplied to the cathode 10 via the air supply line 41. The fuel supply valve 34 is closed after a predetermined amount of liquid fuel is supplied.

At the anode 9, the liquid fuel passes through the fuel supply path 13 while in contact with the anode electrode 11. On the other hand, at the cathode 10, air passes through the air supply path 18 while in contact with the cathode electrode 16.

Then, an electrochemical reaction occurs in each electrode (anode electrode 11 and cathode electrode 16), and an electromotive force is generated.

For example, when the electrolyte layer 8 is an anion exchange film and the liquid fuel is an aqueous solution of hydrazine, for example, an aqueous solution of anhydrous hydrazine (N ₂ H ₄ ), the following formulas (1) to (3) are obtained.
(1) N ₂ H ₄ + ^4OH- → N ₂ + 4H ₂ O + ^4e- (Reaction at anode electrode 11)
(2) O ₂ + 2H ₂ O + ^4e- → ^4OH- (Reaction at cathode electrode 16)
(3) N ₂ H ₄ + O ₂ → N ₂ + 2H ₂ O (reaction in the entire fuel cell 3)
That is, at the anode electrode 11 to which hydrazine is supplied, the hydroxide ion (OH ⁻ ) generated by the reaction at the cathode electrode 16 reacts with the hydrazine (N ₂ H ₄ ) to react with nitrogen (N ₂ (gas)). ) And water (H ₂ O), and electrons (e ⁻ ) are generated (see the above equation (1)).

Further, in the reaction shown in (1) above, ammonia (NH ₃ , NH ₄ ⁺ ) is actually produced as a by-product in addition to nitrogen (N ₂ (gas)) and water (H ₂ O).

The electrons (e ⁻ ) generated at the anode electrode 11 reach the cathode electrode 16 via an external circuit (not shown). That is, the electron (e ⁻ ) passing through this external circuit becomes a current.

On the other hand, in the cathode electrode 16, electrons (e ⁻ ), water (H ₂ O) generated by external supply or reaction in the fuel cell 3, and oxygen (O ₂ ) in the air flowing through the air supply path 18 Reaction with and to generate hydroxide ion (OH ⁻ ) (see equation (2) above).

Then, the generated hydroxide ion (OH ⁻ ) passes through the electrolyte layer 8 and reaches the anode electrode 11, and the same reaction as described above (see the above formula (1)) occurs.

By the continuous electrochemical reaction between the anode electrode 11 and the cathode electrode 16, the reaction represented by the above formula (3) occurs in the fuel cell 3 as a whole, and the fuel cell 3 receives an electromotive force. Occur.

Then, the generated electromotive force is transmitted to the DC / DC converter 36 via the wiring, and is transmitted to the inverter 38 and the motor 37, and / or the power battery 40 in the power unit 7. Then, in the motor 37, the electric energy converted into the three-phase AC power by the inverter 38 is converted into the mechanical energy for driving the wheels of the electric vehicle 1. On the other hand, in the power battery 40, the electric power is charged.

Further, in the fuel supply / discharge unit 4, the liquid fuel discharged from the anode 9 (including used and unreacted liquid fuel, by-produced nitrogen gas (N ₂ ) and ammonia (NH ₃ , NH ₄ ⁺ )). Passes through the fuel discharge line 31 and flows into the gas-liquid separator 23 from the bottom flow port 24 on the upstream side.

In the gas-liquid separator 23, a liquid pool due to the discharged liquid is generated in the hollow portion of the gas-liquid separator 23, and a part of the gas (nitrogen gas (N ₂ ) or the like) contained in the discharged liquid is above the liquid pool. Separated into space.

In this way, in the gas-liquid separator 23, the discharged liquid is separated into a liquid fuel and a gas.

The gas separated in the gas-liquid separator 23 is discharged to the outside through the gas discharge pipe 26 by opening the gas discharge valve 27.

On the other hand, the liquid fuel separated in the gas-liquid separator 23 flows into the circulating fuel tank 47 via the recirculation line 32, is circulated as a supply liquid (secondary supply liquid), and is refueled from the fuel supply port 15 again. It flows into the supply channel 13.

Further, when the fuel concentration in the liquid fuel becomes low due to the circulation use of the secondary supply liquid, the liquid fuel separated by the gas-liquid separator 23 and flowing into the circulation fuel tank 47 is the fuel supply valve 34. The fuel is mixed with the liquid fuel (primary (high concentration) supply liquid) transported from the high concentration fuel tank 22 by opening and closing, and after the concentration is adjusted, the fuel supply port 15 is used again as the supply liquid (secondary supply liquid). Flows into the fuel supply path 13.

In this way, the liquid fuel circulates in the fuel circulation path (circulation line 32, circulating fuel tank 47, fuel supply line 30, fuel discharge line 31, gas-liquid separator 23 and fuel supply path 13).

4. Ammonia Concentration and Ammonia Decomposition As shown in the above formula (3), in the fuel cell system 2, when a hydrazine aqueous solution is used as a liquid fuel, nitrogen gas is produced by the reaction of hydrazine (N ₂ H ₄ ) and oxygen (O ₂ ). Produces (N ₂ ) and water (H ₂ O).

In this reaction, in addition to nitrogen gas (N ₂ ) and water (H ₂ O), ammonia (NH ₃ , NH ₄ ⁺ ) is by-produced, and ammonia is contained in the liquid fuel.

Therefore, in this fuel cell system 2, the above-mentioned ammonia decomposition method is carried out in the storage tank 54 and the circulating fuel tank 47 interposed in the fuel circulation path (closed line).

More specifically, in this method, first, in the storage tank 54, a part of the water contained in the hydrazine aqueous solution is separated, and the hydrazine aqueous solution is concentrated (concentration step).

That is, when ammonia is generated in the fuel cell 3, the liquid fuel containing ammonia (that is, the hydrazine aqueous solution containing ammonia) is discharged from the fuel cell 3 to the fuel discharge line 31 and passes through the gas-liquid separator 23. Then, it is retained in the storage tank 54.

On the other hand, in the storage tank 54, the air flowing in the air supply line 41 is supplied into the water separation pipe 55 (hollow fiber membrane).

That is, in the concentrating device 51, the liquid fuel (hydrazine aqueous solution containing ammonia) is retained in the storage tank 54, the water separation pipe 55 is immersed in the liquid fuel (hydrazine aqueous solution containing ammonia), and the water thereof. Air passes through the inside of the separation tube 55.

In such a concentrator 51, when air passes through the inside of the water separation pipe 55, a part of the water contained in the liquid fuel around the water separation pipe 55 is vaporized, and the water vapor is transferred to the water separation pipe 55. Passes through the water separation membrane. That is, as a result, a part of the water in the liquid fuel (hydrazine aqueous solution containing ammonia) is introduced into the water separation pipe 55.

On the other hand, hydrazine and ammonia in the liquid fuel remain in the storage tank 54 without being vaporized.

This separates only water from the liquid fuel and concentrates hydrazine and ammonia. The concentration of hydrazine and the concentration of ammonia after concentration are in the above range.

Specifically, in the storage tank 54, the ammonia concentration of the liquid fuel is measured by an ammonia densitometer (not shown). Then, the liquid fuel is concentrated until the ammonia concentration is equal to or higher than the above lower limit, that is, 2.0% by mass or more with respect to the total amount of the liquid fuel.

Then, when the ammonia concentration of the liquid fuel becomes equal to or higher than the above lower limit, the on-off valve 60 is opened by operating the control unit 29.

As a result, the concentrated liquid fuel (hydrazine aqueous solution containing ammonia) is supplied to the circulating fuel tank 47 via the reflux line 32 as shown in FIG.

At this time, the circulating fuel tank 47 is also used as the plasma reaction vessel 52 in the ammonia decomposition device 50, and a pair of electrodes 62 are provided on the peripheral wall surface thereof.

Therefore, by supplying the concentrated liquid fuel to the circulating fuel tank 47, a pair of electrodes 62 are arranged to face each other in the liquid fuel (preparation step).

Then, under the above-mentioned conditions (that is, conditions for generating bubbles in the solution), the electrode 62 is energized to generate plasma in the hydrazine aqueous solution. As a result, the ammonia contained in the hydrazine aqueous solution can be decomposed.

Then, as described above, the liquid fuel in which ammonia is decomposed is mixed with the liquid fuel (primary (high concentration) supply liquid) transported from the high concentration fuel tank 22 as necessary, and the concentration is adjusted. , As a supply liquid (secondary supply liquid), flows into the fuel supply path 13 again from the fuel supply port 15.

According to such an ammonia decomposition method, in the fuel cell system 2, ammonia contained in the circulating liquid fuel can be decomposed in the liquid fuel.

In particular, in the above-mentioned ammonia decomposition method, first, the ammonia concentration in the liquid fuel is adjusted to 2.0% by mass or more, and then the gas phase (bubbles) is generated in the liquid fuel by energizing the liquid fuel. Moreover, plasma is generated in the gas phase under the condition that the insulation is destroyed by the gas phase (bubbles).

In other words, when plasma is generated, the ammonia concentration in the hydrazine aqueous solution is adjusted to 2.0% by mass or more.

As a result, ammonia in the liquid fuel can be efficiently decomposed while suppressing the decomposition of hydrazine.

As a result, the fuel cell system 2 can efficiently generate electricity without the need for further purification treatment of nitrogen oxides.

The water separated from the liquid fuel is introduced into the water separation pipe 55 and mixed with air. This humidifies the air. The humidified air passes through the water separation pipe 55 (hollow fiber membrane) and is supplied to the fuel cell 3 via the air supply line 41 (air supply line 41 downstream of the storage tank 54).

In such a fuel cell system 2, the water contained in the exhaust liquid discharged from the fuel cell 3 can be recovered, and the water can be used to moisten the electrolyte layer 8, thereby improving the power generation efficiency. Can be done.

5. Modification example In the above description, first, the concentrating device 51 concentrates the liquid fuel to a predetermined concentration, and then the opening / closing of the on-off valve 60 is controlled to intermittently supply the liquid fuel to the circulating fuel tank 47. The ammonia in the liquid fuel is decomposed intermittently. For example, by controlling the drive of the second supply pump 35 and adjusting the flow rate of the circulating liquid fuel, the on-off valve 60 is always in the open state. The liquid fuel is continuously supplied to the circulating fuel tank 47, whereby the ammonia in the liquid fuel can be continuously decomposed.

Next, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples. In addition, "part" and "%" are based on mass unless otherwise specified. In addition, specific numerical values such as the compounding ratio (content ratio), physical property values, parameters, etc. used in the following description are the compounding ratios corresponding to them described in the above-mentioned "form for carrying out the invention" (forms for carrying out the invention). Substitute the upper limit value (value defined as "less than or equal to" or "less than") or the lower limit value (value defined as "greater than or equal to" or "excess") such as content ratio), physical property value, parameter, etc. be able to.

Example 1
The ammonia decomposition device shown in FIG. 1 was prepared. The capacity of the plasma reaction vessel was 50 to 100 mL, and a tungsten electrode having a substantially circular cross-sectional shape (diameter 1 mm) was used as the electrode.

Further, as the solution containing ammonia, an aqueous solution of hydrazine containing ammonia was used. Potassium hydroxide was added to the hydrazine aqueous solution, and its conductance was 0.08 S / m.

Moreover, when 50 mL of the hydrazine aqueous solution was measured by ion chromatograph analysis, the hydrazine concentration was 5.2% by mass, and the ammonia concentration was below the detection limit.

Next, a hollow fiber (hollow fiber membrane) made of a water separation membrane was immersed in 50 mL of a hydrazine aqueous solution containing ammonia, and air was passed through the hollow fiber to concentrate the hydrazine aqueous solution. The concentration of hydrazine after concentration was 5.0% by mass, and the concentration of ammonia was 2.0% by mass.

Then, in an argon atmosphere, the power supply is operated under the conditions of a pulse voltage of 5 kV, a frequency of 20 kHz, a pulse width of 2 μs, and an irradiation time of 30 minutes, and the electrodes are energized in a hydrazine aqueous solution to generate bubbles in the solution. Dielectric breakdown was caused by bubbles, and plasma was generated in the bubbles. Also, during the operation, the reaction vessel was cooled to 20-30 ° C with a chiller.

Then, when the power was turned off and the hydrazine aqueous solution after the above treatment was measured by ion chromatograph analysis, the hydrazine concentration was 5.0% by mass and the ammonia concentration was 1.2% by mass.

That is, ammonia could be decomposed without decomposing hydrazine.

Comparative Example 1
In the concentration of the hydrazine aqueous solution, plasma was generated in the hydrazine aqueous solution by the same method as in Example 1 except that the concentrated hydrazine concentration was changed to 5.0% by mass and the ammonia concentration was changed to 1.0% by mass.

Then, when the power was turned off and the hydrazine aqueous solution after the above treatment was measured by ion chromatograph analysis, the hydrazine concentration was 4.9% by mass and the ammonia concentration was 0.68% by mass.

That is, not only ammonia but also hydrazine was decomposed.

1 Electric vehicle 2 Fuel cell system 3 Fuel cell 23 Gas-liquid separator 30 Fuel supply line 31 Fuel discharge line 32 Circulation line 41 Air supply line 47 Circulating fuel tank 51 Concentrator 53 Plasma generator

Claims (2)

A concentration step of adjusting the ammonia concentration of the hydrazine aqueous solution to 2.0% by mass or more by concentrating the hydrazine aqueous solution containing ammonia, and
In the preparatory step of arranging a pair of electrodes facing each other in the aqueous hydrazine solution,
By energizing the electrodes and boiling the hydrazine aqueous solution in the vicinity of the electrodes, a gas phase is generated between the electrodes, and plasma is generated in the gas phase under the condition that dielectric breakdown occurs in the gas phase. A method for decomposing ammonia, which comprises a decomposition step for decomposing ammonia contained in the hydrazine aqueous solution. A fuel cell system capable of decomposing ammonia by the method for decomposing ammonia according to claim 1.
Fuel cells supplied with liquid fuel containing hydrazine,
A fuel tank that stores liquid fuel and
A fuel supply path for supplying liquid fuel from the fuel tank to the fuel cell,
The fuel discharge route for discharging the exhaust liquid from the fuel cell and
A return path for transporting the discharged liquid from the fuel discharge path to the fuel tank,
A gas-liquid separator interposed between the fuel discharge path and the reflux path,
A water separation means for separating water from the liquid fuel, which is interposed in the reflux path,
A fuel cell system comprising a pair of electrodes arranged to face each other in the fuel tank, and a plasma generator including a power source for energizing the electrodes.

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