JPH06310162A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To provide an excellent fuel cell power generating system capable of maintaining the performance of a fuel cell for a long time by preventing the fuel cell from being in a high voltage condition at the time of low load generation, and also preventing the fuel cell from being lack of gas. CONSTITUTION:A fuel cell system includes a fuel cell 11, a fuel reformer 5, an air feed means 19, and an inert gas feed means 28. A flow rate of inert gas flowing in the inert gas exhaust line of a fuel cell container 11C is so devised that it can be adjusted by a first gas flow rate adjusting valve 31. A first and a second bypass line 41 and 42 are provided for the upstream of the first gas flow rate adjusting valve 31 in the inert gas exhaust line, so that inert gas from the fuel cell container 11C can be fed to an oxidant electrode 11B and a fuel electrode 11A respectively. The flow rate of gas flowing in the first and second bypass lines 41 and 42 is so devised that it can be adjusted by a second and a third gas flow rate adjusting valve 32 and 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system provided with a fuel cell, a fuel reformer, an air supply device, and an inert gas supply device, and more particularly to a fuel cell power generation system with low load power generation. The present invention relates to a fuel cell power generation system capable of preventing gas deficiency due to gas distribution unbalance in a voltage state and high load power generation, and preventing performance deterioration of a fuel cell.

[0002]

2. Description of the Related Art A fuel cell is a device that directly converts the chemical energy of fuel into electrical energy. That is, a fuel cell generally has a pair of electrodes composed of a fuel electrode and an oxidizer electrode sandwiching an electrolyte layer, and supplies a fuel gas such as hydrogen gas to the fuel electrode.
By supplying an oxidant gas such as air to the oxidant electrode, an electrochemical reaction that takes place at this time is utilized to take out electric energy from between the electrodes.
Then, in the fuel cell having such a configuration, as long as the fuel gas and the oxidant gas are supplied, electric energy can be extracted with high conversion efficiency.

FIG. 3 is a block diagram showing an example of a conventional fuel cell power generation system. As shown in FIG. 3, raw fuel 1 made of fossil fuel such as natural gas or coal gas
And the steam from the steam supplier 2 are controlled by the raw fuel control valve 3 and the steam flow control valve 4, respectively, so that the mixing molar ratio of steam and carbon is about 3 to 5, and the fuel reforming is performed. It is introduced into the reforming reaction tube 6 in the device 5. In this fuel reformer 5, the raw fuel 1 and steam are
It is heated to about 500-600 ° C to perform the reforming reaction,
Further, after passing through the transformer 7, it becomes a reformed gas having a high hydrogen content, that is, a fuel gas.

After passing through the transformer 7, the fuel gas having a high hydrogen content is sent to the fuel gas steam separator 8 to remove the steam which has become excessive due to the reforming. After this, the fuel gas is sent to the auxiliary burner 9 with its flow rate being controlled by the auxiliary burner fuel gas flow rate control valve 10, and is also fed to the fuel electrode 11A of the fuel cell 11 by the fuel gas flow rate control valve 12. The flow rate is controlled and sent. Of these, hydrogen in the fuel gas flowing into the fuel electrode 11A of the fuel cell 11 undergoes a catalytic reaction with oxygen in the oxidant gas flowing into the oxidant electrode 11B of the fuel cell 11, and as a result, Part is consumed to obtain electric energy and reaction water.

Further, the fuel exhaust gas, which contains a part of the reaction water produced in the fuel cell 11 and exits from the fuel electrode 11A, is sent as the fuel gas for the main burner 13 of the fuel reformer 5. On the way, it passes through the fuel exhaust gas steam separator 16 in order to recover the water content in the gas. And
The fuel exhaust gas sent to the main burner 13 is the fuel reformer 5.
High-temperature exhaust gas 1 after burning inside and heating the reforming reaction tube 6
It is discharged as 7.

Further, the high temperature exhaust gas 17 merges with the oxidant exhaust gas sent from the oxidant electrode 11B of the fuel cell 11 and then is introduced into the mixer 18 to drive the air supply device 19 including the turbine 19A and the compressor 19B. It is used as a part of energy for use. Further, the fuel gas sent to the auxiliary burner 9 burns in the auxiliary burner 9, and this combustion gas passes through the mixer 18 and the air supply device 19
Drive the turbine 19A.

On the other hand, the discharge air from the compressor 19B, which is driven by being connected to the turbine 19A, is the auxiliary burner 9
The air amount is adjusted by the auxiliary burner oxidant gas flow rate control valve 20 and the main burner oxidant gas flow rate control valve 21 and sent to the main burner 13, respectively. The discharge air from the compressor 19B is also sent to the oxidant electrode 11B of the fuel cell 11 with its flow rate controlled by the oxidant gas flow rate control valve 22. The surplus of the discharged air is sent to the mixer 18 as a part of the driving energy of the air supply device 19.

A part of the oxidant gas flowing into the oxidant electrode 11B of the fuel cell 11 is part of the fuel electrode 11 of the fuel cell 11.
After being consumed by reacting with hydrogen in the fuel gas flowing into A, it is discharged including water generated in the oxidant electrode 11B. The discharged oxidant exhaust gas is joined with the high temperature exhaust gas 17 from the fuel reforming device 5 after partially condensing steam by the oxidant exhaust gas-water separator 23, similarly to the fuel exhaust gas described above.

In the fuel cell 11, the oxidant electrode 11B is the positive electrode and the fuel electrode 1 is the catalytic reaction between hydrogen in the fuel electrode 11A and oxygen in the oxidant electrode 11B as described above.
Electric energy is generated so that 1 A becomes a negative electrode, and this electric energy is absorbed by the electric load 24.

Further, the raw fuel supply line, the fuel gas supply line to the fuel electrode 11A of the fuel cell 11, the oxidant electrode 11
In order to increase the pressure and purge the residual gas, the oxidant gas supply line to B is supplied from the inert gas supply device 28.
Raw fuel purge valve 25, fuel gas purge valve 26,
An inert gas such as nitrogen gas is supplied through the oxidant gas purge valve 27. That is, when the fuel cell power generation system is in the stop state, the stop operation state, the power generation preparation state, or the power generation standby state, the fuel gas is replaced with an inert gas so as not to mix with the oxidant gas. There is.

Further, the fuel cell container 11C is provided with a cell container purge valve 29 from the inert gas supply device 28 in order to prevent leakage of fuel gas from the fuel electrode 11A and air from the oxidant electrode 11B. An inert gas is supplied through the inside of the container 11C, so that
A pressure higher than that of A and the oxidant electrode 11B is maintained.
In this case, the inert gas supplied into the fuel cell container 11C passes through the fuel cell container 11C and the oxidizer electrode 11
It joins the air exhaust gas from B and is sent to the mixer 18.

[0012]

In the fuel cell power generation system as described above, the fuel cell 11 is in a high voltage state at the time of low load power generation, and the fuel gas is unbalanced due to the fuel gas distribution unbalance at the time of high load power generation. Battery 11
Gas deficiency may occur in some areas. This deteriorates the performance of the fuel cell 11 and hinders stable and long-term operation of the fuel cell 11.

Conventionally, as a method of avoiding such an inconvenience, for example, a part of the air exhaust gas at the outlet of the oxidant electrode 11B and a part of the fuel exhaust gas at the outlet of the fuel electrode 11A are respectively introduced into the oxidant electrode 11B inlet by using a recirculation device. Returning to the inlet of the fuel electrode 11A, the oxygen concentration is mainly reduced at the inlet of the oxidant electrode 11B, the generated voltage is adjusted by the concentration polarization action of the fuel cell 11, and the supply gas amount is mainly increased at the inlet of the fuel electrode 11A. Methods to prevent deficiency have been adopted.

However, in such a method, the oxygen concentration at the inlet of the oxidizer electrode 11B has a limited oxygen concentration adjusting ability because it recirculates a part of the air exhaust gas, and the oxygen concentration of the recirculation device is limited. The larger the volume, the more oxidizer electrode 1
It takes time to adjust the oxygen concentration at the 1B inlet, and high voltage cannot be sufficiently prevented. Further, when the recirculation device is started / stopped, the gas flow rate fluctuates greatly, and an excessive pressure difference occurs between the oxidizer electrode 11B and the fuel electrode 11A, which may damage the fuel cell 11.

The present invention has been proposed in order to solve the above problems of the prior art, and its purpose is to:
The oxygen concentration of the oxidant electrode inflow gas can be easily reduced without increasing the amount of other gas and the oxidant electrode inflow gas can be easily increased. This prevents the high voltage state of the fuel cell during low load power generation, prevents the fuel cell from running out of gas during high load power generation, and maintains the performance of the fuel cell for a long period of time. It is to provide a power generation system.

[0016]

A fuel cell power generation system according to the present invention basically comprises a fuel cell, a fuel reformer, an air supply device, and an inert gas supply device.
In this case, the fuel cell includes a fuel electrode and an oxidant electrode in the container, introduces the fuel gas into the fuel electrode, introduces the oxidant gas into the oxidant electrode, and causes an electrochemical reaction caused by these reaction gases. A device for extracting electric energy from between the electrodes and introducing an inert gas into the container. Further, the fuel reformer is a device that reforms the raw fuel of the mixed components into a fuel gas having a high hydrogen content and supplies the fuel gas to the fuel electrode. Further, the air supply device is a device that supplies compressed air as an oxidant gas to the oxidant electrode. On the other hand, the inert gas supply device includes a fuel gas supply line for supplying a fuel gas to the fuel electrode, an oxidant gas supply line for supplying air to the oxidant electrode, and an inert gas in the fuel cell container. It is a device that supplies an inert gas to each of the inert gas supply lines to be supplied through a separate line. Furthermore, the fuel cell power generation system of the present invention includes a plurality of devices as described above,
The exhaust gas discharged from the fuel electrode is introduced as a combustion fuel for the fuel reforming device, and the exhaust gas discharged from the oxidant electrode is introduced as a part of driving energy for the air supply device. To be done.

The fuel cell power generation system according to the present invention has the following features in addition to the basic structure described above. That is, a first gas flow rate control valve that controls a gas flow rate flowing through an inert gas discharge line that discharges an inert gas from the fuel cell container, and the first gas flow rate control valve from the fuel cell container in the inert gas discharge line. A first bypass line for bypassing the gas flowing up to the gas flow rate control valve to the oxidant gas supply line, and a second gas flow rate control valve for controlling the gas flow rate flowing through the first bypass line. A second bypass line for bypassing a gas flowing in a portion of the inert gas discharge line between the fuel cell container and the first gas flow rate control valve to the fuel gas supply line; And a third gas flow rate adjusting valve for adjusting the flow rate of the gas flowing through the bypass line.

[0018]

The operation of the fuel cell power generation system of the present invention having the above structure is as follows.

First, at the time of low load power generation, the third gas flow rate control valve is closed, and the first gas flow rate control valve and the second gas flow rate control valve are adjusted to remove the inert gas passing through the fuel cell. Supply to the oxidizer electrode via the first bypass line. As a result, the oxygen concentration of the gas supplied to the oxidant electrode can be reduced, so that the generated voltage of the fuel cell can be reduced.

On the other hand, at the time of high load power generation, the second gas flow rate control valve is closed and the first gas flow rate control valve and the third gas flow rate control valve are adjusted so that the inert gas passing through the fuel cell is removed. It is supplied to the fuel electrode via the second bypass line. As a result, the flow rate of the gas supplied to the fuel electrode can be increased, and gas starvation of the fuel cell can be prevented.

[0021]

EXAMPLES Two examples of the fuel cell power generation system according to the present invention will be specifically described below with reference to FIGS. 1 and 2. Here, FIG. 1 is a block diagram showing a first embodiment of a fuel cell power generation system according to the present invention, and FIG.
FIG. 3 is a block diagram showing a second embodiment of the fuel cell power generation system according to the present invention. Incidentally, the same parts as those of the conventional example shown in FIG.

(1) First Embodiment ... FIG. 1 The fuel cell power generation system of the first embodiment shown in FIG. 1 basically has the same configuration as the conventional example shown in FIG. And in this embodiment, in addition to this basic configuration,
First to third gas flow rate control valves 31 to 33 and first and second bypass lines 41 and 42 are provided.

That is, as shown in FIG. 1, a first gas flow rate control valve 31 for adjusting the flow rate of gas flowing through the inert gas discharge line is provided on the inert gas discharge line of the fuel cell container 11C. ing. Then, the fuel cell container 1 in the inert gas discharge line of the fuel cell container 11C
In a portion between the 1C outlet and the first gas flow rate control valve 31, a first bypass line 4 that bypasses the gas flowing through this portion to the oxidant gas supply line of the oxidant electrode 11B.
1 is provided. Further, on the first bypass line 41, a second gas flow rate adjusting valve 32 that adjusts the flow rate of the gas flowing through the first bypass line 41 is provided.

In addition to the first bypass line 41, this portion of the inert gas discharge line of the fuel cell container 11C between the outlet of the fuel cell container 11C and the first gas flow rate control valve 31 is also provided. A second bypass line 42 is further provided for bypassing the gas flowing through to the fuel gas supply line of the fuel electrode 11A. A third gas flow rate adjusting valve 33 that adjusts the flow rate of the gas flowing through the second bypass line 42 is provided on the second bypass line 42. The other parts are configured in exactly the same manner as the conventional example shown in FIG.

The operation of the fuel cell power generation system of this embodiment having the above structure is as follows.

First, at the time of low load power generation, the third gas flow rate adjusting valve 33 is closed and the first gas flow rate adjusting valve 31 and the second gas flow rate adjusting valve 32 are adjusted. Specifically, the first gas flow rate control valve 31 is throttled and the second gas flow rate control valve 32 is opened. By such an operation, the compressor 19B is connected to the oxidizer electrode 11B via the first bypass line 41.
A mixed gas of discharged air from the fuel cell and the inert gas from the fuel cell container 11C is sent. That is, during low-load power generation, the discharge air from the compressor 19B flows on the oxidant gas supply line with its flow rate controlled by the oxidant gas flow rate control valve 22, while the air discharged from the fuel cell container 11C is discharged. Since the active gas is bypassed onto the oxidant gas supply line by the first bypass line 41,
The air and the inert gas merge to form a mixed gas, and this mixed gas is supplied to the oxidizer electrode 11B of the fuel cell 11. In this case, the fuel electrode 1 of the fuel cell 11
The fuel gas having a high hydrogen content, which has been reformed by the fuel reforming device 5, is sent to 1A with its flow rate controlled by the fuel gas flow rate control valve 12, as in the conventional example described above.

On the other hand, during high load power generation, the second gas flow rate adjusting valve 32 is closed and the first gas flow rate adjusting valve 31 and the third gas flow rate adjusting valve 32 are adjusted. Specifically, the first gas flow rate control valve 31 is throttled and the third gas flow rate control valve 32 is opened. By such an operation, the second
A mixed gas of a fuel gas having a high hydrogen content from the fuel reforming device 5 and an inert gas from the fuel cell container 11C is sent through the bypass line 42 of FIG. That is, during high-load power generation, the fuel gas from the fuel reforming device 5 flows on the fuel gas supply line with its flow rate controlled by the fuel gas flow rate control valve 12, while the fuel gas discharged from the fuel cell container 11C is discharged. Since the active gas is bypassed onto the fuel gas supply line by the second bypass line 42, these fuel gas and the inert gas join together to form a mixed gas, and this mixed gas becomes the fuel electrode 11A of the fuel cell 11. Is supplied to. In this case, the oxidizer electrode 11B of the fuel cell 11 is connected to the compressor 1 as in the conventional example described above.
The air discharged from 9B is sent with its flow rate controlled by the oxidant gas flow rate control valve 22.

As described above, according to the fuel cell power generation system of this embodiment, the oxidizer electrode 1 is used during low load power generation.
To reduce the oxygen concentration of the gas supplied to the oxidant electrode 11B of the fuel cell 11 by mixing the inert gas discharged from the fuel cell container 11C into the air flowing on the oxidant gas supply line 1B. Therefore, the generated voltage of the fuel cell can be reduced. During high-load power generation, the fuel gas flowing on the fuel gas supply line of the fuel electrode 11A is supplied to the fuel electrode 11A of the fuel cell 11 by mixing the inert gas discharged from the fuel cell container 11C. Since the gas flow rate can be increased, it is possible to prevent gas starvation of the fuel cell 11. Therefore, according to the present embodiment, it is possible to realize an excellent fuel cell power generation system capable of maintaining the performance of the fuel cell for a long period of time.

(2) Second Embodiment ... FIG. 2 The fuel cell power generation system of the second embodiment shown in FIG. 2 has the same configuration as that of the first embodiment described above, and further includes the first and second embodiments. Gas flow meters 51 and 52 are provided. First, as shown in FIG. 2, in the merging portion downstream of the first bypass line 41 in the oxidant gas supply line of the oxidant electrode 11B, the mixed gas flowing in this portion, that is, the discharge air from the compressor 19B. A first gas flow meter 51 for measuring the flow rate of the mixed gas of the inert gas from the fuel cell container 11C is provided. Further, in the confluent portion of the fuel gas supply line of the fuel electrode 11A downstream of the second bypass line 42, the mixed gas flowing in this portion, that is, the fuel gas from the fuel reformer 5 and the fuel cell container 11C A second gas flow meter 52 for measuring the flow rate of the mixed gas with the inert gas is provided.
The other parts are constructed in exactly the same manner as in the first embodiment described above.

In the fuel cell power generation system of the present embodiment having the above-mentioned structure, in addition to the same operation as that of the first embodiment, the following operation is further obtained.

First, when the second gas flow rate control valve 32 is opened and the inert gas from the fuel cell container 11C is supplied to the oxidant electrode 11B via the first bypass line 41, The first gas flow meter 51 can measure the flow rate of the mixed gas of the air and the inert gas flowing through the merging portion on the oxidant gas supply line. Therefore, while measuring the flow rate of such a mixed gas, by adjusting the oxidant gas flow rate control valve 22 within a range not exceeding the flow rate of the gas supplied to the oxidant electrode 11B, the amount of air supplied can be appropriately reduced. can do.

When the third gas flow rate control valve 33 is opened and the inert gas from the fuel cell container 11C is supplied to the fuel electrode 11A through the second bypass line 42, The gas flow meter 52 of No. 2 can measure the flow rate of the mixed gas of the fuel gas and the inert gas flowing in this joining portion on the fuel gas supply line. Therefore, while the flow rate of the mixed gas is measured, the third gas flow rate control valve 33 is adjusted so that the gas flow rate supplied to the fuel electrode 11A does not reach its lower limit. The amount of the inert gas to be supplied can be increased appropriately.

As described above, according to the fuel cell power generation system of the present embodiment, compared with the first embodiment, the first and second gas flowmeters 51 and 52 are used.
While measuring the flow rate of the mixed gas, the amount of air supplied to the oxidant electrode 11B and the amount of inert gas supplied to the fuel electrode 11A can be adjusted appropriately. That is, the oxygen concentration of the mixed gas supplied to the oxidant electrode 11B of the fuel cell 11 can be adjusted in a wide range, and the flow rate of the mixed gas supplied to the fuel electrode 11A is kept within the lower limit thereof. can do. Therefore, according to the present embodiment, it is possible to realize an excellent fuel cell power generation system having higher practicality than the first embodiment and capable of maintaining the performance of the fuel cell for a long period of time. .

(3) Other Embodiments The present invention is not limited to the above-described embodiments, but can be carried out in various modifications without departing from the scope of the invention. For example, it is possible to adjust the second gas flow rate control valve and the third gas flow rate control valve at the same time so that the respective required flow rates are flowed, or only one of the flow rate control valves is adjusted. It can also be configured as follows.

[0035]

As described above, in the present invention, the first to third gas flow rate control valves and the first and second gas flow rate control valves are provided.
By the simple structure of providing the bypass line of, without the need for a recirculation device as in the past, and
The oxygen concentration of the oxidant electrode inflow gas can be easily reduced without increasing the amount of other gas, and the fuel electrode inflow gas can be easily increased, so that the high voltage of the fuel cell can be used during low load power generation. It is possible to provide an excellent fuel cell power generation system capable of preventing the state, preventing gas shortage of the fuel cell during high-load power generation, and maintaining the performance of the fuel cell for a long period of time.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a second embodiment of the fuel cell power generation system according to the present invention.

FIG. 3 is a block diagram showing an example of a conventional fuel cell power generation system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Raw fuel 2 ... Steam supply device 3 ... Raw fuel control valve 4 ... Steam flow control valve 5 ... Fuel reforming device 6 ... Reforming reaction tube 7 ... Transformer 8 ... Fuel gas steam separator 9 ... Auxiliary burner 10 Auxiliary burner fuel gas flow rate control valve 11 ... Fuel cell 11A ... Fuel electrode 11B ... Oxidizer electrode 11C ... Fuel cell container 12 ... Fuel gas flow rate control valve 13 ... Main burner 16 ... Fuel exhaust gas / water separator 17 ... High temperature exhaust gas 18 Mixer 19 Air supply device 19A Turbine 19B Compressor 20 Auxiliary burner oxidant gas flow rate control valve 21 Main burner oxidant gas flow rate control valve 22 Oxidant gas flow rate control valve 23 Oxidant exhaust gas air-water separation Unit 24 ... Electric load 25 ... Raw fuel purge valve 26 ... Fuel gas purge valve 27 ... Oxidant gas purge valve 28 ... Inert gas supply device 29 ... Battery container purge valve 31 ... No. Gas flow rate control valve 32 ... Second gas flow rate control valve 33 ... Third gas flow rate control valve 41 ... First bypass line 42 ... Second bypass line 51 ... First gas flow meter 52 ... Second Gas flow meter

Claims (1)

[Claims] 1. A container is provided with a fuel electrode and an oxidant electrode, a fuel gas is introduced into the fuel electrode, an oxidant gas is introduced into the oxidant electrode, and an electrochemical reaction caused by these reaction gases causes both A fuel cell that takes out electrical energy from between the electrodes and introduces an inert gas into the container, and a fuel reformer that reforms the raw fuel of the mixed components into a fuel gas having a high hydrogen content and supplies the fuel gas to the fuel electrode. An air supply device for supplying compressed air to the oxidant electrode as an oxidant gas, and a fuel gas supply line for supplying a fuel gas to the fuel electrode,
An oxidant gas supply line for supplying air to the oxidant electrode,
And an inert gas supply device for supplying an inert gas to each of the inert gas supply lines for supplying the inert gas into the fuel cell container via a separate line, the fuel electrode A fuel configured to introduce exhaust gas discharged from the fuel reforming device as combustion fuel and to introduce exhaust gas discharged from the oxidizer electrode as part of driving energy of the air supply device. In the battery power generation system, a first gas flow rate control valve that controls a gas flow rate flowing through an inert gas discharge line that discharges an inert gas from the fuel cell container, and the fuel cell container from the fuel cell container in the inert gas discharge line. A first bypass line for bypassing a gas flowing up to a first gas flow rate control valve to the oxidant gas supply line; A second gas flow rate control valve for controlling the flow rate of gas flowing through the bypass line of the fuel cell, and a gas flowing in a portion of the inert gas discharge line between the fuel cell container and the first gas flow rate control valve, A fuel cell power generation system comprising: a second bypass line that bypasses the fuel gas supply line; and a third gas flow rate control valve that controls the flow rate of the gas flowing through the second bypass line.