JPH03219565A - Fuel cell power generation system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to control of the gas phase in a steam separator forming a cooling system of a fuel cell power generation system.

[Conventional technology]

A fuel cell extracts electric power to the outside by continuously supplying a fuel gas containing hydrogen to a fuel electrode and air to an air electrode to cause an oxidation-reduction reaction. In order to remove the heat associated with this reaction, the fuel cell is equipped with a cooler, and the fuel cell is cooled by cooling water flowing from the battery cooling system, which consists of a battery cooling water pump and a steam separator. be exposed.

Fuel cells require a certain operating temperature (e.g. 200°C) to promote reactions, and for this reason the cell cooling water is maintained at around 170°C during operation, but this depends on the pressure or temperature of the steam separator. This is done under the control of

Figure 3 shows, for example, "On-site fuel cell technical survey report" published by the Japan Industrial Machinery Manufacturers Association (May 1981).
FIG. 1 is a system diagram showing a conventional fuel cell power generation system shown on pages 1 to 12.

(1) (2) In the figure, (1) is the fuel electrode (la) and the air electrode (lb).
, and a cooler (1c) that removes the heat accompanying the reaction between the two poles.
(2) is the reaction part (2a)
, a reformer consisting of a burner section (2b), (3) a steam separator in which battery cooling water is separated into a liquid phase section (4) and a gas phase section (5), and (6) a battery cooling water Pump, (7a), (
7b) is the battery cooling water pipe, (8) is the steam supply pipe,
(9) is a steam control valve or a shutoff valve, (10) is an ejector, and (11) is a heat exchanger provided on the battery cooling water pipe (7a).

Next, the operation of this prior art will be explained. The fuel cell main body (1) sends hydrogen-rich reformed gas sent from the reaction section (2a) of the reformer (2) to the fuel electrode (1a), and sends it to the air electrode (1b) using a blower or the like (not shown). Electricity is extracted outside by supplying air sent from each of the above and causing an oxidation-reduction reaction. In order to remove the reaction heat generated during the reaction, cell cooling water is supplied to the fuel cell main body (1) from steam separation @ (3) via a cell cooling water pump (6).
It is supplied and circulated to the cooler (1c). The heat removed is recovered in the form of steam in a steam separator (3), and steam is generated in the steam separator (3). Steam separator (
In 3), the battery cooling water flows into the liquid phase part (4) and the gas phase part (5).
). Some steam from the gas phase part (5)
the reformer (2) via the steam control valve or cutoff valve (9), the steam supply pipe (8), and the ejector (10).
and is subjected to a reforming reaction there. Ejector (1
0) has the function of sucking and mixing raw fuel, natural gas, with steam pressure. In order to improve the reaction of the fuel cell body (1) and to limit the temperature of the materials used, the temperature inside the steam separator (3) is maintained at, for example, about 170° C. during operation.

For this purpose, it is necessary to remove heat from the battery cooling water, but since heat removal is insufficient by consuming only the steam for the reforming reaction mentioned above, heat removal equipment is installed on the battery cooling water piping (7a) (7b). Heat removal and temperature maintenance are performed by providing a heat exchanger (11) to keep the temperature or pressure of the steam separator (3) constant. Waterfish (3) (4) Since the gas phase part (5) of the gas separator (3) is saturated steam,
Temperature can be maintained by controlling pressure. The remaining reformed gas consumed at the fuel electrode (1a) of the fuel cell body (1) is sent to the burner section (2b) of the reformer (2),
There, it is burned to provide the heat necessary for the reforming reaction.

On the other hand, while the fuel cell power generation system is stopped, it is desirable to store the fuel cell main body (1) at a low temperature from the viewpoint of preventing oxidation of the material. Keep at ℃. Therefore, when the operation is stopped, the fuel cell main body (1
), lower the temperature of the battery, and add battery cooling water to 50-60℃ during stopped storage.
Maintain and circulate at around ℃. When starting up the system from this state, the battery cooling water is raised to operating temperature using some heating means, such as an electric heater.

(Problems to be Solved by the Invention) In such conventional technology, the temperature of the battery cooling water in the steam separator (3) crosses the normal pressure boiling point (100°C) of water between operation and shutdown, If the steam separator (3) becomes negative pressure at 100 degrees Celsius or less during shutdown and sucks in the surrounding air, that is, if air gets mixed into the gas phase section (5) of the steam separator (3), air will enter the battery cooling water. Oxygen inside melts into the cooler (IC) of the fuel cell main body (1) and the cell cooling water piping (7a).
), (7b) were corroded. In particular, the cooler (IC) of the fuel cell main body (1) is composed of thin tubes, and if oxidation corrosion occurs, water flow may be blocked and the cooling function may be lost.

In addition, at startup, since non-condensable gas (air) exists in the gas phase (5) of the steam separator (3), when the temperature rises, the pressure of the steam separator (3) decreases to the saturated vapor pressure of water. There is a problem that the temperature rises above 100%, making it difficult to control the temperature by pressure, and that the reforming reaction steam contains a portion of air that is harmful to the reforming device.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a system that does not allow harmful air to enter the steam separator even when the steam separator is stopped.

[Means to solve the problem]

The fuel cell power generation system according to the present invention comprises, as invention (1), a fuel cell main body formed by stacking a fuel electrode, an air electrode, and a cooler for removing heat accompanying the reaction between the above-mentioned two electrodes, and a circulation circuit with the above-mentioned cooler. Consists of a steam separator that forms a cooling system and separates cooling water into a gas phase and a liquid phase, and a pressurizing means that maintains the gas phase part of the steam separator higher than atmospheric pressure by pressurizing an inert gas. Invention (2) is a fuel cell main body formed by stacking a fuel electrode, an air electrode, and a cooler for removing heat accompanying the reaction between the two electrodes, and a cooling system formed by a circulation circuit with the cooler. It is composed of a steam separator that separates water into a gas phase and a liquid phase, and a gas discharge means that releases the gas phase to the atmosphere and releases noncondensable gas when the temperature rises upon startup.

[Effect]

The cooling system pressurizing means in the fuel power generation system of the present invention pressurizes the gas phase of the steam separator to maintain the internal pressure above atmospheric pressure and prevent inert gas from entering.

Further, the gas exhaust means provided in the gas phase part of the cooling system opens the gas phase part to the atmosphere when the temperature rises at startup, and releases non-condensable gas.

(Embodiment of the Invention) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
FIG. 2 is a system diagram showing a fuel cell power generation system according to the present invention, and FIG. 2 is a system diagram showing a fuel cell power generation system according to another embodiment of the invention.

In the figure, (1) to (11) are the same as the conventional fuel cell power generation system shown in FIG. 3, so their explanation will be omitted. (20) is nitrogen equipment, (22) is nitrogen equipment (20)
These (2) are connected to the steam separator gas phase section (5) by nitrogen pressurizing piping having a pressure reducing valve (21) and a check valve (23).
0) to (23) constitute a pressurizing means (24). (2
5) It has a steam separator gas phase section (7
) (8) This (25) is the atmospheric discharge piping that releases (5) to the atmosphere.
(26) constitutes gas exhaust means (27). Next, the operation of the embodiment shown in FIG. 1 will be explained. The operation of the system during operation is similar to the conventional configuration shown in Figure 3.
The explanation thereof will be omitted here. The gas phase portion (5) of the steam separator (3) is constantly pressurized with nitrogen from the nitrogen equipment (20) via the nitrogen pressurization pipe (22). The pressurizing pressure of nitrogen is controlled by the pressure reducing valve (21) on the nitrogen pressurizing pipe (22), from 1 to 588/crr? It is adjusted to about g. The pressure inside the steam separator (3) during operation is normally between 7 and 87C.
m'g, which is higher than the nitrogen pressurization pressure.

Therefore, during operation, nitrogen is not supplied to the gas phase of the steam separator (3), and the check valve (23) provided on the nitrogen pressurizing pipe (22) prevents nitrogen from being supplied to the steam separator (3).
3) The water vapor inside will not flow back. Now, with such a configuration, when the system stops, the following operations are performed.

In the fuel cell main body (1), the reaction stops and no heat is generated, so the temperature of the cell cooling water in the steam separator (3) decreases.
Cooling of the fuel cell body (1) is performed. The temperature of the battery cooling water is reduced by natural heat radiation or by active cooling of the battery cooling water by a heat exchanger (11). At this time, the pressure of the steam separator (3) also decreases as the temperature of the battery cooling water decreases, but this pressure is equal to the pressurizing pressure of nitrogen, for example 2
, 0K8/crn2g, nitrogen is removed from the nitrogen equipment (20) of the pressurizing means (24) to the steam separator (
3) is supplied to the gas phase section (5), and thereafter the water vapor separator (3)
) is kept constant at 2,0 K8/crn'.

During stopped storage, the temperature of the battery cooling water is maintained at approximately 50 to 60°C, but even in this state, the water vapor separator (3)
The pressure is maintained at 2,0 K8/crn' of the nitrogen pressurization pressure. That is, by providing such a pressurizing means (24), it is possible to prevent the water vapor separator (3) from becoming under negative pressure when the fuel cell main body (1) is cooled during shutdown.
Therefore, suction of ambient air, which would cause corrosion, is prevented. Even if nitrogen exists in the gas phase (5) of the steam separator (3), there is no problem since nitrogen (9) (10) itself is inert.

Next, another embodiment of the invention shown in FIG. 1 will be described.

When the system starts up, during the temperature rising process of the battery cooling water,
The steam separator (3) is in a nitrogen pressurized state halfway, but if its saturated vapor pressure exceeds the nitrogen pressurization pressure, the nitrogen pressurization becomes ineffective, and the gas phase part of the steam separator (3) ( 5)
The nitrogen gas is replaced by saturated steam. At this time, due to the action of the check valve (23), saturated steam is released from the nitrogen pressurization circuit (2
2) There is no backflow to the side. Here, after the saturated steam pressure exceeds the nitrogen pressurization pressure, the shutoff valve (25) of the gas discharge means (27) is opened for a certain period of time, and the steam separator (3)
The remaining nitrogen and residual air are actively released into the atmosphere. As a result, the inside of the steam separator (3) is free of non-condensable gases, particularly air, which has a large influence, and contains only saturated steam, making it possible to maintain an appropriate pressure and monitor an appropriate temperature.

By providing a nitrogen pressurization circuit and an atmospheric release circuit for the steam separator (3) in this way, it is possible to prevent the intrusion of air that causes corrosion, and it is also possible to prevent inconveniences in monitoring the condition when the temperature rises at startup. Non-condensable gas can be removed quickly.

In addition, in the above embodiment, a check valve (23) was provided on the nitrogen pressurizing pipe (22), but a shutoff valve may be provided in place of the check valve (23). An example is shown in FIG. In the figure, (28) is a shutoff valve provided on the nitrogen pressurization pipe (22). During operation, the shutoff valve (28) is closed, and the function of the shutoff valve (28) at this time is the same as that of a check valve. When stopped, the shutoff valve (2) closes before the pressure of the steam separator (3) drops to atmospheric pressure (OK8/crn2).
6) and pressurize the gas phase section (5) of the steam separator (3) with nitrogen. The effect obtained by this is the same as in the case of a check valve. At startup, the temperature of the steam separator (3) exceeds 100°C, that is, the saturated vapor pressure is atmospheric pressure (OK8
/crn'), the shutoff valve (28) is closed to disconnect the nitrogen pressurization.

Thereafter, the shutoff valve (26) of the atmospheric discharge means (27) is opened for a certain period of time, and the nitrogen in the steam separator (3) (11) (12) is discharged to the outside. The effect obtained by this is also the same as in the case of the above-mentioned check valve.

In addition, in Figures 1 and 2, nitrogen pressurization piping (22
) and the atmosphere discharge pipe (25) are connected to the gas phase part (5) of the steam separator (3), but it is not necessarily limited to that position, and the gas phase part of the steam separator (3) Department (
5) may be connected on the pipe where it is connected, for example, on the steam supply pipe (8).

〔Effect of the invention〕

As described above, according to the first claim of the present invention, the fuel electrode,
The fuel cell body is made up of a stack of coolers that remove the heat associated with the reaction between the air electrode and both electrodes, and a circulation circuit with the cooler forms a cooling system, and water vapor separation separates the cooling water into a gas phase and a liquid phase. The device is constructed with a pressurizing means that maintains the gas phase of the steam separator higher than atmospheric pressure by pressurizing the steam separator with inert gas, preventing air from entering the steam separator even when the steam separator is stopped, making it inert. This has the effect of providing a fuel cell power generation system that prevents corrosion of coolers, piping, etc. due to gas.

Further, according to the second claim of the present invention, the gas phase of the steam separator is opened to the atmosphere at the time of startup temperature rise, and a gas exhaust means is provided to release non-condensable gas. This has the effect of providing a fuel cell power generation system in which pressure can be maintained and normal temperature monitoring can be performed using pressure.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a fuel cell power generation system according to an embodiment of the present invention, FIG. 2 is a system diagram showing a fuel cell power generation system according to another embodiment of the invention, and FIG. 3 is a system diagram showing a fuel cell power generation system according to another embodiment of the invention. It is a system diagram showing a power generation system. In the figure, (1) is the fuel cell main body, (3) is the steam separator, (4) is the liquid phase, (5) is the gas phase, (24) is the pressurizing means, and (27) is the gas exhausting means. . In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A cooling system is formed by a circulation circuit between the fuel cell body, which is made up of a fuel electrode, an air electrode, and a cooler that removes the heat accompanying the reaction between the two electrodes, and the cooler, and the cooling water is in the gas phase. A fuel cell power generation system comprising a water vapor separator that separates the water vapor into a liquid phase, and a pressurizing means that maintains the gas phase portion of the water vapor separator at a pressure higher than atmospheric pressure by pressurizing an inert gas. (2) A cooling system is formed by a circulation circuit between the fuel cell body, which is made up of a fuel electrode, an air electrode, and a cooler that removes heat accompanying the reaction of the above-mentioned two electrodes, and the above-mentioned cooler, and the cooling water is in a gas phase. A fuel cell power generation system comprising: a water vapor separator 1 that separates into a liquid phase; and a gas discharge means that releases the gas phase to the atmosphere and releases non-condensable gas at the time of startup and temperature rise.