JPH01151162A - Pressure difference suppressing method for fuel cell plant - Google Patents

Abstract

PURPOSE:To prevent a trouble of the pressure difference suppressing operation due to the wasteful time by determining the change rate of the pressure difference between an oxidizer gas electrode and a fuel electrode with a computer and changing the operation starting level of bleed valves in response to it. CONSTITUTION:Nitrogen is fed to a cell container 2 via an inlet flow control valve 1, the pressure difference between the container 2 and an oxidizer gas electrode 4 is controlled by a pressure difference control valve 3 at the outlet side. The pressure difference between the gas electrode 4 and a fuel electrode 9 is controlled by a pressure difference control valve 10 at the outlet side of the fuel electrode 9. In this case, the control valve 10 is operated by a pressure difference transmitter 11. Bleed valves 12 and 13 provided at the gas electrode 4 and the fuel electrode 9 suppress the pressure difference due to the disturbance not fully controlled by the control valve 10 and are operated by signals from a computer 14. The change rate by the pressure difference is determined by the computer 14, the operation starting level of the bleed valves 12 and 13 is changed in response to the change rate. The delay of the pressure difference suppressing operation due to the wasteful time of the bleed valves can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for suppressing differential pressure in a fuel cell plant.

[Conventional technology]

The conventional method for suppressing differential pressure in fuel cell plants is disclosed in Japanese Patent Application Laid-Open No. 1986-
As described in Japanese Patent No. 241661, the number of operations of the bleed valve is changed depending on the speed of change (rate of change) of the differential pressure, thereby preventing the differential pressure from exceeding a certain value.

That is, FIG. 2 shows a differential pressure suppression device for a fuel cell plant. As shown in the figure, nitrogen is supplied to the cell container 2 via the inlet flow rate control valve 1, and the outlet side is supplied with nitrogen. The differential pressure regulating valve 3 controls the differential pressure between the battery container 2 and the oxidizing gas electrode 4. In this case, the differential pressure regulating valve 3 may be provided between the battery container 2 and the oxidizing gas electrode 4. A differential pressure transmitter 5
It works by On the oxidizing gas electrode side, air is supplied to the oxidizing gas electrode 4 via the inlet flow rate control valve 6, and the oxidizing gas electrode exhaust gas is mixed with the container outlet gas and then sent to the reformer combustion section 7.
flows into. On the fuel electrode side, reformed gas from a fuel reformer (not shown) flows into the fuel electrode 9 via an inlet flow control valve 8, and fuel electrode exhaust gas flows into the reformer combustion section 7. On the fuel electrode outlet side, the differential pressure between the oxidizing gas electrode 4 and the fuel electrode 9 is controlled by the differential pressure regulating valve 10. In this case, the differential pressure regulating valve 1
0 is operated by a differential pressure transmitter 11 provided between the oxidant gas electrode 4 and the fuel electrode 9. A bleed valve 12 provided at the oxidizing gas electrode 4. Bleed valve 1 provided at fuel electrode 9
3 is an oxidizing gas electrode 4. It suppresses the differential pressure caused by a large disturbance that cannot be controlled by the differential pressure regulating valve 10 between the fuel electrodes 9, and is operated by a signal from a control computer 14 that receives a signal from a differential pressure transmitter 11. In order to suppress the differential pressure between the oxidizing gas electrode 4 and the fuel electrode 9 in such a differential pressure suppressing device of a fuel cell plant, conventionally, a signal from the differential pressure transmitter 11 is input to the control computer 14. When the differential pressure exceeds a certain value (operation start level), an open signal is sent to the bleed valve on the higher pressure side, reducing the pressure at this electrode.

[Problem that the invention seeks to solve]

Although the above-mentioned conventional technology has a large effect of controlling the differential pressure after the start of the bleed valve operation, it lacks consideration of the validity of the differential pressure signal itself, and therefore has the disadvantage that the start of the bleed valve operation itself is delayed.

This drawback will be explained based on FIG. The figure shows, as an example, the opening and closing operation states of the bleed valve of the oxidizing gas electrode. In the figure, A is the operating start level of the bleed valve of the oxidant gas electrode, B is the differential pressure occurring in the actual system, C is the differential pressure measured via the differential pressure transmitter, and D is the measured pressure. This is the flow rate of the bleed valve of the oxidant gas electrode, which operates based on the differential pressure. Note that the horizontal axis is time. As shown in the figure, there is a measurement dead time Δt1 between the true differential pressure B and the measured differential pressure C, so the measured differential pressure C reaches the bleed valve operation start level A. When it reaches true differential pressure B
exceeds operation start level A. Furthermore, since the dead time Δt2 of the bleed valve operation is added, the differential pressure at the time the bleed valve starts operating becomes a value far away from the set value, and the differential pressure between the oxidant gas electrode and the fuel electrode is controlled to be below the predetermined value. I couldn't do it.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for suppressing differential pressure in a fuel cell plant, which makes it possible to prevent malfunctions in differential pressure suppressing operation due to dead time in the system. It is something.

[Means for solving problems]

The above object is achieved by changing the operation start level according to the rate of change in differential pressure determined by the control computer.

[Effect]

Since the operation start level changes depending on the rate of change in differential pressure,
The bleed valve operates according to the rate of change in the differential pressure, thereby avoiding delays in differential pressure suppression based on the bleed valve operation dead time and measurement dead time. Malfunctions in the differential pressure suppression operation are prevented.

〔Example〕

The present invention will be explained below based on the illustrated embodiments. FIG. 1 shows an embodiment of the invention. As shown in the figure, in this embodiment, the operation start level is changed in accordance with the rate of change in the differential pressure determined by the control computer.

By doing this, malfunctions in the differential pressure suppression operation due to dead time in the system can be prevented, making it possible to prevent malfunctions in the differential pressure suppression operation due to dead time in the system. A method for suppressing differential pressure can be obtained.

In other words, the figure shows, as an example, how the bleed valve operates in relation to the oxidizing gas polar system.The vertical axis shows the differential pressure at which the bleed valve starts operating (bleed valve operating start level), and the horizontal axis shows the rate of change in the differential pressure. The relationship between the rate of change in differential pressure and the differential pressure at which the bleed valve starts operating is shown. The rate of change in differential pressure is determined from the differential pressure measured in the control computer (see Figure 2). In the computer, the differential pressure change rate and the bleed valve operation start differential pressure as shown in the figure are stored in advance. The opening operation is performed when the measured differential pressure and rate of change in differential pressure fall within the shaded area in the figure. That is, when the rate of change in differential pressure is large, the operation start level of the bleed valve is lowered. In this way, by opening the bleed valve early in consideration of the differential pressure change rate and measurement dead time, the generated differential pressure can be suppressed within an allowable value. As described above, according to this embodiment, the differential pressure between the oxidant gas electrode and the fuel electrode of the battery can be suppressed within a certain value, and the reliability of battery operation can be improved.

〔Effect of the invention〕

As described above, the present invention prevents malfunctions in the differential pressure suppressing operation due to dead time of the system, and provides a fuel cell that makes it possible to prevent malfunctions in the differential pressure suppressing operation based on the dead time of the system. A method for suppressing differential pressure in a plant can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the differential pressure at the start of bleed valve operation and the rate of change in differential pressure in an embodiment of the method for suppressing differential pressure in a fuel cell plant of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between differential pressure control in a fuel cell plant An explanatory diagram showing the system of the device, Fig. 3 shows the operation start level of the bleed valve according to the differential pressure suppression method of a conventional fuel cell plant;
FIG. 2 is an explanatory diagram showing the relationship among the differential pressure occurring in an actual system, the differential pressure measured via a differential pressure transmitter, and the flow rate of a bleed valve that operates based on the measured differential pressure. 4... Oxidizing gas electrode, 9... Fuel electrode, 11... Differential pressure transmitter, 12.13... Bleed valve, 14... Control computer.

Claims (1)

[Claims] 1. A signal from a differential pressure transmitter that measures and transmits the differential pressure between the oxidizing gas electrode and the fuel electrode is taken into a control computer, and the differential pressure is detected by a bleed valve provided at the both electrodes. When the operation start level is reached, the control computer sends a signal to the bleed valve of the electrode on the higher pressure side among the bleed valves to release gas from the electrode on the higher pressure side. A method for suppressing differential pressure in a fuel cell plant, characterized in that the operation start level is changed in accordance with a rate of change in the differential pressure determined by the control computer. 2. The method for suppressing differential pressure in a fuel cell plant according to claim 1, wherein the operation start level is lowered as the rate of change in the differential pressure increases.