JPS6028173A - Operating and controlling method for exhaust heat collection turbine - Google Patents

Abstract

PURPOSE:To suppress variation in gas turbine inlet pressure at the time of starting or suspending operation thereof within the specified value by controlling amount of fuel to be supplied to the burner apparatus based on an output of fuel battery and a number of rotations of turbine in case the gas turbine and air compressor are started or suspended. CONSTITUTION:A fuel battery 10, a fuel reformer 20 which supplies the fuel to this battery 10, a plurality of electric compressors 31, 33 which supply the gas for oxidation to the battery 10, a plurality of exhaust heat collection gas turbines 30, 32 which drive the air compressors 31, 33, a burner apparatus which generates the gas to the gas turbines 30, 32 and a means 100 for adjusting amount of fuel to be supplied to the burner apparatus, etc. are provided. At the time of starting exhaust heat collection turbines 30, 32 in such a fuel battery power generation plant, a fuel gas is generated in such amount as equal to the rated gas flow of turbine to be started and the fuel for combustion is adjusted so that generation of fuel gas is reduced when the turbines is stopped. Moreover, amount of fuel matching the energy required until the turbine started reaches the specified number of rotations is supplied excessively or reduced, and the variation is controlled large at the initial time of starting and stoppage and it is reduced with passage of time.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for controlling the operation of a gas turbine for exhaust heat recovery in a fuel cell power generation plant, and particularly to a method for controlling the operation of a gas turbine for exhaust heat recovery in a fuel cell power generation plant, and in particular, a method for controlling the operation of a gas turbine for exhaust heat recovery in a fuel cell power generation plant. The present invention relates to an operation control method suitable for.

[Background of the invention]

In order to operate a fuel cell, it is necessary to control the supply amount, pressure, etc. of fuel and oxidizing gas to the cell to predetermined values.

A specific method for this is to control the amount of air supplied to the fuel cell and the amount of recirculation according to the load current (Japanese Patent Publication No. 48
-41352), a method of controlling the amount of fuel supplied to the reformer by battery relaxation (Hibiko Kosho No. 50-15050), a method of improving controllability by maintaining the reformer pressure higher than that of batteries (special No. 81923/1983), etc. have been proposed. These control methods have many advantages, mainly in terms of flow control methods when the battery load changes, but are insufficient in terms of operational control of the exhaust heat recovery gas turbine.

In a fuel cell power generation plant, in order to improve power generation efficiency at each load level, multiple gas turbines are installed to effectively recover waste heat and are operated partially depending on the load level. However, when the gas turbine is started or stopped, the pressure of the gas turbine inlet gas fluctuates, and this influence causes the gas pressure within the fuel cell to fluctuate, but this is not taken into account in the control method described above.

[Purpose of the invention]

An object of the present invention is to provide an operation control method for suppressing fluctuations in gas turbine inlet pressure within a predetermined value during startup and shutdown of an exhaust heat recovery turbine in a fuel cell power generation plant.

[Summary of the invention]

In the present invention, when starting the exhaust heat recovery turbine, combustion gas corresponding to the rated gas flow rate of the turbine to be started is generated,
When the engine is stopped, the combustion fuel is adjusted to reduce the amount of combustion gas generated. Furthermore, by supplying an excessive amount of energy or reducing it in proportion to the amount of energy required for the starting turbine to reach its rated rotation speed, the amount of change is large during the plastic phase of starting and stopping, and becomes smaller over time. This suppresses fluctuations in gas turbine inlet pressure.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows a fuel cell 10, a fuel reformer 20, exhaust heat recovery turbines 30, 32. , air compressor 31°33, load 80,
This is an example in which a control device 100 according to the present invention is applied to a fuel cell power generation plant comprising a load following control device 90.

Fossil fuels 40 such as methane and methanol are supplied to the control valve 44
The gas is sent to the fuel reformer 20 via the reaction chamber 21, converted into a hydrogen-rich gas, and sent to the anode chamber 11 of the fuel cell 10 via a flow control system 46 having a flow meter 45 and a control valve 47. It will be done. On the other hand, air compressed to a predetermined value by the air compressors 31 and 33 is sent to the cathode chamber 12 of the fuel cell via a flow control system 76 having a flow meter 73 and a control valve 75. Here, a voltage is generated by the electrochemical reaction at the electrodes 13 , 14 and the electrolyte 15 to supply power to the external load 80 . Unreacted fuel and oxidizing gas in the fuel cell are transferred to the combustion chamber 22 of the reformer 20 via pressure control systems 53.56 each having a pressure gauge 52.55 and a control valve 54.57.
and is combusted together with the auxiliary fuel 60 sent from the control valve 62. A part of the combustion energy is consumed as reaction energy in the reaction chamber 21, and the rest is sent to the exhaust heat recovery gas turbine 30.32. The recovered power from the gas turbine drives air compressors 31 and 33.

The flow rate set value of the flow control system 46.74 is determined by another control device 9.
Given from 0. This control device is, for example,
This is a load following control device that generates a signal proportional to the load current, as proposed in Japanese Patent Publication No. 8-41352 and Japanese Patent Publication No. 15050/1982. The pressure control system 43, 53° 56.77 adjusts the gas flow rate so that the pressure of the pressure gauges 42.52, 55.76 is constant. Even during transient times such as during load fluctuations, the anode chamber 11 and cathode chamber 12 of the fuel cell 1o
Maintain the pressure constant.

The control device 100 is an example to which the method according to the present invention is applied, and performs a predetermined calculation using a signal 83 based on the load current and a signal 84 based on the turbine rotation speed, and controls the gas inflow valve 64 to the turbine 32 and the burner. The opening degree of the fuel supply valve 62 is controlled.

Next, the necessity and operating method of the control device 100 will be explained using FIGS. 2 and 3. FIG. 2 shows the relationship between the output of the fuel cell 10 and the fuel supply amount 60 to the burner section. When only energy balance is considered, the ratio of change in fuel cell output and fuel supply amount can normally be set to 1:1, but when applied to the power generation plant shown in FIG. 1, the pressure control system 53' , 56.77 control ranges need to be considered. If the amount of fuel supplied is too large, burner chamber 2
If the pressure in the control valves 54 and 57 increases and the pressure difference across the control valves 54 and 57 is small, the control system 53 and 56 may become uncontrollable.

This state is shown in Figure 2.1. Corresponds to the upper side of the operating range of ■.

If the amount of fuel supplied is too small, the power recovered by the turbine and air compressor will decrease, the air pressure 6 will decrease, and the pressure control system 77 may become inoperable. This state is the second
Figure I.

Corresponds to the lower side of the operating range of ■. In other words, the operating range in consideration of controllability is as shown in FIG.

When the battery output is reduced, the amount of fuel supplied becomes relatively large (Fig. 2, 1), and the power generation efficiency decreases. In order to improve power generation efficiency at low output, it is effective to operate a gas turbine for exhaust heat recovery, which increases efficiency at low output combustion gas flow rates. For example, if the gas turbine is switched to a gas turbine with half the rated capacity, the characteristics shown in FIG.

On the other hand, when the load on the fuel cell is changed and the number of operating turbines is changed, the pressure in the burner chamber 22 fluctuates, and the pressure control systems 53, 56, 77 may temporarily become uncontrollable. In Figure 2, when transitioning from A at low load to D at rated load, the method shown by the broken line A-+B-+D will deviate from the operating range, so the method shown by the solid line A-+B-)C-+D is used. I need to take it. In this case as well, the burner chamber 22
1, which can be solved by the method of the present invention. FIG. 3 shows the configuration of a control device 100 according to the present invention. 101,102゜103.104 in Figure 3,
105 is a computing unit, 106 is a timer, 107 is a switch,
108 is a computing unit.

A current signal 83 is input to 101 and outputs a signal to 109 when it exceeds a set signal. 109 signal is 102.10
3, 104, and 106, and a signal to open the valve 64 is issued at 102. In this embodiment, a delay element is used. The arithmetic unit 103 calculates the opening degree of the valve 62. In order to keep the combustion gas pressure in the burner chamber constant, it is sufficient to generate combustion gas equal to the gas flowing into the startup turbine 32, and this amount is replenished with the fuel 60. It is a matter of course that air for complete combustion of the fuel 60 is supplied to the burner chamber 22, so it is omitted in FIG. That is, if the rated gas flow rate of the startup turbine 32 is F32 and the fuel is methane, the amount of increase in the fuel 60 is determined by the following formula. l ΔF60=F32/(11Xk60) ・・・・・・
(1) In equation (1), 60 is the excess air ratio required to completely burn the fuel.

When the control valve 64 is opened, the gas turbine 32 starts rotating, and a rotation signal 84 is input to the computing unit 105. 105
Now, generate a signal that is inversely proportional to the rotation signal, and press switch 1.
07 to the arithmetic unit 10B. Switch 107 is turned on and off by the output of timer 106, and when the signal at 109 increases, it sends the signal at 112 to 114 for a certain period of time. The arithmetic unit 108 multiplies 110 and 114 and outputs it to 86. With this operation, the signal 86 indicates that fuel corresponding to the energy required by the starting turbine 32 to reach the rated rotational speed has been supplied.

109 when the current signal 83 becomes less than the setting signal.
signal decreases. This signal causes the arithmetic unit 104 to start operating, and outputs a signal to 111 that decreases over time.

Ideally, it is desirable that the signal output to 112 be equal to the signal output to 112, but since the signal of 112 often changes depending on the operating conditions of the gas turbine 32 and air compressor 33, the signal required to start up is smaller than the rotational moment of the stopped turbine. A method may also be used in which the output is generated only for a set time. switch 10
7 sends a signal 111 for a certain period of time to 114. With this operation, the signal 86 indicates that the fuel equivalent to the rotational energy of the stopped turbine has been reduced.

Next, the control characteristics of the conventional control system and the present invention will be explained with reference to FIG. Figure 4V o + P ”o +
D P o is Vl when switching of gas turbine is frequent.
+ph1 and DPI are the flowmeter 67 and control valve 62 in Fig. 1.
Feedback control characteristics in the flow control system 61 having
V2', Ph2. DP2 is a control characteristic when the control system 100 of the present invention is added to the flow rate control system 61.

When the output of the fuel cell is increased to W, the valve 64 is opened at time 10 and the gas turbine 32 is started. As the gas flows toward the gas turbine 32, the fuel gas pressure decreases, and the output of the gas turbine 30 temporarily decreases, causing the compressor discharge pressure to decrease slightly, and the pressure control system 76 lowers the amount released into the atmosphere 72. reduce This signal is detected by the flow meter 67 and sent to the flow control system 61, which opens the valve 62 to compensate.

The air supply amount 71 to the battery decreases slightly due to the decrease in compressor discharge pressure, and the flow rate of the fuel cell pressure control valves 54 and 57 increases due to the decrease in combustion gas pressure, resulting in a decrease in gas pressure within the battery. do. The rate of decrease in gas pressure within the battery is greater on the cathode side (air side) by the amount of decrease in compressor discharge force, resulting in an increase in gas pressure difference.

In the present invention, at the same time as the valve 64 is opened, the opening degree of the valve 62 is changed as shown by the solid line to suppress fluctuations in the pressure of the combustion gas, thereby making it possible to reduce fluctuations in the gas differential pressure within the battery.

In addition, in Fig. 4, the combustion gas pressure becomes high due to the large output of the fuel cell, but this is because a pressure regulating valve is not used at the turbine inlet for the purpose of increasing the exhaust heat recovery efficiency. does not affect the effectiveness of

In the present invention, when the exhaust heat recovery turbine is started, combustion gas corresponding to the rated gas flow rate of the turbine to be started is generated, and when the turbine is stopped, the combustion type is adjusted so that the amount of combustion gas generated is reduced. Suppress pressure fluctuations? i+lJ, and the gas differential pressure in the fuel cell can be reduced.

Although the present invention has been described above with reference to specific embodiments thereof, it will be appreciated by those skilled in the art that the present invention is not limited to the described embodiments, and that various applications are possible within the scope of the present invention. it is obvious.

For example, in Fig. 1, the input signals to the control device 100 are the load current and the rotation speed, but electric power may be used instead of the load current, and the number of exhaust heat recovery gas turbines is not limited to two. However, this control method is not unique to the present invention, but describes a method that has been proposed in the past.

For example, as a compressor discharge pressure adjustment method, the amount of recovered power is changed by bypassing the combustion gas side to the atmosphere.

It is conceivable to mix the air released into the atmosphere 72 with the combustion gas. Although the installation locations of the pressure control system 77 and flow meter 67 in this case will be different from those shown in FIG. 1, it is clear that the present invention can be applied to this case as well.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(1) Fluctuations in the gas turbine inlet pressure (combustion gas pressure) when starting and stopping the exhaust heat recovery gas turbine can be reduced.

(2) With the reduction in combustion gas pressure fluctuations, gas differential pressure fluctuations between the anode and cathode of the fuel cell can be suppressed, the probability of gas crossover occurring is reduced, and the safety of the device is improved.

(3) By including the start and stop of the exhaust heat recovery gas turbine, the range of load changes can be increased, increasing the degree of freedom in operation. In other words, it is possible to provide a power generation system that can cope with large load demands.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an example of a fuel cell power generation plant using the present invention, Fig. 2 is a characteristic diagram for explaining the present invention in detail, and Fig. 3 is a diagram for explaining the control method of the present invention. FIG. 4 is a characteristic diagram for explaining the present invention in detail. 10... fuel cell, 20... state reformer, 30.3
2...Gas turbine, 31.33...Air compressor,
80... Load, 90... Load following control device, 61.
... Mosashi Rukatsu? Kasumi

Claims (1)

[Claims] 1. A fuel cell, a fuel reformer that supplies fuel to the battery, a plurality of air compressors that supply oxidizing gas to the battery, and a plurality of air compressors that drive the air compressors. A fuel cell power generation plant having at least one set of a gas turbine and an air compressor; An exhaust heat recovery device characterized in that when starting (stopping) the machine, the amount of fuel supplied to the burner device is controlled based on the output of the battery and the rotation speed of the turbine to be started. Turbine operation control method. 2. The operation control method according to claim 1, wherein the amount of fuel supplied to the burner device is inversely proportional to the rotational speed of the turbine to be started. operation control method. 36 In the operation control method according to claim 1, the maximum change flow rate of the fuel supplied to the burner device is determined by the start-up (
The rated gas flow rate of the turbine to be started (stopped) is set to the amount that generates the rated gas flow rate, and the fuel supplied to the burner is supplied in excess of the amount of energy required for the turbine to start (stop) to reach its rated rotation speed. 1. A method for controlling the operation of a turbine for exhaust heat recovery, characterized in that: 4. In the operation control method according to claim 1, the maximum change flow rate of fuel supplied to the burner device is controlled by starting (
A method for controlling the operation of a turbine for exhaust heat recovery, in which the 4V characteristic is controlled so that it is large at the beginning of the shutdown and becomes small over time.