JPH03269957A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To prevent previously the reverse flow of combustion gas from a reforming unit combustion chamber toward a fuel cell when the operation of a plant is stopped, by providing a correction device of a pressure set value to correct a pressure set value in the outlet side of the reforming unit combustion chamber. CONSTITUTION:A differential pressure (b) between a fuel electrode 3 and a reforming unit combustion chamber 4 detected with a differential pressure detector 5 is compared with a inner preset reference value, and when the differential pressure (b) is lower than the reference value, a pressure correction value (c) is generated to reduce a pressure set value (a) basing on the deviation, and the value is converted and outputted as a last set value of pressure (d). Thereby the opening of a depressurizing regulation valve 9 becomes larger than that where the value (c) is zero. Then the gas flow ejected to the atmosphere from the combustion chamber 4 is increased to lower the pressure in the chamber 4, and the pressure loss between the fuel electrode 3 and the combustion chamber 4 can be increased to prevent the reverse flow of gas from the combustion chamber 4 to the fuel electrode 3.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a fuel cell power generation system equipped with a fuel cell and a reformer combustion chamber, and particularly relates to a fuel cell power generation system that is equipped with a fuel cell and a reformer combustion chamber. This relates to preventing backflow of combustion gas from the reformer combustion chamber to the fuel cell side, which is easy to do.

(Prior Art) FIG. 3 is a schematic diagram of a conventional fuel cell power generation system of this type. In the same figure, a fuel cell 1 includes an oxidizer electrode 2 and a fuel electrode 3, which lead to a reformer combustion chamber 4.
Combustion gas is supplied to the This reformer combustion chamber 4
A pressure-reducing control valve 9 is provided on the gas release side, and a pressure detector 7 is provided to detect the pressure on the gas release side. The regulator 8 is configured to control the pressure-reducing control valve 9 so that the deviation between the pressure setting value a and the pressure value e detected by the pressure detector 7, that is, the pressure deviation f, becomes zero.

Here, if the detected pressure value e is higher than the pressure setting value a,
The regulator 8 increases the opening degree of the pressure-reducing control valve 9 to increase the flow rate of gas discharged from the reformer combustion chamber 4 to the atmosphere.

As a result, the pressure in the reformer combustion chamber 4 decreases, so
When the pressure drop between the fuel electrode 3 and the reformer combustion chamber 4 increases (the pressure difference becomes larger), the pressure in the plant is lowered.

(Problems to be Solved by the Invention) During normal operation of the above-mentioned fuel cell power generation system, gas flows from the oxidizer electrode 2 to the reformer combustion chamber 4, and the gas flows from the fuel electrode 3 to the reformer combustion chamber 4.
to the reformer combustion chamber 4.

However, when the plant is shut down, the supply of air to the oxidizer electrode 2 and the supply of fuel gas to the fuel electrode 3 are usually stopped, so the flow of air from the oxidizer electrode 2 to the combustion chamber 4 of the reformer, The flow of each gas from the reformer combustion chamber 4 to the reformer combustion chamber 4 becomes small, and the pressure drop becomes small. As a result, gas tends to flow back from the reformer combustion chamber 4 to the oxidizer electrode 2 and fuel electrode 3.

Note that gas flowing backward from the reformer combustion chamber 4 to the fuel cell 1 side means that high-temperature gas flows into the oxidizer electrode 2 and fuel electrode 3, or combustible gas flows into the oxidizer electrode 2, This means that oxygen gas flows into the fuel electrode 3, and if this situation occurs, it is not only extremely dangerous, but also the fuel type;
There is an extremely high possibility of damaging the 41.

On the other hand, in the above-mentioned fuel cell power generation system, the focus is not on the state quantity on the upstream side of the reformer combustion chamber 4 when the pressure is lowered by the pressure lowering control valve 9; Even if gas flows backward from the oxidizer electrode 2 or fuel electrode 3 to the oxidizer electrode 2 or the fuel electrode 3, this works to lower the outlet pressure (pressure detection value e) of the reformer combustion chamber 4, so the pressure is lowered successfully. There is a risk of creating an illusion.

Incidentally, if we consider a case where the gas backflow as described above occurs and the detected pressure value e is lower than the pressure setting value a, the pressure reducing control valve 9 is adjusted in the closing direction, and the gas backflow becomes more intense.

Therefore, in the conventional fuel cell power generation system shown in Fig. 3, if the pressure setting value a during pressure reduction is not set very well,
The backflow of gas from the reformer combustion chamber 4 to the oxidizer electrode 2 or the fuel electrode 3 could not be suppressed, and the risk of damaging the fuel cell 1 was extremely high.

This invention was made to solve the above problems, and can prevent the backflow of gas from the reformer combustion chamber to the fuel cell side, which is likely to occur when the plant is stopped, thereby protecting the fuel cell 1 and The purpose of the present invention is to provide a fuel cell power generation system that can stably stop a plant.

[Structure of the invention]

(Means for Solving the Problems) This invention burns gas supplied from a fuel cell including an oxidizer electrode and a fuel electrode in a reformer combustion chamber, and releases gas from the reformer combustion chamber. In a fuel cell power generation system, a pressure-reducing control valve is provided on the side of the oxidizer electrode and the reformer combustion chamber, and the pressure-reducing control valve is adjusted so that the outlet pressure of the reformer combustion chamber matches a set value. gas flow trend detection means for detecting a gas flow trend between the chambers and at least one of the fuel electrode and the reformer combustion chamber; and based on the detected gas flow trend, the reformer combustion chamber The present invention is characterized by comprising a pressure setting value correcting means for correcting a pressure setting value on the outlet side of the reformer combustion chamber so that combustion gas does not flow backward from the combustion chamber to the fuel cell side.

(Function) In the present invention, trends in the gas flow between the oxidizer electrodes and between the fuel electrodes with respect to the combustion chamber of the reformer, such as pressure difference and flow rate, are detected and based on the detected values. Since the output side pressure setting value of the reformer combustion chamber is corrected so that the combustion gas does not flow back when the plant is stopped, it is possible to prevent the gas from flowing back from the reformer combustion chamber to the fuel cell side.

(Embodiment) FIG. 1 is a schematic diagram of an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 3 showing the conventional device indicate the same elements. This is because the pressure setting value a is corrected based on the differential pressure detector 5 that detects the pressure between the fuel electrode 3 and the reformer combustion chamber 4, and the differential pressure detection value of this differential pressure detector 5. The difference from FIG. 3 is that a pressure correction value calculator 6 is added which generates the pressure correction value C of , and also subtracts the pressure correction value C from the pressure setting value a to output the final pressure setting value d. .

The operation of the present embodiment configured as described above will be described in the case where the pressure difference between the fuel electrode 3 and the reformer combustion chamber 4 decreases.

The pressure correction value calculator 6 compares the detected differential pressure value between the fuel electrode 3 and the reformer combustion chamber 4 detected by the differential pressure detector 5 with a reference value set internally in advance, and determines this reference value. When the detected differential pressure value is lower than
Furthermore, the pressure correction value C is subtracted from the pressure setting value a to output the final pressure setting value d. As a result, the pressure setting value becomes a value lower than the original pressure setting value a, that is, a pressure setting value d that promotes pressure reduction, so the opening of the pressure reduction control valve 9 is lower than when the pressure correction value C is zero. The degree increases. When the opening degree of the pressure-reducing control valve 9 becomes wide (when the opening degree of the pressure-reducing control valve 9 becomes large, the flow rate of gas released from the reformer combustion chamber 4 to the atmosphere increases and the pressure in the reformer combustion chamber 4 decreases, so that the fuel electrode 3 and the reformer quality equipment combustion chamber 4
(as the pressure drop between the two ends increases, the pressure difference also increases), which acts to prevent the backflow of gas from the reformer combustion chamber 4 to the fuel electrode 3.

Thus, in this embodiment, since the pressure setting value during pressure reduction is corrected based on the pressure difference between the fuel electrode 3 and the reformer combustion chamber 4, the pressure setting value during pressure reduction is corrected based on the pressure difference between the fuel electrode 3 and the reformer combustion chamber 4. It is possible to prevent the backflow of gas to the plant, and it is possible to stably stop the plant (lower pressure).

FIG. 2 is a schematic configuration diagram of another embodiment of the present invention, and in the figure, the same elements as in FIG. Here, the pressure difference between the fuel electrode 3 and the reformer combustion chamber 4 is detected by a differential pressure detector 5, and the pressure difference between the oxidizer electrode 2 and the reformer combustion chamber 4 is detected by a differential pressure detector IO. , the detected value of the differential pressure between the fuel electrode 3 and the combustion chamber 4 of the reformer, and the detected value of the differential pressure between the oxidizer electrode 2 and the combustion chamber 4 of the reformer are manually inputted to the low value priority circuit 11. The selected low value i is manually input to the pressure correction value calculator 6 described above.

Next, the operation of this embodiment will be explained. Here, the pressure difference between the fuel electrode 3 and the reformer combustion chamber 4 is detected by the differential pressure detector 5, and the pressure difference between the oxidizer electrode 2 and the reformer combustion chamber 4 is detected by the differential pressure detector IO. be done. Then, when the detected differential pressure between the fuel electrode 3 and the reformer combustion chamber 4 is inputted to the low value priority circuit 11, the detected differential pressure between the oxidizer electrode 2 and the reformer combustion chamber 4 is This low value priority circuit 11 compares these values, selects the smaller side, that is, the differential pressure detection value i of the line where gas is likely to flow back from the reformer combustion chamber 4, and applies it to the pressure correction value calculator 6. . The pressure correction value calculator 6 compares the detected differential pressure value i selected by the low value priority circuit 11 with a reference value set internally in advance, and when the detected differential pressure value l is lower than this reference value, A pressure correction value C is generated to lower the pressure setting value a based on the deviation, and the pressure correction value C is further subtracted from the pressure setting value a to output a final pressure setting value d. As a result, the pressure setting value becomes a value lower than the original pressure setting value a, that is, a pressure setting value d that promotes pressure reduction, so the opening of the pressure reduction control valve 9 is lower than when the pressure correction value C is zero. The degree increases. When the opening degree of the pressure-reducing control valve 9 increases, the flow rate of gas released from the reformer combustion chamber 4 to the atmosphere increases and the pressure in the reformer combustion chamber 4 decreases, so that the fuel electrode 3 and the reformer (The pressure drop between the combustion chambers 4 increases and the pressure difference becomes large), and acts to prevent gas from flowing back from the reformer combustion chamber 4 to the fuel electrode 3.

Thus, in this example, the pressure difference between the fuel electrode 3 and the reformer combustion chamber 4 is compared with the pressure difference between the oxidizer electrode 2 and the reformer combustion chamber 4, and the pressure difference between the fuel electrode 3 and the reformer combustion chamber 4 is compared. Since the pressure setting value during pressure reduction is corrected based on the low value where gas is likely to backflow, the reformer combustion chamber 4, which is likely to occur when the plant is stopped,
Backflow of gas from the oxidizer electrode 2 to the fuel electrode 3 can be prevented.

In addition, in the above embodiment, the pressure setting value was corrected based on the differential pressure between the oxidizer electrode 2 and the reformer combustion chamber 4, or the differential pressure between the fuel electrode 3 and the reformer combustion chamber 4. Instead, the gas flow rate flowing from the oxidizer electrode 2 to the reformer combustion chamber 4 or the gas flow rate flowing from the fuel electrode 3 to the reformer combustion chamber 4 is measured, and these gas flow rates are used as differential pressure detection values. It is clear that the same correction as described above can be made even if used in place of , h. Therefore, a gas flow trend detection means for detecting the trend of gas flow at least one of between the oxidizer electrode 2 and the reformer combustion chamber 4 and between the fuel electrode 3 and the reformer combustion chamber 4 is provided, and the detected gas flow is Based on this trend, the output side pressure setting value of the reformer combustion chamber 4 may be corrected so that combustion gas does not flow back from the reformer combustion chamber 4 to the fuel cell 1 side when the plant is stopped.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, gas flow trend detection detects at least one of the gas flow trends between the oxidizer electrode and the reformer combustion chamber and between the fuel electrode and the reformer combustion chamber. and a pressure setting that corrects the outlet pressure set value of the reformer combustion chamber based on the detected gas flow trend to prevent combustion gas from flowing back from the reformer combustion chamber to the fuel cell side when the plant is stopped. Since it is equipped with a value correction means, it is possible to prevent the backflow of gas from the reformer combustion chamber to the oxidizer electrode or fuel electrode when the plant is stopped, thereby stably stopping the plant (pressure reduction). It has the effect of being able to

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of one embodiment of the present invention, FIG. 2 is a schematic diagram of another embodiment, and FIG. 3 is a schematic diagram of a conventional fuel cell power generation system. 1... Fuel cell, 2... Oxidizer electrode, 3... Fuel electrode, 4... Reformer combustion chamber, 5. IO... Differential pressure detector, 6... Pressure correction value calculator, 7... Pressure detector, 8...
- Regulator, 9: Step-down control valve, U: Low value priority circuit.

Claims (1)

[Claims] A gas supplied from a fuel cell including an oxidizer electrode and a fuel electrode is combusted in a reformer combustion chamber, and a pressure-reducing control valve is provided on the gas discharge side of the reformer combustion chamber. In a fuel cell power generation system in which the pressure-reducing control valve is adjusted so that the pressure on the outlet side of the combustion chamber matches a set value, there is a gap between the oxidizer electrode and the reformer combustion chamber, and between the fuel electrode and the reformer combustion chamber. a gas flow trend detection means for detecting a trend of at least one of the gas flows; and based on the detected gas flow trend, prevent combustion gas from flowing back from the reformer combustion chamber to the fuel cell side when the plant is stopped; A fuel cell power generation system comprising: pressure set value correction means for correcting the outlet side pressure set value of the reformer combustion chamber.