JP2001006707A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system high in net output. SOLUTION: This fuel cell system is characterized by having a combustion means 3 for combusting unused fuel gas in a fuel cell 2 that generates electricity by an electrochemical reaction between a hydrogen-containing fuel gas and an oxygen-containing oxidant gas, an oxidant gas supply means 4 for supplying the oxidant gas to the fuel cell 2 by the power of a turbine 41 rotated by an exhaust gas from the combustion means 3, and a fuel storing means 6 for storing a combustible fuel to be supplied to the combustion means 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fuel cell system.

[0002]

2. Description of the Related Art In order to reduce air pollution as much as possible, it is important to take measures against exhaust gas from automobiles, and as one of the measures, electric vehicles are used. Has not been reached.

[0003] Fuel cells have attracted attention as clean power generation devices that generate no electricity other than water using hydrogen and oxygen by the reverse reaction of electrolysis, and automobiles that use the fuel cells are most likely to be used in the future. It is believed to be a clean car with potential. Among the above fuel cells, a solid polymer electrolyte fuel cell operates at a low temperature and is most promising for automobiles.

[0004] The solid polymer electrolyte fuel cell system generally has a fuel in which a large number of cells having a structure in which a solid polymer electrolyte is sandwiched between two electrodes (a fuel electrode and an oxidant electrode) are stacked. The fuel cell comprises a reformer for producing and supplying a fuel gas containing hydrogen as a main component to the fuel cell, an oxidizing gas supply means and a gas pipe for supplying an oxidizing gas, and a control device for controlling them. I have. The fuel gas is sent to the fuel electrode side and the oxidant gas is sent to the oxidant electrode side, and power is generated by an electrochemical reaction.

In this fuel cell system, reducing the auxiliary power such as a compressor used as an oxidant gas supply means, various pumps for transporting liquid, and various valves for controlling gas, reduces the total output of the system ( Net output). The power consumed by driving the compressor is very large. As the pressure and flow rate of the oxidizing gas supplied to the fuel cell increase, the power consumption of the compressor increases. Therefore, reducing the power consumption of the compressor is important to increase the net output of the fuel cell system.

As a prior art, Japanese Patent Application Laid-Open No. 8-45525 discloses a state of supplying compressed air to a fuel cell by controlling a compressor control means in accordance with an output state of the fuel cell in order to reduce auxiliary machine power. There is disclosed a control device for a fuel cell that controls the fuel cell.

[0007]

However, the prior art is not suitable for a vehicle such as a vehicle which has a large load fluctuation.
The control method is not always considered efficient. That is, while it takes a certain amount of time to change the air flow rate and the pressure of the compressor, the load change of the vehicle is extremely often performed at a speed higher than that.
In such a case, it is very difficult to control the compressor flow rate and the pressure with values that match the required load, and therefore, in practice, it is not possible to efficiently control instantaneous load fluctuations. In addition, adverse effects such as a lack of gas and an excessive supply of fuel occur due to a response delay of the compressor.

The present invention has solved the above-mentioned problems, and provides a fuel cell system having a high net output.

[0009]

Means for Solving the Problems In order to solve the above technical problems, the technical means (hereinafter referred to as first technical means) taken in claim 1 of the present invention contains hydrogen. Combustion means for burning unused fuel gas of a fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas containing oxygen, and a turbine rotated by exhaust gas from the combustion means, and the oxidant gas is driven by the power of the turbine. A fuel cell system comprising: an oxidizing gas supply unit that supplies the fuel cell; and a fuel storage unit that stores combustible fuel that is supplied to the combustion unit.

The effects of the first technical means are as follows.

That is, by supplying the combustible fuel to the combustion means, the combustion gas temperature of the combustion means can be kept constant, so that the rotation speed of the turbine can be kept constant. Thus, the oxidizing gas supply means can be designed so as to be most efficient at the rotation speed, so that the oxidizing gas supply means consumes little power and the net output of the fuel cell system can be increased.

[0012] In order to solve the above technical problem, the technical means (hereinafter referred to as second technical means) taken in claim 2 of the present invention is a current means for detecting an output current of the fuel cell. Detecting means, and temperature detecting means for detecting the temperature of the combustion means, wherein the flammability supplied from the fuel storage means to the combustion means based on information of at least one of the current detecting means and the temperature detecting means. 2. The fuel cell system according to claim 1, further comprising a flow control means for controlling a flow rate of the fuel.

The effects of the second technical means are as follows.

That is, since the amount of combustible fuel supplied to the combustion means can be controlled by the output current of the fuel cell, the temperature of the combustion gas of the combustion means can be kept constant even if the load varies. Further, since the amount of combustible fuel supplied to the combustion means can be controlled by the temperature detection means, the combustion gas temperature of the combustion means can be controlled to be constant even when the load fluctuates greatly.

[0015] In order to solve the above technical problems, the technical means (hereinafter referred to as third technical means) taken in claim 3 of the present invention is a hydrocarbon fuel storage for storing hydrocarbon fuel. Means, and a reformer for producing the fuel gas by reforming the hydrocarbon fuel stored in the hydrocarbon storage means, wherein the combustion of the hydrocarbon fuel stored in the hydrocarbon storage means is performed. The fuel cell system according to claim 1, wherein the fuel cell system is supplied to a means.

The effects of the third technical means are as follows.

That is, since the fuel supplied to the reformer and the fuel supplied to the combustion means can be made common, only one storage means is required and the fuel cell system can be downsized.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
Description will be given based on the drawings.

FIG. 1 is a diagram of a solid polymer electrolyte fuel cell system according to an embodiment of the present invention. The configuration of the present embodiment will be described. The solid polymer electrolyte fuel cell system includes a reformer 1, a fuel cell 2, a burner 3 as a combustion means, and a turbo assist compressor 4. Further, the solid polymer electrolyte fuel cell system includes a water tank 5, a methanol tank 6, a control device 7, three-way switching valves 8, 9, and the like.

The reformer 1 is a device for reforming water and methanol, which are fuels, into a fuel gas containing hydrogen as a main component. The reformer 1 has a combustion unit 101, an evaporation unit 102, a reforming unit 103, and a CO reduction unit. It comprises a unit 104. The reformer 1
Is connected to a methanol tank 6 storing methanol via a methanol pump P3, and is connected to an air compressor C1 via an air line 13. The evaporator 102 of the reformer 1 is connected to a water tank 5 storing water via a water pump P1, and is connected to the methanol tank 6 via a methanol pump P2.

The reformer 1 is connected to a three-way switching valve 8 via a fuel gas line 14. The three-way switching valve 8
Is connected to the fuel gas supply port 21 of the fuel cell 2 via the fuel gas pipe 15. Further, the three-way switching valve 8 is connected to the air supply port 31 of the burner 3 via the fuel gas pipe 12.

The turbo assist compressor 4 comprises a turbine 41, a motor 42, and a compressor 43. The compressor 43 is an oxidizing gas supply unit that compresses air, which is an oxidizing gas, and supplies the compressed air to the fuel cell 2, and is connected to the three-way switching valve 9 via the air line 16. The compressor 43 is connected to a flow control valve V1 via an air line 16a branched from the air line 16.
And the air line 16 which is also branched from the air line 16
It is connected to the flow control valve V2 via b.

The flow control valve V1 is connected to the air line 16c.
And the flow control valve V2 is connected to the reforming section 103 of the reformer 1 through the air line 16d.
It is connected to the reduction unit 104. The three-way switching valve 9 is connected to an air supply port 22 of the fuel cell 2 via an air pipe 17. The three-way switching valve 9 is also connected to the air supply port 34 of the burner 3 via the air line 18.

Unused fuel gas outlet 2 of the fuel cell 2
3 is connected to the check valve 11 through an unused fuel gas line 19. The check valve 11 is connected to the unused fuel gas line 2.
5 is connected to a fuel gas supply port 32 of the burner 3. An unused air outlet 24 of the fuel cell 2 is connected to the check valve 10 via an unused air line 20. The check valve 10 is connected to an air supply port 33 of the burner 3 through an unused air line 26.

The burner 3 is a combustion means for burning unused fuel gas, fuel gas having a high carbon monoxide concentration, and methanol. The fuel gas supply port 35 of the burner 3 is connected to the methanol tank 6 via a methanol pump P4. The exhaust gas outlet 36 of the burner 3 is connected to the exhaust gas line 2.
7, the turbine 4 of the turbo assist compressor 4
It is connected to 1. The burner 3 is provided with a temperature detector 50 as temperature detecting means for detecting the temperature.

The fuel cell 2 is provided with a current detector 54 as current detecting means for detecting the output current. The current detector 54 is connected to the control device 7 via the signal line 51. The control device 7 is a flow rate control means for controlling the methanol flow rate supplied to the burner 3 by controlling the methanol pump P4. The control device 7 includes a signal line 53
And to the methanol pump P4 via a signal line 52.

The operation and operation of this embodiment will be described below.

When the fuel cell system is started, methanol is supplied from the methanol tank 6 to the combustion section 101 of the reformer 1 by the methanol pump P3, and methanol is supplied from the methanol tank 6 to the burner 3 by the methanol pump P3. You. At the same time, the motor 42 of the turbo assist compressor 4 rotates, the compressor 43 is started, and the air compressor C1 is also started. At startup, the three-way switching valve 9 is switched to the burner 3 side, and the air compressed by the compressor 43 is sent to the burner 3.

The methanol supplied to the combustion section 101 burns the air supplied from the air compressor C1 as a combustion aid, and heats the evaporator 102. The methanol supplied to the burner 3 burns using the air supplied from the compressor 43 as a combustion aid.

Water is supplied from the water tank 5 by the water pump P1.
Methanol is supplied from the methanol tank 6 to the evaporator 102 of the reformer 1 by the methanol pump P2.
The supplied water and methanol are supplied to the evaporator 1 of the reformer 1.
It is vaporized in 02 and sent to the reforming unit 103.

In the reforming section 103, steam of water and methanol is supplied to the compressor 4 of the turbo assist compressor 4.
3 is mixed with air sent through a flow control valve V1, and reformed into a fuel gas containing hydrogen as a main component by a reforming catalyst (for example, a Pd catalyst and a Cu—Zn catalyst).
It is sent to the reduction unit 104.

The fuel gas contains 0.5 to 1% of carbon monoxide.
Including and in the CO reduction portion 104 CO removal catalyst (e.g., Pt catalyst and the like) converted into CO ₂ by oxidation with air to carbon monoxide was fed through a flow control valve V2 from the compressor 43 by one It is sent to the fuel cell 2 with the carbon oxide concentration set to 10 ppm or less.

Since the temperature of the reforming section 103 has not sufficiently risen immediately after the start-up, the concentration of carbon monoxide discharged from the reformer 1 at a predetermined concentration (for example, 10 p
pm). Therefore, the three-way switching valve 8 is switched to the burner 3 side, and the fuel gas is supplied to the fuel gas line 1.
2 to a burner 3. At this time, the three-way switching valve 9
Is switched to the burner 3 side, and the compressor 43
To the burner 3.

The burner 3 burns the fuel gas sent from the reformer 1 using the air sent from the compressor 43 as an auxiliary agent. The exhaust gas from the burner 3 is sent to the turbine 41 of the turbo assist compressor 4 to rotate the turbine 41. The rotation of the turbine 41 causes the compressor 4
3 is rotated, the load on the motor 42 is reduced, and power can be saved. This effect is important in an in-vehicle fuel cell system such as an automobile where the auxiliary power is limited.

When the carbon monoxide concentration of the fuel gas discharged from the reformer 1 becomes lower than a predetermined concentration, the three-way switching valve 8 is switched to the fuel cell 2 side, and the fuel gas is supplied to the fuel gas supply port of the fuel cell 2. From 21, the fuel is sent to the fuel electrode side of the fuel cell 2. At the same time, the three-way switching valve 9 is also switched to the fuel cell 2 side, and air is sent from the air supply port 22 of the fuel cell 2 to the oxidant electrode side of the fuel cell 2.

The fuel cell 2 generates power by an electrochemical reaction using hydrogen in the supplied fuel gas and oxygen in the air. In the fuel cell 2, the hydrogen in the fuel gas is 100%
It is not used and is about 80% utilization.
Unused fuel gas not used in the fuel cell 2 is sent to the fuel gas supply port 32 of the burner 3 through unused fuel gas pipes 19 and 25. On the other hand, the fuel cell 2 has
Since excess air is sent, unused air is discharged from the unused air outlet 24. The unused air is sent to the air supply port 34 of the burner 3 through the unused air lines 20 and 26.

The burner 3 burns with unused fuel gas and unused air sent from the fuel cell 2. The exhaust gas from the burner 3 is sent to the turbine 41 of the turbo assist compressor 4 to rotate the turbine 41. Thus, the fuel cell system enters a steady operation state.

Since the compressor 43 is rotated by the rotation of the turbine 41, the load on the motor 42 is reduced, and power can be saved. At the time of steady operation of the fuel cell system, there is sufficient combustion energy of unused fuel gas, so that it is not necessary to operate the motor, and the motor is stopped.

During steady operation, control is performed so that the amount of air supplied from the compressor 43 to the fuel cell 2 is constant. That is, the turbo assist compressor 4 is operated at a constant rotation.

It is necessary to vary the output current generated by the fuel cell 2 according to the external load. For this purpose, the output current is detected by a current detector 54. When the output current is large, the amounts of water and methanol to be charged into the evaporator 102 of the reformer 1 are increased to increase the amount of fuel gas. When the output current is small, the amount of water and methanol supplied to the evaporator 102 is reduced, and the amount of fuel gas is reduced. These controls are performed by controlling the water pump P1 and the methanol pump P2 by the control device 7, although the signal lines are not shown.

The amount of hydrogen in the unused fuel gas supplied to the burner 3 varies depending on the amount of hydrogen in the fuel gas supplied to the fuel cell 2 and the amount of hydrogen consumed in the fuel cell 2. On the other hand, the amount of oxygen in the unused air supplied to the burner 3 varies depending on the amount of oxygen consumed in the fuel cell 2. That is, since the amount of air supplied to the fuel cell 2 is controlled to be constant, when the output current of the fuel cell 2 is large, the amount of oxygen in the unused air decreases, and when the output current is small, The amount of oxygen in unused air increases.

The combustion gas temperature of the burner 3 fluctuates depending on the amount of the unused fuel gas supplied to the burner 3, the hydrogen content thereof, and the oxygen content in the unused air. This changes the exhaust gas energy of the burner 3 and thus changes the rotation speed of the turbine 41. In this embodiment, the amount of methanol supplied to the burner 3 is controlled in order to keep the combustion gas temperature of the burner 3 constant.

More specifically, the amount of methanol to be supplied to the burner 3 is determined in advance based on the output current value of the fuel cell 2. Accordingly, the control device 7 controls the signal line 52 based on the output current detected by the current detector 54.
To control the amount of methanol supplied to the burner 3 by controlling the methanol pump P4. When the load fluctuates greatly and the combustion gas temperature of the burner 3 fluctuates greatly,
Based on the combustion gas temperature detected by the temperature detector 50, the controller 7 controls the methanol pump P4 via the signal line 52 to finely adjust the amount of methanol supplied to the burner 3.

As a result, the turbo assist compressor 4
Can be designed so that the efficiency is highest at the set constant rotation. As a result, during steady operation of the fuel cell system, the turbo assist compressor 4 consumes little power and the net output of the fuel cell system increases. Furthermore, since control of the pressure and flow rate of the air supplied to the fuel cell 2 is not performed, response delay and the like can be eliminated, and control of the fuel cell system can be simplified.

[0045]

As described above, the present invention provides a combustion means for burning unused fuel gas of a fuel cell which generates power by an electrochemical reaction between a fuel gas containing hydrogen and an oxidizing gas containing oxygen. An oxidant gas supply means for rotating the turbine with the exhaust gas of the combustion means and supplying the oxidant gas to the fuel cell with its power, and a fuel storage means for storing a combustible fuel to be supplied to the combustion means are provided. The fuel cell system is characterized in that the net output can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram of a solid polymer electrolyte fuel cell system according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reformer 2 ... Fuel cell 3 ... Burner (combustion means) 4 ... Turbo assist compressor (oxidant gas supply means) 6 ... Methanol pump (fuel storage means, hydrocarbon storage means) 7 ... Flow control device (flow control) Means) 41 Turbine 42 Motor 43 Compressor 50 Temperature detector (temperature detecting means) 54 Current detector (current detecting means)

Claims (3)

[Claims] 1. A combustion means for burning unused fuel gas of a fuel cell which generates electricity by an electrochemical reaction between a fuel gas containing hydrogen and an oxidizing gas containing oxygen, and a turbine is rotated by exhaust gas from the combustion means. A fuel cell system comprising: an oxidizing gas supply unit that supplies the oxidizing gas to the fuel cell with the power; and a fuel storage unit that stores flammable fuel to be supplied to the combustion unit. . 2. A fuel cell system comprising: a current detecting means for detecting an output current of the fuel cell; and a temperature detecting means for detecting a temperature of the combustion means, wherein information of at least one of the current detecting means and the temperature detecting means is also provided. 2. The fuel cell system according to claim 1, further comprising a flow rate control means for controlling a flow rate of flammable fuel supplied from said fuel storage means to said combustion means. 3. A hydrocarbon fuel storage means for storing hydrocarbon fuel, and a reformer for reforming the hydrocarbon fuel stored in the hydrocarbon storage means to produce the fuel gas, wherein: The hydrocarbon fuel stored in the hydrocarbon storage means is supplied to the combustion means.
The fuel cell system as described.