JPH0345867B2 - - 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 oxidant 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 power source for compressing air can be found in the exhaust gas energy of the system, it will have a great 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, where a part of the air compressed by the compressor 3a passes through the flow rate control valve 5 for reaction in the fuel cell 1, and the remaining air passes through the flow rate control valve 6. After being used for combustion in the reformer 2, each exhaust gas is input into 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 a small air flow rate, the efficiency of the turbo compressor 3 is lower than that under rated load, and the power of the turbine 3b tends to be insufficient. In such a case, open the flow control valve 7 and compressor 3.
A part of the discharged air of the turbine 3b is guided to the auxiliary combustion furnace 4, and its combustion gas is added to the exhaust gas of the system, thereby covering the lack of power 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, there is a turbine bypass control valve 9 and a turbine nozzle (not shown) for load adjustment during operation. Although not shown, a compressed air supply device for system startup is installed on the inlet or outlet side of the compressor 3a.

The fuel cell power generation system is configured as described above, and various operation modes have been considered for the fuel cell power generation system, one of which is a warm-up mode. This mode is an operation mode in which the battery main body 1 and the reformer 2 are maintained at a temperature close to the loaded operating state in a so-called no-load state in which the system does not generate electric power. This operation mode is intended to shift the system to load operation within a short period of time, and creates a so-called standby state of the system. In this state, the battery body 1 can be easily kept warm with a heater or other means, but the reformer 2
The only way to keep warm is through combustion. In the warm maintenance mode, the combustion energy required to keep the reformer 2 warm is very small, and therefore the amount of air required for combustion is very small, for example, less than 1/10 of the rated combustion air amount. It is. On the other hand, if the turbo compressor 3 is used for this air, it is necessary to provide a large amount of air flow bypass to avoid surging of the compressor 3a, which results in unnecessary consumption of auxiliary combustion energy.
To give an example of a trial calculation, in this case, the auxiliary combustion energy amounting to about 6% of the rated power generated by the battery is consumed. Another method is to use the compressed air supply device for starting the system for warm combustion in the reformer 2, but the capacity of the device is relatively large,
For example, it consumes electrical energy of about 5% of the rated power generated by the battery. Therefore, both of the above cases are undesirable because more energy than necessary is consumed to maintain the warm-up operation. Due to its purpose, warm-up operation should be kept to the minimum necessary energy consumption rate.

[Summary of the invention]

This invention was made in view of the above-mentioned drawbacks of the conventional system, and by installing a separate compressor or blower that supplies the minimum amount of air necessary to keep the system warm when the system is stopped, The present invention provides a fuel cell power generation system that can keep the system warm at the minimum necessary energy consumption rate.

[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
On the line that supplies compressed air to the fuel cell main body 1 and the reformer 2, a separate compressor or Blower 11 is a check valve. The operation when entering warm-up operation from system load operation is described below. First, the separately installed compressor or blower 10 is started. Next, the auxiliary combustion furnace 4 is stopped, the control valves 7 and 8 are closed, and the control valve 9 is opened. Also, since the battery body 1 is kept warm by another means, the control valve 5 is closed. In this state, the turbo compressor 3 is stopped, and air from the separate compressor or blower 10 is supplied to the reformer 2. This separate compressor or blower 10 has the minimum capacity required to keep the reformer 2 warm, and therefore, combustion is performed to keep the reformer 2 warm.
In this way, warm-up operation of the system is achieved. When performing warm-up operation using such means, the power consumption of the separately installed compressor or blower 10 is small, and its value is, for example, on the order of 1% or less of the rated output of the fuel cell.

Although the above embodiment describes the case of maintaining the temperature at atmospheric pressure, the turbine inlet nozzle (not shown) of the turbo compressor 3 is closed, the control valve 9 is throttled, or the outlet of the reformer 2 is Throttle valve (not shown)
By inserting it, it is possible to maintain heat in the same high pressure state as during load operation.

Further, the separate compressor or blower 10 can be located anywhere on the circuit downstream of the outlet side check valve 11 of the compressor 3a and up to each of the control valves 5, 6, 7, and 8. It may be installed in
The same effects as in the above embodiment are achieved.

〔Effect of the invention〕

As explained above, this invention keeps the system warm at the minimum energy consumption rate by installing a separate compressor or blower that supplies the minimum amount of air necessary to keep the system warm when the system is stopped. It is possible to obtain a fuel cell power generation system that can perform the following steps.

[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 separate compressor or blower. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[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 air at the air electrode outlet of the fuel cell and the reformer. In a fuel cell power generation system, the fuel cell power generation system is equipped with a turbo compressor that is driven by both the exhaust gas of , is installed separately from the turbo compressor, and is operated on a line that supplies compressed air to the fuel cell and reformer when the system is stopped, supplying the minimum amount of air necessary to keep the reformer warm. A fuel cell power generation system characterized by being equipped with a compressor or a blower.