JP2004342479A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge pump for supplying a raw material to a reformer, being smaller in size and lighter in weight and requiring lower power consumption. <P>SOLUTION: The fuel cell system comprises a fuel cell 23 for receiving supply of fuel gas and oxygen gas to generate electric power, an air compressor 12 for supplying the oxygen gas to the fuel cell 23, a tank 24 for storing the raw material for generating fuel gas, the reformer 22 for reforming the raw material to a hydrogen-rich fuel gas, and an air driving pump 18 for supplying the raw material to the reformer 22 to be stored in the raw material tank 24, upon receiving supply of operation air from the air compressor 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system, and more particularly, to a technique for improving a discharge pump for supplying raw fuel to a reformer.
[0002]
[Prior art]
In a fuel cell electric vehicle that operates a fuel cell system as an on-board generator, a system is used in which a hydrocarbon-based liquid raw fuel such as methanol is stored in a raw fuel tank and is reformed on the vehicle into hydrogen-rich fuel gas. It has been known. A liquid fuel is excellent in the mountability and portability of a vehicle, and is also superior in terms of energy density as compared with a method of storing hydrogen gas. Conventionally, an electric discharge gear pump has been used as a discharge pump for supplying the raw fuel stored in the raw fuel tank to the reformer, and by providing a relief valve in the raw fuel supply path, the discharge pressure fluctuates. Accordingly, the over-pressurized raw fuel is returned to the raw fuel tank so that the discharge pressure of the pump becomes constant. For example, Japanese Patent Application Laid-Open No. 2001-247200 is known as a document that discloses a configuration in which methanol is supplied to a reformer by a motor-driven discharge pump.
[0003]
[Patent Document 1]
JP 2001-247200 A
[Problems to be solved by the invention]
However, in the raw fuel supply line for supplying the raw fuel from the raw fuel tank to the reformer, the pressure on the upstream side becomes high (for example, 350 kPa Abs), so that the electric pump is required to have high discharge capacity. . In order to satisfy such demands, both the pump for pumping the raw fuel from the raw fuel tank and the motor for driving the pump have a large size (capacity) and weight. Further, the electric motor needs to be constantly operated at a constant rotation speed, and the power consumption of the auxiliary equipment increases. In a fuel cell system mounted on a vehicle, it is desirable that auxiliary equipment such as a pump be small in size, light in weight, and low in power consumption.
[0005]
Accordingly, an object of the present invention is to solve such a problem and to propose a fuel cell system provided with a raw fuel discharge pump of small size, light weight, and low power consumption.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, a fuel cell system according to the present invention includes a fuel cell that receives power of a fuel gas and an oxidizing gas to generate power, an air compressor that supplies an oxidizing gas to the fuel cell, and a fuel gas. A raw fuel tank that stores raw fuel (liquid raw fuel) to be produced, a reformer that reforms the raw fuel into hydrogen-rich fuel gas, and a raw fuel tank that receives working air from an air compressor An air-driven pump for supplying the raw fuel stored in the tank to the reformer is provided. By employing an air-driven pump as a discharge pump for supplying raw fuel to the reformer, a small size and light weight can be achieved. Further, since electric power for driving the discharge pump is not required, it is suitable as auxiliary equipment mounted on a fuel cell electric vehicle.
[0007]
As a preferred embodiment of the present invention, in addition to the above-described configuration, based on a pressure detection unit that detects an air pressure of working air supplied from the air compressor to the air-driven pump, based on the air pressure detected by the pressure detection unit Pressure control means for controlling the working air to a predetermined air pressure is provided. Since the working air supplied to the air-driven pump is required to be stable air with no pressure fluctuation, it is desirable to adjust the pressure so that the working air pressure becomes substantially constant.
[0008]
Here, the above-mentioned "pressure detection stage" includes not only a pressure sensor for measuring the working air pressure, but also, for example, an air pressure estimating means for estimating the working air pressure from the rotation speed of an air compressor serving as a working air generation source. Is included. In addition, the air pressure estimating means for estimating the operating air pressure from the duty value of a PWM control type control valve installed in the operating air flow path for supplying the operating air from the air compressor to the air driven pump is also used for pressure detection. Included in the means. The "pressure control means" includes not only means for feedback-controlling the rotation speed of the air compressor based on the working air pressure, but also, for example, a working air flow for supplying working air from the air compressor to the air-driven pump. Means for performing PWM control of a control valve installed in a road are included.
[0009]
As an air-driven pump for supplying raw fuel to the reformer, an air-driven diaphragm pump is suitable.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment of the Invention]
Hereinafter, a preferred first embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a system configuration diagram centering on a raw fuel supply path for supplying raw fuel from a raw fuel tank to a reformer. This fuel cell system mainly includes a raw fuel tank 24 for storing a liquid raw fuel, a reformer 22 for reforming the raw fuel into a hydrogen-rich fuel gas, and a supply of oxidizing gas and fuel gas. A fuel cell 23 for generating electric power upon receiving the fuel, an air-driven pump 18 for supplying raw fuel stored in a fuel tank 24 to the reformer 22, and an air-driven pump 18 for supplying working air to the air-driven pump 18. The air compressor 12 includes a control unit 40 that controls the driving of accessories such as the air compressor 12 according to a required load.
[0011]
The air compressor 12 is operated by the rotation torque supplied from the motor 13, and pressurizes air sucked from outside the vehicle via the air filter 11. Part of the pressurized air (compressed air) output from the air compressor 12 is supplied to the air electrode of the fuel cell 23 via the oxidizing gas flow path 31 and is used as an oxidizing gas to be used for a cell reaction. Another part of the pressurized air output from the air compressor 12 is supplied to the surge tank 15 via the working air flow path 32 branched from the oxidizing gas flow path 31 to operate the air-driven pump 18. It is used as working air. By temporarily storing the working air in the surge tank 15, the pulsation of the air pressure can be absorbed. The surge tank 15 is provided with a pressure sensor 25 for detecting an internal pressure (back pressure). When the internal pressure fluctuates, the control unit 40 controls the air compressor 12 so that the internal pressure is maintained at a substantially constant value. Is rotationally controlled by feedback.
[0012]
The pressurized air introduced into the surge tank 15 passes through the working air flow path 33 and operates the air-driven pump 18. It is desirable that the operating air for operating the air-driven pump 18 has a stable air pressure with as little pressure fluctuation as possible and has a small impurity content. Therefore, the working air flow path 33 has an air filter 16 for removing dust, moisture, oil, oil mist, and the like contained in the pressurized air, and the air pressure is adjusted to a constant value (for example, 300 kPa Abs). A regulator 17 is provided for performing the operation. As the air-driven pump 18, an air-driven diaphragm pump (process pump) is suitable.
[0013]
The raw fuel tank 24 stores a mixed solution in which methanol (C ₂ H ₅ OH) and water are mixed at a predetermined ratio in advance. Here, a mixed solution of methanol and water is exemplified as a raw fuel, but is not limited thereto. For example, methane (CH ₄ ), ethane (C ₂ H ₅ ), propane (C ₃ H ₈ ), butane (C ₄ H ₁₀ ), ethanol (C ₂ H ₅ OH), dimethyl ether (CH ₃ OCH ₃ ), acetone (CH ₃ C (＝ O) CH ₃ ), gasoline, light oil, natural gas and other hydrocarbon-based liquid sources Fuel can be used. The air-driven pump 18 receives the supply of the working air adjusted to a constant air pressure, draws the raw fuel from the raw fuel tank 24, and discharges the raw fuel to the raw fuel supply path 50. Since the raw fuel needs to be supplied to the reformer 22 at a stable pressure, the raw fuel supply path 50 includes a damper 19 for absorbing the pulsation of the air-driven pump 18 and absorbing the pressure fluctuation, and A regulator 20 for adjusting the fuel pressure to a constant value is provided.
[0014]
The injector 21 sprays the raw fuel supplied from the raw fuel supply path 50 into the reformer 22 in a mist state. The raw fuel supplied to the reformer 22 is converted into a hydrogen-rich fuel gas by the action of a reforming reaction after being vaporized. Combination of steam reforming (Steam reforming) with excellent reforming efficiency and partial oxidation reforming (Partial oxidation reforming) with excellent startability is used as a reforming reaction for reforming raw fuel into fuel gas. Auto thermal reforming and the like. When steam reforming is performed by bringing methanol into contact with a reforming catalyst such as a copper-zinc catalyst, a methanol decomposition reaction represented by the following equation (1) and a carbon monoxide shift reaction represented by the following equation (2) occur. Simultaneously, the reforming reaction shown in equation (3) occurs as a whole.
[0015]
CH ₃ OH → CO + 2H ₂ -90.0 kJ / mol (1)
CO + H ₂ O → CO ₂ + H ₂ +40.5 kJ / mol (2)
CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ −49.5 kJ / mol (3)
[0016]
The fuel gas generated by the reformer 22 is supplied to the fuel electrode of the fuel cell 23 via the fuel gas flow path 34 after the CO component is removed. At the same time, the pressurized oxidizing gas is supplied from the air compressor 12 to the air electrode of the fuel cell 23 via the oxidizing gas flow path 31. At the fuel electrode of the fuel cell 23, the oxidation reaction of the formula (4) occurs, and at the air electrode, the reduction reaction of the formula (5) occurs. An electromotive reaction of the formula (6) occurs in the entire fuel cell 23. The supply amounts of the fuel gas and the oxidizing gas to the fuel cell 20 are adjusted by adjusting the openings of the pressure adjusting valves 14 and 26. The oxidizing gas and the fuel gas subjected to the cell reaction are discharged from the fuel cell 23 as an oxygen off gas and a hydrogen off gas, respectively.
[0017]
H ₂ → 2H ⁺⁺ 2e ⁻ (4)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (5)
H ₂ + (１ ／) O ₂ → H ₂ O (6)
[0018]
As the fuel cell 23, a solid polymer electrolyte fuel cell, an alkaline electrolyte fuel cell, an acidic electrolyte fuel cell, a molten salt electrolyte fuel cell, a solid electrolyte fuel cell, a phosphoric acid fuel cell, or the like can be used. However, among these, a solid polymer electrolyte fuel cell is desirable. Polymer electrolyte fuel cells have the advantages of being able to start at room temperature, have a short start-up time, obtain a high current density at room temperature, can operate at low loads, and can be reduced in size and weight. It has excellent characteristics as a battery.
[0019]
The control unit 40 is configured as a computer system centered on a microcomputer, and includes a ROM 41 storing various programs and various data necessary for system control, and a CPU 42 reading and executing the programs stored in the ROM 41. And a RAM 43 functioning as a work memory of the CPU 42, and various sensor signals such as a pressure sensor 25, an accelerator opening sensor 61, and a vehicle speed sensor 62, and based on these sensor signals, the motor 13, the injector 21, the pressure regulating valve It is provided with an input / output port 44 for outputting a signal for controlling the driving of accessories such as 14, 26.
[0020]
The control unit 40 calculates the required load from the accelerator opening signal, the vehicle speed signal, and the like output from the accelerator opening sensor 61 and the vehicle speed sensor 62, and controls the air compressor 12 to obtain the amount of power generation required for the fuel cell 23. By controlling the number of revolutions of the motor 13 for driving and adjusting the spray amount of the injector 21 and the opening degree of the pressure regulating valves 14 and 26, the amount of the raw fuel supplied to the reformer 22 and the amount of fuel The flow rate of the reaction gas (fuel gas, oxidizing gas) supplied to the battery 23 is adjusted. Further, as described above, the control unit 40 adjusts the pressure so that the internal pressure of the surge tank 15 becomes substantially constant by acquiring the sensor signal of the pressure sensor 25.
[0021]
According to the present embodiment, by employing the air-driven pump 18 as the discharge pump for supplying the raw fuel to the reformer, the size of the discharge pump can be reduced and the weight can be reduced. . Since the auxiliary equipment mounted on the fuel cell electric vehicle is required to be as small and light as possible, the air-driven pump 18 is suitable as a raw fuel discharge pump. Furthermore, since no power is consumed to drive the air-driven pump 18, power consumption can be reduced.
[0022]
Further, since the working air is supplied from the air compressor 12 for supplying the oxidizing gas to the fuel cell 23 to the air-driven pump 18, it is necessary to provide a dedicated air compressor for driving the air-driven pump 18. Therefore, the number of parts, weight and cost can be reduced.
[0023]
In the above description, an example in which the pressure sensor 25 is used as the means for measuring the operating air pressure has been described. However, the present invention is not limited to this. For example, the operation may be performed based on the rotation speed of the air compressor 12 serving as a source of operating air. Air pressure estimating means for estimating the air pressure may be used. In addition, a control valve (not shown) of a PWM control type may be installed in the working air passage 32, and the working air pressure may be estimated from the duty value of the control valve. Further, in the above description, an example has been described in which the pressure is adjusted so that the operating air pressure becomes substantially constant by performing feedback control of the rotation speed of the air compressor 12 based on the operating air pressure. Instead, for example, a PWM control type control valve (not shown) may be provided in the working air flow path 32, and the duty value of the control valve may be adjusted so that the working air pressure becomes substantially constant. The same applies to a second embodiment described later.
[0024]
[Embodiment 2 of the invention]
Hereinafter, a preferred second embodiment of the present invention will be described with reference to FIG.
In the figure, the devices and the like having the same reference numerals as those in FIG. 1 indicate the same devices, and a detailed description thereof will be omitted. In the first embodiment described above, the mixed solution of methanol and water is stored in the raw fuel tank 24, pumped by the air-driven pump 18 and supplied to the raw fuel supply path 50. , A hydrocarbon-based liquid raw fuel such as methanol and water for a reforming reaction are stored in separate raw fuel tanks 24-1 and 24-2, respectively, and each is stored in a first air-driven pump 18 -1 and the second air-driven pump 18-2, and supplies the raw fuel to the raw fuel supply path 50-1 and the water supply path 50-2.
[0025]
More specifically, a first working air flow path 33-1 and a second working air flow path 33-2 are connected to the surge tank 15 via an air filter 16, and are stored in the surge tank 15. The working air is supplied to each of the first air-driven pump 18-1 and the second air-driven pump 18-2. A first regulator 17-1 and a second regulator 17-2 are provided in the first working air flow path 33-1 and the second working air flow path 33-2, respectively, to adjust the working air pressure to a constant value. are doing. The raw fuel stored in the raw fuel tank 24-1 is sucked by the first air-driven pump 18-1 and supplied to the raw fuel supply path 50-1. The raw fuel supply path 50-1 is provided with a first damper 19-1 for pulsing and a first regulator 20-1 for adjusting the raw fuel pressure to a constant level. The raw fuel is supplied to the raw fuel injector 21-1 while the pressure is kept constant.
[0026]
On the other hand, the water stored in the water tank 24-2 is sucked by the second air-driven pump 18-2 and supplied to the water supply path 50-2. The water supply path 50-2 is provided with a second damper 19-2 for pulsing and a second regulator 20-2 for adjusting the water pressure to a constant value, so that the water pressure is maintained at a constant value. The water is supplied to the water injector 21-2 in a state where the water is injected. The amount of raw fuel sprayed from the injector for fuel injection 20-1 to the reformer 22 and the amount of water sprayed from the injector for water injection 20-2 to the reformer 22 depend on the operating state of the fuel cell 23 and the required load. Control is appropriately performed by the control unit 40 according to the conditions.
[0027]
According to the present embodiment, by supplying the raw fuel and the water to the reformer 22 in different systems, the ratio between the raw fuel amount and the water amount is adjusted to a suitable value according to the operation state of the fuel cell 23. Therefore, the reforming efficiency can be increased. Further, by employing an air-driven pump as a discharge pump for supplying each of the raw fuel and water to the reformer 22, the size, weight, and power consumption of the discharge pump can be reduced. This is suitable as an auxiliary device mounted on a fuel cell electric vehicle.
[0028]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, small size and weight reduction can be achieved by employ | adopting an air drive type pump as a discharge pump for supplying raw fuel to a reformer. Further, since electric power for driving the discharge pump is not required, it is suitable as auxiliary equipment mounted on a fuel cell electric vehicle.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a fuel cell system according to a first embodiment.
FIG. 2 is a configuration diagram of a fuel cell system according to a second embodiment.
[Explanation of symbols]
12 air compressor 13 motor 15 surge tank 18 air-driven pump 22 reformer 23 fuel cell 24 raw fuel tank

Claims (3)

A fuel cell that receives power of fuel gas and oxidizing gas to generate power,
An air compressor for supplying the oxidizing gas to the fuel cell,
A raw fuel tank for storing raw fuel for producing the fuel gas,
A reformer for reforming the raw fuel into a hydrogen-rich fuel gas,
An air-driven pump that receives supply of working air from the air compressor and supplies raw fuel stored in the raw fuel tank to the reformer,
A fuel cell system comprising: The fuel cell system according to claim 1, wherein
Pressure detection means for detecting the air pressure of the working air supplied from the air compressor to the air-driven pump,
A fuel cell system comprising pressure control means for controlling the working air to a predetermined air pressure based on the air pressure detected by the pressure detection means. The fuel cell system according to claim 1 or 2, wherein
The fuel cell system, wherein the air-driven pump is an air-driven diaphragm pump.

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