JPH0352188B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention provides compressed air necessary for the fuel cell and the reformer, which is driven by excess air at the air electrode outlet of the fuel cell and exhaust gas from the reformer. This invention relates to a fuel cell power generation system equipped with a turbo compressor.

[Prior art]

Fuel cell power generation systems have advantages over conventional steam power generation, such as higher efficiency and better environmental protection, and have been actively developed in recent years with the aim of putting them into practical use. A fuel cell power generation system basically consists of a battery, a reformer, and an inverter, but there is also a turbo compressor as an essential component for improving the efficiency of the system.

The fuel cell main body uses a hydrogen-rich reformed gas obtained by reforming a hydrocarbon fuel such as natural gas as the fuel gas, and air as the oxidizing gas. The performance of the battery body tends to improve as the pressure of each reaction gas increases, so the operating pressure of each reaction gas, fuel and air, is, for example, 3 to 6 kg/cm ² g.
The pressure is maintained at a certain level. At this time, compressing the air requires a large amount of power, amounting to about 20% of the energy generated by the battery. On the other hand, the reforming reaction to generate fuel gas for the battery is carried out at a high temperature of approximately 800°C, and high temperature exhaust gas is discharged from the reformer. Therefore, if the exhaust gas energy of the system can be used as the power source for compressing air, it will have a significant effect on improving the efficiency of the system. A turbo compressor is introduced for this purpose; it recovers energy from the system's exhaust gas with a turbine, supplies the necessary compressed air with a coaxial compressor, and recovers power within the system. This aims to improve system efficiency.

Figure 1 shows an air circuit diagram of a typical fuel cell power generation system. In the figure, 1 is the fuel cell main body, 2 is the reformer, 3 is the turbo compressor, 3
a and 3b are the compressor and turbine of the turbo compressor 3, respectively; a part of the air compressed by the compressor 3a passes through the flow rate control valve 5 and is reacted in the fuel cell main body 1, and the remaining air is sent to the flow rate control valve 6.
After being used as fuel for the reformer 2, each exhaust gas is input to the turbine 3b. Reference numeral 4 denotes an auxiliary combustion furnace that compensates for the insufficient power of the turbine 3b, and is used in combination with the turbo compressor 3. Generally, under partial load operating conditions with low air flow, the efficiency of the turbo compressor 3 is lower than when under rated load.
The power of the turbine 3b tends to be insufficient. In such a case, by opening the flow control valve 7 and guiding a part of the air discharged from the compressor 3a to the auxiliary combustion furnace 4, and adding the combustion gas to the exhaust gas of the system,
This covers the power shortage of the turbine 3b. Also, when it is necessary to prevent surging of the compressor 3a in a low load range, the control valve 8 is opened to bypass a portion of the air. Guide and supplement air. In addition, a turbine bypass control valve 9 and a turbine nozzle (not shown) are used for load adjustment during operation.
There is.

The fuel cell power generation system is configured as described above, but in order to start up such a fuel cell power generation system, it is usually started by raising the temperature of the reformer 2, which has a high reaction temperature and a large thermal time constant. , which requires air for combustion. On the other hand, the turbo compressor 3 cannot start up on its own without some kind of input. Therefore, in order to start the fuel cell power generation system, it is necessary to apply some kind of external energy to start the turbo compressor 3. This turbo compressor 3 has conventionally been commonly used in auxiliary power units (APUs) and air conditioning systems (ECS) in the field of aircraft, and in this case, the turbo compressor 3 is activated by, for example, a jet engine compressor. This was done by introducing a portion of the compressed air into the turbine, or by using a direct starter motor system. However, in a fuel cell power generation system, when the system is stopped, there is no usable power source (compressed air) around to provide the driving force to start the turbo compressor 3. It is necessary to configure a means for starting the shank 3. Therefore,
In the fuel cell power generation system, it is conceivable to configure the starting means for the turbo compressor 3 using a direct-coupled cell motor system, but in this case, there are disadvantages that the system configuration becomes complicated and the operating efficiency of the turbo compressor 3 decreases. Ta.

[Summary of the invention]

This invention was made in view of the drawbacks of the conventional ones as described above, and is installed on the compressor outlet side of the turbo compressor and is operated when the system is started to supply compressed air to the reformer. The turbo compressor is operated efficiently with a simple configuration by providing a starting compressed air supply device that provides combustion energy by combusting the air and supplying a part of the compressed air to the auxiliary combustion furnace after combustion in the reformer. This provides a fuel cell power generation system that can.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIG. 2. In the figure, numerals 1 to 9 are similar to the conventional structure described above. 10 is turbo compressor 3
The compressor 3a is installed on the outlet side of the compressor 3a, and is operated when the system is started, and the resulting compressed air is sent to the reformer 2.
A starting compressed air supply device 11 supplies the compressed air to the compressor for combustion, and after combustion in the reformer 2 supplies a part of the compressed air to the auxiliary combustion furnace 4 to provide auxiliary combustion energy. The surge prevention valve to be released, 12, is a check valve.

The operation of starting up the fuel cell power generation system will be described next. First, start the compressed air supply device 10,
The control valve 6 is opened to introduce air to the reformer 2, and combustion in the reformer 2 is started. At this time, if the outlet side of the compressor 3a is closed, surging will occur, so the surge prevention valve 11 is opened to open the outlet side of the compressor 3a to the atmosphere. Check valve 1
2 prevents the air from the compressed air supply device 10 from flowing back toward the compressor 3a.
When the control valve 9 is closed, the rotation of the turbo compressor 3 starts at the same time that air is introduced into the reformer 2, and as the temperature of the exhaust gas from the reformer 2 rises, the rotation speed of the turbo compressor 3 increases. , the discharge flow rate of the compressor 3a increases. When the control valve 9 is open, the turbo compressor 3 remains stopped. When the temperature of the exhaust gas from the reformer 2 rises to a certain degree, the control valve 7 is opened to introduce air into the auxiliary combustion furnace 4, and at the same time, fuel is introduced into the auxiliary combustion furnace 4 to start combustion in the auxiliary combustion furnace 4. At this time, the air from the compressed air supply device 10 is transferred to the reformer 2 and the auxiliary combustion furnace 4.
distributed to. If the temperature of the exhaust gas from the auxiliary combustion furnace 4 rises, the conditions for self-operation of the turbo compressor 3 are satisfied. That is, when the control valve 9 is closed,
If the surge prevention valve 11 is closed when the temperature of the exhaust gas from the auxiliary combustion furnace 4 rises and reaches a sufficient discharge flow rate from the compressor 3a, the discharge pressure of the compressor 3a will exceed the discharge pressure of the compressed air supply device 10, and the check valve will close. 12 is opened and the air discharged from the compressor 3a is supplied to the reformer 2 and the auxiliary combustion furnace 4. Also, when the control valve 9) is open, if the control valve 9 is gradually closed at this point, the turbo compressor 3 will start up, and from then on, the same procedure as above will be used to transfer the air discharged from the compressor 3a to the reformer 2 and the auxiliary combustion furnace. It can lead to 4. After that,
When the compressed air supply device 10 is stopped, the turbo compressor 3 enters self-operation. Once the turbo compressor 3 enters self-operation, air necessary for subsequent system start-up is supplied from the turbo compressor 3. Thereafter, the control valve 5 is opened to supply air to the fuel cell main body 1. In this way, while effectively utilizing the exhaust gas energy of the reformer 2, the turbo compressor 3 is
and start the system.
The use of the exhaust gas energy of the reformer 2 by the turbo compressor 3 for self-operation has the advantage that the auxiliary combustion furnace 4 can be made smaller accordingly. for example,
As an example of a trial calculation, the auxiliary combustion furnace 4 is ignited at the same time as the reformer 2 starts combustion, and the turbo compressor 3
When operating on its own, 15% of the energy generated by the battery is
% to 20% of the capacity is required. On the other hand, when the auxiliary combustion furnace 4 is ignited after the temperature of the reformer 2 has been sufficiently raised and the turbo compressor 3 is operated on its own, the capacity of the auxiliary combustion furnace 4 may be about 5% of the energy generated by the battery. Note that if the ignition of the auxiliary combustion furnace 4 is delayed more than necessary, the operating time of the compressed air supply device 10 will become longer and the total energy consumption required for starting the system will increase. An appropriate timing is determined by taking into consideration both the capacity of the auxiliary combustion furnace 4 and the amount of energy consumed at the time of system startup. As described above, with a simple configuration in which the starting compressed air supply device 10 is installed on the outlet side of the compressor 3a, the turbo compressor 3 can be started and self-powered at system startup without reducing the operating efficiency of the turbo compressor 3. I try to drive.

The compressed air supply device 10 of the above embodiment only needs to have enough capacity to initially start up the turbo compressor 3, and for example, a compressor or blower driven by electric or other means is used.

The compressed air supply device 10 can be located anywhere on the circuit downstream of the compressor 3a outlet side check valve 12 and up to each of the control valves 5, 6, 7, and 8. It may be installed, and the same effect as the above embodiment is produced.

〔Effect of the invention〕

As explained above, this invention is installed on the compressor outlet side of a turbo compressor, is operated when the system is started, supplies the accompanying compressed air to the reformer for combustion, and after combustion in the reformer, the compressed air To obtain a fuel cell power generation system capable of efficiently operating a turbo compressor with a simple configuration by providing a starting compressed air supply device that supplies a part of fuel to an auxiliary combustion furnace to provide auxiliary combustion energy. I can do it.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a general fuel cell power generation system, and FIG. 2 is a system diagram showing a fuel cell power generation system according to an embodiment of the present invention. In the figure, 1 is the fuel cell main body, 2 is a reformer,
3 is a turbo compressor, 4 is an auxiliary combustion furnace, and 10 is a compressed air supply device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A fuel cell, a reformer that reforms hydrocarbon fuel and supplies hydrogen gas to the fuel cell, and exhaust gas from the reformer or surplus at the air electrode outlet of the fuel cell. a turbo compressor having a compressor and a turbine driven by both air and the exhaust gas of the reformer to supply the compressed air necessary for the fuel cell and the reformer; In a fuel cell power generation system equipped with an auxiliary combustion furnace that is installed on a circuit that bypasses the turbine inlet circuit and supplements the insufficient power of the turbine, the furnace is installed on the compressor outlet side of the turbo compressor and is operated at the time of system startup. A starting compressed air supply device is provided for supplying compressed air to the reformer for combustion, and for supplying a part of the compressed air after combustion in the reformer to the auxiliary combustion furnace to provide auxiliary combustion energy. A fuel cell power generation system characterized by: 2. The fuel cell power generation system according to claim 1, wherein the compressed air supply device is a compressor. 3. The fuel cell power generation system according to claim 1, wherein the compressed air supply device is a blower.