JPS58166671A - Pressure control method of fuel cell power generating system - Google Patents

Abstract

PURPOSE:To stabilize the operation of a compressor and prevent the generation of surging by detecting load current of a fuel cell and decreasing the number of rotations and discharge pressure of a compressor which supplies oxidizing gas when the load current was decreased. CONSTITUTION:Fuel supplied to a reaction part 22 of a fuel reformer 20 is reformed with heat of a combustion room 21, and supplied to a fuel room 12 of a fuel cell, and air from a compressor 31 is supplied to an air room 11 to react, and the electric power is supplied to a load 20. Unreacting fuel is burned in the combustion room 21 and part of it is supplied to a gas turbine. The current detecting value of a load 40 is inputted to a control system 120, and to control flow rate setting values B1-B4 by following the load, and to control pressure setting values C1-C3. By this process, when the load current was decreased, the number of rotations and discharge pressure of the compressor are decreased. Therefore, when the load was decreased, the generation of surging in the compressor is prevented, and operation is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for a fuel cell power generation system.
The present invention relates to a pressure control method for a fuel cell power generation system having a turbo compressor for exhaust heat recovery.

To operate a fuel cell efficiently, K is the flow rate.

It is necessary to control the pressure, temperature, etc.), and for specific methods, refer to the method for controlling the amount of air supplied to the fuel cell and the amount of recirculation according to the load current (41 Chosho 4111-4135).
2), a method of controlling the supply flow rate to the reformer by battery current and reformer temperature (Special Publication No. 50-1 Osho No. 8), and a method of increasing the pressure of the reformer higher than that of the battery (418111). @5
3-511923) etc., these O control methods have many advantages and IA control methods are insufficient as a control method for a system having a turbo compressor for waste heat recovery. 6. For example, when the battery O load decreases, the amount of air required decreases and the discharge flow rate decreases. In this case, although there is a possibility that a surging phenomenon may occur if the discharge pressure is kept constant, the Fi
Not considered.

An object of the present invention is to provide a control method that stabilizes the operation of a turbo compressor of a fuel cell and optimizes the operating pressure.

In the present invention, the rotation speed and discharge pressure of the turbo compressor for exhaust heat recovery are changed according to the load of the fuel cell.For example, if the load decreases, the required air amount decreases, A must! Because the number of rotations decreases, in the case of ζO, if the compression heat discharge pressure is kept high, there is a strong possibility that a phenomenon in which the air is not compressed (nursing phenomenon) will occur. By operating in a manner that reduces the nursing phenomenon, the occurrence of the nerging phenomenon can be prevented.

Hereinafter, one embodiment of the present invention will be explained by JllmlK.
The recommended IE is fuel cell 10. Fuel reforming SSO.

This is nine examples in which the control device (1) according to the present invention is applied to a battery power generation system in category #a consisting of a turbine 30 and a compressor 31. In the C0 diagram, S2 is a reformed gas flow rate control device, 62
111 is a fuel flow rate control device for reformer combustion; 72 is a battery fuel pressure control device; 82 is a battery air flow rate control device; 92 is a battery air pressure control device; 10m is a reformer combustion air flow rate control device; is a compressor discharge pressure control device. 51.・
l.

81 and 101 are flow meters, 71.91 and 111 are pressure gauges, 53, 68, 78, 418.・8°103 and 113 are Choso Shin. These 0 controllers include controller 120KjDB1. Bs −Bm e B4 @C
1s c, a c, i.e., the settings of the flow control devices 82, 102, 52 and 62 are 81 g Bm m Bm m B4, and the settings of the pressure control devices 92, 72 and 112. is 01 a C1#
c.

Give with. A signal A detected from the load 40 and proportional to the load is input to the control device 120 .

The fuel supplied to the reaction section 22 of the fuel reformer 20 through the pipe 50 is reformed by heat from the combustion chamber 21 and becomes a hydrogen-rich gas, which is supplied to the fuel chamber 12 of the fuel cell 10 through the pipe 54. be done. Air from the air compressor 31 is supplied to the air chamber 11 of the fuel cell lO through the pipe 100.80, and hydrogen and oxygen react electrochemically to form the electrodes 13 and 1.
The generated power is supplied by a circuit 41 to an external load 40 . Fuel 1! Unreacted fuel in the pond 10 is discharged to a pipe 70 and nitrogen is discharged to a pipe 90. The unreacted fuel is combusted in the combustion chamber 21 of the fuel reformer 20 together with the combustion fuel supplied through the pipe 60. A portion of the combustion energy is consumed for reforming. The remaining energy is supplied to the gas turbine 30 through the pipe 23 as combustion gas.

The control system 120 of the present invention includes a conventionally known load following control), and sets a flow rate set value Bl e according to the load.
Bm m Bl # Output B4. In the reformer combustion air flow control device 102, air is guided throughout the piping 100 according to the flow rate of unreacted fuel and combustion fuel supplied through the piping 70 and 60 to optimize the combustion state. Adjust air flow. When the load changes, the amount of hydrogen consumed in the fuel cell 10 changes, and the amount of water in the unreacted fuel changes.

In this case, the theoretical air flow rate when the fuel led to the fuel reformer 2o is methane is as follows (7
The Arade constant is 9650Qc/mot).

-)-2XFso) ・・・・・・・・・
...(1) Here, Fl... is the theoretical air flow*(m
ol/a) FI is the flow rate of romethane gas entering the reformer reaction section (mot/s) F'@o is the flow rate of methane gas at the inlet of the reformer combustion chamber (moj/
(Hata) M is the number of fuel cells connected in series, l is the load current (A).

[114+The air flow rate in the device lO8 is set to a value that is, for example, L3 times the equation (1).

Next, a method of setting the pressure of the pressure control devices 72, 92, 112 will be explained using FIG. 2. Load change is setting change I11
Let's consider the case where it is large. If the load decreases, the amount of reaction in the fuel cell 1G decreases, so the flow rate of each flow control system is set to be small.
The air compressor 310 discharge flow rate is reduced by rounding, 1 in FIG.
A must at 22! Find the air flow rate. The relationship between the air compressor 310 discharge flow rate (Q) and the discharge pressure (H) is generally as shown in Fig. 3, and the discharge flow rate is equal to the air pressure #horizontal rotation,
The discharge pressure is proportional to the square of the rotational speed. In step 123 of FIG. 2, the number of revolutions n is calculated in proportion to the discharge flow rate, and in step 124, the discharge pressure is calculated in proportion to the m-th power (usually squared) of the number of revolutions. That is, when the load decreases, the rotational speed is decreased in proportion to the load, and the discharge pressure is decreased in proportion to the m power of the load. The operating status of the compressor 31 in this case will be explained using diagram jI3. When the rotation speed is In1 during rated operation, R
Assume that you are driving at point 1. When the load decreases and the rotational speed decreases by nsK, the engine is operated at point RsQ when the discharge pressure is constant. When the discharge flow rate decreases, surging, a phenomenon in which air is not compressed, occurs in the air compressor 31. This state is shown by 3 in the ms diagram, and the point Rs is a state on the verge of surging occurrence. In this case, if the discharge pressure is lowered by 1% Rs, for example, the risk of surging will be eliminated.

The pressure setting signal from the control device 120 is C15C,aC
, but in the example of the Is1 diagram, C■
It is necessary to make the value higher than that of C1 and C snow.

Next, the electromotive force of the fuel cell 10 when the load changes will be explained with reference to Fig. 4 and Fig. S.

Figure 4 shows the relationship between load current and electromotive force, and the JIIS diagram shows the relationship between battery gas pressure and electromotive force.

When the load current decreases, the electromotive force of the fuel cell increases1
In the present invention, when the load is reduced, the operation is performed so as to reduce the gas pressure, but when the gas pressure is reduced, the electromotive force is reduced, which offsets the increase in the electromotive force caused by the reduction in the load current. In other words, the output voltage fluctuation when the load changes becomes smaller.

Although the present invention has been described above with reference to specific embodiments thereof, it is understood that the present invention is not limited to the described embodiments and that various applications are possible within the scope of the present invention. This is obvious to painters.

For example, the input signal to the controller 120 may be electrical power instead of load current to achieve the same effect. (9) Although the compressor discharge pressure is adjusted by the air discharge amount 110, a method of bypassing the turbine inlet gas may also be used, and a method of releasing the battery outlet air 90 to atmospheric pressure may also be considered.

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

(1) Compressor operation becomes stable and surging can be prevented.

(2) Fuel cell voltage fluctuations during load fluctuations can be reduced.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an example of a fuel cell power generation system to which the present invention is applied, Fig. 11112 is a flow diagram explaining the present invention in detail, and Fig. 5FjA shows the relationship between the discharge flow rate and discharge force of the compressor. The characteristic diagrams shown in FIGS. 4 and 6 are the ninth fuel cell O characteristic diagrams explaining the present invention in detail. lO...Fuel cell, 20...Fuel reformer, 3G...
・Turbine, 31...pressure 111 machine, 12G...control device. Agent: Patent Attorney Akio Takahashi Figure 1 Figure 3 Disclosure amount σ('/, )

Claims (1)

[Claims] 1. A method for controlling the VST AO pressure for fuel cell power generation, which comprises a fuel cell, means for supplying fuel to the fuel cell, and a compressor for supplying oxidizing gas to the fuel cell,
The fuel cell power generation system is characterized in that the load current of the fuel cell O is detected, and based on the decrease in the load current, the rotation of the compressor and the oxidant gas discharge pressure of the compressor are reduced. Pressure control method.